Interrelations between fat distribution, muscle lipid content, adipocytokines, and insulin resistance: effect of moderate weight loss in older women.

BACKGROUND Interrelations between fat distribution, muscle lipid infiltration, adipocytokines, insulin resistance, and moderate weight loss have not been investigated in obese older subjects. OBJECTIVE The objective was to evaluate relations between fat distribution, muscle lipid content, adipocytokines, and insulin resistance in older women and the effects of moderate weight loss. DESIGN In 35 healthy women aged 58-83 y, body mass index, waist circumference, sagittal abdominal diameter (SAD), and body composition measured by dual-energy X-ray absorptiometry were evaluated. A midthigh single computed tomography scan was performed to determine subcutaneous adipose tissue (AT), intermuscular AT (IAT), muscular tissue, and muscle lipid infiltration, evaluated as low-density lean tissue. Metabolic variables, insulin resistance measured by homeostasis model assessment, adiponectin, leptin, and high-sensitivity C-reactive protein were measured in all subjects and after weight loss in a subgroup of 15 obese women. RESULTS Waist circumference and SAD were positively correlated with leptin and insulin resistance and negatively correlated with adiponectin. Adiponectin was associated negatively with insulin resistance and positively with HDL cholesterol, whereas leptin was positively associated with insulin resistance and triacylglycerols. Midthigh subcutaneous AT was associated with insulin resistance and leptin, whereas IAT was associated with triacylglycerols. Stepwise regression with insulin resistance as the dependent variable and body mass index, SAD, triacylglycerols, HDL cholesterol, adiponectin, leptin, high-sensitivity C-reactive protein, and midthigh subcutaneous AT as independent variables showed that SAD entered the regression first (R(2) = 0.492) followed by adiponectin (R(2) = 0.63). After moderate weight loss, midthigh subcutaneous AT, IAT, low-density lean tissue, leptin, and insulin resistance decreased significantly; no significant changes in adiponectin were observed. CONCLUSIONS Fat distribution indexes and adiponectin are independently associated with insulin resistance. Even in older women, moderate weight loss improves body fat distribution, muscle lipid infiltration, and insulin resistance. Moderate weight loss results in a significant decrease in leptin but no changes in adiponectin.