Measuring adherence to smoking cessation pharmacotherapy is important to evaluating its effectiveness. Blood levels are considered the most accurate measure of adherence but are invasive and costly. Pill counts and self-report are more practical, but little is known about their relationship to blood levels. This study compared the validity of pill count and self-report against plasma varenicline concentration for measuring pharmacotherapy adherence.
Data were obtained from a randomized pilot study of varenicline for smoking cessation among African American smokers. Adherence was measured on Day 12 via plasma varenicline concentration, pill count, 3-day recall, and a visual analogue scale (VAS; adherence was represented on a line with two extremes “no pills” and “all pills”).
The sample consisted of 55 African American moderate to heavy smokers (average 16.8 cigarettes/day, SD = 5.6) and 63.6% were female. Significant correlations (p < .05) were found between plasma varenicline concentration and pill count (r = .56), 3-day recall (r = .46), and VAS (r = .29). Using plasma varenicline concentration of 2.0 ng/ml as the cutpoint for adherence, pill count demonstrated the largest area under the receiver operating characteristic curve (AUC = 0.85, p = .01) and had 88% sensitivity (95% CI = 75.0–95.0) and 80% specificity (95% CI = 30.0–99.0) for detecting adherence.
Of 3 commonly used adherence measures, pill count was the most valid for identifying adherence in this sample of African American smokers. Pill count has been used across other health domains and could be incorporated into treatment to identify nonadherence, which, in turn, could maximize smoking cessation pharmacotherapy use and improve abstinence rates.
Cigarette smoking behavior in bipolar disorder (BPD), including the effects of mood-stabilizing medications, has not been well characterized.
We compared serum nicotine, nicotine metabolite levels, and smoking topography in 75 smokers with BPD to 86 control smokers (CON). For some comparisons, an additional control group of 75 smokers with schizophrenia (SCZ) were included.
There were no differences between the BPD and CON groups in baseline smoking characteristics or serum nicotine or cotinine levels. Fifty-one smokers with BPD (68.9%) were taking one of the following mood stabilizers: valproic acid, lamotrigine, carbamazepine, oxcarbazepine, lithium, or topiramate. The 3-hydroxycotinine-to-cotinine ratio, a marker of cytochrome P450 2A6 (CYP2A6) metabolic activity, was significantly higher in BPD versus CON and versus SCZ (0.68 versus 0.49 versus 0.54; p = 0.002). The difference between groups, however, was no longer significant when the analysis was repeated with those taking hepatic enzyme-inducing drugs (carbamazepine, oxcarbazepine, and topiramate) included as a covariate. The time between puffs, or interpuff interval (IPI), was shorter in BPD versus CON by an average of 3.0 sec (p < 0.05), although this was no longer significant when we removed smokers from the analysis of those taking hepatic enzyme inducers.
Smokers with BPD are not different from CON on most measures of nicotine intake and smoking topography. We found an increased rate of nicotine metabolism in smokers taking mood stabilizers that are hepatic enzyme inducers, including carbamazepine, oxcarbazepine, and topiramate. Smokers with rapid nicotine metabolism might be expected to smoke more intensely to compensate for the more rapid disappearance of nicotine from the blood and brain, and may have more difficulty in quitting smoking, although this requires further study.
bipolar disorder; cotinine; metabolism; nicotine; smoking
CYP2A6 metabolizes nicotine to its primary metabolite cotinine and also mediates the metabolism of cotinine to trans-3′-hydroxycotinine (3HC). The ratio of 3HC to cotinine (the “nicotine metabolite ratio”, NMR) is an in vivo marker for the rate of CYP2A6 mediated nicotine metabolism, and total nicotine clearance, and has been associated with differences in numerous smoking behaviors. The clearance of 3HC, which affects the NMR, occurs via renal excretion and metabolism by UGT2B17, and possibly UGT2B10, to 3HC-glucuronide. We investigated whether slower 3HC glucuronidation alters NMR, altering its ability to predict CYP2A6 activity and reducing its clinical utility.
Plasma NMR, three urinary NMRs, three urinary 3HC glucuronidation phenotypes and total nicotine equivalents were examined in 540 African American smokers. The UGT2B17 gene deletion and UGT2B10*2 were genotyped.
The UGT2B17 gene deletion, but not UGT2B10*2 genotype, was associated with slower 3HC glucuronidation (indicated by three 3HC-glucuronidation phenotypes), indicating its role in this glucuronidation pathway. However, neither lower rates of 3HC glucuronidation, nor the presence of a UGT2B17 and UGT2B10 reduced function allele, altered plasma or urinary NMRs or levels of smoking.
