Catechol-O-methyl-transferase functional polymorphism and nicotine dependence: an evaluation of nonreplicated results

Interaction between cytochrome P450 2A6 and Catechol-O-Methyltransferase genes and their association with smoking risk in young men

BACKGROUND

Although some effects of gene-gene interactions on nicotine-dopamine metabolism for smoking behavior have been reported, polymorphisms of cytochrome P450 (CYP) 2A6 and catechol-O-methyltransferase (COMT) have not been studied together to determine their effects on smokers. The aim of this study was to investigate the effects of the interaction between the CYP 2A6 and COMT genes on smoking behavior in young Taiwanese men.

RESULTS

A self-report questionnaire regarding smoking status was administered to 500 young men. Polymorphisms of the CYP 2A6 and COMT genes as well as urinary nicotine and urinary cotinine levels were determined. The odds ratio for starting smoking was significantly lower in subjects carrying a CYP2A6 low activity/variant COMT rs4680 genotype than in those possessing a CYP2A6 wild-type/variant COMT rs4680 genotype (0.44, 95% confidence interval = 0.19-0.98, P = 0.043). Comparisons of Fagerstrom Test for Nicotine Dependence (FTND), Physiological Cigarette Dependence Scale (PCDS), and Cigarette Withdrawal symptoms (CWS-21) among the smokers with different CYP2A6/COMT polymorphisms were not significantly different. The adjusted urinary nicotine concentrations were not significantly different between the two groups carrying different genotypes. The adjusted urinary cotinine level was significantly different between the COMT rs4680 wild-type group and COMT rs4680 variant group [92.46 ng/μL vs. 118.24 ng/μL (median value), P = 0.041] and between the COMT rs4680 wild-type/COMT rs165599 variant group and COMT rs4680 variant/COMT rs165599 variant group (97.10 ng/μL vs. 122.18 ng/μL, P = 0.022).

CONCLUSIONS

These findings suggest that a single nucleotide polymorphism (rs4680) of the COMT gene and the interaction between the CYP 2A6 and COMT genes affect smoking status in young Taiwanese men.

Sufentanil and Midazolam Dosing and Pharmacogenetic Factors in Pediatric Analgosedation and Withdrawal Syndrome

Our aim was to describe the effect of dosing and genetic factors on sufentanil- and midazolam-induced analgosedation and withdrawal syndrome (WS) in pediatric population. Analgosedation and withdrawal syndrome development were monitored using COMFORT-neo/-B scores and SOS score. Length of therapy, dosing of sufentanil and midazolam were recorded. Genotypes of selected candidate polymorphisms in CYP3A5, COMT, ABCB1, OPRM1 and PXR were analysed. In the group of 30 neonates and 18 children, longer treatment duration with midazolam of 141 h (2 – 625) vs. 88 h (7 – 232) and sufentanil of 326.5 h (136 – 885) vs. 92 h (22 – 211) (median; range) was found in the patients suffering from WS vs. non-WS group, respectively. Median midazolam cumulative doses were in the respective values of 18.22 mg/kg (6.93 – 51.25) vs. 9.94 mg/kg (2.12 – 49.83); P=0.03, and the respective values for sufentanil were 88.60 µg/kg (20.21 – 918.52) vs. 21.71 µg/kg (4.5 – 162.29); P<0.01. Cut off value of 177 hours for sufentanil treatment duration represented predictive factor for WS development with 81 % sensitivity and 94 % specificity. SNPs in the candidate genes COMT, PXR and ABCB1 affected the dosing of analgosedative drugs, but were not associated with depth of analgosedation or WS. Cumulative dose and length of analgosedative therapy with sufentanil significantly increases the risk of WS in critically ill neonates and children.

