tag:blogger.com,1999:blog-64598011616449659092024-02-07T17:52:40.337+01:00Giovanni's houseBoNewshttp://www.blogger.com/profile/14996032718916828654noreply@blogger.comBlogger13125tag:blogger.com,1999:blog-6459801161644965909.post-21777421742771872952016-05-23T00:03:00.001+02:002016-05-23T00:03:22.061+02:00Metabolismo del collageno<div><div class="separator" style="clear: both;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimXRZ-gAgJpN19QMG3xt8knIan2ol666fyqF4vXcKpwK8YTlisPlHgnMdf5t4VPBfmSQk75cUFJaW8OWieR5Vox6K9P4Wx8UoNf2vgXr7FgVwiq4z1qfrtWVcJfA19qt-kGizA6OVYn9Uo/s640/blogger-image--113843552.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimXRZ-gAgJpN19QMG3xt8knIan2ol666fyqF4vXcKpwK8YTlisPlHgnMdf5t4VPBfmSQk75cUFJaW8OWieR5Vox6K9P4Wx8UoNf2vgXr7FgVwiq4z1qfrtWVcJfA19qt-kGizA6OVYn9Uo/s640/blogger-image--113843552.jpg"></a></div> </div><div><br></div><div>Il termine collagene deriva da un termine inglese di circa 150 anni fa, indicante l'aspetto gelatinoso che assumevano il tessuto connettivo di quasi tutte le forme viventi, incluse il corallo e le anemoni di mare, se portate ad ebollizione. Questo dato dimostra l'importanza dal punto di vista filogenetico del collageno per gli esseri viventi multicellulari. </div><div>Il tessuto connettivo è appunto il cemento che unisce differenti tipi cellulari a formare gli organi complessi che permettono la vita agli organismi pluricellulari.</div><div>I componenti fondamentali del tessuto connettivo sono la componente cellulare ( fibrociti e fibroblasti ) e la matrice extracellulare composta dal collagene, da proteine non collageniche, e dai fattori di crescita in grado di modulare l'attività delle cellule circostanti.</div><div><br></div><div>Al momento esistono circa 28 tipi di collageno descritti nell'uomo.</div><div>La molecola del collagene è formata da una proteina la cui struttura primaria è caratterizzata dalla presenza di uno o più domini proteici che permettono di assumere la tipica conformazione spaziale della tripla elica. </div><div>La " tripla elica " è in definitiva ciò che caratterizza le fibre collagene ed è determinata dalla presenza di una seguenza aminoacidica contenente la caratteristica tripletta:</div><div><br></div><div> X - Y - Gly</div><div><br></div><div>Dove la glicina è seguita in circa un terzo dei casi dalla Prolina ( X ) e dalla Idrossiprolina ( Y ). Ciascuna catena contenente tale struttura forma un'elica levogira. </div><div>Ciascuna catena proteica o protomero forma un'elica levogira, è assemblata con altre due catene similari, in modo da formare una proteina a triplice elica destrogira per formare una molecola di pro-collagene. </div><div>In tale molecola tripeptidica i residui di Glicina sono posti al centro della struttura a triplice elica, mentre i residui di Prolina e Idrossiprolina sono disposti in modo da esporre il loro radicale ( R ) lateralmente alla struttura aminoacidica ( CO-CH-NH ).</div><div>Pertanto prima di essere assemblato ciascun protomero deve venire sottoposto a reazioni di idrossilazione a livello del reticolo endoplasmatico rugoso dei fibroblasti. Qui sono presenti gli enzimi chiamati idrossilasi in grado di trasferire un ossidrile su un amni acido di Prolina o di Lysina. Avremo quindi :</div><div><br></div><div>4 Idrossi Prolina idrossilasi tipo 1 ubiquitario e tipo 2 presente nei condrociti, negli osteoblasti, nelle cellule endoteliali.</div><div>3 Idrossi Prolina idrossilasi è formata da un complesso enzimatico formato da Ciclofillina B, CTRAP, P3H1 ne esistono 5 isoenzimi, e la sua mutazione è responsabile di due forme ereditarie di Osteogenesi Imperfetta tipo 7 e 9.</div><div>Idrossi Lisina idrossilasi ne esistono 4 isoenzimi. Una rara forma di Osteogenesi Imperfetta tipo 8 è legata al difetto nella sintesi del tipo 1 ( LH1 ) telopetide lisil ossidasi chiamata anche Sindrome di Bruck. Il tipo 2 ( LH2 ) anche conosciuta come procollagene lisina 2 ossoglutarato 5 diossigenasi (PLOD-2) è stata identificata sul cromosoma 3. L'uso enzima tipo 3 ( LH3 ) è un enzima multifunzionale in grado di svolgere anche attività galattosil transferasica e glucosil transferasica. La preponderanza di aldeidi di idrossilisina a livello dei telopetidi del collagene osseo assicura che si formino legami stabili tra catene Alfa adiacenti. Nell'osso si forma idrossiallisina e ketoimine che danno origine ai legami crociati del Piridinio, nella cute l'allisina dà origine ai Pirroli.</div><div>Galattosiltransferasi </div><div>Glucosiltransferasi </div><div>Protein disulfide isomerasi agisce anche come subunità beta del tetramero prolil idrossilasi alfa2 beta2</div><div><br></div><div>Tali reazioni richiedono alfa cheto glutarato, ione ferroso, ossigeno molecolare ed acido ascorbico. L'utilizzo di alfa cheto glutarato è abbastanza insolito tra le idrossilasi, pertanto tali enzimi vengono anche chiamate 2 oxo glutarato Ossidasi.</div><div>Esse infatti non richiedono il gruppo protoemo come gruppo prostetico per legare la molecola di ossigeno. </div><div>Tali enzimi sono in grado di legare lo ione ferrico all'ossigeno semplicemente con l'aiuto dei prodotti del Ciclo di Krebs ed in particolare dell'alfa cheto glutarato e l'Acido piruvico. </div><div>Gli HIFs Alfa e Beta ( Hipoxia Inducing Factors ) sono regolati dalle 2 oxo glutarato deidrogenasi, il primo indotto dagli stati di ipossia tissutale, il secondo attivo in modo constitutivo nelle cellule. Pertanto possono essere considerati enzimi a basso consumo energetico, in grado di utilizzare i soli prodotti della glicolisi aerobica come donatore di energia.</div><div>Tali enzimi, localizzati nella matrice mitocondriale, catalizzano reazioni di decarbossilazione ossidativa del substrato keto-acido come l'Acido piruvico o l'alfa cheto glutarato. I fattori indotti dall'ipossia possegono dei siti che sono idrossilati da tali enzimi a livelli dell'aminoacido Prolina. L'idrossilazione ne stimola la degradazione proteosomica. Nei mammiferi tali enzimi entrano a far parte della sintesi del collagene e della biosintesi della carnitina.</div><div><br></div><div>Tutti i residui di lisina idrossilati vengono poi attaccati da altri enzimi che sono le glucosiltransferasi o le galattosiltransferasi. Tali enzimi possono agire sulla proteina solo se non è ancora in forma elicoidale e più sono corti i peptidi sui quali agiscono più facilmente agiscono sugli aminoacidi.</div><div>Sembra poi evidente che i ponti disulfuro interpeptidici si possono formare solo dopo che la struttura elicoidale del procollagene maturo si è assemblata a formare la tripla elica. La struttura elicoidale si può formare solo a livello dell'apparato del Golgi o del reticolo endoplasmatico liscio. Solo a questo punto potrebbero agire le protein disulfide isomerasi, enzimi in grado di formare ponti disulfuro tra le molecole di pro-collageno.</div><div>A livello extracellulare il pro-collageno è trasformato in collagene maturo con l'intervento di almeno due enzimi a livello extracellulare:</div><div>la procollageno aminoproteasi in grado di rimuovere gli aminopeptidi all'estremità N terminale del collagene ( ADAMs A Disintegrin And Metalloproteinase )</div><div>la procollageno corbossipeptidasi che rimuove l'estremità C-terminale con l'aiuto di calcio.</div><div><br></div><div><br></div><div>Le molecole di collagene maturo spontaneamente si assemblano in fibrille con le caratteristiche fisico chimiche e le esatte dimensioni di quelle osservate al microscopio elettronico.</div><div>Da un punto vista fisicochimico, la struttura ricca di Idrossiprolina preceduta da Prolina non idrossilata a elica levogira è essenziale per rendere stabile la proteina a triplice elica destrogira del collagene.</div><div>Dallo studio della nefropatia diabetica gli studiosi scroprirono che le molecole che formano il collagene maturo sono di tipi differenti e individuarono negli anni '60 le catene α1 e α2 che sono responsabili della formazione di molecole di collageno detto "Fibrillare".</div><div><br></div><div><br></div><div>Al momento attuale 6 tipi di molecole α sono state identificate, codificate dai rispettivi geni:</div><div>α 1 localizzato sul cromosoma 13q 21.3 - 22</div><div>α 2 localizzato sul cromosoma 13q 21.3 - 22</div><div>α 3 localizzato sul cromosoma. 2 q 35 - 37</div><div>α 4 localizzato sul cromosoma 2 q 35 - 37</div><div>α 5 localizzato sul cromosoma X q 26 - 48</div><div>α 6 localizzato sul cromosoma X q 26 - 48</div><div><br></div><div><br></div><div> Collagene fibrillare</div><div>Il collageno fibrillare è stato il primo ad essere scoperto dagli studi di Nageotte nel 1920 che in seguito alla descrizione istologica della natura fibrillare della matrice extra cellulare del tessuto connettivo dimostrò la sua insolubilità in acqua, ma la formazione di un agglomerato gelatinoso ( da cui prende il nome ) ma la sua solubiltà negli acidi. </div><div>Con l'utilizzo della diffrazione ai raggi X e della microscopia elettronica tali fibre solubili in acido vennero identificate come molecole di collageno assemblate in uno specifico ordine di modo che ciascuna molecola di collagene era distante dalla seguente di 40 nm, ma si sovrapponeva lateralmente ad un'altra fibra di collagene per 300 nm. Inoltre ciascuna fibra di collagene era sfasata lateralmente con la vicina di 67 nm, in modo che una sorta di scalini della profondità di 67 nm si formavano tra una fibra di collagene e quella che scorreva parallela lateralmente.</div><div>La lunghezza di ciascuna fibra collagenica risultava quindi pari a circa 400 nm e si sovrapponeva per circa 1/3 della sua lunghezza a quella che scorreva parallela ad essa. </div><div>Alla microscopia elettronica questa struttura era visivamente evidente dalla bandeggiatura di una struttura altamente organizzata del collageno di tipo I, dove ciascuna fibra era distanziata da quella che scorreva ad essa parallela di circa 100 nm ( 67 + 40 nm ), lasciando 300 nm della molecola di collagene sovrapposta a quella adiacente.</div><div><br></div><div>Ciascun protomero al polo N-terminale ha una tripla elica a 7S, seguito da una struttura collagenica a tripla elica nella porzione mediana della molecola, e finalmente al lato C-terminale da un trimero non-collagenico ( NCI ). La caratteristica più importante è l'interruzione della caratteristica tripletta Glicina-X-Y nelle porzioni C- terminali e N-terminali della molecola. Tale caratteristica permette alla struttura una volta assemblata flessibilità, permettendo di formare " looping e supercoiling ".</div><div><br></div><div>Ai collageni fibrillare appartengono i collageni tipo I , II , III , V , XI , XXVI , XXVII caratterizzati dalla struttura fibrillare microscopicamente descritta più sopra.</div><div>Il tipo I è formato da complessi eterotrimerici di 2 catene α1 e 1 catena α2 è presente per la maggior parte nel tessuto connettivo, e nel tessuto osso maturo. La mutazione spesso nei residui di glicina è responsabile di gran parte delle forme conosciute di Osteogenesi Imperfetta ( tipo 1, 2, 3 e 4 )</div><div>Il tipo II è formato da complessi homotrimerici di 3 catene α1 è presente nella matrice extra cellulare della cartilagine.</div><div>Il tipo III è formato da complessi homotrimerici di 3 catene α1 è presente associato all'elastina nel tessuto elastico.</div><div>Il tipo V è formato da complessi eterotrimerici di 1 catena α1, 1 catena α2, 1 catena α3 o una catena α4.</div><div>Il tipo IX è formato da complessi eterotrimerici di 1 catena α1, 1 catena α2, 1 catena α3.</div><div>Il tipo XXIV è formato da complessi homotrimerici di 3 catene α1, è presente nei centri di ossificazione delle ossa craniofaciali, degli arti e delle vertebre.</div><div>Il tipo XXVII è formato da complessi homotrimerici di 3 catene α1, è presente negli abbozzi cartilaginei degli elementi scheletrici.</div><div><br></div><div> Collagene non fibrillare, o solubile o globulare.</div><div>Si identificano con tale termine le molecole di collagene facilmente solubili in acqua. Queste molecole sono state identificate in seguito agli studi su particolari malattie ereditarie come la Sindrome di Goodpasture e la Sindrome di Alport.</div><div>Nel 1927 Arthur Cecil Alport descrisse una sindrome caratterizzata da sordità sensitivo - neurogena in una famiglia che era pure affetta da nefropatia familiare, lenticono della capsula ottica anteriore, retinopatia, e talvolta ritardo mentale e leiomiomatosi.</div><div>La causa della Sindrome di Alport rimase sconosciuta fino al 1990 quando Trygvanson scoprì una mutazione nel gene che codifica per il Collagene tipo IV ed in particolare nel gene per la catena α5. Oggi più di 300 mutazioni in questo gene sono state identificate e tre forme geneticamente differenti della Sindrome di Alport sono state identificate rispettivamente legate a mutazioni dei geni che codificano per la catena α3, la catena α4, la catena α5 del collageno tipo IV.</div><div>Interessante notare che mutazioni eterozigoti per le forme di Alport α3 e α4 sono associate solo a piccole alterazioni della filtrazione renale che sono in grado di causare solo piccole anomalie della funzione renale.</div><div><br></div><div>La Sindrome di Goodpasture deve il suo nome ad Ernest W. Goodpasture che nel 1919, mentre serviva come Ufficiale Medico nella Marina Militare assegnato all'Ospedale Navale Chelsea, vicino a Boston, descrisse un paziente di 18 anni affetto da emorragia polmonare associata a glomerulonefrite rapidamente progressiva, e fatale; malattia che lo stesso Goodpasture attribuì ad una grave epidemia influenzale. </div><div>Tale osservazione clinica venne trascurata finché Stanton e Tange la riscoprirono nel 1958 e le darono l'eponimo di Goodpasture.</div><div>Ora indicata l'associazione di vasculite e porpora polmonare associata a nefrite viene identificata con tale eponimo, qualsiasi ne sia l'eziopatogenesi. </div><div>Conosciamo differenti meccanismi patogenetici che stanno alla base di tale associazione sindromica, tanto che si possono distinguere disordini immuno-mediati, malattie infettive e disordini vari. Tra questi ricordiamo:</div><div>anticorpi anti membrana basale glomerulare ( MBG ) o Malattia di Goodpasture</div><div><br></div><div>Sindromi di Goodpasture ( porpora polmonare e nefropatia )</div><div>la poliangioite microscopica ( con anticorpi antimieloperossidasi ANCA )</div><div>granulomatosi con poliangioite ( detta di Wegener - con anticorpi anti proteinasi-3 ANCA )</div><div>vasculite granulomatosa eosinofilica ( detta di Churg-Strauss )</div><div>porpora di Henoch-Schönlein</div><div>sindrome di Behçet</div><div>lupus eritematoso sistemico ( con ANCA, anticorpi antifosfolipidi, anticorpi anti membrana basale glomerulare )</div><div>nefropatia da IgA</div><div>crioglobulinemia mista IgG e IgM</div><div>tromboembolia polmonare con coesistente glomerulopatita membranosa</div><div>sindrome emolitico-uremica ( con glomerulonefrite trombotica microangiopatica ).</div><div><br></div><div>Sicuramente anche se la forma legata alla presenza di autoanticorpi diretti contro la membrana basale glomerulare è una delle forme meno comuni di tale sindrome, bisogna considerare questa forma per comprenderne l'importanza nella scoperta del collageno di tipo non fibrillare.</div><div>Lerner RA ( 1967 ) trasferì passivamente in primati anticorpi anti membrana basale glomerulare di pazienti affetti da malattia di Goodpasture e dimostrarono che da soli questi autoanticorpi potevano causare la malattia. </div><div>In seguito il target di tali autoanticorpi venne identificato il tratto non colagenico-1 ( NC-1 ) della catena α3 del collagene tipo IV. Ulteriori studi rivelarono che il collagene di tipo IV è formato da una famiglia di tre proteine formate dall'associazione di tutte e sei le molecole di collegeno finora conosciute:</div><div>Collageno IVα1 o embrionale formato dall'associazione di 2 catene α1, e 1 catena α2</div><div>Collagene IVα2 o adulto formato dall'associazione di1 catena α3, 1 catena α4, e 1 catena α5</div><div>Collagene IVα3 formato dall'associazione di 2 catene α5 e 1 catena α6.</div><div>Le proteine del collageno tipi IVα1 all'estremità N- terminale ha numerose oligosaccaridi legati a residui di azoto, e numerosi disaccaridi lungo la struttura collagenica centrale vera e propria. Come accennato tale molecola è presente solo nel tessuto embrionale.</div><div>Al contrario il collagene tipo IVα2 possiede parecchi ponti disulfuro tra le varie molecole che lo compongono anche a livello delle porzioni N-terminali 7S che a livello N-terminale NC1, tali interazioni intramolecolari danno la tipica struttura alla molecola matura, che è tipica dell'organismo adulto ed è in grado di formare la rete extracellulare della membrana basale presente nell'organismo adulto.</div><div>Mentre l'associazione a livello del l'estremità N-terminale porta direttamente alla formazione della caratteristica tripla elica destrogira e alla susseguente associazione termino-terminale delle molecole di collagene, a livello dell'estremità C-terminale le strutture non collageniche formano legami tra due protomeri di collageno vicini in modo da formare un esamero NC1. La maggior parte degli esameri NC1 è rinforzata da nuovi ponti sulfiliminici che devono essere dissociati perchè si possano legare gli autoanticorpi.</div><div>Pertanto è opinione diffusa che gli autoanticorpi siano diretti contro gli esameri α3,4,5,NC1 presenti sia nella Sindrome di Alport sia nella Malattia di Goodpasture. Sarebbe la dissociazione di tali strutture esameriche presenti a livello dell'estremità C terminale della molecole di collagene tipo IV la causa scatenante la reazione immunitaria diretta contro i neo antigeni formatisi a livello della membrana basale.</div><div>La malattia di Goodpasture risulterebbe pertanto una "conformeropatia" vale a dire una malattia scatenata dal cambiamento di conformazione del collageno della membrana basale, come probabilmente altre malattie autoimmunitarie quale il Morbo di Basedow , il Lupus e l'Artrite Reumatoide.</div><div>Semplificando forse in maniera eccessiva le malattie del tessuto connettivo in genere, anche chiamate connettiviti o collagenopatie potrebbero essere riviste alla luce di quanto prima esposto come disordini del metabolismo del collageno, in grado di scatenare reazioni immunitarie con danno tissutale conseguente e deficit funzionale degli organi colpiti.</div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div> Bibliografia</div><div><br></div><div><br></div><div>Prockop DJ, Kivirikko KI, Tuderman L et al. The biosynthesis of collagen and its disorders ( First of two parts ). New Engl J Med 1979;301:13-23.</div><div><br></div><div>Prockop DJ, Kivirikko KI, Tuderman L et al. The biosynthesis of collagen and its disorders ( Second of two parts ). New Engl J Med 1979;301:77-85.</div><div><br></div><div>Spiro RG. Biochemistry of renal glomerular basement membrane and its alterations in diabetes mellitus. N Engl J Med 1973;288:1337-42.</div><div><br></div><div>Sykes B, Francis MJO, Smith R. Altered relation of two collagen types in osteogenesis imperfecta. N Engl J Med 1977;296:1200-3.</div><div><br></div><div>Uitterlinden AG, Burger H, Huang Q et al. Relation of alleles of the collagen type 1 alfa (I) gene to bone density and the risk of osteoporotic fractures in postmenopausal women. N Engl J Med 1991;338:1016-21.</div><div><br></div><div>Barnes AM, Chang W, Morello R et al. Deficiency of cartilage associated protein in recessive lethal osteogenesis imperfecta. N Engl J Med 2006;355:2757-64.</div><div><br></div><div>Barnes AM, Carter EM, Cabral WA et al. Lack of cyclophillin B in Osteogenesis Imperfecta ( IX ) with normal collagen folding. N Engl J Med 2010;362:521-8.</div><div><br></div><div>Hudson BG, Tryggvanson K, Sundaramoorthy M et al. Alport's syndrome, Goodpasture's syndrome, and type IV collagen. N Engl J Med 2003;348:2543-56.</div><div><br></div><div>Pedchenko V, Bondar O, Fogo A et al. Molecular architecture of the Goodpasture autoantigen in Anti-GBM nephritis. N Engl J Med 2010;363:343-54.</div><div><br></div><div>Salant DJ. Goodpasture's disease - New secrets revealed. N Engl J Med 2010;363:388-91.</div>BoNewshttp://www.blogger.com/profile/14996032718916828654noreply@blogger.comtag:blogger.com,1999:blog-6459801161644965909.post-65694682728846272042016-05-08T23:59:00.001+02:002016-05-09T00:09:02.146+02:00L'uso degli oppiacei nella terapia del dolore cronico non oncologico<div><div class="separator" style="clear: both;"><br></div><div class="separator" style="clear: both;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhp2QXeLIuHL-CyUsTOByoSqJ6bskktjpIZknZ38UHhQ4KBH_kaaf7cPsFduPZ6GTmZSTK-7qiePN5M84PB01TH1Sh8vsYH9ifzaLg_RgZLaFhTAlKERWMJ7aQp7vX2ySXW4qusyH2LeXj_/s640/blogger-image-1958468240.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhp2QXeLIuHL-CyUsTOByoSqJ6bskktjpIZknZ38UHhQ4KBH_kaaf7cPsFduPZ6GTmZSTK-7qiePN5M84PB01TH1Sh8vsYH9ifzaLg_RgZLaFhTAlKERWMJ7aQp7vX2ySXW4qusyH2LeXj_/s640/blogger-image-1958468240.jpg"></a></div> </div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div>Trattare il dolore è da sempre uno dei principali obbiettivi della professione medica e si può dire che dall'epoca di Ippocrate, il bravo medico si adoperava per prima cosa, per lenire dal dolore i propri pazienti, prima ancora di capire l'origine dello stesso.</div><div>La farmacologia e le tecniche chirurgiche hanno dato un importante aiuto all'opera del Medico nel tentativo di alleviare le sofferenze dei propri pazienti. Tuttavia l'uso dei farmaci antidolorifici per eccellenza gli opioidi, dopo essere stato per così dire avallato anche nel trattamento del dolore cronico non oncologico, tanto da produrre cambiamenti legislativi sulle modalità di prescrizione, viene ora messo in discussione specie nei Paesi Industrializzati per l'aumento dei casi di dipendenza, come dimostrano i recenti fatti di cronaca di " morti " eccellenti di personaggi del mondo dello spettacolo associate spesso all'uso di antidolorifici.</div><div><br></div><div>La valutazione dell'intensità del dolore mediante scale validate universalmente è il primo passo verso una scelta del giusto analgesico.</div><div>La scala VAS ( VISUAL ANALGOGIC SCALE ) costituita da una linea , lunga 10 cm, che visivamente rappresenta l'ampiezza del dolore. Tra le due estremità della linea corrispondenti a " nessun dolore " e " il più forte dolore immaginabile " abbiamo la possibilità di individuare differenti gradi intermedi. Il paziente deve indicare sulla linea l' intensità del dolore avvertito. Richiede al paziente capacità visiva e motoria.</div><div><br></div><div>La scala di WONG-BAKER, costituita da una serie di disegni che raffigurano le espressioni del volto corrispondenti a diversi gradi del dolore ( sorridente, in lacrime ecc ). La scala è mostrata al paziente che deve indicare la faccia che a suo parere meglio esprime l'intensità del dolore provato.</div><div><br></div><div>La scala FLACC utile nei soggetti che per età, deficit motori, o deficit cognitivi non sono in gr,ADI di dare una valutazione soggettiva del dolore si ricorre ad una valutazione oggettiva di parametri come l'espressione del volto, il movimento delle gambe, la posizione del corpo, la presenza o meno del pianto, la consolabilità. Ad ognuno di questi 5 fattori si assegna un punteggio che va da 0 a 2. Dove 0 è il dato più positivo e 2 il dato più negativo. Il valore del punteggio complessivo ottenuto, scaturito dalla somma delle 5 valutazioni, quantifica l'intensità del dolore in base ad un punteggio da 0 a 10.</div><div>( FLACC : Face, Legs, Activity, Cry, Consolability )</div><div><br></div><div>La scala NOPPAIN utile nei soggetti che per età, deficit motori, deficit cognitivi non possono fornire una stima soggettiva del dolore si ricorre ad una stima oggettiva da altre di un operatore esterno. La scala utilizzabile soprattutto nei paziente affetti da demenza, valuta la presenza di comportamenti o comunicazioni verbali che suggeriscono dolore durante esecuzione di specifiche manovre assistenziali. Il punteggio totale varia da 0 a 55 e un punteggio superiore a 3 indica la presenza di dolore da sottoporre a un esame più approfondito.</div><div><br></div><div>La valutazione del dolore permette di scegliere i farmaci analgesici corretti relativamente a quelli a nostra disposizione.</div><div><br></div><div>Con gli anni '60 abbiamo assistito ad uno uso sempre crescente di farmaci antidolorifici dapprima gli steroidi, scoperti negli anni '50 e sintetizzati in laboratorio con svariata capacità antidolorifica e antinfiammatoria, ma gravati da importanti effetti collaterali di tipo metabolico. </div><div><br></div><div>FANS</div><div>Altre molecole a struttura non steroidea antinfiammatorie ( FANS : Farmaci Antifiammatori Non Steroidei ) con attività antidolorifica sono state sintetizzate nei laboratori nell'intento di sollevare i pazienti dal dolore senza arrecare importanti danni. Tutti accumunati dallo stesso meccanismo d'azione, vale a dire dall'inibizione dell'enzima Ciclossigenasi ( COX ), che permette la trasformazione dell'acido arachidonico in prostaglandina H2. I FANS vengono anche classificati in base alla loro azione specifica sul tipo di Ciclossigenasi. Infatti esistono una Ciclossigenasi constitutiva (COX-1) ed una Ciclossigenasi inducibile in caso di danno tissutale ( COX-2). Tutti i FANS agiscono variamente su entrambi gli isoenzimi e il rapporto di inibizione (COX1/COX2) è un indice della loro azione antinfiammatoria.</div><div><br></div><div>Indolici come l' Indometacina fortemente gastrolesiva.</div><div>Fenilacetici come il Diclofenac forse tra i più utilizzati nella pratica clinica.</div><div>Fenamici come l'Acido Flufenamico e l'Acido Meclofenamico.</div><div>Acidi propionici come Ibuprofene, Ketoprofene, Naprossene. Sostanze assai efficaci e meglio tollerate a livello gastrointestinale. Assorbiti rapidamente a livello orale sono secreti per via renale. L'ibuprofene è in genere considerato quello meno gastrolesivo.</div><div>Pirazolonici come la noramidopirina o metamizolo, gravato da importanti interazioni farmacologiche con antidiabetici orali, antipertensivi e diuretici.</div><div>Oxicam come il piroxicam, meloxicam, lornoxicam che necessitano di una sola somministrazione giornaliera.</div><div>Nimesulide molto attivo in particolare per i tessuti molli, ma gravato da notevole epatotossicità, qualora si superi il dosaggio raccomandato di 100 mg al dì</div><div>Salicilati come l'Acido acetilsalicilico che oltre a possedere un effetto antinfiammatorio, antidolorifico è pure un potente antipiretico e un buon anti aggregante piastrinico a basse dosi pari anche a 75-100 mg al dì. L'effetto antinfiammatorio invece si esplica a dosi pari a 1 gr al giorno.</div><div>COXIBs: farmaci altamente selettivi per la COX-2, sono stati messi sul mercato farmaceutico circa 10 - 15 anni or sono due molecole con indicazione nel trattamento principalmente del dolore osteoarticolare in particolare nell'artrosi, nell'artrite reumatoide, nella spondilite anchilosante, nella gotta. Essi sono il celecoxib e etoricoxib.</div><div><br></div><div><br></div><div>I FANS sono tuttavia gravati da importanti effetti collaterali quali disturbi a carico dell'apparato digerente come epigastralgie, nausea, ulcere gastroduodenali. L'uso dei FANS pertanto richiede l'utilizzo concomitante di farmaci inibitori di pompa protonica, gli unici antiacidi ad essere validati per tale utilizzo, cosa che non è stato dimostrato per gli anti-istaminici come la ranitidina e la famotidina. Inoltre possono creare danno ai pazienti affetti da malattia infiammatoria intestinale cronica. A livello renale bloccando le prostaglandine E2 riducono la perfusione renale portando ad insufficienza renale. I FANS sono inoltre associati ad aumentato rischio cardiovascolare, per i COXIBs con un aumento del rischio di infarto miocardico, riducendo l'effetto dei farmaci antipertensivi, dei diuretici, oltre ad aggravare il grado di insufficienza renale. Oltre a tossicità epatica, tali farmaci sono gravati dalla possibile comparsa di eruzioni cutanee, come prurito, rash, orticaria.</div><div>Particolare cautela è richiesta poi nell'uso di tali farmaci nei pazienti in trattamento con anticoagulanti orali, sia per l'aumentato rischio di sanguinamento gastrointestinale, sia per lo spiazzamento degli anticoagulanti dal legamento proteico con variazioni dell'INR non prevedibili.</div><div>I FANS hanno invece il loro maggior utilizzo in tutte quelle manifestazioni a carico dell'apparato muscolo-scheletrico sostenute dalla presenza di fenomeni di tipo infiammatorio. Possono essere utili inoltre per sedare dolori post-partum, in seguito a piccoli interventi pstchirurgici, in caso di cefalee, dolori mestruali, odontalgie.</div><div>Alcuni prodotti per via iniettiva come il Diclofenac, il Ketoralac trovano impiego anche nel dolore di origine postraumatica, postoperatorio, o da spasmo della muscolatura liscia come nelle coliche renali.</div><div><br></div><div>PARACETAMOLO</div><div>Per tali motivi l'anti dolorifico per eccellenza è da considerare il Paracetamolo o acetaminofene le cui spiccate azioni analgesiche, e antipiretiche, conosciute da oltre un secolo, hanno un buon profilo di efficacia e tollerabilità tale da renderla una delle molecole ore più utilizzate al mondo in tale categoria farmacologica.</div><div>Il Paracetamolo ha un ottimo assorbimento per via orale e le numerose formulazioni farmacologiche disponibili in commercio, inclusa quella parenterale disponibile solo per uso ospedaliero come pro-paracetamolo, fa di tale farmaco la molecola di prima scelta nel trattamento del dolore cronico lieve moderato.</div><div>Il Paracetamolo ha in comune con i FANS l'effetto antidolorifico e antipiretico, ma non l'effetto antinfiammatorio, e la sua azione si esplica principalmente a livello del sistema nervoso centrale, nelle vie neuro regolatrici delle afferenze doloriche, dove interferisce con le vie degli oppioidi e della serotonina.</div><div>Dal punto di vista farmacocinetico raggiunge la sua concentrazione massima nel plasma dopo 30-60 minuti e ha una emivita plasmatica di 2 ore. Il dosaggio massimo consigliato è di 4 grammi al giorno suddiviso in 4 dosi di 1 grammo ciascuna. </div><div>Per l'FDA la soglia di epatotossicità del farmaco è ben al di sotto dei 4 gr, intorno ai 3 gr, dove è possibile già evidenziare la presenza di epatotossicità, tale da indurre " necrosi epatica fulminante " caratterizzata da nausea, vomito, dolore addominale, ed aumento delle transaminasi, della bilirubina specie in soggetti dediti all'alcool. Come antidoto in tali casi è di norma utilizzata l'acetil cisteina anche per via orale, in grado di risolvere e ripristinare la funzionalità epatica danneggiata da un uso occasionale di paracetamolo.</div><div><br></div><div><br></div><div>Farmaci adiuvanti</div><div>Nel dolore cronico lieve-moderato vengono utilizzati spesso in associazione farmaci adiuvanti. Questi ultimi sono farmaci che agiscono in presenza di modificazioni della fibra nervosa periferica come la Carbamazepina e l'oxcarbamazepina ( nella nevralgia del trigemino ), gli antidepressivi triciclici, gli anestetici locali come la lidocaina.</div><div>Farmaci che agiscono in presenza di sensibilizzazione dei neuroni spinali per afferenze nocicettive e riduzione dei sistemi inibitori come i gabapentinoidi ( gabapentin e pregabalin ), clonazepam, antidepressivi triciclici e non.</div><div>Farmaci che agiscono in presenza di flogosi delle vie nervose dove il ruolo dei recettori periferici delle piccole terminazioni nocicettive del perinervio hanno grande importanza. Questi sono i corticosteroidi.</div><div><br></div><div>Oppiacei</div><div>Da sempre è comune convinzione che i pazienti affetti da dolore persistente di natura non oncologica e sottoposti a trattamento con oppiacei, dovessero inevitabilmente sviluppare una dipendenza.</div><div>Tale convinzione venne messa in dubbio negli anni '60, quando alcuni studiosi evidenziarono che, in presenza di benefici accettabili, i rischi di una tossicodipendenza in seguito a trattamento con oppiacei erano minimi o pressoché nulli.</div><div>Tale ipotesi venne avvalorata da studi di ricerca di base sul dolore cronico non oncologico Tali studi dimostravano che l'uso medicale degli oppiacei non creava dipendenza qualora fosse presente dolore. Infatti, se in situazione di dolore si somministra un oppiaceo, questo di lega tutto sui recettori siti nel corno dorsale del midollo pronti a modulare l'input doloroso; in caso contrario l'oppiaceo va a interferire sul sistema dopaminergico a livello del nucleo accumbens con il rischio di innescare meccanismi che portano alla tossicodipendenza.</div><div>Il loro utilizzo è stato ampiamente rivisto recentemente è regolamentato dalla Legge 38 che permette la prescrizione di farmaci oppiacei, utilizzati per la terapia del dolore su ricettario del Servizio Sanitario Regionale, per un fabbisogno di 30 giorni, con l'avvertenza di identificare lo stato di necessità del paziente con la sigla TDL ( Terapia Del Dolore ).</div><div><br></div><div>Il dolore cronico non oncologico ( CNCP ) di origine neuropatica o propriocettiva è una sorgente di importante morbidità. Il dolore cronico non oncologico è presente in seguito ad interventi di chirurgia maggiore, come l'impianto protesico di ginocchio o di anca ( dal 10 al 50% dei pazienti ) in circa l'8,2% dei diabetici. La lombalgia ( 15% degli USA ), l' osteoartrite sono due cause molto comuni di dolore cronico non oncologico.</div><div><br></div><div> <img src="webkit-fake-url://6a42b2cb-7bba-4a7a-aeff-1da6b41768ab/imagepng"></div><div>Localizzazione dei recettori Mu per gli oppioidi.</div><div>Tali recettori sono localizzati nel cervello umano principalmente nel talamo, nella sostanza grigia periacqueduttale, nell'insula, nel giro cingolato anteriore dove sono coinvolti nella percezione del dolore. Al contrario nell'area tegmentale ventrale e nel nucleo accumbens tali recettori sono coinvolti nella sensazione di ricompensa e benessere. A livello dell'Amigdala sono implicati nella reattività emotiva al dolore, mentre nel midollo allungato regolano il centro del respiro. A livello delle corna posteriori del midollo estinte la più alta concentrazione dei recettori Mu per gli oppioidi e qui modulano la percezione del dolore, mentre a livello del piccolo intestino regolano la motilità intestinale.</div><div><br></div><div>Gli analgesici oppiacei sono ampiamente usati nel trattamento di tale tipo di dolore mentre effetti collaterali a breve termine includono la sedazione, declino cognitivo, depressione respiratoria, l'overdose, la dipendenza farmacologica, pertanto è importante che la prescrizione di opioidi sia adeguata alle necessità di ciascun individuo.</div><div>Tuttavia mentre gli analgesici oppioidi sono in grado di alleviare il dolore non oncologico acuto senza causare danni, il beneficio di tali farmaci nel trattamento del dolore cronico non oncologico non ha ancora chiare linee guida di consenso sul loro utilizzo.</div><div><br></div><div>Due fattori sono universalmente evidenti:</div><div>Gli analgesici oppioidi sono ampiamente e impropriamente prescritti, tanto che il loro uso ha creato negli USA una epidemia vera e propria di morti da overdose e dipendenza da oppiacei.</div><div>La principale fonte di tali farmaci oppioidi sono le prescrizioni mediche.</div><div>Per tali motivi le associazioni mediche hanno iniziato a porsi il problema di regolamentare la loro prescrizione, in particolare per quanto concerne la terapia del dolore cronico non oncologico.</div><div>Non sembra affatto universalmente accettato che la presenza di dolore protegga i pazienti dallo sviluppare dipendenza dall'utilizzo farmacologico di oppioidi. Studiosi hanno dimostrato che la prescrizione di medicamenti contenti oppiacei per il dolore acuto è la maggior fonte di misuso di farmaci.</div><div><br></div><div><br></div><div>Gli oppioidi differiscono per la loro affinità e selettività di legame per i recettori Mu, in quanto possono levare anche i recettori kappa e delta o anche a recettori per altri neurotramsmettitori. L'effetto degli oppioidi, in particolare modo quello esplicato sul nucleo accumbens e nell'area tegmentale ventrale che sono responsabili della sensazione di ricompensa e benessere , sono maggiormente accentuate quando i farmaci sono rilasciati rapidamente a livello cerebrale. Per tale motivo la FDA ha incoraggiato e approvato formulazioni che evitino l'uso iniettivo delle formulazioni farmaceutiche di oppioidi.</div><div><br></div><div>Molti medici non distinguono tra dipendenza fisica e psichica. La prima è dovuto al fenomeno della tolleranza farmacologica è legata alla down regalati in recettoriale dei recettori a livello intracellulare.</div><div>La dipendenza psichica c'è solo in una piccola parte dei soggetti esposti agli oppioidi, si sviluppa lentamente non termina semplicemente smettendo di utilizzare gli oppioidi, ma ci può essere un elevato rischio di ricaduta anche per parecchi anni senza adeguato trattamento.</div><div>Noi non siamo in grado di conoscere la dose totale di oppioidi in grado di dare dipendenza psichica, ma sappiamo che il rischio di procurarla varia sostanzialmente tra le persone, che la variabilità genetica rende conto almeno del 35 - 40% del rischio associato alla dipendenza psichica e che gli adolescenti sono a maggior rischio di svilupparla in quanto il loro cervello ha ancora una elevata neuroplasticita e il loro lobo frontale non ancora del tutto sviluppato ( parte del cervello necessaria per un autocontrollo adeguato ).</div><div>Pertanto il rischio di sviluppare dipendenza da oppioidi negli adolescenti è maggiore che negli adulti.</div><div><br></div><div>Per molto tempo si è pensato che la presenza di dolore fosse sufficiente per evitare la dipendenza da oppioidi. Tuttavia studi epidemiologici hanno dimostrato che la dipendenza psicologica da oppioidi in pazienti affetti da dolore cronico non oncologico sia possibile e presente.</div><div>È quindi necessario attuare sforzi per prevenire l'emergenza di dipendenza iniziate durante il trattamento da parte di medici di medicina generale. È necessario quindi valuatare attentamente il rischio di dipendenza farmacologica con opportune scale di valutazione. Monitorare regolarmente sulle urine la concentrazione dei farmaci ed inviare ai centri di terapia del dolore tali soggetti, considerati a rischio.</div><div>Si suggerisce pertanto di non superare le 8 settimane di trattamento con oppioidi per pazienti affetti da dolore cronico non oncologico, tenere conto che aumentando il dosaggio ( > 100 MME ), la durata e forse l'uso di opioidi a lunga durata d'azione può facilitare l'insorgere a di dipendenza.</div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div>Per ottenere la dose equivalente alla Morfina dei comuni opioidi:</div><div><br></div><div>Buprenorphine cerotti MME x 12,6</div><div>Buprenorphine cp MME. x 10</div><div>Codeine MME x 0.15</div><div>Dihydrocodeine MME X 0,25</div><div>Fentanyl cerotti. MME x. 2,4</div><div>Fentanyl ev. MME x 100</div><div>Fenatnyl os. MME x 0,13</div><div>Hydrocodone. MME x 1</div><div>Methadone. MME. x 3</div><div>Oxycodone MME. x 1.5</div><div>Pentazocine. MME x 0,37</div><div>Tapentadolo. MME. x 0,4</div><div>Tramandolo. MME. x 0,1</div><div><br></div><div><br></div><div>Bibliografia</div><div><br></div><div>Volkow ND, McLellan AT. Opioid abuse in chronic pain - Misconception and mitigation strategies. N Engl J Med 2016;374:1253-63.</div><div><br></div><div>Kornetsky C, Bain G. Morphine: single dose tolerance. Science 1968;162:1011-2.</div>BoNewshttp://www.blogger.com/profile/14996032718916828654noreply@blogger.comtag:blogger.com,1999:blog-6459801161644965909.post-56518977123533903712016-04-03T21:14:00.003+02:002016-04-03T21:27:37.654+02:00Nuove strategie terapeutiche nella trombosi venosa profonda<div class="separator" style="clear: both;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEheGznO_NCybitzidddtNW57TuBD2KlaxUKOwQOuowTUpYru6AVakVJ-gaxjR8WSoYCSEkpkS4NJCNJqTQKz7Dsgtbb98VQKA6dHhR3FMn7yAuVGjxzEQqRI8mBuBstW_QQyQhk3lAsCp9-/s640/blogger-image--563043566.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEheGznO_NCybitzidddtNW57TuBD2KlaxUKOwQOuowTUpYru6AVakVJ-gaxjR8WSoYCSEkpkS4NJCNJqTQKz7Dsgtbb98VQKA6dHhR3FMn7yAuVGjxzEQqRI8mBuBstW_QQyQhk3lAsCp9-/s640/blogger-image--563043566.jpg"></a></div> <br>
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La tromboembolia venosa è la terza principale causa di morte vascolare, con una elevata incidenza specie tra gli anziani.<br>
L’incidenza aumenta dall’ 1 su 10.000 persone per anno tra le persone con meno di 40 anni a quasi 1 per 100 persone per anno tra gli ottantenni e ultra ottantenni ( 80 anni ).<br>
Complessivamente più di un terzo dei casi di TVP si presenta in persone con piu’ di 60 anni.<br>
Si stima che all'incirca l'embolia polmonare sia responsabile di 100.000 - 180.000 morti per anno , pur essendo la causa di morte più facile da prevenire nei pazienti Ospedalizzati.<br>
I sopravvissuti all'embolia polmonare spesso hanno come feliquati una ipertensione polmonare cronica tromboembolica o una sindrome postrombotica.<br>
La prima si manifesta con dispnea, mancanza del respiro, specie sotto sforzo; mentre la sindrome postrombotica anche chiamata " insufficienza venosa cronica " è caratterizzata dalla presenza di danno delle valvole di Valsalva presenti nei vasi venosi degli arti inferiori, con conseguente rigonfiamento a carico delle caviglie e del calcagno e dolore urente alle gambe in toto, in particolare dopo prolungata stazione eretta. In situazioni di grave compromissione del letto vascolare venoso possiamo anche avere ulcere cutanee specialmente localizzate a livello dei malleoli laterali.<br>
La formazione di trombi a livello arterioso coinvolge principalmente l’omeostasi endoteliale, mentre la formazione di trombi a livello venoso coinvolge principalmente l’omeostasi piastrinica e dei fattori o cellule circolanti, monociti, fattori della coagulazione, fattore tissutale, senza che necessariamente si debba pensare a danno-attivazione endoteliale come primum movens.<br>
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Eziologia<br>
Le nuove conoscenze di fisiopatologia molecolare hanno permesso di chiarire importanti concetti che stanno alla base del processo di formazione del trombo.sia questo a livello venoso o arterioso<br>
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Il concetto basilare è naturalmente quello che vede le piastrine circolanti che sono reclutate sulla superficie del vaso danneggiato, dove esse diventano il principale componente dello sviluppo del trombo. Inoltre i fattori della coagulazione ed in primo luogo il “ fattore tissutale “ prendono pare alla formazione a partire dal fibrinogeno circolante dei monomeri fibrina.<br>
