Frontal lobe metabolism and cerebral morphology in schizophrenia: 31P MRS and MRI studies

Interrelationships Between Oxidative Stress, Cytokines, and Psychotic Symptoms and Executive Functions in Patients With Chronic Schizophrenia

OBJECTIVE

Accumulating evidence has demonstrated that the pathophysiology of schizophrenia is involved in various abnormalities in oxidative stress markers and cytokines closely related to synaptic plasticity. However, the interactive effects among key cytokines, oxidative stress, and executive dysfunction and symptoms of schizophrenia have not been investigated yet.

METHODS

A total of 189 patients with chronic schizophrenia and 60 controls were recruited in the current study. Tumor necrosis factor α (TNF-α), interleukin (IL)-8, IL-6, and IL-2 levels; catalase, glutathione peroxidase, and superoxide dismutase (SOD) activities; and malondialdehyde (MDA) levels were determined in patients and controls. Executive function was evaluated by the Wisconsin card sorting tests, the verbal fluency tests, and the Stroop word-color test. Clinical symptoms were evaluated by the Positive and Negative Syndrome Scale.

RESULTS

Relative to the controls, the patients had lower activities of SOD and glutathione peroxidase and levels of TNF-α, but higher levels of MDA, IL-8, IL-6, and IL-2 (all p values < .05). A significant negative relationship between SOD activity and IL-8 levels was found only in patients (β = -0.44, p = .008). Furthermore, we found that an interactive effect of low TNF-α level and high MDA level was associated with negative symptoms (β = -0.02, p = .01). Moreover, the interactive effects of IL-8 and MDA or IL-8 and SOD were correlated with executive function only in patients (β = 0.23, p = .02; β = 0.09, p = .03).

CONCLUSIONS

Our findings suggest that the interrelationships between oxidative stress markers and cytokines occur in schizophrenia patients, which may be the basis of their pathological mechanisms underlying clinical symptoms and cognitive dysfunction.

Regionally Distinct Alterations in Membrane Phospholipid Metabolism in Schizophrenia: A Meta-analysis of Phosphorus Magnetic Resonance Spectroscopy Studies

BACKGROUND

Existing data on altered membrane phospholipid metabolism in schizophrenia are diverse. We conducted a meta-analysis of studies of phosphorus magnetic resonance spectroscopy, a noninvasive imaging approach that can assess molecular biochemistry of cortex by measuring phosphomonoester (PME) and phosphodiester (PDE) levels, which can provide evidence of altered biochemical processes involved in neuropil membrane expansion and contraction in schizophrenia.

METHODS

We analyzed PME and PDE data in the frontal and temporal lobes in subjects with schizophrenia from 24 peer-reviewed publications using the MAVIS package in R by building random- and fixed-effects models. Heterogeneity of effect sizes, effects of publication bias, and file drawer analysis were also assessed.

RESULTS

Subjects with schizophrenia showed lower PME levels in the frontal regions (p = .008) and elevated PDE levels in the temporal regions (p < .001) with significant heterogeneity. We noted significant publication bias and file drawer effect for frontal PME and PDE and temporal PDE levels, but not for temporal PME levels. Fail-safe analysis estimated that a high number of negative studies were required to provide nonsignificant results.

CONCLUSIONS

Despite methodological differences, these phosphorus magnetic resonance spectroscopy studies demonstrate regionally specific imbalance in membrane phospholipid metabolism related to neuropil in subjects with schizophrenia compared with control subjects reflecting neuropil contraction. Specifically, decreased PME levels in the frontal regions and elevated PDE levels in the temporal regions provide evidence of decreased synthesis and increased degradation of neuropil membrane, respectively. Notwithstanding significant heterogeneity and publication bias, a large number of negative studies are required to render the results of this meta-analysis nonsignificant. These findings warrant further postmortem and animal studies.

Effects of 12-month, double-blind N-acetyl cysteine on symptoms, cognition and brain morphology in early phase schizophrenia spectrum disorders

BACKGROUND

Currently approved medications for schizophrenia are relatively ineffective for negative symptoms and cognitive impairment. N-Acetyl Cysteine (NAC) is a neuroprotective agent that improved general symptoms, cognitive impairment and negative symptoms in some but not all studies, but failed to improve positive symptoms in patients with schizophrenia. Progressive brain mass loss (PBML) has been consistently observed in early phase schizophrenia. NAC mitigates the deleterious effects oxidative stress, inflammation and glutamatergic excitotoxicity and these three pathological processes are hypothesized to contribute to PBML.

