31Phosphorus magnetic resonance spectroscopy of the temporal lobes in schizophrenia

Gene Expressions Preferentially Influence Cortical Thickness of Human Connectome Project Atlas Parcellated Regions in First-Episode Antipsychotic-Naïve Psychoses

Altered gene expressions may mechanistically link genetic factors with brain morphometric alterations. Existing gene expression studies have examined selected morphometric features using low-resolution atlases in medicated schizophrenia. We examined the relationship of gene expression with cortical thickness (CT), surface area (SA), and gray matter volume (GMV) of first-episode antipsychotic-naïve psychosis patients (FEAP = 85) and 81 controls, hypothesizing that gene expressions often associated with psychosis will differentially associate with different morphometric features. We explored such associations among schizophrenia and non-schizophrenia subgroups within FEAP group compared to controls. We mapped 360 Human Connectome Project atlas-based parcellations on brain MRI on to the publicly available brain gene expression data from the Allen Brain Institute collection. Significantly correlated genes were investigated using ingenuity pathway analysis to elucidate molecular pathways. CT but not SA or GMV correlated with expression of 1137 out of 15 633 genes examined controlling for age, sex, and average CT. Among these ≈19%, ≈39%, and 8% of genes were unique to FEAP, schizophrenia, and non-schizophrenia, respectively. Variants of 10 among these 1137 correlated genes previously showed genome-wide-association with schizophrenia. Molecular pathways associated with CT were axonal guidance and sphingosine pathways (common to FEAP and controls), selected inflammation pathways (unique to FEAP), synaptic modulation (unique to schizophrenia), and telomere extension (common to NSZ and healthy controls). We demonstrate that different sets of genes and molecular pathways may preferentially influence CT in different diagnostic groups. Genes with altered expressions correlating with CT and associated pathways may be targets for pathophysiological investigations and novel treatment designs.

Evidence for altered energy metabolism, increased lactate, and decreased pH in schizophrenia brain: A focused review and meta-analysis of human postmortem and magnetic resonance spectroscopy studies

Though the pathophysiology of schizophrenia remains poorly understood, altered brain energy metabolism is increasingly implicated. Here, we conduct meta-analyses of the available human studies measuring lactate or pH in schizophrenia brain and discuss the accumulating evidence for increased lactate and decreased pH in schizophrenia brain and evidence linking these to negative and cognitive symptom severity. Meta-analysis of six postmortem studies revealed a significant increase in lactate in schizophrenia brain while meta-analysis of 14 magnetic resonance spectroscopy studies did not reveal a significant change in brain pH in schizophrenia. However, only five of these studies were likely sufficiently powered to detect differences in brain pH, and meta-analysis of these five studies found a nonsignificant decrease in pH in schizophrenia brain. Next, we discuss evidence for altered brain energy metabolism in schizophrenia and how this may underlie a buildup of lactate and decreased pH. This alteration, similar to the Warburg effect extensively described in cancer biology, involves diminished tricarboxylic acid cycle and oxidative phosphorylation along with a shift toward increased reliance on glycolysis for energy production. We then explore the role that mitochondrial dysfunction, oxidative stress, and hypoxia-related changes in gene expression likely play in this shift in brain energy metabolism and address the functional consequences of lowered brain pH in schizophrenia including alterations in neurotransmitter regulation, mRNA stability, and overall patterns of gene expression. Finally, we discuss how altered energy metabolism in schizophrenia brain may serve as an effective target in the treatment of this illness.

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.

Brain lactate and pH in schizophrenia and bipolar disorder: a systematic review of findings from magnetic resonance studies

Converging evidence from molecular to neuroimaging studies suggests brain energy metabolism abnormalities in both schizophrenia and bipolar disorder. One emerging hypothesis is: decreased oxidative phosphorylation leading to accumulation of lactic acid from glycolysis and subsequent acidification of tissue. In this regard, integrating lactate and pH data from magnetic resonance spectroscopy (MRS) studies in both diseases may help us understand underlying neurobiological mechanisms. In order to achieve this goal, we performed a systematic search of case-control studies examining brain lactate or pH among schizophrenia and/or bipolar patients by using MRS. Medline/Pubmed and EBSCO databases were searched separately for both diseases and outcomes. Our search yielded 33 studies in total composed of 7 lactate and 26 pH studies. In bipolar disorder, 5 out of 6 studies have found elevated lactate levels especially in the cingulate cortex and 4 out of 13 studies reported reduced pH in the frontal lobe. In contrast, in schizophrenia a single study has examined lactate and reported elevation, while only 2 out of 13 studies examining pH have reported reduction in this measure. There were no consistent patterns for the relationship between lactate or pH levels and medication use, disease type, mood state, and other clinical variables. We highlight the need for future studies combining 1H-MRS and 31P-MRS approaches, using longitudinal designs to examine lactate and pH in disease progression across both schizophrenia and bipolar disorders.

