Exercise training increases sarcolemmal GLUT-4 protein and mRNA content in diabetic heart

Osborn, Brett A., June T. Daar, Richard A. Laddaga, Fred D. Romano, and Dennis J. Paulson. Exercise training increases sarcolemmal GLUT-4 protein and mRNA content in diabetic heart. J. Appl. Physiol. 82(3): 828-834, 1997.This study determined whether dynamic exercise training ofdiabetic rats would increase the expression of the GLUT-4 glucosetransport protein in prepared cardiac sarcolemmal membranes. Fourgroups were compared: sedentary control, sedentary diabetic, trainedcontrol, and trained diabetic. Diabetes was induced by intravenousstreptozotocin (60 mg/kg). Trained control and diabetic rats were runon a treadmill for 60 min, 27 m/min, 10% grade, 6 days/wk for 10 wk.Sarcolemmal membranes were isolated by using differentialcentrifugation, and the activity of sarcolemmalK⁺-p-nitrophenylphosphatase( pNPPase; an indicator ofNa⁺-K⁺-adenosinetriphosphataseactivity) was quantified. Hearts from the sedentary diabetic groupexhibited a significant depression of sarcolemmal pNPPaseactivity. Exercise training did not significantly alterpNPPase activity. Sedentary diabetic rats exhibited an 84 and 58% decrease in GLUT-4 protein and mRNA, respectively, relative tocontrol rats. In the trained diabetic animals, sarcolemmal GLUT-4protein levels were only reduced by 50% relative to control values,whereas GLUT-4 mRNA were returned to control levels. The increase inmyocardial sarcolemmal GLUT-4 may be beneficial to the diabetic heartby enhancing myocardial glucose oxidation and cardiac performance