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

Altered phospholipid and high-energy phosphate metabolism in the basal ganglia and thalamus of severe obsessive compulsive patients with treatment resistance: A phosphorus 31 nuclear magnetic resonance spectroscopy study

INTRODUCTION

Cerebral metabolism in obsessive-compulsive-disorder(OCD) has been the subject of numerous studies using proton magnetic resonance spectroscopy(MRS). Despite heterogeneous results, some studies have unraveled membrane turnover and energy metabolism abnormalities in different brain regions, suggesting that alterations in these processes may contribute to the pathophysiology. So far, no authors have explored phospholipids and high-energy phosphate metabolism using ³¹P-MRS, which allows in vivo quantification of phosphorus metabolites that are considered to be related to membrane turnover and energy metabolism.

MATERIALS AND METHODS

The aim of our study was to describe and compare brain metabolic changes using ³¹P-MRS in the striatum and the thalamus, between 23 severe OCD patients and 22 healthy controls. All subject underwent a clinical examination and a same ³¹P-MRS protocol.

RESULTS

Significantly, increased concentrations of PC, PDE,PME,GPC,PME/PCr,PDE/PCr were found in patients compared to controls in the striatum and the thalamus. PCr and tATP were decreased in the striatum. Finally, significant correlations were found in the striatum and the thalamus between illness duration and some specific measured parameters.

CONCLUSION

Our results showed significant modifications of the membrane and energy metabolism in the basal ganglia of severe OCD patients and suggests a link between energetic buffer and serotonin metabolism disorder.

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.

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.

Creatine as a booster for human brain function. How might it work?

Creatine, a naturally occurring nitrogenous organic acid found in animal tissues, has been found to play key roles in the brain including buffering energy supply, improving mitochondrial efficiency, directly acting as an anti-oxidant and acting as a neuroprotectant. Much of the evidence for these roles has been established in vitro or in pre-clinical studies. Here, we examine the roles of creatine and explore the current status of translation of this research into use in humans and the clinic. Some further possibilities for use of creatine in humans are also discussed.

Impaired metabolic reactivity to oxidative stress in early psychosis patients

Because increasing evidence point to the convergence of environmental and genetic risk factors to drive redox dysregulation in schizophrenia, we aim to clarify whether the metabolic anomalies associated with early psychosis reflect an adaptation to oxidative stress. Metabolomic profiling was performed to characterize the response to oxidative stress in fibroblasts from control individuals (n = 20) and early psychosis patients (n = 30), and in all, 282 metabolites were identified. In addition to the expected redox/antioxidant response, oxidative stress induced a decrease of lysolipid levels in fibroblasts from healthy controls that were largely muted in fibroblasts from patients. Most notably, fibroblasts from patients showed disrupted extracellular matrix- and arginine-related metabolism after oxidative stress, indicating impairments beyond the redox system. Plasma membrane and extracellular matrix, 2 regulators of neuronal activity and plasticity, appeared as particularly susceptible to oxidative stress and thus provide novel mechanistic insights for pathophysiological understanding of early stages of psychosis. Statistically, antipsychotic medication at the time of biopsy was not accounting for these anomalies in the metabolism of patients' fibroblasts, indicating that they might be intrinsic to the disease. Although these results are preliminary and should be confirmed in a larger group of patients, they nevertheless indicate that the metabolic signature of reactivity to oxidative stress may provide reliable early markers of psychosis. Developing protective measures aimed at normalizing the disrupted pathways should prevent the pathological consequences of environmental stressors.

31P RINEPT MRSI and VBM reveal alterations in brain aging associated with major depression

PURPOSE

Phosphomono- and diesters, the major components of the choline peak in (1) H magnetic resonance spectroscopy, are associated with membrane anabolic and catabolic mechanisms. With the refocused insensitive nuclei-enhanced polarization transfer technique, these phospholipids are edited and enhanced in the (31) P MR spectrum. In depressed patients, alterations of the choline peak and cerebral volume have been found, indicating a possible relation. Thus, combining MR phosphorous spectroscopy and volumetry in depressed patients seems to be a promising approach to detect underlying pathomechanisms.

METHODS

Depressed in-patients were either treated with antidepressive medication or with electroconvulsive therapy and compared to matched healthy controls. (31) P magnetic resonance spectroscopy imaging was conducted before and after the treatment phases. A 3D MRI dataset for volumetry was acquired in a dedicated (1) H head coil.

RESULTS

Phosphocholine and phosphoethanolamine were increased in depressed patients. Though patients responded to the treatments, phospholipids were not significantly altered. An increased age-related gray matter loss in fronto-limbic regions along with an altered relation of phosphomonoesters/phosphodiesters with age were found in depressed patients.

