The effect of folate supplementation and genotype on cardiovascular and epigenetic measures in schizophrenia subjects

Profiling the Skeletal Muscle Proteome in Patients on Atypical Antipsychotics and Mood Stabilizers

Atypical antipsychotics (AAP) are used in the treatment of severe mental illness. They are associated with several metabolic side effects including insulin resistance. The skeletal muscle is the primary tissue responsible for insulin-stimulated glucose uptake. Dysfunction of protein regulation within the skeletal muscle following treatment with AAPs may play a role in the associated metabolic side effects. The objective of this study was to measure protein abundance in the skeletal muscle of patients on long-term AAP or mood stabilizer treatment. Cross-sectional muscle biopsies were obtained from patients with bipolar disorder and global protein abundance was measured using stable isotope labeling by amino acid (SILAC) combined with high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). Sixteen patients completed muscle biopsies and were included in the proteomic analyses. A total of 40 proteins were significantly different between the AAP group and the mood stabilizer group. In-silico pathway analysis identified significant enrichment in several pathways including glucose metabolism, cell cycle, apoptosis, and folate metabolism. Proteome abundance changes also differed based on protein biological processes and function. In summary, significant differences in proteomic profiles were identified in the skeletal muscle between patients on AAPs and mood stabilizers. Future work is needed to validate these findings in prospectively sampled populations.

Associations of Genetic Variants of Methylenetetrahydrofolate Reductase and Serum Folate Levels with Metabolic Parameters in Patients with Schizophrenia

The one-carbon metabolism pathway is a suitable candidate for studying the genetic and epigenetic factors contributing to metabolic abnormalities in patients with schizophrenia. We recruited 232 patients with schizophrenia and analyzed their serum folate, vitamin B12, and homocysteine levels and metabolic parameters to investigate the associations of genetic variants of methylenetetrahydrofolate reductase (MTHFR) and folate levels with metabolic parameters. MTHFR C677T and MTHFR A1298C were genotyped. Results showed that MTHFR 677T allele carriers had lower levels of total cholesterol and low-density lipoprotein cholesterol than those with the 677CC genotype. Metabolic parameters did not differ between MTHFR 1298C and 1298AA carriers. Patients with a low folate level had a lower high-density lipoprotein cholesterol level than those with a normal folate level, but the effect disappeared after adjustment for age, sex, and types of antipsychotics used. We found significant interactions between MTHFR A1298C and the folate level status (low vs. normal) in terms of body mass index and waist circumference. In conclusion, genetic variants in one-carbon metabolism might play a role in antipsychotic-induced metabolic abnormalities. Prospective studies on drug-naïve, first-episode patients with schizophrenia are warranted to identify key regions of DNA methylation changes accounting for antipsychotic-induced metabolic abnormalities.

Genetic and Metabolite Variability in One-Carbon Metabolism Applied to an Insulin Resistance Model in Patients With Schizophrenia Receiving Atypical Antipsychotics