Da un lato fattori che contrastano la formazione dei trombi sono presenti sulla superficie endoteliale e sono:<br>
la produzione di monossido d’azoto ( NO )<br>
Il rilascio di prostacicline<br>
la formazione di enzimi ectonucleotidosici ( CD39 )<br>
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Cattura e blocco delle piastrine sulla superficie del vaso danneggiata.<br>
Un ruolo molto importante è svolto dall’esposizione sulla superficie del vaso leso dei monomeri di collageno di tipo III presenti nella membrana basale dei vasi, oltre che dei restanti componenti della matrice extracellulare.<br>
Il collageno tipo III in grado di legare quando esposto ai componenti del plasma al “ fattore di von Willebrand “ attraverso l’interazione tra la glicoproteina piastrinica VI con il collageno e del complesso piastrino formato dalla glicoproteina Ib-V-IX con il fattore di von Willebrand.<br>
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Interazione tra le piastrine<br>
La conglomerazione di differenti piastrine è invece mediata dal legame dellì’integrina alfa IIb beta III con il fibrinogeno ed il fattore di von Willebrand.<br>
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Attivazione piastrinica<br>
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Una ulteriore via dia attivazione pietrifica è però giocata dalla sintesi del fattore tessutale.<br>
Tale fattore tissutale è un analogo di recettori per le citochine presente sulla superficie cellulare sia monocitica, pericitica che endoteliale che è attivo se legato al fattore VIIa. Il fattore tessutale circola libero nel plasma formando microparticelle a struttura vescicolare del diametro inferiore a 100 nm. Tali microparticelle durante la formazione del trombo sono in grado di legare una selectina, chiamata selectina P, espressa dalla piastrine attivate, tramante un controrecettore della selectina P presente sulle microparticelle chiamato PSGL-1.<br>
Il fattore tessutale esiste in due forme una latente che non ha attività procoagulante ed una attiva con attività coagulante. E’ probabile che la dimerizzazione, la riorganizzazione lipidica accanto alla trasformazione della struttura allosterica in particolare dei legami disulfuro presenti nel fattore tessutale influiscano sulla funzione della proteina. L’enzima PDI rilasciato dalle piastrine e dall’endotelio attivato è in grado di ossidare i radicali tiolici presenti nella forma inattiva del fattore tessutale e formare ponti disulfuro in grado di spiegare il cambiamento conformazione che permette al complesso fattore tissutale- fattore VIIa di legare e di solo con l’attivazione del fattore VIII e del fattore V, attivare il fattore X.<br>
L’enzima chiamato “ protein disulfide isomerasi ( PDI ) è anche necessario per la rottura e la formazione di nuovi ponti disulfuro tra i residui di cisteina presenti sull’integrina piastrinica alfaIIb beta 3. Tale reazione biochimica è necessaria in quanto le piastrine legate all’endotelio subiscono un transizione di conformazione che aumenta l’affinità delle piastrine ai suoi legandi ( fibrinogeno e fattore di von willebrand ). Non è ancora chiaro il vero ruolo e l’importanza esercitata per l’adesione piastrina dal collageno e dal fattore di von Willebrand, ma è certo che quest’ultimo deve legarsi ad un’altra integrino chiamata glycoproteina Ib.<br>
Si formano quindi dei veri e propri complessi sinaptici tra le differenti piastrine conglomerate nell’intento di creare uno spazio interstiziale protetto interpiastrinico che stabilizza il trombo.<br>
Tuttavia per formare trombina in quantità sufficiente sono necessari anche il fattore VIII e il fattore V che vengono tuttavia attivati dalla piccola quantità di trombina formata nei primi step di formazione della trombina localmente con formazione del fattore VIIIa e fattore Va.<br>
La trombina è così in grado di scindere il fibrinogeno in fibrina formato un complesso enzimatico con fattore VIIa e successiva cattura delle piastrine con contemporanea lisi sulla superficie piastrina del suo recettore chiamato Protease Activated Receptor 1 ( Par1 ), effettore dell’attivazione pastrinica.<br>
E’ interessante notare che in ratti non in grado di sintetizzare il recettore per la trombina Par4 riescono ugualmente a formare fibrina, anche se la trombina non si puo’ legare al recettore Par1. Tali dati suggeriscono che esistano altre enzimi proteolitici in grado di svolgere l’azione della trombina.<br>
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Le alterazione patofisiologiche che colpiscono gli arti affetti da TVP includono la cosiddetta Triade di Virchow:<br>
infiammazione<br>
Ipercoagulabilità<br>
danno endoteliale<br>
Tali modificazioni della emoreologia vascolare venosa portano ad attivazione di piastrine attivate, che rilasciano microparticelle. Tali microparticelle contengono i mediatori proinfiammatori in grado di legare i neutrofili, e stimolare il rilascio da parte di questi di materiale facente parte del nucleo cellulare e pertanto formare una rete extra cellulare chiamata " traps " extra cellulare di derivazione neutrofila.<br>
Tali formazioni di materiale del nucleo di neutrofili contengono istoni in grado di stimolare l'aggregazione piastrinica e promuovere la generazione di trombina piastrino dipendente.<br>
I trombi di origine venosa si formano e aumentano di dimensioni nel contesto di stasi venosa, bassa tensione di ossigeno, e aumento della trascrizione genica proinfiammatoria.<br>
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Stati protrombotici<br>
Esistono situazione in grado di favorire la formazione di trombi venosi; fortunatamente tali situazioni sono abbastanza rare e sono rappresentate da:<br>
mutazioni geniche del Fattore V di Leiden autosomico dominanti che causano resistenza a fattori coagulanti endogeni<br>
mutazioni geniche della Proteina C in grado normalmente di attivare il fattore V ed il fattore VIII della coagulazione<br>
mutazioni geniche del gene codificante per la protrombina, in grado di aumentare la concentrazione di protrombina.<br>
Deficit di Antitrombina III normalmente inibitori della coagulazione<br>
Deficit di Proteina S normalmente inibitori della coagulazione<br>
Sono abbastanza rare e associate a TVE ( tromboembolia venosa )<br>
La sindrome da anticorpi antifosfolipidi è la più comune delle forme acquisite trombofiliche ed è associata con trombosi sia arteriosa che venosa.<br>
Fattori di rischio per la formazione di trombi venosi sono pure il fumo di sigaretta, viaggi aerei di lunga durata, inquinamento atmosferico, bronchite cronica ostruttiva, gravidanza, contraccettivi orali, terapia estrogenica sostitutiva.<br>
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Embolizzazione<br>
Quando un trombo venoso si stacca dalla parete della vena dove si è formato, forma un embolo che è destinato a percorrere la circolazione venosa e pertanto raggiunge la vena cava, l'atrio di destra, e il ventricolo di destra. Da qui passa nel circolo polmonare arterioso, causando quindi la " Embolia Polmonare " acuta. Tali trombi talvolta attraverso un forame ovale pervio a livello atriale o un difetto del setto inter atriale possono embolizzare nel letto vascolare arterioso.<br>
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Diagnosi Clinica<br>
La diagnosi clinica della Trombosi Venosa Profonda è caratterizzata dal principale sintomo rappresentato dai “ crampi “ o da “ dolore acuto al calcagno “ che persiste e si intensifica nel corso di alcuni giorni. Sono stati sviluppati degli “ score “ di stima della probabilita’ clinica di Trombosi Venosa Profonda e di Edema Polmonare che tengono conto sia della sintomatologia accusata dal paziente che dei fattori di rischio presentati dallo stesso.<br>
Tra questi score quello di Wells’ è forse quello piu’ utilizzato e piu’ validato clinicamente e permette di categorizzare i pazienti sospetti di TVP in tre gruppi:<br>
con Wells 1 : probabilita’ basa di TVP<br>
con Wells tra 1 e 2: probabilità media di TVP<br>
con Wells 3 : probabilita’ elevata di TVP<br>
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Diagnosi precoce con Score di Wells<br>
cancro in fase attiva 1<br>
Paralisi e/o paresi o immobilizzazione prolungata 1<br>
Piccola chirurgia > 3 giorni 1<br>
Grossa chirurgia < 4 settimane 1<br>
Localizzata dolorabilità del sistema venoso profondo 1<br>
Gonfiore di tutta la gamba 1<br>
Gonfiore del calcagno > 3 cm 1<br>
Pitting edema 1<br>
Vene superficiali collaterali 1<br>
Storia di trombosi venosa 1<br>
Età 1<br>
Sesso femminile 1<br>
Diagnosi alternativa - 2<br>
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Punteggio di Wells per TVP : punteggio > 3 probabilità alta<br>
punteggio 1-2 probabilità media<br>
punteggio 0 probabilità bassa<br>
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Il passo successivo è il dosaggio del D-dimero del fibrinogeno nel plasma e l’ecografia a compressione (CUS). Tralasciando per ora i problemi connessi con l’interpretazione corretta dei valori ottenuti dal dosaggio il cui valori di cutoff non sono ancore per nulla chiari essendo fortemente influenzati dal sesso e dall’età del paziente, si puo’ affermare a grandi linee che per i pazienti individuati come moderata di TVP il passaggio successivo dovrebbe essere il dosaggio di un marker affidabile dell’avveduta trombosi venosa ( per ora i prodotti di degradazione del d-dimero ), mentre i pazienti individuati a probabilità elevata di TVP possono ovviare al dosaggio del D-dimero e devono essere sottoposti a ecodopler degli arti inferiori semplificato come test di compressione in due punti significativi : alla femorale superficiale inguinale ed a livello della vena poplitea ( CUS test ).<br>
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Abbiamo già accennato alla scarsa attendibilità del dosaggio del D-dimero per la diagnosi di TVP. Attualmente il dosaggio è gravato da una elevata sensibilità e da una scarsa specificità, per cui da un gran numero di falsi positivi.<br>
Abbiamo dei cult-off che variano con l’età ed il sesso essendo piu’ elevato con l’aumentare dell’eta’ e nel sesso femminile.<br>
I falsi positivi del D-dimero sono in effetti un problema di laboratorio importante. Molte patologie risultano positive al dosaggio del D dimero, anche la stessa gravidanza, tuttavia nel dubbio di una TVP, un valore di D dimero non disabile e pertanto negativo esclude la presenza della trombosi venosa stessa.<br>
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Valutazione clinica del rischio trombotico<br>
Tramite sistemi computerizzati di valutazione del rischio trombotico i pazienti sono assegnati a profilassi anti trombotica.<br>
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La valutazione del rischio viene stratificata su tre categorie:<br>
rischio basso < 5%<br>
rischio medio 5 -10 %<br>
rischio elevato > 10 %<br>
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Fattori di rischio trombotico maggiori:<br>
cancro<br>
pregressa tromboembolia venosa<br>
ipercoagulabilità : fattore V di Leiden, anticorpi antifosfolipidi lupici e anticardiolipina<br>
Fattori di rischio trombotico medi:<br>
interventi chirurgici<br>
Fattori di rischio trombotico minori:<br>
età avanzata<br>
obesità<br>
allettamento<br>
utilizzo di terapia ormonale sostitutiva o anticoncezionale.<br>
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Terapia medica<br>
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La terapia anticoagulante è indicata nel trattamento del pazienti con trombo embolia venosa (VTE) per ridurre la probabilità di ricaduta di trombosi venosa profonda (TVP) come pure di embolia polmonare (EP).<br>
Più di una generazione di medici hanno avuto a che fare con il trattamento della TVP acuta che utilizzava la terapia anticoagulante per un breve periodo di tempo, usualmente 3.5 giorni ( bridging therapy ) con eparina per via parenterale a basso peso molecolare che veniva sovrapposta al vero e proprio trattamento con antagonisti della K come la warfrina.<br>
Visto la rapida espansione delle conoscenze sulla eziopatogenesi ed il trattamento della tromboembolia venosa, risulta importante ed essenziale considerare attentamente come trasportare i nuovi dati scientifici nella pratica clinica.<br>
Gli anticoagulanti (NAO) diretti hanno diversi vantaggi farmacologici nei confronti degli antagonisti della vitamina K, tra i quali una più ampia finestra terapeutica, un inizio di azione rapido, e una emivita più breve che è compresa tra le 7 e le 14 ore in individui sani. Gli anticoagulanti orali diretti sono somministrati a dosi fisse agli adulti senza necessità di monitoraggio con esami di laboratorio; pertanto sono più convenienti della warfrina che richiede il monitoraggio dell' International Normalized Ratio e periodici aggiustamenti del dosaggio. In studi randomizzati con un buon monitoraggio del dosaggio della warfrina, gli anticoagulanti diretti si sono dimostrati non inferiori alla warfrina nel ridurre le recidive di eventi trombotici e addirittura hanno ridotto del 28 % gli episodi di sánguinamento maggiore e del 50% le emorragie intra craniche e fatali.<br>
Diversi studi clinici hanno esaminato l’efficacia dei nuovi anticoagulanti orali, che agiscono inibendo la trombina o il fattore Xa della cascata della coagulazione.<br>
Purtroppo il sistema nazionale italiano richiede che la prescrizione di tali farmaci per il trattamento della TVP venga effettuata solo dopo valutazione internistica specialistica o di chirurgo vascolare e previa redazione di Piano Terapeutico della validità di 6 mesi al massimo. Non così avviene per il trattamento post chirurgico in seguito a protesi d'anca o del ginocchio dove non è necessario piano terapeutico.<br>
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Nello studio RE_COVER i ricercatori nel 2009 hanno valutato la non-inferiorità di un inibitore diretto della trombina, chiamato DABIGATRAN, sulla WARFARINA studiando 1274 pazienti affetti da trombosi venosa profonda o embolia polmonare. I pazienti erano inizialmente trattati per almeno 5 giorni con anticoagulanti per via parenterale ( eparina frazionata ) e susseguentemente ricevevano o DABIGATRAN o WARFARIN.<br>
Non erano presenti differenze significative tra i due gruppi negli obbiettivi primari composti dello studio che consideravano l’incidenza del ricorso di eventi di trombo embolia venosa sintomatica o decessi causati dalla trombo embolia dopo 6 mesi di terapia.<br>
Non c’erano differenze significative negli episodi di sanguinante maggiorata i gruppi, sebbene l’incidenza di sanguinolento maggiore o di sanguinamento minore clinicamente rilevante era ridotto nei pazienti trattati con DABIGATRAN,<br>
DABIGATRAN, un inibitori diretto del trombina, è stato approvato per l’uso negli Stati Uniti nel 2010 per la prevenzione dello stroke nei pazienti con fibrillazione atriale; tale procedimento è stato rapidamente seguito dall’approvazione degli inibitori diretti del fattore Xa della coagulazione come il RIVAROXABAN, l’APIXABAN e l’ENDOXABAN nel giro di 5 anni.<br>
Nello studio EINSTEIN-DVT, sono state paragonate l’efficacia clinica e la sicurezza del RIVAROXABAN, un inibitori orale del fattore Xi della coagulazione, con gli antagonisti della vitamina K in 3.449 pazienti da tromboembolia venosa profonda acuta sintomatica. I pazienti venivano divisi in due gruppi scelti a random, un gruppo trattato con dosi fisse di RIVAROXABAN, e un gruppo trattato con antagonisti della Vitamina K preceduta da una “ bridging therapy “ di 3 -4 giorni con eparina frazionata a basso peso molecolare.<br>
Il Rivaroxaban non è risultato inferiore agli antagonisti della vitamin K per prevenire la tromboembolia venosa. Nessuna differenza significativa è stata osservata negli eventi primari di sanguinamento maggiore or minore clinicamente rilevanti.<br>
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Nel complesso tali evidenze scientifiche indicano che tali nuovo anticoagulanti orali sono efficaci e sicuri come la WARFARINA o antagonisti della vitamina K similari. Inoltre tali farmaci hanno dimostrato un profilo di sicurezza farmacologica simile se non addirittura superiore, e pertanto possono essere considerati una sicura alternativa alla WARFRINA nel trattamento della tromboembolia venosa acuta.<br>
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La spinta per lo sviluppo di tali farmaci proviene dal massiccio uso che si è fatto in questi anni di farmaci anticoagulanti disponibili anche per il trattamento ambulatoriale, vale a dire delle eparina frazionate sottocutanee e degli antagonisti orali della vitamina K. sebbene tali farmaci rappresentino un importante sviluppo della terapia anticoagulante, dubbi sul loro effettivo utilizzo in terapia provenivano dall’assenza, fino a poco tempo fa di antagonisti o antidoti che potessero contrastarne l’azione in caso di sovradosaggio.<br>
Sebbene l'attività della warfrina sia prontamente bloccata dagli analoghi della Vitamina K, dal plasma fresco, da concentrati del complesso protrombinico, gli eventi emorragici maggiori che avvengono in pazienti trattati con warfrina spesso portano a morte. Circa il 10% dei pazienti ospedalizzati per emorragia dovuta all'uso di warfrina muoiono in 3 mesi, e la mortalitá tra i pazienti con emorragia intra cranica di può considerare pari al 50%. L'alta mortalità è in parte attribuitile alle condizioni coesistenti in tali pazienti. Dati sperimentali suggeriscono che agenti non specifici come concentrati di complessi protrombinici o il fattore VIIa ricombinante possono ridurre l'effetto anticoagulante degli anticoagulanti diretti in vitro, in modelli animali e in volontari umani. D'altra parte tali sostanze sono di non provata efficacia nel migliorare l'emostasi in pazienti con emorragia grave e trattati con anticoagulanti diretti possono comportare un aumento del rischio di trombosi.<br>
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La necessità di antidoti d’altra parte era stata prontamente avvertita. Due candidati come farmaci antidoti , ADNEXANET ALFA e CIRAPARATANG sono in svariato stadio di sviluppo, e nell’Ottobre del 2015 , IDARUCIZUMAB, un anticorpo monoclinale umanizzato grado di riconoscere come antigene legare il DABIGATRAN, è stato prontamente approvato dall’FDA per l’utilizzo negli USA.<br>
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l’ANDEXANET alfa rappresenta un eccitante nuovo approccio all’inibizione dei farmaci anticoagulanti, La tecnologia ricombinante genetica è stata utilizzata per creare una molecolare simile al fattore Xa modificata con una mutazione nel sito catalitico in grado di abolire l’attività procoagulante del fattore Xa ma mantiene la struttura nativa. Ciò permette agli inibitori del fattore Xadi legarsi con con grande affinità ed effettivamente neutralizzare la loro attività anticoagulante.Le dimensioni della molecola sono inoltre state sviluppate in modo da prevenire l’interazione con altri fattori della coagulazione.<br>
Tale molecola è pertanto in grado di legarsi sia direttamente agli inibitori del fattore Xa, come il RIVAROXABAN, APIXABAN, EDOXABAN sia agli inibitori del fattore Xa che agiscono tramite l’antitrombina vale dire al FUNDAPARINUX ed alle EPARINA DI BASSO PESO MOLECOLARE.<br>
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Nel 2000 al 2010 trials clinici hanno dimostrato ed evidenziato le linee guida per il trattamento delle malattie vascolari periferiche arteriosclerotiche e della trombosi venosa.<br>
La prossima decade dal 2010 al 2020 ci aspetta con nuove scoperte nel trattamento volto a ridurre il rischio di nuovi eventi arteriosclerotici, di inibire la crescita degli aneurismi aortici, migliorare i sintomi delle malattie arteriose periferiche, e migliorare la prognosi dei pazienti affetti da trombosi venosa ed embolia polmonare.<br>
Possibili vie da investigare sono in particolare l’interazione delle microparticelle contenti il fattore tessutale rilasciato dai macrofagi o dalle cellule tumorali e le piastrine. In particolare si potrebbe ipotizzare l’inibizione del legame tra la selectina P e il recettore PSGL-1 nel tentativo di bloccare l’accumulo delle microparticelle derivati dai monoliti nello sviluppo del trombo. Altro punto debole potrebbe essere il blocco del fattore XI. Tale razionale terapeutico sarebbe in particolare utile nel caso di integrità dell’endotelio e nelle forme di trombosi legate al cancro.<br>
La terapia ideale per la trombosi venosa profonda dovrebbe essere in grado di inibire il processo di formazione del trombo senza alterare l’emostasi<br>
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Bibliografia<br>
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Furie B, Furie BC. Mechanisms of thrombus formation N Engl J Med 2008;359:938-49.<br>
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Schulman S, Hedin AS, Lindmarker P et al. A comparison of six weeks with six months of oral anticoagulant therapy after a first episode of venous thromboembolism. N Engl J Med 1995;332:1661-5.<br>
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Agnelli G, Prandoni P, Santamaria MG et al. Three months versus one year of oral anticoagulant therapy for idiopathic venous thromboembolism. N Engl J Med 2001;345:165-9.<br>
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Keaton C, Gent M, Hirsh J et al. A comparison of three months of anticoagulation with extended anticoagulation for a first episode of idiopathic venous thromboembolism. N Engl J Med 1999;340:901-7.<br>
Schulman S, Kearin C, Kakkar AK et al. Dabigatran versus warfarin in the treatment of acute venous thromboembolism. RE-COVER study. N Engl J Med 2009;361:2342.52.<br>
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Agnelli G, Buller HR, Cohen A et al. Apixaban for extended treatment of venous thromboembolism. N Engl J Med 2013;368:699-708.<br>
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Schulman S, Keaton C, Kakkar AK et al. Extended use of Dabigatran, Warfarin, or Placebo in Venous Thromboembolism. N Engl J Med 2013;368:709-18.<br>
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<br><br><div class="separator" style="clear: both;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjBtX34yrQSzjes6XJd3iLZQcHj_Ncf6o3FfvGYEriw7hVhPMi5CN4C_OjcDR6iSfyZybEYAUYlNjiMe4El5hbLLI4vObsZW6ysW4Y1N5M0C5RA9wO9o_NxThWq-vc3EA3ElTSgt9CrXPct/s640/blogger-image-187881605.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjBtX34yrQSzjes6XJd3iLZQcHj_Ncf6o3FfvGYEriw7hVhPMi5CN4C_OjcDR6iSfyZybEYAUYlNjiMe4El5hbLLI4vObsZW6ysW4Y1N5M0C5RA9wO9o_NxThWq-vc3EA3ElTSgt9CrXPct/s640/blogger-image-187881605.jpg"></a></div>BoNewshttp://www.blogger.com/profile/14996032718916828654noreply@blogger.comtag:blogger.com,1999:blog-6459801161644965909.post-28993812301309140172012-03-27T21:20:00.000+02:002016-04-25T20:28:27.655+02:00Understanding mineralization process: the role of TNSALP and Matrix
Vescicles.<p align="center"><font size="6" face="Verdana"></font></p> <p align="center"><font size="6" face="Verdana"></font></p> <p align="center"><font size="6" face="Verdana"></font></p> <p align="center"></p><div class="separator" style="clear: both;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhWIY3czaogBlHZLzMwW3Dec0GoPLBhWJcwmk1sO0MLMpnA3qfpNQF-X5YuypO6_ZfUBmt4AtqJ6h2s20xQctT-mvSQ23vu7tv8thzXFPz3fKcR6GzNBdWQlwjh1W5PAwyBzB592oExl0me/s640/blogger-image-1819659079.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhWIY3czaogBlHZLzMwW3Dec0GoPLBhWJcwmk1sO0MLMpnA3qfpNQF-X5YuypO6_ZfUBmt4AtqJ6h2s20xQctT-mvSQ23vu7tv8thzXFPz3fKcR6GzNBdWQlwjh1W5PAwyBzB592oExl0me/s640/blogger-image-1819659079.jpg"></a></div><font size="6"> </font><p></p> <p align="center"><font size="6" face="Verdana"></font></p> <p align="center"><font size="6" face="Verdana"></font></p> <p align="center"><font size="6" face="Verdana">Alkaline phosphatases</font></p> <p align="center"><font size="6" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Alkaline phosphatase (ALP) was discovered in 1923 by Robert Robinson in young rats and rabbits within ossifying bone and cartilage. However , never Robinson referred to this enzyme as “alkaline” phosphatase, term introduced only later. For most of the past eight decades physicians have recognized the important clinical insight that can come from measurement of ALP activity in serum. Detection and monitoring of hepatobiliary and skeletal disease are generally possible. In fact, since 1930 ALP detection and quantification in serum has been routine in hospital laboratories.</font></p> <p align="justify"><font size="3" face="Verdana">Nevertheless, the physiologiocal function of ALP, is largely unknown.</font></p> <p align="justify"><font size="3" face="Verdana">At the end of 1960s, electron microscopy helped to rejuvenate Robinson’s hypothesis, when the earliest site of hydroxyapatite crystal deposition in the developing skeleton was noted by<strong> E. Bonucci</strong> and <strong>HC Anderson</strong> to be within novel extracellular structures called matrix vescicles (1969). These vescicles were found to be rich in ALP activity and later they have been demonstrated to be replenished by many enzymes and constituents such as: </font></p> <ol> <li> <div align="justify"><font size="3" face="Verdana">Inorganic pyrophosphatase (PPi-ase)</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">ATPase</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">phospholipids</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">polysaccarides</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">glycolipids</font></div> </li> </ol> <p align="justify"><font size="3" face="Verdana">During early phase (primary) of mineralization , hydroxyapatite crystals appear and grow within these structres. Soon after , the vescicles rupture and extravescicular (secondary) mineralization occurs as crystal propagation continues.</font></p> <p align="justify"><font size="3" face="Verdana">Actually the proposed biological roles of ALP in mammals are numerous including:</font></p> <p align="justify"><font size="3" face="Verdana">- hydrolysis of phosphate esters to supply the nonphosphate moiety</font></p> <p align="justify"><font size="3" face="Verdana">- transferase action for the synthesis of phosphate ester</font></p> <p align="justify"><font size="3" face="Verdana">- regulation of Pi metabolism</font></p> <p align="justify"><font size="3" face="Verdana">- maintenance of steady-state levels of phosphoryl metabolites</font></p> <p align="justify"><font size="3" face="Verdana">- action on phoshoprotein pshosphatases</font></p> <p align="justify"><font size="3" face="Verdana">-</font></p> <p align="justify"><font size="3" face="Verdana">At plasmamembrane level it has been proposed that ALP can function not only such as an active P transporter but also for:</font></p> <p align="justify"><font size="3" face="Verdana">- calcium muvement regulator</font></p> <p align="justify"><font size="3" face="Verdana">- Na+/K+ exchange regulator</font></p> <p align="justify"><font size="3" face="Verdana">- Fat exchange</font></p> <p align="justify"><font size="3" face="Verdana">- Protein exchange</font></p> <p align="justify"><font size="3" face="Verdana">- Carbohydrate exchange</font></p> <p align="justify"><font size="3" face="Verdana">Interestingly sequence analysis of ALP demonstrated that this enzyme can be coupled with other proteins, for example adhering to collagen, and it has been suggested that this physical property of ALP should be considered when we examined the action for example of ALP on skeletal matrix such as phosphoprotein phosphatase.</font></p> <p align="justify"><font size="3" face="Verdana">It has to be outlined that ALP function mainly such as a cell surface enzyme, but at some stages during embryo formation ALP may acts also intracellularly.</font></p> <p align="justify"><font size="3" face="Verdana">The role of ALP in skeletal mineralization should be resumed considering ALP as “inhibitor” of pyrophosphate deposition (a potent inhibitor of hydroxyapatite formation):</font></p> <ol> <li> <div align="justify"><font size="3" face="Verdana">Locally increase P concentration</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">Destruction of inhibitors of hydroxyapatite crystal growth</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">Transport of P</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">Calcium binding protein ( used by cells such as uptake enzyme for calcium)</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">Ca++/Mg++ ATPase</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">Tyrosine specific phosphoprotein phosphatase</font></div> </li> </ol> <p align="justify"><font size="3" face="Verdana">Recently these different activities previously attribute only to Alkaline Phosphatase activity, have been studies in more details.</font></p> <p align="justify"><font size="3" face="Verdana">It is interesting to note that in normal adolescents 13 to 14 years old pyridoxal-5-phosphate concentrations have been reported to be approximately 40 nmol/L, also if this developmental stage is associated with high alkaline phosphatase activity. </font><font size="3" face="Verdana">Low levels of Pyridoxal-5-phosphate are also observed in patients with hypophosphatemic rickets and the researchers attributed this data to increased activity of alkaline phosphatase enzymes. However most of alkaline phosphatase values are within the normal range for children. </font><font size="3" face="Verdana">It has also been suggested the presence of so called “functional hypophosphatasia” in patients affected by renal osteodystrophy were normal alkaline phosphatase levels are coupled with high serum inorganic phosphate levels. </font><font size="3" face="Verdana">In other words in these pathophysiological conditions no correlation exists between alkaline phosphatase activity and pyridoxal-5-phosphate concentrations. </font><font size="3" face="Verdana">However in these conditions plasma levels of inorganic phosphate are also higher than normal suggesting that the main factor in decreased pyridoxal 5 phosphate concentration would be low phosphate concentration rather than high levels of alkaline phosphatase.</font></p> <p align="justify"><font size="3" face="Verdana">An emerging role in Pyrophosphate production has been recently attributed to Ectonucleotide Pyrophosphatase/phosphodiesterase 1 (NPP1), previously referred such as plasma cell membrane glycoprotein 1. This enzyme has been found in mineralizing tissues such as bones and teeth. </font><font size="3" face="Verdana">Mutations in NPP1 cause the generalized arterial calcification of infancy due to inability of vascular cells to form pyrophosphate. </font><font size="3" face="Verdana">Moreover, mutations in NPP1 have also been reported as a second cause of autosomal recessive Hypophosphatemic Rickets, the first being attributed to mutations in Dentin Matrix Protein 1 (DMP1). </font><font size="3" face="Verdana">The role of NPP1 would be the hydrolyis from Adenosine Triphosphate (ATP) of Pyrosphosphate. </font><font size="3" face="Verdana">NPP1 clearly has a role in PPi generation at the level of chondrocyte and osteoblast membranes, whereas at level of Matrix Vecicles NPP1 does not use ATP efficiently.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Another pathway for generation of pyrophosphate production is the secretion from cells by the transmembrane spanning cell surface protein Ankylosis Human homologue of the mouse progressive ankylosis protein (ANKH). </font><font size="3" face="Verdana">Two autosomal dominant human diseases have to date been reported:</font></p> <p align="justify"><font size="3" face="Verdana">- Craniometaphyseal Dysplasia </font></p> <p align="justify"><font size="3" face="Verdana">- Chondrocalcinosis-2</font></p> <p align="justify"><font size="3" face="Verdana">Data conerning the possible presence of an autosomal recessive form linked to a mutation on exon 6 of the 12 exons constituting ANKH gene has to be clarified by further studies. </font><font size="3" face="Verdana">Anyway ANKH protein seems to be important for mediating intracellular to extracellular channeling of pyrophosphate.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Interestingly another protein called Phosphatase PHOSPHO-1, first identified in chick as a member of the haloacid dehalogenase (HAD) superfamily of Magnesium dependent hydrolases, is expresed at levels 100-fold higher in mineralizing tissues compared to nonmineralizing ones. </font><font size="3" face="Verdana">PHOSPHO-1 shows high phosphohydrolase activity toward Phosphoetanolamine (PEA) and Phosphocholine (PCho); it is active inside chondrocytes and osteoblast derived Matrix Vescicles. </font><font size="3" face="Verdana">The role of PHOSPHO-1 is to maintain the concentration of inorganic Pyrophosphate (PP i) so that the ratio of inorganic phosphate to inorganic pyrophosphate would be permissive of a normal mineralization process. </font><font size="3" face="Verdana">Inside Matrix Vescicles (MV) soluble phosphatase PHOSPHO-1 , with specificty for phosphoethanolamine and phosphocholine, increases the local intravescicular concentration of inorganic phosphate (P i) to change the Pi/PPi ratio in favor of precipitation of hydroxyapatite seed crystals.</font></p> <p align="justify"><font size="3" face="Verdana">In summary given the role of FGF23/Klotho pathway in inorganic phosphorus metabolism, as well’s of Vitamin D3 metabolites, more important role should be attributed to inorganic phosphate concentration that to enzymatic phosphatase activity for study derangements in bone mineralization.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">ALP is found in nearly all plants and animals. In humans, four ALP isoenzymes are encoded by four separate genes. Three of these are expressed in a tissue-specific manner are they are called:</font></p> <p align="justify"><font size="3" face="Verdana">- placental</font></p> <p align="justify"><font size="3" face="Verdana">- intestinal</font></p> <p align="justify"><font size="3" face="Verdana">- germ-cell (placental-like)</font></p> <p align="justify"><font size="3" face="Verdana">- Tissue Non Specific</font></p> <p align="justify"><font size="3" face="Verdana">The fourth ALP isoenzyme is ubiquitous, but expecially abundant in hepatic, skeletal and renal tissues (liver/Bone/kiney ALP) and it is called tissue non specific ALP (TNSALP). </font><font size="3" face="Verdana">Interestingly TNSALP is a family of “secondary” isoenzymes (isoforms), with the same polypeptide sequence, encoded by one gene (TNSALP) but different each other only by posttranslational modification involving a different glycosylation pattern (carbohydrate). </font><font size="3" face="Verdana">TNSALP is located on <b>chromosome 1p36.1-34</b> near the end of shot arm; the genes coding for placental, intestinal and germ-cells ALP are found near the tip of the long arm of <b>chromosome 2q34-37</b>. </font><font size="3" face="Verdana">The TNSALP chromosome structure is represented by 12 exons, 11 of which are translated into a 507 aminoacid nascent enzyme. The promoter region of TNSALP is located within 610 nucleotides 5’ to the transcription start site and it contains TATA box and an Sp1 binding site acting as regulatory elements. </font><font size="3" face="Verdana">It is believed that basal levels of TNSALP expression reflect inherent “housekeeping” promoter effects, whereas differential expression in various tissues should be mediated by a postranslational mechanism. Interestingly 5’ untranslated region differ between the bone and liver TSNALP isoforms. </font><font size="3" face="Verdana">From phylogenetic point of view, the TNSALP should represent an ancestral gene, whereas the tissue-specific ALPs is likely originated from a series of gene duplications. </font><font size="3" face="Verdana">Human ALP isoenzymes gene sequence indicates that the nascent polypeptide has a short signal sequence of 17 or 21 aminoacids residues and a hydrophobic domain at its c terminal site. </font><font size="3" face="Verdana">The active site is coded by six exons and it is composed by 15 aminoacid residues with a nucleotidic sequence well conserved throught nature. </font><font size="3" face="Verdana">ALPs is a metalloenzyme linking Zinc atom, the link of Zn++ atom stabilizes the tertiary structure. </font><font size="3" face="Verdana">In summary the structure of these enzymes is formed to link a dinuclear metal cofactor structure so that a common cathalytic mechanism for enzymes involved in phosphotransfer reactions has been identified involving spin-coupled metal binding site formed by a scaffold structure at active metal linking site constituted by the same repeated tertiary spatial construct.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="center"><font size="3" face="Verdana">Β sheet – α helix - Β sheet - α helix - Β sheet</font></p> <p align="center"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">The 3 β strands of this structure form a parallel sheet that is capped by intervening α helices. Two metal ions are positioned at the apex of this fold forming a dinuclear metal center with 3.0 - 4.0 Ǻ between metal ions, with 4 of the metal ligands provided by residues in the loops between β sheets and α helices. </font><font size="3" face="Verdana">ALP in E. Coli has been extensively studied and a Mg++ with a Zn-Zn dinuclear center reminiscent of the dinuclera metal site of seine/threonine phosphatase has been identified. </font><font size="3" face="Verdana">In E.coli His 372 forms an hydrogen bond with Asp 327 , an aminoacid involved into didentate Zn stabilization) and it is thought to lower the pKa of the Zn atom involved to binding a water molecule. </font><font size="3" face="Verdana">Cathalytic activity require multimeric configuration of identical subunits, each monmer having an active site and two Zn atoms. </font><font size="3" face="Verdana">The role of Zn atoms is probably those of allowing the formation of a nucleophil reactant by hydroxyl group of serine residue located on cathalitic site, that attract the phosphoric group disrupting the esteric link. </font><font size="3" face="Verdana">The mechanism of enzymatic reaction in ALP present in E. Coli has been elucidated for phosphate ester hydrolysis forming first an intermediate phosphoenzyme. In particular ALP of E. Coli cathalizes the transfert of phosphoryl group throught the formation of a transient link with a Serine residue located on active catalitic site. Later this phosphate group is released and the cathalitic site left free to react with anoter phosphoester group. </font><font size="3" face="Verdana">If ALP in serum is present as a dimer with α/β topology with a 10 –stranded beta sheets in its center, ALP at membrane level is linked as a homotetramer. </font><font size="3" face="Verdana">ALP is linked to plasmamembrane surface, through a polar head group of a phosphatidylinositol glycan and it can be released by a specific phospholipase. </font><font size="3" face="Verdana">Intracellualr degradation of ALPs can involve proteasomal structures. </font><font size="3" face="Verdana">Release from plasma membrane could involve phosphatidase C or D. </font></p> <p align="justify"><font size="3" face="Verdana">Clearance of circulating ALP, as for many plasma proteins is assumed to occur via uptake by the liver.</font></p> <p align="justify"><font size="3" face="Verdana">Whereas in children ALP plasma activity is mainly of bone origin and the remaining is of intestinal isotype; interestingly an old data report that blood type (0 and B are secretors) influences the level of placental isoenzyme of ALP in the blood after an ingestion of a fatty meal. </font><font size="3" face="Verdana">In adult blood, ALP activity reflects equal amounts of hepatic and bone isotypes. </font><font size="3" face="Verdana">Interestingly only recently on 2000 the crystal structure of placental isoform of ALP was isolated and studied on X ray crystallography.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">TNSALP has a major role in two kind of reactions involved into mineralization process:</font></p> <p align="justify"><font size="3" face="Verdana">- <strong>Pyrophosphatase</strong> : hydrolizing pyrophosphate into two inorganic phosphate ions</font></p> <p align="justify"><font size="3" face="Verdana">-<strong> ATPase/ADPase</strong>: hydrolizing Adenosin triphosphate into Adenosin bisphosphate and one molecule of inorganic phosphate.</font></p> <p align="justify"><font size="3" face="Verdana">Accordingly TNSALP partecipates in the calcification process both by restricting the concentration of extracellular inorganic pyrophosphate PPi and by contributing to the inorganic phosphate (Pi) pool available for calcification.