Catechol-O-methyltransferase gene methylation and substance use in adolescents: the TRAILS study

Substance use often starts in adolescence and poses a major problem for society and individual health. The dopamine system plays a role in substance use, and catechol-O-methyltransferase (COMT) is an important enzyme that degrades dopamine. The Val(108/158) Met polymorphism modulates COMT activity and thus dopamine levels, and has been linked to substance use. COMT gene methylation, on the other hand, may affect expression and thus indirectly COMT activity. We investigated whether methylation of the COMT gene was associated with adolescents' substance use. Furthermore, we explored whether the COMT Val(108/158) Met polymorphism interacts with COMT gene methylation in association with substance use. In 463 adolescents (mean age=16, 50.8% girls), substance use (cigarette smoking, alcohol and cannabis use) was assessed with self-report questionnaires. From blood samples, COMT Val(108/158) Met genotype and methylation rates of membrane bound (MB) and soluble (S) COMT promoters were assessed. MB-COMT promoter methylation was associated with non-daily smoking [odds ratio (OR)=1.82, P=0.03], but not with daily smoking (OR=1.20, P=0.34), MB-COMT promoter methylation was not associated with alcohol use. Adolescents with the Met/Met genotype and high rates of MB-COMT promoter methylation were less likely to be high-frequent cannabis users than adolescents with the Val/Val or Val/Met genotype. S-COMT promoter methylation was not associated with substance use. These results indicate that there is an association between substance use and COMT gene methylation. Although this association is complex, combining genetic and epigenetic variation of the COMT gene may be helpful in further elucidating the influence of the dopamine system on substance use in adolescence.

Genetic variation in three candidate genes and nicotine dependence, withdrawal and smoking cessation in hospitalized patients

AIMS

This study evaluates the relationship of six polymorphisms found in the CHRNA3, DRD2 and COMT genes with nicotine dependence, the ability to quit smoking and the occurrence of withdrawal symptoms after short-term use of nicotine patch in hospitalized patients.

MATERIALS & METHODS

The study included 233 participants from a double-blind, placebo-controlled trial of nicotine patch substitution with a 6-month follow-up period. Nicotine dependence was assessed by the Fagerström Test for Nicotine Dependence (FTND) questionnaire, withdrawal symptoms by the Minnesota Nicotine Withdrawal Scale questionnaire and smoking cessation by self-reported abstinence at 1 week, 1 month and 6 months after treatment.

RESULTS

After correcting for multiple testing, three polymorphisms in the DRD2 gene (Taq1A, Taq1B and Pro319Pro) were significantly associated with nicotine dependence (p = 0.018, p = 0.048 and p = 0.006, respectively). Using a cutoff point for the FTND score, the CHRNA3 Tyr215Tyr (rs1051730) polymorphism was also associated with nicotine dependence (p = 0.037 and p = 0.074 after correction for multiple testing). No association of any of the studied polymorphisms was observed with either smoking cessation or the occurrence of withdrawal symptoms.

CONCLUSION

This study confirms the reported association of the CHRNA3 locus with nicotine dependence and shows the involvement of two independent DRD2 polymorphisms in nicotine dependence.

The catechol-O-methyl transferase Val158Met polymorphism and experience of reward in the flow of daily life

Genetic moderation of experience of reward in response to environmental stimuli is relevant for the study of many psychiatric disorders. Experience of reward, however, is difficult to capture, as it involves small fluctuations in affect in response to small events in the flow of daily life. This study examined a momentary assessment reward phenotype in relation to the catechol-O-methyl transferase (COMT) Val(158)Met polymorphism. A total of 351 participants from a twin study participated in an Experience Sampling Method procedure to collect daily life experiences concerning events, event appraisals, and affect. Reward experience was operationalized, as the effect of event appraisal on positive affect (PA). Associations between COMT Val(158)Met genotype and event appraisal on the one hand and PA on the other were examined using multilevel random regression analysis. Ability to experience reward increased with the number of 'Met' alleles of the subject, and this differential effect of genotype was greater for events that were experienced as more pleasant. The effect size of genotypic moderation was quite large: subjects with the Val/Val genotype generated almost similar amounts of PA from a 'very pleasant event' as Met/Met subjects did from a 'bit pleasant event'. Genetic variation with functional impact on cortical dopamine tone has a strong influence on reward experience in the flow of daily life. Genetic moderation of ecological measures of reward experience is hypothesized to be of major relevance to the development of various behavioral disorders, including depression and addiction.

