Tryptophan Supplementation Increases the Production of Microbial-Derived AhR Agonists in anIn VitroSimulator of Intestinal MicrobialEcosystem

The aryl hydrocarbon receptor (AhR) plays an important role in intestinal homeostasis, and some microbialmetabolites of tryptophan are known AhR agonists. In this study, we assessed the impact of tryptophan supplementation on theformation of tryptophan metabolites, AhR activation, and microbiota composition in the simulator of the human intestinal microbialecosystem (SHIME). AhR activation, microbial composition, and tryptophan metabolites were compared during high tryptophansupplementation (4 g/L tryptophan), control, and wash-out periods. During tryptophan supplementation, the concentration ofseveral tryptophan metabolites was increased compared to the control and wash-out period, but AhR activation by fermentersupernatant was significantly decreased. This was due to the higher levels of tryptophan, which was found to be an antagonist of AhRsignaling. Tryptophan supplementation induced most microbial changes in the transverse colon including increased relativeabundance of lactobacillus. We conclude that tryptophan supplementation leads to increased formation of AhR agonists in the colon

Automated summary

This study assessed the impact of tryptophan supplementation on tryptophan metabolites, AhR activation, and microbiota composition. The results showed that tryptophan supplementation led to changes in microbiota and increased formation of AhR agonists.