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="center"><font size="3" face="Verdana">ATP > ADP > AMP + 2 Pi</font></p> <p align="center"><font size="3" face="Verdana">PPi > Pi</font></p> <p align="center"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">The working model in bone and cartilage supposed that bone mineralization is first initiated within the lumen of Matrix Vescicles (MVs). In a second time, hydroxyapatite crystals grow beyond the confines of the MVs and become exposed to the extracellular milieu, where they continue to propagate along collagen fibrils. </font><font size="3" face="Verdana">Hydroxyapatite seed crystals are formed in the sheltered interior of MVs favored by the Pi-generating activity of PHOSPHO-1 fosfatase enzyme,as well’s by the transport function of Pyrophosphate (PPi) transporters, such as ANKH. The keys rate limiting step seems to be the ratio between Pi/PPi concentrations:</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="center"><font size="3" face="Verdana">Pi/PPi > Mineralization</font></p> <p align="center"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">In other words an increased concentration of inorganic pyrophosphate (PPi) inhibits the crystalization process of hydroxyapatite, whereas increase increased concentration of inorganic phosphate ions (Pi) promote both crystalization and nucleation processes. </font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"> </p> <p align="justify"><a href="http://lh4.ggpht.com/-v130r-NMQcs/T3IWf8la0xI/AAAAAAAADP8/cLe_DM2nDBY/s1600-h/clip_image002%25255B3%25255D.jpg"><font size="3" face="Verdana"></font></a><font size="3" face="Verdana"><a href="http://lh4.ggpht.com/-v130r-NMQcs/T3IWf8la0xI/AAAAAAAADQA/VSDtCSfn64w/s1600-h/clip_image002%25255B6%25255D.jpg"><img style="background-image: none; border-bottom: 0px; border-left: 0px; padding-left: 0px; padding-right: 0px; display: block; float: none; margin-left: auto; border-top: 0px; margin-right: auto; border-right: 0px; padding-top: 0px" title="clip_image002" border="0" alt="clip_image002" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg2KhcyyJYzefrCUdbBoNfAc7txcGYstlqvEZ4tcfixXymSuaHwB5a5cbtZr4ngAsLEBvGyKJ-Osb3zL52GPIgZsJpdmEZgiek2sWorZWZvCW6rTvrDG-Oqn0FQhWL6G_7yteQqKUnuOX2A/?imgmax=800" width="672" height="504"></a></font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Human diseases characterized by an abnormal decrease or increase in ALP blood levels are called respectively:</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">- Hypophosphatasias</font></p> <p align="justify"><font size="3" face="Verdana">- Aphosphatasia</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">- Hyperphosphatasias or Paget disease of bone</font></p> <p align="justify"><font size="3" face="Verdana">- Familial Expansile Osteolysis</font></p> <p align="justify"><font size="3" face="Verdana">- Expansile skeletal Hyperphosphatasias</font></p> <p align="justify"><font size="3" face="Verdana">- Early onset Paget’s disease of bone in Japan</font></p> <p align="justify"><font size="3" face="Verdana">- Hereditary Hyperphosphatasia (Juvenile Paget’s disease)</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="center"><font size="6" face="Verdana">Hypophosphatasia</font></p> <p align="center"><font size="6" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">In 1948 a Canadian pediatrician John Campbell Rathbun coined the term hypophosphatasia reporting a boy who developed and died from severe rickets with epilepsy, whose ALP activity in serum, bone and other tissues was paradoxically subnormal. </font></p> <p align="justify"><font size="3" face="Verdana">Present in all races, however this condition is expecially frequent in inbred Mennonite families from Mannitoba, Canada, where about 1 every 25 individuals is a carrier and 1:2500 newborns manifests severe disease.</font></p> <p align="justify"><font size="3" face="Verdana">Six forms of hypophosphatasias have been individuated, the earlier is the presentation of symptoms and more severe is the skeletal disease and the biochemical manifestations:</font></p> <ol> <li> <div align="justify"><font size="3" face="Verdana">Perinatal : autosomal recessive</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">Infantile : autosomal recessive</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">Childhood : autosomal dominant or recessive </font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">adult: autosomal dominant or recessive</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">odontohypophosphatasia: autosomal dominat or recessive</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">pseudohypophosphatasia</font></div> </li> </ol> <p align="justify"><font size="3" face="Verdana">Laboratory findings include elevated values of phosphoethanolamine, pyridoxalphosphate, inorganic pyrophosphate.</font></p> <p align="justify"><font size="3" face="Verdana">Hypophosphatasia is a rare heritable disordercaused by a loss-of-function mutation in the ALP gene encoding for the tissue non specific alkaline phosphatase (TNSALP). </font><font size="3" face="Verdana">It is characterized by deficiency in serum and bone alkaline phosphatse and defective bone and tooth mineralization.</font></p> <p align="justify"><font size="3" face="Verdana">Nearly all babies with perinatal hypophosphatsia die in utero or shortly after birth.</font></p> <p align="justify"><font size="3" face="Verdana">Those with infantile form present before 6 months of age with rickets, failure to thrive, or vitamin B6-dependent seizures, and approximately 50% die for respiratory failure because of poor lung development or progressive hypomineralization of the rib cage. </font></p> <p align="justify"><font size="3" face="Verdana">Adult hypophosphtasia typicaly manifests during middle age as recurrent, slowly healing metatarsal fractures, followed by painful nonhealing proximal femur fractures or pseudofractures.</font></p> <p align="justify"><font size="3" face="Verdana">The bone symptoms are highly variable in their clinical expression, which ranges from stillbirth without mineralized bone to pathological fractures developing only late in adulthood.</font></p> <p align="justify"><font size="3" face="Verdana">Odontohypophosphatasia is characterized by premature exfoliation of primary teeth with roots intact and/or several dental caries, not associated with abnormalities of the skeletal system.</font></p> <p align="justify"><font size="3" face="Verdana">Severe forms of the disease such as perinatal and infantile forms are transmitted as an autosomal recessive trait, whereas both autosomal recessive and autosomal dominant transmission may be found in milder forms, especially odontohypophosphatasia.</font></p> <p align="justify"><font size="3" face="Verdana">The tissue nonspecific ALP (TNSALP) gene is localized on chromosome 1p36.1 and it consits of 12 exons distributed ober 50 Kbases. More than 160 mutations have been described to date in the TNSALP gene. In North American, Japanese, and European patients, indicating a very strong allelic heterogeneity in the disease. This variety of mutations results in highly variable clinical expression and a great number of compound heterozygous genotypes with missense mutations that account for 82% of mutations. The remaining mutations are:</font></p> <p align="justify"><font size="3" face="Verdana">- missense mutations (82%)</font></p> <p align="justify"><font size="3" face="Verdana">- microlesions (11%)</font></p> <p align="justify"><font size="3" face="Verdana">- splicing mutations (4%)</font></p> <p align="justify"><font size="3" face="Verdana">- nonsense mutations (3%)</font></p> <p align="justify"><font size="3" face="Verdana">- a nucleotide substitution on major transcription initiation site</font></p> <p align="justify"><font size="3" face="Verdana">- a denovo mutation on heterozygous carrier of a missense mutation </font></p> <p align="justify"><font size="3" face="Verdana">The affected individuals carry one or two loss-of-function mutations within the TNSALP gene alleles. This experiment of the nature, inherited as either an autosomal dominant or autosomal recessive trait, reveals a crucial role for TNSALP in skeletal mineralization. </font><font size="3" face="Verdana">There is no established medical treatment for hypophosphatasia. Augmenting circulating alkaline phosphatase activity into or even above the normal range for several months using intravenously administered ALP from various tissues sources has had no convincing beneficial effects. Also transplantation therapy with cultured osteoblasts and bone fragments was quite unsuccessful and experiments suggested that we must lower PPi at mineralization sites. Accordingly TNSALP activity must be increased at mineralization sites more than at plasma level.</font></p> <p align="justify"><font size="3" face="Verdana">Recently a recombinant fusion protein including TNSALP ectodomain, the constant region of IgG1 Fc domain, and the terminal deca-aspartate motif has been admnistered in 11 patients with perinatal or infantile forms of hypophosphatasia. Treatment was associated with healing of skeletal manifestations of hypophosphatasia as well’s with improvement in respiratory and motor functions. Improvement is still being observed in patients receiving treatment for more than 3 years.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="center"><font size="4" face="Verdana">References</font></p> <p align="center"><font size="4" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Robinson R. The possible significance of hexosephosphoric esters in ossification. Biochem 1923;17:286-293.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Anderson HC. Vescicles associated with calcification in the matrix of epiphyseal cartilage. J Cell Biol 1969;41:59-72.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">deBernard B, Bianco P, Bonucci E et al. Biochemical and immunohistochemical evidence that in cartilage an alkaline phosphatase is a Ca++ -binding glycoprotein. J Cell Biol 1986;103:1615-23.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Coleman JE. Structure and mechanism of alkaline phosphatase. Ann Rev Biophys Biomol Struct 1992;21:441-83.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Coleman JE, Gettins P. Alkaline phosphatase p, solution structure, and mechanism . Adv Enzymol 1983;55:381-452.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Kim EE, Wyckoff HW. Reaction mechanism of alkaline phosphatase based on crystal structures: two metal ions catalysis. J Mol Biol 1991;218:449-64.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Xu X, Qin XQ, Kantrowitz ER. Probing the role of histidine-372 in zinc binding and the cathalitic mechanism of escherichia coli alkaline phsosphatase by site-specific mutagenesis. Biochemistry 1994;33:2279-84.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Whyte MP. Hypophosphatasia and the role of alkaline phosphatase in skeletal mineralization. Endocr Rev 1994;15:439-61.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Le Due HM, Stigbrand T, Taussig MJ et al. Crystal structure of alkaline phosphatase from human placenta at 1.8 Ǻ resolution. J Biological Chem 2000;275:9158-65.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Levy-Litan V, Hershkovitz E, Avizov L et al. Autosomal recessive hypophosphatemic rickets is associated with an inactivating mutation in the ENPP1 gene. Am J Hum Genet 2010;86:273-8.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Hessle L, Johnson KA, Anderson HC et al. Tissue non specific alkaline phosphatase and plasma cell membrane glycoprotein1 are central antagonistic regulators of bone mineralization. Proc Nat Acad Sci USA 2002;99:9445-9.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Lorenz-Depiereux B, Schnabel D, Tiosano D et al. Loss-of-function ENPP1 mutations cause both generalized arterial calcification of infancy and autosomal recessive hypophosphatemic rickets. Am J Hum Genet 2010;86:267-72.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Collins MT, Boehm M. It ANKH necessarily so. J Clin Endocrinol Metab 2011;96:72-4.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Ciancaglini P, Yadav MC, Simao AMS et al. Kinetic analysis of substrate utilization by native and TNAP, NPP or PHOSPHO1-Deficient matrix vescicles. J Bone Miner Res 2010;25:716-23.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Yadav MC, Simao AMS, Narisawa S et al. Loss of skeletal mineralization by the simultaneous ablation of PHOSPHO1 and Alkaline Phosphatase function: a unified model of the mechanisms of initiation of skeletal calcification. J Bone Miner Res 2011;26:286-97.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Whyte MP, Obrecht SE, Finnegan PM et al. Osteoprotegerin deficiency and Juvenile Paget’s disease. N Engl J Med 2002;347:175-84.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Whyte MP, Hughes AE. Expansile skeletal hyperphosphatasia is caused by a 15 base pair tandem duplication in TNFRSFIIA encoding RANK and is allelic to Familial Expansile Osteolysis. J Bone Min Res 2002;17:26-9.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Taillandier A, Sallinen SL, Brun-Heath P et al. Childhood hypophosphatasia due to a de novo missense mutation in the tissue nonspecific alkaline phosphatase gene. J Clin Endocrinol Metab 2005;90:2436-9.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Cahil RA, Wenkert D, Perlman SA et al. Infantile hypophosphatasia: transplantation therapy trial using bone fragments and cultured osteoblasts. J Clin Endocrinol Metab 2007;92:2923-30.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Schalin-Jantti C, Mornet E, Lamminen A et al. Parathyroid hormone treatment improves pain and fracture healing in adult hypophosphatasia. J Clin Endocrinol Metab 2010;95:5174-9.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Whyte MP, Greenberg CR, Salman NJ et al. Enzyme replacement therapy in life threatening hypophosphatasia. N Engl J Med 2012;366:904-13.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Thanks to <strong>Ivy</strong> for her support.</font></p> <p align="justify"><font size="3" face="Verdana"> </font></p> <p align="justify"><font size="3" face="Verdana"></font></p> BoNewshttp://www.blogger.com/profile/14996032718916828654noreply@blogger.comtag:blogger.com,1999:blog-6459801161644965909.post-29335422213719092052011-08-26T15:57:00.000+02:002016-04-25T20:23:14.762+02:00VITAMIN D: how a vitamin becomes a true hormone.<p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="center"> </p><div class="separator" style="font-family: 'Helvetica Neue Light', HelveticaNeue-Light, helvetica, arial, sans-serif; clear: both;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiTvNGqOuVNwXDYHmiSgzKWkCvbRVI9oeW-4HzvYeZhTeRiZ1CAQVmFs3i7Z5bcYzaUOUh8b9_Khw_4C0TXDPTQPXEgPut9SP1orjz1jfvukHV4n41csayzPwD7B75Zj2OrXmpT7yVpX6dM/s640/blogger-image--436777156.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiTvNGqOuVNwXDYHmiSgzKWkCvbRVI9oeW-4HzvYeZhTeRiZ1CAQVmFs3i7Z5bcYzaUOUh8b9_Khw_4C0TXDPTQPXEgPut9SP1orjz1jfvukHV4n41csayzPwD7B75Zj2OrXmpT7yVpX6dM/s640/blogger-image--436777156.jpg"></a></div><font face="Helvetica Neue Light, HelveticaNeue-Light, helvetica, arial, sans-serif"> </font><p></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana">Calcium intake is well know to represent a very important factor affecting bone mass, bone biomechanical alteration and consequntly bone fracture incidence. </font><font size="3" face="Verdana">Low calcium intake in particular with consequent decrease in intestinal calcium absorption is the gatekeeper in bone disease induction. </font><font size="3" face="Verdana">It has been demonstrated from basic studies on osteoporotic patients that low intestinal calcium absorption is striclty related to loss or decrease activity of steroid hormonal compounds such as estrogens and activated form of Vitamin D3 (1,25 dihydrixyVitamin D3) at epithelial intestinal level. </font><font size="3" face="Verdana">With aging in particular there is a decline in calcium absorption efficiency, related to intestinal loss of Vitamin D3 receptors or resistance/lower actictivity of these receptors to the action of 1,25 dihydroxyVitamin D3. </font><font size="3" face="Verdana">Also seasonal variations in sunlight exposure profundly affect the level of Vitamin D3 synthetized in our skin by irradiation with ultraviolet wave length of our skin tissue. </font><font size="3" face="Verdana">Pre Vitamin D2 and Pre Vitamin D3 better called ergocalciferol and colecalciferol, introduced with the diet respectively from vegetable and from animals foods, are efectively transformed on skin tissue in true Vitamin D2 and Vitamin D3 by automaintained non enzymatic reaction due only to exposure of our skin tissue to sunlight ultraviolet irradiation.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="center"><font size="3" face="Verdana"><strong>CYP27A1 hydroxylase</strong></font></p> <p align="justify"><font size="3" face="Verdana">After sunlight activation Vitamin D3 is transported into our body linked to protein carriers on the first time to the liver, where it is hydroxylated by a cytocrome P450 dependent enzyme called 25 hydroxylase CYP27A1. </font><font size="3" face="Verdana">At this level a first selection is performed by hydroxylating electively the choleclaciferol derivatives (i.e. Vitamin D3) more than ergocalciferol derivatives (i.e. Vitamin D2). From this first evidence is not effective the therapeutical administration of vegetable form of vitamin D, leading on the contrary to adecrease in levels of active hydroxylated forms of Vitamin D3. </font><font size="3" face="Verdana">Measurement of plasma levels of 25-hydroxy Vitamin D3 is universally considered the main index of individual body reserve of Vitamin D3. </font><font size="3" face="Verdana">However, many controversies exist, and recently published Guidelines outlined this topic, about optimal plasmatic levels achievable in human in order to prevent Vitamin D3 deficiency. </font><font size="3" face="Verdana">Accordingly, a seasonal fluctuation in hormonal vitamin D3 are present in humans related to sunlight exposure with greater levels reached during spring and summer seasons, and lower levels during fall and winter seasons. </font><font size="3" face="Verdana">Again, interindividual variations between individuals are present according to proportion of time spent in indoor and outdoor activities. </font><font size="3" face="Verdana">Moreover, also variations according to latitute degree of countries where people live are present if we consider that sunlight irradiation is most importantat near tropical area of the world compared to northern countries.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="center"><font size="3" face="Verdana"><strong>CYP27B1 hydroxylase</strong></font></p> <p align="justify"><font size="3" face="Verdana">After liver activation 25 hydroxyVitamin D3 is transported to the kidney proxymal convoluted tubules in order to be fully activated by 1-alfa hydroxylase enzyme cytocrome P450 CYP27B1. </font><font size="3" face="Verdana">This hydroxylative enzyme has been profoundly studied thanks to the more evident regulation by hormonal axis devoted to calcium-phosphate homeostasis. However, as we can see later, 1 alfa hydroxylase activity is not so relevant to know the individual needs of Vitamin D3 supplementation with fortified foods. </font><font size="3" face="Verdana">On the contrary, it is important for the synthesis of active hormonal Vitamin D3 hydroxylated in 25 and 1 alfa carbons allowing a global interaction with zinc fingher sites of intranuclear Vitamin D receptors present in target tissues. </font><font size="3" face="Verdana">In particular , it has been largely demonstrated both in vitro and in vivo that 1 alfa hydroxylase is sensitive to stimulating action of parathyroid hormone, estrogens and probably androgenic steroids hormones, Growth Hormone/Insulin growth factor 1. </font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="center"><font size="3" face="Verdana"><strong>CYP24A1 hydroxylase</strong></font></p> <p align="justify"><font size="3" face="Verdana">Responsible for catabolism of Vitamin D3 into liver secreted “ calcitroic acid “ 24 hydroxylase enzyme CYP24A1 has been only recently subjected to an accurated studies. In particular the genetic demonstrations of genetic polymorphisms leading to inactive mutated forms of CYP24A1 hydroxylase has been recently confirmed also in clinical background as responsible of Vitamin D3 toxicity. In particular the Idiopathic Infantile Hypercalcemia ( milder form ) also called Lightwood type (OMIM 143880) has been demonstrated in 3 affected patients linked to mutations in CYP24A1 gene expression. </font><font size="3" face="Verdana">It is possible that clinically noted interindividual variations in Vitamin D3 need by fortified foods in humans could be due to inactivating mutations in CYP24A1 gene. </font><font size="3" face="Verdana">Interestingly a new hormonal axis has been invoved into regulation of CYP24A1 expression: called FGF23/KLOTHO axis. </font><font size="3" face="Verdana">Klotho is a protein with glycosidase activity able to modify the FGF Receptor present at kidney level for FGF23. FGF23 as bee demonstrated to be a potent stimulator of CYP24A1 and a potent inhibitor of CYP27B1 suggesting in this way a more complex picture compared to the past, involving two homeostatic system for phospho-calcium metabolism:</font></p> <p align="justify"><font size="3" face="Verdana"> PTH/ Vitamin D3 axis: CYP27B1</font></p> <p align="justify"><font size="3" face="Verdana"> FGF23/ KLOTHO axis: CYP27B1 and CYP24A1</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="center"><font size="3" face="Verdana"><strong>References</strong></font></p> <p align="justify"><font size="3" face="Verdana">Koro-o M, Matsumura Y, Aizawa H et al. Mutation of the mouse klotho gene leads to a syndrome resembling ageing. Nature 1997;390:45-51.</font></p> <p align="justify"><font size="3" face="Verdana">Urakawa I, Yamazaki Y, Shimada T et al. Klotho converts canonial FGF receptor into a specific receptor for FGF23. Nature 2006;444:770-4.</font></p> <p align="justify"><font size="3" face="Verdana">Makishima M, Lu TT, Xie W et al. Vitamin D erceptor as an intestinal bile acid sensor. Science 2002;296:1313-6.</font></p> <p align="justify"><font size="3" face="Verdana">Kurosu H, Yamamoto M, Clark JD et al. Suppression of aging in mice by the hormone Klotho. Science 2005;309:1829-33.</font></p> <p align="justify"><font size="3" face="Verdana">Chang Q, Hoefs S, van der Kemp AW et al. The beta glucosidase Klotho hydrolyzes and activates the TRPV5 Channel. Science 2005;310:490-3.</font></p> <p align="justify"><font size="3" face="Verdana">Imura A, Tsuji Y, Murata M et al. Alfa Klotho as a regulator of calcium homeostasis. Science 2007;316:1615-6.</font></p> <p align="justify"><font size="3" face="Verdana">Cai Q, Hodgsan SF, Kao PC et al. Inhibition of renal phosphate transport by a tumor product in a patients with a oncogenic osteomalacia. N Engl J Med 1994;330:1645-9.</font></p> <p align="justify"><font size="3" face="Verdana">Econs MJ, Drezner MK. Tumor induced osteomalacia – unveiling a new homone. N Engl J Med 1994;330:1679-81.</font></p> <p align="justify"><font size="3" face="Verdana">Kronenberg HM. NPT2a – The key to phosphate homeostasis. N Engl J Med 2002;347:1022-4.</font></p> <p align="justify"><font size="3" face="Verdana">Priè D, Huart V, Bakouh N et al. Nephrolithiasis and osteoporosis associated with hypophosohatemia caused by mutations in the type 2a sodium-phosphate cotransporter. N Engl J Med 2002;347:983-91.</font></p> <p align="justify"><font size="3" face="Verdana">Johnsson KB, Zahradnik R, Larsson T et al. Fibroblast growth factor 23 in oncogenic osteomalacia and X linked hypophosphatemia. N Engl J Med 2003;348:1656-63.</font></p> <p align="justify"><font size="3" face="Verdana">Karim Z, Gérard B, Bakouh N et al. NHERF1 mutations and responsiveness of renal parathyroid hormone. N Engl J Med 2008;359:584-92.</font></p> <p align="justify"><font size="3" face="Verdana">Priè D, Friedlander G. Genetic disorders of renal phosphate transport. N Engl J Med 2010;362:362:<a dir="ltr" href="tel:2399-2409" x-apple-data-detectors="true" x-apple-data-detectors-type="telephone" x-apple-data-detectors-result="1">2399-2409</a>. </font></p> <p align="justify"><font size="3" face="Verdana">Schlingmann KP, Kaufmann M, Weber S et al. Mutations in CYP24A1 and Idiopathic Infantile Hypercalcemia. N Engl J Med 2011;365:410-21.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> BoNewshttp://www.blogger.com/profile/14996032718916828654noreply@blogger.comtag:blogger.com,1999:blog-6459801161644965909.post-36926307824222208902011-05-02T10:22:00.000+02:002016-04-25T22:17:51.244+02:00FRAX Index and osteoporosis prevention: clinical application of risks
stratification studies.<p align="center"></p><div class="separator" style="clear: both;"><br></div><div class="separator" style="clear: both;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9VtKcjqtrynml2y_dVNXpfSFEjLRop5bTnny7Wp-C1qPXjef3O_TcbqtQhkknVXJxDahxY1Yvv22YoJ16KIshWfc4PAuXze7t0xBo3xa3R2NNehqgUY-mDaR26-kI3k3CAU1GZATbTNUQ/s640/blogger-image--1365915663.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9VtKcjqtrynml2y_dVNXpfSFEjLRop5bTnny7Wp-C1qPXjef3O_TcbqtQhkknVXJxDahxY1Yvv22YoJ16KIshWfc4PAuXze7t0xBo3xa3R2NNehqgUY-mDaR26-kI3k3CAU1GZATbTNUQ/s640/blogger-image--1365915663.jpg"></a> </div><p align="center"><br></p><p align="center"><strong style="font-family: Verdana;">Vertebral fractures</strong></p> <p align="center"><strong><font size="6" face="Verdana"></font></strong></p> <p align="justify"> </p> <p align="justify"><font size="3" face="Verdana">Accurate detection of vertebral fracture is essential for risk assessment of individual patients in clinical practice, for determining the drug efficacy in clinical trials and for evaluating the prevalence and incidence of osteoporotic disease in a given population.</font></p> <p align="justify"><font size="3" face="Verdana">A prevalent vertebral fracture is the strongest predictor of subsequent vertebral fracture as well’s of any subsequent osteoporotic fracture.</font></p> <p align="justify"><font size="3" face="Verdana">A vertebral fracture results in a 4.4 fold increase risk of future vertebral fracture in people with a prevalent fracture.</font></p> <p align="justify"><font size="3" face="Verdana">Although bone mass is an important component of the risk of fracture, other abnormalities occur in the skeleton that contribute to fragility fractures. </font></p> <p align="justify"><font size="3" face="Verdana">In addition, a variety of nonskeletal factors, such as the liability to fall and force of impact, contribute to fracture risk. In this view an accurate assessment of fracture risk should ideally take into account other readly measured indices of fracture risk, including in particular those adding more informations to that provided by Bone Mineral Density measurement.</font></p> <p align="justify"><font size="3" face="Verdana">It has been suggested that the ability of Bone Mineral Density to predict a fracture is comparable to the use of blood pressure measurements to predict stroke and better than serum cholesterol levels to predict myocardial infarction.</font></p> <p align="justify"><font size="3" face="Verdana">At the age of 50 years, the proportion of women with osteoporosis who will fracture their hip, spine, forearm or proximal humerus in the next 10 years is about 45%. However the detection rate of these fractures (i.e. sensitivity) is low, and 90% of such fractures would occur in women without osteoporosis.</font></p> <p align="justify"><font size="3" face="Verdana">Low sensitivity is one of the reasons why widespread population-based screening is not widely recommended in women at the time of menopause.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="center"><b><font size="3" face="Verdana">Vertebral fractures assessment</font></b></p> <p align="justify"><font size="3" face="Verdana">The problem is besides all the definition of vertebral fracture, at present there’s no Consensus Giudelines on osteoporotic vertebral fracture definition. </font></p> <p align="justify"><font size="3" face="Verdana">Identification of vertebral fracture can be very difficult, because the shape of normal vertebral bodies varies widely between individuals. Vertebral bodies can be present abnormal features because non-osteoporotic deformities and errors in radiological projection can induce a misdiagnosis of fractured body. </font></p> <p align="justify"><font size="3" face="Verdana">We have to remember that about 50% of vertebral fractures are asymptomatic and therefore are only casually identified. They are not the source of pain !Even when chest radiographs or vertebral images are correctly obtained only 35 to 50% of all radiographic vertebral fractures are correctly reported. It has been estimated that only 19% of these fractures reach clinical attention and can be correctly treated with a antiosteoporotic treatment. In view of high radiation exposure routine chest and lumbar radiographs are not recommended, but the availability of vertebral imaging using DEXA take the advantage of utilize an image of near radiographic quality available with a low fraction of the radiation dose.</font></p> <p align="justify"><font size="3" face="Verdana">Imaging vertebral fractures using DXA is called <b>Vertebral Fracture Assessment</b> (VFA).</font></p> <p align="justify"><font size="3" face="Verdana">The disadvantage of VFA is poor image resolution compared to conventional radiography, CT or MRI and the increased difficulties in imaging the thoracic spine, expecially above T7. Between 5 to 15% of thoracic vertebrae can be visualized only by conventioonal radiography.</font></p> <p align="justify"><font size="3" face="Verdana">The sensitivity and specicificty of this approach compared with conventional radiography varies with the kind of approach used to definy a vertebral fracture:</font></p> <p align="justify"><font size="3" face="Verdana">- Morphometric</font></p> <p align="justify"><font size="3" face="Verdana">- Semiquantitative (SQ)</font></p> <p align="justify"><font size="3" face="Verdana">- Visual identification</font></p> <p align="justify"><font size="3" face="Verdana">Irrespective of the approach, sensitivity is only moderated for for mild fractures corresponding to Genant grade 1 vertebral fracture showing a sensitivity of 54%, due to low imge resolution of this technique.</font></p> <p align="justify"><font size="3" face="Verdana">The sensitivity for identifying moderate to severe vertebral fractures (corresponding to Genant grade 2 and 3 fractures ) is substantial higher ranging from 90 to 94%.</font></p> <p align="justify"><font size="3" face="Verdana">Specificity is high, with a result between 94 to 99%, compared to conventional radiography.</font></p> <p align="justify"><font size="3" face="Verdana">Morphometric and visual identification using DXA images in children can be especially problematic because currently available software cannot detect the vertebrae in most children. That’s why we use total body DXA evaluation in children.</font></p> <p align="justify"><font size="3" face="Verdana">One advantage of DXA imaging is that the scan are not subjected to the same degree of projection distortion as conventional radiography because the X-ray beam is always orthogonal to the spine. Reducing the X ray diffraction effect.</font></p> <p align="justify"><font size="3" face="Verdana">Moreover DXA reduces the frequency that soft tissue obscure the endplates compared to single energy mode.</font></p> <p align="justify"><font size="3" face="Verdana">Side-by-side viewing facilitates the identification of incidental vertebral fractures.</font></p> <p align="center"><b><font size="3" face="Verdana">Morphometrical analysis</font></b></p> <p align="justify"><font size="3" face="Verdana">It uses the measurement of vertebral height to define vertebral fractures. A normative daatabase is established against which the vertebrae are compared, There are a number of different morphometric approaches that vary with the criteria by which they define a vertebral fracture and in the reference data used, The most widely used approaches to identify prevalent and incidental vertebral fractures are the two different algorithms proposed by McCloskey et al (3) and Eastell R et al (4). Morphometric analysis has a high sensitivity and moderate high specificity in discriminating between normal vertebrae and fractured vertebrae. Moreover, all the morphometric approaches for defining prevalent and incident vertebral fractures are correlated with clinical risk factors for vertebral fractures.</font></p> <p align="justify"><font size="3" face="Verdana">The approach used can ahve a significant impact on the prevalence of vertebral fractures identified, varying from 3% to 90%.</font></p> <p align="justify"><font size="3" face="Verdana">A loss of vertebral height of 20 to 25 % is usually used to define an incident vertebral fracture; using this definition comparable ability to identify any vertebral frcture is present irrespective of aproach used to define a baseline fracture.</font></p> <p align="justify"><font size="3" face="Verdana">As mentioned above VFA is more effective in identifying moderate to severe deformities with a sensitivity of 81.6% for grade 2 deformities, whereas mild grade 1 deformities identifiation has a sensitivity as low as 22%.</font></p> <p align="justify"><font size="3" face="Verdana">Finally , the precision error is small if compared with the reduction in vertebral height of 20 to 25% threshold used to define vertebral fractures and it is less using conventional radiology than using VFA.</font></p> <p align="center"><b><font size="3" face="Verdana">Semiquantitative analysis</font></b></p> <p align="justify"><font size="3" face="Verdana">SQ analysis combines measurements of vertebral height with subsequent evaluation of all vertebrae with a short vertebral height by an expert reader. This combined approach enables the identification of non-osteoporotic fracture vertebral deformities, which are not identified using morphometric analysis alone. As a consequence, SQ analysis is able to reduces false positive results.</font></p> <p align="justify"><font size="3" face="Verdana">The most widely used SQ analysis is that of <b>Genant HK</b> (6). Baseline or prevalent vertebral fractures are graded from “0” equal to normal to “3” equal to severe fracture, and incident fractures are defined as an increase of more than or equal than 1 grade on follow-up radiographs. </font></p> <p align="justify"><font size="3" face="Verdana">Genant grade 1 corresponds to an 20 to 25% reduction in anterior, middle or posterior height </font></p> <p align="justify"><font size="3" face="Verdana">Genant grade 2 corresponds to a 25 to 40% reduction in any height</font></p> <p align="justify"><font size="3" face="Verdana">Genant grade 3 corresponds to more than 40% reduction in any vertebral height</font></p> <p align="justify"><font size="3" face="Verdana">Mild grade 1 SQ vertebral deformities are frequently not associated with low BMD values. </font></p> <p align="justify"><font size="3" face="Verdana">The interobserver agreement for conventional radiographs or DXA images is similar with a K score of 0.53 and 0.51 respectively.</font></p> <p align="justify"><font size="3" face="Verdana">This approach is currently those recommended by International Society of Clinical Densitometry for diagnosing vertebral fractures with VFA.</font></p> <p align="center"><font size="3" face="Verdana">Visual Identification by an expert reader (<b>Algorithm Based Qualitative Approach</b>)</font></p> <p align="justify"><font size="3" face="Verdana">ABQ approach differs from SQ analysis because the last one is based only on variations of vertebral height; not considering variations on endplates cracks or breaks as the primary event with a subsequent evaluation of vertebral height. ABQ focus more attention on the vertebral endplate alterations rather than on short vertebral height. Using ABQ we have a greater association with low BMD and interobserver agreement for radiography and DXA images of 0.74 and 0.65 respectively. So that mild vertebral fractures identified with ABQ are more strngly associated with osteoporosis than when this mild fractures are identified with SQ method.</font></p> <p align="justify"><font size="3" face="Verdana">The definition of vertebral fractures includes the presence of breaks in the cortex of vertebral body; these breaks always occurs in the center or either the superior or inferior endplates that are the weakest area of endplate because it is more distant from the strong outer vertebral ring. As a consequence, the endplate buckles or collapses under pressure because of interventebral disc and it results in a concave appearance to the superior and/or inferior endplate. If the concavity extend beyond the inner border of the vertebral ring , it is unlikely to represent an osteoporotic fracture. A vertebral fracture initially involves a crack of the superior or inferior endplate with or without the simultaneous loss of vertebral height. As severity of the fracture progresses, the vertebral ring fractures resulting in loss of height and buckling of the anterior, lateral and occasionally posterior cortex. It is important to outlined these aspects because there is considerable variation in vertebral shape resulting in osteoporotic and non osteoporotic deformities that can result in considerable intraobserver error even among expert readers.</font></p> <p align="justify"><font size="3" face="Verdana">Commonly we can see <b>wedge deformity fracture</b> associated with endplate fracture where is present a fracture of the anterior cortex of vertebral body.</font></p> <p align="justify"><font size="3" face="Verdana">A true <b>compression fracture</b> associated with endplate fracture is an osteoporotic compression fracture of superior endplate associated with fracture of anterior and posterior cortex of vertebral body.</font></p> <p align="justify"><font size="3" face="Verdana">It is also important to identify the different characteristics of high trauma burst fractures. There is usually an history of high trauma injury (such as a car accident, fall from a significant height) immediately resulting in acute, severe, localized back pain with localized tenderness.</font></p> <p align="justify"><font size="3" face="Verdana">Also the presence of intravertebral edema during MRI, used in the studies under discussion is not universally accepted target of vertebral osteoporotic fracture. Such as CT scan, also MRI, are usually only required in the presence of localized pain, focal neurological signs, or symptoms suggesting cord compression or a radiculopathy, or the clinical suspicion of primary or metastatic lesions, but not in osteoporotic patients.</font></p> <p align="justify"><font size="3" face="Verdana">Osteoporotic fractures are rare above T4 and in this settings, it is very important to consider metastatic lesions and , if appropriate to investigate for a primary neoplastic lesion.</font></p> <p align="justify"><font size="3" face="Verdana">Variations in shape or size of the vertebrae or of the vertebral endplate can be caused by degenerative diseases (osteoarthrosis), congenital deformities and metastatic lesions. </font></p> <p align="justify"><font size="3" face="Verdana">In addition, the aging skeleton, particularly in women, may develop slight wedging because of remodelling without depression or break in the endplate or cortex.</font></p> <p align="justify"><font size="3" face="Verdana">Scheuermann’s disease is frequently associated with a short anterior vertebral height in combination with irregularity of the whole superioe and/or inferior endplates. It appears to be isolated in a single vertebral body or involving adjacent vertebrae.</font></p> <p align="justify"><font size="3" face="Verdana">Schmorl’s nodes consist of a rounded flash-like break in the superior or inferior endplatein either the anteroposterior or lateral view, which rarely affects more than 25% of the endplate. They are found in about 35-75% of population and are formed by extrusion or erniation of the nuclear material from the interventebral disk into the vertebral body.</font></p> <p align="justify"><font size="3" face="Verdana">Degenerative osteomalacic changes are present in a vertebral body involved by an uniform or symmetrical concavity of the superior and inferior endplates. It is associated with a generalized thinning and reduced density of all vertebral bodies.</font></p> <p align="justify"><font size="3" face="Verdana">Clinical recommendations for screening for vertebral fractures</font></p> <p align="justify"><font size="3" face="Verdana">The current recommendations for using fracture assessment through DXA imaging (VFA) by the International Society of Clinical Densitometry are:</font></p> <ol> <li> <div align="justify"><font size="3" face="Verdana">When the results may influence clinical management</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">If BMD is indicated then consider performing VTA if clinically indicated in:</font></div> </li> </ol> <p align="justify"><font size="3" face="Verdana">- Documented height loss greater than 2 cm</font></p> <p align="justify"><font size="3" face="Verdana">- Historical height loss greater than 4 cm since young adult</font></p> <p align="justify"><font size="3" face="Verdana">- History of fracture after 50 years old</font></p> <p align="justify"><font size="3" face="Verdana">- Commitment to long term oral or parental glucocorticoid therapy</font></p> <p align="justify"><font size="3" face="Verdana">- History or findings suggestive of vertebral fracture not documented by previous radiographic imaging</font></p> <p align="justify"><font size="3" face="Verdana">Althoough risk factors can provide guidance to identify which patients require screening for osteoporosis, very few subjects would be prepared to initiate long-term therapy to prevent a fracture without confirmation of a diagnosis of osteoporosis using DXA scan.</font></p> <p align="justify"><font size="3" face="Verdana">If a patient has osteopenia and a fragility fracture at any site, the majority of physicians would intervene with therapy. </font></p> <p align="justify"><font size="3" face="Verdana">Therefore, it is reasonable to screen all patients with osteopenia using VFA, if it will alter the management of the patient. In a study at Mayo Clinic 16% of patients 60 to 69 years old and 45% of those older than 70 years had a previously undiagnosed vertebral fracture on VFA.</font></p> <p><font size="3" face="Verdana"></font></p> <p align="center"><b><font size="3" face="Verdana">Fracture Risk Quantification</font></b></p> <p align="justify"><font size="3" face="Verdana">Concurrent considerations of risk factors that operate independently of BMD improuve evaluation of fracture risk.</font></p> <p align="justify"><font size="3" face="Verdana">The best example is age. The same T-score (i.e. the number of Standard Deviations from BMD found on people 35 years old) has different significance at different ages. For any BMD value, fracture risk is much higher in the elderly than in the young people. This is because age contributes to fracture risk indepently of BMD.</font></p> <p align="justify"><font size="3" face="Verdana">In general, risk factor scores show relative poor specificity and sensitivity in predicting either BMD or fracture risk. However, some risk factors vary in importance according to age. For example risk factors for falling, such as reduced mobility, sedatives use, visual impairment are more strongly predictive of fracture in the elderly than in younger individuals.</font></p> <p align="justify"><font size="3" face="Verdana">A series of meta-analyses has been undertaken to identify clinical risk factors that could be used in case finding strategies with or without the use of BMD measurement:</font></p> <ol> <li> <div align="justify"><font size="3" face="Verdana">Low body mass index (BMI): A low BMI is a significant risk factors for hip fracture. 20 kg/m2 vs 25 kg/m2 shows a RR of 1.27, whereas 30 Kg/m2 vs 25 Kg/m2 shows a RR of 0.89.