Combining renin-angiotensin system blockade and sodium-glucose cotransporter-2 inhibition in experimental diabetes results in synergistic beneficial effects

BACKGROUND

Sodium-glucose cotransporter-2 (SGLT2) inhibition exerts cardioprotective and renoprotective effects, often on top of renin-angiotensin system (RAS) blockade. We investigated this in diabetic hypertensive (mREN2)27 rats.

METHODS

Rats were made diabetic with streptozotocin and treated with vehicle, the angiotensin receptor blocker valsartan, the SGLT2 inhibitor empagliflozin, or their combination. Blood pressure (BP) was measured by telemetry.

RESULTS

Diabetes resulted in albuminuria, accompanied by glomerulosclerosis, without a change in glomerular filtration rate. Empagliflozin did not lower BP, while valsartan did, and when combined the BP drop was largest. Only dual blockade reduced cardiac hypertrophy and prevented left ventricular dilatation. Valsartan, but not empagliflozin, increased renin, and the largest renin rise occurred during dual blockade, resulting in plasma angiotensin II [but not angiotensin-(1-7)] upregulation. In contrast, in the kidney, valsartan lowered angiotensin II and angiotensin-(1-7), and empagliflozin did not alter this. Although both valsartan and empagliflozin alone tended to diminish albuminuria, the reduction was significant only when both drugs were combined. This was accompanied by reduced glomerulosclerosis, no change in glomerular filtration rate, and a favorable expression pattern of fibrosis and inflammatory markers (including SGLT2) in the kidney.

CONCLUSION

RAS blockade and SGLT2 inhibition display synergistic beneficial effects on BP, kidney injury and cardiac hypertrophy in a rat with hypertension and diabetes. The synergy does not involve upregulation of angiotensin-(1-7), but may relate to direct RAS-independent effects of empagliflozin in the heart and kidney.

Application of a Biomimetic Nanoparticle-Based Mock Virus to Determine SARS-CoV-2 Neutralizing Antibody Levels in Blood Samples Using a Lateral Flow Assay

The presence of neutralizing antibodies against SARS-CoV-2 in blood, acquired through previous infection or vaccination, is known to prevent the (re)occurrence of outbreaks unless the virus mutates. Therefore, the measurement of neutralizing antibodies constitutes an indispensable tool in assessing an individual's and a population's immunity against SARS-CoV-2. For this reason, we have developed an innovative lateral flow assay (LFA) capable of detecting blood-derived neutralizing antibodies using a biomimetic SARS-CoV-2 mock virus system. Here, functionalized gold nanoparticles (AuNPs) featuring the trimeric spike (S) protein at its surface imitate the virus's structure and are applied to monitor the presence and efficacy of neutralizing antibodies in blood samples. The detection principle relies on the interaction between mock virus and the immobilized angiotensin-converting enzyme 2 (ACE2) receptor, which is inhibited when neutralizing antibodies are present. To further enhance the sensitivity of our competitive assay and identify low titers of neutralizing antibodies, an additional mixing pad is embedded into the device to increase the interaction time between mock virus and neutralizing antibodies. The developed LFA is benchmarked against the WHO International Standard (21/338) and demonstrated reliable quantification of neutralizing antibodies that inhibit ACE2 binding events down to a detection limit of an antibody titer of 59 IU/mL. Additional validation using whole blood and plasma samples showed reproducible results and good comparability to a laboratory-based reference test, thus highlighting its applicability for point-of-care testing.

Profiling endogenous adrenal function during veno-venous ECMO support in COVID-19 ARDS: a descriptive analysis

Background

Prolonged critical illness is often accompanied by an impairment of adrenal function, which has been frequently related to conditions complicating patient management. The presumed connection between hypoxia and the pathogenesis of this critical- illness- related corticosteroid insufficiency (CIRCI) might play an important role in patients with severe acute respiratory distress syndrome (ARDS). Since extracorporeal membrane oxygenation (ECMO) is frequently used in ARDS, but data on CIRCI during this condition are scarce, this study reports the behaviour of adrenal function parameters during oxygenation support with veno-venous (vv)ECMO in coronavirus disease 2019 (COVID-19) ARDS.

Methods

A total of 11 patients undergoing vvECMO due to COVID-19 ARDS at the Medical University of Vienna, who received no concurrent corticosteroid therapy, were retrospectively included in this study. We analysed the concentrations of cortisol, aldosterone, and angiotensin (Ang) metabolites (Ang I-IV, Ang 1-7, and Ang 1-5) in serum via liquid chromatography/tandem mass spectrometry before, after 1 day, 1 week, and 2 weeks during vvECMO support and conducted correlation analyses between cortisol and parameters of disease severity.

Results

Cortisol concentrations appeared to be lowest after initiation of ECMO and progressively increased throughout the study period. Higher concentrations were related to disease severity and correlated markedly with interleukin-6, procalcitonin, pH, base excess, and albumin during the first day of ECMO. Fair correlations during the first day could be observed with calcium, duration of critical illness, and ECMO gas flow. Angiotensin metabolite concentrations were available in a subset of patients and indicated a more homogenous aldosterone response to plasma renin activity after 1 week of ECMO support.

Conclusion

Oxygenation support through vvECMO may lead to a partial recovery of adrenal function over time. In homogenous patient collectives, this novel approach might help to further determine the importance of adrenal stress response in ECMO and the influence of oxygenation support on CIRCI.

