Kynurenine pathway

From MEpedia, a crowd-sourced encyclopedia of ME and CFS science and history

The kynurenine pathway or tryptophan kynurenine pathway is the primary route for metabolizing the essential amino acid tryptophan in humans and other mammals[1] in order to generate cellular energy in the form of nicotinamide adenine dinucleotide (NAD+).[2][3]

If the kynurenine pathway becomes dysregulated or overactive, it can activate the immune system and result in a build-up of potentially neurotoxic compounds in the body.[3]

Function[edit | edit source]

Schematic representation of the kynurenine pathway.
Key: IDO1: indoleamine 2,3-dioxygenase 1; IDO2: indoleamine 2,3-dioxygenase 2; TDO2: tryptophan 2,3-dioxygenase; TPH1: Tryptophan hydroxylase 1; TPH2: Tryptophan hydroxylase 2; AFMID: arylformamidase; KMO: kynurenine 3-monooxygenase; CCBL1: kynurenine aminotransferase I; AADAT: kynurenine aminotransferase II; CCBL2: kynurenine aminotransferase III; KYNU: kynureninase; HAAO: 3-hydroxyanthranilate 3,4-dioxygenase; QPRT, quinolinate phosphoribosyl transferase; ACMSD: aminocarboxymuconate semialdehyde decarboxylase. Source: Favennec et al. (2016). PLoS ONE 11(6): e0158051

ME/CFS[edit | edit source]

The metabolic trap hypothesis suggests that a metabolic problem exists in one or more areas of a person with ME/CFS, with a defect in the IDO2 enzyme of the tryptophan kynurenine pathway being identified as a possible metabolic trap.

In April 2020, the Open Medicine Foundation announced a pilot treatment trial of kynurenine for ME/CFS patients.[4]

Notable studies[edit | edit source]

  • 2022, Post-acute COVID-19 cognitive impairment and decline uniquely associate with kynurenine pathway activation: a longitudinal observational study[5] - (Full text)- not yet peer reviewed
  • 2022, Could the kynurenine pathway be the key missing piece of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) complex puzzle?[6] - (Full text)
  • 2021, Role of Kynurenine Pathway in Oxidative Stress during Neurodegenerative Disorders[7] - (Full text)
  • 2021, Kynurenine Pathway of Tryptophan Metabolism in Migraine and Functional Gastrointestinal Disorders[8] - (Full text)
  • 2021, Incomplete Systemic Recovery and Metabolic Phenoreversion in Post-Acute-Phase Nonhospitalized COVID-19 Patients: Implications for Assessment of Post-Acute COVID-19 Syndrome[9] - (Full text)
  • 2021, Co-players in chronic pain: Neuroinflammation and the tryptophan-kynurenine metabolic pathway[10] - (Full text)
  • 2021, Tryptophan Metabolites, Cytokines, and Fatty Acid Binding Protein 2 in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome[11] - (Full text)
  • 2021, Kynurenine Metabolites and Ratios Differ Between Chronic Fatigue Syndrome, Fibromyalgia, and Healthy Controls[12] - (Full text)
  • 2021, Increased Kynurenine Indicates a Fatal Course of COVID-19[13] - (Full text)
  • 2021, A map of metabolic phenotypes in patients with myalgic encephalomyelitis/chronic fatigue syndrome[14] - (Full text)
  • 2020, The kynurenine pathway: a finger in every pie[2] - (Full text)
  • 2020, IDO and kynurenine metabolites in peripheral and CNS disorders[15] - (Full text)
  • 2020, Chronic fatigue and depression due to multiple sclerosis: Immune-inflammatory pathways, tryptophan catabolites and the gut-brain axis as possible shared pathways[16] - (Full text)
  • 2020, Accumulation of kynurenine elevates oxidative stress and alters microRNA profile in human bone marrow stromal cells[17] - (Full text)
  • 2019, The plasma [kynurenine]/[tryptophan] ratio and indoleamine 2, 3-dioxygenase: time for appraisal[18] - (Full text)
  • 2019, The IDO Metabolic Trap Hypothesis for the Etiology of ME/CFS[19] - (Full text)
  • 2018, Tryptophan-Kynurenine Metabolites in Exercise and Mental Health[20] - (Chapter)
  • 2017, Kynurenines: Tryptophan's metabolites in exercise, inflammation, and mental health[21] - (Abstract)
  • 2017, Indoleamine 2,3-Dioxygenase and Tolerance: Where Are We Now?[22] - (Full text)
  • 2017, The Kynurenine Pathway As a Novel Link between Allergy and the Gut Microbiome[23] - (Full text)
  • 2015, What is the tryptophan kynurenine pathway and why is it important to neurotherapeutics?[3] - (Full text)
  • 2014, Activation of the kynurenine pathway in the acute phase of stroke and its role in fatigue and depression following stroke[24] - (Full text)
  • 2004, Heterogeneity of serum tryptophan concentration and availability to the brain in patients with the chronic fatigue syndrome[25] - (Full text)
  • 1992, Quinolinic acid and kynurenine pathway metabolism in inflammatory and non-inflammatory neurological disease[26] - (Full text)

