Glucose transport and cell surface GLUT-4 protein in skeletal muscle of the obese Zucker rat.
The relationship between 3-O-methyl-D-glucose transport and 2-N-4-(1-azi-2,2,2-trifluoroethyl)-benzoyl-1, 3-bis-(D-mannos-4-yloxy)-2-propylamine (ATB-BMPA)-labeled cell surface GLUT-4 protein was assessed in fast-twitch (epitrochlearis) and slow-twitch (soleus) muscles of lean and obese (fa/fa) Zucker rats. In the absence of insulin, glucose transport as well as cell surface GLUT-4 protein was similar in both epitrochlearis and soleus muscles of lean and obese rats. In contrast, insulin-stimulated glucose transport rates were significantly higher for lean than obese rats in both soleus (0.74 +/- 0.05 vs. 0.40 +/- 0.02 mumol.g-1.10 min-1) and epitrochlearis (0.51 +/- 0.05 vs. 0.17 +/- 0.02 mumol.g-1.10 min-1) muscles. The ability of insulin to enhance glucose transport in fast- and slow-twitch muscles from both lean and obese rats corresponded directly with changes in cell surface GLUT-4 protein. Muscle contraction elicited similar increases in glucose transport in lean and obese rats, with the effect being more pronounced in fast-twitch (0.70 +/- 0.07 and 0.77 +/- 0.04 mumol.g-1.10 min-1 for obese and lean, respectively) than in slow-twitch muscle (0.36 +/- 0.03 and 0.40 +/- 0.02 mumol.g-1.10 min-1 for obese and lean, respectively). The contraction-induced changes in glucose transport directly corresponded with the observed changes in cell surface GLUT-4 protein. Thus the reduced glucose transport response to insulin in skeletal muscle of the obese Zucker rat appears to result directly from an inability to effectively enhance cell surface GLUT-4 protein.
Etgen
G J
GJ
Department of Kinesiology, University of Texas at Austin 78712, USA.
Wilson
C M
CM
Jensen
J
J
Cushman
S W
SW
Ivy
J L
JL
D000345:Affinity Labels; D000818:Animals; D001386:Azides; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D004187:Disaccharides; D005121:Extremities; D005260:Female; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4; D006003:Glycogen / Q000378:metabolism; D006027:Glycosides; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009119:Muscle Contraction; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000378:metabolism*; D009765:Obesity / Q000378:metabolism*; 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; D006003:Glycogen; D005947:Glucose