Intestinal chemosensitivity in irritable bowel syndrome associates with small intestinal TRPV channel expression

Summary Background Irritable bowel syndrome (IBS) patients often experience meal‐associated symptoms. However, the underlying mechanisms are unclear. Aim To determine small intestinal mechanisms of lipid‐induced symptoms and rectal hypersensitivity in IBS Methods We recruited 26 IBS patients (12 IBS‐C, 14 IBS‐D) and 15 healthy volunteers (HV). In vivo permeability was assessed using saccharide excretion assay. Rectal sensitivity was assessed using a barostat before and after small bowel lipid infusion; symptoms were assessed throughout. Next, an extended upper endoscopy with probe‐based confocal laser endomicroscopy (pCLE) was performed with changes induced by lipids. Duodenal and jejunal mucosal biopsies were obtained for transcriptomics. Results Following lipid infusion, a higher proportion of HV than IBS patients reported no pain, no nausea, no fullness and no urgency ( P < 0.05 for all). In a model adjusted for sex and anxiety, IBS‐C and IBS‐D patients had lower thresholds for first rectal sensation ( P = 0.0007) and pain ( P = 0.004) than HV. In vivo small intestinal permeability and mean pCLE scores were similar between IBS patients and HV. Post‐lipid, pCLE scores were higher than pre‐lipid but were not different between groups. Baseline duodenal transient receptor potential vanilloid (TRPV) 1 and 3 expression was increased in IBS‐D, and TRPV3 in IBS‐C. Duodenal TRPV1 expression correlated with abdominal pain ( r = 0.51, FDR = 0.01), and inversely with first rectal sensation ( r = −0.48, FDR = 0.01) and pain ( r = −0.41, FDR = 0.02) thresholds. Conclusion Lipid infusion elicits a greater symptom response in IBS patients than HV, which is associated with small intestinal expression of TRPV channels. TRPV‐mediated small intestinal chemosensitivity may mediate post‐meal symptoms in IBS.