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 women would be relatively resi stant to insulin-mediated glucose disposal, hyperinsulinemic, and dysl ipidemic as compared to a matched group of non-Hispanic White (NHW) wo men. Methods. The study, cross-sectional in nature, involved 14 Mexica n American and 19 NHW healthy, normotensive, nondiabetic, postmenopaus al women of similar age and body mass index. It took place in the Gene ral Clinical Research Center 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 ora l glucose challenge. Resistance to insulin-mediated glucose disposed w as estimated by the steady-state plasma glucose (SSPG) concentration a chieved at the end of a 3-hour constant infusion of glucose, insulin, and somatostatin. Results. Mexican American women had significantly gr eater glucose (p < .001) and insulin (p < .001) responses to the oral glucose challenge than did the NHW women. Resistance to insulin-mediat ed glucose disposal was increased in Mexican American women (SSPG 195 +/- 25 mg/dl compared to 137 +/- 18 mg/dl in NHW; p < .001). While tot al cholesterol, low density lipoprotein (LDL)-cholesterol, and triglyc eride concentrations were not significantly different in the two ethni c 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, g lucose intolerant, and hyperinsulinemic, and have a lower HDL-choleste rol than a matched group of non-Hispanic White peers. These results we re observed despite the exclusion of individuals with non-insulin depe ndent diabetes mellitus (NIDDM).