Association of FTO, LEPR and MTHFR gene polymorphisms with metabolic syndrome in schizophrenia patients receiving antipsychotics

Body mass index, waist circumference, insulin, and leptin plasma levels differentiate between clozapine-responsive and clozapine-resistant schizophrenia

BACKGROUND

Between 25% and 50% of patients suffering from treatment-resistant schizophrenia fail to achieve a clinical response with clozapine. The rapid identification and treatment of this subgroup of patients represents a challenge for healthcare practice.

AIMS

To evaluate the relationship between metabolic alterations and the clinical response to clozapine.

METHODS

A multicenter, observational, case-control study was performed. Patients diagnosed with schizophrenia treated with clozapine were eligible (minimum dose 400 mg/d for at least 8 weeks and/or clozapine plasma levels ⩾ 350 µg/mL). According to the Positive and Negative Syndrome Scale (PANSS) total score, patients were classified as clozapine-responsive (CR) (<80 points) or clozapine non-responsive (CNR) (⩾80 points). Groups were compared based on demographic and treatment-related characteristics, together with body mass index (BMI), waist circumference, insulin, leptin, and C-reactive protein plasma levels. Plasma levels of clozapine and its main metabolite, nor-clozapine, were measured in all the participants. In addition, the potential relationship between PANSS scores and leptin or insulin plasma levels was assessed.

RESULTS

A total of 46 patients were included: 25 CR and 21 CNR. BMI and waist circumference, fasting insulin and leptin plasma levels were lower in the CNR group, while C-reactive protein was not different. Moreover, significant negative correlations were observed between PANSS positive and general psychopathology subscores, on one hand, and insulin and leptin plasma levels, on the other hand, as well as between PANSS negative subscores and leptin plasma levels.

CONCLUSIONS

Our results suggest that the lack of metabolic effect induced by clozapine is associated with the lack of clinical response.

Coordination of RNA modifications in the brain and beyond

Gene expression regulation is a critical process throughout the body, especially in the nervous system. One mechanism by which biological systems regulate gene expression is via enzyme-mediated RNA modifications, also known as epitranscriptomic regulation. RNA modifications, which have been found on nearly all RNA species across all domains of life, are chemically diverse covalent modifications of RNA nucleotides and represent a robust and rapid mechanism for the regulation of gene expression. Although numerous studies have been conducted regarding the impact that single modifications in single RNA molecules have on gene expression, emerging evidence highlights potential crosstalk between and coordination of modifications across RNA species. These potential coordination axes of RNA modifications have emerged as a new direction in the field of epitranscriptomic research. In this review, we will highlight several examples of gene regulation via RNA modification in the nervous system, followed by a summary of the current state of the field of RNA modification coordination axes. In doing so, we aim to inspire the field to gain a deeper understanding of the roles of RNA modifications and coordination of these modifications in the nervous system.

Association Study of BDNF, SLC6A4, and FTO Genetic Variants with Schizophrenia Spectrum Disorders

Schizophrenia spectrum disorders (patients with a diagnosis of schizophrenia, schizotypal, and delusional disorders: F20-F29 according to International Classification of Diseases 10th revision (ICD-10)) are considered highly heritable heterogeneous psychiatric conditions. Their pathophysiology is multifactorial with involved dysregulated serotonergic neurotransmission and synaptic plasticity. The present study aimed to evaluate the association of SLC6A4 (5-HTTLPR), FTO (rs9939609), and BDNF (rs6265, rs962369) polymorphisms with schizophrenia spectrum disorders in Slovak patients. We analyzed the genotypes of 150 patients with schizophrenia, schizotypal, and delusional disorders and compared them with genotypes from 178 healthy volunteers. We have found a marginally protective effect of LS + SS genotypes of 5-HTTLPR variant of the serotonin transporter SLC6A4 gene against the development of schizophrenia spectrum disorders, but the result failed to remain significant after Bonferroni correction. Similarly, we have not proven any significant association between other selected genetic variants and schizophrenia and related disorders. Studies including a higher number of subjects are warranted to reliably confirm the presence or absence of the studied associations.

