Association study between variants of AMP-activated protein kinase catalytic and regulatory subunit genes with antipsychotic-induced weight gain

Sex effects on DNA methylation affect discovery in epigenome-wide association study of schizophrenia

Sex differences in the epidemiology and clinical characteristics of schizophrenia are well-known; however, the molecular mechanisms underlying these differences remain unclear. Further, the potential advantages of sex-stratified meta-analyses of epigenome-wide association studies (EWAS) of schizophrenia have not been investigated. Here, we performed sex-stratified EWAS meta-analyses to investigate whether sex stratification improves discovery, and to identify differentially methylated regions (DMRs) in schizophrenia. Peripheral blood-derived DNA methylation data from 1519 cases of schizophrenia (male n = 989, female n = 530) and 1723 controls (male n = 997, female n = 726) from three publicly available datasets, and the TOP cohort were meta-analyzed to compare sex-specific, sex-stratified, and sex-adjusted EWAS. The predictive power of each model was assessed by polymethylation score (PMS). The number of schizophrenia-associated differentially methylated positions identified was higher for the sex-stratified model than for the sex-adjusted one. We identified 20 schizophrenia-associated DMRs in the sex-stratified analysis. PMS from sex-stratified analysis outperformed that from sex-adjusted analysis in predicting schizophrenia. Notably, PMSs from the sex-stratified and female-only analyses, but not those from sex-adjusted or the male-only analyses, significantly predicted schizophrenia in males. The findings suggest that sex-stratified EWAS meta-analyses improve the identification of schizophrenia-associated epigenetic changes and highlight an interaction between sex and schizophrenia status on DNA methylation. Sex-specific DNA methylation may have potential implications for precision psychiatry and the development of stratified treatments for schizophrenia.

Polymorphism of sheep PRKAA2 gene and its association with growth traits

Small ruminants farming plays an important role in the livelihood of a large part of the population. Herein we aimed to analyze the effects of single nucleotide polymorphisms in PRKAA2 gene on the growth-related traits of Hu sheep and Dorper sheep. The body weight and body type of 1254 sheep were measured at 80, 100, 120, 140, 160 and 180d, and 37620 phenotypic data were collected. RT-qPCR analysis was performed to test PRKAA2 gene expressed in different tissues of sheep, with the highest expression level in spleen, followed by kidney. In the present study, the PRKAA2 gene sequencing revealed one polymorphism located on Chr1 (Oar_rambouillet_v1.0), termed as chr1:32832382 G > A, and were significantly associated with growth traits of sheep (p < 0.05). The body weight, body length, chest circumference, and cannon circumference of individuals with AA genotype were significantly higher than those with the GG and GA genotypes (p < 0.05). Our findings reveal that PRKAA2 gene could be used as a marker-assisted selection to improve the growth-related traits of sheep.

miR-1227-3p participates in the development of fetal growth restriction via regulating trophoblast cell proliferation and apoptosis

Fetal growth restriction (FGR) is a common obstetric disease, which is harmful to the pregnant women and fetuses. It has many influencing factors, but the specific etiology is not clear. MiRNA plays an important role in the fetal growth and development. In this article, we use TaqMan Low-Density Array to screen and analyze the differently expressed miRNAs in FGR-affected placenta (n = 40) and the normal placenta (n = 40). A total of 139 abnormally expressed miRNAs in the FGR-affected placenta were identified, and miR-1227-3p was the most highly downregulated miRNA. Importantly, miR-1227-3p may promote the proliferation in HTR-8/SVneo cells, while inhibited the apoptosis of HTR-8/SVneo cells. DAVID was used to analyze the pathway enrichment of target genes of miR-1227-3p to predict its mechanism of action. Furthermore, the putative targets of miR-1227-3p were predicted using the TargetScan, PicTar, DIANA LAB, and miRWalk database. The potential expression of target genes of miR-1227-3p, including PRKAB2, AKT1, PIK3R3, and MKNK1 were significantly increased in FGR-affected placenta. Taken together, miR-1227-3p may participate in the development of FGR via regulating trophoblast cell proliferation and apoptosis by targeting genes involved in the insulin pathway. MiR-1227-3p may have a potential clinical value in the prevention and treatment of FGR, we need to study further to prove its value in the future.

