Chemical structures and descriptions

Tryptophan metabolites, kynurenines

trp-met

What is measured?

Kynurenine (Kyn), kynurenic acid (KA), quinaldic acid (Qld), anthranilic acid (AA), 3-hydroxykynurenine (HK), xanthurenic acid (XA) and 3-hydroxyanthranilic acid (HAA), picolinic acid (Pic), quinolinic acid (QA), nicotinic acid (NA), nicotinamide (NAM), N1-methylnicotinamide (mNAM).
Method(s): LC-MS/MS (1).

Tryptophan metabolites of the kynurenine pathway

The amino acid tryptophan (Trp) is catabolized mainly through the kynurenine pathway, forming metabolites collectively referred to as kynurenines. Some kynurenines are neuroactive compounds with immunomodulatory effects.
The intial step in this pathway, the conversion of Trp to formylkynurenine (fKyn), is catalyzed by indoleamine 2,3-dioxygenase (IDO), which is activated by pro-inflammatory cytokines, like INFγ and TNFα. fKyn is converted to Kyn, wich in turn is metabolized to HK by the FAD-dependent kynurenine mono-oxygenase (KMO), and then cleaved to HAA by the pyridoxal 5´-phosphate (PLP)-dependent enzyme, kynureninase (KYNU), which also catalyzes the conversion of Kyn to AA. The PLP-dependent enzyme kynurenine transaminase (KAT) catalyzes the formation of two end-stage metabolites, KA (from Kyn) and XA (from HK) (2) (Figure 1).
The downstream metabolite, QA, is converted to nicotinic acid mononucleotide, which is a precursor of niacin and nicotinamide dinucleotide (NAD), i.e. B3 vitamers. N1-methylnicotinamide (mNAM) in urine is used as a marker of niacin status, and administration of NAM resulted in increased plasma concentrations of both NAM and mNAM.
Kynurenic acid (KA) and picolinic acid (Pic) are considered as neuroprotective, whereas 3-hydroxykynurenine (HK) and in particular quinolinic acid (QA) have neuroexcitatory effects (Figure 1). These kynurenines are suggested to be involved in the pathogenesis of some neurodegenerative and neuropsychiatric diseases (2).
The CSF levels of neuroactive kynurenines, KA and HK, show no change (KA) or decrease (HK) with age, whereas the neurotoxic kynurenine, QA, in CSF shows a remarkably strong positive associations with age, but also with markers of neuroinflammation, like neopterin and KTR. These age-related changes may be associated with increasing incidence of neurodegenerative diseases with age (3).
A composite index involving five kynurenines, HKr (HK:(KA+AA+XA+HAA)), is a functional marker of B6 status.

Indication(s)

Investigating risk and pathogenesis of neuropsychiatric, neurodegenerative, cardiovascular, dysmetabolic diseases, cancer and other common chronic conditions.

Specimen, collection and processing

Matrix: EDTA plasma (preferred) or serum. 3-Hydroxykynurenine (HK) and 3-hydroxyanthranilic acid (HAA) decrease (up to 40-70%) whereas anthranilic acid (AA) and in particular nicotinamide (NAM) increase (AA, up to 30%; NAM, up to 300 %) in samples with hemolysis.
Volume: Minimum volume is 60 µL, but 200 µL is optimal and allows reanalysis.
Preparation and stability: The kynurenines have different stability. Kyn and KA are stable, whereas HK and HAA decrease while AA increases during storage of serum/plasma samples. Samples should be put on ice immediately after collection and stored at -80 °C.

Transportation

Frozen, on dry ice. (for general instruction on transportation, click here)

Reported values, interpretation

Reported values: Kyn: 1.0-3.3 µmol/L; KA: 20-100 nmol/L; Qld: 0.2-100 nmol/L; AA: 7-30 nmol/L; HK: 25-80 nmol/L; XA: 2-35 nmol/L; HAA: 10-80 nmol/L; Pic: 20-100 nmol/L; QA: 150-700 nmol/L; NA: < 20 nmol/L; NAM: 100-600 nmol/L; mNAM: 20-250 nmol/L.
Intraclass correlation coefficient (ICC): Kyn: 0.68; KA: 0.68; Qld: na; AA: 0.64; HK: 0.62; XA: 0.58; HAA: 0.54; Pic, na; QA: na; NA: na; NAM: na; mNAM: na.

Literature

1. Midttun, O., Hustad, S., and Ueland, P.M. (2009). Quantitative profiling of biomarkers related to B-vitamin status, tryptophan metabolism and inflammation in human plasma by liquid chromatography/tandem mass spectrometry. Rapid Commun Mass Sp 23, 1371-79.
2. Ueland, P.M., McCann, A., Midttun, Ø., and Ulvik, A. (2017). Inflammation, vitamin B6 and related pathways. Mol Aspects Med 53, 10-27.
3. de Bie, J., Guest, J., Guillemin, G.J., and Grant, R. (2016). Central kynurenine pathway shift with age in women. J Neurochem 136, 995-1003.

