Abstract:
BACKGROUND: Acute exercise tends to cause skeletal muscle tissue damage and lipid metabolism disorders in vivo, but the mechanism by which acute exercise combined with electroacupuncture modulates metabolic and autophagic pathways in vivo is unclear.
OBJECTIVE: To observe the changes in metabolic enzymes and autophagy levels in skeletal muscle of rats subjected to acute exercise by electroacupuncture at the acupoints of “Zusanli” and “Huantiao.”
METHODS: Fifty male Sprague-Dawley rats were randomly divided into three groups: quiet control group (n=10), model group (n=20), and reverse electroacupuncture group (n=20). The latter two groups were set up with two time points, i.e. immediate and 3 hours after exercise groups (n=10 per time point). The model group and the reverse electroacupuncture group underwent acute exercise training after adaptive treadmill training. The rats in the reverse electroacupuncture group underwent electroacupuncture treatment (parameters: electroacupuncture on both sides of the rats at the acupoints of “Zusanli” and “Huantiao,” continuous wave, frequency of 2 Hz, intensity of 2 mA, leaving the needle in the body for 30 minutes, once a day for 7 consecutive days) before treadmill training. Bilateral gastrocnemius muscle tissues were taken under anesthesia immediately after exercise and 3 hours after exercise, and hematoxylin-eosin staining was used to observe the histopathological changes of rat skeletal muscle. ELISA kit was used to detect the activities of hepatic lipase, fatty acid synthase, hormone-sensitive lipase, and carnitine palmitoyltransferase 1 in rat skeletal muscle tissues. Immunohistochemistry and western blot were used to detect the changes in the expression of autophagy genes.
RESULTS AND CONCLUSION: After hematoxylin-eosin staining, the arrangement of gastrocnemius muscle fibers in the model group was disturbed, swollen and ruptured immediately after exercise and 3 hours after exercise. In the reverse electroacupuncture group, gastrocnemius muscle fibers were tightly arranged and the number of swollen and ruptured cells was greatly reduced immediately after exercise and 3 hours after exercise, and there was no significant difference when compared with the quiet control group. Compared with the quiet control group, the activities of hepatic lipase and fatty acid synthase were lower while the activities of lipoprotein lipase, hormone-sensitive lipase, and carnitine palmitoyltransferase 1 were higher in the model group and the reverse electroacupuncture group 3 hours after exercise (P < 0.05 or P < 0.01). Compared with the model group, the activities of lipoprotein lipase and carnitine palmitoyltransferase 1 were higher in the reverse electroacupuncture group immediately after exercise (P < 0.05), while the activity of lipoprotein lipase was higher and the activity of hormone-sensitive lipase was lower in the reverse electroacupuncture group 3 hours after exercise (P < 0.01). Immunohistochemical results showed that compared with the quiet control group, the expression of P62, autophagy-related gene 5 and autophagy-related gene 7 was higher in the model group immediately and 3 hours after exercise, as well as in the reverse electroacupuncture group immediately after exercise (P < 0.05 or P < 0.01); compared with the model group, the expression of P62 and autophagy-related gene 7 was lower in the reverse electroacupuncture group immediately and 3 hours after exercise (P < 0.05). Western blot results showed that the protein expression of P62 and autophagy-related gene 7 in the reverse electroacupuncture group was lower than that in the model group immediately after exercise (P < 0.05); the protein expression of Parkin in the model group was higher than that in the quiet control group immediately and 3 hours after exercise (P < 0.05); and the protein expression of Parkin in the reverse electroacupuncture group was lower than that in the model group immediately and 3 hours after exercise (P < 0.05). To conclude, acute exercise induces disorders, swelling and rupture of gastrocnemius muscle fibers in rats and electroacupuncture on both sides of the acupoints of “Zusanli” and “Huantiao” can improve the level of lipid metabolism and regulate autophagy cells in rat skeletal muscle, preventing the disorders of lipid metabolism and damage of gastrocnemius muscle tissues caused by acute exercise. The mechanism may be closely related to the regulation of autophagy-related factor P62, autophagy-related gene 5, autophagy-related gene 7, and Parkin protein expression to promote the occurrence of autophagy or regulate the autophagy pathway in rat skeletal muscle cells. 

Key words: electroacupuncture, acute exercise, gastrocnemius muscle, tissue metabolic enzyme, autophagy gene