Depressive Symptoms and Brain Metabolite Alterations in Subjects at Ultra-high Risk for Psychosis: A Preliminary Study

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.

Dorsolateral Prefrontal Cortex Glutamate/Gamma-Aminobutyric Acid (GABA) Alterations in Clinical High Risk and First-Episode Schizophrenia: A Preliminary 7-T Magnetic Resonance Spectroscopy Imaging Study

Converging lines of evidence suggest that an imbalance between excitation and inhibition is present in the dorsolateral prefrontal cortex (DLPFC) of schizophrenia (SCZ). Gamma-aminobutyric-acid (GABA) and, to a lesser extent, glutamate (Glu) abnormalities were reported in the DLPFC of SCZ patients, especially on the right hemisphere, by post-mortem studies. However, in vivo evidence of GABA, Glu, and Glu/GABA DLPFC abnormalities, particularly on the right side and the early stages of illness, is limited. In this preliminary study, we utilized 7-Tesla magnetic resonance spectroscopic imaging (MRSI) to investigate bilateral Glu/Creatine (Cre), GABA/Cre, and Glu/GABA in the DLPFC of sixteen first episode schizophrenia (FES), seventeen clinical high risk (CHR), and twenty-six healthy comparison (HC) subjects. FES and CHR had abnormal GABA/Cre and Glu/GABA in the right DLPFC (rDLPFC) compared with HC participants, while no differences were observed in the left DLPFC (lDLPFC) among the three groups. Furthermore, HC had higher Glu/GABA in rDLPFC compared to lDLPFC (R > L), whereas the opposite relationship (R < L) was observed in the DLPFC Glu/GABA of FES patients. Altogether, these findings indicate that GABA/Cre and Glu/GABA DLPFC alterations are present before illness manifestation and worsen in FES patients, thus representing a putative early pathophysiological biomarker for SCZ and related psychotic disorders.

Dopamine and glutamate in individuals at high risk for psychosis: a meta-analysis of in vivo imaging findings and their variability compared to controls

Dopaminergic and glutamatergic dysfunction is believed to play a central role in the pathophysiology of schizophrenia. However, it is unclear if abnormalities predate the onset of schizophrenia in individuals at high clinical or genetic risk for the disorder. We systematically reviewed and meta-analyzed studies that have used neuroimaging to investigate dopamine and glutamate function in individuals at increased clinical or genetic risk for psychosis. EMBASE, PsycINFO and Medline were searched form January 1, 1960 to November 26, 2020. Inclusion criteria were molecular imaging measures of striatal presynaptic dopaminergic function, striatal dopamine receptor availability, or glutamate function. Separate meta-analyses were conducted for genetic high-risk and clinical high-risk individuals. We calculated standardized mean differences between high-risk individuals and controls, and investigated whether the variability of these measures differed between the two groups. Forty-eight eligible studies were identified, including 1,288 high-risk individuals and 1,187 controls. Genetic high-risk individuals showed evidence of increased thalamic glutamate + glutamine (Glx) concentrations (Hedges' g=0.36, 95% CI: 0.12-0.61, p=0.003). There were no significant differences between high-risk individuals and controls in striatal presynaptic dopaminergic function, striatal D2/D3 receptor availability, prefrontal cortex glutamate or Glx, hippocampal glutamate or Glx, or basal ganglia Glx. In the meta-analysis of variability, genetic high-risk individuals showed reduced variability of striatal D2/D3 receptor availability compared to controls (log coefficient of variation ratio, CVR=-0.24, 95% CI: -0.46 to -0.02, p=0.03). Meta-regressions of publication year against effect size demonstrated that the magnitude of differences between clinical high-risk individuals and controls in presynaptic dopaminergic function has decreased over time (estimate=-0.06, 95% CI: -0.11 to -0.007, p=0.025). Thus, other than thalamic glutamate concentrations, no neurochemical measures were significantly different between individuals at risk for psychosis and controls. There was also no evidence of increased variability of dopamine or glutamate measures in high-risk individuals compared to controls. Significant heterogeneity, however, exists between studies, which does not allow to rule out the existence of clinically meaningful differences.

