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1School of Exercise and Nutrition Sciences, Deakin University, Burwood, Victoria, Australia; 2Department of Nutrition and Dietetics, Harokopio University, Athens, Greece; and 3Department of Physiology, The University of Melbourne, Parkville, Victoria, Australia
Submitted 28 November 2005 ; accepted in final form 19 May 2006
To examine the influence of exercise intensity on the increases in vastus lateralis GLUT4 mRNA and protein after exercise, six untrained men exercised for 60 min at 39 ± 3% peak oxygen consumption (
O2 peak) (Lo) or 27 ± 2 min at 83 ± 2%
O2 peak (Hi) in counterbalanced order. Preexercise muscle glycogen levels were not different between trials (Lo: 408 ± 35 mmol/kg dry mass; Hi: 420 ± 43 mmol/kg dry mass); however, postexercise levels were lower (P < 0.05) in Hi (169 ± 18 mmol/kg dry mass) compared with Lo (262 ± 35 mmol/kg dry mass). Thus calculated muscle glycogen utilization was greater (P < 0.05) in Hi (251 ± 24 mmol/kg) than in Lo (146 ± 34). Exercise resulted in similar increases in GLUT4 gene expression in both trials. GLUT4 mRNA was increased immediately at the end of exercise (
2-fold; P < 0.05) and remained elevated after 3 h of postexercise recovery. When measured 3 h after exercise, total crude membrane GLUT4 protein levels were 106% higher in Lo (3.3 ± 0.7 vs. 1.6 ± 0.3 arbitrary units) and 61% higher in Hi (2.9 ± 0.5 vs. 1.8 ± 0.5 arbitrary units) relative to preexercise levels. A main effect for exercise was observed, with no significant differences between trials. In conclusion, exercise at
40 and
80%
O2 peak, with total work equal, increased GLUT4 mRNA and GLUT4 protein in human skeletal muscle to a similar extent, despite differences in exercise intensity and duration.
gene expression; glucose; protein expression
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