NAT2 Acetylation Phenotype Research Articles

High-Dose Isoniazid Lacks EARLY Bactericidal Activity against Isoniazid-resistant Tuberculosis Mediated by katG Mutations: A Randomized Phase II Clinical Trial.

Rationale: Observational studies suggest that high-dose isoniazid may be efficacious in treating multidrug-resistant tuberculosis. However, its activity against Mycobacterium tuberculosis (M.tb) with katG mutations (which typically confer high-level resistance) is not established. Objectives: To characterize the early bactericidal activity (EBA) of high-dose isoniazid in patients with tuberculosis caused by katG-mutated M.tb. Methods: A5312 was a phase IIA randomized, open-label trial. Participants with tuberculosis caused by katG-mutated M.tb were randomized to receive 15 or 20 mg/kg isoniazid daily for 7 days. Daily sputum samples were collected for quantitative culture. Intensive pharmacokinetic sampling was performed on Day 6. Data were pooled across all A5312 participants for analysis (drug-sensitive, inhA-mutated, and katG-mutated M.tb). EBA was determined using nonlinear mixed-effects modeling. Measurements and Main Results: Of 80 treated participants, 21 had katG-mutated M.tb. Isoniazid pharmacokinetics were best described by a two-compartment model with an effect of NAT2 acetylator phenotype on clearance. Model-derived maximum concentration and area under the concentration-time curve in the 15 and 20 mg/kg groups were 15.0 and 22.1 mg/L and 57.6 and 76.8 mg ⋅ h/L, respectively. Isoniazid bacterial kill was described using an effect compartment and a sigmoidal maximum efficacy relationship. Isoniazid potency against katG-mutated M.tb was approximately 10-fold lower than in inhA-mutated M.tb. The highest dose of 20 mg/kg did not demonstrate measurable EBA, except against a subset of slow NAT2 acetylators (who experienced the highest concentrations). There were no grade 3 or higher drug-related adverse events. Conclusions: This study found negligible bactericidal activity of high-dose isoniazid (15-20 mg/kg) in the majority of participants with tuberculosis caused by katG-mutated M.tb. Clinical trial registered with www.clinicaltrials.gov (NCT01936831).

Model-Informed Precision Dosing of Isoniazid: Parametric Population Pharmacokinetics Model Repository.

Isoniazid (INH) is a crucial first-line anti tuberculosis (TB) drug used in adults and children. However, various factors can alter its pharmacokinetics (PK). This article aims to establish a population pharmacokinetic (popPK) models repository of INH to facilitate clinical use. A literature search was conducted until August 23, 2022, using PubMed, Embase, and Web of Science databases. We excluded published popPK studies that did not provide full model parameters or used a non-parametric method. Monte Carlo simulation works was based on RxODE. The popPK models repository was established using R. Non-compartment analysis was based on IQnca. Fourteen studies included in the repository, with eleven studies conducted in adults, three studies in children, one in pregnant women. Two-compartment with allometric scaling models were commonly used as structural models. NAT2 acetylator phenotype significantly affecting the apparent clearance (CL). Moreover, postmenstrual age (PMA) influenced the CL in pediatric patients. Monte Carlo simulation results showed that the geometric mean ratio (95% Confidence Interval, CI) of PK parameters in most studies were within the acceptable range (50.00-200.00%), pregnant patients showed a lower exposure. After a standard treatment strategy, there was a notable exposure reduction in the patients with the NAT2 RA or nonSA (IA/RA) phenotype, resulting in a 59.5% decrease in AUC0-24 and 83.2% decrease in Cmax (Infants), and a 49.3% reduction in AUC0-24 and 73.5% reduction in Cmax (Adults). Body weight and NAT2 acetylator phenotype are the most significant factors affecting the exposure of INH. PMA is a crucial factor in the pediatric population. Clinicians should consider these factors when implementing model-informed precision dosing of INH. The popPK model repository for INH will aid in optimizing treatment and enhancing patient outcomes.

Association between cigarette smoking and ovarian reserve among women seeking fertility care.