METHODS

In this study, we assessed the effects NAC (3600mg/day) in a 52-week, double-blind, placebo controlled trial on symptoms, and cognition in early phase schizophrenia spectrum disorders (N=60). In the context of the clinical trial, we explored the effects of NAC on brain morphology.

RESULTS

NAC significantly improved (time×group) PANSS total (F=14.7, p<0.001), negative (F=5.1, p=0.024) and disorganized thought (F=13.7, p<0.001) symptom scores. NAC failed to improve PANSS positive symptoms and BACS cognitive scores. In preliminary analyses, baseline right (r=-0.48, p=0.041) and left (r=-0.45, p=0.018) total cortical thickness, and thickness in other cortical regions, were associated with NAC related improvement in PANSS total scores, but NAC, as compared to placebo, did not significantly impact brain morphology over the study treatment period.

CONCLUSIONS

These results replicate some but not all previous findings of NAC efficacy. Preliminary results suggest that NAC's symptom effects may be related to structural integrity, but NAC failed to demonstrate treatment effects on longitudinal measures of brain morphology. ClinicalTrials.gov Identifier: NCT01339858.

Consensus paper of the WFSBP Task Force on Biological Markers: Criteria for biomarkers and endophenotypes of schizophrenia, part III: Molecular mechanisms

OBJECTIVES

Despite progress in identifying molecular pathophysiological processes in schizophrenia, valid biomarkers are lacking for both the disease and treatment response.

METHODS

This comprehensive review summarises recent efforts to identify molecular mechanisms on the level of protein and gene expression and epigenetics, including DNA methylation, histone modifications and micro RNA expression. Furthermore, it summarises recent findings of alterations in lipid mediators and highlights inflammatory processes. The potential that this research will identify biomarkers of schizophrenia is discussed.

RESULTS

Recent studies have not identified clear biomarkers for schizophrenia. Although several molecular pathways have emerged as potential candidates for future research, a complete understanding of these metabolic pathways is required to reveal better treatment modalities for this disabling condition.

CONCLUSIONS

Large longitudinal cohort studies are essential that pair a thorough phenotypic and clinical evaluation for example with gene expression and proteome analysis in blood at multiple time points. This approach might identify biomarkers that allow patients to be stratified according to treatment response and ideally also allow treatment response to be predicted. Improved knowledge of molecular pathways and epigenetic mechanisms, including their potential association with environmental influences, will facilitate the discovery of biomarkers that could ultimately be effective tools in clinical practice.

Phosphorus magnetic resonance spectroscopy studies in schizophrenia

Phosphorus magnetic resonance spectroscopy ((31)P MRS) allows in vivo quantification of phosphorus metabolites that are considered to be related to membrane turnover and energy metabolism. In schizophrenia (SZ), (31)P MRS studies found several abnormalities in different brain regions suggesting that alterations in these pathways may be contributing to the pathophysiology. In this paper, we systematically reviewed the (31)P MRS studies in SZ published to date by taking patient characteristics, medication status and brain regions into account. Publications written in English were searched on http://www.ncbi.nlm.nih.gov/pubmed/, by using the keywords 'phosphomonoester', 'phosphodiester', 'ATP', 'phosphocreatine', 'phosphocholine', 'phosphoethanolamine','glycerophosphocholine', 'glycerophosphoethanolamine', 'pH', 'schizophrenia', and 'MRS'. Studies that measured (31)P metabolites in SZ patients were included. This search identified 52 studies. Reduced PME and elevated PDE reported in earlier studies were not replicated in several subsequent studies. One relatively consistent pattern was a decrease in PDE in chronic patients in the subcortical structures. There were no consistent patterns for the comparison of energy related phosphorus metabolites between patients and controls. Also, no consistent pattern emerged in studies seeking relationship between (31)P metabolites and antipsychotic use and other clinical variables. Despite emerging patterns, methodological heterogeneities and shortcomings in this literature likely obscure consistent patterns among studies. We conclude with recommendations to improve study designs and (31)P MRS methods in future studies. We also stress the significance of probing into the dynamic changes in energy metabolism, as this approach reveals abnormalities that are not visible to steady-state measurements.

