Selective deficit of hippocampal N-acetylaspartate in antipsychotic-naive patients with schizophrenia

Meta-analytic evidence of elevated choline, reduced N-acetylaspartate, and normal creatine in schizophrenia and their moderation by measurement quality, echo time, and medication status

BACKGROUND

Brain metabolite abnormalities measured with magnetic resonance spectroscopy (MRS) provide insight into pathological processes in schizophrenia. Prior meta-analyses have not yet answered important questions about the influence of clinical and technical factors on neurometabolite abnormalities and brain region differences. To address these gaps, we performed an updated meta-analysis of N-acetylaspartate (NAA), choline, and creatine levels in patients with schizophrenia and assessed the moderating effects of medication status, echo time, measurement quality, and other factors.

METHODS

We searched citations from three earlier meta-analyses and the PubMed database after the most recent meta-analysis to identify studies for screening. In total, 113 publications reporting 366 regional metabolite datasets met our inclusion criteria and reported findings in medial prefrontal cortex (MPFC), dorsolateral prefrontal cortex, frontal white matter, hippocampus, thalamus, and basal ganglia from a total of 4445 patient and 3944 control observations.

RESULTS

Patients with schizophrenia had reduced NAA in five of the six brain regions, with a statistically significant sparing of the basal ganglia. Patients had elevated choline in the basal ganglia and both prefrontal cortical regions. Patient creatine levels were normal in all six regions. In some regions, the NAA and choline differences were greater in studies enrolling predominantly medicated patients compared to studies enrolling predominantly unmedicated patients. Patient NAA levels were more reduced in hippocampus and frontal white matter in studies using longer echo times than those using shorter echo times. MPFC choline and NAA abnormalities were greater in studies reporting better metabolite measurement quality.

CONCLUSIONS

Choline is elevated in the basal ganglia and prefrontal cortical regions, suggesting regionally increased membrane turnover or glial activation in schizophrenia. The basal ganglia are significantly spared from the well-established widespread reduction of NAA in schizophrenia suggesting a regional difference in disease-associated factors affecting NAA. The echo time findings agree with prior reports and suggest microstructural changes cause faster NAA T2 relaxation in hippocampus and frontal white matter in schizophrenia. Separating the effects of medication status and illness chronicity on NAA and choline abnormalities will require further patient-level studies. Metabolite measurement quality was shown to be a critical factor in MRS studies of schizophrenia.

Constrained neuro fuzzy inference methodology for explainable personalised modelling with applications on gene expression data

Interpretable machine learning models for gene expression datasets are important for understanding the decision-making process of a classifier and gaining insights on the underlying molecular processes of genetic conditions. Interpretable models can potentially support early diagnosis before full disease manifestation. This is particularly important yet, challenging for mental health. We hypothesise this is due to extreme heterogeneity issues which may be overcome and explained by personalised modelling techniques. Thus far, most machine learning methods applied to gene expression datasets, including deep neural networks, lack personalised interpretability. This paper proposes a new methodology named personalised constrained neuro fuzzy inference (PCNFI) for learning personalised rules from high dimensional datasets which are structurally and semantically interpretable. Case studies on two mental health related datasets (schizophrenia and bipolar disorders) have shown that the relatively short and simple personalised fuzzy rules provided enhanced interpretability as well as better classification performance compared to other commonly used machine learning methods. Performance test on a cancer dataset also showed that PCNFI matches previous benchmarks. Insights from our approach also indicated the importance of two genes (ATRX and TSPAN2) as possible biomarkers for early differentiation of ultra-high risk, bipolar and healthy individuals. These genes are linked to cognitive ability and impulsive behaviour. Our findings suggest a significant starting point for further research into the biological role of cognitive and impulsivity-related differences. With potential applications across bio-medical research, the proposed PCNFI method is promising for diagnosis, prognosis, and the design of personalised treatment plans for better outcomes in the future.

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.

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.

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.

Proton magnetic resonance spectroscopy changes in a longitudinal schizophrenia study: a pilot study in eleven patients

PURPOSE

Investigation of the longitudinal effect of schizophrenia on changes in various brain-metabolite levels and their relationships with cognitive deficits that have not been fully explained yet.

METHODS

Five years subsequent to their first examination for their first episode of schizophrenia, eleven patients from an original group of 30 were reexamined. Their cognitive functions were assessed with the Wisconsin Card Sorting Test. Magnetic resonance imaging and proton magnetic resonance spectroscopy were performed on a 1.5 T scanner. Voxels of 8 cm³ were positioned in the left frontal lobe, left temporal lobe, and the left thalamus. The study had a naturalistic design, and patients were treated with various antipsychotics.

RESULTS

No significant statistical differences between the baseline and follow-up in N-acetylaspartate (NAA:creatine plus phosphocreatine [Cr] and NAA/H₂O) levels were observed in any region of interest. We found a significant statistical correlation between 5-year difference in frontal NAA/Cr levels and duration of the last antipsychotic treatment in this period (R=0.908, P=0.012). We found a trend (P=0.068) toward lower choline-containing compounds (Cho/Cr ratio) in the temporal lobe over 5 years and a trend (P=0.079) in higher glutamate-glutamine- GABA (Glx/H₂O) levels in the left thalamus. The patients showed social and clinical improvement at follow-up examination, and there were no changes in Wisconsin Card Sorting Test results.

CONCLUSION

The observed tendency toward decline in choline ratio might have been due to decreased temporal cell density or impaired neuron-membrane or myelin functions. A tendency for higher Glx levels suggest the involvement of thalamus dysfunction in the chronic schizophrenia process. The lack of NAA decrease might have been due to effective antipsychotic treatment. Further longitudinal studies on large patient groups are required to confirm these metabolic changes in schizophrenia.

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.

Brain Functional Effects of Psychopharmacological Treatments in Schizophrenia: A Network-based Functional Perspective Beyond Neurotransmitter Systems

Psychopharmacological treatments for schizophrenia have always been a matter of debate and a very important issue in public health given the chronic, relapsing and disabling nature of the disorder. A thorough understanding of the pros and cons of currently available pharmacological treatments for schizophrenia is critical to better capture the features of treatment-refractory clinical pictures and plan the developing of new treatment strategies. This review focuses on brain functional changes induced by antipsychotic drugs as assessed by modern functional neuroimaging techniques (i.e. fMRI, PET, SPECT, MRI spectroscopy). The most important papers on this topic are reviewed in order to draw an ideal map of the main functional changes occurring in the brain during antipsychotic treatment. This supports the hypothesis that a network-based perspective and a functional connectivity approach are needed to fill the currently existing gap of knowledge in the field of psychotropic drugs and their mechanisms of action beyond neurotransmitter systems.

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.