This study examined the association of smoking with ovarian reserve in a cross-sectional study of 207 women enrolled in the Louisville Tobacco Smoke Exposure, Genetic Susceptibility, and Infertility (LOUSSI) Study and assessed effect modification by NAT2 acetylator phenotype. Information on current smoking status was collected using a structured questionnaire and confirmed by cotinine assay. Serum anti-Müllerian hormone (AMH) levels were used to assess ovarian reserve. Diminished ovarian reserve (DOR) was defined as AMH <1ng/mL. Single nucleotide polymorphisms in the NAT2 gene, which metabolizes toxins found in cigarette smoke, were analyzed to determine NAT2 acetylator status. Linear and logistic regression were used to determine the effects of smoking on ovarian reserve and evaluate effect modification by NAT2. Regression analyses were stratified by polycystic ovary syndrome (PCOS) status and adjusted for age. Current smoking status, either passive or active as measured by urinary cotinine assay, was not significantly associated with DOR. For dose-response assessed using self-report, the odds of DOR increased significantly for every additional cigarette currently smoked (Odds ratio, OR:1.08; 95% confidence interval, 95%CI:1.01-1.15); additionally, every 1 pack-year increase in lifetime exposure was associated with an increased odds of DOR among women without PCOS (OR: 1.08 95%CI: 0.99-1.18). These trends appear to be driven by the heavy or long-term smokers. Effect modification by NAT2 genotype was not established. A history of heavy smoking may indicate increased risk of diminished ovarian reserve.

Genomewide Association Study Confirming the Association of NAT2 with Susceptibility to Antituberculosis Drug-Induced Liver Injury in Thai Patients.

Antituberculosis drug-induced liver injury (ATDILI) is a common side effect leading to tuberculosis (TB) treatment disruption. The mechanism of the disease remains poorly understood. We conducted a genomewide association study (GWAS) to investigate all possible genetic factors of ATDILI in Thai patients. This study was carried out in Thai TB patients, including 79 ATDILI cases and 239 tolerant controls from our network hospitals in Thailand. Nearly 1 million single-nucleotide polymorphisms (SNPs) were genotyped across the whole genome using an Illumina OmniExpress Exome BeadChip array. In the discovery stage, we identified strong association signals on chromosome 8 originating from the N-acetyltransferase (NAT2) region. The A allele of rs1495741, the top SNP in the intergenic region of NAT2 and PSD3 (14 kb from NAT2), was significantly associated with ATDILI (recessive model, odds ratio of 6.01 [95% confidence interval, 3.42 to 10.57]; P = 6.86E-11). This particular SNP was reported as a tag SNP for NAT2 inferred phenotypes. The AA, AG, and GG genotypes represented NAT2 slow acetylators, intermediate acetylators, and fast acetylators, respectively. The tag SNP genotypes demonstrated a concordance rate of 94.98% with NAT2 acetylator phenotypes. This GWAS shows that NAT2 is the most important risk factor for ATDILI in the Thai population.

GWAS identifies an NAT2 acetylator status tag single nucleotide polymorphism to be a major locus for skin fluorescence.

Aims/hypothesisSkin fluorescence (SF) is a non-invasive marker of AGEs and is associated with the long-term complications of diabetes. SF increases with age and is also greater among individuals with diabetes. A familial correlation of SF suggests that genetics may play a role. We therefore performed parallel genome-wide association studies of SF in two cohorts.MethodsCohort 1 included 1,082 participants, 35–67 years of age with type 1 diabetes. Cohort 2 included 8,721 participants without diabetes, aged 18–90 years.Resultsrs1495741 was significantly associated with SF in Cohort 1 (p < 6 × 10−10), which is known to tag the NAT2 acetylator phenotype. The fast acetylator genotype was associated with lower SF, explaining up to 15% of the variance. In Cohort 2, the top signal associated with SF (p = 8.3 × 10−42) was rs4921914, also in NAT2, 440 bases upstream of rs1495741 (linkage disequilibrium r 2 = 1.0 for rs4921914 with rs1495741). We replicated these results in two additional cohorts, one with and one without type 1 diabetes. Finally, to understand which compounds are contributing to the NAT2–SF signal, we examined 11 compounds assayed from skin biopsies (n = 198): the fast acetylator genotype was associated with lower levels of the AGEs hydroimidazolones of glyoxal (p = 0.017).Conclusions/interpretationWe identified a robust association between NAT2 and SF in people with and without diabetes. Our findings provide proof of principle that genetic variation contributes to interindividual SF and that NAT2 acetylation status plays a major role.Electronic supplementary materialThe online version of this article (doi:10.1007/s00125-014-3286-9) contains peer-reviewed but unedited supplementary material, which is available to authorised users.