Variation in 3HC glucuronidation activity, including these caused by UGT2B17 gene deletions, did not significantly alter NMR and is therefore unlikely to affect the clinical utility of NMR in smoking behavior and cessation studies. This study demonstrates that NMR is not altered by differences in the rate of 3HC glucuronidation, providing further support that NMR is a reliable indicator of CYP2A6 mediated nicotine metabolism.
CYP2A6 is the main nicotine metabolizing enzyme in humans. We investigated the relationships between CYP2A6 genotype, baseline plasma 3HC/COT (a phenotypic marker of CYP2A6 activity), and smoking behaviors in African-American light smokers. Cigarette consumption, age of initiation, and dependence scores did not differ between 3HC/COT quartiles or CYP2A6 genotype groups. Slow metabolizers (both genetic and phenotypic) had significantly higher plasma nicotine levels suggesting cigarette consumption was not reduced to adjust for slower rates of nicotine metabolism. Individuals in the slowest 3HC/COT quartile had higher quit rates with both placebo and nicotine gum treatments (OR 1.85, 95% CI 1.08-3.16, p = 0.03). Similarly, the slowest CYP2A6 genotype group had higher quit rates, although this did not reach significance (OR 1.61, 95% CI 0.95-2.72, p = 0.08). 3HC/COT ratio, and possibly CYP2A6 genotype, may be useful in the future for personalizing the choice of smoking cessation treatment for African-American light smokers.
Cytochrome P450 2A6; CYP2A6; nicotine; cotinine; trans-3′-hydroxycotinine; African-Americans; smoking; light smokers
Nicotine metabolism and genetic variation have an impact on nicotine addiction and smoking abstinence, but further research is required. The nicotine metabolite ratio (NMR) is a robust biomarker of nicotine metabolism used to categorize slow and normal nicotine metabolizers (lower 25th quartile cutoff). In two randomized clinical trials of smoking abstinence treatments, we conducted NMR-stratified analyses on smoking abstinence across 13 regions coding for nicotinic acetylcholine receptors and proteins involved in the dopamine reward system. Gene × NMR interaction P-values were adjusted for multiple correlated tests, and we used a Bonferroni-corrected α-level of 0.004 to determine system-wide significance. Three SNPs in DRD1 (rs11746641, rs2168631, rs11749035) had significant interactions (0.001 ≤ adjusted P-values ≤ 0.004), with increased odds of abstinence within slow metabolizers (ORs=3.1–3.5, 95% CI 1.7–6.7). Our findings support the role of DRD1 in nicotine dependence, and identify genetic and nicotine metabolism profiles that may interact to impact nicotine dependence.
Genetic association studies; heterogeneity; smoking abstinence; nicotine metabolism; nicotine metabolite ratio; DRD1
The nicotine metabolite ratio (NMR or 3-hydroxycotinine/cotinine) has been used to phenotype CYP2A6-mediated nicotine metabolism. Our objectives were to analyze (a) the stability of NMR in plasma, saliva, and blood in various storage conditions, (b) the relationship between NMRs derived from blood, plasma, saliva, and urine, and (c) the reproducibility of plasma NMR in ad libitum cigarette smokers.
We analyzed data from four clinical studies. In studies 1 and 2, we assessed NMR stability in saliva and plasma samples at room temperature (~22°C) over 14 days and in blood at 4°C for up to 72 hours. In studies 2 and 3, we used Bland-Altman analysis to assess agreement between blood, plasma, saliva, and urine NMRs. In study 4, plasma NMR was measured on 6 occasions over 44 weeks in 43 ad libitum smokers.
Reliability coefficients for stability tests of NMR in plasma and saliva at room temperature were 0.97 and 0.98, respectively, and 0.92 for blood at 4°C. Blood NMR agreed consistently with saliva and plasma NMRs but showed more variability in relation to urine NMR. The reliability coefficient for repeated plasma NMR measurements in smokers was 0.85.
The NMR is stable in blood, plasma, and saliva at the conditions tested. Blood, plasma, and saliva NMRs are similar while urine NMR is a good proxy for these NMR measures. Plasma NMR was reproducible over time in smokers.
One measurement may reliably estimate a smoker’s NMR for use as an estimate of the rate of nicotine metabolism.
Nicotine metabolite ratio (NMR); cotinine; 3-hydroxycotinine; biological stability; chemical stability
The prevalence of tobacco use, both cigarette smoking and smokeless, including iqmik (homemade smokeless tobacco prepared with dried tobacco leaves mixed with alkaline ash), and of tobacco-related cancer is high in Alaskan Native people (AN). To investigate possible mechanisms of increased cancer risk we studied levels of nicotine and tobacco-specific nitrosamines (TSNA) in tobacco products and biomarkers of tobacco toxicant exposure in Southwestern AN people.
Participants included 163 cigarette smokers, 76 commercial smokeless tobacco, 20 iqmik, 31 dual cigarette smokers and smokeless tobacco, and 110 nontobacco users. Tobacco use history, samples of tobacco products used, and blood and urine samples were collected.