Genetics and smoking behavior

Accumulating data support the role of genetic factors in smoking initiation, progression to tobacco dependence, and smoking persistence. This review summarizes current research on the heritability of tobacco use phenotypes and genetic association studies of smoking-related behaviors. Although progress has been made in genetics research on smoking behavior, many studies have methodological limitations, including insufficient samples for detecting gene-gene and gene-environment interactions and use of less refined phenotypes. Pharmacogenetic investigations also are identifying variants in drug-metabolizing enzymes, receptors, and transporters that modify therapeutic response to smoking cessation medications; however, the field is relatively new, and most findings in this area have yet to be replicated. As this research advances, it will be important to study and address practical, economic, ethical, and social barriers to the translation of genetics research on tobacco use to clinical practice.

Association of COMT Val108/158Met genotype with smoking cessation in a nicotine replacement therapy randomized trial

We investigated the association of catechol O-methyltransferase (COMT) genotype with abstinence following a smoking cessation attempt among a large cohort of smokers who attempted to quit using either the nicotine transdermal patch or placebo and were followed up over an 8-year period following their initial cessation attempt. In addition, we examined the possible moderating influence of sex on any association. The genotype x treatment interaction effect at 12-week follow-up indicated a greater benefit of active nicotine replacement treatment compared with placebo on likelihood of abstinence in the COMT Met/Met genotype group (33% versus 12%), in comparison to the Met/Val + Val/Val group (22% versus 16%). Our results indicate that COMT genotype may moderate the effect of active transdermal nicotine patch compared with placebo, with reduced relative benefit of nicotine replacement therapy in individuals with Met/Val or Val/Val genotype. Our data follow an emerging pattern of results suggesting that genetic variation in the dopamine pathway may provide a future basis for tailored smoking cessation therapies, but indicate that different genes influencing various components of this pathway may have different effects on response to smoking cessation pharmacotherapy.

Genetic variation in catechol-O-methyltransferase (COMT) and obesity in the prostate, lung, colorectal, and ovarian (PLCO) cancer screening trial

Catechol-O-methyltransferase (COMT) is an important modulator in the catabolism of extraneural dopamine, which plays an important role in drug reward mechanisms. It is hypothesized that genetic variations in the COMT gene, which can result in a three to fourfold difference in COMT enzyme activity, may be associated with several reward-motivated behaviors. The aim of our study was to examine the relationship between COMT polymorphisms with smoking, obesity and alcohol. Three single nucleotide polymorphisms (SNPs) in COMT were genotyped in 2,371 participants selected randomly from the screening arm of the PLCO Cancer Screening Trial after stratifying by sex, age, and smoking status. Smoking, obesity, and alcohol consumption were assessed by questionnaire. SNP and haplotype associations were estimated using odds ratios (ORs) and 95% confidence intervals (CIs) derived from conditional logistic regression models, adjusted for race/ethnicity. The COMT Ex4-76C > G (Leu136Leu) polymorphism was statistically significantly associated with individuals who had >30% increases in BMI from ages 20 to 50 years, compared to those with 0-5% increase in BMI (0-5%) over the same age period: (CC is referent; OR(CG )= 1.42, OR(GG )= 1.46, P (trend )= 0.06). By sex, the increased risk was further pronounced among females (OR(CG )= 1.50, OR(GG )= 2.10, P (trend )= 0.03). Consistent with our analyses of single polymorphisms, individuals whose BMI increased >30% from ages 20 to 50 years were more likely than individuals with 0-5% increases in BMI to possess COMT haplotypes [COMT Ex3-104C > T-COMT Ex4-76 C > G-COMT Ex4-12 A > G] that included the variant allele for COMT Ex4-76 C > G: C-G-G (T-C-A is referent: OR(C-G-G )= 1.33, 95% CI 1.01-1.77) and C-G-A (OR(C-G-A )= 1.79, 95% CI 0.72-4.49). We observed no association between any of the COMT polymorphisms with smoking behavior or alcohol intake. The COMT Ex4-76C > G (Leu136Leu) polymorphism appears to play a role in large increases in BMI. The null association with smoking and alcohol and the pronounced association with increasing BMI among women further implicates COMT's role in estrogen metabolism as a potentially culpable pathway. Our results support a need for comprehensive evaluation of COMT variations and their functional relevance as COMT may be an important molecular target to evaluate for new treatments regarding obesity.

