Progressive increase in glucose transport and GLUT-4 in human sarcolemmal vesicles during moderate exercise.
Muscle glucose uptake increases progressively during moderate-intensity exercise. To elucidate whether this is due to a progressive increase in sarcolemmal glucose transport capacity, nine men exercised for 40 min at 75% maximal oxygen uptake on a bicycle ergometer. Muscle biopsies were obtained from the vastus lateralis at rest (0 min) and after 5 and 40 min of exercise and used for production of sarcolemmal giant (SG) vesicles. SG vesicle glucose transport at 5 mM increased (P < 0.05) by 38 and 93% after 5 and 40 min of exercise, respectively, compared with glucose transport at rest. The SG vesicle GLUT-4 protein content increased (P < 0.05) by 36 and 91% after 5 and 40 min of exercise, respectively, compared with rest. Thus the increase in vesicle glucose transport was accompanied by a similar increase in SG vesicle GLUT-4 protein content. Muscle glucose and glucose 6-phosphate were low at rest, increased (P < 0.05) 2.2- and 2.3-fold, respectively, after 5 min of exercise, and returned to resting values after 40 min of exercise. It is concluded that the progressive increase in muscle glucose uptake during moderate-intensity exercise may be due at least in part to a progressive increase in sarcolemmal glucose transport and GLUT-4 protein content.
Kristiansen
S
S
Copenhagen Muscle Research Centre, University of Copenhagen, Denmark.
Hargreaves
M
M
Richter
E A
EA
D000328:Adult; D001692:Biological Transport; D015153:Blotting, Western; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4; D006801:Humans; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D009132:Muscles / Q000378:metabolism*; D005082:Physical Exertion; D012508:Sarcolemma / Q000378:metabolism*
D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495692:SLC2A4 protein, human; D005947:Glucose