The Vietnamese Khin Population Harbors Particular N-Acetyltransferase 2 Allele Frequencies

NAT2 Gene rs1041983 is Associated with Anti-Tuberculosis Drug Induced Hepatotoxicity Among Pediatric Tuberculosis in Bandung, Indonesia

Background

As pediatric tuberculosis (TB) globally is still reported challenging in diagnosis, to date, a lot of efforts have been established to eliminate the disease including proper treatment regimen using anti-TB drugs. However, antituberculosis drug-induced hepatotoxicity (ADIH) is known to interfere the success of the prescribed therapy. ADIH was found to be correlated with polymorphisms of NAT2 gene, that is responsible to transcript the NAT2 enzyme, a metabolizer of isoniazid (INH). The most common NAT2 gene polymorphisms in Asian population associated with ADIH are rs1041983, rs1799929, rs1799930 and rs1799931. The study aimed to investigate the 4 single nucleotide polymorphisms (SNPs) in pediatric TB that experienced ADIH.

Methods

We conducted a case-control study comparing 31 each of pediatric TB experience with and without ADIH. All pediatric TB was selected from 451 pediatric TB Registry of Respirology Division, Department of Child Health Faculty of Medicine Universitas Padjadjaran/Dr Hasan Sadikin Hospital during January 2016 to July 2018. Genomic DNA PCR and sequencing to identify polymorphisms of rs1041983, rs1799929, rs1799930 and rs1799931 were performed in both groups. Data analysis was performed using the Epi info Ver. 7 software.

Results

Thirty-one pediatric TB experiences with and without ADIH were enrolled in this study. SNP rs1041983 significantly affected the occurrence of ADIH (OR 2.39, CI 95% (1.15-4.96), p=0.019). The rs1799929, rs1799930 and rs1799931 did not significantly affect the occurrence of ADIH (p=0.133, p=0.150 and p=0.659, respectively).

Conclusion

Polymorphism SNP rs1041983 had association with the occurrence of ADIH.

NAT2 sequence polymorphisms and acetylation profiles in Indians

BACKGROUND

NAT2, a broad-spectrum drug-metabolizing gene, is of high pharmacogenetic interest. Based on seven different mutations in the NAT2 gene, an individual can either be categorized as a slow or fast acetylator.

MATERIALS & METHODS

In order to characterize acetylation profiles of Indians, where data are poorly available, we sequenced the 873 bp NAT2 coding region in 250 Indians, covering the whole of India including three tribes.

RESULTS

Altogether, 35 NAT2 alleles forming two acetylator phenotypes (distributed almost in equal proportion in India) were found; while the alleles determining slow acetylators were highly differentiated, the fast acetylator alleles were less in number but highly frequent.

CONCLUSION

Interestingly, distribution of two different acetylation phenotypes correlated well with historical dietary pattern in India. The neighbor-joining phylogenetic tree based on NAT2 gene polymorphisms in worldwide humans revealed genetic affinities among populations with similar acetylation phenotypes, which also placed Indians and Africans together in a single cluster.

Population differences in major functional polymorphisms of pharmacokinetics/pharmacodynamics-related genes in Eastern Asians and Europeans: implications in the clinical trials for novel drug development

Drug lag, recently discussed extensively in Japan, can be divided into two phases: clinical development time and application review time. The former factor is still an important problem that might be improved by promoting multi-regional clinical trials and considering the results from other similar populations with Japanese, such as Koreans and Chinese. In this review, we compare the allelic or genotype frequencies of 30 relatively common functional alleles mainly between Eastern Asians and Europeans as well as among 3 major populations in Eastern Asian countries, Japan, Korea, and China, in 12 pharmacokinetics (PK)/pharmacodynamics (PD)-related genes; CYP2C9 (*2 and *3), CYP2C19 (*2, *3 and *17), 13 CYP2D6 haplotypes including *4, *5 and *10, CYP3A5 (*3), UGT1A1 (*28 and *6), NAT2 (*5, *6 and *7), GSTM1 and GSTT1 null genotypes, SLCO1B1 521T>C, ABCG2 421C>A, and HLA-A*31:01 and HLA-B*58:01. In this review, differences in allele frequencies (AFs) or genotype frequencies (GFs) less than 0.1 (in the cases of highest AF (GF) ≥0.1) or less than 0.05 (in the cases of lowest AF (GF) <0.1) were regarded as similar. Between Eastern Asians and Europeans, AFs (or GFs) are regarded as being different for many alleles such as CYP2C9 (*2), CYP2C19 (*2, *3 and *17), CYP2D6 (*4 and *10), CYP3A5 (*3), UGT1A1 (*28 and *6), NAT2 (*5*7), GSTT1 null and ABCG2 421C>A. Among the 3 Eastern Asian populations, however, only AFs of CYP2C19*3, CYP2D6*10, HLA-A*31:01 and HLA-B*58:01 are regarded as dissimilar. For CYP2C19*3, the total functional impact on CYP2C19 could be small if the frequencies of the two null alleles CYP2C19*2 and *3 are combined. Regarding CYP2D6*10, frequency difference over 0.1 is observed only between Japanese and Chinese (0.147). Although environmental factors should be considered for PK/PD differences, we could propose that among Japan, Korea, and China, genetic differences are very small for the analyzed common PK-related gene polymorphisms. On the other hand, AFs of the two HLA alleles important for cutaneous adverse drug reactions are diverse even among Eastern Asians and thus should be taken into account.

Pharmacogenetic tools for malaria and TB in the Developing World

Some of the largest therapeutic drug exposures in the planet involve drugs employed against malaria and TB, two main global infectious diseases. Amodiaquine for malaria and isoniazid for TB are two pivotal drugs in the management of these diseases. Both drugs have been associated with severe adverse events. Amodiaquine and isoniazid are metabolized polymorphically by CYP2C8 and N-acetyltransferase 2, respectively. The polymorphic genes coding for these enzymes presently represent the best candidates for the application of personal pharmacogenetics for these diseases. We review the main reasons for this view, while asking the pivotal question of whether it is presently possible for pharmacogenetic-based personalized medicine to be applied in the malaria and TB settings of the Developing World.