Regulation of hexokinase II activity and expression in human muscle by moderate exercise.
A single bout of exercise increases the rate of insulin-stimulated glucose uptake and metabolism in skeletal muscle. Exercise also increases insulin-stimulated glucose 6-phosphate in skeletal muscle, suggesting that exercise increases hexokinase activity. Within 3 h, exercise increases hexokinase II (HK II) mRNA and activity in skeletal muscle from rats. It is not known, however, if a single bout of moderate-intensity exercise increases HK II expression in humans. The present study was undertaken to answer this question. Six subjects had percutaneous biopsies of the vastus lateralis muscle before and 3 h after a single 3-h session of moderate-intensity aerobic (60% of maximal oxygen consumption) exercise. Glycogen synthase, HK I, and HK II activities as well as HK I and HK II mRNA content were determined from the muscle biopsy specimens. The fractional velocity of glycogen synthase was increased by 446 +/- 84% after exercise (P < 0.005). Hexokinase II activity in the soluble fraction of the homogenates increased from 1.2 +/- 0.4 to 4.5 +/- 1.6 pmol.min-1.microgram-1 (P < 0.05) but was unchanged in the particulate fraction (4.3 +/- 1.3 vs. 5.3 +/- 1.5). HK I activity in neither the soluble nor particulate fraction changed after exercise. Relative to a 28S rRNA control signal, HK II mRNA increased from 0.091 +/- 0.02 to 0.195 +/- 0.037 (P < 0.05), whereas HK I mRNA was unchanged (0.414 +/- 0.061 vs. 0.498 +/- 0.134, P < 0.20). The increase in HK II activity after moderate exercise in healthy subjects could be one factor responsible for the enhanced rate of insulin-stimulated glucose uptake seen after exercise.
Koval
J A
JA
Department of Medicine, University of Texas Health Science Center at San Antonio 78284-7886, USA.
DeFronzo
R A
RA
O'Doherty
R M
RM
Printz
R
R
Ardehali
H
H
Granner
D K
DK
Mandarino
L J
LJ
D000328:Adult; D000818:Animals; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D006006:Glycogen Synthase / Q000378:metabolism; D006593:Hexokinase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology*; D010101:Oxygen Consumption; D005082:Physical Exertion / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats
D012333:RNA, Messenger; D006006:Glycogen Synthase; D006593:Hexokinase