Genetic polymorphisms in dopamine-related genes and smoking cessation in women: a prospective cohort study

Background

Genes involved in dopaminergic neurotransmission have been suggested as candidates for involvement in smoking behavior. We hypothesized that alleles associated with reduced dopaminergic neurotransmission would be more common in continuing smokers than among women who quit smoking.

Methods

The study included 593 women aged 26–65 years who participated in a twelve month smoking cessation trial conducted in 1993–1994. Participants were contacted three years after the trial to obtain updated smoking history and biological specimens. Seven polymorphisms were assessed in genes involved in dopamine synthesis (tyrosine hydoxylase [TH]), receptor activation (dopamine receptors [DRD2, DRD3, DRD4]), reuptake (dopamine transporter [SLC6A3]), and metabolism (catechol-o-methyltransferase [COMT]). Smoking cessation was assessed as "short-term" quitting (abstinence for the seven days before the conclusion of the trial) and "long-term" quitting (abstinence for the six months before a subsequent interview conducted several years later).

Results

We observed no association of any polymorphism with either short- or long-term quitting. Although some relative risk estimates were consistent with weak associations, either the direction of effect was opposite of that hypothesized, or results of the short- and long-term cessation endpoints differed. However, effect modification on smoking cessation was observed between DRD2 Taq1A and SLC6A3 VNTR polymorphisms, DRD3 Ser/Gly and d,1-fenfluramine, and DRD4 VNTR and d,1-fenfluramine.

Conclusion

Although these results fail to support prior findings of independent associations of these polymorphisms with smoking status, our exploratory findings suggestive of gene-gene and gene-treatment interactions warrants further investigation.

Overview of the pharmacogenomics of cigarette smoking

Cigarette smoking increases the risk of numerous health problems, including cancer, cardiovascular and pulmonary disorders, making smoking the leading cause of preventable death in the world. Nicotine is primarily responsible for the highly addictive properties of cigarettes. Although the majority of smokers express a desire to quit, few are successful in doing so. Twin and family studies have indicated substantial genetic contributions to smoking behaviors. One major research focus has been to elucidate the specific genes involved; this has been accomplished primarily through genome-wide linkage analyses and candidate gene association studies. Much attention has focused on genes involved in the neurotransmitter pathways for the brain reward system and genes altering nicotine metabolism. This paper reviews the current state of knowledge for genetic factors implicated in smoking behaviors, and examines how genetic variations may affect therapeutic outcomes for drugs used to assist smoking cessation.

Catechol-O-methyltransferase (COMT) gene variants predict response to bupropion therapy for tobacco dependence

BACKGROUND

Although bupropion is efficacious for smoking cessation, only a minority of smokers are able to quit. Pharmacogenetic research may improve treatment outcomes through discovery of DNA sequences predictive of successful pharmacotherapy for subgroups of smokers. We investigated variants in the catechol-O-methyltransferase (COMT) gene in a smoking cessation trial of bupropion.

METHODS

A double-blind, placebo-controlled, 10-week trial of bupropion and counseling (with a 6-month follow-up period) was conducted at two university-based smoking cessation research programs. Abstinence was biochemically verified at the end of treatment and at 6 months after the target quit date.

RESULTS

At the end of the treatment phase, statistically significant interaction effects indicated that COMT haplotypes of two SNPs (rs737865 and rs165599) predicted the efficacy of bupropion compared with placebo. This interaction effect was attenuated at 6-month follow-up.