</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">Fragility fracture after 50 years of age : RR 1.86. In other words the presence of prior vertebral fracture approximately doubles the risk of having another fracture.</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">Parental history of hip fracture : RR 1.54 an increase in risk independent from BMD value.</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">Smoking is a RR 1.29</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">Ever use of corticosteroids: RR 1.65</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">Alcohol intake shows an increase in fracture risk that is dose dependent. Where the alcohol intake is on average 2 Units or less daily,there is no increase in risk. Intakes of 3 or more Units daily are associated with a dose-dependent increase in risk. RR 1.38</font></div> </li> <li> <div align="justify"><font size="3" face="Verdana">Rheumatoid Arthritis RR 1.56. In contrast to many causes of secodary forms of osteoporosis rheumatoid arthritis causes an increase in fracture risk indenpendently of BMD and the use of glucocorticoids.</font></div> </li> </ol> <p align="justify"><font size="3" face="Verdana">The multiplicity of these risk factors poses problems in the units of risk to be used. Also if the Relative Risk can be used, the best suited for clinician is the absolute risk ( or probability ) of fracture. The absolute risk dependes on age and life expenctancy, as well’s from the current relative risk. In general lifetime risk of fracture decreases with age, in particular after 70 years of age, because the risk of death with age outweight the increasing incidence of fracture. Estimates of lifetime risk are less relevant in assessing individual clinical risk of fracture in order to choose a therapeutic intervention. So that it has been recommended the use of a short term absolute risk ( i.e. a probability over 10-year interval), 10 years interval covers the likely duration of treatment and average life expectancy in elderly 60 year or older.</font></p> <p align="justify"><font size="3" face="Verdana">What about heart failure ?</font></p> <p align="justify"><font size="3" face="Verdana">Recently Heart failure has been identified such a risk factor for fragility fractures in two large studies by Ezekowitz JA on 2008 and by Carbone L on 2010.</font></p> <p align="justify"><font size="3" face="Verdana">Heart Failure is a leading cause of hospitalization and mortality in Europe and North America. Successfully enhanced treatment rates of hypertension and survival after myocardial infarction have produced a delay in the incidence in heart failure. So that the median age of heart failure patients in clinical trials and large epidemiological studies ranges between 65 and 75 years of age. Such patients are notably at risk for other co-morbid conditions causally related or not such as bone fracture.</font></p> <p align="justify"><font size="3" face="Verdana">Osteoporosis is one of such co-morbidity affecting 1 in 4 women and 1 in 8 men over 50 years old and it is known to be clinically evident with fragility fractures.</font></p> <p align="justify"><font size="3" face="Verdana">A central unanswered question is now evident: does heart failure lead to osteoporosis and fragility fractures or is it a passive participant in a population at risk of both diseases ? </font></p> <p align="justify"><font size="3" face="Verdana">A first answer comes on 1997 in a description of 101 patients with endstage heart failure awaiting cardiac transplantation, low bone mass was common, as vitamin D deficiency and Hyperparathyroidism. </font></p> <p align="justify"><font size="3" face="Verdana">What are the possible links between osteoporosis, fragility fractures, and heart failure ? Many scientists point to shared risk factors for both diseases such as older age, smoking, diabetes, renal dysfunction, inactivity, and poor nutrition.</font></p> <p align="justify"><font size="3" face="Verdana">An interesting role in linking bone loss to heart failure should be hyperaldosteronism always present in heart failure.</font></p> <p align="justify"><font size="3" face="Verdana">Elevated aldosterone levels have been associated with urinary magnesium and calcium wasting, causing secondary hyperparathyroidism.</font></p> <p align="justify"><font size="3" face="Verdana">Heart failure patients treated with spironolactone, a known aldosterone antagonist, showed few fractures compared to matching heart failure affected patients. It is not established if the consequent reduction in hyperparathyroidism is the cause of increased bone repair, increased mineralization, or mineral retentions in particular calcium and magnesium.</font></p> <p align="justify"><font size="3" face="Verdana">Future researches are needed in order to examine biomarkers, imaging, and clinical outcomes related to bone health after carefully clinically phenotyping patients with heart failure.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <p align="center"><font size="3" face="Verdana">References</font></p> <p align="justify"><font size="3" face="Verdana">Cameron JR, Sorenson J. Measurement of bone mineral in vivo: an improved method. Science 1963;142:230-2.</font></p> <p align="justify"><font size="3" face="Verdana">Smith R, Walker R. Femoral expansion in aging women: implications for osteoporosis and fractures. Science 1964;217:945-8.</font></p> <p align="justify"><font size="3" face="Verdana">Tinetti ME. Clinical Practice. Preventing falls in elderly persons. N Engl J Med 2003;348:42-9.</font></p> <p align="justify"><font size="3" face="Verdana">Ahlborg HG, Johnell O, Turner CH et al. Bone loss and bone size after menopause. N Engl J Med 2003;349:327-334.</font></p> <p align="justify"><font size="3" face="Verdana">Khosla S, Melton LJ III. Osteopenia. N Engl J Med 2007;356:<a dir="ltr" href="tel:2293-300" x-apple-data-detectors="true" x-apple-data-detectors-type="telephone" x-apple-data-detectors-result="1">2293-300</a>.</font></p> <p align="justify"><font size="3" face="Verdana">Abendschein W, Hyatt GW. Ultrasonic and selected physical properties of bone. Clin Orthop 1970;69:294-301.</font></p> <p align="justify"><font size="3" face="Verdana">Ahlborg HG, Nguyen ND, Nguyen TV et al. Contribution of hip strength indeces to hip fracture risk in elderly men and women. J Bone Min Res 2005;20:1820-27.</font></p> <p align="justify"><font size="3" face="Verdana">Bolotin HH, Sievanen H. Inaccuracies inherent in dual-energy X-ray absorptiometry in vivo bone mineral density can seriously mislead diagnostic/prognostic interpretations of patients-specific bone fragility. J Bone Miner Res 2001;16:799-805.</font></p> <p align="justify"><font size="3" face="Verdana">Looker AC, Beck TJ, Orwoll ES. Does body size account for gender differences in femur bone density and geometry? J Bone Miner Res 2001;16:1291-9.</font></p> <p align="justify"><font size="3" face="Verdana">Richards JB, Leslie WD, Joseph L et al. Changes to osteoporosis prevalence according to method of risk assessment. J Bone Miner Res 2007;22:228-34.</font></p> <p align="justify"><font size="3" face="Verdana">Lewis CE, Ewing SK, Taylor BC et al. Predictors of non-spine fracture in elderly men: the MrOS study. J Bone Miner Res 2007;22:211-9.</font></p> <p align="justify"><font size="3" face="Verdana">Mussolino ME, Looker AC, Madans JH et al. Risk fators for hip fracture in white men: the NHANES I epidemiologic follow up study. J Bone Miner Res 1998;13:918-24.</font></p> <p align="justify"><font size="3" face="Verdana">Melton LJ III, Atkinson EJ, O’Connor MK et al. Bone density and fracture risk in men. J Bone Miner Res 1998;13:1915-23.</font></p> <p align="justify"><font size="3" face="Verdana">Amin S, Zhang Y, Felson DT et al. Estradiol, testosterone, and the risk for hip fractures in elderly men from the Framingham study. Am J Med 2006;119:426-33.</font></p> <p align="justify"><font size="3" face="Verdana">McCloskey EV, Spector TD, Eyres KS et al. The assessment of vertebral deformity: A method for use in population studies and clinical trials. Osteoporosis Int 1993;3:138-47.</font></p> <p align="justify"><font size="3" face="Verdana">Eastell R, Cedel SL, Wahner HW et al. Classification of vertebral fractures. J Bone Miner Res 1991;6:207-15.</font></p> <p align="justify"><font size="3" face="Verdana">Genant HK, Jergas M, Palermo L et al. Comparison of semiquantitative visual and quantitative morphometric assessment of prevalent and incident vertebral fractures in osteopororsis. The Study of Osteoporotic Fractures Research Group. J Bone Miner Res 1996;11:984-96.</font></p> <p align="justify"><font size="3" face="Verdana">Rea JA, Li J, Blake GM et al. Visual assessment of vertebral deformity by X-ray absorptiometry: A highly predictive method to exclude vertebral deformity. Osteoporosis Int 2000;11:660-8.</font></p> <p align="justify"><font size="3" face="Verdana">Siminoski K, Jiang G, Adachi JD et al. Accuracy of height loss during prospective monitoring for detection of incident vertebral fractures. Osteoporosis Int 2005;16:403-10.</font></p> <p align="justify"><font size="3" face="Verdana">Siminoski K, Warshawski RS, Jen H et al. The acuracy of historical height loss for the detection of vertebral fractures in postmenopausal women. Osteoporosis Int 2006;17:290-6. </font></p> <p align="justify"><font size="3" face="Verdana">Schousboe JT, Ensrud KE, Nyman JA et al. Cost-effectiveness of vertebral fracture assessment to detect prevalent vertebral deformity and select postmenopausal women with a femoral neck T-score lower than 2.5 SD for alendronate therapy: A modeling Study. J Clin Densitom 2006;9:133-43.</font></p> <p align="justify"><font size="3" face="Verdana">Hiu SL, Slemenda CW, Johnston CC. Age and bone mass sd predictor of fracture in a prospective study. J Clin Invest 1988;81:1804-9.</font></p> <p align="justify"><font size="3" face="Verdana">Kanis JA, McCloskey EV. Evaluation of the risk of hip fracture. Bone 1996;18:127-32.</font></p> <p align="justify"><font size="3" face="Verdana">Kanis JA, Johnell O, Oden A et al. Ten-year risk of osteoporotic fracture and the effect of risk factors on screening strategies. Bone 2001;30:251-8.</font></p> <p align="justify"><font size="3" face="Verdana">Kanis JA. Diagnosis of osteoporosis and assessment of fracture risk. Lancet 2002;359:1929-36.</font></p> <p align="justify"><font size="3" face="Verdana">Shane E, Mancini D, Aaronson K et al. Bone mass, vitamin D deficiency, and hyperparathyroidism in congestive heart failure. Am J Med 1997;103:197-207.</font></p> <p align="justify"><font size="3" face="Verdana">Jankowska EA, Jakubaszko J, Cwynar A et al. Bone mineral status and bone loss over time in men with chronic systolic heart failure and their clinical and hormonal determinats. Eur J Heart Fail 2009;11:28-38.</font></p> <p align="justify"><font size="3" face="Verdana">Van Diepen S, Majumdar SR, Bakal JA et al. Heart failure is a risk factor for orthopedic fracture: a population-based analysis of 16.294 patients. Circulation 2008;118:1946-52.</font></p> <p align="justify"><font size="3" face="Verdana">Carbone L, Buzkova P, Fink HE et al. Hip fractures and heart failure: findings from the Cardiovascular Health Study. Europ Heart J 2010;31:77-84.</font></p> <p align="justify"><font size="3" face="Verdana">Carbone LD, Cross JD, Raza SH et al. Fracture risk in men with congestive heart failure risk reduction with spironolactone. J Am Coll Cardiol 2008;52:135-8.</font></p> <p align="justify"><font size="3" face="Verdana"></font></p> <div class="separator" style="clear: both;"><br></div>BoNewshttp://www.blogger.com/profile/14996032718916828654noreply@blogger.comtag:blogger.com,1999:blog-6459801161644965909.post-38244713998965565732010-07-12T22:08:00.000+02:002016-04-25T20:36:18.023+02:00Klotho more than “ninphae”<p align="center"><br></p><p align="center"><br></p><p align="center"></p><div class="separator" style="clear: both;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgpseMwSs2sObPQNYbLJ70T2h94mm1kdYx6WBe0L-0BtXsm5NlG0aFHx-me6U5Vj4pIL4z77ZECtX1wOjabqyXgnSgxZUtuWQ4X6AU8o73WQ8eHCqNd9MPcUty1eZ9PgMXmStSf_oG-PkhR/s640/blogger-image--131712058.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgpseMwSs2sObPQNYbLJ70T2h94mm1kdYx6WBe0L-0BtXsm5NlG0aFHx-me6U5Vj4pIL4z77ZECtX1wOjabqyXgnSgxZUtuWQ4X6AU8o73WQ8eHCqNd9MPcUty1eZ9PgMXmStSf_oG-PkhR/s640/blogger-image--131712058.jpg"></a></div> <p></p><p align="center"> </p> <p align="center" style="text-align: start;"><span style="font-family: Verdana;">From Greek mythology “</span><b style="font-family: Verdana;">Klotho</b><span style="font-family: Verdana;">” was one of three Moirae. She is responsible for spinning the thread of human life, so that she mades major decisons when a person is born. She controls who born through his life she also decide who has to be saved or put to death.</span></p> <p align="justify"><font face="Verdana">Two other sisters , Lachesis and Atropos, are responsible of human destiny and influence their misery and suffering.</font></p> <p align="justify"><font face="Verdana"><b>Clotho assisted Hermes to create the alphabet</b>, and forced the goddess Afrodite into making love with other gods, killed the Titan Typhon with poison fruits and <b>persuaded Zeus to kill Asclepius with a bolt of lightning</b>.</font></p> <p align="justify"><font face="Verdana">As you know Asclepius, the Roman Esculapius, is the god of Medicine and Healing. Asclepius has a daughter Epione ( Goddess of soothin of pain) and he his the father of : Hygieia (Hygiene), Panacea (Universal Remedy), Aceso (Goddess of Healing process), Leso or Laso (Goddess of recuperation from illness), Aglaea or Aglaia (Shining one, splendor, brillant, Healthy Glow) wife of Hephaesto and mother of Eucleia (good repute), Eupheme (Acclaim), Euthenia (Prosperity), Philophrosyne (Welcome).</font></p> <p align="justify"><font face="Verdana">The rod of Asclepius, a snake-entwined staff, remains a symbol of medicine today, also if <u>sometimes a staff with two snakes (the caduceus) is mistakenly used instead</u>. </font></p> <p align="justify"><font face="Verdana">He was one of the Apollo’s sons.</font></p> <p><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMdVb7TqBN-nDKK2J-VtsYugJg4rj64zl6XhZLIDXpTbFXRnY1w8xMCSUPfSb7duipQ9BVLRTMRrj4ird7FIhOfWpAA4zxN2jS4hzcRP-4O_7XfR0qHCZdL_PiPWhz4cTkUGKnQW7JARez/s1600-h/Asklepios%5B5%5D.jpg"><font color="#000000" face="Verdana"><img style="border-right-width: 0px; display: block; float: none; border-top-width: 0px; border-bottom-width: 0px; margin-left: auto; border-left-width: 0px; margin-right: auto" title="Asklepios" border="0" alt="Asklepios" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjD_dzkX9XrzTcrm0qy4udI-j6_6539EaMwq2bWmq01YHxcmAGndrI5NUAgfqPvovA6iELgYUg6AdVJL5zsvrrZVMwQqj0G8tqmEoWFCWzn2bLRYESbPUDWS0T-N8OkqjhAZaQG_i9ntL0v/?imgmax=800" width="360" height="480"></font></a><font face="Verdana"> </font></p> <p align="center"><font face="Verdana">Asclepius </font></p> <p align="center"><font face="Verdana">God of Medicine</font></p> <p align="center"><font face="Verdana"></font></p> <p align="center"><font face="Verdana"></font></p> <p align="center"><font face="Verdana">Is KLOTHO, an anti-ageing hormone ?</font></p> <p align="justify"><font face="Verdana">The KLOTHO gene was identified serendipitously through a hypomorphic allele that results in severe early degenerative changes and short lifespan ( Nature 1997). The homozygous mutant animals develop normally until 3 weeks of age, then exhibit severe growth retardation, osteoporosis, ectopic calcification, aterosclerosis, emphysema and atrophy of the skin, thymus, testes and ovaries, and die at an average age of 61 days.</font></p> <p align="justify"></p> <p align="justify"><font face="Verdana"></font></p> <font face="Verdana">KLOTHO prolong lifespan at least in part by inhibiting insulin-IGF-1 signalling. </font><font face="Verdana">KLOTHO may be secreted by KIDNEY cells blocking both IGF-1 and Insulin receptor action at adipocytes and target tissue levels.</font> <p></p> <p align="justify"><a href="http://lh4.ggpht.com/_FLe5Kbctaeg/TDt2Ul3iBQI/AAAAAAAAC14/HHZlTmqKr5Q/s1600-h/clip_image002%5B7%5D.jpg"><font color="#000000" face="Verdana"><img style="border-right-width: 0px; display: block; float: none; border-top-width: 0px; border-bottom-width: 0px; margin-left: auto; border-left-width: 0px; margin-right: auto" title="clip_image002" border="0" alt="clip_image002" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjA6MzGKs7oGt4TCNzBUB8uWQJIJlepAKJblxCFJI6W9qdoErX-ARba6jDU8T-dKIEL5Z5d6ic7fb80NLLvzMLsqJpujsgrQgqTe9KvQ5ga8tpbkXoBHbxV4B8jH6EUw8MWd2Gox17JZTjE/?imgmax=800" width="538" height="237"></font></a></p> <p align="justify"><font face="Verdana">Levels of calcium and phosphate are elevated in KLOTHO deficient mice, demonstrating that this protein has a role in calcium and phoshate homeostasis. The altered calcium and phoshate levels are due to elevated 1,25 OH Vitamin D3 levels, which result from increased expression of 1alfa hydroxylase gene activity at kidney level.</font></p> <p align="justify"><font face="Verdana">Normalization of 1,25 OH Vitamin D3 with a Vitamin D deficient diet partially rescued some of the KLOTHO deficient phenotypes, including slow growth, ectopic calcification and early death. This suggests that the putative pro-ageing effect of KLTHO deficiency is not associated with ageing itself, but rather that the pathology is related to altered Vitamin D metabolism.</font></p> <p align="justify"><font face="Verdana">FGF23 KO mice share many features with the KLOTHO deficient mouse, including hypercalcemia, hyperphosphatemia, ectopic calcification, hypoglycaemia, infertility, and very short lifespan.</font></p> <p align="justify"><font face="Verdana">FGF23 is a circulating factor that is produced in the bone and inhibits phosphate transport in renal proximal tubular cells. FGF23 deficiency results in phosphate retention and hyperphosphatemia, constitutively elevated expression of 1 alfa hydroxylase, elevated levels of 1,25 OH Vitamin D3 and hypercalcaemia.</font></p> <p align="justify"></p> <p align="justify"><font face="Verdana"></font></p> <font face="Verdana"><strong>Interestingly without KLOTHO the functions of FGF23 is literally abolished.</strong></font> <p></p> <p align="justify"><font face="Verdana">Many tissues express FGF Receptors subtypes that interact with the KLOTHO-FGF23 complex, therefore it is possible that KLOTHO exerts his anti-ageing action through the activation of his enzymatic activity i.e. beta glucoronidation.</font></p> <p align="justify"><font face="Verdana">We know that all steroids enzymes including all lipophilic vitamins such as Vitamin D, with a steroid like structure, can be glucuronized in order to achieve a better hydrophility and flow into the blood vessels. The pool of glucuronide-linked steroids hormones is an inactive quote of hormones, those destiny is in normal condition to be metabolized further into hepatic cells or recycled by endocrine organs. </font></p> <p align="justify"><font face="Verdana">KLOTHO can hydrolyse STEROID GLUCURONIDES, including estradiol, estrone, estriol and vitamin D so that some effects of KLOTHO can occur through processing of inactive streroid glucuronides to active steroids hormones. Steroid hormones could have a role in the regulation of ageing in mammals. </font></p> <p align="justify"> </p> <p align="justify"><a href="http://lh6.ggpht.com/_FLe5Kbctaeg/TDt2WFp6VGI/AAAAAAAAC2A/cQkZ4qqr02A/s1600-h/clip_image003%5B8%5D.jpg"><font color="#000000" face="Verdana"><img style="border-right-width: 0px; display: block; float: none; border-top-width: 0px; border-bottom-width: 0px; margin-left: auto; border-left-width: 0px; margin-right: auto" title="clip_image003" border="0" alt="clip_image003" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi0dHw9zWEuzByloUOWx81sTqFjju0_eYd6ZZrt7f-FIV31sThgOtB8h32ZxbUMDnhfYH4VJnlBSHY2llaQnCmfq5_A7ht7-UtTd2nNYWNajAE4KByYhXniycftR6iz5mSTAEUhQ_PlD6a3/?imgmax=800" width="514" height="398"></font></a></p> <p align="justify"> </p> <p align="justify"><font face="Verdana"></font></p> <p align="center"><font face="Verdana">References</font></p> <p align="justify"><font face="Verdana">Arking DE, Krebsova A, Macek M Sr et al. Association of human aging with a functional variant of klotho. Proc Natl Acad Sci USA 2002;99:856-61.</font></p> <p align="justify"><font face="Verdana">Duce JA, Podvin S, Hollander W et al. Gene profiling analysis implicates klotho as an important contributor to aging changes in brain white matter of rhesus monkey. Glia 2008;56:106-117. </font></p> <p align="justify"><font face="Verdana">Arking DE, Becker DM, Yanek LR et al. KLOTHO allele status and the risk of early-onset occult coronary artery disease. Am J Hum Genet 2003;72:1154-61.</font></p> <p align="justify"><font face="Verdana">Mitani H, Ishizaka T, Aizawa T et al. In vivo klotho gene transfer ameliorates angiotensin II-induced renal damage. Hypertension 2002;39:838-43.</font></p> <p align="justify"><font face="Verdana">Ogata N, Matsumura Y, Shiraki M et al. Association of klotho gene polymorphism with bone density and spondylosis of the lumbar spine in postmenopausal women. Bone 2002;31:37-42.</font></p> <p align="justify"><font face="Verdana">Yamada Y, Ando F, Niino N et al. Association of polymorphisms of the androgen receptor and klotho genes with bone mineral density in Japanese women. J Mol Med 2005;83:50-7.</font></p> <p align="justify"><font face="Verdana">Mullin BH, Wilson SG, Islam FM etr al. Klotho gene polymorphisms are associated with osteocalcin levels but not bone density of aged postmenopausal women. Calcif Tissue Int 2005;77:145-51.</font></p> <p align="justify"><font face="Verdana">Kawano K, Ogata N, Chiano M et al. Klotho gene polymorphisms associated with bone density of aged postmenopausal women. J Bone Miner Res 2002;17:1744-51. </font></p> <p align="justify"><font face="Verdana">Kuro-o M, Matsumura Y, Aizawa H et al. Mutation of the mouse klotho gene leads to a syndrome resembling ageing. Nature 1997;390:45-51.</font></p> <p align="justify"><font face="Verdana">Roth GS, Lane MA, Ingram DK et al. Biomarkers of caloric restriction may predict longevity in humans. Science 2002;297:811.</font></p> <p align="justify"><font face="Verdana">Kurosu H, Yamamoto M, Clark JD et al. Suppression of aging in mice by the hormone Klotho. Science 2005;309:1829-33.</font></p> <p align="justify"><font face="Verdana">Chang Q, Hoefs S, van der Kemp AW et al. The beta glucuronidase Klotho hydrolyzes and activates the TRPV5 channel. Science 2005;310:490-3.</font></p> <p align="justify"><font face="Verdana">Russell SJ, Kahn CR. Endocrine regulation of aging. Nat Rev Mol Cell Biol 2007;8:681-91.</font></p> <p align="justify"><font face="Verdana">Sohal RS, Weindruch R. Oxidative stress, caloric restriction, and aging. Science 1996;273:59-63.</font></p> <p align="justify"><font face="Verdana">Ingram DK, Cutler RG, Weindruch R et al. Dietary restriction and aging: the initiation of a primate study. J Gerontol 1990;45:B148-B163.</font></p> <p align="justify"><font face="Verdana">Sohal RS, Argarwal S, Candas M et al. Effect of age and caloric restriction on DNA oxidative damage in different tissues of C57BL/6 mice. Mech Ageing Dev 1994;76:215-24.</font></p> <p align="justify"><font face="Verdana">Lee C-K, Klopp RG, Weindruch R et al. Gene expression profile of aging and its retardation by caloric restriction. Science 1999;285:1390-3.</font></p> <p align="justify"><font face="Verdana">Kujoth GC, Hiona A, Pugh TD et al. Mitochondrial DNA mutations, oxidative stress, and apoptosis in mammalian aging. Science 2003;309:481-4.</font></p> <p align="justify"><font face="Verdana">Weindruch R, Sohal RS. Caloric intake and aging. N Engl J Med 1997;337:986-94.</font></p> <p align="justify"><font face="Verdana">Priè D, Friedlander G. Genetic disorders of renal phosphate transport. N Engl J Med 2010;362:<a dir="ltr" href="tel:2399-2409" x-apple-data-detectors="true" x-apple-data-detectors-type="telephone" x-apple-data-detectors-result="0">2399-2409</a>.</font></p> BoNewshttp://www.blogger.com/profile/14996032718916828654noreply@blogger.comtag:blogger.com,1999:blog-6459801161644965909.post-62791279951299258482010-05-31T15:42:00.000+02:002016-04-25T22:20:58.652+02:00High Resolution peripheral Quantitative Tomography and bone quality.<div align="center"> </div> <div align="center"><div class="separator" style="clear: both;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhl7GXgz4l5-0QUFdm2uMjcnu0quXAaq6N7qLS_HwZ9BeRBhY5Yygg8Zx93pIu-5npFeDjzTDTpVFUF-0sXtTPD9LMrjj2oVlkLI0eoSreoGrJcOf8NjGB6-XwJEhF523b2EoxANdxNvBzt/s640/blogger-image--1879347544.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhl7GXgz4l5-0QUFdm2uMjcnu0quXAaq6N7qLS_HwZ9BeRBhY5Yygg8Zx93pIu-5npFeDjzTDTpVFUF-0sXtTPD9LMrjj2oVlkLI0eoSreoGrJcOf8NjGB6-XwJEhF523b2EoxANdxNvBzt/s640/blogger-image--1879347544.jpg"></a></div> </div> <div align="center"> </div> <div align="center"> </div> <p align="center"><font face="Tahoma">Bisphosphonates</font></p> <p align="justify"><font face="Tahoma">Bisphosphonates (BP) are synthetic analogues of inorganic pyrphosphate with a central carbon instead of an oxigen element that protect BPs from biological degradation.</font></p> <p align="center"><font face="Tahoma">P – O – P inorganic pyrophosphate</font></p> <p align="center"><font face="Tahoma">P – C – P bisphosphonates</font></p> <p align="justify"><font face="Tahoma">Thos P-C-P backbone is identical across all types of BPs, and two sidechains account for their biological diversity: a hydroxyl residue at the R1 side chain enhances the affinity to bone, whereas nitrogen residues at the R2 side chain account for their potency, mechanism of action, and side effects. </font><font face="Tahoma">Developed and traditionally used to soften water in irrigation systems in the 19<sup>th</sup> century, BPs were introduced into clinical medicine in the 1970s and 1980s in the treatment of Paget’s disease of bone and hypercalcemia of malignancy. </font><font face="Tahoma">Bisphosphonates (BP) may act via many signalling pathways, some of which are specific for a given BP. </font></p> <p align="justify"><font face="Tahoma">First of all two groups of BPs have been identified to date acting in a different ways:</font></p> <ol> <li> <div align="justify"><font face="Tahoma">Non-amino bisphosphonates act through ATP block producing toxic analogs of ATP and causing cells death.</font></div> </li> <li> <div align="justify"><font face="Tahoma">Amino bisphosphonates act through inhibition of an enzyme called farnesyl pyrophosphate synthase, an enzyme present in in the 3 hydroxymethyl glutaryl Co A reductase pathway.</font></div> </li> </ol> <p align="justify"><font face="Tahoma">Other oossible intracellular pathways have been proposed some of wich are specific for some bisphosphonates. These includes:</font></p> <p align="justify"><font face="Tahoma">- Altering key apoptotic proteins, specifically increasing BAX and decreasing Bcl-2.</font></p> <p align="justify"><font face="Tahoma">- Activating mitochondrial pathway via translocation of apoptosis iducing factor.</font></p> <p align="justify"><font face="Tahoma">- Inhibiting mitochondrial adenine nucleatide translocase (ANT), known to be involved in causing apoptosis</font></p> <p align="justify"><font face="Tahoma">- Inducing ApppI ( an densoine triphosphate analog), which triggers direct apoptosis through blockade of mitochondrial ANT.</font></p> <p align="justify"><font face="Tahoma">- Inhibiting metalloproteinases necessary for proteolytic degradation of the extracellular matrix (ECM).</font></p> <p align="justify"><font face="Tahoma">- Inhibiting cancer cell adhesion ( ICMA-1, VCAM-1) and prevents cancer cells spreading at lower concentration than those required to cause apoptosis.</font></p> <p align="justify"><font face="Tahoma">Main characteristics of BPs are:</font></p> <p align="justify"><font face="Tahoma">- Poor oral bioavailability</font></p> <p align="justify"><font face="Tahoma">- High affinity for, and accumulation in bone</font></p> <p align="justify"><font face="Tahoma">- Target FPP synthase in osteoclasts</font></p> <p align="justify"><font face="Tahoma">- Efficiency across a broad spectrum of osteoclast mediated diseases</font></p> <p align="justify"><font face="Tahoma">Stimulated by the launch of alendronate, the first potent oral aminobisphosphonate, the mechanisms of this drug class were elucidated in the ’90. After parenteral and oral administration in which less than 1% is absorbed, BPs bind to hydroxyapatite crystals and concentrate at skeletal sites where active remodeling takes place. Following embedding into the skeleton, BPs inhibit osteoclasts activity and, under acidic conditions in resorption lacunae, are incorporated into osteoclasts.</font><font face="Tahoma">Nitrogen-containing BPs, the most widely used class of antiosteoporosis drugs, which includes alendronate, risendronate, ibandronate, and zolendronic acid interfere with the mevalonate pathway and inhibit Farnesyl Pyrophosphate synthase (FPPS). </font><font face="Tahoma">FPPS is the enzyme that generates Farnesyl Pyrophosphate and Geranyl-geranyl Pyrophosphate (GGPP), essential for post-translational isoprenylation reaction of small GTPases. These enzymes are able to modulate and coordinate subcellular protein trafficking, cell survival, and cytoskeletal integrity (called Ras, Rho, Rac, Rap).</font><font face="Tahoma">The potency of BPs depends upon the inhibitory effect on FPP synthase activity and the affinity for mineral bone.</font></p> <p align="justify"><font face="Tahoma">In theory, the enzyme hydroxymethy glutaryl (HMG) Coenzyme A reductase inhibitors ( also called “statins”), used usually in therapy for reducing plasma cholesterol, which inhibit the production of mevalonate, also have an osteotropic effect. Due to their lipophilic properties, they preferentially target the liver, but not the skeletal tissue. </font><font face="Tahoma">Inhibition of FPPS by BPs results in decreased osteoclast activity, enhanced osteoclast apoptosis and a profound antiresorptive affect. A relevant finding obtained from bone biopsies of patients treated for long term with bisphosphonates is the increased number of giant, hypernucleated osteoclasts that are detached from bone lacunae and undergone slowly a protracted apoptotic process. (see Manolagas NEJM ). </font><font face="Tahoma">Apart from their specific antiosteoclastic activity, BPs protect osteoblasts and osteocytes against apoptosis, enhancing osteoblastic differentiation, and increasing osteoblastic production of Osteoprotegerin.</font><font face="Tahoma">Since the first BP, alendronate, was approved in 1995 these agents have been the first therapy for treating postmenopausal osteoporosis, male osteoporosis, glucocorticoid-induced osteoporosis, Paget’s disease of bone, Hypercalcemia of malignancy, multiple myeloma of bone, and skeletal metastases. </font></p> <p align="justify"><font face="Tahoma">Bone loss associated with aromatase inhibitor therapy in women with breast cancer, which is associated with very low estrogen levels, has been treated with zolendronic acid administered twice per year.</font><font face="Tahoma">In malignant skeletal diseases, intravenous BPs ( such as zolendronic acid 4 mg, or pamidronate 90 mg) are administered every 4 weeks or also more frequently. The shorter therapy interval is required in order to control excessively enhanced bone resorption in malignant conditions. Under this regimen, the rate of side effects is considerably higher, including renal toxicity and the development of osteonecrosis of the jaw (ONJ), particularly in patients with myeloma or breast cancer following dental procedures. </font><font face="Tahoma">The reported decrease in hip fracture rates in long term clinical studies reported for osteoporosis treatment results from multiple factors. BP effectively reduce fracture risk in postmenopausal women over a period of at least 10 year, but preclinical studies demonstrated that they also negatively affect bone quality.</font></p> <p align="justify"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiJEwp3JwgXPbK7xLX0y_FdIqT4Jz6_9yBPMpp3AbbIPuyJ6-_XzkCQqwhEZq_kjWjJ6Tm4TUgTavIPkRZpUNDW6NejoB_TLm4oV1JGwekLfYInrVuCz_eiDDzT-TcCxZhzDSyhgy6DKE3k/s1600-h/clip_image003%5B3%5D.jpg"><font color="#000000" face="Tahoma"></font></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiKLq3e3aZnA7-Y9dNc-mSRYOGxCm0UiD3yO37Qe55YR4OkgLdy4xlxo3_bmPLdNRB_WjzIf5bf-nUBjvKSwiRmtj-9Em-NXK4eBGjN7QgsL84sPGBxWzrHRtJHyE8KxjJnxfuWS6JaddD0/s1600-h/clip_image003%5B6%5D.jpg"><img style="border-right-width: 0px; display: block; float: none; border-top-width: 0px; border-bottom-width: 0px; margin-left: auto; border-left-width: 0px; margin-right: auto" title="clip_image003" border="0" alt="clip_image003" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhYnoOObW-VZUFYnK7n0nKU9RgsHq-DVeO6brLJSFa8fOzwXPRxu6SgLX0r30C2IozdBzhBszb9H_1AfiAIEC242WAuTCA0N6SyD3YNT5luKNEF28bYQs04dujIAR67_nNQRGZIFYdcdNY8/?imgmax=800" width="456" height="480"></a></p> <p align="center"><font face="Tahoma">Bone quality</font></p> <p align="justify"><font face="Tahoma"><b>Not all fractures have the same pathogenesis or structural abnormalities that cause bone fragility.</b> Some fractures are associated with reduced tissue mineral density; in others, there is a reduced density of osteocytes.</font><font face="Tahoma">Women with fractures may have high, normal, or low rates of remodeling. Some women with fractures have a negative balance in the bone multicellular units owing to reduced bone formation, increased bone resorption, or both; other women with fractures have no negative balance in the bone multicellular unit balance.</font><font face="Tahoma">The heterogeneity of mechanisms suggests that <b>all patients with fragility fractures should not be treated in the same way.</b></font><font face="Tahoma">In most postmenopausal women, the remodeling rate is high; in other words a large number of bone multicellular units excavate cavities while other units are at various stages involved in the completion of remodeling. When an antiresorptive agents is given, this steady state is perturbed. The birth rate of new bone multicellular units decreases quickly when treatment is started, whereas the many bone multicellular units at various stages in the remodeling cycle complete the remodeling process by depositing a volume of new bone that reduces the depth of the escavated site.</font><font face="Tahoma">The newly deposite bone undergoes primary mineralization during the deposition of osteoid (normally a rapid process) and then slower secondary mineralization with enlargement of newly yet formed crystal occurred thereafter.</font><font face="Tahoma">The increased tissue mineral density and reduced porosity slightly improve bone strength. During treatment with antiresorptive agents, the slow remodeling rate and the reduced depth of a decreased number of excavated sites produces bone loss and structural decay also if more slowly than before, and bone fragility reemerges.</font><font face="Tahoma">Fractures continue but are less frequent than in untreated controls with a rapid remodeling and a negative balance in bone multicellular units exponentially increase bone fragility.</font></p> <p align="justify"><font face="Tahoma">Antiresorptive agents finally <b>slow the progression of fragility</b> by suppressing the rate of remodeling and reducing the depth of resorption in each of the reduced number of bone multicellular units engaged into remodeling bone.</font><font face="Tahoma">Since remodeling is slow during treatment with antiresorptive agents, more time is available for secondary mineralization of new mineral bone both in sites actively resorbing before drug exposure and in sites distant from endosteal surface. So that slower remodeling allows increased bone mineral density with more homogenous distribution of mineral between adjacent regions.</font></p> <p align="justify"><font face="Tahoma">However <b>greater secondary mineralization</b> rate increases tissue stiffness, thereby predisposing to bone microdamage.</font></p> <p align="justify"><font face="Tahoma">Whereas the <b>greater homogeneity</b> in tissue density offers less resistance to the propagation of cracking.</font></p> <p align="justify"><font face="Tahoma">Reducing remodeling may also reduce removal of microdamage in bone.</font></p> <p align="justify"><font face="Tahoma">Studies in dogs shows a nearly 30% decline in material toughness ( the normalized energy to fracture ) over 3 years of reatment at doses that stimulate those used in treating osteoporosis in postmenopausal women. This creates a material more brittle that untreated bone, facilitating microdamage, which, combined with the natural suppression of remodeling to repair it, significantly increases its burden in bone.</font><font face="Tahoma">Micro-damage accumulation is likely a consequence of the increased brittleness and reduced toughness, not its cause.</font></p> <p align="center"><font face="Tahoma">HR-pQCT</font></p> <p align="justify"><font face="Tahoma">Advances in non invasive techniques are likely to provide insights into the effects of these therapeutic agents on bone structure and increasingly accurate information concerning the structural heterogeneity of bone fragility from patient to patient and so may improve the sensitivity of the prediction of fracture risk.</font><font face="Tahoma">Whereas DEXA has become the most commonly used technique worldwide to predict fracture risk and assess response to therapy, based on a two dimensional interpretation of skeletal tissue; it’s increasingly evident that it provides limited interpretation of three dimensional skeletal properties and so on its structural charateristics.</font><font face="Tahoma">Other imaging modalities such as CT and MRI offer considerable greater charaterization of bone architecture, but their software and technical evolution has not been validated until recently.</font></p> <p align="justify"><font face="Tahoma">High Resolution three dimensional peripheral QuantitativeTomography (HR-pQCT) device has been developed by Xtreme CT, Scanco Medical AG, Bassersdorf, Switzerland in order to provides measures of bone microachitecture and micro Finite Element analysis software for numerical quantification of mechanical properties of bone in vivo.</font><font face="Tahoma">In the following diagram we can see the difference between osteopenic postmenopausal women and osteporotic women with fracture using DXA (BMD) and HR-pQCT parameters. Clearly the differences between two groups is more evident with the later technique.</font></p> <p align="justify"> </p> <p align="justify"><br></p> <p align="justify"><font face="Tahoma">This system, first described in detail by <b>Andreas Laib</b> on 1998, uses a two dimensional detector array in combination with a 0.08 mm point-focus X ray tube, enabling the simultaneous acquisition of a stack of 116 high-resolution parallel CT slices, using an effective energy of 40 keV, X-ray tube current of 95 mA, slice thickness of 89 μm, field of view of 90 mm, image matrix of 1536 x 1536 pixels, and pixel size of 82 μm (voxel size).</font><font face="Tahoma">Older 3-D pQCT devices used before have a voxel size of 165 μm, the need to have an higher resolution value is due to adequately solve the distance between the trabecular ridges ( about 300-500 μm) and not necessary to resolve individular trabeculae (100 μm or less ). </font><font face="Tahoma">At each site 110 CT slices were obtained, thus delivering a three dimensional representation of about 9 mm in the axial direction. The arm of leg of the patient was immobilized during the examination in an anatomically formed carbon fiber shell. An anteroposterior scout view was used to define the measurement region. Briefly, a reference line was manually placed at the endplates of the radius and the tibia. The first CT slice was 9.5 mm and 22.5 mm proximal to the reference line for the distal radius and tibia , respectively. The effective dose was less than 3 microSievert per measurement with a measurement time of 2.8 minutes.</font><font face="Tahoma">Quality control, based on Shewart rules, was monitored by daily scans of a phantom containing rods of HA ( densities of 0, 100, 200, 400, 800 mg HA/cm<sup>3</sup> ) embedded in a soft tissue equivalent resin (QRM Moehrendorf, Germany).</font><font face="Tahoma">The entire volume of interest was automatically separated into a cortical and trabecular region using a threshold based algorithm. The threshold used to discrimite cortical from trabecular bone was set to one third of the apparent cortical bone density value (D cort). Mean cortical thicknes (CTh) was defined as the mean cortical volume diveded by the outer boe surface.</font><font face="Tahoma">Trabecular bone density (D trab) in gHA/cm<sup>3<s> </s></sup>was compouted as the average mineral density whitin the trabecular volume of interest.</font><font face="Tahoma">Trabecular bone volume (BV) fraction (BV/TV Trabecular volume %) was then expressed from trabecular density assuming fully mineralized bone to have a mineral density of 1.2 gHA/cm<sup>3 </sup></font></p> <p align="center"><font face="Tahoma">BV/TV %= 100 x 1200 mgHA/cm<sup>3</sup></font></p> <p align="justify"><font face="Tahoma">Because the thickness of every trabeculae cannot be measured accurately because of partial volume effects, a thickness independent algorithm was used to assess trabecular structure.</font><font face="Tahoma">First, a mid-axis transformation method was used to identify trabecular elements and the distance between them assessed threedimensionally using the distance transform method. Trabeculae cannot be resolved at their correct thickness because of partial volume effects, to avoid this problem the center point of every trabecula is detected in the gray-level image and called the 3-D ridges. Trabecular number is taken as the inverse of the mean spacing of the ridges.</font><font face="Tahoma">Trabecular number (TbN, mm<sup>-1</sup>) was defined as the inverse of the mean spacing of the mid-axes and is thus truly three-dimensional and it does not depend on “a priori” assumptions regarding the plate or rod-like nature of the underlying nature.</font></p> <p align="center"><font face="Tahoma">TbN = 1/Mean Tb space = nTb/mm</font></p> <p align="justify"><font face="Tahoma">Trabecular thickness (TbTh, μm) and separation (TbSp, μm) were derived from BV/TV and TbN using a standard methods from histomorphometry.