Influence of the NAT2 gene polymorphic markers on the effectiveness and safety of treatment in patients with newly diagnosed pulmonary tuberculosis based on peripheral red blood cell dynamics

Background. Individual sensitivity to isoniazid in tuberculosis patients is determined by the presence of N-acetyltransferase 2 (NAT2) enzyme gene allelic variants in genome. Evaluation of quantitative and qualitative alterations in peripheral blood can be used for diagnosis, disease severity estimation, or as a clue for estimation of anti-tuberculosis chemotherapy effectiveness and safety.Aim: Find associations between acetylation type and peripheral red blood cell (RBC) dynamics; determine the effect of NAT2 acetylation rate on the effectiveness and safety of treatment in patients with newly identified pulmonary tuberculosis (TB) residing in the Sakha Republic (Yakutia).Methods. This study included 146 patients with various clinical forms of newly diagnosed pulmonary TB. Oral isoniazid, rifampicin, pyrazinamide, and ethambutol were administered patients. Genotyping was performed via real time PCR.Results. Rapid and intermediate acetylators showed an increase in hemoglobin concentrations and RBC erythrocyte hemoglobin content by the end of chemotherapy (P<0.05). Incidence of anemia was lower in intermediate acetylators, compared to rapid or slow acetylators (P=0.013). Negative correlation was established between absolute RBC count and slow acetylation type (P=0.017). Patients with rapid acetylation type showed increased RBC distribution width indexes RDW-CV and RDW-SD (P<0.05).Conclusions. An adequate therapeutic effect was achieved with standard doses of anti-TB medications in patients with intermediate acetylation type. Rapid and slow acetylators required anti-TB medication dose correction. Genotyping for NAT2 gene in patients with pulmonary TB enables clinicians to choose the optimal dose of anti-TB medications, specifically, isoniazid dose.

Association of N-acetyltransferases 1 and 2 Polymorphisms with Susceptibility to Head and Neck Cancers—A Meta-Analysis, Meta-Regression, and Trial Sequential Analysis

Background and objective: N-acetyltransferases 1 and 2 (NAT1 and NAT2) genes have polymorphisms in accordance with slow and rapid acetylator phenotypes with a role in the development of head and neck cancers (HNCs). Herein, we aimed to evaluate the association of NAT1 and NAT2 polymorphisms with susceptibility to HNCs in an updated meta-analysis. Materials and methods: A search was comprehensively performed in four databases (Web of Science, Scopus, PubMed/Medline, and Cochrane Library until 8 July 2021). The effect sizes, odds ratio (OR) along with 95% confidence interval (CI) were computed. Trial sequential analysis (TSA), publication bias and sensitivity analysis were conducted. Results: Twenty-eight articles including eight studies reporting NAT1 polymorphism and twenty-five studies reporting NAT2 polymorphism were involved in the meta-analysis. The results showed that individuals with slow acetylators of NAT2 polymorphism are at higher risk for HNC OR: 1.22 (95% CI: 1.02, 1.46; p = 0.03). On subgroup analysis, ethnicity, control source, and genotyping methods were found to be significant factors in the association of NAT2 polymorphism with the HNC risk. TSA identified that the amount of information was not large enough and that more studies are needed to establish associations. Conclusions: Slow acetylators in NAT2 polymorphism were related to a high risk of HNC. However, there was no relationship between NAT1 polymorphism and the risk of HNC.

Polymorphism of NAT2, PXR, ABCB1, and GSTT1 genes among tuberculosis patients of North Eastern States of India