Renin-angiotensin system inhibitor discontinuation in COVID-19 did not modify systemic ACE2 in a randomized controlled trial

Despite the similar clinical outcomes after renin-angiotensin system (RAS) inhibitor (RASi) continuation or withdrawal in COVID-19, the effects on angiotensin-converting enzyme 2 (ACE2) and RAS metabolites remain unclear. In a substudy of the randomized controlled Austrian Corona Virus Adaptive Clinical Trial (ACOVACT), patients with hypertension and COVID-19 were randomized 1:1 to either RASi continuation (n = 30) or switch to a non-RASi medication (n = 29). RAS metabolites were analyzed using a mixed linear regression model (n = 30). Time to a sustained clinical improvement was equal and ACE2 did not differ between the groups but increased over time in both. Overall ACE2 was higher with severe COVID-19. ACE-S and Ang II levels increased as expected with ACE inhibitor discontinuation. These data support the safety of RASi continuation in COVID-19, although RASi were frequently discontinued in our post hoc analysis. The study was not powered to draw definite conclusions on clinical outcomes using small sample sizes.

Association of Elevated Serum Aldosterone Concentrations in Pregnancy with Hypertension

Emerging evidence indicates a previously unrecognized, clinically relevant spectrum of abnormal aldosterone secretion associated with hypertension severity. It is not known whether excess aldosterone secretion contributes to hypertension during pregnancy. We quantified aldosterone concentrations and angiotensin peptides in serum (using liquid chromatography with tandem mass spectrometry) in a cohort of 128 pregnant women recruited from a high-risk obstetrics clinic and followed prospectively for the development of gestational hypertension, pre-eclampsia, superimposed pre-eclampsia, chronic hypertension, or remaining normotensive. The cohort was grouped by quartile of aldosterone concentration in serum measured in the first trimester, and blood pressure, angiotensin peptides, and hypertension outcomes compared across the four quartiles. Blood pressures and body mass index were greatest in the top and bottom quartiles, with the top quartile having the highest blood pressure throughout pregnancy. Further stratification of the top quartile based on increasing (13 patients) or decreasing (19 patients) renin activity over gestation revealed that the latter group was characterized by the highest prevalence of chronic hypertension, use of anti-hypertensive agents, pre-term birth, and intrauterine growth restriction. Serum aldosterone concentrations greater than 704 pmol/L, the 75th percentile defined within the cohort, were evident across all categories of hypertension in pregnancy, including normotensive. These findings suggest that aldosterone excess may underlie the development of hypertension in pregnancy in a significant subpopulation of individuals.

Activation of the Renin-Angiotensin-Aldosterone System Is Attenuated in Hypertensive Compared with Normotensive Pregnancy

Hypertension during pregnancy increases the risk of adverse maternal and fetal outcomes, but the mechanisms of pregnancy hypertension are not precisely understood. Elevated plasma renin activity and aldosterone concentrations play an important role in the normal physiologic adaptation to pregnancy. These effectors are reduced in patients with pregnancy hypertension, creating an opportunity to define the features of the renin-angiotensin-aldosterone system (RAAS) that are characteristic of this disorder. In the current study, we used a novel LC-MS/MS-based methodology to develop comprehensive profiles of RAAS peptides and effectors over gestation in a cohort of 74 pregnant women followed prospectively for the development of gestational hypertension and pre-eclampsia (HYP, 27 patients) versus those remaining normotensive (NT, 47 patients). In NT pregnancy, the plasma renin activity surrogate, (PRA-S, calculated from the sum of Angiotensin I + Angiotensin II) and aldosterone concentrations significantly increased from the first to the third trimester, accompanied by a modest increase in the concentrations of angiotensin peptide metabolites. In contrast, in HYP pregnancies, PRA-S and angiotensin peptides were largely unchanged over gestation, and third-trimester aldosterone concentrations were significantly lower compared with those in NT pregnancies. The results indicated that the predominant features of pregnancies that develop HYP are stalled or waning activation of the RAAS in the second half of pregnancy (accompanied by unchanging levels of angiotensin peptides) and the attenuated secretion of aldosterone.

Cluster analysis of angiotensin biomarkers to identify antihypertensive drug treatment in population studies

BACKGROUND

The recent progress in molecular biology generates an increasing interest in investigating molecular biomarkers as markers of response to treatments. The present work is motivated by a study, where the objective was to explore the potential of the molecular biomarkers of renin-angiotensin-aldosterone system (RAAS) to identify the undertaken antihypertensive treatments in the general population. Population-based studies offer an opportunity to assess the effectiveness of treatments in real-world scenarios. However, lack of quality documentation, especially when electronic health record linkage is unavailable, leads to inaccurate reporting and classification bias.

METHOD

We present a machine learning clustering technique to determine the potential of measured RAAS biomarkers for the identification of undertaken treatments in the general population. The biomarkers were simultaneously determined through a novel mass-spectrometry analysis in 800 participants of the Cooperative Health Research In South Tyrol (CHRIS) study with documented antihypertensive treatments. We assessed the agreement, sensitivity and specificity of the resulting clusters against known treatment types. Through the lasso penalized regression, we identified clinical characteristics associated with the biomarkers, accounting for the effects of cluster and treatment classifications.

RESULTS

We identified three well-separated clusters: cluster 1 (n = 444) preferentially including individuals not receiving RAAS-targeting drugs; cluster 2 (n = 235) identifying angiotensin type 1 receptor blockers (ARB) users (weighted kappa κw = 74%; sensitivity = 73%; specificity = 83%); and cluster 3 (n = 121) well discriminating angiotensin-converting enzyme inhibitors (ACEi) users (κw = 81%; sensitivity = 55%; specificity = 90%). Individuals in clusters 2 and 3 had higher frequency of diabetes as well as higher fasting glucose and BMI levels. Age, sex and kidney function were strong predictors of the RAAS biomarkers independently of the cluster structure.

