Proton magnetic resonance spectroscopy in 22q11 deletion syndrome

Using transcranial alternating current stimulation to enhance working memory skills in youths with 22q11.2 deletion syndrome: A randomized double-blind sham-controlled study

Abnormal cognitive development, particularly working memory (WM) deficits, is among the first apparent manifestations of psychosis. Yet, cognitive impairment only shows limited response to current pharmacological treatment. Alternative interventions to target cognition are highly needed in individuals at high risk for psychosis, like carriers of 22q11.2 deletion syndrome (22q11.2DS). Here we applied theta-tuned transcranial alternating current stimulation (tACS) between frontal and temporal regions during a visual WM task in 34 deletion carriers. We conducted a double-blind sham-controlled study over three consecutive days. The stimulation parameters were derived from individual structural MRI scan and HD-EEG data acquired at baseline (Day 1) to model current intensity and individual preferential theta peak. Participants were randomized to either sham or tACS (Days 2 and 3) and then completed a visual WM task and a control task. Our findings reveal that tACS was safe and well-tolerated among participants. We found a significantly increased accuracy in the visual WM but not the control task following tACS. Moreover, this enhancement in WM accuracy was greater after tACS than during tACS, indicating stronger offline effects than online effects. Our study therefore supports the application of repeated sessions of brain stimulation in 22q11.2DS.

Clozapine Use in 22q11.2 Deletion Syndrome: A Systematic Review of the Literature

BACKGROUND

22q11.2 deletion syndrome confers significant risk for the development of schizophrenia. While current recommendations regarding the management of psychotic symptoms in affected individuals are generally in keeping with treatment guidelines for general schizophrenia populations, evidence for the use of clozapine has come from case reports and retrospective observational data. As no reviews on the topic currently exist, a systematic review of clozapine use in 22q11.2 deletion syndrome was completed.

METHODS

In November 2023, a literature search was completed using both PubMed and Scopus to identify English-language articles that reported the use of clozapine in humans with 22q11.2 deletion syndrome.

RESULTS

Twenty-six articles describing 57 individuals were deemed eligible for inclusion. Most individuals had a diagnosis of treatment-resistant schizophrenia. Where reported, the mean or median dose of clozapine was relatively low, and the majority of individuals exhibited a good response (approximately 65.5% across individual case reports/series). While seizures were unsurprisingly the most commonly reported serious adverse effect, the majority of individuals were able to remain on (or be restarted on) clozapine by having their dose decreased and/or by adding an anticonvulsant (most commonly valproate).

CONCLUSIONS

This review reaffirms that individuals with 22q11.2 deletion syndrome may benefit from clozapine therapy even at a low dose, assuming they meet criteria for treatment-resistant schizophrenia and provided no contraindications exist. However, given the increased incidence of seizures in 22q11.2 deletion syndrome, the use of prophylactic anticonvulsant therapy should be considered, and hypoparathyroidism/hypocalcemia screened for and corrected before the initiation of clozapine. It is also recommended that clozapine blood levels be monitored.

Brain evolution and the meaning of catatonia - An update

Back in 2004, in a chapter titled "Brain Evolution and the Meaning of Catatonia", a case was made that the syndrome's core meaning is embedded in millions of years of vertebrate brain evolution. (Fricchione, 2004) In this update, advances over the last almost 20 years, in catatonia theory and research in particular, and pertinent neuropsychiatry in general, will be applied to this question of meaning. The approach will rely heavily on a number of thought leaders, including Nicos Tinbergen, Paul MacLean, John Bowlby, M. Marsel Mesulam, Bruce McEwen and Karl Friston. Their guidance will be supplemented with a selected survey of 21sty century neuropsychiatry, neurophysiology, molecular biology, neuroimaging and neurotherapeutics as applied to the catatonic syndrome. In an attempt to address the question of the meaning of the catatonic syndrome in human life, we will employ two conceptual networks representing the intersubjectivity of the quantitative conceptual network of physical terms and the subjectivity of the qualitative conceptual network of mental and spiritual terms. In the process, a common referent providing extensional identity may emerge (Goodman, 1991). The goal of this exercise is to enhance our attunement with the experience of patients suffering with catatonia. A deeper understanding of catatonia's origins in brain evolution and of the challenges of individual epigenetic development in the setting of environmental events coupled with appreciation of what has been described as the most painful mammalian condition, that of separation, has the potential to foster greater efforts on the part of clinicians to diagnose and treat patients who present with catatonia. In addition, in this ancient and extreme tactic, evolved to provide safety from extreme survival threat, one can speculate what is at the core of human fear and the challenge it presents to all of us. And when the biology, psychology and sociology of catatonia are examined, the nature of solutions to the challenge may emerge.

Atypical cortical networks in children at high-genetic risk of psychiatric and neurodevelopmental disorders

Although many genetic risk factors for psychiatric and neurodevelopmental disorders have been identified, the neurobiological route from genetic risk to neuropsychiatric outcome remains unclear. 22q11.2 deletion syndrome (22q11.2DS) is a copy number variant (CNV) syndrome associated with high rates of neurodevelopmental and psychiatric disorders including autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD) and schizophrenia. Alterations in neural integration and cortical connectivity have been linked to the spectrum of neuropsychiatric disorders seen in 22q11.2DS and may be a mechanism by which the CNV acts to increase risk. In this study, magnetoencephalography (MEG) was used to investigate electrophysiological markers of local and global network function in 34 children with 22q11.2DS and 25 controls aged 10-17 years old. Resting-state oscillatory activity and functional connectivity across six frequency bands were compared between groups. Regression analyses were used to explore the relationships between these measures, neurodevelopmental symptoms and IQ. Children with 22q11.2DS had altered network activity and connectivity in high and low frequency bands, reflecting modified local and long-range cortical circuitry. Alpha and theta band connectivity were negatively associated with ASD symptoms while frontal high frequency (gamma band) activity was positively associated with ASD symptoms. Alpha band activity was positively associated with cognitive ability. These findings suggest that haploinsufficiency at the 22q11.2 locus impacts short and long-range cortical circuits, which could be a mechanism underlying neurodevelopmental and psychiatric vulnerability in this high-risk group.

