Schizophrenia and impaired homocysteine metabolism: a possible association

Association between serum folate levels and schizophrenia based on sex

AIM

Sex differences in serum folate concentrations are well known, but no studies have investigated the association between serum folate levels and schizophrenia based on sex. With this study in a Japanese population, we examined the difference in serum folate levels between patients with schizophrenia and non-psychiatric controls stratified by sex. The relations among serum folate levels, plasma total homocysteine (tHcy), and serum vitamin B6 (pyridoxal) levels were also examined using data from our previous studies.

METHODS

The serum folate concentrations of 482 patients diagnosed with schizophrenia and 1350 non-psychiatric control subjects were measured. We conducted an analysis of covariance to examine the differences in serum folate levels between the two groups based on sex. Spearman's rank correlation was used to evaluate the relations among folate, tHcy, and vitamin B6 levels.

RESULTS

In the control group, serum folate concentrations were higher in women than in men. Lower levels of serum folate were observed in both male and female patients with schizophrenia. An inverse correlation between serum folate and plasma tHcy and a weak positive correlation between serum folate and vitamin B6 were observed in the combined cohort.

CONCLUSION

Our findings suggest that: (i) a low serum folate level may be associated with schizophrenia regardless of sex; and (ii) folate administration may be beneficial for the treatment of schizophrenia. In schizophrenic patients with low serum folate levels, folate administration might result in improvements in high tHcy and an increase in low vitamin B6 levels.

The Role of Amino Acids in Neurotransmission and Fluorescent Tools for Their Detection

Neurotransmission between neurons, which can occur over the span of a few milliseconds, relies on the controlled release of small molecule neurotransmitters, many of which are amino acids. Fluorescence imaging provides the necessary speed to follow these events and has emerged as a powerful technique for investigating neurotransmission. In this review, we highlight some of the roles of the 20 canonical amino acids, GABA and β-alanine in neurotransmission. We also discuss available fluorescence-based probes for amino acids that have been shown to be compatible for live cell imaging, namely those based on synthetic dyes, nanostructures (quantum dots and nanotubes), and genetically encoded components. We aim to provide tool developers with information that may guide future engineering efforts and tool users with information regarding existing indicators to facilitate studies of amino acid dynamics.

Serum folate levels in schizophrenia: A meta-analysis

To clarify the relationship between serum folate and schizophrenia (SZ) risk, the meta-analysis was conducted. PubMed, Embase, and Web of Science were searched without language restrictions. Weighted mean difference (WMD) as a summary statistic was used in this meta-analysis. Subgroup analyses by publication language (English and non-English), ethnicity (Caucasian, Asian, African, Latino, and mixed population), duration (acute, chronic, patients including both acute and chronic SZ, and not mentioned about either chronic or acute), measurement time (before drugs using and after drugs using), gender (male and female) and age (<50 years old and >50 years old) were performed. Power analysis was also conducted to detect the reliability of the meta-analyses' results. In summary, the subgroups which failed to detect significant decreased associations were always with lower statistic power and could not be confirmed. The results supported that decreased serum folate was associated with SZ risk in total studies and subgroups of English publications, Caucasians, Asians, acute SZ patients, measurement after drugs using in SZ patients, and age<50 with the great enough powers, respectively. In conclusion, the present meta-analysis found that folate deficiency is associated to SZ, and subgroups which did not reach enough statistical power need further investigation in the future.

Homocysteine levels in schizophrenia patients newly admitted to an acute psychiatric ward

OBJECTIVE

After the discovery of 'homocystinuria syndrome', many studies have suggested that high blood levels of homocysteine may be associated with schizophrenia. The aim of this study was to analyse the association between hyperhomocysteinaemia and schizophrenia.

METHODS

In a population of inpatients suffering from exacerbated schizophrenic disorders (N=100), we evaluated homocysteine levels the day after their admission to an acute psychiatric ward and compared it with that of a non-patient control group (N=110), matched for age and gender. We statistically analysed the correlation between homocysteine levels and selected variables: gender, age, years of illness and number of previous psychiatric admissions as well as Brief Psychiatric Rating Scale, Positive Negative Syndrome Scale and Global Assessment Functioning (GAF) Scores.

RESULTS

We observed elevated homocysteine levels (an increase of 7.84 µM on average per patient) in 32% of the patients, but we did not find any statistically significant difference between the homocysteine levels of our patients and controls. Hyperhomocysteinaemia presented a positive statistically significant correlation with years of illness (p<0.005) and a negative statistically significant correlation with GAF score (p<0.001), but not with other clinical variables.

CONCLUSIONS

Hyperhomocysteinaemia, which occurred in our schizophrenia patients with poor social and relational functioning after many years of illness, could represent an effect of altered lifestyle due to psychosis, but not a specific marker for schizophrenia.

Homocysteine as a potential biomarker in bipolar disorders: a critical review and suggestions for improved studies

INTRODUCTION

Homocysteine levels have been associated with major depression, but associations with bipolar disorder remain less clear. Some data suggest homocysteine levels have potential as a biomarker of treatment response; however the literature is mixed.

AREAS COVERED

Oxidized forms of homocysteine can be potentially neurotoxic leading to glutamate toxicity, apoptotic transformation and neurodegenerative processes. High homocysteine may be a risk biomarker for bipolar disorders, but the empirical base remains too weak for firm conclusions. This review discusses the current literature for homocysteine levels as a biomarker.

EXPERT OPINION

It is premature to foreclose the utility of homocysteine levels as a biomarker for bipolar disorder due the methodological inadequacies in the existing literature. These methodological design issues include lack of control for the confounding variables of concurrent medication, phase of bipolar disorder, gender, age, nutritional status, thyroid, liver and renal function, smoking or lean body mass. Well-powered association studies with confounder control could help shed more light on the important clinical question of homocysteine's utility as a biomarker in bipolar disorder. Future experiments are needed to examine the outcome of interventions modulating homocysteine for treating bipolar disorder. Only prospective randomized control trials will provide definitive evidence of the utility of homocysteine as a biomarker or therapeutic target.

A snapshot of plasma metabolites in first-episode schizophrenia: a capillary electrophoresis time-of-flight mass spectrometry study

Few biomarkers have been known that can easily measure clinical conditions in mental illnesses such as schizophrenia. Capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS) is a new method that can measure ionized and low-molecular-weight metabolites. To explore global metabolomic alterations that characterize the onset of schizophrenia and identify biomarkers, we profiled the relative and absolute concentrations of the plasma metabolites from 30 patients with first-episode schizophrenia (FESZ, four drug-naïve samples), 38 healthy controls and 15 individuals with autism spectrum disorders using CE-TOFMS. Five metabolites had robust changes (increased creatine and decreased betaine, nonanoic acid, benzoic acid and perillic acid) in two independent sample sets. Altered levels of these metabolites are consistent with well-known hypotheses regarding abnormalities of the homocysteine metabolism, creatine kinase-emia and oxidative stress. Although it should be considered that most patients with FESZ received medication, these metabolites are candidate biomarkers to improve the determination of diagnosis, severity and clinical stages, especially for FESZ.