Impact of population diversity on the prediction of 7-SNP NAT2 phenotypes using the tagSNP rs1495741 or paired SNPs

A novel NAT2 tagSNP (rs1495741) and a 2-SNP genotype (rs1041983 and rs1801280) have been recently shown to accurately predict the NAT2 acetylator phenotypes in populations of exclusive or predominant European/White ancestry. We confirmed the accuracy of the tagSNP approach in White Brazilians, but not in Brown or Black Brazilians, sub-Saharan Mozambicans, and Guarani Amerindians. The combined rs1041983 and rs1801280 genotypes provided considerably better prediction of the NAT2 phenotype in Guarani, but no consistent improvement in Brown or Black Brazilians and Mozambicans. Best predictions of the NAT2 phenotype in Mozambicans using NAT2 SNP pairs were obtained with rs1801280 and rs1799930, but the accuracy of the estimates remained inadequate for clinical use or for investigations in this sub-Saharan group or in Brazilians with considerable African ancestry. In conclusion, the rs1495741 tagSNP cannot be applied to predict the NAT2 acetylation phenotype in Guarani and African-derived populations, whereas 2-SNP genotypes may accurately predict NAT2 phenotypes in Guarani, but not in Africans.

Accuracy of Various Human NAT2 SNP Genotyping Panels to Infer Rapid, Intermediate and Slow Acetylator Phenotypes

Humans exhibit genetic polymorphism in NAT2 resulting in rapid, intermediate and slow acetylator phenotypes. Over 65 NAT2 variants possessing one or more SNPs in the 870-bp NAT2 coding region have been reported. The seven most frequent SNPs are rs1801279 (191G>A), rs1041983 (282C>T), rs1801280 (341T>C), rs1799929 (481C>T), rs1799930 (590G>A), rs1208 (803A>G) and rs1799931 (857G>A). The majority of studies investigate the NAT2 genotype assay for three SNPs: 481C>T, 590G>A and 857G>A. A tag-SNP (rs1495741) recently identified in a genome-wide association study has also been proposed as a biomarker for the NAT2 phenotype. Sulfamethazine N-acetyltransferase catalytic activities were measured in cryopreserved human hepatocytes from a convenience sample of individuals in the USA with an ethnic frequency similar to the 2010 US population census. These activities were segregated by the tag-SNP rs1495741 and each of the seven SNPs described above. We assessed the accuracy of the tag-SNP and various two-, three-, four- and seven-SNP genotyping panels for their ability to accurately infer NAT2 phenotype. The accuracy of the various NAT2 SNP genotype panels to infer NAT2 phenotype were as follows: seven-SNP: 98.4%; tag-SNP: 77.7%; two-SNP: 96.1%; three-SNP: 92.2%; and four-SNP: 98.4%. A NAT2 four-SNP genotype panel of rs1801279 (191G>A), rs1801280 (341T>C), rs1799930 (590G>A) and rs1799931 (857G>A) infers NAT2 acetylator phenotype with high accuracy, and is recommended over the tag-, two-, three- and (for economy of scale) the seven-SNP genotyping panels, particularly in populations of non-European ancestry.