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

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

Glutamatergic and GABAergic metabolite levels in schizophrenia-spectrum disorders: a meta-analysis of 1H-magnetic resonance spectroscopy studies

BACKGROUND

The glutamate (Glu) and gamma aminobutyric acid (GABA) hypotheses of schizophrenia were proposed in the 1980s. However, current findings on those metabolite levels in schizophrenia have been inconsistent, and the relationship between their abnormalities and the pathophysiology of schizophrenia remains unclear. To summarize the nature of the alterations of glutamatergic and GABAergic systems in schizophrenia, we conducted meta-analyses of proton magnetic resonance spectroscopy (¹H-MRS) studies examining these metabolite levels.

METHODS

A systematic literature search was conducted using Embase, Medline, PsycINFO, and PubMed. Original studies that compared four metabolite levels (Glu, glutamine [Gln], Glx [Glu+Gln], and GABA), as measured by ¹H-MRS, between individuals at high risk for psychosis, patients with first-episode psychosis, or patients with schizophrenia and healthy controls (HC) were included. A random-effects model was used to calculate the effect sizes for group differences in these metabolite levels of 18 regions of interest between the whole group or schizophrenia group and HC. Subgroup analysis and meta-regression were performed based on the status of antipsychotic treatment, illness stage, treatment resistance, and magnetic field strength.

RESULTS

One-hundred-thirty-four studies met the eligibility criteria, totaling 7993 participants with SZ-spectrum disorders and 8744 HC. 14 out of 18 ROIs had enough numbers of studies to examine the group difference in the metabolite levels. In the whole group, Glx levels in the basal ganglia (g = 0.32; 95% CIs: 0.18-0.45) were elevated. Subgroup analyses showed elevated Glx levels in the hippocampus (g = 0.47; 95% CIs: 0.21-0.73) and dorsolateral prefrontal cortex (g = 0.25; 95% CIs: 0.05-0.44) in unmedicated patients than HC. GABA levels in the MCC were decreased in the first-episode psychosis group compared with HC (g = -0.40; 95% CIs: -0.62 to -0.17). Treatment-resistant schizophrenia (TRS) group had elevated Glx and Glu levels in the MCC (Glx: g = 0.7; 95% CIs: 0.38-1.01; Glu: g = 0.63; 95% CIs: 0.31-0.94) while MCC Glu levels were decreased in the patient group except TRS (g = -0.17; 95% CIs: -0.33 to -0.01).

CONCLUSIONS

Increased glutamatergic metabolite levels and reduced GABA levels indicate that the disruption of excitatory/inhibitory balance may be related to the pathophysiology of schizophrenia-spectrum 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.

Psychiatric phenotypes associated with hyperprolinemia: A systematic review

Hyperprolinemia Type I and II are genetic metabolic disorders caused by disrupted proline degradation. It has been suggested that hyperprolinemia is associated with increased risk of developmental and mental disorders but detailed information on the psychiatric phenotype in hyperprolinemic patients is limited. Following PRISMA guidelines, we carried out a systematic review to clarify psychiatric phenotypes in patients with hyperprolinemia. We screened 1753 studies and included 35 for analysis, including 20 case reports and 15 case-control and cohort studies. From these studies, a common psychiatric phenotype is observed with a high prevalence of developmental delay, intellectual disability, autism spectrum disorders, and psychosis spectrum disorders. In most cases, a genetic cause of hyperprolinemia was known, these included mutations in the PRODH and ALDH4A1 genes and deletions of chromosome 22q11.2. No evidence for a biochemical phenotype-clinical phenotype correlation was found; that is, no association between higher proline levels and specific psychiatric phenotypes was observed. This suggests that genomic and environmental factors are likely to contribute to clinical outcomes. More studies are needed to clarify whether hyperprolinemia is a primary causal factor underlying the increased risk of developing psychiatric disorders seen in patients with hyperprolinemia, or whether hyperprolinemia and psychiatric disorders are both consequences of a shared underlying mechanism.

Layers II/III of Prefrontal Cortex in Df(h22q11)/+ Mouse Model of the 22q11.2 Deletion Display Loss of Parvalbumin Interneurons and Modulation of Neuronal Morphology and Excitability

The 22q11.2 deletion has been identified as a risk factor for multiple neurodevelopmental disorders. Behavioral and cognitive impairments are common among carriers of the 22q11.2 deletion. Parvalbumin expressing (PV⁺) interneurons provide perisomatic inhibition of excitatory neuronal circuits through GABA_A receptors, and a deficit of PV⁺ inhibitory circuits may underlie a multitude of the behavioral and functional deficits in the 22q11.2 deletion syndrome. We investigated putative deficits of PV⁺ inhibitory circuits and the associated molecular, morphological, and functional alterations in the prefrontal cortex (PFC) of the Df(h22q11)/+ mouse model of the 22q11.2 hemizygous deletion. We detected a significant decrease in the number of PV⁺ interneurons in layers II/III of PFC in Df(h22q11)/+ mice together with a reduction in the mRNA and protein levels of GABA_A (α3), a PV⁺ putative postsynaptic receptor subunit. Pyramidal neurons from the same layers further experienced morphological reorganizations of spines and dendrites. Accordingly, a decrease in the levels of the postsynaptic density protein 95 (PSD95) and a higher neuronal activity in response to the GABA_A antagonist bicuculline were measured in these layers in PFC of Df(h22q11)/+ mice compared with their wild-type littermates. Our study shows that a hemizygotic deletion of the 22q11.2 locus leads to deficit in the GABAergic control of network activity and involves molecular and morphological changes in both the inhibitory and excitatory synapses of parvalbumin interneurons and pyramidal neurons specifically in layers II/III PFC.

