Effects of exercise training on skeletal muscle glucose uptake and transport.
Exercise training increases the concentration of GLUT-4 protein in skeletal muscle that is associated with an increase in maximal insulin-stimulated glucose transport. The purpose of this study was to determine whether exercise training results in a long-lasting increase in insulin-stimulated glucose transport in rat skeletal muscle. Glucose uptake and skeletal muscle 3-O-methyl-D-glucose (3-MG) transport were determined during hindlimb perfusion in the presence of a maximally stimulating concentration of insulin (10 mU/ml). Hindlimb glucose uptake was approximately 29% above sedentary (Sed) levels in rats examined within 24 h (24H) of their last exercise session. However, when rats were examined 48 h (48H) after their last exercise session, hindlimb glucose uptake was not different from Sed levels. Maximal 3-MG transport was enhanced, above Sed levels, in red (RG; 72% increase) and white (WG; 44% increase) gastrocnemius and plantaris (Plan; 67% increase) muscles, but not soleus (Sol), of 24H rats. GLUT-4 protein content was significantly elevated in those muscles that exhibited enhanced 3-MG transport in 24H rats. GLUT-4 protein content was also elevated in RG, WG, and Plan of 48H rats and was not different from 24H rats. Despite the elevated GLUT-4 protein content, 3-MG transport in 48H rats was only slightly, although statistically not significantly, higher than in Sed rats. These results provide evidence that exercise training does not result in a persistent increase in skeletal muscle glucose uptake or transport, despite an increase in GLUT-4 protein content.
Etgen
G J
GJ
Department of Kinesiology, University of Texas, Austin 78712.
Brozinick
J T
JT
Kang
H Y
HY
Ivy
J L
JL
D019325:3-O-Methylglucose; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005947:Glucose / Q000378:metabolism / Q000493:pharmacokinetics*; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000494:pharmacology; D008757:Methylglucosides / Q000493:pharmacokinetics; D009004:Monosaccharide Transport Proteins / Q000032:analysis / Q000378:metabolism; D009124:Muscle Proteins; D009132:Muscles / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D010805:Physical Conditioning, Animal; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D051275:Glucose Transporter Type 4; D007328:Insulin; D008757:Methylglucosides; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495694:Slc2a4 protein, rat; D019325:3-O-Methylglucose; D005947:Glucose