Effect of prior moderate exercise on postprandial metabolism in men with type 2 diabetes: Heterogeneity of responses

Prior moderate exercise has been shown consistently to reduce postprandial triglyceride (TG) concentrations in non-diabetic adults, but its effects in men with type 2 diabetes are not known. This study aimed to determine the effect of moderate exercise on postprandial metabolism in men with type 2 diabetes. Ten middle-aged men with type 2 diabetes underwent two oral fat tolerance tests (blood taken fasting and for 8 h after a meal containing 80 g fat, 70 g carbohydrate) in random order. On the afternoon before one test, participants performed a 90-min treadmill walk (Exercise); no exercise was performed before the Control test. Exercise significantly reduced fasting glucose (Control: 9.08 ± 0.75 mmol l^-1, Exercise: 8.40 ± 0.72 mmol l^-1, p = 0.033) and insulin (Control: 8.01 ± 0.98 μU ml^-1, Exercise: 6.81 ± 0.93 μU ml^-1, p = 0.046) and increased fasting 3-hydroxybutyrate (Control: 87.1 ± 19.2 μmol l^-1, Exercise: 134.3 ± 28.4 μmol l^-1, p = 0.011); reduced postprandial insulin by 11.0% (p = 0.04) and increased postprandial 3-hydroxybutrate by 31.8% (p = 0.03); but did not significantly change fasting or postprandial triglyceride or NEFA concentrations. However, the exercise-induced change in postprandial triglyceride concentration ranged from -32.3 to +28.3% and the exercise-induced change in fasting 3-hydroxybutyrate concentration (a marker of hepatic fatty acid oxidation) was highly correlated with the exercise-induced changes in fasting and postprandial triglyceride (r = 0.68, p = 0.03 for both). Thus, inter-individual variation in propensity to increase hepatic fatty acid oxidation following exercise may account for the considerable heterogeneity in triglyceride responses to moderate exercise observed in men with type 2 diabetes.