Decreased insulin response to sustained hyperglycemia in exercise-trained rats

Male Wistar rats were studied to determine if exercise training reduces the insulin response to sustained hyperglycemia. Training (TN) for 8 wk on a treadmill resulted in significantly (P less than 0.05) increased time to exhaustion in TN compared to control animals (CN). Hyperglycemic glucose clamps at 11 mM for 90 min resulted in elevations of arterial plasma insulin to 23.6 +/- 4.3 ng.ml-1 (mean +/- SE, N = 7) in CN and 11.8 +/- 1.1 ng.ml-1 (N = 7) in TN (P less than 0.05). No significant difference between groups existed for the level of imposed hyperglycemia. Glucose infusion rates required to maintain the sustained hyperglycemia were 62.7 +/- 3.2 mg.kg-1 min-1 in CN and 68.5 +/- 3.0 mg.kg-1.min-1 in TN (P greater than 0.05) at the end of the glucose clamp. These data show that exercise training reduces the insulin response to sustained steady state hyperglycemia.