Genetic Variation of the Mu Opioid Receptor (OPRM1) and Dopamine D2 Receptor (DRD2) is Related to Smoking Differences in Patients with Schizophrenia but not Bipolar Disorder.

It is not known why mentally ill persons smoke excessively. Inasmuch as endogenous opioid and dopaminergic systems are involved in smoking reinforcement, it is important to study mu opioid receptor (OPRM1) A118G (rs1799971), dopamine D2 receptor (DRD2) Taq1A (rs1800497) genotypes, and sex differences among patients with schizophrenia or bipolar disorder. Smokers and nonsmokers with schizophrenia (n=177) and bipolar disorder (n=113) were recruited and genotyped. They were classified into three groups: current smoker, former smoker, and never smoker by tobacco smoking status self-report. The number of cigarettes smoked per day was used as the major tobacco smoking parameter. In patients with schizophrenia, tobacco smoking prevalence was greater in males than in females as expected, but women had greater daily cigarette consumption (p<0.01). Subjects with schizophrenia who had the OPRM1 *G genotype smoked more cigarettes per day than the AA allele carriers with schizophrenia (p<0.05). DRD2 Taq1A genotype differences had no effect on the number of cigarettes smoked per day. However, female smokers with schizophrenia who were GG homozygous of the DRD2 receptor smoked more than the *A male smokers with schizophrenia (p<0.05). In bipolar patients, there were no OPRM1 and DRD2 Taq1A genotype differences in smoking status. There also were no sex differences for smoking behavior among the bipolar patients. The results of this study indicate that single nucleotide polymorphism (SNP) of the less functional mu opioid receptor increases tobacco smoking in patients with schizophrenia. Alteration of DRD2 receptor function also increased smoking behavior in females with schizophrenia.

Metabolic syndrome in bipolar disorder and schizophrenia: dietary and lifestyle factors compared to the general population.

OBJECTIVE: Since a poor diet is often cited as a contributor to metabolic syndrome for subjects diagnosed with bipolar disorder and schizophrenia, we sought to examine dietary intake, cigarette smoking, and physical activity in these populations and compare them with those for the general population. METHODS: Individuals diagnosed with bipolar disorder (n = 116) and schizophrenia (n = 143) were assessed for dietary intake, lifestyle habits, and metabolic syndrome and compared to age-, gender-, and race-matched subjects from the National Health and Nutrition Examination Survey (NHANES) 1999-2000. Additionally, matched subgroups within the patient populations were compared to elicit any differences. RESULTS: As expected, the metabolic syndrome rate was higher in the samples with bipolar disorder (33%) and schizophrenia (47%) compared to matched NHANES controls (17% and 11%, respectively), and not different between the patient groups. Surprisingly, both subjects with bipolar disorder and those with schizophrenia consumed fewer total calories, carbohydrates and fats, as well as more fiber (p < 0.03), compared to NHANES controls. No dietary or activity differences between patient participants with and without metabolic syndrome were found. Subjects with schizophrenia had significantly lower total and low-density cholesterol levels (p < 0.0001) compared to NHANES controls. Subjects with bipolar disorder smoked less (p = 0.001), exercised more (p = 0.004), and had lower body mass indexes (p = 0.009) compared to subjects with schizophrenia. CONCLUSIONS: Counter to predictions, few dietary differences could be discerned between schizophrenia, bipolar disorder, and NHANES control groups. The subjects with bipolar disorder exhibited healthier behaviors than the patients with schizophrenia. Additional research regarding metabolic syndrome mechanisms, focusing on non-dietary contributions, is needed.

P-glycoprotein (PGP) polymorphisms and sexual dysfunction in female patients with depression and SSRI-associated sexual side effects.

Sexual dysfunction is common with selective serotonin reuptake inhibitor use for major depressive disorder. Studies have shown associations between genetic variation in the adenosine triphosphate (ATP)-binding cassette, subfamily B, member 1 gene (ABCB1), which encodes the drug efflux transporter P-glycoprotein (PGP), and selective serotonin reuptake inhibitor response. This study measured functionally implicated ABCB1 variants (rs2235015, rs1128503, rs2032582, and rs1045642) and sexual dysfunction using the Changes in Sexual Functioning Questionnaire. This study included outpatients (18-40 years of age) treated for major depressive disorder with a selective serotonin reuptake inhibitor for 6 weeks. Changes in Sexual Functioning Questionnaire outcomes were stratified by ABCB1 genotype and PGP substrate status. The authors recruited 82 individuals (22 men and 57 women). Women receiving a PGP substrate with a rs1128503 TT genotype had a significantly lower Changes in Sexual Functioning Questionnaire total score (37.2 ± 5.4), indicating greater sexual dysfunction, than did those with the CT (42.9 ± 6.3) or CC genotypes (46.6 ± 5.6), F(2) = 6.00, p = .005, p = .02, with multiple testing correction. The results indicate a relationship between genotypes at rs1128503, total sexual dysfunction, and PGP substrates use for women and may explain some of the sexual dysfunction variability seen with selective serotonin reuptake inhibitor treatment. Results need to be confirmed with a larger sample size that includes men.

