Slow Acetylators Research Articles

Induction of glucose production by heterocyclic amines is dependent on N-acetyltransferase 2 genetic polymorphism in cryopreserved human hepatocytes

Heterocyclic amines (HCAs) are mutagenic compounds found in cooked meat. Recent epidemiological studies reported significant associations between dietary HCA exposure and insulin resistance and type II diabetes, and we recently reported that HCAs induce insulin resistance and glucose production in human hepatocytes. It is well known that HCAs require hepatic bioactivation by cytochrome P450 1A2 (CYP1A2) and N-acetyltransferase 2 (NAT2). NAT2 expresses a well-defined genetic polymorphism in humans that, depending on the combination of NAT2 alleles, correlates to rapid, intermediate, or slow acetylator phenotype that exhibits differential metabolism of aromatic amines and HCAs. No previous studies have examined the role of NAT2 genetic polymorphism in the context of HCA-mediated induction of glucose production. In the present study, we assessed the effect of three HCAs commonly found in cooked meat (2-amino-3,4-dimethylimidazo[4,5-f]quinoline [MeIQ], 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline [MeIQx], and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine [PhIP]) on glucose production in cryopreserved human hepatocytes with slow, intermediate, or rapid NAT2 acetylator phenotype. HCA treatment did not affect glucose production in slow NAT2 acetylator hepatocytes, while a slight increase in glucose production was observed in intermediate NAT2 acetylators treated with MeIQ or MeIQx. However, significant increases in glucose production were observed in rapid NAT2 acetylators following each HCA. The current findings suggest that individuals who are rapid NAT2 acetylators may be at a greater risk of developing hyperglycemia and insulin resistance following dietary exposure to HCAs.

NAT2 phenotype alters pharmacokinetics of rivaroxaban in healthy volunteers

Rivaroxaban is a direct inhibitor of factor Xa, a member of direct oral anticoagulant group of drugs (DOACs). Despite being a widely extended alternative to vitamin K antagonists (i.e., acenocoumarol, warfarin) the interindividual variability of DOACs is significant, and may be related to adverse drug reaction occurrence or drug inefficacy, namely hemorrhagic or thromboembolic events. Since there is not a consistent analytic practice to monitor the anticoagulant activity of DOACs, previously reported polymorphisms in genes coding for proteins responsible for the activation, transport, or metabolism of DOACs were studied. The study population comprised 60 healthy volunteers, who completed two randomized, crossover bioequivalence clinical trials between two different rivaroxaban formulations. The effect of food, sex, biogeographical origin and 55 variants (8 phenotypes and 47 single nucleotide polymorphisms) in drug metabolizing enzyme genes (such as CYP2D6, CYP2C9, NAT2) and transporters (namely, ABCB1, ABCG2) on rivaroxaban pharmacokinetics was tested. Individuals dosed under fasting conditions presented lower tmax (2.21 h vs 2.88 h, β = 1.19, R2 =0.342, p = 0.012) compared to fed volunteers. NAT2 slow acetylators presented higher AUC∞ corrected by dose/weight (AUC∞/DW; 8243.90 vs 7698.20 and 7161.25 h*ng*mg /ml*kg, β = 0.154, R2 =0.250, p = 0.044), higher Cmax/DW (1070.99 vs 834.81 and 803.36 ng*mg /ml*kg, β = 0.245, R2 =0.320, p = 0.002), and lower tmax (2.63 vs 3.19 and 4.15 h, β = −0.346, R2 =0.282, p = 0.047) than NAT2 rapid and intermediate acetylators. No other association was statistically significant. Thus, slow NAT2 appear to have altered rivaroxaban pharmacokinetics, increasing AUC∞ and Cmax. Nonetheless, further research should be conducted to verify NAT2 involvement on rivaroxaban pharmacokinetics and to determine its clinical significance.

Pharmacogenetic interactions of efavirenz or rifampin and isoniazid with levonorgestrel emergency contraception during treatment of HIV or tuberculosis.

