The effects of olanzapine on genome-wide DNA methylation in the hippocampus and cerebellum

Olanzapine's effects on hypothalamic transcriptomics and kinase activity

Olanzapine is a second-generation antipsychotic that disrupts metabolism and is associated with an increased risk of type 2 diabetes. The hypothalamus is a key region in the control of whole-body metabolic homeostasis. The objective of the current study was to determine how acute peripheral olanzapine administration affects transcription and serine/threonine kinase activity in the hypothalamus. Hypothalamus samples from rats were collected following the pancreatic euglycemic clamp, thereby allowing us to study endpoints under steady state conditions for plasma glucose and insulin. Olanzapine stimulated pathways associated with inflammation, but diminished pathways associated with the capacity to combat endoplasmic reticulum stress and G protein-coupled receptor activity. These pathways represent potential targets to reduce the incidence of type 2 diabetes in patients taking antipsychotics.

Genome-wide DNA methylation analysis in schizophrenia with tardive dyskinesia: a preliminary study

BACKGROUND

Tardive dyskinesia (TD) develops in 20-30% of schizophrenia patients and up to 50% in patients > 50 years old. DNA methylation may play an important role in the development of TD.

OBJECTIVE

DNA methylation analyses in schizophrenia with TD.

METHODS

We conducted a genome-wide DNA methylation analysis in schizophrenia with TD using methylated DNA immunoprecipitation coupled with next-generation sequencing (MeDIP-Seq) in a Chinese sample including five schizophrenia patients with TD and five without TD (NTD), and five healthy controls. The results were expressed as the log2FC, fold change of normalized tags between two groups within the differentially methylated region (DMR). For validation, the pyrosequencing was used to quantify DNA methylation levels of several methylated genes in an independent sample (n = 30).

RESULTS

Through genome-wide MeDIP-Seq analysis, we identified 116 genes that were significantly differentially methylated in promotor regions in comparison of TD group with NTD group including 66 hypermethylated genes (top 4 genes are GABRR1, VANGL2, ZNF534, and ZNF746) and 50 hypomethylated genes (top 4 genes are DERL3, GSTA4, KNCN, and LRRK1). Part of these genes (such as DERL3, DLGAP2, GABRR1, KLRG2, LRRK1, VANGL2, and ZP3) were previously reported to be associated with methylation in schizophrenia. Gene Ontology enrichment and KEGG pathway analyses identified several pathways. So far, we have confirmed the methylation of 3 genes (ARMC6, WDR75, and ZP3) in schizophrenia with TD using pyrosequencing.

CONCLUSIONS

This study identified number of methylated genes and pathways for TD and will provide potential biomarkers for TD and serve as a resource for replication in other populations.

Building better brains: the pleiotropic function of neurotrophic factors in postnatal cerebellar development

The cerebellum is a multifunctional brain region that controls diverse motor and non-motor behaviors. As a result, impairments in the cerebellar architecture and circuitry lead to a vast array of neuropsychiatric and neurodevelopmental disorders. Neurotrophins and neurotrophic growth factors play essential roles in the development as well as maintenance of the central and peripheral nervous system which is crucial for normal brain function. Their timely expression throughout embryonic and postnatal stages is important for promoting growth and survival of both neurons and glial cells. During postnatal development, the cerebellum undergoes changes in its cellular organization, which is regulated by a variety of molecular factors, including neurotrophic factors. Studies have shown that these factors and their receptors promote proper formation of the cerebellar cytoarchitecture as well as maintenance of the cerebellar circuits. In this review, we will summarize what is known on the neurotrophic factors' role in cerebellar postnatal development and how their dysregulation assists in developing various neurological disorders. Understanding the expression patterns and signaling mechanisms of these factors and their receptors is crucial for elucidating their function within the cerebellum and for developing therapeutic strategies for cerebellar-related disorders.

Risperidone-induced changes in DNA methylation in peripheral blood from first-episode schizophrenia patients parallel changes in neuroimaging and cognitive phenotypes

BACKGROUND

Second generation antipsychotics such as risperidone are first-line pharmacotherapy treatment choices for schizophrenia. However, our ability to reliably predict and monitor treatment reaction is impeded by the lack of relevant biomarkers. As a biomarker for the susceptibility of schizophrenia and clozapine treatment response, DNA methylation (DNAm) has been studied, but the impact of antipsychotics on DNAm has not been explored in drug-naïve patients.

OBJECTIVE

The aim of the present study was to examine changes of DNAm after short-term antipsychotic therapy in first-episode drug-naïve schizophrenia (FES) to identify the beneficial and adverse effect of risperidone on DNAm and their relation to treatment outcome.

METHODS

Thirty-eight never treated schizophrenia patients and 38 demographically matched individuals (healthy controls) were assessed at baseline and at 8-week follow-up with symptom ratings, and cognitive and functional imaging procedures, at which time a blood draw for DNAm studies was performed. During the 8-week period, patients received treatment with risperidone monotherapy. An independent data set was used as replication.

RESULTS

We identified brain related pathways enriched in 4,888 FES-associated CpG sites relative to controls. Risperidone administration in patients altered DNAm in 5,979 CpG sites relative to baseline. Significant group differences in DNAm at follow-up were seen in FES patients at 6,760 CpG sites versus healthy controls. Through comparison of effect size, we found 87.54% out of the risperidone-associated changes in DNAm showed possible beneficial effect, while only 12.46% showed potential adverse effect. There were 580 DNAm sites in which changes shifted methylation levels to be indistinguishable from controls after risperidone treatment. The DNAm changes of some sites that normalized after treatment were correlated with treatment-related changes in symptom severity, spontaneous neurophysiological activity, and cognition. We replicated our results in an independent data set.

CONCLUSION

The normalizing effect of risperidone monotherapy on gene DNAm, and its correlation with clinically relevant phenotypes, indicates that risperidone therapy is associated with DNAm changes that are related to changes in brain physiology, cognition and symptom severity.

Methylome-wide Association Study of Patients with Recent-onset Psychosis

Objective

Dysregulation of gene expression through epigenetic mechanisms may have a vital role in the pathogenesis of schizophrenia (SZ). In this study, we investigated the association of altered methylation patterns with SZ symptoms and early trauma in patients and healthy controls.

Methods

The present study was conducted to identify methylation changes in CpG sites in peripheral blood associated with recent-onset (RO) psychosis using methylome-wide analysis. Lifestyle factors, such as smoking, alcohol, exercise, and diet, were controlled.

Results

We identified 2,912 differentially methylated CpG sites in patients with RO psychosis compared to controls. Most of the genes associated with the top 20 differentially methylated sites had not been reported in previous methylation studies and were involved in apoptosis, autophagy, axonal growth, neuroinflammation, protein folding, etc. The top 15 significantly enriched Kyoto Encyclopedia of Genes and Genomes pathways included the oxytocin signaling pathway, long-term depression pathway, axon guidance, endometrial cancer, long-term potentiation, mitogen-activated protein kinase signaling pathway, and glutamatergic pathway, among others. In the patient group, significant associations of novel methylated genes with early trauma and psychopathology were observed.

Conclusion

Our results suggest an association of differential DNA methylation with the pathophysiology of psychosis and early trauma. Blood DNA methylation signatures show promise as biomarkers of future psychosis.

Epigenetic insights in the diagnosis, prognosis, and treatment selection in CRC, an updated review

BACKGROUND/AIM

The gradual accumulation of genetic and epigenetic alterations can lead to the development of colorectal cancer. In the last decade much research has been done to discover how methylation as an epigenetic alteration leads to carcinogenesis. While Methylation is a biological process, it can influence gene expression by affecting the promoter activity. This article reviews the role of methylation in critical pathways in CRC.