Scroll to Top
562 entries « 1 of 29 »
1.

Bakker, Lieke; Ramakers, Inez H G B; van Greevenbroek, Marleen M J; Backes, Walter H; Jansen, Jacobus F A; Schram, Miranda T; van der Kallen, Carla J H; Schalkwijk, Casper G; Wesselius, Anke; Ulvik, Arve; Ueland, Per M; Verhey, Frans R J; Eussen, Simone J P M; Köhler, Sebastian

The kynurenine pathway and markers of neurodegeneration and cerebral small vessel disease: The Maastricht Study Journal Article

In: J Neurol Sci, vol. 474, pp. 123522, 2025, ISSN: 1878-5883.

Abstract | Links | BibTeX

2.

Holthuijsen, Daniëlle D B; van Roekel, Eline H; Bours, Martijn J L; Ueland, Per M; Breukink, Stéphanie O; Janssen-Heijnen, Maryska L G; Konsten, Joop L; Keulen, Eric T P; McCann, Adrian; Brezina, Stefanie; Gigic, Biljana; Kok, Dieuwertje E; Ulrich, Cornelia M; Weijenberg, Matty P; Eussen, Simone J P M

Modeling how iso-caloric macronutrient substitutions are longitudinally associated with plasma kynurenines in colorectal cancer survivors up to 12 months post-treatment Journal Article

In: J Nutr Biochem, vol. 141, pp. 109910, 2025, ISSN: 1873-4847.

Abstract | Links | BibTeX

3.

Belen, Sergen; Patt, Nadine; Kupjetz, Marie; Ueland, Per M; McCann, Adrian; Gonzenbach, Roman; Bansi, Jens; Zimmer, Philipp

Vitamin B status is related to disease severity and modulated by endurance exercise in individuals with multiple sclerosis: a secondary analysis of a randomized controlled trial Journal Article

In: Am J Clin Nutr, vol. 121, no. 6, pp. 1403–1414, 2025, ISSN: 1938-3207.

Abstract | Links | BibTeX

4.

Dahl, Tuva B; Aftab, Friha; Prebensen, Christian; Berdal, Jan-Erik; Ueland, Thor; Barratt-Due, Andreas; Riise, Anne Ma Dyrhol; Ueland, Per Magne; Hov, Johannes R; Trøseid, Marius; Aukrust, Pål; Gregersen, Ida; Myhre, Peder L; Omland, Torbjørn; Halvorsen, Bente

Imidazole propionate is increased in severe COVID-19 and correlates with cardiac involvement Miscellaneous

2025, ISSN: 1532-2742.

Links | BibTeX

5.

Banjara, Sarala; Berggreen, Ellen; Igland, Jannicke; Åstrøm, Anne-Kristine; Midttun, Øivind; Bunæs, Dagmar; Sulo, Gerhard

Plasma levels of immune system activation markers Neopterin and Kynurenine-to-Tryptophan Ratio, and oral health among community-dwelling adults in Norway: a population-based, cohort study Journal Article

In: Acta Odontol Scand, vol. 84, pp. 218–225, 2025, ISSN: 1502-3850.

Abstract | Links | BibTeX

6.

Holthuijsen, Daniëlle D B; Rijnhart, Judith J M; Bours, Martijn J L; van Roekel, Eline H; Ueland, Per M; Breukink, Stéphanie O; Janssen-Heijnen, Maryska L G; Konsten, Joop L; Keulen, Eric T P; McCann, Adrian; Brezina, Stefanie; Gigic, Biljana; Ulrich, Cornelia M; Weijenberg, Matty P; Eussen, Simone J P M

Longitudinal associations of dietary intake with fatigue in colorectal cancer survivors up to 1 year post-treatment, and the potential mediating role of the kynurenine pathway Journal Article

In: Brain Behav Immun, vol. 126, pp. 144–159, 2025, ISSN: 1090-2139.

Abstract | Links | BibTeX

7.

Joisten, Niklas; Reuter, Marcel; Rosenberger, Friederike; Venhorst, Andreas; Kupjetz, Marie; Walzik, David; Schenk, Alexander; McCann, Adrian; Ueland, Per Magne; Meyer, Tim; Zimmer, Philipp

Exercise training restores longevity-associated tryptophan metabolite 3-hydroxyanthranilic acid levels in middle-aged adults Journal Article

In: Acta Physiol (Oxf), vol. 241, no. 5, pp. e70041, 2025, ISSN: 1748-1716.

Abstract | Links | BibTeX

8.