Background: Patients with schizophrenia are at high risk of pre-mature mortality due to cardiovascular disease (CVD). Our group has completed studies in pharmacogenomics and metabolomics that have independently identified perturbations in one-carbon metabolism as associated with risk factors for CVD in this patient population. Therefore, this study aimed to use genetic and metabolomic data to determine the relationship between folate pharmacogenomics, one-carbon metabolites, and insulin resistance as measured using the homeostatic model assessment for insulin resistance (HOMA-IR) as a marker of CVD. Methods: Participants in this pilot analysis were on a stable atypical antipsychotic regimen for at least 6 months, with no diabetes diagnosis or use of antidiabetic medications. Participant samples were genotyped for MTHFR variants rs1801131 (MTHFR A1298C) and rs1801133 (MTHFR C677T). Serum metabolite concentrations were obtained with NMR. A least squares regression model was used to predict log(HOMA-IR) values based on the following independent variables: serum glutamate, glycine, betaine, serine, and threonine concentrations, and carrier status of the variant alleles for the selected genotypes. Results: A total of 67 participants were included, with a median age of 47 years old (IQR 42-52), 39% were female, and the median BMI was 30.3 (IQR 26.3-37.1). Overall, the model demonstrated an ability to predict log(HOMA-IR) values with an adjusted R ² of 0.44 and a p-value of < 0.001. Glutamate, threonine, and carrier status of the MTHFR 1298 C or MTHFR 677 T allele were positively correlated with log(HOMA-IR), whereas glycine, serine, and betaine concentrations trended inversely with log(HOMA-IR). All factors included in this final model were considered as having a possible effect on predicting log(HOMA-IR) as measured with a p-value < 0.1. Conclusions: Presence of pharmacogenomic variants that decrease the functional capacity of the MTHFR enzyme are associated with increased risk for cardiovascular disease, as measured in this instance by log(HOMA-IR). Furthermore, serine, glycine, and betaine concentrations trended inversely with HOMA-IR, suggesting that increased presence of methyl-donating groups is associated with lower measures of insulin resistance. Ultimately, these results will need to be replicated in a significantly larger population.

LINE-1 hypomethylation is associated with poor risperidone response in a first episode of psychosis cohort

Aim: We investigated the DNA methylation profile over LINE-1 in antipsychotic-naive, first-episode psychosis-patients (n = 69) before and after 2 months of risperidone treatment and in healthy controls (n = 62). Materials & methods: Patients were evaluated using standardized scales and classified as responders and nonresponders. DNA from blood was bisulfite converted and LINE-1 fragments were amplified and pyrosequencing was performed. Results: Lower LINE-1 methylation was observed in antipsychotic-naive first-episode psychosis patients than in healthy controls. Lower DNA methylation levels before treatment were associated with poor risperidone responses. A positive correlation was observed between LINE-1 methylation levels and positive symptoms response. Conclusion: Our study brings new insight regarding how epigenomic studies and clinical correlation studies can supplement psychosis treatment.

Antipsychotic Medications and DNA Methylation in Schizophrenia and Bipolar Disorder: A Systematic Review

The pharmacoepigenetics of antipsychotic treatment in severe mental illness is a growing area of research that aims to understand the interface between antipsychotic treatment and genetic regulation. Pharmacoepigenetics may some day assist in identifying treatment response mechanisms or become one of the components in the implementation of precision medicine. To understand the current evidence regarding the effects of antipsychotics on DNA methylation a systematic review with qualitative synthesis was performed through Pubmed, Embase and Psychinfo from earliest data to June 2019. Studies were included if they analyzed DNA methylation in an antipsychotic-treated population of patients with schizophrenia or bipolar disorder. Data extraction occurred via a standardized format and study quality was assessed. Twenty-nine studies were identified for inclusion. Study design, antipsychotic type, sample source, and methods of DNA methylation measurement varied across all studies. Eighteen studies analyzed methylation in patients with schizophrenia, four studies in patients with bipolar disorder, and seven studies in a combined sample of schizophrenia and bipolar disorder. Twenty-two studies used observational samples whereas the remainder used prospectively treated samples. Six studies assessed global methylation, five assessed epigenome-wide, and 15 performed a candidate epigenetic study. Two studies analyzed both global and gene-specific methylation, whereas one study performed a simultaneous epigenome-wide and gene-specific study. Only three genes were analyzed in more than one gene-specific study and the findings were discordant. The state of the pharmacoepigenetic literature on antipsychotic use is still in its early stages and uniform reporting of methylation site information is needed. Future work should concentrate on using prospective sampling with appropriate control groups and begin to replicate many of the novel associations that have been reported.

Influence of nutrients involved in one-carbon metabolism on DNA methylation in adults—a systematic review and meta-analysis

Context

Aberrant DNA methylation is linked to various diseases. The supply of methyl groups for methylation reactions is mediated by S-adenosylmethionine, which depends on the availability of folate and related B vitamins.

Objectives

To investigate the influence of key nutrients involved in 1-carbon metabolism on DNA methylation in adults.