METHODS

In this study using appropriate keywords, all research and review articles related to the role of methylation on different cancers were collected and analyzed. Also, existing information on methylation detection methods and therapeutic sensitivity or resistance due to DNA methylation were reviewed.

RESULTS

The results of this survey revealed that while Methylation is a biological process, it can influence gene expression by affecting the promoter activity. Promoter methylation is associated with up or downregulation of genes involved in critical pathways, including cell cycle, DNA repair, and cell adherence. Hence promoter methylation can be used as a molecular tool for early diagnosis, improving treatment, and predicting treatment resistance.

CONCLUSION

Current knowledge on potential methylation biomarkers for diagnosis and prognoses of CRC has also been discussed. Our survey proposes that a multi-biomarker panel is more efficient than a single biomarker in the early diagnosis of CRC.

Risperidone Induced DNA Methylation Changes in Dopamine Receptor and Stathmin Genes in Mice Exposed to Social Defeat Stress

Objective

Methods

Results

Conclusion

Present and future antipsychotic drugs: a systematic review of the putative mechanisms of action for efficacy and a critical appraisal under a translational perspective

Antipsychotics represent the mainstay of schizophrenia pharmacological therapy, and their role has been expanded in the last years to mood disorders treatment. Although introduced in 1952, many years of research were required before an accurate picture of how antipsychotics work began to emerge. Despite the well-recognized characterization of antipsychotics in typical and atypical based on their liability to induce motor adverse events, their main action at dopamine D2R to elicit the "anti-psychotic" effect, as well as the multimodal action at other classes of receptors, their effects on intracellular mechanisms starting with receptor occupancy is still not completely understood. Significant lines of evidence converge on the impact of these compounds on multiple molecular signaling pathways implicated in the regulation of early genes and growth factors, dendritic spine shape, brain inflammation, and immune response, tuning overall the function and architecture of the synapse. Here we present, based on PRISMA approach, a comprehensive and systematic review of the above mechanisms under a translational perspective to disentangle those intracellular actions and signaling that may underline clinically relevant effects and represent potential targets for further innovative strategies in antipsychotic therapy.

Novel Treatment Strategies Targeting Myelin and Oligodendrocyte Dysfunction in Schizophrenia

Oligodendrocytes are the glial cells responsible for the formation of the myelin sheath around axons. During neurodevelopment, oligodendrocytes undergo maturation and differentiation, and later remyelination in adulthood. Abnormalities in these processes have been associated with behavioral and cognitive dysfunctions and the development of various mental illnesses like schizophrenia. Several studies have implicated oligodendrocyte dysfunction and myelin abnormalities in the disorder, together with altered expression of myelin-related genes such as Olig2, CNP, and NRG1. However, the molecular mechanisms subjacent of these alterations remain elusive. Schizophrenia is a severe, chronic psychiatric disorder affecting more than 23 million individuals worldwide and its symptoms usually appear at the beginning of adulthood. Currently, the major therapeutic strategy for schizophrenia relies on the use of antipsychotics. Despite their widespread use, the effects of antipsychotics on glial cells, especially oligodendrocytes, remain unclear. Thus, in this review we highlight the current knowledge regarding oligodendrocyte dysfunction in schizophrenia, compiling data from (epi)genetic studies and up-to-date models to investigate the role of oligodendrocytes in the disorder. In addition, we examined potential targets currently investigated for the improvement of schizophrenia symptoms. Research in this area has been investigating potential beneficial compounds, including the D-amino acids D-aspartate and D-serine, that act as NMDA receptor agonists, modulating the glutamatergic signaling; the antioxidant N-acetylcysteine, a precursor in the synthesis of glutathione, protecting against the redox imbalance; as well as lithium, an inhibitor of glycogen synthase kinase 3β (GSK3β) signaling, contributing to oligodendrocyte survival and functioning. In conclusion, there is strong evidence linking oligodendrocyte dysfunction to the development of schizophrenia. Hence, a better understanding of oligodendrocyte differentiation, as well as the effects of antipsychotic medication in these cells, could have potential implications for understanding the development of schizophrenia and finding new targets for drug development.

Psychotropic drug-induced genetic-epigenetic modulation of CRTC1 gene is associated with early weight gain in a prospective study of psychiatric patients

BACKGROUND

Metabolic side effects induced by psychotropic drugs represent a major health issue in psychiatry. CREB-regulated transcription coactivator 1 (CRTC1) gene plays a major role in the regulation of energy homeostasis and epigenetic mechanisms may explain its association with obesity features previously described in psychiatric patients. This prospective study included 78 patients receiving psychotropic drugs that induce metabolic disturbances, with weight and other metabolic parameters monitored regularly. Methylation levels in 76 CRTC1 probes were assessed before and after 1 month of psychotropic treatment in blood samples.

RESULTS

Significant methylation changes were observed in three CRTC1 CpG sites (i.e., cg07015183, cg12034943, and cg 17006757) in patients with early and important weight gain (i.e., equal or higher than 5% after 1 month; FDR p value = 0.02). Multivariable models showed that methylation decrease in cg12034943 was more important in patients with early weight gain (≥ 5%) than in those who did not gain weight (p = 0.01). Further analyses combining genetic and methylation data showed that cg12034943 was significantly associated with early weight gain in patients carrying the G allele of rs4808844A>G (p = 0.03), a SNP associated with this methylation site (p = 0.03).

CONCLUSIONS

These findings give new insights on psychotropic-induced weight gain and underline the need of future larger prospective epigenetic studies to better understand the complex pathways involved in psychotropic-induced metabolic side effects.

Skeletal muscle DNA methylation modifications and psychopharmacologic treatment in bipolar disorder

Both severe mental illness and atypical antipsychotics have been independently associated with insulin resistance and weight gain. Altered regulation of skeletal muscle DNA methylation may play a role. We aimed to evaluate DNA methylation modifications in human skeletal muscle samples to further understand its potential role in the metabolic burden observed in psychiatric patients and psychopharmacologic treatment. Subjects were included in our study if they had a bipolar diagnosis and were currently treated with a mood stabilizer or atypical antipsychotic. A healthy control group free of psychiatric or physical disease was also included for comparisons. Anthropometric, BMI and hemoglobin A1C (HbA1C%) were measured. Fasting skeletal muscle biopsies were obtained and methylation levels of 5-methycytosine (5-mC), 5-hydroxymethylcytosine (5-hmC) and 5-formylcytosine (5-fC) were measured. Skeletal muscle global methylation of 5-mC and 5-fC were significantly higher in bipolar subjects compared to healthy controls. 5-mC was significantly higher in the AAP group compared to the mood stabilizer group. Significant correlations were observed between 5-fC methylation and HbA1C%. Our findings suggest that psychiatric disease and treatment may influence some methylation measures in the skeletal muscle of patients with bipolar disorder, which may be further influenced by medication treatment.