Altered phospholipid metabolism in schizophrenia: a phosphorus 31 nuclear magnetic resonance spectroscopy study

Phospholipid (PL) metabolism is investigated by in vivo 31P magnetic resonance spectroscopy (MRS). Inconsistent alterations of phosphocholine (PC), phosphoethanolamine (PE), glycerophosphocholine (GPC) and glycerophosphoethanolamine (GPE) have been described in schizophrenia, which might be overcome by specific editing techniques. The selective refocused insensitive nuclei-enhanced polarization transfer (RINEPT) technique was applied in a cross-sectional study involving 11 schizophrenia spectrum disorder patients (SZP) on stable antipsychotic monotherapy and 15 matched control subjects. Metabolite signals were found to be modulated by cerebrospinal fluid (CSF) content and gray matter/brain matter ratio. Corrected metabolite concentrations of PC, GPC and PE differed between patients and controls in both subcortical and cortical regions, whereas antipsychotic medication exerted only small effects. Significant correlations were found between the severity of clinical symptoms and the assessed signals. In particular, psychotic symptoms correlated with PC levels in the cerebral cortex, depression with PC levels in the cerebellum and executive functioning with GPC in the insular and temporal cortices. In conclusion, after controlling for age and tissue composition, this investigation revealed alterations of metabolite levels in SZP and correlations with clinical properties. RINEPT 31P MRS should also be applied to at-risk-mental-state patients as well as drug-naïve and chronically treated schizophrenic patients in order to enhance the understanding of longitudinal alterations of PL metabolism in schizophrenia.

Meta-analysis of oxidative stress in schizophrenia

BACKGROUND

Schizophrenia is associated with impaired antioxidant defense, including abnormal serum, plasma, and red blood cell (RBC) oxidative stress parameters. We performed a meta-analysis of these associations, considering the effect of clinical status and antipsychotic treatment after an acute exacerbation of psychosis.

METHODS

We identified articles by searching PubMed, PsychInfo, and Institute for Scientific Information, and the reference lists of identified studies.

RESULTS

Forty-four studies met the inclusion criteria. Total antioxidant status seemed to be a state marker, because levels were significantly decreased in cross-sectional studies of serum and plasma in first-episode psychosis (FEP) and significantly increased in longitudinal studies of antipsychotic treatment for acute exacerbations of psychosis (p < .01 for each). The RBC catalase and plasma nitrite seemed to be state-related markers, because levels in cross-sectional studies were significantly decreased in FEP (p < .01) and significantly increased in stable outpatients (p = .01). In contrast, RBC superoxide dismutase seemed to be a trait marker for schizophrenia, because levels in cross-sectional studies were significantly decreased in acutely relapsed inpatients, FEP, and stable outpatients (p < .01 for each).

CONCLUSIONS

Oxidative stress abnormalities in FEP suggest an effect that might be independent of antipsychotic medications. Although some parameters (total antioxidant status, RBC catalase, and plasma nitrite) might be state markers for acute exacerbations of psychosis, others (RBC superoxide dismutase) might be trait markers; however, more longitudinal studies are needed. Our findings suggest that oxidative stress might serve as a potential biomarker in the etiopathophysiology and clinical course of schizophrenia.

Gray matter volumetric abnormalities associated with the onset of psychosis

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

Meta-analysis of magnetic resonance imaging studies of the corpus callosum in schizophrenia

OBJECTIVES

The corpus callosum plays a pivotal role in inter-hemispheric transfer and integration of information. Magnetic resonance studies have reported callosal abnormalities in schizophrenia but findings have been inconsistent. Uncertainty has persisted despite a meta-analytic evaluation of this structure several years ago. We set out to perform a further meta-analysis with the addition of the numerous reports published on the subject to test the hypothesis that the corpus callosum is abnormal in schizophrenia.

METHOD

A systematic search was carried out to identify suitable magnetic resonance studies which reported callosal areas in schizophrenia compared to controls. Results from the retrieved studies were compared in a meta-analysis whilst the influence of biological and clinical variables on effect size was ascertained with meta-regression analysis.

RESULTS

Twenty-eight studies were identified. Corpus callosum area was reduced in schizophrenia in comparison to healthy volunteers. This effect was larger in first episode patients. Similarly, heterogeneity detected among the studies was associated with course of illness indicating that chronic subjects with schizophrenia showed larger callosal areas. There was no evidence of publication bias.

CONCLUSIONS

This study confirms the presence of reduced callosal areas in schizophrenia. The effect is of a larger magnitude at first presentation and less so in subjects with a chronic course generally medicated with antipsychotics.