DISCUSSION

The findings of increased phosphomonoesthers and an age*group interaction for gray matter volumes need further research to define the role of phospholipids in major depression and possible associations to gray matter loss.

Lipidomics reveals early metabolic changes in subjects with schizophrenia: effects of atypical antipsychotics

There is a critical need for mapping early metabolic changes in schizophrenia to capture failures in regulation of biochemical pathways and networks. This information could provide valuable insights about disease mechanisms, trajectory of disease progression, and diagnostic biomarkers. We used a lipidomics platform to measure individual lipid species in 20 drug-naïve patients with a first episode of schizophrenia (FE group), 20 patients with chronic schizophrenia that had not adhered to prescribed medications (RE group), and 29 race-matched control subjects without schizophrenia. Lipid metabolic profiles were evaluated and compared between study groups and within groups before and after treatment with atypical antipsychotics, risperidone and aripiprazole. Finally, we mapped lipid profiles to n3 and n6 fatty acid synthesis pathways to elucidate which enzymes might be affected by disease and treatment. Compared to controls, the FE group showed significant down-regulation of several n3 polyunsaturated fatty acids (PUFAs), including 20:5n3, 22:5n3, and 22:6n3 within the phosphatidylcholine and phosphatidylethanolamine lipid classes. Differences between FE and controls were only observed in the n3 class PUFAs; no differences where noted in n6 class PUFAs. The RE group was not significantly different from controls, although some compositional differences within PUFAs were noted. Drug treatment was able to correct the aberrant PUFA levels noted in FE patients, but changes in re patients were not corrective. Treatment caused increases in both n3 and n6 class lipids. These results supported the hypothesis that phospholipid n3 fatty acid deficits are present early in the course of schizophrenia and tend not to persist throughout its course. These changes in lipid metabolism could indicate a metabolic vulnerability in patients with schizophrenia that occurs early in development of the disease.

Progressive membrane phospholipid changes in first episode schizophrenia with high field magnetic resonance spectroscopy

Patients with a first episode of schizophrenia generally have increased phospholipid membrane breakdown products within the brain, while findings in chronic patients have been inconsistent. In this study we examine progressive changes in phosphorus membrane metabolites in the same patient group through the early years of schizophrenia in brain regions associated with the disease. Sixteen never-treated and medicated first episode schizophrenic patients were assessed at 10 months and 52 months after diagnosis. Sixteen matched volunteers were assessed at baseline and after 35 months. Phospholipid membrane metabolism was assessed with phosphorous magnetic resonance spectroscopy in the thalamus, cerebellum, hippocampus, anterior/posterior cingulate, prefrontal cortex, parieto-occipital cortex, superior temporal gyrus and temporal pole. At 10 months, glycerophosphocholine was increased in the anterior cingulate in patients as compared to controls. Glycerophosphocholine was decreased in the anterior cingulate and increased in the posterior cingulate and left superior temporal gyrus; glycerophosphoethanolamine was decreased in the left thalamus and increased in the left hippocampus within patients over time. At 52 months, compared to controls phosphocholine was increased in the left thalamus and glycerophosphoethanolamine was increased in the left hippocampus. These results imply a gradual inclusion of brain regions in schizophrenia where an initial increase, followed by a decrease in phospholipid membrane metabolites was observed. This pattern, observed in the early years of schizophrenia, is consistent with excitotoxic neural membrane breakdown in these regions.

Proton Magnetic Resonance Spectroscopy in adult cancer patients with delirium

Delirium is associated with a host of negative outcomes, including increased risk of mortality, longer hospital stay, and poor long-term cognitive function. The pathophysiology of delirium is not well understood. Cancer patients undergoing a bone marrow transplant (BMT) are at high risk for developing delirium and Proton Magnetic Resonance Spectroscopy ((1)H MRS) could lead to better understanding of the delirium process. Fourteen BMT patients and 10 controls completed (1)H MRS, positioned above the corpus callosum, shortly after delirium onset or at study end if no delirium occurred. In the BMT-delirium group, statistically significantly elevated tCho/tCr was found in contrast to the BMT-no delirium group. The BMT-delirium group also showed statistically significantly lesser NAA/tCho compared with both controls and the BMT-no delirium group. Elevated choline and reduced NAA indicate inflammatory processes and white matter damage as well as neuronal metabolic impairment. Further research is needed to separate the choline peaks, as well as more detailed collection of medication regimens to determine whether a higher choline concentration is a function of the delirium process or cancer treatment effects.