Glutamatergic and GABAergic reactivity and cognition in 22q11.2 deletion syndrome and healthy volunteers: A randomized double-blind 7-Tesla pharmacological MRS study

AIMS

22q11.2 deletion syndrome (22q11.2DS) is associated with impaired cognitive functioning. Glutamatergic pathways have been linked with cognition and are hypothesized to be disrupted in 22q11.2DS patients, possibly 'shifting' the excitatory (glutamate)/inhibitory (GABA) balance. Hence, the glutamate/GABA balance may constitute a target for pharmacological treatment. We aimed to examine alterations of glutamate/GABA metabolites in 22q11.2DS in vivo using riluzole, a compound with glutamate/GABA-modulating action, as pharmacological challenge.

METHODS

Seventeen 22q11.2DS patients and 20 matched healthy controls were enrolled in this randomized double-blind placebo-controlled crossover study. Glutamate and glutamine concentrations in the anterior cingulate cortex (ACC) and striatum, as well as ACC GABA concentrations were obtained after placebo and after a single dose of 50 mg riluzole using 7-Tesla magnetic resonance spectroscopy (MRS). Within the 22q11.2DS group, the relationship between metabolite concentrations and cognition was examined.

RESULTS

No group differences were found in ACC and striatal metabolite concentrations following placebo. Riluzole numerically decreased ACC (η2= 0.094) but not striatal glutamate concentrations as well as ACC GABA concentrations (η2= 0.176) in all subjects. In both regions, riluzole did not alter glutamine concentration. No interaction effects were found. Although not significant after Bonferroni correction, ACC glutamate concentrations were inversely correlated with cognitive functions in 22q11.2DS patients.

DISCUSSION

We did not demonstrate altered ACC and striatal metabolite concentrations in 22q11.2DS. Nevertheless, these results suggest that glutamate and GABA can be modulated with a single dose of riluzole. Possibly, riluzole may have memory-enhancing effects in 22q11.2DS. Future studies should examine the long-term effects of riluzole on cognition.

Glutamatergic function in a genetic high-risk group for psychosis: A proton magnetic resonance spectroscopy study in individuals with 22q11.2 deletion

Glutamatergic dysregulation is one of the leading theories regarding the pathoaetiolopy of schizophrenia. Meta-analysis of magnetic resonance spectroscopy studies in schizophrenia shows increased levels of glutamate and glutamine (Glx) in the medial frontal cortex and basal ganglia in clinical high-risk groups for psychosis and increased glutamine levels in the thalamus, but it is unclear if this is also the case in people at genetic high risk for psychosis. The aim of this study was to investigate glutamatergic function in the anterior cingulate cortex, striatum and thalamus in carriers of a genetic variant (22q11.2 deletion) associated with a high risk for psychosis. 53 volunteers (23 22q11.2 deletion carriers and 30 controls) underwent proton magnetic resonance spectroscopy imaging and neuropsychological assessments for prodromal psychotic symptoms, schizotypy, anxiety, depression and FSIQ. We did not find any difference between groups in Glx in the anterior cingulate cortex, striatum or thalamus (Glx: t(50)=-1.26, p = 0.21; U = 251, z = -0.7, p = 0.49; U = 316, z= -0.26, p = 0.79, respectively). No correlation was detected between Glx levels in any region and symptomatology or FSIQ. Our findings indicate that glutamatergic function is not altered in people at genetic high risk of psychosis due to the 22q11.2 deletion, which could suggest that this is not the mechanism underlying psychosis risk in 22q11.2 deletion carriers.

Neurobiological perspective of 22q11.2 deletion syndrome

22q11.2 deletion syndrome is characterised by a well defined microdeletion that is associated with a high risk of neuropsychiatric disorders, including intellectual disability, schizophrenia, attention-deficit hyperactivity disorder, autism spectrum disorder, anxiety disorders, seizures and epilepsy, and early-onset Parkinson's disease. Preclinical and clinical data reveal substantial variability of the neuropsychiatric phenotype despite the shared underlying deletion in this genetic model. Factors that might explain this variability include genetic background effects, additional rare pathogenic variants, and potential regulatory functions of some genes in the 22q11.2 deletion region. These factors might also be relevant to the pathophysiology of these neuropsychiatric disorders in the general population. We review studies that might provide insight into pathophysiological mechanisms underlying the expression of neuropsychiatric disorders in 22q11.2 deletion syndrome, and potential implications for these common disorders in the general (non-deleted) population. The recurrent hemizygous 22q11.2 deletion, associated with 22q11.2 deletion syndrome, has attracted attention as a genetic model for common neuropsychiatric disorders because of its association with substantially increased risk of such disorders.¹ Studying such a model has many advantages. First, 22q11.2 deletion has been genetically well characterised.² Second, most genes present in the region typically deleted at the 22q11.2 locus are expressed in the brain.^3-5 Third, genetic diagnosis might be made early in life, long before recognisable neuropsychiatric disorders have emerged. Thus, this genetic condition offers a unique opportunity for early intervention, and monitoring individuals with 22q11.2 deletion syndrome throughout life could provide important information on factors contributing to disease risk and protection. Despite the commonly deleted region being shared by about 90% of individuals with 22q11.2 deletion syndrome, neuropsychiatric outcomes are highly variable between individuals and across the lifespan. A clear link remains to be established between genotype and phenotype.^3,5 In this Review, we summarise preclinical and clinical studies investigating biological mechanisms in 22q11.2 deletion syndrome, with a focus on those that might provide insight into mechanisms underlying neuropsychiatric disorders in 22q11.2 deletion syndrome and in the general population.