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.

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.

Cerebral Glutamate and Gamma-Aminobutyric Acid Levels in Individuals at Ultra-high Risk for Psychosis and the Association With Clinical Symptoms and Cognition

BACKGROUND

Studies examining glutamate or gamma-aminobutyric acid (GABA) in ultra-high risk for psychosis (UHR) and the association with pathophysiology and cognition have shown conflicting results. We aimed to determine whether perturbed glutamate and GABA levels in the anterior cingulate cortex and glutamate levels in the left thalamus were present in UHR individuals and to investigate associations between metabolite levels and clinical symptoms and cognition.

METHODS

We included 122 UHR individuals and 60 healthy control subjects. Participants underwent proton magnetic resonance spectroscopy to estimate glutamate and GABA levels and undertook clinical and cognitive assessments.

RESULTS

We found no differences in metabolite levels between UHR individuals and healthy control subjects. In UHR individuals, we found negative correlations in the anterior cingulate cortex between the composite of glutamate and glutamine (Glx) and the Comprehensive Assessment of At-Risk Mental States composite score (p = .04) and between GABA and alogia (p = .01); positive associations in the anterior cingulate cortex between glutamate (p = .01) and Glx (p = .01) and spatial working memory and between glutamate (p = .04), Glx (p = .04), and GABA (p = .02) and set-shifting; and a positive association in the thalamus between glutamate and attention (p = .04). No associations between metabolites and clinical or cognitive scores were found in the healthy control subjects.

CONCLUSIONS

An association between glutamate and GABA levels and clinical symptoms and cognition found only in UHR individuals suggests a loss of the normal relationship between metabolite levels and cognitive function. Longitudinal studies with investigation of clinical and cognitive outcome and the association with baseline levels of glutamate and GABA could illuminate whether glutamatergic and GABAergic dysfunction predicts clinical outcome.

Cerebral glutamate and GABA levels in high-risk of psychosis states: A focused review and meta-analysis of 1H-MRS studies

Disturbances in the brain glutamate and GABA (γ-aminobutyric acid) homeostasis may be markers of transition to psychosis in individuals at high-risk (HR). Knowledge of GABA and glutamate levels in HR stages could give an insight into changes in the neurochemistry underlying psychosis. Studies on glutamate in HR have provided conflicting data, and GABA studies have only recently been initialized. In this meta-analysis, we compared cerebral levels of glutamate and GABA in HR individuals with healthy controls (HC). We searched Medline and Embase for articles published on ¹H-MRS studies on glutamate and GABA in HR states until April 9th, 2019. We identified a total of 28 eligible studies, of which eight reported GABA (243 HR, 356 HC) and 26 reported glutamate (299 HR, 279 HC) or Glx (glutamate + glutamine) (584 HR, 632 HC) levels. Sample sizes varied from 6 to 75 for HR and 10 to 184 for HC. Our meta-analysis of ¹H-MRS studies on glutamate and GABA in HR states displayed significantly lower (P = 0.0003) levels of thalamic glutamate in HR individuals than in HC and significantly higher (P = 0.001) Glx in the frontal lobe of genetic HR individuals (1st-degree relatives) than in HC. No other significant differences in glutamate and GABA levels were found. Subject numbers in the studies on glutamate as well as GABA levels were generally small and the data conflicting. Our meta-analytical findings highlight the need for larger and more homogeneous studies of glutamate and GABA in high-risk states.

