Microorganisms, tryptophan metabolism, and kynurenine pathway

a complex interconnected loop influencing human health status

Mona Dehhaghi, Hamed Kazemi Shariat Panahi, Gilles J. Guillemin*

*Corresponding author for this work

Research output: Contribution to journalArticle

26 Citations (Scopus)
16 Downloads (Pure)


The kynurenine pathway is important in cellular energy generation and limiting cellular ageing as it degrades about 90% of dietary tryptophan into the essential co-factor NAD+ (nicotinamide adenine dinucleotide). Prior to the production of NAD+, various intermediate compounds with neuroactivity (kynurenic acid, quinolinic acid) or antioxidant activity (3-hydroxykynurenine, picolinic acid) are synthesized. The kynurenine metabolites can participate in numerous neurodegenerative disorders (Alzheimer disease, amyotrophic lateral sclerosis, Huntington disease, and Parkinson disease) or other diseases such as AIDS, cancer, cardiovascular diseases, inflammation, and irritable bowel syndrome. Recently, the role of gut in affecting the emotional and cognitive centres of the brain has attracted a great deal of attention. In this review, we focus on the bidirectional communication between the gut and the brain, known as the gut-brain axis. The interaction of components of this axis, namely, the gut, its microbiota, and gut pathogens; tryptophan; the kynurenine pathway on tryptophan availability; the regulation of kynurenine metabolite concentration; and diversity and population of gut microbiota, has been considered.

Original languageEnglish
Pages (from-to)1-10
Number of pages10
JournalInternational Journal of Tryptophan Research
Publication statusPublished - 19 Jun 2019

Bibliographical note

Copyright the Author(s) 2019. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.


  • gut microbiota
  • gut-brain axis
  • indoleamine 2,3-dioxygenase
  • kynurenine pathway
  • neurodegenerative disorder
  • tryptophan

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