Frequency of glutathione-S-transferase null-M1 and null-T1 genotypes among the Turabah population in Saudi Arabia

Glutathione-S-transferases (GST) are key phase II detoxifying enzymes that play critical roles in protection against products of oxidative stress and against electrophiles. Glutathione S-transferase mu (GST-M1) and theta (GST-T1) are isoforms of glutathione transferase enzymes that participate in the metabolism of a wide range of chemicals. Deletion variants that are associated with a lack of enzyme function exist at both these loci. The frequencies of homozygous GSTM1 and GSTT1 deletion carriers are very high in most of the populations studied to date. The aim of this study was to investigate the frequencies of GSTM1 and GSTT1 genotypes among the Turabah population in Saudi Arabia in comparison with the data published for some other Arabic populations. The subjects consisted of 164 unrelated healthy individuals from the Turabah population. GST genotyping was performed by multiplex polymerase chain reaction-based methods. The GSTM1 deletion homozygosity was 56.1% and GSTT1 deletion homozygosity was 20.7%, while the GSTM1 and GSTT1 double-deletion homozygosity was 11.0%. Comparison with published data from Bahraini, Lebanese, and Tunisian populations demonstrated no significant difference for GSTM1 between these populations. The GSTT1 null-allele frequency was significantly lower than those for the Lebanese and Tunisian populations (P = 0.001) but similar to that for the Bahraini population (P = 0.099). Characterization of GST genetic polymorphisms in the Saudi population may aid in genetic studies on the association of GSTM1 and GSTT1 polymorphisms with disease risks and the pharmacogenetics of chemotherapy.