Serum osteoprotegerin and renal osteodystrophy.
BACKGROUND
Numerous growth factors and cytokines are known to modulate bone turnover. An important, recently discovered complex involved in osteoclastogenesis is the osteoprotegerin/osteoprotegerin-ligand (OPG/OPGL) cytokine complex, which is produced by osteoblasts. Many factors, including parathyroid hormone (PTH), appear to affect bone turnover through this pathway. In this disorder, the role of the OPG/OPGL system in the pathogenesis of renal osteodystrophy, a disease with either low or high bone turnover, has not been investigated so far.


METHODS
Thirty-nine chronic haemodialysis patients had bone biopsies, including histomorphometric and histodynamic examinations. In addition, the following serum biochemistry parameters were measured: serum OPG, intact PTH, PTH 1-84, total PTH, osteocalcin, total and bone alkaline phosphatases, 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol.


RESULTS
On average, serum OPG levels were above the normal range. They were lower in adynamic bone disease (ABD) patients, than in patients with predominant hyperparathyroidism (HP) or mixed osteodystrophy (MO). Significant negative correlations were found between serum OPG and PTH levels, and between serum OPG and parameters of bone resorption (ES/BS) and bone formation (ObS/BS and BFR/BS) in HP and MO patients with PTH values < or =1000 pg/ml. For intact PTH levels < or =300 pg/ml, serum OPG was significantly lower in the group with ABD than in those with HP or MO (P<0.05).


CONCLUSIONS
In renal osteodystrophy the OPG/OPGL system is involved in the regulation of bone turnover induced by PTH. The determination of serum OPG levels could be of use in the diagnosis of low turnover bone disease, at least in association with PTH levels < or =300 pg/ml.
Coen
Giorgio
G
Department of Nephrology, Second Medical Faculty, La Sapienza University, Rome, Italy. coen.gf@flashnet.it
Ballanti
Paola
P
Balducci
Alessandro
A
Calabria
Santo
S
Fischer
Maria Stephanie
MS
Jankovic
Ljiljana
L
Manni
Micaela
M
Morosetti
Massimo
M
Moscaritolo
Eleonora
E
Sardella
Daniela
D
Bonucci
Ermanno
E
D000368:Aged; D016723:Bone Remodeling; D001862:Bone Resorption / Q000097:blood; D001842:Bone and Bones / Q000473:pathology; D012080:Chronic Kidney Disease-Mineral and Bone Disorder / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D005260:Female; D006023:Glycoproteins / Q000097:blood*; D006801:Humans; D006961:Hyperparathyroidism / Q000097:blood; D007676:Kidney Failure, Chronic / Q000097:blood / Q000473:pathology / Q000628:therapy; D008297:Male; D008875:Middle Aged; D053244:Osteoprotegerin; D010281:Parathyroid Hormone / Q000097:blood; D018160:Receptors, Cytoplasmic and Nuclear / Q000097:blood*; D018124:Receptors, Tumor Necrosis Factor; D006435:Renal Dialysis
D006023:Glycoproteins; D053244:Osteoprotegerin; D010281:Parathyroid Hormone; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; C506030:TNFRSF11B protein, human