Angiotensinogen Concentration Research Articles

Enlighten the association of Angiotensinogen gene (AGT) polymorphisms and hypertension in Jammu region of north Indian population: A case-control study

BackgroundHypertension is a common cause associated with various life-threatening disorders such as stroke, heart attack, etc. AGT, with its two common polymorphisms, i.e., rs699 and rs4762, has been associated with variation in plasma angiotensinogen concentration and linked to essential hypertension. AimIn the present study, we aimed to find the association between the two polymorphisms, namely rs699 and rs4762 of the AGT gene, with the risk of hypertension in people of the Jammu region of Jammu and Kashmir. MethodTo achieve the aim, an observational with case-control study design was utilized where the descriptive and inferential data were presented in frequency, and an Odds ratio with a 95% Confidence Interval was used for determining the risk association, respectively. Online free statistical tools were used for the statistical analysis. The pairwise linkage disequilibrium (LD) and its respective measures (D′ & r(Mills et al., 2020 (Mills et al., 2020))) for the SNPs among the hypertensive patients and controls were calculated using Haploview software. ResultA total of 180 cases and 350 controls were enrolled, where “rs699” showed an increased risk (OR: 1.72 [1.28–2.31], p-value =0.0003) for hypertension in contrast to “rs4762” which showed a protective role (OR: 0.55 [0.37–0.82], p-value <0.002) in the population of Jammu. After linkage disequilibrium analysis, the risk of disease due to haplotype was also analyzed, and it was found that CC (rs699/ rs4762) significantly (p-value <0.00001) increases the risk by 1.9-fold. ConclusionThe present study concluded that “rs699” showed an increased risk for hypertension in the population of the Jammu region in contrast to “rs4762”.

Abstract 11373: Suppression of Plasma Angiotensin II by GLP-1 in Humans is Independent of Changes in Plasma Angiotensinogen

Introduction: In humans, the natriuretic effect of GLP-1 depends on GLP-1 receptor interaction, is independent of changes in renal blood flow, renin, ANP, and aldosterone but is accompanied by suppression of angiotensin II (ANGII). The mechanism by which GLP-1 reduces ANGII independently of changes in renin is not clarified. Hypothesis: It was hypothesized that GLP-1 suppresses renin substrate, angiotensinogen, in plasma. Methods: To test this proposal, we measured arterial angiotensinogen concentration in biobanked plasma samples from healthy males during a 3-hour GLP-1 infusion that induced natriuresis (1). Samples were from a study with fixed sodium intake where eight healthy men were examined twice in random order during a 3-hour infusion of either GLP-1(1.5 pmol kg -1 min -1 ) or vehicle together with an intravenous infusion of 0.9% NaCl (750 mL/hour). Arterial plasma angiotensinogen was measured in plasma by dilution (1:200) and addition of excess exogenous human renin (Inst. Of Biological Standards UK). After prolonged incubation, ANGI was quantified by radioimmunoassay. Intraassay variation was 9-12%. Results: Arterial plasma angiotensinogen and renin levels decreased similarly and modestly (~15 and ~30%, respectively) after NaCl infusion during both studies whereas ANGII levels decreased significantly (~25%) only during GLP-1 infusion. Conclusions: Suppression of plasma angiotensinogen is less likely to account for GLP-1-mediated ANGII suppression in healthy young males. In perspective, GLP-1 could enhance pathways of ANGII degradation rather than inhibit its formation. 1. Asmar A et al. Extracellular fluid volume expansion uncovers a natriuretic action of GLP-1: a functional GLP-1-renal axis in man. J Clin Endocrinol Metab. 2019 Jul 1;104(7):2509-2519.

Functional Exploration of Conserved Sequences in the Distal Face of Angiotensinogen-Brief Report.

Angiotensinogen (AGT) is an essential component in the renin-angiotensin system. AGT has highly conserved sequences in the loop and β-sheet regions among species; however, their functions have not been studied. Adeno-associated viral vector (AAV) serotype 2/8 encoding mouse AGT with mutations of conserved sequences in the loop (AAV.loop-Mut), β-sheet (AAV.βsheet-Mut), or both regions (AAV.loop/βsheet-Mut) was injected into male hepatocyte-specific AGT-deficient (hepAGT-/-) mice in an LDL (low-density lipoprotein) receptor-deficient background. AAV containing mouse wild-type AGT (AAV.mAGT) or a null vector (AAV.null) were used as controls. Two weeks after AAV administration, all mice were fed a western diet for 12 weeks. To determine how AGT secretion is regulated in hepatocytes, AAVs containing the above mutations were transducted into HepG2 cells. In hepAGT-/- mice infected with AAV.loop-Mut or βsheet-Mut, plasma AGT concentrations, systolic blood pressure, and atherosclerosis were comparable to those in AAV.mAGT-infected mice. Interestingly, plasma AGT concentrations, systolic blood pressure, and atherosclerotic lesion size in hepAGT-/- mice infected with AAV.loop/βsheet-Mut were not different from mice infected with AAV.null. In contrast, hepatic Agt mRNA abundance was elevated to a comparable magnitude as AAV.mAGT-infected mice. Immunostaining showed that AGT protein was accumulated in hepatocytes of mice infected with AAV.loop/βsheet-Mut or HepG2 cells transducted with AAV.loop/βsheet-Mut. Accumulated AGT was not located in the endoplasmic reticulum. The conserved sequences in either the loop or β-sheet region individually have no effect on AGT regulation, but the conserved sequences in both regions synergistically contribute to the secretion of AGT from hepatocytes.