Plasma homocysteine levels in depression and schizophrenia in South Indian Tamilian population

CONTEXT

Hyperhomocysteinemia has been associated with psychiatric diseases in non-Indian populations.

OBJECTIVES

We aimed to determine if total plasma Homocysteine (Hcys) is associated with schizophrenia or depression in South Indian Tamil patients and if so, to correlate their severity and phenomenology to Hcys levels.

SETTINGS AND DESIGN

40 patients each with schizophrenia and depression and 40 healthy controls were recruited from the psychiatry department of a quaternary referral centre. Association between Hcys and psychiatric disorders was determined using a Case- control design. Hcys levels were correlated with age, gender and severity and duration of the disease by appropriate statistical methods using SPSS17.

MATERIALS AND METHODS

Schizophrenia and depression were defined using ICD10 DCR version. Severity of depression was assessed by Hamilton Depression Rating Scale and that of schizophrenia using Positive and Negative Schizophrenia scales (PANSS). Hcys levels were determined using automated chemiluminiscence immunoassay (74-76).

STATISTICAL ANALYSIS

Differences between the mean values of plasma homocysteine levels among schizophrenia, depression and control groups were compared using analysis of variants. The association between the severity and duration of schizophrenia and depression and the plasma homocysteine levels were determine using Pearson correlation.

CONCLUSIONS

In Tamilian population, schizophrenia and depression are associated with total plasma Hcys levels which correlated with the duration and severity of psychosis.

Future perspectives on the treatment of cognitive deficits and negative symptoms in schizophrenia

Drug discovery based on classic models for cognitive impairment and negative symptoms of schizophrenia have met with only modest success. Because cognitive impairment and negative symptoms may result from disruptions in neurodevelopment, more complex developmental models that integrate environmental and genetic risk factors are needed. In addition, it has become clear that biochemical pathways involved in schizophrenia form complex, interconnected networks. Points at which risk factors converge, such as brain-derived neurotrophic factor (BDNF) and protein kinase B (AKT), and from which processes involved in neuroplasticity diverge, are of particular interest for pharmacologic interventions. This paper reviews elements of neurodevelopmental models for cognitive deficits and negative symptoms of schizophrenia with the aim of identifying potential targets for interventions.

Determination of olanzapine and N-desmethyl-olanzapine in plasma using a reversed-phase HPLC coupled with coulochemical detection: correlation of olanzapine or N-desmethyl-olanzapine concentration with metabolic parameters

BACKGROUND

Olanzapine (OLZ) is one of the most prescribed atypical antipsychotic drugs but its use is associated with unfavorable metabolic abnormalities. N-desmethyl-olanzapine (DMO), one of the OLZ metabolites by CYP1A2, has been reported to have a normalizing action on metabolic abnormalities, but this remains unclear. Our aim was to explore the correlation between the concentrations of OLZ or DMO with various metabolic parameters in schizophrenic patients.

METHODS

The chromatographic analysis was carried out with a solvent delivery system coupled to a Coulochem III coulometric detector to determine OLZ and DMO simultaneously in OLZ-treated patients. The correlation between the concentration of OLZ or DMO and the metabolic parameters was analyzed by the Spearman rank order correlation method (r s).

PRINCIPAL FINDINGS

The established analytical method met proper standards for accuracy and reliability and the lower limitation of quantification for each injection of DMO or OLZ was 0.02 ng. The method was successfully used for the analysis of samples from nonsmoking patients (n = 48) treated with OLZ in the dosage range of 5-20 mg per day. There was no correlation between OLZ concentrations and tested metabolic parameters. DMO concentrations were negatively correlated with glucose (r s = -0.45) and DMO concentrations normalized by doses were also negatively correlated with insulin levels (r s = -0.39); however, there was a marginally positive correlation between DMO and homocysteine levels (r s = +0.38).

CONCLUSIONS

The observed negative correlations between levels of DMO and glucose or insulin suggest a metabolic normalization role for DMO regardless of its positive correlation with a known cardiovascular risk factor, homocysteine. Additional studies of the mechanisms underlying DMO's metabolic effects are warranted.

Antipsychotic drugs and venous thromboembolism

Since preliminary case reports suggesting a possible association between first generation of antipsychotics and venous thromboembolism (VTE), consistent epidemiological data is now available suggesting a moderate association between antipsychotics and VTE. However, despite several hypotheses, the underlying mechanisms remain unknown or uncertain. In addition, if the association between antipsychotics and VTE is plausible, the intensity of this risk and the dose effect relationship do not have yet been determined. Prospective data is therefore needed in order to confirm and to quantify this association. Because of the level of uncertainty, the clinical impact on the prevention and the treatment of VTE in patients with a psychiatric illness appears to be low.

Risperidone and pulmonary embolism: a harmful association? Case series and review of the literature

Gallerani M, Imberti D, Mari E, Marra A, Manfredini R. Risperidone and pulmonary embolism: a harmful association? Case series and review of the literature.

Objective: Risperidone is an atypical antipsychotic drug used to treat a number of psychiatric diseases, such as schizophrenia, schizoaffective and bipolar disorders and irritability in children with autism. Moreover, it is also often administered for short-term treatment of persistent aggression in people with moderate-to-severe Alzheimer's dementia. A possible association between risperidone and venous thromboembolism (VTE) has been described. We intended to verify the dimension of the problem in our hospital setting.

Methods: We considered all consecutive patients hospitalised in our Internal Medicine Department from January 2004 to December 2010, who were treated with risperidone and presented pulmonary embolism (PE).

Results: Four cases of patients, apparently free from the well-known major risk factors for VTE (i.e. cancer, prolonged immobilisation, acute cardiac and respiratory failure, infections), who presented PE associated with risperidone therapy, were reported in details.

Conclusions: A review of the available literature, discussing the possible different pathogenic reasons for this increased risk of VTE, is provided.

One-carbon metabolism in psychiatric illness

The cost of psychiatric illness to the UK economy was recently estimated at pound77 billion annually. Despite years of research no firm aetiological explanation exists, and with no physiological or biochemical markers diagnosis is made entirely on a behavioural basis. All current pharmacological therapies are associated with serious long-term side effects. Substantial evidence supports the involvement of one-carbon cycle dysregulation in psychiatric illness, but this is not currently used as a basis for diagnosis or treatment. The present paper reviews the evidence for one-carbon cycle dysregulation in schizophrenic, bipolar, depressed and autistic patients. Also presented are novel findings from the field of epigenetics, which demonstrate how the one-carbon cycle-derived methyl donor S-adenosylmethionine influences the expression of key genes in the brain affecting memory, learning, cognition and behaviour, genes whose expression is reduced to varying degrees in these patient groups. Clinical evidence that nutritional supplements can rectify one-carbon cycle activity, and restore normal gene expression, suggests a novel approach to the development of biochemical tests and simple, non-harmful treatments for some psychiatric patients. Conversely, evidence from animal studies highlights the dangers of exposing the unborn fetus to very high dietary levels of folic acid, a one-carbon cycle cofactor. Fetal adaptations to a high-folate environment may interfere with folate metabolism postnatally, with serious consequences for the epigenetic regulation of gene expression. The public health implications of these diverse scenarios indicate an urgent need for further research in this field.

