Do maternal folate and homocysteine levels play a role in neurodevelopmental processes that increase risk for schizophrenia?

Prenatal folate deficiency impairs sociability and memory/recognition in mice offspring

Folate is essential for the normal growth and development of the fetus. Folic acid supplementation during the fetal period affects postnatal brain development and reduces the incidence of mental disorders in animal and human studies. However, the association between folate deficiency (FD) during pregnancy and developmental disorders in children remains poorly understood. In this study, we investigated whether prenatal FD is associated with neurodevelopmental disorders in offspring. ICR mice were fed a control diet (2 mg folic acid/kg diet) or a folate-deficient diet (0.3 mg folic acid/kg diet) from embryonic day 1 until parturition. We evaluated locomotor activity, anxiety, grooming, sociability and learning memory in male offspring at 7-10 weeks of age. No differences were found in locomotor activity or anxiety in the open field test, nor in grooming time in the self-grooming test. However, sociability, spatial memory, and novel object recognition were impaired in the FD mice compared with control offspring. Furthermore, we measured protein expression levels of the NMDA and AMPA receptors, as well as PSD-95 and the GABA-synthesizing enzymes GAD65/67 in the frontal cortex and hippocampus. In FD mice, expression levels of AMPA receptor 1 and PSD-95 in both regions were reduced compared with control mice. Moreover, NMDA receptor subunit 2B and GAD65/67 were significantly downregulated in the frontal cortex of prenatal FD mice compared with the controls. Collectively, these findings suggest that prenatal FD causes behavioral deficits together with a reduction in synaptic protein levels in the frontal cortex and hippocampus.

Biological hypotheses, risk factors, and biomarkers of schizophrenia

Both the discovery of biomarkers of schizophrenia and the verification of biological hypotheses of schizophrenia are an essential part of the process of understanding the etiology of this mental disorder. Schizophrenia has long been considered a neurodevelopmental disease whose symptoms are caused by impaired synaptic signal transduction and brain neuroplasticity. Both the onset and chronic course of schizophrenia are associated with risk factors-induced disruption of brain function and the establishment of a new homeostatic setpoint characterized by biomarkers. Different risk factors and biomarkers can converge to the same symptoms of schizophrenia, suggesting that the primary cause of the disease can be highly individual. Schizophrenia-related biomarkers include measurable biochemical changes induced by stress (elevated allostatic load), mitochondrial dysfunction, neuroinflammation, oxidative and nitrosative stress, and circadian rhythm disturbances. Here is a summary of selected valid biological hypotheses of schizophrenia formulated based on risk factors and biomarkers, neurodevelopment, neuroplasticity, brain chemistry, and antipsychotic medication. The integrative neurodevelopmental-vulnerability-neurochemical model is based on current knowledge of the neurobiology of the onset and progression of the disease and the effects of antipsychotics and psychotomimetics and reflects the complex and multifactorial nature of schizophrenia.

Prenatal methotrexate injection increases behaviors possibly associated with depression and/or autism in rat offspring; A new animal model for mental disorder, based on folate metabolism deficit during pregnancy

Background

Deficiency of folate, an essential vitamin for DNA synthesis and methylation, is reported as a risk factor for mental disorders. Considering a possibility that folate metabolism deficit during pregnancy may disturb CNS development and increase mental disorders in offspring, we treated pregnant rats with methotrexate (MTX), an inhibitor of folate metabolic enzyme, and evaluated offspring behaviors.

Methods

Saline or MTX was intraperitoneally administered to female SD rats on gestational day 17. Offspring behaviors were evaluated during approximately 6–9 weeks old; prepulse inhibition (PPI), social interaction (SI), locomotor activity (LA), and forced swimming test (FST) for evaluation of schizophrenia, depression, and autism related behaviors; the elevated plus maze (EPM) and the light–dark box (LD) test for evaluation of anxiety.

Results

Compared to saline‐treated group, MTX‐treated group showed decrease of SI and increase of immobility time in FST. In addition, increases of time spent in the light box and shuttling between the light–dark boxes were observed in LD test. On the other hand, no changes were confirmed in EPM, LA, and PPI.

Conclusion

Decrease of SI and increase of immobility time in FST may suggest association of this animal model with depression and/or autism. Increase of time spent in the light box and shuttling between the light–dark boxes may indicate changes in anxiety or cognitive level to environment, or repetitive behaviors in autism. Although further studies are warranted to characterize this animal model, at least we can say that prenatal MTX exposure, possibly causing folate metabolism deficit, affects offspring behaviors.

Maternal serum Vitamin B12 and offspring attention-deficit/hyperactivity disorder (ADHD)

Maternal Vitamin B12 deficiency during pregnancy is associated with offspring neuropsychiatric disorders. Few previous studies examining this association with attention-deficit/hyperactivity disorder (ADHD) report inconsistent findings. The study examines the association between maternal serum Vitamin B12 levels and offsprings' risk of ADHD. This study is based on the Finnish Prenatal Study of ADHD with a nested case-control design. All the singleton children born in Finland between January 1998 and December 1999 and diagnosed with ADHD were included in the study. A total of 1026 cases were matched with an equal number of controls on sex, date of birth and place of birth. Maternal Vitamin B12 levels were assessed using a chemiluminescence microparticle immunoassay and archived from maternal serum banks, collected during the first and early second trimester of pregnancy. Lower maternal Vitamin B12 levels when analyzed as a continuous variable was not associated with offspring ADHD (aOR 0.97, 95% CI 0.79-1.18, p = 0.75). No significant associations were seen in the lowest quintile of Vitamin B12 levels (aOR 0.96, 95% CI 0.73-1.27, p = 0.80). This is the first study examining maternal sera Vitamin B12 levels during early pregnancy and offspring ADHD. The result suggests that Vitamin B12 deficiency during early pregnancy has specificity for some disorders but not with offspring ADHD.

Maternal folate levels during pregnancy and offspring brain development in late childhood

BACKGROUND

Cumulative evidence shows that low maternal folate levels during pregnancy are associated with offspring neuropsychiatric disorders even in the absence of neural tube defects. However, the relationship between prenatal exposure to folate and brain development in late childhood has been rarely investigated.

METHODS

In 2095 children from a prospective population-based cohort in Rotterdam, the Netherlands, we examined the association of maternal folate levels during pregnancy with downstream brain development in offspring. Maternal folate concentrations were measured from venous blood in early gestation. Child structural neuroimaging data were measured at age 9-11 years. In addition, measures of child head circumference using fetal ultrasound in the third trimester and total brain volume using magnetic resonance imaging at age 6-8 years were used for analyses with repeated assessments of brain development.

