Background: Increasing evidence proves the pivotal role of gut microbiota in mammals’ homeostasis. Gut
bacterial metabolites may exert local effects on the intestines, and may enter the circulation, affecting the functions
of virtually all organs. Here, we review the available evidence on metabolism and biological effects of gut microbiota-
Methods: The PUBMED database and Google Scholar were searched to identify experimental and clinical studies
investigating biological effects of gut bacteria-derived indoles. Key words included: gut microbiota, indoles, indole
Results: Indoles represent a wide group of gut bacteria-derived compounds produced from tryptophan, an essential
amino acid and the precursor of endogenous synthesis of tryptamine, serotonin and melatonin. Ample evidence suggests
that indoles derived from gut microbiota metabolism exert significant biological effects and may contribute to
the etiology of cardiovascular, metabolic, and psychiatric diseases. However, a majority of the research is limited to
experimental studies and only a small number of clinical trials.
Conclusion: Bacterial indoles affect the function of many biological systems. Whether gut-derived indoles contribute
to pathogenesis of cardiovascular, metabolic and other diseases, requires further clinical studies.