Homocysteine and cognition in first-episode psychosis patients

In the last years, there has been growing evidence linking elevated homocysteine levels with cognitive dysfunction in several neurological and neuropsychiatric diseases. The aim of the present study was to investigate the potential relationship between elevated homocysteine levels and cognitive deficits in first-episode psychosis patients. Plasma levels and cognitive performance of 139 patients and 99 healthy volunteers were compared. Patients were classified as elevated homocysteine (>90 percentile for controls) and normal and compared on 22 cognitive outcome measures grouped into cognitive domains known to be impaired in schizophrenia. Patients had a statistically significant increase in plasmatic homocysteine levels. In addition, they presented with significantly increased cognitive deficits. However, no relationship between homocysteine levels and cognitive impairment was detected. These results suggest the need for further studies to clarify the role of homocysteine in the etiology and prognosis of psychosis.

Serum homocysteine and folate levels in korean schizophrenic patients

OBJECTIVE

This study was conducted to confirm the results of the authors' previous research on schizophrenia manifesting high serum homocysteine and low folate levels. This study is anchored on a theory that a high serum homocysteine concentration affects schizophrenia by virtue of a neurotoxic mechanism, and on a report that some schizophrenia patients with high homocysteine levels benefited from high folate ingestion.

METHODS

The serum homocysteine, folate, and vitamin B(12) levels of 236 normal-control-group subjects and 234 schizophrenia subjects who met the diagnostic criteria based on DSM-IV-TR were compared. The homocysteine levels were measured via fluorescence polarization immunoassay, and the folate and vitamin B(12) levels were determined via radioimmunoassay.

RESULTS

The homocysteine levels of the patient group were significantly higher than those of the normal control group. The homocysteine level was more negatively correlated with the folate level in the schizophrenia group than in the control group. The percentages of female and male schizophrenia subjects manifesting high homocysteine levels were 33.8 and 51.5%, respectively. The percentage of schizophrenia subjects with low folate levels was 66.2%. In the low- and normal-folate-level groups, the patient group showed significantly higher homocysteine levels than the normal control group. The low-folate-level patient group particularly showed significantly higher homocysteine levels than the low-folate-level normal control group.

CONCLUSION

Some schizophrenia patients with high serum homocysteine levels may have the genetic defect of having low folate serum levels. In such cases, folate ingestion may be a good management modality for clinical improvement.

Adhesio interthalamica alterations in schizophrenia spectrum disorders: A systematic review and meta-analysis

Magnetic resonance imaging (MRI) studies have reported a variety of brain abnormalities in association with schizophrenia. These include a higher prevalence of an absent adhesio interthalamica (AI; also known massa intermedia), a gray matter junction that is present between the two thalami in approximately 80% of healthy subjects. In this meta-analytic review, we describe and discuss the main AI MRI findings in schizophrenia spectrum disorders (SSDs) to date. The MEDLINE and ISI Web of Knowledge databases were searched up to December 2010, for studies that used MRI to assess AI in patients with SSD and controls. From fourteen potential reports, eleven were eligible to be part of the current review. These studies included 822 patients with SSD and 718 healthy volunteers. There was a large degree of variability in the MRI methods they employed. Patients with SSD had a higher prevalence of absent AI than healthy volunteers (odds ratio = 1.98; 95% confidence interval 1.33-2.94; p = 0.0008). This association was evident in both male and female SSD subjects, and there was no evidence that the prevalence was related to age or duration of illness. The significance of the absence of an AI for SSD may be clarified by studies in large, longitudinal community-based samples using standardized methods.

Prevention and schizophrenia--the role of dietary factors

Adequate prenatal nutrition is essential for optimal brain development. There is a growing body of evidence from epidemiology linking exposure to nutritional deprivation and increased risk of schizophrenia. Based on studies from the Netherlands and China, those exposed to macronutrient deficiencies during famine have an increased risk of schizophrenia. With respect to micronutrients, we focus on 3 candidates where there is biological plausibility for a role in this disorder and at least 1 study of an association with schizophrenia. These nutrients include vitamin D, folic acid, and iron. While the current evidence is incomplete, we discuss the potential implications of these findings for the prevention of schizophrenia. We argue that schizophrenia can draw inspiration from public health interventions related to prenatal nutrition and other outcomes and speculate on relevant factors that bear on the nature, risks, impact, and logistics of various nutritional strategies that may be employed to prevent this disorder.

A functional polymorphism in the reduced folate carrier gene and DNA hypomethylation in mothers of children with autism

The biologic basis of autism is complex and is thought to involve multiple and variable gene-environment interactions. While the logical focus has been on the affected child, the impact of maternal genetics on intrauterine microenvironment during pivotal developmental windows could be substantial. Folate-dependent one carbon metabolism is a highly polymorphic pathway that regulates the distribution of one-carbon derivatives between DNA synthesis (proliferation) and DNA methylation (cell-specific gene expression and differentiation). These pathways are essential to support the programmed shifts between proliferation and differentiation during embryogenesis and organogenesis. Maternal genetic variants that compromise intrauterine availability of folate derivatives could alter fetal cell trajectories and disrupt normal neurodevelopment. In this investigation, the frequency of common functional polymorphisms in the folate pathway was investigated in a large population-based sample of autism case-parent triads. In case-control analysis, a significant increase in the reduced folate carrier (RFC1) G allele frequency was found among case mothers, but not among fathers or affected children. Subsequent log linear analysis of the RFC1 A80G genotype within family trios revealed that the maternal G allele was associated with a significant increase in risk of autism whereas the inherited genotype of the child was not. Further, maternal DNA from the autism mothers was found to be significantly hypomethylated relative to reference control DNA. Metabolic profiling indicated that plasma homocysteine, adenosine, and S-adenosylhomocyteine were significantly elevated among autism mothers consistent with reduced methylation capacity and DNA hypomethylation. Together, these results suggest that the maternal genetics/epigenetics may influence fetal predisposition to autism.