Abnormal development of early auditory processing in 22q11.2 Deletion Syndrome

The 22q11.2 Deletion Syndrome (22q11.2 DS) is one of the highest genetic risk factors for the development of schizophrenia spectrum disorders. In schizophrenia, reduced amplitude of the frequency mismatch negativity (fMMN) has been proposed as a promising neurophysiological marker for progressive brain pathology. In this longitudinal study in 22q11.2 DS, we investigate the progression of fMMN between childhood and adolescence, a vulnerable period for brain maturation. We measured evoked potentials to auditory oddball stimuli in the same sample of 16 patients with 22q11.2 DS and 14 age-matched controls in childhood and adolescence. In addition, we cross-sectionally compared an increased sample of 51 participants with 22q11.2 DS and 50 controls divided into two groups (8-14 and 14-20 years). The reported results are obtained using the fMMN difference waveforms. In the longitudinal design, the 22q11.2 deletion carriers exhibit a significant reduction in amplitude and a change in topographic patterns of the mismatch negativity response from childhood to adolescence. The same effect, reduced mismatch amplitude in adolescence, while preserved during childhood, is observed in the cross-sectional study. These results point towards functional changes within the brain network responsible for the fMMN. In addition, the adolescents with 22q11.2 DS displayed a significant increase in amplitude over central electrodes during the auditory N1 component. No such differences, reduced mismatch response nor increased N1, were observed in the typically developing group. These findings suggest different developmental trajectories of early auditory sensory processing in 22q11.2 DS and functional changes that emerge during the critical period of increased risk for schizophrenia spectrum disorders.

Neuropsychiatric expression and catatonia in 22q11.2 deletion syndrome: An overview and case series

Individuals with 22q11.2 deletion syndrome (22q11.2DS) are at elevated risk of developing treatable psychiatric and neurological disorders, including anxiety disorders, schizophrenia, seizures, and movement disorders, often beginning in adolescence or early to mid-adulthood. Here, we provide an overview of neuropsychiatric features associated with 22q11.2DS in adulthood. Results of a new case series of 13 individuals with 22q11.2DS and catatonic features together with 5 previously reported cases support a potential association of this serious psychomotor phenotype with the 22q11.2 deletion. As in the general population, catatonic features in 22q11.2DS occurred in individuals with schizophrenia, other psychotic and non-psychotic psychiatric disorders, and neurological disorders like Parkinson's disease. We place the results in the context of an updated review of catatonia in other genetic conditions. The complex neuropsychiatric expression and risk profile of 22q11.2DS highlights the need to consider co-morbid factors and provide care tailored to the individual patient. The results reinforce the need for periodic monitoring for the emergence of psychiatric and neurological manifestations including catatonic features. Pending further research, enhanced recognition and informed anticipatory care promise to facilitate the early diagnosis that allows for timely implementation and optimization of effective treatments.

Evidence for regional hippocampal damage in patients with schizophrenia

PURPOSE

Schizophrenia patients show cognitive and mood impairments, including memory loss and depression, suggesting damage in the brain regions. The hippocampus is a brain structure that is significantly involved in memory and mood function and shows impairment in schizophrenia. In the present study, we examined the regional hippocampal changes in schizophrenia patients using voxel-based morphometry (VBM), Freesurfer, and proton magnetic resonance spectroscopy (¹H MRS) procedures.

METHODS

¹H MRS and high-resolution T1-weighted magnetic resonance imaging were collected in both healthy control subjects (N = 28) and schizophrenia patients (N = 28) using 3-Tesla whole body MRI system. Regional hippocampal volume was analyzed using VBM and Freesufer procedures. The relative ratios of the neurometabolites were calculated using linear combination model (LCModel).

RESULTS

Compared to controls, schizophrenia patients showed significantly decreased gray matter volume in the hippocampus. Schizophrenia patients also showed significantly reduced glutamate (Glu) and myo-inositol (mI) ratios in the hippocampus. Additionally, significant positive correlation between gray matter volume and Glu/tCr was also observed in the hippocampus in schizophrenia.

CONCLUSION

Our findings provide an evidence for a possible association between structural deficits and metabolic alterations in schizophrenia patients.

Cortical Morphology Differences in Subjects at Increased Vulnerability for Developing a Psychotic Disorder: A Comparison between Subjects with Ultra-High Risk and 22q11.2 Deletion Syndrome

Introduction

Subjects with 22q11.2 deletion syndrome (22q11DS) and subjects with ultra-high risk for psychosis (UHR) share a risk of approximately 30% to develop a psychotic disorder. Studying these groups helps identify biological markers of pathophysiological processes involved in the development of psychosis. Total cortical surface area (cSA), total cortical grey matter volume (cGMV), cortical thickness (CT), and local gyrification index (LGI) of the cortical structure have a distinct neurodevelopmental origin making them important target markers to study in relation to the development of psychosis.

Materials and Methods

Structural T1-weighted high resolution images were acquired using a 3 Tesla Intera MRI system in 18 UHR subjects, 18 22q11DS subjects, and 24 matched healthy control (HC) subjects. Total cSA, total cGMV, mean CT, and regional vertex-wise differences in CT and LGI were assessed using FreeSurfer software. The Positive and Negative Syndrome Scale was used to assess psychotic symptom severity in UHR and 22q11DS subjects at time of scanning.

