Potential binding modes of the gut bacterial metabolite, 5-hydroxyindole, to the intestinal L-type calcium channels and its impact on the microbiota in rats

Previously we have shown, that a wide variety of gut bacteria can produce 5-hydroxyindole from its precursor 5-hydroxytryptophan.Here we show, using 16S rRNA sequencing and further microbiota analysis, that 5-hydroxyindole has only a marginal effect on the richness and composition of the cecal microbiota when orally administered to the wild-type Groningen rats. Additionally, accelerated total gut transit time showed only a slight association with the cecal bacterial composition. Together, our study proposes 5-hydroxyindole as a potentially safe, microbiota-derived metabolite that might be used as a targeted drug to stimulate gut transit time in gastrointestinal disorders, such as constipation.