N-Acetyltransferase 2 Polymorphisms, Tobacco Smoking, and Breast Cancer Risk in the Breast and Prostate Cancer Cohort Consortium

Common polymorphisms in the N-acetyltransferase 2 gene (NAT2) modify the association between cigarette smoking and bladder cancer and have been hypothesized to determine whether active cigarette smoking increases breast cancer risk. The authors sought to replicate the latter hypothesis in a prospective analysis of 6,900 breast cancer cases and 9,903 matched controls drawn from 6 cohorts (1989-2006) in the National Cancer Institute's Breast and Prostate Cancer Cohort Consortium. Standardized methods were used to genotype the 3 most common polymorphisms that define NAT2 acetylation phenotype (rs1799930, rs1799931, and rs1801280). In unconditional logistic regression analyses, breast cancer risk was higher in women with more than 20 pack-years of active cigarette smoking than in never smokers (odds ratio (OR) = 1.28, 95% confidence interval (CI): 1.17, 1.39), after controlling for established risk factors other than alcohol consumption and physical inactivity. However, associations were similar for the slow (OR = 1.25, 95% CI: 1.11, 1.39) and rapid/intermediate (OR = 1.24, 95% CI: 1.08, 1.42) acetylation phenotypes, with no evidence of interaction (P = 0.87). These results provide some support for the hypothesis that long-term cigarette smoking may be causally associated with breast cancer risk but underscore the need for caution when interpreting sparse data on gene-environment interactions.

Abstract LB-287: Spermidine/spermine actyltransferase is responsible for the metabolism of triethylenetetramine and other polyamine analogs in humans

Abstract Triethylenetetramine (TETA), a copper II chelator traditionally used for the treatment of Wilson's disease, and a number of structural analogs are currently in clinical trials for cancer. However, the metabolism of TETA has never been thoroughly investigated, which is crucial for its further development in cancer treatment. The two major metabolites of TETA found in humans are N1-acetyl-TETA (MAT) and N1, N10-diacetyl-TETA (DAT). Traditionally, acetylation of drug is thought to be catalyzed by N-acetyltransferase (NAT2). FDA requires that pharmacological properties of any drug metabolized via acetylation route have to be investigated in population with different NAT2 phenotype. However, our recent clinical study showed that there was no significant difference in pharmacokinetic, pharmacodynamic and metabolites profiles of healthy volunteers with fast or slow NAT2 acetylation phenotype. We therefore hypothesize that the enzyme responsible to TETA acetylation is spermidine/spermine acetyltransferase (SSAT), which has never before been considered as a drug metabolizing enzyme, rather than the NAT2. We carried out in vitro drug metabolism assays to pin-point the enzyme responsible for TETA metabolism. TETA and MAT (as substrate) and acetyl-coenzyme A were incubated with human liver microsome and cytosol from 5 individuals in the presence or absence of pentamidine or acetaminophen separately. The formation of MAT from TETA and DAT from MAT was detected and measured using our LC-MS method published previously. Both liver microsome and cytosol could catalyze the biotransformation of TETA and MAT. The rate of metabolism in microsome and cytosol within each individual varies. The rates of metabolism in microsome and cytosol also varied between individuals (Km range 223 - 909 M, Vmax range 96 - 482 pg/min/mg protein). Pentamidine, a specific inhibitor for x SSAT, could inhibit the reaction and increase Km by over 30%. While acetaminophen, a specific inhibitor for NAT2, did not show any inhibition effect. Same experiments had been performed in rat liver microsome and cytosol, and similar results were obtained apart from the Km and Vmax values. TETA and two other analogs of polyamine, diethylnorspermine and diethylspermine, all of which are under investigation for the treatment of cancer, were incubated with pure whole-recombinant human SSAT protein, and formation of acetylated metabolites were found. The identification of SSAT, which has never been before considered to be a xenobiotic metabolizing enzyme, as the enzyme to catalyze the actylation of polyamine analogs, have a significant importance in the clinic, especially in clinical trial situations. Many polyamine analogs have been developed as potential cancer drugs and many of them, including TETA, are being investigated in clinical trials. Finding the right enzyme (i.e. SSAT instead of traditional NAT2) to study their biotransformation is crucial for understanding their pharmacology, which is essential for the overall drug study. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-287.

