Investigation of GSTM1 and GSTT1 null genotypes as risk factors for Bronchial asthma in a population of central Bulgaria

In the present study we aimed to explore the possible role of the null polymorphisms in two genes of xenobiotic-metabolizing enzymes, GSTM1 and GSTT1 as predisposing factors for Bronchial asthma in a population of central Bulgaria. A statistically significant prevalence of the null GSTM1 genotype (0.55) was observed in asthmatics compared to the control individuals (0.38, p=0.041), which determined 2.01-fold higher risk for Bronchial asthma (OR=2.01, 95% CI, 1.03-3.92). Moreover, patients with GSTM1 null genotype had higher relative risk to develop the disease before 35 years of old (RR=2.31, 95% CI, 1.10-5.14). Regarding the GSTT1 null polymorphism, there was no significant difference of genotype distributions between cases and controls (p=0.323). In conclusion, our current results suggest that the inherited absence of GST-mu, but not GST-theta, due to the homozygous null genotype, appeared to be a low penetrance susceptibility factor for Bronchial asthma and may determine an early onset of the disease.