Response to genetic manipulations of liver angiotensinogen in the physiological range

Genetic variation in the human angiotensinogen gene (AGT) influences plasma AGT concentration and susceptibility to essential hypertension by a mechanism that remains to be clarified. When one or two additional copies of the gene were inserted by gene titration (by homologous recombination with gap-repair at the AGT locus), both plasma AGT and arterial pressure were elevated in the physiological range in the mouse. The causal dependency between plasma AGT and blood pressure and the relative contribution of the various tissues that express AGT to these two phenotypic parameters remained to be determined. To address these issues, we generated a transgenic mouse with overexpression of the mouse AGT gene restricted to the liver. The transgene was examined in two contrasted genetic backgrounds, the sodium-sensitive C57BL/6J and the sodium-resistant A/J. Transgenic and control male animals underwent continuous cardiovascular monitoring by telemetry for 14 days while under a standard sodium diet (0.2%). Moderate but significant increases in plasma AGT (40%, p = 0.01) and systolic blood pressure (4-6 mmHg, p ranging from 0.01 to <0.001) were observed in the sodium-sensitive background, but not in the sodium-resistant animals. Statistical analysis of a large number of consecutive, repeated measurements of blood pressure afforded power to detect small effects in the physiological range by use of advanced mixed models of analysis of variances and covariances. Although plasma renin activity was increased in the sodium-sensitive background, it did not reach statistical significance. These observations underline a potential contribution of systemic AGT to the mechanism of AGT-mediated hypertension, but the significance of sodium sensitivity in the genetic background suggests participation of the kidney in expression of the elevated blood pressure phenotype, a matter that will warrant further studies. They also highlight the challenge of identifying the contribution of individual genes in complex inheritance, as their effects are modulated by other genetic and environmental determinants.     

血管紧张素转换酶基因、血管紧张素原基因M235T变异与高原肺水肿的关系

目的     

Antisense inhibition of angiotensinogen attenuates vasopressin release in the paraventricular hypothalamic nucleus of spontaneously hypertensive rats

It has been reported that intracerebroventricularly injected antisense oligonucleotide to angiotensinogen reduces arterial pressure in spontaneously hypertensive rats (SHR), but the mechanism and the sites of action remain unclear. In the present study, we examined whether injection of antisense oligonucleotide to angiotensinogen into the paraventricular hypothalamic nucleus (PVN) would influence arterial pressure and vasopressin release. For this purpose, 12-week-old male SHR were cannulated into the bilateral PVN. One week later, we injected antisense or sense oligonucleotide to angiotensinogen into the bilateral PVN (0.2 nmol/200 nl each side). After 24 h, we directly monitored arterial pressure, and then took blood samples to measure plasma vasopressin, catecholamines and renin activity. Mean arterial pressure did not change in either group (from 144+/-3 to 154+/-4 mmHg for the antisense oligonucleotide group, n=11; from 147+/-4 to 156+/-3 mmHg for the sense oligonucleotide group, n=11). Antisense oligonucleotide attenuated vasopressin release compared with sense oligonucleotide (1.30+/-0.28 vs. 3.29+/-0.60 pg/ml, respectively, P<0.01). Plasma catecholamines also decreased in the antisense oligonucleotide group compared with the sense oligonucleotide group. However, the plasma renin activity did not differ between the groups. In the additional experiment, we examined the neurohormonal and cardiovascular effects of intracerebroventricularly injected antisense oligonucleotide to angiotensinogen in SHR. Mean arterial pressure, plasma vasopressin and plasma norepinephrine were significantly lower in the antisense oligonucleotide group than in the sense oligonucleotide group. These results suggest that angiotensinogen in PVN plays important roles in vasopressin release and sympathetic nerve activity, but may not contribute to the maintenance of arterial pressure in SHR.     

