Inverse Association between Serum Osteoprotegerin and Bone Mineral Density in Renal Transplant Recipients

Background Osteoprotegerin (OPG) has pleiotropic effects on bone metabolism as well as endocrine function. Our aim was to evaluate the relationship between bone mineral density (BMD) and serum OPG concentration in renal transplant recipients. Methods Fasting blood samples were obtained from 69 renal transplant recipients. BMD was measured in lumbar vertebrae (L2-L4) by dual-energy X-ray absorptiometry. Eight patients (11.6%) had BMD values indicative of osteoporosis, 28 patients (40.6%) had BMD values indicative of osteopenia, and 33 patients had normal BMD values. Increased serum OPG levels (P <.001), decreased body mass index (BMI) (P =.033), and decreased body weight (P =.010) were significantly correlated with low lumbar T-score cut-off points between groups (normal, osteopenia, and osteoporosis). Results Women had significantly lower lumbar BMD values than men (P =.013). Menopause (P =.005), use of tacrolimus (P =.020), and use of cyclosporine (P =.046) were associated with lower lumbar BMD in renal transplant recipients. Univariate linear regression analysis revealed that lumbar BMD was positively correlated with height (P =.016), body weight (P =.001), and BMI (P =.015) and negatively correlated with age (P =.039) and log-OPG (P =.001). Multivariate linear regression analysis revealed that log-OPG (β: -0.275, R² change = 0.154, P =.014), body weight (β: 0.334, R² change = 0.073, P =.004), and age (β: -0.285, R² change = 0.079, P =.008) were independent predictors of lumbar BMD values in renal transplant recipients. Conclusions Serum OPG concentration correlated negatively with lumbar BMD values in renal transplant recipients.