CYP2A6 associates with respiratory disease risk and younger age of diagnosis: a phenome-wide association Mendelian Randomization study.

CYP2A6, a genetically variable enzyme, inactivates nicotine, activates carcinogens, and metabolizes many pharmaceuticals. Variation in CYP2A6 influences smoking behaviors and tobacco-related disease risk. This phenome-wide association study examined associations between a reconstructed version of our weighted genetic risk score (wGRS) for CYP2A6 activity with diseases in the UK Biobank (N = 395 887). Causal effects of phenotypic CYP2A6 activity (measured as the nicotine metabolite ratio: 3'-hydroxycotinine/cotinine) on the phenome-wide significant (PWS) signals were then estimated in two-sample Mendelian Randomization using the wGRS as the instrument. Time-to-diagnosis age was compared between faster versus slower CYP2A6 metabolizers for the PWS signals in survival analyses. In the total sample, six PWS signals were identified: two lung cancers and four obstructive respiratory diseases PheCodes, where faster CYP2A6 activity was associated with greater disease risk (Ps < 1 × 10-6). A significant CYP2A6-by-smoking status interaction was found (Psinteraction < 0.05); in current smokers, the same six PWS signals were found as identified in the total group, whereas no PWS signals were found in former or never smokers. In the total sample and current smokers, CYP2A6 activity causal estimates on the six PWS signals were significant in Mendelian Randomization (Ps < 5 × 10-5). Additionally, faster CYP2A6 metabolizer status was associated with younger age of disease diagnosis for the six PWS signals (Ps < 5 × 10-4, in current smokers). These findings support a role for faster CYP2A6 activity as a causal risk factor for lung cancers and obstructive respiratory diseases among current smokers, and a younger onset of these diseases. This research utilized the UK Biobank Resource.

Characterisation of the Paenarthrobacter nicotinovorans ATCC 49919 genome and identification of several strains harbouring a highly syntenic nic-genes cluster.

BACKGROUND: Paenarthrobacter nicotinovorans ATCC 49919 uses the pyridine-pathway to degrade nicotine and could provide a renewable source of precursors from nicotine-containing waste as well as a model for studying the molecular evolution of catabolic pathways and their spread by horizontal gene transfer via soil bacterial plasmids. RESULTS: In the present study, the strain was sequenced using the Illumina NovaSeq 6000 and Oxford Nanopore Technology (ONT) MinION platforms. Following hybrid assembly with Unicycler, the complete genome sequence of the strain was obtained and used as reference for whole-genome-based phylogeny analyses. A total of 64 related genomes were analysed; five Arthrobacter strains showed both digital DNA-DNA hybridization and average nucleotide identity values over the species threshold when compared to P. nicotinovorans ATCC 49919. Five plasmids and two contigs belonging to Arthrobacter and Paenarthrobacter strains were shown to be virtually identical with the pAO1 plasmid of Paenarthrobacter nicotinovorans ATCC 49919. Moreover, a highly syntenic nic-genes cluster was identified on five plasmids, one contig and three chromosomes. The nic-genes cluster contains two major locally collinear blocks that appear to form a putative catabolic transposon. Although the origins of the nic-genes cluster and the putative transposon still elude us, we hypothesise here that the ATCC 49919 strain most probably evolved from Paenarthrobacter sp. YJN-D or a very closely related strain by acquiring the pAO1 megaplasmid and the nicotine degradation pathway. CONCLUSIONS: The data presented here offers another snapshot into the evolution of plasmids harboured by Arthrobacter and Paenarthrobacter species and their role in the spread of metabolic traits by horizontal gene transfer among related soil bacteria.

Predicting nicotine metabolism across ancestries using genotypes.