Emerging Roles of FTO in Neuropsychiatric Disorders

FTO (fat mass and obesity associated) is a recently discovered gene related to obesity and expressed in various tissues of the human body, especially with high expression in the brain. Earlier studies have found that FTO is involved in several biological processes, including brain development and function. In particular, recent studies have found that FTO is a demethylase of N6-methyladenosine (m6A) and it can affect neurological function through the m6A modification of mRNA. At present, a number of studies have shown that FTO is associated with many neuropsychiatric disorders. This paper reviews the discovery, structure, function, and tissue expression of FTO followed by discussing the relationship between FTO and neuropsychiatric diseases. In addition, the potential roles of FTO gene in drug addiction, major depression (MDD), and schizophrenia (SCZ) through regulating m6A modification of dopamine related genes were also highlighted.

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.

Search for Possible Associations of FTO Gene Polymorphic Variants with Metabolic Syndrome, Obesity and Body Mass Index in Schizophrenia Patients

Purpose

Metabolic syndrome (MetS) is characterized by abdominal obesity, hyperglycaemia, dyslipidaemia and hypertension. FTO gene has been implicated in the pathogenesis of obesity, but the available scientific data concerning their relationship to antipsychotic drug-induced obesity and metabolic syndrome is still incomplete and inconsistent, which indicates that continuing the investigation of this gene’s role is necessary.

Patients and Methods

In the present study, 517 patients with schizophrenia underwent antipsychotic drug treatment, and two groups were identified: patients with MetS and without MetS. Genotyping of 6 SNPs in the FTO gene was performed, and the results analyzed using R-programme.

Results

We performed a statistical analysis to identify possible associations of the frequencies of genotypes and alleles of the studied polymorphisms with the presence of metabolic syndrome in schizophrenia patients, with the presence of abdominal obesity, and with an increased body mass index. The rs7185735 polymorphism did not meet the Hardy-Weinberg criterion and was excluded. After correcting for differences in age, gender and duration of illnesses, none of the variants was shown to be related to metabolic syndrome or abdominal obesity, but rs9939609, rs1421085, rs3751812 and rs8050136 were associated with body mass index.

Conclusion

The present study provides additional support for these SNP’s roles as a pharmacogenetic biomarker that may become useful in the framework of the personalized medicine approach.

Clinical, Biochemical and Genetic Variables Associated With Metabolic Syndrome in Patients With Schizophrenia Spectrum Disorders Using Second-Generation Antipsychotics: A Systematic Review

Background: Individuals with severe mental illness experience increased morbidity and mortality compared to the general population. Adverse effects of antipsychotics, including weight gain, may contribute to the development of metabolic syndrome (MetS), which is associated with increased risks of all-cause and cardiovascular disease mortality. We aim to provide a comprehensive overview of clinical, biochemical and genetic factors associated with MetS among patients with schizophrenia spectrum disorders using second-generation antipsychotics (SGA). Methods: A literature search was performed in Pubmed and Embase to identify all cohort studies, cross-sectional studies and clinical trials investigating associations with MetS in patients with schizophrenia spectrum disorders using SGAs. We extracted and enumerated clinical, biochemical and genetic factors reported to be associated with MetS. We defined factors associated with MetS as factors being reported as associated with MetS in two or more studies. Results: 58 studies were included in this review (n = 12,123). In total, 62 factors were found to be associated with increased risk of MetS. Thirty one out of 58 studies investigated factors that were reported as associated with MetS in two or more studies. With regard to clinical factors, we found gender, higher age, concomitant use of mood stabilizers, higher baseline and current BMI, earlier SGA exposure, higher dose, longer duration of treatment, psychosis and tobacco smoking to be significantly associated with MetS. Furthermore, the biochemical factors hypo-adiponectinemia, elevated levels of C-reactive protein (CRP) and higher white blood cell (WBC) count were identified as factors associated with MetS. Among pharmacogenetic factors, the rs1414334 C-allele of the HTR2C-gene was associated with MetS in patients using SGA. Conclusion: In this systematic review investigating clinical, biochemical and genetic factors associated with MetS in patients using SGAs we found that higher age, higher baseline BMI, higher current BMI and male as well as female gender were positively associated with MetS across all antipsychotics. This study may set the stage for the application of clinical, biochemical and genetic factors to predict the risk of developing MetS in patients using SGAs. Future research is needed to determine which patients using SGAs are at risk to develop MetS in clinical practice.