Retinoic acid-mediated phospholipase A2 signaling in the nucleus

Retinoic acid modulates a wide variety of biological processes including proliferation, differentiation, and apoptosis. It interacts with specific receptors in the nucleus, the retinoic acid receptors (RARs). The molecular mechanism by which retinoic acid mediates cellular differentiation and growth suppression in neural cells remains unknown. However, retinoic acid-induced release of arachidonic acid and its metabolites may play an important role in cell proliferation, differentiation, and apoptosis. In brain tissue, arachidonic acid is mainly released by the action of phospholipase A2 (PLA2) and phospholipase C (PLC)/diacylglycerol lipase pathways. We have used the model of differentiation in LA-N-1 cells induced by retinoic acid. The treatment of LA-N-1 cells with retinoic acid produces an increase in phospholipase A2 activity in the nuclear fraction. The pan retinoic acid receptor antagonist, BMS493, can prevent this increase in phospholipase A2 activity. This suggests that retinoic acid-induced stimulation of phospholipase A2 activity is a retinoic acid receptor-mediated process. LA-N-1 cell nuclei also have phospholipase C and phospholipase D (PLD) activities that are stimulated by retinoic acid. Selective phospholipase C and phospholipase D inhibitors block the stimulation of phospholipase C and phospholipase D activities. Thus, both direct and indirect mechanisms of arachidonic acid release exist in LA-N-1 cell nuclei. Arachidonic acid and its metabolites markedly affect the neurite outgrowth and neurotransmitter release in cells of neuronal and glial origin. We propose that retinoic acid receptors coupled with phospholipases A2, C and D in the nuclear membrane play an important role in the redistribution of arachidonic acid in neuronal and non-nuclear neuronal membranes during differentiation and growth suppression. Abnormal retinoid metabolism may be involved in the downstream transcriptional regulation of phospholipase A2-mediated signal transduction in schizophrenia and Alzheimer disease (AD). The development of new retinoid analogs with diminished toxicity that can cross the blood-brain barrier without harm and can normalize phospholipase A2-mediated signaling will be important in developing pharmacological interventions for these neurological disorders.

The relationship between membrane pathology and language disorder in schizophrenia

Receptive language disorder in schizophrenia has been hypothesized to involve a fundamental deficit in the temporal (time-based) dynamics of brain function that includes disruptions to patterns of activation and synchronization. In this paper, candidate mechanisms and pathways that could account for this basic deficit are discussed. Parallels are identified between the patterns of language dysfunction observed for schizophrenia and dyslexia, two separate clinical disorders that may share a common abnormality in cell membrane phospholipids. A heuristic is proposed which details a trajectory involving an interaction of brain fatty acids and second-messenger function that modulates synaptic efficacy, and, in turn, influences language processing in schizophrenia patients. It is additionally hypothesized that a primary deficit of functional excitation originating in the cerebellum, in combination with a compensatory decrease of functional inhibition in the prefrontal cortex, influences receptive language dysfunction in schizophrenia.

Phospholipid and eicosanoid signaling disturbances in schizophrenia

A variety of biochemical, clinical and genetic evidence suggests that phospholipid metabolism may play an aetiological role in schizophrenia. A key piece of evidence is the reduced vasodilatory response of patients with schizophrenia to nicotinic acid (NA). NA causes vasodilation via the activation of phospholipase A2 (PLA2) leading to the release of free fatty acids from membrane phospholipids and the subsequent production of prostaglandins. Insensitivity to NA may be due to a 'block' in the downstream signaling pathway used by the drug to evoke its response. It can be argued that if such an abnormality occurs in neurons, impaired PLA2-dependent signaling could result in altered glutamateric and dopaminergic transmission in such a way as to produce or exacerbate psychotic symptoms. The complimentary finding of increased PLA2 activity in schizophrenia may be an attempt to overcome the signaling block. It is suggested that intervention aimed at increasing the activity of PLA2-dependent signaling systems may be therapeutically useful in the treatment of the illness.

Smoking, gender, and dietary influences on erythrocyte essential fatty acid composition among patients with schizophrenia or schizoaffective disorder

BACKGROUND

Prior reports of decreased levels of essential fatty acids among schizophrenic patients have generated several hypotheses proposing inherent abnormalities in phospholipid and fatty acid metabolism and have provided the basis for treatment trials; however, these essential fatty acid aberrations may be attributable to uncontrolled factors, such as smoking, rather than abnormalities inherent to schizophrenia.

METHODS

Erythrocyte fatty acid compositions were quantified in 72 medicated schizophrenic or schizoaffective patients both at baseline and after 16 weeks of supplementation with 3 g/day of either ethyl-eicosapentaenoic acid or placebo. Current smoking status, gender, dietary survey, and Montgomery Asburg Depression Rating Scale, Repeatable Battery for the Assessment of Neuropsychological Status, Abnormal Involuntary Movement Scale, and Positive and Negative Syndrome Scale scores were assessed.