See also[edit | edit source]

Learn more[edit | edit source]

References[edit | edit source]

  1. Chen, Yiquan; Guillemin, Gilles J. (January 8, 2009). "Kynurenine Pathway Metabolites in Humans: Disease and Healthy States". International Journal of Tryptophan Research : IJTR. 2: 1–19. ISSN 1178-6469. PMC 3195227. PMID 22084578.
  2. 2.0 2.1 Savitz, Jonathan (January 2020). "The kynurenine pathway: a finger in every pie". Molecular Psychiatry. 25 (1): 131–147. doi:10.1038/s41380-019-0414-4. ISSN 1476-5578.
  3. 3.0 3.1 3.2 Davis, I.; Liu, A. (July 2015). "What is the tryptophan kynurenine pathway and why is it important to neurotherapeutics?". Expert review of neurotherapeutics. 15 (7): 719–721. doi:10.1586/14737175.2015.1049999. ISSN 1473-7175. PMID 26004930.
  4. Open Medicine Foundation (April 26, 2020). "Kynurenine Clinical Trial for ME/CFS". Open Medicine Foundation. Retrieved May 1, 2020.
  5. Cysique, Lucette A.; Jakabek, David; Bracken, Sophia G.; Allen-Davidian, Yasmin; Heng, Benjamin; Chow, Sharron; Dehhaghi, Mona; Pires, Ananda Staats; Darley, David R.; Byrne, Anthony; Phetsouphanh, Chansavath (June 7, 2022). "Post-acute COVID-19 cognitive impairment and decline uniquely associate with kynurenine pathway activation: a longitudinal observational study". Medrxiv: 2022.06.07.22276020. doi:10.1101/2022.06.07.22276020v1.
  6. Kavyani, Bahar; Lidbury, Brett A.; Schloeffel, Richard; Fisher, Paul R.; Missailidis, Daniel; Annesley, Sarah J.; Dehhaghi, Mona; Heng, Benjamin; Guillemin, Gilles J. (July 11, 2022). "Could the kynurenine pathway be the key missing piece of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) complex puzzle?". Cellular and Molecular Life Sciences. 79 (8): 412. doi:10.1007/s00018-022-04380-5. ISSN 1420-9071. PMC 9276562. PMID 35821534.
  7. Mor, Adrian; Tankiewicz-Kwedlo, Anna; Krupa, Anna; Pawlak, Dariusz (June 26, 2021). "Role of Kynurenine Pathway in Oxidative Stress during Neurodegenerative Disorders". Cells. 10 (7): 1603. doi:10.3390/cells10071603. ISSN 2073-4409. PMC 8306609. PMID 34206739.
  8. Fila, Michal; Chojnacki, Jan; Pawlowska, Elzbieta; Szczepanska, Joanna; Chojnacki, Cezary; Blasiak, Janusz (September 20, 2021). "Kynurenine Pathway of Tryptophan Metabolism in Migraine and Functional Gastrointestinal Disorders". International Journal of Molecular Sciences. 22 (18): 10134. doi:10.3390/ijms221810134. ISSN 1422-0067. PMC 8469852. PMID 34576297.
  9. Holmes, Elaine; Wist, Julien; Masuda, Reika; Lodge, Samantha; Nitschke, Philipp; Kimhofer, Torben; Loo, Ruey Leng; Begum, Sofina; Boughton, Berin; Yang, Rongchang; Morillon, Aude-Claire (June 4, 2021). "Incomplete Systemic Recovery and Metabolic Phenoreversion in Post-Acute-Phase Nonhospitalized COVID-19 Patients: Implications for Assessment of Post-Acute COVID-19 Syndrome". Journal of Proteome Research. 20 (6): 3315–3329. doi:10.1021/acs.jproteome.1c00224. ISSN 1535-3893. PMC 8147448. PMID 34009992.