Nicotine concentrations were highest in cigarette tobacco and TSNAs highest in commercial smokeless tobacco products. The AN participants smoked on average 7.8 cigarettes per day. Nicotine exposure, assessed by several biomarker measures, was highest in iqmik users, and similar in smokeless tobacco and cigarette smokers. TSNA exposure was highest in smokeless tobacco users, and polycyclic aromatic hydrocarbon exposure was highest in cigarette smokers.
Despite smoking fewer cigarettes per day, AN cigarette smokers had similar daily intake of nicotine compared to the general U.S. population. Nicotine exposure was greatest from iqmik, likely related to its high pH due to preparation with ash, suggesting high addiction potential compared to other smokeless tobacco products. TSNA exposure was much higher with smokeless tobacco than other product use, possibly contributing to the high rates of oral cancer.
Our data contribute to an understanding of the high addiction risk of iqmik use and of the cancer-causing potential of various forms of tobacco use among AN people.
We conducted gender-stratified analyses on a systems-based candidate gene study of 53 regions involved in nicotinic response and the brain-reward pathway in two randomized clinical trials of smoking cessation treatments (placebo, bupropion, transdermal and nasal spray nicotine replacement therapy). We adjusted P-values for multiple correlated tests, and used a Bonferroni corrected α-level of 5 × 10−4 to determine system-wide significance. Four SNPs (rs12021667, rs12027267, rs6702335, rs12039988; r2>0.98) in erythrocyte membrane protein band 4.1 (EPB41) had a significant male-specific marginal association with smoking abstinence (OR=0.5; 95% CI 0.3–0.6) at end of treatment (adjusted P<6 × 10−5). rs806365 in cannabinoid receptor 1 (CNR1) had a significant male-specific gene-treatment interaction at 6-month follow-up (adjusted P=3.9 × 10−5); within males using nasal spray, rs806365 was associated with a decrease in odds of abstinence (OR=0.04; 95% CI 0.01–0.2). While the role of CNR1 in substance abuse has been well studied, we report EPB41 for the first time in the nicotine literature.
Genetic association studies; heterogeneity; smoking cessation
Alaska Native people (AN) have a high prevalence of tobacco use and associated morbidity and mortality when compared to the general U.S. population. Variation in the CYP2A6 and CYP2B6 genes, encoding enzymes responsible for nicotine metabolic inactivation and procarcinogen activation, has not been characterized in AN and may contribute to the increased risk.
AN people (n = 400) residing in the Bristol Bay region of South Western Alaska were recruited for a cross-sectional study on tobacco use. They were genotyped for CYP2A6*1X2A, *1X2B, *1B, *2, *4, *7, *8, *9, *10, *12, *17, *35 and CYP2B6*4, *6, *9 and provided plasma and urine samples for measurement of nicotine and metabolites.
CYP2A6 and CYP2B6 variant frequencies among the AN Yupik people (n=361) were significantly different from other ethnicities. Nicotine metabolism (as measured by the plasma and urinary ratio of metabolites trans-3’hydroxycotinine to cotinine [(3HC/COT)] was significantly associated with CYP2A6 (P< 0.001) but not CYP2B6 genotype (P = 0.95) when controlling for known covariates. Of note, plasma 3HC/COT ratios were high in the entire Yupik people, and among the Yupik CYP2A6 wild-type participants they were substantially higher than previously characterized racial/ethnic groups (P < 0.001 vs. Caucasians and African Americans).
Yupik AN people have a unique CYP2A6 genetic profile which associated strongly with in vivo nicotine metabolism. More rapid CYP2A6-mediated nicotine and nitrosamine metabolism in the Yupik people may modulate tobacco-related disease risk.
CYP2A6; CYP2B6; nicotine; tobacco; smoking; genetic variation; Alaska Native people
Despite the widespread use of mentholated cigarettes, lower cessation rates, and disproportionately high smoking–related morbidity among Blacks, the possible role of menthol in smokers’ response to pharmacotherapy has not been well-studied. This study examined the effects of menthol on the pharmacokinetic (PK) profiles of bupropion and its principal metabolites, hydroxybupropion, threohydrobupropion, and erythrohydrobupropion among Black smokers.
After a 7-day placebo run-in period, participants received 150 mg bid sustained-release bupropion for 20–25 days. Blood samples were drawn for PK analysis on 2 occasions, 10–15 days after the commencement of bupropion while participants were still smoking (smoking phase) and at days 20–25 when they were asked not to smoke (nonsmoking phase).
