Effects of 7 days of exercise training on insulin sensitivity and responsiveness in type 2 diabetes mellitus

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Abstract
The objectives of this study were to determine whether 1) the improvement in insulin action induced by short-term exercise training in patients with type 2 diabetes is due to an improvement in insulin sensitivity, an improvement in insulin responsiveness, or a combination of improved insulin sensitivity and responsiveness and 2) short-term exercise training results in improved suppression of hepatic glucose production by insulin. Fourteen obese patients with type 2 diabetes, age 64 ± 2 yr, underwent a two-stage hyperinsulinemic euglycemic clamp procedure, first stage 40 mU·m−2·min−1insulin infusion, second stage 1,000 mU·m−2·min−1insulin infusion, together with a [3-3H]glucose infusion, before and after 7 days of exercise. The training consisted of 30 min of cycling and 30 min of treadmill walking at ∼70% of maximal aerobic capacity daily for 7 days. The exercise program resulted in improvements in insulin action in the absence of weight loss. Glucose disposal rates during the euglycemic clamp were significantly increased at both hyperinsulinemic stages after training (40 mU: 1.84 ± 0.32 to 2.67 ± 0.37 mg·kg−1·min−1, P < 0.0001; 1,000 mU: 7.57 ± 0.61 to 8.84 ± 0.56 mg·kg−1·min−1, P = 0.008). Hepatic glucose production, both in the basal state (3.17 ± 0.43 vs. 2.54 ± 0.26 mg·kg−1·min−1, P = 0.05) and during the 40-mU clamp stage (1.15 ± 0.41 vs. 0.46 ± 0.20 mg·kg−1·min−1, P = 0.03), was significantly reduced after training. One week of vigorous exercise training can induce significant improvements in insulin action in type 2 diabetes. These improvements include increased peripheral insulin sensitivity and responsiveness as well as enhanced suppression of hepatic glucose production.