SynthesisBMC infectious diseases2022
The tryptophan catabolite or kynurenine pathway in COVID-19 and critical COVID-19: a systematic review and meta-analysis.
Synthesis in BMC infectious diseases, 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 45 papers, 4 of them syntheses that pooled it.
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Who cites it
45 citing papers in PubMed, 4 syntheses or guidelines pooled it, 75 citations in OpenAlex.
- The association between depressive symptoms and sleep quality in patients with multiple sclerosis: a systematic review and meta-analysis.BMC neurology · 2026Pooled it
- Possible temporal relationship between SARS-CoV-2 infection and anti-NMDA receptor encephalitis: a meta-analysis.Translational psychiatry · 2024Pooled it
- Meta-Analysis of COVID-19 Metabolomics Identifies Variations in Robustness of Biomarkers.International journal of molecular sciences · 2023Pooled it
- Pooled it
- The Divergent Metabolomic Landscape of COVID-19 and Community-Acquired Pneumonia.Critical care explorations · 2026Observational
- Tracking COVID-19 Severity and Progression Through Amines and Lipid Mediators.Journal of medical virology · 2026Article
- Transcriptome changes in circulating immune cells of critical COVID-19 patients predict a specific metabolic and epigenetic imprint.Journal of translational medicine · 2026Article
- Severity-dependent metabolic rewiring in COVID-19 based on untargeted metabolomic profiling of patient plasma.PloS one · 2026Article
- The kynurenine pathway in RNA virus infection: immunometabolic control of antiviral defense and viral persistence.Frontiers in immunology · 2026Review
- Harnessing Dietary Tryptophan: Bridging the Gap Between Neurobiology and Psychiatry in Depression Management.International journal of molecular sciences · 2026Review
- Altered milk tryptophan and tryptophan metabolites in women living with HIV.Nature communications · 2025Article
- Metabolomics Signatures of a Respiratory Tract Infection During an Altitude Training Camp in Elite Rowers.Metabolites · 2025Article
- Gut microbiota alterations are linked to COVID-19 severity in North African and European populations.NPJ biofilms and microbiomes · 2025Article
- Hydrogen sulfide (H2S) coordinates redox balance, carbon metabolism, and mitochondrial bioenergetics to suppress SARS-CoV-2 infection.PLoS pathogens · 2025Article
- CD103+ dendritic cell-fibroblast crosstalk via TLR9, TDO2, and AHR signaling drives lung fibrogenesis.JCI insight · 2025Article
- Complementary immunoregulatory effects ofCurrent research in microbial sciences · 2025Article
- Respiratory diseases and the gut microbiota: an updated review.Frontiers in cellular and infection microbiology · 2025Review
- Longitudinal Metabolomics Reveals Metabolic Dysregulation Dynamics in Patients with Severe COVID-19.Metabolites · 2024Article
- The Biology and Biochemistry of Kynurenic Acid, a Potential Nutraceutical with Multiple Biological Effects.International journal of molecular sciences · 2024Review
- Laboratory parameters related to disease severity and physical performance after reconvalescence of acute COVID-19 infection.Scientific reports · 2024Article
Corrections and comments
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Authors and funding
6 authors at 4 institutions in 4 countries.
Funding
No grant is acknowledged in the PubMed record.
Abstract
backgroundCoronavirus disease 2019 (COVID-19) is accompanied by activated immune-inflammatory pathways and oxidative stress, which both induce indoleamine-2,3-dioxygenase (IDO), a key enzyme of the tryptophan (TRP) catabolite (TRYCAT) pathway. The aim of this study was to systematically review and meta-analyze the status of the TRYCAT pathway, including the levels of TRP and kynurenine (KYN) and the activity of IDO, as measured by the ratio of KYN/TRP.
methodsThis systematic review searched PubMed, Google Scholar, and Web of Sciences and included 14 articles that compared TRP and tryptophan catabolites (TRYCATs) in COVID-19 patients versus non-COVID-19 controls, as well as severe/critical versus mild/moderate COVID-19. The analysis was done on a total of 1269 people, including 794 COVID-19 patients and 475 controls.
resultsThe results show a significant (p < 0.0001) increase in the KYN/TRP ratio (standardized mean difference, SMD = 1.099, 95% confidence interval, CI: 0.714; 1.484) and KYN (SMD = 1.123, 95% CI: 0.730; 1.516) and significantly lower TRP (SMD = - 1.002, 95%CI: - 1.738; - 0.266) in COVID-19 versus controls. The KYN/TRP ratio (SMD = 0.945, 95%CI: 0.629; 1.262) and KYN (SMD = 0.806, 95%CI: 0.462; 1.149) were also significantly (p < 0.0001) higher and TRP lower (SMD = - 0.909, 95% CI: - 1.569; - 0.249) in severe/critical versus mild/moderate COVID-19. No significant difference was detected in kynurenic acid (KA) and the KA/KYN ratio between COVID-19 patients and controls.
conclusionsOur results indicate increased activity of the IDO enzyme in COVID-19 and severe/critical patients. The TRYCAT pathway is implicated in the pathophysiology and progression of COVID-19 and may signal a worsening outcome of the disease.
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Registered trials
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