Decreased synaptic and mitochondrial density in the postmortem anterior cingulate cortex in schizophrenia

Schizophrenia (SZ) is a mental illness characterized by psychosis, negative symptoms, and cognitive deficits. The anterior cingulate cortex (ACC), a structurally and functionally diverse region, is one of several brain regions that is abnormal in SZ. The present study compared synaptic organization and mitochondrial number and morphology in postmortem ACC in SZ versus normal control (NC). Total synaptic density in the combined ACC was decreased in SZ, to 72% of normal controls (NCs), due to selective decreases in axospinous synapses, both asymmetric (excitatory) and symmetric (inhibitory). These changes were present in layers 3 and 5/6. The density of mitochondria in all axon terminals combined in SZ was decreased to 64% of NC. In layer 3, mitochondrial density was decreased only in terminals forming asymmetric synapses with spines, while in layers 5/6 mitochondrial density was decreased in terminals forming symmetric synapses with spines and dendrites. The proportion of terminals making symmetric synapses that contained mitochondria was significantly lower in SZ than in NCs, especially for symmetric axospinous synapses. The number of mitochondria per neuronal somata was decreased in the ACC in SZ compared to NCs; this finding was present in layers 5-6. The size of mitochondria in neuronal somata and throughout the neuropil was similar in SZ and NCs. Our results, though preliminary, are well supported by the literature, and support an anatomical substrate for some of the altered executive functions found in SZ.

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.

The predictive value of baseline NAA/Cr for treatment response of first-episode schizophrenia: A ¹H MRS study

The study focused on the predictive value of baseline metabolite ratios in bilateral hippocampus of first-episode schizophrenia by using proton magnetic resonance spectroscopy ((1)H MRS). (1)H MRS data were acquired from 23 hallucination and 17 non-hallucination first-episode schizophrenia patients compared with 17 healthy participants. Clinical characteristics of patients were rated using the Positive and Negative Syndrome Scale (PANSS) before and after 3-month treatment. The schizophrenia patients showed lower NAA/Cr ratio than healthy participants respectively (p=0.024; p=0.001), and non-hallucination patients had even lower NAA/Cr ratio than hallucination patients (p=0.033). After 3-month treatment, hallucination patients had greater improvement in negative symptoms than non-hallucination patients (p=0.018). The reduction of PANSS total score and negative factor score was positively correlated with the left NAA/Cr in both group patients (p<0.05). Given that the bilateral hippocampal baseline NAA/Cr had predictive value for the whole treatment response, and the left hippocampal NAA/Cr can predict the prognosis of negative symptoms during acute phase medication in first-episode schizophrenia.

N-acetylaspartate reduction in the medial prefrontal cortex following 8 weeks of risperidone treatment in first-episode drug-naïve schizophrenia patients

It is unclear whether N-acetylaspartate (NAA) depletions documented in schizophrenia patients might be due to the disease progression or medications. Here we investigated longitudinal NAA changes in drug-naïve first-episode patients (FEP) who are relatively free from chronicity. Forty-two drug-naïve FEP and 38 controls were enrolled in this study to explore the effect of 8-week risperidone monotherapy on NAA. All spectra were obtained from the medial prefrontal cortex (MPFC) on a 3.0 T MRI and analyzed with LCModel. At baseline, patients presented no significant differences in NAA (P = 0.084) or NAA/Cr + Pcr (P = 0.500) compared to controls; NAA levels were negatively correlated with PANSS total scores (P = 0.001) and WCST-PE (P = 0.041). After treatment, patients demonstrated significant reductions of NAA (P < 0.001) and NAA/Cr + Pcr (P < 0.001), and significant improvement in PANSS-P (P < 0.001) and PANSS-G (P < 0.001) symptoms. We detected no significant correlations between NAA alterations and PANSS-P (P = 0.679) or PANSS-G (P = 0.668) symptom changes; nor did NAA/Cr + Pcr changes with alterations in PANSS-P (P = 0.677) and PANSS-G (P = 0.616). This is the first evidence that short-term risperidone treatment induces an acute reduction of MPFC NAA during the early phase of schizophrenia, which may be a previously unavailable biomarker to indicate risperidone with a similar pharmacological mechanism, although the functional significance is still unclear.

N-acetyl-aspartate (NAA) as a correlate of pharmacological treatment in psychiatric disorders: a systematic review

The amino-acid N-acetyl-aspartate (NAA) is located in neurons and the concentration of NAA correlates with neuronal mitochondrial function. The signal of NAA, as measured with proton magnetic resonance spectroscopy (1H-MRS), is considered to reflect both, neuronal density and integrity of neuronal mitochondria. A reduction of the NAA concentrations has been found in several psychiatric disorders. Newer studies report reversal of decreased NAA concentration with treatment. The objective of this review is to summarize the literature on NAA changes in association with psychopharmacological treatment in psychiatric disorders (affective disorders, obsessive-compulsive disorder, schizophrenia and dementia). The majority of studies identified increased NAA concentrations in response to treatment, while a smaller number of studies did not find this effect. The NAA increase seems to be neither specific for a certain disorder nor for a specific intervention. This suggests that the reduction of NAA may represent an altered functional (metabolic) state of neurons common to different psychiatric disorders and the increase after treatment to indicate functional restoration as one general effect of interventions.

Reduced frontal glutamate + glutamine and N-acetylaspartate levels in patients with chronic schizophrenia but not in those at clinical high risk for psychosis or with first-episode schizophrenia

Changes in brain pathology as schizophrenia progresses have been repeatedly suggested by previous studies. Meta-analyses of previous proton magnetic resonance spectroscopy ((1)H MRS) studies at each clinical stage of schizophrenia indicate that the abnormalities of N-acetylaspartate (NAA) and glutamatergic metabolites change progressively. However, to our knowledge, no single study has addressed the possible differences in (1)H MRS abnormalities in subjects at 3 different stages of disease, including those at ultrahigh risk for psychosis (UHR), with first-episode schizophrenia (FES), and with chronic schizophrenia (ChSz). In the current study, 24 patients with UHR, 19 FES, 25 ChSz, and their demographically matched 3 independent control groups (n = 26/19/28 for the UHR, FES, and ChSz control groups, respectively) underwent (1)H MRS in a 3-Tesla scanner to examine metabolites in medial prefrontal cortex. The analysis revealed significant decreases in the medial prefrontal NAA and glutamate + glutamine (Glx) levels, specifically in the ChSz group as indexed by a significant interaction between stage (UHR/FES/ChSz) and clinical status (patients/controls) (P = .008). Furthermore, the specificity of NAA and Glx reductions compared with the other metabolites in the patients with ChSz was also supported by a significant interaction between the clinical status and types of metabolites that only occurred at the ChSz stage (P = .001 for NAA, P = .004 for Glx). The present study demonstrates significant differences in (1)H MRS abnormalities at different stages of schizophrenia, which potentially correspond to changes in glutamatergic neurotransmission, plasticity, and/or excitotoxicity and regional neuronal integrity with relevance for the progression of schizophrenia.