Mr Spectroscopy in Clinical Research

MR spectroscopy (MRS) offers unique possibilities for non-invasive evaluation of biochemistry in vivo. During recent years there has been a growing body of evidence from clinical research studies on human beings using 31P and 1H MRS. The results indicate that it is possible to evaluate phosphorous energy metabolism, loss of neurones, and lactate production in a large number of brain diseases. Furthermore, 31P and 1H MRS may be particularly clinically useful in evaluation of various disorders in skeletal muscle. In the heart 31P MRS seems at the moment the most suitable for evaluation of global affections of the myocardium. In the liver 31P MRS appears to be rather insensitive and non-specific, but absolute quantification of metabolite concentrations and using metabolic “stress models” may prove useful in the future. The clinical role of MRS in oncology is still unclear, but it may be useful for noninvasive follow-up of treatment.

Taken together, the evidence obtained so far certainly shows some trends for clinical applications of MRS. Methods are now available for the clinical research necessary for establishing routine clinical MRS examinations.

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.

In vivo evidence for cerebral bioenergetic abnormalities in schizophrenia measured using 31P magnetization transfer spectroscopy

IMPORTANCE

Abnormalities in neural activity and cerebral bioenergetics have been observed in schizophrenia (SZ). Further defining energy metabolism anomalies would provide crucial information about molecular mechanisms underlying SZ and may be valuable for developing novel treatment strategies.

OBJECTIVE

To investigate cerebral bioenergetics in SZ via measurement of creatine kinase activity using in vivo 31P magnetization transfer spectroscopy.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional case-control study in the setting of clinical services and a brain imaging center of an academic psychiatric hospital. Twenty-six participants with chronic SZ (including a subgroup diagnosed as having schizoaffective disorder) and 26 age-matched and sex-matched healthy control subjects (25 usable magnetic resonance spectroscopy data sets from the latter).

INTERVENTION

31P magnetization transfer spectroscopy.

MAIN OUTCOMES AND MEASURES

The primary outcome measure was the forward rate constant (k(f)) of the creatine kinase enzyme in the frontal lobe. We also collected independent measures of brain intracellular pH and steady-state metabolite ratios of high-energy phosphate-containing compounds (phosphocreatine and adenosine triphosphate [ATP]), inorganic phosphate, and the 2 membrane phospholipids phosphodiester and phosphomonoester.

RESULTS

A substantial (22%) and statistically significant (P = .003) reduction in creatine kinase kf was observed in SZ. In addition, intracellular pH was significantly reduced (7.00 in the SZ group vs 7.03 in the control group, P = .007) in this condition. The phosphocreatine to ATP ratio, inorganic phosphate to ATP ratio, and phosphomonoester to ATP ratio were not substantially altered in SZ, but a significant (P = .02) reduction was found in the phosphodiester to ATP ratio. The abnormalities were similar between SZ and schizoaffective disorder.

CONCLUSIONS AND RELEVANCE

Using a novel 31P magnetization transfer magnetic resonance spectroscopy approach, we provide direct and compelling evidence for a specific bioenergetic abnormality in SZ. Reduced kf of the creatine kinase enzyme is consistent with an abnormality in storage and use of brain energy. The intracellular pH reduction suggests a relative increase in the contribution of glycolysis to ATP synthesis, providing convergent evidence for bioenergetic abnormalities in SZ. The similar phosphocreatine to ATP ratios in SZ and healthy controls suggest that the underlying bioenergetics abnormality is not associated with change in this metabolite ratio.

Creatine metabolism and psychiatric disorders: Does creatine supplementation have therapeutic value?

Athletes, body builders, and military personnel use dietary creatine as an ergogenic aid to boost physical performance in sports involving short bursts of high-intensity muscle activity. Lesser known is the essential role creatine, a natural regulator of energy homeostasis, plays in brain function and development. Creatine supplementation has shown promise as a safe, effective, and tolerable adjunct to medication for the treatment of brain-related disorders linked with dysfunctional energy metabolism, such as Huntington's Disease and Parkinson's Disease. Impairments in creatine metabolism have also been implicated in the pathogenesis of psychiatric disorders, leaving clinicians, researchers and patients alike wondering if dietary creatine has therapeutic value for treating mental illness. The present review summarizes the neurobiology of the creatine-phosphocreatine circuit and its relation to psychological stress, schizophrenia, mood and anxiety disorders. While present knowledge of the role of creatine in cognitive and emotional processing is in its infancy, further research on this endogenous metabolite has the potential to advance our understanding of the biological bases of psychopathology and improve current therapeutic strategies.