RESULTS

Maternal folate deficiency (i.e., <7 nmol/L) during pregnancy was associated with smaller total brain volume (B = -18.7 cm³, 95% CI -37.2 to -0.2) and smaller cerebral white matter (B = -7.2 cm³, 95% CI -11.8 to -2.6) in children aged 9-11 years. No differences in cortical thickness or surface area were observed. Analysis of the repeated brain assessments showed that children exposed to deficient folate concentrations in utero had persistently smaller brains compared to controls from the third trimester to childhood (β = -0.4, 95% CI -0.6 to -0.1).

CONCLUSIONS

Low maternal folate levels during pregnancy are associated with altered offspring brain development in childhood, suggesting the importance of essential folate concentrations in early pregnancy.

Reduced Intellectual Ability in Offspring Born from Preeclamptic Mothers: A Prospective Cohort Study

Background

Severe preeclampsia may affect placental development, and high homocysteine (Hcy) levels are linked to intellectual disability. However, the correlation between perinatal Hcy levels and intellectual ability remains unknown in severe preeclampsia-affected offspring.

Objective

We aimed to investigate the intellectual ability in offspring born from preeclamptic mothers and examine the role of prenatal Hcy in the prediction of intellectual disability in preschool-aged offspring.

Methods

The IQ scores were compared between 101 children born to mothers with severe preeclampsia and 202 offsprings born to normotensive mothers. Maternal Hcy levels within 7 days prior to delivery and postnatal cord blood Hcy were measured. The associations of Hcy with IQ scores were evaluated, and the optimal cut-off values for predicting intellectual disability in the offspring were estimated.

Results

The children born to mothers with severe preeclampsia had a greater postnatal cord blood Hcy than those born from normotensive mothers (P < 0.001), and the mothers with severe preeclampsia presented a higher prenatal Hcy (P < 0.001). The children born to mothers with severe preeclampsia had significantly lower IQ scores than those born from normotensive mothers, and a higher Hcy was associated with a lower IQ in preeclampsia-affected offspring. The prevalence of intellectual disability was 2.86 times higher in severe preeclampsia-affected offspring than in children born from normotensive mothers, and the prevalence of low IQ was greater in children born to mothers with severe preeclampsia than in those from normotensive mothers. ROC curve analysis showed that both maternal and cord blood Hcy were predictors of intellectual disability, and the optimal cut-off for predicting intellectual disability was 17.7 and 9.75 μmol/L for maternal and cord blood Hcy.

Conclusion

Perinatal exposure to severe preeclampsia has an adverse effect on postnatal intellectual development, and high maternal and cord blood Hcy may contribute to this association.

Investigation of Schizophrenia with Human Induced Pluripotent Stem Cells

Schizophrenia is a chronic and severe neuropsychiatric condition manifested by cognitive, emotional, affective, perceptual, and behavioral abnormalities. Despite decades of research, the biological substrates driving the signs and symptoms of the disorder remain elusive, thus hampering progress in the development of treatments aimed at disease etiologies. The recent emergence of human induced pluripotent stem cell (hiPSC)-based models has provided the field with a highly innovative approach to generate, study, and manipulate living neural tissue derived from patients, making possible the exploration of fundamental roles of genes and early-life stressors in disease-relevant cell types. Here, we begin with a brief overview of the clinical, epidemiological, and genetic aspects of the condition, with a focus on schizophrenia as a neurodevelopmental disorder. We then highlight relevant technical advancements in hiPSC models and assess novel findings attained using hiPSC-based approaches and their implications for disease biology and treatment innovation. We close with a critical appraisal of the developments necessary for both further expanding knowledge of schizophrenia and the translation of new insights into therapeutic innovations.

The Importance of Maternal Folate Status for Brain Development and Function of Offspring

The importance of an adequate periconceptional maternal folate status to prevent fetal neural tube defects has been well demonstrated and resulted in the recommendation for women to use folic acid supplements during the periconception period. The importance of maternal folate status for offspring neurodevelopment and brain health is less well described. We reviewed the current evidence linking maternal folate status before conception and during pregnancy with neurodevelopment and cognition of the offspring. We discuss both animal and human studies. Preclinical research revealed the importance of maternal folate status for several key processes required for normal neurodevelopment and brain functioning in the offspring, including DNA synthesis, regulation of gene expression, synthesis of phospholipids and neurotransmitters, and maintenance of healthy plasma homocysteine concentrations. Human observational studies are inconclusive; about half have shown a positive association between maternal folate status and cognitive performance of offspring. Whereas some studies suggest a positive association between maternal folate intake and cognition of offspring during childhood, data from interventional studies are too limited to conclude that there is a direct effect. Future preclinical studies are needed to help us characterize the behavioral effects, understand the underlying mechanisms, and to establish an optimal dosage and time window of folate supplementation. Moreover, more conclusive data from well-designed human observational studies and randomized controlled trials are needed to determine whether current recommendations for folic acid supplementation during pregnancy cover the needs for normal cognitive development in the offspring.

Iron as a model nutrient for understanding the nutritional origins of neuropsychiatric disease

Adequate nutrition during the pre- and early-postnatal periods plays a critical role in programming early neurodevelopment. Disruption of neurodevelopment by nutritional deficiencies can result not only in lasting functional deficits, but increased risk of neuropsychiatric disease in adulthood. Historical periods of famine such as the Dutch Hunger Winter and the Chinese Famine have provided foundational evidence for the long-term effects of developmental malnutrition on neuropsychiatric outcomes. Because neurodevelopment is a complex process that consists of many nutrient- and brain-region-specific critical periods, subsequent clinical and pre-clinical studies have aimed to elucidate the specific roles of individual macro- and micronutrient deficiencies in neurodevelopment and neuropsychiatric pathologies. This review will discuss developmental iron deficiency (ID), the most common micronutrient deficiency worldwide, as a paradigm for understanding the role of early-life nutrition in neurodevelopment and risk of neuropsychiatric disease. We will review the epidemiologic data linking ID to neuropsychiatric dysfunction, as well as the underlying structural, cellular, and molecular mechanisms that are thought to underlie these lasting effects. Understanding the mechanisms driving lasting dysfunction and disease risk is critical for development and implementation of nutritional policies aimed at preventing nutritional deficiencies and their long-term sequelae.