31P NMR spectroscopy of phospholipid metabolites in postmortem schizophrenic brain

Evidence has been accumulating that schizophrenia involves abnormalities in the composition and metabolism of cell membrane phospholipids (PLs) in the brain. In vivo 31P MRS has been used to measure the metabolic precursors and degradation products of PL metabolism in schizophrenia. Because in vivo line widths are substantially broader than in solution, only the broad phosphomonoester (PME) and phosphodiester bands, or partly resolved resonances of individual metabolites, are typically measured in vivo in the 31P spectrum. In addition to poor resolution, the relatively low signal-to-noise ratio (SNR) makes precise quantitation difficult. An alternative with substantially better resolution and precision for quantitation is high-resolution NMR spectroscopy of extracts of samples from postmortem brain. Here we determine absolute concentrations of the individual PL metabolites phosphocholine (pc), phosphoethanolamine (pe), glycerophosphocholine (gpc), and glycerophosphoethanolamine in aqueous extracts of tissue from frontal, temporal, and occipital cortex of postmortem brain for schizophrenics, controls, and patients with other mental illnesses (psychiatric controls [PC]) using high-resolution 31P NMR spectroscopy. For the complete groups, which included both males and females, there were no statistically significant differences for schizophrenics vs. controls for any of the four PL metabolites in any of the three brain regions. Trends (0.05 < P < 0.10) were noted for increased gpc in schizophrenia in all three regions. PC differed from both controls and schizophrenics in several measures. When only males were considered, gpc was significantly (P < 0.05) elevated in all three brain regions in schizophrenia.

A study of the PEMT gene in schizophrenia

The phospholipid hypothesis of schizophrenia is becoming popular because of the findings from the niacin flush test, the treatment with polyunsaturated fatty acids (PUFAs), biochemical studies for the phospholipid metabolism pathway and genetic studies of phospholipase A2. The present study attempted to investigate the gene coding for phosphatidylethanolamine N-methyltransferase (PEMT), which is an important enzyme for the synthesis of membrane phospholipids. We recruited 271 Chinese parent-offspring trios of Han descent and detected 3 single nucleotide polymorphisms (SNPs) at the PEMT locus. The transmission disequilibrium test (TDT) showed allelic association for rs464396 (X2=9.4, P=0.002), but not for the other two. The 2-SNP haplotype analysis showed haplotypic association for both the rs936108-rs464396 haplotypes (X2=25.7, d.f.=3, P=0.00001) and the rs464396-rs4244593 haplotypes (X2=17.3, d.f.=3, P=0.0006). The 3-SNP haplotype analysis also showed a haplotypic association (X2=24.4, d.f.=7, P=0.0006). The present results suggest that the PEMT gene may contribute to the etiology of schizophrenia.

Metabolic mapping using 2D 31P-MR spectroscopy reveals frontal and thalamic metabolic abnormalities in schizophrenia

(31)Phosphorus magnetic resonance spectroscopy ((31)P-MRS) allows in vivo investigation of cerebral phospholipid and energy metabolism. Using 2D chemical shift imaging, this method can be applied to study multiple brain areas and to assess concentrations of both phospholipids and high-energy phosphates. The purpose of our study was to assess multiregional metabolic profiles in schizophrenia using a 2D-resolved MRS technique, and to assess the intercorrelation of findings. We applied (31)P-MRS chemical shift imaging in 31 schizophrenia patients (12 antipsychotic-naïve first-episode and 19 antipsychotic-free multi-episode patients) and 31 healthy age- and sex-matched controls. Spatially resolved maps were compared for the main metabolites of the (31)P spectrum. Metabolites of phospholipid (PME and PDE) and energy (PCr and Pi) metabolism were significantly reduced in bilateral prefrontal and medial temporal (including hippocampal) brain regions, caudate nucleus, thalamus and anterior cerebellum as compared to controls. Moreover, factor analysis of these changes showed a characteristic spatial pattern of changes, which demonstrates significant associations between alterations of phospholipid and energy metabolism, and between metabolic alterations and severity of symptoms (BPRS total score, but not SANS or SAPS scores). This suggests a pattern of intercorrelated changes of these metabolic markers. Results support the notion of disturbed phospholipid turnover in schizophrenia, probably unrelated to prior pharmacological treatment, and associated with increased energy demand.

