The Effects Of Successive High Intensity Interval Training On Protein Metabolism Of Skeletal Muscle In Rats

Objective:On the basis of the effects of 4,8,12 weeks high intensity interval training on the skeletal muscle mass,exploring the inner relationship between protein synthesis and proteolysis under HIIT in middle aged rats,hoping to propose a new strategy which can postpone the muscle loss.Methods:9 months old,male Wistar rats were randomly divided into the control group(C group),moderate training group(M group)and HIIT group(H group).The V02max,running time and distance,the weight of extensor digitorum longus(EDL)and soleus muscle,single muscle fiber cross-section area,autophagosome,the expression of protein synthesis related proteins,ubiquitin,MuRF-1,MAFbx,autophagy-related proteins were tested before the experiment,4th week,8th week and 12th week after the experiment respectively.Results:(1)For C group,the wet muscle mass were decreased,the protein expression of Akt Ser473,Beclin-1 of EDL,4E-BP1 Thr37/46,LC3II,Beclin-lof soleus were decreased,MAFbx,P62 of EDL and MAFbx of soleus were increased in the 12th week.(2)Compared with C group,exercise inhibited the loss of muscle mass in the 12th week.HIIT improved the V02max from the 4th week,and running time and distance as well,when going along with the M group.(3)Compared with C group,HIIT improved the phosphorylated protein expression of Akt,P70 S6K,4E-BP1 and S6 in EDL from the 4th week;exercise differently improved the phosphorylated protein expression of mTOR,P70 S6K and S6 in soleus muscle from the 8th week.(4)Compared with C group,exercise decreased the protein expression of MAFbx in EDL from the 8th week.Exercise decreased the protein expression of MuRF-1 and HIIT increased the MuRF-1 in soleus mucle in the 4th week;exercise differently decreased the protein expression of MAFbx and MuRF-1 in soleus muscle from the 8th week.(4)Compared with C group,exercise improved the protein expression of LC3II/LC3I,COXIV,PGC-1 and decreased the P62 in EDL from the 8th week.HIIT improved the soleus protein expression of LC3II/LC3I in the 8th week and COXIV protein expression in the 12th week.Conclusions:(1)HIIT maintained skeletal muscle mass,which might be benefit from:promoting the protein synthsis by the mTOR signal;adjusting the appropriate activation level of the ubiquitin-proteasome pathway by decreasing the MuRF-land MAFbx expression;improving the basic autophagic activity and autophagy flow.(2)HIIT had more chronergy on improving protein synthesis of EDL and adjusting ubiquitin-proteasome and autophagy activity of soleus muscle.(3)The protein synthesis of EDL and the ubiquitin-prot easome of soleus were more sensitive to HIIT,indicating the specificity of muscle fiber.This study highlights that HIIT might be an effective way for mucle mass maintaining.