Combined protective effects of dairy propionic bacteria and n-6 polyunsaturated fatty acids on the intestinal epithelial barrier

Introduction Intestinal epithelial barrier (IEB) integrity plays a central role in the pathogenesis of inflammatory bowel disease (IBD). There is a growing interest in dietary compounds that can strengthen IEB. First, candidate strains of dairy propionic bacteria such as Propionibacterium freudenreichii are able to reduce inflammation and improve barrier strength. Knowing that certain products of omega-6 polyunsaturated fatty acid (n-6 PUFA) metabolism also reinforce IEB, and that bacteria can modulate the bioavailability of host lipid compounds, this project aims to identify strains of P. freudenreichii that could protect against colitis by strengthening IEB and increasing the bioavailability of certain n-6 PUFA. MethodsA screening of thirty-three strains of P. freudenreichii was performed based on the following criteria: 1) characterization of the ability to induce production of anti-inflammatory cytokines (IL-10) by stimulation of human PBMCs 2) identification of surface proteins (S-layer protein) responsible for anti-inflammatory properties 3) measurement of their ability to increase the bioavailability of certain n-6 PUFAs, such as conjugated linoleic acids (CLAs). The ability of the selected fermented products to prevent the inflammation-induced increase in permeability of an IEB was then studied. ResultsAll strains are able to induce IL-10 production and release CLAs. Ten strains show an anti-inflammatory S-layer profile. Some fermented products significantly prevent the inflammation-induced increase in permeability, and may involve surface proteins and bioactive lipids. DiscussionThese results will allow the selection of strains with anti-inflammatory as well as pro-repair potential to be tested in vivo to reduce colitis, with or without n-6 PUFA supplementation.