ArticleInternational journal of tryptophan research : IJTR2016
Assessment of the Human Kynurenine Pathway: Comparisons and Clinical Implications of Ethnic and Gender Differences in Plasma Tryptophan, Kynurenine Metabolites, and Enzyme Expressions at Baseline and After Acute Tryptophan Loading and Depletion.
Article in International journal of tryptophan research : IJTR, 2016. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 46 papers, 3 of them syntheses 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
46 citing papers in PubMed, 3 syntheses or guidelines pooled it, 72 citations in OpenAlex.
- Sex Differences in Tryptophan Metabolism: A Systematic Review Focused on Neuropsychiatric Disorders.International journal of molecular sciences · 2023Pooled it
- A systematic review and meta-analysis of the kynurenine pathway of tryptophan metabolism in rheumatic diseases.Frontiers in immunology · 2023Pooled it
- Systematic Review of the Kynurenine Pathway and Psychoneurological Symptoms Among Adult Cancer Survivors.Biological research for nursing · 2020Pooled it
- Tryptophan challenge in individuals with schizophrenia and healthy controls: acute effects on circulating kynurenine and kynurenic acid, cognition and cerebral blood flow.Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology · 2023Trial
- Effects of biperiden and acute tryptophan depletion and their combination on verbal word memory and EEG.Psychopharmacology · 2017Trial
- Dietary tryptophan augments cancer-associated venous thrombogenicity mitigated by indoleamine 2,3-dioxygenase 1 inhibition.Blood advances · 2025Article
- Association of habitual diet with skeletal muscle composition in a cross-sectional, population-based imaging study.Nutrition journal · 2025Article
- Serum metabolomic analysis of lumbar disc herniation at different location based on UPLC-QTOF-MS/MS: a population study.Journal of orthopaedics · 2025Article
- Review
- The Kynurenine Pathway and Indole Pathway in Tryptophan Metabolism Influence Tumor Progression.Cancer medicine · 2025Review
- Dysregulated tryptophan metabolism contributes to metabolic syndrome in Chinese community-dwelling older adults.BMC endocrine disorders · 2025Article
- Advances in the Treatment of Cognitive Impairment in Schizophrenia: Targeting NMDA Receptor Pathways.International journal of molecular sciences · 2024Review
- The Complex World of Kynurenic Acid: Reflections on Biological Issues and Therapeutic Strategy.International journal of molecular sciences · 2024Review
- Salivary Tryptophan as a Metabolic Marker of HER2-Negative Molecular Subtypes of Breast Cancer.Metabolites · 2024Article
- Sex- and suicide-specific alterations in the kynurenine pathway in the anterior cingulate cortex in major depression.Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology · 2024Article
- Periconceptional Non-medical Maternal Determinants Influence the Tryptophan Metabolism: The Rotterdam Periconceptional Cohort (Predict Study).International journal of tryptophan research : IJTR · 2024Article
- Article
- Lower levels of the neuroprotective tryptophan metabolite, kynurenic acid, in users of estrogen contraceptives.Scientific reports · 2023Article
- The kynurenine pathway of tryptophan metabolism: a neglected therapeutic target of COVID-19 pathophysiology and immunotherapy.Bioscience reports · 2023Article
- Quantitation of tryptophan and kynurenine in human plasma using 4-vinylphenylboronic acid column by capillary electrochromatography coupled with mass spectrometry.Electrophoresis · 2023Article
Corrections and comments
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Authors and funding
2 authors at 2 institutions in 2 countries.
Funding
Abstract
Tryptophan (Trp) metabolism via the kynurenine pathway (KP) was assessed in normal healthy US volunteers at baseline and after acute Trp depletion (ATD) and acute Trp loading (ATL) using amino acid formulations. The hepatic KP accounts for ~90% of overall Trp degradation. Liver Trp 2,3-dioxygenase (TDO) contributes ~70% toward Trp oxidation, with the remainder achieved by subsequent rate-limiting enzymes in the KP. TDO is not influenced by a 1.15 g Trp load, but is maximally activated by a 5.15 g dose. We recommend a 30 mg/kg dose for future ATL studies. ATD activates TDO and enhances the Trp flux down the KP via its leucine component. Higher plasma free [Trp] and lower total [Trp] are observed in women, with no gender differences in kynurenines. Kynurenic acid is lower in female Caucasians, which may explain their lower incidence of schizophrenia. African-American and Hispanic women have a lower TDO and Trp oxidation relative to free Trp than the corresponding men. African-American women have a potentially higher 3-hydroxyanthranilic acid/anthranilic acid ratio, which may protect them against osteoporosis. Future studies of the KP in relation to health and disease should focus on gender and ethnic differences.
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