| Background:The aging of human body is a natural phenomenon.How to delay aging is a problem concerned by the academia and the public.Skeletal muscle attenuation caused by aging is mainly manifested in the decline of muscle mass,strength and physical activity ability,which seriously affects the quality of life of individuals.Skeletal muscle remodeling relies on skeletal muscle satellite cells(also known as skeletal muscle stem cells)to activate,proliferate,differentiate,and fuse.The activation of satellite cells is related to their microenvironment.With aging,changes in the microenvironment of the satellite cells will adversely affect the activation of the satellite cells and hinder the remodeling of skeletal muscle.It was pointed out that exercise training can activate muscle satellite cells to promote muscle hypertrophy and increase muscle strength.In the state of aging,whether exercise can affect the capillarity of skeletal muscle and improve the microenvironment for the survival of muscle satellite cells,and the activation of satellite cells to promote skeletal muscle remodeling still needs further discussion.Objectives:The purpose of this study was to investigate the intrinsic relationship between aerobic exercise and resistance exercise on skeletal muscle capillarity and satellite cell activation in senescent mice,and to provide a theoretical basis for exercise to improve skeletal muscle attenuation.Methods:In this study,21 BALB/C male mice aged 4 weeks were selected and randomly divided into 3 groups after 9 mouths of feeding under standard conditions.The control group was quiet(group C: n=7),eating and drinking normally,and not participating in sports training.In the aerobic exercise group(group A: n=7),the treadmill training was conducted for 9 weeks,3 times of a week,with the treadmill speed of 0.8km/h and the exercise time of 40min/ time.Resistance exercise group(R group: n=7)carried out tail weight climbing training for 9 weeks,3 times of a week,5groups for each training,each group trained 3 times,2 times,1 time,2 times,3 times of "Pyramid" training mode,in which the interval between groups was 2min,1min interval between times.Body weight and grip strength were measured at a fixed time each week throughout the exercise.Twelve hours after the end of the last training,the weight of the mice and grip strength of their limbs were measured,and the mice were immediately sacrificed by cervical dislocation,followed by quadriceps femoris SCle sampling.The m RNA expression levels of CD31,VEGF,HIF-1α,ERR-α,Pax7,MMP2 and MMP9 in mouse quadriceps femoris were detected by Real-Time PCR.Western blotting technique was used to detect the protein expression levels of CD31,VEGF,PGC-1α,HIF-1α,ERR-α,Pax7,MMP2 and MMP9 in mouse quadriceps femoris.The localization and expression of VEGF and CD31 in mouse quadriceps femoris were detected by immunofluorescence assay.Results:(1)Changes in body weight and quadriceps wet weight/body weight: after 9 weeks of training,the body weight of mice in the exercise training group was higher than that in the quiet control group(group R > group A > group C),and at week 7,the body weight of the R group was significantly higher than that of the C group(P<0.05).At week 8,there was an extremely significant difference(P<0.01),and there was no difference in body weight among the other groups.Consistent with the changes in body weight,the wet weight/body weight of the quadriceps femoris in group R was significantly higher than that in group C(P<0.05),and there was no significant difference between other groups.(2)Changes in the relative grip strength of the four limbs of mice: in this study,the relative grip strength of the four limbs of mice in each group increased with the increase of the number of weeks,in group R,> group A,> group C,and starting from week 8,the relative grip strength of group R was significantly higher than that of group C(P<0.05).(3)Changes of VEGF and capillary-related factors: 1)m RNA level changes: m RNA expression levels of HIF-1α and ERR-α in the quadriceps femoris of the R group were significantly higher than those of the C group(P<0.05),and m RNA expression levels of VEGF in the quadriceps femoris of the R group were significantly higher than those of the C group(P<0.01).The m RNA level of VEGF in the quadriceps femoral of group A was significantly higher than that of group C(P<0.05),and the m RNA level of CD31 was also significantly higher than that of group C(P<0.01).2)Protein level changes: no significant difference was found in the protein expression levels of PGC-1α and ERR-α in the quadriceps femoris of group A and group R,while the protein expression levels of HIF-1α and VEGF were significantly higher than those of group C(P<0.05).The protein expression level of VEGF in group A was significantly higher than that in group C(P<0.05),and the protein expression level of CD31 was extremely significantly higher than that in group C(P<0.01).There was no significant difference in each index between group R and group A.(4)Changes in extracellular matrix MMPs: compared with group C,the expression levels of MMP2 m RNA and protein in the quadriceps femoris of group A and group R were significantly increased(P<0.05).The expression level of MMP9 m RNA in the quadriceps femoris of group A had no significant change compared with that of group C,but its protein expression level was significantly higher than that of group C(P<0.05).Compared with group C,the expression level of MMP9 m RNA in the quadriceps femoris of group R was significantly increased(P<0.05),but there was no significant change in the protein expression level.(5)Changes of Pax7 in satellite cells: compared with group C,the m RNA expression level of Pax7 in the quadriceps femoris of group R showed A significant increase(P<0.01),while the m RNA expression level of Pax7 in the quadriceps femoris of group A showed no significant difference.Compared with group C,the protein expression level of Pax7 in the quadriceps femoris of group R showed an extremely significant increase(P<0.01),while the m RNA expression level of Pax7 in the quadriceps femoris of group A showed no significant difference.Compared with group A,the protein expression level of Pax7 in the quadriceps femoris of group R was significantly increased(P<0.01).Conclusions:(1)The effect of resistance exercise on skeletal muscle mass,muscle strength and satellite cell proliferation was better than that of aerobic exercise.(2)Both resistance exercise and aerobic exercise have positive effects on skeletal muscle capillary-related factors and extracellular matrix,but the effect of aerobic exercise is superior to that of resistance exercise.(3)In resistance exercise,capillary density has a positive effect on the proliferation of skeletal muscle satellite cells,but not a dominant effect.Its mechanism needs further discussion. |
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