Polymorphisms of glutathione S-transferase M1 and male infertility in Taiwanese patients with varicocele

Background: To examine glutathione S-transferase M1 (GST M1) gene polymorphism and male infertility in Taiwanese patients with varicocele, 80 young male patients with varicocele (group 1), 62 young male patients with subclinical varicocele (group 2) and 60 normal young males (group 3) were recruited in this study. Methods: GST M1 null homozygous genotype [GST M1 (-)] and the occurrence of a 4977 bp deletion of sperm mitochondrial DNA (mtDNA) were determined by polymerase chain reaction. The 8-hydroxy-2′-deoxyguanosine (8-OHdG) content of sperm DNA was measured by high-performance liquid chromatography. Results: The frequencies of GST M1 (-) genotype were 43.8, 41.9 and 45% for patients in groups 1, 2 and 3 respectively. In group 1 patients with GST M1 (-) genotype, the frequency of the presence of the 4977 bp deletion in sperm mtDNA (54.3%) was significantly higher than that of the patients without the 4977 bp deletion in sperm mtDNA (45.7%, OR: 2.63, P = 0.04). Patients of groups 1 and 2 with GST M1 (-) genotype had significantly higher 8-OHdG content in sperm DNA and lower protein thiols and ascorbic acid in seminal plasma than those with GST M1 (+) genotype. Conclusion: GST M1 (-) genotype predisposes to increased oxidative damage to sperm of patients with varicocele.