Increased small intestinal permeability and RNA expression profiles of mucosa from terminal ileum in patients with diarrhoea-predominant irritable bowel syndrome.

Abstract Background Altered intestinal permeability in diarrhoea-predominant irritable bowel syndrome (IBS-D) has been reported in some studies. Aims The study aimed to investigate the altered intestinal permeability and its associated clinical characteristics and RNA expression profiles in IBS-D. Methods We stratified IBS-D patients into two groups according to the P 95 value of the permeability in controls. The clinical characteristics of the two groups were evaluated, and two biopsy cases from each of the two groups were selected for the RNA-seq analysis. Results IBS-D patients had a significant increase in the small intestinal permeability compared with controls [0.0245 (0.0229) median (interquartile range)] versus 0.0156 (0.0098), P  = 0.010), but no significant difference was found in the colonic permeability [23.286 (10.470) versus 21.650 (6.650), P  = 0.574]. The IBS-D patients with increased small intestinal permeability had worse psychological effects ( P  = 0.027) and quality of life ( P  = 0.044). Analysis of RNA-seq data revealed 185 genes differentially expressed, many of which were related to mucosal inflammation and immunity. Conclusions Small intestinal permeability, but not colonic permeability, is increased in IBS-D patients. IBS-D patients with increased small intestinal permeability tend to be more severely impaired in terms of psychological effects and quality of life, and analysis of RNA-seq data reveals that increased small intestinal permeability is related to mucosal inflammation and immunity.