Influence of gender on the relationship between insulin sensitivity, adiposity, and plasma lipids in lean nondiabetic subjects.

Individuals with obesity frequently have an atherogenic lipid profile. It has been proposed that the insulin resistance observed in these individuals is involved in the development of these lipid abnormalities. However, most studies that have examined the relationship between insulin resistance and lipid abnormalities have included subjects who are either obese and/or glucose intolerant, 2 factors that may affect lipid levels independent of insulin resistance. We have therefore examined the impact of insulin resistance on plasma lipids in a healthy, lean (average body mass index <24 kg/m(2)), nondiabetic population (N = 104). In our subjects, we observed a wide range of values for insulin sensitivity index (ISI) as calculated by the formula of Matsuda and DeFronzo. Lipid values ranged considerably in this population, but incidence of hypertriglyceridemia and hypercholesterolemia was low in the absence of obesity. We first examined the relationship between ISI and total and regional adipose stores as assessed by dual-energy x-ray absorptiometry. In men, we observed higher values for indices of total and central adipose stores that were significantly associated with decreased insulin sensitivity. In contrast, in women, ISI values were not associated with any variables related to either total or regional adiposity. In men, ISI was also significantly associated with higher triglycerides levels (P < .01) when adjusted for age and percentage of truncal fat. In women however, there was no significant association between ISI and triglycerides (P = .14). Instead, in women, total fat and truncal fat were independent predictors of several lipid levels. These results both highlight sex differences in the associations between insulin resistance, regional adipose stores, and lipids values and emphasize the importance of adipose stores on the development of an individual's lipid profile.