Microbiome mediated impact of food grade carrageenan on the intestinal barrier function

Carrageenan (CGN) comprises a family of high-molecular-weight sulfated polysaccharides used as emulsifiers (E-407) in foods. Concerns about the safety of this additive have lately emerged. This work assessed the intestinal microbiome mediated impact of food grade CGN on the intestinal barrier. Increased doses of CGN were added to a four-stage reactor system stabilized with faecal microbiota. 16 S rDNA amplicon-based metagenomics analysis showed an increase in pro-inflammatory species such as Desulfovibrio desulfuricans and Bilophila spp. among Desulfovibrionaceae and Ruminococcus torques, Clostridium scindens and Eisenbergiella spp. among Lachnospiraceae upon increasing doses of CGN. In contrast, Bifidobacterium catenulatum decreased when CGN doses increased. Results showed that CGN had no effect on Caco-2 cell viability or epithelial monolayer integrity, but acid-hydrolyzed CGN did. Nonetheless, supernatants of CGN-fed microbiota caused epithelial integrity loss and a rise in paracellular permeability in a dose-dependent manner. The modified microbiota itself did not disrupt epithelial integrity at any CGN dose. This microbiome-mediated impact of CGN triggers a disruption of the epithelial barrier in a dose-dependent manner by means of a decrease expression of tight junction proteins, mainly zonula occludens 2 and claudins 3 and 4. Intestinal permeability caused by CGN was evaluated in vivo during an exploratory assay using CD-1 mice. Intestinal permeability and pro-inflammatory biomarkers were quantified in blood serum. CGN-fed mice showed an increased intestinal permeability involving an increase in TNF-alpha, which is likely microbiome-mediated. Our findings highlight the significance of including the intestinal microbiome in CGN risk evaluation.