CONCLUSIONS

Unsupervised clustering of angiotensin-based biomarkers is a viable technique to identify individuals on specific antihypertensive treatments, pointing to a potential application of the biomarkers as useful clinical diagnostic tools even outside of a controlled clinical setting.

Angiotensin pathways under therapy with empagliflozin in patients with chronic heart failure

AIMS

Large outcome studies demonstrated a reduction of heart failure hospitalization or cardiovascular death in patients with chronic heart failure (CHF). The renin-angiotensin system (RAS) is a key player in fluid and sodium regulation. The classic angiotensin-converting enzyme-angiotensin II-angiotensin-1 receptor axis (Ang I-ACE-Ang II receptor axis) is predominantly angiotensin II (Ang-II) induced and promotes vasoconstriction. In contrast, the angiotensin-converting-enzyme-2-angiotensin-(1-7)-Mas axis (Mas-axis) is mediated by the metabolites angiotensin-1-7 (Ang-(1-7)) and angtiotensin-1-5 (Ang-(1-5)) and exerts cardioprotective effects.

METHODS

We previously investigated the effect of empagliflozin on the systemic haemodynamic in patients with stable CHF (NYHA II-III) in a randomized placebo-controlled clinical trial 'Analysing the Effect of Empagliflozin on Reduction of Tissue Sodium Content in Patients With Chronic Heart Failure (ELSI)'. In a post hoc analysis, we now analysed whether empagliflozin has an effect on the RAS by measuring detailed RAS profiles (LC-MS/MS-based approach) in 72 patients from ELSI. We compared RAS parameters after 1-month and 3-months treatment with empagliflozin or placebo to baseline. The secondary goal was to analyse whether the effect of empagliflozin on RAS parameters was dependent on angiotensin-receptor-blocking (ARB) or angiotensin-converting-enzyme-inhibitor (ACEI) co-medication.

RESULTS

Empagliflozin medication induced a significant rise in Ang-II [68.5 pmol/L (21.3-324.2) vs. 131.5 pmol/L (34.9-564.0), P = 0.001], angiotensin-I (Ang-I) [78.7 pmol/L (21.5-236.6) vs. 125.9 pmol/L (52.6-512.9), P < 0.001], Ang-(1-7) [3.0 pmol/L (3.0-15.0) vs. 10.1 pmol/L (3.0-31.3), P = 0.006], and Ang-(1-5) [5.4 pmol/L (2.0-22.9) vs. 9.9 pmol/L (2.8-36.4), P = 0.004], which was not observed in the placebo group (baseline to 3-months treatment). A significant rise in Ang-II (206.4 pmol/L (64.2-750.6) vs. 568.2 pmol/L (164.7-1616.4), P = 0.001), Ang-(1-7) (3.0 pmol/L (3.0-14.1) vs. 15.0 pmol/L (3.0-31.3), P = 0.017), and Ang-(1-5) [12.2 pmol/L (3.8-46.6) vs. 36.4 pmol/L (11.1-90.7), P = 0.001] under empagliflozin treatment was only seen in the subgroup of patients with ARB co-medication, whereas no change of Ang-II (16.7 pmol/L (2.0-60.8) vs. 26.4 pmol/L (10.7-63.4), P = 0.469), Ang-(1-7) (6.6 pmol/L (3.0-20.7) vs. 10.5 pmol/L (3.0-50.5), P = 0.221), and Ang-(1-5) (2.7 pmol/L (2.0-8.4) vs. 2.8 pmol/L (2.0-6.9), P = 0.851) was observed in patients with empagliflozin that were on ACEI co-medication (baseline to 3-months treatment).

CONCLUSIONS

Our data indicate that empagliflozin might lead to an activation of both the Ang I-ACE-Ang II receptor axis and the Mas-axis pathway. Activation of the Ang I-ACE-Ang II receptor axis and the protective Mas-axis pathway after initiating treatment with empagliflozin was only seen in patients with ARB co-medication, in contrast to co-medication with ACEI.

The systemic and hepatic alternative renin-angiotensin system is activated in liver cirrhosis, linked to endothelial dysfunction and inflammation

We aimed to assess the systemic and hepatic renin-angiotensin-system (RAS) fingerprint in advanced chronic liver disease (ACLD). This prospective study included 13 compensated (cACLD) and 12 decompensated ACLD (dACLD) patients undergoing hepatic venous pressure gradient (HVPG) measurement. Plasma components (all patients) and liver-local enzymes (n = 5) of the RAS were analyzed using liquid chromatography-tandem mass spectrometry. Patients with dACLD had significantly higher angiotensin (Ang) I, Ang II and aldosterone plasma levels. Ang 1-7, a major mediator of the alternative RAS, was almost exclusively detectable in dACLD (n = 12/13; vs. n = 1/13 in cACLD). Also, dACLD patients had higher Ang 1-5 (33.5 pmol/L versus cACLD: 6.6 pmol/L, p < 0.001) and numerically higher Ang III and Ang IV levels. Ang 1-7 correlated with HVPG (ρ = 0.655; p < 0.001), von Willebrand Factor (ρ = 0.681; p < 0.001), MELD (ρ = 0.593; p = 0.002) and interleukin-6 (ρ = 0.418; p = 0.047). Considerable activity of ACE, chymase, ACE2, and neprilysin was detectable in all liver biopsies, with highest chymase and ACE2 activity in cACLD patients. While liver-local classical and alternative RAS activity was already observed in cACLD, systemic activation of alternative RAS components occurred only in dACLD. Increased Ang 1-7 was linked to severe liver disease, portal hypertension, endothelial dysfunction and inflammation.

