Frequency of Null Phenotypes of Glutathione S-Transferase M1 and T1 among the Populations of Tabuk (Northwestern Part of Saudi Arabia)

Background: The variability in the distribution of the null phenotypes of GSTM1 and GSTT1, due to total or partial gene deletion resulting in the lack of the active enzyme, has been reported in different populations, especially in ethnically well-defined groups but not in Tabuk. This study investigated the variability in the distribution of the null phenotypes of GSTM1 and GSTT1 in the population of Tabuk (northwestern part of Saudi Arabia). Method: This study was conducted on 200 subjects of Tabuk—northwestern part of Saudi Arabia among which 100 were chronic smokers and 100 were nonsmokers. The subjects were reporting to hospital for routine checkup. All were without past history of any chronic disease and no significant abnormality. GST genotyping was done by multiplex PCR-based methods. The smoker and control groups were compared using a chi-square test with P GSTM1 deletion homozygosity of 14% and 1% was reported among non smokers and smokers, respectively whereas GSTT1 deletion homozygosity of 28% and 6% was reported among non smokers and smokers, respectively. Our results indicate that there are major differences in allelic distribution of GSTM1 and GSTT1 genes between the two groups investigated. Combined analysis of both genes revealed that 15% of smokers and non smokers harbor the deleted genotype of GSTM1 and 34% of smokers and non smokers harbor the deleted genotype of GSTT1 with significant differences. Conclusion: This study enables selecting subgroups among the general population who are more susceptible to DNA damage and will help genetic studies on the association of GST polymorphisms with disease risks and drug effects in Arab population. Studies with a larger sample size are needed to evaluate and confirm the validity of our results.