Background: Anti-tuberculosis drug-induced liver injury (AT-DILI) in tuberculosis (TB) patients has been linked to polymorphisms in genes encoding drug metabolism enzymes and proteins. Objective: This study aimed to monitor polymorphisms of NAT2, PXR, ABCB1, and GSTT1 genes in TB patients from three states (Manipur, Tripura, and Nagaland) in the North Eastern Region of India. Methods: Genomic DNA was isolated from the whole blood samples of TB patients (n=219; Manipur:139; Tripura: 60; Nagaland: 20). The TaqMan allelic discrimination assay and statistical tools were used to investigate single nucleotide polymorphisms (SNP) patterns in NAT2, PXR, ABCB1, and GSTT1 genes. Results: In the study population, ten distinct genotypes of the NAT2 gene and single variation in the PXR, ABCB1, and GSTT1 genes were identified. A strong linkage disequilibrium (LD) was observed between rs1801280 and rs1799931 of the NAT2 gene. Majority of the study populations were intermediate (~46.1%), rest were either slow acetylators (~35.6%) or fast acetylators. Interestingly, ~55% of the TB patients in Tripura were slow acetylators and majority in Manipur and Nagaland were of intermediate acetylator genotypes. For all of the markers investigated, the population had a greater prevalence of ancestral alleles and genotypes. According to a combinational study of the genotypes linked to AT-DILI, ~26.1% of the population possessed the risk genotypes. Conclusion: These TB patients from north eastern states of India were found as carriers of the ancestral alleles and genotypes. And the risk for AT-DILI during TB treatment is low. Expanding such studies with additional markers and larger sample sizes will be useful to generate precise population-specific pharmacogenomics details for efficient TB management.

Functional Characterization of the Effects of N-acetyltransferase 2 Alleles on N-acetylation of Eight Drugs and Worldwide Distribution of Substrate-Specific Diversity

Variability in the enzymatic activity of N-acetyltransferase 2 (NAT2) is an important contributor to interindividual differences in drug responses. However, there is little information on functional differences in N-acetylation activities according to NAT2 phenotypes, i.e., rapid, intermediate, slow, and ultra-slow acetylators, between different substrate drugs. Here, we estimated NAT2 genotypes in 990 Japanese individuals and compared the frequencies of different genotypes with those of different populations. We then calculated in vitro kinetic parameters of four NAT2 alleles (NAT2∗4, ∗5, ∗6, and ∗7) for N-acetylation of aminoglutethimide, diaminodiphenyl sulfone, hydralazine, isoniazid, phenelzine, procaineamide, sulfamethazine (SMZ), and sulfapyrizine. NAT2∗5, ∗6, and ∗7 exhibited significantly reduced N-acetylation activities with lower Vmax and CLint values of all drugs when compared with NAT2∗4. Hierarchical clustering analysis revealed that 10 NAT2 genotypes were categorized into three or four clusters. According to the results of in vitro metabolic experiments using SMZ as a substrate, the frequencies of ultra-slow acetylators were calculated to be 29.05–54.27% in Europeans, Africans, and South East Asians, whereas Japanese and East Asian populations showed lower frequencies (4.75 and 11.11%, respectively). Our findings will be helpful for prediction of responses to drugs primarily metabolized by NAT2.

Study of the Effect of Polymorphic Markers of the NAT2 Gene on the Risk of Adverse Drug Reactions in Patients with Pulmonary Tuberculosis Who Received Isoniazid and Rifampicin

Tuberculosis remains one of the most dangerous and widespread infectious diseases. More than 20 medicinal products are currently available for the treatment of tuberculosis. One of the most serious adverse drug reactions (ADRs) associated with anti-tuberculosis medicines is hepatotoxicity.The aim of the study was to assess the effect of polymorphic markers of the NAT2 gene on the ADR risk in patients with pulmonary tuberculosis who received isoniazid and rifampicin.Materials and methods. The study included 67 patients with different forms of pulmonary tuberculosis who received combination therapy with isoniazid and rifampicin. Single nucleotide polymorphisms (SNPs) of the NAT2 gene were determined by real-time PCR. Statistical processing was performed using SPSS Statistics 20.0.Results: Six SNPs were identified in the NAT2 gene. Based on these SNPs the following phenotypes were determined by the rate of NAT2 acetylation: fast acetylators—6 subjects, intermediate acetylators—24 subjects, and slow acetylators—37 subjects. The study assessed the relationship between the acetylator phenotype and the development of ADRs during combination therapy with isoniazid and rifampicin. Slow acetylators had a significantly greater increase in total bilirubin level (p=0.011) compared to intermediate acetylators. Loss of appetite was more often observed in fast acetylators than in intermediate acetylators (p=0.021).Conclusions. The obtained data suggest interrelation between the slow type of NAT2 acetylation and the risk of ADRs in patients undergoing pulmonary tuberculosis chemotherapy with isoniazid and rifampicin. Out of all the ADRs registered in the study, the fast acetylators were more likely to have loss of appetite, however, the expansion of the study population is needed to verify this observation. The studied polymorphisms have an impact on the development of ADRs in patients undergoing pulmonary tuberculosis chemotherapy with isoniazid and rifampicin and may be used to predict the safety profile of pharmacotherapy in this group of patients.

