N-acetyltransferase 2 genotypes amongst Zulu Speaking South Africans and isoniazid /N-acetyl-isoniazid pharmacokinetics during anti-tuberculosis treatment

Abstract

AbstractBackgroundDistribution ofN-acetyltransferase2(NAT2) polymorphisms varies considerably among different ethnic groups. Information onNAT2single-nucleotide polymorphisms in South African population is limited. We investigatedNAT2polymorphisms and their effect on isoniazid pharmacokinetics in Zulu black HIV-infected South Africans in Durban, South Africa. Methods: HIV-infected participants with culture-confirmed pulmonary tuberculosis (TB) were enrolled from two unrelated studies. Culture-confirmed participants were genotyped forNAT2polymorphisms 282C>T, 341T>C, 481C>T, 857G>A, 590G>A and 803A>G using Life Technologies pre-validated Taqman assays (Life Technologies, Paisley, UK). Participants underwent sampling for determination of plasma isoniazid andN-acetylisoniazid concentrations.ResultsAmongst the 120 patients, 63/120 (52.5%) were slow metabolisers (NAT2*5/*5), 43/120 (35.8%) had intermediate (NAT2*5/12), and 12/120 (11.7%) had rapid genotype (NAT2*4/*11, NAT2*11/12andNAT2*12/12). NAT2 alleles in this study were *4, *5C, *5D, *5E, *5J, *5K, *5KA, *5T, *11A, *12A/12C and *12M. NAT2*5 was the most frequent allele (70.4%) followed byNAT2*12 (27.9%). 34/40 had both PK results andNAT2genotyping results. The median area under the concentration-time-curve to infinity (AUC0-∞) interquartile range (IQR) was 7.81 (5.87 – 16.83) μg/ml/hr and maximum concentration (Cmax) 3.14 μg/ml (2.42 – 4.36) μg/mL. Individual polymorphisms were not equally distributed, with some represented in small numbers. Genotype did not correlate with phenotype, rapid genotype showing higher AUC0-∞than slow but not significant, p=0.43.ConclusionThere was high prevalence of slow followed by intermediate then rapid acetylator genotypes. The poor concordance between genotype and phenotype suggests that other factors or genetic loci influence INH metabolism, and warrants further investigation in this population.