Analysis of methylation and -141C Ins/Del polymorphisms of the dopamine receptor D2 gene in patients with schizophrenia

The gene for dopamine receptor D2 (DRD2) is associated with schizophrenia (SCZ). Epigenetic changes may be related to SCZ pathology. The -141C Ins/Del polymorphism in DRD2 (rs1799732) is functional and associated with SCZ. Fifty SCZ patients and 50 control subjects were newly recruited and analyzed in addition to 50 previously reported SCZ samples and 50 previously reported control samples. Genomic DNA from peripheral leukocytes was analyzed. We replicated analysis of DNA methylation rates at seven CpG sites (CpG 1-1 to 1-7) and also analyzed five additional sites (CpG 2-1 to 2-5) in the upstream region of DRD2. We also performed genotyping of -141C IIns/Del and analyzed the effects of -141C Ins/Del on methylation of DRD2. Methylation rates were significantly lower in SCZ patients compared to control subjects, respectively. In control subjects, the methylation rates were significantly lower in individuals with the Ins/Ins genotype than in Del allele carriers. We replicated hypomethylation of the DRD2 promoter region in SCZ patients compared to age-matched control subjects. The -141C Ins/Del polymorphism affected the methylation rates in regions of DRD2. Hypomethylation and the -141C Ins/Del polymorphism of DRD2 may be biomarkers for SCZ.

The Effect of Citalopram on Genome-Wide DNA Methylation of Human Cells

Commonly used pharmaceutical drugs might alter the epigenetic state of cells, leading to varying degrees of long-term repercussions to human health. To test this hypothesis, we cultured HEK-293 cells in the presence of 50 μM citalopram, a common antidepressant, for 30 days and performed whole-genome DNA methylation analysis using the NimbleGen Human DNA Methylation 3x720K Promoter Plus CpG Island Array. A total of 626 gene promoters, out of a total of 25,437 queried genes on the array (2.46%), showed significant differential methylation (p < 0.01); among these, 272 were hypomethylated and 354 were hypermethylated in treated versus control. Using Ingenuity Pathway Analysis, we found that the chief gene networks and signaling pathways that are differentially regulated include those involved in nervous system development and function and cellular growth and proliferation. Genes implicated in depression, as well as genetic networks involving nucleic acid metabolism, small molecule biochemistry, and cell cycle regulation were significantly modified. Involvement of upstream regulators such as BDNF, FSH, and NFκB was predicted based on differential methylation of their downstream targets. The study validates our hypothesis that pharmaceutical drugs can have off-target epigenetic effects and reveals affected networks and pathways. We view this study as a first step towards understanding the long-term epigenetic consequences of prescription drugs on human health.

Effects of Antipsychotic Drugs on the Epigenetic Modification of Brain-Derived Neurotrophic Factor Gene Expression in the Hippocampi of Chronic Restraint Stress Rats

Recent studies have shown that antipsychotic drugs have epigenetic effects. However, the effects of antipsychotic drugs on histone modification remain unclear. Therefore, we investigated the effects of antipsychotic drugs on the epigenetic modification of the BDNF gene in the rat hippocampus. Rats were subjected to chronic restraint stress (6 h/d for 21 d) and then were administered with either olanzapine (2 mg/kg) or haloperidol (1 mg/kg). The levels of histone H3 acetylation and MeCP2 binding at BDNF promoter IV were assessed with chromatin immunoprecipitation assays. The mRNA levels of total BDNF with exon IV, HDAC5, DNMT1, and DNMT3a were assessed with a quantitative RT-PCR procedure. Chronic restraint stress resulted in the downregulation of total and exon IV BDNF mRNA levels and a decrease in histone H3 acetylation and an increase in MeCP2 binding at BDNF promoter IV. Furthermore, there were robust increases in the expression of HDAC5 and DNMTs. Olanzapine administration largely prevented these changes. The administration of haloperidol had no effect. These findings suggest that the antipsychotic drug olanzapine induced histone modification of BDNF gene expression in the hippocampus and that these epigenetic alterations may represent one of the mechanisms underlying the actions of antipsychotic drugs.

Understanding the influence of antipsychotic drugs on global methylation events and its relevance in treatment response

Aim: The present study intends to evaluate whether antipsychotic drugs can modulate the host epigenome and if so whether drug-induced epigenetic modulation can explain the heterogeneity in drug response. Methods: Present study was conducted in in vitro cells and significance of these in vitro observations was further evaluated in a clinical setting, between drug responsive and nonresponsive schizophrenia patients. A number of DNA modifications were assessed at global level using 5-methylcytosine, 5-hydroxymethylcytosine and 5-formylcytosine followed by evaluating the expression of epigenetic modifier genes and their crosstalk with miRNAs. Results: In vitro data demonstrated that antipsychotic drugs induce epigenetic response by downregulating miRNA that target DNA methyltransferases, resulting in global hypermethylation. Similar trend was observed in clinical setting too and alterations were markedly associated with drug response rather than disease pathogenesis. Conclusion: Study demonstrates that antipsychotic drugs can influence host methylome and thereby indicating its role in mediating a strong pharmacoepigenomic response.

DNA methylation and antipsychotic treatment mechanisms in schizophrenia: Progress and future directions

Antipsychotic response in schizophrenia is a complex, multifactorial trait influenced by pharmacogenetic factors. With genetic studies thus far providing little biological insight or clinical utility, the field of pharmacoepigenomics has emerged to tackle the so-called "missing heritability" of drug response in disease. Research on psychiatric disorders has only recently started to assess the link between epigenetic alterations and treatment outcomes. DNA methylation, the best characterised epigenetic mechanism to date, is discussed here in the context of schizophrenia and antipsychotic treatment outcomes. The majority of published studies have assessed the influence of antipsychotics on methylation levels in specific neurotransmitter-associated candidate genes or at the genome-wide level. While these studies illustrate the epigenetic modifications associated with antipsychotics, very few have assessed clinical outcomes and the potential of differential DNA methylation profiles as predictors of antipsychotic response. Results from other psychiatric disorder studies, such as depression and bipolar disorder, provide insight into what may be achieved by schizophrenia pharmacoepigenomics. Other aspects that should be addressed in future research include methodological challenges, such as tissue specificity, and the influence of genetic variation on differential methylation patterns.

Systematic Review of Epigenetic Effects of Pharmacological Agents for Bipolar Disorders

Epigenetic effects of medications are an evolving field of medicine, and can change the landscape of drug development. The aim of this paper is to systematically review the literature of the relationship between common medications used for treatment of bipolar disorders and epigenetic modifications. MedLine/PubMed searches were performed based on pre-specified inclusion criteria from inception to November 2017. Six animal and human studies met the inclusion criteria. These studies examined the epigenetic changes in the main classes of medications that are used in bipolar disorders, namely mood stabilizers and antipsychotics. Although these initial studies have small to moderate sample size, they generally suggest an evolving and accumulating evidence of epigenetic changes that are associated with several of the medications that are used in bipolar I and II disorders. In this manuscript, we describe the specific epigenetic changes that are associated with the medications studied. Of the studies reviewed, five of the six studies revealed epigenetic changes associated with the use of mood stabilizers or antipsychotic medications. This review contributes to future research directions. Further understanding of the complexities of the epigenome and the untangling of the effects and contributions of disease states versus medications is crucial for the future of drug design and the development of new therapeutics. Epigenetic therapeutics hold great promise for complex disease treatment and personalized interventions, including psychiatric diseases.

Haloperidol induces pharmacoepigenetic response by modulating miRNA expression, global DNA methylation and expression profiles of methylation maintenance genes and genes involved in neurotransmission in neuronal cells

Introduction

Haloperidol has been extensively used in various psychiatric conditions. It has also been reported to induce severe side effects. We aimed to evaluate whether haloperidol can influence host methylome, and if so what are the possible mechanisms for it in neuronal cells. Impact on host methylome and miRNAs can have wide spread alterations in gene expression, which might possibly help in understanding how haloperidol may impact treatment response or induce side effects.

