Molecular Approach for Assessing the Risk Factors for Anti-tubercular Therapy-Induced Hepatotoxicity

Abstract

Introduction: The present study was designed to study the role of genetic risk factors like N-acetyl transferase2 (NAT2) polymorphism and glutathione S-transferase (GST T1 and M1) mutations for increasing the susceptibility of anti tubercular therapy (ATT)-induced hepatotoxicity. Methods: Forty pulmonary tuberculosis patients who developed hepatotoxicity while on treatment with antituberculosis drug (ATD) were included. Sixty pulmonary tuberculosis patients without clinical symptoms and biochemical evidence of liver dysfunction, who were on antitubercular treatment, were included as controls. NAT2 genotyping was performed by generation of 895 bp intronless NAT2 PCR fragment. NAT2 genotyping was carried out by PCR-RFLP at 3 major polymorphic sites of gene coding for T481C (rs1799929, NAT2*5), G509A (rs1799930, NAT2*6), and G587A (rs1799931, NAT2*7). Genotyping of GST M1 and GST T1 genes was carried out by multiplex polymerase chain reaction protocol. Results: Out of the 40 patients of ATT-induced hepatitis, 67.50% were slow acetylators as compared to 35% in the control group. The risk of anti-TB DIH occurrence was significantly higher in slow acetylators than in rapid/intermediate acetylator (56.25% vs. 25%, p value 0.05). Slow acetylator phenotype was found to be a risk factor for anti-TB drug-induced hepatitis having an odds ratio of 3.85 (95% confidence interval [CI] 1.68-8.84; p value 0.02). The GSTM1 null mutation was found in 19 out of 40 cases (47.5%) compared to 15 out of 60 controls (25.0%). Subjects with GSTM1 null genotype were found to be at a 2.72 times risk of developing ATT induced hepatitis than those who had GSTM1 gene (p value 0.02). Similarly, the frequency of GSTT1 null mutation was found to be 32.50% in the ATT-induced hepatitis group as compared to 13.33% in the control group and GSTT1 null genotype, was also found to be an independent risk factor with an odds ratio of 3.12 (95% CI 1.18-8.22; p value- 0.02). It was also observed that presence of GSTM1 and GSTT1 null genotype together increased the likelihood of developing ATT induced hepatitis to up to 17 times (p value 0.002). Conclusion: This study could establish a positive co-relation between NAT2 slow acetylators, GSTM1 null mutation, GSTT1 null mutation, and ATT induced hepatitis. Thus, it will be prudent on the part of the clinicians to look for the above risk factors while treating Koch’s patients with anti-tubercular therapy.