ArticleInternational journal of tryptophan research : IJTR2023
Normative Data on Serum and Plasma Tryptophan and Kynurenine Concentrations from 8089 Individuals Across 120 Studies: A Systematic Review and Meta-Analysis.
Article in International journal of tryptophan research : IJTR, 2023. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 11 papers, 1 of them a synthesis that pooled it.
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Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
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Who cites it
11 citing papers in PubMed, 1 synthesis or guideline pooled it, 9 citations in OpenAlex.
- Pooled it
- Methods for storage and determination of tryptophan and serotonin in bovine blood by high-performance liquid chromatography with fluorescence detection.Veterinary and animal science · 2026Article
- Chicken IDO2 and TDO2: Biochemical Characteristics and Regulatory Roles in Avian Tryptophan Metabolism and Inflammatory Response.Animals : an open access journal from MDPI · 2026Article
- Tryptophan-Serotonin-Melatonin Pathway as a Contributor to Changes in Mood and Cognitive Functions Induced by Sleep Deprivation.International journal of molecular sciences · 2026Article
- The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of gut health.Nature reviews. Gastroenterology & hepatology · 2026Article
- Kynurenic acid signaling expands in human and nonhuman primates and impairs dorsolateral prefrontal cortical cognition that is key to mental illness.Molecular psychiatry · 2026Article
- The gut microbiota-aromatic amino acid axis in cardiovascular disease: pathophysiological roles, translational biomarkers, and therapeutic targeting.Frontiers in cardiovascular medicine · 2026Review
- The kynurenine pathway in depression and schizophrenia: convergent signals, divergent states, and clinical signatures.EXCLI journal · 2026Review
- Production, Mechanisms, and Therapeutic Strategies of Tryptophan Metabolites in CNS Diseases.Molecular neurobiology · 2025Review
- Functional characterization of engineered bacterial biosensors for kynurenine detection.Access microbiology · 2025Article
- Comparing plasma levels and ratios of tryptophan, serotonin, kynurenine and quinolinic acid between patients with bipolar disorder and healthy controls: impact of depressive episode or post-traumatic stress disorder symptoms.Frontiers in psychiatry · 2025Article
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
5 authors at 3 institutions in 1 country.
Funding
No grant is acknowledged in the PubMed record.
Abstract
In this systematic review and meta-analysis, a normative dataset is generated from the published literature on the kynurenine pathway in control participants extracted from case-control and methodological validation studies. Study characteristics were mapped, and studies were evaluated in terms of analytical rigour and methodological validation. Meta-analyses of variance between types of instruments, sample matrices and metabolites were conducted. Regression analyses were applied to determine the relationship between metabolite, sample matrix, biological sex, participant age and study age. The grand mean concentrations of tryptophan in the serum and plasma were 60.52 ± 15.38 μM and 51.45 ± 10.47 μM, respectively. The grand mean concentrations of kynurenine in the serum and plasma were 1.96 ± 0.51 μM and 1.82 ± 0.54 μM, respectively. Regional differences in metabolite concentrations were observed across America, Asia, Australia, Europe and the Middle East. Of the total variance within the data, mode of detection (MOD) accounted for up to 2.96%, sample matrix up to 3.23%, and their interaction explained up to 1.53%; the latter of which was determined to be negligible. This review was intended to inform future empirical research and method development studies and successfully synthesised pilot data. The pilot data reported in this study will inform future precision medicine initiatives aimed at targeting the kynurenine pathway by improving the availability and quality of normative data.
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