Methods

SK-N-SH, a neuroblasoma cell line was treated with haloperidol at 10μm concentration for 24 hours and global DNA methylation was evaluated. Methylation at global level is maintained by methylation maintenance machinery and certain miRNAs. Therefore, the expression of methylation maintenance genes and their putative miRNA expression profiles were assessed. These global methylation alterations could result in gene expression changes. Therefore genes expressions for neurotransmitter receptors, regulators, ion channels and transporters were determined. Subsequently, we were also keen to identify a strong candidate miRNA based on biological and in-silico approach which can reflect on the pharmacoepigenetic trait of haloperidol and can also target the altered neuroscience panel of genes used in the study.

Results

Haloperidol induced increase in global DNA methylation which was found to be associated with corresponding increase in expression of various epigenetic modifiers that include DNMT1, DNMT3A, DNMT3B and MBD2. The expression of miR-29b that is known to putatively regulate the global methylation by modulating the expression of epigenetic modifiers was observed to be down regulated by haloperidol. In addition to miR-29b, miR-22 was also found to be downregulated by haloperidol treatment. Both these miRNA are known to putatively target several genes associated with various epigenetic modifiers, pharmacogenes and neurotransmission. Interestingly some of these putative target genes involved in neurotransmission were observed to be upregulated while CHRM2 gene expression was down regulated.

Conclusions

Haloperidol can influence methylation traits thereby inducing a pharmacoepigenomic response, which seems to be regulated by DNMTs and their putative miRNA expression. Increased methylation seems to influence CHRM2 gene expression while microRNA could influence neurotransmission, pharmacogene expression and methylation events. Altered expression of various therapeutically relevant genes and miRNA expression, could account for their role in therapeutic response or side effects.

Genome-wide DNA methylation patterns in coronary heart disease

BACKGROUND

To better understand the molecular mechanisms of atherosclerosis, we conducted a comparative analysis of DNA methylation patterns in right coronary arteries in the area of advanced atherosclerotic plaques (CAP), great saphenous vein (GSV), and internal mammary artery (IMA) of patients affected by coronary heart disease.

METHODS

DNA methylation data (accession number E‑GEOD-62867) were divided into three paired groups: CAP vs. IMA, CAP vs. GSV, and IMA vs. GSV. Differentially methylated genes (DMGs) were extracted to analyze the changes in the DMGs in the three different tissues. The gplots package was used for the clustering and heatmap analysis of DMGs. Subsequently, DMG-related pathways were identified using DAVID (Database for Annotation, Visualization and Integrated Discovery) and transcription factors (TFs) were predicted.

RESULTS

Based on the filtering criterion of p < 0.05, and a mean beta value difference of ≥0.2, there were 252, 373, and 259 DMGs, respectively, in the CAP vs. IMA, CAP vs. GSV, and IMA vs. GSV groups. Interestingly, the S100A10 gene was hypomethylated in CAP compared with IMA and GSV. Clustering and heatmap analyses suggested that DMGs were segregated into two distinct clusters. Hypermethylated genes in CAP as compared with GSV were only involved in the pathway of fat digestion and absorption, while hypomethylated genes in CAP compared with GSV mainly participated in immune response-associated pathways (cytokine-cytokine receptor interaction, MAPK signaling pathway).

CONCLUSION

The DNA methylation differences in vascular tissues of patients with coronary artery disease may provide new insights into the mechanisms underlying the development of atherosclerosis. The functions identified here-cytokine-cytokine receptor interaction, MAPK signaling pathway, DMG (S100A10), and TF (NF-kB)-may serve as potential targets in the treatment of atherosclerosis.

Antenatal antipsychotic exposure induces multigenerational and gender-specific programming of adiposity and glucose tolerance in adult mouse offspring

Second-generation antipsychotics (SGAs) are well known for their metabolic side effects in humans, including obesity and diabetes. These compounds are maintained during pregnancy to prevent the relapse of psychoses, but they readily diffuse across the placenta to the fetus, as documented with the widely-prescribed drug olanzapine (OLZ). However, observational studies have provided conflicting results on the potential impact of SGAs on fetal growth and body weight, and their effects on metabolic regulation in the offspring. For this reason, our study has tested whether antenatal exposure of CD1 mice to OLZ influenced metabolic outcomes in the offspring of the first (F1) and second (F2) generations. In F1 mice, OLZ antenatal treatment caused a decrease in neonatal body weight in both genders, an effect that persisted throughout life only in male animals. Interestingly, F1 female mice also displayed altered glucose homoeostasis. F2 mice, generated by mating normal males with F1 female mice exposed to OLZ during antenatal life, exhibited higher neonatal body weights which persisted only in F2 female animals. This was associated with expansion of fat mass and a concordant pattern of adipose tissue gene expression. Moreover, male and female F2 mice were glucose-intolerant. Thus, our study has demonstrated that antenatal OLZ exposure induces multigenerational and gender-specific programming of glucose tolerance in the offspring mice as adults, and points to the need for careful monitoring of children exposed to SGAs during pregnancy.

Understanding epigenetics of schizophrenia in the backdrop of its antipsychotic drug therapy

The diatheses of gene and environment interaction in schizophrenia (SCZ) are becoming increasingly evident. Genetic and epigenetic backgrounds are being considered in stratifying and addressing phenotypic variation and drug response in SCZ. But how much of these epigenetic alterations are the primary contributing factor, toward disease pathogenesis and drug response, needs further clarity. Evidence indicates that antipsychotic drugs can also alter the epigenetic homeostasis thereby inducing pharmacoepigenomic effects. We re-examine the context of epigenetics in disease pathogenesis and antipsychotic drug therapy in SCZ to understand how much of these observations act as real indicators of the disease or therapeutic response. We propose that epigenetic viewpoint in SCZ needs to be critically examined under the genetic, epigenetic and pharmacoepigenetic background.

Effect of Clozapine on DNA Methylation in Peripheral Leukocytes from Patients with Treatment-Resistant Schizophrenia

Clozapine is an atypical antipsychotic, that is established as the treatment of choice for treatment-resistant schizophrenia (SCZ). To date, no study investigating comprehensive DNA methylation changes in SCZ patients treated with chronic clozapine has been reported. The purpose of the present study is to reveal the effects of clozapine on DNA methylation in treatment-resistant SCZ. We conducted a genome-wide DNA methylation profiling in peripheral leukocytes (485,764 CpG dinucleotides) from treatment-resistant SCZ patients treated with clozapine (n = 21) in a longitudinal study. Significant changes in DNA methylation were observed at 29,134 sites after one year of treatment with clozapine, and these genes were enriched for “cell substrate adhesion” and “cell matrix adhesion” gene ontology (GO) terms. Furthermore, DNA methylation changes in the CREBBP (CREB binding protein) gene were significantly correlated with the clinical improvements. Our findings provide insights into the action of clozapine in treatment-resistant SCZ.

Genetic Variation in One-Carbon Metabolism and Changes in Metabolic Parameters in First-Episode Schizophrenia Patients

BACKGROUND

In this study, we aimed to investigate the effects of polymorphisms in genes encoding 1-carbon metabolism enzymes on differential development of metabolic parameters during 12 weeks of treatment with second-generation antipsychotics in first-episode schizophrenia patients.

METHODS

The following polymorphisms in 1-carbon metabolism genes were genotyped: MTHFR (C677T and A1298C), MTHFD1 (G1958A), MTRR (A66G), and BHMT (G742A). A broad panel of metabolic parameters including body mass index, waist circumference, total cholesterol low and high density lipoproteins, triglycerides, homocysteine, folate, and vitamin B12 was determined.