Data sources

Systematic literature searches were conducted in the Cochrane Library, Medline, Embase, Cumulative Index to Nursing and Allied Health Literature Plus, Scopus, and Web of Science databases. Studies that met the inclusion criteria and were published in English were included.

Data extraction

The first author, study design, sample size, population characteristics, type and duration of intervention, tissue type or cells analyzed, molecular techniques, and DNA methylation outcomes.

Data synthesis

A meta-analysis of randomized, controlled trials (RCTs) was conducted to investigate the effect of 1-carbon metabolism nutrients on global DNA methylation. Functional analysis and visualization were performed using BioVenn software.

Results

From a total of 2620 papers screened by title, 53 studies met the inclusion criteria. Qualitative analysis indicated significant associations between 1-carbon metabolism nutrients and DNA methylation. In meta-analysis of RCTs stratified by method of laboratory analysis, supplementation with folic acid alone or in combination with vitamin B12 significantly increased global DNA methylation in studies using liquid chromatography–mass spectrometry, which had markedly lower heterogeneity (n = 3; Z = 3.31; P = 0.0009; I2 = 0%) in comparison to other methods. Functional analysis highlighted a subset of 12 differentially methylated regions that were significantly related to folate and vitamin B12 biomarkers.

Conclusion

This study supports significant associations between 1-carbon metabolism nutrients and DNA methylation. However, standardization of DNA methylation techniques is recommended to reduce heterogeneity and facilitate comparison across studies.

Systematic Review registration

PROSPERO registration number: CRD42018091898.

Dietary Glutamic Acid, Obesity, and Depressive Symptoms in Patients With Schizophrenia

Introduction: Schizophrenia is a lifelong condition associated with several comorbid conditions such as physical illnesses like obesity, as well as co-occurring psychiatric symptoms such as depression. Research regarding susceptibility to some of these comorbidities has primary focused on genetic risks or neurotransmitters and very little work has been done to understand environmental factors such as diet. In particular, understanding the role of dietary glutamic acid consumption on co-morbidities in patients with schizophrenia is important, as evidence suggests that glutamic acid consumption may directly influence glutamatergic neurotransmission; a key neurotransmitter related to schizophrenia, its associated co-morbidities, and depression. Therefore, the aim of this study was to examine the potential relationship between dietary glutamic acid and depressive symptomatology in patients with schizophrenia, stratified by obesity status, due to its relationship with inflammation, antipsychotic use, and depressive symptoms. Methods: Subjects included in this analysis, were part of a parent cross-sectional study in which included three dietary recalls analyzed using protocols outlined as part of the National Health and Nutrition Examination Surveys (NHANES) standardized criteria. Additionally, body mass index (BMI), and Beck Depression Inventory were obtained at this visit. Subjects with a BMI ≥ 30 kg/m² were included in the obesity group, and the relationship between glutamic acid consumption and BDI scores was analyzed after controlling for age, race, sex, antidepressant and antipsychotic use, and animal and vegetable protein intake which provide natural forms of dietary glutamic acid. Results: A total of 168 participants were included in this study, of which 42.5% were female and 52.9% were White. The mean BMI for the group as a whole was 33.5 ± 8.7 (kg/m²) and the mean BDI was 14.5 ± 10.2 (range 2-50). No differences were found between obesity groups, other than a greater hyperlipidemia, hypertension, and lower waist to hip ratio. Overall, no relationship was found between dietary glutamic acid and BDI scores, However, for non-obese participants, diets higher levels of glutamic acid were associated with greater depression symptomatology (p = 0.021). Conclusion: These preliminary results indicate a possible correlation between dietary glutamic acid a depressive symptoms in non-obese patients with schizophrenia, although further research is needed to specifically examine this relationship.

