Tnull and Mnull genotypes of the glutathione S-transferase gene are risk factor for CAD independent of smoking

Background: The association of the deletion in GSTT1 and GSTM1 genes with coronary artery disease ( CAD) among smokers is controversial. In addition, no such investigation has previously been conducted among Arabs. Methods: We genotyped 1054 CAD patients and 762 controls for GSTT1 and GSTM1 deletion by multiplex polymerase chain reaction. Both CAD and controls were Saudi Arabs. Results: In the control group ( n = 762), 82.3% had the T (wild) M (wild)genotype, 9% had the T-wild M (null), 2.4% had the T-null M wild and 6.3% had the T-null M (null) genotype. Among the CAD group ( n = 1054), 29.5% had the T-wild M (wild) genotype, 26.6% ( p <.001) had the T-wild M (null), 8.3% ( p <.001) had the T-null M (wild) and 35.6% ( p <.001) had the T-null M (null) genotype, indicating a significant association of the Twild M (null), Tnull M (wild) and T-null M (null) genotypes with CAD. Univariate analysis also showed that smoking, age, hypercholesterolemia and hypertriglyceridemia, diabetes mellitus, family history of CAD, hypertension and obesity are all associated with CAD, whereas gender and myocardial infarction are not. Binary logistic regression for smoking and genotypes indicated that only M (null) and T(null)are interacting with smoking. However, further subgroup analysis stratifying the data by smoking status suggested that genotype- smoking interactions have no effect on the development of CAD. Conclusion: GSTT1 and GSTM1 null- genotypes are risk factor for CAD independent of genotype-smoking interaction.