BACKGROUND: There is a need to match characteristics of tobacco users with cessation treatments and risks of tobacco attributable diseases such as lung cancer. The rate in which the body metabolizes nicotine has proven an important predictor of these outcomes. Nicotine metabolism is primarily catalyzed by the enzyme cytochrone P450 (CYP2A6) and CYP2A6 activity can be measured as the ratio of two nicotine metabolites: trans-3'-hydroxycotinine to cotinine (NMR). Measurements of these metabolites are only possible in current tobacco users and vary by biofluid source, timing of collection, and protocols; unfortunately, this has limited their use in clinical practice. The NMR depends highly on genetic variation near CYP2A6 on chromosome 19 as well as ancestry, environmental, and other genetic factors. Thus, we aimed to develop prediction models of nicotine metabolism using genotypes and basic individual characteristics (age, gender, height, and weight). RESULTS: We identified four multiethnic studies with nicotine metabolites and DNA samples. We constructed a 263 marker panel from filtering genome-wide association scans of the NMR in each study. We then applied seven machine learning techniques to train models of nicotine metabolism on the largest and most ancestrally diverse dataset (N=2239). The models were then validated using the other three studies (total N=1415). Using cross-validation, we found the correlations between the observed and predicted NMR ranged from 0.69 to 0.97 depending on the model. When predictions were averaged in an ensemble model, the correlation was 0.81. The ensemble model generalizes well in the validation studies across ancestries, despite differences in the measurements of NMR between studies, with correlations of: 0.52 for African ancestry, 0.61 for Asian ancestry, and 0.46 for European ancestry. The most influential predictors of NMR identified in more than two models were rs56113850, rs11878604, and 21 other genetic variants near CYP2A6 as well as age and ancestry. CONCLUSIONS: We have developed an ensemble of seven models for predicting the NMR across ancestries from genotypes and age, gender and BMI. These models were validated using three datasets and associate with nicotine dosages. The knowledge of how an individual metabolizes nicotine could be used to help select the optimal path to reducing or quitting tobacco use, as well as, evaluating risks of tobacco use.

A Type VI Secretion System Facilitates Fitness, Homeostasis, and Competitive Advantages for Environmental Adaptability and Efficient Nicotine Biodegradation.

Gram-negative bacteria employ secretion systems to translocate proteinaceous effectors from the cytoplasm to the extracellular milieu, thus interacting with the surrounding environment or microniche. It is known that bacteria can benefit from the type VI secretion system (T6SS) by transporting ions to combat reactive oxygen species (ROS). Here, we report that T6SS activities conferred tolerance to nicotine-induced oxidative stress in Pseudomonas sp. strain JY-Q, a highly active nicotine degradation strain isolated from tobacco waste extract. AA098_13375 was identified to encode a dual-functional effector with antimicrobial and anti-ROS activities. Wild-type strain JY-Q grew better than the AA098_13375 deletion mutant in nicotine-containing medium by antagonizing increased intracellular ROS levels. It was, therefore, tentatively designated TseN (type VI secretion system effector for nicotine tolerance), homologs of which were observed to be broadly ubiquitous in Pseudomonas species. TseN was identified as a Tse6-like bacteriostatic toxin via monitoring intracellular NAD+ TseN presented potential antagonism against ROS to fine tune the heavy traffic of nicotine metabolism in strain JY-Q. It is feasible that the dynamic tuning of NAD+ driven by TseN could satisfy demands from nicotine degradation with less cytotoxicity. In this scenario, T6SS involves a fascinating accommodation cascade that prompts constitutive biotransformation of N-heterocyclic aromatics by improving bacterial robustness/growth. In summary, the T6SS in JY-Q mediated resistance to oxidative stress and promoted bacterial fitness via a contact-independent growth competitive advantage, in addition to the well-studied T6SS-dependent antimicrobial activities.IMPORTANCE Mixtures of various pollutants and the coexistence of numerous species of organisms are usually found in adverse environments. Concerning biodegradation of nitrogen-heterocyclic contaminants, the scientific community has commonly focused on screening functional enzymes that transform pollutants into intermediates of attenuated toxicity or for primary metabolism. Here, we identified dual roles of the T6SS effector TseN in Pseudomonas sp. strain JY-Q, which is capable of degrading nicotine. The T6SS in strain JY-Q is able to deliver TseN to kill competitors and provide a growth advantage by a contact-independent pattern. TseN could monitor the intracellular NAD+ level by its hydrolase activity, causing cytotoxicity in competitive rivals but metabolic homeostasis on JY-Q. Moreover, JY-Q could be protected from TseN toxicity by the immunity protein TsiN. In conclusion, we found that TseN with cytotoxicity to bacterial competitors facilitated the nicotine tolerance of JY-Q. We therefore reveal a working model between T6SS and nicotine metabolism. This finding indicates that multiple diversified weapons have been evolved by bacteria for their growth and robustness.