Plasma homocysteine in schizophrenia: determinants and clinical correlations in Tunisian patients free from antipsychotics

The existence of association between hyperhomocysteinaemia (HHC) and schizophrenia has been suggested by several recent studies. This study aimed to determine the prevalence of HHC and its main determinants, and sought a correlation with clinical features in Tunisian patients with schizophrenia. Plasma homocysteine (Hcy), folate, and vitamin B12, as well as the C677T methylene tetrahydrofolate reductase (MTHFR) polymorphism, were studied in 33 patients with schizophrenia, all free from antipsychotic treatment, and 35 age- and smoking-habit-matched healthy subjects as controls. Biochemical determinations and psychometric evaluations were carried out in patients before the administration of antipsychotics. The prevalence of HHC was higher and plasma B12 vitamin was significantly lower in patients. There was no significant difference in genotypic distribution and allelic frequency of the C677T MTHFR polymorphism between groups. Hcy was significantly correlated to the 'anhedonia-asociality' subscales of the Scale for the Assessment of Negative Symptoms (SANS). This study showed an association between HHC and schizophrenia, especially with the negative symptoms of the disease. In the Tunisian population, HHC in schizophrenia seems to be linked to vitamin B12 deficiency, likely caused by a lack of dietary animal proteins.

Reduced folic acid, vitamin B12 and docosahexaenoic acid and increased homocysteine and cortisol in never-medicated schizophrenia patients: implications for altered one-carbon metabolism

Abnormal one-carbon metabolism has long been suggested as one of the mechanisms for neuropathology and psychopathology of schizophrenia. Variable levels of components of one-carbon metabolism (folic acid and vitamin B12) and consequent altered levels of homocysteine and phospholipid docosahexaenoic acid (DHA) have been independently reported, mostly in medicated patients. This study examined the simultaneous levels of these key components of one-carbon metabolism and its consequences in unique, medication-naïve first-episode psychotic patients (FEP, n=31) and healthy controls (HC, n=48) matched for confounds such as race, diet and lifestyle to reduce the variability. Significantly lower levels of folate and vitamin B12 in plasma and folate in red blood cells were observed in FEP compared to HC. These reductions paralleled the significant increase in plasma homocysteine and cortisol levels. Significantly reduced levels of membrane DHA were also observed in FEP compared to HC. This study, using a unique cohort, provided a broader mechanism (disturbed folic acid-vitamin B12-DHA balance) of altered one-carbon metabolism and one of its key consequential components, an increased homocysteine level that together with cortisol, can contribute to the neuropathology of psychosis. These data may have important implications for the amelioration of psychopathology in schizophrenia.

The 844ins68 polymorphism of the cystathionine beta-synthase gene is associated with schizophrenia

A subtle genetic defect in homocysteine metabolism is thought to play an etiologic role in schizophrenia. Cystathionine-beta-synthase (CBS) is a key enzyme related to homocysteine levels. The aim of the present study was to search for association between the 844ins68 polymorphism of the CBS gene and schizophrenia in a large Russian sample using case-control and family-based designs. The sample comprised 1135 patients, 626 controls and 172 families. There was a trend for association between the 844ins68 polymorphism and schizophrenia in the case-control study, with higher frequency of the insertion in the control group. The FBAT revealed a statistically significant difference in transmission of alleles from parents to the affected proband, with preferential transmission of the variant without insertion. When the sample of patients was stratified by sex and forms of schizophrenia, the significantly lower frequency of insertion was observed in the group of female patients with chronic schizophrenia (n=180) as compared to psychiatrically well women. The insertion variant has been reported earlier to be related to decreased levels of homocysteine and thus thought to play a protective role. In conclusion, our study revealed a possible relation of the CBS 844ins68 polymorphism to schizophrenia.

Folic acid efficacy as an alternative drug added to sodium valproate in the treatment of acute phase of mania in bipolar disorder: a double-blind randomized controlled trial

OBJECTIVE

The purpose of this study was to evaluate the efficacy of adding folic acid to sodium valproate in the acute phase of mania.

METHOD

Following a double-blind randomized controlled trial, 88 clinically manic patients with diagnosis of type I bipolar disorder (BID) were divided randomly into two groups (case and control). The case group was treated with folic acid and sodium valproate and the control group with sodium valproate and placebo. The severity of mania was assessed using the Young Mania Rating Scale (YMRS) at the beginning and end of the first, second and third weeks of the study.

RESULTS

The case group's mean manic YMRS measurements (SD) before the initiation of therapy and in the first, second and third weeks of treatment were 34.0 +/- 7.7, 26.7 +/- 2.1, 18.1 +/- 2.1 and 7.1 +/- 0.9 respectively. The control group's measurements were 34.7 +/- 3.8, 27.3 +/- 2.3, 20.7 +/- 2.5 and 10.1 +/- 1.1. There was a statistically significant difference in YMRS scaling results between the case and control groups after 3 weeks of treatment (7.1 +/- 0.9 vs. 10.1 +/- 1.1, P = 0.005).

CONCLUSION

Based on our findings, folic acid seems to be an effective adjuvant to sodium valproate in the treatment of the acute phase of mania in patients with bipolar disorder.

Epigenetic mediation of environmental influences in major psychotic disorders

The major psychotic disorders schizophrenia and bipolar disorder are etiologically complex involving both heritable and nonheritable factors. The absence of consistently replicated major genetic effects, together with evidence for lasting changes in gene expression after environmental exposures, is consistent with the concept that the biologic underpinnings of these disorders are epigenetic in form rather than DNA sequence based. Psychosis-associated environmental exposures, particularly at key developmental stages, may result in long-lasting epigenetic alterations that impact on the neurobiological processes involved in pathology. Although direct evidence for epigenetic dysfunction in both schizophrenia and bipolar disorder is still limited, methodological technologies in epigenomic profiling have advanced. This means that we are at the exciting stage where it is feasible to start investigating molecular modifications to DNA and histones and examine the mechanisms by which environmental factors can act upon the genome to bring about epigenetic changes in gene expression involved in the etiology of these disorders. Given the dynamic nature of the epigenetic machinery and potential reversibility of epigenetic modifications, the understanding of such mechanisms is of key relevance for clinical psychiatry and for identifying new targets for prevention and/or intervention.