High throughput lipidomic profiling of schizophrenia and bipolar disorder brain tissue reveals alterations of free fatty acids, phosphatidylcholines, and ceramides

A mass spectrometry based high throughput approach was employed to profile white and gray matter lipid levels in the prefrontal cortex (Brodmann area 9) of 45 subjects including 15 schizophrenia and 15 bipolar disorder patients as well as 15 controls samples. We found statistically significant alterations in levels of free fatty acids and phosphatidylcholine in gray and white matter of both schizophrenia and bipolar disorder samples compared to controls. Also, ceramides were identified to be significantly increased in white matter of both neuropsychiatric disorders as compared to control levels. The patient cohort investigated in this study includes a number of drug naive as well as untreated patients, allowing the assessment of drug effects on lipid levels. Our findings indicate that while gray matter phosphatidylcholine levels were influenced by antipsychotic medication, this was not the case for phosphatidylcholine levels in white matter. Changes in free fatty acids or ceramides in either white or gray matter also did not appear to be influenced by antipsychotic treatment. To assess lipid profiles in the living patient, we also profiled lipids of 40 red blood cell samples, including 7 samples from drug naive first onset patients. We found significant alterations in the concentrations of free fatty acids as well as ceramide. Overall, our findings suggest that lipid abnormalities may be a disease intrinsic feature of both schizophrenia and bipolar disorder reflected by significant changes in the central nervous system as well as peripheral tissues.

Impaired niacin sensitivity in acute first-episode but not in multi-episode schizophrenia

Niacin (vitamin B3) flushing--a marker of altered prostaglandin signaling--is indirectly linked to the phospholipid-prostaglandin metabolism. Diminished skin flushing was repeatedly found in schizophrenia, but has not been systematically investigated at different stages of disorder as yet. We compared niacin sensitivity of 32 first-episode and 32 multi-episode patients (mainly on stable medication) with age and gender matched healthy controls. Methylnicotinate was applied in three concentrations onto the inner forearm skin. Flush response was assessed in 3 min intervals over 15 min using optical reflection spectroscopy. Whereas first-episode patients showed significantly diminished flush response as compared to controls, comparable differences were not found between multi-episode patients and controls. Comparison of niacin sensitivity at different stages of schizophrenia support the notion of altered prostaglandin signaling primarily at the onset of disorder. Longitudinal studies have to rule out possible long-term effects of neuroleptic medication.

Increased calcium-independent phospholipase A2 activity in first but not in multiepisode chronic schizophrenia

BACKGROUND

Increased activity of calcium independent phospholipase A2 (iPLA2) has repeatedly been found in the serum of unmedicated first-episode schizophrenia patients and assumed to reflect a pertubation of phospholipid metabolism. Previous studies in chronic schizophrenia were less conclusive. To explore whether iPLA2 changes are stage dependent, we investigated serum iPLA2 activity in various stages of schizophrenia.

METHODS

iPLA2 activity was assessed in the serum of 30 first-episode and 23 multiepisode schizophrenia patients and 53 healthy control subjects matched for age and gender. A fluorimetric assay was applied using the PLA2 specific substrate NBDC6-HPC, thin-layer chromatography of reaction products, and digital image scanning for signal detection.

RESULTS

Group comparison between first-episode and multiepisode patients and corresponding control groups revealed significantly increased iPLA2 activity only in first-episode patients. Enzyme activity in first-episode patients was also markedly increased, compared with chronic patients. iPLA2 changes observed were irrespective of neuroleptic medication, age, or gender.

CONCLUSIONS

Our results suggest increased lipid turnover in the acute early phase of schizophrenia that is less obvious in chronic stages. Future longitudinal studies involving iPLA2 activity and phosphorous magnetic resonance spectroscopy need to address the relation between perturbed brain lipid metabolism and iPLA2 increment in the course of schizophrenia.

Phosphorus magnetic resonance spectroscopy: its utility in examining the membrane hypothesis of schizophrenia

A novel approach to understanding the pathophysiology of schizophrenia has been the investigation of membrane composition and functional perturbations, referred to as the "Membrane Hypothesis of Schizophrenia." The evidence in support of this hypothesis has been accumulating in findings in patients with schizophrenia of reductions in phospholipids and essential fatty acids various peripheral tissues. Postmortem studies indicate similar reductions in essential fatty acids in the brain. However, the use of magnetic resonance spectroscopy (MRS) has provided an opportunity to examine aspects of membrane biochemistry in vivo in the living brain. MRS is a powerful, albeit complex, noninvasive quantitative imaging tool that offers several advantages over other methods of in vivo biochemical investigations. It has been used extensively in investigating brain biochemistry in schizophrenia. Phosphorus MRS (31P MRS) can provide important information about neuronal membranes, such as levels of phosphomonoesters that reflect the building blocks of neuronal membranes and phosphodiesters that reflect breakdown products. 31P MRS can also provide information about bioenergetics. Studies in patients with chronic schizophrenia as well as at first episode prior to treatment show a variety of alterations in neuronal membrane biochemistry, supportive of the membrane hypothesis of schizophrenia. Below, we will briefly review the principles underlying 31P MRS and findings to date. Magnetic resonance spectroscopy (MRS) is a powerful, albeit complex, imaging tool that permits investigation of brain biochemistry in vivo. It utilizes the magnetic resonance imaging hardware. It offers several advantages over other methods of in vivo biochemical investigations. MRS is noninvasive, there is no radiation exposure, does not require the use of tracer ligands or contrast media. Because of it is relatively benign, repeated measures are possible. It has been used extensively in investigating brain biochemistry in 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.