Combined angiotensin-converting enzyme and aminopeptidase inhibition for treatment of experimental ventilator-induced lung injury in mice

Introduction: Ventilator-induced lung injury (VILI) may aggravate critical illness. Although angiotensin-converting enzyme (ACE) inhibition has beneficial effects in ventilator-induced lung injury, its clinical application is impeded by concomitant hypotension. We hypothesized that the aminopeptidase inhibitor ALT-00 may oppose the hypotension induced by an angiotensin-converting enzyme inhibitor, and that this combination would activate the alternative renin-angiotensin system (RAS) axis to counteract ventilator-induced lung injury. Methods: In separate experiments, C57BL/6 mice were mechanically ventilated with low (LVT, 6 mL/kg) and high tidal volumes (HVT, 30 mL/kg) for 4 h or remained unventilated (sham). High tidal volume-ventilated mice were treated with lisinopril (0.15 μg/kg/min) ± ALT-00 at 2.7, 10 or 100 μg/kg/min. Blood pressure was recorded at baseline and after 4 h. Lung histology was evaluated for ventilator-induced lung injury and the angiotensin (Ang) metabolite profile in plasma (equilibrium levels of Ang I, Ang II, Ang III, Ang IV, Ang 1-7, and Ang 1-5) was measured with liquid chromatography tandem mass spectrometry at the end of the experiment. Angiotensin concentration-based markers for renin, angiotensin-converting enzyme and alternative renin-angiotensin system activities were calculated. Results: High tidal volume-ventilated mice treated with lisinopril showed a significant drop in the mean arterial pressure at 4 h compared to baseline, which was prevented by adding ALT-00 at 10 and 100 μg/kg/min. Ang I, Ang II and Ang 1-7 plasma equilibrium levels were elevated in the high tidal volumes group versus the sham group. Lisinopril reduced Ang II and slightly increased Ang I and Ang 1-7 levels versus the untreated high tidal volumes group. Adding ALT-00 at 10 and 100 μg/kg/min increased Ang I and Ang 1-7 levels versus the high tidal volume group, and partly prevented the downregulation of Ang II levels caused by lisinopril. The histological lung injury score was higher in the high tidal volume group versus the sham and low tidal volume groups, and was attenuated by lisinopril ± ALT-00 at all dose levels. Conclusion: Combined angiotensin-converting enzyme plus aminopeptidase inhibition prevented systemic hypotension and maintained the protective effect of lisinopril. In this study, a combination of lisinopril and ALT-00 at 10 μg/kg/min appeared to be the optimal approach, which may represent a promising strategy to counteract ventilator-induced lung injury that merits further exploration.

Blood pressure-independent renoprotective effects of small interference RNA targeting liver angiotensinogen in experimental diabetes

BACKGROUND AND PURPOSE

Small interfering RNA (siRNA) targeting liver angiotensinogen lowers blood pressure, but its effects in hypertensive diabetes are unknown.

EXPERIMENTAL APPROACH

To address this, TGR (mRen2)27 rats (angiotensin II-dependent hypertension model) were made diabetic with streptozotocin over 18 weeks and treated with either vehicle, angiotensinogen siRNA, the AT₁ antagonist valsartan, the ACE inhibitor captopril, valsartan + siRNA or valsartan + captopril for the final 3 weeks. Mean arterial pressure (MAP) was measured via radiotelemetry.

KEY RESULTS

MAP before treatment was 153 ± 2 mmHg. Diabetes resulted in albuminuria, accompanied by glomerulosclerosis and podocyte effacement, without a change in glomerular filtration rate. All treatments lowered MAP and cardiac hypertrophy, and the largest drop in MAP was observed with siRNA + valsartan. Treatment with siRNA lowered circulating angiotensinogen by >99%, and the lowest circulating angiotensin II and aldosterone levels occurred in the dual treatment groups. Angiotensinogen siRNA did not affect renal angiotensinogen mRNA expression, confirming its liver-specificity. Furthermore, only siRNA with or without valsartan lowered renal angiotensin I. All treatments lowered renal angiotensin II and the reduction was largest (>95%) in the siRNA + valsartan group. All treatments identically lowered albuminuria, whereas only siRNA with or without valsartan restored podocyte foot processes and reduced glomerulosclerosis.

CONCLUSION AND IMPLICATIONS

Angiotensinogen siRNA exerts renoprotection in diabetic TGR (mRen2)27 rats and this relies, at least in part, on the suppression of renal angiotensin II formation from liver-derived angiotensinogen. Clinical trials should now address whether this is also beneficial in human diabetic kidney disease.

Abstract P350: Profiling Of The Renin Angiotensin Aldosterone System In High Risk Human Pregnancy

Hypertensive disorders of pregnancy (HDP) are a leading cause of maternal and infant morbidities and mortalities. There is a lack of clinical tools identifying subtypes of this heterogenous group of disorders, which limits optimization of individual patient care. The RAAS, a hormonal system activated during pregnancy, is suppressed in pregnancies with hypertension, but key RAAS biomarkers in subgroups of HDP have not been defined. We quantified serum biomarkers of the RAAS using LC-MS/MS in the first and third trimesters of pregnancy in a cohort of n=92 women at high-risk for preeclampsia. Data are expressed as median [IQR] of the delta of the third - first trimester. There were n=15 women that developed gestational hypertension (GH) and n=12 women that developed pre-eclampsia (Pre-e). Serum aldosterone levels increased with pregnancy in high-risk women with no adverse outcomes, but not in women that developed GH (GH, n=15: 19.4 [-321.6 - 661.6] versus Control, n=22: 502.5 [161-1019]; Data are pmol/L; P<0.01). PRA-S, a marker for activity of the RAAS that normally increases in healthy pregnancy, did not increase with pregnancy in patients that developed GH, and was further reduced in patients that developed Pre-e (GH: -17.4 [-57.1 to 2.2] versus Pre-E: -56.3 [-160.9 to -3.5] pmol/L; P<0.05). In high-risk patients that developed pre-eclampsia, aldosterone levels varied widely, depending pre-existing risk factors, such as chronic hypertension.

