Tryptophan metabolism as a target in gut microbiota, ageing and kidney disease

Aromatic amino acid tryptophan metabolism, particularly three main metabolism pathways including kynurenine, serotonin and indole-derived pathways are under the direct or indirect modulation of host-microbiota crosstalk in human physiology. Tryptophan metabolism is involved in the regulation of aging, immunity and intestinal homeostasis. Dysregulation of tryptophan metabolism ranging from bowel disease to kidney disease allow us to therapeutic targeting the tryptophan metabolism. This review summarizes recent advances in physiological and pathophysiological roles of tryptophan metabolism in health and disease such as ageing-related disease, bowel disease and renal disease. Decoding the sophisticated imbalance between tryptophan metabolism pathways will expedite a comprehensive understanding of the pathogenesis of human diseases and highlight the opportunities and challenges for medication research and development in multiple diseases. This review presents concept-driven diagnostic and therapeutic strategies for the management of patients with kidney disease by gut-kidney-aging axes.