Effect of grape pomace skin colonic ferments on differentiated monolayers of Caco-2 cells

Dietary fibre usually comes associated with phenolic compounds either trapped in a network formed by indigestible polysaccharides or, in some cases, bound to this matrix by covalent bonds. This natural association protects some phenolic compounds during their journey through the gastrointestinal tract, reaching the colon, where most polysaccharides undergo fermentation, weakening the matrix and promoting the release of these compounds to exert benefits by modulating intestinal function. Unfortunately, there are still difficulties in investigating the impact of the human microbiota on the release of phenolic compounds from the indigestible fraction and on their effects on the intestinal epithelium. In this study, grape pomace skin was subjected to in vitro digestion to obtain an indigestible fraction, which was further incorporated into SHIME bioreactors with human colonic microbiota. Throughout these stages, we monitored the release of phenolic compounds using HPLC-DAD. We determined the impact of a phenolic-rich indigestible fraction on the fermentative capacity of human microbiota by measuring the short-chain fatty acids (SCFA) levels and the effect of the resulting colonic ferments on the barrier properties of differentiated monolayers of Caco-2 cells by monitoring the transepithelial electrical resistance and the transcriptomic profile by RNA sequencing.