Effects of alpha-AMPK knockout on exercise-induced gene activation in mouse skeletal muscle
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We tested the hypothesis that 5'AMP-activated protein kinase (AMPK) plays an important role in regulating the acute, exercise-induced activation of metabolic genes in skeletal muscle, which were dissected from whole-body a2- and a1-AMPK knockout (KO) and wild-type (WT) mice at rest, after treadmill running (90 min), and in recovery. Running increased a1-AMPK kinase activity, phosphorylation (P) of AMPK, and acetyl-CoA carboxylase (ACC)ß in a2-WT and a2-KO muscles and increased a2-AMPK kinase activity in a2-WT. In a2-KO muscles, AMPK-P and ACCß-P were markedly lower compared with a2-WT. However, in a1-WT and a1-KO muscles, AMPK-P and ACCß-P levels were identical at rest and increased similarly during exercise in the two genotypes. The a2-KO decreased peroxisome-proliferator-activated receptor ¿ coactivator (PGC)-1a, uncoupling protein-3 (UCP3), and hexokinase II (HKII) transcription at rest but did not affect exercise-induced transcription. Exercise increased the mRNA content of PGC-1a, Forkhead box class O (FOXO)1, HKII, and pyruvate dehydrogenase kinase 4 (PDK4) similarly in a2-WT and a2-KO mice, whereas glucose transporter GLUT 4, carnitine palmitoyltransferase 1 (CPTI), lipoprotein lipase, and UCP3 mRNA were unchanged by exercise in both genotypes. CPTI mRNA was lower in a2-KO muscles than in a2-WT muscles at all time-points. In a1-WT and a1-KO muscles, running increased the mRNA content of PGC-1a and FOXO1 similarly. The a2-KO was associated with lower muscle adenosine 5'-triphosphate content, and the inosine monophosphate content increased substantially at the end of exercise only in a2-KO muscles. In addition, subcutaneous injection of 5-aminoimidazole-4-carboxamide-1-ß-4-ribofuranoside (AICAR) increased the mRNA content of PGC-1a, HKII, FOXO1, PDK4, and UCP3, and a2-KO abolished the AICAR-induced increases in PGC-1a and HKII mRNA. In conclusion, KO of the a2- but not the a1-AMPK isoform markedly diminished AMPK activation during running. Nevertheless, exercise-induced activation of the investigated genes in mouse skeletal muscle was not impaired in a1- or a2-AMPK KO muscles. Although it cannot be ruled out that activation of the remaining a-isoform is sufficient to increase gene activation during exercise, the present data do not support an essential role of AMPK in regulating exercise-induced gene activation in skeletal muscle.
|Journal||The FASEB Journal|
|Number of pages||3|
|Publication status||Published - 2005|