Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder involving dysregulation of the microbiota-gut-brain (MGB) axis. Acupuncture effectively alleviates IBS symptoms, yet its underlying mechanisms remain incompletely understood. This review synthesizes current evidence to propose a mechanistic framework by which acupuncture treats IBS through MGB axis modulation. We systematically examine: (1) MGB axis dysfunction in IBS pathophysiology across neural, endocrine, and immune pathways; (2) acupuncture’s modulation of gut microbiota structure (alpha/beta diversity, specific bacterial genera); (3) functional consequences including enhanced short-chain fatty acid production and tryptophan metabolism; (4) causal evidence from fecal microbiota transplantation; (5) correlations between microbiota changes and clinical improvement. Key findings reveal that acupuncture induces “convergent remodeling” of microbial structure toward a healthy profile, exerts “bidirectional regulation” on beneficial and harmful bacteria, and establishes a “niche selection” mechanism via neuro-immune pathways. These microbiota-mediated effects integrate with neural, endocrine, and immune pathways, forming a “point-to-surface” networked regulatory pattern that explains acupuncture’s dual efficacy in alleviating both gastrointestinal and psychological symptoms. This review provides a novel theoretical framework for understanding acupuncture’s therapeutic mechanisms and supports its clinical application in IBS management.
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