Effects Of Resistance And Aerobic Exercise On Skeletal Muscle Hypertrophy Mediated By ITGB1 Signaling Pathway

Background:Sarcopenia is a kind of senile disease caused by the decline of muscle mass and strength,which causes a decline in muscle function.The risk of mild Sarcopenia in people over 60 years old is as high as 50%,which seriously affects the quality of life.Aging leads to satellite cells(SC)activating hardly and protein synthesis dysfunction.It remains to be unclear that exercise is conductive to remodel muscle and increase protein synthesis,improving muscle mass.It has been shown that ?1integrin(ITGB1)and its downstream focal adhesion kinase(FAK)are related to muscle hypertrophy,and ITGB1 also regulates the composition and metabolism of extracellular matrix(ECM).Whether exercise regulates collagen deposition through ITGB1 and promotes muscle protein synthesis remains to further studies.Objective: To start with ITGB1 signaling pathway to study the effects of resistance and aerobic exercise on muscle strength in middle-aged mice,to explore the molecular mechanism of the ITGB1-FAK-m TORC1 signaling pathway and collagen deposition on SC,which leads to muscle hypertrophy,so that it can provide a new perspective and new approaches to prevent Sarcopenia.Method: 18 healthy C57 BL / 6J mice were kept under standard conditions until 12.5 months of age,then randomly divided into 3 groups,namely,control group;resistance training group,receiving 8 weeks and three times a week of ladder training;aerobic training group receiving treadmill running for 8 weeks,three times a week training.The weight and grip of each mouse were measured every Sunday,and the maximum load of each mouse in resistance training group was tested.After the experiment,the mice were executed by Cervical dislocation,and the gastrocnemius muscles on both sides were quickly peeled off for use.Western Blotting technique was used to detect protein expression of ITGB1,Pax7,Myf5 and m TORC1,FAK,SRC and its phosphorylation level in gastrocnemius muscle;immunofluorescence was used to co-localize collagen and laminin in gastrocnemius.ANOVA and the paired sample t test were used under the help of SPSS.Results:(1)Changes to weight,grip strength and muscle wet weight: after the experiment,the body weight of the control group increased significantly(p <0.05).Compared with mice in control group,the weight of mice in the resistance training group was significantly reduced(p <0.05),while the ratio of gastrocnemius muscle wet weight / weight,grip strength and relative grip strength were significantly increased(p <0.05).After the training,compared with the mice in aerobic training group,the mice in the resistance training group also increased significantly(p <0.05).(2)Changes to indicators of the activation in skeletal muscle SC: Compared with the mice in the control group,the protein expression of Pax7 in the resistance training group was highly significantly increased of gastrocnemius muscle(p <0.01),which volume fraction of collagen decreased significantly(p <0.05).There was no significant difference in the protein expression of Myf5 among the three groups of mice,and there was no significant difference in the number of average nucleus in single muscle fiber.(3)Changes to the number and area of muscle fibers: In the same field of view,compared with the control group,the number of muscle fibers in the resistance training group decreased significantly(p <0.05),but the average area of singal muscle fiber increased significantly(p <0.05).(4)Changes to ITGB1 and protein related to intracellular signaling pathway: Compared with the control group,the protein expression of ITGB1 in the gastrocnemius muscle of the resistance training group was significantly increased(p <0.05),and the phosphorylation m TORC1,FAK and SRC were significantly increased(p <0.05).Conclusions:(1)The weight of middle-aged mice would rise with the increasing ages,but exercise could maintain its stability.(2)8-week resistance exercise can effectively increase the ratio of wet weight / weight of the gastrocnemius muscle and the grip strength,and prevent the skeletal muscle from Sarcopenia.However aerobic exercise training didn't have obvious effects on strength.(3)8-week resistance exercise can ameliorate collagen deposition to activate SC through ITGB1.(4)8-week resistance exercise promotes the phosphorylation of FAK and SRC through ITGB1,facilitating the activation of m TORC1 signaling pathway,which may be the main reason why resistance exercise helps muscle hypertrophy.