1652-P: Suppression of Plasma Angiotensin II by GLP-1 in Humans Is Independent of Changes in Plasma Angiotensinogen

In humans, the natriuretic effect of GLP-1 depends on GLP-1 receptor interaction, is independent of changes in renal blood flow, renin, ANP, and aldosterone but is accompanied by suppression of angiotensin II (ANGII). The mechanism by which GLP-1 reduces ANGII independently of changes in renin is not clarified. It was hypothesized that GLP-1 suppresses renin substrate, angiotensinogen, in plasma. To test this proposal, we measured arterial angiotensinogen concentration in biobanked plasma samples from healthy males during a 3-hour GLP-1 infusion that induced natriuresis (1). Samples were from a study with fixed sodium intake where eight healthy men were examined twice in random order during a 3-hour infusion of either GLP-1(1.5 pmol kg-1 min-1) or vehicle together with an intravenous infusion of 0.9% NaCl (750 mL/hour). Arterial plasma angiotensinogen was measured in plasma by dilution (1:200) and addition of excess exogenous human renin (Inst. of Biological Standards UK). After prolonged incubation, ANGI was quantified by radioimmunoassay. Intraassay variation was 9-12%. Arterial plasma angiotensinogen and renin levels decreased similarly and modestly (~15 and ~30%, respectively) after NaCl infusion during both studies whereas ANGII levels decreased significantly (~25%) only during GLP-1 infusion. Suppression of plasma angiotensinogen is less likely to account for GLP-1-mediated ANGII suppression in healthy young males. In perspective, GLP-1 could enhance pathways of ANGII degradation rather than inhibit its formation. 1. Asmar A et al. Extracellular fluid volume expansion uncovers a natriuretic action of GLP-1: a functional GLP-1-renal axis in man. J Clin Endocrinol Metab. 2019 Jul 1;104(7):2509-2519. Disclosure B.L.Jensen: None. A.Asmar: Research Support; Novo Nordisk A/S.

Antisense oligonucleotides targeting hepatic angiotensinogen reduce atherosclerosis and liver steatosis in hypercholesterolemic mice.

Hepatocyte-derived angiotensinogen (AGT) is the precursor of angiotensin II (AngII). We determined the effects of hepatocyte-specific (N-acetylgalactosamine-conjugated) antisense oligonucleotides targeting AGT (GalNAc AGT ASO) on AngII-mediated blood pressure (BP) regulation and atherosclerosis and compared its effects with losartan, an AngII type 1 (AT1) receptor blocker, in hypercholesterolemic mice. Eight-week-old male low-density lipoprotein (LDL) receptor deficient mice were administered vehicle or GalNAc AGT ASO (1, 2.5, or 5 mg/kg) subcutaneously beginning 2 weeks before the initiation of Western diet feeding. All mice were fed Western diet for 12 weeks. Their systolic BP was monitored by the tail-cuff technique, and the atherosclerotic lesion area was measured by an en face method. Although the effects of all 3 doses of GalNAc AGT ASO on plasma AGT concentrations were similar, GalNAc AGT ASO reduced BP and atherosclerotic lesion size in a dose-dependent manner. Subsequently, we compared the effects of GalNAc AGT ASO (5 mg/kg) with losartan (15 mg/kg/day). Compared to losartan, GalNAc AGT ASO led to more profound increases in plasma renin and reduction in BP but had similar effects on atherosclerosis. Remarkably, GalNAc AGT ASO also reduced liver steatosis, which was not observed in losartan-treated mice. In conclusion, the BP increase and atherosclerosis development in hypercholesterolemic mice are dependent on AngII generated from hepatic AGT. Deleting hepatic AGT improves diet-induced liver steatosis, and this occurs in an AT1 receptor-independent manner.

