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Blood-based kynurenine pathway alterations in schizophrenia spectrum disorders

Journal Contribution - Journal Article

Subtitle:a meta-analysis
Introduction: The kynurenine pathway (KP) has been proposed as indirect link between systemic immune responses and clinical symptom development in schizophrenia spectrum disorders (SSD). Empirical evidence for such immune-related KP shifts in SSD has however resulted in divergent findings. Methods: We conducted a systematic literature search in PubMed. Thirty papers (total number of patients n = 1506; controls: n = 1432) reported on peripheral concentrations of KP metabolites in SSD patients versus controls. Six KP metabolites were included in a meta-analysis, with secondary analysis of covariate and subgroup effects of patients' symptomatic state, age and duration of illness. Results: Tryptophan (SMD: -0.30; p = .003) and Xanthurenic Acid (SMD: -0.80; p < .001) were significantly decreased in SSD compared to controls, while Quinolinic Acid (SMD: -0.40; p = .08) and Kynurenic Acid (SMD: -0.39; p = .04) were only significantly decreased in patients with acute or highly symptomatic illness. Finally, in relatively older patient cohorts Kynurenine (SMD: -0.31; p = .02) and Kynurenic Acid (SMD: -0.40; p = .002) were found to be decreased. Conclusion: A partial downregulation of the KP is observed in SSD patients, in particular during acute symptomatic states and in older age, effects that were independent from each other. In contrast, younger and stable or remitted patients display limited to no KP metabolite abnormalities. The current meta-analysis illustrates the dynamic nature of KP abnormalities. It should be noted that all included studies investigated peripheral KP metabolites, which do not necessarily reflect central KP metabolite abnormalities in schizophrenic patients. (C) 2020 Elsevier B.V. All rights reserved.
Journal: Schizophrenia research
ISSN: 0920-9964
Volume: 223
Pages: 43 - 52
Publication year:2020
Keywords:A1 Journal article
BOF-keylabel:yes
BOF-publication weight:2
CSS-citation score:1
Authors from:Higher Education
Accessibility:Closed