Genome-wide association study on antipsychotic-induced weight gain in the CATIE sample.

Antipsychotic-induced weight gain (AIWG) is a common side effect with a high genetic contribution. We reanalyzed genome-wide association study (GWAS) data from the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) selecting a refined subset of patients most suitable for AIWG studies. The final GWAS was conducted in N=189 individuals. The top polymorphisms were analyzed in a second cohort of N=86 patients. None of the single-nucleotide polymorphisms was significant at the genome-wide threshold of 5x10(-8). We observed interesting trends for rs9346455 (P=6.49x10(-6)) upstream of OGFRL1, the intergenic variants rs7336345 (P=1.31 × 10(-5)) and rs1012650 (P=1.47 × 10(-5)), and rs1059778 (P=1.49x10(-5)) in IBA57. In the second cohort, rs9346455 showed significant association with AIWG (P=0.005). The combined meta-analysis P-value for rs9346455 was 1.09 × 10(-7). Our reanalysis of the CATIE GWAS data revealed interesting new variants associated with AIWG. As the functional relevance of these polymorphisms is yet to be determined, further studies are needed.The Pharmacogenomics Journal advance online publication, 1 September 2015; doi:10.1038/tpj.2015.59.

Genetic association study between antipsychotic-induced weight gain and the melanocortin-4 receptor gene.

Antipsychotic-induced weight gain (AIWG) may result in the metabolic syndrome in schizophrenia (SCZ) patients. Downstream variants of the melanocortin-4 receptor (MC4R) gene have been associated with obesity in various populations. Thus, we examined single-nucleotide polymorphisms (SNPs) in the MC4R region for association with AIWG in SCZ patients. Four SNPs (rs2229616, rs17782313, rs11872992 and rs8087522) were genotyped in 224 patients who underwent treatment for SCZ and were evaluated for AIWG for up to 14 weeks. We compared weight change (%) across genotypic groups using analysis of covariance for three SNPs (r²≤0.8). European-ancestry patients who were rs8087522 A-allele carriers (AG+AA) on clozapine gained significantly more weight than non-carriers (P=0.027, n=69). These observations were marginal after correction for multiple testing. We performed in vitro electrophoretic mobility-shift assay that suggested that the presence of the A-allele may create a transcription factor-binding site. Further investigation is warranted for both these exploratory findings.

Association study of cannabinoid receptor 1 (CNR1) gene in tardive dyskinesia.

Tardive dyskinesia (TD) is a severe, debilitating movement disorder observed in 25-30% of the patients treated with typical antipsychotics. Cannabinoid receptor 1 (CNR1) activators tend to inhibit movement, an effect prevented by rimonabant and other selective CNR1 antagonists. Furthermore, CNR1 receptor is downregulated in Huntington's disease and upregulated in Parkinson's disease. Twenty tagSNPs spanning the CNR1 gene were analyzed in schizophrenia patients of European ancestry (n=191; 74 with TD). Significant genotypic (P=0.012) and allelic (P=0.012) association was observed with rs806374 (T>C). Carriers of the CC genotype were more likely to be TD positive (CC vs TT+TC, odds ratio=3.4 (1.5-7.8), P=0.003) and had more severe TD (CC vs TT+TC; 9.52±9.2 vs 5.62±6.9, P=0.046). These results indicate a possible role of CNR1 in the development of TD in our patient population. However, these observations are marginal after correcting for multiple testing and need to be replicated in a larger patient population.

Systematic analysis of dopamine receptor genes (DRD1-DRD5) in antipsychotic-induced weight gain.

Antipsychotic-induced weight gain has emerged as a serious complication in the treatment of patients with most antipsychotics. We have conducted the first in-depth examination of dopamine receptor genes in antipsychotic-induced weight gain. A total of 206 patients (139 of European descent and 56 African Americans) who underwent treatment for chronic schizophrenia or schizoaffective disorder were evaluated after on average over 6 weeks of treatment. Thirty-six tag single nucleotide polymorphisms (SNPs) and one variable-number tandem repeat, spanning the five dopamine receptor genes (DRD1-DRD5) were analyzed. In the total sample, we found a nominally significant association between the DRD2 rs1079598 marker and weight change using a cutoff of 7% gain (P=0.03). When stratifying the sample according to ethnicity and antipsychotics with highest risk for weight gain, we found significant associations in three DRD2 SNPs: rs6277 (C957T), rs1079598 and rs1800497 (TaqIA). The other genes were primarily negative. We provide evidence that dopamine receptor DRD2 gene variants might be associated with antipsychotic-induced weight gain in chronic schizophrenia patients.

Association study of tardive dyskinesia and five DRD4 polymorphisms in schizophrenia patients.