Tetra-ARMS-PCR assay development for genotyping of AGT rs699 T/C polymorphism, its comparison with PCR-RFLP and application in a case-control association study of cardiovascular disease patients

Genetic variations in the AGT gene play a significant role in controlling the plasma concentration of angiotensinogen (precursor protein of bioactive octapeptide angiotensin II) and the efficacy of antihypertensive drugs. In the current study, Tetra–Amplification Refractory Mutation System–Polymerase Chain Reaction (T-ARMS-PCR) was developed for genotyping of AGT rs699 T/C polymorphism and validated through Sanger DNA sequencing. Its efficiency was also tested using 474 human DNA samples [control, n = 181; cardiovascular disease (CVD) patients, n = 293]. Results showed that T-ARMS-PCR is superior to the commonly used PCR-Restriction Fragment Length Polymorphism (PCR-RFLP). Statistical analysis revealed that the AGT rs699 CC genotype is more prevalent in the CVD patient group (37% vs. 28%) and AGT rs699 C allele and CC genotype increased the risk of CVD by 1.4 and 1.9 fold, respectively. In summary, T-ARMS-PCR is the most suitable approach for quick and efficient genotyping of AGT rs699 T/C polymorphism in a large population in resource-limited countries, Furthermore, AGT rs699 T/C polymorphism is associated with the risk of CVD in the Punjabi Pakistani population.

LRP1 protects against excessive superior mesenteric artery remodeling by modulating angiotensin II-mediated signaling.

Vascular smooth muscle cells (vSMCs) exert a critical role in sensing and maintaining vascular integrity. These cells abundantly express the low-density lipoprotein receptor-related protein 1 (LRP1), a large endocytic signaling receptor that recognizes numerous ligands, including apolipoprotein E-rich lipoproteins, proteases, and protease-inhibitor complexes. We observed the spontaneous formation of aneurysms in the superior mesenteric artery (SMA) of both male and female mice in which LRP1 was genetically deleted in vSMCs (smLRP1-/- mice). Quantitative proteomics revealed elevated abundance of several proteins in smLRP1-/- mice that are known to be induced by angiotensin II-mediated (AngII-mediated) signaling, suggesting that this pathway was dysregulated. Administration of losartan, an AngII type I receptor antagonist, or an angiotensinogen antisense oligonucleotide to reduce plasma angiotensinogen concentrations restored the normal SMA phenotype in smLRP1-/- mice and prevented aneurysm formation. Additionally, using a vascular injury model, we noted excessive vascular remodeling and neointima formation in smLRP1-/- mice that was restored by losartan administration. Together, these findings reveal that LRP1 regulates vascular integrity and remodeling of the SMA by attenuating excessive AngII-mediated signaling.

Variations in Urinary Renin-Angiotensin-Aldosterone Component Concentrations in Paediatric IgA Vasculitis Nephritis

IgA Vasculitis (IgAV) is the most common form of vasculitis in children, and 1–2% of patients develop chronic kidney disease. In other forms of glomerulonephritis, there is strong evidence to support the role of the renin-angiotensin-aldosterone system (RAAS); however, data are lacking in IgAV nephritis. This study evaluated urinary RAAS components in children with IgA vasculitis, both with nephritis (IgAVN) and without nephritis (IgAVwoN). Urinary concentrations of renin, angiotensinogen and aldosterone were quantified using ELISAs. In total, 40 patients were included: IgAVN n = 9, IgAVwoN n = 17, HC n = 14, with a mean age of 8.3 ± 3.3 years. Urinary renin demonstrated no trend with nephritis. Urinary angiotensinogen was statistically significantly elevated in IgAV (1.18 ± 1.16 ng/mmol) compared to HC (0.28 ± 0.27 ng/mmol, p = 0.0015), and IgAVN (2.00 ± 1.22 ng/mmol) was elevated compared to IgAVwoN (0.74 ± 0.89 ng/mmol, p = 0.0492) and HC (p = 0.0233). Urinary aldosterone levels were significantly elevated in IgAV (1236 ± 1438 pg/mmol) compared to HC (73.90 ± 65.22 pg/mmol, p &lt; 0.0001); this was most increased in IgAVwoN patients (1793 ± 1507 pg/mmol; IgAVN 183.30 ± 111.30 pg/mmol, p = 0.0035, HC p &lt; 0.0001). As expected, the RAAS system is activated in patients with IgAVN and, more surprisingly, even in those without active nephritis. Further studies are needed to fully understand the role of the RAAS system in IgA vasculitis.

Conventional Vasopressor and Vasopressor-Sparing Strategies to Counteract the Blood Pressure-Lowering Effect of Small Interfering RNA Targeting Angiotensinogen.