Evaluation of Breast Cancer Risk in a Multigenic Model Including Low Penetrance Genes Involved in Xenobiotic and Estrogen Metabolisms

Breast cancer has become the most frequent cancer among women in Westernized countries. The majority of breast cancers are due to low penetrance genes, which can act with environmental factors, particularly nutrition. Polymorphisms in gene coding for xenobiotic and estrogen metabolic pathways could increase individual cancer susceptibility and lead to the indication of individuals at higher cancer risk. A population-based, case-control study consisting of 911 breast cancer cases and 1,000 healthy control cases was performed. The association between 11 single nucleotide polymorphisms (SNP) in 7 genes and breast cancer risk was investigated in a multigenic model. The CYP1B1-432 Leu-Val and Val-Val genotypes significantly increased risk [odds ratio (OR) = 1.23, 95% confidence interval (CI) = 1.08–1.39; OR = 1.51, 95% CI = 1.17–1.94, respectively] similarly as observed with CYP1B1-453 (Asn-Ser genotype: OR = 1.17, 95% CI = 1.00–1.37; Ser-Ser genotype: OR = 1.38, 95% CI = 1.00–1.89). We showed that catechol-O-methyltransferase (COMT) could modulate the risk conferred by CYP1B1, ESR, GSTP1, and NAT2 acetylation phenotype. Additionally, a higher risk conferred by the variant for COMT was noted only for individuals presenting a high waist-to-hip ratio (COMT Val-Met, OR = 1.60, 95% CI = 1.04–2.44; COMT Met-Met, OR = 1.57, 95% CI = 0.98–2.53), suggesting a relationship with abdominal adiposity. In conclusion, COMT constitutes a crucial element in estrogen metabolism by regulating carcinogen metabolites elimination and, consequently, is a major factor in breast cancer risk.

N-acetyltransferase 2 gene polymorphisms and susceptibility to prostate cancer: a pilot study in the Turkish population

To investigate the association between the 3 most frequently observed single nucleotide polymorphisms of the NAT2 gene and the risk of developing prostate cancer in the Turkish population. Materials and methods: A total of 110 unrelated patients with prostate cancer were included in this case-control association study and constituted the study group. The control group also consisted of 150 unrelated but healthy men. Genomic DNA was isolated from peripheral blood leukocytes of all patients and analyzed with a sensitive real-time PCR method. After melting curve analysis genotypes were identified for the NAT2*5A, NAT2*6A, and NAT2*7A/B polymorphisms. Results: Prostate cancer patients had a higher frequency of the mutant NAT2*6A (13.6% versus 4.0%, P = 0.009) and heterozygote NAT2*7A/B (20.9% versus 9.3%, P = 0.008) genotypes when compared with the controls. Conclusion: The NAT2*6A and NAT2*7A/B gene polymorphisms were significantly associated with prostate cancer in the Turkish population. Real-time PCR analysis of the NAT2 acetylator phenotype can therefore be used to recognize individuals with a high risk of developing prostate cancer.

Evaluating NAT2PRED for inferring the individual acetylation status from unphased genotype data

BackgroundGenetically determined differences in N-acetylation capacity have proved to be important determinants of both the effectiveness of therapeutic response and the development of adverse drug reactions and toxicity during drug treatment. NAT2PRED is a web-server that allows a fast determination of NAT2 acetylation phenotype from genotype data without taking the extra step of reconstructing haplotypes for each individual (publicly available at http://nat2pred.rit.albany.edu). However, the classification accuracy of NAT2PRED needs to be assessed before its application can be advocated at a large scale.MethodsThe ability of NAT2PRED to classify individuals according to their acetylation status (slow, intermediate and rapid acetylators) was evaluated in a worldwide dataset composed of 56 population samples (8,489 individuals) from four continental regions.ResultsNAT2PRED correctly identified slow acetylators with a sensitivity above 99% for all populations outside sub-Saharan Africa. Nevertheless, NAT2PRED showed a poor ability to distinguish between intermediate and rapid acetylators, with a classification error rate reaching up to 10% in the non-African samples.ConclusionNAT2PRED is an excellent tool to infer the individual acetylation status from NAT2 genotype data when the main interest is to distinguish slow acetylators from the others. This should facilitate the determination of the individual acetylation status in routine clinical practice and lead to better monitoring of risks associated with cancer and adverse drug reactions.

