Background & aims

Alterations in microRNA (miRNA) and in the intestinal barrier are putative risk factors for irritable bowel syndrome (IBS). We aimed to identify differentially expressed colonic mucosal miRNAs, their targets in IBS compared to healthy controls (HCs), and putative downstream pathways.

Methods

Twenty-nine IBS patients (15 IBS with constipation [IBS-C], 14 IBS with diarrhea [IBS-D]), and 15 age-matched HCs underwent sigmoidoscopy with biopsies. A nCounter array was used to assess biopsy specimen-associated miRNA levels. A false discovery rate (FDR) < 10% was considered significant. Real-time polymerase chain reaction (PCR) was used to validate differentially expressed genes. To assess barrier function, trans-epithelial electrical resistance (TEER) and dextran flux assays were performed on Caco-2 intestinal epithelial cells that were transfected with miRNA-inhibitors or control inhibitors. Protein expression of barrier function associated genes was confirmed using western blots.

Results

Four out of 247 miRNAs tested were differentially expressed in IBS compared to HCs (FDR < 10%). Real-time PCR validation suggested decreased levels of miR-219a-5p and miR-338-3p in IBS (P = .026 and P = .004), and IBS-C (P = .02 and P = .06) vs. HCs as the strongest associations. Inhibition of miR-219a-5p resulted in altered expression of proteasome/barrier function genes. Functionally, miR-219a-5p inhibition enhanced the permeability of intestinal epithelial cells as TEER was reduced (25-50%, P < .05) and dextran flux was increased (P < .01). Additionally, inhibition of miR-338-3p in cells caused alterations in the mitogen-activated protein kinase (MAPK) signaling pathway genes.

Conclusion

Two microRNAs that potentially affect permeability and visceral nociception were identified to be altered in IBS patients. MiR-219a-5p and miR-338-3p potentially alter barrier function and visceral hypersensitivity via neuronal and MAPK signaling and could be therapeutic targets in IBS.

BACKGROUND: Stress reactivity (SR) is associated with increased risk of flares in ulcerative colitis (UC) patients. Because both preclinical and clinical data support that stress can influence gut microbiome composition and function, we investigated whether microbiome profiles of SR exist in UC. METHODS: Ninety-one UC subjects in clinical and biochemical remission were classified into high and low SR groups by questionnaires. Baseline and longitudinal characterization of the intestinal microbiome was performed by 16S rRNA gene sequencing and fecal and plasma global untargeted metabolomics. Microbe, fecal metabolite, and plasma metabolite abundances were analyzed separately to create random forest classifiers for high SR and biomarker-derived SR scores. RESULTS: High SR reactivity was characterized by altered abundance of fecal microbes, primarily in the Ruminococcaceae and Lachnospiraceae families; fecal metabolites including reduced levels of monoacylglycerols (endocannabinoid-related) and bile acids; and plasma metabolites including increased 4-ethyl phenyl sulfate, 1-arachidonoylglycerol (endocannabinoid), and sphingomyelin. Classifiers generated from baseline microbe, fecal metabolite, and plasma metabolite abundance distinguished high vs low SR with area under the receiver operating characteristic curve of 0.81, 0.83, and 0.91, respectively. Stress reactivity scores derived from these classifiers were significantly associated with flare risk during 6 to 24 months of follow-up, with odds ratios of 3.8, 4.1, and 4.9. Clinical flare and intestinal inflammation did not alter fecal microbial abundances but attenuated fecal and plasma metabolite differences between high and low SR. CONCLUSIONS: High SR in UC is characterized by microbial signatures that predict clinical flare risk, suggesting that the microbiome may contribute to stress-induced UC flares.