Serum tryptophan, kynurenine, phenylalanine, tyrosine and neopterin concentrations in 100 healthy blood donors

Abstract

<jats:title>Abstract</jats:title><jats:p>Formation of neopterin, a biomarker of the activated human immune system, is linked with tryptophan (TRP) and phenylalanine (PHE) metabolism. To obtain normal values, in this study, serum concentrations of neopterin as well as of TRP, PHE and their respective metabolites kynurenine (KYN) and tyrosine (TYR) were investigated in 100 successive blood donor serum specimens from the University Clinics of Innsbruck, Austria. In addition, nitrite concentrations were determined. Donors had passed anamnestic examination at entry and were therefore considered as healthy. The mean age of participants was 49±11.4 (mean±SD) years; 18% were older than 60 years. Both genders were included in the analysis. Neopterin concentrations measured by enzyme-linked immunosorbent assay were 5.9±1.6 nmol/L (mean±SD). Levels of amino acids and metabolites were determined by HPLC. Mean KYN and TRP concentrations were 1.78±0.42 μmol/L and 67.4±10.2 μmol/L, respectively. KYN to TRP ratio (KYN/TRP), an estimate for the activity of tryptophan-degrading enzyme indoleamine 2,3-dioxygenase, was 26.7±6.2 μmol/mmol. Mean PHE and TYR concentrations were 65.2±11.1 μmol/L and 90.6±22.9 μmol/L. PHE to TYR ratio (PHE/TYR), an estimate for the activity of PHE-converting enzyme phenylalanine hydroxylase, was 0.75±0.14 μmol/μmol. Nitrite concentrations, estimated by Griess-Ilosvay reagent, were 44.9±32.0 μmol/L. Males were taller and heavier than females (both p&lt;0.01), but body mass index did not differ. Males presented with significantly higher TRP and TYR concentrations than females (both p&lt;0.05). There existed significant correlations between neopterin and KYN (rs=0.368), KYN/TRP (rs=0.453), TYR (rs=–0.267; all p&lt;0.01) and PHE/TYR (rs=0.236; p&lt;0.05) concentrations. Data indicate that also in a population of healthy individuals an association exists between “low-grade” immune activation as is indicated by slightly higher neopterin concentrations and biochemical alterations in the amino acid metabolism. Although minor, such changes may interfere with psychoneuroimmunological regulatory networks and thus be of clinical relevance.</jats:p>

Assessment of neopterin and indoleamine 2,3‐dioxygenase activity in patients with seasonal influenza: A pilot study

“…Fourteen serum samples of patients with confirmed influenza infection (Flu A: Flu B = 13:1) were identified in our biobank and subsequently analyzed and compared to a healthy historical cohort. The exact details of the control cohort are described elsewhere …”

“…These results were compared to a historical cohort of 100 healthy volunteers . The healthy volunteers were recruited from the Central Institute of Blood Transfusion and Immunology of the University Clinics Innsbruck after exclusion of infection or active diseases.…”

“…The mean age of the cohort was 49 ± 11.4 years, and 42 participants were women. (The demographics of the cohort are described in Table and were published previously ).…”

Probiotic Supplements Beneficially Affect Tryptophan–Kynurenine Metabolism and Reduce the Incidence of Upper Respiratory Tract Infections in Trained Athletes: A Randomized, Double-Blinded, Placebo-Controlled Trial

“…Pro-inflammatory cascades were found to be associated with disturbed PAH activity [37]. Serum neopterin concentrations were measured by ELISA (BRAHMS Diagnostics, Hennigsdorf, Germany) following the manufacturer’s instructions [38]. …”

Examination of Kynurenine Toxicity on Corneal and Conjunctival Epithelium: In vitro and in vivo Studies

“…The content of KYN estimated by means of paper chromatography and fluorescence spectral analysis is 1 nmol/mL in human aqueous humor and 10–100 nmol/g in lenses [25]. In comparison, the concentration of KYN in human cerebrospinal fluid is 134.5 nM [26] and in serum 1.8 μM [27, 28]. A topical application of KYN is considered to be safe [7].…”