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.

Association between the -2548G/A polymorphism of the leptin gene and antipsychotic-induced weight gain: Analysis of the CATIE sample and meta-analysis

BACKGROUND

Antipsychotics, especially most of the second-generation antipsychotics, have a high risk for metabolic syndrome and antipsychotic-induced weight gain (AIWG). A promoter variant of the leptin (LEP) gene, -2548G/A (rs7799039), has been associated with AIWG in several studies. The aim of this study was to evaluate this association in the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) sample, followed by meta-analysis.

METHODS

We investigated the association between rs7799039 and AIWG in a sub-sample of European (N = 164) individuals from the CATIE study. Body mass index (BMI) change and weight gain (presence or absence) was analyzed using ANCOVA and logistic regression, respectively. For the meta-analysis, a literature search was conducted using MEDLINE, Embase, and PsycINFO up to October 2019. The pooled odds ratio was calculated for presence or absence of weight gain (≥7% weight change) using a random effects model.

RESULTS

We did not detect an association between rs7799039 and BMI change or weight gain (presence or absence) in the CATIE sample. As for the meta-analysis, we included 12 studies. No significant associations between the LEP rs7799039 polymorphism and AIWG were observed under the allelic genetic model (allele A vs. allele G) (OR = 1.10 [0.71, 1.70], p = .68). In the subgroup analyses of first-episode schizophrenia patients, a significant association between the A-allele and weight gain was observed, respectively (OR = 2.32 [1.41, 3.82], p = .0009).

CONCLUSIONS

The present meta-analysis showed no significant effect of rs7799039 on AIWG. However, this variant may influence AIWG in first-episode schizophrenia patients. Further investigation of a larger and more homogenous sample is required to elucidate the role of the LEP gene in AIWG.

Association study of candidate genes with obesity and metabolic traits in antipsychotic-treated patients with first-episode psychosis over a 2-year period

AIMS

Patients with a first episode of psychosis (FEP) often display different metabolic disturbances even independently of drug therapy. However, antipsychotic (AP) treatment, especially with second-generation APs, is strongly linked to weight gain, which increases patients' risk of developing obesity and other metabolic diseases. There is an important genetic risk component that can contribute to the appearance of these disturbances. The aim of the present study was to evaluate the effect of polymorphisms in selected candidate genes on obesity and other anthropometric and metabolic traits in 320 AP-treated FEP patients over the course of a 2-year follow-up.

METHODS

These patients were recruited in the multicentre PEPs study (Phenotype-genotype and environmental interaction; Application of a predictive model in first psychotic episodes). A total of 127 validated single nucleotide polymorphisms (SNPs) in 18 candidate genes were included in the genetic analysis.

RESULTS

After Bonferroni correction, SNPs in ADRA2A, FTO, CNR1, DRD2, DRD3, LEPR and BDNF were associated with obesity, abdominal circumference, triglycerides, HDL cholesterol, and/or percentage of glycated haemoglobin.

CONCLUSIONS

Although our results should be interpreted as exploratory, they support previous evidence of the impact of these candidate genes on obesity and metabolic status. Further research is required to gain a better knowledge of the genetic variants that can be considered relevant metabolic risk factors. The ability to identify FEP patients at higher risk for these metabolic disturbances would enable clinicians to better select and control their AP treatment.

Psychiatric drugs impact mitochondrial function in brain and other tissues

Mitochondria have been linked to the etiology of schizophrenia (SZ). However, studies of mitochondria in SZ might be confounded by the effects of pharmacological treatment with antipsychotic drugs (APDs) and other common medications. This review summarizes findings on relevant mitochondria mechanisms underlying SZ, and the potential impact of psychoactive drugs including primarily APDs, but also antidepressants and anxiolytics. The summarized data suggest that APDs impair mitochondria function by decreasing Complex I activity and ATP production and dissipation of the mitochondria membrane potential. At the same time, in the brains of patients with SZ, antipsychotic drug treatment normalizes gene expression modules enriched in mitochondrial genes that are decreased in SZ. This indicates that APDs may have both positive and negative effects on mitochondria. The available evidence suggests three conclusions i) alterations in mitochondria functions in SZ exist prior to APD treatment, ii) mitochondria alterations in SZ can be reversed by APD treatment, and iii) APDs directly cause impairment of mitochondria function. Overall, the mechanisms of action of psychiatric drugs on mitochondria are both direct and indirect; we conclude the effects of APDs on mitochondria may contribute to both their therapeutic and metabolic side effects. These studies support the hypothesis that neuronal mitochondria are an etiological factor in SZ. Moreover, APDs and other drugs must be considered in the evaluation of this pathophysiological role of mitochondria in SZ. Considering these effects, pharmacological actions on mitochondria may be a worthwhile target for further APD development.