Results

22q11DS subjects had lower total cSA and total cGMV compared to UHR and HC subjects. The 22q11DS subjects showed bilateral lower LGI in the i) prefrontal cortex, ii) precuneus, iii) precentral gyrus and iv) cuneus compared to UHR subjects. Additionally, lower LGI was found in the left i) fusiform gyrus and right i) pars opercularis, ii) superior, and iii) inferior temporal gyrus in 22q11DS subjects compared to HC. In comparison to 22q11DS subjects, the UHR subjects had lower CT of the insula. For both risk groups, positive symptom severity was negatively correlated to rostral middle frontal gyrus CT.

Conclusion

A shared negative correlation between positive symptom severity and rostral middle frontal gyrus CT in UHR and 22q11DS may be related to their increased vulnerability to develop a psychotic disorder. 22q11DS subjects were characterised by widespread lower degree of cortical gyrification linked to early and postnatal neurodevelopmental pathology. No implications for early neurodevelopmental pathology were found for the UHR subjects, although they did have distinctively lower insula CT which may have arisen from defective pruning processes during adolescence. Implications of these findings in relation to development of psychotic disorders are in need of further investigation in longitudinal studies.

Assessing the Cognitive Translational Potential of a Mouse Model of the 22q11.2 Microdeletion Syndrome

A chromosomal microdeletion at the 22q11.2 locus is associated with extensive cognitive impairments, schizophrenia and other psychopathology in humans. Previous reports indicate that mouse models of the 22q11.2 microdeletion syndrome (22q11.2DS) may model the genetic basis of cognitive deficits relevant for neuropsychiatric disorders such as schizophrenia. To assess the models usefulness for drug discovery, a novel mouse (Df(h22q11)/+) was assessed in an extensive battery of cognitive assays by partners within the NEWMEDS collaboration (Innovative Medicines Initiative Grant Agreement No. 115008). This battery included classic and touchscreen-based paradigms with recognized sensitivity and multiple attempts at reproducing previously published findings in 22q11.2DS mouse models. This work represents one of the most comprehensive reports of cognitive functioning in a transgenic animal model. In accordance with previous reports, there were non-significant trends or marginal impairment in some tasks. However, the Df(h22q11)/+ mouse did not show comprehensive deficits; no robust impairment was observed following more than 17 experiments and 14 behavioral paradigms. Thus - within the current protocols - the 22q11.2DS mouse model fails to mimic the cognitive alterations observed in human 22q11.2 deletion carriers. We suggest that the 22q11.2DS model may induce liability for cognitive dysfunction with additional "hits" being required for phenotypic expression.

Cross-sectional Study of Glutamate in the Anterior Cingulate and Hippocampus in Schizophrenia

BACKGROUND

There has been growing support for dysfunctions of the excitatory glutamatergic system and its implications for the psychophysiology of schizophrenia. However, previous studies reported mixed results regarding glutamate concentrations in schizophrenia with varying deviations across brain regions.

METHODS

We used an optimized proton magnetic resonance spectroscopy procedure to measure absolute glutamate concentrations in the left hippocampal region and the anterior cingulate cortex (ACC) in 29 medicated patients with schizophrenia and in 29 control participants without mental disorder.

RESULTS

The glutamate concentrations were significantly lower in the ACC but higher in the hippocampus of patients compared to controls. ACC and hippocampal glutamate concentrations correlated positively in patients but not in controls. ACC glutamate was weakly associated with Clinical Global Impression score and duration of illness in patients.

CONCLUSION

Glutamate concentrations in schizophrenia deviate from controls and show associations with disease severity. A higher concentration of hippocampal glutamate in schizophrenia compared to controls is shown. The association between ACC and hippocampus glutamate concentrations in patients with schizophrenia suggests an abnormal coupling of excitatory systems compared to controls as predicted by previous glutamate models of schizophrenia.

PRODH rs450046 and proline x COMT Val¹⁵⁸ Met interaction effects on intelligence and startle in adults with 22q11 deletion syndrome

RATIONALE

22q11 deletion syndrome (22q11DS) is associated with an increased risk for psychotic disorders, suggesting a relationship between genotypes and the pathophysiology of psychotic disorders. Two genes in the deleted region, catechol-O-methyl-transferase (COMT) and proline dehydrogenase (oxidase) 1 (PRODH), contain polymorphisms associated with neuropsychiatric phenotypes.

OBJECTIVES

Here, we explored the association between polymorphisms and full-scale intelligence (FSIQ), startle reactivity (SR) and prepulse inhibition (PPI) in adults with 22q11DS.

METHODS

Forty-five adults with 22q11DS were genotyped for PRODH rs450046, rs372055 and COMT Val(158)Met. Plasma proline levels, FSIQ, SR and PPI were measured.

RESULTS

Thirty-five percent of the subjects were hyperprolinemic with a median proline value of 456 μmol/L. C allele carriers of PRODH rs450046 had a lower FSIQ compared to T allele carriers, indicating the C allele to be a risk allele (C allele: mean FSIQ 60.2 (sd 8.7); T allele: mean FSIQ 73.7 (sd 11.5); F 1,43 = 7.59; p = 0.009; partial η (2) = 0.15). A significant interaction effect of proline levels and COMT Val(158)Met genotype was found for SR (F 1,16 = 7.9; p = 0.01; partial η (2) = 0.33), but not for PPI and FSIQ. In subjects with hyperprolinemia, the COMT Val(158)Met genotype effect on SR was stronger than in subjects with normal proline levels.

CONCLUSIONS

Overall, these data provide further evidence for the risk effect of elevated proline levels combined with the COMT Met allele and support the possibilities of using 22q11DS as a model to investigate genotype effects on psychiatric disorders.