Do neuroleptics alter the cerebral intracellular pH value in schizophrenics?-a (31)P-MRS study on three different patient groups

The intracellular pH value has a profound influence on cerebral metabolism. Thus, inadequate pH control may intensify local metabolic deficits. To investigate the influence of neuroleptics on cerebral intracellular pH, we retrospectively evaluated the findings from three independent phosphorous-31 magnetic resonance spectroscopy ((31)P-MRS) studies on schizophrenic patients. A total sample of 72 patients and 32 healthy controls was investigated. A modified pH value was found only in those schizophrenic patients treated with the atypical neuroleptic clozapine.

Implications of lipid biology for the pathogenesis of schizophrenia

OBJECTIVE

Preclinical and clinical data suggest that lipid biology is integral to brain development and neurodegeneration. Both aspects are proposed as being important in the pathogenesis of schizophrenia. The purpose of this paper is to examine the implications of lipid biology, in particular the role of essential fatty acids (EFA), for schizophrenia.

METHODS

Medline databases were searched from 1966 to 2001 followed by the cross-checking of references.

RESULTS

Most studies investigating lipids in schizophrenia described reduced EFA, altered glycerophospholipids and an increased activity of a calcium-independent phospholipase A2 in blood cells and in post-mortem brain tissue. Additionally, in vivo brain phosphorus-31 Magnetic Resonance Spectroscopy (31P-MRS) demonstrated lower phosphomonoesters (implying reduced membrane precursors) in first- and multi-episode patients. In contrast, phosphodiesters were elevated mainly in first-episode patients (implying increased membrane breakdown products), whereas inconclusive results were found in chronic patients. EFA supplementation trials in chronic patient populations with residual symptoms have demonstrated conflicting results. More consistent results were observed in the early and symptomatic stages of illness, especially if EFA with a high proportion of eicosapentaenoic acid was used.

CONCLUSION

Peripheral blood cell, brain necropsy and 31P-MRS analysis reveal a disturbed lipid biology, suggesting generalized membrane alterations in schizophrenia. 31P-MRS data suggest increased membrane turnover at illness onset and persisting membrane abnormalities in established schizophrenia. Cellular processes regulating membrane lipid metabolism are potential new targets for antipsychotic drugs and might explain the mechanism of action of treatments such as eicosapentaenoic acid.

Schizophrenia and viral infection during neurodevelopment: a focus on mechanisms

The task of defining schizophrenia pathogenesis has fascinated and frustrated researchers for nearly a century. In recent years, unprecedented advances from diverse fields of study have given credence to both viral and developmental theories. This review considers possible mechanisms by which viral and developmental processes may interact to engender schizophrenia. Many of the current controversies in schizophrenia pathogenesis are reviewed in light of the viral hypothesis, including: epidemiological findings and the role of a genetic diathesis, phenotype heterogeneity, abnormalities in excitatory and inhibitory neurotransmitter systems, anomalous cerebral latereralization, and static vs progressive disease. The importance of animal models in elucidating the impact of viral infections on developing neurons is illustrated by recent studies in which neonatal rats are infected with lymphocytic choriomeningitis virus in order to examine alterations in hippocampal circuitry. Finally, consideration is given to a new hypothesis that some cases of schizophrenia could be instigated by a viral infection that disrupts developing inhibitory circuits, consequently unleashing glutamatergic neurotransmission leading to selective excitotoxicity, and a degenerative disease course.

31P Nuclear magnetic resonance spectroscopy findings in bipolar illness: a meta-analysis

Published literature comparing 31P MR brain spectra of bipolar patients to healthy controls was evaluated, focusing on phosphomonoester (PME)/phosphodiester (PDE) resonance areas because these metabolites are related to membrane phospholipids and membrane defects in bipolar disorder have been suggested. Studies comparing PME and/or PDE values of bipolar subjects to values observed in healthy controls were reviewed. Data from the studies meeting our inclusion criteria (8 reports involving 139 bipolar and 189 comparison subjects) were grouped according to the mood state of the subjects. Meta-analyses of data were performed to compare PME and PDE levels of euthymic bipolar patients to healthy controls, as well as comparing PME levels during euthymia in bipolar subjects to values observed during manic and depressed states. The PME values of euthymic bipolar patients were found to be significantly lower than PME values of healthy controls. Depressed bipolar patients had significantly higher PME values in comparison to euthymic bipolar patients. No significant difference could be detected between the PDE values of bipolars and controls. This meta-analysis found support for trait- and possibly state-dependent abnormalities of membrane phospholipid metabolism, which may reflect a dysregulation in brain-signal transduction systems of relevance in bipolar illness.

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.

