The influence of aerobic exercise on the structure, function and expression of energy metabolism-related molecules in skeletal muscle of aged rats

Abstract

Objective To examine the effects of aerobic exercise on muscle morphology, oxidation resistance, energy metabolism, mitochondrial biogenesis-related signal transduction pathway molecules, and energy metabolism-related enzyme proteins expression in aged rats and to explore the molecular mechanisms of skeletal muscle aging and aerobic exercise intervention. Methods Male Sprague Dawley rats were divided into a normal group, a model group, and an exercise group, with the latter two groups receiving a subcutaneous injection of 10% D-galactose(0.1 mg·g-1·d-1)for 10 weeks.Then aerobic and anaerobic exercise capacity of each group were tested by treadmill; the cross-sectional area of rats' gastrocnemius was examined via light microscopy; levels of serum superoxide dismutase(SOD)activity and malondialdehyde(MDA)were determined by spectrophotometry; serum β-Galase levels were tested by enzyme-linked immunosorbent assay(ELISA); levels of adenosine triphosphate(ATP), adenosine diphosphate(ADP)and adenosine monophosphate(AMP)in gastrocnemius tissue were measured by high performance liquid chromatography(HPLC)-ultraviolet detection; expression levels of mitochondrial biosynthesis-related signal transduction molecules(such as p38MAPK, CaMKⅡ, PGC-1α, MEF2C, COXⅣ and ATPase)were tested by real-time RT-PCR. Results Compared with the normal group, the model group's cross-sectional area of muscle fibers, serum SOD activity, ATP content, and EC values all markedly decreased, while serum MDA, β-Galase, AMP content in skeletal muscle significantly increased(all P<0.05). Levels of mRNA expression of CaMKⅡ, MEF2C, ATPaseβ, COXIV, and PCG-1 alpha in model rats notably decreased(all P<0.05), whereas mRNA expression levels of P38MAPK significantly increased(P<0.05). Compared with the model group, aerobic exercise increased the cross-sectional area of muscle fibers(P<0.01)and serum SOD activity(P<0.05), reduced serum MDA content(P<0.01), clearly increased CaMKⅡ and ATPaseβ mRNA expression(both P<0.01), and reduced the expression of P38MAPK mRNA(P<0.01). Conclusions Aerobic exercise can improve the activity of SOD, reduce the accumulation of oxygen free radicals, resist oxidation damage, correct the abnormal activity of P38MAPK, and promote the expression of mitochondrial biosynthesis-related signal molecules, such as CaMKⅡ, PCG-1 alpha, and MEF2C, thus boosting the expression and activity of energy metabolism enzyme protein COX Ⅳ, ATPase, promoting energy metabolism, improving the production of ATP, and slowing down the ageing process of the body and skeletal muscle. Key words: Aerobic exercise; Aging; Skeletal muscle; Antioxidant capacity; Energy metabolism; Mitochondrial biogenesis