Effects Of Exercise On Micrornas And Sarcopenia-associated Genes Expression In Skeletal Muscle Of Natural Aging Mouse

Sarcopenia is a kind of age-degenerative syndrome that characterized by a progressive loss of skeletal muscle mass and strength, loss of muscular endurance and metabolic ability.lt have a negative impact on daily lives of the elderly, but also increase the risk of falls which led to the occurrence of fractures, and be a burden to individuals, families and society. Despite the serious consequences for sarcopenia to elderly individuals, families, social, but the mechanism is not very clear. Although many scholars from different angles to illustrate the mechanism, no one from the microRNA angle especially muscle specific microRNA to explore the pathogenesis of sarcopenia, and mechanism of exercise intervention sarcopenia.Objective:this experiment is designed to determine the alterations of muscle specific microRNA and sarcopenia-associated genes expression in natural aging mice with real-time fluorescence quantitative polymerase chain reaction (PCR), and to observe the effect of a life-long endurance and resistance exercise on the muscle specific microRNA and sarcopenia-associated genes. In the end, through microRNA angle especially muscle specific microRNA to explore the pathogenesis of sarcopenia, and mechanism of exercise intervention sarcopenia.Methods:54C57BL/6mice were randomly divided into youth control group (YC), old age control group (OC), lifelong aerobic group (LE), lifelong resistance group (LR), old age aerobic group (OE), old age resistance group (OR) six groups. The age of YC group mice are3months and other groups are raised naturally to20months. LE group and the LR group were engaged in a treadmill and ladder-climbing training for17months respectively, OE group and OR group engaged in a treadmill and ladder-climbing training only for2months respectively. The exercise performed once a day and three days a week. After that RT-PCR was used to detect muscle specific microRNA and sarcopenia-associated genes expression.Results:using real-time fluorescence quantitative polymerase chain reaction (RT-PCR) to determine sarcopenia-associated genes IGF-1and PGC-1alpha, MAFbx, Myostatin and muscle specific microRNA expression.1) Naturally grow to20months C57BL/6mice have appeared sarcopenia phenomenon.2) Compared with YC group, IGF-1mRNA express was significantly reduced in OC group, and was significantly difference; LR group IGF-1mRNA express significantly increased, and significantly difference; old age exercise group (OE, OR group) skeletal muscle of IGF-1mRNA expression increases, and significantly difference.3) Compared with YC group, OC group PGC-1a mRNA expression was reduced, but not significant difference; compared with OC group, each group PGC-1a mRNA expression increases, but not significant differences.4) Compared with YC group, OC MAFbx mRNA expression was increased, but not significant difference; compared with OC group, LE group MAFbx mRNA expression is reduced, but not have significant difference; LR group MAFbx mRNA express rise and has significant difference; OE group MAFbx mRNA increased expression, and has significant difference; OR group of MAFbx mRNA expression and has increased significantly difference.5) Compared with YC group, OC group Myostatin mRNA expression to have some degree of increased, but not significant difference; compared with OC group, LE group Myostatin mRNA express rise but not significant differences; LR group Myostatin mRNA expression elevated also has significant difference; OE, OR group of Myostatin mRNA rise but not significant difference.6) Compared with YC group, OC, LR group microRNA-1expression is reduced, but not significant difference; Compared with OC group, LR group microRNA-1expression is reduced, but do not have significant difference; LE, OE, OR group of microRNA-1expression increases, but not significant differences.7) Compared with YC group, OC group of microRNA-133-a in lower expression, but not significant difference; compared with OC group, LE, LR group of microRNA-133a expression increases, but not significant difference; OE, OR group of microRNA-133in a lower expression, but also not significant differences.8)Compared with OC group, LE group microRNA-133b expression to have certain rise, but do not have significant difference; LR group of microRNA-133b expression was reduced, but also not significant difference; OE and OR group microRNA-133b expression increased, but also not significant differences.9) Compared with YC group, OC group microRNA-206expression increases, but not significant difference; compared with OC group, LE, LR group microRNA-206express is reduced, but not significant difference; OE, OR group microRNA-206express were reduced, but also not significant differences.Conclusion:1) Naturally grow to20months C57BL/6mice can be used as Sarcopenia ideal research animal model.2) Naturally grow to20months C57BL/6mice IGF-1and PGC-1a mRNA expression is reduced, and MAFbx and Myostatin mRNA expression is increased, this may be one reason of elder happen sarcopenia.3) Lifelong aerobic exercise group (LE group) can control mice weight until middle age, although their weight between old age aerobic exercise group (OE group) was no difference, their wet weight of skeletal muscle is difference. LE group IGF-1and PGC-1a mRNA expression have some degree increases, and at the same time MAFbx and Myostatin mRNA expression is rising. Despite that lifelong aerobic exercise can control mice weight to a certain extent, increase the quality of skeletal muscle, but from the mRNA expression level, LE mice also in slowly into the Sarcopenia state.4) Lifelong resistance exercise group (LR) make the mice weight has remained at a low levle, explain resistance exercise has an important role in maintain weight. LR group GF-1mRNA expression significantly increased, and have significantly difference, explain that resistance exercise has a key role in suspending skeletal muscle atrophy. At the same time, LR group MAFbx and Myostatin mRNA expression of the rise and has significant difference. The old Sarcopenia that the occurrence of skeletal muscle protein is the degradation of between the results of the synthesis and wrestling. The occurrence of Sarcopenia is a result of wrestling between skeletal muscle protein degradation and synthesis.5) Old age exercise group (OE, OR group) weight appeared a certain degree reduction in old age, but not as good as life-long exercise group (LE, LR group). Old age exercise group (OE, OR group) IGF-1, PGC-1a mRNA expression increase, also has significantly difference.It is said that the old age began to exercise the similar benefits. OE, OR group of MAFbx mRNA express increase and has significant difference, Myostatin mRNA increase but not significant difference, this may be older mice when they began to exercise has been in sarcopenia state,2months exercise can’t reduce these gene expression.6) Muscle specific microRNA plays an important role in skeletal muscle growth process and adjusts a lot of gene expression. miR-1and miR-133expression rreduction may promote muscle hypertrophy, and with the IGF-1and PGC-1a mRNA expression increase. The microRNA may play an important role in delay sarcopenia happened mechanism.