In AIDS Clinical Trials Group study A5375, a pharmacokinetic trial of levonorgestrel emergency contraception, double-dose levonorgestrel (3 mg, versus standard dose 1.5 mg) offset the induction effects of efavirenz or rifampin on plasma levonorgestrel exposure over 8 h post-dose (AUC 0-8h ). We characterized the pharmacogenetics of these interactions. Cisgender women receiving efavirenz- or dolutegravir-based HIV therapy, or on isoniazid-rifampin for tuberculosis, were followed after a single oral dose of levonorgestrel. Linear regression models, adjusted for BMI and age, characterized associations of CYP2B6 and NAT2 genotypes (which affect plasma efavirenz and isoniazid exposure, respectively) with levonorgestrel pharmacokinetic parameters. Of 118 evaluable participants, 17 received efavirenz/levonorgestrel 1.5 mg, 35 efavirenz/levonorgestrel 3 mg, 34 isoniazid-rifampin/levonorgestrel 3 mg, and 32 (control group) dolutegravir/levonorgestrel 1.5 mg. There were 73 Black and 33 Asian participants. Regardless of genotype, women on efavirenz and isoniazid-rifampin had higher levonorgestrel clearance. In the efavirenz/levonorgestrel 3 mg group, CYP2B6 normal/intermediate metabolizers had levonorgestrel AUC 0-8h values similar to controls, while CYP2B6 poor metabolizers had AUC 0-8h values of 40% lower than controls. In the isoniazid-rifampin group, NAT2 rapid/intermediate acetylators had levonorgestrel AUC 0-8h values similar to controls, while NAT2 slow acetylators had AUC 0-8h values 36% higher than controls. CYP2B6 poor metabolizer genotypes exacerbate the efavirenz-levonorgestrel interaction, likely by increased CYP3A induction with higher efavirenz exposure, making the interaction more difficult to overcome. NAT2 slow acetylator genotypes attenuate the rifampin-levonorgestrel interaction, likely by increased CYP3A inhibition with higher isoniazid exposure.

N -acetyltransferase 2 haplotype modifies risks for both dyslipidemia and urinary bladder cancer.

A novel haplotype in N -acetyltransferase 2 ( NAT2 ) composed of seven non-coding variants (rs1495741, rs4921913, rs4921914, rs4921915, rs146812806, rs35246381, and rs35570672) has been linked to dyslipidemia by multiple, independent genome-wide association studies. The haplotype is located approximately 14 kb downstream of NAT2-coding region (ch8:18,272,377-18,272,881; GRCh38/hg38) and represents a non-coding, intergenic haplotype. Interestingly, the same dyslipidemia NAT2 haplotype is also linked to urinary bladder cancer risk. Dyslipidemia risk alleles are associated with rapid acetylator phenotype, whereas bladder cancer risk alleles are associated with slow acetylator, suggesting that the level of systemic NAT2 activity modifies the risk of these pathologies. We speculate that rs1495741 (and its associated haplotype) belongs to a distal regulatory element of human NAT2 gene (e.g., enhancer or silencer), and the genetic variation at the newly discovered haplotype results in a differential level of NAT2 gene expression. Understanding how this NAT2 haplotype contributes to not only urinary bladder cancer but also to dyslipidemia will ultimately help devise strategies to identify and protect susceptible individuals.

Effect of N-acetyltransferase 2 genetic polymorphism on 4,4'-methylenebis(2-chloroaniline)-induced genotoxicity and oxidative stress.

4,4'-Methylenebis(2-chloroaniline) or MOCA is an aromatic amine used primarily in polyurethane and rubber industry. MOCA has been linked to hepatomas in animal studies while limited epidemiologic studies reported the association of exposure to MOCA and urinary bladder and breast cancer. We investigated MOCA-induced genotoxicity and oxidative stress in DNA repair-deficient Chinese hamster ovary (CHO) cells stably transfected with human metabolizing enzymes CYP1A2 and N-acetyltransferase 2 (NAT2) variants as well as in rapid, intermediate, and slow NAT2 acetylator cryopreserved human hepatocytes. N-acetylation of MOCA was highest in UV5/1A2/NAT2*4 followed by UV5/1A2/NAT2*7B and UV5/1A2/NAT2*5B CHO cells. Human hepatocytes showed a NAT2 genotype-dependent response with highest N-acetylation in rapid acetylators followed by intermediate and slow acetylators. MOCA induced higher levels of mutagenesis and DNA damage in UV5/1A2/NAT2*7B compared to UV5/1A2/NAT2*4 and UV5/1A2/NAT2*5B cells (p < 0.0001). MOCA also induced higher levels of oxidative stress in UV5/1A2/NAT2*7B cells. MOCA caused concentration-dependent increase in DNA damage in cryopreserved human hepatocytes (linear trend p < 0.001) which was NAT2 genotype dependent i.e., highest in rapid acetylators, lower in intermediate acetylators, and lowest in slow acetylators (p < 0.0001). Our findings show that N-acetylation and genotoxicity of MOCA is NAT2 genotype dependent and suggest that individuals possessing NAT2*7B are at higher risk to MOCA-induced mutagenicity. DNA damage, and oxidative stress. They confirm significant differences in genotoxicity between the NAT2*5B and NAT2*7B alleles, both of which are associated with slow acetylator phenotype.

