Tryptophan metabolism and the gut-brain axis: focus on specific gut microbial genera

Abstract

The gut-brain axis (GBA) is a crucial connection that enables bidirectional communication between the central nervous system and gastrointestinal tract. Serotonin is a tryptophan (Trp) metabolite and an important gastrointestinal signaling molecule. Kynurenine and indole derivatives mediate the central nervous system, thereby affecting neurological diseases. The gut microbiota has direct or indirect impact on Trp metabolism. Different genera of gut microbiota affect Trp metabolites in different ways, thus changing the communication between the brain and gastrointestinal tract. This review highlights the triangular relationship between the GBA, Trp metabolism, and gut microbiota and summarizes the types of relevant gut microbiota genera involved in this triangular relationship. By modulating the gut microbiota through probiotics, dietary interventions, fecal microbiota transplantation, and other methods, improving Trp metabolism and thereby influencing metabolites provides potential targets for treating GBA-related diseases.