Atypical antipsychotic drug treatment for 6 months restores N-acetylaspartate in left prefrontal cortex and left thalamus of first-episode patients with early onset schizophrenia: A magnetic resonance spectroscopy study

Early onset schizophrenia (EOS) is often associated with poorer outcomes, including lack of school education, higher risk of mental disability and resistance to treatment. But the knowledge of the neurobiological mechanism of EOS is limited. Here, using proton magnetic resonance spectroscopy, we investigated the possible neurochemical abnormalities in prefrontal cortex (PFC) and thalamus of first-episode drug-naïve patients with EOS, and followed up the effects of atypical antipsychotic treatment for 6 months on neurochemical metabolites and clinical symptoms. We measured the ratios of N-acetylaspartate (NAA), choline (Cho) to creatine (Cr) in 41 adolescents with first episode of EOS and in 28 healthy controls matched for age, gender, and years of education. The EOS patients presented with abnormally low NAA/Cr values in the left PFC and left thalamus with a reduced tendency in the right PFC compared with healthy controls. No significant differences were detected between groups for Cho/Cr in PFC and thalamus in any hemisphere. After atypical antipsychotic treatment for 6 months, the reduced NAA/Cr in the left PFC and left thalamus in EOS patients was elevated to the normal level in healthy controls, without any alteration in Cho/Cr. We also found that there was no significant correlation between the neurochemical metabolite ratios in the PFC and thalamus in patients with EOS, and clinical characteristics. Our results suggest that there was neurochemical metabolite abnormalities in PFC and thalamus in EOS patients, atypical antipsychotic treatment can effectively relieve the symptoms and restore the reduced NAA in PFC and thalamus.

Use of proton magnetic resonance spectroscopy in the treatment of psychiatric disorders: a critical update

Because of the wide availability of hardware as well as of standardized analytic quantification tools, proton magnetic resonance spectroscopy ((1)H-MRS) has become widely used to study psychiatric disorders. (1)H-MRS allows measurement of brain concentrations of more traditional singlet neurometabolites like N-acetylaspartate, choline, and creatine. More recently, quantification of the more complex multiplet spectra for glutamate, glutamine, inositol, and γ-aminobutyric acid have also been implemented. Here we review applications of (1)H-MRS in terms of informing treatment options in schizophrenia, bipolar disorder, and major depressive disorders. We first discuss recent meta-analytic studies reporting the most reliable findings. Then we evaluate the more sparse literature focused on 1H-MRS-detected neurometabolic effects of various treatment approaches in psychiatric populations. Finally we speculate on future developments that may result in translation of these tools to improve the treatment of psychiatric disorders.

The effect of atypical antipsychotics on brain N-acetylaspartate levels in antipsychotic-naïve first-episode patients with schizophrenia: a preliminary study

PURPOSE

To investigate the correlates of a clinical therapeutic response by using the parameters measured by proton magnetic resonance spectroscopy after the administration of atypical antipsychotics.

PATIENTS AND METHODS

Twenty-five antipsychotic-naïve first-episode patients with schizophrenia were monitored for 12 months. The patients were evaluated using (1)H magnetic resonance spectroscopy in the dorsolateral prefrontal cortex and Positive and Negative Syndrome Scale, Clinical Global Impression Scale of Severity, Tower of London - Drexel University, Letter-Number Span Test, Trail Making Test A, and Personal and Social Performance Scale. They were administered atypical antipsychotics, starting with quetiapine. In the absence of a therapeutic response, another antipsychotic was introduced.

RESULTS

After 12 study months, the N-acetylaspartate/creatine (NAA/Cr) level did not significantly change at the whole-group level. Additional analysis revealed a significant rise in the NAA/Cr level in the study group that stayed on the same antipsychotic throughout the study course (P=0.008) and a significant drop in NAA/Cr in the study group that switched antipsychotics (P=0.005). On the whole-group level, no significant correlations between NAA/Cr values and other scores were found at either baseline or after 12 study months.

CONCLUSION

One-year treatment with atypical antipsychotics administered to antipsychotic-naïve patients didn't result in a significant rise in the NAA/Cr ratio. However, a significant rise was witnessed in the study group in which a satisfactory therapeutic response had been achieved with a single antipsychotic administration.

T2 relaxation effects on apparent N-acetylaspartate concentration in proton magnetic resonance studies of schizophrenia

Over the past two decades, many magnetic resonance spectroscopy (MRS) studies reported lower N-acetylaspartate (NAA) in key brain regions of patients with schizophrenia (SZ) compared to healthy subjects. A smaller number of studies report no difference in NAA. Many sources of variance may contribute to these discordant results including heterogeneity of the SZ subject populations and methodological differences such as MRS acquisition parameters, and post-acquisition analytic methods. The current study reviewed proton MRS literature reporting measurements of NAA in SZ with a focus on methodology. Studies which reported lower NAA were significantly more likely to have used longer echo times (TEs), while studies with shorter TEs reported no concentration difference. This suggests that NAA quantitation using MRS was affected by the choice of TE, and that published MRS literature reporting NAA in SZ using a long TE is confounded by apparent differential T2 relaxation effects between SZ and healthy control groups. Future MRS studies should measure T2 relaxation times. This would allow for spectral concentration measurements to be appropriately corrected for these relaxation effects. In addition, as metabolite concentration and T2 relaxation times are completely independent variables, this could offer distinct information about the metabolite of interest.

Proton magnetic resonance spectroscopy of the substantia nigra in schizophrenia

BACKGROUND

Converging evidence in schizophrenia points to disruption of the dopamine and glutamate neurotransmitter systems in the pathophysiology of the disorder. Dopamine is produced in the substantia nigra, but few neuroimaging studies have specifically targeted this structure. In fact, no studies of the substantia nigra in schizophrenia have used proton magnetic resonance spectroscopy (MRS). We sought to demonstrate the feasibility of acquiring single-voxel MRS measurements at 3T from the substantia nigra and to determine which metabolites could be reliably quantified in schizophrenia patients and healthy controls.

METHODS

We used a turbo spin echo sequence with magnetization transfer contrast to visualize the substantia nigra and single-voxel proton MRS to quantify levels of N-acetylaspartate, glutamate and glutamine (Glx), and choline in the left substantia nigra of 35 people with schizophrenia and 22 healthy controls.

RESULTS

We obtained spectra from the substantia nigra and quantified neurometabolites in both groups. We found no differences in levels of N-acetylaspartate/creatine, Glx/creatine, or choline/creatine between the groups. We found a significant correlation between Glx/creatine and overall cognitive performance, measured with the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), in controls but not patients, a difference that was statistically significant.

CONCLUSIONS

Our study demonstrates the feasibility of obtaining single-voxel MRS data from the substantia nigra in schizophrenia. Such measurements may prove useful in understanding the biochemistry underlying cellular function in a region implicated in the pathophysiology of schizophrenia.

Clinical and cognitive correlates of the proton magnetic resonance spectroscopy measures in chronic schizophrenia

Background

Proton magnetic resonance spectroscopy (¹H MRS) allows for examining brain functions in vivo in schizophrenic patients. Correlations between N-acetylaspartate (NAA) level in the frontal lobe and cognitive functions and clinical symptoms have been observed. The aim of the present study was evaluation of relationship between clinical symptoms, cognitive outcomes and brain function in ¹H MRS measures in schizophrenic patients.

Material/Methods

The study included a group of 47 patients with chronic schizophrenia. Patients were assessed by means of PANSS, CGI, and a battery of cognitive tests: WCST, TMT, and verbal fluency test. MRI and MRS procedures were performed. Regions of interest were located in the left frontal lobe, temporal lobe and thalamus. Metabolite (NAA, choline, myoinositol and Glx complex) ratios to creatine were calculated.

