Experimental Research On The Mechanism Of Exercise Intervention To Age-related Muscle Atrophy

Purposes: With human-being entering into an aging society, the increasingoccurrence of aging-related diseases has become a great potential threat to public healthproblems. In aging process, the function decline of skeletal muscle, the most importantmovement organ in human body, is one of the most important signs of aging. Theprevention and intervention in the skeletal muscle aging is an important medical issueand topic at the forefront research, the effect and mechanism research of movementdelay on aging have importantly theoretical and practical significance. Studies havesuggested that strength training has a positive effect on weight control and prevention ofosteoporosis and typeⅡdiabetes, but few application to fitness practice in the elderlypopulation，its role has not been taken seriously and given full play to. The decline inskeletal muscle mass, strength and vitality of the aging process may be related to themuscle regeneration capacity of damaged cells (the defect of protein update andsatellite), oxidative stress level rise, the loss of the motor nerve cell, endocrine disorders,immune system function decline, state of chronic inflammation and apoptosis in skeletalmuscle and other factors, but its mechanism is still lack of comprehensive theory. Thisstudy selects aged rats(18months) as objects to explore the effects of aerobicexercise(swimming) and resistance training(ladder-climbing) on the skeletal musclemorphology of aging rats, IGF-1/IGF-1R signal pathway and mitochondrial medicatedapoptosis signaling pathway in an effort to provide theoretical and experimental basis toclarify the mechanism of aerobic exercise and strength training intervention inage-related muslce atrophy, the clinical prevention and treatment of age-related muslceatrophy.Methods:36male Sprague-Dawley rats(18months old) were randomly dividedinto sedentary control group(C), anti-resistance training group(LC), weight-bearing swimming group(SW1), non-weight-bearing swimming group(SW2),9for each group;swimming rats were trained for five days weekly,30min per day and a total of nineweeks, the weigh-bearing rats loaded1%of body-weight; anti-resistance training groupwere trained3day a week for a total of nine weeks, the initial load was10%of bodyweight of rats and added10%of the body weight of rat weekly. The gastrocnemiuscross-sectional change was observed by light microscopy. Elisa detected IGF-1andIGF-1R of skeletal muscle and western-blot analysis detected cytochrome c ofmitochondria and cytoplasm in skeletal muscle.Results:(1) Compared with C group, the muscle fiber diameter of LC group wassignificantly increased (P<0.01), the gastrocnemus diameter of SW1group andSW2group had no significant change; the muscle fiber diameter of LC groupwas significantly greater than SW1and SW2group (P<0.01, P<0.01).(2) Compared with C group, the IGF-1and IGF-1R expression of LC group increasedand the difference was significant (P<0.01), the IGF-1and IGF-1R expression ofSW2group lowered with significant difference (P<0.01), the IGF-1expression ofSW1had no shift without significant difference (P>0.05), the IGF-1R expression ofSW1group was down-regulated with significant difference (P<0.01); The IGF-1and IGF-1R expression of LC group were significantly higher than SW1group andSW2group (P<0.01,P<0.01)(3) Compared with C group, the cytochrome c content of LC group gastrocnemiusincreased with significant difference (P<0.01) in mitochondria and reduced withsignificant difference (P<0.01) in cytoplasm, the cytochrome c content of SW1group had no significant shift (P>0.05) in mitochondria, the cytochrome c content ofSW2group increased significantly(P<0.05) in mitochondria, the cytochrome ccontent of SW1and SW2group in cytoplasm had a downward trend, but nosignificant difference (P>0.05) tested by statistics; the cytochrome c content of SW1and SW2group in mitochondria was significantly lower than LC group(P<0.01,P<0.01); the cytochrome c content of SW1in cytoplasm was significanthigher than LC group, but there is no significant difference of the content in cytoplasm between SW2group and SW2group.Conclusions:(1) Anti-resistance training is better than aerobic exercise in the aspects of increasingthe cross-section area of aging rat gastrocnemius muscle and inducing musclehypertrophy, suggesting that anti-resistance training is an effective means ofintervention in age-related muslce atrophy, has an important significance ofpreventing and delaying the occurrence of the age-realted muscle atrophy andshould be actively promoted in the elderly movement.(2) Anti-resistance training can significantly improve the level of IGF-1and IGF-1R,which may be the mechanism of the anti-resistance training to prevent age-relatedmuscle atrophy.(3) Anti-resistance training is more effective in inhabiting the release of mitochondrialcytochrome c into the cytoplasm and reducing the degree of the aging ratgastrocnemius in some extent，which may be the mechanism of anti-resistancetraining being better than aerobic exercise in the prevention of age-related muslceatrophy.