Tardive dyskinesia (TD) is a side effect of chronic antipsychotic medication exposure. Abnormalities in dopaminergic activity in the nigro-striatal system have been most often suggested to be involved because the agents that cause TD share in common potent antagonism of dopamine D(2) receptors (DRD2). Thus, a number of studies have focused on the association of dopamine system gene polymorphisms and TD, with the most consistent findings being an association between TD and the Ser9Gly polymorphism of the DRD3 gene and the TaqIA site 3' of the DRD2 gene. The DRD4 gene codes for the third member of the D(2)-like dopamine receptor family, and the variable number tandem-repeat polymorphism in exon 3 of DRD4 has been associated with TD. However, other polymorphisms have not been thoroughly examined. In this study, we investigated five polymorphisms spanning the DRD4 gene and their association with TD in our European Caucasian sample (N=171). Although the exon 3 variable number tandem repeat was not associated with TD, haplotypes consisting of four tag polymorphisms were associated with TD in males. This study suggests that DRD4 may be involved in TD in the Caucasian population, although further replication studies are needed.

Methylenetetrahydrofolate reductase gene variants and antipsychotic-induced weight gain and metabolic disturbances.

Weight gain and metabolic disturbances represent serious side-effects in antipsychotic (AP) treatment, particularly with clozapine and olanzapine. The methylenetetrahydrofolate reductase (MTHFR) gene is a key determinant in the folate metabolism and previous studies reported a significant effect on AP-induced weight gain and related metabolic abnormalities. Thus, we investigated MTHFR gene variants and changes in several important metabolic parameters in AP-treated patients. In this study, two functional MTHFR polymorphisms, rs1801133 (C677T) and rs1801131 (A1298C), were investigated for changes in weight and metabolic parameters. Genotypic associations were evaluated in a large population (n = 347 including 66 first episode psychosis, FEP patients) treated mostly with clozapine and olanzapine. We did not detect any genotypic association with weight changes (p > 0.05) in our total sample and in the sample refined for ancestry and medication. In our allelic analyses, we observed a trend for the 677-C allele to be associated with weight gain in the total sample (p = 0.03). This effect appeared to be driven by the FEP patients where those carrying the C-allele gained, on average, twice as much weight. Exploratory analyses revealed a significant association between the C677T and the A1298C polymorphism with HDL cholesterol serum levels in patients (p = 0.031). Overall we did not detect a major effect of two functional MTHFR gene variants and AP-induced weight gain. However, our findings suggest an effect of the C677T polymorphism in FEP patients and changes in weight and cholesterol levels. Further investigations in a larger sample are required.

The role of oxytocin and oxytocin receptor gene variants in childhood-onset aggression.

Aggressive antisocial behaviours are the most common reasons why adolescents are referred to mental health clinics. Antisocial behaviours are costly in social and financial terms. The aetiology of aggressive behaviours is unknown but growing evidence suggests it is heritable, and certain genetic variants have been implicated as contributing factors. The purpose of this study was to determine whether genes regulating the hormone oxytocin (OXT) were associated with aggressive antisocial behaviour. The case-control study sample consisted of 160 cases of children displaying extreme, persistent and pervasive aggressive behaviour. This case sample was compared with 160 adult controls. We used polymerase chain reaction (PCR) to determine the genotype for three oxytocin gene (OXT) single nucleotide polymorphisms (SNPs): rs3761248, rs4813625 and rs877172; and five oxytocin receptor gene (OXTR) SNPs: rs6770632, rs11476, rs1042778, rs237902 and rs53576. Genotypic analyses were performed using stata, while differences in haplotypic and allelic frequencies were analysed using Unphased. We also performed within-case analyses (n = 236 aggressive cases) examining genotypic and allelic associations with callous-unemotional (CU) scores (as measured by the psychopathic screening device). OXTR SNPs rs6770632 and rs1042778 may be associated with extreme, persistent and pervasive aggressive behaviours in females and males, respectively. These and haplotype results suggest gender-specific effects of SNPs. No significant differences were detected with respect to CU behaviours. These results may help to elucidate the biochemical pathways associated with aggressive behaviours, which may aid in the development of novel medications.

Replicated association of the NR4A3 gene with smoking behaviour in schizophrenia and in bipolar disorder.

Schizophrenia and bipolar disorder are associated with dopamine neurotransmission and show high comorbidity with tobacco dependence. Recent evidence indicates that the family of the NR4A orphan nuclear receptors, which are expressed in dopamine neurons and in dopaminoceptive brain areas, may play a role in dopamine-mediated effects. We have, therefore, analysed the association of six single nucleotide polymorphisms (SNPs) within the three genes belonging to the NR4A orphan nuclear receptor family, NR4A1 (rs2603751, rs2701124), NR4A2 (rs12803, rs834835) and NR4A3 (rs1131339, rs1405209), with the degree of smoking in a sample of 204 unrelated schizophrenia patients, which included 126 smokers and 78 non-smokers. SNPs within the NR4A3 gene (rs1131339 and rs1405209) were significantly associated with heavy smoking in this cohort, using a stepwise analysis of the escalated number of cigarettes smoked per day (P = 0.008 and 0.006, respectively; satisfying the Nyholt significance threshold of 0.009, an adjustment for multiple testing). We then repeated the association analysis of the NR4A3 markers (rs1131339 and rs1405209) in a larger cohort of 319 patients with bipolar disorder, which included 167 smokers and 152 non-smokers. We have replicated the positive association with smoking of the NR4A3 SNP rs1131339 in this group (P = 0.04), providing an important confirmation of the involvement of the NR4A3 gene in nicotine addiction in patients with mental health disease, a population significantly at risk for nicotine addiction.