18 smokers of nonmenthol cigarettes and 23 smokers of menthol cigarettes were enrolled in this study. No differences were found by menthol smoking status in the Cmax and area under the plasma concentration versus time curve (AUC) of bupropion and its metabolites in the smoking or nonsmoking phases. However, among menthol smokers, the AUC ratios of metabolite/bupropion were lower in the nonsmoking phase compared with the smoking phase (hydro/bup = 31.49 ± 18.84 vs. 22.95 ± 13.27, p = .04; erythro/bup = 1.99 ± 1.02 vs. 1.76 ± 0.75, p = .016; threo/bup = 11.77 ± 8.90 vs. 10.44 ± 5.63, p = .034). No significant differences were found in the metabolite/bup ratios between smoking and nonsmoking conditions among nonmenthol smokers.
We did not find a significant effect of menthol compared with nonmenthol cigarette smoking on the PKs of bupropion and metabolites at steady state. More research is needed to advance the understanding of mechanisms underlying disparities in smoking cessation outcomes related to smoking of menthol cigarettes.
People with schizophrenia are frequent and heavy smokers.
The objective of this study was to measure serum nicotine levels and ad libitum smoking behavior for 24 + 2h using the CReSS micro topography device in 75 smokers with schizophrenia (SCZ) and compare these to 86 control smokers (CON) without mental illness. Mean values of repeatedly measured topography variables were compared using three-level nested linear models to adjust for between subject differences and the double nested data.
Smokers with SCZ smoked more cigarettes in the 24 h period and took an average of 2.8 more puffs per cigarette than CON (p < 0.001). The time between puffs, or interpuff interval (IPI), was shorter in SCZ by an average of 6.5 s (p < 0.001). The peak flow rate was higher in SCZ by an average of 4.9 ml/s (p < 0.05). Smokers with SCZ spent an average of 1.0 min less time smoking a single cigarette vs. CON (p < 0.001). Smokers with SCZ also had shorter IPI and more puffs per cigarette in an analysis of first cigarette of the day. For all subjects, a decrease in IPI by 1s was associated with an increase in serum nicotine of 0.19 ng/ml and in cotinine of 5.01 ng/ml (both p < 0.05). After controlling for diagnosis group, higher craving scores on QSU Factor 2 (urgent desire to smoke) were associated with shorter IPI.
Smokers with schizophrenia demonstrate more intense cigarette puffing that is associated with greater nicotine intake. This pattern may provide insight into other heavily dependent smokers.
Nicotine; Schizophrenia; Smoking; Cotinine
Recent federal legislation gives the FDA authority to regulate the nicotine content of cigarettes. A nationwide strategy for progressive reduction of the nicotine content of cigarettes is a potential way to reduce the addictiveness of cigarettes, to prevent new smokers from becoming addicted and to facilitate quitting in established smokers. We conducted a trial of progressive nicotine content tapering over 6 months to determine the effects on smoking behaviors and biomarkers of tobacco smoke exposure and cardiovascular effects.
135 healthy smokers were randomly assigned to one of two groups. A research group smoked their usual brand of cigarettes followed by 5 types of research cigarettes with progressively lower nicotine content, each smoked for one month. A control group smoked their own brand of cigarettes for the same period of time.
Nicotine intake, as indicated by plasma cotinine concentration, declined progressively as the nicotine content of cigarettes was reduced. Cigarette consumption and markers of exposure to carbon monoxide and polycyclic aromatic hydrocarbons, as well as cardiovascular biomarkers remained stable, while urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) excretion decreased. No significant changes in biomarkers of exposure or cardiovascular effects were observed in controls.
Our data support the proposition that the intake of nicotine from cigarettes of smokers can be substantially lowered without increasing exposure to other tobacco smoke toxins.
These findings support the feasibility and safety of gradual reduction of the nicotine content in cigarettes.
