Proton magnetic resonance spectroscopy and illness stage in schizophrenia--a systematic review and meta-analysis

Applications of MRI in Schizophrenia: Current Progress in Establishing Clinical Utility

Schizophrenia is a severe mental illness that significantly impacts the lives of affected individuals and with increasing mortality rates. Early detection and intervention are crucial for improving outcomes but the lack of validated biomarkers poses great challenges in such efforts. The use of magnetic resonance imaging (MRI) in schizophrenia enables the investigation of the disorder's etiological and neuropathological substrates in vivo. After decades of research, promising findings of MRI have been shown to aid in screening high-risk individuals and predicting illness onset, and predicting symptoms and treatment outcomes of schizophrenia. The integration of machine learning and deep learning techniques makes it possible to develop intelligent diagnostic and prognostic tools with extracted or selected imaging features. In this review, we aimed to provide an overview of current progress and prospects in establishing clinical utility of MRI in schizophrenia. We first provided an overview of MRI findings of brain abnormalities that might underpin the symptoms or treatment response process in schizophrenia patients. Then, we summarized the ongoing efforts in the computer-aided utility of MRI in schizophrenia and discussed the gap between MRI research findings and real-world applications. Finally, promising pathways to promote clinical translation were provided. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 3.

Cortical glutamate, Glx, and total N-acetylaspartate: potential biomarkers of repetitive transcranial magnetic stimulation treatment response and outcomes in major depression

Repetitive transcranial magnetic stimulation (rTMS) is an effective treatment for individuals with major depressive disorder (MDD) who have not improved with standard therapies. However, only 30-45% of patients respond to rTMS. Predicting response to rTMS will benefit both patients and providers in terms of prescribing and targeting treatment for maximum efficacy and directing resources, as individuals with lower likelihood of response could be redirected to more suitable treatment alternatives. In this exploratory study, our goal was to use proton magnetic resonance spectroscopy to examine how glutamate (Glu), Glx, and total N-acetylaspartate (tNAA) predict post-rTMS changes in overall MDD severity and symptoms, and treatment response. Metabolites were measured in a right dorsal anterior cingulate cortex voxel prior to a standard course of 10 Hz rTMS to the left DLPFC in 25 individuals with MDD. MDD severity and symptoms were evaluated via the Inventory of Depression Symptomatology Self-Report (IDS-SR). rTMS response was defined as ≥50% change in full-scale IDS-SR scores post treatment. Percent change in IDS-SR symptom domains were evaluated using principal component analysis and established subscales. Generalized linear and logistic regression models were used to evaluate the relationship between baseline Glu, Glx, and tNAA and outcomes while controlling for age and sex. Participants with baseline Glu and Glx levels in the lower range had greater percent change in full scale IDS-SR scores post-treatment (p < 0.001), as did tNAA (p = 0.007). Low glutamatergic metabolite levels also predicted greater percent change in mood/cognition symptoms (p ≤ 0.001). Low-range Glu, Glx, and tNAA were associated with greater improvement on the immuno-metabolic subscale (p ≤ 0.003). Baseline Glu predicted rTMS responder status (p = 0.025) and had an area under the receiving operating characteristic curve of 0.81 (p = 0.009), demonstrating excellent discriminative ability. Baseline Glu, Glx, and tNAA significantly predicted MDD improvement after rTMS; preliminary evidence also demonstrates metabolite association with symptom subdomain improvement post-rTMS. This work provides feasibility for a personalized medicine approach to rTMS treatment selection, with individuals with Glu levels in the lower range potentially being the best candidates.

Biomarkers for Psychosis: Are We There Yet? Umbrella Review of 1478 Biomarkers

Background and Hypothesis

This umbrella review aims to comprehensively synthesize the evidence of association between peripheral, electrophysiological, neuroimaging, neuropathological, and other biomarkers and diagnosis of psychotic disorders.

Study Design

We selected systematic reviews and meta-analyses of observational studies on diagnostic biomarkers for psychotic disorders, published until February 1, 2018. Data extraction was conducted according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Evidence of association between biomarkers and psychotic disorders was classified as convincing, highly suggestive, suggestive, weak, or non-significant, using a standardized classification. Quality analyses used the Assessment of Multiple Systematic Reviews (AMSTAR) tool.

Study Results

The umbrella review included 110 meta-analyses or systematic reviews corresponding to 3892 individual studies, 1478 biomarkers, and 392 210 participants. No factor showed a convincing level of evidence. Highly suggestive evidence was observed for transglutaminase autoantibodies levels (odds ratio [OR] = 7.32; 95% CI: 3.36, 15.94), mismatch negativity in auditory event-related potentials (standardized mean difference [SMD] = 0.73; 95% CI: 0.5, 0.96), P300 component latency (SMD = -0.6; 95% CI: -0.83, -0.38), ventricle-brain ratio (SMD = 0.61; 95% CI: 0.5, 0.71), and minor physical anomalies (SMD = 0.99; 95% CI: 0.64, 1.34). Suggestive evidence was observed for folate, malondialdehyde, brain-derived neurotrophic factor, homocysteine, P50 sensory gating (P50 S2/S1 ratio), frontal N-acetyl-aspartate, and high-frequency heart rate variability. Among the remaining biomarkers, weak evidence was found for 626 and a non-significant association for 833 factors.

Conclusions

While several biomarkers present highly suggestive or suggestive evidence of association with psychotic disorders, methodological biases, and underpowered studies call for future higher-quality research.

Progress in the application of molecular imaging in psychiatric disorders

Psychiatric disorders have always attracted a lot of attention from researchers due to the difficulties in their diagnoses and treatments. Molecular imaging, as an emerging technology, has played an important role in the researchers of various diseases. In recent years, molecular imaging techniques including magnetic resonance spectroscopy, nuclear medicine imaging, and fluorescence imaging have been widely used in the study of psychiatric disorders. This review will briefly summarize the progression of molecular imaging in psychiatric disorders.

Advanced imaging in first episode psychosis: a systematic review

First-episode psychosis (FEP) is defined as the first occurrence of delusions, hallucinations, or psychic disorganization of significant magnitude, lasting more than 7 days. Evolution is difficult to predict since the first episode remains isolated in one third of cases, while recurrence occurs in another third, and the last third progresses to a schizo-affective disorder. It has been suggested that the longer psychosis goes unnoticed and untreated, the more severe the probability of relapse and recovery. MRI has become the gold standard for imaging psychiatric disorders, especially first episode psychosis. Besides ruling out some neurological conditions that may have psychiatric manifestations, advanced imaging techniques allow for identifying imaging biomarkers of psychiatric disorders. We performed a systematic review of the literature to determine how advanced imaging in FEP may have high diagnostic specificity and predictive value regarding the evolution of disease.

N-Acetylaspartate and Choline Metabolites in Cortical and Subcortical Regions in Clinical High Risk Relative to Healthy Control Subjects: An Exploratory 7T MRSI Study

N-acetylaspartate (NAA) and choline (Cho) are two brain metabolites implicated in several key neuronal functions. Abnormalities in these metabolites have been reported in both early course and chronic patients with schizophrenia (SCZ). It is, however, unclear whether NAA and Cho's alterations occur even before the onset of the disorder. Clinical high risk (CHR) individuals are a population uniquely enriched for psychosis and SCZ. In this exploratory study, we utilized 7-Tesla magnetic resonance spectroscopic imaging (MRSI) to examine differences in total NAA (tNAA; NAA + N-acetylaspartylglutamate [NAAG]) and major choline-containing compounds, including glycerophosphorylcholine and phosphorylcholine [tCho], over the creatine (Cre) levels between 26 CHR and 32 healthy control (HC) subjects in the subcortical and cortical regions. While no tCho/Cre differences were found between groups in any of the regions of interest (ROIs), we found that CHR had significantly reduced tNAA/Cre in the right dorsal lateral prefrontal cortex (DLPFC) compared to HC, and that the right DLPFC tNAA/Cre reduction in CHR was negatively associated with their positive symptoms scores. No tNAA/Cre differences were found between CHR and HC in other ROIs. In conclusion, reduced tNAA/Cre in CHR vs. HC may represent a putative molecular biomarker for risk of psychosis and SCZ that is associated with symptom severity.

Associations between N-Acetylaspartate and white matter integrity in individuals with schizophrenia and unaffected relatives

Compromised white matter has been reported in schizophrenia; however, few studies have investigated neurochemical abnormalities underlying microstructural differences. N-acetylaspartate (NAA) is used to synthesize myelin and is often reduced in persons with schizophrenia (PSZ) and their unaffected first-degree relatives (REL). Low levels of NAA could affect white matter by preventing the synthesis or repair of myelin. We used magnetic resonance spectroscopy and diffusion tensor imaging to investigate the relationship between NAA and white matter integrity in PSZ. REL were included to examine whether putative relationships are associated with symptom expression or illness liability. 52 controls, 23 REL and 25 PSZ underwent 7T proton magnetic resonance spectroscopy and/or 3T diffusion tensor imaging. NAA in the visual cortex and basal ganglia were measured and compared across groups. Diffusivity measures were compared across groups using tract-based spatial statistics and related to NAA concentrations. Visual cortex NAA was significantly reduced in PSZ compared to controls. White matter integrity did not differ between groups. Reduced cortical and subcortical NAA were associated with diffusivity measures of poor white matter microstructure. These data suggest that levels of neural NAA may be related to white matter integrity similarly across individuals with schizophrenia, those at genetic risk, and controls.

