The role of resistance and aerobic exercise training on insulin sensitivity measures in STZ-induced Type 1 diabetic rodents

Individuals with Type 1 Diabetes Mellitus (T1DM) can develop insulin resistance. Regular exercise may improve insulin resistance partially through increased expression of skeletal muscle GLUT4 content. Objective. To examine if different exercise training modalities can alter glucose tolerance through changes in skeletal muscle GLUT4 content in T1DM rats. Methods. Fifty rats were divided into 5 groups; control, diabetic control, diabetic resistance exercised, and diabetic high and low intensity treadmill exercised. Diabetes was induced using multiple low dose Streptozotocin (20 mg/kg/day) injections and blood glucose concentrations were maintained moderately hyperglycemic through subcutaneous insulin pellets. Resistance trained rats climbed a ladder with incremental loads, while treadmill trained rats ran on a treadmill at 27 or 15 m/min, respectively, all for 6 weeks. Results. At weeks 3 and 6, area under the curve measurements following an intravenous glucose tolerance test (AUC-IVGTT) in all diabetic groups were higher than control rats (p < 0.05). At 6 weeks, all exercise groups had significantly lower AUC-IVGTT values than diabetic control animals (p < 0.05). Treadmill trained rats had the lowest insulin dose requirement of the T1DM rats and the greatest reduction in insulin dosage was evident in high intensity treadmill exercise. Concomitant with improvements in glucose handling improvements, tissue-specific elevations in GLUT4 content were demonstrated in both red and white portions of vastus lateralis and gastrocnemius muscles, suggesting that glucose handling capacity was altered in the skeletal muscle of exercised T1DM rats. Conclusions. These results suggest that, while all exercise modalities can improve glucose tolerance, each mode leads to differential improvements in insulin requirements and protein content alterations. (c) 2013 Elsevier Inc. All rights reserved.