Serum levels of RAAS biomarkers differed by pregnancy outcome and were influenced by pre-existing risk. Declining aldosterone and PRA-S over gestation may be indicative of development of Pre-e in women with clinical risk factors for Pre-e.

Abstract P251: Assay Performance And System Compatibility For RAAS Triple-A Analysis In Hypertension Profiling

Recent studies revealed major concerns related to the accuracy of widely used clinical assays for aldosterone and renin, fueling the need for alternative and more robust bio-analytical solutions for assessment of the Renin-Angiotensin-Aldosterone-System (RAAS) in clinical samples. RAAS Triple-A profiling is a high-throughput mass-spectrometry based assay for quantification of Angiotensin I (Ang I), Angiotensin II (Ang II) and Aldosterone in serum samples. Quantified hormone levels are used to calculate markers for plasma-renin-activity (PRA-S), plasma angiotensin-converting-enzyme activity (ACE-S) and adrenal aldosterone secretion (AA2-Ratio), which can be used for clinical profiling in patients with uncontrolled hypertension. A RAAS Triple-A LC-MS/MS kit was recently launched as an In Vitro Diagnostic (IVD) device in Europe for hypertension profiling. In the current study, a comparative approach was used to assess analytical performance of the RAAS Triple-A assay on three different LC-MS/MS systems, Altis+ (Thermo Scientific), Xevo TQ-S (Waters), and Triple Quad 6500+ (Sciex) located in three different laboratories. RAAS Triple-A kits (96-well format) were used to analyze one set of n=50 triplicate human serum samples at each location. At each site, samples were sample preparation and LC-MS/MS analysis according to the RAAS Triple-A kit manual. Analytical validation of assay linearity, precision, and accuracy were evaluated at each site, and Bland-Altman-Analysis was used to test for quantification bias between sites. Results demonstrate the measured concentrations for each analyte, Ang I, Ang II, and aldosterone, were strongly correlated between sites (R 2 = Ang I: 0.996; Ang II: 0.991; Aldo: 0.983). Performance characteristics of all target analytes were in compliance with European Medical Agency (EMA) standards for bio-analytical assays on each instrument. Robust assay performance across laboratories and different LC-MS/MS systems allows for a broad clinical application of RAAS Triple-A profiling potentially improving treatment efficacy in hypertension by supporting treatment decisions with individual RAAS Triple-A profiles.

Aldosterone and angiotensin II profiles in young black and white women using different hormonal contraceptives: the African-PREDICT study

Exogenous estrogens and progestins may affect the components of the renin-angiotensin-aldosterone system (RAAS). Changes in ventricular blood volume are associated with increased secretion of N-terminal pro-hormone B-type natriuretic peptide (NT-proBNP), which may also be affected by hormonal contraceptives. In this study, we aimed to compare components of the RAAS and NT-proBNP between groups using different hormonal contraceptives, including the combination pill, the injection or implant, and controls (no contraception) in black and white women of fertile age (20 - 30 years). Secondly, we determined whether blood pressure and NT-proBNP are associated with the RAAS components. We included 397 black and white women not using contraceptives, 120 using the combination pill, and 103 receiving an injection/implant. RAAS Triple-A analysis was carried out with LC-MS/MS quantification, and blood pressure measurements (ABPM) taken over 24 h. We found that serum aldosterone was higher (475.7 vs. 249.2 pmol/L; p < 0.001) in the combination pill group than in the no contraception group of white women. The aldosterone-angiotensin II ratio (AA2) was higher (5.4 vs. 2.5; p < 0.001) in the combination pill group than in the no contraception group. In the black women using the combination pill, we found a borderline-positive and borderline-negative association between 24-h systolic blood pressure and NT-proBNP with equilibrium (eq) Ang II, respectively. In white women using the combination pill, only CRP contributed positively and independently to NT-proBNP. To conclude, activation of RAAS by different hormonal contraceptives may increase future risk for the development of hypertension in young black and white women.

The Effect of FGF23 on Cardiac Hypertrophy Is Not Mediated by Systemic Renin-Angiotensin- Aldosterone System in Hemodialysis

Fibroblast growth factor 23 (FGF23) is elevated in patients with chronic kidney disease and contributes to left ventricular hypertrophy (LVH). The aim of the analysis was to determine whether this effect is mediated by the renin-angiotensin-aldosterone system (RAAS) in hemodialysis. Serum samples from 62 randomized hemodialysis patients with LVH were analyzed for plasma renin activity (PRA-S), angiotensin II (AngII), and metabolites, angiotensin-converting enzyme-2 (ACE2) and aldosterone using a high throughput mass spectrometry assay. Compared to healthy individuals, levels of the RAAS parameters PRA-S, AngII and aldosterone were generally lower [median (IQR) PRA-S 130 (46–269) vs. 196 (98, 238) pmol/L; AngII 70 (28–157) vs. 137 (76, 201) pmol/L; Aldosterone 130 (54, 278) vs. 196 (98, 238) pmol/L]. We did not find an indication that the effect of FGF23 on LVH was mediated by RAAS parameters, with all estimated indirect effects virtually zero. Furthermore, FGF23 was not associated with RAAS parameter levels throughout the study. While there was a clear association between FGF23 levels and left ventricular mass index (LVMI) at the end of the study and in the FGF23 fold change and LVMI change analysis, no association between RAAS and LVMI was observed. Serum concentrations of PRA-S, AngII, and aldosterone were below the ranges measured in healthy controls suggesting that RAAS is not systemically activated in hemodialysis patients. The effect of FGF23 on LVMI was not mediated by systemic RAAS activity. These findings challenge the current paradigm of LVH progression and treatment with RAAS blockers in dialysis.