Plasma homocysteine levels in young male patients in the exacerbation and remission phase of schizophrenia

High levels of homocysteine (Hcy) were suggested to contribute to the pathogenesis of schizophrenia. Recent investigations have shown that treatment with folic acid, vitamin B-12 and pyridoxine are effective in reducing Hcy levels while concomitantly reducing the score of positive and negative symptoms in schizophrenic patients. In addition to the availability of nutrients (mainly folate, vitamins B6 and B12), plasma Hcy concentrations are dependent on complex metabolic regulation that could be disrupted in schizophrenia. This study was designed to test the influence of disease activity on plasma Hcy levels. Plasma Hcy concentrations were measured in male chronic schizophrenic patients with a predominantly positive (SCH (+)) or predominantly negative (SCH (-)) syndrome in schizophrenia immediately upon admission to the hospital (exacerbation phase) and one month later (remission phase). During this period patients received antipsychotic medications without vitamin therapy. The effects of age, duration of illness, folate and B12 concentrations, as well as smoking and coffee consumption habits on the observed changes were evaluated. Age- and sex-matched subjects were included in the control group. In the control group plasma Hcy concentration was 8.75+/-1.84 micromol/L. In the exacerbation phase plasma Hcy concentrations were significantly increased both in SCH (+) (14.91+/-6.19 micromol/L) and SCH (-) groups (12.8+/-3.27 micromol/L). There was no difference in plasma Hcy concentrations between SCH (+) and SCH (-) patients. Serum folate and B12 concentrations were not significantly different in any of the investigated groups of subjects. The plasma Hcy concentrations could not be correlated with age, duration of illness, the score of positive symptoms or the concentration of folate and vitamin B12. A positive correlation was found between plasma Hcy level and score of negative symptoms in both groups of patients. No correlation was found between smoking or coffee consumption habits and plasma Hcy concentrations. All patients exhibited decreased plasma Hcy levels in the remission phase of the illness, with a mean decrease of 2.68+/-1.57 micromol/L. Folate and B12 levels did not differ in the exacerbation and remission phases of the illness. The significant decrease of plasma Hcy levels, without changes in folate and vitamin B12 concentrations in the remission phase of schizophrenia, could indicate an influence of a pathogenetic process involved in schizophrenia on Hcy metabolism.

Prenatal nutritional deficiency and risk of adult schizophrenia

Converging evidence suggests that a neurodevelopmental disruption plays a role in the vulnerability to schizophrenia. The authors review evidence supporting in utero exposure to nutritional deficiency as a determinant of schizophrenia. We first describe studies demonstrating that early gestational exposure to the Dutch Hunger Winter of 1944--1945 and to a severe famine in China are each associated with an increased risk of schizophrenia in offspring. The plausibility of several candidate micronutrients as potential risk factors for schizophrenia and the biological mechanisms that may underlie these associations are then reviewed. These nutrients include folate, essential fatty acids, retinoids, vitamin D, and iron. Following this discussion, we describe the methodology and results of an epidemiologic study based on a large birth cohort that has tested the association between prenatal homocysteine, an indicator of serum folate, and schizophrenia risk. The study capitalized on the use of archived prenatal serum specimens that make it possible to obtain direct, prospective biomarkers of prenatal insults, including levels of various nutrients during pregnancy. Finally, we discuss several strategies for subjecting the prenatal nutritional hypothesis of schizophrenia to further testing. These approaches include direct assessment of additional prenatal nutritional biomarkers in relation to schizophrenia in large birth cohorts, studies of epigenetic effects of prenatal starvation, association studies of genes relevant to folate and other micronutrient deficiencies, and animal models. Given the relatively high prevalence of nutritional deficiencies during pregnancy, this work has the potential to offer substantial benefits for the prevention of schizophrenia in the population.

Association between antipsychotic drugs, antidepressant drugs and venous thromboembolism: results from the EDITH case-control study

Cohort studies suggest that exposure to antipsychotic agents may be associated with an increased risk of venous thromboembolism (VTE). Few data concerning antidepressant drugs are available. Using a different methodological approach, the aim of this study was to estimate the association between neuroleptic and antidepressant drug use and the risk of VTE. We report the results of a case-control study designed to evaluate interactions between acquired and inherited risk factors of VTE. We included 677 cases hospitalized with deep vein thrombosis and or pulmonary embolism with no major acquired risk factor for VTE, and 677 controls matched for gender and age. Drug exposure was defined as current use of drugs at admission. Neuroleptic exposure was associated with an increased risk of VTE (OR = 2.1, 95% CI 1.4-3.2). Among neuroleptics, antipsychotic agent use was associated with a 3.5-fold increased risk of VTE (OR = 3.5, 95% CI 2.0-6.2). No association was found between antidepressant drug exposure and the risk of VTE (OR = 1.1, 95% CI 0.9-1.5). In this hospital-based case-control study, exposure to antipsychotic drugs was associated with an increased risk of VTE. These results, added to previous results, suggest that clinicians should consider antipsychotic drug exposure as a potential risk factor of VTE. More studies are needed in order to further elucidate this adverse effect, and to determine the possible predisposing factors and the biological mechanisms involved.

Altered red cell membrane compositions related to functional vitamin B12 deficiency manifested by elevated urine methylmalonic acid concentrations in patients with schizophrenia

Background

Abnormal cell membrane composition and functional cobalamin (vitamin B12) deficiency was reported in schizophrenic individuals. We aimed to investigate the relationship between cobalamin state and cell membrane composition in patients with schizophrenia.

Methods

Malondialdehyde (MDA), cholesterol, and phospholipid classes in the erythrocyte membranes of 18 schizophrenic and 20 healthy individuals of the same age and sex distribution were determined. Serum vitamin B12, plasma total homocysteine, serum folate, and urine methylmalonic acid (uMMA) concentrations were measured in both groups.

Results

In the schizophrenic group, uMMA, membrane MDA, membrane cholesterol, membrane phosphatidylinositol concentrations were significantly higher and the membrane phosphatidylserine concentrations were lower than the control group values. In schizophrenic individuals, uMMA concentrations have a significant positive correlation with membrane MDA and a negative correlation with membrane cholesterol concentrations ( P < 0.05). The negative correlation of uMMA with membrane cholesterol concentrations may be a biological response to the increased membrane rigidity. Also, a free radical elevation related to the elevated uMMA concentrations in the erythrocyte membrane, might reflect the role of methylmalonic acid (MMA) in membrane damage.

Conclusion

Our present findings suggest that, functional vitamin B12 deficiency representing itself by MMA elevations in schizophrenic individuals could damage cell membrane.

Coronary artery disease risk factors in patients with schizophrenia: effects of short term antipsychotic treatment

The aim of the present study was to investigate serum paraoxonase/arylesterase activities and oxidation/oxidizability of apolipoprotein B-containing lipoproteins and several coronary artery disease risk factors, including homocysteine, high sensitive C-reactive protein, tumour necrosis factor-alpha, leptin and adiponectin in patients with schizophrenia. Oxidation of lipoproteins plays an important role in atherogenesis, and the enzyme paraoxonase has been shown to prevent lipoprotein oxidation. Furthermore, low paraoxonase activity has been suggested to predict coronary artery disease. Forty patients who fully met the fourth Diagnostic and Statistical Manual of Mental Disorders criteria for schizophrenia and 35 healthy control subjects were included in the study. Serum paraoxonase/arylesterase activities were determined spectrophotometrically. Malondialdehyde levels of apolipoprotein B-containing lipoproteins were determined before and after incubation with copper-sulphate, which yielded basal- and Delta-malondialdehyde values, respectively. Homocysteine and highly sensitive C-reactive protein levels were determined using a fluorescence-polarization immunoassay and immunonephelometry, respectively. Leptin and adiponectin levels were measured with radioimmunoassay and tumour necrosis factor-alpha was determined by enzyme linked immunosorbent assay. Serum paraoxonase and arylesterase activities were significantly lower and Delta-malondialdehyde levels were significantly higher in the schizophrenia group compared with the control group. However, there were not any significant differences in other parameters of the study between the study groups. There was a significant increase in body mass index and serum triglyceride and very low density lipoprotein cholesterol levels in the schizophrenic group after 6 weeks of treatment. These parameters were significantly increased in patients treated with atypical antipsychotics but not in patients treated with typic or long acting antipsychotics. The results of the present study suggest that patients with schizophrenia might have increased risk for coronary artery disease related to reduced serum paraoxonase activity and increased oxidizability of apolipoprotein B-containing lipoproteins.