An integrative study of the microbiome gut-brain-axis and hippocampal inflammation in psychosis: Persistent effects from mode of birth

The mechanism producing psychosis appears to include hippocampal inflammation, which could be associated with the microbiome-gut-brain-axis (MGBS). To test this hypothesis we are conducting a multidisciplinary study, herein described. The procedures are illustrated with testing of a single subject and group level information on the impact of C-section birth are presented.

METHOD

Study subjects undergo research diagnostic interviews and symptom assessments to be categorized into one of 3 study groups: psychosis, nonpsychotic affective disorder or healthy control. Hippocampal volume and metabolite concentrations are assessed using 3-dimensional, multi-voxel H1 Magnetic Resonance Imaging (MRSI) encompassing all gray matter in the entire hippocampal volume. Rich self-report information is obtained with the PROMIS interview, which was developed by the NIH Commons for research in chronic conditions. Early trauma is assessed and cognition is quantitated using the MATRICS. The method also includes the most comprehensive autonomic nervous system (ANS) battery used to date in psychiatric research. Stool and oral samples are obtained for microbiome assessments and cytokines and other substances are measured in blood samples.

RESULTS

Group level preliminary data shows that C-section birth is associated with higher concentrations of GLX, a glutamate related hippocampal neurotransmitter in psychotic cases, worse symptoms in affective disorder cases and smaller hippocampal volume in controls.

CONCLUSION

Mode of birth appears to have persistent influences through adulthood. The methodology described for this study will define pathways through which the MGBA may influence the risk for psychiatric disorders.

Markers of Schizophrenia—A Critical Narrative Update

Schizophrenia is a long-term mental disease, associated with functional impairment. Therefore, it is important to make an accurate diagnosis and implement the proper treatment. Biomarkers may be a potential tool for these purposes. Regarding advances in biomarker studies in psychosis, the current symptom-based criteria seem to be no longer sufficient in clinical settings. This narrative review describes biomarkers of psychosis focusing on the biochemical (peripheral and central), neurophysiological, neuropsychological and neuroimaging findings as well as the multimodal approach related with them. Endophenotype markers (especially neuropsychological and occulomotor disturbances) can be currently used in a clinical settings, whereas neuroimaging glutamate/glutamine and D2/D3 receptor density changes, as well as immunological Th2 and PRL levels, seem to be potential biomarkers that need further accuracy tests. When searching for biochemical/immunological markers in the diagnosis of psychosis, the appropriate time of body fluid collection needs to be considered to minimize the influence of the stress axis on their concentrations. In schizophrenia diagnostics, a multimodal approach seems to be highly recommended.

Ex vivo 1H-MRS brain metabolic profiling in a two-hit model of neurodevelopmental disorders: Prenatal immune activation and peripubertal stress

Prenatal infections are environmental risk factors for neurodevelopmental disorders. In addition, traumatic experiences during adolescence in individuals exposed to infections during gestation could increase the risk of schizophrenia. It is of the most crucial importance to discover potential markers of the disease in its early stages or before its onset, so that therapeutic strategies may be implemented. In the present study, we combined a proposed two-hit model of schizophrenia-related symptoms with proton magnetic resonance spectroscopy (¹H-MRS) to discover potential biomarkers. To this end, we i.p. injected 100 μg/kg/ml of lipopolysaccharide (LPS) or saline on gestational days 15 and 16 to pregnant rats. Their male offspring were then subjected to five episodes of stress or handling on alternate days during postnatal days (PND) 28-38. Once the animals reached adulthood (PND70), we evaluated prepulse inhibition (PPI). At PND90, we performed an ex vivo ¹H-MRS study in the cortex and striatum. While we did not detect alterations in PPI at the age tested, we found neurochemical disturbances induced by LPS, stress or (more interestingly) their interaction. LPS decreased glucose levels in the cortex and striatum and altered glutamate, glutamine and N-acetylaspartate levels. Glutamate and glutamine levels in the left (but not right) striatum were differentially affected by prenatal LPS exposure in a manner that depended on stress experiences. These results suggest that alterations in the glutamate cycle in the striatum could be used as early markers of developmental disorders.

Neurometabolic patterns of an "at risk for mental disorders" syndrome involve abnormalities in the thalamus and anterior midcingulate cortex

BACKGROUND

The ultra-high risk (UHR) paradigm allows the investigation of individuals at increased risk of developing psychotic or other mental disorders with the aim of making prevention and early intervention as specific as possible in terms of the individual outcome.

METHODS

Single-session ¹H-/³¹P-Chemical Shift Imaging of thalamus, prefrontal (DLPFC) and anterior midcingulate (aMCC) cortices was applied to 69 UHR patients for psychosis and 61 matched healthy controls. N-acetylaspartate (NAA), glutamate/glutamine complex (Glx), energy (PCr, ATP) and phospholipid metabolites were assessed, analysed by ANOVA (or ANCOVA [with covariates]) and correlated with symptomatology (SCL-90R).

RESULTS

The thalamus showed decreased NAA, inversely correlated with self-rated aggressiveness, as well as increased PCr, and altered phospholipid breakdown. While the aMCC showed a pattern of NAA decrease and PCr increase, the DLPFC showed PCr increase only in the close-to-psychosis patient subgroup. There were no specific findings in transition patients.

CONCLUSION

The results do not support the notion of a specific pre-psychotic neurometabolic pattern, but likely reflect correlates of an "at risk for mental disorders syndrome". This includes disturbed neuronal (mitochondrial) metabolism in the thalamus and aMCC, with emphasis on left-sided structures, and altered PL remodeling across structures.

Glutamate and N-Acetylaspartate Alterations Observed in Early Phase Psychosis: A Systematic Review of Proton Magnetic Resonance Spectroscopy Studies

Glutamate and N-acetylaspartate have been investigated in the neuropathology of chronic schizophrenia, with fewer studies focusing on early phase psychosis. Additionally, there has been little review and synthesis of the literature focused on multiple brain regions. This systematic review aims to provide a clear report of the current state of research on glutamate and n-acetylaspartate concentrations in early phase psychosis (defined as the first five years following psychosis onset) in multiple brain regions. Existing literature was searched systematically to compile reports of glutamate/glutamate+glutamine (Glx) and n-acetylaspartate absolute levels and ratios in both male and female individuals with early phase psychosis. Reports on glutamate/Glx concentrations in the medial prefrontal region and thalamus were varied, but the majority of reports suggested no alterations in EPP. No studies reported glutamate alterations in the hippocampus or cerebellum. There was no evidence for n-acetylaspartate alterations in the caudate, basal ganglia, and medial prefrontal cortex, and minimal evidence for NAA reductions in the thalamus, anterior cingulate cortex, and hippocampus. Future research should focus on the regions that are less commonly reported, and should aim to explore possible confounds, such as medication status and substance use.

Cumulative meta-analysis: What works

To present time-varying evidence, cumulative meta-analysis (CMA) updates results of previous meta-analyses to incorporate new study results. We investigate the properties of CMA, suggest possible improvements and provide the first in-depth simulation study of the use of CMA and CUSUM methods for detection of temporal trends in random-effects meta-analysis. We use the standardized mean difference (SMD) as an effect measure of interest. For CMA, we compare the standard inverse-variance-weighted estimation of the overall effect using REML-based estimation of between-study variance τ 2 with the sample-size-weighted estimation of the effect accompanied by Kulinskaya-Dollinger-Bjørkestøl (Biometrics. 2011; 67:203-212) (KDB) estimation of τ 2 . For all methods, we consider Type 1 error under no shift and power under a shift in the mean in the random-effects model. To ameliorate the lack of power in CMA, we introduce two-stage CMA, in which τ 2 is estimated at Stage 1 (from the first 5-10 studies), and further CMA monitors a target value of effect, keeping the τ 2 value fixed. We recommend this two-stage CMA combined with cumulative testing for positive shift in τ 2 . In practice, use of CMA requires at least 15-20 studies.

Reduced GABA/glutamate in the thalamus of individuals at clinical high risk for psychosis

Youth at clinical high risk (CHR) are a unique population enriched for precursors of major psychiatric disorders, especially schizophrenia (SCZ). Recent neuroimaging findings point to abnormalities in the thalamus of patients with SCZ, including chronic and early course patients, as well as in CHR individuals relative to healthy comparison groups, thus suggesting that thalamic dysfunctions are present even before illness onset. Furthermore, modeling data indicate that alteration between excitatory and inhibitory control, as reflected by alteration in GABAergic and glutamatergic balance (i.e., GABA/Glu), may underlie thalamic deficits linked to the risk and development of psychosis. There is, however, a lack of in vivo evidence of GABA/Glu thalamic abnormalities in the CHR state. Magnetic resonance spectroscopic imaging (MRSI) 7 Tesla (7 T) provides enhanced resolution to quantify GABA and Glu levels in the thalamus of CHR individuals. In this study, we performed 7 T MRSI in 15 CHR and 20 healthy control (HC) participants. We found that GABA/Glu was significantly reduced in the right medial anterior and right medial posterior thalamus of CHR relative to HC groups. The GABA/Glu reduction was negatively correlated with general symptoms in the right medial anterior thalamus, as well as with disorganization symptoms in the right medial posterior thalamus. Altogether, these findings indicate that GABA/Glu abnormalities are present in the thalamus before the onset of full-blown psychosis and are associated with symptom severity, thus providing putative molecular and neuronal targets for early interventions in youth at CHR.

