Review

Kynurenines: Tryptophan’s metabolites in exercise, inflammation, and mental health

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Science  28 Jul 2017:
Vol. 357, Issue 6349, eaaf9794
DOI: 10.1126/science.aaf9794

Figures

  • The kynurenine pathway generates tryptophan metabolites with diverse biological activities throughout the body.

    Although mainly studied in relation to the brain and mental health, the action of kynurenine metabolites on peripheral tissues might be even more profound. They serve as important mediators of interorgan and interkingdom cross-talk, connecting seemingly diverse processes such as the effects of exercise training and pathologies such as inflammatory diseases, cancer, and depression.

  • Fig. 1 Overview of the kynurenine pathway of tryptophan degradation.

    3HAO, 3-hydroxyanthranilic acid oxygenase; NAPRT1, nicotinate phosphoribosyltransferase.

  • Fig. 2 Evolutionary conservation of enzymes of the kynurenine pathway.

    KYNU, Kynureninase.

  • Fig. 3 Activity, uptake, and conversion of tryptophan and its metabolites in peripheral tissues during unchallenged conditions.

    5-HT, 5-hydroxy tryptamine; ROS, reactive oxygen species.

  • Fig. 4 Activity, uptake, and conversion of tryptophan and its metabolites in peripheral tissues during disease states and challenges to homeostasis.

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