Methylenetetrahydrofolate reductase and psychiatric diseases

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme for the critical process of one-carbon metabolism involving folate and homocysteine metabolisms. It is known that some polymorphism of MTHFR would result in reduction of MTHFR enzyme activity as well as DNA methylation process, later shown to have significant impacts in various psychiatric diseases. However, it is unclear whether the polymorphism of MTHFR could be an independent or an add-on risk factor for specific psychiatric symptoms, such as anxiety, depression, positive, or negative symptoms of schizophrenia, or acts as risk factor for specific psychiatric disorders, such as schizophrenia, major depression, autisms, and bipolar disorders. It is also understudied on whether folate supplements could be an effective treatment for psychiatric patients with defect MTHFR activity. In this review, we not only gathered the most recent discoveries on MTHFR polymorphism and related DNA methylation in various psychiatric disorders, but also highlighted the potential relationships between MTHFR activity and implication of folate-related function in specific mental diseases.

The effects of high and low doses of folic acid on oxidation of protein levels during pregnancy: a randomized double-blind clinical trial

Objective

Oxidants include important active molecules which are created in the body and attack biological molecules especially lipids, carbohydrates, nucleic acids and proteins, and cause oxidation and various diseases in the body. Antioxidants existing in the body help to avoid the incidence of these injuries. Pregnant women are among those where oxidation of biological molecules may do irreparable damage to them and their embryos. So, the purpose of this study was to review the effect of folic acid with both high (5 mg/day) and low (0.5 mg/day) doses on the changes of oxidative protein in reducing plasma homocystein concentration during pregnancy.

Materials and methods

Forty-five pregnant women participated in this study. They were divided into two groups: group 1 included 23 women who received 5 mg/day folic acid and group 2 included 23 women who took 0.5 mg/day folic acid before pregnancy till the 36th week pregnancy. We measured the biochemical variables in the serum of pregnant women at the beginning and at the end of the study.

Results

Folic acid reduced plasma homocytein in both low and high dose groups (p = 0.035, p = 0.012, respectively). Also, the results showed that folic acid prescription led to reduce plasma level of carbonyl groups in both low and high dose groups (p = 0.01, p = 0.03, respectively). Furthermore, the results showed that there is no significant difference between two groups and folic acid affects both groups equally.

Conclusion

It is possible that folic acid administration can reduce plasma homocysteine and carbonyl levels during pregnancy in dose independent manner

Prenatal one-carbon metabolism dysregulation programs schizophrenia-like deficits

The methionine-folate cycle-dependent one-carbon metabolism is implicated in the pathophysiology of schizophrenia. Since schizophrenia is a developmental disorder, we examined the effects that perturbation of the one-carbon metabolism during gestation has on mice progeny. Pregnant mice were administered methionine equivalent to double their daily intake during the last week of gestation. Their progeny (MET mice) exhibited schizophrenia-like social deficits, cognitive impairments and elevated stereotypy, decreased neurogenesis and synaptic plasticity, and abnormally reduced local excitatory synaptic connections in CA1 neurons. Neural transcript expression of only one gene, encoding the Npas4 transcription factor, was >twofold altered (downregulated) in MET mice; strikingly, similar Npas4 downregulation occurred in the prefrontal cortex of human patients with schizophrenia. Finally, therapeutic actions of typical (haloperidol) and atypical (clozapine) antipsychotics in MET mice mimicked effects in human schizophrenia patients. Our data support the validity of MET mice as a model for schizophrenia, and uncover methionine metabolism as a potential preventive and/or therapeutic target.

S-Adenosyl Methionine and Transmethylation Pathways in Neuropsychiatric Diseases Throughout Life

S-Adenosyl methionine (SAMe), as a major methyl donor, exerts its influence on central nervous system function through cellular transmethylation pathways, including the methylation of DNA, histones, protein phosphatase 2A, and several catecholamine moieties. Based on available evidence, this review focuses on the lifelong range of severe neuropsychiatric and neurodegenerative diseases and their associated neuropathologies, which have been linked to the deficiency/load of SAMe production or/and the disturbance in transmethylation pathways. Also included in this review are the present-day applications of SAMe in the treatment in these diseases in each age group.

A Computational Approach to Identify the Biophysical and Structural Aspects of Methylenetetrahydrofolate Reductase (MTHFR) Mutations (A222V, E429A, and R594Q) Leading to Schizophrenia

The association between depression and methylenetetrahydrofolate reductase (MTHFR) has been continually demonstrated in clinical studies, yet there are sparse resources available to build a relationship between the mutations associated with MTHFR and depression. The common mutations found to be associated with schizophrenia and MTHFR are A222V, E429A, and R594Q. Although abundant research on structural and functional effects caused by A222V mutation is available, very less amount of studies have been done on the other two mutants (E429A and R594Q). Hence in this study, a comparative analysis was carried out between the most common A222V mutation, a prevalent E429A mutation, and a less prevalent and less deleterious R594Q mutation. To predict structural rearrangements upon mutation, we proposed a computational pipeline using in silico prediction tools, molecular docking, and molecular dynamics simulation analysis. Since the association of flavin adenine dinucleotide (FAD) is important for the functioning of the protein, binding analysis between protein and the coenzyme was performed. This would enable us to understand the interference level of each mutation over FAD-binding activity. Consequently, we found that two mutations (A222V and E429A) showed lesser binding activity and structural deviations when compared to the native molecule and mutant R594Q. Comparatively, higher structural changes were observed with A222V mutant complex in comparison to other mutant complexes. Computational studies like this could render better insights into the structural changes in the protein and their relationship with the disease condition.

Randomized multicenter investigation of folate plus vitamin B12 supplementation in schizophrenia

IMPORTANCE

More effective treatments are needed for negative symptoms of schizophrenia, which are typically chronic, disabling, and costly. Negative symptoms have previously been associated with reduced blood folate levels, especially among patients with low-functioning variants in genes that regulate folate metabolism, suggesting the potential utility of folate supplementation.

OBJECTIVES

To determine whether folic acid plus vitamin B12 supplementation reduces negative symptoms of schizophrenia and whether functional variants in folate-related genes influence treatment response.

DESIGN

Parallel-group, randomized, double-blind, placebo-controlled clinical trial of 16 weeks of treatment with 2 mg of folic acid and 400 μg of vitamin B12.

SETTING

Three community mental health centers affiliated with academic medical centers in the United States.

PARTICIPANTS

Outpatients with chronic schizophrenia who were psychiatrically stable but displayed persistent symptoms despite antipsychotic treatment. Eligible patients were 18 to 68 years old, were treated with an antipsychotic agent for 6 months or more at a stable dose for 6 weeks or more, and scored 60 or more on the Positive and Negative Syndrome Scale.

INTERVENTION

One hundred forty subjects were randomized to receive daily oral folic acid plus vitamin B12 or placebo.

MAIN OUTCOME MEASURES

Change in negative symptoms (Scale for the Assessment of Negative Symptoms [SANS]), as well as positive and total symptoms (Positive and Negative Syndrome Scale).