Influence of the Acetylation Type on the Incidence of Isoniazid-Induced Hepatotoxicity in Patients with Newly Diagnosed Pulmonary Tuberculosis

Introduction. Liver damage can be a dangerous side effect of using isoniazid. Individual susceptibility to isoniazid in humans is dependent on the presence of N-acetyltransferase 2 allelic variants in genome. It was imperative to assess the effect of genetically determined isoniazid acetylation rate in terms of risk of developing isoniazid-induced hepatotoxicity, as well as prevention of potential hepatopathy, and improvement of tuberculosis chemotherapy safety. Aim. To study the effect of acetylation type on the incidence of isoniazid hepatotoxicity in residents of the Sakha Republic (Yakutia) with newly diagnosed pulmonary tuberculosis. Methods. The study included 112 patients with newly diagnosed pulmonary tuberculosis. Genotyping was performed using real-time polymerase chain reaction. The following single nucleotide polymorphisms were studied: rs1801280, rs1799930, rs1799931, rs1799929, rs1208, rs1041983. Hepatotoxicity was determined based on the results of clinical laboratory monitoring and using the criteria developed by the European Association for the Study of the Liver (2019). Results. Hepatotoxic reactions developed more often in slow acetylators (43.2%), compared to fast acetylators (20.7%) and intermediate acetylators (10.9%); p=0.002. Serum alanine aminotransferase activity was 5 or more times above the upper limit of normal activity in 37.8% of slow acetylators, and in 8.7% of intermediate acetylators; p=0.001. Clinical manifestations of isoniazid hepatotoxicity were observed more often in slow acetylators (29.7%), than in fast acetylators (3.4%); p=0.000. Conclusion. Slow acetylation type ought to be considered an important risk factor for developing isoniazid hepatotoxicity in patients with pulmonary tuberculosis.

Study on Genotyping Polymorphism and Sequencing of N-Acetyltransferase 2 (NAT2) among Al-Ahsa Population

One of the well-studied phase II drug metabolizing enzymes is N-acetyltransferase 2 (NAT2) which has an essential role in the detoxification and metabolism of several environmental toxicants and many therapeutic drugs like isoniazid (antituberculosis, TB) and antimicrobial sulfonamides. According to the variability in the acetylation rate among different ethnic groups, individuals could be classified into slow, intermediate, and fast acetylators; these variabilities in the acetylation rate are a result of single nucleotide polymorphisms (SNPs) in the coding sequence of NAT2. The variety of NAT2 acetylation status is associated with some diseases such as bladder cancer, colorectal cancer, rheumatoid arthritis, and diabetes mellitus. The main objectives of this research are to describe the genetic profile of NAT2 gene among the people of the Al-Ahsa region, to detect the significant SNPs of this gene, to determine the frequency of major NAT2 alleles and genotypes, and then categorize them into fast, intermediate, and slow acetylators. Blood samples were randomly collected from 96 unrelated people from Al-Ahsa population, followed by DNA extraction then amplifying the NAT2 gene by polymerase chain reaction (PCR); finally, functional NAT2 gene (exon 2) was sequenced using the Sanger sequencing method. The well-known seven genetic variants of NAT2 gene are 191G>A, 282C>T, 341T>C, 481C>T, 590G>A, 803A>G, and 857G>A were detected with allele frequencies 1%, 35.4%, 42.7%, 41.1%, 29.2%, 51%, and 5.7%, respectively. The most common NAT2 genetic variant among Al-Ahsa population was 803A>G with a high frequency 0.510 (95% confidence interval 0.44-0.581) followed by 341T>C 0.427 (95% confidence interval 0.357-0.497). The most frequent two haplotypes of NAT2 were NAT2∗6C (25.00%) and NAT2∗5A (22.92%) which were classified as a slow acetylators. According to trimodal distribution of acetylation activity, the predicted phenotype of Al-Ahsa population was found to be 5.21% rapid acetylators, 34.38% intermediate acetylators, and 60.42% were slow acetylators. In addition, this study found four novel haplotypes NAT2∗5TB, NAT2∗5AB, NAT2∗5ZA, and NAT2∗6W which were slow acetylators. This study revealed a high frequency of the NAT2 gene with slow acetylators (60.42%) in Al-Ahsa population, which might alter the drug’s efficacy and vulnerability to some diseases.