Study objectives were (1) to investigate the selectivity of polycyclic aromatic hydrocarbon (PAH) metabolites for tobacco smoke exposure, and (2) to determine half-lives of PAH metabolites in smokers. There were 622 participants from the United States (US) and Poland, and of these 70% were smokers. All subjects provided spot urine samples and 125 smokers provided blood samples. Urinary PAH metabolite half-lives were determined in 8 smokers. In controlled hospital studies of 18 smokers, the associations between various measures of nicotine intake and urinary excretion of PAH metabolites were investigated. Plasma nicotine was measured by GC. LC-MS/MS was used to measure the plasma levels of cotinine and trans-3′-hydroxycotinine, and urine levels of nicotine and its metabolites, total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and PAH metabolites (2-naphthol, 1-, 2- and 3-hydroxyfluorenes, 1-, 2-, 3-, and 4-hydroxyphenanthrenes, and 1-hydroxypyrene). Regardless of smoking status, PAH metabolite excretion was higher in Polish subjects than in US subjects (p-values<0.001). 1-Hydroxyfluorene exhibited the greatest difference between smokers and non-smokers, with a 5-fold difference in Polish subjects and a 25-fold difference in US subjects, followed by 3- and 2-hydroxyfluorenes, 2-naphthol and 1-hydroxypyrene. The differences for hydroxyphenanthrenes were small or non-significant. 1-Hydroxyfluorene had the highest correlation with urine nicotine equivalents (r=0.77) and urine NNAL (r=0.64). While the half-lives of PAH metabolites were <10 h in smokers, 1-hydroxyfluorene had the largest ratio of initial to terminal urine concentration (58.4±38.6, mean±SD) after smoking. Receiver Operating Characteristic (ROC) analysis of PAHs among Polish and US subjects further showed that hydroxyfluorenes are most highly discriminative of smokers from nonsmokers followed by 2-naphthol and 1-hydroxypyrene. In conclusion, hydroxyfluorenes, particularly 1-hydroxyfluorene, and 2-naphthol are more selective of tobacco smoke than 1-hydroxypyrene and hydroxyphenanthrenes. Characterization of hydroxyfluorene and 2-naphthol metabolites in urine may improve the characterization of PAHs from tobacco smoke and related disease risks among smokers and nonsmokers.
To date, most genetic association studies of tobacco use have been conducted in European American subjects using the phenotype of smoking quantity (cigarettes per day). However, smoking quantity is a very imprecise measure of exposure to tobacco smoke constituents. Analyses of alternate phenotypes and populations may improve our understanding of tobacco addiction genetics. Cotinine is the major metabolite of nicotine, and measuring serum cotinine levels in smokers provides a more objective measure of nicotine dose than smoking quantity. Previous genetic association studies of serum cotinine have focused on individual genes. We conducted a genetic association study of the biomarker in African American (N=365) and European American (N=315) subjects from the Coronary Artery Risk Development in Young Adults study using a chip containing densely-spaced tag SNPs in ∼2100 genes. We found that rs11187065, located in the non-coding region (intron 1) of insulin-degrading enzyme (IDE), was the most strongly associated SNP (p=8.91 × 10−6) in the African American cohort, whereas rs11763963, located on chromosome 7 outside of a gene transcript, was the most strongly associated SNP in European Americans (p=1.53 × 10−6). We then evaluated how the top variant association in each population performed in the other group. We found that the association of rs11187065 in IDE was also associated with the phenotype in European Americans (p=0.044). Our top SNP association in European Americans, rs11763963 was non-polymorphic in our African American sample. It has been previously shown that psychostimulant self-administration is reduced in animals with lower insulin because of interference with dopamine transmission in the brain reward centers. Our finding provides a platform for further investigation of this, or additional mechanisms, involving the relationship between insulin and self-administered nicotine dose.
cotinine; nicotine; IDE; CARDIA; MORF4L1; IMAT-Broad-CARe; behavioral science; neurogenetics; addiction & substance abuse; pharmacogenetics/pharmacogenomics; cotinine; nicotine; IDE; CARDIA; MORF4L1
Previous research demonstrated the efficacy of sustained release bupropion (bupropion SR) for smoking cessation in whites as well as moderate to heavy (≥10 cigarettes per day [CPD]) African American smokers. We evaluated whether bupropion SR was effective for smoking cessation among African American light smokers (≤10 CPD).
A randomized, double-blind placebo-controlled trial was conducted from December 27, 2007, to May 13, 2010. All participants were African American light smokers (≤10 CPD), aged 18 years or older. Participants were randomly assigned to receive 300 mg bupropion SR (150 mg once daily for 3 days and then 150 mg twice daily) (n = 270 participants) or placebo (n = 270 participants) for 7 weeks, and up to six sessions of health education counseling. Serum cotinine was measured at baseline (week 0). The primary outcome was salivary cotinine–verified 7-day point prevalence smoking abstinence at week 26; a cut point of 15 ng/mL differentiated smokers from nonsmokers. Salivary cotinine–verified smoking abstinence at end of medication treatment at week 7 was also examined. Odds ratios (OR) for smoking abstinence and 95% confidence intervals (CIs) were calculated using logistic regression models. All statistical tests were two-sided.
Participants at baseline visit (week 0) smoked an average of 8.0 CPD and had a mean serum cotinine level of 275.8 ng/mL (SD = 155.8 ng/mL); most used menthol cigarettes (83.7%) and smoked within 30 minutes of waking (72.2%). After imputing those lost to follow-up as smokers, no statistically significant difference in long-term smoking abstinence rates at week 26 was observed between bupropion SR and placebo groups (13.3% vs 10.0%, OR = 1.39, 95% CI = 0.82 to 2.35, P = .23). Cotinine-verified smoking abstinence rate at end of medication week 7 was higher in the bupropion SR vs placebo group (23.7% vs 9.6%, OR = 2.92, 95% CI = 1.78 to 4.77, P < .001).