RESULTS

There was a significant effect of the interaction between the MTHFR C677T polymorphism and time on body mass index and waist circumference in the allelic and genotype analyses. Indeed, patients with the MTHFR 677CC genotype had higher increase in body mass index and waist circumference compared with other corresponding genotypes or the MTHFR 677T allele carriers (CT and TT genotypes). In addition, patients with the MTHFR 677TT genotype had higher waist circumference in all time points. Similarly, patients with the MTHFR 677TT genotype had higher body mass index in all time points, but this effect was not significant after correction for multiple testing.

CONCLUSIONS

Our results indicate that the MTHFR C677T polymorphism may predict antipsychotic-induced weight gain. Effects of the MTHFR C677T polymorphism might be different in initial exposure to antipsychotics compared with long-term perspective.

Understanding the genetic liability to schizophrenia through the neuroepigenome

The Psychiatric Genomics Consortium-Schizophrenia Workgroup (PGC-SCZ) recently identified 108 loci associated with increased risk for schizophrenia (SCZ). The vast majority of these variants reside within non-coding sequences of the genome and are predicted to exert their effects by affecting the mechanism of action of cis regulatory elements (CREs), such as promoters and enhancers. Although a number of large-scale collaborative efforts (e.g. ENCODE) have achieved a comprehensive mapping of CREs in human cell lines or tissue homogenates, it is becoming increasingly evident that many risk-associated variants are enriched for expression Quantitative Trait Loci (eQTLs) and CREs in specific tissues or cells. As such, data derived from previous research endeavors may not capture fully cell-type and/or region specific changes associated with brain diseases. Coupling recent technological advances in genomics with cell-type specific methodologies, we are presented with an unprecedented opportunity to better understand the genetics of normal brain development and function and, in turn, the molecular basis of neuropsychiatric disorders. In this review, we will outline ongoing efforts towards this goal and will discuss approaches with the potential to shed light on the mechanism(s) of action of cell-type specific cis regulatory elements and their putative roles in disease, with particular emphasis on understanding the manner in which the epigenome and CREs influence the etiology of SCZ.

Dissecting bipolar disorder complexity through epigenomic approach

In recent years, numerous studies of gene regulation mechanisms have emerged in neuroscience. Epigenetic modifications, described as heritable but reversible changes, include DNA methylation, DNA hydroxymethylation, histone modifications and noncoding RNAs. The pathogenesis of psychiatric disorders, such as bipolar disorder, may be ascribed to a complex gene-environment interaction (G × E) model, linking the genome, environmental factors and epigenetic marks. Both the high complexity and the high heritability of bipolar disorder make it a compelling candidate for neurobiological analyses beyond DNA sequencing. Questions that are being raised in this review are the precise phenotype of the disorder in question, and also the trait versus state debate and how these concepts are being implemented in a variety of study designs.

Epigenetic Modifications, Alcoholic Brain and Potential Drug Targets

Acute and chronic alcohol exposure evidently influences epigenetic changes, both transiently and permanently, and these changes in turn influence a variety of cells and organ systems throughout the body. Many of the alcohol-induced epigenetic modifications can contribute to cellular adaptations that ultimately lead to behavioral tolerance and alcohol dependence. The persistence of behavioral changes demonstrates that long-lasting changes in gene expression, within particular regions of the brain, may contribute importantly to the addiction phenotype. The research activities over the past years have demonstrated a crucial role of epigenetic mechanisms in causing long lasting and transient changes in the expression of several genes in diverse tissues, including brain. This has stimulated recent research work that is aimed at characterizing the influence of epigenetic regulatory events in mediating the long lasting and transient effects of alcohol abuse on the brain in humans and animal models of alcohol addiction. In this study, we update our current understanding of the impact of alcohol exposure on epigenetic mechanisms in the brain and refurbish the knowledge of epigenetics in the direction of new drugs development.

Gene-specific DNA methylation may mediate atypical antipsychotic-induced insulin resistance

OBJECTIVES

Atypical antipsychotics (AAPs) carry a significant risk of cardiometabolic side effects, including insulin resistance. It is thought that the insulin resistance resulting from the use of AAPs may be associated with changes in DNA methylation. We aimed to identify and validate a candidate gene associated with AAP-induced insulin resistance by using a multi-step approach that included an epigenome-wide association study (EWAS) and validation with site-specific methylation and metabolomics data.

METHODS

Subjects with bipolar disorder treated with AAPs or lithium monotherapy were recruited for a cross-sectional visit to analyze peripheral blood DNA methylation and insulin resistance. Epigenome-wide DNA methylation was analyzed in a discovery sample (n = 48) using the Illumina 450K BeadChip. Validation analyses of the epigenome-wide findings occurred in a separate sample (n = 72) using site-specific methylation with pyrosequencing and untargeted metabolomics data. Regression analyses were conducted controlling for known confounders in all analyses and a mediation analysis was performed to investigate if AAP-induced insulin resistance occurs through changes in DNA methylation.

RESULTS

A differentially methylated probe associated with insulin resistance was discovered and validated in the fatty acyl CoA reductase 2 (FAR2) gene of chromosome 12. Functional associations of this DNA methylation site with untargeted phospholipid-related metabolites were also detected. Our results identified a mediating effect of this FAR2 methylation site on AAP-induced insulin resistance.

CONCLUSIONS

Going forward, prospective, longitudinal studies assessing comprehensive changes in FAR2 DNA methylation, expression, and lipid metabolism before and after AAP treatment are required to assess its potential role in the development of insulin resistance.

DNA Methylation Profiling at Single-Base Resolution Reveals Gestational Folic Acid Supplementation Influences the Epigenome of Mouse Offspring Cerebellum

It is becoming increasingly more evident that lifestyle, environmental factors, and maternal nutrition during gestation can influence the epigenome of the developing fetus and thus modulate the physiological outcome. Variations in the intake of maternal nutrients affecting one-carbon metabolism may influence brain development and exert long-term effects on the health of the progeny. In this study, we investigated whether supplementation with high maternal folic acid during gestation alters DNA methylation and gene expression in the cerebellum of mouse offspring. We used reduced representation bisulfite sequencing to analyze the DNA methylation profile at the single-base resolution level. The genome-wide DNA methylation analysis revealed that supplementation with higher maternal folic acid resulted in distinct methylation patterns (P < 0.05) of CpG and non-CpG sites in the cerebellum of offspring. Such variations of methylation and gene expression in the cerebellum of offspring were highly sex-specific, including several genes of the neuronal pathways. These findings demonstrate that alterations in the level of maternal folic acid during gestation can influence methylation and gene expression in the cerebellum of offspring. Such changes in the offspring epigenome may alter neurodevelopment and influence the functional outcome of neurologic and psychiatric diseases.

