Electroacupuncture improves obesity and promotes white adipose tissue browning by regulating central glucagon-like peptide-1

Abstract

To observe the effect of electroacupuncture （EA） on white adipose tissue （WAT） browning by regulating central glucagon-like peptide-1 （GLP-1）, so as to explore the possible central mechanisms of EA in improving obesity. Thirty male Wistar rats were randomly divided into normal group, model group, EA group, HM3D group, and EA+HM4D group, with 6 rats in each group. The obesity rat model was obtained by feeding with high-fat diet for 8 weeks. Adeno-associated virus combined with DREADDs was injected into bilateral nucleus of solitary tract （NTS）, with rAAV-GLP-1+rAAV-4D applied to the EA+HM4D group, rAAV-GLP-1+rAAV-3D applied to the HM3D group, and rAAV-GLP-1+rAAV-GFP applied to other 3 groups. After modeling, rats in the EA and EA+HM4D groups received EA treatment at bilateral "Zusanli"（ST36）, "Fenglong"（ST40）, "Guanyuan"（CV4） and "Zhongwan"（CV12）, with successive waves （2 Hz, 1 mA） for 10 minutes, 3 times a week, for a total of 8 weeks. Body mass of rats in each group were measured before and 2, 4, 6, and 8 weeks after intervention. Abdominal and perirenal WAT mass was weighed, serum triglyceride （TG） and total cholesterol （TC） contents were detected by using automatic analyzer, and nonestesterified fatty acid （NEFA） content was detected by using colorimetric assay kit. The morphology of abdominal WAT lipid droplets was observed by HE staining. The mRNA expressions of GLP-1 in NTS, AMPK in ventromedial nucleus of hypothalamus（VMH）, UCP1 and PGC-1α in subcutaneous fat were detected by real-time PCR. The protein expression levels of GLP-1, AMPK, phosphorylated-AMPK, UCP1 and PGC-1α were detected by Western blot. The activation level of GLP-1 neurons in NTS was observed by immunofluorescence. Compared with the normal group, abdominal WAT lipid droplets were enlarged, body weight, serum TG, TC, NEFA contents, abdominal and perirenal WAT mass, mRNA and protein expression levels of AMPK were significantly increased（P<0.01, P<0.05）, while GLP-1 neurons activation level, mRNA and protein expression levels of GLP-1, UCP1 and PGC-1α, and AMPK protein phosphorylation were decreased （P<0.01） in the model group. After EA intervention, body weight at 6 and 8 weeks after intervention and other indexes mentioned above were all significantly reversed （P<0.01, P<0.05） in the EA group in comparison with those of the model group. Compared with the EA group, the HM3D group had reduced abdominal WAT lipid droplets size, decreased serum TG, TC, and NEFA contents, and protein expression level of AMPK（P<0.01, P<0.05）, with increased mRNA and protein expression levels of GLP-1, UCP1 and PGC-1α, and phosphorylation level of AMPK protein（P<0.01, P<0.05）, while the EA+HM4D group had enlarged abdominal WAT lipid droplets, increased body weight 6 and 8 weeks after intervention, abdominal and renal WAT mass, and NEFA content （P<0.01, P<0.05）, with decreased serum TG content, activation level of GLP-1 neurons in the NTS, mRNA and protein expression levels of GLP-1, UCP1 and PGC-1α （P<0.01, P<0.05）, as well as down-regulated phosphorylation of AMPK protein and mRNA （P<0.01, P<0.05）. EA can effectively promote the browning of WAT, which may be related to the activation of GLP-1 neurons in the NTS, as well as the promotion of the phosphorylation of AMPK in the VMH and up-regulation of UCP1.