Peripheral mechanisms of acute olanzapine induced metabolic dysfunction: A review of in vivo models and treatment approaches

Antipsychotic (AP) medications are associated with an increased risk for developing metabolic side effects including weight gain, dyslipidemia, hypertension, type 2 diabetes (T2D), and cardiovascular disease. Previous reviews have focused on the chronic metabolic side effects associated with AP use. However, an underappreciated aspect of APs are the rapid perturbations in glucose and lipid metabolism that occur with each dose of drug. The purpose of this narrative review is to summarize work examining the peripheral mechanisms of acute olanzapine-induced related metabolic disturbances. We also discuss recent studies that have attempted to elucidate treatment approaches to mitigate AP-induced impairments in fuel metabolism.

AMPK Subunits Harbor Largely Nonoverlapping Genetic Determinants for Body Fat Mass, Glucose Metabolism, and Cholesterol Metabolism

CONTEXT

Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is a heterotrimeric enzyme and central regulator of cellular energy metabolism. The impact of single nucleotide polymorphisms (SNPs) in all 7 AMPK subunit genes on adiposity, glucose metabolism, and lipid metabolism has not yet been systematically studied.

OBJECTIVE

To analyze the associations of common SNPs in all AMPK genes, and of different scores thereof, with adiposity, insulin sensitivity, insulin secretion, blood glucose, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, total cholesterol, and triglycerides.

STUDY DESIGN AND METHODS

A cohort of 2789 nondiabetic participants from the Tübingen Family study of type 2 diabetes, metabolically characterized by oral glucose tolerance test and genotyped by genome-wide SNP array, was analyzed.

RESULTS

We identified 6 largely nonoverlapping SNP sets across 4 AMPK genes (PRKAA1, PRKAA2, PRKAG2, PRKAG3) associated with adiposity, insulin sensitivity, insulin secretion, blood glucose, total/LDL cholesterol, or HDL cholesterol, respectively. A genetic score of body-fat-increasing alleles revealed per-allele effect sizes on body mass index (BMI) of +0.22 kg/m2 (P = 2.3 × 10-7), insulin sensitivity of -0.12 × 1019 L2/mol2 (P = 9.9 × 10-6) and 2-hour blood glucose of +0.02 mmol/L (P = 0.0048). Similar effects on blood glucose were observed with scores of insulin-sensitivity-reducing, insulin-secretion-reducing and glucose-raising alleles, respectively. A genetic cholesterol score increased total and LDL cholesterol by 1.17 mg/dL per allele (P = 0.0002 and P = 3.2 × 10-5, respectively), and a genetic HDL score decreased HDL cholesterol by 0.32 mg/dL per allele (P = 9.1 × 10-6).

CONCLUSIONS

We describe largely nonoverlapping genetic determinants in AMPK genes for diabetes-/atherosclerosis-related traits, which reflect the metabolic pathways controlled by the enzyme. Formation of trait-specific genetic scores revealed additivity of allele effects, with body-fat-raising alleles reaching a marked effect size. (J Clin Endocrinol Metab XX: 0-0, 2019).

Hepatic gene expression explains primary drug toxicity in bipolar disorder

In bipolar disorder (BPD), long-term psychotropic drug treatment is often necessary to prevent relapse or recurrence. Nevertheless, adverse drug effects including disturbances in hepatic metabolism are observed and still poorly understood. Here, the association between hepatic gene expression and histopathological changes of the liver was investigated. By the use of microarrays (Affymetrix U133 plus2.0), a genome-wide expression study was performed on BPD patients with psychotropic drug treatment (n = 29) compared to unaffected controls (n = 20) and validated by quantitative real-time PCR. WebGestalt was used to identify over-represented functional pathways of the Reactome database. Association analyses between histopathological changes and differentially expressed genes comprised in the over-represented functional pathways were performed using regression analyses, from which feature-expression heatmaps were drawn. The majority of identified genes were underexpressed and involved in energy supply, metabolism of lipids and proteins, and the innate immune system. Positive associations were found for genes involved in all pathways and degenerative changes. The strongest negative association was observed between genes involved in energy supply and hepatic activity, as well as inflammation. In summary, we found a possible association between gene expression involved in various biological pathways and histopathological changes of the liver in BPD. Further, we found support for the probable primary toxic effect of psychotropic drugs on hepatic injury in BPD. Even if the safety of psychotropic drugs improves, adverse effects especially on hepatic function should not be underestimated.

