Mechanisms underlying impaired GLUT-4 translocation in glycogen-supercompensated muscles of exercised rats.
Exercise training induces an increase in GLUT-4 in muscle. We previously found that feeding rats a high-carbohydrate diet after exercise, with muscle glycogen supercompensation, results in a decrease in insulin responsiveness so severe that it masks the effect of a training-induced twofold increase in GLUT-4 on insulin-stimulated muscle glucose transport. One purpose of this study was to determine whether insulin signaling is impaired. Maximally insulin-stimulated phosphatidylinositol (PI) 3-kinase activity was not significantly reduced, whereas protein kinase B (PKB) phosphorylation was approximately 50% lower (P < 0.01) in muscles of chow-fed, than in those of fasted, exercise-trained rats. Our second purpose was to determine whether contraction-stimulated glucose transport is also impaired. The stimulation of glucose transport and the increase in cell surface GLUT-4 induced by contractions were both decreased by approximately 65% in glycogen-supercompensated muscles of trained rats. The contraction-stimulated increase in AMP kinase activity, which has been implicated in the activation of glucose transport by contractions, was approximately 80% lower in the muscles of the fed compared with the fasted rats 18 h after exercise. These results show that both the insulin- and contraction-stimulated pathways for muscle glucose transport activation are impaired in glycogen-supercompensated muscles and provide insight regarding possible mechanisms.
Kawanaka
K
K
Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Nolte
L A
LA
Han
D H
DH
Hansen
P A
PA
Holloszy
J O
JO
D019325:3-O-Methylglucose / Q000493:pharmacokinetics; D055372:AMP-Activated Protein Kinases; D000345:Affinity Labels; D000818:Animals; D001386:Azides; D001692:Biological Transport / Q000502:physiology; D004040:Dietary Carbohydrates / Q000494:pharmacology; D004187:Disaccharides; D051275:Glucose Transporter Type 4; D006003:Glycogen / Q000378:metabolism*; D006027:Glycosides; D007328:Insulin / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000201:enzymology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D005082:Physical Exertion / Q000187:drug effects / Q000502:physiology*; D011437:Propylamines; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology; D014316:Tritium
D019325:3-O-Methylglucose; D055372:AMP-Activated Protein Kinases; D000345:Affinity Labels; D001386:Azides; D004040:Dietary Carbohydrates; D004187:Disaccharides; D051275:Glucose Transporter Type 4; D006003:Glycogen; D006027:Glycosides; D007328:Insulin; D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; D009097:Multienzyme Complexes; D009124:Muscle Proteins; D019869:Phosphatidylinositol 3-Kinases; D011437:Propylamines; D017346:Protein Serine-Threonine Kinases; D014316:Tritium; C495694:Slc2a4 protein, rat; C065412:2-N-(4-(1-azitrifluoroethyl)benzoyl)-1,3-bis-(mannos-4-yloxy)-2-propylamine