Metabolic syndrome is negatively associated with cognition among endothelial nitric oxide synthase (eNOS)- 786C carriers in schizophrenia-spectrum disorders

Although metabolic syndrome and cognitive inefficiencies are well-described common complications of schizophrenia, their association remains inconsistent, potentially due to poorly understood mechanisms underlying their relationship. Variability in the endothelial nitric oxide synthase (eNOS) gene, specifically the T-786C variant, has been separately associated with cognition and metabolic syndrome, with worse outcomes for eNOS-786C carriers likely occurring via negative effects on blood vessel functioning. However, the interaction between eNOS and metabolic syndrome in cognition among adults with schizophrenia is unknown. This study aimed to test the main and interaction effects of the eNOS-786C allele in cognition using hierarchical regression analyses controlling for age, sex, education, race, and antipsychotic exposure. Metabolic syndrome, eNOS T-786C genotype, and cognitive performance were assessed in 226 community-dwelling participants with chronic schizophrenia-spectrum disorders. Results demonstrated a significant interaction between metabolic syndrome and the eNOS-786C allele. Specifically, among eNOS-786C carriers only, metabolic syndrome was independently associated with lower scores in processing speed and verbal fluency, and predicted 12.5% and 15.8% of variance in performance, respectively. These results suggest that the additive negative effects of eNOS-786C and metabolic syndrome on blood vessel functioning may be severe enough to negatively impact cognition. The finding that metabolic syndrome is associated with worse cognition only in the presence of the eNOS-786C allele may clarify extant inconsistencies in the literature. These findings provide preliminary evidence that may inform interventions to reduce cognitive morbidity among adults with schizophrenia.

Nutrient and genetic biomarkers of nutraceutical treatment response in mood and psychotic disorders: a systematic review

Objective: Nutrient and genetic biomarkers in nutraceutical trials may allow for the personalisation of nutraceutical treatment and assist in predicting treatment response. We aimed to synthesise the findings of trials which have included these biomarkers to determine which may be most useful for predicting nutraceutical response in mood and psychotic disorders.Methods: A systematic review was conducted assessing available literature concerning nutraceutical clinical trials in mood and psychotic disorders (major depression, bipolar disorder, schizophrenia) with baseline and endpoint blood nutrient markers or genetic data available.Results: We identified 35 eligible studies (total n = 3836 participants) examining baseline and endpoint nutrient biomarkers and/or genetic polymorphisms. The key result, as reported in 10 out of 11 omega-3 studies, was a strong association between polyunsaturated fatty acid concentrations (mostly EPA and DHA) and psychiatric outcomes, although the exact nature of the association varied between studies and diagnoses. There was no consistent evidence for levels of other nutrients (including Vitamin D, SAM/SAH ratios, carnitine, folate and vitamin B12) relating to treatment response. The evidence for associations between one-carbon cycle genotypes (e.g. MTHFR C677 T, MTR and FOLH1) and treatment response was also inconsistent.Discussion: The available data tentatively supports omega-3 indices as biomarkers of response to omega-3 treatments in mood disorders. Further research with larger samples examining combinations of polymorphisms is required to determine if any genetic factors influence nutraceutical response in mood and psychotic disorders.

Antipsychotics-induced metabolic alterations: Recounting the mechanistic insights, therapeutic targets and pharmacological alternatives

