The relationship of ghrelin and adiponectin with bone mineral density and bone turnover markers in elderly men

Body weight is commonly considered a significant predictor of bone mineral density (BMD). Adiponectin, an adipocyte-derived hormone, could modulate BMD. Moreover, recent studies have reported that ghrelin is able to stimulate bone formation. In this study, we investigated any associations of adiponectin and ghrelin serum levels with bone turnover markers and BMD in elderly men. In 137 men aged 55 years and older ( mean age 67.4 +/- 5.4 years, mean body mass index [BMI] 26.6 +/- 3.4 kg/m(2)), we evaluated serum adiponectin, serum ghrelin, body composition ( fat mass and lean mass), BMD, bone alkaline phosphatase ( ALP), and the carboxy-terminal telopeptide of type I collagen (beta CTX). Ghrelin showed significant correlations with BMD at the femoral neck (r = 0.25, P<0.01), total femur (r = 0.22, P<0.05), and whole body (r = 0.18, P<0.05). However, after adjusting for age, BMI, and calcium intake, the correlation remained significant only for femoral neck BMD. Ghrelin showed a significant correlation with lean mass but not with fat mass and bone turnover markers. Adiponectin showed a positive association with both bone ALP and bCTX; the correlation between adiponectin and bone ALP (r = 0.25, P<0.01) remained significant after adjusting for confounding variables. No significant correlations between adiponectin and BMD at all skeletal sites were observed. In conclusion, our study suggests that in elderly Italian men serum ghrelin was significantly associated with femoral neck BMD and that adiponectin was positively associated with bone ALP. Further studies are needed to elucidate the role of adipocytokines in bone metabolism.