MR spectroscopy: its potential role for drug development for the treatment of psychiatric diseases

Magnetic resonance spectroscopy (MRS) is likely in the near future to play a key role in the process of drug discovery and evaluation. As the pharmaceutical industry seeks biochemical markers of drug delivery, efficacy and toxicity, this non-invasive technique offers numerous ways to study adults and children repeatedly and without ionizing radiation. In this article, we survey an array of the information that MRS offers about neurochemistry in general and psychiatric disorders and their treatment in particular. We also present growing evidence of glial abnormalities in neuropsychiatric disorders and discuss what MRS is contributing to that line of investigation. The third major direction of this article is the discussion of where MRS techniques are headed and how those new techniques can contribute to studies of mechanisms of psychiatric disease and drug discovery.

Bioactive lipids in schizophrenia

Bioactive lipids, in particular arachidonic acid (AA), are vital for monoaminergic neurotransmission, brain development and synaptic plasticity. Phospholipases A2 (PLA2) are key-enzymes in AA metabolism and are activated during monoaminergic neurotransmission. Reduced membrane AA levels, and an altered activity of PLA2 have been found in peripheral membranes of drug-naïve patients with schizophrenia with some conflicting results in more chronic patient populations. Furthermore, in vivo brain phosphorus-31 magnetic resonance spectroscopy suggests reduced lipid membrane precursors (phosphomonoesters) and increased membrane breakdown products (phosphodiesters) in drug-naïve or early treated first-episode schizophrenia patients compared to age-matched controls or chronic populations and these changes were correlated with peripheral red blood cell membrane AA levels. We postulate that processes modulating membrane lipid metabolism are associated with psychotic illnesses and might partially explain the mechanism of action of antipsychotic agents, as well as experimental agents such as purified ethyl-eicosapentaenoic acid (E-EPA). Recent supplementation trials suggest that E-EPA is a modestly effective augmentation treatment resulting in reduced doses of antipsychotic medication in acutely ill patients with schizophrenia (but not in residual-type schizophrenia). This review investigates the role of bioactive lipids in schizophrenia and its treatment, as well as its potential use in prevention.

Grey and white matter differences in brain energy metabolism in first episode schizophrenia: 31P-MRS chemical shift imaging at 4 Tesla

Altered high energy and membrane metabolism, measured with phosphorus magnetic resonance spectroscopy (31P-MRS), has been inconsistently reported in schizophrenic patients in several anatomical brain regions implicated in the pathophysiology of this illness, with little attention to the effects of brain tissue type on the results. Tissue regression analysis correlates brain tissue type to measured metabolite levels, allowing for the extraction of "pure" estimated grey and white matter compartment metabolite levels. We use this tissue analysis technique on a clinical dataset of first episode schizophrenic patients and matched controls to investigate the effect of brain tissue specificity on altered energy and membrane metabolism. In vivo brain spectra from two regions, (a) the fronto-temporal-striatal region and (b) the frontal-lobes, were analyzed from 12 first episode schizophrenic patients and 11 matched controls from a (31)P chemical shift imaging (CSI) study at 4 Tesla (T) field strength. Tissue regression analyses using voxels from each region were performed relating metabolite levels to tissue content, examining phosphorus metabolite levels in grey and white matter compartments. Compared with controls, the first episode schizophrenic patient group showed significantly increased adenosine triphosphate levels (B-ATP) in white matter and decreased B-ATP levels in grey matter in the fronto-temporal-striatal region. No significant metabolite level differences were found in grey or white matter compartments in the frontal cortex. Tissue regression analysis reveals grey and white matter specific aberrations in high-energy phosphates in first episode schizophrenia. Although past studies report inconsistent regional differences in high-energy phosphate levels in schizophrenia, the present analysis suggests more widespread differences that seem to be strongly related to tissue type. Our data suggest that differences in grey and white matter tissue content between past studies may account for some of the variance in the literature.

A family based study of the genetic association between the PLA2G4D gene and schizophrenia

The present study detected two single nucleotide polymorphisms (SNPs) at the PLA2G4D locus, rs2459692 and rs4924618, to investigate a genetic association between the PLA2G4D gene and schizophrenia. A total of 236 Chinese parent-offspring trios of Han descent were recruited for the genetic analysis. The transmission disequilibrium test (TDT) did not show allelic association either for rs2459692 (chi(2) = 0.217, P = 0.641) or for rs4924618 (chi(2) = 0.663, P = 0.416). To see the combined effect of the PLA2G4D locus with the other three PLA2G4 genes, we applied the above two SNPs as a conditional marker to test the pair-wise combination for a disease association. The conditioning on allele (COA) test revealed a weak association for the rs2459692-PLA2G4A combination (chi(2) = 6.03, df = 2, P = 0.049), the rs2459692-PLA2G4B combination (chi(2) = 7.16, df = 3, P = 0.028) and the rs4924618-PLA2G4C combination (chi(2) = 7.01, df = 2, P = 0.03), whereas the conditioning on genotype (COG) test showed a weak association only for the rs4924618-PLA2G4C combination (chi(2) = 8.52, df = 3, P = 0.036). Because we performed a multi-locus analysis in this study, the weak association shown by the conditional tests could make little biological sense. In conclusion, the PLA2G4D gene may not be involved in a susceptibility to schizophrenia.

