Acute Exercise and Glucose Tolerance

Type 2 diabetes mellitus (T2DM) is characterised by insulin resistance and impaired glucose tolerance. The role of beta-cell dysfunction in the progression of this disease has become increasingly accepted, why prevention and reversal of this dysfunction is key in reversing T2DM. Lifestyle interventions including exercise training can improve insulin sensitivity in healthy and T2DMs. However, the specific exercise-derived effects on beta-cells and glucose tolerance are not fully understood. So, the main purpose is to investigate the effects of exercise on glucose tolerance in both healthy male subjects (NGT), subjects with impaired glucose tolerance (IGT) or with T2DM.

Subjects will be screened and undergo measures of body composition (DXA-scan), maximal aerobic capacity (VO2max) and maximal power output (Watt max). Subjects will withhold any oral antidiabetic as well as cholesterol and/or blood pressure lowering medication for 3 days prior to testing. On two separate occasions 24 male subjects (NGT n=8, IGT n=8, T2DM n=8) will undergo a 3-hour oral glucose tolerance test (OGTT) after an hour of exercise (EX) and rest (CON). Blood is drawn at baseline and every 10th minutes from 30 minutes into the exercise bout and throughout the OGTT to measure glucose, insulin and c-peptide. The exercise will be performed on a bike cycle ergometer at 50% of Watt max. Insulin secretion rates (ISR; pmol/min) in response to glucose will be deconvoluted from peripheral blood C-peptide concentrations using standard parameters for C-peptide clearance.

End points:

Effects of 1 hour of exercise on:

• glucose tolerance measured by OGTT
• beta-cell function expressed as ISR during OGTT