Non-coding and intergenic genetic variants of human arylamine N-acetyltransferase 2 (NAT2) gene are associated with differential plasma lipid and cholesterol levels and cardiometabolic disorders.

Arylamine N-acetyltransferase 2 (NAT2) is a phase II metabolic enzyme, best known for metabolism of aromatic amines and hydrazines. Genetic variants occurring in the NAT2 coding region have been well-defined and are known to affect the enzyme activity or protein stability. Individuals can be categorized into rapid, intermediate, and slow acetylator phenotypes that significantly alter their ability to metabolize arylamines, including drugs (e.g., isoniazid) and carcinogens (e.g., 4-aminobiphenyl). However, functional studies on non-coding or intergenic variants of NAT2 are lacking. Multiple, independent genome wide association studies (GWAS) have reported that non-coding or intergenic variants of NAT2 are associated with elevated plasma lipid and cholesterol levels, as well as cardiometabolic disorders, suggesting a novel cellular role of NAT2 in lipid and cholesterol homeostasis. The current review highlights and summarizes GWAS reports that are relevant to this association. We also present a new finding that seven, non-coding, intergenic NAT2 variants (i.e., rs4921913, rs4921914, rs4921915, rs146812806, rs35246381, rs35570672, and rs1495741), which have been associated with plasma lipid and cholesterol levels, are in linkage disequilibrium with one another, and thus form a novel haplotype. The dyslipidemia risk alleles of non-coding NAT2 variants are associated with rapid NAT2 acetylator phenotype, suggesting that differential systemic NAT2 activity might be a risk factor for developing dyslipidemia. The current review also discusses the findings of recent reports that are supportive of the role of NAT2 in lipid or cholesterol synthesis and transport. In summary, we review data suggesting that human NAT2 is a novel genetic factor that influences plasma lipid and cholesterol levels and alters the risk of cardiometabolic disorders. The proposed novel role of NAT2 merits further investigations.

Allelic Frequencies of Single Nucleotide Polymorphisms (SNPs) in the N-acetyltransferase 2 (NAT2) Gene of Filipinos

Objectives. The present study aims to determine the frequency of occurrence of NAT2*4, NAT2*5A, NAT2*6B, NAT2*7A and NAT2*14A alleles by PCR-RFLP among Filipino volunteers. These alleles correspond to substitutions in the following sites: C341T, G590A, G857A and G191A, respectively, of the NAT2 gene. The presence of specific SNP combination was also used to deduce acetylation status and estimate genotype frequency and describe them in comparison with other populations based on literature.&#x0D; Methods. Genomic DNA from peripheral blood lymphocytes from 129 healthy Filipino volunteers was used to amplify the NAT2 gene segment. The RFLP analysis was done by restricting the expected PCR product with Kpn1, Taq1, BamH1 and Msp1/Al1, respectively, to detect the 4 alleles: NAT2*4, NAT2*5A, NAT2*6B, NAT2*7A and NAT2*14A.&#x0D; Results. The calculated allelic frequencies in Hardy-Weinberg equilibrium of NAT2*5A (C481T), NAT2*6B (G590A), NAT2*7A (G857A) and NAT2*14A (G191A) were 0.058, 0.097, 0.182 and 0.046, respectively. NAT2*4 had an allele frequency of 0.617. Nine genotypes were determined: NAT2*4/*4, NAT2*4/*5A, NAT2*4/*6B, NAT2*4/*7A, NAT2*4/*14A, NAT2*5A/*7A, NAT2*6B/*7A, NAT2*6B/*14A and NAT2*7A/*14A. From these genotypes, acetylator phenotypes were deduced. A trimodal pattern of distribution was established: rapid, intermediate and slow acetylators with the following percentages, 47.3%, 41.1 % and 11.6%. Among the slow acetylator SNPs determined, NAT2*7A was found as the most frequent allele and NAT2*14A was found as the least frequent allele.&#x0D; Conclusion. The study showed the mutation profile and observed genotypic similarities and differences of Filipinos with other Asian populations and Americans and other Caucasians based on literature. The results also suggest a trimodal pattern of distribution of acetylators and lesser number of slow acetylators among Filipino populations, a characteristic similar to other Asian populations but significantly different from Americans and other Caucasians. The occurrence of NAT2*7A and NAT2*14A can be further sequenced to verify the observed genotype.&#x0D;