Alterations of neurometabolism in the dorsolateral prefrontal cortex and thalamus in transition to psychosis patients change under treatment as usual - A two years follow-up 1H/31P-MR-spectroscopy study

BACKGROUND

The ultra-high risk (UHR) paradigm allows early contact with patients developing acute psychosis and the study of treatment effects on the underlying pathology.

METHODS

29 patients with first acute psychosis according to CAARMS criteria (transition patients, TP) (T0) and thereof 22 patients after two-year follow-up (mean 788 d) (T1) underwent ¹H-/³¹P-MR spectroscopy of the prefrontal (DLPFC) and anterior midcingulate (aMCC) cortices and the thalamus. N-acetylaspartate (NAA), glutamate (Glu, Glx), energy (PCr, ATP) and phospholipid metabolites (PME, PDE) were compared to 27 healthy controls by ANCOVA and correlated with patients' symptom ratings (BPRS-E, SCL-90R). For longitudinal analysis, linear mixed model (LMM) and ANCOVA for repeated measures were used.

RESULTS

DLPFC: In patients, NAA and PME were decreased bilaterally and Glu on the left side at T0. Left-sided Glu and NAA (trend) and bilateral Glx increased during follow-up. Thalamus: In TP, bilateral NAA, left-sided Glu and right-sided Glx were decreased at T0; bilateral NAA and left-sided Glx increased during follow-up. aMCC: In TP, bilateral NAA, right-sided Glu, and bilateral PME and PDE were decreased, while left-sided PCr was increased at T0. No changes were observed during follow-up.

CONCLUSION

Regardless of the long-term diagnosis, the psychotic state of illness includes disturbed neuronal function in the DLPFC, thalamus and aMCC. Treatment-as-usual (TAU), including antipsychotic/antidepressant medication and supportive psychotherapy, had an effect on the thalamo-frontal area but not or less pronounced on the neurometabolic deficits of the aMCC.

The potential of 1H-MRS in CNS drug development

RATIONALE

Proton magnetic resonance spectroscopy (¹H-MRS) is a cross-species neuroimaging technique that can measure concentrations of several brain metabolites, including glutamate and GABA. This non-invasive method has promise in developing centrally acting drugs, as it can be performed repeatedly within-subjects and be used to translate findings from the preclinical to clinical laboratory using the same imaging biomarker.

OBJECTIVES

This review focuses on the utility of single-voxel ¹H-MRS in developing novel glutamatergic or GABAergic drugs for the treatment of psychiatric disorders and includes research performed in rodent models, healthy volunteers and patient cohorts.

RESULTS

Overall, these studies indicate that ¹H-MRS is able to detect the predicted pharmacological effects of glutamatergic or GABAergic drugs on voxel glutamate or GABA concentrations, although there is a shortage of studies examining dose-related effects. Clinical studies have applied ¹H-MRS to better understand drug therapeutic mechanisms, including the glutamatergic effects of ketamine in depression and of acamprosate in alcohol dependence. There is an emerging interest in identifying patient subgroups with 'high' or 'low' brain regional ¹H-MRS glutamate levels for more targeted drug development, which may require ancillary biomarkers to improve the accuracy of subgroup discrimination.

CONCLUSIONS

Considerations for future research include the sensitivity of single-voxel ¹H-MRS in detecting drug effects, inter-site measurement reliability and the interpretation of drug-induced changes in ¹H-MRS metabolites relative to the known pharmacological molecular mechanisms. On-going technological development, in single-voxel ¹H-MRS and in related complementary techniques, will further support applications within CNS drug discovery.

Advances in multimodal data fusion in neuroimaging: Overview, challenges, and novel orientation

Multimodal fusion in neuroimaging combines data from multiple imaging modalities to overcome the fundamental limitations of individual modalities. Neuroimaging fusion can achieve higher temporal and spatial resolution, enhance contrast, correct imaging distortions, and bridge physiological and cognitive information. In this study, we analyzed over 450 references from PubMed, Google Scholar, IEEE, ScienceDirect, Web of Science, and various sources published from 1978 to 2020. We provide a review that encompasses (1) an overview of current challenges in multimodal fusion (2) the current medical applications of fusion for specific neurological diseases, (3) strengths and limitations of available imaging modalities, (4) fundamental fusion rules, (5) fusion quality assessment methods, and (6) the applications of fusion for atlas-based segmentation and quantification. Overall, multimodal fusion shows significant benefits in clinical diagnosis and neuroscience research. Widespread education and further research amongst engineers, researchers and clinicians will benefit the field of multimodal neuroimaging.

Thalamus-related anomalies as candidate mechanism-based biomarkers for psychosis

Identification of reliable biomarkers of prognosis in subjects with high risk to psychosis is an essential step to improve care and treatment of this population of help-seekers. Longitudinal studies highlight some clinical criteria, cognitive deficits, patterns of gray matter alterations and profiles of blood metabolites that provide some levels of prediction regarding the conversion to psychosis. Further effort is warranted to validate these results and implement these types of approaches in clinical settings. Such biomarkers may however fall short in entangling the biological mechanisms underlying the disease progression, an essential step in the development of novel therapies. Circuit-based approaches, which map on well-identified cerebral functions, could meet these needs. Converging evidence indicates that thalamus abnormalities are central to schizophrenia pathophysiology, contributing to clinical symptoms, cognitive and sensory deficits. This review highlights the various thalamus-related anomalies reported in individuals with genetic risks and in the different phases of the disorder, from prodromal to chronic stages. Several anomalies are potent endophenotypes, while others exist in clinical high-risk subjects and worsen in those who convert to full psychosis. Aberrant functional coupling between thalamus and cortex, low glutamate content and readouts from resting EEG carry predictive values for transition to psychosis or functional outcome. In this context, thalamus-related anomalies represent a valuable entry point to tackle circuit-based alterations associated with the emergence of psychosis. This review also proposes that longitudinal surveys of neuroimaging, EEG readouts associated with circuits encompassing the mediodorsal, pulvinar in high-risk individuals could unveil biological mechanisms contributing to this psychiatric disorder.

Thalamic Nuclei Volumes in Psychotic Disorders and in Youths With Psychosis Spectrum Symptoms

OBJECTIVE

Thalamus models of psychosis implicate association nuclei in the pathogenesis of psychosis and mechanisms of cognitive impairment. Studies to date have provided conflicting findings for structural deficits specific to these nuclei. The authors sought to characterize thalamic structural abnormalities in psychosis and a neurodevelopmental cohort, and to determine whether nuclear volumes were associated with cognitive function.

METHODS

Thalamic nuclei volumes were tested in a cross-sectional sample of 472 adults (293 with psychosis) and the Philadelphia Neurodevelopmental Cohort (PNC), consisting of 1,393 youths (398 with psychosis spectrum symptoms and 609 with other psychopathologies), using a recently developed, validated method for segmenting thalamic nuclei and complementary voxel-based morphometry. Cognitive function was measured with the Screen for Cognitive Impairment in Psychiatry in the psychosis cohort and the Penn Computerized Neurocognitive Battery in the PNC.

RESULTS

The psychosis group had smaller pulvinar, mediodorsal, and, to a lesser extent, ventrolateral nuclei volumes compared with the healthy control group. Youths with psychosis spectrum symptoms also had smaller pulvinar volumes, compared with both typically developing youths and youths with other psychopathologies. Pulvinar volumes were positively correlated with general cognitive function.

CONCLUSIONS

The study findings demonstrate that smaller thalamic association nuclei represent a neurodevelopmental abnormality associated with psychosis, risk for psychosis in youths, and cognitive impairment. Identifying specific thalamic nuclei abnormalities in psychosis has implications for early detection of psychosis risk and treatment of cognitive impairment in psychosis.

Metabolite abnormalities in psychosis risk: A meta-analysis of proton magnetic resonance spectroscopy studies

Accumulating evidence implicates that individuals at high-risk of psychosis have already exhibited pathophysiological changes in brain metabolites including glutamate, gamma-Aminobutyric Acid (GABA), N-Acetylaspartate (NAA), creatine (Cr), myo-inositol (MI) and choline (Cho). These changes may contribute to the development of schizophrenia and associate with psychotic genes. However, specific metabolic changes of brain sub-regions in individuals at risk have still been controversial. Thus, the current study aimed to investigate the brain metabolic changes including glutamate, Glx, GABA, GABA/Glx, NAA, Cr, MI and Cho levels in individuals at risk by conducting a case-control meta-analysis and meta-regression of proton magnetic resonance spectroscopy studies. Primary outcomes revealed that individuals at risk exhibited increased Cr levels at the rostral medial prefrontal cortex (rmPFC), decreased NAA and Cr levels at the thalamus, and increased MI levels at the dorsolateral prefrontal cortex. Sub-group analyses further indicated that individuals with clinical high-risk (CHR) exhibited increased Cr levels at the medial prefrontal cortex (mPFC) and decreased Glx levels at the thalamus, while individuals with genetic risk (siblings of psychiatric patients) exhibited significant increased Glx and MI levels at the mPFC. However, GABA, GABA/Glx and Cho levels showed no significant result. These findings suggest that the dysfunctional metabolites at the mPFC and the thalamus may be an essential neurobiological basis at the early stage of psychosis.