Clinical and Genetic Factors Associated with Resistance to Treatment in Patients with Schizophrenia: A Case-Control Study

Objectives: To assess clinical and genetic factors affecting response to treatment in a sample of patients with schizophrenia (treatment-resistant patients versus treatment responders). We also aimed at examining if these factors are different when we consider two different resistance classifications (the positive and negative syndrome scale, PANSS and the brief psychiatric rating scale, BPRS). Material and Methods: A case-control study included treatment-resistant patients and good responders. Patients were stratified in two groups based on the established criteria for treatment-resistant schizophrenia using BPRS and PANSS. The study was approved by the ethical committees (references: CEHDF1017; HPC-017-2017) and all patients/legal representatives gave their written consent. Clinical factors were assessed. DNA was obtained using a buccal swab and genotyping for OPRM1, COMT, DRD2 et MTHFR genes using the Lightcycler^® (Roche). Results: Some discrepancies between the BPRS and PANSS definitions were noted in our study when assessing the patients’ psychopathological symptoms and response to treatment. The multivariable analysis, taking the presence versus absence of treatment resistance as the dependent variable, showed that that family history of schizophrenia, university studies, time since the beginning of treatment and chlorpromazine equivalent dose as well as the COMT gene are associated with resistance to treatment. In addition, a gender-related difference was noted for COMT SNP; men with at least one Met allele were more prone to be resistant to treatment than Val/Val patients. Conclusion: Uncovering the clinical and genetic factors associated with resistance to treatment could help us better treat our schizophrenic patients in a concept of personalized medicine.

Pharmacogenetic Correlates of Antipsychotic-Induced Weight Gain in the Chinese Population

Antipsychotic-induced weight gain (AIWG) is a common adverse effect of this treatment, particularly with second-generation antipsychotics, and it is a major health problem around the world. We aimed to review the progress of pharmacogenetic studies on AIWG in the Chinese population to compare the results for Chinese with other ethnic populations, identify the limitations and problems of current studies, and provide future research directions in China. Both English and Chinese electronic databases were searched to identify eligible studies. We determined that > 25 single-nucleotide polymorphisms in 19 genes have been investigated in association with AIWG in Chinese patients over the past few decades. HTR2C rs3813929 is the most frequently studied single-nucleotide polymorphism, and it seems to be the most strongly associated with AIWG in the Chinese population. However, many genes that have been reported to be associated with AIWG in other ethnic populations have not been included in Chinese studies. To explain the pharmacogenetic reasons for AIWG in the Chinese population, genome-wide association studies and multiple-center, standard, unified, and large samples are needed.

A Genetic Association Study of MTHFR C677T Polymorphism with Risk of Metabolic Syndrome: A Systematic Review and Meta-Analysis

Methylenetetrahydrofolate reductase (MTHFR) is an enzyme that plays a crucial role as a methyl-group donor in demethylation of homocysteine. The aim of this systematic review and meta-analysis was to study the relationship between MTHFR gene polymorphism and metabolic syndrome (MS). We used search engines and databases such as Science Direct, Google Scholar, Embase, Cochrane Library, and PubMed to identify eligible studies up to 2018. The articles were studied based on keywords including MTHFR, mutation, variant, and polymorphism in combination with MS. Data was analyzed using Comprehensive Meta-Analysis version 2.2.064 software. After extracting the data from seven articles, the total number of subjects was 1280 in the patient group and 1374 in the control group. The odds ratio was estimated to be 1.078 for the allele model of T vs. C (95% confidence interval [CI]: 1.626-0.715), 1.157 for the allele model of CC vs. CT (95% CI: 0.829-1.615), 1.020 for the allele model of CT + TT vs. CC (95% CI: 1.611-0.646) and 0.799 for the allele model of TT vs. CC + CT (95% CI: 1.185- 0.539). As well, the results showed no statistically significant correlation between polymorphism genotypes of the MTHFR gene and MS (P<0.05). In general, this study showed that the presence of C677T polymorphism in the MTHFR gene has no effect on the incidence of MS.