RESULTS

Schizophrenic patients who smoked had lower baseline erythrocyte docosahexaenoic acid percent (2.98 +/-.7 vs. 3.59 +/- 1.2, p <.005) and eicosapentaenoic acid (EPA) percent (.39 +/-.13 vs. 47 +/-.22, p <.05), compared with nonsmokers, with a significant gender interaction (p <.01) in multivariate analyses of variance. Baseline arachidonic acid did not differ. Smokers reported lower dietary intake (percent total fat) of linolenic acid (F = 10.1, p <.003) compared with nonsmokers. Nonsmoking women reported greater dietary intake of EPA compared with smoking men or nonsmokers of either gender.

CONCLUSIONS

Smoking status, gender, and dietary intake significantly predicted erythrocyte polyunsaturated fatty acid status among schizophrenic patients. No evidence was found for subgroups of schizophrenia or relationships to specific symptom severity on the basis of erythrocyte fatty acids. Prior reports of abnormalities of essential fatty acid metabolism among schizophrenic patients may have been an artifact of patients' smoking behavior and differences in dietary intake of omega-3 fatty acids.

Is schizophrenia a metabolic brain disorder? Membrane phospholipid dysregulation and its therapeutic implications

The dysregulation of membrane phospholipid metabolism exists throughout the body from the onset of psychosis in schizophrenic patients. This dysregulation is primarily due to altered contents of phospholipid bound EPUFAs, AA and DHA. These EPUFAs are highly enriched in the brain and are crucial for brain and behavioral development. A phospholipid metabolic defect may preexist the onset of psychosis, even through early embryonic stages. Because these membrane phospholipids play a crucial role in the membrane receptor-mediated signal transduction of several neuro-transmitters and growth factors, their altered metabolism may contribute to the reported abnormal information processing in schizophrenia. Severity of symptoms seems to correlate with the membrane AA and DHA status, which is influenced by patients' dietary intake and lifestyle. Such a metabolic defect can be prevented, however, and some membrane pathology can be corrected by dietary supplementation with a combination of AA and DHA and antioxidants such as vitamins E and C. In schizophrenia, it may be advisable to provide supplementation at the early stages of illness, when brain has a high degree of plasticity. Finally, at this time, supplementation has to be considered as an augmentation of conventional antipsychotic treatment.

Essential polyunsaturated fatty acid and lipid peroxide levels in never-medicated and medicated schizophrenia patients

BACKGROUND

Reduced levels of membrane essential polyunsaturated fatty acids (EPUFAs) and increased levels of lipid peroxidation products (thiobarbituric acid reactive substances; TBARS) have been observed in chronic medicated schizophrenics. The relationship of EPUFA and TBARS to psychopathology is unclear, since their levels may be altered differentially by duration of illness and antipsychotic treatment. To minimize these confounds, their levels were compared among never-medicated patients in early illness, medicated patients and control subjects with similar lifestyle and common ethnic background.

METHODS

RBC membrane EPUFAs, plasma TBARS, and various dimensions of psychopathology were measured using established procedures in never-medicated (n = 20) and medicated (n= 32) schizophrenia patients and in control subjects (n= 45).

RESULTS

Reduced levels of EPUFAs, particularly arachidonic acid (AA) and docosahexaenoic acid (DHA), were found in never-medicated compared with control subjects; however, the reductions in levels of both AA and DHA were much smaller in medicated versus never-medicated patients; AA levels were similar to levels in control subjects. Only DHA levels were significantly reduced in medicated patients. Lower membrane AA levels were associated with increased levels of plasma TBARS in never-medicated patients. Lower levels of membrane EPUFAs and higher levels of plasma TBARS were associated with the severe symptoms in never-medicated versus medicated patients.

CONCLUSIONS

Data indicate that reduced EPUFAs and increased TBARS exist in never-medicated patients, and these measures correlate with the severity of psychopathology indicating that the membrane EPUFA status may reflect the outcome of schizophrenia.

Mesial temporal lobe Cho to Cr(PCr) ratio asymmetry in chronic schizophrenics

Proton magnetic resonance spectra (MRS) were acquired from 1.5 x 1.5 x 1.5-cm voxels in the left and right mesial temporal lobes of 20 schizophrenic patients and 20 non-psychiatric comparison subjects. Choline (Cho) to creatine (and phosphocreatine) (Cr(PCr)) ratios were estimated as were the percent gray matter, white matter and CSF contributing to the voxel. The Cho/Cr(PCr) metabolite ratio was significantly lower in the left temporal lobe than in the right temporal lobe for both the schizophrenia subjects and control group. This difference was greater in the schizophrenia subjects. Left temporal lobe gray matter voxel content was significantly higher and white matter content was significantly lower than in the right temporal lobe for both the schizophrenia subjects and control group. This difference was the same for the schizophrenia subjects and control group. Left voxel gray matter and white matter content correlated with Cho/Cr(PCr) metabolite ratios for the schizophrenic subjects but not for the control subjects. No such correlations were noted on the right side. No significant difference was found between Cho/Cr(PCr) in the left temporal lobe or in the right temporal lobe of the schizophrenia subjects vs. the control group.