Antipsychotics Promote Metabolic Disorders Disrupting Cellular Lipid Metabolism and Trafficking

Antipsychotics frequently cause obesity and related metabolic disorders that current psychopharmacological/endocrinological theories do not explain consistently. An integrative/alternative theory implies metabolic alterations happening at the cellular level. Many observations in vitro and in vivo, and pivotal observations in humans, point towards chemical properties of antipsychotics, independent of receptor binding characteristics. Being amphiphilic weak bases, antipsychotics can disrupt lysosomal function, affecting cholesterol trafficking; moreover, by chemical mimicry, antipsychotics can inhibit cholesterol biosynthesis. These two molecular adverse effects may trigger a cascade of transcriptional and biochemical events, ultimately reducing available cholesterol while increasing cholesterol precursors and fatty acids. The macroscopic manifestation of these molecular alterations includes decreased high-density lipoprotein and increased very low-density lipoprotein and triglycerides that may translate into obesity and related metabolic disorders.

Adjunctive α-lipoic acid reduces weight gain compared with placebo at 12 weeks in schizophrenic patients treated with atypical antipsychotics: a double-blind randomized placebo-controlled study

α-Lipoic acid (ALA) has been reported to be effective in reducing body weight in rodents and obese patients. Our previous open trial showed that ALA may play a role in reducing weight gain in patients with schizophrenia on atypical antipsychotics. The present study evaluated the efficacy of ALA in reducing weight and BMI in patients with schizophrenia who had experienced significant weight gain since taking atypical antipsychotics. In a 12-week, double-blind randomized placebo-controlled study, 22 overweight and clinically stable patients with schizophrenia were randomly assigned to receive ALA or placebo. ALA was administered at 600-1800 mg, as tolerated. Weight, BMI, abdomen fat area measured by computed tomography, and metabolic values were determined. Adverse effects were also assessed to examine safety. Overall, 15 patients completed 12 weeks of treatment. There was significant weight loss and decreased visceral fat levels in the ALA group compared with the placebo group. There were no instances of psychopathologic aggravation or severe ALA-associated adverse effects. ALA was effective in reducing weight and abdominal obesity in patients with schizophrenia who had experienced significant weight gain since beginning an atypical antipsychotic regimen. Moreover, ALA was well tolerated throughout this study. ALA might play an important role as an adjunctive treatment in decreasing obesity in patients who take atypical antipsychotics.

Haloperidol inactivates AMPK and reduces tau phosphorylation in a tau mouse model of Alzheimer's disease

INTRODUCTION

The use of antipsychotic medications in Alzheimer's disease has been associated with an increased risk of mortality in clinical trials. However, an older postmortem literature suggests that those with schizophrenia treated in an era of exclusively conventional antipsychotic medications had a surprisingly low incidence of tau pathology. No previously published studies have investigated the impact of conventional antipsychotic exposure on tau outcomes in a tau mouse model of AD.

METHODS

In two experiments, transgenic rTg (tauP301L) 4510 tau mice were treated with either haloperidol or vehicle and phosphotau epitopes were quantified using high-sensitivity tau ELISA.

RESULTS

After treatments of 2 and 6 week's duration, mice treated with haloperidol evidenced a significant reduction in tau phosphorylation associated with an inactivation of the tau kinase AMPK.

DISCUSSION

The data suggest that D2 receptor blockade reduces tau phosphorylation in vivo. Future studies are necessary to investigate the impact of this reduction on tau neuropathology.