Plasma homocysteine, folate and B12 in chronic schizophrenia

Elevated plasma levels of the amino acid homocysteine have been associated with schizophrenia, particularly in young male patients. Among other factors, low folate and vitamin B12 levels have been implicated in the increase in homocysteine. In order to investigate this association, we determined plasma homocysteine, folate and B12 levels in 97 (67 males and 30 females) inpatients with chronic schizophrenia and 103 (46 males and 57 females) controls. Patients and controls did not differ in folate or B12 levels, after adjusting for age. Patients with schizophrenia had higher plasma homocysteine than controls (mean=15.42 micromol/l in cases versus 11.54 micromol/l in controls: F(1,195)=17.978; p<0.001). This difference persisted after controlling for folate and B12 concentrations. Both male and female patients had increased plasma homocysteine compared to controls [(males: mean=16.61 micromol/l in cases versus mean=13.72 in controls: F(1,110)=5.54; p=0.020) (females: mean=12.78 micromol/l in cases versus mean=9.79 micromol/l in controls: F(1,84)=13.54; p<0.001)]. When dividing our sample into two age groups (age < and > or =50 years), both young and older females and younger males with schizophrenia had increased plasma homocysteine compared to controls. We therefore suggest that homocysteinemia is a general risk factor for schizophrenia. We further suggest that it is not limited to young male patients and is not necessarily associated with low folate or B12 levels.

Glutamate and schizophrenia: phencyclidine, N-methyl-D-aspartate receptors, and dopamine-glutamate interactions

Schizophrenia is a serious mental disorder that affects up to 1% of the population worldwide. As of yet, neurochemical mechanisms underlying schizophrenia remain unknown. To date, the most widely considered neurochemical hypothesis of schizophrenia is the dopamine hypothesis, which postulates that symptoms of schizophrenia may result from excess dopaminergic neurotransmission particularly in striatal brain regions, along with dopaminergic deficits in prefrontal brain regions. Alternative neurochemical models of schizophrenia, however, have been proposed involving glutamatergic mechanisms in general and N-methyl-D-aspartate (NMDA) receptors in particular. A potential role for glutamatergic mechanisms in schizophrenia was first proposed approximately 15 years ago based on the observation that the psychotomimetic agents phencyclidine (PCP) and ketamine induce psychotic symptoms and neurocognitive disturbances similar to those of schizophrenia by blocking neurotransmission at NMDA-type glutamate receptors. Since that time, significant additional evidence has accumulated supporting a role for NMDA hypofunction in the pathophysiology of schizophrenia. Clinical challenge studies with PCP and ketamine have confirmed the close resemblance between NMDA antagonist-induced symptoms and neurocognitive deficits and those observed in schizophrenia, and suggest that NMDA dysfunction may lead to secondary dopaminergic dysregulation in striatal and prefrontal brain regions. As compared to dopaminergic agents, NMDA antagonists induce negative and cognitive symptoms of schizophrenia, as well as positive symptoms. Treatment studies with NMDA modulators, such as glycine, d-serine, and glycine transport inhibitors (GTIs), have yielded encouraging findings, although results remain controversial. Finally, genetic linkage and in vivo neurochemical studies in schizophrenia highlight potential etiological mechanisms giving rise to glutamatergic/NMDA dysfunction in schizophrenia.

No association between MTHFR A1298C and MTRR A66G polymorphisms, and MS in an Australian cohort

Multiple sclerosis (MS) is a complex neurological disease that affects the central nervous system (CNS) resulting in debilitating neuropathology. Pathogenesis is primarily defined by CNS inflammation and demyelination of nerve axons. Methionine synthase reductase (MTRR) is an enzyme that catalyzes the remethylation of homocysteine (Hcy) to methionine via cobalamin and folate dependant reactions. Cobalamin acts as an intermediate methyl carrier between methylenetetrahydrofolate reductase (MTHFR) and Hcy. MTRR plays a critical role in maintaining cobalamin in an active form and is consequently an important determinant of total plasma Hcy (pHcy) concentrations. Elevated intracellular pHcy levels have been suggested to play a role in CNS dysfunction, neurodegenerative, and cerebrovascular diseases. Our investigation entailed the genotyping of a cohort of 140 cases and matched controls for MTRR and MTHFR, by restriction length polymorphism (RFLP) techniques. Two polymorphisms: MTRR A66G and MTHFR A1298C were investigated in an Australian age and gender matched case-control study. No significant allelic frequency difference was observed between cases and controls at the alpha = 0.05 level (MTRR chi2 = 0.005, P = 0.95, MTHFR chi2 = 1.15, P = 0.28). Our preliminary findings suggest no association between the MTRR A66G and MTHFR A1298C polymorphisms and MS.

Homocysteine levels in adolescent schizophrenia patients

Homocysteine is a sulfur containing amino acid that has been widely investigated for its putative role in cardiovascular and neuropsychiatric disorders. It has been suggested that homocysteine has implications especially in young, male schizophrenia patients. In this prospective case-control study, we compared plasma homocysteine levels in a group of adolescent schizophrenia inpatients (aged 14-21 years; n=23) to normal healthy controls (n=51). Mean plasma homocysteine levels were significantly higher in the patient group than in the control group (15.40+/-2.00 and 9.78+/-0.33 micromol/L, respectively, p<0.032). The difference was almost entirely attributable to the male schizophrenia subgroup (18.18+/-5.65 in male patients vs. 10.31+/-5.33 micromol/L in female patients). The group x sex interaction was statistically significant (p=0.0035). These data indicate that a subgroup of male adolescent schizophrenia patients has high homocysteine blood levels. The role of homocysteine in the pathophysiology of adolescent-onset schizophrenia merits further investigation.

Homocysteine-reducing strategies improve symptoms in chronic schizophrenic patients with hyperhomocysteinemia

BACKGROUND

An elevated homocysteine level is reported to be a risk factor for several diseases, including Alzheimer's and cerebrovascular disease. Recently, several studies have reported that homocysteine levels are elevated in many schizophrenic patients. Homocysteine levels can be lowered by oral folic acid, B-12, and pyridoxine.

