Ethnic Differences in Insulin Resistance and Its Consequences in Older Mexican American and Non-Hispanic White Women

Background. This study was initiated to test the hypothesis that older, healthy, nondiabetic Mexican American womenwould be relatively resistant to insulin-mediated glucose disposal, hyperinsulinemic, and dyslipidemic as compared to amatched group of non-Hispanic White (NHW) women. Methods. The study, cross-sectional in nature, involved 14 Mexican American and 19 NHW healthy, normotensive,nondiabetic, postmenopausa! women of similar age and body mass index. It took place in the General Clinical ResearchCenter at Stanford Medical Center. Measurements were made of fasting plasma glucose, insulin and lipid concentrations,and plasma glucose and insulin concentrations following a 75 gram oral glucose challenge. Resistance to insulinmediatedglucose disposal was estimated by the steady-state plasma glucose (SSPG) concentration achieved at the end ofa 3-hour constant infusion of glucose, insulin, and somatostatin. Results. Mexican American women had significantly greater glucose (p < .001) and insulin (p < .001) responses to theoral glucose challenge than did the NHW women. Resistance to insulin-mediated glucose disposal was increased in Mexican American women (SSPG 195 ± 25 mg/dl compared to 137 ± 18 mg/dl in NHW; p < .001). While total cholesterol, low density lipoprotein (LDL)-cholesterol, and triglyceride concentrations were not significantly different in the two ethnic groups, high density lipoprotein (HDL)-cholesterol was significantly lower in the Mexican American women (51 mg/dl vs 61 mg/dl; p = .04). Conclusion. Older Mexican American women are more insulin resistant, glucose intolerant, and hyperinsulinemic,and have a lower HDL-cholesterol than a matched group of non-Hispanic White peers. These results were observeddespite the exclusion of individuals with non-insulin dependent diabetes mellitus (NIDDM).