The Respective Potential of Endurance Training, Resistance Exercise and Mixing Type Training on the Satellite Cell Activation Signaling Pathway in Adult C57BL/6 Mouse Skeletal Muscle
|School||East China Normal University|
|Course||Human Movement Science|
|Keywords||satellite cell Endurance training Resistance training Mixing type training Sarcopenia Neuronal nitric oxide synthase(nNOS) Matrix metalloproteinase-2 (MMP2) Hepatocyte growth factor(HGF) c-met|
Satellite cells, resident mygenic stem cells found between the basement membrane and the sarcolemma, are normally quiscent in adult muscles. But when muscle is injured, exercised, or mechanically stretched, these cells are activated to enter the cell cycle, proliferation, differentiate, and fuse with the adjacent muscle fiber.In this way, satellite cells are responsible for regeneration and exercise-induced hypertrophy of muscle fibers. Sarcopenia is defined as the gradual decline in skeletal muscle mass and strength with aging. On a myocellular level, sarcopenia is characterized by a reduction in the number of muscle fibers and specific TypeⅡmuscle fiber atrophy. Recently, study has shown that TypeⅡmuscle fiber atrophy in older adults is associated with a specific decline in TypeⅡmuscle fiber satellite cell content. As such, an age-related decline in satellite cell number and/or function could have an important role in the etiology of sarcopenia. Recent studies show that the increase in muscle mass and myonuclear content in response to exercise is accompanied by an increase in satellite cell number and satellite cell number activation status.The first step in the process of fusing to form new myofibers or allowing extensive hypertorphy of existing muscle fibers is the activation of satellite cells. Recent studies demonstrated the essential role of hepatocyte growth factor (HGF)and nitric oxide(NO) radical in the activation pathway. These experiments also showed that mechanically streching cultured satellite cells or living skeletal muscles stimulates satellite cell activation. This is achieved by rapid release of HGF form its tethering in the extracellular matrix and its presentation to c-met receptor. HGF release has been shown to depend on ON radical production by nitric oxide synthase(NOS) in satellite cells and/or muscle fibers, and relies on the subsequent upregulation of matrix metalloproteinase(MMP) actibity.To distinguish the respective potential of different type exercise training to activate satellite cells, exercise prograns of endurance training(treadimill running exercise), resistance exercise(ladder climbing) and mixing type training(combined treadimill running and ladder climbing) were found in the study. The aim of this study was to investigate the effects of different type exercise training on genes expression of the activation pathway(NO-MMP2-HGF-cmet) in adult C57BL/6 mice and assess the impact of different type exercise training on satellite activation.Methods:32 three-month-old male C57BL/6 mices were randomly distributed into four groups:sedentary(C, n=8), endurance training(E, n=8), resistance exercise(R, n=8), mixing type training(M,n=8). After 28 weeks exercise intervening, quantitative Real-time PCR method is used to detect nNOS,MMP2,HGF,c-met mRNA expression in Tibialis anterior muscles.Results:(1) Endurance training significantly increased nNOS, HGF, c-met mRNA transcription except MMP2 mRNA.(2) Resistance training significantly increased nNOS, MMP2, HGF, c-met mRNA transcription.(3) Mixing type training significantly increased HGF mRNA transcription, but had no apparent effect on nNOS, MMP-2, HGF, c-met mRNA transcription.Conclusion:(1)When C57BL/6 mice body weight increased stabilized, the body weight of the three exercise training groups were significantly less than the controls, indicating that exercise training can control body weight gain.(2) Compared with the controls, tibialis anterior and the weight ratio increases in three types of exercise training. It may because endurance training reduced body fat, resistance training induced tibialis anterior hypertrophy adaptation and mixing type training induced tibialis anterior hypertrophy adaptation and reduced body fat.(3)Compared with the controls, resistance training upregulated each of the activation pathway (NO-MMP2-HGF-cmet) gene transcription in adult C57BL/6 mice Tibialis anterior muscles. We speculated that resistance exercise would play an important role in satellite cell activation, which may be important in maintaining the number of satellite cell pool and promoting extensive skeletal muscle hypertrophy.(4) Compared with the controls endurance training upregulated each of the activation pathway (NO-HGF-cmet) gene transcription except MMP2 in adult C57BL/6 mice Tibialis anterior muscles. We speculated that endurance exercise could also promote the activation of satellite cells and would also have its merits in the prevention the number of satellite cells reduction and maintenance skeletal muscle mass and strength.(5)Compared with the controls, the transcription of nNOS, MMP2, HGF mRNA in Tibialis anterior muscle had no significantly increased afte mixing type training except HGF-met mRNA. In our study, the mixed type training could not play an composite effect of endurance and resistance exercise in the activation process of satellite cell. It suggested that we should consider the intensity, time and frequency when we arrange endurance and resistance exercise to sustain the number of skeletal muscle satellite cells and promote muscle hypertrophy.