Magnetic resonance spectroscopy in schizophrenia: methodological issues and findings--part II

Magnetic resonance spectroscopy allows investigation of in vivo neurochemical pathology of schizophrenia. "First generation" studies, focusing on phosphorus and proton magnetic resonance spectroscopy, have suggested alterations in membrane phospholipid metabolism and reductions in N-acetyl aspartate in the frontal and temporal lobes. Some discrepancies remain in the literature, perhaps related to the variations in medication status and phase of illness in the patients examined, as well as in magnetic resonance spectroscopy methodology; the pathophysiologic significance of the findings also remains unclear. Technologic advances in magnetic resonance spectroscopy in recent years have expanded the potential to measure several other metabolites of interest such as the neurotransmitters glutamate and gamma-aminobutyric acid and macromolecules such as membrane phospholipids and synaptic proteins. Issues of sensitivity, specificity, measurement reliability, and functional significance of the magnetic resonance spectroscopy findings need to be further clarified. The noninvasive nature of magnetic resonance spectroscopy allows longitudinal studies of schizophrenia both in its different phases and among individuals at genetic risk for this illness. Future studies also need to address confounds of prior treatment and illness chronicity, take advantage of current pathophysiologic models of schizophrenia, and be hypothesis driven.

Schizophrenia: a purinergic hypothesis

Knowledge of the physiological roles of the purinergic system and its influence on other neurotransmitter systems has greatly advanced. In this article, a purinergic model is proposed as an attempt to integrate several findings in schizophrenia. According to this hypothesis, a purinergic system dysfunction would mainly result in reduced adenosinergic activity. This model also addresses the systemic aspects of schizophrenia, based on peripheral roles of purines, such as modulation of the immune system.

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.

Neurochemical brain imaging investigations of schizophrenia

Neurochemical brain imaging methods developed over the past 20 years offer significant promise for elucidating the biochemical underpinnings of schizophrenia. The two general methodologies used for these studies have been: 1) radiotracer imaging: PET (positron emission tomography) and SPECT (single photon emission computed tomography); and 2) NMR (nuclear magnetic resonance) imaging: fMRI (functional magnetic resonance imaging) and MRS (magnetic resonance spectroscopy). Despite conflicting findings, striatal D2 receptor density may be elevated in some, but not all patients. Elevated synthesis, and increased release of dopamine after amphetamine challenge have also been reported. Imaging of cortical 5-HT2A receptors suggests that this system is unaffected, in conflict with findings of postmortem studies. Although prior postmortem studies suggested an increase in cortical GABAA receptors, three SPECT studies have found no significant changes. MRS studies have shown decreased levels of NAA (N-acetyl-aspartate) moieties in hippocampus and frontal cortex of schizophrenic patients, which is consistent with the reported loss of neurons and neuropil in postmortem brains. In conclusion, developments in radiotracer and NMR imaging have provided promising leads to the biochemical abnormalities associated with schizophrenia. Future significant understanding is likely to occur with the development of new probes and enhanced instrument technology, when applied with an appreciation of the heterogeneity of the disorder and the need for careful clinical assessment of patients.

A 1H-decoupled 31P chemical shift imaging study of medicated schizophrenic patients and healthy controls

BACKGROUND

Current 31P spectroscopy research in schizophrenia has examined phospholipid metabolism by measuring the sum of phosphomonoesters and the sum of phosphodiester-containing molecules. Proton decoupling was implemented to measure the individual phosphomonoester and phosphodiester components. This is the first study employing this technique to examine schizophrenic patients.

METHODS

Multivoxel two-dimensional chemical shift in vivo phosphorous-31 magnetic resonance spectroscopy with proton decoupling was used to examine a 50-cm3 volume in prefrontal, motor, and parieto-occipital regions in the brain. Eleven chronic medicated schizophrenic patients were compared to 11 healthy controls of comparable gender, education, parental education, and handedness.

RESULTS

A significant increase in the mobile phospholipid peak area and its full width at half maximum was observed in the medicated schizophrenic patients compared to the healthy controls in the prefrontal region. Inorganic orthophosphate and phosphocholine were lower in the schizophrenic group in the prefrontal region.

CONCLUSIONS

The increased sum of phosphodiester [mobile phospholipid + glycerol-3-phosphoethanolamine (GPEth) + glycerol-3-phosphocholine (GPCh)] in schizophrenic patients, measured in earlier studies, arises from the phospholipid peak (MP) and not the more mobile phosphodiesters (GPEth, GPCh) as was originally suspected. A decrease in the phosphocholine component of the phosphomonoesters was also observed in the schizophrenic patients. These findings are consistent with an abnormality in membrane metabolism in the prefrontal region in schizophrenics.

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.

Chemical and physiologic brain imaging in schizophrenia

Technologic advances in functional brain imaging have provided exciting and informative insights into the functional neuroanatomy and neurochemistry of schizophrenia. Using MR spectroscopy, it has been possible to examine in vivo brain metabolism and to relate observed changes to physiological processes occurring at a cellular level. Positron emission tomography and single photon emission computed tomography have revealed disturbances of cerebral blood flow and glucose metabolism in patients with schizophrenia. More recently, these tools have also proved most useful in studying the relative receptor occupancy of typical and atypical antipsychotic medications.

