Exercise, Glucose Kinetics, and the Incretin Effect

The Effects of Acute Exercise on Glucose Kinetics, Beta-cell Function and the Incretin Effect in Subjects Representative of the Whole Glucose Tolerance Continuum

Human volunteers will be stratified by oral glucose tolerance status: normal glucose tolerant, impaired glucose tolerant, and type 2 diabetic. All subjects will undergo 4 experimental trials: [1] an oral glucose tolerance test (OGTT) combined with infused and ingested stable isotopes of glucose to assess glucose kinetics. [2] a 1 hour bout of cycling exercise at 50% of maximum power output, immediately followed by the same OGTT combined with stable isotope glucose tracers used in trial 1. [3] an isoglycemic clamp to match the plasma glucose profile measured in trial 1. [4] a 1 hour bout of cycling exercise at 50% of maximum power output, immediately followed by an isoglycemic clamp to match the plasma glucose profile measured in trial 2. Exercise-induced changes in oral glucose tolerance, glucose kinetics, insulin and glucagon secretion, and the incretin effect will be examined. The exercise responses will be compared between the subjects groups of different glucose tolerance status.

Exercise, Physical activity, Type 2 diabetes, Obesity, Incretin effect, GLP-1, GIP, Insulin secretion, Glucagon, Beta-cell function, Disposition Index

Plasma glucose will be measured at 10 minute intervals during the OGTT (3 hours) immediately following the period of rest or exercise

Plasma insulin and C-peptide will be measured at 10 minute intervals during the OGTT (3 hours) and isoglycemic clamp (3 hours) immediately following the period of rest or exercise

Inclusion Criteria: age 18-60 years BMI 18-35 kg/m2 Exclusion Criteria: insulin dependency pregnancy presence or history of chronic cardiovascular, pulmonary, hepatic, renal, or hematological disease, or cancer contraindication to physical activity as assessed by ECG