The challenge of testing chemicals for potential carcinogenicity using multiple short-term assays: An analysis of a proposed test battery for hair dyes

Recent reports of the association of hair dyes usage with increased bladder cancer risk in women with the slow NAT-2 acetylator phenotype have resulted both in attempts to identify the putative carcinogen as well as in devising batteries of tests that could be used to screen for such putative carcinogens in hair dye formulations, their intermediates and final products. Analytical studies have reported the presence of traces (∼0.5 ppm) of the carcinogen 4-aminobiphenyl in some hair dye preparations. In parallel, SCCNFP (Scientific Committee on Cosmetic and Non-Food Products Intended for Consumers) has suggested the deployment of a battery of six in vitro assays followed by an in vivo assay. The practicality of deploying and interpreting such a battery is analyzed herein as it is expected to result in 64 and 128 possible test results and SCCNFP does not provide detailed guidance of how the test results are to be interpreted. In this study we have applied a previously described Bayesian approach which takes advantage of the known predictive performances of individual assays, to analyze the possible outcomes of the 6–7 test batteries. While the SCCNFP battery is clearly risk-averse, it is shown that performing all of the assays is not always necessary and moreover it does not necessarily improve predictive performance. Finally, based upon the reported mutagenicity of 4-aminobiphenyl, it is doubtful that this “impurity” would be detected by the test battery.

Cigarette Smoking, N -Acetyltransferase Genes and the Risk of Advanced Colorectal Adenoma

Cigarette use is associated with greater risk for colorectal adenoma, a colorectal cancer precursor. N-acetyltransferases, NAT1 and NAT2, are important enzymes involved in the metabolism of aromatic amine carcinogens present in cigarette smoke. Our interest is in the polymorphisms within the NAT1 and NAT2 genes that influence the tobacco-colorectal tumor relationship by impacting on the metabolic activation and detoxification of tobacco smoke-derived carcinogens. In the Prostate, Lung, Colorectal and Ovarian (PLCO) cancer screening trial, we compared NAT1 and NAT2 gene variant distributions for 772 cases with left-sided advanced adenoma and 777 gender and age-matched controls. Individual NAT1 and NAT2 diplotypes were assigned and NAT2 acetylator phenotypes were derived. Risks for advanced colorectal adenoma were significantly increased among recent smokers (current smokers or those who quit less than 10 years ago) (odds ratio [OR] = 2.3, 95% confidence interval [CI]: 1.7-3.1) and among those who smoked more than 20 cigarettes per day (OR = 1.7, 95% CI: 1.3-2.2), compared with nonsmokers. Risk decreased with increasing NAT2 phenotypic activity (0: slow, 1: intermediate, and 2: rapid) (OR trend: 0.8; 95% CI: 0.7-1.0, p-trend = 0.04) overall. When stratified by smoking status, significant phenotype-associated trends were observed among recent smokers (OR trend = 0.4, 95% CI: 0.3-0.7, p trend <0.001) (p-interaction = 0.02), but not among past or nonsmokers. Diplotypes most strongly associated with lower risks in smokers were NAT2*4/*5B (OR = 0.3, 95% CI: 0.1-0.8, p = 0.01) and NAT2*4/*4 (OR = 0.2, 95% CI: 0.04-0.7, p = 0.02), categorized as intermediate and rapid acetylators, respectively. One NAT1 diplotype, NAT1*4/*10 (OR = 0.5, 95% CI: 0.3-0.9, p = 0.03), was also associated with a decreased risk in smokers. Our study indicated that NAT2 gene variants associated with a slow acetylator phenotype were more susceptible to the effects of tobacco smoking with respect to adenoma risk, providing leads for disease prevention.

Flame-broiled food, NAT2acetylator phenotype, and breast cancer risk among women with benign breast disease