Multiple regression analysis of relationship between frontal lobe phosphorus metabolism and clinical symptoms in patients with schizophrenia

We investigated the differences among diagnostic types of 36 schizophrenic patients in the brain phosphorus metabolism in the frontal lobe. We performed phosphorus-31 magnetic resonance spectroscopy (31P-MRS) in the frontal region in patients with schizophrenia of the catatonic (n = 4), disorganized (n = 8), paranoid (n = 10) and undifferentiated (n = 14) types. In the disorganized type, the PME level was significantly decreased compared to those in the other three types, while the phosphodiester (PDE) level tended to be higher, although not significantly, than those in the other types. Using multiple regression analysis, we investigated whether or not the clinical symptoms were correlated with the brain phosphorus metabolism. An increased motor retardation factor score was significantly correlated with decreased PME level, whereas more severe emotional withdrawal and blunted affect were associated with increased PDE level. These results suggest that altered membrane phospholipid metabolism in the frontal region may be associated with negative symptoms and that schizophrenia of the disorganized type is associated with more severe negative symptoms and may present more severe brain abnormalities compared to the other types.

In vitro 1H-magnetic resonance spectroscopy of postmortem brains with schizophrenia

Some evidence suggests that thalamic dysfunction could explain some of the signs and symptoms of schizophrenia. We measured the absolute concentrations of amino acid metabolites in thalamus, frontal pole, and cerebellar vermis in extracts of postmortem brains from 8 schizophrenics and 10 controls using high-resolution 1H-magnetic resonance spectroscopy. The concentrations of N-acetyl aspartate, glutamate, and valine tended to be reduced in the thalamus of the schizophrenic group. Although it is difficult to ascribe significance to the "tendencies," these data may tend to support other data suggesting decreased thalamic volume or neuronal number in schizophrenia.

31P magnetic resonance spectroscopy in the dorsolateral prefrontal cortex of schizophrenics with a volume selective technique--preliminary findings

Pettegrew et al (Arch Gen Psychiatry 48:563-568, 1991) were the first to determine abnormalities concerning phospholipids and high energy metabolites in the dorsolateral prefrontal cortex of drug-naive schizophrenics with 31P magnetic resonance spectroscopy (MRS). Other investigations could not replicate these findings. We included in our study 13 schizophrenic inpatients and 14 age-matched controls. Whereas Pettegrew et al found increased levels of phosphodiesters and decreased levels of phosphomonoesters we measured decreased levels of phosphodiesters in the schizophrenics as compared to controls. One possible explanation for the contradictory findings of the both trials might be the different localization techniques used.

Clinical symptoms of schizophrenia affect reference-independent measures of task-induced EEG alpha asymmetry

Differential patterns of EEG alpha asymmetry during verbal and spatial cognitive activity are commonly described and are thought to reflect predominance of left- vs. right-sided cortical activation. Although these patterns have been difficult to elicit reliably in schizophrenics, the authors have previously suggested that clinical status may have confounded results. Therefore, EEG data from 17 additional schizophrenic patients, 16 mood disorder patient controls, and 17 normal controls were used to examine the relationship between severity of schizophrenic symptoms and task induced alpha asymmetry. Subjects performed verbal and spatial tasks during recording of 16-channel EEG. After transformation to the average reference, log alpha power from central and temporal leads was analyzed by MANOVA and MANCOVA. The expected task-side interaction (P < 0.02) was present for the total sample and for each control group when analyzed alone. However, it was only present in schizophrenics when the BPRS score was entered as a covariable. Patterns of correlations between BPRS scores, left temporal alpha power, right/left temporal alpha ratios, and task differences in ratios suggested that higher symptom levels were associated with excessive left-sided activation during spatial activity. This is consistent with other evidence of left hemisphere overactivity in schizophrenics.

Reduction in hippocampal formation volume is caused mainly by its shortening in chronic schizophrenia: assessment by MRI

We performed contiguous, 1 mm thick, magnetic resonance imaging scans in 18 men with chronic schizophrenia and in 18 age-matched healthy subjects to test in living patients the findings of a previous postmortem study. The schizophrenic patients showed bilaterally shortening (left, -6%; right, -9%) and volume reduction (left, -9%; right, -11%) of the hippocampal formation (HF). Volumes of HF correlated positively with HF length in the schizophrenic patients. The reduction in bilateral HF volumes was small after controlling for HF lengths (left, -3%; right, -3%). In schizophrenic patients, significant negative correlations were found bilaterally between the length of HFs and the scores for attention, bizarre behavior, and positive formal thought disorder. The results suggest that the volume reduction seen in the HFs of schizophrenic patients was caused mainly by a shortening of the HF and that these clinical symptoms may be associated with shorter HF length.