RESULTS

Folate plus vitamin B12 improved negative symptoms significantly compared with placebo (group difference, -0.33 change in SANS score per week; 95% CI, -0.62 to -0.05) when genotype was taken into account but not when genotype was excluded. An interaction of the 484C>T variant of FOLH1 (rs202676) with treatment was observed (P = .02), where only patients homozygous for the 484T allele demonstrated significantly greater benefit with active treatment (-0.59 change in SANS score per week; 95% CI, -0.99 to -0.18). In parallel, we observed an inverse relationship between red blood cell folate concentration at baseline and 484C allele load (P = .03), which persisted until 8 weeks of treatment. Change in positive and total symptoms did not differ between treatment groups.

CONCLUSIONS

Folate plus vitamin B12 supplementation can improve negative symptoms of schizophrenia, but treatment response is influenced by genetic variation in folate absorption. These findings support a personalized medicine approach for the treatment of negative symptoms.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00611806.

Association of MTHFR C677T polymorphism with schizophrenia and its effect on episodic memory and gray matter density in patients

Growing evidence suggests that the methylenetetrahydrofolate reductase (MTHFR) may play a role in the pathogenesis of schizophrenia. Recent studies suggested that the MTHFR 677T, as a risk allele, has an impact on brain activation and memory function in schizophrenia patients. To confirm further the association between this functional polymorphism and schizophrenia, we detected genotypes of MTHFR C677T polymorphism in 1002 schizophrenic patients and 1036 controls of Chinese Han population, by using direct DNA sequencing method. To explore further effects of MTHFR C677T polymorphism on memory and brain function in schizophrenia, 33 schizophrenia patients and 29 healthy participants were selected from above samples to be assessed with MRI scanning and episodic memory (EM) examination. The case-control association study results showed that the MTHFR C677T was associated with schizophrenia (χ(2)=14.11, P=1.74 × 10(-4), OR=0.79; 95% CI=0.70-0.89). We also found that the MTHFR 677T allele had a load-dependent effect on EM in schizophrenic patients, but not in healthy control participants. Further analysis on gray matter density (GMD) revealed significant diagnostic effects in bilateral frontal cortices, bilateral insula, left medial temporal cortex and bilateral occipital cortices, effects of MTHFR genotype in the right insula, right inferior frontal gyrus, right rolandic opercula, right parahippocampal gyrus and right medial temporal pole, and effects of genotype-diagnosis interaction in the right temporal gyrus. Our findings suggested that the MTHFR 677T allele might have effect on risk of schizophrenia, memory impairment and GMD changes in patients.

Glutamate carboxypeptidase II and folate deficiencies result in reciprocal protection against cognitive and social deficits in mice: implications for neurodevelopmental disorders

Interactions between genetic and environmental risk factors underlie a number of neuropsychiatric disorders, including schizophrenia (SZ) and autism (AD). Due to the complexity and multitude of the genetic and environmental factors attributed to these disorders, recent research strategies focus on elucidating the common molecular pathways through which these multiple risk factors may function. In this study, we examine the combined effects of a haplo-insufficiency of glutamate carboxypeptidase II (GCPII) and dietary folic acid deficiency. In addition to serving as a neuropeptidase, GCPII catalyzes the absorption of folate. GCPII and folate depletion interact within the one-carbon metabolic pathway and/or of modulate the glutamatergic system. Four groups of mice were tested: wild-type, GCPII hypomorphs, and wild-types and GCPII hypomorphs both fed a folate deficient diet. Due to sex differences in the prevalence of SZ and AD, both male and female mice were assessed on a number of behavioral tasks including locomotor activity, rotorod, social interaction, prepulse inhibition, and spatial memory. Wild-type mice of both sexes fed a folic acid deficient diet showed motor coordination impairments and cognitive deficits, while social interactions were decreased only in males. GCPII mutant mice of both sexes also exhibited reduced social propensities. In contrast, all folate-depleted GCPII hypomorphs performed similarly to untreated wild-type mice, suggesting that reduced GCPII expression and folate deficiency are mutually protective. Analyses of folate and neurometabolite levels associated with glutamatergic function suggest several potential mechanisms through which GCPII and folate may be interacting to create this protective effect.

Proposed remedies for some developmental disorders

Developmental disorders (DDs) are important leading cause of disability in developed countries and also in the United States. DDs are a group of individual conditions that result from abnormal nervous system development and cause altered function. They can begin at any time from prenatal to 22 years of age and the disability usually presents itself throughout a person's life time. Down syndrome, autism, neural tube defects, schizophrenia, cretinism, and attention-deficit hyperactivity disorder are among the most common DDs that currently plague numerous countries and have varying incidence rates. Their occurrence may be partially attributable to the lack of certain dietary nutrients. Notably, essential vitamins, minerals, and ω-3 fatty acids are often deficient in the general population of America and developed countries and are exceptionally deficient in patients suffering from mental disorders. Typically, most of these disorders are treated with prescription drugs, but many of these drugs cause unwanted side effects. Therefore, psychiatrists recommend alternative or complementary nutritional remedies to overcome the adverse effects of those drugs. Studies have shown that daily supplements of vital nutrients, such as that contain amino acids, often effectively reduce symptoms of the patients, because they are converted into neurotransmitters that alleviate depression and other mental disorders. The aim of this article is to discuss the role of dietary imbalances in the incidence of DD and to emphasize which dietary supplements can aid in the treatment of the above-mentioned DD.

A systematic meta-review grading the evidence for non-genetic risk factors and putative antecedents of schizophrenia

INTRODUCTION

Identifying the relative strength of evidence associated with non-genetic risk factors and putative antecedents of schizophrenia will guide research and may inform the design of early detection and intervention strategies.

AIMS

To present and quality assess current evidence for non-genetic risk factors and putative antecedents derived from well-conducted systematic reviews that report pooled data.

METHOD

Medline, Embase, CINAHL, Current Contents, and PsycINFO databases were searched systematically, and supplemented by hand searching. Review reporting quality was assessed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist, review methodology was assessed using the Assessment of Multiple Systematic Reviews (AMSTAR) checklist, and evidence quality was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

RESULTS

Twenty-four reviews met inclusion criteria. The risk factors with the highest quality evidence, reporting medium effect sizes, were advanced paternal age, obstetric complications, and cannabis use. The strongest evidence among the putative antecedents was identified for motor dysfunction and low IQ.

CONCLUSIONS

More research is required that applies sound methodological practices, taking into consideration specificity for schizophrenia and possible confounding factors, to robustly identify the non-genetic risk factors and putative antecedents of schizophrenia.

