Impact of exercise on diurnal and nocturnal markers of glycaemic variability and oxidative stress in obese individuals with type 2 diabetes or impaired glucose tolerance

Objective: We measured the effects of a single bout of exercise on diurnal and nocturnal oxidative stress and glycaemic variability in obese subjects with type 2 diabetes mellitus or impaired glucose tolerance versus obese healthy controls. Methods: Subjects (in random order) performed either a single 30-min bout of moderate-intensity exercise or remained sedentary for 30min at two separate visits. To quantify glycaemic variability, standard deviation of glucose (measured by continuous glucose monitoring system) and continuous overlapping net glycaemic action of 1-h intervals (CONGA-1) were calculated for three 12-h intervals during each visit. Oxidative stress was measured by 15-isoprostane F-2t levels in urine collections for matching 12-h intervals. Results: Exercise reduced daytime glycaemic variability (Delta CONGA-1=-12.62 +/- 5.31mg/dL, p=0.04) and urinary isoprostanes (Delta CONGA-1=-0.26 +/- 0.12ng/mg, p=0.04) in the type 2 diabetes mellitus/impaired glucose tolerance group. Daytime exercise-induced change in urinary 15-isoprostane F-2t was significantly correlated with both daytime standard deviation (r=0.68, p=0.03) and with subsequent overnight standard deviation (r=0.73, p=0.027) in the type 2 diabetes mellitus/impaired glucose tolerance group. Conclusion: Exercise significantly impacts the relationship between diurnal oxidative stress and nocturnal glycaemic variability in individuals with type 2 diabetes mellitus/impaired glucose tolerance.