Phosphorus magnetic resonance spectroscopy in schizophrenia: correlation between membrane phospholipid metabolism in the temporal lobe and positive symptoms

1. To determine any correlations between phosphorus metabolites in the temporal lobes and clinical symptoms in schizophrenic patients, the authors performed 31phosphorus magnetic resonance spectroscopy in 31 medicated patients and age- and sex- matched normal subjects. 2. Schizophrenic patients demonstrated an increased level of phosphodiesters (PDE) in the temporal lobes bilaterally and a decreased level of beta-adenosine triphosphate (beta-ATP) in the left temporal lobe. 3. A significant positive correlation was observed between the level of PDE in the left temporal lobe and the score of positive symptoms on the Brief Psychiatric Rating Scale. 4. These results suggest that altered membrane phospholipid metabolism in the left temporal lobe is associated with neuroleptic-resistant positive symptoms in schizophrenic patients.

What have we learned from functional imaging studies in schizophrenia? The role of frontal, striatal and temporal areas

OBJECTIVES

Functional imaging technologies allow assessment of cerebral blood flow, cerebral metabolism, cellular metabolic processes, cerebral receptor density and occupancy. This review examines the contribution of such studies to our understanding of schizophrenia. The role of the frontal lobes, the basal ganglia, the temporal lobes and the neuronal circuits which connect them is examined with respect to this literature.

METHOD

All studies in schizophrenia using positron emission tomography, single photon emission computerised tomography, xenon studies, functional and spectroscopic magnetic resonance imaging formed the basis of this review. Only those studies published in English were reviewed.

RESULTS

The most consistent finding in schizophrenia has been that of hypofrontality, while the results of studies examining subcortical structures provide preliminary support for the concept of fronto-striatal dysfunction. Functional imaging has not yet provided consistent results in the study of temporal lobe function. Although receptor studies have shed light on the actions of antipsychotic medications, the findings for dopamine receptor numbers remain controversial. Spectroscopic and functional MRI remain in their infancy as research tools in schizophrenia.

CONCLUSIONS

Although there are significant methodological issues to be addressed, functional imaging technology is providing increasing insights into schizophrenia and its treatment. Future research will be truly multidisciplinary as it will require the collaboration of psychiatrists, imaging physicians, neuropsychologists and neuroscientists.

Proton magnetic resonance spectroscopy of the temporal lobes in schizophrenics and normal controls

Previous research has found structural and functional abnormalities in the temporal lobes of schizophrenic patients, often with greater impairment on the left side. This study applied proton MRS to both right and left temporal lobes of schizophrenic patients and normal control subjects. Reductions in the NAA/Cr ratio were found bilaterally for schizophrenic patients as compared to normal controls, and may be associated with reduced neuronal integrity. These results strengthen the evidence for biochemical abnormalities in the temporal lobes in schizophrenia.

Proton magnetic resonance spectroscopy: an in vivo method of estimating hippocampal neuronal depletion in schizophrenia

Diffuse loss of cortical volume and ventricular enlargement have been demonstrated in schizophrenia using imaging. In addition, histological studies have provided evidence that the number of neurons in the medial temporal lobe structures is reduced and that the cytoarchitecture is abnormal. In an attempt to correlate these histological findings with in vivo estimates of neuronal integrity we have studied the concentration of the neuronal marker N-acetyl aspartate (NAA) in the hippocampi of schizophrenics using in vivo Magnetic Resonance Spectroscopy (MRS). Compared with a group of healthy volunteers schizophrenics showed a 22% loss of NAA in the left hippocampus. Two other metabolites, choline and creatine showed bilateral reduction in schizophrenics and these achieved significance in the left hippocampus. These results indicate a significant depletion of NAA in schizophrenia and are in close agreement with the reported neuronal loss in the hippocampus detected histologically. We propose that in vivo MRS is a valid measure of integrity of neuronal populations in schizophrenia.

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.

Asymmetry of temporal lobe phosphorous metabolism in schizophrenia: a 31phosphorous magnetic resonance spectroscopic imaging study

In vivo 31Phosphorous magnetic resonance spectroscopic imaging (31P MRSI) was performed on 18 chronic schizophrenic patients and 14 normal controls to determine if there was asymmetry of high-energy phosphorous metabolism in the temporal lobes of schizophrenic patients. Temporal lobe phosphorous metabolites were also correlated with severity of psychiatric symptomatology as assessed by the Brief Psychiatric Rating Scale (BPRS). Schizophrenics demonstrated significantly higher right relative to left temporal phosphocreatine/adenosine triphosphate (PCr/ATP), phosphocreatine/inorganic phosphate (PCr/Pi), and PCr as well as significantly lower right relative to left temporal ATP. There were no asymmetries of temporal lobe phosphorous metabolites in the control group. In addition, both left temporal PCr and the degree of asymmetry of temporal lobe PCr were highly correlated with the thinking disturbance subscale of the BPRS. This study provides further support for temporal lobe metabolic asymmetry in schizophrenia and its possible association with clinical symptoms.

