Efficacy and mechanisms of vagus nerve stimulation in irritable bowel syndrome: a comprehensive literature review

Irritable bowel syndrome (IBS) is a common non-organic functional gastrointestinal disorder. Recently, vagus nerve stimulation (VNS) has been a novel therapeutic strategy for the treatment of IBS. This review provided an overview of the mechanisms of VNS in IBS and clinical applications. Studies about VNS in the treatment of IBS were systematically retrieved from PubMed, EMbase and CNKI databases. Mechanically, pre-clinical evidence highlights VNS as a multifaceted therapy for IBS, including reducing inflammation via α7 nicotinic acetylcholine receptor-mediated suppression of TNF-α, alleviating visceral hypersensitivity, increasing colorectal distension thresholds, enhancing motility through M3 receptor activation and gastric emptying, restoring gut microbiota diversity via elevating bifidobacterium abundance and short-chain fatty acids, and improving intestinal barrier integrity. Consistent with its mechanism, the reduced inflammation biomarkers, improved metabolism content, increased genus bifidobacterium, and improved intestinal barrier integrity are confirmed in clinical patients with IBS after VNS therapy. Besides, clinical studies reveal that VNS can increase the complete spontaneous bowel movements per week, decrease the visual analog scale for abdominal pain and IBS symptom score, improve rectoanal inhibitory reflex, rectal sensation, and improve sustained quality of life. In summary, noninvasive VNS is an effective and novel therapy option for patients with IBS, and its integrative effects are multi-factorial.