Activation of AMP-activated protein kinase induce expression of FoxO1, FoxO3a, and myostatin after exercise-induced muscle damage.
AMP-activated protein kinase (AMPK) has been shown to regulate protein metabolism in skeletal muscle. We previously found that levels of Forkhead box proteins, FoxO1 and FoxO3a, and myostatin in rat gastrocnemius increased after exercise-induced muscle damage (EIMD). Eccentric muscle contractions (ECs), defined as elongation of muscle under tension, were used for inducing EIMD. The objective of this study was to clarify whether AMPK participates in activation and expression of FoxO proteins and myostatin in rat gastrocnemius muscle after EIMD. Wistar rats were randomly assigned into the following three groups; CON (n = 6), 180ECs group (ankle angular velocity, 180°/s; n = 6), and 30ECs group (ankle angular velocity, 30°/s; n = 6). 20 ECs were conducted with percutaneous electrical stimulation of gastrocnemius and simultaneous forced dorsiflexion of ankle joint (from 0° to 45°). To evaluate activation of AMPK, we measured the phosphorylated states of AMPK and acetyl CoA carboxylase. For evaluation of the direct relationships of AMPK and other proteins, we also examined contents of FoxOs and myostatin with stimulation of L6 myotube with AMPK agonist, 5 -aminoimidazole -4 -carboxamide -1-β-d-ribofuranoside (AICAR) (0.1, 0.5, 1, 1.5, and 2 mM). Western blotting was employed for protein analysis. Significant torque deficit was only observed in the 180ECs, suggesting EIMD. We also observed that phosphorylated AMPKα was induced in response to 180ECs (p < 0.01 vs. CON). Additionally, the level of phosphorylated acetyl CoA carboxylase was significantly higher in response to 180ECs and 30ECs. The phosphorylated states of FoxO1, FoxO3a, and myostatin expression were increased significantly in response to 180ECs. Furthermore, treatment of L6 myotubes with AICAR showed similar tendencies to that observed in in vivo gastrocnemius muscle treated with 180ECs. Therefore, we conclude that activation of AMPK plays a key role in increasing the level of FoxO1, FoxO3a, and myostatin in gastrocnemius after EIMD.
Graduate School of Health and Sport Sciences, Nippon Sport Science University, 7-1-1, Fukasawa, Setagaya, Tokyo 158-8508, Japan; Korea Institute of Sports Science, San223-19, Gongneung-dong Nowon-gu Seoul 139-242, South Korea. Electronic address: lkhlike82@yahoo.co.jp.
Kihyuk
K
Lee
Graduate School of Education, Okayama University, 3-1-1, Tsushimanaka, Kita, 700-8530, Okayama, Japan. Electronic address: eisukeochi@cc.okayama-u.ac.jp.
Eisuke
E
Ochi
Korea Institute of Sports Science, San223-19, Gongneung-dong Nowon-gu Seoul 139-242, South Korea. Electronic address: hongsun71@naver.com.
Hongsun
H
Song
Graduate School of Health and Sport Sciences, Nippon Sport Science University, 7-1-1, Fukasawa, Setagaya, Tokyo 158-8508, Japan. Electronic address: nakazato@nittai.ac.jp.
Koichi
K
Nakazato
D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000737:chemistry; D000818:Animals; D004789:Enzyme Activation; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D007596:Joints / Q000473:pathology; D035002:Lower Extremity / Q000473:pathology; D008297:Male; D009119:Muscle Contraction; D018485:Muscle Fibers, Skeletal / Q000473:pathology; D018482:Muscle, Skeletal / Q000473:pathology; D009132:Muscles / Q000473:pathology*; D055435:Myostatin / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010766:Phosphorylation; D010805:Physical Conditioning, Animal / Q000009:adverse effects*; D051381:Rats; D017208:Rats, Wistar; D012265:Ribonucleotides / Q000737:chemistry; D000071161:Forkhead Box Protein O1
D055372:AMP-Activated Protein Kinases; D000620:Aminoimidazole Carboxamide; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D055435:Myostatin; D009419:Nerve Tissue Proteins; D012265:Ribonucleotides; C499515:FOXO3 protein, rat; C525913:Mstn protein, rat; C074639:Foxo1 protein, rat; D000071161:Forkhead Box Protein O1; C031143:AICA ribonucleotide
Animal model; Cell culture; Protein degradation; Strain injury