Comprehensive Scanning Of The Entire Mitochondrial DNA Mutations In Patients With Essential Hypertension

Essential hypertension (EHT) is one of the most common cardiovascular diseases with high incidence (>20%) and mortality resulting from stroke, myocardial infarction, congestive heart failure and end-stage renal disease. The pathogenesis of hypertension remains unknown in the vast majority subjects. It is likely that the interactions of polygenic disorders and environmental factors are responsible for hypertension. Estimates of genetic contribution to the variability of blood pressure rang from 30 to 50%. Studies to identify "hypertension" genes have focused on the assessment of markers and candidate genes in the nuclear genome. What role that mitochondrial DNA (mtDNA) variations play in the pathogenesis of hypertension is still needed to search for. To explore the relationship between mtDNA and EHT, evaluate the mtDNA variations in EHT patients and whether mtDNA mutations act as genetic markers for susceptible to hypertension, we intensively investigated the entire mtDNA variations in EHT paitents and normotensives (NT) in this study.Samples used in this study were from 20 cases of EHT and NT respectively. Entire mtDNA 16.6kb extracted from their peripheral blood was amplified using 32 overlapping primer pairs. Mutations were screened with temporal temperature gradient gel electrophoresis and identified by direct sequencing. The frequency, density, type and evolution conservative of mtDNA variations were comprehensively analysed. We also reconstructed the Neighbor-Joining tree, detected the large-scale deletion mutations and mitochondrial microsatellite instability in all subjects.The results showed (1) ENT patients had much more mtDNA variations in frequency and density (both p<0.05) than NT. The mtDNA variations were mainly distributed in D-loop region, and statistically difference between ENT and NT in regions of tRNA, 12S rRNA, COXI and mtTFl binding site. (2) The constitution of mtDNA-3-nucleotide substitutions in EHT was different from that in NT. The rates of nucleotide transvertion and missense mutation were significantly higher in EHT than those in NT (both pO.OOOl). In addition, -80% missense mutations in EHT located in the evolution conservative areas, which were very important to the maintaining of mitochondrial normal functions. (3) The EHT patients possessed much more 152 T->C than NT (p<0.05), which was possibly the high-risk variation susceptible to hypertension. Other potential high-risk variations included 143Gx 12705C\ 16311C and et al. (4) There was microsatellite instability in mtDNA npl 6184-16193 in EHT. (5) Through reconstruction of Neighbor-Joining tree, we found a trend that some EHT patients gathered in one family branch with pretty higher mutation frequency and density than those in other EHT patients and NT (both pO.OOOl). The mutations of 13506C->T> 247G->A were possibly the genetic characteristics of this family. (6) The common deletion (4977bp) and other large-scale deletions were not detected in all subjects.The founding in this study demonstrated that the density of mtDNA variations, frequency of nucleotide transvertions and missense mutations were significantly higher in EHT than those in NT, and also displayed the trend that one family branch harbored the ENT patients with much more mtDNA variations than others by Neighbor-Joining tree analysis. It was suggested that mtDNA variations may be involved in the pathogenesis of hypertension through mediating the over production of reactive oxidative species and then resulting in the vascular endothelial dysfunction.