Exercise training increases sarcolemmal GLUT-4 protein and mRNA content in diabetic heart.
This study determined whether dynamic exercise training of diabetic rats would increase the expression of the GLUT-4 glucose transport protein in prepared cardiac sarcolemmal membranes. Four groups were compared: sedentary control, sedentary diabetic, trained control, and trained diabetic. Diabetes was induced by intravenous streptozotocin (60 mg/kg). Trained control and diabetic rats were run on a treadmill for 60 min, 27 m/min, 10% grade, 6 days/wk for 10 wk. Sarcolemmal membranes were isolated by using differential centrifugation, and the activity of sarcolemmal K(-)-p-nitrophenylphosphatase (pNPPase; an indicator of Na(+)-K(+)-adenosinetriphosphatase activity) was quantified. Hearts from the sedentary diabetic group exhibited a significant depression of sarcolemmal pNPPase activity. Exercise training did not significantly alter pNPPase activity. Sedentary diabetic rats exhibited an 84 and 58% decrease in GLUT-4 protein and mRNA, respectively, relative to control rats. In the trained diabetic animals, sarcolemmal GLUT-4 protein levels were only reduced by 50% relative to control values, whereas GLUT-4 mRNA were returned to control levels. The increase in myocardial sarcolemmal GLUT-4 may be beneficial to the diabetic heart by enhancing myocardial glucose oxidation and cardiac performance.
Osborn
B A
BA
Department of Physiology, Midwestern University, Downers Grove, Illinois 60515, USA.
Daar
J T
JT
Laddaga
R A
RA
Romano
F D
FD
Paulson
D J
DJ
D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D051275:Glucose Transporter Type 4; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D009206:Myocardium / Q000378:metabolism*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012508:Sarcolemma / Q000378:metabolism*
D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; C495694:Slc2a4 protein, rat