BEVITAL AS

Targeted Metabolomics Services

Tryptophan, kynurenine and the KTR

kyn-trp
Updated 21/12/2022

What is the kynurenine/tryptophan ratio (KTR)?

Kynurenine (Kyn) is formed from the essential amino acid tryptophan (Trp). One enzyme involved in this reaction is indolamine 2,3-dioxygenase (IDO), which is upregulated by various cytokines, in particular INF-gamma. This explains why immune activation leads to formation of kynurenine and depletion of tryptophan. Thus, the kynurenine/tryptophan ratio (KTR) is a marker of cellular (Th-1 type) immune response (3).
Method: LC-MS/MS

Indication(s)

Assessment of cellular immune response.

Specimen, collection and processing

Patient/subject: Reduced kynurenine levels are observed after reduced dietary intake of tryptophan.
Matrix: EDTA plasma and serum.
Volume: Minimum volume is 60 µL, but 200 µL is optimal and allows reanalysis.
Preparation and stability: The blood sample must be centrifuged and the plasma/serum fraction put on ice, and frozen. Kynurenine and tryptophan are stable.

Transportation

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

Reported values, interpretation

Reported values: Kyn: 1.0-3.3 µmol/L; Trp: 40-90 µmol/L.
Intraclass correlation coefficients (ICC) (Kyn/Trp/KTR): 0.68/0.51/0.67.

Literature

1. Midttun, Ø., McCann, A., Aarseth, O., Krokeide, M., Kvalheim, G., Meyer, K., and Ueland, P.M. (2016). Combined measurement of 6 fat-soluble vitamins and 26 water-soluble functional vitamin markers and amino acids in 50 μL of serum or plasma by high-throughput mass spectrometry. Anal Chem 88, 10427-436.
2. 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.
3. Ueland, P. M., A. McCann, O. Midttun and A. Ulvik (2017) Inflammation, vitamin B6 and related pathways. Mol Aspects Med 53:10-27.

This website uses cookies. By continuing to use this site, you accept our use of cookies.  Learn more

Scroll to Top

Join our Mailing list!

Get updates of our latest articles, events and method developments.