Supplementation of antipsychotic treatment with sarcosine – GlyT1 inhibitor – causes changes of glutamatergic (1)NMR spectroscopy parameters in the left hippocampus in patients with stable schizophrenia

Glutamatergic system, the main stimulating system of the brain, plays an important role in the pathogenesis of schizophrenia. Hippocampus, a structure crucial for memory and cognitive functions and rich in glutamatergic neurons, is a natural object of interest in studies on psychoses. Sarcosine, a glycine transporter (GlyT-1) inhibitor influences the function of NMDA receptor and glutamate-dependent transmission. The aim of the study was to assess the effects of sarcosine on metabolism parameters in the left hippocampus in patients with schizophrenia. Assessments were performed using proton nuclear magnetic resonance ((1)H NMR) spectroscopy (1.5T). Fifty patients diagnosed with schizophrenia (DSM-IV-TR), with dominant negative symptoms, in stable clinical condition and stable antipsychotics doses were treated either with sarcosine (n=25) or placebo (n=25). Spectroscopic parameters were evaluated within groups and between two groups before and after 6-month intervention. All patients were also assessed with the Positive and Negative Syndrome Scale (PANSS). In the sarcosine group, after 6-month treatment, we found significant decrease in hippocampal Glx/Cr (Glx-complex of glutamate, glutamine and GABA, Cr-creatine) and Glx/Cho (Cho-choline), while N-acetylaspartate (NAA), myo-inositol (mI), Cr and Cho parameters remained stable along the study and also did not differ significantly between both groups. This is the first study showing that a pharmacological intervention in schizophrenia, particularly augmentation of the antypsychotic treatment with sarcosine, may reverse the pathological increase in glutamatergic transmission in the hippocampus. The results confirm involvement of glutamatergic system in the pathogenesis of schizophrenia and demonstrate beneficial effects of GlyT-1 inhibitor on the metabolism in the hippocampus and symptoms of schizophrenia.

Magnetic resonance spectroscopy and tissue protein concentrations together suggest lower glutamate signaling in dentate gyrus in schizophrenia

Hippocampal dysfunction in schizophrenia is widely acknowledged, yet the mechanism of such dysfunction remains debated. In this study we investigate the excitatory and inhibitory hippocampal neurotransmission using two complementary methodologies, proton magnetic resonance spectroscopy (MRS) and tissue biochemistry, sampling individuals with schizophrenia in vivo and postmortem hippocampal tissue in vitro. The results show significantly lower glutamate concentrations in hippocampus in schizophrenia, an in vivo finding mirrored by lower GluN1 protein levels selectively in the dentate gyrus (DG) in vitro. In a mouse model with a DG knockout of the GRIN1 gene, we further confirmed that a selective decrease in DG GluN1 is sufficient to decrease the glutamate concentrations in the whole hippocampus. Gamma-aminobutyric acid (GABA) concentrations and GAD67 protein were not significantly different in hippocampus in schizophrenia. Similarly, GABA concentrations in the hippocampi of mice with a DG knockout of the GRIN1 gene were not significantly different from wild type. These findings provide strong evidence implicating the excitatory system within hippocampus in the pathophysiology of schizophrenia, particularly indicating the DG as a site of pathology.

Glutamatergic markers, age, intellectual functioning and psychosis in 22q11 deletion syndrome

RATIONALE

Patients with 22q11 deletion syndrome (22q11DS) have a high prevalence of intellectual disabilities and psychiatric disorders, including psychosis. Haplo-insufficiency of genes in the deleted region may offer a partial explanation for the increased vulnerability for psychosis and intellectual disability. One gene of particular interest is the gene coding for proline dehydrogenase (PRODH), an enzyme responsible for the conversion of proline into glutamate.

OBJECTIVES

Because abnormalities in glutamatergic signaling are thought to be responsible for cognition and psychosis in the general population, we hypothesized that PRODH haplo-insufficiency may underlie some of the cognitive and psychotic features seen in 22q11DS.

METHODS

In this explorative study, we investigated the relation between plasma proline, glutamate, and glutamine and age, intelligence, and psychosis in 64 adults with 22q11DS.

RESULTS

Hyperprolinemia was found in 31.3% of subjects with 22q11DS. A relation between glutamine, glutamate, proline, and presence of psychosis was not observed. Regression analysis revealed a positive relation between plasma glutamate and age, a positive relation of glutamate with antipsychotic drugs, a relation of glutamine and gender, and a positive relation of glutamine and mood stabilizing drugs, and a negative relation of the ratio glutamine/glutamate and age. The group with relatively lower IQ had higher glutamate levels compared to the group with relatively higher IQ.

CONCLUSIONS

Our results suggest that 22q11DS is accompanied by abnormalities in glutamatergic metabolism. Future longitudinal studies are needed to further investigate the glutamatergic system in 22q11DS and how this affects the development of cognitive problems and psychopathology.

Psychopathology in adults with 22q11 deletion syndrome and moderate and severe intellectual disability

BACKGROUND

22q11 deletion syndrome (22q11DS) is associated with mild or borderline intellectual disability (ID). There are hardly any reports on subjects with 22q11DS with moderate or severe ID, and therefore its behavioural and psychiatric characteristics are unknown.

METHOD

We describe behavioural and psychiatric characteristics of 33 adults with 22q11DS and a Full-Scale IQ (FSIQ) below 55. Participants were divided into two groups: one group having a FSIQ ≤ 55 caused by intellectual decline (n = 21) and one group with a FSIQ ≤ 55 who had always functioned at this level (n = 12).

RESULTS

High scores on psychopathology sub-scales were found for both subgroups. 22q11DS patients with intellectual decline showed higher rates of co-morbid psychopathology, particularly psychosis. Furthermore, psychosis and intellectual decline were positive correlated.

CONCLUSION

This is the first report addressing adult patients with 22q11DS and moderate to severe ID. Overall we found high levels of psychopathology with higher scores of psychopathology in the intellectual decline group. Life time psychosis seems to be related to deterioration.

