A postbiotic fermented oat gruel may have a beneficial effect on the colonic mucosal barrier in patients with irritable bowel syndrome.

BACKGROUND: Impaired intestinal permeability and microbial dysbiosis are important pathophysiological mechanisms underlying irritable bowel syndrome (IBS). ReFerm(®), also called Profermin(®), is a postbiotic product of oat gruel fermented with Lactobacillus plantarum 299v. In this study, we investigated whether ReFerm(®) has a beneficial effect on the intestinal epithelial barrier function in patients with IBS. MATERIALS AND METHODS: Thirty patients with moderate to severe IBS-diarrhoea (IBS-D) or IBS-mixed (IBS-M) were treated with enema containing ReFerm(®) or placebo. The patients underwent sigmoidoscopy with biopsies obtained from the distal colon at baseline and after 14 days of treatment with ReFerm(®) or placebo twice daily. The biopsies were mounted in Ussing chambers, and paracellular and transcellular permeabilities were measured for 120 min. In addition, the effects of ReFerm(®) or placebo on the epithelial barrier were investigated in vitro using Caco-2 cells. RESULTS: ReFerm(®) reduced paracellular permeability (p < 0.05) and increased transepithelial resistance (TER) over time (p < 0.01), whereas the placebo had no significant effect in patients. In ReFerm(®)-treated Caco-2 cells, paracellular and transcellular permeabilities were decreased compared to the control (p < 0.05) and placebo (p < 0.01). TER was increased in Caco-2 ReFerm(®)-treated cells, and normalised TER was increased in ReFerm(®)-treated Caco-2 cells compared to control (p < 0.05) and placebo-treated (p < 0.05) cells. CONCLUSION: ReFerm(®) significantly reduced paracellular permeability and improved TER in colonic biopsies collected from patients with IBS and in a Caco-2 cell model. Our results offer new insights into the potential benefits of ReFerm(®) in IBS management. Further studies are needed to identify the molecular mechanisms underlying the barrier-protective properties of ReFerm(®). CLINICAL TRIAL REGISTRATION: [https://clinicaltrials.gov/], identifier [NCT05475314].