Association between partial indexes of angiotensinogen gene polymorphisms and the risk of essential hypertension:A community case-control study / 中国组织工程研究

ABSTRACT

BACKGROUND: Angiotensinogen (AGT) gene is the firstly discovered candidate gene for essential hypertension, both the T174M and M235T polymorphisms locate at the second exons of AGT gene, and there is existence of linkage disequilibrium. The polymorphism at A-6G and G-217A sites in promotor region plays an important role in regulating the gene expression, and the products of keep close correlation with the level of blood pressure. OBJECTIVE: To investigate the association between the polymorphism of AGT gene at A-6G, T174M and G-217A sites and the risk for the attack of essential hypertension in Chinese Han population, DESIGN: A cluster sampling and case-control analysis. SETTINGS Department of Geriatrics and Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University; Southern Research Center of National Human genome; Department of Cardiology, Dongtai People's Hospital of Jiangsu Province. PARTICIPANTS: The experiment was carried out in the countryside of Dongtai county, Yancheng city, Jiangsu province. All the subjects were selected from the countryside of Dongtai county, Yancheng city, Jiangsu province. Totally 177 patients with essential hypertension who had never accepted any drug treatment, were taken as the essential hypertension group, and hypertension was diagnosed according to the diagnostic standard of hypertension set by WHO/ISH in 1999 (systolic blood pressure ≥ 140 mm Hg and/or diastolic blood pressure ≥ 90 mm Hg); Another 86 normal person were taken as the normal control group. ② Inclusive criteria The enrolled subjects should be Han nationality; long-term local residents but not from other places; able to answer questions clearly; diagnosed by disease history, clinical symptoms, physical signs and assistant examinations; have complete data of investigation of uniform questionnaires by face-to-face interview (including demographic information, profession history, family history and life styles of smoking, drinking, drinking tea, etc.). ③ Exclusive criteria The patients with secondary hypertension in the essential hypertension group, subjects having family hisory of hypertension in the normal control group, and those with chronic diseases of liver and kidney, and diabetes mellitus in both groups were excluded. METHODS: Peripheral venous blood samples (3 mL) were collected, and DNA was extracted from human peripheral blood with FlexiGene DNA Kit (250). The Primer3 software was applied to design primers, and the polymorphism sites in the primer sequence were excluded. After multiplex polymerase chain reaction (PCR), 3 μL products were selected to detected the amplified results by agarose gel electrophoresis. The successfully amplified PCR products were purified with the QIAquick PCR Purification Kit, and the purified products were fragmentized with Dnase Ⅰ . The fragmentized products of enzyme digestion were labeled with fluorescein by deoxynucleotide terminal transferase. Two allele specific probes and one mismatched probe were designed respectively for each single nucleotide polymorphism. The chips were prepared with the OmniGridTM 100 TLC samler, each probe was repeated for three times to form three matrix. The hyridization solution was degenerated at 95 ℃ for 10 minutes, and then immediately cut on ice. 10 μL hybridization solution was added onto the chip matrix, hybridized at 50 ℃ for 2 hours, then washed and dried. The chips were scanned with the GenePix 4000B laser confocal scanner (Figure 2),and the intensity of the fluorescent signal for each probe was extracted with GenePix Pro, and the allele score of each single nucleotide polymorphism was calculated to judge the genotype. MAIN OUTCOME MEASURES: ① Comparison of the frequencies of genotype distribution at each polymorphism site of AGT gene in both groups; ② Correlation analysis of the polymorphism of AGT gene at A-6G and T-174M sites with the risk for the attack of essential hypertension; ③ Effects of the polymorphism of AGT gene at A-6G, T-174M and G-217A sites on blood pressure.RESULTS: According to the intention-to-treat analysis,all the 263 subjects were involved in the analysis of results. ① At the A-6G site of AGT gene, the frequencies of AA, AG and GG genotypes (P=0.014) and A and G alleles (P=0.004, OR=0.44) had significant differences between the essential hypertension group and normal control group; At the T174M site, the frequencies of CC, CT and TT genotypes (P=0.031) and A and G alleles (P=0.014, OR=0.55) were significantly different; At the G-217A site, no obvious differences were found in the GG, AG and AA genotypes (P=0.722) and G and A alleles (P=0.403, OR=0.80). ② The risk of essential hypertension in the individuals carrying AA genotype of A-6G polymorphism and CC genotype of T174M polymorphism was reduced by 57% (95%CI= 0.23-0.82, P= 0.010) and 56% (95%CI= 0.25-0.79, P= 0.006) respectively. ③ There were no significant differences in the systolic blood pressure, diastolic blood pressure and mean arterial pressure among different genotypes at the A-6G, T174M sites and G-217A sites (F=0.100- 2.911, P ＞ 0.05). CONCLUSION: The AA genope at A-6G and the CC genotype at T174M site of AGT gene may reduce the risk for the attack of essential hypertension in Chinese Hun population, and no significant correlation was found between the genotype of G-217A polymorphism and the attack of essential hypertension.