The effect of folic acid on ovine fetuses in utero during late gestation

To investigate whether folic acid would have toxic effects on fetal cardiac, hepatic, and renal functions, this was the first in utero fetal study testing acute effects of folic acid at the last third of gestation. Folic acid (5 mg/day) or 0.9% saline as the control was intragastricly administrated into pregnant ewes. Both maternal and fetal blood were analyzed for pH, PO(2), PCO(2), SO(2)%, hemoglobin, hematocrit, glucose, lactic acid, osmolality, Na(+), and K(+) concentrations. Maternal and fetal cardiovascular functions were assessed by examining cardiac enzymes and cardiovascular responses in vivo. Fetal hepatic and renal functions were examined by analysis of biochemistry index and renal excretion. Folic acid did not alter the blood values in both ewes and fetuses. Cardiac enzyme activities remained unchanged, and no alteration in cardiovascular responses was observed. Folic acid did not affect fetal urine volume, urine electrolytes, and osmolality. Enzyme activities related to hepatic and renal functions were not changed. In addition, maternal application of folic acid had no effect on maternal and fetal lipid profile. The results showed that folic acid used (5 mg/day) during the last third of gestation did not cause biochemical changes related to cardiac, hepatic, and renal functions in both maternal and fetal sheep, providing new information for use of folic acid during late pregnancy.

Genomic and epigenomic instability, fragile sites, schizophrenia and autism

Increasing evidence links genomic and epigenomic instability, including multiple fragile sites regions to neuropsychiatric diseases including schizophrenia and autism. Cancer is the only other disease associated with multiple fragile site regions, and genome and epigenomic instability is a characteristic of cancer. Research on cancer is far more advanced than research on neuropsychiatric disease; hence, insight into neuropsychiatric disease may be derived from cancer research results. Towards this end, this article will review the evidence linking schizophrenia and other neuropsychiatric diseases (especially autism) to genomic and epigenomic instability, and fragile sites. The results of studies on genetic, epigenetic and environmental components of schizophrenia and autism point to the importance of the folate-methionine-transulfuration metabolic hub that is diseases also perturbed in cancer. The idea that the folate-methionine-transulfuration hub is important in neuropsychiatric is exciting because this hub present novel targets for drug development, suggests some drugs used in cancer may be useful in neuropsychiatric disease, and raises the possibility that nutrition interventions may influence the severity, presentation, or dynamics of disease.

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.

Homocysteine in pregnancy

The aim of this review is to evaluate the evidence for and against fasting plasma total homocysteine (tHcy) as a biomarker/risk factor of impaired reproductive function before and during pregnancy. Apart from nutritional and lifestyle factors, tHcy is also influenced by physiological factors specific to pregnancy such as hemodilution, increased glomerular filtration rate, and endocrinological changes. These lead to a considerable reduction under normal circumstances in tHcy by midpregnancy. Stimulating excess endogenous homocysteine production before and during pregnancy in animal experiments and adding exogenous homocysteine to cell cultures result in the impairment of reproductive and developmental processes from preconception throughout pregnancy and during subsequent development of the offspring. Different studies have confirmed that elevated tHcy is a risk factor for subfertility, congenital developmental defects, preeclampsia, and intrauterine growth retardation. There is conflicting evidence that elevated tHcy is a risk factor for miscarriage, gestational diabetes, premature rupture of the membranes, placental abruption, and offspring with Down syndrome. Prospective, sufficiently powered, studies from preconception/early pregnancy are required to determine whether tHcy is a risk factor for these pregnancy complications.

The environment and susceptibility to schizophrenia

In the present article the putative role of environmental factors in schizophrenia is reviewed and synthesized. Accumulating evidence from recent studies suggests that environmental exposures may play a more significant role in the etiopathogenesis of this disorder than previously thought. This expanding knowledge base is largely a consequence of refinements in the methodology of epidemiologic studies, including birth cohort investigations, and in preclinical research that has been inspired by the evolving literature on animal models of environmental exposures. This paper is divided into four sections. In the first, the descriptive epidemiology of schizophrenia is reviewed. This includes general studies on incidence, prevalence, and differences in these measures by urban-rural, neighborhood, migrant, and season of birth status, as well as time trends. In the second section, we discuss the contribution of environmental risk factors acting during fetal and perinatal life; these include infections [e.g. rubella, influenza, Toxoplasma gondii (T. gondii), herpes simplex virus type 2 (HSV-2)], nutritional deficiencies (e.g., famine, folic acid, iron, vitamin D), paternal age, fetal/neonatal hypoxic and other obstetric insults and complications, maternal stress and other exposures [e.g. lead, rhesus (Rh) incompatibility, maternal stress]. Other putative neurodevelopmental determinants, including cannabis, socioeconomic status, trauma, and infections during childhood and adolescence are also covered. In the third section, these findings are synthesized and their implications for prevention and uncovering biological mechanisms, including oxidative stress, apoptosis, and inflammation, are discussed. Animal models, including maternal immune activation, have yielded evidence suggesting that these exposures cause brain and behavioral phenotypes that are analogous to findings observed in patients with schizophrenia. In the final section, future studies including new, larger, and more rigorous epidemiologic investigations, and research on translational and clinical neuroscience, gene-environment interactions, epigenetics, developmental trajectories and windows of vulnerability, are elaborated upon. These studies are aimed at confirming observed risk factors, identifying new environmental exposures, elucidating developmental mechanisms, and shedding further light on genes and exposures that may not be identified in the absence of these integrated approaches. The study of environmental factors in schizophrenia may have important implications for the identification of causes and prevention of this disorder, and offers the potential to complement, and refine, existing efforts on explanatory neurodevelopmental models.

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.

Methylated spirits: epigenetic hypotheses of psychiatric disorders

Our spirits may be regulated by the methylation of our genes. Methylation, acetylation, and other biochemical processes are the molecular switches for turning genes on and off. There is evidence now that certain behaviors, feelings, and psychiatric symptoms may be modified by turning various genes on or off. If classical genetics is the sequence of DNA that is inherited, then epigenetics is a parallel process determining whether a given gene (ie, a sequence of DNA coding for transcription) is expressed into its RNA or is silenced. Epigenetics is now entering psychiatry with the hypothesis that normal genes as well as risk genes can both contribute to a mental disorder. That is, it has long been hypothesized that when “abnormal” genes with an altered sequence of DNA are inherited as risk genes for a mental illness, these risk genes will make an abnormal gene product in neurons, contributing to inefficient information processing in various brain circuits and creating risk for developing a symptom of a mental illness. Now comes the role of epigenetic actions in mental illnesses.

