Endocrine Abstracts

Introduction: Renal transplant receivers (RTR) have a higher risk for osteoporosis, obesity and sarcopenia, which all seem to be interrelated. FGF23 and adipokine disorders, often recognized in RTR, might be involved in the fat-muscle-bone crosstalk. The current study aims to evaluate the influence of body compartiments and adipokines on bone mass in RTR.

Methods: Thiscross-sectional study investigates the predictive role of body composition, adipokines (leptin, adiponectin, resistin) and FGF23 upon bone mineral density (BMD) and bone metabolism parameters (osteocalcin, C-terminal telopeptide of type I collagen (CTx), calcium, phosphate) in 59 RTR and 59 age, sex and BMI-matched healthy controls, using correlation and multiple linear regression analysis.

Results: Comparative analysis of the two groups confirmed lower BMD in the RTR group at the hip, neck, forearm and whole body locations (P < 0.005). In the RTR group, mean GFR was 53.93 ± 23.98 ml/min/1.23 m², 86% have osteoporosis, 13.6% have sarcopenia and 47.5% are overweight.

Total lean mass (TLM), lean mass index (LMI) and appendicular lean mass index (ALMI) were mildly positively correlated with all bone parameters (P < 0.001 for all). Fat mass percentage (FM%) was a negative predictor for BMD at the level of forearm (Coef R2 = 0.152, P = 0.002) and whole body (Coef R 2 = 0.098, P = 0.016).

Negative correlations were found between adiponectin, resistin, and lumbar and forearm BMD, respectively (P < 0.05). Adiponectin is also positively correlated with osteocalcin (r = 0.540, P < 0.001), but negatively associated with CTx (r = −0.375, P = 0.007). Leptin negatively impacts forearm (r = −0.449) and whole body BMD (r = −0.419 ) (P < 0.005 for all) and is positively correlated with osteocalcin (r = 0.280, P < 0.05). No relationship was observed between serum FGF-23 or klotho levels and BMD values.

TLM and FM% remained the only independent predictors of forearm, hip and whole-body BMD inmultiple regression analysis (P < 0.001) after adjusting for confounders such as age, sex, cumulative dose of corticosteroids, dialysis time period, smoking, adipokines levels, graft function.

Conclusions: This is the first study confirming the predictive role of TLM on BMD after renal transplantation, with predilection at the forearm level. Adipokines interfere with bone remodeling, both leptin and adiponectin being associated with higher levels of bone formation markers andlower level of bone resorbtion markers. Their overall negative effect on bone mineral density implies a compound effect yet to be determined.