Inverse association of serum osteocalcin and bone mineral density in renal transplant recipients.

Objectives: Osteocalcin, a protein from osteoblasts, affects bone mineralization and turnover. This study evaluates the association between fasting serum osteocalcin and bone mineral density (BMD) in renal transplant recipients.

Materials and methods: This study recruited 66 renal transplant recipients. We analyzed blood biochemistry studies from fasting blood samples. The serum osteocalcin levels were measured using a commercial enzyme immunoassay kit. We measure BMD by dual-energy X-ray absorptiometry in lumbar vertebrae (L2-L4). By the World Health Organization classification, we group recipients into three groups: normal, osteopenia, and osteoporosis.

Results: Of the renal transplant recipients, 8 patients (12.1%) were osteoporosis, and 28 patients (42.4%) were osteopenia. From normal to osteoporosis groups, the osteoporosis group has highest serum osteocalcin (P < 0.001), alkaline phosphatase (P = 0.005), lowest body mass index (P = 0.015), and body weight (P = 0.008). Females had lower lumbar BMD than males among recruited renal transplant recipients (P = 0.023). In the multivariate forward stepwise linear regression analysis, body weight (adjusted R² change = 0.138; P = 0.010), and logarithmically transformed osteocalcin (log-osteocalcin; adjusted R² change = 0.131; P = 0.012) can predict lumbar BMD in the renal transplant recipients.

Conclusion: Our study showed that fasting serum osteocalcin concentration was negatively correlated with the lumbar BMD in renal transplant recipients.