Combined sodium glucose co-transporter-2 inhibitor and angiotensin-converting enzyme inhibition upregulates the renin-angiotensin system in chronic kidney disease with type 2 diabetes: Results of a randomized, double-blind, placebo-controlled exploratory trial

AIM

Sodium glucose co-transporter-2 inhibitors (SGLT-2i) improve cardiorenal outcomes in patients with chronic kidney disease (CKD), with and without type 2 diabetes. The molecular mechanisms underlying these pleiotropic effects remain unclear, yet it is speculated that SGLT-2i elicit a neurohormonal modulation resulting in renin-angiotensin system (RAS) activation. We hypothesized that combined SGLT-2 and angiotensin-converting enzyme inhibition (ACEi) favours RAS regulation towards the beneficial angiotensin-(1-7)-driven axis.

MATERIALS AND METHODS

This randomized controlled prospective study investigated the effect of 12 weeks treatment with the SGLT-2i empagliflozin on top of ACEi on the molecular RAS dynamics in 24 diabetic and 24 non-diabetic patients with CKD. Systemic RAS peptides were quantified by mass spectrometry.

RESULTS

In patients with type 2 diabetes, combined SGLT-2i and ACEi significantly upregulated plasma renin activity [pre-treatment median and interquartile range 298.0 (43.0-672.0) pmol/L versus post-treatment 577.0 (95.0-1543.0) pmol/L; p = .037] and angiotensin I levels [pre-treatment 289.0 (42.0-668.0) pmol/L versus post-treatment 573.0 (93.0-1522.0) pmol/L; p = .037], together with a significant increase of angiotensin-(1-7) levels [pre-treatment 14.0 (2.1-19.0) pmol/L versus post-treatment 32.0 (5.7-99.0) pmol/L; p = .012]. Empagliflozin treatment resulted in a 1.5 to 2-fold increase in main RAS peptides in patients with diabetes compared with placebo. No significant effect of empagliflozin on top of ACEi on RAS peptides was found in patients with CKD without diabetes.

CONCLUSION

A distinct RAS modulation by SGLT-2i occurs in diabetic kidney disease reflected by enhancement of the beneficial angiotensin-(1-7) providing a molecular background for this renoprotective therapeutic approach.

Dysregulation of ACE (Angiotensin-Converting Enzyme)-2 and Renin-Angiotensin Peptides in SARS-CoV-2 Mediated Mortality and End-Organ Injuries

ACE (angiotensin-converting enzyme)-2 as the target for SARS-CoV-2 also negatively regulates the renin-angiotensin system. Pathological activation of ADAM17 (A disintegrin and metalloproteinase-17) may potentiate inflammation and diminish ACE2-mediated tissue protection through proteolytic shedding, contributing to SARS-CoV-2 pathogenesis. We aim to examine plasma soluble ACE2 and angiotensin profiles in relation to outcomes by enrolling consecutive patients admitted for COVID-19 with baseline blood collection at admission and repeated sampling at 7 days. The primary outcome was 90-day mortality, and secondary outcomes were the incidence of end-organ injuries. Overall, 242 patients were included, the median age was 63 (52-74) years, 155 (64.0%) were men, and 57 (23.6%) patients reached the primary end point. Baseline soluble ACE2 was elevated in COVID-19 but was not associated with disease severity or mortality. In contrast, an upward trajectory of soluble ACE2 at repeat sampling was independently associated with an elevated risk of mortality and incidence of acute myocardial injury and circulatory shock. Similarly, an increase in soluble tumor necrosis factor receptor levels was also associated with adverse outcomes. Plasma Ang I, Ang 1-7 (angiotensin 1-7) levels, and the Ang 1-7/Ang II (angiotensin II) ratio were elevated during SARS-CoV-2 infection related to downregulation of ACE activity at baseline. Moreover, patients having an upward trajectory of soluble ACE2 were characterized by an imbalance in the Ang 1-7/Ang II ratio. The observed dysregulation of ACE2 and angiotensin peptides with disease progression suggest a potential role of ADAM17 inhibition and enhancing the beneficial Ang 1-7/Mas axis to improve outcomes against SARS-CoV-2 infection.

Selective Inhibition of the C-Domain of ACE (Angiotensin-Converting Enzyme) Combined With Inhibition of NEP (Neprilysin): A Potential New Therapy for Hypertension

[Figure: see text].

Effect of Mineralocorticoid Receptor Antagonism and ACE Inhibition on Angiotensin Profiles in Diabetic Kidney Disease: An Exploratory Study

BACKGROUND

Renin-angiotensin-aldosterone system (RAAS) blockade with angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARB) is the cornerstone of antihypertensive treatment in patients with chronic kidney disease (CKD) and diabetes mellitus. Mineralocorticoid receptor antagonists (MRA) on top of conventional RAAS blockade confer cardio- and renoprotective effects. Yet, the detailed effects of this therapeutic approach on key RAAS effectors have not been elucidated to date.

