Tryptophan (Trp) is not only a nutrient enhancer but also has systemic effects. Trp metabolites signaling through the well-known aryl hydrocarbon receptor (AhR) constitute the interface of microbiome-gut-brain axis. However, the pathway through which Trp metabolites affect central nervous system (CNS) function have not been fully elucidated. AhR participates in a broad variety of physiological and pathological processes that also highly relevant to intestinal homeostasis and CNS diseases. Via the AhR-dependent mechanism, Trp metabolites connect bidirectional signaling between the gut microbiome and the brain, mediated via immune, metabolic, and neural (vagal) signaling mechanisms, with downstream effects on behavior and CNS function. These findings shed light on the complex Trp regulation of microbiome-gut-brain axis and add another facet to our understanding that dietary Trp is expected to be a promising noninvasive approach for alleviating systemic diseases.
Bibliographical noteFunding Information:
This work was supported by the National Key R&D Program of China (2018YFD0500601 and 2017YFD0500501), the National Natural Science Foundation of China (31930106, 31829004 and 31722054), the National Ten-thousand Talents Program of China (23070201) and the 111 project (B16044).
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- Tryptophan metabolites
- aryl hydrocarbon receptor (AhR)
- central nervous system (CNS)
- microbiome-gut-brain axis