Heritability of cerebral glutamate levels and their association with schizophrenia spectrum disorders: a 1[H]-spectroscopy twin study

Research findings implicate cerebral glutamate in the pathophysiology of schizophrenia, including genetic studies reporting associations with glutamatergic neurotransmission. The extent to which aberrant glutamate levels can be explained by genetic factors is unknown, and if glutamate can serve as a marker of genetic susceptibility for schizophrenia remains to be established. We investigated the heritability of cerebral glutamate levels and whether a potential association with schizophrenia spectrum disorders could be explained by genetic factors. Twenty-three monozygotic (MZ) and 20 dizygotic (DZ) proband pairs con- or discordant for schizophrenia spectrum disorders, along with healthy control pairs (MZ = 28, DZ = 18) were recruited via the National Danish Twin Register and the Psychiatric Central Register (17 additional twins were scanned without their siblings). Glutamate levels in the left thalamus and the anterior cingulate cortex (ACC) were measured using 1[H]-magnetic resonance spectroscopy at 3 Tesla and analyzed by structural equation modeling. Glutamate levels in the left thalamus were heritable and positively correlated with liability for schizophrenia spectrum disorders (phenotypic correlation, 0.16, [0.02-0.29]; p = 0.010). The correlation was explained by common genes influencing both the levels of glutamate and liability for schizophrenia spectrum disorders. In the ACC, glutamate and glx levels were heritable, but not correlated to disease liability. Increases in thalamic glutamate levels found in schizophrenia spectrum disorders are explained by genetic influences related to the disease, and as such the measure could be a potential marker of genetic susceptibility, useful in early detection and stratification of patients with psychosis.

Nonmotor Symptoms in Vascular and Other Secondary Parkinsonism

Vascular parkinsonism (VP) is a relatively frequent variant of secondary parkinsonism caused by ischemic or hemorrhagic lesions of basal ganglia, midbrain, or their links with frontal cortex. According to different investigations, various forms of cerebrovascular disease cause 1%-15% of parkinsonism cases. Nonmotor symptoms are frequently found in VP and may negatively influence on quality of life. However, nonmotor symptoms such as hallucinations, orthostatic hypotension, REM-sleep behavior disorder, and anosmia are rarely revealed in VP, which may be noted to another diagnosis or mixed pathology. Clinical value of nonmotor symptoms in normal pressure hydrocephalus, toxic, and drug-induced parkinsonism is also discussed.

STRUCTURAL AND FUNCTIONAL CONNECTIVITY IN POSTTRAUMATIC STRESS DISORDER: ASSOCIATIONS WITH FKBP5

BACKGROUND

The integrity of connections between the hippocampus and the anterior cingulate cortex (ACC) is critical for adaptive cognitive and emotional processing; these connections may be compromised in posttraumatic stress disorder (PTSD). However, there is a lack of PTSD research that combines structural and functional connectivity data, and no studies have examined whether abnormal ACC-hippocampal connectivity is associated with genetic variability, particularly for polymorphisms of a gene that has been previously associated with PTSD, FKBP5. This was the goal of the present study.

METHODS

Fifty-four women with and without PTSD underwent diffusion tensor imaging and resting-state MRI. Probabilistic tractography was used to examine ACC-hippocampal structural connectivity; mean fractional anisotropy (FA) values were extracted from connectivity streamlines, which represent the cingulum bundle. Genotype data were collected for a single nucleotide polymorphism (SNP) of FKBP5, rs1360780.

RESULTS

Participants with PTSD demonstrated poorer structural connectivity (lower cingulum FA) compared to traumatized controls (F1, 50 = 6.77, P < .05). An interaction of FKBP5 genotype and diagnostic group was also observed (F1, 37 = 4.52, P = .04), indicating lower cingulum FA in carriers of two risk alleles for this SNP, compared to other diagnostic and genotype groups. Carriers of two FKBP5 risk alleles also demonstrated poorer hippocampus-ACC connectivity at rest (P < .05). When cingulum FA was used a regressor in a brain-wide, seed-based regression analysis, significant associations were found between the hippocampus and dorsal regions of the ACC (P < .05).