Bupropion SR was effective in promoting smoking cessation during the medication phase of treatment but showed no effect on long-term smoking cessation among African American light smokers. More research is needed to identify strategies for sustaining abstinence among African American light smokers.
We utilized a cohort of 828 treatment seeking self-identified white cigarette smokers (50% female) to rank candidate gene single nucleotide polymorphisms (SNPs) associated with the Fagerström Test for Nicotine Dependence (FTND), a measure of nicotine dependence which assesses quantity of cigarettes smoked and time- and place-dependent characteristics of the respondent’s smoking behavior. 1123 SNPs at 55 autosomal candidate genes, nicotinic acetylcholine receptors and genes involved in dopaminergic function, were tested for association to baseline FTND scores adjusted for age, depression, education, sex and study site. SNP P values were adjusted for the number of transmission models, the number of SNPs tested per candidate gene, and their intragenic correlation. DRD2, SLC6A3 and NR4A2 SNPs with adjusted P values < 0.10 were considered sufficiently noteworthy to justify further genetic, bioinformatic and literature analyses. Each independent signal among the top-ranked SNPs accounted for ~1% of the FTND variance in this sample. The DRD2 SNP appears to represent a novel association with nicotine dependence. The SLC6A3 SNPs have previously been shown to be associated with SLC6A3 transcription or dopamine transporter density in vitro, in vivo and ex vivo. Analysis of SLC6A3 and NR4A2 SNPs identified a statistically significant gene-gene interaction (P=0.001), consistent with in vitro evidence that the NR4A2 protein product (NURR1) regulates SLC6A3 transcription. A community cohort of N=175 multiplex ever smoking pedigrees (N=423 ever smokers) provided nominal evidence for association with the FTND at these top ranked SNPs, uncorrected for multiple comparisons.
dopamine transporter; Fagerström Test for Nicotine Dependence; single nucleotide polymorphism; candidate gene association scan; gene-gene interaction
Smoking tobacco preparations in a waterpipe (hookah) is widespread in many places of the world, including the US, where it is especially popular among young people. Many perceive waterpipe smoking to be less hazardous than cigarette smoking. We studied systemic absorption of nicotine, carbon monoxide, and carcinogens from one waterpipe smoking session.
Sixteen subjects smoked a waterpipe on a clinical research ward. Expired carbon monoxide and carboxyhemoglobin were measured, plasma samples were analyzed for nicotine concentrations, and urine samples were analyzed for the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1- butanol (NNAL) and polycyclic aromatic hydrocarbon (PAH) metabolite biomarker concentrations.
We found substantial increases in plasma nicotine concentrations, comparable to cigarette smoking, and increases in carbon monoxide levels that are much higher than is typically observed from cigarette smoking, as previously published. Urinary excretion of NNAL and PAH biomarkers increased significantly following waterpipe smoking.
Absorption of nicotine in amounts comparable to cigarette smoking indicates a potential for addiction, and absorption of significant amounts of carcinogens raises concerns of cancer risk in people who smoke tobacco products in waterpipes.
Our data contributes to an understanding of the health impact of waterpipe use.
Black smokers are reported to have higher lung cancer rates and greater tobacco dependence at lower levels of cigarette consumption compared to non-Hispanic White smokers. We studied the relationship between cigarettes per day (CPD) and biomarkers of nicotine and carcinogen exposure in Black and White smokers.
In 128 Black and White smokers, we measured plasma nicotine and its main proximate metabolite cotinine, urine nicotine equivalents, 4-(methylnitrosamino)-1-(3)pyridyl-1-butanol (NNAL), and polycyclic aromatic hydrocarbon (PAH) metabolites.
The dose–response between CPD and nicotine equivalents, and NNAL and PAH was flat for Black but positive for White smokers (Race × CPD interaction, all ps < .05). Regression estimates for the Race × CPD interactions were 0.042 (95% CI 0.013–0.070), 0.054 (0.023–0.086), and 0.028 (0.004–0.052) for urine nicotine equivalents, NNAL, and PAHs, respectively. In contrast there was a strong correlation between nicotine equivalents and NNAL and PAH independent of race. Nicotine and carcinogen exposure per individual cigarette was inversely related to CPD. This inverse correlation was stronger in Black compared to White smokers and stronger in menthol compared to regular cigarette smokers (not mutually adjusted).
Our data indicate that Blacks on average smoke cigarettes differently than White smokers such that CPD predicts smoke intake more poorly in Black than in White smokers.
Rationale: Cigarette smoking has been demonstrated in laboratory studies to have effects on lung epithelial and endothelial function similar to those observed in acute lung injury (ALI). However, the association between active and passive cigarette smoke exposure and susceptibility to ALI has not been prospectively studied.