Effects of maternal hyperhomocysteinemia induced by methionine intake on oxidative stress and apoptosis in pup rat brain

Maternal hyperhomocysteinemia is associated with a number of complications such as preeclampsia syndrome, thromboembolic events, repeated miscarriages, abruptio placentae, in utero fetal death, intrauterine fetal growth restriction and fetal neural tube defects. However, little is known about the mechanism of homocysteine on the degeneration of fetal brain. Thus, our study is aimed to investigate the effects of maternal hyperhomocysteinemia on oxidative stress and apoptosis in pup brain. Hyperhomocysteinemia was induced in female rats by way of administrating methionine dissolved in water at a dose of 1g/kg body weight throughout the pregnancy. After delivery, level of lipid peroxidation (LPO; as malondialdehyde+4-hydroxyalkenals) was determined in various fractions of pub brains. Furthermore, DNA fragmentation, levels of Bcl-2 protein and p53 mRNA expression were determined to evaluate apoptosis. Significant elevation was found in the levels of LPO in subcellular fractions of pup brains delivered from hyperhomocysteinemic mothers. DNA fragmentation, a hallmark of apoptosis was observed in the brain of pups of homocysteine group while significant reduction was seen in the levels of anti-apoptotic Bcl-2 levels. In addition, maternal hyperhomocysteinemia increased cerebral p53 mRNA expression above the control value. As a conclusion, we demonstrate and suggest that the pups of hyperhomocysteinemic mothers have an increased oxidative stress in brain tissues. The increased oxidative stress appears to cause apoptosis and cell death. These results may be significant to understand chronic pathology of the complications of hyperhomocysteinemia and congenital malformations of fetuses.

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.

One-carbon metabolism and schizophrenia: current challenges and future directions

Schizophrenia is a heterogeneous disease generally considered to result from a combination of heritable and environmental factors. Although its pathophysiology has not been fully determined, biological studies support the involvement of several possible components including altered DNA methylation, abnormal glutamatergic transmission, altered mitochondrial function, folate deficiency and high maternal homocysteine levels. Although these factors have been explored separately, they all involve one-carbon (C1) metabolism. Furthermore, C1 metabolism is well positioned to integrate gene-environment interactions by influencing epigenetic regulation. Here, we discuss the potential roles of C1 metabolism in the pathophysiology of schizophrenia. Understanding the contribution of these mechanisms could yield new therapeutic approaches aiming to counteract disease onset or progression.

Clair D, He L. Prenatal malnutrition and adult schizophrenia: further evidence from the 1959-1961 Chinese famine

OBJECTIVE

Evidence from the 1944-1995 Dutch Hunger Winter and the 1959-1961 Chinese famines suggests that those conceived or in early gestation during famines, have a 2-fold increased risk of developing schizophrenia in adult life. We tested the hypothesis in a second Chinese population and also determined whether risk differed between urban and rural areas.

METHOD

The risk of schizophrenia was examined in Liuzhou prefecture of Guangxi autonomous region. Rates were compared among those conceived before, during, and after the famine years. Based on the decline in birth rates, we predicted that those born in 1960 and 1961 would have been exposed to the famine during conception or early gestation. All psychiatric case records in Liuzhou psychiatric hospital for the years 1971 through 2001 were examined and clinical/sociodemographic data extracted by psychiatrists blind to exposure status. Data on births and deaths in the famine years were also available, and cumulative mortality was estimated from later demographic surveys. Evidence of famine was verified, and results were adjusted for mortality. Relative risks (RRs) for schizophrenia were calculated for the region as a whole and for urban and rural areas separately.

RESULTS

Mortality-adjusted RR for schizophrenia was 1.5 (1960) and 2.05 (1961), respectively. However, the effect was exclusively from the rural areas RR = 1.68 (1960) and RR = 2.25 (1961).

CONCLUSIONS

We observe a 2-fold increased risk of schizophrenia among those conceived or in early gestation at the height of famine with risk related to severity of famine conditions.

Genomic imprinting in the development and evolution of psychotic spectrum conditions

I review and evaluate genetic and genomic evidence salient to the hypothesis that the development and evolution of psychotic spectrum conditions have been mediated in part by alterations of imprinted genes expressed in the brain. Evidence from the genetics and genomics of schizophrenia, bipolar disorder, major depression, Prader-Willi syndrome, Klinefelter syndrome, and other neurogenetic conditions support the hypothesis that the etiologies of psychotic spectrum conditions commonly involve genetic and epigenetic imbalances in the effects of imprinted genes, with a bias towards increased relative effects from imprinted genes with maternal expression or other genes favouring maternal interests. By contrast, autistic spectrum conditions, including Kanner autism, Asperger syndrome, Rett syndrome, Turner syndrome, Angelman syndrome, and Beckwith-Wiedemann syndrome, commonly engender increased relative effects from paternally expressed imprinted genes, or reduced effects from genes favouring maternal interests. Imprinted-gene effects on the etiologies of autistic and psychotic spectrum conditions parallel the diametric effects of imprinted genes in placental and foetal development, in that psychotic spectrum conditions tend to be associated with undergrowth and relatively-slow brain development, whereas some autistic spectrum conditions involve brain and body overgrowth, especially in foetal development and early childhood. An important role for imprinted genes in the etiologies of psychotic and autistic spectrum conditions is consistent with neurodevelopmental models of these disorders, and with predictions from the conflict theory of genomic imprinting.

Effect of the methylenetetrahydrofolate reductase gene polymorphisms on homocysteine, folate and vitamin B12 in patients with bipolar disorder and relatives

We investigated the effect of polymorphic variants of c.1298A>C (Glu429Ala) and c.677C>T (Ala222Val) in methylenetetrahydrofolate (MTHFR) gene on the total homocysteine (tHcy), folate and B12 levels in patients with bipolar disorder, first-degree relatives of patients, and controls. The c.677C>T and c.1298A>C polymorphisms in MTHFR were determined by polymerase chain reaction-restriction fragment length polymorphism in 197 bipolar patients, 278 relatives and 238 controls. tHcy and folate and vitamin B12 levels were measured by Fluorescence Polarization Immunoassay and Electrochemiluminescence, respectively. The tHcy was significantly increased in patients and relatives. In contrast, folate and B12 were significantly lower in patients and relatives. Gender was not considered as a significant determinant in the multivariate analysis. Genotypes of c.1298A>C and c.677C>T were correlated with tHcy, folate and B12. Patients and relatives carrying TT and/or AA and AC genotypes had elevated tHcy and reduced folate and B12 levels. High tHcy but low folate and vitamin B12 levels may be a risk factor for development of bipolar disorder.