BackgroundA single dose of small interfering RNA (siRNA) targeting liver angiotensinogen eliminates hepatic angiotensinogen and lowers blood pressure. Angiotensinogen elimination raises concerns for clinical application because an angiotensin rise is needed to maintain perfusion pressure during hypovolemia. Here, we investigated whether conventional vasopressors can raise arterial pressure after angiotensinogen depletion.Methods and ResultsSpontaneously hypertensive rats on a low‐salt diet were treated with siRNA (10 mg/kg fortnightly) for 4 weeks, supplemented during the final 2 weeks with fludrocortisone (6 mg/kg per day), the α‐adrenergic agonist midodrine (4 mg/kg per day), or a high‐salt diet (all groups n=6–7). Pressor responsiveness to angiotensin II and norepinephrine was assessed before and after siRNA administration. Blood pressure was measured via radiotelemetry. Depletion of liver angiotensinogen by siRNA lowered plasma angiotensinogen concentrations by 99.2±0.1% and mean arterial pressure by 19 mm Hg. siRNA‐mediated blood pressure lowering was rapidly reversed by intravenous angiotensin II or norepinephrine, or gradually reversed by fludrocortisone or high salt intake. Midodrine had no effect. Unexpectedly, fludrocortisone partially restored plasma angiotensinogen concentrations in siRNA‐treated rats, and nearly abolished plasma renin concentrations. To investigate whether this angiotensinogen originated from nonhepatic sources, fludrocortisone was administered to mice lacking hepatic angiotensinogen. Fludrocortisone did not increase angiotensinogen in these mice, implying that the rise in angiotensinogen in the siRNA‐treated rats must have depended on the liver, most likely reflecting diminished cleavage by renin.ConclusionsIntact pressor responsiveness to conventional vasopressors provides pharmacological means to regulate the blood pressure–lowering effect of angiotensinogen siRNA and may support future therapeutic implementation of siRNA.

ANTISENSE OLIGONUCLEOTIDES TARGETING HEPATIC ANGIOTENSINOGEN DOSE-DEPENDENTLY REDUCE ATHEROSCLEROSIS AND LIVER STEATOSIS IN HYPERCHOLESTEROLEMIC MICE

Objective: Liver-derived angiotensinogen (AGT) is the substrate from which renin and ACE generate angiotensin (Ang) II. Ang II not only increases blood pressure, but also is a major determinant of atherosclerosis in hypercholesteremic mice. Here we investigated the effect of hepatocyte-specific (N-acetylgalactosamine-conjugated) antisense oligonucleotides targeting AGT (GalNAc AGT ASOs) on blood pressure and atherosclerosis in hypercholesterolemic mice. Design and method: Eight-week-old male LDL receptor deficient mice were fed a Western diet for 12 weeks, after receiving vehicle, GalNAc control ASO, or 1, 2.5 or 5 mg/kg of GalNAc AGT ASO on day 1, 3, 5 and 7 in the week prior the start of the diet (n = 6–10/group). Treatment was continued thereafter on a weekly basis. Systolic blood pressure (SBP) was monitored by tail cuff. After 12 weeks, mice were euthanized and plasma was collected. Plasma AGT concentration was measured by ELISA kit, and aortic atherosclerotic lesion area was measured by an en face method. Results: The 3 GalNAc AGT ASO doses decreased plasma AGT from 10.3 ± 0.8 to 1.4 ± 0.1, 0.9 ± 0.1 and 0.7 ± 0.1 g/mL, respectively. These decreases were paralleled by dose-dependent SBP reductions from 114 ± 3 to 96 ± 2, 92 ± 2, and 84 ± 2 mmHg, respectively, and atherosclerotic lesion area reductions from 27.4 ± 0.9 to 15.1 ± 1.4, 10.8 ± 1.2, and 7.7 ± 1.0%, respectively. Yet, the attenuation of liver steatosis (liver triglyceride/weight from 139.7 ± 35.7 to 26.8 ± 4.5, 19.9 ± 1.2 and 36.0 ± 3.6 g/mg, liver total cholesterol/weight from 19.8 ± 1.6 to 8.6 ± 0.9, 6.1 ± 0.6 and 8.2 ± 0.7 g/mg) was identical for each GalNAc AGT ASO dose. GalNAc control ASO did not have effects on plasma AGT, SBP, atherosclerosis lesion area, or liver steatosis vs. vehicle. Conclusions: In hypercholesterolemic mice, inhibition of hepatic AGT reduces systolic blood pressure and atherosclerosis dose-dependently, while liver steatosis was prevented in dose-independent manner.

