Endocrine Abstracts

Aim: Acute bouts of exercise are known to have a beneficial effect on glucose homeostasis immediately following exercise in people with Type 2 Diabetes. Evidence suggests that this effect is independent of the effects of insulin. In this study we compare recently developed indices of insulin sensitivity derived from the oral glucose tolerance test to determine whether the improvements in glucose homeostasis following physical activity are independent of the effects of insulin. Methods: 12 sedentary individuals, 6 with and 6 without Type 2 Diabetes were studied following an overnight fast on two separate occasions during a two hour 75g Oral Glucose Tolerance Test (OGTT). Subjects were examined in both the rested state and immediately after 60 minutes of exercise at 90% of a predetermined lactate threshold. Fingertip and Venous blood samples were taken every 10 minutes for 120 minutes and analysed for glucose and insulin concentrations. Experimental procedures were approved by the East Sussex Local Research Ethics Committee. The Oral Glucose Insulin Sensitivity (OGIS), the whole-body insulin sensitivity Index (ISI-composite) and the product of glucose/insulin area under the curve ratio were employed to measure insulin sensitivity. Results: The calculated rate constant for glucose decay from peak glucose concentration was greater following exercise in both groups. This effect was more pronounced in the Type 2 Diabetes group (8.2 vs. 4.7 mmol.h-1). Neither the product of glucose and insulin area under the curves, the ISI-composite or the OGIS highlighted any changes in whole body insulin sensitivity in either group despite an improvement in glucose control following exercise. Conclusion: Improvements in glucose homeostasis immediately after an acute bout of exercise seem to be independent of the action of insulin.