The objective of this study was to examine the association between flame-broiled food consumption, a source of heterocyclic amine exposure, and the development of breast cancer among cohort of women with benign breast disease (BBD). The variation of the association by acetylation phenotype, as determined by the genotypes of selected N-acetyltransferase 2 (NAT2) enzymes, was also examined. Among participants in an ongoing cohort study, 1187 women reported having a breast biopsy for BBD and completed a food frequency questionnaire. NAT2 G857A, NAT2 T341C, and NAT2 G590A genotypes were determined using DNA extracted from blood specimens collected in 1989. Incident cases of breast cancer were identified through linkage of the cohort participants with the Washington County Cancer Registry and the Maryland State Cancer Registry. Follow-up for the BBD cohort began at study entry in 1989 and ended on April 28, 2003. Of the women in this study, 77 subsequently developed breast cancer. Results showed that, among rapid acetylators, flame-broiled food intake was associated with a statistically significant increase in the risk of breast cancer (odds ratio (OR) 2.62; 95% confidence interval (CI) 1.06, 6.46). No association was observed between flame-broiled food intake and breast cancer among slow acetylators (OR 0.75; 95% CI 0.39, 1.43). These findings suggest that flame-broiled food may be a modifiable risk factor for the progression of BBD to invasive breast cancer among women who have genotypes consistent with rapid acetylation.

Association of N-acetyl transferase 2 gene polymorphism and slow acetylator phenotype with young onset and late onset Parkinson's disease among Indians

To investigate the association of (i) seven SNPs and SNP haplotypes in the phase II conjugating enzyme N-acetyl transferase 2 gene; and (ii) slow acetylator phenotype, with the development of young onset (YO) and late onset (LO) Parkinson's disease (PD) among Indians. A total of 267 cases (132 YOPD, age at onset < or =40 years; 135 LOPD, age at onset >40 years) and 324 age and sex matched controls (132 for YOPD and 192 for LOPD) were genotyped for NAT2 SNPs. Allelic, genotypic and haplotypic association was tested by chi2 using a case-control approach. Chi2 test of association of acetylation phenotype (by genotype) with PD was also carried out. Of the seven SNPs genotyped, SNP191 was monomorphic and therefore, not included for analysis. With SNPs 590 and 857 a significant allelic [OR (95% CI) 4.147 (2.28-7.54) for A allele and 2.565 (1.34-4.92) for A allele, respectively] and genotypic [OR (95% CI) 0.27 (0.14-0.52) for GG and 0.35 (0.174-0.712) for GG, respectively] association with YOPD was observed. There was a significant allelic and genotypic association of SNP 282 with LOPD [chi2 = 8.92, P = 0.003 and chi2 = 10.2, P = 0.006, respectively]. There was also a significant association of protective and predisposing haplotypes TCGG and TCAG [OR (95% CI) 0.446 (0.31-0.63) and 3.742 (2.0-6.99), respectively] with YOPD and predisposing haplotype TCGA [OR (95% CI) 3.214 (1.43-7.22)] with LOPD. Slow acetylator phenotype was significantly associated with YOPD [OR (95% CI) 2.32 (1.2-4.48)]. Specific SNPs and SNP haplotypes in NAT2 and slow acetylator phenotype are significantly associated with YOPD and to a lesser extent with LOPD among Indians.

Influence of CYP1A2 and NAT2 Metabolic Phenotypes on Smokers' Urinary Mutagenicity

The influence of the metabolic phenotypes NAT2 and CYP1A2 on urinary mutagenicity of 118 smokers was studied. Mutagenicity of urine samples was determined by Ames test (preincubation plate incorporation assay on YG1024 Salmonella typhimurium strain with S9 mix). Urinary nicotine plus its metabolites were determined to check cigarette smoke intake. The N -acetyltransferase (NAT2) and cytochrome P450 1A2 (CYP1A2) phenotypes were measured by the molar ratio of urinary caffeine metabolites, determined by HPLC analysis. Urinary mutagenicity was significantly higher in smokers CYP1A2 extensive (EM) than in CYP1A2 poor metabolizers (PM) (Mann-Whitney U test, p = 0.020). Linear multiple regression analysis shows that an increase in urinary mutagenicity levels was significantly related to cigarette smoke intake and to CYP1A2 N -hydroxylation activity ( t = 5.06, p < 0.001, and t = 2.33, p = 0.021), but not to NAT2 acetylation phenotype. In conclusion, phenotypic differences in metabolic activation of tobacco smoke mutagens are able to modulate the presence of mutagens in urine of cigarette smokers and, consequently, the potential genotoxic risk.

Urothelial cell DNA adducts in rubber workers.

