Food additives impair gut microbiota from healthy individuals and IBD patients in a colonic in vitro fermentation model.

Intestinal fibrosis is a long-term complication of inflammatory bowel diseases (IBD). Changes in microbial populations have been linked with the onset of fibrosis and some food additives are known to promote intestinal inflammation facilitating fibrosis induction. In this study, we investigated how polysorbate 80, sucralose, titanium dioxide, sodium nitrite and maltodextrin affect the gut microbiota and the metabolic activity in healthy and IBD donors (patients in remission and with a flare of IBD). The Simulator of the Human Intestinal Microbial Ecosystem (SHIME®) with a static (batch) configuration was used to evaluate the effects of food additives on the human intestinal microbiota. Polysorbate 80 and sucralose decreased butyrate-producing bacteria such as Roseburia and Faecalibacterium prausnitzii. Both compounds, also increased bacterial species positively correlated with intestinal inflammation and fibrosis (i.e.: Enterococcus, Veillonella and Mucispirillum schaedleri), especially in donors in remission of IBD. Additionally, polysorbate 80 induced a lower activity of the aryl hydrocarbon receptor (AhR) in the three groups of donors, which can affect the intestinal homeostasis. Maltodextrin, despite increasing short-chain fatty acids production, promoted the growth of Ruminococcus genus, correlated with higher risk of fibrosis, and decreased Oscillospira which is negatively associated with fibrosis. Our findings unveil crucial insights into the potential deleterious effects of polysorbate 80, sucralose and maltodextrin on human gut microbiota in healthy and, to a greater extent, in IBD patients.

Unveiling the influence of a probiotic combination of Heyndrickxia coagulans and Lacticaseibacillus casei on healthy human gut microbiota using the TripleSHIME® system.

Probiotics are host-friendly microorganisms that can have important health benefits in the human gut microbiota as dietary supplements. Maintaining a healthy gut microbial balance relies on the intricate interplay among the intestinal microbiota, metabolic activities, and the host's immune response. This study aims to explore if a mixture of Heyndrickxia coagulans [ATB-BCS-042] and Lacticaseibacillus casei [THT-030-401] promotes in vitro this balance in representative gut microbiota from healthy individuals using the Triple-SHIME® (Simulation of the Human Intestinal Microbial Ecosystem). Metataxonomic analysis of the intestinal microbes revealed that the probiotic mix was not causing important disruptions in the biodiversity or microbial composition of the three simulated microbiota. However, some targeted populations analyzed by qPCR were found to be disrupted at the end of the probiotic treatment or after one week of washout. Populations such as Cluster IV, Cluster XVIa, and Roseburia spp., were increased indicating a potential gut health-promoting butyrogenic effect of the probiotic supplementation. In two of the systems, bifidogenic effects were observed, while in the third, the treatment caused a decrease in bifidobacteria. For the health-detrimental biomarker Escherichia-Shigella, a mild decrease in all systems was observed in the proximal colon sections, but these genera were highly increased in the distal colon sections. By the end of the washout, Bacteroides-Prevotella was found consistently boosted, which could have inflammatory consequences in the intestinal context. Although the probiotics had minimal influence on most quantified metabolites, ammonia consistently decreased after one week of daily probiotic supplementation. In reporter gene assays, aryl hydrocarbon receptor (AhR) activation was favored by the metabolic output obtained from post-treatment periods. Exposure of a human intestinal cell model to fermentation supernatant obtained after probiotic supplementation induced a trend to decrease the mRNA expression of immunomodulatory cytokines (IL-6, IL-8). Overall, with some exceptions, a positive impact of H. coagulans and L. casei probiotic mix was observed in the three parallel experiments, despite inter-individual differences. This study might serve as an in vitro pipeline for the impact assessment of probiotic combinations on the human gut microbiota.