Faecal bile acids and colonic bile acid membrane receptor correlate with symptom severity of diarrhoea-predominant irritable bowel syndrome: A pilot study

Aims: To compare both the faecal bile acids (BAs) and the levels of two bile acid receptors, Takeda G protein-coupled receptor 5 (TGR5) and vitamin D receptor (VDR), in the colonic mucosa between patients with irritable bowel syndrome with predominant diarrhea (IBS-D) and healthy controls, and explore the correlations among clinical characteristics, bile acid receptors expression, and BAs. Methods: The severity of abdominal pain and diarrhoea was assessed in IBS-D patients using validated questionnaires, faecal BAs were measured by ultraperformance liquid chromatography coupled to tandem mass spectrometry, and rectosigmoid biopsies were taken for the analyses of TGR5 and VDR expression using immunohistochemistry. Results: The level of TGR5 immunoreactivity in rectosigmoid mucosal biopsies was significantly higher in IBS-D patients than in controls, while the VDR immunoreactivity displayed no significant difference between patients and controls. The patients with more severe or more frequent abdominal pain had significantly higher TGR5 level. Faecal primary BAs were significantly increased in IBS-D patients and were positively correlated with the severity of diarrhoea. The level of TGR5 was positively associated with primary BAs and negatively associated with secondary BAs among all participants providing both mucosal and stool samples. Conclusions: Colonic mucosal TGR5 protein expression and faecal bile acids were correlated with the symptom severity of IBS-D patients. (c) 2021 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

Automated summary

The expression levels of TGR5 in colonic mucosa were significantly higher in IBS-D patients compared to controls, while VDR levels showed no significant difference. Patients with more severe or frequent abdominal pain had higher levels of TGR5. Primary BAs in feces were increased in IBS-D patients and correlated with the severity of diarrhea. The level of TGR5 was positively associated with primary BAs and negatively associated with secondary BAs in participants providing both mucosal and stool samples.