Association of PCK1 with Body Mass Index and Other Metabolic Features in Patients With Psychotropic Treatments

Weight gain is a major health problem among psychiatric populations. It implicates several receptors and hormones involved in energy balance and metabolism. Phosphoenolpyruvate carboxykinase 1 is a rate-controlling enzyme involved in gluconeogenesis, glyceroneogenesis and cataplerosis and has been related to obesity and diabetes phenotypes in animals and humans. The aim of this study was to investigate the association of phosphoenolpyruvate carboxykinase 1 polymorphisms with metabolic traits in psychiatric patients treated with psychotropic drugs inducing weight gain and in general population samples. One polymorphism (rs11552145G > A) significantly associated with body mass index in the psychiatric discovery sample (n = 478) was replicated in 2 other psychiatric samples (n1 = 168, n2 = 188), with AA-genotype carriers having lower body mass index as compared to G-allele carriers. Stronger associations were found among women younger than 45 years carrying AA-genotype as compared to G-allele carriers (-2.25 kg/m, n = 151, P = 0.009) and in the discovery sample (-2.20 kg/m, n = 423, P = 0.0004). In the discovery sample for which metabolic parameters were available, AA-genotype showed lower waist circumference (-6.86 cm, P = 0.008) and triglycerides levels (-5.58 mg/100 mL, P < 0.002) when compared to G-allele carriers. Finally, waist-to-hip ratio was associated with rs6070157 (proxy of rs11552145, r = 0.99) in a population-based sample (N = 123,865, P = 0.022). Our results suggest an association of rs11552145G > A polymorphism with metabolic-related traits, especially in psychiatric populations and in women younger than 45 years.

Pharmacogenetics of clozapine treatment response and side-effects in schizophrenia: an update

INTRODUCTION

Clozapine (CLZ) is the most effective treatment for treatment-resistant schizophrenia (SCZ) patients, with potential added benefits of reduction in suicide risk and aggression. However, CLZ is also mainly underused due to its high risk for the potentially lethal side-effect of agranulocytosis as well as weight gain and related metabolic dysregulation. Pharmacogenetics promises to enable the prediction of patient treatment response and risk of adverse effects based on patients' genetics, paving the way toward individualized treatment.

AREA COVERED

This article reviews pharmacogenetics studies of CLZ response and side-effects with a focus on articles from January 2012 to February 2015, as an update to the previous reviews. Pharmacokinetic genes explored primarily include CYP1A2, while pharmacodynamic genes consisted of traditional pharmacogenetic targets such as brain-derived neurotrophic factor as well novel mitochondrial genes, NDUFS-1 and translocator protein.

EXPERT OPINION

Pharmacogenetics is a promising avenue for individualized medication of CLZ in SCZ, with several consistently replicated gene variants predicting CLZ response and side-effects. However, a large proportion of studies have yielded mixed results. Large-scale Genome-wide association studies (e.g., CRESTAR) and targeted gene studies with standardized designs (response measurements, treatment durations, plasma level monitoring) are required for further progress toward clinical translation. Additionally, in order to improve study quality, we recommend accounting for important confounders, including polypharmacy, baseline measurements, treatment duration, gender, and age at onset.

Weight gain and obesity in schizophrenia: epidemiology, pathobiology, and management

OBJECTIVE

To review recent advances in the epidemiology, pathobiology, and management of weight gain and obesity in patients with schizophrenia and to evaluate the extent to which they should influence guidelines for clinical practice.

METHOD

A Medline literature search was performed to identify clinical and experimental studies published in 2005-2014 decade.

RESULTS

Weight gain and obesity increase the risk of adult-onset diabetes mellitus and cardiovascular disorders, non-adherence with pharmacological interventions, quality of life, and psychiatric readmissions. The etiology includes adverse effects of antipsychotics, pretreatment/premorbid genetic vulnerabilities, psychosocial and socioeconomic risk factors, and unhealthy lifestyle. Patients with schizophrenia have higher intake of calories in the form of high-density food and lower energy expenditure. The inverse relationship between baseline body mass index and antipsychotic-induced weight gain is probably due to previous antipsychotic exposure. In experimental models, the second-generation antipsychotic olanzapine increased the orexigenic stimulation of hypothalamic structures responsible for energy homeostasis.

CONCLUSION

The management of weight gain and obesity in patients with schizophrenia centers on behavioural interventions using caloric intake reduction, dietary restructuring, and moderate-intensity physical activity. The decision to switch antipsychotics to lower-liability medications should be individualized, and metformin may be considered for adjunctive therapy, given its favorable risk-benefit profile.

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.