</font></p> <p align="center"><font face="Tahoma">TbTh = (BV/TV)/TbN</font></p> <p align="center"><font face="Tahoma">TbSp = (1-BV/TV)/TbN</font></p> <p align="justify"><font face="Tahoma">Distance transformation techniques also enable the calculation of intra-individual distribution of separation (TbSp SD, μm) quantified bt the umeber of Standard Deviation (SD) of the separation mean, a parameter reflecting the heterogeneity of trabecular network.</font><font face="Tahoma">For follow-up measurements, an algorithm automatically uses the cross-sectional area (CSA, mm<sup>2</sup> ) within the periosteal boundary of the radius and tibia to match the volumes of interest (VOI) on the baseline and fllow-up scans, and thus only the bone volume common to previous scans is used to assess density and microarchitectural measurements.</font><font face="Tahoma">Thus, of the initial 110 slices, on average 103 (range 93 to 108) were analyzed in the follow-up scans.</font></p> <p align="justify"><font face="Tahoma">The outcome variables used in this analyses included volumetrical bone density (gHA/cm<sup>3</sup>) for entire (D<sub>tot</sub>), trabecular (D<sub>trab</sub>), and cortical (D<sub>cort</sub>) regions; cortical thickness (CTh, μm), trabecular bone volume fraction (BV/TV, %), trabecular thickness (TbTh, μm), trabecular number (TbN*, mm<sup>-1</sup>), trabecular separation (TbSp, μm), and intra-individual distribution of separation (TbSp SD, μm).</font></p> <p align="justify"><font face="Tahoma">Interestingly trabecular and cortical densities obtained with HR-pQCT are only moderately related to each other and trabecular density is strongly correlated to trabecular achitectural measurements at both distal radius and tibia. </font><font face="Tahoma">On the contrary, <u>cortical density is higly correlated with cortical thickness</u> but weakly correlated with trabecular architecture <u>in normal subject</u>.</font><font face="Tahoma">Postmenopausal osteopenic and osteoporotic women show density and architectural parameters significantly different, <b>with the exception of cortical density</b>. Compared with those classified as osteopenic, osteoporotic women have lower bone density, decreased trabecular number and trabecular thickness, increased trabecular separartion and intra-individual distribution of separation, and <b>decreased cortical thickness. </b></font><font face="Tahoma">Osteopenic women with and without an <b>history of fracture</b> did not differ with regard to BMD (measured with classic Hologic densitometr) at lumbar spine and femoral neck, nor in HR-pQCT measurements at the distal tibia. However, <b>at the distal radius</b> density and architectural parameters were significantly different in women with an history of fracture compared with those with no previous fractures.</font><font face="Tahoma">In <b>men</b> trabecular bone volume declines similarly as women over life, however the microstructural basis for the decrease in trabecular volume differ between sexes. In women there appear to be loss of trabeculae with decrease in trabecular number and incresed intertrabecular space, whereas <b>in men the primary mechanism for the decrease in trabecular volume is trabecular thinning.</b></font></p> <p align="justify"><font face="Tahoma">This mechanism in turn is likely to have a significant impact on age related changes in bone strength in women compared to men, because the reduction in trabecular number has a 2 or 5 times greater impact on bone strength compared with reduction in trabecular thickness that result in similar decreases in bone volume.</font></p> <p align="center"><font face="Tahoma">Micro-finite element analysis using HR-pQCT</font></p> <p align="justify"><font face="Tahoma">Micro-finite element analysis (μFE) tecniques applied to HR-pQCT data sets provide an estimate of bone mechanical competence (stiffness) that distinguishes between groups of subjects with and without fractures.</font><font face="Tahoma">Each subvolume of HR-pQCT image oof the distal radius and distal tibia is converted to a micro-finite element (μFE) with an element size of 82 x 82 x 82 μm<sup>3</sup>.</font><font face="Tahoma">The HR-pQCT measurement, as writed above, include 116 slices, corresponding to a 9.02 mm sections along the axial skeleton, with a nominal voxel size of 82 μm.</font><font face="Tahoma">The mineralized phase was thresholded automatically, using Laplace-Hamming filter followed by a global threshold using a fixed value of 40% of the maximal grayscale value of the images.</font><font face="Tahoma">Using customized element-by-element pre-conditioned conjugate gradient solver, 6 μFEs were performed for each model, representing 3 uniaxial compression tests along 3 imaging axes and 3 uniaxial shear tests.</font><font face="Tahoma"><u>The trabecular bone tissue is considered as an isotropic</u>, linear elastic material with a Young’s modulus (E) of 15 Gpa and a Poisson’s ratio of 0.3 for all uniaxial model.</font><font face="Tahoma">The general anysotropic stifness of bone matrix is transformed into a new value through the calculation by means of appropriate algorithm, called Powell’s method, of full orthotopic stiffness tensor value by best orthotopic symmetry through the new chosed coordinate system formed by <u>chosed 3 orthotopic axes</u> ( X<sub>1</sub>, X<sub>2</sub>, X<sub>3</sub> ) representing the best orthotopic symmetry calculated using an optimization procedure.</font><font face="Tahoma">The elastic constants and stiffness matrix moduli were sorted so that E<sub>11</sub> was in the <u>medial-to-lateral direction</u> ( representing the lowest axial modulus), E<sub>22</sub> along the <u>antero-posterior direction</u>, whereas E<sub>33 </sub>was in the direction of the <u>highest axial direction.</u></font></p> <p align="justify"><font face="Tahoma">Finally 6 elastic moduli were derived from the orthotopic system tensor value:</font></p> <p align="justify"><font face="Tahoma">3 Young moduli: E<sub>11</sub> < E<sub>22 </sub>< E<sub>33</sub> for unaxial compression tests</font></p> <p align="justify"><font face="Tahoma">3 Shear moduli: G<sub>23</sub> < G<sub>31</sub> < G<sub>12</sub> for unaxial shear tests</font></p> <p align="justify"><font face="Tahoma">Several studies have reported that HR-pQCT parameters discriminate between postmenopausal women with and without fractures, whereas BMD by DEXA did not.</font><font face="Tahoma">Melton LJ III and Delmas PJ groups reported that decreased vBMD, microstructure, and stiffness estimated by μFE of the radius are associted with forearm fracture in postmenopausal women.</font><font face="Tahoma">Patients studied with postmenopausal osteopenia, radius but not tibia HR-pQCT measurements discriminated between those with and without fractures. It is also important because tibia is a weight bearing bone and it would be predicted that mechanical loading would result in a relative sparing at this site. </font><font face="Tahoma">The study by Cohen A. confirms these data by providing the evidence of cortical and trabecular microarchitectural deterioration at both radius and tibia in premenopausal women with idiopatic osteoporosis, whether or not they have had fracture.</font><font face="Tahoma">Estimated stiffness was significantly lower in all directions at both radius and tibia. Noteworthy was the finding that trabecular bone microachitecture and stiffness were severely affected at radial site in women with low BMD (measured with standard Hologic densitometry) who had an adult low trauma fracture.</font></p> <p align="center"><font face="Tahoma">Bisphosphonates</font></p> <p align="justify"><font face="Tahoma">The excessive suppression of bone remodeling by high doses of bisphosphonates is thought to compromise bone integrity by accumulation of microdamage (microcraks).</font><font face="Tahoma">However,the microdame ge accumulation has been demonstrated to peak during early period of high dose bisphosphonate treatment and the drugs does not continue to accumulate with longer treatment periods, Determinats of bone strength including ultimate load, stiffness, anergy to failure as well’s other material properties including bone maximum stress and modulus have been shown to be unaffected and preserved after three years of daily alendronate treatment also in preclinical animal models.</font><font face="Tahoma">The role of other material properties has been found to be altered by bisphosphonate treatment but they role in alteration of fracture stiffness is less evident. We talk mainly of alterations of bone mineralization quality, collagen ultrastructural quality, and mineral hydroxyapatite quality. </font><font face="Tahoma">Concerning the possible role of increased quantity of mineralized bone it is quite clear that higher bone mineralization is beneficial in increasing bone stiffness and reducing the incidence of new fractures at any site. The report of possible brittleness of new bone formed and the increasing report of new subtrochanteric and mid shaft femur fractures have not be considered osteoporotic fractures, so not related to disease treated by bisphosphonates, but related to intensity work load in a possible normal bone.</font></p> <p align="justify"><font face="Tahoma">The change in bone tissue is more likely caused by larger accumulation of advanced glycation end-products, called AGEs and directly related to increased glucose levels.</font><font face="Tahoma">AGEs are the by-products of the formation of collagen cross-links by non-enzymatic processes, and naturally accumulates in bone as it ages. Undernormal bone turnover rates, AGEs are prevented from accumulating to high levels. When bone turnover is suppressed, however, they can accumulate, and laboratory studies show them to be associated with increased brittleness.</font><font face="Tahoma">The micro-damage accumulation, and possibly the build-up of AGEs in the bone extracellular matrix, can only be reversed by bone anabolic agents such as teriparatide.</font></p> <p align="justify"><font face="Tahoma">Intravenous BPs and in particular zolendronic acid may be associated with hypocalcemia, renal toxicity, and an acute phase reaction with flulike symptoms during drugs infusion. The latter is thought to be due to extraskeletal effects of aminobisphosphonates, the release of cytokines from macrophages, and the activation of T lymphocytes linking to γδ T cell receptor (see NEJM letter).</font><font face="Tahoma">Accordingly, aminobisphosphonats, and in particular zolendronic acid, may also induce apoptosis in breast cancer cells, although the clinical relevance of this effect is not clear.</font><font face="Tahoma">We know that bone remodelling is a process involving T lymphocytes, bone marrow stromal cells, machrophages (antigen presenting cells) in a complex signalling pathway involving the activation of osteocytes, osteoblasts and finally osteoclasts through a signaling sequences very complexes and those more intensely studied require TNF alfa related factors and their receptors (RANK/RANKL/OPG). So that in any changes of bone turnover level a true inflammatory-like pathway is activated at bone marrow-trabecular interfaces.</font></p> <p align="justify"><font face="Tahoma">According to my opinion all side-effects founded in long term studies using bisphosphonates and in particular after their parenteral administration one a months or yearly is due to an increase in local inflammatory tissutal answer, finally accounting for:</font></p> <ol> <li> <div align="justify"><font face="Tahoma">Osteonecrosis of the jaw (ONJ)</font></div> </li> <li> <div align="justify"><font face="Tahoma">Atrial Fibrillation (AF)</font></div> </li> <li> <div align="justify"><font face="Tahoma">Esophageal cancer</font></div> </li> <li> <div align="justify"><font face="Tahoma">Musculoskeletal pain</font></div> </li> <li> <div align="justify"><font face="Tahoma">Atypical fractures due to increased skeletal fragility at diaphyseal or subtrochanteric femur regions.</font></div> </li> </ol> <p align="justify"><font face="Tahoma">Since late 2003 there have been reports in the literature of a possible association between bisphosphonate use and the appearance of avascular necrosis of the jaw. Marx on 2003 described a group of 36 American patients who received either pamidronate or zoledronate iv for the management of bone disease associated with metastatic cancer, multiple myeloma and osteoporosis and who subsequently developed avascular necrosis of the jaws. In the majority of patients, the latter condition developed after dental extraction, but in about 30% of cases, it apparently occurred spontaneously.</font></p> <p align="justify"><font face="Tahoma">Bisphosphonates related osteomyelitis (BON) and necrosis of the jaw possibly results from the inability of hypodynamic and hypovascular bone to meet an increased demand for repair and remodeling owing to physiological stress (mastication), iatrogenic trauma ( tooth extraction or denture induced local injury ), or tooth infection in a environment that is both trauma intense and plenty of bacteria.</font><font face="Tahoma">Cofactors may include the use of other medications with antiangiogenic properties such as glucocorticoids, diabetes mellitus, irradiation of jaw bone, peripheral vascular disease, hyperviscosity syndrome such as in multiple myeloma.</font><font face="Tahoma">Bisphosphonate related osteomyelitis (BON) is a true bone infection due to direct effect of bisphosphonates on bone turnover and subsequent physiolgical reaction even more increased if we look at region with increased work load and stress such as daily work activity we spend during mastication. A great work load per cm square is exerted on oral cavity bones so that these bone regions require a very intense answer by extracellular matrix structures.</font></p> <p align="justify"><font face="Tahoma">Concerning the presence of Advanced glycation end products, we know that increasing the concentration of glucose, the link of glucose to all proteins present in our body increases from hemoglobin to proteins present in the ocular structures (both cornea and retinal epithelial cells). Glycation reactions changes the biochemical properties of enzymatic proteins, or receptor proteins, or structural proteins such as collagen fibers. We can postulate that also the presence of increased Atrial Fibrillation should be attributed to altered glycations and expression at myocardial level of proteins forming ion channels, and in the presence of altered calcium homeostasis ( as we have during osteoporotic bone resorption) we have an increased probability to develop myocardial depolarizarion leading finally to Atrial Fibrillation.</font><font face="Tahoma">Cellular electrophysiolgical studies have revealed a marked reduction in the densities of L-type volatage gated Calcium channels, transient outward Potassium currents, and ultrarapid delayed rectifier Potassium currents in atrial myocites of patients affected by Atrial Fibrillation.</font><font face="Tahoma">Interestingly similar ( but not identical ) changes are present in canine models of Atrial Fibrillation, where changes in ions currents are correlated with reduced expression of the underlying channels forming subunits.</font><font face="Tahoma">In both human and canine Atrial Fibrillation, reduced Calcium voltage currents seem to be enought to explaine the reduction action potentials in duration and effective refractory period characteristics of remodelling atria.</font><font face="Tahoma">In addition the sarcoplasmic expression of Calcium dependent ATPase is reduced in myocites, suggesting that calcium cycling is affected in atrial fibrillated myocites.</font></p> <p align="justify"><font face="Tahoma"></font></p> <p align="justify"><font face="Tahoma">References</font></p> <p align="justify"><font face="Tahoma">Seeman E, Delmas PD. Bone quality – The material and structural basis of bone strength and fragility. N Engl J Med 2006;354:2250-61.</font></p> <p align="justify"><font face="Tahoma">Watts NB, Diab DL. Long term use of bisphosphonates in osteoporosis. J Clin Endocrinol Metab 2010;95:1555-65.</font></p> <p align="justify"><font face="Tahoma">Liberman UA, Weiss SR, Bröll J et al. Effects of oral alendronate on bone mineral density and the incidence of fractures in postmenopausal osteoporosis. The Alendronate Phase III Osteoporosis Treatment Study Group. N Engl J Med 1995;333:1437-43.</font></p> <p align="justify"><font face="Tahoma">Orwoll E, Ettinger M, Weiss S et al. Alendronate for the treatment of osteoporosis in men. N Engl J Med 2000;343:604-10.</font></p> <p align="justify"><font face="Tahoma">Reid IR, Brown JP, Burkhardt P et al. Intravenous Zolendronic acid in postmenopausal women with low bone mineral density. N Engl J Med 2002;346:653-61.</font></p> <p align="justify"><font face="Tahoma">Bone HG, Hosking D, Devogelaer JP et al. Ten years experience with alendronate for osteoporosis in postmenopausal women. N Engl J Med 2004;350:1189-99.</font></p> <p align="justify"><font face="Tahoma">Black DM, Delmas PD, Eastell R et al. for the HORIZON Pivotal Fracture Trial. Once-yearly zolendronic acid for treatment of postmenopausal osteoporosis. N Engl J Med 2007;356:1809-22.</font></p> <p align="justify"><font face="Tahoma">Cummings SR, Schwartz AV, Black DM. Alendronate and atrial fibrillation. N Engl J Med 2007;356:1895-6.</font></p> <p align="justify"><font face="Tahoma">Lyles KW, Colòn-Emeric CS, Magaziner JS et al. HORIZON Recurrent fracture trial. Zolendronic acid and clinical fractures and mortality after hip fracture. N Engl J Med 2007;357:<a dir="ltr" href="tel:1799-809" x-apple-data-detectors="true" x-apple-data-detectors-type="telephone" x-apple-data-detectors-result="4">1799-809</a>.</font></p> <p align="justify"><font face="Tahoma">Lenart BA, Lorich DG, Lane JM. Atypical fractures of the femoral diaphysis in postmenopausal women taking alendronate. N Engl J Med 2008;358:1304-6.</font></p> <p align="justify"><font face="Tahoma">Weinstein RS, Roberson PK, Manolagas SC. Giant osteoclast formation and long term oral bisphosphonate therapy. N Engl J Med 2009;360:53-62.</font></p> <p align="justify"><font face="Tahoma">Black DM, Kelly MP, Genant HK et al. Bisphosphonates and fractures of the subtrochanteric or diaphyseal femur. N Engl J Med 2010;362:1761-71.</font></p> <p align="justify"><font face="Tahoma">Shane E. Evolving data about subtrochanteric fractures and bisphosphonates. N Engl J Med 2010;362:1825-7.</font></p> <p align="justify"><font face="Tahoma">Allen MR, Burr DB. Three years of alendronate treatment results in similar levels of vertebral microdamage as after one year of treatment. J Bone Miner Res 2007;22:1759-65.</font></p> <p align="justify"><font face="Tahoma">Allen MR, Gineyts E, Leeming DJ et al. Bisphosphonates alter trabecular bone collagen cross-linking and isomerization in beagle dog vertebra. Osteoporosis Int 2008;19:329-337.</font></p> <p align="justify"><font face="Tahoma">Saito M, Mori S, Mashiba T et al. Collagen maturity, glycation induced-pentosidine, and mineralization are increased following 3 yeras treatment with incadronate in dogs. Osteoporosis Int 2008;19:1343-54.</font></p> <p align="justify"><font face="Tahoma">Wang X, Shen X, Li X et al. Age-related changes in the collagen network and toughness of bone. Bone 2002;31:1-7.</font></p> <p align="justify"><font face="Tahoma">Khamaisi M, Yarom N, Avni B et al. Possible association between diabetes and bisphosphonate-related jaw osteonecrosis. J Clin Endocrinol Metab 2007;92:1172-5.</font></p> <p align="justify"><font face="Tahoma">Aviles RJ, Martin DO, Apperson-Hansen C et al. Inflammation as a risk factor for atrial fibrillation. Circulation 2003;108:3006-10.</font></p> <p align="justify"><b><font face="Tahoma"></font></b></p> <p align="justify"><b><font face="Tahoma">HR-pQCT</font></b></p> <p align="justify"><font face="Tahoma">Muller R, Hildebrand T, Ruegsegger P. Non-invasive bone biopsy: a new method to analyse and display the three-dimensional structure of trabecular bone. Phys Med Biol 1994;39:145-64.</font></p> <p align="justify"><font face="Tahoma">Van Rietbergen B, Weinans H, Huiskes R et al. A new method to determine trabecular elastic properties and loading using micromechanical finite-element model. J Biomech. 1995;28:69-81.</font></p> <p align="justify"><font face="Tahoma">Laib A, Hildebrand T, Houselmann HJ et al. Ridge number density: a new parameter for in vivo bone structure analysis. Bone 1997;21:541-46.</font></p> <p align="justify"><font face="Tahoma">Laib A, Hauselmann HJ, Ruegsegger P. In vivo high resolution 3D-QCT of the human forearm. Technol Health Care 1998;6:329-37.</font></p> <p align="justify"><font face="Tahoma">Laib A, Ruegsegger P. Comparison of structure extraction methods for in vivo trabecular bone measurements. Comput Med Imaging Graph 1999;23:69-74.</font></p> <p align="justify"><font face="Tahoma">Laib A, Ruegsegger P. Calibration of trabecular bone structure measurements of in vivo three-dimensional peripheral quantitative computed tomography with 28-micron-resolution microcomputed tomography. Bone 1999;24:35-39.</font></p> <p align="justify"><font face="Tahoma">Ulrich D, van Rietbergen B, Laib A et al. The ability of three dimensional structural indices to reflect mechanical aspects of trabecular bone. Bone 1999;25:55-60.</font></p> <p align="justify"><font face="Tahoma">Boutroy S, Bouxsein ML, Munoz F et al. In vivo assessment of trabecular bone microarchitecture by high resolution peripheral quantitative computed tomography. J Clin Endocrinol Metab 2005;90:6508-15.</font></p> <p align="justify"><font face="Tahoma">Khosla S, Riggs BL, Robb RA et al. Relationship of volumetric bone density and structural parameters at different skeletal sites to sex steroid level in women. J Clin Endocrinol Metab 2005;90:<a dir="ltr" href="tel:5096-5103" x-apple-data-detectors="true" x-apple-data-detectors-type="telephone" x-apple-data-detectors-result="6">5096-5103</a>.</font></p> <p align="justify"><font face="Tahoma">Khosla S, Melton LJ III, Robb RA et al. Relationship of volumetric BMD and structural parameters at different skeletal sites to sex steroid level in men. J Bone Miner Res 2005;20:730-40. </font></p> <p align="justify"><font face="Tahoma">Khosla S, Riggs BL, Atkinson EJ et al. Effects of sex and age on bone microstructure at the ultradistal radius: a population based noninvasive in vivo assessment. J Bone Miner Res 2006;21:124-31.</font></p> <p align="justify"><font face="Tahoma">Melton LJ 3<sup>rd</sup>, Riggs BL, van Lenthe GH et al. Contribution of in vivo structural measurememnts and load/strength ratios to the determination of forearm fracture risk in postmenopausal women. J Bone Miner Res 2007;22:1442-8.</font></p> <p align="justify"><font face="Tahoma">Boutroy S, Van Rietbergen B, Sornay-Rendu E et al. Finite element analysis on in vivo HR-pQCT images of the distal radius is associated with wrist fracture in postmenopausal women. J Bone Miner Res 2008;23:392-9.</font></p> <p align="justify"><font face="Tahoma">Macneil JA, Boyd SK. Bone strength at the distal radius can be estimated from high-resolution peripheral quantitative tomography and the finite element method. Bone 2008;42:1203-13.</font></p> <p align="justify"><font face="Tahoma">Cohen A, Liu S, Stein EM et al. Bone microarchitecture and stiffness in premenopausal women with idiopatic osteoporosis. J Clin Endocrinol Metab 2009;94:4351-60.</font></p> <p align="justify"><font face="Tahoma">Wren TAL, Gilsanz V. Evolving role of imaging in the evaluation of bone structure. J Bone Miner Metab 2009;24:1943-45.</font></p> <p align="justify"><font face="Tahoma">Burghardt AJ, Kazakia GJ, Ramachandran S et al. Age and gender related differences in the geometric properties and biomechanical significance of intracortical porosity in the distal radius and tibia. J Bone Miner Res 2010;25:983-93.</font></p> <p align="justify"><font face="Tahoma">Smith RW, Walker RR. Femoral expansion in aging women: implications for osteoporosis and fractures. Science 1964;145:156-7.</font></p> <p align="justify"><font face="Tahoma">Ruff CB, Hayes WC. Subperiosteal expansion and cortical remodeling of the human femur and tibia with aging. Science 1982;217:945-8.</font></p> <p align="justify"><font face="Tahoma">Currey JD, Pitchford JW, Baxter PD. Variability of mechanical properties of bone, and its evolutionary consequences. J R Soc Interface 2007;4:127-35.</font></p> <p align="justify"><font face="Tahoma"> </font></p> <p align="justify"><font face="Tahoma"></font></p> BoNewshttp://www.blogger.com/profile/14996032718916828654noreply@blogger.comtag:blogger.com,1999:blog-6459801161644965909.post-9825197466303420252010-04-14T20:13:00.001+02:002016-04-25T21:35:33.064+02:00FGFs : New player in bone metabolism.<h3 align="justify"><b><font size="3" face="Verdana"></font></b></h3> <p align="justify"><a href="http://lh6.ggpht.com/_FLe5Kbctaeg/S51hLW8LVnI/AAAAAAAACuo/HuXyeelJ4KI/s1600-h/image0-1%5B5%5D.jpg"><font color="#000000" face="Verdana"></font></a></p> <p></p> <p></p> <p></p> <h3 align="center"><b><font size="3" face="Verdana"></font></b></h3> <h3 align="center" style="text-align: start;"><font color="#000000" style="font-weight: normal; font-size: 17px; -webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);"> </font><span style="font-family: 'Helvetica Neue Light', HelveticaNeue-Light, helvetica, arial, sans-serif; font-size: 17px; font-weight: normal;"> </span></h3> <h3 align="center"><b><font size="3" face="Verdana"><div class="separator" style="clear: both;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhVePll6k5InM4LVrdMibZrLCGhyphenhyphenHc_d4LmMpJ71zs8NfF-fndaYoZsMrcOLd4uBrdfaVmQ8ljBpAXHmPwjtkXlucZQ4WyF0dB_PTF9NvdLiNiioBb-YI53gVAtdDnrxnvRxzK37Rs0wxIj/s640/blogger-image--610584377.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhVePll6k5InM4LVrdMibZrLCGhyphenhyphenHc_d4LmMpJ71zs8NfF-fndaYoZsMrcOLd4uBrdfaVmQ8ljBpAXHmPwjtkXlucZQ4WyF0dB_PTF9NvdLiNiioBb-YI53gVAtdDnrxnvRxzK37Rs0wxIj/s640/blogger-image--610584377.jpg"></a></div> </font></b></h3><h3 align="center"><b><font size="3" face="Verdana">Rickets</font></b></h3> <p align="justify"><font face="Verdana">Old English term for Rickets was “Wrickken“ as described by Glisson F, Bate G and Regemorter A on 1651 as a common disease present in children. Near 350 years have been elapsed since the first monograph publication on wrickken and many spectacular advances in our understanding of Vitamin D dependent metabolism have enriched our knowledge wallet.</font></p> <p align="justify"><font face="Verdana">Last century was plenty of relevant discoveries from isolation of nuclear receptor for Vitamin D, identification of metabolic pathways of vitamin D synthesis, activation and degradation, until to isolation of genes coding for enzymes and co-factors as well’s hormonal factors involved into vitamin D cycle.</font></p> <p align="justify"><font face="Verdana">We can define rickets the defect in bone mineralization leading to formation of a normal bone matrix whithout deposition of calcium salts. Anatomically speaking this alteration in bone structure is called “osteomalacia”, whereas clinically propension to multiple fractures, short stature, bone deformities and renal alterations are often found. Initially the defect was ascribed to a loss of vitamin D expecially in young adults presenting lower exposure to sunlight; later it was clear that different forms of rickets are present; some involving abnormalities in vitamin D metabolism, other involving renal cells alterations.</font></p> <p align="justify"><font face="Verdana">It’s quite surprising that the horthologues of oncogenes designed such as “Interruptor-1” and “Interruptor-2” have been demonstrated to be involved into phosphate homeostasis. Int-1 is Wnt family growth factors, whereas Int-2 is FGFs family growth factor; both are very important in molecular embriology influencing cellular condensation and diffusion. Phosphate ions with carbon and azote ions, can be considered the base for live organisms in the earth, forming the backbone of all biomolecular structures. It is surprising that a so higly conserved and sophysticated biochemical pathway has been created to conserve adequate levels of phosphate in our organisms.</font></p> <p align="justify"><font face="Verdana">Interestingly<i>, it is not at present clear the relation between bone loss and kidney stone formation.</i> Excessive bone reabsorption clearly leads to hypercalciuria and hyperphsophaturia for example by excessive production of parathyroid hormone or vitamin D3. Excessive increase in urinary calcium excretion from bone can also be observed in osteogenesis imperfecta and in McCune-Albright syndrome; however, nephrolithiasis is very rare in these disorders. </font></p> <p align="justify"><font face="Verdana">On the other side, many studies have reported lower bone density in renal calcium stone formers compared to controls. The mechnisms underlying these findings is not clear, but may involve hyper responsiveness to calcitriol or to parathormone or bone abnormalities. However, low bone density in calcum stome formers has not been associated with increased bone resorption or with any gene mutations or polymorphisms. </font></p> <p align="justify"><font face="Verdana">According to my opinion, whereas osteoporotic bone disease can be truly considered an alteration of bone cells, osteomalacia (rickets) is better considered a bone symptom of a kidney disease. In the first situation we have altered bone turnover due to alterations of bone regulatory factors, in the second we have bone disease as secondary and sporadic manifestation of primary kidney disease.</font></p> <p align="justify"><font face="Verdana">Among the causes of defects of inadequate mineralization of bone (osteomalacia) and defective mineralization of cartilage (rickets) are renal phosphate wasting disorders that produce hypophosphatemia.</font></p> <p align="justify"><b><font face="Verdana">Kidney stones</font></b></p> <p align="justify"><font face="Verdana">Urinary PH determines the solubility of various substances in urine, Low PH decreases uric acid solubility but prevents calcium-phosphate crystal formation in contrast to a PH > 7 that augments urate solubility but precipitates calcium-phosphate salts. Urinary PH depends on the proton load in the diet and on the ability of kidney to buffer free proton in the urine. Renal acidosis is due to a defect of the renal tubule in secreting protons while buffers are normally produced, resulting in urinary PH > 5.5 and in metabolic acidosis. Patients with renal acidosis frequently have hypercalciuria and hyperphosphaturia. This may be due to calcium and phosphate release from bone because of proton buffering by bone.</font></p> <p align="justify"><font face="Verdana">Nephrolithiasis and nephrocalcinosis are frequent in these disorders. Distal renal acidosis is due to mutations in the chloride-bicarbonate exchanger or in proton ATP ase subunits.</font></p> <p align="justify"><font face="Verdana">Uric acid</font></p> <p align="justify"><font face="Verdana">Uric acid stones are less frequent than calcium stones and they represent 5 to 10% of nephrolithiasis. Uric acid is the final breakdown product of purine metabolism and it also derives from amino acid catabolism. Two-third of uric acid production are eliminated by the kidneys in humans. Uric acid is filtered at the glomerulus and then it is almost completely reabsorbed in the initial part of the proximal tubule by at least two transporters, called URAT1 , coded by gene SLC22A12) and GLUT9 ( coded by gene SLC2A9). A member of the ATP binding cassette family (ABCG2) is expressed in proximal tubular cells and secretes urate into the urine. </font></p> <p align="justify"><font face="Verdana">Two factors increase the risk of uric acid stone formation: low PH and hyperuricosuria. Genetic disorders can increase uric acid production or alter urate tubular transport. An increase in uric acid production induces hyperuricemia, as in the case of hypoxantine-guanine- phosphorybosyl transferase or in glucose-6-phosphatase deficiencies, and in phosporybosyl pyrophosphatase synthetase over-activity.</font></p> <p align="justify"><font face="Verdana">In contrast mutations in urate transporters result in hypouricemia and hyperuricosuria. Hence loss-of-function mutations in the URAT1 transporter decrease urate reabsorption in the proximal tubule. Functional experiments demonstrated that SLC9A2, is expressed at the apical and basolateral sides of proximal tubular cells, it transport urate, and that polymorphisms decrease urate reuptake increasing uric acid secretion in urine.</font></p> <p align="justify"><font face="Verdana">Inactivating mutations in tha ABCG2 gene have been identified as cause of gout increasing uric acid concentration in plasma. </font></p> <p align="justify"><font face="Verdana">Oxalate</font></p> <p align="justify"><font face="Verdana">Elevatd urinary oxalate excretion is critical for the growth of renal stones, Oxalate comes from the diet and it is produced by the liver and arythrocytes from glyoxalate. It is filtered freely at the glomerulus and probably reabsorbed ad then secreted in the proximal tubule. In the intestine, oxalate is also absorbed and secreted, but absorption exceeds secretion.</font></p> <p align="justify"><font face="Verdana">Enzymatic defects (primary hyperoxalurias) can induce oxalate overproduction. </font></p> <p align="justify"><font face="Verdana">The gene SLCA26A6 encodes an oxalate-chloride exchanger that is expressed in the intestine and in the renal proximal tubule. The disruption of this gene in mice results in an increase in oxalate plasma concentration, hyperoxaluria and renal calcium oxalate stone formation. The role of SLC26A6 is probably to secrete oxalate in feces. Its role in proximal tubule is not clear. Mutations in this gene have not been identified in humans.</font></p> <p align="justify"><b><font face="Verdana">Claudins</font></b></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><font face="Verdana">The selecive permeability of the intercellular unctions to calcium and magnesium ions is due to expression of claudin-16 , also known such as paracellin. This protein acts as a specific gate for clacium and magnesium. Mutations in claudin 16 abolished the permeability of the intercellular pathway to calcium, and are a rare cause of hypercalciuria, hypomagnesemia and calcium renal stones.</font></p> <p align="justify"><font face="Verdana">Variants of the gne enchoding claudin 14 have recently been asociated with kidney stones and low bone mineral density in a genome wide association study performed in patients from the Netherlands, Iceland, and Denmark, Claudin 14 is a tight junction protein expressed in the proximal tubule and in the loop of Henle. The mechanism by which these variants are associated with renal stones is unclear since they were not associated with calcium or phosphate concentration in plasma or urine, but only associted with serum PTH and bone markers.</font></p> <p align="justify"><font face="Verdana"></font></p> <p align="center"><font face="Verdana"><strong>OSTEOMALACIA</strong></font></p> <p align="justify"><font face="Verdana"><strong>Vitamin D metabolism abnormalities</strong></font></p> <p align="justify"><font face="Verdana">Rickets-Vitamin-D-dependent-type-I </font><font face="Verdana">1ahydroxylaseD3 (Ch12q14)</font></p> <p align="justify"><font face="Verdana">Rickets-Vitamin-D-dependent-type-II Vit.-D receptor (Ch12q13-14)</font></p> <p align="justify"><font face="Verdana">Rickets-PseudoVitamin-D-deficiency 1ahydroxylaseD3(Ch12q13.3) point mutation </font></p> <p align="justify"><font face="Verdana"><strong>Kidney Proximal tubular defect</strong></font></p> <p align="justify"><font face="Verdana">Rickets hypophosphatemic with Hypercalciuria NTP2c gene (HHRH)(NPT2 genes Ch5q35.1-q35.3)</font></p> <p align="justify"><font face="Verdana">Autosomal dominant hypophosphatemic Rickets FGF23 gene (ADHR) OMIM 193100 of the young (Ch.12p13.3) </font></p> <p align="justify"><font face="Verdana">X Linked Hypophosphatemic Richets PHEX gene (HYP) like OMIM adult female (Ch. Xq22.1)</font></p> <p align="justify"><font face="Verdana">Tumor Induced Osteomalacia FRP4 gene(OHO) (Ch.7q14.1)</font></p> <p align="justify"><font face="Verdana">Hyperphosphatemic Familial Tumoral Calcinosis KLOTHO (HFTC) OMIM 21900</font></p> <p align="justify"><font face="Verdana">Hypeostosis-hyperphosphatemia syndrome GALNT3 (HHS) OMIM 610233</font></p> <p align="justify"><font face="Verdana">Renal Tubular Acidosis type II NPT2a gene (Fanconi’s Syndrome) (Ch5q35.1-q35.3)</font></p> <p align="justify"> </p> <h4 align="justify"><font face="Verdana">Distal tubular defect</font></h4> <p align="justify"><font face="Verdana">Renal-Tubular-Acidosis-type-I Basolateral-</font><font face="Verdana"> Cl/HCO3 </font><font face="Verdana">(RTA Distal) Proton-ATPase</font></p> <p align="justify"><font face="Verdana">Hyperkalemic RTA type IV Hyporeninemic Hyperaldosteronism</font></p> <p align="justify"><font face="Verdana">Bartter’s syndrome Na-K-2Cl transporter mutation</font></p> <p align="justify"><font face="Verdana">(Henle loop hyperca) K channel-calcium sensing receptor</font></p> <p align="justify"><font face="Verdana"> Chloride channel (CICKa-b)-Barttrin</font></p> <p align="justify"><font face="Verdana">Gitelman’s syndrome Na-Cl transporter thiazide sensitive</font></p> <p align="justify"><font face="Verdana">(distal hyperca)</font></p> <p align="justify"><font face="Verdana">Dent’s disease Voltage gated Chloride channel</font></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><strong><font face="Verdana"></font></strong></p> <p align="justify"><strong><font face="Verdana"></font></strong></p> <p align="center"><b><font face="Verdana">INHERITED BONE DISEASES</font></b></p> <p align="center"><strong><font face="Verdana"></font></strong></p> <p align="justify"><font face="Verdana">Autosomal dominant Aplasia of FGF10 gene</font></p> <p align="justify"><font face="Verdana">Lacrimal and Salivary glands</font></p> <p align="justify"><font face="Verdana"></font></p> <p align="justify"><font face="Verdana">Autosomal dominant Cerebellar FGF14 gene</font></p> <p align="justify"><font face="Verdana">Ataxia</font></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><font face="Verdana"><b></b></font></p> <p align="justify"><font face="Verdana"><b>Craniosynostosis disorders</b> FGFR type 2 (Pro250X)</font></p> <p align="justify"><font face="Verdana"><b>Achondroplasia </b>FGFR type 3<b> </b>(Ch4p16.3)<b> </b></font></p> <p align="justify"><font face="Verdana"><b>Hypochondroplasia </b>FGFR type 3<b></b></font></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><font face="Verdana"><b>Spondyloepiphyseal dysplasia</b> * FGFR type 3 stop codon</font></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><font face="Verdana"><b>Stickler syndrome</b> * FGFR type 3 Lys650Glu</font></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><font face="Verdana">*thanatophoric dysplasia type I and type II.</font></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><font face="Verdana"><b>Pfeiffer syndrome</b> FGFR type 1 Pro252Arg</font></p> <p align="justify"><font face="Verdana"><b>Apert syndrome</b> </font><font face="Verdana">FGFR type 2 Pro253Arg</font></p> <p align="justify"><font face="Verdana"><b>Muenke craniosynostosis</b> FGFR type 3 Pro 250Arg</font></p> <p align="justify"><font face="Verdana"><b>Crouzon syndrome</b> FGFR type 2 Cys342Arg</font></p> <p align="justify"><font face="Verdana"><b>Jackson-Weiss syndrome</b> FGFR type 2 Cys342Arg</font></p> <p align="justify"><font face="Verdana"></font></p> <p align="justify"><font face="Verdana"></font></p> <p align="justify"><font face="Verdana"></font></p> <p align="justify"><font face="Verdana">Phosphate wasting is either inherited as X-linked hypophosphatemic rickets or autosomal dominant hypophosphatemic rickets, or acquired, as can occur in patients with a variety of benign mesenchimal tumors such as hemangiopericytomas, fibromas, angiosarcomas. Osteomalacia induced by tumors is invariably curable if the tumor can be found and resected, indicating that it may have an humoral basis. </font><font face="Verdana">However the pathogenesis of rachitic syndromes requires also defective mineralization coupled with phosphate wasting.</font></p> <p align="justify"><font face="Verdana">Phosphatonins have been demonstrated to be able to impair the action of kidney 1a hydroxylasis, activating 24-hydroxylasis, and mediating the parathyroid action on many cell types, including kidney proximal cells.</font></p> <p align="justify"><font face="Verdana">However no clear action at bone forming units has been at present demonstrated by “phosphatonins” per se.</font></p> <p align="justify"><font face="Verdana"></font></p> <p align="center"><b><font face="Verdana">NPT2 and NHERF</font></b></p> <b></b> <p align="justify"><font face="Verdana">We are understanding the mechanisms exerted by epithelial scaffold proteins in regulation of renal phosphate handling. These PDZ-containing proteins are able to form macromolecular complexes with true Na/Pi channels. </font></p> <p align="justify"><font face="Verdana">Called Na<sup>+</sup>/H<sup>+</sup> Exchangers Regulatory Factor (NHERFs), they are known to be present on apical microvillar structure (NHERF1) or at the base of microvilli in the vescicle rich domains (NHERF2). They are ancillary cytoplasmic proteins, responsive to hormonal stimulation such as parathyroid hormone, and directing the localization of ion channel proteins (NPT2) at specific sites of cellular membrane. Their action has been demonstrated for microvillar apical membrane of proximal kidney tubular cells, but they probably, as PDZ-containing proteins, are ubiquitariously active in regulating the activity, internalization and recycling, of true receptors. </font></p> <p align="justify"><font face="Verdana">Their action is strictly dependent from transmembrane potential and finally from different concentration of sodium and potassium ions outside and inside cells respectively. As we know cell life is linked to the presence of this different concentration, allowing the formation of true concentration gradient across a lipid bilayer.</font></p> <p align="justify"><font face="Verdana">Moreover they are co-responsive of the presence of a difference in proton concentration (i.e.PH) across plasmamembrane. The PH difference across lipid bilayer between inner and extracellular fluid account for a different solubility or organic and inorganic salts as well’s of cathalization of enzymatic reactions possible only at a given PH.