Variability and magnitude of brain glutamate levels in schizophrenia: a meta and mega-analysis

Kate Merritt, Robert A McCutcheon, André Aleman, Sarah Ashley, Katherine Beck, Wolfgang Block, Oswald J N Bloemen, Faith Borgan, Christiana Boules, Juan R Bustillo, Aristides A Capizzano, Jennifer M Coughlin, Anthony David, Camilo de la Fuente-Sandoval, Arsime Demjaha, Kara Dempster, Kim Q Do, Fei Du, Peter Falkai, Beata Galińska-SkokJürgen Gallinat, Charles Gasparovic, Cedric E Ginestet, Naoki Goto, Ariel Graff-Guerrero, Beng-Choon Ho, Oliver Howes, Sameer Jauhar, Peter Jeon, Tadafumi Kato, Charles A Kaufmann, Lawrence S Kegeles, Matcheri S Keshavan, Sang-Young Kim, Bridget King, Hiroshi Kunugi, J Lauriello, Pablo León-Ortiz, Edith Liemburg, Meghan E Mcilwain, Gemma Modinos, Elias Mouchlianitis, Jun Nakamura, Igor Nenadic, Dost Öngür, Miho Ota, Lena Palaniyappan, James Stone, Philip McGuire, Alice Egerton

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

Glutamatergic dysfunction is implicated in schizophrenia pathoaetiology, but this may vary in extent between patients. It is unclear whether inter-individual variability in glutamate is greater in schizophrenia than the general population. We conducted meta-analyses to assess (1) variability of glutamate measures in patients relative to controls (log coefficient of variation ratio: CVR); (2) standardised mean differences (SMD) using Hedges g; (3) modal distribution of individual-level glutamate data (Hartigan's unimodality dip test). MEDLINE and EMBASE databases were searched from inception to September 2022 for proton magnetic resonance spectroscopy (1H-MRS) studies reporting glutamate, glutamine or Glx in schizophrenia. 123 studies reporting on 8256 patients and 7532 controls were included. Compared with controls, patients demonstrated greater variability in glutamatergic metabolites in the medial frontal cortex (MFC, glutamate: CVR = 0.15, p < 0.001; glutamine: CVR = 0.15, p = 0.003; Glx: CVR = 0.11, p = 0.002), dorsolateral prefrontal cortex (glutamine: CVR = 0.14, p = 0.05; Glx: CVR = 0.25, p < 0.001) and thalamus (glutamate: CVR = 0.16, p = 0.008; Glx: CVR = 0.19, p = 0.008). Studies in younger, more symptomatic patients were associated with greater variability in the basal ganglia (BG glutamate with age: z = -0.03, p = 0.003, symptoms: z = 0.007, p = 0.02) and temporal lobe (glutamate with age: z = -0.03, p = 0.02), while studies with older, more symptomatic patients associated with greater variability in MFC (glutamate with age: z = 0.01, p = 0.02, glutamine with symptoms: z = 0.01, p = 0.02). For individual patient data, most studies showed a unimodal distribution of glutamatergic metabolites. Meta-analysis of mean differences found lower MFC glutamate (g = -0.15, p = 0.03), higher thalamic glutamine (g = 0.53, p < 0.001) and higher BG Glx in patients relative to controls (g = 0.28, p < 0.001). Proportion of males was negatively associated with MFC glutamate (z = -0.02, p < 0.001) and frontal white matter Glx (z = -0.03, p = 0.02) in patients relative to controls. Patient PANSS total score was positively associated with glutamate SMD in BG (z = 0.01, p = 0.01) and temporal lobe (z = 0.05, p = 0.008). Further research into the mechanisms underlying greater glutamatergic metabolite variability in schizophrenia and their clinical consequences may inform the identification of patient subgroups for future treatment strategies.

Original languageEnglish
Pages (from-to)2039-2048
Number of pages10
JournalMolecular Psychiatry
Volume28
Issue number5
Early online date17 Feb 2023
DOIs
Publication statusPublished - May 2023

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