Effects of Folate and Vitamin B12 Deficiencies During Pregnancy on Fetal, Infant, and Child Development

The importance of folate in reproduction can be appreciated by considering that the existence of the vitamin was first suspected from efforts to explain a potentially fatal megaloblastic anemia in young pregnant women in India. Today, low maternal folate status during pregnancy and lactation remains a significant cause of maternal morbidity in some communities. The folate status of the neonate tends to be protected at the expense of maternal stores; nevertheless, there is mounting evidence that inadequate maternal folate status during pregnancy may lead to low infant birthweight, thereby conferring risk of developmental and long-term adverse health outcomes. Moreover, folate-related anemia during childhood and adolescence might predispose children to further infections and disease. The role of folic acid in prevention of neural tube defects (NTD) is now established, and several studies suggest that this protection may extend to some other birth defects. In terms of maternal health, clinical vitamin B12 deficiency may be a cause of infertility or recurrent spontaneous abortion. Starting pregnancy with an inadequate vitamin B12 status may increase risk of birth defects such as NTD, and may contribute to preterm delivery, although this needs further evaluation. Furthermore, inadequate vitamin B12 status in the mother may lead to frank deficiency in the infant if sufficient fetal stores of vitamin B12 are not laid down during pregnancy or are not available in breastmilk. However, the implications of starting pregnancy and lactation with low vitamin B12 status have not been sufficiently researched.

Prevention inherent in services for women with schizophrenia

OBJECTIVE

Effective care to women with serious mental illness provides an opportunity for prevention of mental health problems in their offspring. The objective of this study is to outline the preventive possibilities of a service targeted to women with schizophrenia.

METHOD

An analysis of recently published literature on women suffering from schizophrenia, focusing on intervention.

RESULTS

Genetic counselling, prenatal care, prevention of obstetrical complications, substance abuse reduction, appropriate antipsychotic treatment, parenting support, safety issues, quality of life, ethics, cultural competence, and advocacy are components of a comprehensive service to women with schizophrenia.

CONCLUSIONS

These components improve maternal health and, by also ensuring fetal and neonatal health, are potentially preventive against schizophrenia in the second generation.

Associations of blood homocysteine concentrations in Arab schizophrenic patients

BACKGROUND

This study aimed to evaluate the blood homocysteine concentration in Arab patients with schizophrenia and assess its associations with clinical phenotypes of the disease.

SUBJECTS AND METHODS

Two age-matched groups of subjects were studied: (1) Healthy Controls, HC, n=165; (2) patients with schizophrenia, SZ: n=207. Each subject was evaluated with a standard questionnaire for age at disease onset, family history, disease severity and outcome. Plasma homocysteine levels (Hcys) were measured by immunoassay and serum levels of other biochemical parameters were measured by routine Autoanalyzer techniques.

RESULTS AND DISCUSSION

Group HC was heavier (body mass index, BMI) while SZ had greater waist-hip ratio (WHR) and plasma Hcys levels. In SZ, there were significant correlations between Hcys and BMI, triglycerides and HDL. Hcys levels in SZ were highest in the younger male patients.

CONCLUSION

Schizophrenic patients have increased blood Hcys levels which correlate with components of the metabolic syndrome. Hcys levels were highest in the younger male patients and were not influenced by prognostic features of the disease.

Promoter analysis of human glutamate carboxypeptidase II

The expression of glutamate carboxypeptidase II (GCP II) is reduced in selective brain regions in schizophrenic patients. To investigate transcriptional mechanisms regulating the human GCP II gene, a 3460 bp DNA fragment comprised of the proximal 3228 bp of 5' untranscribed sequence and first 232 bp of 5' UTR portion of this gene was cloned into the mammalian luciferase reporter gene vector pGL3-Basic. Transfection assays in human astrocyte-derived SVG and human prostate tumor-derived LNCaP cells demonstrated that constructs with 3460, 1590 and 761 bp portions of 5' region of human GCP II gene were able to drive the luciferase reporter gene. Additional deletion constructs showed that in the SVG cell line, constructs with 511 and 411 bp of GCP II gene fragments yielded highest transcriptional activity, with declining activity upon further removal of 5' sequences. 15 bp of the promoter 5' to a 225 bp GCP II fragment were essential for luciferase expression. Thus, in the SVG cells, the proximal 240 bp of the human GCP II promoter (232 bp of the 5' UTR and 8 bp of 5' untranscribed sequences) may represent the core promoter. Further, while a LyF-1 site lies within and overlaps a transcription start site in the 15 bp sequence, site-directed mutagenesis shows that LyF-1 is not the transcription initiator for the "TATA and CAAT" box lacking GCP II gene in the SVG cells. Finally, pattern differences in GCP II gene promoter expression in SVG and LNCaP cells suggest that sequences beyond 240 bp may be important for tissue-specific GCP II expression.

The role of one-carbon metabolism in schizophrenia and depression

OBJECTIVE

Physicians often check folate and cobalamin levels in patients with schizophrenia and depression. The reasons for this practice are reviewed, as well as implications for treatment.

METHOD

The physiology of the one-carbon cycle, involving folate, cobalamin, homocysteine, S-adenosyl-methionine, and methylene tetrahydrofolate reductase (MTHFR) is first reviewed, and then the particular contributions of folate and B12 are reviewed. PubMed was searched for studies of the association between folate, cobalamin, homocysteine, and MTHFR polymorphisms and schizophrenia and depression.

RESULTS

The recent key studies from the large literature addressing these topics are summarized. Treatment implications are discussed.

CONCLUSION

It is important to check folate and B12 levels in certain situations, such as alcoholism, malnutrition, malabsorption, and the concurrent use of some medications. Checking homocysteine and methylmalonic levels might be useful. With respect to treatment, folate and cobalamin deficiencies should be corrected. Cobalamin supplementation is probably not helpful. Folate supplementation is indicated in pregnancy but may exacerbate the effects of cobalamin deficiency. SAMe may prove to be a useful antidepressant. In the future, screening for MTHFR polymorphisms might be useful.