Jørgensen, Silje F; Braadland, Peder R; Ueland, Thor; Fraz, Mai S A; Michelsen, Annika E; Holm, Kristian; Osnes, Liv T; Trøseid, Marius; Ueland, Per Magne; Fevang, Børre; Aukrust, Pål; Hov, Johannes R

Tryptophan-kynurenine metabolites associate with inflammation and immunologic phenotypes in common variable immunodeficiency Journal Article

In: J Allergy Clin Immunol, 2025, ISSN: 1097-6825.

Abstract | Links | BibTeX

9.

Grytten, Elise; Laupsa-Borge, Johnny; Cetin, Kaya; Bohov, Pavol; Nordrehaug, Jan Erik; Skorve, Jon; Berge, Rolf K; Strand, Elin; Bjørndal, Bodil; Nygård, Ottar K; Rostrup, Espen; Mellgren, Gunnar; Dankel, Simon N

Inflammatory markers after supplementation with marine n-3 or plant n-6 PUFAs: A randomized double-blind crossover study Journal Article

In: J Lipid Res, vol. 66, no. 4, pp. 100770, 2025, ISSN: 1539-7262.

Abstract | Links | BibTeX

10.

Trollebø, Marte A; Tangvik, Randi J; Skeie, Eli; Nygård, Ottar; Eagan, Tomas M L; McCann, Adrian; Dierkes, Jutta

Metabolic profiles and malnutrition in hospitalized adults: A metabolomic cohort study Journal Article

In: JPEN J Parenter Enteral Nutr, vol. 49, no. 3, pp. 365–372, 2025, ISSN: 1941-2444.

Abstract | Links | BibTeX

11.

Valim, Valéria; Oliveira, Fabíola R; Miyamoto, Samira T; Serrano, Érica V; Balarini, Gabriela M; Tanure, Leandro A; Ferreira, Gilda A; Zandonade, Eliana; Brun, Johan G; Jonsson, Malin; Maeland, Elisabeth; Ulvik, Arve; Ueland, Per Magne; Jonsson, Roland; Mydel, Piotr M

Kynurenines and neopterin are interferon-gamma-inducible biomarkers for Sjögren's disease Journal Article

In: Rheumatology (Oxford), 2025, ISSN: 1462-0332.

Abstract | Links | BibTeX

12.

Wilson, Edward N; Umans, Jacob; Swarovski, Michelle S; Minhas, Paras S; Mendiola, Justin H; Midttun, Øivind; Ulvik, Arve; Shahid-Besanti, Marian; Linortner, Patricia; Mhatre, Siddhita D; Wang, Qian; Channappa, Divya; Corso, Nicole K; Tian, Lu; Fredericks, Carolyn A; Kerchner, Geoffrey A; Plowey, Edward D; Cholerton, Brenna; Ueland, Per M; Zabetian, Cyrus P; Gray, Nora E; Quinn, Joseph F; Montine, Thomas J; Sha, Sharon J; Longo, Frank M; Wolk, David A; Chen-Plotkin, Alice; Henderson, Victor W; Wyss-Coray, Tony; Wagner, Anthony D; Mormino, Elizabeth C; Aghaeepour, Nima; Poston, Kathleen L; Andreasson, Katrin I

Parkinson's disease is characterized by vitamin B6-dependent inflammatory kynurenine pathway dysfunction Journal Article

In: NPJ Parkinsons Dis, vol. 11, no. 1, pp. 96, 2025, ISSN: 2373-8057.

Abstract | Links | BibTeX

13.

Ramos-Rodríguez, Carla; Rojas-Gomez, Alejandra; Santos-Calderón, Luis A; Ceruelo, Santiago; Ríos, Lídia; Ueland, Per M; Fernandez-Ballart, Joan D; Salas-Huetos, Albert; Murphy, Michelle M

The l-Arginine pathway may act as a mediator in the association between impaired one-carbon metabolism and hypertension Journal Article

In: Biochimie, vol. 230, pp. 86–94, 2025, ISSN: 1638-6183.

Abstract | Links | BibTeX

14.

Svenningsson, Mads M; Svingen, Gard Ft; Ueland, Per M; Sulo, Gerhard; Bjørnestad, Espen Ø; Pedersen, Eva R; Dhar, Indu; Nilsen, Dennis W; Nygård, Ottar

Elevated plasma trimethyllysine is associated with incident atrial fibrillation Journal Article

In: Am J Prev Cardiol, vol. 21, pp. 100932, 2025, ISSN: 2666-6677.

Abstract | Links | BibTeX

15.

