DMET Genes, Nicotine Metabolism and Prospective Abstinence

This study (DA033813; PI: Andrew W Bergen; PMID:26132489) includes samples from two laboratory studies of nicotine metabolism. The Pharmacokinetics of Nicotine Metabolism in Twins study (PKTWIN; PI: Gary E Swan; PMID: 15527659) was based on recruitment from a twin registry (PMID: 23084148). The Integrated Research Project on Tobacco Use and Dependence (IRP; PI: Gary E Swan; PMID: 14578134) was based on recruitment from a pedigree-based longitudinal study of risk factors for substance use, the Smoking in Families study (SMOFAM; DA03706; PI: Hy Hops). These two laboratory studies (PKTWIN and IRP/SMOFAM) served as the Stage I dataset to interrogate Drug Metabolizing Enzyme and Transporter genes with a targeted SNP array for association with the Nicotine Metabolite Ratio (NMR, ratio of trans-3'-hydroxycotinine and cotinine), an established biomarker of nicotine metabolism. In addition to the laboratory studies, samples from eight RCTs (PMID: 23249876) with the NMR and smoking-related measures used to test SNPs identified in Stage I (PMID: 26132489). In a third stage, a lung cancer meta-analysis database (PMID: 24880342) was used to assess association of SNPs identified in Stage II with lung cancer. The objectives of the study were to identify novel genes and SNPs contributing to nicotine metabolism (Stage I), and to validate PK SNPs associated with the NMR from individuals participating in a clinical laboratory protocol with the NMR obtained from treatment-seeking smokers, and then to investigate association with prospective smoking cessation (Stage II). This study built upon existing studies of nicotine metabolism and randomized trials of smoking cessation therapies. Enhanced knowledge of the genes influencing nicotine metabolism and prospective abstinence may help personalize smoking cessation treatment and risk assessment for smoking-related diseases. For Stage I, both subject [fixed-dose NMR, covariates (age, BMI, ethnicity, sex, smoking status, and hormone use), and pedigree relationships] and sample (common DMET SNP genotype, genotyping quality control) data are available in this accession. The analysis protocol, quality control summaries, summary genotype, summary phenotype, and analysis results are available for Stage I, II and III samples (PMID: 26132489). Extensive discussion of the prior CYP2A6 association literature with the NMR, abstinence, smoking heaviness and lung cancer risk is available (PMID: 26132489). The NMR has previously been associated with CYP2A6 activity, response to smoking cessation treatments, and cigarette consumption. We searched for drug metabolizing enzyme and transporter (DMET) gene variation associated with the NMR and prospective abstinence in 2,946 participants of laboratory studies of nicotine metabolism and of clinical trials of smoking cessation therapies. Stage I was a meta-analysis of the association of 507 common single nucleotide polymorphisms (SNPs) at 173 DMET genes with the NMR in 449 participants of two laboratory studies. Nominally significant associations were identified in ten genes after adjustment for intragenic SNPs; CYP2A6 and two CYP2A6 SNPs attained experiment-wide significance adjusted for correlated SNPs (CYP2A6 PACT=4.1E-7, rs4803381 PACT=4.5E-5, rs1137115, PACT=1.2E-3). Stage II was mega-regression analyses of 10 DMET SNPs with pretreatment NMR and prospective abstinence in up to 2,497 participants from eight trials. rs4803381 and rs1137115 SNPs were associated with pretreatment NMR at genome-wide significance. In post-hoc analyses of CYP2A6 SNPs, we observed nominally significant association with: abstinence in one pharmacotherapy arm; cigarette consumption among all trial participants; and lung cancer in four case:control studies. CYP2A6 minor alleles were associated with reduced NMR, CPD, and lung cancer risk. We confirmed the major role that CYP2A6 plays in nicotine metabolism, and made novel findings with respect to genome-wide significance and associations with CPD, abstinence and lung cancer risk. Additional multivariate analyses with patient variables and genetic modeling will improve prediction of nicotine metabolism, disease risk and smoking cessation treatment prognosis.]]>
PKTWIN Existing data (the fixed-dose NMR and covariates) and DNA samples were selected from a twin registry based study of nicotine metabolism and the impact of genetics and environment on nicotine metabolism (PMID:15527659). Twins from the Registry were recruited into the laboratory study of nicotine metabolism if both twins (monozygotic or dizygotic) were interested and eligible based on a three-stage screening procedure consisting of initial telephone-based screening, secondary in-person screening, and tertiary in-hospital review by the project physician. Exclusion criteria consisted of the following criteria: age <18 years or >65 years; weight >130% ideal height-adjusted weight; pregnancy; use of drug metabolism-altering medications such as anticonvulsants and barbiturates; uncontrolled hypertension; diabetes; history of heart disease; Raynaud's disease; cancer, chronic liver or kidney disease, and/or asthma that was not stable or in remission for at least one year; migraine; anemia; abnormal blood-sugar levels; substance abuse or dependence, excluding nicotine dependence; psychiatric disorders that could limit study compliance or require use of metabolism altering psychotropic medication; HIV+ status; Hepatitis B or Hepatitis C; history of vasovagal reactions; discomfort with venipuncture procedures or history of difficult veins. Verbal consent was obtained from participants prior to collection of possible exclusion criteria, description of study procedures and distribution of a health and smoking history questionnaire (first screen). Written informed consent, which explained study procedures, risks and benefits, was obtained from each co-twin in turn prior to collection of concomitant medications, vital status, and biospecimens (blood and urine). At each of these stages, screening of collected data was performed by a medical doctor to judge whether the co-twin was eligible and medically approved, prior to repeating the process for the co-twin. Prior to the in hospital nicotine infusion, an electrocardiogram, vital status, and a brief physical exam were conducted before final medical approval. Recruitment incentives include monetary compensation for full participation and the opportunity to participate in the laboratory study portion simultaneously with the participant's co-twin. IRP/SMOFAM For an integrated research project studying the environmental, genetic and metabolic determinants of tobacco use (PMID:14578134), probands and family members were recruited from those SMOFAM families in which the proband had completed at least seven of the first ten assessments on tobacco use and elected to provide a blood sample for DNA analysis. Probands and each first degree relative completed a family history of tobacco use including sex, age, relationship to proband (biological or nonbiological; full-, half-, or nonbiological sibling), vital status, lifetime “ever” smoking of 100 cigarettes, ever regular use of cigars, pipes, or smokeless tobacco, age at initiation of daily cigarette smoking, average number of cigarettes smoked per day when smoking, ever tried to quit, and success in permanent quitting. Informed consent was obtained from all participants for each the questionnaire, blood collection, and laboratory study components of the study. Permission to store biospecimens and to conduct additional genetic analyses was obtained. Participants agreed to the provision that genetic test results would not be made available to participants. A United States Department of Health and Human Services certificate of confidentiality was obtained for the study. ]]>
PKTWIN The Northern California Twin Registry was created in 1995 to provide a sample of twins for studies of nicotine metabolism and effects on smoking behavior (PMID:15527659); >1000 twins were recruited into the Registry using an advertising campaign based on local print, cinema and radio media. Twins from the Registry were recruited into the laboratory study of nicotine metabolism if both twins (monozygotic or dizygotic) were interested and eligible based on a three-stage screening procedure consisting of initial telephone-based screening, secondary in-person screening, and tertiary in-hospital review by the project physician. Exclusion criteria consisted of the following criteria: age <18 years or >65 years; weight >130% ideal height-adjusted weight; pregnancy; use of drug metabolism-altering medications such as anticonvulsants and barbiturates; uncontrolled hypertension; diabetes; history of heart disease; Raynaud's disease; cancer, chronic liver or kidney disease, and/or asthma that was not stable or in remission for at least one year; migraine; anemia; abnormal blood-sugar levels; substance abuse or dependence, excluding nicotine dependence; psychiatric disorders that could limit study compliance or require use of metabolism altering psychotropic medication; HIV+ status; Hepatitis B or Hepatitis C; history of vasovagal reactions; discomfort with venipuncture procedures or history of difficult veins. IRP/SMOFAM The Integrated Research Project on Tobacco Use and Dependence (PMID: 14578134), was based on the Smoking in Families study. Probands aged 11-15 were initially recruited using print, television/radio and flyers at middle and upper schools in four Pacific Northwest cities with populations from 30,000 to 175,000, into a longitudinal, repeated measures cohort study on factors influencing substance use tobacco use (SMOFAM). The requirements for SMOFAM recruitment were that the proband had to have tried tobacco or another substance, and that at least one parent agreed to participant. The original cohort numbered 763 children aged 11-15, their parents and siblings. 481 probands who completed >6 annual assessments in the first 10 years of the study completed a Family History of Tobacco Use to confirm relationships of household members and to characterize their tobacco use histories. Families were prioritized for the collection of blood for genetic studies by the presence of at least two individuals who were ever-smokers among either proband, siblings or parents. A Smoking History Questionnaire was developed to supplement existing data and administered to 378 probands to add more demographics, environment, tobacco exposures, tobacco product use and quitting and withdrawal history to the database. Families selected for the analysis of nicotine metabolism consisted of the proband and at least two ever-smoking (>100 cigarettes lifetime), first-degree relatives. Individuals with impaired renal or hepatic function, or who were taking drug metabolism-altering medications such as anticonvulsants and barbiturates were excluded from the protocol.]]>