血管紧张素转换酶及血管紧张素原基因多态性与高血压左室肥厚的相关研究

目的探讨血管紧张素转换酶(ACE)基因插入/缺失(I/D)多态性及血管紧张素原(AGT)基因M235T多态性与高血压左室肥厚(LVH)的关系。方法对68例超声心动图诊断的未接受治疗的高血压合并LVH患者与76例高血压非LVH患者进行病例对照研究。采用聚合酶链式反应(PCR)与限制性片段长度多态性(RFLP)技术检测ACE基因I/D多态性及AGT基因M235T变异。以二维引导的M型超声心动图测量并计算左室重量。结果①该组高血压患者ACE与AGT基因型的分布均符合Hardy Weinberg平衡。②ACE基因I/D基因型在LVH组与非LVH组的分布差异有显著性(χ2=6.777,P<0.05)。LVH组DD基因型与D等位基因的频率均高于非LVH组(DD基因型:0.31vs0.13,χ2=6.674,P=0.01;D等位基因:0.54vs0.41,χ2=4.837,P<0.05)。③AGT基因M235T基因型在LVH组与非LVH组的分布差异有显著性(χ2=7.133,P<0.05)。LVH组TT基因型与T235等位基因的频率均高于非LVH组(TT基因型:0.62vs0.40,χ2=7.133,P<0.01;T235等位基因:0.78vs0.65,χ2=5.741,P<0.05)。④联合基因分析显示,LVH组ACE DD+AGT TT基因型频率显著高于非LVH组(0.22vs0.05,χ2=8.839,P<0.01),具有该联合基因型者发生LVH的风险比数比(OR=5.094)明显高于单独具有ACE DD基因型(OR=2.949)或AGT TT基因型(OR=2.477)者。结论ACE     

血清血管紧张素转换酶和血管紧张素原水平与妊娠高血压综合征的相关性及其危险因素

目的 探讨血清中血管紧张素转换酶(ACE)和血管紧张素原 (AGT)与妊娠期高血压综合征（HDCP）的相关性及HDCP发病的危险因素。 方法 选择135例妊娠高血压患者（HDCP组）和100例正常孕妇（CK组）,用ELISA法检测各组的血清ACE、AGT水平,并进行相关性分析;抽取两组孕产妇的年龄、怀孕天数、孕前体质量指数（BMI）、产次、产检次数、高血压糖尿病家族史、文化程度等一般资料,对孕产妇患HDCP的危险因素进行单因素分析,将单因素回归分析中有统计学意义的因素进行多因素 Logistic 回归分析。 结果 HDCP组血清ACE水平（90.49±47.65）μg/L明显高于CK组（58.72±27.58）μg/L,P<0.05,差异有统计学意义;HDCP组血清AGT水平（64.57±19.71）μg/L高于CK组（58.22±18.64）μg/L,P>0.05,差异无统计学意义;单因素分析结果显示,年龄、BMI、高血压、糖尿病家族史、ACE水平是孕产妇患HDCP的危险因素（P<0.05）,怀孕天数、产次、产检次数、文化程度比较差异无统计学意义（P>0.05）;多因素分析显示：年龄、BMI、高血压糖尿病史、ACE水平是妊娠性高血压的危险因素。 结论 ACE水平与HDCP有关,AGT水平与HDCP无关;年龄大、BMI值高、有高血压糖尿病史者,ACE水平增高发生妊娠高血压综合征的风险增加。     

血管紧张素原及载脂蛋白E基因多态性与冠心病关系的研究

目的：研究血管紧张素原(AGT)基因M235T多态性及载脂蛋白E(ApoE)基因多态性与中国人群冠心病的关联。方法:分别用PCR—RFLP技术检测了129例冠心病患者及90例健康人AGT及ApoE基因型。结果：(1)冠心病组ε3/4基因型及ε4等位基因频率显著高于健康对照组，ε3/3基因型及ε3等位基因频率则显著低于对照组;(2)AGT各基因型及等位基因频率在两组间无显著差异;(3)携带ε4等位基因的不同AGT基因型在两组间也无显著差异。结论:(1)ε4等位基因是冠心病的遗传易患因子；(2)AGT基因与冠心病发病无显著关联，与ApoE基因间也无协同作用。     

Association analyses of NsiI RFLP of human insulin receptor gene in hypertensives

Plasma angiotensinogen is elevated in essential hypertensives and shows a strong correlation with blood pressure. Patients with hypertension often display insulin resistance and we have found previously an association of a Rsal RFLP in intron 9 of the insulin receptor gene (INSR) with hypertension. Since insulin resistance is accompanied by hyperinsulinaemia and insulin can stimulate angiotensinogen production, we hypothesized that hypertension-associated genotypes of INSR may be associated with elevation in plasma angiotensinogen. We used PCR to detect a N sil RFLP in exon 8 of INSR and examined its relationship with plasma angiotensinogen, as well as hypertension, in 134 Caucasian hypertensives with two hypertensive parents and in 126 normotensives. Plasma angiotensinogen tracked weakly with the major allele of the N sil RFLP in hypertensives (p=0.08). Moreover, the frequency of this allele was higher in lean hypertensives than in lean normotensives (p<0.05) and in normolipidaemic hypertensives than normolipidaemic normotensives (p<0.02). The present study thus suggests that there could be a relationship of plasma angiotensinogen with INSR genotype, and of each with hypertension.     

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。