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.

New findings in pharmacogenetics of schizophrenia

PURPOSE OF REVIEW

This review highlights recent advances in the investigation of genetic factors for antipsychotic response and side effects.

RECENT FINDINGS

Antipsychotics prescribed to treat psychotic symptoms are variable in efficacy and propensity for causing side effects. The major side effects include tardive dyskinesia, antipsychotic-induced weight gain (AIWG), and clozapine-induced agranulocytosis (CIA). Several promising associations of polymorphisms in genes including HSPG2, CNR1, and DPP6 with tardive dyskinesia have been reported. In particular, a functional genetic polymorphism in SLC18A2, which is a target of recently approved tardive dyskinesia medication valbenazine, was associated with tardive dyskinesia. Similarly, several consistent findings primarily from genes modulating energy homeostasis have also been reported (e.g. MC4R, HTR2C). CIA has been consistently associated with polymorphisms in the HLA genes (HLA-DQB1 and HLA-B). The association findings between glutamate system genes and antipsychotic response require additional replications.

SUMMARY

The findings to date are promising and provide us a better understanding of the development of side effects and response to antipsychotics. However, more comprehensive investigations in large, well characterized samples will bring us closer to clinically actionable findings.

Influence of polygenic risk scores on lipid levels and dyslipidemia in a psychiatric population receiving weight gain-inducing psychotropic drugs

OBJECTIVES

Dyslipidemia represents a major health issue in psychiatry. We determined whether weighted polygenic risk scores (wPRSs) combining multiple single-nucleotide polymorphisms (SNPs) associated with lipid levels in the general population are associated with lipid levels [high-density lipoprotein (HDL), low-density lipoprotein (LDL), total cholesterol (TC), and triglycerides] and/or dyslipidemia in patients receiving weight gain-inducing psychotropic drugs. We also determined whether genetics improve the predictive power of dyslipidemia.

PATIENTS AND METHODS

The influence of wPRS on lipid levels was firstly assessed in a discovery psychiatric sample (n=332) and was then tested for replication in an independent psychiatric sample (n=140). The contribution of genetic markers to predict dyslipidemia was evaluated in the combined psychiatric sample.

RESULTS

wPRSs were significantly associated with the four lipid traits in the discovery (P≤0.02) and in the replication sample (P≤0.03). Patients whose wPRS was higher than the median wPRS had significantly higher LDL, TC, and triglyceride levels (0.20, 0.32 and 0.26 mmol/l, respectively; P≤0.004) and significantly lower HDL levels (0.13 mmol/l; P<0.0001) compared with others. Adding wPRS to clinical data significantly improved dyslipidemia prediction of HDL (P=0.03) and a trend for improvement was observed for the prediction of TC dyslipidemia (P=0.08).

CONCLUSION

Population-based wPRSs have thus significant effects on lipid levels in the psychiatric population. As genetics improved the predictive power of dyslipidemia development, only 24 patients need to be genotyped to prevent the development of one case of HDL hypocholesterolemia. If confirmed by further prospective investigations, the present results could be used for individualizing psychotropic treatment.

Pharmacogenomics in Psychiatric Practice

Pharmacogenomic testing in psychiatry is becoming an established clinical procedure. Several vendors provide clinical interpretation of combinatorial pharmacogenomic testing of gene variants that have documented predictive implications regarding either pharmacologic response or adverse effects in depression and other psychiatric conditions. Such gene profiles have demonstrated improvements in outcome in depression, and reduction of cost of care of patients with inadequate clinical response. Additionally, several new gene variants are being studied to predict specific response in individuals. Many of these genes have demonstrated a role in the pathophysiology of depression or specific depressive symptoms. This article reviews the current state-of-the-art application of psychiatric pharmacogenomics.

