Effects Of MOTS-c On The Decreased Motor Ability Of Mice Caused By Hypoxia And Its Preliminary Mechanis

Background:The plateau environment is mainly characterized by low oxygen content,low air pressure and low temperature.With the development of economic construction and the deepening of scientific research,a large number of people need to enter high-altitude areas,when we enter high-altitude areas from the plain,it will be due to acute plateau leading to hypoxia,dehydration,difficulty in thermoregulation and other phenomena,these characteristics will have different effects on human exercise capacity,hypoxia will reduce exercise oxygen consumption and exercise capacity,increase heart rate and blood pressure,cause headache,fatigue and other symptoms,dehydration will reduce blood flow and circulation efficiency,increase the risk of myocardial ischemia and arrhythmia,Low temperatures increase the difficulty of muscle contraction and the risk of muscle damage,which can lead to a decrease in the body’s exercise capacity and inconvenience to our activities in a low-oxygen environment on the plateau.Mitochondria are one of the most important organelles during exercise,which can provide energy for skeletal muscle during exercise,actively participate in transmitting exercise-induced signals to other organs,and regulate the body’s metabolism and energy supply.The study found that mitochondria have a unique circular genome(containing only 13 protein-coding genes)with bioactive peptides(MDPs)produced by short open reading frames(s ORFs)encoded in this genome with a wide range of physiological functions.Among them,MOTS-c(12S r RNA-c type mitochondrial ORF)is a recently discovered MDP that promotes metabolic homeostasis,and the study found that the level of endogenous MOTS-c in humans increases with the increase of exercise,and MOTS-c treatment significantly improves the exercise capacity of young,middle-aged and elderly mice in a normoxic environment,and regulates skeletal muscle metabolism and gene expression,but its role on exercise capacity in a hypoxic environment is still unclear and needs in-depth research and discussion.Objective:In this study,8-week-old male Kunming mice were first selected for8-week intraperitoneal injection of different doses of MOTS-c to screen out the most suitable dose in line with subsequent experiments,and then the 6-week intraperitoneal injection of MOTS-c and treadmill exercise were selected to intervene in 8-week-old male Kunming mice to investigate the effect of exercise and MOTS-c on the decline of exercise capacity caused by acute hypoxia,and to verify that MOTS-c had a preventive effect on the decline of exercise capacity caused by acute hypoxia.The mechanism of MOTS-c in preventing the decline of exercise capacity caused by acute hypoxia in mice was preliminarily discussed,which provided a reference for the development of new drugs to prevent the decline of exercise capacity caused by high-altitude hypoxic environment.Methods:(1)Using 40 8-week-old male Kunming mice,Kunming mice were randomly divided into control group and administration group,that is,they were randomly divided into high-dose MOTS-c group(HM group,n=10),medium-dose MOTS-c group(MM group,n=10),low-dose MOTS-c group(LM group,n=10),and control group(C group,n=10).Mice in the dosing group were administered intraperitoneally for 8 weeks from 9 weeks of age and weekly treadmill exercise ability tests were performed to detect the exercise ability of mice.After 8 weeks of administration,a hypoxic capacity test(stuffy tank experiment)was performed to detect the viability of mice in a hypoxic environment.After the stuffy tank experiment,mice were anesthetized and necked and sacrificed,and whole blood and skeletal muscle tissue were taken.The biochemical kit detects the content of serum urea nitrogen(BUN),lactate dehydrogenase(LDH),glutathione(GSH),hemoglobin(Hb)content in plasma,and the content of liver glycogen(HG)in liver tissue and muscle glycogen(MG)in skeletal muscle in the blood of mice.RT-PCR methods detect m RNA expression levels in mice such as Sirt1,MOTS-c,PGC-1α,and AMPK.The Western Blot experiment measured the expression levels of mouse proteins such as the proteasome Sirt1,MOTS-c,PGC-1α and AMPK.