Blood Leptin and Adiponectin as Possible Mediators of the Relation Between Fat Mass and BMD in Perimenopausal Women

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Abstract
Fat mass is a predictor of BMD; however, the mechanisms involved remain uncertain. Two adipokines, leptin and adiponectin, were examined as potential mediators of this relation in 80 perimenopausal women. Adiponectin did not exert any effect on BMD, whereas leptin exerted a negative one, with insulin acting as a confounder to this relation. Fat mass is an important determinant of bone density, but the mechanism involved in this relation is uncertain. Leptin and adiponectin, as circulating peptides of adipocyte origin, are potential contributors to this relation. We investigated the role of leptin and adiponectin in mediating fat mass effects on the skeleton of perimenopausal women. Twenty-five premenopausal and 55 postmenopausal, healthy women (42-68 years old) participated in our study. Lumbar spine BMD (BMD(L2-L4)) and total body BMC (TBBMC) were measured with DXA, leptin levels with ELISA, and adiponectin levels with radioimmunoassay (RIA). Additionally, body composition analysis was performed, as well as measurements of several hormones. It was shown that serum leptin levels were negatively correlated with BMD (beta = -0.005, p = 0.027) and TBBMC (beta = -14.32, p = 0.013). The above correlation was observed only when serum insulin levels were included, as an independent variable, in the regression analysis model. Adiponectin was not significantly correlated with BMD(L2-L4) nor with TBBMC, either in the presence or absence of insulin. Circulating adiponectin does not seem to exert any effect on bone mass. In contrast, circulating leptin showed a negative correlation with bone mass, dependent on serum insulin levels.