Microbial tryptophan metabolism

Microbial tryptophan metabolism refers to the biochemical process by which commensal gut bacteria break down the essential amino acid tryptophan into a variety of bioactive metabolites, including indoles, tryptamine, and kynurenine derivatives (Roager & Licht, 2018, Nature Communications). These metabolites play a critical role in host physiology by acting as ligands for the Aryl hydrocarbon receptor (AhR), which regulates immune responses and maintains the integrity of the intestinal epithelial barrier (Agus et al., 2018, Nature Reviews Gastroenterology & Hepatology). Dysregulation of this pathway is strongly associated with several pathologies; for instance, a reduction in protective indole metabolites is observed in inflammatory bowel disease, while the accumulation of the microbial metabolite indoxyl sulfate contributes to cardiovascular complications in chronic kidney disease (Laurans et al., 2018, Cell Host & Microbe). Furthermore, the pathway is a key component of the gut-brain axis, as microbial products can influence the availability of tryptophan for host serotonin synthesis and produce neuroactive compounds that affect mood and cognition (O'Mahony et al., 2015, Behavioural Brain Research). Therapeutic interventions currently under investigation include the use of specific probiotic strains to enhance beneficial metabolite production and the development of small-molecule inhibitors targeting bacterial enzymes like tryptophanase to prevent the formation of toxic byproducts (Devlin et al., 2016, Science).

Other names

Gut microbiota tryptophan metabolismBacterial tryptophan degradationIndole metabolic pathwayMicrobiome-derived tryptophan catabolism

Therapeutic modulation involves altering the composition of the gut microbiota or inhibiting specific bacterial enzymes to shift the balance of tryptophan metabolites toward those that promote host homeostasis and away from those that induce toxicity.