Relationship between functional Nrf2 gene promoter polymorphism and sperm DNA damage in male infertility

Abstract

ABSTRACT This study examines the association of the −617 C > A polymorphism in the Nrf2 gene (rs6721961) with male infertility in a Turkish population and determines its functional role in spermatogenesis in correlation with the impact of different levels of DNA damage on the genotypes. A total of 100 infertile men and 100 healthy fertile men were included in the study. Nrf2 genotyping was performed with the PCR-based restriction fragment length gene polymorphism (RFLP-PCR) analysis. According to our results, the Nrf2 CC, CA, and AA genotype distribution frequencies were 58.6%, 38.4%, and 3% in the control group, respectively, and 38%, 48%, and 14% in the infertile men, respectively. The AA genotype was significantly higher in the patient group. In smokers, a significant difference was found in progressive motility values between the genotypes (p = 0.001). Also, sperm progressive motility and concentration decreased significantly in those smokers with the AA genotype; smokers carrying this genotype were also 5.75 times more likely to have oligoasthenozoospermia than those with CC (p < 0.05). There was a significant relationship between the number of cases with high sperm-DNA damage when comparing the frequency of Nrf2 AA genotype carriers with the CC genotype 16.3% vs. 6.9%, respectively (p < 0.001). These results suggest the importance of the Nrf2 gene C > A (rs 6,721,961) polymorphism in the etiology of sperm DNA damage as a risk factor for male infertility. Smokers carrying the AA genotype are more likely to impair seminal parameters through antioxidant mechanisms. Abbreviations: Polymerase chain reaction (PCR)-based restriction fragment length gene polymorphism (RFLP-PCR); reactive oxygen species (ROS); deoxyribonucleic acid (DNA); catalases (CATs); superoxide dismutase (SOD); glutathione peroxidase (GPX); glutathione-S-transferase (GST); Nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2); basic leucine zipper (bZIP); antioxidant response element (ARE); World Health Organization (WHO);normospermia(NS);asthenozoospermia(AS);oligozoospermia(OS);oligoasthenozoospermia (OAS); follicle stimulating hormone (FSH); ultraviolet (UV); low-melting-point agarose (LMA); normal-melting-point agarose (NMA); arbitrary units (AU); total comet score (TCS); A one-way analysis of variance (ANOVA); standard deviation (SD); N-acetyltransferase (NAT2); small non-coding RNAs (ncRNAs); microRNAs (miRNA)