| Background:Myocardial infarction(MI)can lead to the impairment of heart function,accumulation of other organs,pathological remodeling of distant organs and other complications,such as the impairment of skeletal muscle,liver and kidney functions.Clinical studies have shown that cardiac cachexia syndrome,characterized by skeletal muscle reduction,is an important cause of death in patients with myocardial infarction.The decrease of skeletal muscle leads to exercise intolerance,fatigue resistance and dyspnea,which seriously affects the quality of life of patients with myocardial infarction.Therefore,it is of great significance to inhibit the decrease of skeletal muscle and improve the quality and function of skeletal muscle for improving the survival rate and quality of life of patients.It has been reported in the literature that Irisin is closely related to sarcopenia,and exogenous injection of Irisin recombinant protein can significantly inhibit sarcopenia.Exercise intervention can effectively stimulate the secretion and expression of skeletal muscle Irisin,and play an important role in reducing oxidative stress,inhibiting apoptosis and promoting cell proliferation.The high expression of ALCAT1 leads to the mass production of ROS in tissue cells,and the deletion of ALCAT1 can significantly reduce oxidative stress damage in the body.Is there a difference in exercise intensity in skeletal muscle secretion of Irisin stimulated by exercise?Does Irisin play a role in exercise improvement of myocardial infarction induced skeletal muscle loss?Can the Irisin-PI3K-Akt pathway be activated to inhibit skeletal muscle cell apoptosis by reducing the expression of ALCAT1 and oxidative stress?Does it promote skeletal muscle cell proliferation by activating the Irisin-PI3K-Akt-mTOR pathway?There is still a lack of literature reports.Objectives:The purpose of this study was to investigate the endogenous Irisin secretion stimulated by aerobic exercise,the inhibition of ALCAT1 expression,and the improvement of skeletal muscle loss induced by myocardial infarction and its mechanism.This study will provide experimental basis for the selection of rehabilitation methods and methods for myocardial infarction induced skeletal muscle loss.Methods:In vivo animal experiments:Healthy male 2-month-old C57BL/6J wild-type(WT)mice were randomly divided into quiet control group(C),60%VO2 max exercise intensity group(CSE),76%VO2max exercise intensity group(CME),85%VO2max exercise intensity group(CHE),pseudomyocardial infarction group(S),myocardial infarction group(MI)and myocardial infarction exercise group(ME).Healthy male 2-month-old alcat1 gene knockout(ALCAT1-/-)mice were randomly divided into sham infarction group(KS),myocardial infarction group(KMI)and myocardial infarction exercise group(KME).There were 10 in each group.The CSE group ran at 8m/min,CME at 12m/min,CHE group ran at 18m/min,slope was 0°,60min/d,5d/wkx4wk.The gastrocnemius muscle was separated 24 hours after exercise.RT-qPCR was used to detect alcatl mRNA expression in skeletal muscle,Western blotting was used to detect Irisin,ALCAT1,SOD1 and SOD2 protein expression in skeletal muscle,and enzyme activity kit was used to detect oxidative stress index in skeletal muscle.Mouse MI model was established by ligation of the left anterior descending coronary artery(LAD),in which the S group and the KS group only had thorpectomy without ligation.The ME group and the KME group performed platform running at 12m/min at lwk after the operation,and the slope was 0°,60min/d,5d/wk×6wk.24 hours after the end of the 6wk exercise,the samples were collected,the cardiac function was detected by ultrasonic echocardiography,and the gastrocnemius muscle was quickly cut and weighed.The ratio of gastrocnemius muscle weight to body weight was calculated.Masson staining was used to observe and