Association of angiotensinogen haplotypes with angiotensinogen levels but not with blood pressure or coronary artery disease: the Ludwigshafen Risk and Cardiovascular Health Study

Angiotensinogen and its cleaved forms angiotensin I and angiotensin II are important regulators of blood pressure. The gene for angiotensinogen (AGT) carries two common polymorphisms, T207M and M268T (previously described as T174M and M235T). To investigate the role of haplotypes formed by these polymorphisms for angiotensinogen levels we examined blood pressure, coronary artery disease (CAD), myocardial infarction (MI), and AGT genotypes and haplotypes in 2,575 patients with angiographically documented CAD and 731 individuals in whom CAD had been ruled out by angiography. Three haplotypes, designated as Hap1 (T207, M268), Hap2 (T207, T268) and Hap3 (M207, T268), accounted for more than 99% of alleles. The AGT Hap2 haplotype was significantly associated with angiotensinogen levels; one additional Hap2 allele accounted for an approx. 8% increase in angiotensinogen. This association was stronger than that of either single polymorphism. AGT genotypes or haplotypes were not related to hypertension, CAD or MI. We conclude that a common haplotype of the angiotensinogen gene is linked to angiotensinogen levels but has no major impact on blood pressure, hypertension, or cardiovascular risk.     

Studies on the activity of the renin-angiotensin-aldosterone system (RAAS) in patients with cirrhosis of the liver

Summary Plasma renin activity (PRA), plasma renin concentration (PRC), angiotensinogen, angiotensin II (AT II) and plasma aldosterone were determined by radioimmunoassay in 77 patients with cirrhosis of the liver [group I: with ascites, untreated (n=23); group II: patients with ascites during treatment (n=32); group III: after removal of fluids, but under further spironolactone therapy (n=10); group IV: untreated subjects without ascites (n=12)]. With the exception of decreased angiotensinogen values in all groups ranging between 39% (group IV) and 73% (group III) no significant changes of the other parameters of the RAAS were found in untreated patients. A highly significant increase of PRA, PRC, AT II and plasma aldosterone was observed in treated cirrhotics with (group II) or without (group III) ascites. In the total series of patients AT II was closely related to PRA, PRC and aldosterone emphasizing again the predominant role of AT II to stimulate aldosterone secretion. Plasma sodium was inversely correlated to PRA, PRC, AT II and aldosterone, but no relationship was detected between these parameters of the RAAS and plasma potassium.Our results indicate that hyperaldosteronism in cirrhosis appears unlikely to be the major determinant of avid renal sodium retention and ascites formation. An increased activity of the RAAS is most often initiated by therapeutic factors and/or markedly altered electrolyte metabolism. Therefore, basal conditions of the patients to be studied must be well defined to exclude any artificially induced stimulation of the RAAS.     

The origin and the clinical significance of urinary angiotensinogen in proteinuric IgA nephropathy patients

Abstract

Background. Urinary angiotensinogen (AGT) was reported as a marker of renal injury in chronic kidney disease patients. However, the main source of urinary AGT is unknown in proteinuric patients because the disrupted filtration barrier might cause AGT filtration. We investigated the origin and the clinical importance of urinary AGT in proteinuric IgA nephropathy (IgAN) patients.

Methods. In patients with biopsy-proven IgAN, urinary and plasma AGT was measured using a sandwich ELISA and compared with intrarenal AGT expression. The patients were followed up for 3 years.

Results. Natural logarithm of the urinary AGT/creatinine (ln (urinary AGT/Cr)) was positively correlated with intrarenal expression of AGT (ln (urinary AGT/Cr) versus AGT/β-actin, r = 0.620, P < 0.0001; ln (urinary AGT/Cr) versus AGT density, r = 0.452, P = 0.007). Ln (urinary AGT/Cr) showed a positive correlation with urinary protein/creatinine ratio (PCR) but a negative correlation with estimated glomerular filtration rate (eGFR). Regression analyses showed that ln (urinary AGT/Cr) was a significant determinant of urinary PCR and eGFR 3 years after biopsy.

Conclusions. Urinary AGT reflects intrarenal AGT expression and correlates with the extent of proteinuria and renal function. Our study indicates the intrarenal compartment as the main source of urinary AGT, suggesting its clinical implication as an important biomarker in proteinuric IgAN patients.     