Damerell, Victoria; Klaassen-Dekker, Niels; Brezina, Stefanie; Ose, Jennifer; Ulvik, Arve; van Roekel, Eline H; Holowatyj, Andreana N; Baierl, Andreas; Böhm, Jürgen; Bours, Martijn J L; Brenner, Hermann; de Wilt, Johannes H W; Grady, William M; Habermann, Nina; Hoffmeister, Michael; Keski-Rahkonen, Pekka; Lin, Tengda; Schirmacher, Peter; Schrotz-King, Petra; Ulrich, Alexis B; van Duijnhoven, Fränzel J B; Warby, Christy A; Shibata, David; Toriola, Adetunji T; Figueiredo, Jane C; Siegel, Erin M; Li, Christopher I; Gsur, Andrea; Kampman, Ellen; Schneider, Martin; Ueland, Per M; Weijenberg, Matty P; Ulrich, Cornelia M; Kok, Dieuwertje E; and, Biljana Gigic

Circulating tryptophan-kynurenine pathway metabolites are associated with all-cause mortality among patients with stage I-III colorectal cancer Journal Article

In: Int J Cancer, vol. 156, no. 3, pp. 552–565, 2025, ISSN: 1097-0215.

Abstract | Links | BibTeX

16.

Fossdal, Guri; Braadland, Peder; Hov, Johannes Roksund; Husebye, Eystein Sverre; Folseraas, Trine; Ueland, Per Magne; Ulvik, Arve; Karlsen, Tom Hemming; Berge, Rolf Kristian; Vesterhus, Mette

Mitochondrial dysfunction and lipid alterations in primary sclerosing cholangitis Journal Article

In: Scand J Gastroenterol, vol. 60, no. 2, pp. 165–173, 2025, ISSN: 1502-7708.

Abstract | Links | BibTeX

17.

Walzik, David; Joisten, Niklas; Schenk, Alexander; Trebing, Sina; Schaaf, Kirill; Metcalfe, Alan J; Spiliopoulou, Polyxeni; Hiefner, Johanna; McCann, Adrian; Watzl, Carsten; Ueland, Per Magne; Gehlert, Sebastian; Worthmann, Anna; Brenner, Charles; Zimmer, Philipp

Acute exercise boosts NAD metabolism of human peripheral blood mononuclear cells Journal Article

In: Brain Behav Immun, vol. 123, pp. 1011–1023, 2025, ISSN: 1090-2139.

Abstract | Links | BibTeX

18.

Santos-Calderón, Luis A; Cavallé-Busquets, Pere; Ramos-Rodríguez, Carla; Grifoll, Carme; Rojas-Gómez, Alejandra; Ballesteros, Mónica; Ueland, Per M; Murphy, Michelle M

Folate and cobalamin status, indicators, modulators, interactions, and reference ranges from early pregnancy until birth: the Reus-Tarragona birth cohort study Journal Article

In: Am J Clin Nutr, vol. 120, no. 5, pp. 1269–1283, 2024, ISSN: 1938-3207.

Abstract | Links | BibTeX

19.

Anfinsen, Åslaug Matre; Myklebust, Vilde Haugen; Johannesen, Christina Osland; Christensen, Jacob Juel; Laupsa-Borge, Johnny; Dierkes, Jutta; Nygård, Ottar; McCann, Adrian; Rosendahl-Riise, Hanne; Lysne, Vegard

Serum concentrations of lipids, ketones and acylcarnitines during the postprandial and fasting state: the Postprandial Metabolism (PoMet) study in healthy young adults Journal Article

In: Br J Nutr, vol. 132, no. 7, pp. 851–861, 2024, ISSN: 1475-2662.

Abstract | Links | BibTeX

20.

Holthuijsen, Daniëlle D B; van Roekel, Eline H; Bours, Martijn J L; Ueland, Per M; Breukink, Stéphanie O; Janssen-Heijnen, Maryska L G; Keulen, Eric T P; Brezina, Stefanie; Gigic, Biljana; Peoples, Anita R; Ulrich, Cornelia M; Ulvik, Arve; Weijenberg, Matty P; Eussen, Simone J P M

Longitudinal associations of plasma kynurenines and ratios with fatigue and quality of life in colorectal cancer survivors up to 12 months post-treatment Journal Article

In: Int J Cancer, vol. 155, no. 7, pp. 1172–1190, 2024, ISSN: 1097-0215.

Abstract | Links | BibTeX

562 entries « 1 of 29 »

Olink Proteomics

Please fill out the fields below (*required).
We will respond to you ASAP.
Thank you!

Customized analyses

Please fill out the fields below (*required).
We will reply to you soon for a detailed project discussion.
Thank you for reaching out to Bevital!

Mix-and-Match

Please fill out the fields below (*required).
We will respond to you as soon as possible.

Ready-to-Run

Please fill out the fields below (*required).
We will respond ASAP.
Thank you!

Thanks for joining!

Get updates about new method developments, publications and comming events.