Results

We observed a significant negative correlation between myoinositol level in the frontal lobe and WSCT test performance. These data were confirmed by further analysis, which showed a significant correlation between WCST outcome, negative symptoms score, education level and myoinositol ratio in the frontal lobe. When analyzing negative symptoms as independent variables, the analysis of regression revealed a significant relationship between negative symptoms score and verbal fluency score, together with choline level in the thalamus.

Conclusions

The above data seem to confirm a significant role of the thalamus – a “transmission station” involved in connections with the prefrontal cortex – for psychopathology development (especially negative) in schizophrenia. Moreover, our results suggest that a neurodegenerative process may be involved in schizophrenia pathogenesis.

Multimodal analysis of the hippocampus in schizophrenia using proton magnetic resonance spectroscopy and functional magnetic resonance imaging

BACKGROUND

Studies have shown that individuals with schizophrenia suffer from memory impairments. In this study, we combined proton magnetic resonance spectroscopy (¹H-MRS) and functional magnetic resonance imaging (fMRI) to clarify the neurobiology of memory deficits in schizophrenia.

METHODS

We used single-voxel MRS acquired in the left hippocampus and fMRI during performance of a memory task to obtain measures of neurochemistry and functional response in 28 stable, medicated participants with schizophrenia (SZ) and 28 matched healthy controls (HC).

RESULTS

The SZ group had significantly decreased blood oxygen level-dependent (BOLD) signal in left inferior frontal gyrus (IFG) during encoding and in the anterior cingulate cortex (ACC) and superior temporal gyrus (STG) during retrieval. We did not find significant differences in N-acetylaspartate/creatine (NAA/Cr) or glutamate+glutamine (Glx/Cr) levels between the groups, but did find a significant positive correlation between NAA/Cr and Glx/Cr in the HC group that was absent in the SZ group. There were no significant correlations between BOLD and MRS measured in the hippocampus. Further analyses revealed a negative correlation between left IFG BOLD and task performance in the SZ group. Finally, in the HC group, the left IFG BOLD was positively correlated with Glx/Cr.

CONCLUSIONS

We replicated findings of reduced BOLD signal in left IFG and of an altered relationship between IFG BOLD response and task performance in the SZ. The absence of correlation between NAA/Cr and Glx/Cr levels in patients might suggest underlying pathologies of the glutamate-glutamine cycle and/or mitochondria.

Neurometabolites in schizophrenia and bipolar disorder - a systematic review and meta-analysis

This meta-analysis evaluates alterations of neurometabolites in schizophrenia and bipolar disorder. PubMed was searched to find controlled studies evaluating N-acetylaspartate (NAA), Choline (Cho) and Creatine (Cr) assessed with ((1))H-MRS (proton magnetic resonance spectroscopy) in patients with schizophrenia and bipolar disorder up to September 2010. Random effects meta-analyses were conducted to estimate pooled standardized mean differences. The statistic was used to quantify inconsistencies. Subgroup analyses were conducted to explore potential explanations for inconsistencies. The systematic review included 146 studies with 5643 participants. NAA levels were affected in schizophrenia and bipolar disorder. Decreased levels in the basal ganglia and frontal lobe were the most consistent findings in schizophrenia; decreased levels in the basal ganglia were the most consistent findings in bipolar disorder. Cho and Cr levels were not altered in either disorder. Findings for Cr were most consistent in the thalamus, frontal lobe and dorsolateral prefrontal cortex in schizophrenia and the basal ganglia and frontal lobe in bipolar disorder. Findings for Cho were most consistent in the thalamus, frontal lobe and anterior cingulate cortex in schizophrenia and basal ganglia in bipolar disorder. Large, carefully designed studies are needed to better estimate the extent of alterations in neurometabolites.

Detection of metabolites in the white matter of frontal lobes and hippocampus with proton in first-episode treatment-naïve schizophrenia patients

AIM

This study aimed to investigate the changes of the metabolites in the white matter of frontal lobes and hippocampus in schizophrenia by using proton magnetic resonance spectroscopy ((1) H-MRS).

METHODS

Sixty-three first-episode treatment-naïve schizophrenia (FES) patients and 63 age-, gender- and education level-matched healthy controls were recruited. The relative levels of metabolites including N-acetylaspartate (NAA), choline-containing compounds (Cho), (Cr) and myo-inositol (MI) were detected with (1) H-MRS, and the laterality index (Li) was calculated. The severity of symptoms was assessed using the Positive and Negative Syndrome Scale.

RESULTS

Compared with controls, FES patients did not show significant differences in all metabolites. The severity of positive symptoms was negatively correlated with the NAA/Cho in the white matter of the left frontal lobe and positively correlated with the Cho/Cr in the right white matter of frontal lobes. A negative correlation was observed between the severity of negative symptoms and the NAA/Cr in the white matter of bilateral frontal lobes. No difference was shown in the Li of metabolites between FES patients and controls.

CONCLUSIONS

The metabolites such as NAA, Cho and MI in white matter of frontal lobes and hippocampus were not significantly altered in FES patients. The lower axonal integrity/number (NAA concentration) may be associated with more severe negative symptoms, and dysmetabolism in process of myelination in the white matter of frontal lobes associated with more severe positive symptoms.

Association of the brain-derived neurotrophic factor val66met polymorphism with magnetic resonance spectroscopic markers in the human hippocampus: in vivo evidence for effects on the glutamate system

The brain-derived neurotrophic factor (BDNF) is a key regulator of synaptic plasticity and has been suggested to be involved in the pathophysiology and pathogenesis of psychotic disorders, with particular emphasis on dysfunctions of the hippocampus. The aim of the present study was to replicate and to extend prior findings of BDNF val66met genotype effects on hippocampal volume and N-acetyl aspartate (NAA) levels. Hundred and fifty-eight caucasians (66 schizophrenic, 45 bipolar, and 47 healthy subjects; 105 subjects underwent MRI and 103 MRS scanning) participated in the study and were genotyped with regard to the val66met polymorphism (rs6265) of the BDNF gene. Hippocampal volumes were determined using structural magnetic resonance imaging (MRI), and measures of biochemical markers were taken using proton magnetic resonance spectroscopy ((1)H-MRS) in the hippocampus and other brain regions. Verbal memory was assessed as a behavioral index of hippocampal function. BDNF genotype did not impact hippocampal volumes. Significant genotype effects were found on metabolic markers specifically in the left hippocampus. In particular, homozygous carriers of the met-allele exhibited significantly lower NAA/Cre and (Glu + Gln)/Cre metabolic ratios compared with val/val homozygotes, independently of psychiatric diagnoses. BDNF genotype had a numerical, but nonsignificant effect on verbal memory performance. These findings provide first in vivo evidence for an effect of the functional BDNF val66met polymorphism on the glutamate system in human hippocampus.