A study of the combined effect of the CLDN5 locus and the genes for the phospholipid metabolism pathway in schizophrenia

The present study attempts to test the combined effect of the CLDN5 gene and those for the phospholipid metabolism pathway, including PTGS1, PTGS2, PLA2G4A and PLA2G4C. We detected five single nucleotide polymorphisms (SNPs) present in these genes among 131 British family trios of schizophrenic patients. The transmission disequilibrium test (TDT) showed that BanI-SNP located in the 5'-flanking region of the PLA2G4A gene was associated with schizophrenia (chi(2) = 5.16, P = 0.023) although the others failed to show such allelic associations. The global P-value was 0.150 for 1000 permutations with the TDT analysis. The conditioning on genotype test, but not on allele test, revealed a strong association for the combination of the CLDN5 gene with the PLA2G4A gene (chi(2) = 10.17, df = 2, P = 0.006). The present results suggest that the PLA2G4A locus may be involved in schizophrenia and its combination with the CLDN5 gene may increase further the risk for the illness.

A genetic study of two calcium-independent cytosolic PLA2 genes in schizophrenia

The present study detected 9 single nucleotide polymorphisms (SNPs) at the PLA2G4C and PLA2G6 loci among 240 Chinese parent-offspring trios of Han descent. Of these 9 SNPs, 5 showed highly polymorphic in the Chinese population. They were then applied as genetic markers to test the genetic association of these two calcium-independent cytosolic PLA2 genes with schizophrenia. The transmission disequilibrium test (TDT) showed that rs1549637 at the PLA2G4C locus was the only SNP associated with the illness (chi(2) = 5.63, P = 0.018). The global P-value was 0.082 for 1000 permutations with the TDT analysis. Neither the conditional on allele test nor the conditional on genotype test showed a disease association for the combination of these two genes. Because the PLA2G4C association is so weak, this initial finding should be interpreted with caution.

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.

No association between the PTGS2/PLA2G4A locus and schizophrenia in a Chinese population

The present study was undertaken to replicate an association between the PTGS2/PLA2G4A locus and schizophrenia among a Chinese population. We recruited 168 Chinese parent-offspring trios of Han descent, consisting of fathers, mothers and affected offspring with schizophrenia. Of 3 informative SNPs genotyped, no one showed allelic association with schizophrenia; the haplotype analysis also failed to capture a haplotypic association with the illness. Because the frequencies of alleles and genotypes of SNPs analyzed differ in the Chinese population as compared with a British population that initially showed the genetic association between the PTGS2/PLA2G4A locus and schizophrenia, the ethnic background may be a major reason for poor replication of the initial finding.

Comparative study of proton and phosphorus magnetic resonance spectroscopy in schizophrenia at 4 Tesla

This study used high-field magnetic resonance spectroscopy to examine the correlation of 1H and 31P metabolite levels in patients with schizophrenia and normal controls. 1H and 31P in vivo spectra were acquired successively from the left anterior cingulate and left thalamus of nine chronic schizophrenic patients and eight comparable healthy controls. A significant positive correlation between glutamine (Gln) and phosphoethanolamine (PEtn) was found in the left anterior cingulate of patients. In the left thalamus of patients, a significant negative correlation between N-acetylaspartate (NAA) and glycerophosphocholine (GroPCho) was found. No significant correlations were found in controls. The correlation between glutamine and phosphoethanolamine may reflect a link between neurotransmission alterations and membrane phospholipid metabolism alterations. The negative correlation between N-acetylaspartate and glycerophosphocholine may reflect the presence of neurodegeneration.