Glutamatergic abnormalities in schizophrenia: a review of proton MRS findings

The last fifteen years have seen a great increase in our understanding of the role of glutamate in schizophrenia (SCZ). The glutamate hypothesis focuses on disturbances in brain glutamatergic pathways and impairment in signaling at glutamate receptors. Proton Magnetic Resonance Spectroscopy ((1)H-MRS) is an MR-based technique that affords investigators the ability to study glutamate function by measuring in vivo glutamatergic indices in the brains of individuals with SCZ. (1)H-MRS studies have been performed comparing glutamatergic levels of individuals with SCZ and healthy control subjects or studying the effect of antipsychotic medications on glutamatergic levels. In this article we summarize the results of these studies by brain region. We will review the contribution of (1)H-MRS studies to our knowledge about glutamatergic abnormalities in the brains of individuals with SCZ and discuss the implications for future research and clinical care.

Imaging glutamate in schizophrenia: review of findings and implications for drug discovery

Currently, all treatments for schizophrenia (SCZ) function primarily by blocking D(2)-type dopamine receptors. Given the limitations of these medications, substantial efforts have been made to identify alternative neurochemical targets for treatment development in SCZ. One such target is brain glutamate. The objective of this article is to review and synthesize the proton magnetic resonance spectroscopy ((1)H MRS) and positron emission tomography (PET)/single-photon emission computed tomography (SPECT) investigations that have examined glutamatergic indices in SCZ, including those of modulatory compounds such as glutathione (GSH) and glycine, as well as data from ketamine challenge studies. The reviewed (1)H MRS and PET/SPECT studies support the theory of hypofunction of the N-methyl-D-aspartate receptor (NMDAR) in SCZ, as well as the convergence between the dopamine and glutamate models of SCZ. We also review several advances in MRS and PET technologies that have opened the door for new opportunities to investigate the glutamate system in SCZ and discuss some ways in which these imaging tools can be used to facilitate a greater understanding of the glutamate system in SCZ and the successful and efficient development of new glutamate-based treatments for SCZ.

Converging levels of analysis on a genomic hotspot for psychosis: insights from 22q11.2 deletion syndrome

Schizophrenia is a devastating neurodevelopmental disorder that, despite extensive research, still poses a considerable challenge to attempts to unravel its heterogeneity, and the complex biochemical mechanisms by which it arises. While the majority of cases are of unknown etiology, accumulating evidence suggests that rare genetic mutations, such as 22q11.2 Deletion Syndrome (22qDS), can play a significant role in predisposition to the illness. Up to 25% of individuals with 22qDS eventually develop schizophrenia; conversely, this deletion is estimated to account for 1-2% of schizophrenia cases overall. This locus of Chromosome 22q11.2 contains genes that encode for proteins and enzymes involved in regulating neurotransmission, neuronal development, myelination, microRNA processing, and post-translational protein modifications. As a consequence of the deletion, affected individuals exhibit cognitive dysfunction, structural and functional brain abnormalities, and neurodevelopmental anomalies that parallel many of the phenotypic characteristics of schizophrenia. As an illustration of the value of rare, highly penetrant genetic subtypes for elucidating pathological mechanisms of complex neuropsychiatric disorders, we provide here an overview of the cellular, network, and systems-level anomalies found in 22qDS, and review the intriguing evidence for this disorder's association with schizophrenia. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.

An epigenetic framework for neurodevelopmental disorders: from pathogenesis to potential therapy

Neurodevelopmental disorders (NDDs) are characterized by aberrant and delayed early-life development of the brain, leading to deficits in language, cognition, motor behaviour and other functional domains, often accompanied by somatic symptoms. Environmental factors like perinatal infection, malnutrition and trauma can increase the risk of the heterogeneous, multifactorial and polygenic disorders, autism and schizophrenia. Conversely, discrete genetic anomalies are involved in Down, Rett and Fragile X syndromes, tuberous sclerosis and neurofibromatosis, the less familiar Phelan-McDermid, Sotos, Kleefstra, Coffin-Lowry and "ATRX" syndromes, and the disorders of imprinting, Angelman and Prader-Willi syndromes. NDDs have been termed "synaptopathies" in reference to structural and functional disturbance of synaptic plasticity, several involve abnormal Ras-Kinase signalling ("rasopathies"), and many are characterized by disrupted cerebral connectivity and an imbalance between excitatory and inhibitory transmission. However, at a different level of integration, NDDs are accompanied by aberrant "epigenetic" regulation of processes critical for normal and orderly development of the brain. Epigenetics refers to potentially-heritable (by mitosis and/or meiosis) mechanisms controlling gene expression without changes in DNA sequence. In certain NDDs, prototypical epigenetic processes of DNA methylation and covalent histone marking are impacted. Conversely, others involve anomalies in chromatin-modelling, mRNA splicing/editing, mRNA translation, ribosome biogenesis and/or the regulatory actions of small nucleolar RNAs and micro-RNAs. Since epigenetic mechanisms are modifiable, this raises the hope of novel therapy, though questions remain concerning efficacy and safety. The above issues are critically surveyed in this review, which advocates a broad-based epigenetic framework for understanding and ultimately treating a diverse assemblage of NDDs ("epigenopathies") lying at the interface of genetic, developmental and environmental processes. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.

Altered development of the dorsolateral prefrontal cortex in chromosome 22q11.2 deletion syndrome: an in vivo proton spectroscopy study

BACKGROUND

Chromosome 22q11.2 deletion syndrome (22q11DS), the most common microdeletion in humans, is associated with multiple medical features, almost universal cognitive deficits, and a high risk of schizophrenia. The metabolic basis of the psychological/psychiatric features is not well understood. Volumetric brain imaging studies have shown that gray matter abnormalities in the dorsolateral prefrontal cortex (DLPFC), an area that is believed to be integral for higher neurocognition, as well as being involved in schizophrenia, are associated with the psychological manifestations. However, studies have not characterized any possible metabolite alterations within the DLPFC of children with 22q11DS and their correlations with the psychological findings.

