Normalization of Insulin Sensitivity in Type I Diabetic Subjects by Physical Training During Insulin Pump Therapy

Abstract

Seven type I (insulin-dependent) diabetic patients previously treated with continuous subcutaneous insulin infusion therapy participated in a 6-wk training program consisting of cycle ergometer exercise 1 h/day 4 times a week. Six nontraining pump-treated type I diabetic patients and 19 healthy subjects were studied as controls. The training improved maximal aerobic power (VO2 max) by 8% (P < 0.05). Hemoglobin A1 was in the high normal range before training (8.6 ± 0.4%) and remained unchanged. The ratio of HDL cholesterol to total cholesterol rose by 16% in the training group (P < 0.01) but remained unchanged in the sedentary diabetic patients. Mean daily insulin requirements fell by 6< in the training group (P < 0.01). This reduction occurred in the lunch and dinner boluses whereas the basal infusion rate remained unchanged. Insulin sensitivity as determined by the euglycemic clamp technique was 25–40% lower in the training group (5.24 ± 0.48 mg/kg/min) and sedentary diabetic group (6.55 ± 0.82 mg/kg/min) as compared with controls (8.69 ± 0.77 mg/kg/min, P < 0.025). After the training, the rate of glucose uptake rose by 60% (P < 0.001) to 8.48 ± 0.77 mg/kg/min, which was comparable to that in the controls, but remained unaltered in the sedentary diabetic group. Insulin binding to erythrocytes was comparable in the diabetic and healthy subjects, and remained unchanged. Basal hepatic glucose production was elevated in both groups of diabetic patients (P < 0.05), whereas the suppression by insulin was normal, and both of these were unaltered by training. In conclusion, our data demonstrate that a controlled physical training program in pump-treated diabetic patients (1) does not change an already near-normal glycemic control, (2) improves body sensitivity to insulin and reduces insulin requirements, and (3) increases the HDL cholesterol to total cholesterol ratio.