Ethnicity affects the postprandial regulation of glycogenolysis

We investigated the effect of nutrient intake on glucose metabolism in norm al Mexican-Americans (n = 6) and European-Americans (n = 6). Subjects were studied after an 18-h fast and after 5-6 h of ingestion of hourly meals tha t supplied 6.35 or 12.75 mu mol glucose.kg(-1).min(-1). Endogenous glucose production (EGP), gluconeogenesis (GNG), and glycogenolysis (GLY) were esti mated by mass isotopomer analysis with [U-C-18]glucose infusions. Fasting E GP, GNG, and GLY did not differ between the groups. Food ingestion lowered the molar rate of GNG by only 31%. However, while consuming the lower quant ity of nutrients, Mexican-Americans had higher plasma glucose (P < 0.05), a 39% higher rate of EGP (P < 0.05), and a 68% (P < 0.025) higher rate of GL Y than the European-Americans. At the higher intake, EGrP and GLY were supp ressed completely in both groups. There was a linear relationship between i nsulin concentrations, EGP, and GLY in both groups, but the slope of the li ne was significantly (P < 0.05) greater in the European-Americans. We concl ude that the sensitivity of GLY to nutrient intake differs between ethnic g roups and that this may play a role in the increased predisposition of Mexi can-Americans to type II diabetes.