In vivo31P NMR spectroscopy shows an increase in glycerophosphorylcholine concentration without alterations in mitochondrial function in the prefrontal cortex of medicated schizophrenic patients at rest

The (31)P NMR localised method was used to study the metabolism of phospholipid and high energy phosphate in the prefrontal cortex. The spectra were taken from patients with schizophrenia (11 males) receiving neuroleptic medication, and were compared to normal controls (15 males). Their spectral intensities were analysed using a non-linear least-squares method with a prior knowledge of the fixed chemical shifts and linewidths, leading to further resolution into resonances of glycerophosphorylethanolamine (GPE), glycerophosphorylcholine (GPC), phosphorylethanolamine (PE) and phosphorylcholine (PC). The metabolite concentrations were calculated referring to the spectral intensities of phosphate phantoms with known concentrations. T1 values of phantom and cerebrum were estimated from a series of localised inversion recovery spectra to correct for the signal saturation effects. The schizophrenic patients showed an increased concentration of GPC but not GPE, PE or PC. Furthermore, no difference was observed regarding the concentration of high-energy phosphates such as phosphocreatine, inorganic phosphate and ATP. The patients did not show any differences in mitochondrial function such as phosphorylation potential and the ratio of the rate of ATP synthesis. Thus, an increase in GPC concentration in the prefrontal cortex could be characteristic of the pathophysiology of schizophrenia with mild negative symptoms.

A study of a genetic association between the PTGS2/PLA2G4A locus and schizophrenia

Six single nucleotide polymorphisms (SNPs) present in the PTGS2/PLA2G4A locus were detected among 118 British family trios of schizophrenia patients. The transmission disequilibrium test showed that SNP4 located in the 5'-flanking region of the PLA2G4A gene was associated with schizophrenia and that the haplotype analysis also showed a genetic association between the PTGS2 gene and schizophrenia. Because these two genes are arranged in a head-to-head configuration and separated by just about 149kb of DNA, they may have a combined effect on susceptibility to schizophrenia in some cases.

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.

Signal enhancement through heteronuclear polarisation transfer in in-vivo 31P MR spectroscopy of the human brain

Significant (31)P NMR signal enhancement through heteronuclear polarisation transfer was obtained in model solutions and in vivo on a 1.5-T whole-body MR scanner equipped with two RF channels. The much higher population differences involved in proton Zeeman energy levels can be transferred to the (31)P levels with the refocused INEPT (insensitive nucleus enhancement by polarisation transfer) double-resonance experiment by means of a series of simultaneously applied broadband RF pulses. INEPT achieves a polarisation transfer from (1)H to (31)P spin states by directly reordering the populations in spin systems with heteronuclear scalar coupling. Thus, only the (31)P NMR signal of metabolites with scalar (1)H-(31)P coupling is amplified, while the other metabolite signals in the spectra are suppressed. Compared to Ernst-angle excitation, a repetition-time-dependent signal enhancement of eta=(29+/-3)% for methylene diphosphonic acid (MDPA) and eta=(56+/-1)% for phosphorylethanolamine (PE) was obtained on model solutions through optimisation of the temporal parameters of the pulse experiment. The results are in good agreement with numerical calculations of the theoretical model for the studied spin systems. With optimised echo times, in-vivo (31)P signal enhancement of the same order was obtained in studies of the human brain.

Prefrontal membrane phospholipid metabolism of child and adolescent offspring at risk for schizophrenia or schizoaffective disorder: an in vivo 31P MRS study

In vivo (31)P magnetic resonance spectroscopy ((31)P MRS) studies have shown abnormal membrane phospholipid metabolism in the prefrontal cortex (PF) in the early course of schizophrenia. It is unclear, however, whether these alterations also represent premorbid risk indicators in schizophrenia. In this paper, we report in vivo (31)P MRS data on children and adolescents at high risk (HR) for schizophrenia. In vivo (31)P MRS studies of the PF were conducted on 16 nonpsychotic HR offspring of parents with schizophrenia or schizoaffective disorder, and 37 age-matched healthy comparison (HC) subjects. While 11 of the HR subjects had evidence of Axis I psychopathology (HR-P), five HR subjects had none (HR-NP). We quantified the freely mobile phosphomonoester (PME) and phosphodiester (PDE) levels reflecting membrane phospholipid precursors and breakdown products, respectively, and the relatively broad signal underlying PDE and PME peaks, comprised of less mobile molecules with PDE and PME moieties (eg, synaptic vesicles and phosphorylated proteins). Compared to HC subjects, HR subjects had reductions in freely mobile PME; the differences were accounted for mainly by the HR-P subjects. Additionally, HR-P subjects showed increases in the broad signal underlying the PME and PDE peaks in the PF. To conclude, these data demonstrate new evidence for decreased synthesis of membrane phospholipids and possibly altered content or the molecular environment of synaptic vesicles and/or phosphoproteins in the PF of young offspring at risk for schizophrenia. Follow-up studies are needed to examine the predictive value of these measures for future emergence of schizophrenia in at-risk individuals.

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.

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.

