Exercise training reverses insulin resistance in muscle by enhanced recruitment of GLUT-4 to the cell surface.
The effects of exercise training on cell surface GLUT-4 in skeletal muscle of the obese (fa/fa) Zucker rat were investigated using the impermeant glucose transporter photoaffinity reagent 2-N-4-(1-azi-2,2,2-trifluoroethyl)-benzoyl-1,3-bis- (D-mannos-4-yloxy)-2-propylamine (ATB-BMPA). In the absence of insulin, 3-O-methyl-D-glucose transport activity was no different in either fast-twitch (epitrochlearis) or slow-twitch (soleus) muscles of trained and sedentary obese rats. Likewise, basal ATB-BMPA-labeled GLUT-4 was not altered in these muscles with training. In contrast, the trained group exhibited significantly greater insulin-stimulated (2 mU/ml) glucose transport activity in epitrochlearis muscles than the sedentary group (0.53 +/- 0.03 vs. 0.18 +/- 0.03 mumol.g-1 x 10 min-1 for trained and sedentary, respectively), which was paralleled by a significant enhancement of insulin-stimulated cell surface GLUT-4 (5.33 +/- 0.20 vs. 1.57 +/- 0.14 disintegrations.min-1.mg-1 for trained and sedentary, respectively). Exercise training, however, did not alter insulin-stimulated glucose transport activity or cell surface GLUT-4 in soleus muscles. Finally, exercise training did not alter the ability of muscle contraction to elevate glucose transport activity or cell surface GLUT-4 in either epitrochlearis or soleus muscles of the obese rat. These results indicate that training improves insulin-stimulated glucose transport in muscle of the obese Zucker rat by increasing GLUT-4 content and by altering the normal intracellular distribution of these transporters such that they are now capable of migrating to the cell surface in response to the insulin stimulus.
Etgen
G J
GJ
Department of Kinesiology, University of Texas at Austin 78712, USA.
Jensen
J
J
Wilson
C M
CM
Hunt
D G
DG
Cushman
S W
SW
Ivy
J L
JL
D000345:Affinity Labels; D000818:Animals; D001386:Azides; D002462:Cell Membrane / Q000378:metabolism; D004187:Disaccharides; D005260:Female; D051275:Glucose Transporter Type 4; D006027:Glycosides; D007333:Insulin Resistance; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009119:Muscle Contraction; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D009765:Obesity / Q000378:metabolism; D010805:Physical Conditioning, Animal; D011437:Propylamines; D051381:Rats; D011924:Rats, Zucker
D000345:Affinity Labels; D001386:Azides; D004187:Disaccharides; D051275:Glucose Transporter Type 4; D006027:Glycosides; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D011437:Propylamines; C495694:Slc2a4 protein, rat; C065412:2-N-(4-(1-azitrifluoroethyl)benzoyl)-1,3-bis-(mannos-4-yloxy)-2-propylamine