关键词: 温针灸, 慢性疲劳综合征, 骨骼肌, PINK1/Parkin通路, 线粒体自噬 

Abstract: BACKGROUND: It has been found that mitochondrial function is abnormal in patients with chronic fatigue syndrome, and the administration of coenzymes can improve the symptoms. Warm acupuncture is one of the most important treatments for this disease, but its mechanism of action is unclear.
OBJECTIVE: To investigate the effects of warm acupuncture on the phosphatase and tensin inducible kinase 1 (PINK1)/Parkin pathway in the skeletal muscle of rats with chronic fatigue syndrome. 
METHODS: After 3 days of adaptive feeding, 32 male Sprague-Dawley rats were randomly divided into normal control, model, warm acupuncture, and coenzyme Q groups with 8 rats in each group. The chronic fatigue syndrome model was established by multiple factors, including swimming exhaustion, chronic immobilization and fasting. After successful modeling, the normal group and the model group were treated with the same fixation and gavage procedures, and the warm acupuncture group was treated with acupuncture at Guanyuan, Zhongwan and Zusanli (bilateral) points, once a day. After the needling was inserted, the moxa pillar was put on the needle handle and ignited, three sessions once. The coenzyme Q group was given 1 mL/kg coenzyme by gavage, once a day for 14 days. The body mass, exhaustive swimming time and food utilization rate during the treatment were recorded. After the treatment, the bilateral gastrocnemius muscles of rats in each group were collected. The pathological morphology of the gastrocnemius muscle was observed by hematoxylin-eosin staining, the mitochondrial morphology and autophagosome of the gastrocnemius muscle were observed by transmission electron microscope. The expression level of microtubule-associated protein light chain 3 (LC3) II protein in the skeletal muscle was detected by immunohistochemistry. Western blot was used to detect the expression of PINK1, Parkin, LC3 I, and LC3 II in the skeletal muscle. 
RESULTS AND CONCLUSION: Compared with the normal group, the gastrocnemius muscle nuclei of the model group were pyknotic, condensed, the number of cells was increased, the cells were arranged disorderly, and the fibers in the gastrocnemius muscle were tightly arranged in the model group. Compared with the model group, the intercellular space became smaller, the nuclei were reduced, and the cell arrangement was orderly in the warm acupuncture group and coenzyme Q group. Compared with the normal group, the skeletal muscle mitochondria in the model group were swollen, fused, and vacuolated seriously, the membrane was partially broken, the matrix was more dissolved, the cristae was broken and disappeared, and autophagy appeared. Compared with the model group, the number of mitochondria increased, the arrangement was relatively neat, mitochondrial vacuolization and rupture of cristae in the gastrocnemius muscle were improved, the membrane structure was relatively intact, and autophagy occurred. Compared with the normal group, the expression of PINK1 protein in the skeletal muscle of the model group was significantly increased (P < 0.05), while the expression of Parkin, LC3 II and LC3 II/I protein was slightly upregulated (P > 0.05). Compared with the model group, the protein expressions of PINK1, Parkin, LC3 II and LC3 II/I were significantly upregulated in the warm acupuncture and coenzyme Q groups (P < 0.05), and the up-regulation was more significant in the warm acupuncture group. To conclude, warm acupuncture can play a role in the treatment of chronic fatigue syndrome by activating the PINK1/Parkin pathway, upregulating LC3 II expression, forming mitochondrial autophagosomes, promoting the degradation of damaged mitochondria, and improving mitochondrial quality.     

Key words: warm acupuncture, chronic fatigue syndrome, skeletal muscle, PINK1/Parkin pathway, mitochondrial autophagy