Population Pharmacokinetic Analysis of Isoniazid among Pulmonary Tuberculosis Patients from China

ABSTRACT The blood concentration of isoniazid (INH) is evidently affected by polymorphisms in N-acetyltransferase 2 (NAT2), an enzyme that is primarily responsible for the trimodal (i.e., fast, intermediate, and slow) INH elimination. The pharmacokinetic (PK) variability, driven largely by NAT2 activity, creates a challenge for the deployment of a uniform INH dosage in tuberculosis (TB) patients. Although acetylator-specific INH dosing has long been suggested, well-recognized dosages according to acetylator status remain elusive. In this study, 175 blood samples were collected from 89 pulmonary TB patients within 0.5 to 6 h after morning INH administration. According to their NAT2 genotypes, 32 (36.0%), 38 (42.7%), and 19 (21.3%) were fast, intermediate, and slow acetylators, respectively. The plasma INH concentration was detected by liquid chromatography-tandem mass spectrometry. Population pharmacokinetic (PPK) analysis was conducted using NONMEM and R software. A two-compartment model with first-order absorption and elimination well described the PK parameters of isoniazid. Body weight and acetylator status significantly affected the INH clearance rate. The dosage simulation targeting three indicators, including the well-recognized efficacy-safety indicator maximum concentration in serum (Cmax; 3 to 6 μg/ml), the reported area under the concentration-time curve from 0 h to infinity (AUC0–∞; ≥10.52 μg·h/ml), and the 2-h INH serum concentrations (≥2.19 μg/ml), was associated with the strongest early bactericidal activity. The optimal dosages targeting the different indicators varied from 700 to 900 mg/day, 500 to 600 mg/day, and 300 mg/day for the rapid, intermediate, and slow acetylators, respectively. Furthermore, a PPK model for isoniazid among Chinese tuberculosis patients was established for the first time and suggested doses of approximately 800 mg/day, 500 mg/day, and 300 mg/day for fast, intermediate, and slow acetylators, respectively, after a trade-off between efficacy and the occurrence of side effects.

Genotype-Guided Hydralazine Therapy

<b><i>Background:</i></b> Despite its approval in 1953, hydralazine hydrochloride continues to be used in the management of resistant hypertension, a condition frequently managed by nephrologists and other clinicians. Hydralazine hydrochloride undergoes metabolism by the N-acetyltransferase 2 (NAT2) enzyme. NAT2 is highly polymorphic as approximately 50% of the general population are slow acetylators. In this review, we first evaluate the link between NAT2 genotype and phenotype. We then assess the evidence available for genotype-guided therapy of hydralazine, specifically addressing associations of NAT2 acetylator status with hydralazine pharmacokinetics, antihypertensive efficacy, and toxicity. <b><i>Summary:</i></b> There is a critical need to use hydralazine in some patients with resistant hypertension. Available evidence supports a significant link between genotype and NAT2 enzyme activity as 29 studies were identified with an overall concordance between genotype and phenotype of 92%. The literature also supports an association between acetylator status and hydralazine concentration, as fourteen of fifteen identified studies revealed significant relationships with a consistent direction of effect. Although fewer studies are available to directly link acetylator status with hydralazine antihypertensive efficacy, the evidence from this smaller set of studies is significant in 7 of 9 studies identified. Finally, 5 studies were identified which support the association of acetylator status with hydralazine-induced lupus. Clinicians should maintain vigilance when prescribing maximum doses of hydralazine. <b><i>Key Messages:</i></b> NAT2 slow acetylator status predicts increased hydralazine levels, which may lead to increased efficacy and adverse effects. Caution should be exercised in slow acetylators with total daily hydralazine doses of 200 mg or more. Fast acetylators are at risk for inefficacy at lower doses of hydralazine. With appropriate guidance on the usage of <i>NAT2</i> genotype, clinicians can adopt a personalized approach to hydralazine dosing and prescription, enabling more efficient and safe treatment of resistant hypertension.