Alcohol Withdrawal and Cerebellar Mitochondria

Cerebellar disorders trigger the symptoms of movement problems, imbalance, incoordination, and frequent fall. Cerebellar disorders are shown in various CNS illnesses including a drinking disorder called alcoholism. Alcoholism is manifested as an inability to control drinking in spite of adverse consequences. Human and animal studies have shown that cerebellar symptoms persist even after complete abstinence from drinking. In particular, the abrupt termination (ethanol withdrawal) of long-term excessive ethanol consumption has shown to provoke a variety of neuronal and mitochondrial damage to the cerebellum. Upon ethanol withdrawal, excitatory neurotransmitter molecules such as glutamate are overly released in brain areas including cerebellum. This is particularly relevant to the cerebellar neuronal network as glutamate signals are projected to Purkinje neurons through granular cells that are the most populated neuronal type in CNS. This excitatory neuronal signal may be elevated by ethanol withdrawal stress, which promotes an increase in intracellular Ca(2+) level and a decrease in a Ca(2+)-binding protein, both of which result in the excessive entry of Ca(2+) to the mitochondria. Subsequently, mitochondria undergo a prolonged opening of mitochondrial permeability transition pore and the overproduction of harmful free radicals, impeding adenosine triphosphate (ATP)-generating function. This in turn provokes the leakage of mitochondrial molecule cytochrome c to the cytosol, which triggers a cascade of adverse cytosol reactions. Upstream to this pathway, cerebellum under the condition of ethanol withdrawal has shown aberrant gene modifications through altered DNA methylation, histone acetylation, or microRNA expression. Interplay between these events and molecules may result in functional damage to cerebellar mitochondria and consequent neuronal degeneration, thereby contributing to motoric deficit. Mitochondria-targeting research may help develop a powerful new therapy to manage cerebellar disorders associated with hyperexcitatory CNS disorders like ethanol withdrawal.

The Ticking of the Epigenetic Clock: Antipsychotic Drugs in Old Age

BACKGROUND

Exposed to antipsychotic drugs (APDs), older individuals with dementing illness are at risk of cerebrovascular adverse effects (CVAE), including sudden death. Transient microvascular dysfunctions are known to occur in younger persons exposed to APDs; however, they seldom progress to CVAE, suggesting that APDs alone are insufficient for engendering this untoward effect. It is, therefore, believed that a preexistent microvascular damage is necessary for CVAE to take place, but the exact nature of this lesion remains unclear. CNS small vessel disease (SVD) is a well-known age-related risk factor for strokes, dementia, and sudden death, which may constitute the initial CVAE-predisposing pathology. Therefore, we propose the two strikes CVAE paradigm, in which SVD represents the first strike, while exposure to APDs, the second. In this model, both strikes must be present for CVAE to take place, and the neuroimaging load of white matter hyperintensities may be directly proportional with the CVAE risk. To investigate this hypothesis at the molecular level, we focused on a seemingly unrelated phenomenon: both APDs and SVD were found protective against a similar repertoire of cancers and their spread to the brain (1-4). Since microRNA-29 has shown efficacy against the same malignancies and has been associated with small vessels pathology, we narrowed our search down to this miR, hypothesizing that the APDs mechanism of action includes miR-29 upregulation, which in turn facilitates the development of SVD.

AIM

To assess whether miR-29 can be utilized as a peripheral blood biomarker for SVD and CVAE risk.

METHOD

We conducted a search of experimentally verified miR-29 target genes utilizing the public domain tools miRanda, RNA22 and Weizemann Institute of Science miRNA Analysis. We identified in total 67 experimentally verified target genes for miR-29 family, 18 of which correlate with microvascular integrity and may be relevant for CVAE.

CONCLUSION

Upregulated microRNA-29 silences the expression of 18 genes connected with capillary stability, engendering a major vulnerability for SVD (first strike) which in turn increases the risk for CVAE after exposure to APDs (second strike).

The association of DNA methylation and brain volume in healthy individuals and schizophrenia patients

Both methylation and brain volume patterns hold important biological information for the development and prognosis of schizophrenia (SZ). A combined study to probe the association between them provides a new perspective to understanding SZ. Genomic methylation of peripheral blood and regional brain volumes derived from magnetic resonance imaging were analyzed using parallel independent component analyses in this study. Nine methylation components and five brain volumetric components were extracted for 94 SZ patients and 106 healthy controls. After controlling for age, sex, race, and substance use, a component comprised primarily of bilateral cerebellar volumes was significantly correlated to a methylation component from 14 CpG sites in 13 genes. Both patients and healthy controls demonstrated similar associations, but patients had significantly smaller cerebellar volumes and dysmethylation in the associated epigenetic component compared to controls. The 13 genes are enriched in cellular growth and proliferation with some genes involved in neuronal growth and cerebellum development (GATA4, ADRA1D, EPHA3, and KCNK10), and these genes are prominently associated with neurological and psychological disorders. Such findings suggest that the methylation pattern of the genes coding for cellular growth may influence the cerebellar development through regulating gene expression, and the alteration in the methylation of these genes in SZ patients may contribute to the cerebellar volume reduction observed in patients.

Lower LINE-1 methylation in first-episode schizophrenia patients with the history of childhood trauma

Aim: We investigated methylation of DNA repetitive sequences (LINE-1 and BAGE) in peripheral blood leukocytes from first-episode schizophrenia (FES) patients and healthy controls (HCs) with respect to childhood adversities. Materials & methods: Patients were divided into two subgroups based on the history of childhood trauma – FES(+) and FES(-) subjects. The majority of HCs had a negative history of childhood trauma – HCs(-) subjects. Results: FES(+) patients had significantly lower LINE-1 methylation in comparison with FES(-) patients or HC(-) subjects. Emotional abuse and total trauma score predicted lower LINE-1 methylation in FES patients, while general trauma score was associated with lower BAGE methylation in HCs. Conclusion: Childhood adversities might be associated with global DNA hypomethylation in adult FES patients.

Epigenetic Basis of Mental Illness

Psychiatric disorders are complex multifactorial illnesses involving chronic alterations in neural circuit structure and function as well as likely abnormalities in glial cells. While genetic factors are important in the etiology of most mental disorders, the relatively high rates of discordance among identical twins, particularly for depression and other stress-related syndromes, clearly indicate the importance of additional mechanisms. Environmental factors such as stress are known to play a role in the onset of these illnesses. Exposure to such environmental insults induces stable changes in gene expression, neural circuit function, and ultimately behavior, and these maladaptations appear distinct between developmental versus adult exposures. Increasing evidence indicates that these sustained abnormalities are maintained by epigenetic modifications in specific brain regions. Indeed, transcriptional dysregulation and the aberrant epigenetic regulation that underlies this dysregulation is a unifying theme in psychiatric disorders. Here, we provide a progress report of epigenetic studies of the three major psychiatric syndromes, depression, schizophrenia, and bipolar disorder. We review the literature derived from animal models of these disorders as well as from studies of postmortem brain tissue from human patients. While epigenetic studies of mental illness remain at early stages, understanding how environmental factors recruit the epigenetic machinery within specific brain regions to cause lasting changes in disease susceptibility and pathophysiology is revealing new insight into the etiology and treatment of these conditions.

Olanzapine-induced DNA methylation in the hippocampus and cerebellum in genes mapped to human 22q11 and implicated in schizophrenia

BACKGROUND

Although there is indirect evidence that the effects of antipsychotic drugs may involve modulation of dopamine transmission, their mechanism of action is poorly understood. We hypothesized that antipsychotic drugs mediate their effects by epigenetic modulation. Here, we tested the effect of an antipsychotic, olanzapine, on the DNA methylation status of genes following chronic treatment using rat-specific methylation arrays.

METHODS

Forty-eight hours after the last dose of olanzapine/vehicle, rats were habituated to an open-field activity-monitoring chamber for 30 min to verify whether stress-induced locomotor activity was reduced in olanzapine-treated rats. To test this hypothesis, we examined the effect of olanzapine, a commonly used atypical antipsychotic drug, on the DNA methylation status of 49 genes mapped to human 22q11 and implicated in schizophrenia. Genomic DNA isolated from the cerebellum, hippocampus, and liver of olanzapine-treated (n=2) and control (n=2) rats were analyzed using rat-specific methylation arrays.