Nuclear magnetic resonance spectroscopy: a review of neuropsychiatric applications

1. Magnetic resonance spectroscopy (MRS) is a powerful new neuropsychiatric research tool which allows for the noninvasive investigation of in vivo biochemistry. This review focuses on the recent applications of MRS to in vivo neuropsychiatric research. 2. The history of MRS as it has progressed from an in vitro method of biochemical analysis to its current in vivo research uses is presented. 3. A brief overview of the physical principles of MRS, including methods for spectral localization, is discussed. 4. Applications of the different MRS modalities (1H, 31P, 19F, 7Li, 13C and 23Na) to various neuropsychiatric disorders such as Alzheimer's disease, schizophrenia, affective disorders, acquired immunodeficiency disease, etc. are reviewed. The study of both fluorinated neuroleptics and the antidepressant fluoxetine using 19F MRS are discussed in greater detail. 5. Finally, potential future neuropsychiatric applications of MRS and specifically 19F MRS are presented.

Decreased temporal lobe phosphomonoesters in bipolar disorder

In vivo [31P]magnetic resonance spectroscopic imaging ([31P]MRSI) was performed on 12 unmedicated, euthymic bipolar patients and 14 control subjects to determine if there were alterations in high-energy P metabolism in the temporal lobes of bipolar patients. Compared with the control group, the patients with bipolar disorder demonstrated significantly lower phosphomonoesters (PME) in both the left and right temporal lobes. No other group differences in P metabolites or lateralized asymmetries were noted. This preliminary study provides support for altered temporal lobe phospholipid metabolism in bipolar disorder.

1H-magnetic resonance spectroscopy of the left temporal and frontal lobes in schizophrenia: clinical, neurodevelopmental, and cognitive correlates

Twenty eight schizophrenic patients and 20 normal volunteers underwent proton magnetic resonance spectroscopy (MRS) on the left temporal and frontal lobe regions. Male patients showed a significant reduction in frontal but not temporal n-acetylaspartate (an intraneuronally distributed metabolite) in comparison with either male controls or female patients; frontal choline was raised in male patients relative to these groups. Putative neurodevelopmental indices, including obstetric complications, family history of schizophrenia, and minor physical anomalies, proved unrelated to MRS resonances. However, multiple aspects of memory function in patients were related to temporal but not frontal creatine, a pattern that was not apparent among controls. These MRS findings complement some previous structural MRI studies and much clinical and epidemiological evidence of important gender differences in schizophrenia. The findings also suggest that memory dysfunction in patients with schizophrenia may be associated with a particular pattern of temporal lobe metabolism on MRS.

31phosphorus magnetic resonance spectroscopy of the frontal and parietal lobes in chronic schizophrenia

In vivo 31Phosphorus magnetic resonance spectroscopic imaging (31P MRSI) was performed on 20 chronic schizophrenic patients and 16 normal controls to determine if there were specific changes in high energy phosphorus and phospholipid metabolism in the frontal lobes of schizophrenic patients. Phosphorous metabolites were assessed in each of the left and right frontal as well as the left and right parietal lobes. Frontal lobe phosphorous metabolites were also correlated with severity of psychiatric symptomatology as assessed by the Brief Psychiatric Rating Scale (BPRS). Schizophrenics demonstrated higher phosphodiesters (PDE) and lower phosphocreatine (PCr) in both the left and right frontal regions compared to controls. There was also lower left frontal inorganic phosphate (Pi) in the schizophrenic group. No group differences were noted in the left or right parietal regions. In addition, right frontal PDE and right frontal PCr were highly correlated with the hostility-suspiciousness and anxiety-depression subscales of the BPRS. This study provides further support for altered frontal lobe phosphorous metabolism in schizophrenia.

Short TE phosphorus spectroscopy using a spin-echo pulse

In vivo phosphorus spectroscopy requires very short acquisition delays in order to capture the signal from components with short transverse relaxation times (T2). The echo time typical of standard slice selective spin-echo pulses are too long for this application, so hard pulse, free induction decay (FID) acquisitions have frequently been used instead. With FID, however, there is an interval between the time of coherence and data acquisition (acquisition delay), with resulting baseline distortions. In this paper we describe the design of a new short TE, slice-selective, composite spin-echo pulse with echo times as short as 2.5 ms. With a long TR, fully relaxed, multislice spectra can be collected. This technique will be useful for assessing in vivo, changes in brain phospholipid activity associated with psychiatric and neurological diseases.

31P magnetic resonance spectroscopy of the medial temporal lobe of schizophrenic patients with neuroleptic-resistant marked positive symptoms

31P magnetic resonance spectroscopy was performed in 16 mediated schizophrenic patients with neuroleptic-resistant marked positive symptoms and in 16 healthy volunteers matched for age and sex in order to determine what changes in phosphorus metabolites are detected in such patients as compared to the controls. The schizophrenic patients showed an increased level of phosphodiesters in the bilateral medial temporal lobes. They also showed a decrease in the level of beta-ATP in the left medial temporal lobe. These findings suggest that schizophrenic patients with prominent positive symptoms refractory to neuroleptics may have a disturbance of bilateral membrane phospholipid and left-sided high-energy phosphate metabolism in the medial temporal lobe.