</font></p> <p align="justify"><font face="Verdana">Finally, these apparent unuseful PDZ-containing proteins should give the life to an inhert lipid bilayer; making it responsive to extracellular hormonal signals and so orchestrating the action of an uncohordinated lipid structure.</font></p> <p align="justify"><font face="Verdana">Their presence at specific sites of plasma membrane explaines the localization and activity of the products of SCL34A1 and SCL34A3 genes located on chromosome 5q35.1-35.3 and coding for (NPT2a) Na/Pi exchanger type IIa and (NPT2c) type IIc respectively. </font><font face="Verdana">The sodium-phosphate cotransporter NTP-2c is responsible for the bulk of phosphate reabsorption in proximal renal tubules and its alteration is the cause of <strong>hypophosphatemic rickets with hypercalciuria</strong>. </font><font face="Verdana">The putative “phosphatonin” should directly inhibit renal sodium-phosphate cotransporter.</font><font face="Verdana">NPT2c is the primary hormone – regulated renal phosphate transporter, localized at the apical membrane of cells of proximal tubule in each nephron. It accounts for 80% of sodium dependent phosphate reabsorption.</font><font face="Verdana">Interestingly dietary phosphate load causes a significant down-regulation of NPT-2c. </font></p> <p align="justify"><font face="Verdana">A distinct apical membrane sodium-phosphate cotransporter called NTP-2a is present in nephrons, sharing homologies with the former responsible for <strong>Proximal Renal Tubular Acidosis</strong> also called Fanconi’s Syndrome.</font><font face="Verdana">It is quite consequential that the phosphaturic action exerted by FGF23 at kidney level is done by a down-regulation or block of the action of NTP-2 gene products mediating the reabsorption of phosphate ions.</font></p> <p align="justify"><font face="Verdana">Hyp mice experiments, showing a 50% reduction in NPT2, and an increase in FGF23 can be a perfect example of what happen in phosphate wasting syndromes.</font></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="center"><b><font face="Verdana">FGF23</font></b></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><b><a href="http://lh3.ggpht.com/_FLe5Kbctaeg/S8YFpuxSgrI/AAAAAAAACxU/K0RWku6c5so/s1600-h/clip_image004%5B3%5D.jpg"><font color="#000000" face="Verdana"></font></a><a href="http://lh3.ggpht.com/_FLe5Kbctaeg/S8YFpuxSgrI/AAAAAAAACxY/CA6r7rSlHoI/s1600-h/clip_image004%5B8%5D.jpg"><img style="border-right-width: 0px; display: block; float: none; border-top-width: 0px; border-bottom-width: 0px; margin-left: auto; border-left-width: 0px; margin-right: auto" title="clip_image004" border="0" alt="clip_image004" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2AA1Ph2UTh30SGx_HpdXVp8hb6lLQjVYonEmtgFNBHmRD1sRFP0ncQLipo_JJ4q88LFElv4Ggrmr1XFOFkGvgEqZ9AdFiPpPvww-qL-Z4V9oZ3qq5pY8dRt9i-8wTfLmRWPegwNZVfRNq/?imgmax=800" width="401" height="605"></a></b></p> <p align="justify"><font face="Verdana">A paper of Shimada et al. on PNAS (2001) identifies a member of the fibroblast growth factor family, FGF23, as the humoral factor that is secreted by tumors to cause tumor-induced osteomalacia. They cloned a cDNA from a hemangiopericytoma that caused hypophosphatemic osteomalacia and found clones identical to FGF23, which was recently identified by positional cloning as the gene responsible for autosomal dominant hypophosphatemic rickets. When injected into mice the recombinant FGF23 produces mild phosphaturia and hypophosphatemia; interestingly Chinese Hamster Ovary (CHO) cells - FGF23, when grown as tumor in nude mice, fully reproduced the human syndrome of severe hypophosphatemia, growth retardation and rickets in the growth plates, deformities in the skeleton, reduced mineralized matrix and seems of unmineralized osteoid in bone. FGF 23 was expressed at high levels in the tumor from which it was cloned, and as recently reported by another group it is also expressed at high levels in other tumors associated with acquired osteomalacia. </font></p> <p align="justify"><font face="Verdana">Its expression in bone reach the highest level, in regions of active bone formation, a strong hybridization signal can be seen in osteoblasts lining bone surfaces. Newly formed osteocytes and osteoprogenitor cells are also labeled. In other tissues it has been detected in particular in parathyroid, thymus, brain, heart, and vascular system. If in the past some contraddictory results have been obtained it was due to difficulties in metods of measurements. In particular it is necessary to evaluate if we have to measure the entire FGF23 or only its biologically active portion, its C terminal (Ct) part.</font></p> <p align="justify"><font face="Verdana">With a 72 aa Ct domain not shared with other family members FGF23 is the largest member of the FGF family. Insight into its functions are provided by demostration that mutations caused hypophosphatemic rickets. Moreover it may seems more soluble that other family members lacking the heparing-binding motif presented in other FGFs.</font></p> <p align="justify"><font face="Verdana">Whyte KE demonstrated that four unrelated families had a missense mutations in one or two closely spaced arginine residues at position 176 and 179 that cosegregates with rickets, with two families sharing the same mutation. This clustering of missense mutations is a disorder with a dominant inheritance and strongly suggest a “gain of function mutation”.</font></p> <p align="justify"><font face="Verdana">Shimada et al demonstrated that arginine 179 and S180 is a processing site in FGF23, because they found in CHO cells expressing FGF23, in addition to the mature protein a fragmented protein beginning with S180. It is believed that mutations of the flanking arginine at position 179 could confer a gain of function on FGF23 by blocking its degradation at cleavage site between the unique Ct domain and the FGF-homologue regions.</font></p> <p align="justify"><font face="Verdana">FGF23 may be the long-sought “phosphatonin”, the phosphaturic factor normally accounting for phosphate homeostasis, independently from parathyroid hormone, so independently from calcium levels. It has been postulated that the main help to FGF23 secretion is the product between the concentration of Calcium and Phosphorus. So acquiring a relevance in regulation of ectopic calcifications such as those present in vascular system with aging.</font><font face="Verdana">It may be that FGF23 is also secreted by one or more normal tissues as a phosphate regulating hormone, and that the blood level of FGF23 in blood is determined in part by the rate of cleavage by Subtilisin-like proprotein convertase (SPC) at R179/S180. Two fragments are present an entire protein of 32 kDa and C terminal segment of 12 kDa.</font><font face="Verdana">On 2004 it was demonstrated the complete action of FGF23 on NTP2 renal cotransporter, giving the final answer to identification of FGF23 such as phosphatonin.</font></p> <p align="justify"><font face="Verdana">Quite recently a longitudinal study demonstrated that in dyalitic patients measurements of FGF23 plasma levels can be useful in assessing normo-phosphatemic patients who should benefits of therapeutic strategies devoted to manage phosphorus balance, considering that hyperphosphatemic hemodyalitic patients show an increased risk of death. This study suggests that hyperphosphatemia in these patients is only partially assessment of risk associated with abnormal phosphorus metabolism. However, <strong>measurement of FGF23</strong> could represent a new biomarker in assessing the risk of death in patients with <strong>early kidney disease</strong> (Wolf M. NEJM August 7, 2008).</font></p> <p align="justify"><br></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="center"><b><font face="Verdana">PHEX</font></b></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><font face="Verdana">The other piece of the hypophosphatemic puzzle is the X-linked hypophosphatemic rickets, the most common disorder of renal phosphate transporter.</font></p> <p align="justify"><font face="Verdana">PHEX belongs to the M13 family of MA clan of Zn-metalloendopeptidases. The prototypic member of this group of type of integral membrane glycoproteins is Neutral Endopeptidase (NEP). These proteins have a short cytoplasmic N-terminal region, a single transmembrane domain, and a large extracellular C-terminal domain with a zinc binding motif.</font></p> <p align="justify"><font face="Verdana">Other members of this group include:</font></p> <p align="justify"><font face="Verdana">. Endothelin Converting Enzyme-1 (ECE-1alfa, ECE-1beta and ECE-2)</font></p> <p align="justify"><font face="Verdana">. ECE-like enzyme/distress induced neuronal endopeptidase (ECEL1/DINE)</font></p> <p align="justify"><font face="Verdana">. Soluble Endopeptidase/NEP-like enzyme-1/Neprilysin-2 (NL1/NEP2)</font></p> <p align="justify"><font face="Verdana">. Membrane Matallo Endopeptidase-like 2 (MMEL-2)</font></p> <p align="justify"><font face="Verdana">. Kell Blood Group Protein antigen (KELL)</font></p> <p align="justify"><font face="Verdana">Neprilysin is aslo calle common acute lymphoblastic leukemia antigen (CALLA), or CD10, NEP, or Enkephilinase.</font></p> <p align="justify"><font face="Verdana">The M13 zinc metallo endopeptidases are integrally involved in several essential elements of cellular regulation and physiology as well’s in diseases including renal function defects, bone mineral loss disorder, cardiovascular diseases, arthritis nd inflammatory disorders.</font><font face="Verdana">In particular PHEX gene is similar to those of NEP family in several important aspects: numebrs of small exons (22 exons characterized for PHEX with a sequence of 749 aminoacids), higly conserved aminoacid Zinc binding motif (HEFTH fof PHEX, HEITH for NEP). </font></p> <p align="justify"><font face="Verdana">Informations concerning the structure and nature of the PHEX gene product catalytic site was acquired from the analysis of 99 families affected by X Linked Hypophosphatemic Richets (HYP) and compter generated physichemical data and site-directed mutagenesis studies published for M13 and M3 metallo peptidases.</font></p> <p align="justify"><font face="Verdana">Interestingly full lenght FGF23 and MEFE do not appear to be PHEX substrates. Remarkably PHEX protects full-leght MEPE from proteolysis, notably by catepsin B cleavage in vitro. In addition, osteocalcin is not degraded by PHEX and inhibits PHEX cleavage of PTHrP.</font></p> <p align="justify"><font face="Verdana">PTHrP is one of the very few naturally occurring substrates cleaved by PHEX.</font></p> <p align="justify"><font face="Verdana">Osteocalcin is not cleaved by PHEX, the negatively charged Gla residues in osteocalcin are thought to interact with higly conserved charged present in PHEX. Similar charged region is present in MEPE and ASARM proteins.</font></p> <p align="justify"><font face="Verdana">In the intact MEPE and PHEX may be associated through the interaction with the MEPE C-terminal ASARM motif. This interaction may not necessarily lead to proteolysis. MEPE-PHEX interaction may therefore prevent proteolytic cleavage and release of ASARM peptide by protecting MEPE from localized matrix proteases. PHEX is localized on plasma membrane surface of osteoblasts, with its extracellular long C terminal region ideally situated in extracellular matrix for protein-protein interactions. </font></p> <p align="justify"><font face="Verdana">Several PHEX mutations has been detected in patients affected by X Linked Hypophosphatemic Richets (HYP) results in sequestration of disease causing PHEX in endoplasmic reticulum and subsequent failure to targeting to plasmamembrane.</font></p> <p align="justify"><font face="Verdana">PHEX play a major role in mineralization and it is expressed predominantly in bones and teeth. </font></p> <p align="justify"><font face="Verdana">The bone expression is localized into osteoblasts, osteocytes (not pre-osteoblasts); in teeth it is present in odontoblasts. </font></p> <p align="justify"><font face="Verdana">Interestingly loss of function of PHEX results in a defective mineralization. Its action on kidney is expressed modulating renal phosphate handling but not directly, suggesting a secondary involvement in regulation of a circulating systemic factor.</font></p> <p align="justify"><font face="Verdana">Finally it is reasonable to speculate that PHEX may well function as a small peptide protease and also as a matix-protein ligand.</font></p> <p align="justify"><b><font face="Verdana">SPC Subtilisin-like proprotein convertase</font></b></p> <p align="justify"><font face="Verdana">The SPC are a family of serine proteases, involved in processing of a wide variety of polypeptides including neuropeptides, growth factors, receptors, blood coagulation factors. Their substrates are cleaved at C terminal side where a specific sequence is present . SPC are present at Golgi apparatus and at trans Golgi network, where they act also on FGF23.</font></p> <p align="justify"><b><font face="Verdana">Matrix Extracellular phosphoglycoprotein (MEPE)</font></b></p> <p align="justify"><font face="Verdana">MEPE was first cloned from a tumor reseacted from a patients with OHO. It belong to a family of proteins that ahve recently been named Shorth Integrin Binding Ligand Interacting Glycoprotein (SIBLINGs). Between them we have:</font></p> <p align="justify"><font face="Verdana">. Osteopontin</font></p> <p align="justify"><font face="Verdana">. Matrix extracellular phosphoprotein (MEPE)</font></p> <p align="justify"><font face="Verdana">. Dentin Matrix Protein 1</font></p> <p align="justify"><font face="Verdana">. Bone Sialoprotein</font></p> <p align="justify"><font face="Verdana">. Dentin Sialo Phosphoprotein</font></p> <p align="justify"><font face="Verdana">. Enamelin</font></p> <p align="justify"><font face="Verdana">All mapping on chromosome 4q21 and sharing many properties. All these proteins have a links with bone/dentin mineralization and phosphate/calcium salts.</font></p> <p align="justify"><font face="Verdana">The structure of these proteins contains RGD motif tipical of integrin ligands, glycosylation pattern very similar between them, phosphorylation pattern again similar, and a so called ASARM motif.</font></p> <p align="justify"><font face="Verdana">ASRM (Acidic Serine Aspartate Rich MEPE associated motif) described a region of these protein able to block the mineralization. However if it is bounded to other extracellular matrix components it may be required a a nucleator of mineralization itself. The ASARM peptide is very stable and it is resistant to know proteases. Free ASARM peptides may also contribute to inhibition of renal phosphate uptake. This mechanism of action is likely to be steric and exacerbating the effect of NTP2 exchanger protein probably with the aids of FGF23. </font></p> <p align="justify"><font face="Verdana">The normal action of MEPE is to act such as mineralization inhibitor, due to the presence of ASARM fragment normally released from the entire protein by the cathepsin C cleavage.</font></p> <p align="justify"><font face="Verdana">Another action of MEPE is a dose dependent inhibition of BMP-2 menediated mineralization in a murine osteoblast cell line in vitro, another effect linked to ASARM presence.</font></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="center"><font face="Verdana"><strong>Mice models</strong></font></p> <p align="justify"><font face="Verdana">From studies in <u>hypophosphatemic mice</u> called “<b>hyp mice</b>” and “<b>gyro mice</b>” it was identified the cause of reduced phosphate reabsorption in a gene located in mouse chromosome X coding for PHEX a metalloproteinase enzyme. This proteins was defective in these mice; in hyp mouse the defect was localized primary in kidney, whereas in gyro mouse the defect was located also in the inner ear and so clinically associated with circling behaviour.</font></p> <p align="justify"><font face="Verdana"><b>KO mice for Na-Pi</b> cotransporter gene called Npt2, showed Pi renal wasting comparable to inactivation of PHEX gene, but in Npt2 KO mice calcitriol responds appropriately to hypophosphatemic challenges, intestinal absorption of both Pi and Ca ensues, and rickets and osteomalcia are absent.</font></p> <p align="justify"><font face="Verdana"><b>MEPE KO mice</b> have increased bone mass, resistance to aging associated trabecular bone loss, increased mineralization apposition rate and a dramatically accelerated mineralization rate in ex vivo osteoblasts cultures.</font></p> <p align="justify"><font face="Verdana">Interestingly Vitamin D3 Receptor KO mice have markedly increased levels of mRNA for MEPE expression.</font></p> <p align="justify"><font face="Verdana">Comparison between these mice models illustrates that renal phosphate wasting can be dissocated from defective synthesis of calcitriol, implying that phosphatonins have at least two independent actions:</font></p> <p align="justify"><font face="Verdana">1. they inhibit the Pi reabsorption</font></p> <p align="justify"><font face="Verdana">2. they impair the synthesis of calcitriol</font></p> <p align="justify"><font face="Verdana">The different phenotypes in Npt2 KO mice and PHEX KO mice also raise the possibility that FGF23 has a direct affect on bone and cartilage that contribute, along with hypophasphatemia to a defect in mineralization.</font></p> <p align="justify"><font face="Verdana">HYP mice model hepl us in understanding a possible explanation; the HYP mouse model of PHEX inactivation responds to phosphate deprivation, with continued phosphaturia relative to wilde type mice.</font></p> <p align="justify"><font face="Verdana">Normally phosphate can be cleared from urine by low dietary Pi intake, protecting against Pi depletion. So that decreased FGF23 secretion could be in this view the humoral factor of this response, coupling with at yet unidentifed phosphate sensor, possibly in the intestinal mucosa, to regulate intestinal phosphate reabsorption. Moreover FGF23 may explaine only a local paracrine regulatory role perhaps even unrelated to Pi homeostasis, and only when it is inappropriately secreted into blood may exert a Pi wasting action.</font></p> <p align="justify"><font face="Verdana">In this scenario, the phosphate wasting in tumor induced osteomalacia would be analogous to the Pi wasting that occurs when tumors overexpress the PTH-related peptides, PTH-rP. PTH-rP is normally a local regulator of cell differentiation, but when overproduction gives it access to the circulation, it co-opts the PTH receptor in kidney to cause phosphaturia.</font></p> <p align="justify"><font face="Verdana">Conerning FGF23 it is the first FGFs for which mutations are associated with a disease, and althought the othr 22 FGFs share only 4 known receptors, it is likely that FGF23 has a different receptor, because cleavage of its unique C terminal domain inactivates it.</font></p> <h4 align="center"><font face="Verdana">Tumor Induced Osteomalacia</font></h4> <p align="justify"><font face="Verdana">In literature about 70 cases have been described with such rare form of hypophosphaturia, which occurs in association with coexisting tumor and resolve after its excision; with a possible relapsing episodes.</font></p> <p align="justify"><font face="Verdana">Hypophosphatemia is probably due to a diminished renal phosphate reabsorption and this phenomenon causes a decrease in 1a hydroxylation of vitamin D3.</font></p> <p align="justify"><font face="Verdana">Tumor are generally of mesenchymal origin ( such as hemangiopericytomas), but also prostate and breast cancer have been described. They are often small and difficult to locate. From Cai Q data on 1994 it was described a “unidentified soluble factor” heat labile that is devoted normally to control renal phosphate reabsorption.</font></p> <p align="justify"><font face="Verdana">Oncogenic osteomalacia has been linked to secretion of a Frizzled receptor protein (FRP4) containing cysteine rich ligand binding domain as well’s hydrophilic C terminal region. The normally bound receptor link Wnt proteins in tandem with LPR family co-receptors. The binding to Wnt proteins to frizzled receptors and LPR5/6 coreceptors in heterotrimeric complexes on the cell surfaces leads to stabilization of intrcellular catenin beta and a complex network of singalling cascade.</font></p> <p align="justify"><font face="Verdana">It has been demonstrated in many cancers both in vivo and in vitro, that this pathways account for bone osteolysis in cancer diffusion to bone tissues.</font></p> <p align="justify"><font face="Verdana">Moreover some rare inherited disorders are characterized by involvement of Wnt/LPR pathways alterations:</font></p> <p align="justify"><font face="Verdana">. osteoporosis pseudoglioma syndrome : congenital blindness and severe chilhood osteoporosis</font></p> <p align="justify"><font face="Verdana">. High Bone Mass syndrome: associated with phenotypical presence of inherited high bone mass level.</font></p> <p align="justify"><font face="Verdana">FRP4 is located on chromosome 7p14.1 and it is conprised of six encoding exons, spanning 10.8 kb of genomic sequence. The translated protein product consist of 346 aminoacids, of which the first 21 residues constitute the predicted signal peptide. Finally the molecular mass of FRP4 is approximately of 40 kDa, but it is glycosylated to form a mature peptide of 48 kDa. It is ubiquitariously expressed, but importantly on bone cells it is present indicating a possible auto and paracrine effect in the skeleton too.</font></p> <p align="justify"><font face="Verdana">Concerning phosphate metabolism the study of Berndt et al (2003) revealed that this peptide has the capacity of inhibit the sodium dependent phosphate reuptake in opossum kidney in vitro experiments. Moreover infusion of FRP4 in vivo in parathyroidectomized mice caused an increase in the fractional excretion of phosphate and subsequent hypophosphatemia, indicating a mechansim of action partially independent from PTH. </font></p> <p align="center"><b><font face="Verdana">Hyperphosphatemic Familial Tumoral Calcinosis</font></b></p> <p align="justify"><font face="Verdana">Recent work regarding fibroblast growth factor 23 addressed the question of pathogenesis of familial tumoral calcinosis. A missense mutation in the gene encoding FGF23 cause autosomal dominant hypophophatemic rickets. In addition FGF23 is highly expressed by tumors causing oncogenic hypophophatemic osteomalacia. FGF23 is therefore a strong candidate for “phophatonin”, the factor implicated as a cause of the phophate wasting in patients with oncogenic hypophosphatemic osteomalacia. The mutations tht cause autosomal dominant hypophosphatemic rickets stabilizes FGF23, potentially elevating its concentration in serum and leading to renal phosphate wasting. The same would be true in oncogenic hypophosphatemic osteomalacia: i.e. a great production of FGF23 by tumor and so increased levels of plasma FGF.</font></p> <p align="justify"><font face="Verdana">The clinical response to octreotide therapy as described by Seufert J in a patients may suggest that secretion of fibroblast growth factor 23 by the tumor can be modulated throught the somatostatin receptor signaling pathway. This protein (FGF23) has been demonstrated to be a substrate for the endopeptidase PHEX and to inhibit the phosphate transport in kidney cells. Moreover in autosomal dominant form of hypophosphatemic rickets, mutations in FGF23 have been identified that render the molecule resistant to cleavage by PHEX. So that in these patients octreotide scanning may be useful in identifying such a small tumors or relapses.</font></p> <p align="justify"><font face="Verdana"></font></p> <p align="justify"> </p> <p align="center"><font face="Verdana">References</font></p> <p align="justify"><font face="Verdana">Resnick M, Pridgen DB, Goodman HO. Genetic predisposition to formation of calcium oxalate renal calculi. N Engl J Med 1968;278:1313-8.</font></p> <p align="justify"><font face="Verdana">Tieder M, Arie R, Modai D et al. Elevated serum 1,25-dihydroxyvitamin D3 concentration in siblings with primary Fanconi’s syndrome. N Engl J Med 1988;319:845-9.</font></p> <p align="justify"><font face="Verdana">Cai Q, Hodgsan SF, Kao PC et al. Brief report:inhibition of renal phosphate transport by a tumor product in a patient with oncogenic osteomalacia. N Engl J Med 1994;330:1645-9.</font></p> <p align="justify"><font face="Verdana">Econs MJ, Drezner MK. Tumor induced osteomalacia – unveiling a new hormone. N Engl J Med 1994;330:1679-81.</font></p> <p align="justify"><font face="Verdana">Seufert J, Ebert K, Muller J et al. Octreotide therapy for tumor induced osteomalacia. N Engl J Med 2001;345:1883-8.</font></p> <p align="justify"><font face="Verdana">Prié D, Huart V, Bakouh N et al. Nephrolithiasis and osteoporosis associated with hypophosphatemia caused by mutations in the type 2a sodium-phosphate cotransporter. N Engl J Med 2002;347:983-91.</font></p> <p align="justify"><font face="Verdana">Kronenberg HM. NPT2a – The key to phosphate homeostasis. N Engl J Med 2002;347:1022-4.</font></p> <p align="justify"><font face="Verdana">Jonsson KB, Zahradnik R, Larsson T et al. Fibroblast growth factor 23 in oncogenic osteomalacia and X-linked hypophosphatemia. N Engl J Med 2003;348:1656-63.</font></p> <p align="justify"><font face="Verdana">Carpenter TO. Oncogenic osteomalacia – A complex dance of factors. N Engl J Med 2003;348:1705-8.</font></p> <p align="justify"><font face="Verdana">Hesse E, Rosenthal H, Bastian L. Radiofrequency ablation of a tumor causing oncogenic osteomalacia. N Engl J Med 2007;357:422-4.</font></p> <p align="justify"><font face="Verdana">Karim Z, Gérard B, Bakouh N et al. NHERF1 mutations and responsiveness of renal parathyroid hormone. N Engl J Med 2008;359:1128-35.</font></p> <p align="justify"><font face="Verdana">Gutiérrez OM, Mannstadt M, Isakova T et al. Fibroblast growth factor 23 and mortality among patients undergoing hemodialysis. N Engl J Med 2008;359:584-92.</font></p> <p align="justify"><font face="Verdana">Reilly BM, Hart PD, Mascarell S et al. A question well put. N Engl J Med 2009;360:1446-51.</font></p> <p align="justify"><font face="Verdana">Magen D, Berger L, Coady MJ et al. A loss of function mutation in NaPiIIa and renal Fanconi’s syndrome. N Engl J Med 2010;362:1102-9.</font></p> <p align="justify"><font face="Verdana">Thorleifsson G, Holm H, Edvardsson V et al. Sequence variants in the CLDN14 gene associate with kidney stones and bone mineral density. Nat Genet 2009;41:926-30.</font></p> <p align="justify"><b><font face="Verdana">NPT2 cotransporter</font></b></p> <p align="justify"><font face="Verdana">Tenenhouse HS, Beck L. Renal Na+-phosphate cotrasporter gene expression in X linked Hyp and Gyro mice. Kidney Int 1996;49:1027-32.</font></p> <p align="justify"><font face="Verdana">Beck L, Karaplis AC, Amizuka N et al. Targeted inactivation of Npt2 in mice leads to severe renal phosphate wasting, hypercalciuria and skeltal abnormalilites. Proc Natl Acad Sci USA 1998;95:5372-7.</font></p> <p align="justify"><font face="Verdana">Tenenhouse HS, Martel J, Gautier C et al. Renal expression of the sodium/phosphate cotransporter gene, Npt2, is not required for regulation of renal 1 alpha-hydroxylase by phosphate. Endocrinology 2001;142:1124-9.</font></p> <p align="justify"><font face="Verdana">White KE, Jonsson KB, Carn G et al. The autosomal dominant hypophosphatemic rickets (ADHR) gene is a secreted polypeptide overexpressed by tumors that cause phosphate wasting. J Clin Endocrinol Metab 2001;86:497-500.</font></p> <p align="justify"><font face="Verdana">Segawa H, Yamanaka S, Ohno Y et al. Correlation between hyperphosphatemia and type II Na-Pi cotransporter activity in KLOTHO mice. Am J Physiol Renal Physiol 2007;292:F769-F779.</font></p> <p align="justify"><b><font face="Verdana">NHERF</font></b></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><font face="Verdana">Mahon MJ, Donwitz M, Yun CC et al. Na/H exchanger regulatory factor 2 directs parathyroid hormone 1 receptor signalling. Nature 2002;417:858-61.</font></p> <p align="justify"><font face="Verdana">Shenolikar S, Voltz JW, Minkoff CM et al. Targeted disruption of the mouse NHERF1 gene promotes internalization of proximal tubule sodium-phosphate cotransporter type IIa and renal phosphate wasting. Proc Natl Acad Sci USA 2002;99:11470-5.</font></p> <p align="justify"><font face="Verdana">Hernando N, Déliot N, Gisler SM et al. PDZ-domain interactions and apical expression of type IIa Na/Pi cotransporters. Proc Natl Acad Sci USA 2002;99:<a dir="ltr" href="tel:11957-62" x-apple-data-detectors="true" x-apple-data-detectors-type="telephone" x-apple-data-detectors-result="4">11957-62</a>.</font></p> <p align="justify"><b><font face="Verdana">PHEX</font></b></p> <p align="justify"><font face="Verdana">The HYP Consortium. A gene (PEX) with homologies to endopeptidases is mutated in patients with X-linked hypophosphatemic rickets. Nat Genet 1995;11:130-6.</font></p> <p align="justify"><font face="Verdana">Boileau G, Tehehhouse HS, Desgroseillers L et al. Chraracterization of PHEX endopeptidase cathalitic activity: identification of parathyroid-hormone –related peptide 107-139 as a substrate and osteocalcin Ppi and phosphate as inhibitors. Biochen J 2001;355:707-13.</font></p> <p align="justify"><font face="Verdana">Bowe AE, Finnegan R, Jan de Beur SM et al. FGF23 inhibits renal tubular phosphate transport and is PHEX substrate. Biochem Biophys Res Commun 2001;284:977-81.</font></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><b><font face="Verdana">FGF23</font></b></p> <p align="justify"><font face="Verdana">The ADHR Consortium. Autosomal dominant hypophosphatemic rickets is associated with mutations in FGF23. Nat Genet 2000;26:345-8.</font></p> <p align="justify"><font face="Verdana">Shimada T, Mizutani S, Muto T et al. Cloning and characterization of FGF23 as a causative factor of tumor-induced osteomalacia. Proc Natl Acad Sci USA 2001;98:6500-5.</font></p> <p align="justify"><font face="Verdana">Strewler GJ. FGF23, hypophosphatemia, and rickets:has phosphatonin been found? Proc Natl Acad Sci USA 2001;98:5945-6.</font></p> <p align="justify"><font face="Verdana">White KE, Carn G, Lorenz-Depiereux B et al. Autosomal-dominant hypophosphatemic rickets (ADHR) mutations stabilizes FGF-23. Kidney Int 2001;60:2079-86.</font></p> <p align="justify"><b><font face="Verdana"></font></b></p> <p align="justify"><font face="Verdana">Shimada T, Muto T, Urakawa I et al. Mutant FGF23 responsible for autosomal dominant hypophosphatemic rickets is resistant to proteolytic cleavage and causes hypophosphatemia in vivo. Endorinology 2002;143:3179-82.</font></p> <p align="justify"><font face="Verdana">Shimada T, Hasegawa H, Yamazzaki Y et al. FGF23 is a potent regulator of vitamin D metabolism and phosphate homeostasis. J Bone Miner Res 2004;19:429-35.</font></p> <p align="justify"><font face="Verdana">Shimada T, Urakawa I, Yamazaki Y et al. FGF23 transgenic mice demonstrated hypophosphatemic richets with reduced expression of sodium phosphate cotransporter type Iia. Biochem Biophys Res Commun 2004;314:409-14.</font></p> <p align="justify"><b><font face="Verdana">Oncogenic Rickets</font></b></p> <p align="justify"><font face="Verdana">Brendt T, Craig TA, Bowe AE et al. Secreted frizzled-related protein 4 is a potent tumor derived phosphaturic agent. J Clin Invest 2003;112:785-94.</font></p> <p align="justify"><font face="Verdana">Kurose K, Sakaguchi N, Nasu Y et al. Decreased expression of REIC/Dkk-3 in human renal clear cells carcinoma. J urol 2004;171:1314-8.</font></p> <p align="justify"><font face="Verdana">Nozaki I, Tsuji T, Iijima O et al. Reduce expression of REIC/Dkk-3 gene in non-small cell lung cancer. Int J Oncol 2001;19:117-21.</font></p> <p align="justify"><font face="Verdana">Tsuji T, Nozaki I, Miyazaki M et al. Antiproliferative activity of REIC/Dkk-3 and its significant down-regulation in non-small cell lung carcinomas. Biochem Biophys Res Commun 2001;289:257-63.</font></p> <p align="justify"><font face="Verdana">Kobayashi K, Ouchida M, Tsuji T et al. Reduced expression of the REIC/Dkk-3 gene by promoter-hypermethylation in human tumor cells. Gene 2002;282:151-8.</font></p> <p align="justify"><font face="Verdana">Surendran K, Schiavi S, Hruska KA. Wnt-dependent beta-catenin signalling is activated after unilateral ureteral obstruction, and recombinant secreted frizzled-related protein 4 alters the progression of renal fibrosis. J Am Soc Nephrol 2005;16:2373-84. </font></p> <p align="justify"><b><font face="Verdana">Tumoral calcinosis</font></b></p> <p align="justify"><font face="Verdana">Inclan A, leon P, Camjeo MG. Tumoral calcinosis. JAMA 1943;121:490-5.</font></p> <p align="justify"><font face="Verdana">Mitnick PD, Goldfarb S, Slatopolsky E et al. Calcium and phosphate metabolism in tumoral calcinosis. Ann Intern Med 1980;92:482-7.</font></p> <p align="justify"><font face="Verdana">Topaz O, Shurman DL, Bergman R et al. Mutations in GALNT3, encoding a protein involved in O-linked glycosylation, cause familial tumoral calcinosis. Nat Genet 2004;36:579-81.</font></p> <p align="justify"><font face="Verdana">Larsson T, Yu X, Davis SI et al. A novel recessive mutation in fibroblast growth factor-23 causes familial tumoral calcinosis. J Clin Endocrinol Metab 2005;90:2424-27.</font></p> <p align="justify"><font face="Verdana">Larsson T, Davis SI, Garringer HJ et al. FGF23 mutants causing familail tumor calcinosis are differentially processed. Endocrinology 2005;146:3883-91.</font></p> <p align="justify"><b><font face="Verdana">FGF References</font></b></p> <p align="justify"><font face="Verdana">Saunders JW Jr. The proximo-distal sequence of the origin of the parts of the chick wing and the role of ectoderm. J Exp Zool 1948;108:363-403.</font></p> <p align="justify"><font face="Verdana">Naski MC, Colvin JS, Coffin JD et al. Repression of hedgehog signaling and BMP4 expression in growth plate cartilage by fibroblast growth factor receptor 3. Development 1998;125:4977-88.</font></p> <p align="justify"><font face="Verdana">Hu MC, Qiu WR, Wang YP et al. FGF-18, a novel member of fibroblast growth factor family, stimulates hepatic and intestinal proliferation. Mol Cell Biol 1998;18:<a dir="ltr" href="tel:6063-6074" x-apple-data-detectors="true" x-apple-data-detectors-type="telephone" x-apple-data-detectors-result="5">6063-6074</a></font></p> <p align="justify"><font face="Verdana">Niswander I, Tickle C, Vogel A et al. FGF-4 replaces the apical ectodermal ridge and directs outgrowth and patterning of the limb. Cell 1993;75:579-587.</font></p> <p align="justify"><font face="Verdana">Fallon J et al. FGF-2: Apical ectodermal ridge growth signal for chick limb development. Science 1994;264:104-7.</font></p> <p align="justify"><font face="Verdana">Sun X et al. Conditional inactivation of FGF4 reveals complexity of signalling during limb bud development. Nature Genet 2000;25:83-6.</font></p> <p align="justify"><b><font face="Verdana">FGF-Receptor linked diseases</font></b></p> <p align="justify"><font face="Verdana">Keegan K, Johnson DE, Williams LT et al. Isolation of an additional member of the fibroblast growth factor receptor family, FGFR-3. Proc Natl Acad Sci USA 1991;88:1095-9.</font></p> <p align="justify"><font face="Verdana">Rousseau F, Bonaventure J, Legeai-Mallet L et al. Mutations in the gene encoding fibroblast growth factor receptor-3 in achondroplasia. Nature 1994;371:252-4</font></p> <p align="justify"><font face="Verdana">Delezoide AL, Benoist-lasselin C, Legeai-Mallet L et al. Spatio-temporal expression of FGFR 1,2 and 3 genes during human embryo-fetal ossification. Mech Dev 1998; 77:19-30.</font></p> <p align="justify"><font face="Verdana">Tavormina PL, Shiang R, Thompson LM et al. Thanatophoric dysplasia /(types I and II) caused by distict mutations in fibroblast growth factor receptor 3. Nat Genet 1995;9:321-8</font></p> <p align="justify"><font face="Verdana">Rousseau F, Saugier P, Le Merrer M et al. Stop codon FGFR3 mutations in thanatophoric dysplasia type I. Nat Genet 1995;10:11-12</font></p> <p align="justify"><font face="Verdana">Hecht JT, Herrera CA, Greebhaw GA et al. Confirmatory linkage of hypochondroplasia to chromosome arm 4p (letter). Am J Med Genet. 1995;57:505-6.</font></p> <p align="justify"><font face="Verdana">Prinstern C, Carrera P, Mora S et al. The two recurrent mutations of FGFR3cause hypochondroplasia in 57% of the Italian patients. Horm Res 1996;46:83 (Abstract)</font></p> <p align="justify"><font face="Verdana">Prinstern C, Carrera P, Del Maschio M et al. Comparison of clinical-radiological and molecular findings in hypochondroplasia. Am J Med Genet 1998;75:109-112.</font></p> <p align="justify"><font face="Verdana">Tavormina PL, Bellus GA, Webster MK et al. A novel skeletal dysplasia with developmental delay and acanthosis nigricans is caused by a Lys650Met mutation in the fibroblast growth factor receptor 3 gene. Am J Hum Genet 1999;64:722-31.</font></p> <p align="justify"><font face="Verdana">Colvin JS, Bohne BA, Harding GW et al. Skeletal overgrowth and deafness in mice lacking firoblast growth factor receptor 3. Nat Genet 1996;12:390-7.</font></p> <p align="justify"><font face="Verdana">Wang Y, Spatz MK, Kannan K et al. A mouse model for achondroplasia produced by targeting fibroblast growth factor receptor 3. Proc Natl Acad Sci USA 1999;96:4455-60.</font></p> <p align="justify"><font face="Verdana">Chen L, Adar R, Yang X et al. Gly369Cys mutation in mouse FGF-R3 causes achondroplasia by affecting both chondrogenesis and osteogenesis. J Clin Invest 1999;104:1517-25.</font></p> <p align="justify"><font face="Verdana">Su WC, Kitagawa M, Xue N et al Activation of STAT1 by mutant fibroblast growth-factor receptor in thanatophoric dysplasia type II dwarfism. Nature;1997:386:288-92.</font></p> <p align="justify"><font face="Verdana"></font></p> <p align="justify"></p> <p align="justify"><font face="Verdana"></font></p> <p align="justify"><font face="Verdana"></font></p> <p align="justify"><font face="Verdana"></font></p> BoNewshttp://www.blogger.com/profile/14996032718916828654noreply@blogger.comtag:blogger.com,1999:blog-6459801161644965909.post-3857872111074964322009-10-28T22:07:00.000+01:002016-04-25T21:51:06.338+02:00Autoinflammatory diseases and osteoclasts mediated osteoimmunology.<p align="center"><b></b></p> <p align="center"></p><div class="separator" style="clear: both;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCQVX41a0BerMfz3tkfjGrN_z1QDxzkpiXlfz4SrnreW7PFBAeBGmsewi22mG8vLGGKpyIqHrN5BBu2EoN-AczQi9QmMwOdAVZBZWL1-A6O4Q94LD_srCHi4-QsodGSnvV5-cEV8Lgk_IJ/s640/blogger-image-1685484938.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCQVX41a0BerMfz3tkfjGrN_z1QDxzkpiXlfz4SrnreW7PFBAeBGmsewi22mG8vLGGKpyIqHrN5BBu2EoN-AczQi9QmMwOdAVZBZWL1-A6O4Q94LD_srCHi4-QsodGSnvV5-cEV8Lgk_IJ/s640/blogger-image-1685484938.jpg"></a></div><br><p></p> <p align="center"><br></p> <p align="center"><b></b></p> <p align="center"><b>TNF family growth factors</b></p> <p align="justify">. Lymphotoxin alfa/TNF alfa</p> <p align="justify">. lymphotoxin beta/TNF beta</p> <p align="justify">. FAS Ligand</p> <p align="justify">. Nerve Growth Factor</p> <p align="justify">. CD40 ligand or CD154</p> <p align="justify">. CD27 ligand </p> <p align="justify">. CD30 ligand</p> <p align="justify">. OX-40 ligand</p> <p align="justify">. 4-IBB ligand</p> <p align="justify">. RANK/ODF/SOFA (Receptor Activator of NF-kB/ Osteoclasts differentiation Factor)</p> <p align="justify">. RANK Ligand</p> <p align="justify">. OPG (Osteoprotegerin)</p> <p align="justify"> </p> <p align="center"><b>Receptors for TNFalfa</b></p> <p align="justify">TNFR1: p55 - CD120a Tumor necrosis factor receptor I (Chr. 12)</p> <p align="justify">TNFR2: p75 - CD120b Tumor necrosis factor receptor II</p> <p align="justify">CD95 FAS</p> <p align="justify">TNFRSF4: OX40, OX40 antigen</p> <p align="justify">TNFRSF5: CD40 B cell associated molecule</p> <p align="justify">TNFRSF9: 4-IBB homologue of mouse 4-IBB</p> <p align="justify">TNFRSF11A: RANK, Receptor Activator of Nuclear factor kB (Chr.18q21-22)</p> <p align="justify">TNFRSF11B: OPG, Osteoprotegerin (Chr. 8q24.2 )</p> <p align="justify">TNFRSF16: Nerve Growth Factor Receptor</p> <p align="justify"> </p> <p align="justify">Recently a classification of these receptors have been reported all containing </p> <p align="justify">1. FADD domain: a protein sequence thought to be Fas-Associated Death Domain: a bipartite bridge that directy binds to CD95 Ligand and to pro-caspase 8.</p> <p align="justify">2. TRADD: an adapter protein with liker function with FADD sequence</p> <p align="justify">The molecular structure of this receptor has been defined as formed by a 55 kDa protein with:</p> <p align="justify">1. four cysteine –rich extracellular domains (the first two are involved in most mutations founded in syndromic complex)</p> <p align="justify">2. Intracellular FADD domain involved in signal transduction through protein-protein interaction.</p> <p align="justify">The receptors at present know are:</p> <p align="justify">- TNF-R1: the true receptor for TNF alpha</p> <p align="justify">- TRAIL-R1: using FADD sequense and linking to pro-caspase 8</p> <p align="justify">- TRAIL-R2: using FADD sequence.</p> <p align="justify">Soluble forms of these last two recptors are present in extracellular fluids, with an inhibitor action on apoptotic signals:</p> <p align="justify">- TRAIL-R3 also know such as TRID</p> <p align="justify">- TRAIL-R4 also know such as TRUNDD</p> <p align="justify">We can consider OPG-Ligand and RANK-Ligand such as TRAIL like molecules ie TNF Related Apoptosis Inducing Ligands.</p> <p align="justify">OPG (Osteoprotegerin) on the contrary is a TRAIL-Receptor soluble form ie with inhiting action on TRAIL-R induced apoptosis.</p> <p align="justify">On the osteoclasts instead of linking to true TRAIL-Rs the ligands can link to RANK a specific receptor able to activate NF-kB.