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Am J Physiol Endocrinol Metab 292: E331-E339, 2007. First published September 5, 2006; doi:10.1152/ajpendo.00243.2006
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Role of AMPK2 in basal, training-, and AICAR-induced GLUT4, hexokinase II, and mitochondrial protein expression in mouse muscle

¹Department of Human Physiology, Copenhagen Muscle Research Centre, Institute of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark; ²Institute Cochin, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche Scientifique, Rene Descartes University, Department of Genetic, Development, and Molecular Pathology, Paris, France; and ³Copenhagen Muscle Research Centre, Department for Molecular Muscle Biology, Rigshospitalet, Copenhagen, Denmark

Submitted 23 May 2006 ; accepted in final form 8 August 2006

We investigated the role of AMPK2in basal, exercise training-, and AICAR-induced protein expression of GLUT4, hexokinase II (HKII), mitochondrial markers, and AMPK subunits. This was conducted in red (RG) and white gastrocnemius (WG) muscle from wild-type (WT) and 2-knockout (KO) mice after 28 days of activity wheel running or daily AICAR injection. Additional experiments were conducted to measure acute activation of AMPK by exercise and AICAR. At basal, mitochondrial markers were reduced by 20% in 2-KO muscles compared with WT. In both muscle types, AMPK2 activity was increased in response to both stimuli, whereas AMPK1 activity was increased only in response to exercise. Furthermore, AMPK signaling was estimated to be 60–70% lower in 2-KO compared with WT muscles. In WG, AICAR treatment increased HKII, GLUT4, cytochrome c, COX-1, and CS, and the 2-KO abolished the AICAR-induced increases, whereas no AICAR responses were observed in RG. Exercise training increased GLUT4, HKII, COX-1, CS, and HAD protein in WG, but the 2-KO did not affect training-induced increases. Furthermore, AMPK1, -2, -1, -2, and -3 subunits were reduced in RG, but not in WG, by 30–60% in response to exercise training. In conclusion, the 2-KO was associated with an 20% reduction in mitochondrial markers in both muscle types and abolished AICAR-induced increases in protein expression in WG. However, the 2-KO did not reduce training-induced increases in HKII, GLUT4, COX-1, HAD, or CS protein in WG, suggesting that AMPK2 may not be essential for metabolic adaptations of skeletal muscles to exercise training.

5'-adenosine monophosphate-activated protein kinase-2; glucose transporter-4; 5-aminoimidazole-1--D-ribofuranoside; exercise training; mitochondrial proteins; skeletal muscle

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