Visceral Fat Is a Negative Predictor of Bone Density Measures in Obese Adolescent Girls

Context: Regional fat is increasingly recognized as a determinant of bone mineral density (BMD), an association that may be mediated by adipokines, such as adiponectin and leptin, and inflammatory fat products. Chronic inflammation is deleterious to bone, and visceral adipose tissue (VAT) predicts inflammatory markers such as soluble intercellular adhesion molecule-1 and E-selectin, whereas sc adipose tissue (SAT) and VAT predict IL-6 in adolescents. Objective: Our objective was to determine associations of regional fat mass and adipokines with BMD. We hypothesized that girls with greater VAT relative to SAT would have lower bone density mediated by inflammatory cytokines, adiponectin, and leptin. Design: This was a cross-sectional study. Setting: The study was conducted at a clinical research center. Subjects: Subjects included 30 girls (15 obese, 15 normal weight) 12–18 yr old, matched for maturity (bone age), race, and ethnicity. Outcome Measures: We assessed regional fat (SAT, VAT) using magnetic resonance imaging, total fat, and BMD using dual-energy x-ray absorptiometry. Fasting leptin, adiponectin, IL-6, soluble intercellular adhesion molecule-1, and E-selectin were obtained. Results: Mean body mass index sd score was 3.7 ± 1.5 in obese subjects and 0.1 ± 0.4 kg/m2 in controls. VAT was a negative predictor of spine BMD and bone mineral apparent density, whole-body BMD and bone mineral content/height in obese girls and whole-body BMD and bone mineral content/height for the group as a whole after controlling for SAT, as was the ratio of VAT to SAT. In a regression model that included VAT/SAT, adipokines, and cytokines, E-selectin and adiponectin were negative predictors of BMD and leptin a positive predictor. Conclusion: VAT is an independent inverse determinant of bone density in obesity. This association may be mediated by adipokines and a chronic inflammatory state.