Investigation of molecular serum profiles associated with predisposition to antipsychotic-induced weight gain

OBJECTIVES

Metabolic disturbances are major adverse side effects in the treatment of schizophrenia patients with antipsychotics. A substantial proportion of patients discontinue treatment with second-generation antipsychotics due to weight gain. The objective of this study was to investigate molecular factors predisposing patients to the development of such metabolic disturbances.

METHODS

We investigated whether serum molecules measured before treatment initiation were associated with subsequent weight gain following a 6-week treatment with antipsychotics. The concentrations of 191 molecules were measured longitudinally in serum from 77 schizophrenia patients using multiplex immunoassays.

RESULTS

This showed that the levels of 10 serum molecules at T0 were significantly associated with ΔBMI, which included interleukin-6 receptor, epidermal growth factor and thyroid stimulating hormone.

CONCLUSIONS

Our results suggest that patients who experience antipsychotic-induced weight gain have specific molecular alterations already prior to treatment. Further studies are required to validate and evaluate current findings in the context of response and side-effect development. This may ultimately lead to molecular tests that can aid in the selection of antipsychotic treatments.

Transcriptome alterations of mitochondrial and coagulation function in schizophrenia by cortical sequencing analysis

Background

Transcriptome sequencing of brain samples provides detailed enrichment analysis of differential expression and genetic interactions for evaluation of mitochondrial and coagulation function of schizophrenia. It is implicated that schizophrenia genetic and protein interactions may give rise to biological dysfunction of energy metabolism and hemostasis. These findings may explain the biological mechanisms responsible for negative and withdraw symptoms of schizophrenia and antipsychotic-induced venous thromboembolism.

We conducted a comparison of schizophrenic candidate genes from literature reviews and constructed the schizophrenia-mediator network (SCZMN) which consists of schizophrenic candidate genes and associated mediator genes by applying differential expression analysis to BA22 RNA-Seq brain data. The network was searched against pathway databases such as PID, Reactome, HumanCyc, and Cell-Map. The candidate complexes were identified by MCL clustering using CORUM for potential pathogenesis of schizophrenia.

Results

Published BA22 RNA-Seq brain data of 9 schizophrenic patients and 9 controls samples were analyzed. The differentially expressed genes in the BA22 brain samples of schizophrenia are proposed as schizophrenia candidate marker genes (SCZCGs). The genetic interactions between mitochondrial genes and many under-expressed SCZCGs indicate the genetic predisposition of mitochondria dysfunction in schizophrenia. The biological functions of SCZCGs, as listed in the Pathway Interaction Database (PID), indicate that these genes have roles in DNA binding transcription factor, signal and cancer-related pathways, coagulation and cell cycle regulation and differentiation pathways.

In the query-query protein-protein interaction (QQPPI) network of SCZCGs, TP53, PRKACA, STAT3 and SP1 were identified as the central "hub" genes. Mitochondrial function was modulated by dopamine inhibition of respiratory complex I activity. The genetic interaction between mitochondria function and schizophrenia may be revealed by DRD2 linked to NDUFS7 through protein-protein interactions of FLNA and ARRB2.

The biological mechanism of signaling pathway of coagulation cascade was illustrated by the PPI network of the SCZCGs and the coagulation-associated genes. The relationship between antipsychotic target genes (DRD2/3 and HTR2A) and coagulation factor genes (F3, F7 and F10) appeared to cascade the following hemostatic process implicating the bottleneck of coagulation genetic network by the bridging of actin-binding protein (FLNA).

Conclusions

It is implicated that the energy metabolism and hemostatic process have important roles in the pathogenesis for schizophrenia. The cross-talk of genetic interaction by these co-expressed genes and reached candidate genes may address the key network in disease pathology. The accuracy of candidate genes evaluated from different quantification tools could be improved by crosstalk analysis of overlapping genes in genetic networks.