</p> <p align="justify"> </p> <p align="center"><strong>Autoinflammatory diseases</strong></p> <p align="justify">The receptor activation of TNF alfa have been clearly demonstrated to be the masterplayers in regulation those we begin to call “autoinflammatory syndromes”. </p> <p align="justify">These are represented by:</p> <p align="justify">- Familial Mediterranean Fever - pyrin</p> <p align="justify">- Familial Hibernian Fever – TNF receptor type 1</p> <p align="justify">- Muckle-Wells syndrome - cryopyrin</p> <p align="justify">- Familial cold urticaria - cryopyrin</p> <p align="justify">- Chronic infantile neurological cutaneous and articular syndrome - cryopyrin</p> <p align="justify">- Neonatal onset multisystem inflammatory disease - cryopyrin</p> <p align="justify">- Hyperimmunoglobulinaemia D and periodic Fever syndrome – mevalonate kinase</p> <p align="justify">First of all we have to remember that these syndromic complexes are very rare diseases and may be only a model of more large diffuse arthritic diseases. Anyway considering the genetic selectivity pressure involving the genes areas mutated in these subjects, we can suppose that the selectivity pressure has favored the selection of heterozygous people. People affected are from Mediterranean ancestral origin such as Sepharditic Jwes, Armenian, Turkish, Greek, Italian people and these diseases affect humans during early year of life. We can suppose that people heterozygous for such mutations react with a very intense systemic way leading to great survival chances.</p> <p align="justify">The molecular pathway involves the cleavage of precursor of IL-1 beta before its secretion affecting a group of proteins showing the same molecular structure now called NALPs proteins able to activate the caspase-1 complex involved in degradation of pro-IL1 ( pyrin ) such in the case of Familial Mediterranean Fever.</p> <p align="justify">The defect of mevalonate kinase involved into the genesis of hyperglobulinemia D is involved in an increased secretion of IL-1 beta that is linked to the production of isopreoid molecules, normally linking IL-1 to the plasmamembrane.</p> <p align="justify">The defect of <strong>TNF receptor type 2</strong> lead to an increase stimulation of TNF alfa, due to defect in cleavage site of this receptor normally acting such as scavenger receptor for circulating TNF alfa, such as the case of so called <b><u>Familial Hibernian fever</u></b><u>. </u>The autosomal dominant inheritance of this syndrome has been reported in many ethnic groups but in particular in Irish and Scottish family. So far more than 20 families have been described in Australia, United States and Europe too. Linkage analysis mapped the susceptibility gene for two separate families to the short arm of chromosome 12. Identifying several missense mutations, at least 16, in the gene for the type 1 TNF receptor in the exons 2,3 and 4 of genomic sequence has lead to hypothesis that receptor activation usually lead to cleavage and shedding of its intracellular portion into the circulation, where it acts as an inhibitor of TNF alpha. Activation of receptor can leads to activation of a protease that shed the TNF receptor from cell surface. It is postulated that in affected patients the TNF receptor cannot be shed by proteases leading to persistent inflammatory response.</p> <p align="justify"><b><u></u></b></p> <p align="justify"><b><u></u></b></p> <p align="justify"><b><u></u></b></p> <p align="justify"><b><u>Familial meditterranean fever</u></b> is defined such as disease linked to an alteration on TNFalfa Receptor but due to a <strong>pyrin </strong>defect. The prolonged attacks, conjunctivitis, and localized myalgias differentiated the TNF-receptor associated periodic fever from other syndromic periodic fever syndromes.</p> <p align="justify">Finally cryopyrin defect is associated at different level with the last three syndromic complexes including <b><u>neonatal-onset multisystem inflammatory diseases.</u></b></p> <p align="justify">Cryopyrin belong to NALP superfamily, and is able to activate caspase system at N terminal site, to link to nucletide sequence in its central portion (Leucine rich repeat), and at C terminal site it shows many similaryties with Toll like receptor family able to link to many bacterial and host molecules. Finally a particular attention deserve the presence in these hereditary periodic fever syndromes of amyloidosis. It’s interesting to note that many bone diseases are characterized by the presence in abnormal level of amyloidotic structures in extracellular space. In particular it would be interesting to evaluate the different arhtropatyes affecting adults for the presence of amyloidotic proteins in synovial flluids or anyway in extracellular degraded matrix. In considerations of recent evidences of involvement of matrix metalloproteinases and aggrecanases gene mutations in diseases affecting cartilagineous structures, it would be intersting to evaluate the hypothesis of an increased production and secretion at kidney level of amyloid like proteins. The pathways of production of amyloid include the gamma secretase enzymes involvement into degradations of HLA linked moleculed in particular of beta2 microglobulin. It has been suggested that after the apototitc processes due to same mechanisms involving the increased secretion of IL-1 beta would produces increased amount of plasmamebrane linked proteins containing strucural motif able to form agregates of fibrils in extracellualr matrix that can only be secreted by kidney with possible damage of renal filtration at glomerular level. Interestingly in the disease affecting older people the levels of amyloid like structures are increased for example at level of cerebral tissue in degenerativve diseases such as Alzheimer’s diseases. The same mechanism would be present also at bone tissue livel in particular at articular level. It si interesting to note that amyloidosis is preset in Armenian people living in Armenia wheres it is absent in Armenian living elsewere; it is possible that the presence of only one allele of this gene responsible of autosomal recessive diseases, previously described, account for an increased production of amyloid proteins, production that require also a predisposition of SAA1 genotype in the amyloid precursors.</p> <p align="justify">Arthritic diseases and malignancies</p> <p align="justify">Virchow suggested in the nineteenth century that chronic inflammation might give rise to malignancy, and the link between inflammation and cancer was not widely inderstood until recently. Clinical evidences of this link is demonstrated by the relationships between chronic infections with hepatitis B virus (HBV) and hepatitis C virus with hepatocellular carcinoma; infections with Helicobacter pylori and association with most gastric cancers; chronic inflammatory bowel diseases, such as Ulceratice colitis, and colorectal cancer; chronic airway irritation and inflammation caused by airborne partocles and tobacco smoke and lung carcinomas. Thus epidemiological studies were an excellent source of new working hypothetis concerning the pathogenesis of cancer. Hanahan and Weinberg summarized the processes underlying the emergence of neoplasia with the presence of self sufficiency in growth signals, insensitivity to growth inhibition signals, evasion from apoptosis, limitless replicative potential, tissue invasion and sustained angiogenesis.</p> <p align="center"><b><u>Osteitis Deformans or Paget’s Disease of bone</u></b></p> <p align="justify">Paget’s disease of bone is also called Osteitis Deformans and it is a more common metabolic disorder resulting from rapid bone remodelling. Interestingly on 1% of affected patients an osteosarcoma, fibrosarcomas or chondrosarcomas are present ; the more common site sarcoma transformed is the femur; higher risk patients are those with polyostotic form of the disease, and it has been linked to the presence of a single gene mutation tightly located on chromosome 18. So that Osteitis Deformans can be considered a precancerous lesion of bone.</p> <p align="justify">Cardiovascular system is affected in polyostotic form with an increase in cardiac output during the active resorbing phase; cardiac failure is rarely present. The increase vascular flow rate is the first sing of Paget disease of bone when it stops after a correct antiresorptive therapy.</p> <p align="justify">The hematic flow increase on skull bone can lead to a cerebral ischaemic attacks like those we see during vertebrobasilar insufficiency.</p> <p align="justify"> </p> <p align="center"><b><u>Alkaline phoshatase linked diseases</u></b></p> <p align="justify">Inherited diseases are known to be associated with an alteration on ALP secretion:</p> <p align="justify">. Hypophosphatasia: low levels of NTS-ALP due to chromosomal alteration on chromosome 1.</p> <p align="justify">. Aphosphatasia: heritable deficit of NTS-ALP</p> <p align="justify">. Inherited Hyperphosphatasia (Paget disease of bone)</p> <p align="center">Aphosphatasia</p> <p align="justify">Is an heritable deficit of NTS-ALP where we have a typical biochemical characterization due to increased levels of:</p> <p align="justify">- Phosphoetanolamine</p> <p align="justify">- Pyridoxate phosphate (Vit. B6)</p> <p align="justify">- Pyrophosphates</p> <p align="justify">All molecules targets of ALP activity under normal conditions.</p> <p align="justify">Recently, after the discovery of Osteoprotegerin as a “uncoupling factor” able to modulate bone remodelling, many studies have been devoted to unravel the gene location and transcription control of Osteoprotegerin-coding genes.</p> <p align="justify">At present two chromosomal loci have been identified coding for two different kind of OPG-like proteins:</p> <p align="justify">1. TNFRSFIIA on chromosome 18q21-22</p> <p align="justify">2. TNFRSFIIB on chromosome 8q24.2</p> <p align="justify">These gene locations have been identified thanks to the study of rare inborn errors of bone metabolism by White’s MP group, and in particular of </p> <p align="justify">- Familial Expansile Osteolysis – MIM174810 - TNFRSFIIA</p> <p align="justify">- Expansile skeletal Hyperphosphatasias – MIM 239000 - TNFRSFIIB</p> <p align="justify">- Early onset Paget’s disease of bone in Japan</p> <p align="justify">- Idiopathic Hyperphosphatasia (Juvenile Paget’s disease) MIM 239000</p> <p align="justify">OPG, a soluble member of the superfamily of TNF receptors, is normally secreted in vivo into the marrow space by cells derived from embrional mesenchimal tissue. Physiological actions of OPG is to function as a decoy receptor free into extracellular space, necessary and sufficient for osteoclasts development.</p> <p align="justify">KO mice for TNFRSFIIB develop osteoporosis with numerous osteoclasts and rapid remodelling bone tissue.</p> <p align="justify">OPG serum levels have been described to be undetectable in patients affected by Hereditary Hyperphosphatasia (Juvenile Paget’s disease) according to the model described above.</p> <p align="justify"><b><u>TNFRSF11B: Osteoprotegerin (C</u></b><b><u>hr. 8q24.2 ) mutations and osteoporosis</u></b></p> <p align="justify">Interestingly, some recent data demonstrated the presence of a genetic polymorphism in the codon 3 at exon 1 of gene coding for OPG, causing an aminoacid substitution from lysine to asparagine at position 3. This gene mutation is presented in osteoporotic fractured older women. Several studies have reported an association between the Asn (C) allele presenting the mutation of Lys3Asn and increased lumbar spine BMD, as well’s lower risk of osteoporosis and osteopenia, with a reduced fracture risk.</p> <p align="justify">Also the Study of Osteoporotic Fractures Research Group (SOF Research) studying 6695 women aged 65 years and older confirmed the previous studies demonstrating an association between high BMD level at diffeent skeletal sites and Ans3Asn (C/C) genotype. In particular C/C genotype is associated in SOF study women with high BMD values at calcaneal level, distal radious, intertrochanter, and lumbar spine. However it is important to note that also fracture risk was strictly related to OPG polymorphism. Interestingly, many of skeletal sites examined showed an association only with high BMD level but not with fracture risk, whereas the largest increase in fracture risk was seen at femural neck level, where there was no significant association with BMD values.</p> <p align="justify">Studies evaluating serum concentration levels of OPG with BMD or fracture risk in humans have yielded conflicting results, partly because serum concentration levels of OPG, don’t reflect the OPG biologic activity within the bone microenvironment.</p> <p align="justify">Genetically determined differences in OPG expression or function may be more reliable indicator of long term OPG activity. This possibility is supported by the association between the OPG Lys3Asn missense polymorphism and the risk of fracture over an average of 13.6 years of follow up in the SOF Research Group. Interestingly, the Lys3 Asn mutation occurs in a potential exonic splicing enhancer site. Changes in these sequences can have functional effect on the protein biologic activity. These findings for OPG Lys 3 Asn polymorphism are consistent with the common disease, common variant model inwhich high frequency alleles may contributes a modest relative risk but an appreciable proportion of disease burden in the population.</p> <p align="center"><b><u>Aseptic losses of periprostetic bone</u></b></p> <p align="justify"><b><u></u></b></p> <p align="justify">Inflammation reaction is strictly related to production and activation of membrane linked lipids mainly derivatives of arachidonic acid able to be transformed into their active metabolites: prostaglandins, leukotrienes, lipoxins and forming sfingolipids.</p> <p align="justify">Between prostaglandins the main metabolic actions are exerted by PGE2 those receptors have been found in humans to be of 4 types EP1,2,3,and 4.</p> <p align="justify">EP1 is linked to IP3 signaling and PLC with subsequent mobilization of intracellular calcium stores.</p> <p align="justify">EP2 and EP4 stimulate formation of cAMP at intracellular level</p> <p align="justify">EP3 activating Gi a G protein able to inhibits the enzyme adenyl cyclase.</p> <p align="justify">Many data seems to demonstrate that the receptor responsible for induction of RANK-L expression by bone cells is represented by EP4.</p> <p align="justify">PGE2 induction by RANKL seems to be mediated by EP4 receptor, so that double KO EP4 mice show few osteoblasts and showed a dramatic reduction in RANKL expression by osteoblastic cells.</p> <p align="justify">Periprostetic osteolysis is a serious orthopedic problem often present at prosthesis / bone interface linked to activation of inflammatory prostaglandins: it is called “Aseptic Loosening of bone”. It leads to great limitation of many total joint replacement surgical interventions.</p> <p align="justify">Wear debris production at tissue implant interfacce stimulates the activation of osteoclasts through RANKL secretion. Possible mediators of osteolytic action of wear debris are believed to be PGE2.</p> <p align="justify">Interestingly sporadic reports of Bone Phenotype in “<b><u>Darier Disease</u></b>” suggested an involvment of SERCA 2b channels.</p> <p align="justify">SERCA 2 b heterozygous mice -/+ showed a reduced frequency of calcium oscillation in bone cell membrane linked to loss of NFATc1 expression and loss of osteoclasts. SERCA 2b channels are present at cellular level at sarco-endoplasmic reticulum surface and they function such as Calcium ATPase type 2 channels involved in processes of osteoclasts differentiation. </p> <p align="justify">These heterozygous mice showed a phenotype very similar to human bone phenotype of Darier disease showing bone tissue affected by bone cyst and fractures as well’s by periodontal gingival and mucosal inflammation.</p> <p align="justify"> </p> <p align="justify">References</p> <p align="justify">Gafni J, Ravid M, Sohar E. The role of amyloidosis in familial Mediterranean Fever: a population study. Isr J Med Sci 1968;4:995-9.</p> <p align="justify">Zemer D, Revach M, Pras M et al. A controlled trial of colchicine in preventing attacks of familial Mediterranean Fever. N Engl J Med 1974;291:932-4.</p> <p align="justify">Dinarello CA, Wolff SM, Goldfinger SE et al. Colchicine therapy for familial Mediterranean Fever: double blind trial. 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N Engl J Med 2005;353:918-23.</p> <p align="justify">Deftos LJ. Treatment of Paget disease – Taming the wild osteoclast. N Engl J Med 2005;353:872-75.</p> <p align="justify">Reid IR, Miller P, Lyles K et al. Comparison of a single infusion zolendronic acid with risendronate for Paget’s Disease. N Engl J Med 2005;353:898-908.</p> <p align="justify">Kim K, Fisher MI, Xu SQ et al. Molecular determinants of esponse to TRAIL: in killing normal and cancer cells. Clin Cancer Res 2000;6:335-346.</p> <p align="justify">Hugher EA, Ralston SH, Whyte MP et al. Mutations in TNFRSFIIA, affecting the signal peptide of RANK, cause Familial Expansile Osteolysis. Nat. Genet 2000;24:45-8.</p> <p align="justify">White MP, Hughes AE. Expansile skeletal hyperphosphatasia is caused by a 15 base pair tandem duplication in TNFRSFIIA encoding RANK and is allelic to Familial Expansile Osteolysis. J Bone Min Res 2002;17:26-9.</p> <p align="justify">White MP, Obrecht SE, Finnegan PM et al. Osteoprotegerin deficiency and Juvenile Paget’s disease. N Engl J Med 2002;347:175-84.</p> <p align="justify">Langdahl BL, Carstens M, Stenjaer L et al. Polymorphisms in the osteoprotegerin gene are associated with osteoporotic fractures. J Bone Miner Res 2002;17:1245-55.</p> <p align="justify">Arko B, Prezelj J, Kocijancic A et al. Association of the osteoprotegerin gene polymorphisms with bone mineral density in postmenopausal women. Maturitas 2005;51:270-9.</p> <p align="justify">Zhao HY, Liu JM, Ning G et al. The influence of Lys3Asn polymorphism in the osteoprotegerin gene on bone mineral density in Chinese postmenopausal women. Osteoporosis Int. 2005;16:1519-24.</p> <p align="justify">Wynne F, Drummond F, O’Sullivan K et al. Investigation of the genetic influence of the OPG, VDR (Fok1), and COL1A1 Sp1 polymorphisms on BMD in the Irish population. Calcif Tissue Int 2002;71:26-35.</p> <p align="justify">Vidal C, Brincat M, Xuereb Anastasi A. TNFRSF11B gene variants and bone mineral density in postmenopausal women in Malta. Maturitas 2006;53:386-95.</p> <p align="justify">Moffett SP, Oakley JI, Cauley JA et al. Osteoprotegerin Lys3Asn polymorphism and the risk of fracture in older women. J Clin Endocrinol Metab 2008;93:2002-8. </p> <p align="justify">Samelson EJ, Broe KE, Demisse S et al. Increased plasma protegerin concentrations are associated with indices og bone strength of the hip. I Clin Endocrinol Metabol 2008;93:1789-95.</p> <p align="justify">Darier disease and periprostetic aseptic bone losses:</p> <p align="justify">Kariya Y, Homma M, Aoki S et al. Vps33a mediates RANKL storage in secretory lysosomes in osteoblastic cells. J Bone Miner Res 2009;24:1741-52.</p> <p align="justify">Tsutsumi R, Xie C, Wei X et al. PGE2 signaling through the EP4 Receptor on fibroblasts upregulates RANKL and stimulates osteolysis. J Bone Miner Res 2009;24:1753-62.</p> <p align="justify">Yang Y-M,Kim MS, Son A et al. Alteration of RANK-L induced osteoclastogenesis in primary cultured osteoclasts from SRCA2-/+ mice. J Bone Mineral Res 2009;24:1763-9.</p> <p align="justify">Frezzini C, Cedro M, Leao JC et al. Darier disease affecting the gingival and oral mucosal surfaces. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006;102:e29-e33.</p> <p align="justify">Menne T, Nielsen AO. Bone cysts and spontaneous fractures in two siblings with dyskeratosis follicularis Darier. Acta Derm Venereol 1978;58:366-7.</p> <p align="justify">Ahn W, Lee MG, Kim KH et al. Multiple effects of SERCA2b mutations associated with Darier’s disease, J Biol Chem 2003;278:<a dir="ltr" href="tel:20795-801" x-apple-data-detectors="true" x-apple-data-detectors-type="telephone" x-apple-data-detectors-result="2">20795-801</a>.</p> <p align="justify">Sheridan AT, Hollowood K, Sakuntabhai A et al. Expression of sarco/endoplasmic reticulum Ca2 ATP ase type 2 isoforms (SERCA2) in normal human skin and mucosa , and in Darier’s disease skin. Br J Dermatol 2002;147:670-4. </p> BoNewshttp://www.blogger.com/profile/14996032718916828654noreply@blogger.comtag:blogger.com,1999:blog-6459801161644965909.post-38750928698523636742009-08-23T17:23:00.000+02:002016-04-25T21:59:54.282+02:00Identification of vertebral fractures<p> </p> <p align="center"></p><div style="text-align: -webkit-center;"><span style="text-align: start;"> </span></div><span style="font-family: 'Helvetica Neue Light', HelveticaNeue-Light, helvetica, arial, sans-serif; text-align: start;"><div class="separator" style="clear: both;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhnweuPN4iivuxp2wDggP63k4fp1bdvIGYAYveUDcisgz74BVXE7iC_FBEMj9xW7PpYsse6iBv8yc9idYV620WXooyUoT0O_wBCmvRWEQfghhOOjdp1G_yZAM2RiI4F7lXvQyJ4om4tBB-5/s640/blogger-image--182875317.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhnweuPN4iivuxp2wDggP63k4fp1bdvIGYAYveUDcisgz74BVXE7iC_FBEMj9xW7PpYsse6iBv8yc9idYV620WXooyUoT0O_wBCmvRWEQfghhOOjdp1G_yZAM2RiI4F7lXvQyJ4om4tBB-5/s640/blogger-image--182875317.jpg"></a></div> </span><p></p> <p> </p> <p align="justify"><font size="4"> Placebo effect has been know from time of Plato cited by Socrates about the cure of headache “ was a kind of leaf, which required to be accompanied by a charm, and if a person would repeat the charm at the same time that he used the cure, he would be made whole; but that without the charm leaf would be of no avail.” However a therapy to be true placebo, ethically speaking, must be safe to use, without any adverse effects and possible less invasive we can. That’s a problem of some “minimally invasive” techniques that in the developed countries during the last decade are increasing exponentially. Future of surgeons would be “endoscopically and fluoroscopically” followed tecniques, allowing shorter hospitalization times, prompt delivery and fast recovery of patients. Radiologists, if not involved into Nuclear Medicine, are better called Interventional Radiologists, a way to identify a Medical Doctor directly involved into the therapeutic measures adopted for increasingly diseases. The old radiologists, reading and comparing X-ray exams, are disappearing and substituted by Neuroradiologist. The problems is a correct use and approach to new available tecniques, too fast approaching on the free market without the due time required to completely understand their potential utility-damage ratio. </font></p> <p align="justify"><font size="4">A clear example of a wrong use of these tecniques is clearly demonstrated by two article published on The Journal on the isssue of August 6, 2009 concerning vertebroplasty use in osteoporotic patients. If we don’t know the pathophysiology of osteoporotic verbral fractures, but also only what is osteoporosis, clearly we could be charmed and easly attracted by these technologically revolutionary tecniques. </font></p> <p align="justify"><font size="4">Under fluoroscopic guidance, the neuroradiologist first infiltrated the skin underlying pedicles of fracture site with a 25 Gauge needle with 1 % lidocaine reacing the subcutaneous tissue. Sorthly after, using a 23 Gauge needle with 0.25% of bupivacaine infiltrated the periostium of the posterior verterbral lamina. At this point aan incision is made on the skin, and a 11-13 Gauge needle is placed postero-laterally relative to the eye of vertebral pedicle. Gently the operator mouves the needle through the pedicle into the anterior two third of the fractured vertebral body following the needle progression with fluoroscopic images antero-posteriorly and laterally. Barium opacified Polymethylmetacrylate (PMMA) is now infused under fluoroscopic lateral control. A Unipedicular approach can be used infusing a total of approximately 3 ml of PMMA injected directly into a single side. However a Bipedicular approach can be used if there is inadequate instillation of cement into vertebral body. </font><font size="4">The PMMA is stopped when a substantial resistance is met or when the PMMA reached the posterior quarter of vertebral body or if the PMMA leaked into extraosseous structures or veins. After the vertebroplasty the patients are followed in the supine position for 1 to 2 hours before discarge administering intravenously immediately after PMMA injection a cephalotin antibiotic treatment.</font></p> <p align="justify"><font size="4">In the two studies cited above the Authors demonstrated quite inequivocably that vertebroplasty is equal to placebo treatment in back pain relief particularly in short term. The anesthetic effect is probably important in explaining the shorter pain relief and easy manipulation by operators of vertebral bodies; however it cannot explaine the beneficial effect the Authors founded also after 4 or 6 weeks in most patients.</font></p> <p align="justify"><font size="4">As the Editor outlines, President Barack Obama recently called for more comparative-effectiveness research in order to establish true safety and effectiveness of a given treatment compared to other one as part of American Recovery and Reinvestement Act (ARRA). People of developed countries probably pay the prize of great advances in technologies, so that in great medical challenges, such as acute pain of vertebral fracture, informed patient take also an less invasive choiche, as vertebroplasty, in order to have best and faster pain relief. However we have to pay attention to correctly inform the patients in order to obtain a true informed choiche, and the demonstration of equal affectiveness of placebo anestetic injection and PMMA vertebral reconstruction help us in doing that.</font></p> <p> </p> <p><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJovS9xuC3sGKBdxI62ahl54_q4o3isufSEM-2orsRsdHFu-ZtOqrHsB7ixBeV3UKH2i0JL00L_ZuqhS334X-ItiZJU_TMDn-ABDSLHdhhOJghEFHtjQfnQKpzvTpHSeqzdRj2rBwuJHnD/s1600-h/%23%207%20Back%20surgery%20emilaminectomy%20and%20laminectomy%5B4%5D.jpg"><img style="border-right-width: 0px; display: block; float: none; border-top-width: 0px; border-bottom-width: 0px; margin-left: auto; border-left-width: 0px; margin-right: auto" title="# 7 Back surgery emilaminectomy and laminectomy" border="0" alt="# 7 Back surgery emilaminectomy and laminectomy" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjA1HPRONpQHyqctGS5WVqfs9afUxzsSVU-4isbioMCFix40uoe7wSZOdh0IBwKpdq-qcHf5uELH9gjO4_nx6vWUPJAaMJIiiQ7hMijhY5wTrEH_hHpIQU_0aBzA6s0PCITnUqIq8NxCe3A/?imgmax=800" width="430" height="480"></a> </p> <p align="justify"><font size="4">Also the presence of intravertebral edema during MRI, used in the studies under discussion, is not universally accepted target of vertebral osteoporotic fracture. Such as CT scan, also MRI, are usually only required in the presence of localized pain, focal neurological signs, or symptoms suggesting cord compression, disc erniation, a radiculopathy, or the clinical suspicion of primary or metastatic lesions, but not in osteoporotic patients.</font></p> <p><font size="4">What is the correct approach to a vertebral fracture?</font></p> <p><a href="http://lh3.ggpht.com/_FLe5Kbctaeg/SpFfBpx_y7I/AAAAAAAACiI/3w7HQ10JoJo/s1600-h/%23%2014%20Bone%20DXA%20scan%5B4%5D.gif"><img style="border-right-width: 0px; display: block; float: none; border-top-width: 0px; border-bottom-width: 0px; margin-left: auto; border-left-width: 0px; margin-right: auto" title="# 14 Bone DXA scan" border="0" alt="# 14 Bone DXA scan" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjRcpDNJa0DLUO2XvV6zZfesKXpCpKsdMn26nraBhzyb46retWXPjWDPdHc1hZJZI4-L9Egm2bnVh-hDrwnsnW2dwUcVM1jP6pJJ-eOoxlz0A4xuTGfC8UTHsOIXVZcCj890Kbw4lj44wxR/?imgmax=800" width="447" height="480"></a> </p> <p> </p> <p></p> <p></p> <p></p> <p></p> <p align="justify"><font size="4">The problem is besides all the <strong>definition of vertebral fracture</strong>, at present there’s no Consensus Giudelines on osteoporotic vertebral fracture definition. </font><font size="4">Identification of vertebral fracture can be very difficult, because the shape of normal vertebral bodies varies widely between individuals. Vertebral bodies can be present abnormal features because non-osteoporotic deformities and errors in radiological projection can induce a misdiagnosis of fractured body. </font><font size="4">We have to remember that about 50% of vertebral fractures are asymptomatic and therefore are only casually identified. They are not the source of pain !Even when chest radiographs or vertebral images are correctly obtained only 35 to 50% of all radiographic vertebral fractures are correctly reported. It has been estimated that only 19% of these fractures reach clinical attention and can be correctly treated with a antiosteoporotic treatment. In view of high radiation exposure routine chest and lumbar radiographs are not recommended, but the availability of vertebral imaging using DEXA take the advantage of utilize an image of near radiographic quality available with a low fraction of the radiation dose.</font></p> <p align="center"><a href="http://lh6.ggpht.com/_FLe5Kbctaeg/Spk5LpwmeEI/AAAAAAAACjQ/fEyNaJNBXso/s1600-h/image0%5B11%5D.jpg"><img style="border-right-width: 0px; margin: 0px; display: inline; border-top-width: 0px; border-bottom-width: 0px; border-left-width: 0px" title="image0" border="0" alt="image0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgl5FGzh2xHiszlm-0PczQv6G_TSTz-ENran934IPj_jBmLpXHlTkaCXPPQ12i6cRoSupAhQTEDOM5N-I1V9xp7ZkFOkmDS2uVSzwPIDYX-2Nscwwz8tjRU_qJauosImVS3GWXEZOnXzSk2/?imgmax=800" width="459" height="343"></a> </p> <p align="justify"><font size="4">Imaging vertebral fractures using DXA is called <b>Vertebral Fracture Assessment</b> (VFA).</font></p> <p align="justify"><font size="4">The disadvantage of VFA is poor image resolution compared to conventional radiography, CT or MRI and the increased difficulties in imaging the thoracic spine, expecially above T7. Between 5 to 15% of thoracic vertebrae can be visualized only by conventioonal radiography.</font><font size="4">The sensitivity and specicificty of this approach compared with conventional radiography varies with the kind of approach used to definy a vertebral fracture:</font></p> <p align="justify"><font size="4">- Morphometric</font></p> <p align="justify"><font size="4">- Semiquantitative (SQ)</font></p> <p align="justify"><font size="4">- Visual identification</font></p> <p align="justify"><font size="4">One advantage of DXA imaging is that the scan are not subjected to the same degree of projection distortion as conventional radiography because the X-ray beam is always orthogonal to the spine. Reducing the X ray diffraction effect. </font><font size="4">Moreover DXA reduces the frequency that soft tissue obscure the endplates compared to single energy mode. </font><font size="4">Side-by-side viewing facilitates the identification of incidental vertebral fractures.</font></p> <p align="justify"><b><font size="4">Morphometrical analysis</font></b></p> <p align="justify"><font size="4">It uses the measurement of vertebral height to define vertebral fractures. A normative daatabase is established against which the vertebrae are compared, There are a number of different morphometric approaches that vary with the criteria by which they define a vertebral fracture and in the reference data used, The most widely used approaches to identify prevalent and incidental vertebral fractures are the two different algorithms proposed by McCloskey et al (3) and Eastell R et al (4). Morphometric analysis has a high sensitivity and moderate high specificity in discriminating between normal vertebrae and fractured vertebrae. Moreover, all the morphometric approaches for defining prevalent and incident vertebral fractures are correlated with clinical risk factors for vertebral fractures. </font><font size="4">A loss of vertebral height of 20 to 25 % is usually used to define an incident vertebral fracture; using this definition comparable ability to identify any vertebral frcture is present irrespective of aproach used to define a baseline fracture. </font><font size="4">As mentioned above VFA is more effective in identifying moderate to severe deformities with a sensitivity of 81.6% for grade 2 deformities, whereas mild grade 1 deformities identifiation has a sensitivity as low as 22%. </font><font size="4">Finally , the precision error is small if compared with the reduction in vertebral height of 20 to 25% threshold used to define vertebral fractures and it is less using conventional radiology than using VFA.</font></p> <p align="justify"><b><font size="4">Semiquantitative analysis</font></b></p> <p align="justify"><font size="4">SQ analysis combines measurements of vertebral height with subsequent evaluation of all vertebrae with a short vertebral height by an expert reader. This combined approach enables the identification of non-osteoporotic fracture vertebral deformities, which are not identified using morphometric analysis alone. As a consequence, SQ analysis is able to reduces false positive results.</font><font size="4">The most widely used SQ analysis is that of <b>Genant HK</b> (6). Baseline or prevalent vertebral fractures are graded from “0” equal to normal to “3” equal to severe fracture, and incident fractures are defined as an increase of more than or equal than 1 grade on follow-up radiographs. </font></p> <p align="justify"><font size="4">Genant grade 1 corresponds to an 20 to 25% reduction in anterior, middle or posterior height </font></p> <p align="justify"><font size="4">Genant grade 2 corresponds to a 25 to 40% reduction in any height</font></p> <p align="justify"><font size="4">Genant grade 3 corresponds to more than 40% reduction in any vertebral height</font></p> <p align="justify"><font size="4">Mild grade 1 SQ vertebral deformities are frequently not associated with low BMD values.</font><font size="4">The interobserver agreement for conventional radiographs or DXA images is similar with a K score of 0.53 and 0.51 respectively.</font><font size="4">This approach is currently those recommended by International Society of Clinical Densitometry for diagnosing vertebral fractures with VFA.</font></p> <p align="center"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgBQpDBfHWCDuirSBWf-Hj4q9kL4sJShxMMXyceUmaIIcxZ4SyQgvuGUq0dO0Q9AT4JX4Cg1RHNso7VlKCDVZmFxJG1uN9p1XCzR5Nci1gHNfiDSHNesX-jY0il1cYU2_vik0rdWX8icZfv/s1600-h/%23%2013%20BMD%20Distribution%20and%20fracture%20rate%5B14%5D.jpg"><img style="border-right-width: 0px; display: block; float: none; border-top-width: 0px; border-bottom-width: 0px; margin-left: auto; border-left-width: 0px; margin-right: auto" title="# 13 BMD Distribution and fracture rate" border="0" alt="# 13 BMD Distribution and fracture rate" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgv5U-jWq0EPfnzZscEOoxcUr66-KnMKXCRcc44E8zA0dKBTiQfY84z1X5bjghtWk9WvQlP_-7b_quOSSocaefRsW2jFp1S5t0gM5I8M8dH5YZoUOqaNp2vgnLizbHo2lxm_AczP_73mmol/?imgmax=800" width="500" height="350"></a> </p> <p align="justify"><font size="4"><b>Algorithm Based Qualitative Approach</b></font></p> <p align="justify"><font size="4">ABQ approach differs from SQ analysis because the last one is based only on variations of vertebral height; not considering variations on endplates cracks or breaks as the primary event with a subsequent evaluation of vertebral height. ABQ focus more attention on the vertebral endplate alterations rather than on short vertebral height. Using ABQ we have a greater association with low BMD and interobserver agreement for radiography and DXA images of 0.74 and 0.65 respectively. So that mild vertebral fractures identified with ABQ are more strngly associated with osteoporosis than when this mild fractures are identified with SQ method. </font><font size="4">The definition of vertebral fractures includes the presence of breaks in the cortex of vertebral body; these breaks always occurs in the center or either the superior or inferior endplates that are the weakest area of endplate because it is more distant from the strong outer vertebral ring. As a consequence, the endplate buckles or collapses under pressure because of interventebral disc and it results in a concave appearance to the superior and/or inferior endplate. If the concavity extend beyond the inner border of the vertebral ring , it is unlikely to represent an osteoporotic fracture. A vertebral fracture initially involves a crack of the superior or inferior endplate with or without the simultaneous loss of vertebral height. As severity of the fracture progresses, the vertebral ring fractures resulting in loss of height and buckling of the anterior, lateral and occasionally posterior cortex. It is important to outlined these aspects because there is considerable variation in vertebral shape resulting in osteoporotic and non osteoporotic deformities that can result in considerable intraobserver error even among expert readers.</font></p> <p align="justify"><font size="4">Commonly we can see <b>wedge deformity fracture</b> associated with endplate fracture where is present a fracture of the anterior cortex of vertebral body.</font></p> <p align="justify"><font size="4">A true <b>compression fracture</b> associated with endplate fracture is an osteoporotic compression fracture of superior endplate associated with fracture of anterior and posterior cortex of vertebral body.</font></p> <p><font size="4">Clinical recommendations for screening for vertebral fractures</font></p> <p align="justify"><font size="4">The current recommendations for using fracture assessment through DXA imaging (VFA) by the International Society of Clinical Densitometry are:</font></p> <ol> <li><font size="4">When the results may influence clinical management</font> </li> <li><font size="4">If BMD is indicated then consider performing VTA if clinically indicated in:</font> </li> </ol> <p><font size="4">- Documented height loss greater than 2 cm</font></p> <p><font size="4">- Historical height loss greater than 4 cm since young adult</font></p> <p><font size="4">- History of fracture after 50 years old</font></p> <p><font size="4">- Commitment to long term oral or parental glucocorticoid therapy</font></p> <p align="justify"><font size="4">- History or findings suggestive of vertebral fracture not documented by previous radiographic imaging</font></p> <p align="justify"><font size="4">Therefore, it is reasonable to screen all patients with osteopenia using VFA, if it will alter the management of the patient. In a study at Mayo Clinic 16% of patients 60 to 69 years old and 45% of those older than 70 years had a previously undiagnosed vertebral fracture on VFA.</font></p> <p align="justify"><font size="4">References</font></p> <p align="justify"><font size="4">Kallmes DF, Comstock BA, Heagerty PJ et al. A randomized trial of vertebroplasty for osteoporotic spinal fractures. N Engl J Med 2009;361:569-79.</font></p> <p align="justify"><font size="4">Buchbinder R, Osborne RH, Ebeling PR et al. A randomized trial of vertebroplasty for painful osteoporotic vertebral fractures. N Engl J Med 2009;361;557-68.</font></p> <p align="justify"><font size="4">Weinstein JN. Balancing science and informed choice in decision about vertebroplasty. N Engl J med 2009;361:619-21.</font></p> <p align="justify"><font size="4">McCloskey EV, Spector TD, Eyres KS et al. The assessment of vertebral deformity: A method for use in population studies and clinical trials. Osteoporosis Int 1993;3:138-47.</font></p> <p align="justify"><font size="4">Eastell R, Cedel SL, Wahner HW et al. Classification of vertebral fractures. J Bone Miner Res 1991;6:207-15.</font></p> <p align="justify"><font size="4">Genant HK, Jergas M, Palermo L et al. Comparison of semiquantitative visual and quantitative morphometric assessment of prevalent and incident vertebral fractures in osteopororsis. The Study of Osteoporotic Fractures Research Group. J Bone Miner Res 1996;11:984-96.</font></p> <p align="justify"><font size="4">Rea JA, Li J, Blake GM et al. Visual assessment of vertebral deformity by X-ray absorptiometry: A highly predictive method to exclude vertebral deformity. Osteoporosis Int 2000;11:660-8.</font></p> <p align="justify"><font size="4">Siminoski K, Jiang G, Adachi JD et al. Accuracy of height loss during prospective monitoring for detection of incident vertebral fractures. Osteoporosis Int 2005;16:403-10.</font></p> <p align="justify"><font size="4">Siminoski K, Warshawski RS, Jen H et al. The acuracy of historical height loss for the detection of vertebral fractures in postmenopausal women. Osteoporosis Int 2006;17:290-6. </font></p> <p align="justify"><font size="4">Schousboe JT, Ensrud KE, Nyman JA et al. Cost-effectiveness of vertebral fracture assessment to detect prevalent vertebral deformity and select postmenopausal women with a femoral neck T-score lower than 2.5 SD for alendronate therapy: A modeling Study. J Clin Densitom 2006;9:133-43.</font></p> BoNewshttp://www.blogger.com/profile/14996032718916828654noreply@blogger.comtag:blogger.com,1999:blog-6459801161644965909.post-51959301989892639712009-06-12T15:58:00.000+02:002016-04-25T22:05:30.262+02:00Collagenopathies and Marfan's Syndrome.<p align="center"><br></p><p align="center"><br></p><p align="center"></p><div class="separator" style="clear: both;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhBgJqGxxJCkk9h3E4MpvXt_bIMt7t5aVAoAgKP2EFjrSAt1BIAy3VwVSccZnibfmnrUuSzWhqVs8A_uR6PnPZfz1daPVGUup9OUAHTQeIIl813Tse86UtMjmy9d56a1wrd2-92W7uT7imk/s640/blogger-image--1232875577.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhBgJqGxxJCkk9h3E4MpvXt_bIMt7t5aVAoAgKP2EFjrSAt1BIAy3VwVSccZnibfmnrUuSzWhqVs8A_uR6PnPZfz1daPVGUup9OUAHTQeIIl813Tse86UtMjmy9d56a1wrd2-92W7uT7imk/s640/blogger-image--1232875577.jpg"></a></div><br><p></p><p align="center"> </p> <p align="center" style="text-align: start;"><span style="font-family: 'Helvetica Neue Light', HelveticaNeue-Light, helvetica, arial, sans-serif;">Here you can found some one-line material concerning my letter to New England about the Dietz's article on Marfan's sindrome and losartan therapy, published on the June 26, 2008 issue of The Journal. As usually all writed material is based on personal reading of scientific articles and possible are apparently unrelated each other. However they represent the course of my scientific actual knowledge concerning collagenopathies and TGFbeta related disease starting from Marfan's syndrome study.</span></p> <p align="justify">Since more than a century ago the <u>first professor in pediatrics</u> in Paris, Antoine Marfan, described a young girl with long, spider-like fingers and other curious skeletal anomalies, understanding of the syndrome that now bears his name.</p> <p align="justify">The Marfan syndrome is an inherited disorder of connective tissue characterized by pleiotropic manifestations of many organs, including the eyes, heart, aorta, skeleton, skin, and lung.