METHODS

In this exploratory placebo-controlled study, 15 patients with CKD stages 2-3 and albuminuria due to diabetic kidney disease (DKD) were randomized to receive the MRA eplerenone or placebo in addition to ACEi therapy. Employing mass-spectrometry, we quantified plasma angiotensin levels [Ang I, Ang II, Ang-(1-7), Ang-(1-5), Ang III, Ang IV], renin and aldosterone in patients before and after 8 weeks of MRA treatment.

RESULTS

While blood pressure and kidney function were similar in the placebo and eplerenone treatment group during the study period, distinct differences in RAAS regulation occurred: eplerenone treatment resulted in an increase in plasma renin activity, Ang I and aldosterone concentrations, indicating global RAAS activation. In addition, eplerenone on top of ACEi profoundly upregulated the alternative RAAS effector Ang-(1-7).

CONCLUSIONS

Combined eplerenone and ACEi therapy increases Ang-(1-7) levels in patients with CKD indicating a unique nephroprotective RAAS pattern with considerable therapeutic implications.

Aldosterone and cortisol synthesis regulation by angiotensin-(1-7) and angiotensin-converting enzyme 2 in the human adrenal cortex

OBJECTIVE

The branch of the renin--angiotensin system constituting angiotensin-(1-7) [Ang-(1-7)], the Ang II type 2 receptor, the Mas receptors and the Ang-(1-7)-forming enzyme ACE-2, by counteracting the Ang II type 1 receptor (AT1R)-mediated effects, are held to be cardiovascular protective in several conditions. However, whether Ang-(1-7) and ACE-2 are detectable in human adrenocortical tissues and whether they affect aldosterone and cortisol biosynthesis was unknown.

METHODS

We measured angiotensin peptides with liquid chromatography tandem-mass spectrometry and ACE-2 mRNA with digital droplet (dd)PCR in human aldosterone-producing adenoma (APA) and APA-adjacent tissue obtained from patients with primary aldosteronism. We also investigated the effects of Ang-(1-7) and the ACE-2 activator diminazene aceturate (DIZE) on aldosterone synthase (CYP11B2) and 11β-hydroxylase (CYP11B1) gene expression, in the absence or presence of the AT1R antagonist irbesartan, or of the MasR antagonist A779.

RESULTS

APA and APA-adjacent adrenocortical tissues express ACE-2 mRNA and contain detectable amounts of Ang II and Ang-(2-8), but not of Ang I, Ang-(1-5), Ang (3-8) and Ang-(1-7). Under unstimulated and Ang II- stimulated conditions Ang-(1-7) did not blunt CYP11B1 and CYP11B2 mRNA. At supraphysiological concentrations (10-4 mol/l), Ang-(1-7) stimulated both CYP11B1 and CYP11B2 mRNA via the AT1R. The ACE-2 activator DIZE increased by 1.5-fold ACE-2 mRNA but did not blunt Ang II- upregulated CYP11B1 and CYP11B2 expression.

CONCLUSION

These results do not support the hypothesis that the ACE-2/Ang-(1-7)/MasR axis play a protective role by counteracting enhanced aldosterone secretion in humans.

Renin Feedback Is an Independent Predictor of Outcome in HFpEF

Drugs which interact with the renin angiotensin aldosterone system (RAAS) aim to reduce the negative effects of angiotensin (Ang) II. Treatment with these drugs anticipate a compensatory up-regulation of renin; however, it has been shown that there is a large variability in circulating plasma renin (PRA), even in patients with optimal medical therapy in patients with heart failure (HF) with reduced ejection fraction (HFrEF). Our aim was to measure plasma renin activity (PRA-S), its response to RAAS inhibitor (RAASi) therapies and its effects on outcome in patients with HF with preserved ejection fraction (HFpEF). For this purpose, 150 HFpEF patients were included into a prospective single-center registry. Equilibrium (eq) angiotensin metabolites were measured from serum samples using mass spectroscopy. PRA-S (eqAng I + eqAng II) was calculated and compared in respect to the primary endpoint defined as all-cause death. PRA-S in patients with RAASi therapy was not significantly higher than in patients without RAASi (p = 0.262). Even after adjusting for confounding factors, PRA-S remained predictive for all-cause death in the multivariable model with a hazard ratio of 2.14 (95%CI 1.20–3.82, p = 0.010). We conclude that high PRA-S is associated with poor prognosis in patients with HFpEF, regardless of RAASi treatment, which could ultimately result in hyperactivated RAAS and consecutive negative effects on the cardiovascular and renal system, leading to poor outcome in patients with HFpEF.

Myocardial Angiotensin Metabolism in End-Stage Heart Failure

BACKGROUND

The myocardium exhibits an adaptive tissue-specific renin-angiotensin system (RAS), and local dysbalance may circumvent the desired effects of pharmacologic RAS inhibition, a mainstay of heart failure with reduced ejection fraction (HFrEF) therapy.

OBJECTIVES

This study sought to investigate human myocardial tissue RAS regulation of the failing heart in the light of current therapy.

METHODS

Fifty-two end-stage HFrEF patients undergoing heart transplantation (no RAS inhibitor: n = 9; angiotensin-converting enzyme [ACE] inhibitor: n = 28; angiotensin receptor blocker [ARB]: n = 8; angiotensin receptor neprilysin-inhibitor [ARNi]: n = 7) were enrolled. Myocardial angiotensin metabolites and enzymatic activities involved in the metabolism of the key angiotensin peptides angiotensin 1-8 (AngII) and Ang1-7 were determined in left ventricular samples by mass spectrometry. Circulating angiotensin concentrations were assessed for a subgroup of patients.