METHODS

We conducted a short echo time, single-voxel, in vivo proton spectroscopy study involving children with 22q11DS (n = 26) and matched control subjects (n = 23).

RESULTS

Absolute N-acetylaspartate (NAA) levels from the DLPFC were significantly elevated in children with 22q11DS compared with control subjects and the elevations were associated with poor global functioning and higher rates of comorbid attention-deficit/hyperactivity disorder. Children with 22q11DS had a lack of an age-associated decrease in NAA levels, a trend seen in the control subjects. However, the results did not remain statistically significant after corrections for multiple comparisons were made.

CONCLUSIONS

These findings represent the first report of proton spectroscopy in children with 22q11DS. The elevated DLPFC NAA levels and the lack of decreasing trends in NAA with age in the 22q11DS group relative to control subjects suggest an alteration in cortical development. Also, such neuronal dysmaturation is associated with psychopathology in children with 22q11DS.

Is there a core neuropsychiatric phenotype in 22q11.2 deletion syndrome?

PURPOSE OF REVIEW

The aim is to discuss the clinical features of psychiatric illness in 22q11.2 deletion syndrome (22q11DS), and to review current evidence that a core neuropsychiatric phenotype could underlie the full spectrum of different presentations.

RECENT FINDINGS

Individuals carrying the 22q11.2 microdeletion are at risk for diverse psychiatric diagnoses across the lifespan, including schizophrenia in a significant minority, and anxiety or mood disorder in the majority. Symptoms and cognitive disruptions can be grouped into domains: attention-executive deficits, social-cognitive deficits, anxiety-affective dysregulation, and psychotic phenomena. These domains do not respect the boundaries of traditional diagnostic categories, and can be consistently recognized in children, adolescents and adults. There is early evidence that some symptom-domain disruptions may predict adult psychiatric morbidity.

SUMMARY

If a core neuropsychiatric phenotype does exist in 22q11DS, its detection is likely to require dimensional assessment of subtle aspects of cognitive and emotional processing, not encompassed by current diagnostic systems. A core phenotype would account for disruptions across multiple symptom domains, directly reflecting genetic and neurobiological mechanisms. Relative severity of a core phenotype would predict risk for multiple psychiatric disorders, and could, therefore, be an important target for therapeutic and preventive interventions. A core phenotype meeting these criteria has not yet been defined for 22q11DS.

Dysregulation of DGCR6 and DGCR6L: psychopathological outcomes in chromosome 22q11.2 deletion syndrome

Chromosome 22q11.2 deletion syndrome (22q11DS) is the most common microdeletion syndrome in humans. It is typified by highly variable symptoms, which might be explained by epigenetic regulation of genes in the interval. Using computational algorithms, our laboratory previously predicted that DiGeorge critical region 6 (DGCR6), which lies within the deletion interval, is imprinted in humans. Expression and epigenetic regulation of this gene have not, however, been examined in 22q11DS subjects. The purpose of this study was to determine if the expression levels of DGCR6 and its duplicate copy DGCR6L in 22q11DS subjects are associated with the parent-of-origin of the deletion and childhood psychopathologies. Our investigation showed no evidence of parent-of-origin-related differences in expression of both DGCR6 and DGCR6L. However, we found that the variability in DGCR6 expression was significantly greater in 22q11DS children than in age and gender-matched control individuals. Children with 22q11DS who had anxiety disorders had significantly lower DGCR6 expression, especially in subjects with the deletion on the maternal chromosome, despite the lack of imprinting. Our findings indicate that epigenetic mechanisms other than imprinting contribute to the dysregulation of these genes and the associated childhood psychopathologies observed in individuals with 22q11DS. Further studies are now needed to test the usefulness of DGCR6 and DGCR6L expression and alterations in the epigenome at these loci in predicting childhood anxiety and associated adult-onset pathologies in 22q11DS subjects.

Imaging as tool to investigate psychoses and antipsychotics

The results of imaging studies have played an important role in the formulation of hypotheses regarding the etiology of psychosis and schizophrenia, as well as in our understanding of the mechanisms of action of antipsychotics. Since this volume is primarily directed to molecular aspects of psychosis and antipsychotics, only the results of molecular imaging techniques addressing these topics will be discussed here.One of the most consistent findings of molecular imaging studies in schizophrenia is an increased uptake of DOPA in the striatum, which may be interpreted as an increased synthesis of L-DOPA. Also, several studies reported an increased release of dopamine induced by amphetamine in schizophrenia patients. These findings played an important role in reformulating the dopamine hypothesis of schizophrenia. To study the roles of the neurotransmitters γ-aminobutyric acid (GABA) and glutamate in schizophrenia, SPECT as well as MR spectroscopy have been used. The results of preliminary SPECT studies are consistent with the hypothesis of NMDA receptor dysfunction in schizophrenia. Regarding the GABA deficit hypothesis of schizophrenia, imaging results are inconsistent. No changes in serotonin transporters were demonstrated in imaging studies in schizophrenia, but studies of several serotonin receptors showed conflicting results. The lack of selective radiotracers for muscarinic receptors may have hampered examination of this system in schizophrenia as well as its role in the induction of side effects of antipsychotics. Interestingly, preliminary molecular imaging studies on the cannabinoid-1 receptor and on neuroinflammatory processes in schizophrenia have recently been published. Finally, a substantial number of PET/SPECT studies have examined the occupancy of receptors by antipsychotics and an increasing number of studies is now focusing on the effects of these drugs using techniques like spectroscopy and pharmacological MRI.