Corpus callosum and P300 in schizophrenia

Functional abnormalities in the interhemispheric transfer via the corpus callosum in schizophrenia may result in filtering problems and information processing problems, which may in turn be related to the synchronization of cortical event-related activity. To explore whether a relationship exists between corpus callosum (CC) size, measured with in-vivo magnetic resonance imaging, and late auditory event-related P300 potentials, 50 patients with schizophrenia as well as 50 healthy controls were examined. The absolute CC size and subregional areas, as well as the CC areas adjusted for total brain volume, were not significantly different between patients with schizophrenia and controls. While no significant group differences were observed for P3a-, P3b-, PSW-amplitudes and P3b-latencies, P3a- and PSW-latencies were significantly prolonged for patients with schizophrenia. Absolute CC total size was significantly correlated with P3b-amplitudes in healthy controls (r=0.29; P=0.044). In patients with schizophrenia, significant correlations were observed between the subregion of the posterior body of the CC and positive slow wave (PSW; r=0.47; P=0.001). P3a-, P3b- and PSW-latencies were not significantly correlated to CC size in either patients with schizophrenia or healthy controls. The results are discussed in terms of the possibility that abnormalities in interhemispheric transfer may underlie the mechanisms of schizophrenia.

Neurochemical investigation of the schizophrenic brain by in vivo phosphorus magnetic resonance spectroscopy

Abnormal phospholipid metabolisms may play important roles in the pathophysiology of schizophrenia. Phosphorus magnetic resonance spectroscopy (31P-MRS) offers a new method for studying phosphorus-related metabolism in vivo. A decrease in the level of phosphomonoesters (PME) and an increase in the level of phosphodiesters (PDE) has been demonstrated in the prefrontal lobe of neuroleptic-naive schizophrenic patients. Most of the studies in medicated schizophrenic patients have shown decreased PME and/or increased PDE. The decreased PME in the frontal lobe appears to be associated with negative symptoms and poor working memory performance. 1H-decoupled 31P-MRS revealed a reduction in the phosphocholine element of PME and an elevation in the mobile phospholipids of PDE in the prefrontal region of medicated schizophrenic patients. PDE were elevated in the temporal lobes of neuroleptic-naive schizophrenic patients, and this increase was partially normalized by haloperidol administration. Data about the temporal lobes of medicated schizophrenic patients have not been consistent. Except for the reduction in the adenosine triphosphate (ATP) in the basal ganglia and the correlation between the increase in the frontal lobe phosphocreatine (PCr) and negative symptomatology, data related to changes in high-energy phosphates are contradictory. No consensus on the effect of neuroleptics on phosphorus metabolites has been achieved. Methodological problems inherent in 31P-MRS may have contributed to the confusion in understanding available data. Future directions of MRS studies are suggested in the last section of the paper.

Shape and size of the corpus callosum in schizophrenia and schizotypal personality disorder

The size and shape of the corpus callosum were assessed on sagittal section magnetic resonance images in 27 patients with schizophrenia, 13 patients with schizotypal personality disorder (SPD), and 30 healthy volunteers. High-resolution 1.2mm axial SPGR images were acquired and resectioned so that the sagittal plane passed through the anterior and posterior commissures and was parallel to the interhemispheric fissure. The corpus callosum and the whole brain were traced on midsagittal section slices of each brain, and the callosum was divided into 30 anteroposterior sectors. Pixel-by-pixel chi-square and thin-plate spline analyses were used to assess between-group shape differences. Size of the corpus callosum was smaller anteriorly in the genu of the corpus callosum and posteriorly in the splenium in schizophrenic patients than in normal controls. The genu of the corpus callosum was larger in SPD patients than in schizophrenic patients or normal controls. The posterior corpus callosum was largest in normal controls, smaller in SPD patients, and smallest in schizophrenic patients. Shape analysis was consistent with these size comparisons, and suggested a downward bowing of the corpus callosum in schizophrenic and SPD patients. SPD patients also had a region of the callosum just posterior to the genu that was narrower than in the other two groups. The decreases in corpus callosal size in schizophrenia varied directly with length of illness, perhaps indicative of a progressive process. The patient-control differences in callosal size and shape are consistent with a hypothesis of decreased connectivity between the left and the right hemispheres in schizophrenia and SPD.

