Genetic Polymorphisms of Drug-Metabolizing Enzymes and Anti-TB Drug-Induced Hepatitis

Abstract

Aims: Although some genetic risk factors have been reported for the development of hepatitis due to anti-TB drugs, an extensive candidate gene approach evaluating drug-metabolizing enzymes has not been attempted. This study aimed to investigate the association of genetic polymorphisms in drug-metabolizing enzymes with anti-TB drug-induced hepatitis. Materials & methods: We compared genotype distributions of tagging SNPs in promoter, exons and haplotypes in seven drug-metabolizing enzyme genes (CYP2C9, CYP2C19, CYP2D6, CYP2E1, NAT2, UGT1A1 and UGT1A3) between 67 cases and 159 controls. Results: Among four tagging SNPs of N-acetyltransferase 2 (NAT2), -9796T>A in promoter and R197Q were significantly associated (p = 0.0016 and p = 0.0007, respectively). NAT2 haplotype 2 [A-A-A-G] carrying A allele of -9796T>A and A allele of R197Q showed significant association (p = 0.0004). However, there was no significant association between genotypes of other enzyme-metabolizing genes and anti-TB drug-induced hepatitis. The constructs containing -9796A of NAT2 showed significantly lower luciferase activity (p < 0.01), suggesting decreased expression of NAT2. The variant alleles and haplotype 2 showed significantly higher peak serum levels of isoniazid, lower acetyl isoniazid:isoniazid ratio and lower isoniazid clearance compared with wild-types. Conclusion: These findings suggest that genetic variants in the promoter and exons of NAT2 increase the risk of anti-TB drug-induced hepatitis by modifying acetylation phenotypes and/or gene expression of NAT2, and there is no essential role for genetic mutation of the other metabolizing enzymes in the development of this adverse reaction.

KEYWORDS::

• anti-TB drug
• drug-metabolizing enzyme
• hepatitis
• N-acetyltransferase 2
• polymorphism

Financial & competing interests disclosure

This study was supported by a grant from the Korea Health 21 R&D Project, Ministry of Health & Welfare, Korea (Grant No. A030001). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Ethical conduct of research

The authors state that they have obtained appropriate institutional review board approval or have followed the principles outlined in the Declaration of Helsinki for all human or animal experimental investigations. In addition, for investigations involving human subjects, informed consent has been obtained from the participants involved.

Additional information

Funding

This study was supported by a grant from the Korea Health 21 R&D Project, Ministry of Health & Welfare, Korea (Grant No. A030001). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed. No writing assistance was utilized in the production of this manuscript.