RESUMO
Adipocytokines secreted by adipose tissue participate in bone metabolism; leptin is one of the circulating peptides secreted by adipose tissue. To determine the serum levels of leptin in obese postmenopausal women in order to correlate these levels with bone mineral density and bone biochemical markers to find out the role of leptin in bone metabolism. This was a cross-sectional study which included 37 obese postmenopausal women with body mass index [BMI] >30 kg/m[2]. Thirty-seven lean postmenopausal women with BMI <25 kg/m[2] were included as control group. Serum leptin, bone specific alkaline phosphatase [BAP], osteocalcin and urine C-telopeptide of type collagen [CTx] were assayed. Bone mineral density [BMD] and soft tissue body composition were determined using dual energy X-ray absorptiometry. There was a statistically highly significant increase in serum leptin levels in obese than lean postmenopausal women [p < 0.0001]. There was a highly significant decrease in BMD of spine and hip [p < 0.0001] in obese than lean postmenopausal women. After adjustment of fat mass, a highly significant positive correlation was found between leptin and BAP [r = 0.562, p < 0.0001], a significant positive correlation was found between leptin and each of osteocalcin and urine CTx [r = 0.423, 0.456 respectively, p < 0.05] but there was no statistically significant correlation between leptin and BMD. Our results support the hypothesis that leptin can act directly or indirectly on bone remodeling by modulating osteoblast activities. Leptin was found to be associated with decreased BMD at different sites of the body and was positively correlated with bone biochemical markers. However, leptin did not come out to be an independent predictor of BMD whereas; fat mass was found to have a role in bone metabolism in postmenopausal women. However these comparisons of a single measurement of leptin with BMD, does not exclude possible long-term strong relationships between leptin and BMD