calculate the percentage of myocardial collagen volume(CVF%).HE staining was used to determine the cross-sectional area of skeletal muscle cells.TUNEL was used to detect the apoptosis of skeletal muscle cells.Transmission electron microscopy was used to observe the formation of autophagy in skeletal muscle.Enzyme activity kit was used to detect the level of oxidative stress in skeletal muscle.RT-qPCR was used to detect the expression of alcatl mRNA in skeletal muscle.Western blotting detection of skeletal muscle pathway related proteins Irisin,ALCAT1,PI3K/pPI3K,Akt/pAkt,mTOR/pmTOR,cell autophagy related proteins ULK1/pULKl,Beclinl,LC3,P62,apoptosis related proteins Bax/Bcl2,Cyt-C,cell proliferation-related proteins P70 S6K/pP70 S6K,Pax7,MyoD,MyoG,Myf5,Myf6,SOD1,SOD2,MuRF1,MAbFx proteins are expressed.In vitro cell experiments:C2C12 myoblasts were given Irisin recombinant protein(rhIRISIN,100ng/ml/24h),AMPK agonist(AICAR,1mM/24h),PI3K inhibitor(LY294002,5uM/24h),mTOR inhibitor(Rapamycin,500nM/24h)and hydrogen peroxide(H2O2,100uM/24h)intervention,divided into normal control group,H2O2 group,Irisin+H2O2 group,AICAR+H2O2 group,LY294002+Irisin+H2O2 group,Rapamycin+Irisin+H2O2 group,LY294002+AICAR+H2O2 group and Rapamycin+AICAR+H2O2 group,a total of 8 groups.CCK-8 method was used to detect cell viability,TUNEL was used to detect apoptosis,fluorescent probe was used to detect ROS,and Western blotting was used to detect Irisin,ALCAT1,PI3K/pPI3K,Akt/pAkt,mTOR/pmTOR,Bcl2,Bax,Cyt-C,P70 S6K/pP70 S6K,Pax7,MyoD,MyoG,Myf5,Myf6,SOD1,SOD2,MuRF1 and MAbFx expression.Results:(1)Different intensity exercise significantly increased the expression of Irisin protein in normal skeletal muscle(P<0.01).(2)Different intensity exercise significantly inhibited the expression of ALCAT1 in normal skeletal muscle,of which 76%VO2max exercise intensity effect was more significant(P<0.05,P<0.01).(3)60%-76%VO2max exercise intensity can activate the normal skeletal muscle oxidation-antioxidation system,while 85%VO2max exercise intensity significantly increases skeletal muscle oxidative stress level,but has no significant effect on skeletal muscle antioxidant capacity(P<0.05,P<0.01).(4)Aerobic exercise significantly increased the relative mass of skeletal muscle and the cross-sectional area of muscle cells,and reduced the expression of MurF 1 and MAFbx proteins in skeletal muscle(P<0.05,P<0.01).It has been shown that aerobic exercise significantly improves myocardial infarction-induced skeletal muscle reduction.(5)Aerobic exercise significantly reduced myocardial infarction-induced skeletal muscle ALCAT1 gene and protein expression and MDA content,increased SOD1 and SOD2 protein expression,and T-SOD activity(P<0.01).It is shown that aerobic exercise significantly inhibits the level of oxidative stress induced by myocardial infarction in skeletal muscle and improves the antioxidant capacity of skeletal muscle.(6)Aerobic exercise significantly increased the expression of Irisin in skeletal muscle induced by myocardial infarction and the ratio of pPI3K/PI3K,pmTOR/mTOR and pAkt/Akt(P<0.01).It is shown that aerobic exercise significantly activates the Irisin-PI3K-Akt-mTOR signaling pathway induced by myocardial infarction.(7)Aerobic exercise inhibits the formation of skeletal muscle autophagosomes induced by myocardial infarction,significantly reduces the pULK1/ULK1 and LC3 ?/? ratio of skeletal muscle and the expression of Beclinl,and increases the expression of P62(P<0.01).It showed that autophagy activity of skeletal muscle cells was significantly enhanced after myocardial infarction,and aerobic exercise significantly reduced the autophagy damage of skeletal muscle cells induced by myocardial infarction.