Subclinical mucosal inflammation in diarrhea-predominant irritable bowel syndrome (IBS) in a tropical setting

Abstract

Background and aims. There is evidence for low-grade inflammation in the pathophysiology of post-infectious irritable bowel syndrome (IBS). We assessed the degree of subclinical intestinal mucosal inflammation in diarrhea-predominant IBS (IBS-D) in a tropical setting. Material and methods. In a prospective study over 1 year, we investigated 49 patients with IBS-D (cases; median age 34 years (range 18–59); M:F 36:13), diagnosed on Rome III criteria. 14 individuals with a family history of colon cancer (median age 46.5 years (range 23–56); M:F 6:8) were selected as controls. Stools of cases and controls were tested for calprotectin. During colonoileoscopy, serial biopsies were obtained. Mucosal mast cells, neutrophils, eosinophils and lymphocytes/plasma cell infiltrate were quantified. Tissue expression of IL-8 and IL-10 was assessed in biopsies by semi-quantitative RT-PCR. Results. A history suggestive of an episode of infectious diarrhea (ID) was present in 16/49 cases and 0/14 controls (p = 0.013). In cases, there were significantly more mucosal mast cells in the ileum and all segments of colon and significantly more eosinophils in the cecum. Tissue expression of IL-8 was significantly higher and IL-10 significantly lower in cases compared with controls (target/standard cDNA ratio, median (range) IL-8: 1.25 (0.75–2) vs. 0.85 (0.63–1.3), p < 0.0001, Mann–Whitney U test; IL-10: 0.33 (0–0.63) vs. 0.55 (0.5–0.7), p < 0.0001). There was a significant inverse correlation between IL-8 and IL-10 expression (Pearson correlation, (-) 0.509; p < 0.01). Conclusion. There was evidence of subclinical intestinal mucosal inflammation in patients with IBS-D. The finding of increased eosinophils is novel, and may be of special relevance to IBS-D in the tropics.

Key Words::

• cytokines
• eosinophils
• IBS
• IBS-D
• inflammation
• mast cells

Acknowledgement

Guarantor of the article: Prof. AP De Silva. Specific author contributions: APDeS, DPJ and HJdeS conceptualized and designed the study. JH performed the histological assessment and AM performed the cytokine assays. SDN, MPA and ASD performed the clinical assessments and data gathering. APDeS, SDN and HJdeS analyzed the data. APDeS and HJdeS wrote the initial draft and the other authors critically revised the manuscript. All authors read and approved the final draft of the manuscript. This study received funding from the National Science Foundation of Sri Lanka.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.