  10. Tanaka, Masaru; Török, Nóra; Tóth, Fanni; Szabó, Ágnes; Vécsei, László (July 26, 2021). "Co-Players in Chronic Pain: Neuroinflammation and the Tryptophan-Kynurenine Metabolic Pathway". Biomedicines. 9 (8): 897. doi:10.3390/biomedicines9080897. ISSN 2227-9059. PMC 8389666. PMID 34440101.
  11. Simonato, Manuela; Dall’Acqua, Stefano; Zilli, Caterina; Sut, Stefania; Tenconi, Romano; Gallo, Nicoletta; Sfriso, Paolo; Sartori, Leonardo; Cavallin, Francesco; Fiocco, Ugo; Cogo, Paola (November 19, 2021). "Tryptophan Metabolites, Cytokines, and Fatty Acid Binding Protein 2 in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome". Biomedicines. 9 (11): 1724. doi:10.3390/biomedicines9111724. ISSN 2227-9059. PMC 8615774. PMID 34829952.
  12. Groven, Nina; Reitan, Solveig Klæbo; Fors, Egil Andreas; Guzey, Ismail Cuneyt (September 1, 2021). "Kynurenine metabolites and ratios differ between Chronic Fatigue Syndrome, Fibromyalgia, and healthy controls". Psychoneuroendocrinology. 131: 105287. doi:10.1016/j.psyneuen.2021.105287. ISSN 0306-4530.
  13. Mangge, Harald; Herrmann, Markus; Meinitzer, Andreas; Pailer, Sabine; Curcic, Pero; Sloup, Zdenka; Holter, Magdalena; Prüller, Florian (December 7, 2021). "Increased Kynurenine Indicates a Fatal Course of COVID-19". Antioxidants (Basel, Switzerland). 10 (12): 1960. doi:10.3390/antiox10121960. ISSN 2076-3921. PMID 34943063.
  14. Hoel, Fredrik; Hoel, August; Pettersen, Ina K.N.; Rekeland, Ingrid G.; Risa, Kristin; Alme, Kine; Sørland, Kari; Fosså, Alexander; Lien, Katarina; Herder, Ingrid; Thürmer, Hanne L. (2021). "A map of metabolic phenotypes in patients with myalgic encephalomyelitis/chronic fatigue syndrome". JCI Insight. 6 (16): e149217. doi:10.1172/jci.insight.149217. ISSN 2379-3708. PMC 8409979. PMID 34423789.
  15. Huang, Yi-Shu; Ogbechi, Joy; Clanchy, Felix I.; Williams, Richard O.; Stone, Trevor W. (2020). "IDO and Kynurenine Metabolites in Peripheral and CNS Disorders". Frontiers in Immunology. 11: 388. doi:10.3389/fimmu.2020.00388. ISSN 1664-3224.
  16. Ormstad, Heidi; Simonsen, Cecilia Smith; Broch, Line; Maes, Dr Michael; Anderson, George; Celius, Elisabeth G. (November 2020). "Chronic fatigue and depression due to multiple sclerosis: Immune-inflammatory pathways, tryptophan catabolites and the gut-brain axis as possible shared pathways". Multiple Sclerosis and Related Disorders. 46: 102533. doi:10.1016/j.msard.2020.102533. ISSN 2211-0356. PMID 33010585.
