Exploring the Mechanism of Low Frequency Electroacupuncture on Aging Rats Skeletal Muscle Atrophy by TGF-β/Smad Signaling Pathway
HU Li, WEN Peitong, ZHANGWeibo, GAO Yuan, SHOUYin, WANG Xiaonan2, and XU Ping 1
(1 Acumox&Tuina College of Shanghai University of Traditional Chinese Medicine, Shanghai 201203; 2 Department of Medicine of Emory University, Atlanta, GA 30322)
Abstract: Background: At present,all countries in the world are facing a serious ageing of population. In the course of aging, muscle atrophy, fibrosis and fat deposition are the main causes of the decrease of muscle function, and the degree of muscular atrophy has become an important predictor of mortality rate. In Traditional Chinese Medicine(TCM), skeletal muscle belongs to "the muscle meridian" (Jing Jin).The symptoms of muscle movement and physical activity dysfunction, during the age-related skeletal muscle atrophy, accord with "Wei Syndrome" in TCM.Based on TCM theory of “treatment for flaccidity aiming at Yang Ming meridian” and"the kidney dominating bone ", we hypothesized that combined togetherZusanli and Shenshucould attenuate aging-induced skeletal muscle atrophy .Objective: Based on TGF-β/Smad signaling pathway to explore the mechanism of low frequency electroacupuncture on aging rats skeletal muscle atrophy, to provide the basis for attenuating age-related skeletal muscle atrophy. Methods:The aging rats of 18 months(YA), 20 months (EA) and 22 months(JA) were used in this study. Two acupoints, Shenshu(BL23) and Zusanli(ST36), were selected. The needles were connected into G6805-2 electronic acupuncture instrument using consistent pulse,electric frequency 2Hz,voltage 2 ～ 4V, electric current 1mA～3mA. The stimulation intensity was suitable for rats with slight limb jitter. The treatment was 15 minutes each time on alternate days with one week of rest after three weeks treatment continually. Treatment durations for each group were YA(12 -18 months)，EA(12 -20 months)，JA(12-22 months).Skeletal muscles of gastrocnemius and soleus,SOD and MDA in serum and HE staining for soleus were measured respectively. Protein expressions, including TGF-β/P-smad2/P-smad3/Smad2-3/Myostatin, which related to skeletal muscle fibrosis signaling proteins and MyoD /Myogenin/eMyHC, which related to muscle myogenesis were measured by Western blot. T-test and ANOVA were used for results statistics. Results: (1)Compared with the controlgroup, the weight of the rats for the 18 months, 20 months and 22 months decreased after the acupuncture treatment but the wet weight of the soleus and gastrocnemius increased. (2)The serum expression of SOD decreased significantly and the MDA expression increased significantlyfor different months, while acupuncture treatment could effectively reverse this tendency (P< 0.05). (3)In control groupof different months, there were signs of aging, which showed that the muscle fibers were more loosely arranged, and the fibroid was round, and the nuclei were more central. After the acupuncture treatment, the muscle fibers were more closely aligned, and the circular fibrosis and nucleus centralization decreased. (4) Compared with 18 months(YC) and 20 months of control groups(EC), acupuncture treatment increased the protein expressionsof TGF-β/Smadsignaling pathway(TGF-β, Smad2, p-smad2, Smad3, psmad3, myostatin), while compared with 22 months control group(JA), acupuncture treatmentdecreasedthe protein expression significantly (P< 0.05).Conclusions: We hold that electric acupuncture could attenuate aging-related rat skeletal muscle atrophy by promoting muscle regeneration and/or reducing skeletal muscle fibrosis in the later stage.
Key words: Skeletal muscle atrophy, Age-related, Skeletal muscle satellite cell, TGF-β/Smad