Aim: The aim of this work was to quantify the magnitude of changes in insulin sensitivity (S(I)) and glucose effectiveness (S(G)) in response to acute exercise in type 2 diabetic (T2D) patients, as previously studied in non-diabetic subjects.
Methods: Seven T2D patients and seven non-diabetic controls participated in the study. Two intravenous glucose tolerance tests (0.5 g/kg) with frequent blood sampling over 180 minutes and mathematical modelling were carried out in a randomized fashion, one at rest and the other immediately following 15 minutes of exercise at 50% of the maximum theoretical heart rate (HR(max)) followed by five minutes at 85% of the HR(max). S(I) and S(G) were calculated using Bergman's minimal model.
Results: After exercise, S(I) was increased by 773% (from 0.62+/-0.16 to 5.41+/-1.59 min(-1) x 10(-4)/(microU/mL) and even reached the zone of control values at rest (5.52+/-2.28), whereas S(G) remained unchanged. The disposition index acute insulin response (AIR(G)) x S(I) and the product of fasting insulin (I(B)) x S(I) also increased after exercise.
Conclusion: A single bout of exercise at moderate intensity in type 2 diabetics did not improve S(G), but markedly improved the low S(I) values found in these patients, indicating that the acute effects of exercise on S(I) are quantitatively important in the interpretation of training-related S(I) changes and may even be therapeutically useful on their own. Surrogates such as homoeostasis model assessment (HOMA) and quantitative insulin-sensitivity check index (QUICKI) were not sensitive enough to detect this increase in S(I) and should probably be used with caution in the follow-up of exercise protocols in diabetic patients.