Atypical antipsychotics (AAPs) are the drug of choice in the management of mental illnesses by virtue of their advantage over typical antipsychotics i.e. least tendency of producing extrapyramidal motor symptoms (EPS) or pseudoparkinsonism. Despite the clinical efficacy, AAPs produces troublesome adverse effects, particularly hyperphagia, hyperglycemia, dyslipidemia weight gain, diabetes mellitus, insulin resistance and QT prolongation which further develops metabolic and cardiac complications with subsequent reduction in life expectancy, poor patient compliance, and sudden death. AAPs-induced weight gain and metabolic alterations are increasing at an alarming rate and became an utmost matter of concern for psychopharmacotherapy. Diverse underlying mechanisms have been explored such as the interaction of AAPs with neurotransmitter receptors, alteration in food reward anticipation behavior, altered expressions of hypothalamic orexigenic and anorexigenic neuropeptides, histamine H₁ receptor-mediated hypothalamic AMP-activated protein kinase (AMPK) activation, increased blood leptin, ghrelin, pro-inflammatory cytokines. Antipsychotics induced imbalance in energy homeostasis, reduction in energy expenditure which is linked to altered expression of uncoupling proteins (UCP-1) in brown adipose tissue and reduced hypothalamic orexin expressions are emerging insights. In addition, alteration in gut-microbiota and subsequent inflammation, dyslipidemia, obesity, and diabetes after AAPs treatment are also associated with weight gain and metabolic alterations. Oral hypoglycemics and lipid-lowering drugs are mainly prescribed in the clinical management of weight gain associated with AAPs while many other pharmacological and nonpharmacological interventions also have been explored in different clinical and preclinical studies. In this review, we critically discuss the current scenario, mechanistic insights, biomarkers, and therapeutic alternatives for metabolic alterations associated with antipsychotics.

Effects of dietary interventions on DNA methylation in adult humans: systematic review and meta-analysis

DNA methylation is a key component of the epigenetic machinery that is responsible for regulating gene expression and, therefore, cell function. Patterns of DNA methylation change during development and ageing, differ between cell types, are altered in multiple diseases and can be modulated by dietary factors. However, evidence about the effects of dietary factors on DNA methylation patterns in humans is fragmentary. This study was initiated to collate evidence for causal links between dietary factors and changes in DNA methylation patterns. We carried out a systematic review of dietary intervention studies in adult humans using Medline, EMBASE and Scopus. Out of 22 149 screened titles, sixty intervention studies were included, of which 65% were randomised (n 39). Most studies (53%) reported data from blood analyses, whereas 27% studied DNA methylation in colorectal mucosal biopsies. Folic acid was the most common intervention agent (33%). There was great heterogeneity in the methods used for assessing DNA methylation and in the genomic loci investigated. Meta-analysis of the effect of folic acid on global DNA methylation revealed strong evidence that supplementation caused hypermethylation in colorectal mucosa (P=0·009). Meta-regression analysis showed that the dose of supplementary folic acid was the only identified factor (P<0·001) showing a positive relationship. In summary, there is limited evidence from intervention studies of effects of dietary factors, other than folic acid, on DNA methylation patterns in humans. In addition, the application of multiple different assays and investigations of different genomic loci makes it difficult to compare, or to combine, data across studies.

Atypical Antipsychotic Exposure May Not Differentiate Metabolic Phenotypes of Patients with Schizophrenia

STUDY OBJECTIVE

Patients with schizophrenia are known to have higher rates of metabolic disease than the general population. Contributing factors likely include lifestyle and atypical antipsychotic (AAP) use, but the underlying mechanisms are unknown. The objective of this study was to identify metabolomic variability in adult patients with schizophrenia who were taking AAPs and grouped by fasting insulin concentration, our surrogate marker for metabolic risk.

DESIGN

Metabolomics analysis PARTICIPANTS: Ninety-four adult patients with schizophrenia who were taking an AAP for at least 6 months, with no changes in their antipsychotic regimen for the previous 8 weeks, and who did not require treatment with insulin, participated in the study. Twenty age- and sex-matched nonobese (10 subjects) and obese (10 subjects) controls without cardiovascular disease or mental health diagnoses were used to match the body mass index (BMI) range of the patients with schizophrenia to account for metabolite concentration differences attributable to BMI.

MEASUREMENTS AND MAIN RESULTS

Existing serum samples were used to identify aqueous metabolites (to differentiate fasting insulin concentration quartiles) and fatty acids with quantitative nuclear magnetic resonance and gas chromatography methods, respectively. To exclude metabolites from our pathway mapping analysis that were due to variability in weight, we also subjected serum samples from the nonobese and obese controls to the same analyses. Patients with schizophrenia had a median age of 47.0 years (interquartile range 41.0-52.0 years). Using a false discovery rate threshold of less than 25%, 10 metabolites, not attributable to weight, differentiated insulin concentration quartiles in patients with schizophrenia and identified variability in one-carbon metabolism between groups. Patients with higher fasting insulin concentrations (quartiles 3 and 4) also trended toward higher levels of saturated fatty acids compared with patients with lower fasting insulin concentrations (quartiles 1 and 2).

