Circadian tryptophan metabolism contributes to systemic aryl hydrocarbon receptor activity

Feb 23, 2026iScience

Daily changes in tryptophan breakdown influence body-wide aryl hydrocarbon receptor activity

AI simplified

Circadian Biology on OpenScience ↗PubMed ↗DOI ↗

Abstract

Quantitative analyses reveal circadian cycling of hepatic tryptophan metabolizing enzymes and serum tryptophan metabolites associated with AHR activity.

Hepatic tryptophan metabolizing enzymes exhibit circadian patterns in expression.
Serum levels of several tryptophan metabolites, known to activate the AHR, also show circadian cycling.
Cyclical AHR activity is influenced by a nocturnal feeding schedule in mice.
Host tryptophan metabolism may establish a daily rhythm that affects AHR activity and related physiological processes.

AI simplified

Diet-phytochemical derived activation, host and microbial tryptophan metabolism represent the dominant route to endogenously mediated stimulation of physiological Ah receptor (AHR) activity. Whether host tryptophan metabolism provides a phytochemical independent circadian AHR tone has not been established. Using mice maintained on a nocturnally restricted feeding schedule with a nutritionally defined diet, we utilized quantitative gene/protein expression analyses in conjunction with targeted metabolomics to examine the temporal relationship between host tryptophan metabolism and circadian AHR activity. Time-resolved, targeted LCMS metabolomic, gene, and protein expression analyses reveal circadian cycling of hepatic tryptophan metabolizing enzymes (TDO2, TAT, GOT1, GOT2, KAT1, KAT2, and IL4I1) and serum tryptophan metabolites (indole-3-acetate, indole-3-lactate, indole-3-propionate, indole aldehyde, kynurenine, kynurenic acid) previously established as AHR ligands. We observed cyclical hepatic AHR activity directed by circadian feeding. These data suggest that a circadian rhythm of tryptophan metabolism orchestrates a daily tone in AHR activity that likely modulates AHR dependent physiology.

Full Text

We can’t show the full text here under this license. Use the link below to read it at the source.

View full text (XML) ↗View full text ↗

Circadian tryptophan metabolism contributes to systemic aryl hydrocarbon receptor activity

Abstract

Full Text

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief

Abstract

Full Text

Related papers

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief