Ethnicity affects the postprandial regulation of glycogenolysis.

We investigated the effect of nutrient intake on glucose metabolism in normal 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 that supplied 6.35 or 12.75 μmol glucose ⋅ kg-1 ⋅ min-1. Endogenous glucose production (EGP), gluconeogenesis (GNG), and glycogenolysis (GLY) were estimated by mass isotopomer analysis with [U-13C]glucose infusions. Fasting EGP, 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 quantity 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 GLY than the European-Americans. At the higher intake, EGP and GLY were suppressed completely in both groups. There was a linear relationship between insulin concentrations, EGP, and GLY in both groups, but the slope of the line was significantly ( P < 0.05) greater in the European-Americans. We conclude that the sensitivity of GLY to nutrient intake differs between ethnic groups and that this may play a role in the increased predisposition of Mexican-Americans to type II diabetes.