A Haplotype-Based Case-Control Study Examining Human Extracellular Superoxide Dismutase Gene and Essential Hypertension

It has been reported that oxidative stress is involved in the pathophysiology of essential hypertension (EH), which is a multifactorial disorder. Extracellular superoxide dismutase (EC-SOD) protects the human body from oxidative stress by converting the toxic superoxide anion (O2−) into less toxic hydrogen peroxide (H2O2). In EC-SOD knockout mice, blood pressure was reported to be significantly higher than that seen in wild-type mice. The aim of this study was thus to investigate the relationship between EH and the human EC-SOD gene by using single-nucleotide polymorphisms (SNPs) in a haplotype-based case-control study. We selected 6 SNPs within the human EC-SOD gene (rs13306703, rs699473, rs699474, rs17881426, rs2536512 and rs1799895), and then performed case-control studies in 243 EH patients and 251 age-matched normotensive (NT) subjects. In Japanese subjects, no heterogeneity was found for rs699474, and no significant differences were observed between the EH and NT groups for the overall distribution of the genotypes or the alleles for each of the SNPs. However, in the haplotype-based case-control study that used rs13306703 and rs2536512, significant differences were observed in the overall distribution (x2 = 14.26, p =0.003). The frequency of the T-A haplotype was significantly higher in the EH group than in the NT group (2.4% vs 0.0 %, p <0.001). Based on the results of our haplotype-based case-control study, the T-A haplotype may be a genetic marker for EH, and thus the EC-SOD gene might be a susceptibility gene for EH.