Abstract 543: Inhibition Of Renin-angiotensin System Failed To Suppress Beta-aminopropionitrile-induced Thoracic Aortopathies In Mice

Objective: Cross-linking of elastin and collagen fibers is a vital process in aortic development. Pharmacological inhibition of aortic cross-linking by β-aminopropionitrile (BAPN) leads to thoracic aortopathies, such as thoracic aortic aneurysm and dissection, in mice. Although the renin angiotensin system (RAS) contributes to several types of thoracic aortopathies, it remains unclear whether inhibition of the RAS protects against aortopathy formation caused by the impairment of elastin and collagen cross-linking in mice. Approach and Results: Either vehicle or losartan (15 mg/kg/d, AT1 receptor blocker) were administered through osmotic pumps for 4 weeks in male C57BL/6J mice (3-4-weeks-old, n=30/group). BAPN (0.5% wt/vol) was given through drinking water to induce aortopathies. Losartan increased plasma renin concentrations significantly compared to vehicle-infused mice, indicating effective blockade of at1 receptors. However, losartan did not suppress BAPN-induced aortic rupture and dilatation. Since losartan is a surmountable inhibitor, we also tested the effects of irbesartan, an insurmountable inhibitor of AT1 receptor blocker, on BAPN-induced aortopathy formation (50 mg/kg/day, diet, n=30/group). Despite the significant increase of plasma renin concentrations, irbesartan did not ameliorate aortic rupture and dilatation in BAPN-administered mice. Thus, BAPN-induced thoracic aortopathies were refractory to angiotensin receptor blockade. We next inhibited angiotensinogen, the unique substrate for angiotensin II, using an antisense oligonucleotide targeting angiotensinogen (AGT-ASO). AGT-ASO decreased plasma angiotensinogen concentrations, while aortic death and dilatations were not attenuated. Since hepatocytes are the major source of angiotensinogen, BAPN-induced thoracic aortopathy formation was also examined in mice with hepatocyte-specific angiotensinogen deletion. Although plasma angiotensinogen concentrations displayed 90% reduction compared to wild type littermates, aortic rupture and aneurysm formation were not suppressed. Conclusion: Inhibition of the RAS does not attenuate BAPN-induced thoracic aortopathy formation in mice.

The Dysregulation of the Renin-Angiotensin System in COVID-19 Studied by Serum Proteomics: Angiotensinogen Increases with Disease Severity.

(1) Background: ACE and CPN serum activity correlated with disease severity in an earlier study of 45 hospitalized COVID-19 patients. The serum protein profile was investigated in the same cohort here to shed more light on the involvement of the renin–angiotensin system (RAS). (2) Methods: High-definition mass spectrometry-based protein expression analysis was performed, followed by multivariate statistical and network analyses. (3) Results: The protein profiles of hospitalized patients (HoP) differed significantly from those of convalescent and healthy probands. Surprisingly, HoP samples separated into six groups according to their protein profiles: group (G) 1 represented the youngest and the least afflicted patients, and G6 the oldest and critically ill patients. At least two major pathophysiological schemes were indicated based on differing involvement of the kallikrein-kinin system (KKS), the RAS and complement activation. The serum angiotensinogen concentration increased with disease severity. (4) Conclusions: The important role of the RAS in the response to COVID-19 infection was substantiated, but other pathways such as the KKS, plasminogen activation and complement activation influence the systemic response to the infection.

Abstract 47: Circulating Human Sprr Increased Blood Pressure In Female Mice Fed A Low-fat Diet

Elevated plasma soluble prorenin receptor (sPRR) is associated with essential hypertension and obesity-hypertension in men. Additionally, our laboratory previously found that the infusion of mouse sPRR elevates systolic blood pressure (SBP) in high-fat (HF) fed male mice through activation of the sympathetic nervous system but did not elevate SBP in HF-fed female mice. Interestingly, mouse sPRR infusion increased renal and hepatic angiotensinogen (AGT) and plasma renin concentration in female mice fed a low-fat diet. However, whether sPRR-activates the renin angiotensin system (RAS) and increases blood pressure in low-fat fed female mice remains to be investigated. Additionally, little is known concerning the influence of human sPRR on blood pressure in women. Therefore, we developed a humanized mouse model with high circulating human sPRR. Human sPRR-Myc-tag transgenic mice were bred with mice expressing Alb/Cre recombinase to induce human sPRR release in the circulation. Control and Alb-HsPRR female mice were fed a LF-diet for 8 months (n=11/groups). Body weight and body composition were examined and blood pressure assessed by radiotelemetry. Human sPRR-Myc-tag was detected in the liver of Alb-HsPRR female mice and plasma sPRR levels increased by 50-fold (CTL: 3.6±0.5 ng/ml, HsPRR:190.5±24.4 ng/ml; P&lt;0.05), which validated the humanized mouse model. Elevated circulating human sPRR did not change body weight (CTL: 22.2±0.37, HsPRR: 23.0±0.32 g) or fat mass (CTL: 2.5±0.2, HsPRR: 3.1±0.2 g). Liver-derived human sPRR significantly elevated SBP in Alb-HsPRR compared to control female mice (Night SBP: CTL: 130.5±1.2 mmHg; Alb-HsPRR: 135.9±2 mmHg; P&lt;0.05) and acute injection of AngII exacerbated SBP elevation. Interestingly, the decrease in blood pressure mediated by losartan was not different between Alb-HsPRR and control female mice (Night ΔSBP: CTL: -13.11±2.2 mmHg; Alb-HsPRR: -14.8±2.7 mmHg; P&gt;0.05). Plasma AGT and renin activity were similar between Alb-HsPRR and control female mice. Therefore, whether the local RAS or the sympathetic nervous system are involved in human sPRR-mediated increase of SBP remains to be examined. Altogether, our results suggest an important role of circulating human sPRR in blood pressure control in women.