CONCLUSIONS

COMT haplotypes at rs737865 and rs165599 may predict a favorable outcome for bupropion treatment for smoking cessation. European-American smokers with a G allele at both SNPs may not benefit from bupropion treatment. Small numbers of some COMT haplotypes limit interpretation of response. If study findings are confirmed in additional large studies, COMT genotyping could be applied to identify likely responders to bupropion treatment for smoking cessation.

The genetics of nicotine dependence: Relationship to pancreatic cancer

Smoking of tobacco products continues to be a major cause of worldwide health problems. Epidemiological studies have shown that tobacco smoking is the greatest risk factor for the development of pancreatic cancer. Smokers who are able to quit smoking can reduce their risk of pancreatic cancer by nearly 50% within two years, however, their risk of developing pancreatic cancer remains higher than that of non-smokers for 10 years. Nicotine is the major psychoactive substance in tobacco, and is responsible for tobacco dependence and addiction. Recent evidence suggests that individuals have genetically based differences in their ability to metabolize nicotine, as well as genetic differences in the psychological reward pathways that may influence individual response to smoking initiation, dependence, addiction and cessation. Numerous associations have been reported between smoking behavior and genetic polymorphisms in genes that are responsible for nicotine metabolism. In addition, polymorphisms in genes that encode neurotransmitters and transporters that function in psychological reward pathways have been implicated in differences in smoking behavior. However, there is a large degree of between-study variability that demonstrates the need for larger, well-controlled case-control studies to identify target genes and deduce mechanisms that account for the genetic basis of inter-individual differences in smoking behavior. Understanding the genetic factors that increase susceptibility to tobacco addiction may result in more effective tobacco cessation programs which will, in turn, reduce the incidence of tobacco related disease, including pancreatic cancer.

The catechol-O-methyl transferase (COMT) gene as a candidate for psychiatric phenotypes: evidence and lessons

The enzyme catechol-O-methyl transferase (COMT), identified in the 1950s, is involved in catabolism of monoamines that are influenced by psychotropic medications, including neuroleptics and antidepressants. The COMT gene lies in a chromosomal region of interest for psychosis and bipolar spectrum disorder and a common polymorphism within the gene alters the activity of the enzyme. As a consequence, COMT has been one of the most studied genes for psychosis. On the basis of prior probabilities it would seem surprising if functional variation at COMT did not have some influence either on susceptibility to psychiatric phenotypes, modification of the course of illness or moderation of response to treatment. There is now robust evidence that variation at COMT influences frontal lobe function. However, despite considerable research effort, it has not proved straightforward to demonstrate and characterise a clear relationship between genetic variation at COMT and psychiatric phenotypes. It is of course, possible that COMT will turn out to be an unusually intractable case but it seems more likely that the experiences with this gene will provide a foretaste of the complexity of genotype-phenotype relationships that will be found for psychiatric traits. In this review, we consider the current state of evidence and the implications both for further studies of COMT and more generally for studies of other genes.

Interaction between variation in the D2 dopamine receptor (DRD2) and the neuronal calcium sensor-1 (FREQ) genes in predicting response to nicotine replacement therapy for tobacco dependence

We have previously demonstrated that a functional dopamine D2 receptor promoter variant (DRD2 -141 Ins/Del) predicts response to nicotine replacement therapy (NRT). The present study extends this finding in the same population of 363 NRT-treated subjects, by examining variation in the gene encoding the neuronal calcium sensor-1 protein (FREQ), which functions to regulate D2 receptor desensitization. The results indicate a statistically significant interaction effect of DRD2-141 and FREQ genotypes on abstinence at the end of the NRT treatment phase; 62% of the smokers with at least one copy of the DRD2 -141 Del allele and two copies of the FREQ rs1054879 A allele were abstinent from smoking, compared to 29-38% abstinence rates for other smokers in the trial. This result suggests that the interaction between variation in the DRD2 and FREQ genes, which both encode components of the D2 dopamine receptor signal transduction pathway, impacts the efficacy of NRT.