RESULTS

Significantly reduced locomotor activity of olanzapine-treated rats confirmed the therapeutic efficacy of the drug administered. The effects of olanzapine have been shown through significantly increased (P<0.01) DNA methylation of genes affecting several networks mainly (i) neurological disease, inflammatory disease, and inflammatory response and (ii) cancer, cell death and survival, tumor morphology. Also, proline degradation and L-DOPA degradation were affected by olanzapine-induced DNA methylation. Further, from a set of genes in the 22q11.2 microdeletions that has been implicated previously in psychosis, 29 genes showed increased methylation following olanzapine treatment.

CONCLUSION

The results showed that considerable number of genes (34/49) mapped to human 22q11 and implicated in schizophrenia were affected by olanzapine-induced DNA methylation. The results suggest that DNA methylation may play a role in the therapeutic efficacy of olanzapine.

DNA methylation, insulin resistance and second-generation antipsychotics in bipolar disorder

AIMS

This study aimed to assess the effect of second-generation antipsychotic (SGA) use and insulin resistance on a global measure of DNA methylation in patients diagnosed with bipolar disorder.

MATERIALS & METHODS

Subjects stable on medication (either mood stabilizer monotherapy or adjuvant SGAs) were assessed for insulin resistance. Global methylation levels were assessed in leukocyte DNA from whole blood using the Luminometric Methylation Assay. Multivariable linear regression was used to investigate the effect of insulin resistance and SGA use on DNA methylation.

RESULTS

A total of 115 bipolar I subjects were included in this study. The average age was 43.1 ±12.2 years and 73% were on SGAs. Average% global methylation was 77.0 ± 3.26 and was significantly influenced by insulin resistance, SGA use and smoking.

CONCLUSION

This is the first study to show a relationship between SGA use, insulin resistance and global DNA methylation. Further work will be needed to identify tissue- and gene-specific methylation changes.

DNA methylation in psychosis: insights into etiology and treatment

Evidence for involvement of DNA methylation in psychosis forms the focus of this perspective. Of interest are results from two independent sets of experiments including rats treated with antipsychotic drugs and monozygotic twins discordant for schizophrenia. The results show that DNA methylation is increased in rats treated with antipsychotic drugs, reflecting the global effect of the drugs. Some of these changes are also seen in affected schizophrenic twins that were treated with antipsychotics. The genes and pathways identified in the unrelated experiments are relevant to neurodevelopment and psychiatric disorders. The common cause is hypothesized to be aberrations resulting from medication use. However, this needs to be established by future studies that address the origin of methylation changes in psychosis.

Insights into the origin of DNA methylation differences between monozygotic twins discordant for schizophrenia

Background

DNA methylation differences between monozygotic twins discordant for schizophrenia have been previously reported. However, the origin of methylation differences between monozygotic twins discordant for schizophrenia is not clear. The findings here argue that all DNA methylation differences may not necessarily represent the cause of the disease; rather some may result from the effect of antipsychotics.

Methods

Methylation differences in rat brain regions and also in two pairs of unrelated monozygotic twins discordant for schizophrenia have been studied using genome-wide DNA methylation arrays at Arraystar Inc. (Rockville, Maryland, USA). The identified gene promoters showing significant alterations to DNA methylation were then further characterized using ingenuity pathway analysis (Ingenuity System Inc, CA, USA).

Results

Pathway analysis of the most significant gene promoter hyper/hypomethylation revealed a significant enrichment of DNA methylation changes in biological networks and pathways directly relevant to neural development and psychiatric disorders. These included HIPPO signaling (p = 3.93E-03) and MAPK signaling (p = 4.27E-03) pathways involving hypermethylated genes in schizophrenia-affected patients as compared to their unaffected co-twins. Also, a number of significant pathways and networks involving genes with hypomethylated gene promoters have been identified. These included CREB signaling in neurons (p = 1.53E-02), Dopamine-DARPP32 feedback in cAMP signaling (p = 7.43E-03) and Ephrin receptors (p = 1.13E-02). Further, there was significant enrichment for pathways involved in nervous system development and function (p = 1.71E-03-4.28E-02).

Conclusion

The findings highlight the significance of antipsychotic drugs on DNA methylation in schizophrenia patients. The unique pathways affected by DNA methylation in the two pairs of monozygotic twins suggest that patient-specific pathways are responsible for the disease; suggesting that patient-specific treatment strategies may be necessary in treating the disorder. The study reflects the need for developing personalized medicine approaches that take into consideration epigenetic variations between patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s40303-015-0013-5) contains supplementary material, which is available to authorized users.

DNA methylation and demethylation as targets for antipsychotic therapy

Schizophrenia (SZ) and bipolar disorder (BPD) patients show a downregulation of GAD67, reelin (RELN), brain-derived neurotrophic factor (BDNF), and other genes expressed in telencephalic GABAergic and glutamatergic neurons. This downregulation is associated with the enrichment of 5-methylcytosine and 5-hydroxymethylcytosine proximally at gene regulatory domains at the respective genes. A pharmacological strategy to reduce promoter hypermethylation and to induce a more permissive chromatin conformation is to administer drugs, such as the histone deacetylase (HDAC) inhibitor valproate (VPA), that facilitate chromatin remodeling. Studies in mouse models of SZ indicate that clozapine induces DNA demethylation at relevant promoters, and that this action is potentiated by VPA. By activating DNA demethylation, clozapine or its derivatives with VPA or other more potent and selective HDAC inhibitors may be a promising treatment strategy to correct the gene expression deficits detected in postmortem brain of SZ and BPD patients.

An update on the epigenetics of psychotic diseases and autism

The examination of potential roles of epigenetic alterations in the pathogenesis of psychotic diseases have become an essential alternative in recent years as genetic studies alone are yet to uncover major gene(s) for psychosis. Here, we describe the current state of knowledge from the gene-specific and genome-wide studies of postmortem brain and blood cells indicating that aberrant DNA methylation, histone modifications and dysregulation of micro-RNAs are linked to the pathogenesis of mental diseases. There is also strong evidence supporting that all classes of psychiatric drugs modulate diverse features of the epigenome. While comprehensive environmental and genetic/epigenetic studies are uncovering the origins, and the key genes/pathways affected in psychotic diseases, characterizing the epigenetic effects of psychiatric drugs may help to design novel therapies in psychiatry.

DNA methylation differences in monozygotic twin pairs discordant for schizophrenia identifies psychosis related genes and networks

Background

Despite their singular origin, monozygotic twin pairs often display discordance for complex disorders including schizophrenia. It is a common (1%) and often familial disease with a discordance rate of ~50% in monozygotic twins. This high discordance is often explained by the role of yet unknown environmental, random, and epigenetic factors. The involvement of DNA methylation in this disease appears logical, but remains to be established.

Methods

We have used blood DNA from two pairs of monozygotic twins discordant for schizophrenia and their parents in order to assess genome-wide methylation using a NimbleGen Methylation Promoter Microarray.

Results

The genome-wide results show that differentially methylated regions (DMRs) exist between members representing discordant monozygotic twins. Some DMRs are shared with parent(s) and others appear to be de novo. We found twenty-seven genes affected by DMR changes that were shared in the affected member of two discordant monozygotic pairs from unrelated families. Interestingly, the genes affected by pair specific DMRs share specific networks. Specifically, this study has identified two networks; “cell death and survival” and a “cellular movement and immune cell trafficking”. These two networks and the genes affected have been previously implicated in the aetiology of schizophrenia.

