Glutathione S-transferase M1 and T1 polymorphisms and the risk of mild hepatotoxicity induced by carbamazepine in a tunisian population study

BACKGROUND The aim of this study was to evaluate whether the glutathione S-transferase M1 (GSTM1) and T1 (GSTT1) null alleles may contribute to carbamazepine-induced hepatotoxicity. METHODS A cross-sectional prospective study was conducted to identify the frequency distribution of GSTM1 and GSTT1 alleles in 129 Tunisian epileptic patients treated with carbamazepine. Null alleles were determined using a Polymerase Chain Reaction. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured by standard methods. RESULTS Our results showed that the frequencies of GSTM1 (-) null allele and GSTT1 null (-) allele were 74.4 and 17.8% respectively. The ALT and AST levels were elevated in 46 (35.7%) and 33 (25.6%) cases. The mean values of ALT and AST were approximately 1.32 and 3.61 times higher than the upper limit of normal levels, respectively. The values of ALT and AST were significantly higher in GSTM1 (-) allele than in GSTM1 (+) (p = 10-3.and 0.004, respectively). The level of ALT was significantly higher in combination of GSTM1 (-)/T1(-) than in combined GSTM1(-)/T1(+) and combined GSTM1(+)/T1(+) (p = 0.2 and 0.03, respectively), and that of AST was significantly higher in combination of GSTM1(-)/T1(-) and in combination of GSTM1(+)/T1(-) than in combination of GSTM1(+)/T1(+) (p = 10-3 and 10-3, respectively). CONCLUSIONS Our findings suggest that the GSTM1 (-) allele may be considered as a key factor for the development of carbamazepine-induced hepatotoxicity. Results related to GSTT (-) allele and elevation in AST levels should be considered with caution as AST may be elevated in other pathophysiological conditions.