Long term antipsychotic treatment does not alter metabolite concentrations in rat striatum: an in vivo magnetic resonance spectroscopy study

Proton magnetic resonance spectroscopy (MRS) studies of schizophrenic patients generally reveal reduced levels of N-acetyl aspartate (NAA) when compared with healthy controls. Whether this reduction is due to the disease or to the drugs used for treatment remains an open question. Numerous human and animal studies have attempted to determine the effects of antipsychotics on NAA levels with mixed results. The majority of the animal studies were ex vivo, which may not accurately reflect the in vivo situation, and limitations of the human studies include previous or concomitant medications or other confounds. To overcome these limitations, we dosed 10 rats/group for six months via drinking water with 0.2 or 2 mg/kg/day haloperidol or 10 or 30 mg/kg/day clozapine. Control rats received unadulterated water. Proton MRS data were collected longitudinally over the six month period from a 64 μL voxel containing primarily the right striatum prior to and monthly during drug administration and used to estimate the concentrations of NAA, creatine, and choline. Ratios of NAA, choline, inositol and glutamate+glutamine to creatine were also calculated. Only the Cho/Cr ratio showed a significant time-by-treatment effect (p=0.0285). These results are in agreement with previous studies of the striatum. However, regional and disease-specific effects remain unresolved.

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

BACKGROUND

It is not known whether regional brain N-acetyl aspartate (NAA) changes in the progression from prodrome to chronic schizophrenia. We used effect size meta-analysis to determine which brain regions show the most robust reductions in NAA first episode and chronic schizophrenia as measured by proton magnetic resonance spectroscopy and to determine whether these changes are present in individuals at high risk of developing schizophrenia.

METHODS

We identified 131 articles, of which 97 met inclusion criteria. Data were separated by stage of illness (at risk, first episode schizophrenia, chronic schizophrenia) and by brain region. For each region, mean and SD of the NAA measure was extracted.

RESULTS

Significant reductions in NAA levels were found in frontal lobe, temporal lobe, and thalamus in both patient groups (effect size > .3; p < .01). In individuals at high risk of schizophrenia (of whom approximately 20% would be expected to undergo transition to psychosis), significant NAA reductions were present in thalamus (effect size = .78; p < .05), with reductions at trend level only in temporal lobe (effect size = .32; p < .1), and no reductions in frontal lobe (effect size = .05; p = .5).

CONCLUSIONS

These data suggest that schizophrenia is associated with loss of neuronal integrity in frontal and temporal cortices and in the thalamus and suggest that these changes in the frontal and temporal lobe might occur in the transition between the at-risk phase and the first episode.

Differential regional N-acetylaspartate deficits in postmortem brain in schizophrenia, bipolar disorder and major depressive disorder

There is substantial evidence for the involvement of the hippocampus and subcortical regions in the neuropathology of schizophrenia. Deficits of N-acetylaspartate (NAA) have been found in schizophrenia and bipolar disorder which may reflect neuronal loss and/or dysfunction. N-acetylaspartylglutamate (NAAG) is the most abundant peptide transmitter in the mammalian nervous system. It is an agonist at presynaptic metabotropic glutamate receptors mGluR3, inhibiting glutamate release. NAA and NAAG and were measured in hippocampal, striatal, amygdala and cingulate gyrus regions of human postmortem tissue from controls and subjects with schizophrenia, bipolar disorder and major depressive disorder. There are significant deficits in hippocampal NAA concentrations in all patient groups. In the amygdala there are significant NAA deficits in schizophrenia and depression and significant deficits of NAAG in the amygdala in the depression group. The deficits in NAA reported in this study confirm the importance of hippocampal and other subcortical structures in the neuropathology of the major psychiatric disorders.

Functional magnetic resonance imaging of a parametric working memory task in schizophrenia: relationship with performance and effects of antipsychotic treatment

RATIONALE

Working memory dysfunction is frequently observed in schizophrenia. The neural mechanisms underlying this dysfunction remain unclear, with functional neuroimaging studies reporting increased, decreased or unchanged activation compared to controls.

OBJECTIVES

We investigated the neural correlates of spatial working memory in schizophrenia with particular consideration of effects of antipsychotic treatment and relation to performance levels in the patient group.

METHOD

We used functional magnetic resonance imaging and studied the blood-oxygen-level-dependent (BOLD) response of 45 schizophrenia outpatients and 19 healthy controls during a parametric spatial n-back task.

RESULTS

Performance in both groups deteriorated with increasing memory load (0-back, 1-back, 2-back), but the two groups did not significantly differ in performance overall or as a function of load. Patients produced stronger BOLD signal in occipital and lateral prefrontal cortex during task performance than controls. This difference increased with increasing working memory load in the prefrontal areas. We also found that in patients with good task performance, the BOLD response in left prefrontal cortex showed a stronger parametric increase with working memory load than in patients with poor performance. Second-generation antipsychotics were independently associated with left prefrontal BOLD increase in response to working memory load, whereas first-generation antipsychotics were associated with BOLD decrease with increasing load in this area.

CONCLUSIONS

Together, these findings suggest that in schizophrenia patients, normal working memory task performance may be achieved through compensatory neural activity, especially in well-performing patients and in those treated with second-generation antipsychotics.

Assessments of function and biochemistry of the anterior cingulate cortex in schizophrenia

BACKGROUND

Neuroimaging and electrophysiologic studies have consistently provided evidence of impairment in anterior cingulate cortex/medial frontal cortex function in people with schizophrenia. In this study, we sought to clarify the nature of this abnormality by combining proton magnetic resonance spectroscopy (1H-MRS) with functional magnetic resonance imaging (fMRI) at 3T.

METHODS

We used single-voxel MRS acquired in the dorsal anterior cingulate cortex and fMRI during performance of a Stroop color-naming task to investigate the neurochemistry and functional response of the anterior cingulate cortex/medial frontal cortex in 26 stable, medicated subjects with schizophrenia and 23 matched healthy control subjects.

RESULTS

In schizophrenia subjects, we found decreased blood oxygen level-dependent signal in the medial frontal wall, with significant clusters restricted to more dorsal regions compared with healthy subjects. In addition, we observed a trend-level decrease in N-acetylaspartate/creatine (NAA/Cr) levels and a significant positive correlation between NAA/Cr level and the blood oxygen level-dependent signal in schizophrenia subjects that did not exist in healthy subjects. Furthermore, in this group of medicated subjects, we did not find evidence of decreased glutamate + glutamine(Glx)/Cr levels, but there was a significant negative correlation between Glx/Cr levels and negative symptoms.

CONCLUSIONS

Our results suggest that abnormal NAA levels, which may reflect a neuronal dysfunction related to schizophrenia, affect neuronal physiology, as evidenced by reduced blood oxygen level-dependent response.