(8)Aerobic exercise significantly reduced the number of TUNEL positive particles,Cyt-C expression and Bax/Bcl2 ratio in skeletal muscle induced by myocardial infarction(P<0.01).It was shown that aerobic exercise significantly inhibited myocardial infarction-induced skeletal muscle cell apoptosis.(9)Aerobic exercise significantly increased the myocardial infarction-induced skeletal muscle pP70 S6K/P70 S6K ratio and the expression of Pax7,MyoD,MyoG,Myf5,and Myf6(P<0.05,P<0.01).It is shown that aerobic exercise significantly promotes myocardial infarction-induced skeletal muscle protein synthesis and muscle cell proliferation.(10)rhIRISIN or AICAR intervention significantly reduced MurFl and MAFbx expression in C2C12 cells(P<0.05,P<0.01).It was shown that rhIRISIN or AICAR intervention significantly inhibited the ubiquitination of C2C12 cell proteins induced by H202.(11)rhIRISIN or AICAR intervention significantly reduced the ROS level and ALCAT1 expression,and increased the expression of SOD1 and SOD2 in C2C12 cells(P<0.01).It was shown that rhIRISIN or AICAR intervention significantly inhibited the level of oxidative stress in C2C12 cells induced by H2O2.(12)rhIRISIN or AICAR intervention significantly reduced the number of TUNEL positive particles,Cyt-C expression,and Bax/Bcl2 ratio in C2C12 cells(P<0.01).It was shown that rhIRISIN or AICAR intervention significantly inhibitedthe apoptosis of C2C12 cells induced by oxidative stress.(13)rhIRISIN or AICAR intervention significantly increased the pP70 S6K/P70 S6K ratio and the expression of Pax7,MyoD,MyoG,Myf5 and Myf6 in C2C12 cells(P<0.01).It was shown that oxidative stress significantly inhibited C2C12 cell proliferation,and rhIRISIN or AICAR intervention significantly promoted C2C12 cell proliferation.(14)LY294002 intervention significantly inhibited the phosphorylation of rhIRISIN or AICAR on PI3K-Akt pathway in C2C12 cells,and increased the number of TUNEL positive particles,Cyt-C expression and Bax/Bcl2 ratio(P<0.05,P<0.01).It is shown that rhIRISIN or AICAR intervention can inhibit the apoptosis of C2C12 cells induced by oxidative stress by activating the PI3K-Akt pathway.(15)LY294002 or Rapamycin intervention significantly inhibited the phosphorylation of PI3K-Akt-mTOR pathway by rhIRISIN or AICAR,reduced the pP70 S6K/P70 S6K ratio and Pax7,MyoD,MyoG,Myf5 and Myf6 expression(P<0.05,P<0.01).It is shown that rhIRISIN or AICAR intervention promotes C2C12 protein synthesis and cell proliferation by activating the PI3K-Akt-mTOR pathway.Conclusion:(1)The changes of skeletal muscle ALCAT1 expression have obvious characteristics of exercise intensity.Different intensity exercise can significantly increase the expression of Irisin in and inhibit the expression of ALCAT1 in normal skeletal muscle.(2)Aerobic exercise significantly stimulates myocardial infarction-induced skeletal muscle Irisin expression,reduces ALCAT1 expression and inhibits oxidative stress and myocardial infarction-induced skeletal muscle cell autophagy and apoptosis,promotes skeletal muscle protein synthesis and cell proliferation,and improves myocardial infarction-induced skeletal muscle loss is closely related.(3)Aerobic exercise significantly activates the Irisin-PI3K-Akt pathway and inhibits skeletal muscle cell apoptosis;significantly activates the Irisin-PI3K-AktmTOR pathway,promotes skeletal muscle protein synthesis and cell proliferation,and improves bones induced by myocardial infarction Important mechanism of muscle loss.In summary,aerobic exercise stimulates myocardial infarction-induced skeletal muscle endogenous Irisin expression and inhibits ALCAT1 expression,activates the skeletal muscle Irisin-PI3K-Akt-mTOR pathway,reduces skeletal muscle oxidative stress levels,inhibit cell autophagy and apoptosis of skeletal muscle,promote skeletal muscle protein synthesis and cell proliferation,and improve skeletal muscle reduction induced by myocardial infarction. |
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