Acute effects of a very low nicotine content cigarette on laboratory smoking lapse: Impacts of nicotine metabolism and nicotine dependence.

Reducing cigarette nicotine content to nonaddictive levels facilitates smoking cessation; however, very low nicotine content cigarettes (VLNCs) may not be equally effective across heterogeneous smokers. We evaluated the impact of acute VLNC smoking versus control (sham puffs) on craving, withdrawal and smoking lapse behaviour and whether genetically influenced differences in nicotine metabolism and individual differences in nicotine dependence moderate observed effects. Thirty-three overnight-abstinent smokers (15 slow vs. 17 normal nicotine metabolizers; 17 low vs. 16 high nicotine dependence) smoked a 0.05-mg nicotine VLNC during one session and took sham VLNC puffs during another session, in a counterbalanced order. Craving and withdrawal were assessed before and after smoking and sham puffing. Next, participants completed the McKee Smoking Lapse Task, which measures ability to resist smoking and quantity of ad libitum smoking. VLNC (vs. sham) reduced craving and withdrawal, increased ability to resist smoking and reduced ad libitum smoking. VLNC-induced reduction in craving for positive reinforcement was greater in slow (vs. normal) metabolizers. Nicotine metabolism did not moderate any other VLNC responses. High-dependence (vs. low-dependence) participants engaged in greater ad lib smoking across VLNC and sham conditions. Nicotine dependence did not moderate VLNC responses. VLNC reduced craving, withdrawal and smoking lapse behaviour. Individual differences in nicotine metabolism and dependence had a minimal impact on VLNC responses; however, VLNCs were less effective at reducing craving for positive reinforcement among normal (vs. slow) metabolizers. These findings suggest that desirable VLNC effects may extend across heterogeneous groups of smokers.

Nicotine metabolite ratios in serum and urine among US adults: variations across smoking status, gender and race/ethnicity.

Purpose: The objective of this study was to evaluate factors affecting variabilities in the observed levels of nicotine metabolite ratios in serum (NMRS, N = 10,234) and urine (NMRU, N = 2286) for US adults aged ≥20 years.Materials and methods: Data from NHANES were used to fit regression models for log10 transformed values of NMRS and NMRU stratified by gender and smoking status.Results: Females had higher NMRS than males among both smokers and non-smokers. Females had lower NMRU than males among both smokers and non-smokers. Smokers had lower levels of both NMRS and NMRU among both males and females. The order in which NMRS by race/ethnicity was observed was non-Hispanic whites > Hispanics and others > non-Hispanic blacks. The order in which NMRU by race/ethnicity was observed was non-Hispanic blacks > non-Hispanic whites > Hispanics and others. Most of the pairwise differences between non-Hispanic blacks and whites were statistically significant (p ≤ 0.02). Exposure to environmental tobacco smoke (ETS) at home was associated with higher NMRU among male smokers (2.13 vs. 1.41, p = 0.01).Conclusions: Data on nicotine metabolite ratios can be used to study differences in how nicotine is metabolized by males and females and by smokers and non-smokers.

Evaluation of a weighted genetic risk score for the prediction of biomarkers of CYP2A6 activity.

The nicotine metabolite ratio (NMR; 3-hydroxycotinine/cotinine) is an index of CYP2A6 activity. CYP2A6 is responsible for nicotine's metabolic inactivation and variation in the NMR/CYP2A6 is associated with several smoking behaviors. Our aim was to integrate established alleles and novel genome-wide association studies (GWAS) signals to create a weighted genetic risk score (wGRS) for the CYP2A6 gene for European-ancestry populations. The wGRS was compared with a previous CYP2A6 gene scoring approach designed for an alternative phenotype (C2/N2; cotinine-d2/(nicotine-d2 + cotinine-d2)). CYP2A6 genotypes and the NMR were assessed in European-ancestry participants. The wGRS training set included N = 933 smokers recruited to the Pharmacogenetics of Nicotine Addiction and Treatment clinical trial [NCT01314001]. The replication cohort included N = 196 smokers recruited to the Quit 2 Live clinical trial [NCT01836276]. Comparisons between the two CYP2A6 phenotypes and with fractional clearance were made in a laboratory-based pharmacokinetic study (N = 92 participants). In both the training and replication sets, the wGRS, which included seven CYP2A6 variants, explained 33.8% (P < 0.001) of the variance in NMR, providing improved predictive power to the NMR phenotype when compared with other CYP2A6 gene scoring approaches. NMR and C2/N2 were strongly correlated to nicotine clearance (ρ = 0.70 and ρ = 0.79, respectively; P < 0.001), and to one another (ρ = 0.82; P < 0.001); however reduced function genotypes occurred in slow NMR but throughout C2/N2. The wGRS was able to predict smoking quantity and nicotine intake, to discriminate between NMR slow and normal metabolizers (AUC = 0.79; P < 0.001), and to replicate previous NMR-stratified cessation outcomes showing unique treatment outcomes between metabolizer groups.