N-acetyl aspartate concentration in the anterior cingulate cortex in patients with schizophrenia: a study of clinical and neuropsychological correlates and preliminary exploration of cognitive behaviour therapy effects

This study investigated the clinical and neuropsychological correlates of N-acetyl aspartate (NAA) concentration in the anterior cingulate cortex (ACC) in schizophrenia, and explored whether ACC NAA concentration is sensitive to symptom change following cognitive behaviour therapy for psychosis (CBTp). Participants comprised 30 patients and 15 healthy controls who underwent magnetic resonance spectroscopy of the ACC and were assessed on frontal lobe based neuropsychological tasks. Twenty-four (of 30) patients were followed-up; 11 subsequently received 8-9 months of CBTp in addition to standard care (CBTp+SC) and 13 received SC only. At baseline (i) NAA and Cr concentrations were lower in patients compared to controls, (ii) in patients, NAA concentration correlated inversely with positive symptoms and general psychopathology (positive symptoms explained 21% of the variance; total variance explained=25%) and Cho concentration correlated inversely with positive symptoms, and (iii) in controls, NAA concentration correlated positively with working and short-term memory and Cr concentration inversely with executive function. NAA concentration tended to increase in CBTp+SC patients at follow-up (n=7 with usable data) concomitant with improvement in positive symptoms. NAA concentration may be more closely associated with symptoms and symptom change than frontal lobe based neuropsychological function in schizophrenia, perhaps because the latter is relatively stable during the long-term illness course.

Interaction of hippocampal volume and N-acetylaspartate concentration deficits in schizophrenia: a combined MRI and 1H-MRS study

BACKGROUND

Volume deficits assessed with magnetic resonance imaging (MRI) and neurochemical dysfunctions (N-acetylaspartate, NAA) diagnosed using proton MR spectroscopy ((1)H-MRS) are reliable observations in the hippocampus of schizophrenic patients. NAA is an important cerebral amino acid in the synthesis pathways of glutamate, which has been implicated as a pathobiological core of schizophrenic symptomatology, of histological alterations and brain volume deficits in schizophrenia. However, the possible interaction between regional NAA reduction and volume deficits has been targeted only marginally in previous investigations.

METHODS

In 29 schizophrenic patients and 44 control subjects, a multimodal imaging study with (1)H-MRS and MRI volumetry of the left hippocampus was performed on a 3-Tesla scanner.

RESULTS

Compared to the control group, the hippocampus of the patients exhibited a significant volume reduction and a significant NAA concentration decrease. In schizophrenic patients, but not in healthy controls, a significant negative correlation between hippocampal NAA concentration and volume (r=-0.455, p=0.017) was observed. None of the imaging parameters was associated with clinical parameters.

CONCLUSIONS

The results argue for a coexistent neurochemical and structural deficit in the hippocampus of schizophrenic patients. The inverse relationship between the two parameters observed in patients only may reflect an interaction of neurochemistry and brain morphology as a pathobiological mechanism in schizophrenia. This observation is compatible with the important role of NAA in the synthesis of excitatory neurotransmitters and the hypothesized role of glutamate for brain morphology. The independence of the measured imaging parameters from clinical parameters is in line with the neurodevelopmental hypothesis of schizophrenia.

1H-MRS at 4 tesla in minimally treated early schizophrenia

We investigated glutamate-related neuronal dysfunction in the anterior cingulate (AC) early in schizophrenia before and after antipsychotic treatment. A total of 14 minimally treated schizophrenia patients and 10 healthy subjects were studied with single-voxel proton magnetic resonance spectroscopy ((1)H-MRS) of the AC, frontal white matter and thalamus at 4 T. Concentrations of N-acetylaspartate (NAA), glutamate (Glu), glutamine (Gln) and Gln/Glu ratios were determined and corrected for the partial tissue volume. Patients were treated with antipsychotic medication following a specific algorithm and (1)H-MRS was repeated after 1, 6 and 12 months. There were group x region interactions for baseline NAA (P=0.074) and Gln/Glu (P=0.028): schizophrenia subjects had lower NAA (P=0.045) and higher Gln/Glu (P=0.006) in the AC before treatment. In addition, AC Gln/Glu was inversely related to AC NAA in the schizophrenia (P=0.0009) but not in the control group (P=0.92). Following antipsychotic treatment, there were no further changes in NAA, Gln/Glu or any of the other metabolites in any of the regions studied. We conclude that early in the illness, schizophrenia patients already show abnormalities in glutamatergic metabolism and reductions in NAA consistent with glutamate-related excitotoxicity.

High energy phosphate abnormalities normalize after antipsychotic treatment in schizophrenia: a longitudinal 31P MRS study of basal ganglia

We reported increased high-energy phosphate metabolism in the basal ganglia of antipsychotic-naïve schizophrenia patients using (31)P Magnetic Resonance Spectroscopy (MRS). These patients were followed up for 1 year and and reassessed using (31)P MRS. Fourteen (8 males) patients with DSM-IV schizophrenia and 14 (11 males) healthy controls underwent (31)P MRS of sub-cortical structures (predominantly basal ganglia) twice (mean+/-S.D. interscan interval 1.15+/-0.17year) on a 1.5T scanner. Total scores on the Positive and Negative Syndrome Scale (PANSS) decreased significantly after treatment in schizophrenia patients. Patients had significantly lower mean PCr/ATP ratios than healthy controls at baseline but not during the follow-up. In patients, there was a significant positive correlation between the magnitude of improvement in PANSS total scores and the extent of change in the PCr/ATP ratio. Findings support the hypothesis that reduction of energy demand or induction of decreased energy-demanding processes might underlie the mechanism of action of antipsychotics in schizophrenia.

Reduced neuronal expression of insulin-degrading enzyme in the dorsolateral prefrontal cortex of patients with haloperidol-treated, chronic schizophrenia

Insulin-degrading enzyme (IDE) is a neutral thiol metalloprotease, which cleaves insulin with high specificity. Additionally, IDE hydrolyzes Abeta, glucagon, IGF I and II, and beta-endorphin. We studied the expression of IDE protein in postmortem brains of patients with schizophrenia and controls because: (1) the gene encoding IDE is located on chromosome 10q23-q25, a gene locus linked to schizophrenia; (2) insulin resistance with brain insulin receptor deficits/receptor dysfunction was reported in schizophrenia; (3) the enzyme cleaves IGF-I and IGF-II which are implicated in the pathophysiology of the disease; and (4) brain gamma-endorphin levels, liberated from beta-endorphin exclusively by IDE, have been reported to be altered in schizophrenia. We counted the number of IDE immunoreactive neurons in the dorsolateral prefrontal cortex, the hypothalamic paraventricular and supraoptic nuclei, and the basal nucleus of Meynert of 14 patients with schizophrenia and 14 matched control cases. Patients had long-term haloperidol treatment. In addition, relative concentrations of IDE protein in the dorsolateral prefrontal cortex were estimated by Western blot analysis. There was a significantly reduced number of IDE expressing neurons and IDE protein content in the left and right dorsolateral prefrontal cortex in schizophrenia compared with controls, but not in other brain areas investigated. Results of our studies on the influence of haloperidol on IDE mRNA expression in SHSY5Y neuroblastoma cells, as well as the effect of long-term treatment with haloperidol on the number of IDE immunoreactive neurons in rat brain, indicate that haloperidol per se, is not responsible for the decreased neuronal expression of the enzyme in schizophrenics. Haloperidol however, might exert some effect on IDE, through changes of the expression levels of its substrates IGF-I and II, insulin and beta-endorphin. Reduced cortical IDE expression might be part of the disturbed insulin signaling cascades found in schizophrenia. Furthermore, it might contribute to the altered metabolism of certain neuropeptides (IGF-I and IGF-II, beta-endorphin), in schizophrenia.

