Abnormal glucoregulation during exercise in type II (non-insulin-dependent) diabetes

We studied the effects of exercise on the levels of plasma glucose and glucoregulatory hormones before and after 6 weeks of thrice-weekly physical training in 20 sedentary type II (non-insulin-dependent) diabetic patients and 11 control subjects matched for previous physical activity. Parameters were measured at rest, after 30 minutes of bicycle exercise at 70% to 75% of maximal oxygen uptake, and after 30 minutes of recovery. In the untrained state exercise resulted in a decrease in plasma glucose levels in diabetics but not in controls (−12 ± 5 v + 4 ± 2 mg/dL, P < .01) and the expected drop in plasma insulin level was absent in diabetics. These differences in glucose and insulin response persisted after physical training. There was a tendency for patients with diabetes to have a smaller R-R interval variation during deep breathing, an abnormal resting heart rate response to physical training, and a lesser increment in plasma epinephrine levels following exercise, findings consistent with autonomic dysfunction. Physical training resulted in a blunting of the exercise-induced increment of plasma epinephrine, growth hormone, and lactate levels in control subjects, but not in diabetics. Our data demonstrate a hypoglycemic effect of exercise in mildly hyperglycemic nonobese type II diabetics. Possible causative factors include: hyperglycemia per se, a lack of physiologic suppression of plasma insulin, and abnormalities of autonomic or hypothalamic regulatory function.