Proton Magnetic Resonance Spectroscopy of N-acetyl Aspartate in Chronic Schizophrenia, First Episode of Psychosis and High-Risk of Psychosis: A Systematic Review and Meta-Analysis

N-acetyl-aspartate (NAA) is a readily measured marker of neuronal metabolism. Previous analyses in schizophrenia have shown NAA levels are low in frontal, temporal and thalamic regions, but may be underpowered to detect effects in other regions, in high-risk states and in first episode psychosis. We searched for magnetic resonance spectroscopy studies comparing NAA in chronic schizophrenia, first episode psychosis and high risk of psychosis to controls. 182 studies were included and meta-analysed using a random-effects model for each region and illness stage. NAA levels were significantly lower than controls in the frontal lobe [Hedge's g = -0.36, p < 0.001], hippocampus [-0.52, p < 0.001], temporal lobe [-0.35, p = 0.031], thalamus [-0.32, p = 0.012] and parietal lobe [-0.25, p = 0.028] in chronic schizophrenia, and lower than controls in the frontal lobe [-0.26, p = 0.002], anterior cingulate cortex [-0.24, p = 0.016] and thalamus [-0.28, p = 0.028] in first episode psychosis. NAA was lower in high-risk of psychosis in the hippocampus [-0.20, p = 0.049]. In schizophrenia, NAA alterations appear to begin in hippocampus, frontal cortex and thalamus, and extend later to many other regions.

Candidate metabolic biomarkers for schizophrenia in CNS and periphery: Do any possible associations exist?

Due to the limitations of analytical techniques and the complicity of schizophrenia, nowadays it is still a challenge to diagnose and stratify schizophrenia patients accurately. Many attempts have been made to identify and validate available biomarkers for schizophrenia from CSF and/or peripheral blood in clinical studies with consideration to disease stages, antipsychotic effects and even gender differences. However, conflicting results handicap the validation and application of biomarkers for schizophrenia. In view of availability and feasibility, peripheral biomarkers have superior advantages over biomarkers in CNS. Meanwhile, schizophrenia is considered to be a devastating neuropsychiatric disease mainly taking place in CNS featured by widespread defects in multiple metabolic pathways whose dynamic interactions, until recently, have been difficult to difficult to investigate. Evidence for these alterations has been collected piecemeal, limiting the potential to inform our understanding of the interactions among relevant biochemical pathways. Taken these points together, it will be interesting to investigate possible associations of biomarkers between CNS and periphery. Numerous studies have suggested putative correlations within peripheral and CNS systems especially for dopaminergic and glutamatergic metabolic biomarkers. In addition, it has been demonstrated that blood concentrations of BDNF protein can also reflect its changes in the nervous system. In turn, BDNF also interacts with glutamatergic, dopaminergic and serotonergic systems. Therefore, this review will summarize metabolic biomarkers identified both in the CNS (brain tissues and CSF) and peripheral blood. Further, more attentions will be paid to discussing possible physical and functional associations between CNS and periphery, especially with respect to BDNF.

Treatment effects on neurometabolite levels in schizophrenia: A systematic review and meta-analysis of proton magnetic resonance spectroscopy studies

BACKGROUND

Although there is growing evidence of alterations in the neurometabolite status associated with the pathophysiology of schizophrenia, how treatments influence these metabolite levels in patients with schizophrenia remains poorly studied.

METHODS

We conducted a literature search using Embase, Medline, and PsycINFO to identify proton magnetic resonance spectroscopy studies that compared neurometabolite levels before and after treatment in patients with schizophrenia. Six neurometabolites (glutamate, glutamine, glutamate + glutamine, gamma-aminobutyric acid, N-acetylaspartate, myo-inositol) and six regions of interest (frontal cortex, temporal cortex, parieto-occipital cortex, thalamus, basal ganglia, hippocampus) were investigated.

RESULTS

Thirty-two studies (n = 773 at follow-up) were included in our meta-analysis. Our results demonstrated that the frontal glutamate + glutamine level was significantly decreased (14 groups; n = 292 at follow-up; effect size = -0.35, P = 0.0003; I² = 22%) and the thalamic N-acetylaspartate level was significantly increased (7 groups; n = 184 at follow-up; effect size = 0.47, P < 0.00001; I² = 0%) after treatment in schizophrenia patients. No significant associations were found between neurometabolite changes and age, gender, duration of illness, duration of treatment, or baseline symptom severity.

CONCLUSIONS

The current results suggest that glutamatergic neurometabolite levels in the frontal cortex and neuronal integrity in the thalamus in schizophrenia might be modified following treatment.

Magnetic resonance spectroscopy studies in subjects with high risk for psychosis: A meta-analysis and review

INTRODUCTION

Even though anomalies on brain metabolites have been found in schizophrenia, researches about subjects with high risk (HR) show heterogeneous results. Thus, this meta-analysis aims to characterize the metabolic profile of HR subjects, first, compared to controls (HC) and then compared to people with schizophrenia.

METHODS

After a systematic database search, means and standard deviations were extracted to calculate standardized mean differences (SMD). Cerebral metabolites levels were compared between HR subjects and HC or patients with schizophrenia in all regions of interest investigated in included studies. Meta-regressions were performed to explore the influence of demographic and clinical variables on metabolites level's SMDs.

RESULTS

Thirty-nine studies were included in this meta-analysis. A higher level of glutamine + glutamate (Glx) was found in the medial prefrontal cortex (mPFC) (p < 0.01) and potentially in the basal ganglia (p = 0,05) as well as a higher level of myo-inositol (mI) in the dorsolateral prefrontal cortex (DLPFC) (p = 0.04) in HR subjects compared to HC. A higher level of choline (Cho) was found in people with schizophrenia compared to HR subjects in the DLPFC (p < 0.001) and the medial temporal lobe (p = 0.02). Meta-regression analyses showed negative associations between SMD for Cho concentration, the percentage of females or the age (p = 0.01).

CONCLUSIONS

The present meta-analysis provides evidence that some brain metabolites concentrations are disrupted before the transition to psychosis and could be considered like a vulnerability.

Ketamine administration induces early and persistent neurochemical imbalance and altered NADPH oxidase in mice

Administration in adulthood of subanaesthetic doses of ketamine, an NMDA receptor (NMDA-R) antagonist, is commonly used to induce psychotic-like alterations in rodents. The NADPH oxidase (NOX) derived-oxidative stress has been shown to be implicated in ketamine-induced neurochemical dysfunctions and in the loss of parvalbumin (PV)-positive interneurons associated to the administration of this NMDA receptor antagonist in adult mice. However, very few data are available on the effects of early ketamine administration and its contribution to the development of long-term dysfunctions leading to psychosis. Here, by administering a subanaesthetic dose of ketamine (30 mg/kg i.p.) to mice at postnatal days (PNDs) 7, 9 and 11, we aimed at investigating early neurochemical and oxidative stress-related alterations induced by this NMDA-R antagonist in specific brain regions of mice pups, i.e. prefrontal cortex (PFC) and nucleus accumbens (NAcc) and to assess whether these alterations lasted until the adult period. To this purpose, we evaluated glutamatergic, glutamine and GABAergic tissue levels, as well as PV amount in the PFC, both two hours after the last ketamine injection (PND 11) and at 10  weeks of age. Dopamine (DA) tissue levels and DA turnover were also evaluated in the NAcc at the same time points. Levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a reliable biomarker of oxidative stress, as well as of the free radical producers NOX1 and NOX2 enzymes, were also assessed in both PFC and NAcc of ketamine-treated pups and adult mice. Ketamine-treated pups showed increased cortical levels of glutamate (GLU) and glutamine, as well as similar GABA amount compared to controls, together with an early reduction of cortical PV levels. In the adult period, the same was observed for GLU and PV, whereas GABA levels were increased and no changes in glutamine amount were detected. Ketamine administration in early life induced a decrease in DA tissue levels and an increase of DA turnover which were also detectable at 10 weeks of age. These alterations were accompanied by 8-OHdG elevations in both PFC and NAcc at the two considered life stages. The expression of NOX1 was significantly reduced in these brain regions following ketamine administration at early life stages, while, in the adult period, significant elevation of this enzyme was observed. Levels of NOX2 were found increased at both time points. Our results suggest that an early increase of NOX2-derived oxidative stress may contribute to the development of neurochemical imbalance in PFC and NAcc, induced by ketamine administration. Modifications of NOX1 expression might represent, instead, an early response of the developing brain to a neurotoxic insult, followed by a later attempt to counterbalance ketamine-related detrimental effects.

Magnetic Resonance Spectroscopy for Psychiatry: Progress in the Last Decade

Psychiatric disorders are common and can be severe. There is a need to identify biomarkers of psychiatric disorders to better diagnose and treat patients with psychiatric symptoms. Magnetic resonance spectroscopy (MRS) is a tool used to measure the levels of various metabolites in the human brain, and MRS studies of psychiatric disorders have identified potentially useful biomarkers of psychiatric illness. There have been significant advances in the way that psychiatric disorders are understood, classified, and researched as well as improvements in magnetic resonance imaging/MRS technology. MRS as a tool has not yet proved helpful to individual patients with psychiatric symptoms.

