Liu · Metabolites 2022 · narrative review · n=?

Microbial Tryptophan Metabolism Tunes Host Immunity, Metabolism, and Extraintestinal Disorders.

Level 5 - mechanism / opinion, no new human data

Narrative review synthesizing mechanistic and physiological literature without original human data or systematic review methodology.

PubMed 36144238 · doi:10.3390/metabo12090834 · record verified 2026-08-26

What was done

This narrative review summarizes recent literature regarding host-microbiota crosstalk mediated by tryptophan-derived metabolites. The authors review mechanistic findings on how gut microbial tryptophan catabolites regulate intestinal homeostasis, immune function, and endocrine signaling, as well as the effects of perturbations in these pathways on inflammatory bowel diseases, metabolic disorders, chronic kidney diseases, and cardiovascular diseases.

What was found

The abstract reports no numerical findings or effect sizes. It qualitatively describes that commensal tryptophan catabolites function as signaling messengers tuning host immune and metabolic responses, and that altered microbial tryptophan metabolism is implicated in various intestinal and extraintestinal disorders.

Why it matters

The review outlines biological pathways connecting gut microbial tryptophan metabolism to systemic host immunity and chronic inflammatory or metabolic diseases.

Limits

As a narrative review, it presents no original empirical data, quantitative results, or systematic search methodology in the abstract. Specific effect sizes and causal clinical relevance in humans cannot be determined from the abstract alone.

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