Adequacy of the 10 mg/kg Daily Dose of Antituberculosis Drug Isoniazid in Infants under 6 Months of Age.

In 2010, the WHO recommended an increase in the daily doses of first-line anti-tuberculosis medicines in children. We aim to characterize the pharmacokinetics of the once-daily isoniazid (INH) dose at 10 mg/kg of body weight in infants <6 months of age. We performed a multicenter pharmacokinetic study in Spain. The N-acetyltransferase 2 gene was analyzed to determine the acetylation status. Samples were analyzed using a validated UPLC-UV assay. A non-compartmental pharmacokinetic analysis was performed. Twenty-three pharmacokinetic profiles were performed in 20 infants (8 females) at a median (IQR) age of 19.0 (12.6-23.3) weeks. The acetylator statuses were homozygous fast (n = 1), heterozygous intermediate (n = 12), and homozygous slow (n = 7). INH median (IQR) Cmax and AUC0-24h values were 4.8 (3.7-6.7) mg/L and 23.5 (13.4-36.7) h*mg/L and the adult targets (>3 mg/L and 11.6-26.3 h*mg/L) were not reached in three and five cases, respectively. The age at assessment or acetylator status had no impact on Cmax values, but a larger INH AUC0-24h (p = 0.025) and trends towards a longer half-life (p = 0.055) and slower clearance (p = 0.070) were observed in homozygous slow acetylators. Treatment was well tolerated; mildly elevated alanine aminotransferase levels were observed in three cases. In our series of young infants receiving isoniazid, no major safety concerns were raised, and the target adult levels were reached in most patients.

Influence of sex on the exposure to isoniazid in patients with pulmonary tuberculosis.

Isoniazid is a key component of tuberculosis treatment. Adequate exposure is a determinant for therapeutic success; however, considerable inter- and intraindividual variations in drug plasma levels can lead to unfavorable outcomes. While some predictors of isoniazid levels are well-known, others, such as sex, yield controversial results, requiring further investigation to optimize exposure. This study investigates whether the sex of patients influences the dose administered and the concentrations of isoniazid in plasma. Levels of isoniazid were associated with the N-acetyltransferase 2 phenotypes. A total of 76 male and 58 female patients were included. Isoniazid was measured by high-performance liquid chromatography, and N-acetyltransferase 2 phenotypes were assessed using molecular techniques. The results show that the dose administered, expressed in mg/kg, was higher in females, but the plasma levels were similar between both sexes. Among patients, 46.2%, 38.8%, and 15% were slow, intermediate, and fast acetylators, respectively. As expected, isoniazid levels were associated with the acetylation phenotypes, with higher concentrations in the slow acetylators. Thus, sex-related difference in isoniazid levels is due to the body weight of patients, and the optimized dose regimen based on patient weight and acetylator phenotypes can improve the treatment outcomes.

