| Research purpose: Skeletal muscle is the largest organ system in the human body,and it is also one of the most vigorous and plastic tissues in the human body.For middle-aged and elderly people,abnormal changes in skeletal muscleare an important cause of disability.The consequences are very serious,directly leading to a happy life for families in the elderly group.Aging is an irreversible process involving multiple organs and multiple factors.In the process of aging,skeletal muscle gradually shrinks and decreases.The influencing factors include changes in cells,hormones,growth factors,etc.,as well as changes in some particularly complex molecular mechanisms,such as apoptosis,autophagy,inflammation,and protein.Changes in intake,etc.,these different influencing factors together lead to the occurrence of skeletal muscle aging.Studies have shown that proper aerobic exercise can increase the body’s autophagy level and fight against many abnormal changes caused by aging.Autophagy is a key catabolic mechanism,which is very important in removing senescent cells in the body and maintaining cell viability.It can be stimulated by various environmentalstresses such as hypoxia,exercise,and oxidative stress.Therefore,autophagy isusually considered Is a survival mechanism.Adenylate-activated protein kinase/target of rapamycin/Unc-51-like kinase 1（AMPK/m TOR/ULK1）signaling pathwayis an important autophagy pathway,which can promote autophagy and combat skeletal muscle aging.This study intends to explore the effect of treadmill exercise stimulation on the AMPK/m TOR/ULK1 signaling pathway in the skeletal muscle of D-galactose-induced aging model rats,so as to provide new scientific basis for exercise to resist skeletal muscle aging and provide new theoreticalsupport for national fitness.Research method:48 male 2-month-old SD rats were randomly divided into 4 groups,each with 12 rats,namely: normal control group（NC）,normal control exercise group（NCE）,aging model group（NE）and aging model exercise group（KE）.After the experiment started,rats in the NE group and KE group were injected with D-galactose[300mg/（kg·d）] every morning for 8 weeks.The NC and NCE groups were injected with normal saline at equal doses.NCE group and KE group practice treadmill every afternoon,every Monday,Tuesday,Wednesday,Friday and Saturday,and rest on Thursday and Sunday for 8 weeks.The specific training program is: 1st to 2nd week,running speed of 10m/min,30 min in total,3rd to 6th week,running speed of 15m/min,45 min in total,7th to 8th week,running speed of 20 m /min,a total of 60 min,in which the treadmill slope is zero.Conduct behavioral experiments immediately after treadmill exercise training to test the behavior and learning and memory abilities of rats.After the behavioral experiment is over,no water and fast food within 24 hours,and thenanesthetize the material.6 rats in each group were directly decapitated and sacrificed.The gastrocnemius muscle was taken out and stored in the refrigerator at-80℃.Western Blot was performed to detect AMPK,m TOR,ULK1,microtubule-as iated protein light chain 3Ⅰ（LC3Ⅰ）,and microtubule-associated protein light chain 3Ⅱ（LC3Ⅱ）Protein content,enzyme-labeled method to detect superoxide dismutase（SOD）and malondialdehyde（MDA）activities.The remaining 6 rats in each group were anesthetized and perfused with paraformaldehyde,the gastrocnemius muscle was taken out,fixed,dehydrated,transparent,and embedded,and HE staining was performed to observe the morphological and structural changes of the gastrocnemius muscle of the rats.Research results: 1)The results of the positioning navigation experiment showed that from the second day,the escape latency of rats in the NE group was increased compared with that in the NC group（P<0.05）,and it increased significantly from the third day to the fifth day（P<0.01）.Compared with the NC group,the escape latency of rats in the KE group increased from the third day（P<0.05）,and significantly increased from the fourth day to the fifth day（P<0.01）.Starting from the third day,the KE group had a shorter escape latency than the NE group（P<0.05）,and it was significantly shorter from the fourth day to the fifth day（P<0.01）.2)The results of space exploration show that the NE group has the shortest stay in the fourth quadrant of the target and the least number of times to traverse the virtual platform.Compared with the NC group,there is a very significant difference（P<0.01）,KE There is no significant difference between the rats in the group and the rats in the NC group;Compared with the NE group,the staying time of the KE group in the fourth quadrant increased significantly（P<0.01）,and the number of crossing the virtual platform also increased significantly（P<0.01）.3)The results of HE staining showed that the skeletal muscle cells of the rats in the NC and NCE groups had a complete and regular structure and arranged neatly.The skeletal muscle cells of the NE group increased in the gap between the skeletal muscle cells,the connective tissue increased,and the morphology and size of muscle cells were different in the KE group.The size of skeletal muscle cells is gradually regular and uniform,the connective tissue between cells is reduced,and the intercellular space is reduced.4)Western Blot experiment results showed that the relative expression of AMPK protein between groups showed that compared with the NC group,the relative expression of rats in the NCE group increased（P<0.05）,and the relative expression of rats in the NE group decreased significantly（P<0.01）.Compared with the NE group,the relative expression of rats in the KE group was significantly increased（P<0.01）;The comparison of m TOR protein expression between groups showed that compared with the NC group,the relative expression of rats in the NE group and the KE group was higher than that in the NC group（P<0.01,P<0.05）.Compared with the NE group,the relative expression of the KE group was Significantly reduced（P<0.01）,there is no significant difference between the NC group and the NCE group;The comparison between ULK1 protein expression groups showed that compared with the NC group,the expression of rats in the NCE group increased（P<0.05）,and the rats in the NE group and the KE group significantly decreased（P<0.01）.Compared with the NE group,KE The expression of rats in the group increased significantly（P<0.01）;Compared with the NC group,the LC3Ⅱ/LC3Ⅰ protein ratio of rats in the NCE group increased（P<0.05）,and the LC3Ⅱ/LC3Ⅰ protein ratio of rats in the NE group was significantly reduced（P<0.01）,compared with the NC group.Compared with group rats,the ratio of LC3Ⅱ/LC3Ⅰ protein in KE group increased significantly（P<0.01）.5)SOD and MDA test results showed that the activity of SOD in the NCE group was the highest,and the activity of MDA was the lowest.Compared with the NC group,the SOD activity of rats in the NE group and the KE group decreased significantly（P<0.01,P<0.05）,and the MDA activity increased significantly（P<0.01,P<0.05）;Compared with the NE group,the SOD activity of the KE group increased significantly（P<0.05）,and the MDA activity decreased significantly,which was statistically significant（P<0.05）.Research conclusions: 1)The 8-week treadmill exercise intervention can improve the learning and memory abilities of aging model rats,and has a certain improvement effect on the delay of aging.2)The 8-week treadmill exercise intervention can significantly increase the SOD content of the skeletal muscle of aging model rats and reduce the MDA activity,thereby reducing the oxidative damage of the skeletal muscle tissue during the aging process.3)The 8-week treadmill exercise intervention can significantly activate the AMPK/m TOR/ULK1 signaling pathway,thereby enhancing the autophagy ability of the skeletal muscle of aging model rats,and alleviating and improving the anti-aging effect of aging model rats. |
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