Effect of 7-10 days of cycle ergometer exercise on skeletal muscle GLUT-4 protein content.
Previous studies in animals and humans have shown that endurance exercise-training protocols of several weeks to many months in duration induce adaptive increases in skeletal muscle GLUT-4 protein concentration. It is generally assumed that the increase in GLUT-4 concentration is a long-term adaptation to training. The present study examined whether 7-10 days of cycle ergometer exercise could induce increases in skeletal muscle GLUT-4 levels. Eight healthy subjects (4 men, 4 women) aged 31 +/- 2 (SE) yr exercised 2 h daily at 65-70% of peak O2 uptake (VO2peak) for either 7 (n = 3) or 10 (n = 5) consecutive days. Muscle biopsies (vastus lateralis) were obtained before initiation of the exercise program and 36-48 h after the final bout of exercise. Glucose transporter protein was quantitated by Western blotting using antiserum specific for GLUT-4. VO2peak was increased by 10% (from 3.0 +/- 0.2 to 3.3 +/- 0.2 l/min; P < 0.01) in response to the training. Body weight did not change (74.3 +/- 4.6 before vs. 75.0 +/- 4.2 kg after) as a result of training. Muscle GLUT-4 immunoreactivity was increased 98% (from 584 +/- 50 to 1,154 +/- 40 counts per minute 125I/25 micrograms protein; P < 0.001) in response to training. Increase in VO2peak and GLUT-4 protein were similar for 7 and 10 days of training. These results suggest that, given an adequate training stimulus, adaptations in skeletal muscle GLUT-4 protein occur very rapidly. Furthermore, the increase in GLUT-4 after 7-10 days of exercise is as large as that reported in studies employing long-term training protocols.
Gulve
E A
EA
Department of Medicine, Washington University School of Medicine, St Louis, Missouri 63110, USA.
Spina
R J
RJ
D000328:Adult; D015153:Blotting, Western; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D005947:Glucose / Q000378:metabolism; D005951:Glucose Tolerance Test; D051275:Glucose Transporter Type 4; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000378:metabolism*
D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495692:SLC2A4 protein, human; D005947:Glucose