1449. Therapeutic Drug Monitoring of Isoniazid and Rifampicin and Clinical Outcomes in Adults with Tuberculosis.

Abstract Background Directly Observed Treatment Short Course for Tuberculosis (TB) (DOTS) treatment currently produces a cure rate of 80%. Rifampicin (RMP) and isoniazid (INH) are the main bactericides; both show wide inter-individual pharmacokinetics and narrow therapeutic range. Therapeutic drug monitoring (TDM) of antiTB drugs is a strategy to improve the response to treatment. The aim of this work was to optimize and individualize antiTB treatment based on plasma concentrations of RMP and INH, NAT2 genotyping and the Bayesian estimation of PK parameters. Methods A prospective and analytical study including TB patients under DOTS scheme was performed. Venous blood samples were drawn 2 and 4 hours after last dose; INH and RMP were quantified by liquid chromatography coupled to tandem mass spectrometry. Anthropometric and clinical information was retrieved from medical records. Acetylator phenotype was determined based on NAT2 genotyping by real-time PCR. Bayesian estimation of the PK parameters was performed using NONMEM and dosing scheme was proposed to achieve therapeutic concentrations of RIF and INH. Results A total 62 patients were included from 18 to 80 years and 35 to 117 kg of total body weight. The most frequent was pulmonary infection (40%), 25% of patients had type 2 diabetes mellitus and 58.5% were slow acetylators for the NAT2 gene. Lower INH and RMP plasma concentrations were related to adverse clinical outcome, compared to those patients classified with early clinical success [1.9 vs 3.7 mg/L and 16.9 vs 10.0 mg/L (p&amp;lt; 0.05)]. Results indicate the need to adjust anti-TB drugs dose to more than 50% of the patients who show plasma concentrations outside the range for both drugs. Bayesian dosing performed was validated after individualization by quantification and interpretation of INH and RMP plasma concentrations followed by a narrow medical follow up. Conclusion Even with standard anti-TB treatment, great proportion of patients show subtherapeutic concentrations of RMP and INH which is associated with overall therapeutic failure. TDM is a useful tool to individualize antimicrobials dose and improve clinical outcomes at early stages of active TB. Disclosures All Authors: No reported disclosures.

Accumulation and distribution of persistent organic pollutants in surface sediment of the estuarine region and correlation between genetic and environmental factors: A case study

In this study, the accumulation and distribution of nine organochlorine pesticides (OCPs) and seven polychlorinated biphenyls (PCBs) in the An Hoa Estuary, Quang Nam Province, Central Vietnam, and the correlation between genetic and environmental factors have been analyzed and assessed. This study analyzed sediment samples from 15 positions in the An Hoa Estuary during the dry season. The OCP concentrations varied between ND (not detected) and 1.82 μ g/kg (S1), mainly consisting of DDE. The total concentration of PCBs ranged between 1.52–19.5 μ g/kg (highest at S13), with PCB-138 and PCB-153 as the congeners most frequently detected in the analyzed samples. The results show that the ecological risk of OCPs and PCBs in the An Hoa Estuary ranges from low to moderate levels. In order to clarify the significance of genetic factors that can be influenced and affected by environmental factors over a certain period, this study also determined the N-acetyltransferase (NAT) enzyme activity in the population residing in the An Hoa Estuary for a period of 30–50 years to show clearly the relationship between weak environmental and genetic factors in determining the risks for environmental health. Based on the results, out of a total of 72 volunteer participants, the phenotype of the N-acetyltransferase system was determined and divided into two groups: rapid (30.6%) and slow (69.4%). Among them, the slow acetylator phenotype is prevalent in two locations, S11 and S13, with 88% and 91.7% of volunteers, respectively. The rapid acetylator phenotype was detected in 17 of 23 participants at location S7, accounting for more than 77% of the total individuals with the rapid acetylator phenotype in this experiment. • The accumulation of nine OCPs and seven PCBs in sediment was determined and assessed. • The highest OCPs (1.82 μ g/kg) and PCBs (19.5 μ g/kg) were detected at sampling sites S1 and S13, respectively. • The activity of xenobiotics biotransformation enzymatic system N-acetyltransferase was determined. • The relationship between weak environmental factors and genetic factors was examined. • The N-acetyltransferase phenotype of citizens was divided into rapid (30.6%) and slow (69.4%).

Very important pharmacogenes polymorphism landscape and potential clinical relevance in the Chinese Mongolian

PurposeOur study genotyped pharmacogenes in 200 individuals from Inner Mongolia Autonomous Region, China. Aim to find distinct pharmacogenomic variations among the Mongolian population and to investigate the potential clinically operable gene-drug connection and genotype-phenotype correlation of differential variation in the Mongolian population. MethodsWe sampled 61 variations of 28 genes in PharmGKB and genotyped them using Agena MassARRAY Assay. We also obtained the allele frequency and genotype distribution data of 26 populations from the 1000 Genomes Project (1000G), and then conducted comparison and statistical analysis. ResultsAfter Bonferroni correction, there were significant genotype frequency distribution differences between the Mongolian and 26 populations: PTGS2 (rs20417), NAT2 (rs1801280, rs1799929, and rs1208), ALOX5(rs2115819), and CYP2D6 (rs1065852). It was also found that the KHV showed the smallest differences from the Mongolian and the GWD showed the largest differences. Furthermore, the differences in variants might be related to the risk of non-steroidal anti-inflammatory drug use, the slow acetylation phenotype, and other pharmacological effectiveness and toxicity in the Mongolian population. ConclusionOur study demonstrates different pharmacogenomic variants in the Mongolian and fills the gaps in pharmacogenomic information of the Mongolian. Our analysis of VIPs variants in the Mongolian population may contribute to the development of safer treatment regimens and the use of personalized treatment approaches.

