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.

色氨酸（Trp）不仅是一种营养增强剂，而且具有全身作用。通过众所周知的芳基碳氢化合物受体（AhR）发出信号的Trp代谢物构成了微生物组-肠道-脑轴的界面。但是，Trp代谢产物影响中枢神经系统（CNS）功能的途径尚未完全阐明。AhR参与了各种各样的生理和病理过程，这些过程也与肠道稳态和CNS疾病高度相关。通过AhR依赖性机制，Trp代谢物通过免疫，代谢和神经（迷走）信号传导机制介导的肠道微生物组和大脑之间的双向信号传导，对行为和CNS功能产生下游影响。