Abstract
Background: Tryptophan metabolism plays important roles in health and diseases. Although simultaneous measurements of tryptophan metabolites are successfully measured, influences of age, gender, and clot formation on the measurements have not been reported. Methods: We took blood from young and old Japanese men and women and compared plasma levels of tryptophan metabolites. We also took plasma and serum from the blood of middle-aged men (n = 10). Metabolites analysis was performed by a liquid chromatograph tandem mass spectrometer, the LCMS-8060 quadrupole mass spectrometer combined with Nexera X2 liquid chromatograph system (Shimadzu Corporation, Kyoto, Japan). Body mass index (BMI) and TRP metabolites have been measured in healthy young men (n = 48), young women (n = 47), old men (n = 44), and old women (n = 39). TRP metabolites were measured by using the ultrahigh speed liquid chromatography-mass spectroscopy (Shimadzu Corporation). Results: Tryptophan and its metabolites such as serotonin, 5-hydroxyindole acetic acid, indole-3-acetic acid, kynurenine, anthranilic acid, were higher in young women and old men than young men and old women. Plasma levels of 3-hydroxykynurenine and xanthurenic acid were lower in young women and old men. Comparison of plasma and serum indicates that most of metabolites were higher in serum than plasma except for 3-hydroxy-kynurenine and quinolinic acid. Conclusion: Metabolites of the upper stream of degradation of tryptophan were higher in young women and old men than young men and old women, which suggests that the degradation of tryptophan was accelerated in young men and old women than young women and old men. Serum preparation may activate tryptophan degradation resulting in higher levels of metabolites in serum than in plasma.
Highlights
Tryptophan (TRP) is an essential amino acid important for protein synthesis, but it becomes a substrate for the generation of several important bioactive compounds
We have recently shown that plasma levels of 5-HT were very low in patients of depression, but 5-HIAA and kynurenine levels were not changed, indicating that the activation of tryptophan in the 5-HT and KYN pathways was not enhanced in depression, but the conversion of 5-HT to 5-HIAA was enhanced [11]
We showed that plasma levels of TRP metabolites were enhanced in patients of type2 diabetes mellitus (DM) [12] [13] [14]
Summary
Tryptophan (TRP) is an essential amino acid important for protein synthesis, but it becomes a substrate for the generation of several important bioactive compounds. Serotonin can be further converted to N-acetylserotonin (NAS) and melatonin, influencing circadian rhythmicity, one of the biological roles for TRP metabolites [2]. In mammals, the majority of free TRP are degraded through the kynurenine (KYN) pathway and generate many metabolites involved in inflammation, immune response, and excitatory neurotransmission [3]. Methods: We took blood from young and old Japanese men and women and compared plasma levels of tryptophan metabolites. Body mass index (BMI) and TRP metabolites have been measured in healthy young men (n = 48), young women (n = 47), old men (n = 44), and old women (n = 39). Results: Tryptophan and its metabolites such as serotonin, 5-hydroxyindole acetic acid, indole-3-acetic acid, kynurenine, anthranilic acid, were higher in young women and old men than young men and old women. Conclusion: Metabolites of the upper stream of degradation of tryptophan were higher in young women and old men than young men and old women, which suggests that the degradation of tryptophan was accelerated in young men and old women than young
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