The importance of gene-environment interactions in human obesity

The worldwide obesity epidemic has been mainly attributed to lifestyle changes. However, who becomes obese in an obesity-prone environment is largely determined by genetic factors. In the last 20 years, important progress has been made in the elucidation of the genetic architecture of obesity. In parallel with successful gene identifications, the number of gene-environment interaction (GEI) studies has grown rapidly. This paper reviews the growing body of evidence supporting gene-environment interactions in the field of obesity. Heritability, monogenic and polygenic obesity studies provide converging evidence that obesity-predisposing genes interact with a variety of environmental, lifestyle and treatment exposures. However, some skepticism remains regarding the validity of these studies based on several issues, which include statistical modelling, confounding, low replication rate, underpowered analyses, biological assumptions and measurement precision. What follows in this review includes (1) an introduction to the study of GEI, (2) the evidence of GEI in the field of obesity, (3) an outline of the biological mechanisms that may explain these interaction effects, (4) methodological challenges associated with GEI studies and potential solutions, and (5) future directions of GEI research. Thus far, this growing body of evidence has provided a deeper understanding of GEI influencing obesity and may have tremendous applications in the emerging field of personalized medicine and individualized lifestyle recommendations.

Pharmacogenomics in Asia: a systematic review on current trends and novel discoveries

While early pharmacogenomic studies have primarily been carried out in Western populations, there has been a notable increase in the number of Asian studies over the past decade. We systematically reviewed all pharmacogenomic studies conducted in Asia published before 2016 to highlight trends and identify research gaps in Asia. We observed that pharmacogenomic research in Asia was dominated by larger developed countries, notably Japan and Korea, and mainly driven by local researchers. Studies were focused on drugs acting on the CNS, chemotherapeutics and anticoagulants. Significantly, several novel pharmacogenomic associations have emerged from Asian studies. These developments are highly encouraging for the strength of regional scientific and clinical community and propound the importance of discovery studies in different populations.

Associations of MTHFR C677T polymorphism with insulin resistance, results of NURSE Study (Nursing Unacquainted Related Stress Etiologies)

Background

The insulin resistance syndrome is one of the major contributors of metabolic syndrome, diabetes Type 2 and atherosclerotic cardiovascular disease. A common mutation (677C to T; Ala to Val) in the methylenetetrahydrofolate reductase (MTHFR) gene is associated with decreased specific MTHFR activity and elevation of the homocysteine. The aim of this study is investigation of association between MTHFR 677C > T polymorphism with insulin resistance by using HOMA (Homeostasis Model Assessment) index in nurses who are potentially prone to develop insulin resistance because of unfavorable effects of shift work.

Method

Nursing Unacquainted Related Stress Etiologies Study (Nurse Study) was conducted in five different educational hospitals of Tehran University of Medical Science (TUMS). The nurses aged 22–57 who have been referred by the matron were recruited. A self-administered questionnaire was completed. Anthropometric measurements including weight, height, waist and hip circumference in addition to blood pressure were measured. Insulin resistance and Insulin sensitivity were measured using the homeostatic model assessment (HOMA) and quantitative insulin sensitivity check index (QUICKI) respectively. The detection of MTHFR C677T polymorphism in exon four of MTHFR gene was performed by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) analysis using HINFI restriction enzyme digestion.

Result

A total of 273 subjects were recruited in the study. CT genotype were detected in 51.6% (129) subjects and CC and TT genotype were seen in 9.2% (25) and 35.2% (96) subjects respectively. Participants with TT genotype (9.65 ± 4.00) have significantly lower insulin level than participants with CT genotype (14.12 ± 15.34) (p-value: 0.01). The same significant difference was observed for HOMA index (p-value: 0.03). Result showed that HOMA is lower in subjects who are taking supplements.

Conclusion

Result of this study showed subjects with TT genotype had significantly lower HOMA compare to CT genotype and the same pattern was seen for insulin level. We also found subjects taking supplement have lower HOMA compared to others regardless of their genotype.

