Effects Of AMPK Activation On Akt-FoxO Signal Pathway About Protein Degradation In Rat Skeletal Muscle Through The Exercise

Purposes:AMPK was an intracellular energy sensor in skeletal muscle, which could activate by exercise,Recently,AMPK has been implicated in the control of protein synthesis in skeletal muscle,but the effect of AMPK activation on myofibrillar protein degradation has yet to be elucidated.So,the question maybe elucidate through animal experiment in this research.Methods:Treadmill exercise and AICAR injection models with rat were used in ExpⅠandⅡ.ExpⅠwas made up by intensity,25m/min,5%slope and 30min,60min time.In ExpⅡ,rats was divided into a bout AICAR injection, with a subcutaneous injection(AICAR;0.5 mg/g body wt;75 mg AICAR/ml saline),or an equivalent volume of normal saline as control.In ExpⅠandⅡ,gastrocnemius samples were collected at 30min,1h、2h and 6h after exercise or at 1h,2h and 7h after AICAR injection.AMP,ATP, 3-MH contents were determined by HPLC.AMPK activity was determined by [γ-32P]ATP as P donor and SAMS peptide as substrate.Phosphorylation mTOR Ser2448 was determined by western blot,as well as total FoxO, totalAkt,total mTOR,Phospho-Fox03a(Ser253),Phosphorylation Akt Ser473. atrogin-1 mRNA,MURF-1 mRNA was determined by Realtime PCR.Results:The AMP The AMP content and AMP/ATP ratio were elevated (P＜0.05) from 30 to 60min exercise;AMPK activity were significantly increased at 30min exercise,and kept increasing from 30min exercise, then to the peaking at 2h postexercise,and then decreased at 6h postexercise but higher than rest;Akt Ser473,Fox03a Ser253 phosphorylation were elevated(P＜0.05) from 30 to 60min exercise,then decreased 1-6h postexercise.In the course of exercise,Akt,Fox03a, mTOR total protein content and ATP content,among the groups there were no significant differences;RUN increased mRNA Expression of MuRFland MAFbx at 1h,2h and 6h postexercise,respectively;RUN significantly increased(P＜0.05) mTOR Ser2448 phosphorylation at 30min,and kept increasing at 60min,but there was no difference;AMPK activity were significantly increased(P＜0.05) at post-inject 1h,2h and 7h,then decreased at post-inject 7h.;Akt Ser473,Fox03a Ser253 and mTOR Ser2448 phosphorylation were decreased(P＜0.05) at post-inject 1h,2h and 7h,In addition to phosphorylation of Fox03a Ser253 has decreased but no significant differences at post-inject 7h.AICAR injection increased mRNA Expression of MuRFl(2.48-fold,2.23-fold)and MAFbx(2-fold,1.98-fold) at post-inject 1h and 2h,respectively.MuRFl mRNA were significantly elevated(P＜0.05),whereas MAFbx mRNA has increased,but no significant differences at post-inject 7h.Conclusion:Protein degradation in rat skeletal muscle did not vary during a prolonged aerobic exercise,while it was increased after exercise. A prolonged aerobic exercise significantly increased AMPK activity. Activated AMPK may promote the protein degradation through the Akt-FoxO signal pathway.