Effects of carotid baroreceptor stimulation on aortic remodeling in obese rats

Background and aimOur previous study found carotid baroreceptor stimulation (CBS) reduces body weight and white adipose tissue (WAT) weight, restores abnormal secretion of adipocytokines and inflammation factors, decreases systolic blood pressure (SBP) by inhibiting activation of sympathetic nervous system (SNS) and renin-angiotensin system (RAS) in obese rats. In this study, we explore effects of CBS on aortic remodeling in obese rats. Methods and resultsRats were fed high-fat diet (HFD) for 16 weeks to induce obesity and underwent either CBS device implantation and stimulation or sham operation at 8 weeks. BP and body weight were measured weekly. RAS activity of WAT, histological, biochemical and functional profiles of aortas were detected after 16 weeks. CBS effectively decreased BP in obese rats, downregulated mRNA expression of angiotensinogen (AGT) and renin in WAT, concentrations of AGT, renin, angiotensin II (Ang II), protein levels of Ang II receptor 1 (AT1R) and Ang II receptor 2 (AT2R) in WAT were declined. CBS inhibited reactive oxygen species (ROS) generation, inflammatory response and endoplasmic reticulum (ER) stress in aortas of obese rats, restrained vascular wall thickening and vascular smooth muscle cells (VSMCs) phenotypic switching, increased nitric oxide (NO) synthesis, promoted endothelium-dependent vasodilatation by decreasing protein expression of AT1R and leptin receptor (LepR), increasing protein expression of adiponectin receptor 1 (AdipoR1) in aortic VSMCs. ConclusionCBS reduced BP and reversed aortic remodeling in obese rats, the underlying mechanism might be related to the suppressed SNS activity, restored adipocytokine secretion and restrained RAS activity of WAT.

Maternal separation-induced increases in vascular stiffness are independent of circulating angiotensinogen levels.

The renin-angiotensin system (RAS) precursor angiotensinogen (AGT) has been implicated in the functional and mechanical alterations of the vascular wall in response to high-fat diet (HFD). Previously, we showed that HFD exacerbates angiotensin II-induced constriction in isolated aortic rings from male rats exposed to maternal separation (MatSep), a model of early-life stress. Thus, the aim of this study was to investigate whether MatSep increases AGT secretion promoting vascular stiffness in rats fed a HFD. Male Wistar-Kyoto MatSep offspring were separated (3 h/day, postnatal days 2-14), and undisturbed littermates were used as controls. At weaning, rats were fed for 17 wk a normal diet (ND) or a HFD, 18% or 60% kcal from fat, respectively. In plasma, there was a main effect of MatSep reducing AGT concentration (P < 0.05) but no effect due to diet. In urine, ND-fed MatSep rats displayed higher AGT concentrations that were further increased by HFD (P < 0.05 vs. control). AGT mRNA abundance and protein expression were increased in adipose tissue from HFD-fed MatSep rats compared with control rats (P < 0.05). No significant differences in liver and kidney AGT levels were found between groups. In addition, MatSep augmented vascular stiffness assessed on freshly isolated aortic rings from ND-fed rats (P < 0.05), yet HFD did not worsen vascular stiffness in either MatSep or control rats. There was no correlation between plasma AGT and vascular stiffness in ND-fed rats; however, this relationship was negative in HFD-fed MatSep rats only (P < 0.05). Therefore, this study shows that MatSep-induced increases in vascular stiffness are independent of diet or plasma AGT.NEW & NOTEWORTHY This study demonstrates that there was no correlation between circulating levels of angiotensinogen (AGT) and the development of vascular stiffness in rats exposed to early-life stress and fed a normal diet. This study also shows that early-life stress-induced hypersensitive vascular contractility to angiotensin II in rats fed a high-fat diet is independent of circulating levels of AGT and occurs without further progression of vascular stiffness. Our data show that early-life stress primes the adipose tissue to secrete AGT in a sex- and species-independent fashion.