  17. Dalton, Sherwood; Smith, Kathryn; Singh, Kanwar; Kaiser, Helen; Kolhe, Ravindra; Mondal, Ashis K.; Khayrullin, Andrew; Isales, Carlos M.; Hamrick, Mark W.; Hill, William D.; Fulzele, Sadanand (February 1, 2020). "Accumulation of kynurenine elevates oxidative stress and alters microRNA profile in human bone marrow stromal cells". Experimental Gerontology. 130: 110800. doi:10.1016/j.exger.2019.110800. ISSN 0531-5565.
  18. Badawy, Abdulla A-B; Guillemin, Gilles (January 1, 2019). "The Plasma [Kynurenine]/[Tryptophan] Ratio and Indoleamine 2,3-Dioxygenase: Time for Appraisal". International Journal of Tryptophan Research. 12: 1178646919868978. doi:10.1177/1178646919868978. ISSN 1178-6469. PMC 6710706. PMID 31488951.
  19. Phair, Robert D.; Davis, Ronald W.; Kashi, Alex A. (2019). "The IDO Metabolic Trap Hypothesis for the Etiology of ME/CFS". Diagnostics. 9 (3): 82. doi:10.3390/diagnostics9030082.
  20. Valente-Silva, Paula; Ruas, Jorge Lira (2017). "Tryptophan-Kynurenine Metabolites in Exercise and Mental Health". In Spiegelman, Bruce (ed.). Hormones, Metabolism and the Benefits of Exercise. Cham (CH): Springer. ISBN 978-3-319-72789-9. PMID 31314466.
  21. Cervenka, Igor; Agudelo, Leandro Z.; Ruas, Jorge L. (July 28, 2017). "Kynurenines: Tryptophan's metabolites in exercise, inflammation, and mental health". Science. 357 (6349): eaaf9794. doi:10.1126/science.aaf9794.
  22. Mellor, Andrew L.; Lemos, Henrique; Huang, Lei (2017). "Indoleamine 2,3-Dioxygenase and Tolerance: Where Are We Now?". Frontiers in Immunology. 8: 1360. doi:10.3389/fimmu.2017.01360. ISSN 1664-3224.
  23. Van der Leek, Aaron P.; Yanishevsky, Yarden; Kozyrskyj, Anita L. (2017). "The Kynurenine Pathway As a Novel Link between Allergy and the Gut Microbiome". Frontiers in Immunology. 8: 1374. doi:10.3389/fimmu.2017.01374. ISSN 1664-3224. PMC 5681735. PMID 29163472.
  24. Ormstad, Heidi; Verkerk, Robert; Amthor, Karl-Friedrich; Sandvik, Leiv (2014). "Activation of the kynurenine pathway in the acute phase of stroke and its role in fatigue and depression following stroke" (PDF). Journal of molecular neuroscience: MN. 54 (2): 181–187. doi:10.1007/s12031-014-0272-0. ISSN 1559-1166. PMID 24664436.
  25. Badawy, Abdulla A.-B.; Morgan, Christopher J.; Llewelyn, Meirion B.; Albuquerque, Selwyn R.J.; Farmer, Anne (July 2005). "Heterogeneity of serum tryptophan concentration and availability to the brain in patients with the chronic fatigue syndrome". Journal of Psychopharmacology (Oxford, England). 19 (4): 385–391. doi:10.1177/0269881105053293. ISSN 0269-8811. PMID 15982993.
  26. Heyes, M.P.; Saito, K.; Crowley, J.S.; Davis, L.E.; Demitrack, M.A.; Der, M.; Dilling, L.A.; Elia, J.; Kruesi, M.J. (October 1992). "Quinolinic acid and kynurenine pathway metabolism in inflammatory and non-inflammatory neurological disease" (PDF). Brain: A Journal of Neurology. 115 (Pt 5): 1249–1273. doi:10.1093/brain/115.5.1249. ISSN 0006-8950. PMID 1422788.