Cytochrome P450 2A6 and 2B6 polymorphisms and smoking cessation success in patients treated with varenicline.

BACKGROUND: The identification of variants in genes involved in nicotine metabolism may have implications for the pharmacological therapy of smoking. In the scenario of precision medicine, the aim of this study was to evaluate a possible association of cytochrome P450 2A6 and 2B6 polymorphisms with varenicline pharmacotherapy. METHODS: The present study included 167 patients treated with varenicline in monotherapy who were from a cohort study of 1049 patients (treated with smoking cessation drugs: nicotine replacement therapy, bupropion, varenicline, or combinations of same). Smoking cessation success was considered for patients who completed 6 months of continuous abstinence. The CYP2A6 rs1801272 and rs28399433 and CYP2B6 rs8109525 polymorphisms were genotyped by real-time PCR using the TaqMan® platform. RESULTS: Patients with AG or GG genotypes for CYP2B6 rs8109525 had a higher success rate of smoking cessation with varenicline (51.2%) compared with carriers of the AA genotypes (33.3%, P = 0.03, n = 167). The AG or GG genotypes were also associated with a higher odds ratio of success, even in a multivariate analysis adjusting for potential confounders (OR = 2.01; 95%CI = 1.01 to 4.00; P = 0.047). CONCLUSION: CYP2B6 rs8109525 was associated with a higher success rate of smoking cessation with varenicline treatment. This finding may be useful in pharmacogenomic strategies for smoking cessation therapy.

Exploration of Nicotine Metabolism in Paenarthrobacter nicotinovorans pAO1 by Microbial Proteomics.

Proteomics, or the large-scale study of proteins, is a post-genomics field that, together with transcriptomics and metabolomics, has moved the study of bacteria to a new era based on system-wide understanding of bacterial metabolic and regulatory networks. The study of bacterial proteins or microbial proteomics has found a wide array of applications in many fields of microbiology, from food, clinical, and industrial microbiology to microbial ecology and physiology. The current chapter makes a brief technical introduction into the available approaches for the large-scale study of bacterial proteins using mass-spectrometry. Furthermore, the advantages and disadvantages of using bacteria for proteomics studies are indicated as well as several example studies where MS-based bacterial proteomics had a fundamental role in deciphering the scientific question. Finally, the proteomics study of nicotine catabolism in Paenarthrobacter nicotinovorans pAO1 using nanoLC-MS/MS is given as an in-depth example for possible applications of microbial proteomics.The nicotine degradation pathway functioning in Paenarthrobacter nicotinovorans is encoded by the catabolic megaplasmid pAO1 that contains about 40 nicotine-related genes making out the nic-gens cluster. Despite the promising biotechnological potential for the production of green-chemicals, only half of the nic-genes have been experimentally linked to nicotine. In an attempt to systematically identify all the proteins involved in nicotine degradation, a gel-based proteomics approach was used to identify a total of 801 proteins when Paenarthrobacter nicotinovorans was grown on three carbon sources: citrate, nicotine and nicotine and citrate. The differences in protein abundance showed that the bacterium is able to switch between deamination and demethylation in the lower nicotine pathway based on the available C source. Several pAO1 putative genes including a hypothetical polyketide cyclase have been shown to have a nicotine-dependent expression and we hypothesize that the polyketide cyclase would hydrolyze the N1-C6 bond from the pyridine ring with the formation of alpha-keto-glutaramate. Two chromosomal proteins, a malate dehydrogenase, and a D-3-phosphoglycerate dehydrogenase were shown to be strongly upregulated when nicotine was the sole carbon source and could be related to the production of the alpha-keto-glutaramate by the polyketide cyclase.