CONCLUSION

Our results illustrate the utility of metabolomics to identify pathways underlying variable fasting insulin concentration in patients with schizophrenia. Importantly, no significant difference in AAP exposure was observed among groups, suggesting that current antipsychotic use may not be a primary factor that differentiates middle-aged adult patients with schizophrenia by fasting insulin concentration.

The Influence of Metabolic Syndrome and Sex on the DNA Methylome in Schizophrenia

Introduction

The mechanism by which metabolic syndrome occurs in schizophrenia is not completely known; however, previous work suggests that changes in DNA methylation may be involved which is further influenced by sex. Within this study, the DNA methylome was profiled to identify altered methylation associated with metabolic syndrome in a schizophrenia population on atypical antipsychotics.

Methods

Peripheral blood from schizophrenia subjects was utilized for DNA methylation analyses. Discovery analyses (n = 96) were performed using an epigenome-wide analysis on the Illumina HumanMethylation450K BeadChip based on metabolic syndrome diagnosis. A secondary discovery analysis was conducted based on sex. The top hits from the discovery analyses were assessed in an additional validation set (n = 166) using site-specific methylation pyrosequencing.

Results

A significant increase in CDH22 gene methylation in subjects with metabolic syndrome was identified in the overall sample. Additionally, differential methylation was found within the MAP3K13 gene in females and the CCDC8 gene within males. Significant differences in methylation were again observed for the CDH22 and MAP3K13 genes, but not CCDC8, in the validation sample set.

Conclusions

This study provides preliminary evidence that DNA methylation may be associated with metabolic syndrome and sex in schizophrenia.

Genetic variants impacting metabolic outcomes among people on clozapine: a systematic review and meta-analysis

Clozapine is the gold standard medication for treatment refractory schizophrenia, but unfortunately, its use is also associated with many adverse metabolic side effects. There may be a strong genetic component to the development of these adverse effects. We undertook a systematic review to examine the evidence for genetic variation being associated with secondary metabolic outcomes in patients with schizophrenia on clozapine, under both longitudinal and cross-sectional study designs. We limited studies to those examining patients definitely taking clozapine, unlike prior reviews that have examined metabolic effects of patients taking a range of antipsychotic medications. We found associations with outcomes such as increases in BMI and metabolic syndrome for variants in genes such as LEP and HTR2C. Meta-analysis of rs381328 in HTR2C revealed that the presence of the T allele led to a 0.63 kg/m² (95% CI - 1.06 to - 0.19; p = 0.005) decrease in BMI compared to the C allele. Study and population heterogeneity and lack of statistical power among reviewed articles mean that evidence is lacking to warrant prophylactic genotyping of patients commencing clozapine to predict those at increased risk of developing adverse metabolic effects. Further efforts to establish collaborative consortia, consensus around study design and replication studies in independent populations should be encouraged.

Institutional profile of pharmacogenetics within University of Michigan College of Pharmacy

The University of Michigan College of Pharmacy has made substantial investment in the area of pharmacogenomics to further bolster its activity in pharmacogenomics research, implementation and education. Four tenure-track faculty members have active research programs that focus primarily on the discovery of functional polymorphisms (HJ Zhu), and genetic associations with treatment outcomes in patients with cancer (DL Hertz), cardiovascular disease (JA Luzum) and psychiatric conditions (VL Ellingrod). Recent investments from the University and the College have accelerated the implementation of pharmacogenetics broadly across the institution and in targeted therapeutic areas. Students within the PharmD and other health science professions receive substantial instruction in pharmacogenomics, in preparation for careers in biomedical health in which they can contribute to the generation, dissemination and utilization of pharmacogenomics knowledge to improve patient care.