</p> <p align="justify">The cardinal ocular manifestation, ectopia lentis, was not recognized as being associated with the skeletal changes for some decades.</p> <p align="justify">The cardiovascular system was found to be involved at about the same time, when severe mitral regurgitation was observed; until 1943 was identified the involvement of aortic root, and it was remained for McKusick to show in 1955 that the disease of the aorta accounted for most deaths. Life expectancy is reduced by one thrid, on average because of emergent cardiovascular complications.</p> <p align="justify">By the 1930s, it was recognized that the disease was transmitted by mendelian dominant phenotype; not until 1949 the study of large pedigrees convinced skeptics that the condition was due to a single mutant gene, which needed to be present in only one copy (heterozygosity) to cause the disease.</p> <p align="justify">Half a century was required to to identify the effect of the mutation of the classic triad of Marfan disease:</p> <ol> <li> <div align="justify">ectopia lentis </div> </li> <li> <div align="justify">cardiovascular disease: aortic aneurism and mitral valve prolapse </div> </li> <li> <div align="justify">skeletal disease: joint laxity and bone overgrowth </div> </li> </ol> <p align="justify">Microfibrillar fibers make up a discrete, widely distributed, and pleiomorphic fiber system in human tissues. When visualized by electron microscopy, the fibers apper as linear bundles containing many individual microfibrils with a tubular cross-section and an average diameter of 10 to 12 nm, showing characteristic like collagen fibers type 3.</p> <p align="justify">Microfibrillar fibers are considered integral components of elastic elements, but such fibers are much more widely distributed than elastin. They have been visualized by immunolocalization studies in skin, tendon, cartilage, muscle, kidney, perichondrium, periosteum, blood vessels, pleura, dura mater, and ciliary zonules of the ocular lens.</p> <p align="justify">In particular <strong>McKusick</strong> has suggested that understanding the common factor in aortic media lamellar structure and the ciliary zonules causing “ectopia lentis” often present in Marfan syndrome may reveal the basic defect of this disease.</p> <p align="justify">The consistent finding of stretched and occasionally broken zonular fibers in the ectopia lentis of patients with Marfan syndrome argues that these microfibrillar fibers are functionally incompetent to resist to normal stress and elongate progressively over time.</p> <p align="justify">The progressive dilatation of aortic root with the fragmentation of elastic lamellae of the tunica media, the striae atrophicae in the skin, pulmonary bullae, dural ectasia as well’s seletal overgrowth can be linked to functional alteration of the lamellar structure. In particual skeltal overgrowth may be linked to diminished forces generated by periosteal and perochondrial membranes that oppose bone growth.</p> <p align="justify">The absence of reticular meshworks on epidermal sections and in dermal fibroblasts culture of patients affected by Marfan syndrome shows that an alterations is present in these extracellular structures.</p> <p align="justify">However other common clinical pictures can present the same alterations in fiber disposition such as in patients affected by:</p> <p align="justify">- Homocystinuria: due to cystationina beta synthse defect</p> <p align="justify">- Ectodermal dysplasia</p> <p align="justify">- Epidermolysis bullosa-like syndrome</p> <p align="justify">- Coronary artery dissection</p> <p align="justify">- Paudoxantoma elasticum</p> <p align="justify">- Cutis laxa: due to elastin gene mutation</p> <p align="justify">The first major advance came in 1991 when missense mutations in the <strong>fibrillin-1 gene</strong> (FBN1) were discovered in two unrelated patients with the syndrome by Dietz HC et collegues. Three works on the same issue of Nature outlined the presence of such a mutation as a cause of syndromic complex. These findings were the culminations of biochemical studies that identified “fibrillin” as an extracellular matrix component and specifically such as the principal component of microfibrils associated with elastin fibers.</p> <p align="justify">Whereas the work of Hollister DW in 1990 demonstrated the fibrillin deficiency in patients affected by Marfan syndrome by immunohystochemical studies, on 1994 Shores demonstrated with genetic investigations that the region of chromosome 15 was linked to marfanoid syndrome and it was shown to contain the gene coding for fibrillin.</p> <p align="justify">The gene FBN1 is located on chromosome 15 q21.1, codes for fibrillin, the 350 kd protein that is the main component of extracellular microfibrils. The gene was demonstrated to be <strong>affected by mutations that resulted in a spectrum of connective tissue disorders, including but not limited to Marfan syndrome</strong>, involving structural fibrillin protein domains distributed uniformly over 10 kb FBN1 DNA sequence. So that such as in neurofibromatosis type 1 we have a relatively common dominant disorder with a high rate of new mutations, so that no easy screening test is possible. So that the demonstration of FBN1 mutation or abnormal fibrillin metabolism don’t permit or confirm the diagnosis of Marfan syndrome.</p> <p align="justify">It has been estimated that the frequecy of fibrillin disorders is considerably greater than the estimated incidence of Marfan syndrome of 1 in 10.000 subjects.</p> <p align="justify">Concerning Marfan syndrome <u>four</u> distinct phenotypically groups have been defined:</p> <p align="justify">- alterations of FBN1 gene disrupting the second disulphidrile bridge in 1 of the 44 domains containing six cysteine residues shown to be related to reduced secretion of fibrillin</p> <p align="justify">- nonsense mutations leading to premature termination of polypeptide synthesis shown to be related to a sinthesis of half the normal amount of fibrillin </p> <p align="justify">- rapidly progressive with aortic dilatation, severe scoliosis, ectopia lentis, variable skeletal abnormalities and negligible cardiac involvement or with mitral valve prolapse with skeltal features (with absent fibrillin)</p> <p align="justify">- adult type with dominant form of slowly progressive aortic aneurism without typical ocular and skeletal findings (with locally absent fibrillin)</p> <p align="justify"><br></p> <p align="justify">The basic paradigm of Marfanoid habitus is that fibrillin gene mutations resulted in the production of abnormal fibrillin protein that, when incorporated into microfibrils along with normal fibrillin, resulted in structurally inferior connective tissue. This adverse effect of mutant proteins on normal ones, which genetists term “dominant negative”, appeared to explain many of the cardianal feaures of Marfan syndrome.</p> <p align="justify">This explanantion was reinforced by the contemporaneous discovery of a <strong>second fibrillin gene</strong>, FNB2 located on chromososme 5, which is associated with a related connective tissue disorder:</p> <p align="justify">. <strong>congenital contractural arachnodactyly</strong> (Beals’ syndrome)</p> <p align="justify">On late ’90 some researchers developed imbred animal models for Marfan syndrome study; the introduction of mutations into the mouse fibrillin-1 gene, FBN1, recapitulated the disorder. Interestingly lungs were more affected in mice bearing the fibrillin gene mutations showing emphysematous changes in alveolar tissue. </p> <p align="justify">However Dietz HC showed that, instead of damages due to increasing breakdown due to repeated stretching of connective tissue, affected lungs presented an abnormal septation of the distal alveoli in newborn mice pups; a finding more consistent with a developmental defects than a decreased elasticyty.</p> <p align="justify">On the same year, on 2003, it was demonstrated that <strong>fibrillin has an homologous structure with Latent TGF beta binding-protein (LTBPs), which serve to hold TGF beta in an inactive</strong> complex in various tissues in extracellular matrix. It was showed tha fibrillin can bind TGF beta and LTBP. Dietz HC group hypothesized that abnormal fibrillin, or reduced levels of fibrillin, in connective tissue might result in an excess of active TGF beta. They demonstrated that blocking TGF beta with neutralizing antibodies, inbred mice strains showed a normalization of lung development.</p> <p align="justify">In <strong>2005 Loeys and Dietz</strong> showed that some patients can be classified such a separated clinical entity overlapping marfan syndrome, presenting:</p> <p align="justify">- aortic aneurysm</p> <p align="justify">- arachnodactyly</p> <p align="justify">- dural ectasia</p> <p align="justify">this syndromic complex is now called Loeys-Dietz syndrome and it was due to mutations affecting genes coding for TGF beta receptor type 1 and TGF beta receptor type 2 (<strong>TGFBR1 and FGFBR2</strong>); one affected patient was found to have an increase TGF beta activity in the aortic tissue. </p> <p align="justify">Interestingly studying a large cohort of patients with TGFBR1 and TGFBR2 mutations, it was demonstrated that some had the classic <strong>Loeys-Dietz syndrome</strong> with better outcome after aortic surgery, whereas others resembling patients with Ehlers-Danlos syndrome known to be linked to defects in collagen type III gene.</p> <p align="justify">Taken together, the genetic findings from these studies help us to describe a group of connective tissue diseases due to inhborn error of extracellular matrix proteins with a larger incidence on populations than previously known, we can call “fibrillinopathies”.</p> <p align="justify">Inhborn error of genes coding for different types of collagens give rise to “collagenopaties”:</p> <p align="justify">- Osteogenesis Imperfecta: due to collagen type 1 defect</p> <p align="justify">- Spondyloepyphiseo dysplasia: due to collagen type 2 defect</p> <p align="justify">- Ehlers-Danlos disease: due to collagen type 3 or type 5 defect </p> <p align="justify">- Mutiple Epiphyseal Dysplasia: due to collagen 9 defect </p> <p align="justify">- Methapyseal Dysplasia Schmid type: due to collagen type 10 defect</p> <p align="justify">- Marshall syndrome: due to collagen type 11 defect</p> <p align="justify"><strong>Its’ becoming clear that collagenopathies and fibrillinopathies show sometimes the same clinical picture in affected patients; and the more common manifestation of more subtle biochemical pathways involved into signal transduction share same proteins present on extracellular matrix space for their final actions.</strong></p> <p align="justify">It’s also likely that understanding the role of these proteins present in large amount on extracellular space may explain the physical properties of tissues such as the skin and bone where connective tissue components play a relevant role.</p> <p align="justify">In particular in view of recent result on marphanoid habits, involving elastin associated microfibrils in TGF beta signal transmission, it is easy to imagine a role of Bone Morphogenetic Proteins action also on mechanical transduction of physical forces applied on bone and on regulation of bone stiffness.</p> <p align="justify">References</p> <p align="justify">Peyritz RE, McKusick VA. The Marfan syndrome: diagnosis and management. N Engl J Med 1979;300:772-7.</p> <p align="justify">Pyeritz RE, McKusick VA. Basic defects in the Marfan syndrome. N Engl J Med 1981;305:1011-2.</p> <p align="justify">Boucek RJ, Noble NL, Gunja-Smith Z et al. The Marfan syndrome: a deficiency in chemically stable collagen-cross-links. N Engl J Med 1981;305:988-91.</p> <p align="justify">Gott VL, Pyeritz RE, Magovern GJ Jr et al. Surgical treatment of aneurysms of the ascending aorta in the Marfan syndrome: results of composite-graft repair in 50 patients. N Engl J Med 1986;314:1070-4.</p> <p align="justify">Sakai LY, Keene DR, Engvall E. Fibrillin, a new 350 kD glycoprotein, is a component of extracellular microfibrils. J Cell Biol 1986;103:<a dir="ltr" href="tel:2499-509" x-apple-data-detectors="true" x-apple-data-detectors-type="telephone" x-apple-data-detectors-result="0">2499-509</a>.</p> <p align="justify">Hollister DW, Godfrey M, Sakai LY et al. Immunologic abnormalities of the microfibrillar-fiber system in the Marfan Syndrome. N Engl J Med 1990;323:152-9.</p> <p align="justify">Kainulainen K, Pulkkinen L, Savolainen A et al. Location on chromosome 15 of the gene defect causing Marfan syndrome. N Engl J Med 1990;323:935-9.</p> <p align="justify">Pyeritz RE. Marfan syndrome. N Engl J Med 1990;323:987-9.</p> <p align="justify">Lee B, Godfrey M, Vitale E et al. Linkage of Marfan syndrome and a phenotypically related disorder to two different fibrillin genes. Nature 1991;352:330-4.</p> <p align="justify">Maslen CL, Corson GM, Maddox BK et al. Partial sequence of a candidate gene for the Marfan syndrome. Nature 1991;352:334-7.</p> <p align="justify">Dietz HC, Cutting GR, Pyeritz RE et al. Marfan syndrome caused by a recurrent de novo missense mutation in the fibrillin gene. Nature 1991;352:337-9.</p> <p align="justify">Tsipouras P, Del Mastro R, Sarfarazi M et al. Genetic linkage of the Marfan syndrome, ectopia lentis, and congenital contractural arachnodactyly to the fibrillin genes on chromosomes 15 and 5. N Engl J Med 1992;326:905-9.</p> <p align="justify">Shores J, Berger KR, Murphy EA et al. Progression of aortic dilatation and the benefit of long term beta adrenergic blockade in Marfan syndrome. N Engl J Med 1994;330:1335-41.</p> <p align="justify">Francke U, Furthmayr H. Marfan’s syndrome and other disorders of fibrillin. N Engl J Med 1994;330:1384-5.</p> <p align="justify">Loeys BL, Chen J, Neptune ER et al. A syndrome of altered cardiovascular, craniofacial, neurocognitive and skeletal development caused by mutations in TGFBR1 or TGFBR2. Nat Genet 2005;37:275-81.</p> <p align="justify">Habashi JP, Judge DP, Holm TM et al. Losartan, an AT1 antagonist, prevents aortic aneurysm in a mouse model of Marfan syndrome. Science 2006;312:117-21.</p> <p align="justify">Loeys BL, Schwarze U, Holm T et al. Aneurysm syndromes caused by mutations in the TGF beta receptor. N Engl J Med 2006;355:788-98.</p> <p align="justify">Gelb BD. Marfan’s syndrome and related disorders – more than tightly connected than we thought. N Engl J Med 2006;355;841-4.</p> <p align="justify">Brooke BS, Habashi JP, Judge DP et al. Angiotensin II blockade and aortic-root dilatation in Marfan's syndrome. N Engl J Med 2008;358:2787-95.</p> <p align="justify">Pyeritz RE. A small molecule for a large disease. N Engl J Med 2008;358:2829-31.</p> BoNewshttp://www.blogger.com/profile/14996032718916828654noreply@blogger.comtag:blogger.com,1999:blog-6459801161644965909.post-70169390608078440282009-06-12T09:52:00.000+02:002016-04-25T22:07:13.601+02:00Hypoparathyroidism and Hypercalciuria<h3 align="center"><b></b></h3> <h3 align="center"><div class="separator" style="clear: both;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3e_VV8EALAkRbpysfkgFlw9Ea_5qg-M4IIgri7c0jz3meUEOSBAjGA3pNUgTnmWO_TS3FdIt2KcIS7Kgsbl_5itVYNcvYe1S7ZCwQxWGIzllKeUfxCrqzCqjP9ZZqj8rLI2olQxbMRptx/s640/blogger-image--632806957.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3e_VV8EALAkRbpysfkgFlw9Ea_5qg-M4IIgri7c0jz3meUEOSBAjGA3pNUgTnmWO_TS3FdIt2KcIS7Kgsbl_5itVYNcvYe1S7ZCwQxWGIzllKeUfxCrqzCqjP9ZZqj8rLI2olQxbMRptx/s640/blogger-image--632806957.jpg"></a></div> </h3><h3 align="center" style="text-align: start;"><font color="#000000" style="font-weight: normal; font-size: 17px; -webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);"> </font></h3><h3 align="center"><b>Calcium homeostasis</b></h3> <p align="center"><br></p> <p align="justify">The present discussion is about the recent articles published on NEJM, concerning Hypoparathyroidism and Hypercalciuria. They represent on line material of my studies on these topics, as I’ve done a summary on my recent letter to the Editor on Brief Report on NHERF1 gene mutations and parathyroid hormone by Prié Dominique working in Paris, France at Hopithal Necker – Enfants Malades. </p> <p align="justify">Calcium crystallization process </p> <p align="justify">Excessively high concentration of calcium ions in the urine is one identifiable and correctable factor in stone formation. Calcium stone formation is a process of mineral crystallization in body tissue or fluid. </p> <p align="justify">Inorganic crystal are shaped to become an integral part of organic tissue to provide strength and hardness. Thsese inorganic substances are capable of reversible interactions with biomolecules so that the crystalline structures can be remodeled for physiological needs. </p> <p align="justify">Calcium salts have an highly adaptable coordination geometry, that greatly facilitates the protein binding, in its solid state or solution, adapting theirself to irregular geometry of proteins. </p> <p align="justify">The physical properties of bone and teeth result from the activities of proteins that functions as the organic-inorganic interface. </p> <p align="justify">Proteins share specific domains that specifically are able to interact with calcium crystals. The sequence below seems to be specific in these extracellular matrix proteins: </p> <p align="justify"><b></b></p> <p align="justify"><b>Aspartate-phosphoserine-phosphoserine-glutamate-glutamate</b> </p> <p align="justify">(DpSpSEE) </p> <p align="justify">The motif described in the saliva protein “<b>statherin</b>” is also found in other calcium crystal-interacting proteins, such as osteopontin. </p> <p align="justify">Interestingly unlike <u>EF domain hand that binds ionic calcium, this structure specifically binds to solid phase calcium phosphate crystals</u> and it is conserved in all phylogenetically evolved forms of life in the heart from invertebrates, such as crustaceans, to higher vertebrates, such as humans. </p> <p align="justify"><b>Physiologic crystallization</b> includes formation of exoskeleton, pearl, endoskeleton, and dentition, whereas <b>pathophysiologic</b> <b>crystallization</b> includes pyroposphate arhtropathy, pigmented gallstones, vascular calcifications, and urolithiasis. </p> <p align="justify">Serum calcium concentration is tightly regulated in humans, so that also small decrement in its concentration can led to clinical manifestations of “tetania”, as we have in hypoparathyroidism where Trousseau and Kwostek signs are present as clinical maifestations of altered muscle cells contraction regulations. </p> <p align="justify">On other side increments of calcium levels can lead to increased urinary calcium secretions with kidney function alterations, hypergastrinemia with gastric ulcer formation, hypertension, bone reabsorption with osteoporomalacia and bone fractures, parodontopathies with alterations in theet adherence to bone stucture in particular of mandible (inferior dental arc), as mention the more important clinical manifestations. </p> <p align="justify">The calcium homeostasis is under control of four main organs, <b>bowel and intestinal system, parathyroid glands, bone tissues, and kidneys</b>. Interestingly small changes in calcium levels can be evident such as alterations in acid-base equilibrium (i.e blood PH), due to important action exerted on these physicochemical equilibrium by renal cells activity of secretion and reabsorption. So that small changes in blood PH have to be resetted by intervention of kidney system ( metabolic acidosis or alkalosis) and only after by lung gas exchanges ( respiratory acidosis or alkalosis). </p> <p align="justify">The secretion and reabsorption of calcium ions by kidney, in that view, is essential to human life. When these equilibrium is altered the first alteration we see is an excessive excretion or loss of calcium ions in urine, so that we call hypercalciuria. </p> <p align="justify">Isolated hypercalciuria per se is not detrimental, but clinician interest in hypercalciuria concerns the complications that include mainly nephrolithiasis and nephrocalcinosis. </p> <p align="justify">Stones formation </p> <p align="justify">It has been suggested that the importance of hypercalciuria versus hyperoxaluria in calcium oxalate stones formers is equal; so that both <b>urinary concentration of calcium and oxalate are important contributing factors <u>in formation of kidney stones.</u></b> </p> <p align="justify"><b></b></p> <p align="justify">Kidney stones have a lifetime incidence of up to 13% in USA; in at least 70% of cases the stones are formed by calcium oxalate crystals, often with calcium phosphate or sodium urate. </p> <p align="justify">For a stone to form there must be “supersaturation” a chemical condition dependent from PH, Ionic strength and Ionic concentration; in the presence of a “nidus” the nucleation process occurs, where the “nidus” is formed by extracellular matrix components or cellular debris. The subsequent step is the formation of of a true stone by crystal growth and aggregation. </p> <p align="justify">The molecular mechanisms underlying the stone formation are described as: </p> <p align="justify">. <i>heterogeneous nucleation</i>: in which the initial ion complex is attached to a foreign surface </p> <p align="justify">. <i>homogeneous nucleation</i>: in which stones are formed independently from a nucleating surface </p> <p align="justify">The heterogeneous nucleation occurs more often, requiring less energy and so at low level of supersaturation. </p> <p align="justify">Some “factors” control the nucleation and crystal growth processes such as lowering supersaturation energy required and the presence of chemical inhibitors of crystal growth such as: </p> <p align="justify">. <b>pyrophosphate inorganic</b> </p> <p align="justify">. <b>citrate</b> </p> <p align="justify">. <b>glycoproteins</b> </p> <p align="justify">The majority of stone formers are defined such as affected by ”idiopathic hypercalciuria” . Any analysis of hypercalciuria should take into account a Pak pioneering work of 1975 introducing a tripartite classification of hypercalciuria: </p> <ol> <li> <div align="justify"><b>Absorptive hypercalciuria</b> </div> </li> <li> <div align="justify"><b>Reabsorptive hypercalciuria</b> </div> </li> <li> <div align="justify"><b>Renal hypercalciuria</b> </div> </li> </ol> <p align="justify">From pathophysiological point of view and also by genetic view, this classification may seem to be very important and today useful. </p> <p align="justify">Accordingly the extracellular fluid compartment can be regulated by the exchanges with three systems: </p> <ol> <li> <div align="justify">Intestinal system </div> </li> <li> <div align="justify">Bone system </div> </li> <li> <div align="justify">Kidney system </div> </li> </ol> <p align="justify">Where the action of main hormones secreted and regulated by parathyroid glands is exerted : parathormone, 1,25 dihydroxy vitamin D3. Interestingly the physiological action exerted by the third hormone “calcitonin” in humans is not relevant, whereas in fish living in water mabient rich in calcium salts, this hormene is very important. </p> <p align="justify">A possible classification of clinical parameters avaible if we consider renal hypercalciuria is the present: </p> <p align="justify">- Parathyroid hormone and 1,25 vitmian D3 are higher than expected </p> <p align="justify">- Hypercalciuria is inappropriate for the slightly elevated parathyroid homone, normal serum calcium, and normal filtered calcium. </p> <p align="justify">- Persistent hypercalciuria is present even during fasting </p> <p align="justify">- Increased bone resorption markers and/or reduced bone mineral density are present. </p> <p align="justify">Interestingly half of patients labeled as havng idipatic hypercalciuria shown a family history of kidney stones. However the genetic rules observed by hypercalciuric patients don’t follow the Mendelian pattern of inheritance, but it seems likely a variable under the effect of </p> <p align="justify">- Polygenic influence </p> <p align="justify">- Polymorphism if a single gene locus (heterogeneity) </p> <p align="justify">- Secondary and compensatory influences by three systems before described </p> <p align="justify">- Under influece of external non genetic factors in particular dietary and lifestyle factors </p> <p align="justify">So that also calciuria can be considered a continous variable with a polygenic determination and those phennotypic expression is modulated by non genetic environmental factors such as blodd pressure and body mass. </p> <p align="justify"><b>Parathyroid hormone hyposecretion or hypoactivity</b> </p> <p align="justify">Post-surgical </p> <p align="justify">Radiation induced </p> <p align="justify">Metastatic infiltration </p> <p align="justify"><b><u>Autoimmune </u></b>(isolated or combined with polyglandular endocrine defects) </p> <p align="justify"><b></b></p> <p align="justify"><b>Autoimmune Polyglandular Syndrome type 1</b> </p> <p align="justify">It is linked to <b>chromosome 21q22.3</b> coding for AIRE gene, inherited as <b>autosomal recessive</b> moitety. Loss-of-function mutation in AIRE, a zinc finger transcription factor present in thymus and lymph nodes, it is critical in mediating central tolerance by the thymus. NALP-5 is an intracellular signalling molecule strongly expressed in the parathyroid, and it can be target of specific parathyroid autoantigens in patients affected by APS-1. <u>Autoantibodies to NALP5</u> were found in 49% of patients with APS-1 and hypoparathyroidism. </p> <p align="justify">Clinical picture is variably present in people concentrated in Finnish, Iranian Jewis, and Sardinian populations, presenting more than 58 mutations. Classic triad is represented by: </p> <ol> <li> <div align="justify">Mucocutaneous candidiasis </div> </li> <li> <div align="justify">Adrenal insufficiency </div> </li> <li> <div align="justify">Hypoparathyroidism </div> </li> </ol> <p align="justify">(any of these two conditions are suffcient to formulate the diagnosis of APS-1). Other different features include hypogonadism, type 1 diabetes, hypothyroidism, vitiligo, alopecia, keratoconjuntivitis, hepatitis, pernicious anemia, and malabsorption. More than 80% of patients with APS-1 have hypoparathyroidism, as sole endocrinopathy. Typically the disease is presented in childhood or adolescence, but patients with only one disease manifestation is folowed long-term for the appearance of other signs of disease. </p> <p align="justify"><b><u>Deposition of heavy metals </u></b></p> <p align="justify">Thalassemia for iron excess </p> <p align="justify">Hemochromathosis </p> <p align="justify">Wilson’s disease </p> <p align="justify"><b>Severe magnesium depletion </b></p> <p align="justify">alchoolism, malnutrition, malabsorption, diabetes, metabolic acidosis, renal disorders leading to magnesium wasting (pyelonephritis, postostructive nephropathy, renal tubular acidosis, acute tubular necrosis, drugs toxicity ( diuretics, cisplatinum, aminoglycoside antibiotics, amphotericin B, cyclosporin) </p> <p align="justify">Primary renal magnesium wasting or <b>familial hypomagnesiemia</b> with hypercalciuria and nephrocalcinosis (<b>OMIM 248250</b>) due to mutations in genes coding for <b>parcellin-1 and claudin 16</b> </p> <p align="justify"><b>Hypermagnesiemia</b> </p> <p align="justify">On patients receiving tocolytic therapy or in patients with chronic kidney disease receiving magnesium supplements, antiacids or laxatives </p> <p align="justify">Genetic disorders of PTH biosynthesis and parathyroid gland development </p> <p align="justify"><b><u>PTH gene mutations</u></b> </p> <p align="justify"><b><u></u></b></p> <p align="justify"><b>Familial Isolated hypoparathyroidism</b> </p> <p align="justify">It is linked to chromosomal alteration of gene coding for <b>pre-pro-PTH located on chromosome 11p15</b>, and it is inherited in an autosomal recessive fashion. <u>Mutations in signal peptides</u>, disrupting PTH secretion, or in a donor splice site of the PTH gene, leading to skipping of PTH exon-2, which contains the initiation codon and signal peptide, are the molecular gene derangements accounting for the clinical picture. Very low or undetectable levels of of PTH and symptomatic hypocalcemia are main features of this syndromic complex. </p> <p align="justify">Instead of mutations in signal peptides, we can have on the same chromosomal locus <u>point mutations in the signal sequence</u> of the pre-pro PTH that prevents processing and translocation of PTH across endoplasmic reticulum and memebrane exocytosis. Mutant PTH is believed to be trapped into endoplasmic reticulum inside cells; resulting stress in endoplasmic reticulum is thought to predispose cells to undergo to apoptosis. </p> <p align="justify">Large deletions in transcription factor for gene coding for PTH called Glial cell Missing B or 2 <u>transcription factor</u> coded on <b>chromosome 6p23-p24 (GCMB or GCM2</b>) are autosomal recessive transmitted gene mutations responsible for forms of familial hypoparathyroidism due to large deletions of these transcription factors with subsequent <u>loss-of-function mutation</u> or point-mutations in the DNA-binding domain of these transcription factors. Leading to loss of transactivating capacity. Interestingly the two transcription factors are highly expressed in parathyroid cells and they controls the embryologic development of parathyroid glands </p> <p align="justify"><b></b></p> <p align="justify"><b>X-linked Hypoparathyroidism</b> </p> <p align="justify">The X linked recessive mutations affecting the chromosome Xq26-27 involve deletions or insertions of genetic material from <b>chromosome 2p25.3 to chromosome Xq27.1</b>, causing a position effect on regulatory elements controlling <b>SOX3 transcription factor</b>. SOX3 transcription factoris believed to be expressed during developement of parathyroid glands and its mutations cause parahtyroid agenesis of these glands. </p> <p align="justify">Hypoparathyroidism may is a part of complex genetic syndromes: </p> <p align="justify"><b>Familial hypocalcemia with hypercalciuria</b>: </p> <p align="justify">The gene locus responsible is located on <b>chromosome 3q13</b> and it is coding for calcium sensing receptor, the mutation is transmitted as <b>autosomal dominant</b> form and the phenotypic appearance of affected patients is cause by a <u>gain-of-function mutation in calcium sensing receptor</u> leading to milf hypocaòcemia and hypomagnesemia with hypocalciuria. Mutant receptors caused a left shifted set point for PTH secretion , definied as extracellualr calcium level necessary for half maximal suppression of PTH secretion. Most than 40 mutations have been identified at present, some of them responsible for the Batter’s syndrome type 5 (OMIM 601199 ). </p> <p align="justify">Constitutive active Calcium Sensing Receptors </p> <p align="justify">Most commonly coused by mutations <u>and rarely caused by acquired antibodies</u> that stimulates the calcium sensing receptor; appears to be among the most common causes of hypoparathyroidism. </p> <p align="justify">Syndrome of <b>hypoparathyroidism, deafness, and renal anomalies</b>. </p> <p align="justify">This syndromic complex is linked to mutations on <b>chromosome 10p14-10pter</b>, coding for the transcription factor <b>GATA3.</b> This mutation is inherited through an autosomal dominant form and interfere with the ability of GATA3 to bind to DNA or other transcriptional complexes. GATA3 is a transcription factor known to be highly expressed in in parathyroid glands, kidney and otic-vescicles during organ development precesses. So that clinical alterations characterizing this syndromic complex are hypoparathyroidism, bilateral sensorineural deafness, and renal anomalies or disfunction. </p> <p align="justify">Syndrome of <b>hypoparathyroidism with growth retardation, mental diseases</b> and dysmorphism. </p> <p align="justify">- Kenny-Caffey syndrome </p> <p align="justify">- Sanjad-Sakati syndrome </p> <p align="justify">The syndromic complex is due to mutations affecting <b>chromosome 1q42-q43</b> coding for transcription factor <b>TBCE</b> and transmitted as autosomal recessive trait. TBCE mutations cause loss of function and alter the assembly of microtubules in affected tissues. Kenny-Caffey syndrome is presented such as hypoparathyroidism probably due to agenesia of the glands, shorth stature, osteosclerosis, cortical bone thickening, calcifications of basal ganglia, ocular abnormalities; whereas Sanjad-Sakati syndrome is characterized by parathyroid aplasia, growth failure, ocular amalformations, microencephaly, and mental retardation. </p> <p align="justify"><b>DiGeorge Syndrome or VeloCardioFacial Syndrome</b> </p> <p align="justify">An heterozygous deletion of <b>chromosome 22q11.2</b> coding for the transcription factor <b>TBX1 </b>is the known cause of this syndrome. Loss of function mutation of TBX1 is responsible for loss of adjuvating action by TBX1 on other transcription factors known to be involved into the development of thymus and parathyroid glands. Embriological alterations are demonstrated to occurs in these patients in the formation and development of thrid and fourth branchial pouches. Wide spectrum of phenotypc expression, may include conotruncal cardiac defects, parathyroid and thymic hypoplasia, neurocognitive problems, and palatal, renal, ocular, and skeletal abnormalities. Hypocalccemia (in 50% of patients) can be transient or permanent and can develop in adulthood. A screening test si available with confirmed dletion by FISH technique. </p> <p align="justify">Mithocondrial disorders with hypoparathyroidism </p> <p align="justify">- <b>Kearns-Sayre syndrome</b> </p> <p align="justify">- <b>MELAS syndrome</b> </p> <p align="justify">- <b>MTPDS syndrome</b> </p> <p align="justify">Are known syndromic complexes due to deletions, mutations, rearrangments and duplications in the mitochondrial genome. These diseases are inherited uniquely by <b>maternal</b> cells (as all mithocondrial structures) and hypopararhytoidism can be present with various syndromic complexes: </p> <p align="justify">In Kearns-Sayre syndrome with progressive external ophtalmoplegy, pigmentary retinopathy, hearth block or cardiomegaly, diabetes. In MELAS syndrome with diabetes only In MTPDS with fatty acids oxidation alterations, peripheral europathy, retinopathy, acute fatty liver in pregnancy. </p> <p align="justify"><b><u>Resistance to PTH action</u></b> </p> <p align="justify"><b>Pseudo-Hypoparathyroisim Type 1a</b> </p> <p align="justify"><b></b></p> <p align="justify">The disease is due to inactivating mutation in the gene coding for the subunit alfa of G protein coupled with PTH Receptor (<b>GNAS gene on chromosome 20q13.3</b>). </p> <p align="justify">GNAS gene is able to code for the a-subunit of the stimulatory G protein (G<sub>S</sub>a) and it is located on Chromosome 20q11, where <b>13 exons</b> are present with differnt promoter regions. It is well demonstrated that this protein is linked to many transmembrane receptors such as Parathyroid hormone receptor, TSH Receptor, FSH and LH Receptors, GH Receptor. </p> <p align="justify">During the past few years it became apparent that GNAS gene enchodes not only for for G<sub>S</sub>a but also for several splice variants: </p> <p align="justify">1. XLas (paternal allele) </p> <p align="justify">2. NESP55 neurosecretory protein (maternal allele) </p> <p align="justify">3. A/B (1A) (paternal allele) </p> <p align="justify">4. Antisense transcript </p> <p align="justify">Later it was demosntrated that the alternative exons and their promoter regions are “methylated” on one parental allele, giving rise only to “<b>non-methylated” allele transcription.</b> </p> <p align="justify">Moreover, in most tissues the transcripts encoding G<sub>S</sub>a are derived from both alleles; whereas in a few tissues such as </p> <p align="justify">. proximal renal tubular cells </p> <p align="justify">. adipocytes </p> <p align="justify">. pituitary cells </p> <p align="justify">G<sub>S</sub>a appears to be expressed only from maternal allele. </p> <p align="justify">In the type 1a the mutation is an heterozygous inactivating mutation transmitted with <b>autosomal dominant</b> pattern with <b>maternal transmission</b> of the biochemical phenotype. Clinical features include those described first as <b>Albright’s Hereditary Osteodystrophy</b> such as round facies, mental retardation, frontal bossing, shorth stature, obesity, brachydactyly, ectopic ossification, hypocalcemia, hyperphopshatemia, evelated PTH levels, hypothyroidism, hypogonadism. </p> <p align="justify"><b>Pseudohypoparathyroidism Type 1b</b> </p> <p align="justify">The disease is due to a <b>partenally imprinted</b> defect in G protein <b>due to methylation defect in exon A and exon B</b>, this alterations lead to a selective resistance only to parathyroid hormone and not to other G coupled receptors linking other hormones. So the features are not those present in classic Albright Hereditary Osteodystrophy but hypoparathyroidism with elevalted PTH values, hypocacemia, hyperphosphatemia and elevated levels of urinary cAMP after administration of PTH. </p> <p align="justify"><b>Pseudohypoparathyroidism Type 2 or Pseudo-pseudo-hypoparathyroidism</b> </p> <p align="justify">It is due to GNAS <b>inactivating mutation paternally inherited</b>; however a resistance to PTH is present so that patients secrete normal urinary cAMP levels but not phosphaturic responses to PTH. It can have inheried or sporadic occurrence. </p> <p align="justify">References </p> <p align="justify"><b>Calcium homeostasis</b> </p> <p align="justify">Starnes CW, Welsh JD. Intestinal sucrase-isomaltase deficiency and renal calculi. N Engl J Med 1970;282:1023-4. </p> <p align="justify">Pak CY, Kaplan R, Bone H et al. A simple test for the diagnosis of absorptive, resorptive and renal hypercalciurias. N Engl J med 1975;292:497-500. </p> <p align="justify">Coe FL, Parks JH, Moore ES. Familial idiopathic hypercalciuria. N Engl J Med 1979;300:337-40. </p> <p align="justify">Tieder M, Modai D, Samuel R et al. Hereditary hypophosphatemic rickets with hypercalciuria. N Engl J Med 1985;312:611-7. </p> <p align="justify">Charnas LR, Bernardini I, Rader D et al. Clinical and laboratory findings in the oculocerebrorenal syndrome of Lowe, with special reference to growth and renal function. N Engl J Med 1991;324:1318-25. </p> <p align="justify">Coe FL, Parks JH, Asplin JR. The pathogenesis and treatment of kidney stones. N Engl J Med 1992;327:1141-52. </p> <p align="justify">Curhan GC, Willet WC, Rimm EB et al. A prospective study of dietary calcium and other nutrients and the risk of symptomatic kidney stones. N Engl J Med 1993;328:833-8. </p> <p align="justify">Lemann J Jr. Composition of diet and calcium kidney stones. N Engl J Med 1993;328:880-2. </p> <p align="justify">Pearce SH, Williamson C, Kifor O et al. A familial syndrome of hypocalcemia with hypercalciuria due to mutations in the calcium-sensing receptor gene. N Engl J Med 1996;335:1115-22. </p> <p align="justify">Simon DB, Lu Y, Choate KA et al. Paracellin-1, a renal tight junction protein required for paracellular Mg2+ resorption. Science 1999;285:103-6. </p> <p align="justify">Borghi L, Schianchi T, Meschi T et al. Comparison of two diets for the prevention of recurrent stones in idiopatic hypercalciuria. N Engl J Med 2002;346:77-84. </p> <p align="justify">Bushinsky DA. Recurrent hypercalciuric nephrolithiasis – Does diet help? N Engl J Med 2002;346:124-5. </p> <p align="justify">Bushinsky DA. Genetic hypercalciuric stone forming rats. Curr Opin Nephrol Hypertens 1999;8:479-488. </p> <p align="justify">Lemann J Jr, Pleuss JA, Worcester EM et al. Urinary oxalate excretion increases with body size and decreases with increasing dietary calcium intake among healthy adults. Kidney Int 1996;49:200-8 [Erratum Kidney Int 1996;50:341] </p> <p align="justify">Phillips MJ, Cooke JNC. Relation between urinary calcium and sodium in patients with idiopathic hypercalciuria. Lancet 1967;1:1354-7. </p> <p align="justify">Silver J, Rubinger D, Friedlander MM et al. Sodium-dependent idiopatic hypercalciuria in renal-stone formers. Lancet 1983;2:484-6. </p> <p align="justify"><b>Parathyroid hormone hyposecretion or hypoactivity</b> </p> <p align="justify"><b></b></p> <p align="justify">Ahonen P, Myllamierni S, Sipila I et al. Clinical variation of autoimmune polyendocrinopathy-candidiasis ectodermal dystrophy (APECED) in a series of 68 patients. N Engl J Med 1990;322:1829-36. </p> <p align="justify">Bilous RW, Murty G, Parkinson DB et al. Autosomal familial hypoparathyroidism, sensorineural deafness and renal dysplasia. N Engl J Med 1992;327:1069-84. </p> <p align="justify">Brown EM, Pollak M, Seidman CE et al. Calcium-ion-sensing cell-surface receptors. N Engl J Med 1995;333:234-40. </p> <p align="justify">Pearce SHS, Williamson C, Kifor O et al. A familial syndrome of hypocalcemia with hypercalciuria due to mutation in the calcium sensing receptor. N Engl J Med 1996;335:1115-22. </p> <p align="justify">Shore EM, Ahn J, de Beur SJ et al. Paternally inherited inactivating mutations of the GNASI gene in progressive osseus heteroplasia. N Engl J Med 2002;346:99-106. </p> <p align="justify">Juppner H. The genetic basis of progressive osseus heteroplasia. N Engl J Med 2002;346:128-130. </p> <p align="justify">Juppner H, Schipani E, Bastepe M et al. The gene responsible for psuedohypoparathyroidism type 1b is paternally imprinted and maps in four unrelated kindreds to chromosome 20q13.3. Proc Nat Acad Sci USA 1998;95:<a dir="ltr" href="tel:11798-830" x-apple-data-detectors="true" x-apple-data-detectors-type="telephone" x-apple-data-detectors-result="2">11798-830</a>. </p> <p align="justify">Bastepe M, Pincus JE, Sugimoto T et al. Positional dissociation between the genetic mutations responsible for pseudohypoparathyroidism type 1b and the associated methylation defect at exon A/B: evidence for a long-range regulatory element within the imprinted GNASI locus. Hum Mol Genet 2001;10:1231-41. </p> <p align="justify">Bastepe M, Lane AH, Juppner H et al. Paternal uniparenteral isodisomy of chromososme 20q – aand the resulting changes in GNASI methylation – as a plausible cause of pseudohypoparathyroism. Am J Hum Genet 2001;6:1283-9.</p> BoNewshttp://www.blogger.com/profile/14996032718916828654noreply@blogger.com