Association of genetic polymorphisms CYP2A6*2 rs1801272 and CYP2A6*9 rs28399433 with tobacco-induced lung Cancer: case-control study in an Egyptian population.

BACKGROUND: Several studies have reported the role of CYP2A6 genetic polymorphisms in smoking and lung cancer risk with some contradictory results in different populations. The purpose of the current study is to assess the contribution of the CYP2A6*2 rs1801272 and CYP2A6*9 rs28399433 gene polymorphisms and tobacco smoking in the risk of lung cancer in an Egyptian population. METHODS: A case-control study was conducted on 150 lung cancer cases and 150 controls. All subjects were subjected to blood sampling for Extraction of genomic DNA and Genotyping of the CYP2A6 gene SNPs (CYP2A6*2 (1799 T > A) rs1801272 and CYP2A6*9 (- 48 T > G) rs28399433 by Real time PCR. RESULTS: AC and CC genotypes were detected in CYP2A6*9; and AT genotype in CYP2A6*2. The frequency of CYP2A6*2 and CYP2A6*9 were 0.7% and 3.7% respectively in the studied Egyptian population. All cancer cases with slow metabolizer variants were NSCLC. Non-smokers represented 71.4% of the CYP2A6 variants. There was no statistical significant association between risk of lung cancer, smoking habits, heaviness of smoking and the different polymorphisms of CYP2A6 genotypes. CONCLUSION: The frequency of slow metabolizers CYP2A6*2 and CYP2A6*9 are poor in the studied Egyptian population. Our findings did not suggest any association between CYP2A6 genotypes and risk of lung cancer.

Impact of smoking on lung cancer treatment effectiveness: a review.

Tobacco smoke contains more than 4000 detectable substances, such as polycyclic aromatic hydrocarbons, nicotine, carbon monoxide and heavy metals, which are considered powerful enzymatic inducers that have notable influence on the efficacy and tolerability of many medications through complex pharmacokinetic and pharmacodynamic interactions. As a result, adjustments of drug dosages are required in smokers, both if they continue to smoke or if they quit after smoking cessation treatment. The purpose of this review is to examine the main drug interactions with tobacco smoke clinically relevant, with a closer look on patients developing oncologic diseases.

Integrative bioinformatics analysis reveals ECM and nicotine-related genes in both LUAD and LUSC, but different lung fibrosis-related genes are involved in LUAD and LUSC.

There are several bioinformatics studies related to lung cancer, but most of them have mainly focused on either microarray data or RNA-Seq data alone. In this study, we have combined both types of data to identify differentially expressed genes (DEGs) specific to lung cancer subtypes. We obtained six microarray datasets from the GEO and also the expression matrix of LUSC and LUAD from TCGA, which were analyzed by GEO2R tool and GEPIA2, respectively. Enrichment analyses of DEGs were performed using the Enrichr database. Protein module identification was done by MCODE plugin in cytoscape software. We identified 30 LUAD-specific, 17 LUSC-specific, and 17 DEGs shared between LUAD and LUSC. Enrichment analyses revealed that LUSC-specific DEGs are involved in lung fibrosis. In addition, DEGs shared between LUAD and LUSC are involved in extracellular matrix (ECM), nicotine metabolism, and lung fibrosis. We identified lung fibrosis-related genes, including SPP1, MMP9, and CXCL2, involved in both LUAD and LUSC, but SERPINA1 and PLAU genes involved only in LUSC. We also found an important module separately for LUAD-specific, LUSC-specific, and shared DEGs between LUSC and LUAD. S100P, GOLM, AGR2, AK1, TMEM125, SLC2A1, COL1A1, and GHR genes were significantly associated with survival. Our findings suggest that different lung fibrosis-related genes may play roles in LUSC and LUAD. Additionally, nicotine metabolism and ECM remodeling were found to be associated with both LUSC and LUAD, regardless of subtype, emphasizing the role of smoking in the development of lung cancer and ECM in the high aggressiveness and mortality of lung cancer.

Biochemical and genetic biomarkers associated with nicotine dependence in Mexican smokers.