Human Angiotensin‐(1‐12) [Ang‐(1‐12)] is a Hypertension and Cardiac Disease Biomarker

BackgroundAng‐(1‐12) is a primary non‐renin dependent substrate for direct tissue angiotensin II (Ang II) formation by chymase. This discovery challenges conventional thinking and explains the large residual risk of cardiovascular events in patients medicated with blockers of the renin angiotensin system (RAS). Here we report the first demonstration of circulating Ang‐(1‐12) as a biomarker of essential hypertension (EH) and cardio‐renal remodeling.MethodsThe cohort of patients from Olmsted County MN included 52 healthy adult volunteers (21 females), age 54 ± 8 years, and 23 essential hypertensive (EH) patients (14 females) age 61 ± 8 years with systolic blood pressure (SBP) ≥140 mm Hg prior to recruitment. Clinical examination, standardized BP measurements, and venous blood were obtained for measurements of plasma concentrations of angiotensinogen (AGT), Ang‐(1‐12), Ang II, aldosterone, renin activity, N‐terminal pro–B‐type natriuretic peptide (NT‐proBNP) and atrial and brain natriuretic peptides (ANP and BNP, respectively). All values are Means ± SD. Data were analyzed by 2‐way ANOVA for sex and hypertension.ResultsPlasma Ang‐(1‐12) levels in EHs [SBP: 134 ± 14 mm Hg; Ang‐(1‐12): 1,463 ± 446] were higher than normotensives [SBP: 117 ± 13 mm Hg; Ang‐(1‐12): 1,353 ± 379 fmol/mL, hypertension effect: P&lt;0.05], irrespective of sex. Hypertension associated with increases in pulse pressure, PRA, and plasma AGT and NT‐proBNP concentrations (see Figure ). The elevation in circulating NT‐proBNP levels with hypertension was accounted for by a 4.6‐fold increase in hypertensive males (165 ± 134 pg/mL) while the 1.5‐fold rise in plasm NT‐proBNP did reach significance (134 ± 127 pg/mL, p&gt; 0.05).ConclusionsWe show for the first time that Ang‐(1‐12) circulates in humans and its concentrations are elevated by chronic hypertension. We further demonstrate a sexual dimorphic pattern in hypertensives with respect to NT‐proBNP, the latter a biomarker for cardiac remodeling. Whether this represents a natriuretic system‐related compensatory mechanism, or worsening pathology, due to an elevated noncanonical RAS specific to male hypertensives remains to be studied. Further investigation to fully define the role of Ang‐(1‐12) as a cardiac disease biomarker in a larger, gender and ethnic diverse population and its relationship to hypertension and myocardial structure is warranted.Support or Funding InformationSupported by grant HL‐051952 from the NHLBI of the NIHLines are means ± SDFigure 1

Reduction in urinary angiotensinogen levels and improvement of proteinuria by renin-angiotensin system blockade in pediatric chronic kidney disease patients with very low birth weight.

Children with low birth weight (LBW) have an increased risk of developing chronic kidney disease (CKD), and no effective strategies have been established to prevent the progression of CKD in these patients. Urinary angiotensinogen (UAGT) may represent a useful marker of intrarenal renin-angiotensin system (RAS) activation, which has been suggested to play a critical role in the development of hypertension and CKD. Herein, we conducted a prospective study to determine whether RAS blockade is beneficial for suppressing the progression of CKD in children with LBW, using UAGT as a surrogate marker of renal impairment. Nine children with CKD (stages: 1-2) who had very low birth weight (VLBW; < 1500g) were started on RAS blockade with candesartan. We measured blood pressure and laboratory parameters, including urinary concentrations of angiotensinogen, protein, albumin, creatinine (Cr), and estimated glomerular filtration rate (eGFR), before and after candesartan treatment. Birth weight was 712g (range, 536-800g). Age at evaluation was 11.6years (range, 10.3-15.6years). After candesartan treatment for 47.6 ± 25.0months, the UAGT to urinary Cr ratio decreased from 61.9 ± 44.7 to 16.8 ± 14.4μg/g (p= 0.015). The urinary protein to Cr and albumin to Cr ratios also decreased (p= 0.008 and p= 0.012, respectively), whereas there was no significant change in eGFR. RAS blockade reduced UAGT levels and improved proteinuria/albuminuria in children with CKD who had VLBW. Suppression of intrarenal RAS activity may slow the progression of CKD in children with LBW.