Research applications of magnetic resonance spectroscopy to investigate psychiatric disorders

Advances in magnetic resonance spectroscopy (MRS) methodology and related analytic strategies allow sophisticated testing of neurobiological models of disease pathology in psychiatric disorders. An overview of principles underlying MRS, methodological considerations, and investigative approaches is presented. A review of recent research is presented that highlights innovative approaches applying MRS, in particular, hydrogen MRS, to systematically investigate specific psychiatric disorders, including autism spectrum disorders, schizophrenia, panic disorder, major depression, and bipolar disorder.

Proton magnetic resonance spectroscopy during initial treatment with antipsychotic medication in schizophrenia

Reduced brain N-acetyl-aspartate (NAA) has been repeatedly found in chronic schizophrenia and suggests neuronal loss or dysfunction. However, the potential confounding effect of antipsychotic drugs on NAA has not been resolved. We studied 32 minimally treated schizophrenia patients and 21 healthy subjects with single-voxel proton magnetic resonance spectroscopy ((1)H-MRS) of the frontal and occipital lobes, caudate nucleus, and cerebellum. Concentrations of NAA, Choline, and Cre were determined and corrected for the proportion of cerebrospinal fluid (CSF) in the voxel. Patients were treated in a randomized-controlled double-blind manner with either haloperidol or quetiapine. (1)H-MRS was repeated every 6 months for up to 2 years. There was a group main effect for baseline NAA with lower global NAA in schizophrenia subjects before treatment compared to healthy controls. Global NAA was directly related to measures of global cognitive performance in the whole subject sample. Following treatment with haloperidol or quetiapine, there were no changes in NAA in any of the regions studied. Early in the illness, schizophrenia patients already demonstrate subtle reductions in NAA. Treatment with typical or atypical antipsychotic medications for several months does not result in NAA changes.

Antipsychotic drugs increase N-acetylaspartate and N-acetylaspartylglutamate in SH-SY5Y human neuroblastoma cells

N-Acetylaspartate (NAA) and N-acetylaspartylglutamate (NAAG) are related neuronal metabolites associated with the diagnosis and treatment of schizophrenia. NAA is a valuable marker of neuronal viability in magnetic resonance spectroscopy, a technique which has consistently shown NAA levels to be modestly decreased in the brains of schizophrenia patients. However, there are conflicting reports on the changes in brain NAA levels after treatment with antipsychotic drugs, which exert their therapeutic effects in part by blocking dopamine D(2) receptors. NAAG is reported to be an agonist of the metabotropic glutamate 2/3 receptor, which is linked to neurotransmitter release modulation, including glutamate release. Alterations in NAAG metabolism have been implicated in the development of schizophrenia possibly via dysregulation of glutamate neurotransmission. In the present study we have used high performance liquid chromatography to determine the effects of the antipsychotic drugs haloperidol and clozapine on NAA and NAAG levels in SH-SY5Y human neuroblastoma cells, a model system used to test the responses of dopaminergic neurons in vitro. The results indicate that the antipsychotic drugs haloperidol and clozapine increase both NAA and NAAG levels in SH-SY5Y cells in a dose and time dependant manner, providing evidence that NAA and NAAG metabolism in neurons is responsive to antipsychotic drug treatment.

Findings of proton magnetic resonance spectometry in the dorsolateral prefrontal cortex in adolescents with first episodes of psychosis

Knowledge of the neurobiology of early onset psychosis is limited. We used proton magnetic resonance spectroscopy to investigate the possible existence of dorsolateral prefrontal brain biochemical abnormalities in adolescents with psychosis and to determine possible differential effects related to specific psychotic diagnoses. We measured the ratios of N-acetyl-aspartate (NAA), choline (Cho), and creatine (Cr) to water in two groups of adolescents with a first episode of psychosis (schizophrenia n=8; non-schizophrenia n=15) and in 32 healthy controls matched for age, gender, and years of education. Proton magnetic resonance spectroscopy at 1.5 T was used to study two 6.75-cc voxels placed in the left and right dorsolateral prefrontal region. The schizophrenia patients presented statistically significant reductions in NAA/water levels in the left dorsolateral prefrontal voxel as compared with non-schizophrenia patients and healthy controls. No significant differences were detected between groups for NAA/water in the right dorsolateral prefrontal voxel or for Cho/water and Cr/water levels in any hemisphere. A reduction of the NAA/water level in the left dorsolateral prefrontal region may be selectively present at the onset of psychosis during adolescence in patients who later progress to schizophrenia, but not in those who later progress to other psychotic disorders.

Cognitive impairment and in vivo metabolites in first-episode neuroleptic-naive and chronic medicated schizophrenic patients: a proton magnetic resonance spectroscopy study

Involvement of the prefrontal cortex in schizophrenia has been implicated by neuropsychological, as well as neuropathological and imaging studies. Reductions of N-acetylaspartate (NAA), an in vivo marker of neuronal integrity, have repeatedly been detected in the frontal lobes of patients with schizophrenia by proton magnetic resonance spectroscopy (1H-MRS). In chronic medicated patients, a positive correlation between NAA levels of the prefrontal cortex and cognitive functioning has been observed, but to date, there have been no studies in first-episode neuroleptic-naive patients. In this study, single-voxel 1H-MRS was used to investigate neuronal function of the dorsolateral prefrontal cortex in 15 first-episode and 20 chronic schizophrenic patients. Outcomes were compared to 20 age-matched healthy controls to assess the relationship between prefrontal metabolism and neuropsychological performance. Patients with chronic schizophrenia had significant reductions of NAA, glutamate/glutamine, and choline levels compared to first-episode patients and healthy controls. Furthermore, creatine and phosphocreatine were significantly reduced in both patient groups compared to healthy controls. In the neuropsychological tests, chronic schizophrenic patients performed significantly poorer in the Auditory Verbal Learning Task (AVLT) compared to first-episode patients. In both patient groups, NAA levels of the left frontal lobe significantly correlated with performances in verbal learning and memory. These results corroborate data from recent structural and spectroscopic imaging studies of the frontal lobes in schizophrenia, in which cortical gray matter reductions after onset of symptoms as well as reduced levels of NAA in chronic, but not in first-episode schizophrenic patients have been reported.