The impact of endurance training and table soccer on brain metabolites in schizophrenia

Higher glutamate and glutamine (together: Glx) and lower N-acetyl-aspartate (NAA) levels were reported in schizophrenia. Endurance training normalizes NAA in the hippocampus, but its effects on other metabolites in the brain and the relationship of metabolites to clinical symptoms remain unknown. For 12 weeks, 20 schizophrenia inpatients (14 men, 6 women) and 23 healthy controls (16 men, 7 women) performed endurance training and a control group of 21 schizophrenia inpatients (15 men, 6 women) played table soccer. A computer-assisted cognitive performance training program was introduced after 6 weeks. We assessed cognitive performance, psychopathological symptoms, and everyday functioning at baseline and after 6 and 12 weeks and performed single voxel magnetic resonance spectroscopy of the hippocampus, left dorsolateral prefrontal cortex (DLPFC), and thalamus. We quantified NAA, Glx, total creatine (tCr), calculated NAA/tCr and Glx/tCr and correlated these ratios with physical fitness, clinical and neurocognitive scores, and everyday functioning. At baseline, in both schizophrenia groups NAA/tCr was lower in the left DLPFC and left hippocampus and Glx/tCr was lower in the hippocampus than in the healthy controls. After 6 weeks, NAA/tCr increased in the left DLPFC in both schizophrenia groups. Brain metabolites did not change significantly in the hippocampus or thalamus, but the correlation between NAA/tCr and Glx/tCr normalized in the left DLPFC. Global Assessment of Functioning improvements correlated with NAA/tCr changes in the left DLPFC. In our study, endurance training and table soccer induced normalization of brain metabolite ratios in the brain circuitry associated with neuronal and synaptic elements, including metabolites of the glutamatergic system.

Age-dependent effects of (+)-MK801 treatment on glutamate release and metabolism in the rat medial prefrontal cortex

NMDAR antagonist treatments in adolescent/young adult rodents are associated with augmented glutamate (Glu) release and perturbed Glu/glutamine (Gln) metabolism in the medial prefrontal cortex (mPFC) resembling those found in first-episode schizophrenia. Few studies, however, investigated NMDAR antagonist-induced changes in the adult mPFC and whether there is an age-dependence to this end. In this study, the effects of acute/repeated (+)-MK801 treatment on Glu release/metabolism were measured in the mPFC of male adolescent (postnatal day 30) and adult (14 weeks) rats. Acute (+)-MK801 treatment at 0.5 mg/kg body weight induced an approximately 4-fold increase of extracellular Glu concentration in the adolescent rats, and repeated treatment for 6 consecutive days significantly increased the levels of Glu + Gln (Glx) and glial metabolites 7 days after the last dose. Histologically (+)-MK801 treatments induced reactive astrocytosis and elevated oxidative stress in the mPFC of adolescent rats, without causing evident neuronal degeneration in the region. All (+)-MK801-induced changes observed in the mPFC of adolescent rats were not present or evident in the adult rats, suggesting that the treatments might have caused less disinhibition in the adult mPFC than in the adolescent mPFC. In conclusion, the effects of (+)-MK801 treatments on the Glu release/metabolism in the mPFC were found to be age-dependent; and the adult mPFC is likely equipped with more robust neurobiological mechanisms to preserve excitatory-inhibitory balance in response to NMDAR hypofunction.

Relationship of auditory electrophysiological responses to magnetic resonance spectroscopy metabolites in Early Phase Psychosis

Both auditory evoked responses and metabolites measured by magnetic resonance spectroscopy (MRS) are altered in schizophrenia and other psychotic disorders, but the relationship between electrophysiological and metabolic changes are not well characterized. We examined the relation of MRS metabolites to cognitive and electrophysiological measures in individuals during the early phase of psychosis (EPP) and in healthy control subjects. The mismatch negativity (MMN) of the auditory event-related potential to duration deviant tones and the auditory steady response (ASSR) to 40 Hz stimulation were assessed. MRS was used to quantify glutamate+glutamine (Glx), N-Acetylasparate (NAA), creatine (Cre), myo-inositol (Ins) and choline (Cho) at a voxel placed medially in the frontal cortex. MMN amplitude and ASSR power did not differ between groups. The MRS metabolites Glx, Cre and Cho were elevated in the psychosis group. Partial least squares analysis in the patient group indicated that elevated levels of MRS metabolites were associated with reduced MMN amplitude and increased 40 Hz ASSR power. There were no correlations between the neurobiological measures and clinical measures. These data suggest that elevated neurometabolites early in psychosis are accompanied by altered auditory neurotransmission, possibly indicative of a neuroinflammatory or excitotoxic disturbance which disrupts a wide range of metabolic processes in the cortex.

Assessing Brain Metabolism With 7-T Proton Magnetic Resonance Spectroscopy in Patients With First-Episode Psychosis

IMPORTANCE

The use of high-field magnetic resonance spectroscopy (MRS) in multiple brain regions of a large population of human participants facilitates in vivo study of localized or diffusely altered brain metabolites in patients with first-episode psychosis (FEP) compared to healthy participants.

OBJECTIVE

To compare metabolite levels in 5 brain regions between patients with FEP (evaluated within 2 years of onset) and healthy controls, and to explore possible associations between targeted metabolite levels and neuropsychological test performance.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional design used 7-T MRS at a research MR imaging facility in participants recruited from clinics at the Johns Hopkins Schizophrenia Center and the local population. Eighty-one patients who had received a DSM-IV diagnosis of FEP within the last 2 years and 91 healthy age-matched (but not sex-matched) volunteers participated.

MAIN OUTCOMES AND MEASURES

Brain metabolite levels including glutamate, glutamine, γ-aminobutyric acid (GABA), N-acetylaspartate, N-acetylaspartyl glutamate, and glutathione, as well as performance on neuropsychological tests.

RESULTS

The mean (SD) age of 81 patients with FEP was 22.3 (4.4) years and 57 were male, while the mean (SD) age of 91 healthy participants was 23.3 (3.9) years and 42 were male. Compared with healthy participants, patients with FEP had lower levels of glutamate (F1,162 = 8.63, P = .02), N-acetylaspartate (F1,161 = 5.93, P = .03), GABA (F1,163 = 6.38, P = .03), and glutathione (F1,162 = 4.79, P = .04) in the anterior cingulate (all P values are corrected for multiple comparisons); lower levels of N-acetylaspartate in the orbitofrontal region (F1,136 = 7.23, P = .05) and thalamus (F1,133 = 6.78, P = .03); and lower levels of glutathione in the thalamus (F1,135 = 7.57, P = .03). Among patients with FEP, N-acetylaspartate levels in the centrum semiovale white matter were significantly correlated with performance on neuropsychological tests, including processing speed (r = 0.48; P < .001), visual (r = 0.33; P = .04) and working (r = 0.38; P = .01) memory, and overall cognitive performance (r = 0.38; P = .01).

CONCLUSIONS AND RELEVANCE

Seven-tesla MRS offers insights into biochemical changes associated with FEP and may be a useful tool for probing brain metabolism that ranges from neurotransmission to stress-associated pathways in participants with psychosis.

Modular Functional-Metabolic Coupling Alterations of Frontoparietal Network in Schizophrenia Patients

Background: Brain functional dysconnectivity, as well as altered network organization, have been demonstrated to occur in schizophrenia. Brain networks are increasingly understood to exhibit modular community structures, which provides advantages in robustness and functional adaptivity. The frontoparietal network (FPN) serves as an important functional module, and metabolic and functional alterations in the FPN are associated with the pathophysiology of schizophrenia. However, how intra-modular biochemical disruptions lead to inter-modular dysfunction of the FPN, remains unclear. In this study, we aim to investigate alterations in the modular functional-metabolic coupling of the FPN, in patients with schizophrenia. Methods: We combined resting-state functional magnetic resonance imaging (rs-fMRI) and magnetic resonance spectroscopy (MRS) technology and acquired multimodal neuroimaging data in 20 patients with schizophrenia and 26 healthy controls. For the MRS, the dorsolateral prefrontal cortex (DLPFC) region within the FPN was explored. Metabolites including gamma aminobutyric acid (GABA), N-aspart-acetyl (NAA) and glutamate + glutamine (Glx) were quantified, using LCModel software. A graph theoretical approach was applied for functional modular parcellation. The relationship between inter/intra-modular connectivity and metabolic concentration was examined using the Pearson correlation analysis. Moreover, correlations with schizophrenia symptomatology were investigated by the Spearman correlation analysis. Results: The functional topological network consisted of six modules in both subject groups, namely, the default mode, frontoparietal, central, hippocampus, occipital, and subcortical modules. Inter-modular connectivity between the frontoparietal and central modules, and the frontoparietal and the hippocampus modules was decreased in the patient group compared to the healthy controls, while the connectivity within the frontoparietal modular increased in the patient group. Moreover, a positive correlation between the frontoparietal and central module functional connectivity and the NAA in the DLPFC was found in the healthy control group (r = 0.614, p = 0.001), but not in the patient group. Significant functional dysconnectivity between the frontoparietal and limbic modules was correlated with the clinical symptoms of patients. Conclusions: This study examined the links between functional connectivity and the neuronal metabolic level in the DLPFC of SCZ. Impaired functional connectivity of the frontoparietal areas in SCZ, may be partially explained by a neurochemical-functional connectivity decoupling effect. This disconnection pattern can further provide useful insights in the cognitive and perceptual impairments of schizophrenia in future studies.