Preventing olanzapine-induced weight gain using betahistine: a study in a rat model with chronic olanzapine treatment

Olanzapine is the one of first line antipsychotic drug for schizophrenia and other serious mental illness. However, it is associated with troublesome metabolic side-effects, particularly body weight gain and obesity. The antagonistic affinity to histamine H₁ receptors (H₁R) of antipsychotic drugs has been identified as one of the main contributors to weight gain/obesity side-effects. Our previous study showed that a short term (2 weeks) combination treatment of betahistine (an H₁R agonist and H₃R antagonist) and olanzapine (O+B) reduced (−45%) body weight gain induced by olanzapine in drug-naïve rats. A key issue is that clinical patients suffering with schizophrenia, bipolar disease and other mental disorders often face chronic, even life-time, antipsychotic treatment, in which they have often had previous antipsychotic exposure. Therefore, we investigated the effects of chronic O+B co-treatment in controlling body weight in female rats with chronic and repeated exposure of olanzapine. The results showed that co-administration of olanzapine (3 mg/kg, t.i.d.) and betahistine (9.6 mg/kg, t.i.d.) significantly reduced (−51.4%) weight gain induced by olanzapine. Co-treatment of O+B also led to a decrease in feeding efficiency, liver and fat mass. Consistently, the olanzapine-only treatment increased hypothalamic H₁R protein levels, as well as hypothalamic pAMPKα, AMPKα and NPY protein levels, while reducing the hypothalamic POMC, and UCP₁ and PGC-1α protein levels in brown adipose tissue (BAT). The olanzapine induced changes in hypothalamic H₁R, pAMPKα, BAT UCP₁ and PGC-1α could be reversed by co-treatment of O+B. These results supported further clinical trials to test the effectiveness of co-treatment of O+B for controlling weight gain/obesity side-effects in schizophrenia with chronic antipsychotic treatment.

Genetics of antipsychotic-induced weight gain: update and current perspectives

Antipsychotic medications are used to effectively treat various symptoms for different psychiatric conditions. Unfortunately, antipsychotic-induced weight gain (AIWG) is a common side effect that frequently results in obesity and secondary medical conditions. Twin and sibling studies have indicated that genetic factors are likely to be highly involved in AIWG. Over recent years, there has been considerable progress in this area, with several consistently replicated findings, as well as the identification of new genes and implicated pathways. Here, we will review the most recent genetic studies related to AIWG using the Medline database (PubMed) and Google Scholar. Among the steadiest findings associated with AIWG are serotonin 2C receptors (HTR2C) and leptin promoter gene variants, with more recent studies implicating MTHFR and, in particular, MC4R genes. Additional support was reported for the HRH1, BDNF, NPY, CNR1, GHRL, FTO and AMPK genes. Notably, some of the reported variants appear to have relatively large effect sizes. These findings have provided insights into the mechanisms involved in AIWG and will help to develop predictive genetic tests in the near future.

Protein kinase cAMP-dependent regulatory type II beta (PRKAR2B) gene variants in antipsychotic-induced weight gain

OBJECTIVE

Antipsychotics are effective in treating schizophrenia symptoms. However, the use of clozapine and olanzapine in particular are associated with significant weight gain. Mouse and human studies suggest that the protein kinase cAMP-dependent regulatory type II beta (PRKAR2B) gene may be involved in energy metabolism, and there is evidence that it is associated with clozapine's effects on triglyceride levels. We aimed at assessing PRKAR2B's role in antipsychotic-induced weight gain in schizophrenia patients.

METHODS

DNA samples from adult schizophrenia or schizoaffective disorder patients of mixed ancestry were genotyped, and weight gain was assessed. We analyzed 16 tag single-nucleotide polymorphisms across the PRKAR2B gene in a Caucasian subset treated either with clozapine or olanzapine (N = 99). Linear regression based on an additive model was performed with the inclusion of relevant covariates.

RESULTS

Normalized per cent weight change was analyzed, revealing that patients with the minor allele at rs9656135 had a mean weight increase of 4.1%, whereas patients without this allele had an increase of 3.4%. This association is not significant after correcting for multiple testing.

CONCLUSIONS

Because of limited power, PRKAR2B's role in antipsychotic-induced weight gain is unclear, but biological evidence suggests that PRKAR2B may be involved. Further research in larger sample sizes is warranted.

Pharmacogenetics in schizophrenia: a review of clozapine studies

OBJECTIVES

Clozapine is quite effective to treat schizophrenia, but its use is complicated by several factors. Although many patients respond to antipsychotic therapy, about 50% of them exhibit inadequate response, and ineffective medication trials may entail weeks of unremitted illness, potential adverse drug reactions, and treatment nonadherence. This review of the literature sought to describe the main pharmacogenetic studies of clozapine and the genes that potentially influence response to treatment with this medication in schizophrenics.