Objectives: We hypothesized that both active and passive cigarette smoke exposure would be associated with increased susceptibility to ALI after severe blunt trauma.
Methods: We measured levels of cotinine, a metabolite of nicotine and validated biomarker of tobacco use, in plasma samples obtained immediately on arrival at the emergency department from 144 adult subjects after severe blunt trauma. Patients were then followed for the development of ALI.
Measurements and Main Results: Increasing quartiles of plasma cotinine were associated with the development of ALI (odds ratio [OR] for developing ALI in highest cotinine quartile, 3.25; 95% confidence interval [CI], 1.22–8.68; P = 0.017 for trend across quartiles). Moderate to heavy passive smoke exposure was associated with nearly the same odds of developing ALI as active smoking (OR for moderate to heavy passive smoking compared with no exposure or low level exposure, 3.03; 95% CI, 1.15–8.04; OR for active smoking, 2.77; 95% CI, 1.28–5.99). This association persisted after adjusting for other predictors of ALI, including Injury Severity Score and alcohol abuse.
Conclusions: Both moderate to heavy passive smoking and active smoking are independently associated with the development of ALI after severe blunt trauma. This finding has important implications both for public health and for understanding the pathogenesis of ALI.
cigarette smoking; acute lung injury; acute respiratory distress syndrome; cotinine; secondhand smoke exposure
Genome-wide association studies have linked single-nucleotide polymorphisms (SNPs) in the CHRNA5/A3/B4 gene cluster with heaviness of smoking. The nicotine metabolite ratio (NMR), a measure of the rate of nicotine metabolism, is associated with the number of cigarettes per day (CPD) and likelihood of cessation. We tested the potential interacting effects of these two risk factors on CPD.
Pretreatment data from three prior clinical trials were pooled for analysis. One thousand and thirty treatment seekers of European ancestry with genotype data for the CHRNA5/A3/B4 SNPs rs578776 and rs1051730 and complete data for NMR and CPD at pretreatment were included. Data for the third SNP, rs16969968, were available for 677 individuals. Linear regression models estimated the main and interacting effects of genotype and NMR on CPD.
We confirmed independent associations between the NMR and CPD as well as between the SNPs rs16969968 and rs1051730 and CPD. We did not detect a significant interaction between NMR and any of the SNPs examined.
This study demonstrates the additive and independent association of the NMR and SNPs in the CHRNA5/A3/B4 gene cluster with smoking rate in treatment-seeking smokers.
Cotinine is the most widely used biomarker to distinguish active versus passive smoking. However, there is an overlap in cotinine levels when comparing light or occasional smokers versus heavily exposed passive smokers. 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) is a tobacco-specific nitrosamine measurable in urine with a much longer half-life than cotinine. The aim of the study was to determine optimal cutoff points to discriminate active versus passive smokers and to compare sensitivity and specificity for the use of cotinine, NNAL, and the ratio of the NNAL/cotinine in urine.
Cotinine and NNAL were measured in urine of 373 active smokers and 228 passive smokers.
Geometric mean cotinine levels were 2.03 ng/ml (interquartile interval: 0.43–8.60) and 1,043 ng/ml (658–2,251) and NNAL levels were 5.80 pg/ml (2.28–15.4) and 165 pg/ml (90.8–360) pg/ml in passive and active smokers, respectively. NNAL/cotinine ratio in urine was significantly higher for passive smokers when compared with active smokers (2.85 vs. 0.16, p < .01). The receiver operating characteristics analysis determined optimal cutoff points to discriminate passive versus active smokers: 31.5 ng/ml for cotinine (sensitivity: 97.1% and specificity: 93.9%), 47.3 pg/ml for NNAL (87.4% and 96.5%), and 0.74 × 10−3 for NNAL/cotinine ratio (97.3% and 87.3%).
Both urine cotinine and NNAL are sensitive and specific biomarkers for discriminating the source of tobacco smoke exposure. Cotinine is the best overall discriminator when biomarkers are measured while a person has ongoing exposure to tobacco smoke. NNAL because of its long half-life would be particularly useful when there is a delay between exposure and biomarker measurement. The NNAL/cotinine ratio provides similar sensitivity but poorer specificity at discriminating passive versus active smokers when compared with NNAL alone.
The nicotine metabolite cotinine is widely used to assess the extent of tobacco use in smokers, and secondhand smoke exposure in non-smokers. The ratio of another nicotine metabolite, trans-3′-hydroxycotinine, to cotinine in biofluids is highly correlated with the rate of nicotine metabolism, which is catalyzed mainly by Cytochrome P450 2A6 (CYP2A6). Consequently, this nicotine metabolite ratio is being used to phenotype individuals for CYP2A6 activity and to individualize pharmacotherapies for tobacco addiction. In this paper we describe a highly sensitive liquid chromatography – tandem mass spectrometry method for determination of the nicotine metabolites cotinine and trans-3′-hydroxycotinine in human plasma, urine, and saliva. Lower limits of quantitation range from 0.02 to 0.1 ng/ mL. The extraction procedure is straightforward and suitable for large-scale studies. The method has been applied to several thousand biofluid samples for pharmacogenetic studies and for studies of exposure to low levels of secondhand smoke. Concentrations of both metabolites in urine of non-smokers with different levels of secondhand smoke exposure are presented.
