SynthesisMolecular psychiatry2022
The tryptophan catabolite or kynurenine pathway in schizophrenia: meta-analysis reveals dissociations between central, serum, and plasma compartments.
Synthesis in Molecular psychiatry, 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 41 papers, 4 of them syntheses that pooled it.
What it found
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Who cites it
41 citing papers in PubMed, 4 syntheses or guidelines pooled it, 78 citations in OpenAlex.
- Multimodal microglial and kynurenine pathway alterations across the affective-psychosis spectrum: a systematic review of patterns, heterogeneity, and dimensional implications.Molecular psychiatry · 2026Pooled it
- The association between depressive symptoms and sleep quality in patients with multiple sclerosis: a systematic review and meta-analysis.BMC neurology · 2026Pooled it
- Pooled it
- The tryptophan catabolite or kynurenine pathway in COVID-19 and critical COVID-19: a systematic review and meta-analysis.BMC infectious diseases · 2022Pooled it
- Bifidobacterium regulates premature infant gut metabolites, reducing serum inflammatory factors: a randomised controlled trial.Pediatric research · 2025Trial
- Schizophrenia: Converging Neurobiological Mechanisms and Emerging Therapeutic Strategies.Biomolecules · 2026Review
- Kynurenine Pathway Metabolite Levels in Drug Naïve and Risperidone Treated Schizophrenia: Insights From Systemic and Post-Mortem Brain Tissue Analysis.Journal of neurochemistry · 2026Article
- Gut Microbiome Dysregulation Across Schizophrenia Spectrum Disorders: Bacteria-, Fungi- and Virome-Level Alterations with Molecular and Immunological Implications.International journal of molecular sciences · 2026Review
- Molecular mechanisms and therapeutic potential of tryptophan metabolism in gut-brain signaling transduction: a narrative review.Journal of neuroinflammation · 2026Review
- Contextual Regulation of the Kynurenine Pathway and Its Relevance for Personalized Psychiatry.Journal of personalized medicine · 2026Review
- Up-Regulation of Anthranilic Acid Formation and Pro-Cognitive Effect of Indoleamine 2,3-Dioxygenase Inhibition.International journal of tryptophan research : IJTR · 2026Article
- Pilot longitudinal integrated transcriptomic-metabolomic study reveals immune and metabolic signatures in non-hospitalized healthcare workers with long COVID.Frontiers in cellular and infection microbiology · 2026Article
- 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
- Molecular Underpinning of Treatment-Resistant Schizophrenia: A Putative Different Neurobiology from Treatment-Responsive Schizophrenia.International journal of molecular sciences · 2025Review
- Review
- Metabolic Syndrome and Schizophrenia: Adding a Piece to the Interplay Between the Kynurenine Pathway and Inflammation.Metabolites · 2025Review
- Peripheral tryptophan-kynurenine pathway dysfunction in first-episode schizophrenia.Scientific reports · 2025Article
- Identification of Two Flavonoids as New and Safe Inhibitors of Kynurenine Aminotransferase II via Computational and In Vitro Study.Pharmaceuticals (Basel, Switzerland) · 2025Article
- Associations between Kynurenine pathway metabolites and cognitive dysfunction in major depressive disorder.PloS one · 2025Article
Corrections and comments
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Authors and funding
7 authors at 5 institutions in 6 countries.
Funding
No grant is acknowledged in the PubMed record.
Abstract
The tryptophan catabolite (TRYCAT) pathway is implicated in the pathophysiology of schizophrenia (SCZ) since the rate-limiting enzyme indoleamine-dioxygenase (IDO) may be induced by inflammatory and oxidative stress mediators. This systematic review searched PubMed, Web of Science, and Google Scholar for papers published from inception until August 2021 and meta-analyzed the association between SCZ and TRYCATs in the central nervous system (CNS) and peripheral blood. We included 61 studies comprising 2813 patients and 2948 healthy controls. In the CNS we found a significant (p < 0.001) increase in the kynurenine/tryptophan (KYN/TRP) (standardized mean difference, SMD = 0.769, 95% confidence interval, CI: 0.456; 1.082) and kynurenic acid (KA)/KYN + TRP (SMD = 0.697, CI: 0.478-0.917) ratios, KA (SMD = 0.646, CI: 0.422; 0.909) and KYN (SMD = 1.238; CI: 0.590; 1.886), while the 3OH-kynurenine (3HK) + KYN-3-monooxygenase (KMO)/KYN ratio was significantly reduced (SMD = -1.089, CI: -1.682; -0.496). There were significant differences between KYN/TRP, (KYN + KA)/TRP, (3HK + KMO)/KYN, KA, and KYN levels among the CNS and peripheral blood, and among serum and plasma KYN. The only useful peripheral marker of CNS TRYCATs findings was the increased KYN/TRP ratio in serum (SMD = 0.211, CI: 0.056; 0.366, p = 0.007), but not in plasma. There was no significant increase in a neurotoxic composite score based on KYN, 3HK, and picolinic, xanthurenic, and quinolinic acid. SCZ is accompanied by increased IDO activity in the CNS and serum, and reduced KMO activity and a shift towards KA production in the CNS. This CNS TRYCATs profile indicates neuroprotective, negative immunoregulatory and anti-inflammatory effects. Peripheral blood levels of TRYCATs are dissociated from CNS findings except for a modest increase in serum IDO activity.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.