Differential Regulation of Angiotensin Peptides in Plasma and Kidney: Effects of Adrenalectomy and Estrogen Treatment

Eight angiotensin peptides [angiotensin-(1–7), angiotensin II, angiotensin-(1–9), angiotensin I, angiotensin-(2–7), angiotensin-(2–8), angiotensin-(2–9), and angiotensin-(2–10)] were measured in plasma and kidney of adrenalectomized rats and estrogen-treated rats. In comparison with sham-operated rats, adrenalectomy increased plasma renin levels by 50-fold and reduced plasma angiotensinogen levels by 67%. Adrenalectomy increased plasma angiotensin peptide levels by 9- to 30-fold, but the increases in renal angiotensin peptide levels were much less than those seen for plasma. In comparison with vehicle-treated rats, estrogen treatment increased plasma angiotensinogen levels by 3-fold and reduced plasma renin levels by 41%. Estrogen treatment decreased plasma angiotensin peptide levels, whereas renal angiotensin peptide levels increased by as much as 2- to 3-fold. These results confirm the differential regulation of angiotensin peptide levels in plasma and kidney, and provide further support for the essential role of angiotensinogen in modulating plasma and tissue angiotensin peptide levels.     

口服避孕药及AGT基因多态性与女性高血压的关系

目的:探讨口服避孕药(OC)暴露、血管紧张素原(AGT)基因多态性及二者联合作用与女性高血压发病风险的关系。方法:采用病例-对照研究方法,在江苏省太仓和如东两地选择621例女性高血压病例和621例对照,进行问卷调查及血压相关体格检查,采集静脉血后,用RFLP-PCR法检测AGT基因的5种基因型。结果:妇女患高血压的风险随OC累积使用时间的增加而增加(P<0.05),且使用OC≥15年的妇女患高血压的风险高于未使用者;AGT基因多态性与高血压患病风险间关联无统计学意义,但综合OC使用时间分析,除C-532T基因型携带者外,携带其他4种基因型的妇女使用OC≥15年患高血压的风险高于未使用者。结论:使用OC≥15年增加妇女患高血压的风险;使用OC≥15年与AGT基因多态性的联合作用可能使妇女患高血压的风险升高。     

脑出血患者血管紧张素原T704C基因多态性分析

目的：探讨脑出血（ICH）患者血管紧张素原（AGT）T704C基因多态性及二者的相关性。方法：采用病例一对照研究,结合聚合酶链反应-限制性片断长度多态性（PCR—RFLP）技术检测70例ICH患者和89例健康体检者的AGTT704C单核苷酸多态性,并将ICH组按是否合并高血压而分为两组：高血压组和非高血压组。比较和分析ICH与对照组间该基因型及等住基因的分布频率差异,并分析该遗传因素对ICH的作用。结果：ICH纽704CC基因型频率41．4％,C等往基因频率67．1％,与对照纽比较,差异元统计学意义（P〉0．05）。结论：AGT T704C基因多态性可能与ICH的发生无关。     

Differential Roles of Angiotensinogen and Angiotensin Receptor type 1 Polymorphisms in Breast Cancer Risk

While angiotensinogen (AGT) seems to have anti proliferative properties, angiotensin II (ATII) is a potent growth factor and it mediates its actions through the angiotensin type 1 receptor (AGTR1). In the AGT gene, the M235T polymorphism has been associated with the variation in angiotensinogen levels and in the AGTR1 gene; the C573T variant is associated with different pathologies. We aimed to evaluate the relationship of these two variants and the risk of breast cancer. These polymorphisms were genotyped in 3787 women participating the Rotterdam Study. We performed a logistic regression and a disease free survival analysis by genotype. The logistic regression yielded an odds ratio of 1.4 (95% CI: 1.1–1.9) for the MM genotype carriers versus the T allele carriers. The breast cancer free survival by AGT genotype was significantly reduced in MM genotype carriers compared to non-carriers (hazard ratio (HR) = 1.5; 95% CI: 1.1–2.2). We did not find any association of the AGTR1 polymorphism and breast cancer risk or disease free survival. Our results suggest that AGT plays a role in breast cancer risk in postmenopausal women, whereas the role of AGTR1 needs further studying.     