Cigarette smoking remains an important health concern and is still a leading cause of preventable mortality. Nicotine is the substance responsible for sustained tobacco use and dependence. Identification of biomarkers underlying nicotine dependence behavior is important to identify people at risk for this dependence. In the present study, we identified biochemical and genetic biomarkers of nicotine dependence detected by the Fagerström Test for Nicotine Dependence (FTDN) in Mexican smokers. The nicotine metabolites nicotine-N'-oxide, trans-3'-hydroxycotinine-glucuronide (3HC-O-Gluc), and nicotine-N-Gluc (Gluc) were useful to differentiate nicotine-dependent from non-dependent subjects (p < .0001) with an area under the curve (AUC) of 0.7818. Genetic variants in CYP2A6, FMO3, and UGT2B7 (rs2431413, rs28363545, and rs7439326, respectively) were associated with nicotine dependence (p = .03, p = .01, p = .01, respectively). Variations in the enzymatic activity of CYP2A6 were associated with altered nicotine-N'-oxide and 3HC-O-Gluc levels. Decreased urinary levels of 3HC-O-Gluc and increased nicotine-N'-oxide were associated with a decrease in the functional activity of CYP2A6. A strong positive correlation was observed between the ratio of urinary 3HC/cotinine, a measure of CYP2A6 activity, and the levels of 3HC-O-Gluc (p < .0001, r = .6835), while a strong negative correlation was observed with nicotine-N'-oxide (p < .0001, r = .6522) in nicotine-dependent subjects. No correlations were observed in non-nicotine-dependent subjects. These data suggest that particular urinary nicotine metabolites and genetic variants involved in nicotine metabolism are useful to identify subjects with nicotine dependence in the Mexican population.

Variation in Nicotine Metabolization According to Biological Factors and Type of Nicotine Consumer.

This study aims to describe the nicotine metabolite ratio among tobacco smokers and electronic cigarette (e-cigarette) users and nonusers. We analyzed pooled data from a longitudinal and a cross-sectional study of the adult population from the city of Barcelona. The final sample included information on 166 smokers, 164 e-cigarettes users with nicotine, 41 e-cigarette users without nicotine, 95 dual users (users of both products), and 508 nonusers. We used log-linear models to control for the potential confounding effect of the daily number of cigarettes smoked. Salivary nicotine metabolic rate assessment included the rate of nicotine metabolism (cotinine/nicotine) and the nicotine metabolite ratio (trans-3'-hydroxycotinine/cotinine). Exclusive users of e-cigarette without nicotine have the lowest rate of nicotine metabolism (Geometric mean: 0.08, p-values < 0.001) while cigarette smokers have the highest (Geometric mean: 2.08, p-values < 0.001). Nonusers have lower nicotine metabolic rate than cigarette smokers (Geometric means: 0.23 vs. 0.18, p-value < 0.05). Younger individuals (18−44 years) have a higher rate of nicotine metabolism than older individuals (45−64 years and 65−89) (Geometric means: 0.53 vs. 0.42 and 0.31, respectively, p-values < 0.01) and individuals with lower body mass index (21−25 kg/m2) have a higher rate of nicotine metabolism than the rest (26−30 kg/m2 and 31−60 kg/m2) (Geometric means: 0.52 vs. 0.35 and 0.36, respectively-values < 0.01). Nicotine metabolic rates are useful biomarkers when reporting smoking status and biological differences between individuals.

Maternal nicotine metabolism moderates the impact of maternal cigarette smoking on infant birth weight: A Collaborative Perinatal Project investigation.

BACKGROUND: Maternal cigarette smoking is an important modifiable risk factor for low birth weight in the US. We investigated the maternal nicotine metabolite ratio (NMR; trans-3'-hydroxycotinine/cotinine) - a genetically-informed biomarker of nicotine clearance - as a moderator of links between prenatal cigarette use and birth weight. We also explored the role of race in these associations. METHODS: Participants were 454 pregnant women (Mage = 25 years; 11% Black) who smoked cigarettes and their 537 infants from the Collaborative Perinatal Project. Cigarettes smoked per day were assessed at each prenatal visit; maternal NMR was assayed from third trimester serum. Birth weight was obtained from medical records. Generalized estimating equations were used to evaluate associations between cigarette smoking, NMR, race, and birth weight. RESULTS: NMR moderated continuous associations between cigarettes per day over pregnancy and infant birth weight (p = .025). Among women who smoked at moderate levels (<15 cigarettes per day), those with slower NMR showed ~50-100 g decrements in birth weight versus those with faster NMR., while there were no significant associations between NMR and birth weight among women who smoked 15+ cigarettes per day. Although effects of NMR on birthweight were similar for Black and white women, Black women showed significantly slower NMR (p < .001). CONCLUSIONS: This is the first demonstration that the maternal nicotine metabolism phenotype moderates associations between maternal smoking during pregnancy and birth weight. Infants of women with slower nicotine metabolism - including disproportionate representation of Black women - may be at heightened risk for morbidity from maternal smoking.