Genetic liability to schizophrenia in Oceanic Palau: a search in the affected and maternal generation

While liability to schizophrenia (Scz) is due to genetic and environmental factors, specific factors are largely unknown. We postulate a two-hit model for Scz, in which initial liability is generated during fetal brain development: this "hit" is precipitated by environmental stressors biologically interacting with maternal genetic vulnerability to the stress. Additional liability to Scz is generated by individual genetic vulnerability. To evaluate these putative levels of vulnerability, we search in the genome of both affected individuals and their mothers for variation that differs, statistically, from that in the general population. For parental analyses, mothers were treated as "affected," rather than their offspring, and the fathers were treated as "controls". We used a sample from the Palauan population: 175 individuals diagnosed with Scz, broadly defined; 87 mothers and 45 fathers of affected individuals. Pedigree and diagnostic data were available on 2,953 living and deceased subjects. DNA from 553 individuals was genotyped for short tandem repeats (STR) spaced approximately every 10 cM across the genome. We tested for association between affection status and STR alleles; such an approach was reasonable, despite the widely spaced markers, because this population has far-ranging linkage disequilibrium (LD). Results for the truly affected individuals were modest, whereas results from the maternal generation were promising. For a recessive model and a test for excess allele matching across mothers, significant findings occurred for D20S481, D10S1221, D6S1021, D13S317, and D18S976. Regions in which at least two adjacent markers produced substantial association statistics include 2p12-11.2, 2q24.1-32.1, 6q12-14.1, 10q23.2-24.21, 12q23.2-24.21 and 17q23.2-23.3.

Schizophrenia: a common disease caused by multiple rare alleles

Schizophrenia is widely held to stem from the combined effects of multiple common polymorphisms, each with a small impact on disease risk. We suggest an alternative view: that schizophrenia is highly heterogeneous genetically and that many predisposing mutations are highly penetrant and individually rare, even specific to single cases or families. This "common disease--rare alleles" hypothesis is supported by recent findings in human genomics and by allelic and locus heterogeneity for other complex traits. We review the implications of this model for gene discovery research in schizophrenia.

Folate, vitamin B12 and total homocysteine levels in neonates from Brazil

OBJECTIVE

To determine folates, vitamin B12 and total homocysteine levels among neonates from mothers of low or high socioeconomic status.

DESIGN

We carried out a cross-sectional transversal study comprising 143 neonates from two maternity hospitals in the city of Salvador, Northeast of Brazil. Cord blood samples were obtained at the time of delivery from newborns from low (group 1, n=77) or high (group 2, n=66) socioeconomic status. The vitamin B12 and folates were analyzed by electrochemiluminescence immunoassay and by a competitive test using a natural folate-binding protein (FBP), respectively. Total homocyteine levels were measured by fluorescence polarization immunoassay. Maternal environmental risk factors for pregnancy complications were obtained from all mothers.

RESULTS

Only 2% of women from group 1 received prenatal care/vitamin supplementation, whereas almost all mothers from group 2 (96%) were properly followed. Anemia and/or infections pre- or during pregnancy was more prevalent among mothers of babies from group 1. Folate levels among newborns from group 1 and 2 were 7.38+/-2.71 and 8.83+/-4.06 ng/ml, respectively. No difference in the vitamin B12 levels was determined between groups. In addition, tHcy serum levels were higher among newborns from group 1 compared to those from group 2 (8.54+/-4.06 vs 6.35+/-1.33 micromol/l, respectively; P=0.005).

CONCLUSION

These results demonstrate that unprivileged young woman has limited accesses to prenatal care, present high-risk factors that hamper both maternal and newborn health. Maternal and newborn health status could be improved by simply reinforcing the use of folate-enriched diet. The work presented illustrates the challenges that developing countries have to face in order to provide preventive adequate health care to the population at large.

Hypomethylation of MB-COMT promoter is a major risk factor for schizophrenia and bipolar disorder

The variability in phenotypic presentations and the lack of consistency of genetic associations in mental illnesses remain a major challenge in molecular psychiatry. Recently, it has become increasingly clear that altered promoter DNA methylation could play a critical role in mediating differential regulation of genes and in facilitating short-term adaptation in response to the environment. Here, we report the investigation of the differential activity of membrane-bound catechol-O-methyltransferase (MB-COMT) due to altered promoter methylation and the nature of the contribution of COMT Val158Met polymorphism as risk factors for schizophrenia and bipolar disorder by analyzing 115 post-mortem brain samples from the frontal lobe. These studies are the first to reveal that the MB-COMT promoter DNA is frequently hypomethylated in schizophrenia and bipolar disorder patients, compared with the controls (methylation rate: 26 and 29 versus 60%; P=0.004 and 0.008, respectively), particularly in the left frontal lobes (methylation rate: 29 and 30 versus 81%; P=0.003 and 0.002, respectively). Quantitative gene-expression analyses showed a corresponding increase in transcript levels of MB-COMT in schizophrenia and bipolar disorder patients compared with the controls (P=0.02) with an accompanying inverse correlation between MB-COMT and DRD1 expression. Furthermore, there was a tendency for the enrichment of the Val allele of the COMT Val158Met polymorphism with MB-COMT hypomethylation in the patients. These findings suggest that MB-COMT over-expression due to promoter hypomethylation and/or hyperactive allele of COMT may increase dopamine degradation in the frontal lobe providing a molecular basis for the shared symptoms of schizophrenia and bipolar disorder.

Cognitive deficits in the families of patients with schizophrenia

PURPOSE OF REVIEW

Studies of first-degree relatives of patients with schizophrenia over the past 25 years have reported a number of cognitive deficits, primarily in the domains of memory and executive function. Nevertheless, due to a number of methodological issues, such as including different types of relatives and not controlling for possible psychopathology, it is not yet clear that these findings can fully support a conclusion of heritability of cognitive dysfunction associated with a schizophrenia genotype.

RECENT FINDINGS

Several recent meta-analyses have shown that the most consistent deficit shown by relatives is impaired performance on 'maintenance plus' frontal-lobe tasks requiring increased effort and higher central executive processing. Studies of multiplex families (multiple diagnoses in one family) also report that family members tend to have more difficulty on executive function tasks. Another interesting trend is research on subgroups of patients and relatives displaying distinct cognitive syndromes, particularly a subgroup with a generalized cognitive deficit.

SUMMARY

As methodological designs improve, this field of study holds promise not only for understanding the neurobiological mechanisms of schizophrenia and the associated cognitive deficits, but also for possibly describing endophenotypes that may lead to identifying at-risk patients and relatives.

A classification of sociomedical health indicators: perspectives for health administrators and health planners

The conceptualization and operationalization of measures of health status are considered. Health indicators are conceived as a subset of social indicators, and therefore, as any social indicator, they are viewed as derivative from social issues. The interrelationships of different frames of reference for defining and measuring health that have accompained three distinct health problem patterns in the United States are viewed from a developmental perspective. Mortality and morbidity rates, the traditional health indicators, by themselves no longer serve to assess health status in developed nations. Their deficiencies as indicators serve as background for a classification schema for sociomedical health status indicators that relates health definition frames of reference, measures of health status, and health problems. The role of a group of health indicators-sociomedical heath indicators-in the current formulation of health status measures is assessed.