Exercise training attenuates the reduction in myocardial GLUT-4 in diabetic rats

The purpose of this study was to determine the interactive effects of 10- 12 wk of streptozotocin-induced diabetes (65 mg/kg) and moderate-intensity exercise training on total myocardial GLUT-4 and GLUT-1 proteins. Sprague- Dawley rats (n = 52) were randomly divided into sedentary control (SC), exercise-trained control (ETC), sedentary diabetic (SD), and exercise- trained diabetic (ETD) groups. Diabetes resulted in a 70% reduction in myocardial GLUT-4 (28.3 ± 3.1 and 94.6 ± 3.4% for SD and SC, respectively; P < 0.0001) and an 18.5% decrease in GLUT-1 (62.5 ± 4.7 and 76.8 ± 4.5% for SD and SC, respectively; P = 0.06). Exercise training increased citrate synthase activity in the medial and long heads of the triceps brachii in both groups (P < 0.001). Fasting blood glucose improved with training in diabetic animals (348 ± 27 and 569 ± 28 mg/dl for ETD and SD, respectively; P < 0.05). The diabetes-induced reduction in GLUT-4 was attenuated with exercise training (46.8 ± 9.3% for ETD; P < 0.02 compared with SD). In contrast, training resulted in a further 25% decrease compared with SD in GLUT-1 in ETD (46.8 ± 9.3%; P < 0.03 compared with SD). Exercise training had no effect on either GLUT-4 (87.2 ± 4.0%) or GLUT-1 (75.4 ± 5.1%) in ETC. GLUT-4 inversely correlated (r = 0.81; P ≤ 0.001) with fasting blood glucose. In conclusion, diabetes resulted in a 70% reduction in myocardial GLUT-4 and an 18% decrease in GLUT-1. Exercise training resulted in divergent regulation of GLUT-4 and GLUT-1 in ETD, whereas it further depressed GLUT-1 compared with SD.