Ginkgo biloba L. flavonoids inhibit CYP 2A5; potential dietary supplement for nicotine replacement therapy enhancement.

Smoking is a public health concern, and even though smoking cessation methods exist, nicotine replacement therapy (NRT) is often ineffective. Smoking behavior is related to the nicotine metabolizing enzyme (NME) P450 2A6 (mouse 2A5) polymorphisms. Accordingly, fast metabolizers are nicotine dependent, and have low quitting rates compared to slow metabolizers. In this study we examined the ability of Ginkgo biloba L (GB) and its constituents to inhibit the NME, using mouse liver microsomes containing the 2A5 enzyme. Our results indicate that GB can inhibit 2A5 (25% inhibition at 5%v/v), with the flavonoids quercetin, isorhamnetin, and kaempferol being responsible for this inhibition (23.5%, 10.7%, 25.2% inhibition at 60 ng/µL, respectively). Importantly, the flavonoids inhibited 2A5 via mechanism based inhibition (for quercetin 30 ng/µl inhibition increased from 20.8% to 26.9% within 15 minutes). Our results suggest that GB if consumed on a regular basis can help NRT enhancement particularly in fast nicotine metabolizers.

SNPs within CHRNA5-A3-B4 and CYP2A6/B6, nicotine metabolite concentrations and nicotine dependence treatment success in smokers.

AIM: Plasma values of nicotine and its metabolites are highly variable, and this variability has a strong genetic influence. In our study, we analysed the impact of common polymorphisms associated with smoking on the plasma values of nicotine, nicotine metabolites and their ratios and investigated the potential effect of these polymorphisms and nicotine metabolite ratios on the successful treatment of tobacco dependence. METHODS: Five variants (rs16969968, rs6474412, rs578776, rs4105144 and rs3733829) were genotyped in a group of highly dependent adult smokers (n=103). All smokers underwent intensive treatment for tobacco dependence; 33 smokers were still abstinent at the 12-month follow-up. RESULTS: The rs4105144 (CYP2A6, P<0.005) and rs3733829 (EGLN2, P<0.05) variants were significantly associated with plasma concentrations of 3OH-cotinine and with 3OH-cotinine: cotinine ratios. Similarly, the unweighted gene score was a significant (P<0.05) predictor of both cotinine:nicotine and 3OH-cotinine:cotinine ratios. No associations between the analysed polymorphisms or nicotine metabolite ratios and nicotine abstinence rate were observed. CONCLUSION: Although CYP2A6 and EGLN2 polymorphisms were associated with nicotine metabolism ratios, neither these polymorphisms nor the ratios were associated with abstinence rates.

Pharmacogenetics factors influencing smoking cessation success; the importance of nicotine metabolism.

Introduction: Smoking remains a worldwide epidemic, and despite an increase in public acceptance of the harms of tobacco use, it remains the leading cause of preventable death. It is estimated that up to 70% of all smokers express a desire to quit, but only 3-5% of them are successful.Areas covered: The goal of this review was to evaluate the current status of smoking cessation treatments and the feasibility of implementing personalized-medicine approaches to these pharmacotherapies. We evaluated the genetics associated with higher levels of nicotine addiction and follow with an analysis of the genetic variants that affect the nicotine metabolic ratio (NMR) and the FDA approved treatments for smoking cessation. We also highlighted the gaps in the process of translating current laboratory understanding into clinical practice, and the benefits of personalized treatment approaches for a successful smoking cessation strategy.Expert opinion: Evidence supports the use of tailored therapies to ensure that the most efficient treatments are utilized in an individual's smoking cessation efforts. An understanding of the genetic effects on the efficacy of individualized smoking cessation pharmacotherapies is key to smoking cessation, ideally utilizing a polygenetic risk score that considers all genetic variation.

Evaluation of nicotine patch adherence measurement using self-report and saliva cotinine among abstainers in a smoking cessation trial.