Characteristics of N-acetyltransferase 2 Phenotype Status and Pharmacokinetic Parameters of Vietnam Pulmonary Tuberculosis Patients

Abstract: We conducted this research to determine the NAT2 gene-phenotype characteristics and pharmacokinetics (PK) parameters of isoniazid among patients with non-MDR pulmonary tuberculosis. Data were collected from 132 patients diagnosed with newly acquired or relapsed tuberculosis and treated at 03 hospitals: Hanoi Lung Hospital, Central Lung Hospital, and National K74 Hospital. PK samples were collected one day from the 10th – 14th day after commencing treatment. The average age of the recruited patients was 45.43 ± 15.76 years; the majority were male (74.24%). The slow and medium acetylator types, as indicated by NAT2 phenotypes, were the two major types (37.88% and 35.6%, respectively). 61.12% of the patients had their Bayesian isoniazid-acetyl isoniazid population PK modeling - determined Cmax value within the therapeutic range of 3 – 6 µg/mL. Acelytator type showed a statistically significant correlation with Cmax.&#x0D; Keywords: Isoniazid, pharmacokinetics, Cmax, tuberculosis.

N-acetyltransferase 2 acetylator genotype-dependent N-acetylation and toxicity of the arylamine carcinogen β-naphthylamine in cryopreserved human hepatocytes.

We used cryopreserved human hepatocytes that express rapid, intermediate, and slow acetylator N-acetyltransferase 2 (NAT2) genotypes to measure the N-acetylation of β-naphthylamine (BNA) which is one of the aromatic amines found in cigarette smoke including E-cigarettes. We investigated the role of NAT2 genetic polymorphism in genotoxicity and oxidative stress induced by BNA. In vitro BNA NAT2 activities in rapid acetylators was 1.6 and 3.5-fold higher than intermediate (p &lt; 0.01) and slow acetylators (p &lt; 0.0001). BNA N-acetylation in situ was 3 to 4- fold higher in rapid acetylators than slow acetylators, following incubation with 10 and 100µM BNA (p &lt; 0.01). DNA damage was two to threefold higher in the rapid versus slow acetylators (p &lt; 0.0001) and 2.5-fold higher in intermediate versus slow acetylators following BNA treatment at 100 and 1000μM, ROS/RNS level was the highest in rapid acetylators followed by intermediate and then slow acetylators (p &lt; 0.0001). Our findings show that theN-acetylation of BNA is NAT2 genotype dependent in cryopreserved human hepatocytes and our data further document an important role for NAT2 genetic polymorphism in modifying BNA-induced genotoxicity and oxidative damage.

Clinical Prediction of Acetylator Phenotype in Tuberculosis Patients on Medicare using Blood Group

ABSTRACT Individual acetylation phenotype detected by metabolic phenotyping tests using a number of surrogate drugs, such as isoniazid is time consuming. The aim of this work was to determine the clinical prediction of acetylator phenotype in tuberculosis patients on medicare using blood group. 150 Tuberculosis patients (102 males and 48 females) on medicare were examined using urinalysis technique for acetylator status and tile method for blood group analysis. The result of the acetylator phenotypes revealed that 46.7% were fast acetylators while 53.3% were slow acetylators. The highest frequency of fast acetylators were subjects with blood groups O+ve and A+ve. Similarly, the highest frequency of slow acetylators were observed in blood groups B+ve and O+ve. Blood groups AB-ve and B-ve formed the lowest frequency of fast acetylators while A-ve and AB-ve formed the lowest percentage of slow acetylators respectively. Analysis of the blood groups and the acetylator phenotype using Pearson’s correlation showed a significant (p &lt; 0.01) relationship with a coefficient of 0.852; between the blood groups of M.Tb patients and the fast and slow acetylators (p &lt; 0.05, with a coefficient of 0.76) respectively. We imply that for standard TB treatment, more treatment time be considered for subjects with blood groups that are predominantly fast acetylators (e.g., O+ve ) and close monitoring through the treatment period for predominantly slow acetylators (e.g B+ve). Further study on the serum concentration of each blood group for the drugs and molecular analysis of the blood phenotypes is advocated. reby recommended.