Regulation of angiotensinogen gene expression and protein in neonatal rat cardiac fibroblasts by glucocorticoid and β-adrenergic stimulation

We previously demonstrated the presence of components for a renin-angiotensin system in fibroblasts cultured from neonatal rat ventricles, the regulation of expression of which has not been studied. Since glucocorticoids and β-adrenergic stimuli have been implicated in cardiac hypertrophy, and function as regulators of the circulating renin-angiotensin system, we examined the effects of dexamethasone and isoproterenol on angiotensinogen mRNA levels and protein secretion in cultured neonatal rat cardiac fibroblasts. Treatment of cardiac fibroblasts for 8 h with 10 μmol/l isoproterenol or 100 nmol/l dexamethasone increased angiotensinogen mRNA levels by 246 ± 7% and 1406 ± 207%, respectively. Over 24 h, dexamethasone and isoproterenol increased angiotensinogen secretion by 148 ± 32% and 123 ± 26%, respectively. Angiotensin II, which has been reported to be a positive regulator of angiotensinogen synthesis and secretion in liver, markedly attenuated the effects of dexamethasone and isoproterenol on angiotensinogen mRNA expression and secretion. In the presence of 1 μmol/l angiotensin II, the stimulation in angiotensinogen secretion observed with dexamethasone and isoproterenol was decreased by 62% and 76%, respectively. The negative feedback of angiotensin II on angiotensinogen expression was primarily mediated through the type one angiotensin II (AT₁) receptor (IC₅₀ = 0.30 ± 0.02 nmol/l). In summary, results from this study demonstrate that angiotensinogen mRNA levels and protein secretion in cardiac fibroblasts are positively regulated by glucocorticoid and β-adrenergic stimulation. In addition, angiotensinogen production by cardiac fibroblasts is under negative feedback control of angiotensin II. Received: 28 October 1999, Returned for revision: 24 November 1999, Revision received: 14 January 2000, Accepted: 26 January 2000     

Angiotensinogen and endothelial nitric oxide synthase gene polymorphisms among Hispanic patients with preeclampsia

OBJECTIVE: We sought to establish an association between preeclampsia and the methionine to threonine polymorphism at amino acid residue 235 (Met235Thr) in angiotensinogen in a Hispanic population. We looked for a relationship between this allele and the allele in the endothelial nitric oxide synthase gene (NOS3) that produces the A form (NOS3*A) with respect to preeclampsia. STUDY DESIGN: Clinical data were collected from 87 patients with preeclampsia and 53 control subjects. Patients and controls were genotyped for the angiotensinogen polymorphism allele (AGT*T) and the NOS3*A polymorphism. We then compared patients with preeclampsia and control subjects and investigated disease severity within the preeclampsia group as a function of genotype. RESULTS: The AGT*T allelic frequencies among patients with preeclampsia and control subjects were 0.72 and 0.70, respectively (P =.84). The blood pressure of patients with an AGT*T allele who also carried a NOS3*A allele was higher at earlier gestational ages (r = -0.052; P =.02). Analysis suggested that the systolic blood pressure differences were due to gestational age effects and the presence of a NOS3*A allele (P <.10). CONCLUSION: The AGT*T allele was not associated with the development of preeclampsia. Independently of the presence of an AGT*T allele, the NOS3*A allele was associated with a higher blood pressure at an earlier gestational age.     

血管紧张素原基因多态性与高血压血尿醛固酮水平相关

目的研究血管紧张素原(Angiotensinogen,AGT)基冈5个单核苷酸多态性(single nucleotide polymorphisms,SNPs)及其构成的单倍型在中国汉族人群中与原发性高血压的相关性及各SNP与高血压患者血浆肾素活性(PRA)、血管紧张素Ⅱ(AngⅡ)、血浆和尿醛固酮(Ald)水平的关系。方法采用MassARRAYTM系统质谱检测技术,在500例原发性高血压患者和500名正常对照者中,对AGT基因启动子区域的C-532T、A-20C、G-6A及编码区的T174M和M235T进行基因分型。用放免法检测高血压患者PRA、AngⅡ、血尿Ald水平。结果5种SNP的等位基因频率和单倍型分布在原发性高血压组和对照组中均无显著差异(P>0．05);男性高血压患者中C-532T多态CT TT基因型个体尿Ald水平显著高于CC型个体(6．52 vs 5．19μg／d,P=0．03);女性高血压患者G-6A多态GG GA基因型个体血Ald水平显著高于AA型个体(78．63 vs 58．86 pg/ml,P=0．015);女性高血压患者M235T多态MM MT基因型个体血Ald水平显著高于TT型个体(78．73 vs 58．81 pg／ml,P=0．03); A-20C多态AC CC基因型与G-6A多态GG GA基因型联合者尿Ald水平(P<0．05)、体重指数(P <0．01)显著高于其他联合基因型。结论AGT基因5个SNP及单倍型分布在高血压患者和正常血压对照之间无显著差异,AGT基因的SNP分布与原发性高血压患者血尿醛固酮水平有关。