7T Proton Magnetic Resonance Spectroscopy of the Anterior Cingulate Cortex in First-Episode Schizophrenia

Recent magnetic resonance spectroscopy (MRS) studies suggest that abnormalities of the glutamatergic system in schizophrenia may be dependent on illness stage, medication status, and symptomatology. Glutamatergic metabolites appear to be elevated in the prodromal and early stages of schizophrenia but unchanged or reduced below normal in chronic, medicated patients. However, few of these studies have measured metabolites with high-field 7T MR scanners, which offer higher signal-to-noise ratio and better spectral resolution than 3T scanners and facilitate separation of glutamate and glutamine into distinct signals. In this study, we examined glutamate and other metabolites in the dorsal anterior cingulate cortex (ACC) of first-episode schizophrenia patients. Glutamate and N-acetylaspartate (NAA) were significantly lower in schizophrenia patients vs controls. No differences were observed in levels of glutamine, GABA, or other metabolites. In schizophrenia patients but not controls, GABA was negatively correlated with the total score on the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) as well as the immediate memory and language subscales. Our findings suggest that glutamate and NAA reductions in the ACC may be present early in the illness, but additional large-scale studies are needed to confirm these results as well as longitudinal studies to determine the effect of illness progression and treatment. The correlation between GABA and cognitive function suggests that MRS may be an important technique for investigating the neurobiology underlying cognitive deficits in schizophrenia.

Is psychosis a multisystem disorder? A meta-review of central nervous system, immune, cardiometabolic, and endocrine alterations in first-episode psychosis and perspective on potential models

People with psychotic disorders show abnormalities in several organ systems in addition to the central nervous system (CNS); and this contributes to excess mortality. However, it is unclear how strong the evidence is for alterations in non-CNS systems at the onset of psychosis, how the alterations in non-CNS systems compare to those in the CNS, or how they relate to symptoms. Here, we consider these questions, and suggest potential models to account for findings. We conducted a systematic meta-review to summarize effect sizes for both CNS (focusing on brain structural, neurophysiological, and neurochemical parameters) and non-CNS dysfunction (focusing on immune, cardiometabolic, and hypothalamic-pituitary-adrenal (HPA) systems) in first-episode psychosis (FEP). Relevant meta-analyses were identified in a systematic search of Pubmed and the methodological quality of these was assessed using the AMSTAR checklist (A Measurement Tool to Assess Systematic Reviews). Case-control data were extracted from studies included in these meta-analyses. Random effects meta-analyses were re-run and effect size magnitudes for individual parameters were calculated, as were summary effect sizes for each CNS and non-CNS system. We also grouped studies to obtain overall effect sizes for non-CNS and CNS alterations. Robustness of data for non-CNS and CNS parameters was assessed using Rosenthal's fail-safe N. We next statistically compared summary effect size for overall CNSand overall non-CNS alterations, as well as for each organ system separately. We also examined how non-CNS alterations correlate CNS alterations, and with psychopathological symptoms. Case-control data were extracted for 165 studies comprising a total sample size of 13,440. For people with first episode psychosis compared with healthy controls, we observed alterations in immune parameters (summary effect size: g = 1.19), cardiometabolic parameters (g = 0.23); HPA parameters (g = 0.68); brain structure (g = 0.40); neurophysiology (g = 0.80); and neurochemistry (g = 0.43). Grouping non-CNS organ systems together provided an effect size for overall non-CNS alterations in patients compared with controls (g = 0.58), which was not significantly different from the overall CNS alterations effect size (g = 0.50). However, the summary effect size for immune alterations was significantly greater than that for brain structural (P < 0.001) and neurochemical alterations (P < 0.001), while the summary effect size for cardiometabolic alterations was significantly lower than neurochemical (P = 0.04), neurophysiological (P < 0.001), and brain structural alterations (P = 0.001). The summary effect size for HPA alterations was not significantly different from brain structural (P = 0.14), neurophysiological (P = 0.54), or neurochemical alterations (P = 0.22). These outcomes remained similar in antipsychotic naive sensitivity analyses. We found some, but limited and inconsistent, evidence that non-CNS alterations were associated with CNS changes and symptoms in first episode psychosis. Our findings indicate that there are robust alterations in non-CNS systems in psychosis, and that these are broadly similar in magnitude to a range of CNS alterations. We consider models that could account for these findings and discuss implications for future research and treatment.

Neurometabolite levels in antipsychotic-naïve/free patients with schizophrenia: A systematic review and meta-analysis of 1H-MRS studies

BACKGROUND

Studies using proton magnetic resonance spectroscopy (¹H-MRS) have reported altered neurometabolite levels in patients with schizophrenia. However, results are possibly confounded by the influence of antipsychotic (AP). Thus, this meta-analysis aimed to examine neurometabolite levels in AP-naïve/free patients with schizophrenia.

METHODS

A literature search was conducted using Embase, Medline, and PsycINFO to identify studies that compared neurometabolite levels in AP-naïve/free patients with schizophrenia to healthy controls (HCs). Eight neurometabolites (glutamate, glutamine, glutamate + glutamine, N-acetylaspartate [NAA], choline, creatine, myo-inositol, and γ-Aminobutyric acid [GABA]) and seven regions of interest (ROI; medial prefrontal cortex, dorsolateral prefrontal cortex, frontal white matter, occipital lobe, basal ganglia, hippocampus/medial temporal lobe, and thalamus) were examined.

RESULTS

Twenty-one studies (N = 1281) were included in the analysis. The results showed lower thalamic NAA levels (3 studies, n = 174, effect size = -0.56, P = 0.0005) in the patient group. No group differences were identified for other neurometabolites.

CONCLUSIONS

Our findings suggest that impaired neuronal integrity in the thalamus may be a potential trait maker in the early stages of schizophrenia.

Magnetic Resonance Spectroscopy in Schizophrenia: Evidence for Glutamatergic Dysfunction and Impaired Energy Metabolism

In the past couple of decades, major efforts were made to increase reliability of metabolic assessments by magnetic resonance methods. Magnetic resonance spectroscopy (MRS) has been valuable for providing in vivo evidence and investigating biomarkers in neuropsychiatric disorders, namely schizophrenia. Alterations of glutamate and glutamine levels in brains of schizophrenia patients relative to healthy subjects are generally interpreted as markers of glutamatergic dysfunction. However, only a small fraction of MRS-detectable glutamate is involved in neurotransmission. Here we review and discuss brain metabolic processes that involve glutamate and that are likely to be implicated in neuropsychiatric disorders.

Proton magnetic resonance spectroscopy changes after lithium treatment. Systematic review

1H MRS is widely used in the research of mental disorders. It enables evaluation of concentration or ratios of several metabolites, which play important roles in brain metabolism: N-acetylaspartate (NAA), choline containing compounds, myo-inositol and glutamate, glutamine and GABA (together as Glx complex or separately). Specifically in bipolar disorder brain metabolite abnormalities include mostly NAA reduces and Glx increases in different brain regions. Bipolar disorder is associated with impairment in neurotrophic and cellular plasticity, resilience pathways and in neuroprotective processes. Lithium, which is commonly used in BD treatment, modulates neurotransmitter release, reduces oxidative stress and apoptosis, induces angiogenesis, neurogenesis and neurotrophic response. Thus brain metabolite abnormalities may elucidate the mechanisms of this processes. In the present article we systematically reviewed 26 studies - the majority of them investigated bipolar disorder ( 7 follow-up and all 11 cross-sectional studies). Moreover we dispute whether the influence of lithium on brain metabolites in bipolar disorder could explain the background of its potential neuroprotective action. The results of our literature review do not equivocally confirm Lithium's influence the metabolite changes in the brain. The majority of the follow-up studies do not support the initially assumed influence of Lithium on the increase of NAA level in various brain structures. The results of studies are inconclusive with regard to levels of Glx or Glu and Lithium intake, rather point a lack of relationship. The above results were reviewed according to the most recent theories in the field accounting for the impact of lithium (1)HMRS measures.

The relationship between the alterations in metabolite levels in the dorsolateral prefrontal cortex and clinical symptoms of patients with first-episode schizophrenia: a one year follow-up study

Background

Reduced brain metabolites such as N-acetyl-aspartate (NAA), glutamate (Glx), Choline (Cho) and myo-inositol (MI) have been repeatedly found in first-episode schizophrenia (FES) and suggest neuronal loss or dysfunction. However, the potential relationship between the metabolite level and the clinical symptoms or the recovery of FES remained unclear.

Objectives

This study aimed to investigate the correlation between the alterations in dorsolateral prefrontal cortex (DLPFC) metabolite levels of patients with first-episode schizophrenia (FES) and the changes in clinical symptoms after one year treatment.

Materials and Methods

FES patients underwent 1H-MRS scan twice: one time at the baseline and the other one year later, while the healthy group patients underwent only once at the baseline time. The symptom severity of patients was measured by PANSS.

Principal Observations

An increase in the NAA/Cr level was detected in the left DLPFC of patients with FES. The change in the NAA/Cr level was significantly correlated with the alteration in their PANSS-P score. The Cho/Cr levels on both sides of DLPFC in patients with FES were lower compared with the healthy controls both at the baseline and after the treatment. The NAA/Cr and MI/Cr levels in the right DLPFC were decreased after the treatment.

Conclusions

(1) the depletion of NAA in left DLPFC might be a state characteristic; (2) the Cho/Cr level might be the potential endophenotype of schizophrenia; (3) the decrease of NAA/Cr and MI/Cr level in right DLPFC might be due to the development of schizophrenia.

