Electroacupuncture Alleviates Obesity in Mice via IL-33/ST2–ILC2 Axis Activation and Gut Microbiota Modulation

Abstract Background Obesity represents a global health crisis driven by chronic energy imbalance and excessive white adipose tissue (WAT) expansion. The inducible browning of WAT—characterized by the emergence of thermogenic beige adipocytes expressing uncoupling protein 1 (UCP1)—has emerged as a compelling therapeutic strategy. The interleukin-33 (IL-33)/suppression of tumorigenicity 2 (ST2) axis and its downstream effector, type 2 innate lymphoid cells (ILC2s), are indispensable regulators of adipose tissue immunometabolism and thermogenic programming. Although electroacupuncture (EA) demonstrates clinically relevant anti-obesity effects, whether it precisely targets the local adipose immune microenvironment to drive WAT browning remains entirely undefined. Objective This study aimed to determine whether EA alleviates diet-induced obesity by activating the IL-33/ST2-ILC2 axis to promote WAT browning and restore metabolic homeostasis. Methods Male SPF mice were fed a high-fat diet (HFD) for eight weeks to establish obesity, followed by four weeks of EA intervention at metabolic-regulatory acupoints (Zhongwan CV12, Tianshu ST25, Zusanli ST36, Sanyinjiao SP6, and Huizong TE7). Comprehensive metabolic phenotyping (body weight, Lee's index, serum lipid profiles, OGTT, and ITT), histopathological evaluation (H&E staining), flow cytometric quantification of adipose immune populations (ILC2s, M1/M2 macrophages), RT-qPCR, Western blot, immunohistochemistry, and 16S rDNA sequencing were performed. To establish causality, an IL-33 pharmacological inhibitor was administered to verify whether the metabolic and browning effects of EA were strictly dependent on this immune pathway. Results EA significantly attenuated HFD-induced weight gain, reduced Lee's index, and corrected dyslipidemia. Histologically, EA ameliorated adipose tissue morphology by reducing white adipocyte hypertrophy and intracellular vacuolization, while restoring brown adipocyte morphology with multilocular lipid droplets. EA elevated serum levels of IL-33 and type 2 cytokines. In adipose tissue, EA increased the proportions of ILC2s and M2 macrophages while reducing M1 macrophage infiltration. Molecularly, EA upregulated IL-33 and ST2 expression and restored thermogenic markers and adipogenic regulators, while decreasing white adipocyte expansion markers. Additionally, EA reshaped gut microbiota composition, increasing α-diversity and remodeling phylum- and genus-level bacterial abundances. Critically, IL-33 inhibitor treatment abolished EA-induced weight loss, adipose tissue remodeling, and thermogenic protein upregulation, and partially attenuated its improvements in lipid metabolism and glucose homeostasis, confirming that IL-33 is an indispensable mediator of EA's anti-obesity and browning effects. Conclusion These findings identify the IL-33/ST2-ILC2 axis as a definitive neuro-immune-metabolic effector of EA. By bridging somatic neuromodulation with local immune-driven adipose tissue plasticity, this study delineates a novel mechanistic pathway for EA-induced WAT browning and provides a robust biological rationale for the clinical application of EA as a precision immunometabolic therapy for obesity and its associated metabolic sequelae.