Magnetic resonance spectroscopy and schizophrenia: what have we learnt?

OBJECTIVE

Magnetic resonance spectroscopy (MRS) has been increasingly used to investigate the in vivo biochemistry of particular regions of the brain in patients with schizophrenia. We review the literature and discuss the theoretical constructs that form the presumed impetus for these studies in light of the current methodological limitations. Future directions are noted.

METHOD

The available published literature in English formed the basis for this review.

RESULTS

The results of 31P-MRS have been interpreted as reflecting a relative increase in cell membrane degradation in prefrontal cortical regions at certain phases of schizophrenia. 1H-MRS studies, though less consistent, provide evidence suggestive of a decrease in neuronal cell mass in the hippocampal region, which supports the findings of volumetric studies. Both groups of MRS studies support a neuro-developmental hypothesis of brain dysfunction in schizophrenia. However, current methodological problems limit the reliable interpretation of MRS data. A clear understanding of the methodology and its reliable interpretation is yet to emerge.

CONCLUSIONS

MRS remains a research instrument that is yet to be fully utilised in schizophrenia research. A few replicated findings are emerging, although the interpretation of these spectroscopic findings needs to be validated.

Differential alteration of phospholipase A2 activities in brain of patients with schizophrenia

We recently reported that the activity of a calcium-independent subtype of phospholipase A2 is increased in blood of patients with schizophrenia. The present investigation examined whether similar changes take place in brain of patients with this disorder, and for comparison, in patients with bipolar disorder. The activity of two classes of PLA2, calcium-stimulated and independent, were assayed in autopsied temporal, prefrontal and occipital cortices, putamen, hippocampus and thalamus of 10 patients with schizophrenia, 8 patients with bipolar disorder and 12 matched control subjects. Calcium-independent PLA2 activity was increased by 45% in the temporal cortex of patients with schizophrenia as compared with the controls but was not significantly altered in other brain areas. In contrast, calcium-stimulated PLA2 activity was decreased by 27-42% in the temporal and prefrontal cortices and putamen, with no significant alterations in other brain regions. Brain PLA2 activity was normal in patients with bipolar disorder. Calcium-stimulated PLA2 activity was normal in cortex, cerebellum and striatum of rats treated acutely or chronically with haloperidol, whereas calcium-independent PLA2 activity was decreased in striatum of chronically treated animals, indicating that altered PLA2 activity in patients with schizophrenia is unlikely to be a direct effect of medication. Studies of the cellular role played by PLA2 suggest that decreased calcium-stimulated PLA2 activity, as also occurs in striatum of chronic human cocaine users, may be due, in part, to increased dopaminergic activity in the disorder, whereas increased calcium-independent PLA2 activity may be related to abnormal fatty acid metabolism and oxidative stress in schizophrenia.

Single-voxel proton magnetic resonance spectroscopy of the pons and cerebellum in patients with schizophrenia: a preliminary study

Magnetic resonance spectroscopy (MRS) is a non-invasive functional imaging technique that can measure various brain tissue metabolites such as N-acetylaspartate (NAA), choline (Cho), creatine-phosphocreatine (Cr), myo-inositol (mI) and other metabolites. Morphological studies have indicated the pons and cerebellum as possible sites of abnormal functioning in schizophrenic patients. This study examines schizophrenic patients for the presence of abnormalities in proton MRS (1H-MRS) measured metabolites in two regions of the posterior fossa. Twelve schizophrenic patients and eight non-schizophrenic control subjects were studied by measuring the ratios of NAA/Cr, Cho/Cr and mI/Cr from 1H-spectra obtained from the pons and right or left cerebellum using an integrated MRI/MRS protocol. Spectra were obtained from a voxel in the pons and voxels from the left and/or right lateral cerebellum. Data were analyzed in the absorption mode and fitted to Lorentzian lineshapes using a Marquart algorithm. Significantly lower NAA/Cr ratios were found in the pons of schizophrenic patients than in the control subjects, but not in the cerebellum. This study is the first to measure brain tissue metabolites using 1H-MRS in the pons and cerebellum of schizophrenic patients. Significant alterations of 1H-MRS metabolites may suggest the involvement of the posterior fossa as a part of the pathological substrate underlying schizophrenia.