Glutamate imaging (GluCEST) reveals lower brain GluCEST contrast in patients on the psychosis spectrum

Psychosis commonly develops in adolescence or early adulthood. Youths at clinical high risk (CHR) for psychosis exhibit similar, subtle symptoms to those with schizophrenia (SZ). Malfunctioning neurotransmitter systems, such as glutamate, are implicated in the disease progression of psychosis. Yet, in vivo imaging techniques for measuring glutamate across the cortex are limited. Here, we use a novel 7 Tesla MRI glutamate imaging technique (GluCEST) to estimate changes in glutamate levels across cortical and subcortical regions in young healthy individuals and ones on the psychosis spectrum. Individuals on the psychosis spectrum (PS; n=19) and healthy young individuals (HC; n=17) underwent MRI imaging at 3 and 7 T. At 7 T, a single slice GluCEST technique was used to estimate in vivo glutamate. GluCEST contrast was compared within and across the subcortex, frontal, parietal and occipital lobes. Subcortical (χ2 (1)=4.65, P=0.031) and lobular (χ2 (1)=5.17, P=0.023) GluCEST contrast levels were lower in PS compared with HC. Abnormal GluCEST contrast levels were evident in both CHR (n=14) and SZ (n=5) subjects, and correlated differentially, across regions, with clinical symptoms. Our findings describe a pattern of abnormal brain neurochemistry early in the course of psychosis. Specifically, CHR and young SZ exhibit diffuse abnormalities in GluCEST contrast attributable to a major contribution from glutamate. We suggest that neurochemical profiles of GluCEST contrast across cortex and subcortex may be considered markers of early psychosis. GluCEST methodology thus shows promise to further elucidate the progression of the psychosis disease state.

Social isolation stress and chronic glutathione deficiency have a common effect on the glutamine-to-glutamate ratio and myo-inositol concentration in the mouse frontal cortex

Environmental stress can interact with genetic predisposition to increase the risk of developing psychopathology. In this work, we tested the hypothesis that social isolation stress interacts with impaired glutathione synthesis and have cumulative effects on the neurochemical profile of the frontal cortex. A mouse model with chronic glutathione deficit induced by knockout (-/-) of the glutamate-cysteine ligase modulatory subunit (Gclm) was exposed to social isolation stress from weaning to post-natal day 65. Using magnetic resonance methods at high-field (14.1 T), we analysed the neurochemical profile in the frontal cortex, brain size and ventricular volume of adult animals. Glutathione deficit was accompanied by elevated concentrations of N-acetylaspartate, alanine, and glutamine, as well as the ratio of glutamine-to-glutamate (Gln/Glu), and by a reduction in levels of myo-inositol and choline-containing compounds in the frontal cortex of -/- animals with respect to wild-type littermates. Although there was no significant interaction between social isolation stress and glutathione deficiency, mice reared in isolation displayed lower myo-inositol concentration (-8.4%, p < 0.05) and larger Gln/Glu (+7.6%, p < 0.05), relative to those in group housing. Furthermore, glutathione deficiency caused a reduction in whole brain volume and enlargement of ventricles, but social isolation had no effect on these parameters. We conclude that social isolation caused neurochemical alterations that may add to those associated to impaired glutathione synthesis.

Sequential change detection and monitoring of temporal trends in random-effects meta-analysis

Temporal changes in magnitude of effect sizes reported in many areas of research are a threat to the credibility of the results and conclusions of meta-analysis. Numerous sequential methods for meta-analysis have been proposed to detect changes and monitor trends in effect sizes so that meta-analysis can be updated when necessary and interpreted based on the time it was conducted. The difficulties of sequential meta-analysis under the random-effects model are caused by dependencies in increments introduced by the estimation of the heterogeneity parameter τ2 . In this paper, we propose the use of a retrospective cumulative sum (CUSUM)-type test with bootstrap critical values. This method allows retrospective analysis of the past trajectory of cumulative effects in random-effects meta-analysis and its visualization on a chart similar to CUSUM chart. Simulation results show that the new method demonstrates good control of Type I error regardless of the number or size of the studies and the amount of heterogeneity. Application of the new method is illustrated on two examples of medical meta-analyses. © 2016 The Authors. Research Synthesis Methods published by John Wiley & Sons Ltd.

Neuroprotective Effect of Modified Electroconvulsive Therapy for Schizophrenia: A Proton Magnetic Resonance Spectroscopy Study

The underlying mechanism of modified electroconvulsive therapy (MECT) treatment for drug-resistant and catatonic schizophrenia remains unclear. Here, we aim to investigate whether MECT exerts its antipsychotic effects through elevating N-acetylaspartate (NAA) concentration measured by proton magnetic resonance spectroscopy (H-MRS). Multiple-voxel H-MRS was acquired in the bilateral prefrontal cortex (PFC) and thalamus to obtain measures of neurochemistry in 32 MECT, 34 atypical antipsychotic-treated schizophrenic patients, and 34 healthy controls. We found that both MECT and atypical antipsychotic treatments showed significant antipsychotic efficacy. MECT and atypical antipsychotic treatments reversed the reduced NAA/creatine ratio (NAA/Cr) in the left PFC and left thalamus in schizophrenic patients compared with healthy controls. Furthermore, the NAA/Cr ratio after treatments was significant higher in the MECT group, but not in the medication group. Our findings demonstrate that eight times of MECT elevated the relative NAA concentration to display neuroprotective effect, which may be the underlying mechanism of rapid antipsychotic efficacy.

Evaluation of neuron-glia integrity by in vivo proton magnetic resonance spectroscopy: Implications for psychiatric disorders

Proton magnetic resonance spectroscopy (¹H-MRS) has been widely applied in human studies. There is now a large literature describing findings of brain MRS studies with mental disorder patients including schizophrenia, bipolar disorder, major depressive disorder, and anxiety disorders. However, the findings are mixed and cannot be reconciled by any of the existing interpretations. Here we proposed the new theory of neuron-glia integrity to explain the findings of brain ¹H-MRS stuies. It proposed the neurochemical correlates of neuron-astrocyte integrity and axon-myelin integrity on the basis of update of neurobiological knowledge about neuron-glia communication and of experimental MRS evidence for impairments in neuron-glia integrity from the authors and the other investigators. Following the neuron-glia integrity theories, this review collected evidence showing that glutamate/glutamine change is a good marker for impaired neuron-astrocyte integrity and that changes in N-acetylaspartate and lipid precursors reflect impaired myelination. Moreover, this new theory enables us to explain the differences between MRS findings in neuropsychiatric and neurodegenerative disorders.

Developmental timing and critical windows for the treatment of psychiatric disorders

There is a growing understanding that pathological genetic variation and environmental insults during sensitive periods in brain development have long-term consequences on brain function, which range from learning disabilities to complex psychiatric disorders such as schizophrenia. Furthermore, recent experiments in animal models suggest that therapeutic interventions during sensitive periods, typically before the onset of clear neurological and behavioral symptoms, might prevent or ameliorate the development of specific pathologies. These studies suggest that understanding the dynamic nature of the pathophysiological mechanisms underlying psychiatric disorders is crucial for the development of effective therapies. In this Perspective, I explore the emerging concept of developmental windows in psychiatric disorders, their relevance for understanding disease progression and their potential for the design of new therapies. The limitations and caveats of early interventions in psychiatric disorders are also discussed in this context.

Elevated Myo-Inositol, Choline, and Glutamate Levels in the Associative Striatum of Antipsychotic-Naive Patients With First-Episode Psychosis: A Proton Magnetic Resonance Spectroscopy Study With Implications for Glial Dysfunction

Glial disturbances are highly implicated in the pathophysiology of schizophrenia and may be linked with glutamatergic dysregulation. Myo-inositol (mI), a putative marker of glial cells, and choline (Cho), representative of membrane turnover, are both present in larger concentrations within glial cells than in neurons, and their elevation is often interpreted to reflect glial activation. Proton magnetic resonance spectroscopy ((1)H-MRS) allows for the evaluation of mI, Cho, glutamate, glutamate + glutamine (Glx), and N-acetylaspartate (NAA). A collective investigation of these measures in antipsychotic-naive patients experiencing their first nonaffective episode of psychosis (FEP) can improve the understanding of glial dysfunction and its implications in the early stages of schizophrenia. 3-Tesla (1)H-MRS (echo time = 35 ms) was performed in 60 antipsychotic-naive patients with FEP and 60 age- and sex-matched healthy controls. mI, Cho, glutamate, Glx, and NAA were estimated using LCModel and corrected for cerebrospinal fluid composition within the voxel. mI, Cho, and glutamate were elevated in the FEP group. After correction for multiple comparisons, mI positively correlated with grandiosity. The relationships between mI and glutamate, and Cho and glutamate, were more positive in the FEP group. These findings are suggestive of glial activation in the absence of neuronal loss and may thereby provide support for the presence of a neuroinflammatory process within the early stages of schizophrenia. Dysregulation of glial function might result in the disruption of glutamatergic neurotransmission, which may influence positive symptomatology in patients with FEP.