(2)Using 90 8-week-old male Kunming mice,Kunming mice were randomly divided into control group,exercise group,administration group and exercise drug group,that is,they were randomly divided into MOTS-c group(OM group,n=15),moderate intensity exercise + MOTS-c group(MEM group,n=15),high-intensity exercise + MOTS-c group(HEM group,n=15),moderate intensity exercise group(EM group,n=15),high-intensity exercise group(HE group,n=15)and control group(C group,n=15).The mice in the dosing group underwent intraperitoneal injection administration with different intensity treadmill exercise for 6weeks from 9 weeks of age,and a maximum speed test was performed weekly to detect the exercise ability of the mice.After 6 weeks of intervention,a hypoxic swimming experiment was performed to detect the exercise ability of mice in a hypoxic environment.After the hypoxic swimming experiment,mice were anesthetized and necked and sacrificed,and whole blood and skeletal muscle tissue were taken.The biochemical kit detects the content of serum urea nitrogen(BUN),lactate dehydrogenase(LDH),glutathione(GSH),hemoglobin(Hb)content in plasma,and the content of liver glycogen(HG)in liver tissue and muscle glycogen(MG)in skeletal muscle in the blood of mice.RT-PCR methods detect m RNA expression levels in mice such as Sirt1,MOTS-c,PGC-1α,and AMPK.The Western Blot experiment measured the expression levels of mouse proteins such as the proteasome Sirt1,MOTS-c,PGC-1α and AMPK.Results:(1)Using 40 8-week-old male Kunming mice,Kunming mice were randomly divided into control group and administration group,that is,they were randomly divided into high-dose MOTS-c group(HM group,n=10),medium-dose MOTS-c group(MM group,n=10),low-dose MOTS-c group(LM group,n=10),and control group(C group,n=10).Mice in the dosing group were administered intraperitoneally for 8 weeks from 9 weeks of age and weekly treadmill exercise ability tests were performed to detect the exercise ability of mice.After 8 weeks of administration,a hypoxic capacity test(stuffy tank experiment)was performed to detect the viability of mice in a hypoxic environment.After the stuffy tank experiment,mice were anesthetized and necked and sacrificed,and whole blood and skeletal muscle tissue were taken.The biochemical kit detects the content of serum urea nitrogen(BUN),lactate dehydrogenase(LDH),glutathione(GSH),hemoglobin(Hb)content in plasma,and the content of liver glycogen(HG)in liver tissue and muscle glycogen(MG)in skeletal muscle in the blood of mice.RT-PCR methods detect m RNA expression levels in mice such as Sirt1,MOTS-c,PGC-1α,and AMPK.The Western Blot experiment measured the expression levels of mouse proteins such as the proteasome Sirt1,MOTS-c,PGC-1α and AMPK.(2)Effect of MOTS-c on the decrease of exercise capacity caused by hypoxia in mice: The experimental detection data of hypoxic swimming showed that the swimming time of the MOTS-c group,the exercise group and the control group were all increased in the acute hypoxic environment,and the swimming time of the MOTS-c group and the exercise group was significantly different(P<0.05).The detection data of ELISA kit showed that T-AOC,MDA,SOD and gsh-PX in the skeletal muscle of mice in MOTS-c group and exercise group had significant differences(P<0.05)compared with the control group,and MOTS-c had significant differences(P<0.05)compared with the control group in serum in the exercise group,the antioxidant capacity of mice was improved,the degree of oxidative damage was improved,and lactic acid and lactate dehydrogenase in the body were reduced,exercise accumulation was reduced,and exercise capacity was enhanced.The above data revealed that MOTS-c could improve the decline in exercise capacity caused by acute hypoxic environment in Kunming mice.(3)Effect of MOTS-c on MOTS-c in skeletal muscle of mice: The results of Western Blot experiments showed that compared with group C,the level of MOTS-c protein in skeletal muscle of mice in group M was significantly increased(P<0.01).Compared with group C,the levels of MOTS-c protein in skeletal muscle of mice in MH,MM,HE and ME groups were significantly increased(P<0.01).The above results show that both motor and exogenous injection of MOTS-c can increase the expression of endogenous MOTS-c.(4)Effect of MOTS-c on AMPK/PGC-1α pathway in mice: Western Blot experiments showed that there was no significant difference in protein expression of AMPK,SIRT1 and PGC-1 α in skeletal muscle of mice in HE and ME groups compared with C group(P>0.05).Compared with the C group,the protein expression of AMPK in skeletal muscle of mice in M,HM and MM groups was significantly increased(P<0.05),and the protein expression of SIRT1 and PGC-1αwas significantly increased(P<0.01).The above data results showed that the AMPK/PGC-1 α signaling pathway in mouse skeletal muscle could be activated under exogenous MOTS-c intervention conditions,and initially exerted anti-hypoxic effects.Conclusion: MOTS-c improves the exercise capacity of mice through the regulatory system,and at the same time enhances the antioxidant capacity of mice and the expression of AMPK through the AMPK/PGC-1 α pathway,thereby promoting metabolism and improving the antioxidant capacity of mice,which has a preventive effect on the decline of exercise capacity caused by acute hypoxia in mice.