In vivo magnetic resonance spectroscopy and its application to neuropsychiatric disorders

In vivo magnetic resonance spectroscopy (MRS) is the only noninvasive imaging technique that can directly assess the living biochemistry in localized brain regions. In the past decade, spectroscopy studies have shown biochemical alterations in various neuropsychiatric disorders. These first-generation studies have, in most cases, been exploratory but have provided insightful biochemical information that has furthered our understanding of different brain disorders. This review provides a brief description of spectroscopy, followed by a literature review of key spectroscopy findings in schizophrenia, affective disorders, and autism. In schizophrenia, phosphorus spectroscopy studies have shown altered metabolism of membrane phospholipids (MPL) during the early course of the illness, which is consistent with a neurodevelopmental abnormality around the critical period of adolescence when the illness typically begins. Children and adolescents who are at increased genetic risk for schizophrenia show similar MPL alterations, suggesting that schizophrenia subjects with a genetic predisposition may have a premorbid neurodevelopmental abnormality. Independent of medication status, bipolar subjects in the depressive state tended to have higher MPL precursor levels and a deficit of high-energy phosphate metabolites, which also is consistent with major depression, though these results varied. Further bipolar studies are needed to investigate alterations at the early stage. Lastly, associations between prefrontal metabolism of high-energy phosphate and MPL and neuropsychological performance and reduced N-acetylaspartate in the temporal and cerebellum regions have been reported in individuals with autism. These findings are consistent with developmental alterations in the temporal lobe and in the cerebellum of persons with autism. This paper discusses recent findings of new functions of N-acetylaspartate.

Magnetic resonance spectroscopy and its applications in psychiatry

OBJECTIVE

This paper briefly describes neuroimaging using magnetic resonance spectroscopy (MRS) and provides a systematic review of its application to psychiatric disorders.

METHOD

A literature review (Index Medicus/Medline) was carried out, as well as a review of other relevant papers and data known to the authors.

RESULTS

Magnetic resonance spectroscopy is a complex and sophisticated neuroimaging technique that allows reliable and reproducible quantification of brain neurochemistry provided its limitations are respected. In some branches of medicine it is already used clinically, for instance, to diagnose tumours and in psychiatry its applications are gradually extending beyond research. Neurochemical changes have been found in a variety of brain regions in dementia, schizophrenia and affective disorders and promising discoveries have also been made in anxiety disorders.

CONCLUSION

Magnetic resonance spectroscopy is a non-invasive investigative technique that has provided useful insights into the biochemical basis of many neuropsychiatric disorders. It allows direct measurement, in vivo, of medication levels within the brain and has made it possible to track the neurochemical changes that occur as a consequence of disease and ageing or in response to treatment. It is an extremely useful advance in neuroimaging technology and one that will undoubtedly have many clinical uses in the near future.

Region-specific changes in phospholipid metabolism in chronic, medicated schizophrenia: (31)P-MRS study at 4.0 Tesla

BACKGROUND

Membrane phospholipid abnormalities in people with schizophrenia, measured with (31)P magnetic resonance spectroscopy ((31)P-MRS), have been previously reported in brain regions involved in this disorder.

AIMS

In this 4.0 Tesla (31)P-MRS study of people with schizophrenia, membrane phospholipid metabolism was examined in brain regions previously inaccessible due to their small volumes.

METHOD

Three-dimensional chemical-shift imaging (3D-CSI) examined 15 cc volumes in 12 brain regions in 11 people with chronic schizophrenia and 11 healthy control volunteers.

RESULTS

Glycerophosphoethanolamine was decreased in the anterior cingulate, right prefrontal cortex and left thalamus, but increased in the left hippocampus and cerebellum in those with schizophrenia. Phosphoethanolamine and glycerophosphocholine were decreased in the right prefrontal region and phosphocholine was decreased in the anterior cingulate. No significant difference in membrane phospholipid levels existed between groups in the parieto-occipital and posterior cingulate regions.

CONCLUSIONS

Altered membrane phospholipid metabolism was demonstrated in all regions implicated in schizophrenia.