A pilot study of alterations in oxidized angiotensinogen and antioxidants in pre-eclamptic pregnancy

The oxidation status of angiotensinogen (AGT) may have a critical role in pre-eclampsia. We used a validated, quantitative, mass spectrometry-based method to measure the oxidized and total AGT levels in plasma of pre-eclamptic women (n = 17), normotensive-matched controls (n = 17), and healthy non-pregnant women (n = 10). Measurements of plasma glutathione peroxidase (GPx) activity and serum selenium concentrations were performed as markers of circulating antioxidant capacity. Higher proportions of oxidized AGT in plasma from pre-eclamptic women compared to matched normotensive pregnant controls (P = 0.006), whilst maintaining a similar total plasma AGT concentration were found. In the pre-eclamptic group, blood pressure were correlated with the proportion of oxidized AGT; no such correlation was seen in the normotensive pregnant women. Plasma GPx was inversely correlated with oxidized AGT, and there was an inverse association between serum selenium concentration and the proportion of oxidized AGT. This is the first time that oxidized AGT in human plasma has been linked directly to antioxidant status, providing a mechanism for the enhanced oxidative stress in pre-eclampsia. We now provide pathophysiological evidence that the conversion of the reduced form of AGT to its more active oxidized form is associated with inadequate antioxidant status and could indeed contribute to the hypertension of pre-eclampsia.

Female Mice Exposed to Postnatal Neglect Display Angiotensin II-Dependent Obesity-Induced Hypertension.

BackgroundWe have previously reported that female mice exposed to maternal separation and early weaning (MSEW), a model of early life stress, show exacerbated diet‐induced obesity associated with hypertension. The goal of this study was to test whether MSEW promotes angiotensin II–dependent hypertension via activation of the renin‐angiotensin system in adipose tissue.Methods and ResultsMSEW was achieved by daily separations from the dam and weaning at postnatal day 17, while normally reared controls were weaned at postnatal day 21. Female controls and MSEW weanlings were placed on a low‐fat diet (LF, 10% kcal from fat) or high‐fat diet (HF, 60% kcal from fat) for 20 weeks. MSEW did not change mean arterial pressure in LF–fed mice but increased it in HF–fed mice compared with controls (P<0.05). In MSEW mice fed a HF, angiotensin II concentration in plasma and adipose tissue was elevated compared with controls (P<0.05). In addition, angiotensinogen concentration was increased solely in adipose tissue from MSEW mice (P<0.05), while angiotensin‐converting enzyme protein expression and activity were similar between groups. Chronic enalapril treatment (2.5 mg/kg per day, drinking water, 7 days) reduced mean arterial pressure in both groups of mice fed a HF (P<0.05) and abolished the differences due to MSEW. Acute angiotensin II–induced increases in mean arterial pressure (10 μg/kg SC) were attenuated in untreated MSEW HF–fed mice compared to controls (P<0.05); however, this response was similar between groups in enalapril‐treated mice.ConclusionsThe upregulation of angiotensinogen and angiotensin II in adipose tissue could be an important mechanism by which female MSEW mice fed a HF develop hypertension.

Activation of the Human Angiotensin-(1-12)-Chymase Pathway in Rats With Human Angiotensinogen Gene Transcripts.

Angiotensin-(1-12) [Ang-(1-12)], an alternate substrate for tissue angiotensin II (Ang II) formation, underscores the importance of alternative renin-independent pathway(s) for the generation of angiotensins. Since renin enzymatic activity is species-specific, a transgenic model of hypertension due to insertion of the human angiotensinogen (AGT) gene in Sprague Dawley rats allowed for characterizing the contribution of a non-renin dependent mechanism for Ang II actions in their blood and heart tissue. With this in mind, we investigated whether TGR(hAGT)L1623 transgenic rats express the human sequence of Ang-(1-12) before and following a 2-week oral therapy with the type I Ang II receptor (AT1-R) antagonist valsartan. Plasma and cardiac expression of angiotensins, plasma renin activity, cardiac angiotensinogen, and chymase protein and the enzymatic activities of chymase, angiotensin converting enzyme (ACE) and ACE2 were determined in TGR(hAGT)L1623 rats given vehicle or valsartan. The antihypertensive effect of valsartan after 14-day treatment was associated with reduced left ventricular wall thickness and augmented plasma concentrations of angiotensin I (Ang I) and Ang II; rat and human concentrations of angiotensinogen or Ang-(1-12) did not change. On the other hand, AT1-R blockade produced a 55% rise in left ventricular content of human Ang-(1-12) concentration and no changes in rat cardiac Ang-(1-12) levels. Mass-Spectroscopy analysis of left ventricular Ang II content confirmed a >4-fold increase in cardiac Ang II content in transgenic rats given vehicle; a tendency for decreased cardiac Ang II content following valsartan treatment did not achieve statistical significance. Cardiac chymase and ACE2 activities, significantly higher than ACE activity in TGR(hAGT)L1623 rats, were not altered by blockade of AT1-R. We conclude that this humanized model of angiotensinogen-dependent hypertension expresses the human sequence of Ang-(1-12) in plasma and cardiac tissue and responds to blockade of AT1-R with further increases in the human form of cardiac Ang-(1-12). Since rat renin has no hydrolytic activity on human angiotensinogen, the study confirms and expands knowledge of the importance of renin-independent mechanisms as a source for Ang II pathological actions.