BACKGROUND: Adherence to nicotine patches relates to cessation. This is the first study to examine the validity of self-reported nicotine patch adherence relative to saliva cotinine. METHODS: We used data from 198 clinical trial participants who received 11 weeks of nicotine patches, self-reported patch use, had saliva cotinine 1-week after the start of treatment assessed, and were not smoking when saliva was collected (CO < 6). Self-reported patch adherence was defined as: 3-day (before saliva collection), 7-day (before saliva collection), 3-week use (7 days before, and 14 days after, saliva collection), and 11-week use (7 days before, and 10 weeks after, saliva collection). Analyses, including receiver operating characteristic curves, considered differences in nicotine metabolism. Sensitivity, specificity and positive (PPV) and negative predictive value (NPV) assessed optimal cotinine cut-point for adherence. RESULTS: Self-reported 7-day (r = 0.13) and 3-week (r = 0.13) patch use marginally correlated with week 1 cotinine (p's = 0.08) but not 3-day or 11-week. Significant area under the curve (AUC) values of 0.67 (95 %CI: 0.55-0.79) and 0.72 (95 %CI: 0.57-0.88) were found using 7-day self-report for the overall sample and for slow metabolizers (p's<0.01), but not for normal metabolizers. Optimal 1-week cotinine cut-points using 7-day self-report were 170 ng/mL (overall) and 184 ng/mL (slow), with sensitivity = 0.56-0.62, specificity = 0.69-0.78, PPV = 0.96-0.97, and NPV = 0.13-0.14. CONCLUSIONS: Among CO-confirmed abstainers, self-reported patch use and saliva cotinine assessed 1-week into treatment, were modestly correlated and optimal cotinine cut-point differed by rate of nicotine metabolism. Seven-day patch use may be a more valid self-report measure of patch adherence based on cotinine than 3-day, 3-week, or 11-week. Rate of nicotine metabolism may affect this relationship.

Does the nicotine metabolite ratio moderate smoking cessation treatment outcomes in real-world settings? A prospective study.

BACKGROUND AND AIMS: In smoking treatment trials comparing varenicline with transdermal nicotine replacement therapy (NRT), stratified by nicotine metabolite (3-hydroxycotinine/cotinine) ratio (NMR), the relative benefit of varenicline is greater among normal rather than slow metabolizers. This study tested if the relative effectiveness of varenicline and NRT is associated with NMR status in a natural treatment setting. A secondary aim was to test if this relationship is moderated by behavioural support. DESIGN: Prospective observational multi-centre study with 4-week and 52-week follow-up. SETTING: Nine English Stop Smoking Services (SSS). PARTICIPANTS: Data came from 1556 smokers (aged ≥ 16 years) attending SSS between March 2012 and March 2013. INTERVENTIONS: Participants received pharmacotherapy together with behavioural support. MEASUREMENTS: The primary outcome was carbon monoxide-verified continuous abstinence at both follow-up times. Main explanatory variables were (1) NMR status [slow (NMR < 0.31, n = 451) versus normal (NMR ≥ 0.31, n = 1105) metabolizers]; (2) pharmacotherapy (varenicline versus NRT) and (3) behavioural support (individual versus group-based treatment). Analyses adjusted for baseline socio-demographic, SSS, mental/physical health and smoking characteristics. FINDINGS: Of participants, 44.2% [95% confidence interval (CI) = 41.7-46.6%] and 8.0% (95% CI = 6.8-9.5%) were continuously abstinent at 4 and 52 weeks. Varenicline was more effective than NRT at 4 weeks (P < 0.001) but only marginally so at 52 weeks (P = 0.061). There was no or inclusive evidence that NMR status moderated relative efficacy of varenicline and NRT at 4- [P = 0.60, Bayes factor (BF) = 0.25] or 52-week follow-ups (P = 0.74, BF = 0.73). However, this relationship was moderated by behavioural support (p = 0.012): the relative benefit of varenicline over NRT at 52-week follow-up was greater in slow, not normal, metabolizers receiving group rather than individual support (P = 0.012). CONCLUSIONS: In a real-world setting, the nicotine metabolite ratio status of treatment-seeking smokers does not appear to contribute substantially to the differential effectiveness of varenicline and nicotine replacement therapy in Stop Smoking Services, when both pharmacotherapy and behavioural support are self-selected.