Differences in β-naphthylamine metabolism and toxicity in Chinese hamster ovary cell lines transfected with human CYP1A2 and NAT2*4, NAT2*5B or NAT2*7B N-acetyltransferase 2 haplotypes.

β-naphthylamine (BNA) is an important aromatic amine carcinogen. Current exposures derive primarily from cigarette smoking including e-cigarettes. Occupational and environmental exposure to BNA is associated with urinary bladder cancer which is the fourth most frequent cancer in the United States. N-acetyltransferase 2 (NAT2) is an important metabolizing enzyme for aromatic amines. Previous studies investigated mutagenicity and genotoxicity of BNA in bacteria and in rabbit or rat hepatocytes. However, the effects of human NAT2 genetic polymorphism on N-acetylation and genotoxicity induced by BNA still need to be clarified. We used nucleotide excision repair-deficient Chinese hamster ovary (CHO) cells that were stably transfected with human CYP1A2 and NAT2 alleles: NAT2*4 (reference allele), NAT2*5B (variant slow acetylator allele common in Europe) or NAT2*7B (variant slow acetylator allele common in Asia). BNA N-acetylation was measured both in vitro and in situ via high-performance liquid chromatography (HPLC). Hypoxanthine phosphoribosyl transferase (HPRT) mutations, double-strand DNA breaks, and reactive oxygen species (ROS) were measured as indices of toxicity. NAT2*4 cells showed significantly higher BNA N-acetylation rates followed by NAT2*7B and NAT2*5B. BNA caused concentration-dependent increases in DNA damage and ROS levels. NAT2*7B showed significantly higher levels of HPRT mutants, DNA damage and ROS than NAT2*5B (p < 0.001, p < 0.0001, p < 0.0001 respectively) although both are slow alleles. Our findings suggest that BNA N-acetylation and toxicity are modified by NAT2 polymorphism. Furthermore, they confirm heterogeneity among slow acetylator alleles for BNA metabolism and toxicity supporting differential risk for individuals carrying NAT2*7B allele.

Pharmacogenetic testing for NAT2 genotypes in a Tanzanian population across the lifespan to guide future personalized isoniazid dosing

Despite updated recommendations for weight-based isoniazid dosing in children with drug-susceptible tuberculosis (TB) and higher dose isoniazid in regimens for adults with drug-resistant TB, individual pharmacokinetic variability can lead to sub-target isoniazid exposure. Host pharmacogenetics and isoniazid exposure remain understudied, especially in the East African population. We therefore employed a real-time polymerase chain reaction (qPCR) assay system to test genomic DNA extracted from saliva samples targeting the NAT2 gene responsible for isoniazid metabolism to describe the frequency of human single nucleotide polymorphisms in NAT2 within populations of children and adults in Tanzania, ascribe those polymorphisms to acetylator phenotype, and correlate to serum isoniazid exposures. In adults treated with higher dose isoniazid, genotypes with a predicted allelic phenotype of slow or intermediate acetylation were able to achieve a 0.41 μg/mL higher Cmax (p = 0.018) and a 2.9h*μg/mL higher AUC0–12 (p = 0.003) per mg/kg increase in isoniazid dosage versus adults with rapid acetylation phenotype. A similar relationship was not found in the younger age population as predicted by timing of NAT2 maturation. This saliva based qPCR assay was fieldable to guide personalized isoniazid dosing in adults but not young children that may not have full NAT2 maturation and activity.