Genetics of Common Antipsychotic-Induced Adverse Effects

The effectiveness of antipsychotic drugs is limited due to accompanying adverse effects which can pose considerable health risks and lead to patient noncompliance. Pharmacogenetics (PGx) offers a means to identify genetic biomarkers that can predict individual susceptibility to antipsychotic-induced adverse effects (AAEs), thereby improving clinical outcomes. We reviewed the literature on the PGx of common AAEs from 2010 to 2015, placing emphasis on findings that have been independently replicated and which have additionally been listed to be of interest by PGx expert panels. Gene-drug associations meeting these criteria primarily pertain to metabolic dysregulation, extrapyramidal symptoms (EPS), and tardive dyskinesia (TD). Regarding metabolic dysregulation, results have reaffirmed HTR2C as a strong candidate with potential clinical utility, while MC4R and OGFR1 gene loci have emerged as new and promising biomarkers for the prediction of weight gain. As for EPS and TD, additional evidence has accumulated in support of an association with CYP2D6 metabolizer status. Furthermore, HSPG2 and DPP6 have been identified as candidate genes with the potential to predict differential susceptibility to TD. Overall, considerable progress has been made within the field of psychiatric PGx, with inroads toward the development of clinical tools that can mitigate AAEs. Going forward, studies placing a greater emphasis on multilocus effects will need to be conducted.

A systematic review of genetic variants associated with metabolic syndrome in patients with schizophrenia

Metabolic syndrome (MetS) is a cluster of factors that increases the risk of cardiovascular disease (CVD), one of the leading causes of mortality in patients with schizophrenia. Incidence rates of MetS are significantly higher in patients with schizophrenia compared to the general population. Several factors contribute to this high comorbidity. This systematic review focuses on genetic factors and interrogates data from association studies of genes implicated in the development of MetS in patients with schizophrenia. We aimed to identify variants that potentially contribute to the high comorbidity between these disorders. PubMed, Web of Science and Scopus databases were accessed and a systematic review of published studies was conducted. Several genes showed strong evidence for an association with MetS in patients with schizophrenia, including the fat mass and obesity associated gene (FTO), leptin and leptin receptor genes (LEP, LEPR), methylenetetrahydrofolate reductase (MTHFR) gene and the serotonin receptor 2C gene (HTR2C). Genetic association studies in complex disorders are convoluted by the multifactorial nature of these disorders, further complicating investigations of comorbidity. Recommendations for future studies include assessment of larger samples, inclusion of healthy controls, longitudinal rather than cross-sectional study designs, detailed capturing of data on confounding variables for both disorders and verification of significant findings in other populations. In future, big genomic datasets may allow for the calculation of polygenic risk scores in risk prediction of MetS in patients with schizophrenia. This could ultimately facilitate early, precise, and patient-specific pharmacological and non-pharmacological interventions to minimise CVD associated morbidity and mortality.

Association of LEPR and ANKK1 Gene Polymorphisms with Weight Gain in Epilepsy Patients Receiving Valproic Acid

BACKGROUND

Weight gain is the most frequent adverse effect of valproic acid (VPA) treatment, resulting in poor compliance and many endocrine disturbances. Similarities in the weight change of monozygotic twins receiving VPA strongly suggests that genetic factors are involved in this effect. However, few studies have been conducted to identify the relevant genetic polymorphisms. Additionally, the causal relationship between the VPA concentration and weight gain has been controversial. Thus, we investigated the effects of single nucleotide polymorphisms (SNPs) in several appetite stimulation and energy homeostasis genes and the steady state plasma concentrations (Css) of VPA on the occurrence of weight gain in patients.

METHODS

A total of 212 epilepsy patients receiving VPA were enrolled. Nineteen SNPs in 11 genes were detected using the Sequenom MassArray iPlex platform, and VPA Css was determined by high-performance liquid chromatography (HPLC).

RESULTS

After 6 months of treatment, 20.28% of patients were found to gain a significant amount of weight (weight gained ≥7%). Three SNPs in the leptin receptor (LEPR), ankyrin repeat kinase domain containing 1 (ANKK1), and α catalytic subunit of adenosine monophosphate-activated protein kinase (AMPK) showed significant associations with VPA-induced weight gain (p < 0.001, p = 0.017 and p = 0.020, respectively). After Bonferroni correction for multiple tests, the genotypic association of LEPR rs1137101, the allelic association of LEPR rs1137101, and ANKK1 rs1800497 with weight gain remained significant. However, the VPA Css in patents who gained weight were not significantly different from those who did not gain weight (p = 0.121).

CONCLUSIONS

LEPR and ANKK1 genetic polymorphisms may have value in predicting VPA-induced weight gain.

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.