Nicotine; Cotinine; trans-3′-hydroxycotinine; Cytochrome P450 2A6 (CYP2A6); tobacco; secondhand smoke
Variability in smoking behavior is partly attributable to heritable individual differences in nicotine clearance rates. This can be assessed as the ratio of the metabolites cotinine (COT) and 3'-hydroxycotinine (3HC) (referred to as the nicotine metabolism ratio, NMR). We hypothesized that faster NMR would be associated with greater cigarette puff volume and higher levels of total NNAL, a carcinogen biomarker.
Current smokers (n=109) smoked one of their preferred brand cigarettes through a smoking topography device and provided specimens for NMR and total NNAL assays.
Faster nicotine metabolizers (third and fourth quartiles versus first quartile) based on the NMR exhibited significantly greater total puff volume and total NNAL; the total puff volume by daily cigarette consumption interaction was a significant predictor of total NNAL level.
A heritable biomarker of nicotine clearance predicts total cigarette puff volume and total NNAL.
If validated, the NMR could contribute to smoking risk assessment in epidemiological studies and potentially in clinical practice.
Despite effective therapies for smoking cessation, most smokers find quitting difficult and most successful quitters relapse. Considerable evidence supports a genetic risk for nicotine dependence; however, less is known about the pharmacogenetics of smoking cessation. In the first pharmacogenetic investigation of the efficacy of varenicline and bupropion, we examined whether genes important in the pharmacodynamics and pharmacokinetics of these drugs and nicotine predict medication efficacy and adverse events. Subjects participated in randomized, double-blind, placebo-controlled smoking cessation clinical trials, comparing varenicline, a nicotinic acetylcholine receptor (nAChR) partial agonist, with bupropion, a norepinephrine/dopamine reuptake inhibitor, and placebo. Primary analysis included 1175 smokers of European ancestry, and 785 single nucleotide polymorphisms from 24 genes, representing 254 linkage disequilibrium (LD) bins (genes included nAChR subunits, additional varenicline-specific genes, and genes involved in nicotine or bupropion metabolism). For varenicline, continuous abstinence (weeks 9–12) was associated with multiple nAChR subunit genes (including CHRNB2, CHRNA5, and CHRNA4) (OR=1.76; 95% CI: 1.23–2.52) (p<0.005); for bupropion, abstinence was associated with CYP2B6 (OR=1.78; 95% CI: 1.27–2.50) (p<0.001). Incidence of nausea was associated with several nAChR subunit genes (OR=0.50; 95% CI: 0.36–0.70) (p<0.0001) and time to relapse after quitting was associated with HTR3B (HR=1.97; 95% CI: 1.45–2.68) (p<0.0001). These data provide evidence for multiple genetic loci contributing to smoking cessation and therapeutic response. Different loci are associated with varenicline vs bupropion response, suggesting that additional research may identify clinically useful markers to guide treatment decisions.
varenicline; bupropion; pharmacogenetics; nicotine; nicotinic receptor; CYP2B6; pharmacogenetics/pharmacogenomics; addiction and substance abuse; clinical pharmacology/clinical trials; neuropharmacology; varenicline; bupropion; nicotine; smoking cessation; nicotinic receptors
Menthol cigarettes are smoked by 27% of U.S. smokers, and there are concerns that menthol might enhance toxicity of cigarette smoking by increasing systemic absorption of smoke toxins. We measured urine menthol concentrations in relation to biomarkers of exposure to nicotine and tobacco carcinogens.
Concentrations of menthol glucuronide (using a novel analytical method), nicotine plus metabolites (nicotine equivalents, NE), 4-(methylnitrosamino)-1-(3)pyridyl-1-butanol (NNAL) and polycyclic aromatic hydrocarbon (PAH) metabolites were measured in the urine of 60 menthol and 67 regular cigarette smokers.
Urine menthol was measurable in 82% of menthol and 54% in regular cigarette smokers. Among menthol smokers urine menthol was highly correlated with NE, NNAL and PAHs. In a multiple regression model NE but not menthol was significantly associated with NNAL and PAHs.
Urine menthol concentration is a novel biomarker of exposure in menthol cigarette smokers, and is highly correlated with exposure to nicotine and carcinogens. Menthol is not independently associated with carcinogen exposure when nicotine intake is considered.