EFFECTS OF EXERCISE TRAINING ON INSULIN SENSITIVITY IN ADOLESCENTS WITH TYPE I DIABETES (IDDM)

Abstract

Although regular exercise is generally considered beneficial for IDDM, an influence of physical training on insulin sensitivity in adolescent IDDM has not previously been documented. We assessed insulin sensitivity via the hyperinsulinemic-euglycemic clamp technique using an insulin infusion of 100 mU/M2/min while maintaining fixed basal glucose levels of 90 mg/dl before and after 12 weeks of a regimen of vigorous structured exercise in 9 IDDM, or no exercise in a pubertally matched IDDM control group. Glucose utilization rate (mg/M2/min; M) was 265 ± 34 (X̄ + SE) before vs 337 ± 31 after exercise representing a 35 ± 10% increase in insulin sensitivity (p <0.05). No change in insulin sensitivity occurred in controls (M = 280 ± 86 vs 281 ± 89). Free insulin levels (IRI) were 724 ± 96 μU/ml during the hyperinsulinemic clamp; no differences were present after the 12 week study in the exercise group (715 ± 113 μU/ml). Insulin sensitivity did not correlate significantly to free IRI. In the exercise group, there were significant increments in maximal O2 consumption (VO2) on a bicycle ergometer (7.01 ± 2.5%; p <0.05), and in lean body mass (LBM; 4.6 ± 1.5%; p <0.02). The increase in insulin sensitivity was not correlated to either VO2 or LBM. We conclude that exercise training independently increases insulin sensitivity, LBM and VO2 in adolescents with IDDM. These changes must occur at receptor or post receptor events and cannot be ascribed to changes in antibody binding since free insulin remained unchanged.