METHODS

Forty-two schizophrenic patients with plasma homocysteine levels >15 micromol/L were treated with these vitamins for 3 months and placebo for 3 months in a study with a randomized, double-blind, placebo-controlled, crossover design.

RESULTS

Homocysteine levels declined with vitamin therapy compared with placebo in all patients except for one noncompliant subject. Clinical symptoms of schizophrenia as measured by the Positive and Negative Syndrome Scale declined significantly with active treatment compared with placebo. Neuropsychological test results overall, and Wisconsin Card Sort (Categories Completed) test results in particular, were significantly better after vitamin treatment than after placebo.

CONCLUSIONS

A subgroup of schizophrenic patients with hyperhomocysteinemia might benefit from the simple addition of B vitamins.

Low essential fatty acid and B-vitamin status in a subgroup of patients with schizophrenia and its response to dietary supplementation

We assessed essential fatty acid (EFA) and B-vitamin status, together with their determinants, in 61 patients with schizophrenia and established whether those with poor status responded biochemically to the appropriate dietary supplements. As a group, the patients had high erythrocyte saturated fatty acids (FAs), monounsaturated FA and low polyunsaturated FA of the omega3 and omega6 series. Patients reporting not to take vitamin supplements had low vitamin B12 and high homocysteine. Homocysteine variance proved best explained by folate in both the total group and male patients, and by vitamins B12 and B6 in females. Alcohol consumption and duration of illness are risk factors for low polyunsaturated FA status (< P2.5 of reference range), while male gender and absence of fish consumption predict hyperhomocysteinemia (> P97.5 of reference range). Two patients exhibited biochemical EFA deficiency and seven showed biochemical signs of omega3/docosahexaenoic acid (DHA) marginality. Four patients exhibited moderate hyperhomocysteinemia with plasma values ranging from 57.5 to 74.8 micromol/L. None of the five patients with either moderate hyperhomocysteinemia, biochemical EFA deficiency, or both, was predicted by their clinicians to have poor diets. That diet was nevertheless at the basis of these abnormalities became confirmed after supplementing 4 of them with B vitamins and with soybean and fish oils. We conclude that a subgroup of patients with schizophrenia has biochemical EFA deficiency, omega3/DHA marginality, moderate hyperhomocysteinemia, or combinations. Correction seems indicated in view of the possible relation of poor EFA and B-vitamin status with some of their psychiatric symptoms, but notably to reduce their high risk of cardiovascular disease.

Homocysteine levels and glucose metabolism in non-obese, non-diabetic chronic schizophrenia

OBJECTIVE

We studied a sample of schizophrenia out-patients to test the hypotheses that serum homocysteine concentrations would correlate positively with measures of glucose metabolism.

METHOD

Subjects underwent a nutritional assessment and fasting plasma, serum insulin and homocysteine tests.

RESULTS

Males had a significantly higher homocysteine levels than females (7.69 +/- 1.42 microM vs. 6.63 +/- 1.40 microM; P = 0.02). Comparing subjects with normal fasting glucose (NFG) (glucose < 100 mg/dl) and impaired fasting glucose (IFG) (> or = 100 mg/dl) subjects with IFG (mean 8.2 +/- 1.5 microM) had significantly higher homocysteine levels than those with NFG (mean 7.2 +/- 1.4 microM, P = 0.03). IFG was also associated with greater mean values for a Homeostatic Model Assessment-Insulin Resistance (HOMA-IR) (P = 0.002) and diastolic blood pressure (P = 0.045).

CONCLUSION

The group with IFG had higher fasting serum homocysteine concentrations than those with NFG which supports a connection to an important cardiovascular risk factor.

Homocysteine, methylenetetrahydrofolate reductase and risk of schizophrenia: a meta-analysis

Elevated plasma homocysteine concentration has been suggested as a risk factor for schizophrenia, but the results of epidemiological studies have been inconsistent. The most extensively studied genetic variant in the homocysteine metabolism is the 677C>T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene, resulting in reduced enzyme activity and, subsequently, in elevated homocysteine. A meta-analysis of eight retrospective studies (812 cases and 2113 control subjects) was carried out to examine the association between homocysteine and schizophrenia. In addition, a meta-analysis of 10 studies (2265 cases and 2721 control subjects) on the homozygous (TT) genotype of the MTHFR 677C>T polymorphism was carried out to assess if this association is causal. A 5 micromol/l higher homocysteine level was associated with a 70% (95% confidence interval, CI: 27-129) higher risk of schizophrenia. The TT genotype was associated with a 36% (95% CI: 7-72) higher risk of schizophrenia compared to the CC genotype. The performed meta-analyses showed no evidence of publication bias or excessive influence attributable to any given study. In conclusion, our study provides evidence for an association of homocysteine with schizophrenia. The elevated risk of schizophrenia associated with the homozygous genotype of the MTHFR 677C>T polymorphism provides support for causality between a disturbed homocysteine metabolism and risk of schizophrenia.

Pharmacologic implications of neurobiological models of schizophrenia

The dopamine model of schizophrenia has been supplanted by several additional models in order to account for genetic findings, risk factors, course of illness, and the diversity of symptom domains. The increasing number and complexity of potential models for this heterogeneous disorder offer new targets for pharmacologic treatment that differ in their appropriate time points for intervention and in their potential effects on the course of illness. This article reviews relevant neurodevelopmental, biochemical, and neurodegenerative models with respect to potential pharmacologic opportunities.

Further evidence that hyperhomocysteinemia and methylenetetrahydrofolate reductase C677T and A1289C polymorphisms are not risk factors for schizophrenia

It has been suggested that total plasma homocysteine (tHcy) concentrations and methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms are risk factors for schizophrenia. We conducted a case-control study to investigate whether tHcy levels and MTHFR C677T and A1298C variants are associated with schizophrenia, giving special consideration to confounding factors. Logistic regression analysis showed that neither tHcy nor MTHFR polymorphisms were associated with schizophrenia. Homozygosity for MTHFR C677T was associated with higher tHcy concentrations in control and schizophrenia groups (P<0.01), which was mainly driven by the male group. The A1298C variant did not show any association with tHcy concentrations. In conclusion, these results do not confirm an independent relationship of tHcy and MTHFR genotype with risk of schizophrenia.

