Exercise training increases sarcolemmal glut-4 protein and mrna
content in the diabetic heart.
Osborn, Brett A., June T. Daar, Richard A. Laddaga, Fred D. Romano,
and Dennis J. Paulson.
Department of Physiology, Midwestern University, 555 31st Street,
Downers Grove, Il 60515
APStracts 3:0510A, 1996.
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 weeks. Sarcolemmal
membranes were isolated using differential centrifugation and the
activity of sarcolemmal K+-pNPPase (an indicator of Na+,K+-ATPase
activity) was quantified. Hearts from the sedentary diabetic group
exhibited a significant depression of sarcolemmal p-NPPase activity.
Exercise training did not significantly alter p-NPPase 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 percent relative to control values, while 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
Received 7 May 1996; accepted in final form 28 October 1996.
APS Manuscript Number A435-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996