Electroacupuncture Alleviates Obesity and Insulin Resistance via the GLP-1-VTADA Reward Circuit.

INTRODUCTION: We investigated the effects of electroacupuncture (EA) on improving obesity and insulin resistance (IR) in high-fat diet-induced (HFDI) obese rats by modulating the nucleus tractus solitarius (NTS) glucagon-like peptide-1 (GLP-1)-ventral tegmental area (VTA) dopamine (DA) neural reward circuit, thereby uncovering a possible central mechanism underlying EA's actions in improving obesity and IR. METHODS: We randomly allocated 45 Wistar male rats to five groups (normal, model, EA, chemogenetic activation, chemogenetic suppression + EA), with 9 rats in each group. All interventions were conducted within 8 weeks after the model was established. We tested rats for obesity phenotypes included body mass, Lee's index, 24-h food intake, and glucose-metabolism parameters. We observed protein and gene expression for GLP-1 in the NTS and tyrosine hydroxylase in the VTA by Western blotting and real-time polymerase chain reaction, as well as their localization by immunofluorescence. We also determined the DA content in the VTA using high-performance liquid chromatography. RESULTS: Obese rats exhibited marked hyperphagia, accompanied by increased excitability of DA neurons in the VTA region and reduced insulin sensitivity. After EA treatment, obese rats showed augmented excitability of NTS GLP-1 and suppression of VTADA neurons with a diminution in food intake, showing results similar to those in the chemogenetic activation group. After EA treatment and while inhibiting GLP-1 neurons by chemogenetics, the effect of EA on activating GLP-1 neurons and inhibiting VTADA was partially abrogated. The effects of improving obesity and insulin sensitivity were likewise also suppressed. CONCLUSION: EA effectively activated GLP-1 neurons in the NTS, thereby inhibited the expression of DA in the VTA and improved obesity and insulin sensitivity in HFDI-obese rats.

Scalp electroacupuncture targeting the VTADA neurons to relieve negative emotions and promote the alleviation of chronic pain.

Object: Chronic pain and negative emotions are often linked, and both can impact the reward circuit. The use of electroacupuncture (EA) has been found to regulate and improve these conditions. This study explores the potential mechanism of chronic pain relief by adding acupoints with emotional regulation effect to the basis of routine EA analgesia, to optimize the acupoint compatibility scheme of EA in the treatment of analgesia. Method: For this study, 42 male Wistar rats were used. Recombinant adeno-associated viruses were used to label and regulate the activity of dopamine (DA) neurons. The rat model was established by complete Freund's adjuvant (CFA). Lower limb electroacupuncture (LEA) was applied to the ST36 and BL60 acupoints. In addition, LEA + scalp EA (SEA) was given using the GV20 and GV24+ acupoints besides ST36 and BL60. To evaluate the pain threshold, we measured 50% paw withdrawal thresholds and thermal paw withdrawal latencies. Negative emotions were evaluated through the open field test, marble-burying test, sucrose preference test, and forced swimming test. Moreover, the conditional place preference test was conducted to measure the reward behavior in response to pain relief. Immunofluorescence staining, Western blotting, and qPCR were used to detect the activity of the VTADA-NAc reward circuit. Result: The injection of CFA significantly lowered the pain threshold. As the pain persisted, the anxiety and depression-like behaviors escalated while the response to reward reduced. Meanwhile, the VTADA-NAc pathway was suppressed with pain chronification. However, activating DA neurons in VTA attenuated the effects induced by CFA. LEA could relieve chronic pain, negative emotions, and reward disorders, while also activating the VTADA-NAc pathway. In addition, LEA + SEA exhibited a more pronounced effect compared with LEA alone. Nevertheless, chemogenetic inhibition of DA neurons decreased the efficacy of LEA + SEA in the treatment of chronic pain and associated comorbidities. Conclusion: Adding SEA to conventional LEA effectively alleviates negative emotions and chronic pain, potentially due to the activation of the VTADA-NAc reward neural circuit. Thus, LEA + SEA is a more effective treatment for hyperalgesia and associated negative emotions compared with LEA alone.