The impact of chronic inflammation on bone turnover in hemodialysis patients

Renal osteodystrophy is very common in hemodialysis (HD) patients. HD is a chronic inflammatory state. Studies in other pathological entities have shown an impact of chronic inflammation on bone metabolism. In the present study, the impact of chronic inflammation on bone turnover in HD patients was evaluated.

Thirty-three anuric HD patients free of other pathological conditions or medications that affect immune system or bone metabolism and 30 healthy volunteers enrolled into the study. Intact parathyroid hormone (iPTH), the markers of inflammation IL-6 and CRP, as well as the markers of bone turnover osteocalcin (OCN) and beta-isomerized C-terminal cross-linked peptide of collagen type I (beta-CTx) were measured in the serum.

All evaluated factors were increased in HD patients. In the HD group, the serum marker of osteoblastic activity OCN was related inversely to patients' age (r = -0.469, p = 0.006), CRP (rho = -0.460, p = 0.007), and IL-6 (r = -0.485, p = 0.004) but positively to iPTH (r = 0.707, p < 0.001). Similarly, the serum marker of osteoclastic activity beta-CTx was related inversely to patients' age (r = -0.383, p = -0.028), CRP (rho = -0.466, p = 0.006), and IL-6 (r = -0.460, p = 0.007) but positively to iPTH (r = 0.657, p < 0.001). Multiple linear regression analysis revealed that IL-6 affects bone turnover independently of PTH and to the opposite direction.

Chronic inflammation has a negative impact on bone turnover in HD patients. Certainly, further research and large clinical trials are needed for definite conclusions and for clarifying the exact molecular mechanisms implicated in the interaction between the immune system and bone metabolism in HD patients.