CONCLUSIONS

Individuals with PTSD demonstrated compromised structural connectivity of the hippocampus-ACC pathway. Altered hippocampus-ACC connectivity may represent a highly salient intermediate neural phenotype for PTSD.

Niacin Skin Sensitivity Is Increased in Adolescents at Ultra-High Risk for Psychosis

Background

Most studies provide evidence that the skin flush response to nicotinic acid (niacin) stimulation is impaired in schizophrenia. However, only little is known about niacin sensitivity in the ultra-high risk (UHR) phase of psychotic disorders.

Methods

We compared visual ratings of niacin sensitivity between adolescents at UHR for psychosis according to the one year transition outcome (UHR-T n = 11; UHR-NT n = 55) with healthy controls (HC n = 25) and first episode schizophrenia patients (FEP n = 25) treated with atypical antipsychotics.

Results

Contrary to our hypothesis niacin sensitivity of the entire UHR group was not attenuated, but significantly increased compared to the HC group, whereas no difference could be found between the UHR-T and UHR-NT groups. As expected, niacin sensitivity of FEP was attenuated compared to HC group. In UHR individuals niacin sensitivity was inversely correlated with omega-6 and -9 fatty acids (FA), but positively correlated with phospholipase A₂ (inPLA₂) activity, a marker of membrane lipid repair/remodelling.

Conclusions

Increased niacin sensitivity in UHR states likely indicates an impaired balance of eicosanoids and omega-6/-9 FA at a membrane level. Our findings suggest that the emergence of psychosis is associated with an increased mobilisation of eicosanoids prior to the transition to psychosis possibly reflecting a “pro-inflammatory state”, whereas thereafter eicosanoid mobilisation seems to be attenuated. Potential treatment implications for the UHR state should be further investigated.

Apoptotic markers in cultured fibroblasts correlate with brain metabolites and regional brain volume in antipsychotic-naive first-episode schizophrenia and healthy controls

Cultured fibroblasts from first-episode schizophrenia patients (FES) have shown increased susceptibility to apoptosis, which may be related to glutamate dysfunction and progressive neuroanatomical changes. Here we determine whether apoptotic markers obtained from cultured fibroblasts in FES and controls correlate with changes in brain glutamate and N-acetylaspartate (NAA) and regional brain volumes. Eleven antipsychotic-naive FES and seven age- and gender-matched controls underwent 3-Tesla magnetic resonance imaging scanning. Glutamate plus glutamine (Glx) and NAA levels were measured in the anterior cingulate (AC) and the left thalamus (LT). Hallmarks of apoptotic susceptibility (caspase-3-baseline activity, phosphatidylserine externalization and chromatin condensation) were measured in fibroblast cultures obtained from skin biopsies after inducing apoptosis with staurosporine (STS) at doses of 0.25 and 0.5 μM. Apoptotic biomarkers were correlated to brain metabolites and regional brain volume. FES and controls showed a negative correlation in the AC between Glx levels and percentages of cells with condensed chromatin (CC) after both apoptosis inductions (STS 0.5 μM: r = -0.90; P = 0.001; STS 0.25 μM: r = -0.73; P = 0.003), and between NAA and cells with CC (STS 0.5 μM induction r = -0.76; P = 0.002; STS 0.25 μM r = -0.62; P = 0.01). In addition, we found a negative correlation between percentages of cells with CC and regional brain volume in the right supratemporal cortex and post-central region (STS 0.25 and 0.5 μM; P < 0.05 family-wise error corrected (FWEc)). We reveal for the first time that peripheral markers of apoptotic susceptibility may correlate with brain metabolites, Glx and NAA, and regional brain volume in FES and controls, which is consistent with the neuroprogressive theories around the onset of the schizophrenia illness.