METHODS

We searched the PubMed database for studies published in English in the last 20 years using keywords related to the topic.

RESULTS AND CONCLUSIONS

Our search yielded 145 studies that met the search and selection criteria. Of these, 21 review articles were excluded. The 124 studies included for analysis showed controversial results. Therefore, efforts to identify key gene mechanisms that will be useful in predicting clozapine response and side effects have not been fully successful. Further studies with new analysis approaches and larger sample sizes are still required.

Exploratory study on association of genetic variation in TBC1D1 with antipsychotic-induced weight gain

BACKGROUND

Previous studies have shown that antipsychotics with high propensity for antipsychotic-induced weight gain (AIWG) influence glucose transporter type 4 (GLUT4) mediated glucose intake. Variation in the gene encoding TBC1 domain family member 1 (TBC1D1), a Rab-GTPase activating protein regulating GLUT4 trafficking, has been associated with obesity. Therefore, we investigated the impact of TBC1D1 polymorphisms on AIWG.

METHODS

We analyzed rs9852 and rs35859249 in TBC1D1 in 195 schizophrenia subjects treated mostly with clozapine or olanzapine for up to 14 weeks. Association was tested using analysis of variance and analysis of covariance with change (%) from baseline weight as the dependent variable.

RESULTS

Analysis of covariance showed a non-significant trend for lower weight gain in carriers of the T-allele of rs9852 than in C-allele homozygotes (p = 0.063). This effect was more pronounced in the subgroup of patients treated with clozapine or olanzapine (p = 0.024). For rs35859249, no significant association with AIWG could be detected.

CONCLUSIONS

This is the first study examining the association between TBC1D1 and AIWG. The moderate association of rs9852, located in the 3'UTR near a miRNA binding site, indicates an influence of TBC1D1 on AIWG. Further investigations remain necessary to elucidate the role of this gene in AIWG.

The pharmacogenetics of antipsychotic-induced adverse events

PURPOSE OF REVIEW

Antipsychotic drugs are effective in alleviating a variety of symptoms and are medication of first choice in schizophrenia. However, a substantial interindividual variability in side effects often requires a lengthy 'trial-and-error' approach until the right medication is found for the right patient. Genetic factors have long been hypothesized to be involved and identification of related gene variants could be used to predict and tailor drug treatment.

RECENT FINDINGS

This review highlighting the most recent genetic findings was conducted on the two most common and most well-studied side effects: antipsychotic-induced weight gain and tardive dyskinesia.

SUMMARY

Regarding weight gain, most promising and most consistent findings were obtained in the serotonergic system (HTR2C) and with hypothalamic leptin-melanocortin genes, in particular with one variant close to the melanocortin-4-receptor (MC4R) gene. With respect to tardive dyskinesia, most interesting findings were generally obtained in genes related to the dopaminergic system (dopamine receptors D2 and D3), and more recently with glutamatergic system genes. Overall, genetic studies have been successful in identifying strong findings, in particular for antipsychotic-induced weight gain and to some extent for tardive dyskinesia. Apart from the need for replication studies in larger and well-characterized samples, the next challenge will be to create predictive algorithms that can be used for clinical practice.

Behavioral interventions for antipsychotic induced appetite changes

Weight gain remains a well recognized yet difficult to treat adverse effect of many anti-psychotic drugs including agents of the first and second generation. The weight gain liabilities of antipsychotic drugs are partly associated with their ability to increase appetite. Most behavioral interventions for weight control remain of limited efficacy, possibly because they do not specifically target the neuroendocrine factors regulating appetite. Identifying new weight management interventions directly acting on the biochemical and neuroendocrine mechanisms of anti-psychotic induced weight gain may help to improve the efficacy of behavioral weight management programs. Such potentially specific strategies include (1) using diets which do not increase appetite despite calorie restriction; (2) countering thirst as an anticholinergic side-effect; (3) discouraging cannabis use and (4) adding metformin to a behavioral intervention. In view of our currently rather limited treatment repertoire it seems timely systematically to explore such novel options.