Conclusions

The results are compatible with the suggestion that DNA methylation may contribute to the discordance of monozygotic twins for schizophrenia. Also, this may be accomplished by the direct effect of gene specific methylation changes on specific biological networks rather than individual genes. It supports the extensive genetic, epigenetic and phenotypic heterogeneity implicated in schizophrenia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-015-0093-1) contains supplementary material, which is available to authorized users.

No association between genetic or epigenetic variation in insulin growth factors and antipsychotic-induced metabolic disturbances in a cross-sectional sample

AIM

Second-generation antipsychotics (SGA) are known to induce metabolic disturbances. Genetic pathways, such as the IGF pathway could be associated with increased metabolic syndrome (MetS). Additionally, IGF2 methylation varies as a function of environmental influences and is associated with schizophrenia and MetS. The current study aims to evaluate whether genetic and epigenetic variation in genes of the IGF pathway are associated with metabolic disturbances in patients under treatment with SGAs.

METHODS

Cross-sectional metabolic data from 438 patients with schizophrenia spectrum disorder was analyzed. Using the Sequenom MassARRAY iPLEX(TM) platform, 27 SNPs of the IGF1 and IGF2 genes and the IGF receptors IGF1R and IGF2R were genotyped. Methylation status of seven IGF2 CpG dinucleotides was evaluated using a Sequenom MALDI-TOF spectrometer.

RESULTS & CONCLUSION

There was a significant association between IGF2 methylation and genotype, but no significant association between genetic or epigenetic variability and metabolic parameters in the present study.

Correlation between DNA methylation and gene expression in the brains of patients with bipolar disorder and schizophrenia

OBJECTIVES

Aberrant DNA methylation and gene expression have been reported in postmortem brain tissues of psychotic patients, but until now there has been no systematic evaluation of synergistic changes in methylation and expression on a genome-wide scale in brain tissue.

METHODS

In this study, genome-wide methylation and expression analyses were performed on cerebellum samples from 39 patients with schizophrenia, 36 patients with bipolar disorder, and 43 unaffected controls, to screen for a correlation between gene expression and CpG methylation.

RESULTS

Out of 71,753 CpG gene pairs (CGPs) tested across the genome, 204 were found to significantly correlate with gene expression after correction for multiple testing [p < 0.05, false discovery rate (FDR) q < 0.05]. The correlated CGPs were tested for disease-associated expression and methylation by comparing psychotic patients with bipolar disorder and schizophrenia to healthy controls. Four of the identified CGPs were found to significantly correlate with the differential expression and methylation of genes encoding phosphoinositide-3-kinase, regulatory subunit 1 (PIK3R1), butyrophilin, subfamily 3, member A3 (BTN3A3), nescient helix-loop-helix 1 (NHLH1), and solute carrier family 16, member 7 (SLC16A7) in psychotic patients (p < 0.05, FDR q < 0.2). Additional expression and methylation datasets were used to validate the relationship between DNA methylation, gene expression, and neuropsychiatric diseases.

CONCLUSIONS

These results suggest that the identified differentially expressed genes with an aberrant methylation pattern may represent novel candidate factors in the etiology and pathology of neuropsychiatric disorders.

Effects of second-generation antipsychotics on selected markers of one-carbon metabolism and metabolic syndrome components in first-episode schizophrenia patients

Purpose

Alterations in one-carbon metabolism (OCM) have been repeatedly reported in schizophrenia. However, there is a scarcity of studies addressing the effects of antipsychotics on selected OCM markers in schizophrenia and provided results are inconsistent.

Methods

We recruited 39 first-episode schizophrenia (FES) patients and determined serum profile of total homocysteine (tHcy), folate, vitamin B12, lipoproteins and glucose at baseline and after 12 weeks of treatment with second-generation antipsychotics (SGA) including olanzapine and risperidone in monotherapy.

Results

After 12 weeks of treatment, all patients had significantly higher body mass index (BMI), serum levels of total cholesterol (TC), low-density lipoproteins (LDL), triglycerides (TG) and tHcy together with significantly lower levels of folate and vitamin B12. The analysis of differences between SGA revealed the same biochemical alterations in patients treated with olanzapine as in the whole group, while those receiving risperidone had no statistically significant changes in serum folate, vitamin B12 and TG. There was a significantly higher increase in BMI and TC in patients treated with olanzapine in comparison with those treated with risperidone. Patients receiving olanzapine had a higher decrease in vitamin B12 than those assigned to the treatment with risperidone. Changes in folate, vitamin B12, tHcy and TC levels were significant only in males, even after Bonferroni correction. Multiple regression analysis revealed that changes in tHcy levels are associated with gender and baseline metabolic parameters (BMI, glucose, TC, LDL and HDL) but not with selected SGA.

Conclusions

These results indicate that SGA may influence OCM, especially in first-episode schizophrenia (FES) males.

Electronic supplementary material

The online version of this article (doi:10.1007/s00228-014-1762-2) contains supplementary material, which is available to authorized users.

Antipsychotic induced weight gain: genetics, epigenetics, and biomarkers reviewed

Antipsychotic-induced weight gain (AIWG) is a prevalent side effect of antipsychotic treatment, particularly with second generation antipsychotics, such as clozapine and olanzapine. At this point, there is virtually nothing that can be done to predict who will be affected by AIWG. However, hope for the future of prediction lies with genetic risk factors. Many genes have been studied for their association with AIWG with a variety of promising findings. This review will focus on genetic findings in the last year and will discuss the first epigenetic and biomarker findings as well. Although there are significant findings in many other genes, the most consistently replicated findings are in the melanocortin 4 receptor (MC4R), the serotonin 2C receptor (HTR2C), the leptin, the neuropeptide Y (NPY) and the cannabinoid receptor 1 (CNR1) genes. The study of genetic risk variants poses great promise in creating predictive tools for side effects such as AIWG.

Olanzapine-induced methylation alters cadherin gene families and associated pathways implicated in psychosis

BACKGROUND

The complex aetiology of most mental disorders involves gene-environment interactions that may operate using epigenetic mechanisms particularly DNA methylation. It may explain many of the features seen in mental disorders including transmission, expression and antipsychotic treatment responses. This report deals with the assessment of DNA methylation in response to an antipsychotic drug (olanzapine) on brain (cerebellum and hippocampus), and liver as a non-neural reference in a rat model. The study focuses on the Cadherin/protocadherins encoded by a multi-gene family that serve as adhesion molecules and are involved in cell-cell communication in the mammalian brain. A number of these molecules have been implicated in the causation of schizophrenia and related disorders.

RESULTS

The results show that olanzapine causes changes in DNA methylation, most specific to the promoter region of specific genes. This response is tissue specific and involves a number of cadherin genes, particularly in cerebellum. Also, the genes identified have led to the identification of several pathways significantly affected by DNA methylation in cerebellum, hippocampus and liver. These included the Gα12/13 Signalling (p = 9.2E-08) and Wnt signalling (p = 0.01) pathways as contributors to psychosis that is based on its responsiveness to antipsychotics used in its treatment.

CONCLUSION

The results suggest that DNA methylation changes on the promoter regions of the Cadherin/protocadherin genes impact the response of olanzapine treatment. These impacts have been revealed through the identified pathways and particularly in the identification of pathways that have been previously implicated in psychosis.