Regional brain atrophy and functional disconnection in Broca's area in individuals at ultra-high risk for psychosis and schizophrenia

Background

Abnormalities in cognitive abilities such as verbal fluency and in cognitive-related brain regions, particularly Broca’s area, have been reported in patients with schizophrenia. Additionally, previous studies have demonstrated that structural and functional abnormalities in Broca’s area were associated with clinical symptoms and cognitive deficits in patients with schizophrenia, suggesting that deficits in this area may reflect the core pathology of schizophrenia. Thus, it is important to understand how the structural volume and functional connectivity in this area changes at rest according to the course of the illness.

Methods/Principal Findings

We used magnetic resonance imaging (MRI) to measure the structural volume of Broca’s area as a region of interest in 16 schizophrenia, 16 ultra-high risk (UHR), and 23 healthy matched controls. We also assessed verbal fluency and analyzed differences across groups in the functional connectivity patterns using resting-state functional MRI. The UHR group showed significantly reduced structural volume in Broca’s area and significantly reduced functional connectivity between Broca’s area and the lateral and medial frontal cortex as well as decreased cognitive performance. Altered functional connectivity in patients was correlated with their positive symptoms.

Conclusions/Significance

Our results suggest the existence of functional disconnections in Broca’s area, even during resting-states, among those with schizophrenia as well as those at UHR for this disorder. These alterations may contribute to their clinical symptoms, suggesting that this is one of the key regions involved in the pathophysiology of schizophrenia.

Gray matter volumetric abnormalities associated with the onset of psychosis

Patients with psychosis display structural brain abnormalities in multiple brain regions. The disorder is characterized by a putative prodromal period called ultra-high-risk (UHR) status, which precedes the onset of full-blown psychotic symptoms. Recent studies on psychosis have focused on this period. Neuroimaging studies of UHR individuals for psychosis have revealed that the structural brain changes observed during the established phases of the disorder are already evident prior to the onset of the illness. Moreover, certain brain regions show extremely dynamic changes during the transition to psychosis. These neurobiological features may be used as prognostic and predictive biomarkers for psychosis. With advances in neuroimaging techniques, neuroimaging studies focusing on gray matter abnormalities provide new insights into the pathophysiology of psychosis, as well as new treatment strategies. Some of these novel approaches involve antioxidants administration, because it is suggested that this treatment may delay the progression of UHR to a full-blown psychosis and prevent progressive structural changes. The present review includes an update on the most recent developments in early intervention strategies for psychosis and potential therapeutic treatments for schizophrenia. First, we provide the basic knowledge of the brain regions associated with structural abnormalities in individuals at UHR. Next, we discuss the feasibility on the use of magnetic resonance imaging (MRI)-biomarkers in clinical practice. Then, we describe potential etiopathological mechanisms underlying structural brain abnormalities in prodromal psychosis. Finally, we discuss the potentials and limitations related to neuroimaging studies in individuals at UHR.

Structural brain alterations in individuals at ultra-high risk for psychosis: a review of magnetic resonance imaging studies and future directions

Individuals at ultra-high-risk (UHR) for psychosis have become a major focus for research designed to explore markers for early detection of and clinical intervention in schizophrenia. In particular, structural magnetic resonance imaging studies in UHR individuals have provided important insight into the neurobiological basis of psychosis and have shown the brain changes associated with clinical risk factors. In this review, we describe the structural brain abnormalities in magnetic resonance images in UHR individuals. The current accumulated data demonstrate that abnormalities in the prefrontal and temporal cortex and anterior cingulate cortex occur before illness onset. These regions are compatible with the regions of structural deficits found in schizophrenia and first-episode patients. In addition, the burgeoning evidence suggests that such structural abnormalities are potential markers for the transition to psychosis. However, most findings to date are limited because they are from cross-sectional rather than longitudinal studies. Recently, researchers have emphasized neurodevelopmental considerations with respect to brain structural alterations in UHR individuals. Future studies should be conducted to characterize the differences in the brain developmental trajectory between UHR individuals and healthy controls using a longitudinal design. These new studies should contribute to early detection and management as well as provide more predictive markers of later psychosis.