DNA methylation in schizophrenia subjects: gender and MTHFR 677C/T genotype differences.

AIM: In schizophrenia, metabolic syndrome incidence is double that of the general population, with women having a higher incidence. Pharmacogenetically regulated folic acid may be related to this risk. DNA methylation and metabolic syndrome within this group has not been previously studied. METHODS: Metabolic syndrome was evaluated with fasting laboratory measurements, and dietary and lifestyle assessments. Methylation analysis used a peripheral sample for the LINE-1 assay. DNA was also genotyped for MTHFR 677C/T. RESULTS: This analysis included 133 subjects. We found a significant relationship between LINE-1 methylation, and an interaction between MTHFR and gender, controlling for serum folate (p = 0.008). Females with the 677TT genotype had the lowest methylation (56%) compared with the other groups (75%). CONCLUSION: TT genotype females had the lowest methylation, which may explain metabolic syndrome gender differences in schizophrenia. Folate supplementation may be a suggested intervention within schizophrenia; however, additional work is required.

Risk factors associated with metabolic syndrome in bipolar and schizophrenia subjects treated with antipsychotics: the role of folate pharmacogenetics.

Folate has been implicated in cardiovascular disease with atypical antipsychotic (AAPs) use, and individuals with methylenetetrahydrofolate reductase (MTHFR) and catechol-O-methyl transferase (COMT) variants are at greater risk. This study examined the relationship between the MTHFR 677C/T, MTHFR 1298A/C, and COMT Val158Met variants; metabolic syndrome; and lifestyle measures in schizophrenia and bipolar subjects. A total of 237 subjects with bipolar or schizophrenia receiving an antipsychotic for at least 6 months were included in this cross-sectional analysis. Subjects were screened for the metabolic syndrome (National Cholesterol Education Program Adult Treatment Panel III criteria) and MTHFR 677C/T, MTHFR 1298A/C, and Val158Met genotypes. In addition, serum folate and homocysteine were measured along with lifestyle factors. The subject's mean age was 44.7 (SD, 11.7) years; 72% were white, and 51% male; 61% were receiving an AAP; the mean body mass index was 32.6 (SD, 8.2) kg/m, and 48% were current smokers. Overall, 41% met metabolic syndrome criteria (n = 98). There were no differences in age, sex, AAP exposure, or body mass index between genotype groups. Metabolic syndrome was related to age, smoking, and the MTHFR 677T and COMT 158Val alleles (χ = 34.4, P < 0.0001). In addition, AAP use showed a trend association with metabolic syndrome (χ = 3.21, P = 0.07). These data support our previous reports and add more data pointing to folate's role in mediating a link between mental illness and cardiovascular disease. Use of this information clinically may help to reduce the risk for AAP metabolic complications in those whose clinical care necessitates the use of AAPs.

Dietary, lifestyle and pharmacogenetic factors associated with arteriole endothelial-dependent vasodilatation in schizophrenia patients treated with atypical antipsychotics (AAPs).

PURPOSE: Within schizophrenia cardiovascular disease (CVD) is highly prevalent secondary to atypical antipsychotic (AAP) use. Thorough assessments of diet, lifestyle, and endothelial functioning have not been done in this population. Omega 3 Fatty Acids (N-3 FAs) have garnered attention in relation to psychopathology as well as cardioprotection. This study examined the status of endothelial function within the schizophrenia population and determined pharmacogenetic, medication, dietary, and lifestyle factors associated with this functioning. METHODS: Schizophrenia subjects were screened for the metabolic syndrome along with physical activity, smoking, and variants related to folate pharmacogenetics in this cross-sectional analysis. Arteriole endothelial-dependent vasodilatation was measured using non-invasive peripheral arterial tonometry (RH-PAT, EndoPAT2000). A 24h dietary food recall was used to construct intake profiles using the Nutrition Data Systems for Research software (NDSR). We examined associations between AAP use and RH-PAT values, and the influence of N-3 FA dietary intake on this measure. Preliminary data are reported in 83 subjects with a mean age (±s.d.) of 45.89 (±11.49), 64% were Caucasian (n=53), 64% were male (n=53), and 77% were receiving AAP treatment (n=63). RESULTS: A significant positive relationship was found between RH-PAT values and N-3 FA intake (F=17.7(1,16), p=0.0007) in subjects not receiving AAPs. This relationship was lost in those treated with AAPs (F=0.25(1,43), p>0.6). Regression analysis confirmed the interaction effect of AAP treatment on the relationship between RH-PAT and N-3 FAs (p=0.0105). Endothelial dysfunction was also related to folate pharmacogenetic variants. CONCLUSIONS: AAPs may counteract some vascular health benefits of a diet high in N-3 FAs. AAP use may necessitate a higher N-3 FA dose to regain these effects, but additional research is necessary to strengthen the preliminary findings. Pharmacogenetic variants related to folate and homocysteine metabolism may also increase endothelial dysfunction risk.