In vivo neurochemistry of the brain in schizophrenia as revealed by magnetic resonance spectroscopy

Magnetic resonance spectroscopy (MRS), an application of the methods of nuclear magnetic resonance (NMR), is a functional imaging modality that provides a view of localized biochemistry in vivo. A number of studies applying MRS to the neurochemistry of schizophrenia have been reported, which encompass a range of patient populations, states of medication, anatomic regions, nuclear species, and MRS techniques. A brief review of the history and methodology of NMR and MRS is presented. Comparison is made of MRS capabilities with other functional imaging modalities. Aspects of the neurochemistry of schizophrenia relevant to MRS studies are reviewed, as are the reported MRS studies involving patients with schizophrenia. Areas of consistent findings include decreased phosphomonoesters and increased phosphodiesters in frontal lobes, and decreases in the putative neuronal cell marker, N-acetylaspartate, in temporal lobes. Studies of neurotransmitters such as glutamate, gamma-aminobutyric acid, and glutamine have generated inconsistent results. New insights into alterations in neurochemistry in schizophrenia have been provided by MRS. Studies of neurotransmitters have future potential with improvements in field strength and in spectral editing techniques. MRS has the potential to measure brain medication levels and simultaneous effects on neurochemistry. MRS may assist in characterizing high-risk populations, and ultimately guide medication use.

Preliminary study of frontal lobe 1H MR spectroscopy in childhood-onset schizophrenia

Cerebral 1H MR spectra were recorded in 13 children and adolescents with schizophrenia and 12 healthy children and adolescents. Stimulated echo acquisition mode (STEAM) sequence was used to localize an 8-ml voxel bilaterally in the frontal gray matter. The frontal gray matter metabolite ratios for NAA/Cr, Ch/Cr, Glx/Cr, and mI/Cr in schizophrenic children and adolescents were 1.08 +/- .28, .64 +/- .23, 1.09 +/- .30, and .60 +/- .24, respectively. In comparison, these ratios were 1.59 +/- .35, .74 +/- .27, 1.23 +/- .36, and .58 +/- .29 in healthy children and adolescents. Decrease in the frontal lobe NAA/Cr of schizophrenic children and adolescents was statistically significant (P < .001). In contrast, the MR spectra localized bilaterally in the occipital gray matter (8 ml) showed no significant changes between the patients and the controls. In the occipital gray matter, the metabolite ratios were 1.21 +/- .26,.52 +/- .08, 1.00 +/- .11, and.55 +/- .12 inpatients versus 1.30 +/- .23, .45 +/- .10, 1.15 +/- .20, and .48 +/- .19 in controls. Our preliminary finding of reduced NAA/Cr ratio in the frontal gray matter is consistent with the neurodevelopmental models emphasizing dysfunction of frontal lobe areas in patients with schizophrenia.

31P magnetic resonance spectroscopy studies in schizophrenia

Phospholipid metabolism abnormalities have been suggested by a number of postmortem brain and red blood cell studies in schizophrenia. 31P magnetic resonance spectroscopy enables the examination of phospholipid metabolism in living patients. These in vivo studies have demonstrated that schizophrenic patients have lower prefrontal levels of phosphomonoesters and higher levels of phosphodiesters compared to matched controls. Patients with psychotic depression also seem to show lower levels of phosphomonoesters compared to controls. This suggests that membrane phospholipid differences may not be specific to schizophrenia. Preliminary 31P magnetic resonance spectroscopy studies at high field strength on postmortem temporal lobe samples show no differences between treated schizophrenic patients and controls for phosphoethanolamine and phosphocholine which are the main constituents of the phosphomonoester peak. Further studies are underway in the prefrontal region. While 31P magnetic resonance spectroscopy studies have demonstrated membrane phospholipid abnormalities in schizophrenia, it is not clear whether these findings are specific to schizophrenia or part of a generalized membrane phospholipid abnormality.

In vivo magnetic resonance spectroscopy. Applications in psychiatry

BACKGROUND

Nuclear magnetic resonance is a non-destructive and non-invasive technology that is highly suited for research in psychiatry. It is establishing itself as a versatile means of studying brain morphology, chemistry and function and is finding a place in the diagnosis of disease, monitoring of treatment and the study of basic brain processes.

METHOD

A literature review was undertaken.

RESULTS

Magnetic resonance spectroscopy has been shown to distinguish between psychiatric disorders, and has provided evidence of their pathophysiological mechanisms.

CONCLUSIONS

Spectroscopy in particular opens a window, for the first time, on the study of in vivo brain chemistry.