High homocysteine serum levels in young male schizophrenia and bipolar patients and in an animal model

Elevated plasma homocysteine has been found to be a risk factor for Alzheimer's disease as well as cerebral vascular disease, suggesting that some risk factors can accelerate or increase the severity of several CNS disease processes. We screened plasma total homocysteine levels of 193 schizophrenic patients vs. 762 controls for plasma homocysteine levels. The effect of schizophrenia was marked (p<0.0001) and mean homocysteine level was 16.3+/-12 (S.D.) microM in schizophrenic patients vs. 10.6+/-3.6 (S.D.) microM in healthy controls. The increase was almost entirely in young male schizophrenic patients. It seemed important to determine if this finding is already present in newly admitted schizophrenic patients. Serum homocysteine levels were studied in 184 consecutively admitted schizophrenic patients and 305 control subjects. Homocysteine levels were markedly increased in this population of newly admitted schizophrenic patients, especially in young males. However, no difference was found for CSF homocysteine levels between schizophrenia patients and controls. We also examined homocysteine levels in 41 euthymic outpatients with bipolar disorder. Functional deterioration in patients was rated as 'present' or 'absent' by consensus of two treating clinicians. Young male bipolar patients were found to have higher homocysteine levels than controls. Among the male subjects, bipolar patients showing deterioration had homocysteine levels which were significantly higher than other patients. We attempted to develop a model of homocysteine neurotoxicity in mice. Mice were fed homocysteine in water at a dose of 200 mg/kg per mouse per day. Independent samples of animals were studied at 2 to 6 months with behavioral tests including apomorphine-induced stereotypy and spatial learning and memory in the Morris Water Maze. Homocysteine levels were elevated up to 800% at months 5 and 6 by this procedure. No homocysteine-induced defects were found in any behavioral test until month 5 when mild but statistically significant abnormalities in the Morris Water Maze were detected.

Homocysteinemia as well as methylenetetrahydrofolate reductase polymorphism are associated with affective psychoses

In the recent years, elevated homocysteine plasma levels have been reported to represent a risk factor not only for atherosclerosis, but also to be associated with dementia, depression and-in a gender-specific manner-schizophrenia. Here, we explored a possible association between homocysteinemia and psychiatric disorders. Fasting homocysteine, vitamin B12 and folate were determined in an ethnically homogeneous female population with different psychiatric disorders. Homocysteine was not elevated in females suffering from schizophrenia (mean, 11.6+/-5.8 micromol/l). As shown previously, increased homocysteine concentrations were associated not only with dementia of different aetiology (mean, 17.2+/-6.7 micromol/l; chi2=23.39, p<0.001, compared to the schizophrenia group), but also with depressive disorders (mean, 12.9+/-3.8 micromol/l; chi2=6.88, p=0.009). B12 and folate levels did not differ between different diagnostic groups. To further explore the connection between homocysteinemia and affective psychoses, a case-control study examining the C677T and the A1298C variants of methylenetetrahydrofolate reductase was conducted. The latter polymorphism not only was associated with affective psychoses in general, but also when divided in unipolar depression and bipolar affective disorder. In conclusion, we suggest that in females homocysteinemia is an unspecific risk factor for organic brain disorders like dementia, and possibly depression, but not for schizophrenia.

Association of the C677T and A1298C polymorphisms of methylenetetrahydrofolate reductase gene with schizophrenia: association is significant in men but not in women

Schizophrenia is a complex and common psychiatric disorder with a polygenic inheritance. In our previous report, we showed an association between the methylenetetrahydrofolate reductase (MTHFR) gene C677T and A1298C polymorphisms and schizophrenia in patients from Bakirkoy in Istanbul, Turkey [Sazci, A., Ergul, E., Guzelhan, Y., Kaya, G., Kara, I., 2003. Methylenetetrahydrofolate reductase gene polymorphisms in patients with schizophrenia. Mol. Brain Res. 117, 104-107]. We wanted also independently to confirm this study in a gender-specific manner with schizophrenic patients from Erenkoy in Istanbul, Turkey. To investigate the role of the C677T and A1298C polymorphisms of methylenetetrahydrofolate reductase gene in schizophrenia in a gender-specific manner, we analyzed the genotypes of MTHFR677 and MTHFR1298 of 297 schizophrenic patients and 341 healthy controls, using a polymerase chain reaction restriction fragment length polymorphism method. The MTHFR 677T allele was significantly distributed (chi2=7.312; P=0.026), between schizophrenic patients and healthy controls. The T677T genotype was overrepresented in the total schizophrenic patients (OR=1.938; 95%CI=1.133-3.315; chi2=5.996; P=0.014). Similarly, the T677T/A1298A compound genotype was the most significant one in the total schizophrenic patients (OR=2.397; 95% CI=1.327-4.330; chi2=8.821; P=0.003). The C1298C genotype was overrepresented in the total schizophrenic patients (OR=1.706; 95%CI=1.014-2.870; chi2=4.126; P=0.042). Likewise, the C677C/C1298C compound genotype was significant in the total schizophrenic patients (OR=1.689; 95%CI=0.985-2.894; chi2=3.695; P=0.055). When schizophrenic patients and healthy controls were stratified according to gender difference, the T677T genotype and T677T/A1298A compound genotype were significantly overrepresented (OR=2.184; 95% CI=1.069-4.462; chi2=4.767; P=0.029; OR=2.748; 95% CI=1.215-6.214; chi2=6.301; P=0.012, respectively) in men schizophrenic patients. However, neither the MTHFR C677T nor the A1298C polymorphisms are associated with schizophrenia in women. In conclusion, the MTHFR 677T allele and T677T, C1298C genotypes, and T677T/A1298A, C677C/C1298C compound genotypes are genetic risk factors for schizophrenia in men but not in women in a gender-specific manner.

Aberrant folate status in schizophrenic patients: what is the evidence?

A vast amount of case reports, open studies and, to a lesser extent, case-control studies have been published on the topic of psychopathology and folate deficiency. These studies reported a high incidence of serum folate deficiency in patients with various psychiatric disorders. Folate deficiency seems to be a particular consistent finding in depressive patients. The evidence for an association between aberrant folate status and schizophrenia seems less convincing. The lack of stringent methodology such as inclusion of age- and sex-matched controls was thought to be the main reason for the inconclusive results. The purpose of this article is to review the published case-control studies that provide data on folate levels in the population of patients with schizophrenia. Data extracted from these studies comprised methodological design, clinical characteristics and folate measurements. We found that none of the 7 case-control studies included in this review (in total 325 cases and 560 control subjects) explicitly reported on all critical factors in the assessment of folate. In addition, only three studies found lower plasma folate levels more frequently in patients with schizophrenia compared to controls. Further research on this topic is required to clarify the relationship between folate status and schizophrenia and should avoid the methodological pitfalls mentioned in this review. In addition, research should also focus on polymorphisms of genes related to folate metabolism.

Homocysteine and schizophrenia: from prenatal to adult life

Homocysteine is becoming increasingly recognized as an important substance in the pathogenesis and pathophysiology of schizophrenia. In this review, we first present background information supporting a role for homocysteine in schizophrenia. We then discuss our work on the role of hyperhomocystinemia during adulthood and risk of schizophrenia, and present preliminary evidence on a potential relationship between prenatal homocysteine and schizophrenia. Finally, we discuss the implications of these findings for future work on nutritional etiologies of schizophrenia.