Relationships between adiponectin and bone: Sex difference.

Abstract

Despite being secreted exclusively by adipocytes, circulating adiponectin (ApN) is negatively associated with obesity. Moreover, obesity is traditionally viewed as leading to increased bone mass and density. Therefore, ApN may play a biological role in regulating fat and bone metabolism. The objective of this study is to evaluate the relationship between ApN, measures of obesity, and bone mineral density (BMD) in healthy adults living in Singapore. We conducted a cross-sectional study of 300 participants (112 men), and measured body composition (i.e., fat mass, fat-free mass, BMD, and bone mineral content) by dual-energy x-ray absorptiometry. Serum leptin and ApN levels were determined by radioimmunoassay. Our results showed that serum ApN levels were significantly associated with obesity measures in both men and women, and the greater effect was observed in men. In contrast, the relationship between ApN and BMD was sex-dependent. Levels of ApN were negatively associated with BMD in women, but not in men. This relationship persisted even after adjustment for potential confounding factors, such as leptin and body mass index. Moreover, serum ApN was found to be a major determinant of BMD in women on the multivariate regression analysis. Our results suggest that ApN, an adipocyte-derived hormone, may affect bone metabolism, which may be mediated by sex hormones.