Prefrontal NAA and Glx Levels in Different Stages of Psychotic Disorders: a 3T 1H-MRS Study

H-Magnetic Resonance Spectroscopy ((1)H-MRS) can offer insights in various neuropathologies by measuring metabolite levels in the brain. In the current study we investigated the levels of glutamate + glutamine (Glx, neurotransmitter and precursor) and N-Acetyl Aspartate + glutamic acid (NAA + NAAG; neuronal viability) in the prefrontal cortex of patients with a psychotic disorder and people at Ultra High Risk (UHR) for psychosis. A (1)H-MRS spectrum was acquired in 31 patients with a recent onset psychotic disorder and 60 with a chronic state, 16 UHR patients and 36 healthy controls. Absolute metabolite levels were calculated using LCModel with a reference water peak. Groups were compared while taking into account age and partial volume effects. Moreover, we investigated associations with positive and negative symptoms, duration of illness, and antipsychotic treatment in patients. The most notable finding is that chronicity of schizophrenia was related to decreased levels of Glx and NAA. On the other hand, although on an exploratory note, UHR showed increased levels of prefrontal Glx and NAA levels with increasing age. Our results may indicate an initial Glx and NAA increase and subsequent decrease during illness progression that may be related to the neurotoxic effects of glutamate.

Reinforcement Learning Performance and Risk for Psychosis in Youth

Early identification efforts for psychosis have thus far yielded many more individuals "at risk" than actually develop psychotic illness. Here, we test whether measures of reinforcement learning (RL), known to be impaired in chronic schizophrenia, are related to the severity of clinical risk symptoms. Because of the reliance of RL on dopamine-rich frontostriatal systems and evidence of dopamine system dysfunction in the psychosis prodrome, RL measures are of specific interest in this clinical population. The current study examines relationships between psychosis risk symptoms and RL task performance in a sample of adolescents and young adults (n = 70) receiving mental health services. We observed significant correlations between multiple measures of RL performance and measures of both positive and negative symptoms. These results suggest that RL measures may provide a psychosis risk signal in treatment-seeking youth. Further research is necessary to understand the potential predictive role of RL measures for conversion to psychosis.

Longitudinal in vivo maturational changes of metabolites in the prefrontal cortex of rats exposed to polyinosinic-polycytidylic acid in utero

Proton magnetic resonance spectroscopy ((1)H MRS) studies in schizophrenia patients generally report decreased levels of N-acetyl-aspartate (NAA), glutamate and glutathione, particularly in frontal cortex. However, these data are inconsistent in part due to confounds associated with clinical samples. The lack of validated diagnostic biomarkers also hampers analysis of the neurodevelopmental trajectory of neurochemical abnormalities. Rodent models are powerful tools to address these issues, particularly when combined with (1)H MRS (clinically comparable technology). We investigated the trajectory of metabolic changes in the prefrontal cortex during brain maturation from adolescence to adulthood in vivo using (1)H MRS in rats exposed prenatally to polyinosinic-polycytidylic acid (POL), a rodent model of maternal immune activation (MIA), an epidemiological risk factor for several psychiatric disorders with a neurodevelopmental origin. Longitudinal in vivo (1)H MRS revealed a significant decrease in PFC levels of GSH and taurine in adult, but not adolescent rats. Significant age×MIA interactions for PFC levels of NAA were also observed. These data replicate some deficits observed in the PFC of patients with schizophrenia. There were no significant changes in the levels of glutamate or any other metabolite. These data suggest prenatal exposure to POL leads to subtle metabolic perturbations of the normal maturing PFC, which may be related to subsequent behavioural abnormalities. Further work is however required to examine any potential confound of shipping stress on the presumed imbalances in PFC metabolites in POL-exposed offspring. Testing the interactions between MIA with stress or genetic risk variants will also be an important advance.

Supplementation of Antipsychotic Treatment with the Amino Acid Sarcosine Influences Proton Magnetic Resonance Spectroscopy Parameters in Left Frontal White Matter in Patients with Schizophrenia

Dysfunction of the glutamatergic system, the main stimulating system in the brain, has a major role in pathogenesis of schizophrenia. The frontal white matter (WM) is partially composed of axons from glutamatergic pyramidal neurons and glia with glutamatergic receptors. The natural amino acid sarcosine, a component of a normal diet, inhibits the glycine type 1 transporter, increasing the glycine level. Thus, it modulates glutamatergic transmission through the glutamatergic ionotropic NMDA (N-methyl-d-aspartate) receptor, which requires glycine as a co-agonist. To evaluate the concentrations of brain metabolites (NAA, N-acetylaspartate; Glx, complex of glutamate, glutamine, and γ-aminobutyric acid (GABA); mI, myo-inositol; Cr, creatine; Cho, choline) in the left frontal WM, Proton Nuclear Magnetic Resonance (¹H-NMR) spectroscopy was used. Twenty-five patients randomly chosen from a group of fifty with stable schizophrenia (DSM-IV-TR) and dominant negative symptoms, who were receiving antipsychotic therapy, were administered 2 g of sarcosine daily for six months. The remaining 25 patients received placebo. Assignment was double blinded. ¹H-NMR spectroscopy (1.5 T) was performed twice: before and after the intervention. NAA, Glx and mI were evaluated as Cr and Cho ratios. All patients were also assessed twice with the Positive and Negative Syndrome Scale (PANSS). Results were compared between groups and in two time points in each group. The sarcosine group demonstrated a significant decrease in WM Glx/Cr and Glx/Cho ratios compared to controls after six months of therapy. In the experimental group, the final NAA/Cr ratio significantly increased and Glx/Cr ratio significantly decreased compared to baseline values. Improvement in the PANSS scores was significant only in the sarcosine group. In patients with schizophrenia, sarcosine augmentation can reverse the negative effect of glutamatergic system overstimulation, with a simultaneous beneficial increase of NAA/Cr ratio in the WM of the left frontal lobe. Our results further support the glutamatergic hypothesis of schizophrenia.

Comparison of Metabolite Concentrations in the Left Dorsolateral Prefrontal Cortex, the Left Frontal White Matter, and the Left Hippocampus in Patients in Stable Schizophrenia Treated with Antipsychotics with or without Antidepressants. ¹H-NMR Spectroscopy Study

Managing affective, negative, and cognitive symptoms remains the most difficult therapeutic problem in stable phase of schizophrenia. Efforts include administration of antidepressants. Drugs effects on brain metabolic parameters can be evaluated by means of proton nuclear magnetic resonance (¹H-NMR) spectroscopy. We compared spectroscopic parameters in the left prefrontal cortex (DLPFC), the left frontal white matter (WM) and the left hippocampus and assessed the relationship between treatment and the spectroscopic parameters in both groups. We recruited 25 patients diagnosed with schizophrenia (DSM-IV-TR), with dominant negative symptoms and in stable clinical condition, who were treated with antipsychotic and antidepressive medication for minimum of three months. A group of 25 patients with schizophrenia, who were taking antipsychotic drugs but not antidepressants, was matched. We compared metabolic parameters (N-acetylaspartate (NAA), myo-inositol (mI), glutamatergic parameters (Glx), choline (Cho), and creatine (Cr)) between the two groups. All patients were also assessed with the Positive and Negative Syndrome Scale (PANSS) and the Calgary Depression Scale for Schizophrenia (CDSS). In patients receiving antidepressants we observed significantly higher NAA/Cr and NAA/Cho ratios within the DLPFC, as well as significantly higher mI/Cr within the frontal WM. Moreover, we noted significantly lower values of parameters associated with the glutamatergic transmission--Glx/Cr and Glx/Cho in the hippocampus. Doses of antipsychotic drugs in the group treated with antidepressants were also significantly lower in the patients showing similar severity of psychopathology.

Adding Sarcosine to Antipsychotic Treatment in Patients with Stable Schizophrenia Changes the Concentrations of Neuronal and Glial Metabolites in the Left Dorsolateral Prefrontal Cortex

The glutamatergic system is a key point in pathogenesis of schizophrenia. Sarcosine (N-methylglycine) is an exogenous amino acid that acts as a glycine transporter inhibitor. It modulates glutamatergic transmission by increasing glycine concentration around NMDA (N-methyl-d-aspartate) receptors. In patients with schizophrenia, the function of the glutamatergic system in the prefrontal cortex is impaired, which may promote negative and cognitive symptoms. Proton nuclear magnetic resonance (¹H-NMR) spectroscopy is a non-invasive imaging method enabling the evaluation of brain metabolite concentration, which can be applied to assess pharmacologically induced changes. The aim of the study was to evaluate the influence of a six-month course of sarcosine therapy on the concentration of metabolites (NAA, N-acetylaspartate; Glx, complex of glutamate, glutamine and γ-aminobutyric acid (GABA); mI, myo-inositol; Cr, creatine; Cho, choline) in the left dorso-lateral prefrontal cortex (DLPFC) in patients with stable schizophrenia. Fifty patients with schizophrenia, treated with constant antipsychotics doses, in stable clinical condition were randomly assigned to administration of sarcosine (25 patients) or placebo (25 patients) for six months. Metabolite concentrations in DLPFC were assessed with 1.5 Tesla ¹H-NMR spectroscopy. Clinical symptoms were evaluated with the Positive and Negative Syndrome Scale (PANSS). The first spectroscopy revealed no differences in metabolite concentrations between groups. After six months, NAA/Cho, mI/Cr and mI/Cho ratios in the left DLPFC were significantly higher in the sarcosine than the placebo group. In the sarcosine group, NAA/Cr, NAA/Cho, mI/Cr, mI/Cho ratios also significantly increased compared to baseline values. In the placebo group, only the NAA/Cr ratio increased. The addition of sarcosine to antipsychotic therapy for six months increased markers of neurons viability (NAA) and neurogilal activity (mI) with simultaneous improvement of clinical symptoms. Sarcosine, two grams administered daily, seems to be an effective adjuvant in the pharmacotherapy of schizophrenia.