Effect of exercise on postprandial insulin responses in Mexican American and non-Hispanic women

Postprandial insulin responses (integrated area under the curve) to an oral glucose load after a period of aerobic exercise and no exercise (control) were compared in sedentary normoglycemic Mexican American and non-Hispanic women pair-matched (n = 9) on total body fat mass (21.8 +/- 3.5 kg). The age (27.4 +/- 3.0 years), body mass index (BMI) (23.6 +/- 1.4 kg/m2), waist to hip ratio (WHR) (0.85 +/- .02), waist circumference (83.5 +/- 4.5 cm), lean mass (36.2 +/- 1.5 kg), and maximal O2 consumption ([VO2 max] 32.9 +/- 1.6 mL x kg(-1) x min(-1)) were similar, although the centrality index (subscapular/triceps skinfolds) was significantly greater in Mexican Americans (0.88 +/- 0.06 v 0.70 +/- 0.05, P < .01). Exercise (treadmill walking for 50 minutes at 70% VO2 max) and control trials were performed 4 weeks apart and 5 to 12 days after the onset of menstruation. A 75-g oral glucose load was administered 15 hours after the completion of each trial, with the subjects 12 hours postprandial. Blood samples were drawn prior to glucose ingestion (fasting, 0 minutes) and at minutes 15, 30, 60, 90, 120, and 150 postingestion. The postprandial insulin response was calculated using a trapezoidal method. In Mexican Americans, significant (P < .02) reductions in the postprandial insulin response (exercise v control, 6.5 +/- 1.0 v 8.5 +/- 1.4 pmol/L x min x 10(4)) and fasting insulin (exercise v control, 77.4 +/- 7.0 v 88.5 +/- 10.3 pmol/L) occurred after exercise compared with the control condition. In non-Hispanics, neither the postprandial insulin response (exercise v control, 7.2 +/- 1.0 v 6.2 +/- 0.9 pmol/L x min x 10(4)) nor fasting insulin (exercise v control, 77.0 +/- 8.2 v 82.9 +/- 8.9 pmol/L) were significantly different between trials. The postprandial insulin response in the control trial was significantly correlated with the change in the insulin response (control minus exercise) in the 18 women (r = .56, P = .01). No trial or group differences were found for postprandial glucose and C-peptide responses. Mexican American women have a high risk of developing type 2 diabetes, and aerobic exercise may be valuable in the prevention or delay of onset of diabetes by reducing peripheral insulin resistance.