RESUMO
OBJECTIVE: To investigate the mechanism of electroacupuncture ï¼EAï¼ in promoting the browning of white adipose tissue in middle-aged and aged obese rats induced by high fat by regulating AMP-activated protein kinase ï¼AMPKï¼ /silence-information regulatory factor 1 ï¼Sirt1ï¼ pathway and neuregulin 4 ï¼Nrg4ï¼. METHODS: Twenty-four male SD rats were randomized into blank control, model and EA groups ï¼n=8 per groupï¼. The obesity model was established by feeding the rats with high-fat diet for 6 weeks. For the EA group, EA ï¼2 Hz/15 Hz, 1.5 mAï¼ was applied to "Guanyuan" ï¼CV4ï¼ and bilateral "Shenshu" ï¼BL23ï¼, "Fenglong" ï¼ST40ï¼ and "Tianshu" ï¼ST25ï¼ for 20 min, once a day, 5 days a week for 6 weeks. Rats of the blank control and model groups were also restrained for 20 min. The body mass and food intake were measured every week, and the Lee's index, epididymal fat, perirenal fat and brown adipose tissue were weighed. The contents of serum total cholesterol ï¼TCï¼, triglyceride ï¼TGï¼, high density lipoprotein cholesterol ï¼HDL-Cï¼, low density lipoprotein cholesterol ï¼LDL-Cï¼ and norepinephrine ï¼NEï¼ were determined by ELISA. H.E. staining was used to observe the morphological changes of white and brown adipose tissue. The mRNA expression levels of mitochondrial uncoupling protein 1 ï¼UCP1ï¼, peroxisome proliferator activated receptor γ co-activator 1α ï¼PGC-1αï¼, PR-domain protein 16 ï¼PRDM16ï¼, peroxisome proliferator activated receptor γ ï¼PPARÎ³ï¼ and Nrg4 in the adipose tissue were detected by quantitative real time PCR, and the protein expression levels of Nrg4, AMPKα, Sirt1 and interleukin-6 ï¼IL-6ï¼ in the white and brown adipose tissue were detected by Western blot. RESULTS: Compared with the blank control group, the body mass, food intake, the Lee's index, epididymal fat and perirenal fat mass, and serum TG, TC and LDL-C contents and the expression level of IL-6 protein were significantly increased ï¼P<0.01, P<0.05, P<0.001ï¼, and the brown adipose mass, serum HDL-C and NE contents, the expression levels of UCP1, PGC-1α, PRDM16, PPARγ and Nrg4 mRNAs, and the protein expression levels of AMPKα, Sirt1 and Nrg4 proteins in both white and brown adipose tissues were significantly decreased in the model group ï¼P<0.01, P<0.05ï¼. After EA intervention, the increased levels of body mass, food intake, Lee's index, epididymal fat and perirenal fat mass, serum TG, TC and LDL-C contents, and the expression of IL-6 protein, and the decreased levels of brown adipose mass, serum HDL-C and NE contents, expression levels of UCP1, PGC-1α, PRDM16, PPARγ and Nrg4 mRNAs, and those of AMPKα, Sirt1 and Nrg4 proteins in both white and brown adipose tissues were apparently reversedï¼P<0.05, P<0.01, P<0.001ï¼. H.E. staining showed an increase of the volume and content of intracellular vacuoles of both white and brown adipose tissues, disordered arrangement of cells with vague boundary in the model group, which was relatively milder including a decrease of volume and content of vacuoles of both white and brown adipose, neat arrangement of cells with clear boundary. CONCLUSION: EA intervention can improve lipid metabolism and promote white adipose tissue browning in middle-aged and aged obese rats, which is possibly associated with its functions in activating AMPK/Sirt1 signaling pathway and up-regulating the level of Nrg4.