Workers employed in the rubber industry appear to have a significant excess cancer risk in a variety of sites, including cancer of the urinary bladder. In this cross-sectional study, we investigated the occurrence of DNA adducts in exfoliated bladder cells of currently exposed, nonsmoking rubber workers (n = 52) and their relationship with occupational exposure estimates and acetylation phenotype (NAT2). Four DNA adducts were identified, with the proportion of positive samples (e.g., DNA samples with quantifiable levels of a specific DNA adduct) ranging from 3.8 to 79%. The highest proportion of positive samples and the highest relative adduct labeling levels were in workers involved in the production functions "mixing" and "curing," areas with potential for substantial exposure to a wide range of chemical compounds used in rubber manufacturing (P < 0.05 for adducts 2 and/or 3, compared to all other departments). No statistically significant relationships were found between identified DNA adducts and urinary mutagenicity or personal inhalable and dermal exposure estimates. Interestingly, subjects with a fast NAT2 acetylation phenotype tended to have higher levels of DNA adducts. This study suggests that rubber workers engaged in mixing and curing may be exposed to compounds that can form DNA adducts in urothelial cells. Larger studies among rubber workers should be conducted to study in more detail the potential carcinogenicity of exposures encountered in these work areas.

Amantadine acetylation may be effected by acetyltransferases other than NAT1 or NAT2

Amantadine is a drug with a primary amino group, and consequently a likely candidate for metabolism by acetylation. This study assessed the possibility that a person's polymorphic (NAT2) acetylator phenotype could be used to predict the extent of amantadine acetylation. Thirty-eight normal, healthy volunteers were NAT2 acetylator phenotyped with sulfapyridine. Of the six fastest (75-86%) and six slowest (34-40%) sulfapyridine acetylators, two and three, respectively, had acetylamantadine present (18-338 µg) in the 8-h urine collection. There was no correlation between NAT2 acetylator phenotype and amantadine acetylation (p &lt; 0.5), and no difference in the total urine amantadine excreted over 8 h between acetylators and nonacetylators (28.3 ± 9.7 vs. 30.4 ± 9.6 mg, respectively, mean ± SD). Acetylamantadine represented 0.1-1.5% (median 0.5%) of urinary drug content over 8 h. Our data confirm that amantadine is acetylated in humans and demonstrate for the first time that the extent is not correlated with NAT2 acetylator phenotype. Parallel in vitro enzyme studies indicate the possibility that neither NAT1 nor NAT2 is responsible for acetylation of amantadine.Key words: amantadine, acetylation, conjugation, drug metabolism.

Rodent models of the human acetylation polymorphism: Comparisons of recombinant acetyltransferases

The acetylation polymorphism is associated with differential susceptibility to drug toxicity and cancers related to aromatic and heterocyclic amine exposures. N-Acetylation is catalyzed by two cytosolic N-acetyltransferases (NAT1 and NAT2) which detoxify many carcinogenic aromatic amines. NAT1 and NAT2 also activate (via O-acetylation) the N-hydroxy metabolites of aromatic and heterocyclic amine carcinogens to electrophilic intermediates which form DNA adducts and initiate cancer. The classical N-acetylation polymorphism is regulated at the NAT2 locus, which segregates individuals into rapid, intermediate, and slow acetylator phenotypes. Some human epidemiological studies associate slow acetylator and rapid acetylator phenotypes with increased susceptibility to urinary bladder and colorectal cancers, respectively. The acetylation polymorphism has been characterized in three rodent species (mouse, Syrian hamster, and rat) to test associations between NAT2 acetylator phenotype and susceptibility to aromatic and heterocyclic amine-induced cancers in various tumor target organs. NAT1 and NAT2 from rapid and slow acetylator mouse, Syrian hamster, and rat each have been cloned and sequenced. Recombinant NAT1 and NAT2 enzymes encoded by these genes have been characterized with respect to their catalytic activities for both activation ( O-acetylation) and deactivation ( N-acetylation) of aromatic and heterocyclic amine carcinogens. The acetylation polymorphisms in mouse, Syrian hamster, and rat are herein reviewed and compared as models of the human acetylation polymorphism.