Phospholipid abnormalities in postmortem schizophrenic brains detected by 31P nuclear magnetic resonance spectroscopy: a preliminary study

It has been hypothesized that schizophrenia arises from cell membrane abnormalities due to changes in phospholipid (PL) composition and metabolism. We have used high resolution, in vitro 31P nuclear magnetic resonance (NMR) to characterize the PLs in left frontal cortex (gray matter) of postmortem brain from four schizophrenics and five controls. High resolution 31P NMR spectra were obtained in an organic-solvent system to resolve PL classes (headgroups) and in a sodium-cholate, aqueous dispersion system to resolve phosphatidylcholine (PC) molecular species. Multivariate analysis which included the major PC molecular species and phosphatidylinositol (PI) showed a significant difference between schizophrenics and controls. Analysis of specific interactions showed that the PI was significantly higher in the schizophrenic group than in the control group. There were no differences between the two groups for other individual PL classes, or for individual PL subclasses determined by the linkage type at the sn-1 position on glycerol. There was a trend for total PL content to be higher in schizophrenics than in controls. There was no evidence for elevated lysophosphatidylcholine or lysophosphatidylethanolamine in schizophrenia. The intensity of the PC peak representing molecular species with one saturated and one unsaturated (one or two double bonds) acyl chain was higher for the schizophrenic group than for the control group. Although these results are not in complete agreement with previous studies, they support the idea that PL abnormalities occur in the brain in schizophrenia and that fatty acid metabolism may be abnormal.

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.

Postprocessing method to segregate and quantify the broad components underlying the phosphodiester spectral region of in vivo (31)P brain spectra

In a typical, in vivo (31)P brain spectrum, the phosphomonoester (PME) and phosphodiester (PDE) spectral region not only contains signals from freely mobile PMEs and PDEs (which are anabolic and catabolic products of membrane phospholipids) but also signals of broader underlying lineshapes from less-mobile molecules. In general, either the PME and PDE resonances are quantified as a combined value of freely mobile metabolites plus less-mobile molecules or the broader underlying signal is reduced/eliminated prior to or post data collection. In this study, a postprocessing method that segregates and quantifies the individual contributions of the freely mobile metabolites and the less-mobile molecules is introduced. To demonstrate the precision and accuracy of the method, simulated data and in vivo (31)P brain spectroscopy data of healthy individuals were quantified. The ability to segregate and quantify these various PME and PDE contributions provides additional spectral information and improves the accuracy of the interpretation of (31)P spectroscopy results. Magn Reson Med 45:390-396, 2001.

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.

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

Our knowledge of the biological basis of schizophrenia has significantly increased with the contribution of in vivo proton and phosphorus magnetic resonance spectroscopy (MRS), a noninvasive tool that can assess the biochemistry from a localized region in the human body. Studies thus far suggest altered membrane phospholipid metabolism at the early stage of illness and reduced N-acetylaspartate, a measure of neuronal volume/viability in chronic schizophrenia. Inconsistencies remain in the literature, in part due to the complexities in the MRS methodology. These complexities of in vivo spectroscopy make it important to understand the issues surrounding the design of spectroscopy protocols to best address hypotheses of interest. This review addresses these issues, including 1) understanding biochemistry and the physiologic significance of metabolites; 2) the influence of acquisition parameters combined with spin-spin and spin-lattice relaxation effects on the MRS signal; 3) the composition of spectral peaks and the degree of overlapping peaks, including the broader underlying peaks; 4) factors affecting the signal-to-noise ratio; 5) the various types of localization schemes; and 6) the objectives to produce accurate and reproducible quantification results. The ability to fully exploit the potentials of in vivo spectroscopy should lead to a protocol best optimized to address the hypotheses of interest.

Reduced phosphodiesters and high-energy phosphates in the frontal lobe of schizophrenic patients: a (31)P chemical shift spectroscopic-imaging study

BACKGROUND

(31)Phosphorous magnetic resonance spectroscopy has been widely used to evaluate schizophrenic patients in comparison to control subjects, because it allows the investigation of both phospholipid and energy metabolism in vivo; however, the results achieved so far are inconsistent. Chemical shift imaging (CSI) has the advantage that instead of only one or a few preselected voxels the tissue of a whole brain slice can be examined. The aim of the present investigation was to determine whether the results of previous studies of our group, showing that phosphodiesters (PDE) are decreased in the frontal lobe of schizophrenic patients as compared to control subjects, might be confirmed in an independent unmedicated patient sample using the CSI technique.

METHODS

A carefully selected new cohort including 11 neuroleptic-free schizophrenic patients and 11 age- and gender-matched healthy control subjects was recruited. CSI was applied and an innovative analysis method for CSI data based on a general linear model was used.

RESULTS

PDE, phosphocreatine, and adenosine triphosphate (ATP) were found to be significantly decreased in the frontal lobe of patients with schizophrenia.

CONCLUSIONS

Because PDE was decreased in schizophrenic patients, the membrane phospholipid hypothesis of schizophrenia could not be corroborated. Further results indicate decreased ATP production in the frontal lobe of patients with schizophrenia.

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.