Reduced N-acetyl-aspartate levels in schizophrenia patients with a younger onset age: a single-voxel 1H spectroscopy study

Schizophrenia is widely considered a neurodevelopmental disorder. The timing of psychosis onset may determine the degree of functional and biological deficits. In this study, the association between age of onset of psychosis and in vivo biochemical levels was assessed in first-episode, antipsychotic-naive (FEAN) schizophrenia subjects. We hypothesized greater biochemical deficits in the younger-onset FEAN subjects. In vivo, (1)H spectroscopy measurements of the left dorsolateral prefrontal cortex (DLPFC) were conducted on FEAN subjects (15 schizophrenia and 3 schizoaffective subjects) and healthy comparison subjects of comparable age and gender distribution (N=61). N-acetyl-aspartate was significantly lower in the left DLPFC of FEAN subjects as compared to healthy comparison subjects. However, there was a significant subject group-by-age interaction for N-acetyl-aspartate. Early-onset FEAN subjects showed lower N-acetyl-aspartate levels compared to the younger healthy comparison subjects, while adult-onset FEAN and older healthy comparison subjects did not differ. The lower N-acetyl-aspartate levels in the DLPFC of early-onset subjects suggest a reduction in functioning neurons or specifically a reduction in the proliferation of dendrites and synaptic connections, which is not apparent in the adult-onset schizophrenia subjects.

Measurement of brain metabolites by 1H magnetic resonance spectroscopy in patients with schizophrenia: a systematic review and meta-analysis

A systematic review of the literature identified 64 published English-language papers that used proton (1H) magnetic resonance spectroscopy to measure N-acetylaspartate (NAA) concurrently in healthy controls and in patients with a diagnosis of schizophrenia (SZ). A total of 1209 controls and 1256 patients have been evaluated, with 88% of studies carried out at 1.5 T field strength, and 77% of studies focused on patients with chronic SZ. There is consistent evidence that NAA is reduced in a broad range of tissues in the SZ brain. Broad consensus (> or =10 studies) is emerging that NAA levels are reduced > or =5% in hippocampus and in both cortical gray matter (GM) and white matter (WM) of the frontal lobe. There is no evidence to support a hypothesis that relative NAA levels are reduced to a different degree in frontal lobe GM and WM, nor is there robust evidence of a difference in NAA levels between patients with first-episode and chronic SZ. Study reliability may be a problem, as most studies appear to be underpowered. With simple assumptions about the inherent difference in NAA levels between patients and controls, it can be calculated that a minimum sample size of approximately 39 patients and 39 controls is required for acceptable statistical power. Only three of 64 studies included enough subjects to have 80% power to detect a 10% NAA reduction in patients, and no studies were adequately powered to detect a 5% NAA reduction with 80% power.

Deficient hippocampal neuron expression of proteasome, ubiquitin, and mitochondrial genes in multiple schizophrenia cohorts

BACKGROUND

Hippocampal dentate granule neurons are altered in schizophrenia, but it is unknown if their gene expressions change in schizophrenia or other psychiatric diseases.

METHODS

Laser-captured dentate granule neurons from two groups of schizophrenia and control cases and from major depression and bipolar disease cases were examined for alterations in gene expression using complementary DNA (cDNA) microarrays and reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

Compared with 24 control cases, the 22 schizophrenia patients in both groups revealed decreases in clusters of genes that encode for protein turnover (proteasome subunits and ubiquitin), mitochondrial oxidative energy metabolism (isocitrate, lactate, malate, nicotinamide adenine dinucleotide [NADH], and succinate dehydrogenases; cytochrome C oxidase; adenosine triphosphate [ATP] synthase), and genes associated with neurite outgrowth, cytoskeletal proteins, and synapse plasticity. These changes were not obtained in 9 bipolar cases or 10 major depression cases and were not associated with age, sex, brain weight, body weight, postmortem interval, or drug history. Brain pH contributed to the variance of some genes but was mostly independent of the disease effect.

CONCLUSIONS

Decreases in hippocampal neuron gene expression are consistent with brain imaging and microarray studies of the frontal cortex in schizophrenia. A mitochondrial and ubiquitin-proteasome hypofunctioning of dentate granule neurons may contribute to the deficits of schizophrenia.

Thiobarbituric acid reactive substances in the cerebrospinal fluid in schizophrenia

Increased levels of lipid peroxidation products (thiobarbituric acid reactive substances [TBARS]) are reported in plasma/serum from patients with schizophrenia. CSF TBARS levels were assessed in 10 neuroleptic-free patients with schizophrenia and in 9 normal controls. Controlling for duration of storage, CSF TBARS content was significantly lower in patients with schizophrenia vs. controls (p<0.002). No significant correlations were found between CSF TBARS and patients' age, gender, or duration of illness. The likely source of reported elevated plasma/serum TBARS in schizophrenia is therefore in the periphery. Degeneration of central neuronal membranes in schizophrenia is not supported by the present study.

Increased N-acetylaspartate in rat striatum following long-term administration of haloperidol

N-acetylaspartate (NAA) is present in high concentrations in the CNS and is found primarily in neurons. NAA is considered to be a marker of neuronal viability. Numerous magnetic resonance spectroscopy (MRS) and postmortem studies have shown reductions of NAA in different brain regions in schizophrenia. Most of these studies involved patients chronically treated with antipsychotic drugs. However, the effect of chronic antipsychotic treatment on NAA remains unclear. In the present study, we measured NAA in brain tissue taken from 43 male Long-Evans rats receiving 28.5 mg/kg haloperidol decanoate i.m. every 3 weeks for 24 weeks and from 21 controls administered with vehicle. Determination of tissue concentrations of NAA was achieved by HPLC of sections of frozen tissue from several brain regions with relevance to schizophrenia. Chronic administration of haloperidol was associated with a significant increase (+23%) in NAA in the striatum (p<0.05) when compared to controls, with no significant changes in the other regions investigated (frontal and temporal cortex, thalamus, hippocampus, amygdala, and nucleus accumbens). NAA appears to be selectively increased in the striatum of rats chronically receiving haloperidol. This increase may reflect a hyperfunction of striatal neurons and relate to the reported increase in somal size of these cells and/or the increase in synaptic density seen in this region following antipsychotic administration. The lack of effect in other regions indicates that the well-documented NAA deficits seen in chronically treated schizophrenia patients is not an effect of antipsychotic medication and may in fact be related to the disease process.

N-acetyl-aspartate levels in the dorsolateral prefrontal cortex in the early years of schizophrenia are inversely related to disease duration

Magnetic resonance spectroscopy studies in schizophrenia have revealed consistently reduced N-acetyl aspartate (NAA) levels in chronic patients, but not in recent-onset patients. Studies on the relationship between this marker and disease duration have commonly been negative, although it is also true that they have been conducted in patients with long-standing disease. We compared NAA levels in the dorsolateral prefrontal cortex in 16 recent-onset patients (duration: 1.8+/-0.6 years), 19 chronic patients (duration: 9.7+/-6.1 years), and 20 healthy controls. We studied the NAA/creatine and choline/creatine ratios in the dorsolateral prefrontal cortex in both hemispheres, controlling for the effect of age. Chronic patients had significantly lower NAA/Cr ratios in the left hemisphere compared to recent-onset patients and healthy controls, with no difference in Cho/Cr ratio. There were no differences between controls and recent-onset patients. There was a significant inverse relationship between left-side NAA/Cr and disease duration, suggesting that prefrontal NAA levels may progressively decrease in schizophrenia. Taken within the context of the existing literature, these results indicate that this process may be limited to the early years following the onset of the disease. Therefore, reduced prefrontal levels of NAA may be limited to chronic schizophrenia patients.