Decreased plasma adiponectin concentrations in nondiabetic women with elevated homeostasis model assessment ratios

Whether the adipocyte-derived protein adiponectin is associated with insulin resistance independently of the effects of adiposity and the diabetic state is an important question. We explored, in a cross-sectional study of 486 Japanese nondiabetic women, the relationship between the calculated insulin resistance (homeostasis model assessment ratio (HOMA-R)) and adiponectin levels determined using a validated sandwich ELISA.

All participants were stratified into tertiles for HOMA-R (approximately <1.5, 1.5< or = approximately <3.0, 3.0< or = approximately ) and the differences across tertiles of continuous variables were tested with ANOVA. Two-way ANOVA was used to determine possible relationships for plasma adiponectin between tertiles of HOMA-R and several stratified parameters. Multiple regression analyses were performed with HOMA-R or fasting serum insulin as dependent variable, and diastolic blood pressure (BP), body mass index (BMI), serum triglyceride (TG), leptin and adiponectin as independent determinants.

Mean plasma adiponectin in the high HOMA-R group decreased compared with that in the low HOMA-R group both before (mean+/-s.e.m. 6.2+/-0.6 vs 9.2+/-0.3 microg/ml, P<0.001) and after adjustment for body fat mass (BFM) as kg or percent (0.31+/-0.04 vs 0.69+/-0.03, 0.18+/-0.02 vs 0.34+/-0.01, both P<0.001). HOMA-R was inversely associated with adiponectin levels both before (r=-0.37, P<0.001) and after adjustment for BFM (r=-0.49, -0.46, both P<0.001). After covariate adjustment for age, diastolic BP, BMI and serum TG, HOMA-R retained a significant correlation with adiponectin/BFM (kg). Both adiponectin and leptin were the significant determinants of HOMA-R or fasting insulin in multiple regression models.

Adiponectin was inversely associated with insulin resistance in nondiabetic subjects, independently from age, BP, adiposity and serum lipids. Because adiponectin is thought to have an anti-atherogenic action, the presence of hypoadiponectinemia may predispose subjects to atherosclerosis, and may progress the atherogenesis in insulin resistance.