ISONIAZID-INDUCED LIVER INJURY: PHARMACOGENETIC ASPECTS

Inter-individual differences in anti-tuberculosis chemotherapy outcomes have been demonstrated in clinical practice, such as, achievement of intended therapeutic effect in some patients, and insufficiency or absence of response to treatment in others, with development of adverse drug reactions, especially, isoniazid-induced liver injury. Isoniazid-induced liver injuries are the main reason for isoniazid discontinuation, which further leads to considerably reduced effectiveness of anti-tuberculosis chemotherapy, increased relapse risk, and secondary drug-resistance of M. tuberculosis. Hepatotoxic reactions to chemotherapy are predicated by mutations in genes encoding enzymes participating in isoniazid biotransformation: N-acetyltransferase 2 (NAT2), cytochrome P450 2Е1, and glutathione-S-transferase. NAT2 gene polymorphism has been identified as risk factor for isoniazid hepatotoxicity. Nucleotide substitutions in NAT2 gene cause modification of enzyme protein structure, reduction of enzyme synthesis and alteration of its activity. Based on genetically-determined isoniazid acetylation rate, patients are referred to three acetylator types: rapid, intermediate, and slow. Correlations have been established in meta-reviews and systematic reviews between slow acetylator type and frequency of hepatotoxic reactions to isoniazid. Based on study findings, interrelation was shown between cytochrome P450 CYP2E1 gene polymorphism and increased risk of liver injury during chemotherapy with isoniazid. Contribution of GSTM1 and GSTT1 genotypes to isoniazid toxicity requires further exploration, as the obtained results were ambiguous and controversial.

NAT2 and CYP2E1 polymorphisms and antituberculosis drug-induced hepatotoxicity in Peruvian patients.

BackgroundIn Peru, 32,970 people were diagnosed with tuberculosis (TB) in 2019. Although TB treatment is effective, 3.4%–13% is associated with significant adverse drug reactions (ADR), considering drug‐induced liver injury (DILI) as the most prevalent. Among the first‐line anti‐TB drugs, isoniazid (INH) is primarily responsible for the occurrence of DILI. INH is metabolized in the liver by the enzymes N‐acetyltransferase‐2 (NAT2) and Cytochrome P450 2E1 (CYP2E1). Based on the previous studies, we hypothesized that the interactions between slow CYP2E1 genotype and NAT2 slow acetylators will induce DILI in TB patients.MethodsIn this cross‐sectional study, all 377 participants completed their anti‐TB treatment, and we genotyped SNPs: rs1041983, rs1801280, rs1799929, rs1799930, rs1208, and rs1799931 for NAT2 and rs3813867 and rs2031920 for CYP2E1.ResultsWe found that rapid, intermediate, and slow NAT2 acetylator were 15%, 38%, and 47%, respectively, in the general population. Intermediate NAT2 acetylator is the least prevalent among patients with adverse reactions (p = 0.024). We did not confirm our hypothesis, however, we found that the combination of intermediate NAT2 acetylators and CYP2E1 c1/c1 genotype significantly protected (OR = 0.16; p = 0.049) against the development of DILI in our population.ConclusionWe propose that the presence of NAT2 intermediate and CYP2E1 c1/c1 genotype could help in therapeutic drug monitoring, and optimize its therapeutic benefits while minimizing its risk for side effects or toxicity.

NAT2 polymorphism and clinical factors that increase antituberculosis drug-induced hepatotoxicity.

Aim: Hepatotoxicity is a known adverse effect of antituberculosis drugs. The NAT2 gene polymorphism has been associated with an increased risk of antituberculosis drug-induced hepatotoxicity (ATDIH). Materials & methods: This study investigates the association of NAT2 polymorphism and clinical risk factors that may contribute to the development of ATDIH. The authors sequenced the NAT2 region of 33 tuberculosis patients who developed ATDIH and 100 tuberculosis patients who did not develop ATDIH during tuberculosis treatment. NAT2 haplotypes were inferred and NAT2 acetylator status was predicted from the combination of the inferred haplotypes. Multiple logistic regression was performed to identify possible factors that are associated with ATDIH. Results: The TT genotype of NAT2*13A and the AA genotype of NAT2*6B were found to be substantially linked with the risk of ATDIH, with odds ratios of 3.09 (95% CI: 1.37-6.95) and 3.07 (95% CI: 1.23-7.69), respectively. NAT2 slow acetylators are 3.39-times more likely to develop ATDIH. Factors that were associated with ATDIH include underlying diabetes mellitus (adjusted odds ratio[AOR]: 2.96; 95% CI: 1.05-8.37), pre-treatment serum bilirubin (AOR: 1.09; 95% CI: 1.02-1.16) and NAT2 slow acetylator (AOR: 3.77; 95% CI: 1.51-9.44). Conclusion: Underlying diabetes mellitus, having a higher baseline bilirubin and being a slow acetylator are identified as the risk factors associated with ATDIH among patients in Malaysia.