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J Appl Physiol 107: 283-289, 2009. First published April 9, 2009; doi:10.1152/japplphysiol.91208.2008
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AMPK activation is fiber type specific in human skeletal muscle: effects of exercise and short-term exercise training

Robert S. Lee-Young,1 Benedict J. Canny,2 Damian E. Myers,1 and Glenn K. McConell1

1Department of Physiology, University of Melbourne, Parkville, Victoria; and 2Department of Physiology, Monash University, Clayton, Victoria, Australia

Submitted 9 September 2008 ; accepted in final form 5 April 2009

AMP-activated protein kinase (AMPK) has been extensively studied in whole muscle biopsy samples of humans, yet the fiber type-specific expression and/or activation of AMPK is unknown. We examined basal and exercise AMPK-{alpha} Thr172 phosphorylation and AMPK subunit expression ({alpha}1, {alpha}2, and {gamma}3) in type I, IIa, and IIx fibers of human skeletal muscle before and after 10 days of exercise training. Before training basal AMPK phosphorylation was greatest in type IIa fibers (P < 0.05 vs. type I and IIx), while an acute bout of exercise increased AMPK phosphorylation in all fibers (P < 0.05), with the greatest increase occurring in type IIx fibers. Exercise training significantly increased basal AMPK phosphorylation in all fibers, and the exercise-induced increases were uniformly suppressed compared with pretraining exercise. Expression of AMPK-{alpha}1 and -{alpha}2 was similar between fibers and was not altered by exercise training. However, AMPK-{gamma}3 was differentially expressed in skeletal muscle fibers (type IIx > type IIa > type I), irrespective of training status. Thus skeletal muscle AMPK phosphorylation and AMPK expression are fiber type specific in humans in the basal state, as well as during exercise. Our findings reveal fiber type-specific differences that have been masked in previous studies examining mixed muscle samples.

muscle fiber; phosphorylation; immunohistochemistry; contraction


Address for reprint requests and other correspondence: R. Lee-Young, Dept. of Molecular Physiology and Biophysics, Vanderbilt Univ. School of Medicine, Nashville, TN 37203 (e-mail: robert.s.lee-young{at}vanderbilt.edu)






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