| Object:Female menopause can lead to the gradual decline of 17β-estradiol(E2)level,resulting in obesity,loss of skeletal muscle mass,and decreased mitochondrial activity.Currently,studies have found that exercise and estrogen replacement therapy play a positive role in skeletal muscle mass and aerobic capacity.In recent years,vibration training has become the choice of more people as a passive exercise mode,but its effects on skeletal muscle mass and skeletal muscle mitochondria need to be further discussed.Meanwhile,whether vibration training combined with estradiol replacement therapy can further improve health problems under low estrogen level still needs to be verified.This study aimed to investigate the effects and related mechanisms of ovariectomy,vibration training,and estradiol replacement therapy on gastrocnemius muscle mass and mitochondrial respiratory function in mice and provide suggestions for the intervention of metabolic changes in menopausal women with low estrogen levels.Methods:(1)In vivo study: forty C57BL/6J female mice(8 weeks of age)were randomly divided into 5 groups: sham operation control group(S group,8 mice),ovariectomy group(O group,8 mice),estradiol group(E group,8 mice),vibration training group(W group,8 mice),vibration training + estradiol group(WE group,8 mice).Before the experiment,sham operation and ovariectomy were performed in group S and the other four groups,respectively,and 17β-estradiol sustained-release tablets(0.36 mg,70day)were embedded in the subcutaneous neck of mice in group E and Group WE.Mice in groups W and WE were subjected to low-intensity vibration training for 8 weeks,5 days a week(30HZ,3mm,30min).During the intervention,the bodyweight of the mice was measured weekly,and the body composition and grasping force of the mice were measured every two weeks.24 h after the last training,the mice were anesthetized for blood collection,and then the mice were sacrificed for bilateral gastrocnemius tissue collection.Serum estradiol level was detected by ELISA.The mitochondrial ATP level of the gastrocnemius muscle was detected by a multifunctional microplate analyzer.The mitochondrial respiratory function and oxidative phosphorylation level of mouse gastrocnemius were measured by a high-resolution respiratory function assay(Oxygraph-2K).Western blotting was used to detect the protein expressions of PGC1-α,TFAM,mitochondrial respiratory chain complex I(NDUFB8),complex II(SDHB),complex III(UQCRC2),complex IV(MTCO1),and complex V(ATP5A)in gastrocnemius mitochondria.(2)In vitro study: Mouse C2C12 myoblasts were divided into control group(group C),estradiol intervention group(group E),and aromatase inhibitor group(group A).Mitochondrial membrane potential was detected by the JC-1 fluorescence probe.Results:(1)In vivo study:(1)The results of body composition and muscle strength showed that the body weight and fat mass of ovariectomized mice were significantly higher than those of sham operation mice(P <0.01),and the muscle ratio was significantly decreased(P <0.05).After the intervention,the body weight and fat mass of mice in the E,W,and WE groups were significantly decreased compared with that in the O group(P <0.05),while the muscle ratio and grasping power were significantly increased(P <0.01,P<0.05).(2)The results of serum estradiol showed that compared with the O group,the estradiol levels in E and WE groups were significantly increased,and the difference was statistically significant(P <0.05).(3)The level of mitochondrial ATP in the skeletal muscle of mice was significantly decreased after ovariectomized compared with the control group(P <0.01).Compared with the O group,mitochondrial ATP content in the E and WE groups was increased,and there was a significant difference(P <0.01).(4)Compared with group S,COXI respiration rate and RCR value in group O were significantly decreased(P <0.01,P <0.05).Compared with group O,COXI,COXIV,COXI respiration rate of group E,COXI respiration rate of group W and COXII of group WE were significantly increased(P <0.01),and RCR values of group W,group E,and group WE were all higher with significant differences(P <0.05).Compared with estradiol alone or vibration training,the respiration rate of COXII in the WE group was higher than that in the W group(P <0.05).(5)The mitochondrial protein expression in skeletal muscle of mice showed that the COXIV protein expression in groups E,W,and WE increased and showed significant differences(P <0.01,P <0.05,P <0.01),and the COXI protein expression in group WE was significantly higher than that in group O(P <0.05).The protein level of PGC1-α in group W was significantly increased(P <0.0)(2)In vitro study:(1)ATP level detection results showed that after estradiol and aromatase inhibitor intervention,THE ATP level in group E was higher than that in the control group,with a significant difference(P <0.05),and the mitochondrial ATP level in group S was lower than that in the control group,but no significant difference was found(P >0.05).(2)Mitochondrial membrane potential test showed that there was no significant difference between the estradiol supplementation group and the control group(P >0.05),and the ratio of red-green fluorescence in group A was lower than that in group C,but there was no significant difference(P >0.05).Conclusion:(1)Decreased estrogen level after ovariectomy leads to decreased lean body weight ratio,weakened muscle strength,and decreased mitochondrial respiratory function.(2)Vibration training and estradiol supplementation can enhance muscle strength,improve mitochondrial respiratory function and affect mitochondrial biogenesis,possibly by regulating PGC1α signaling protein.(3)The intervention of 17β estradiol increased intracellular ATP production,which had a positive effect on mitochondrial respiratory function.The direct intervention of17β estradiol may have no significant effect on mitochondrial membrane potential. |
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