RESULTS

AngII and Ang2-8 (AngIII) were the dominant peptides in the failing heart, while other metabolites, especially Ang1-7, were below the detection limit. Patients receiving an ARB component (i.e., ARB or ARNi) had significantly higher levels of cardiac AngII and AngIII (AngII: 242 [interquartile range (IQR): 145.7 to 409.9] fmol/g vs 63.0 [IQR: 19.9 to 124.1] fmol/g; p < 0.001; and AngIII: 87.4 [IQR: 46.5 to 165.3] fmol/g vs 23.0 [IQR: <5.0 to 59.3] fmol/g; p = 0.002). Myocardial AngII concentrations were strongly related to circulating AngII levels. Myocardial RAS enzyme regulation was independent from the class of RAS inhibitor used, particularly, a comparable myocardial neprilysin activity was observed for patients with or without ARNi. Tissue chymase, but not ACE, is the main enzyme for cardiac AngII generation, whereas AngII is metabolized to Ang1-7 by prolyl carboxypeptidase but not to ACE2. There was no trace of cardiac ACE2 activity.

CONCLUSIONS

The failing heart contains considerable levels of classical RAS metabolites, whereas AngIII might be an unrecognized mediator of detrimental effects on cardiovascular structure. The results underline the importance of pharmacologic interventions reducing circulating AngII actions, yet offer room for cardiac tissue-specific RAS drugs aiming to limit myocardial AngII/AngIII peptide accumulation and actions.

Renoprotective Effects of Small Interfering RNA Targeting Liver Angiotensinogen in Experimental Chronic Kidney Disease

[Figure: see text].

Influence of Antihypertensive Treatment on RAAS Peptides in Newly Diagnosed Hypertensive Patients

(1) Background: Recently, influences of antihypertensive treatment on the renin-angiotensin-aldosterone system (RAAS) has gained attention, regarding a possible influence on inflammatory and anti-inflammatory pathways. We aimed to study the effects of newly initiated antihypertensive drugs on angiotensin (Ang) II and Ang (1-7) as representers of two counter-regulatory axes. (2) Methods: In this randomized, open-label trial investigating RAAS peptides after the initiation of perindopril, olmesartan, amlodipine, or hydrochlorothiazide, Ang II and Ang (1-7) equilibrium concentrations were measured at 8 a.m. and 12 a.m. at baseline and after four weeks of treatment. Eighty patients were randomized (1:1:1:1 fashion). (3) Results: Between the four substances, we found significant differences regarding the concentrations of Ang II (p < 0.0005 for 8 a.m., 12 a.m.) and Ang (1-7) (p = 0.019 for 8 a.m., <0.0005 for 12 a.m.) four weeks after treatment start. Ang II was decreased by perindopril (p = 0.002), and increased by olmesartan (p < 0.0005), amlodipine (p = 0.012), and hydrochlorothiazide (p = 0.001). Ang (1-7) was increased by perindopril and olmesartan (p = 0.008/0.002), but not measurably altered by amlodipine and hydrochlorothiazide (p = 0.317/ 0.109). (4) Conclusion: The initiation of all first line antihypertensive treatments causes early and distinct alterations of equilibrium angiotensin levels. Given the additional AT1R blocking action of olmesartan, RAAS peptides shift upon initiation of perindopril and olmesartan appear to work in favor of the anti-inflammatory axis compared to amlodipine and hydrochlorothiazide.

No evidence for brain renin-angiotensin system activation during DOCA-salt hypertension

Brain renin-angiotensin system (RAS) activation is thought to mediate deoxycorticosterone acetate (DOCA)-salt hypertension, an animal model for human primary hyperaldosteronism. Here, we determined whether brainstem angiotensin II is generated from locally synthesized angiotensinogen and mediates DOCA-salt hypertension. To this end, chronic DOCA-salt-hypertensive rats were treated with liver-directed siRNA targeted to angiotensinogen, the angiotensin II type 1 receptor antagonist valsartan, or the mineralocorticoid receptor antagonist spironolactone (n = 6-8/group). We quantified circulating angiotensinogen and renin by enzyme-kinetic assay, tissue angiotensinogen by Western blotting, and angiotensin metabolites by LC-MS/MS. In rats without DOCA-salt, circulating angiotensin II was detected in all rats, whereas brainstem angiotensin II was detected in 5 out of 7 rats. DOCA-salt increased mean arterial pressure by 19 ± 1 mmHg and suppressed circulating renin and angiotensin II by >90%, while brainstem angiotensin II became undetectable in 5 out of 7 rats (<6 fmol/g). Gene silencing of liver angiotensinogen using siRNA lowered circulating angiotensinogen by 97 ± 0.3%, and made brainstem angiotensin II undetectable in all rats (P<0.05 vs. non-DOCA-salt), although brainstem angiotensinogen remained intact. As expected for this model, neither siRNA nor valsartan attenuated the hypertensive response to DOCA-salt, whereas spironolactone normalized blood pressure and restored brain angiotensin II together with circulating renin and angiotensin II. In conclusion, despite local synthesis of angiotensinogen in the brain, brain angiotensin II depended on circulating angiotensinogen. That DOCA-salt suppressed circulating and brain angiotensin II in parallel, while spironolactone simultaneously increased brain angiotensin II and lowered blood pressure, indicates that DOCA-salt hypertension is not mediated by brain RAS activation.

A novel SGLT-2 score to identify HFpEF patients who may benefit from SGLT-2 inhibitors

Background

Established heart failure (HF) treatments have shown no effects in HF and preserved ejection fraction (HFpEF). Subgroup analyses of the HFpEF populations suggest that certain patients benefit from HF treatments. This underlines the importance of individualized therapy regimens in HFpEF. Sodium-glucose transporter 2 (SGLT-2) inhibitors are emerging as a promising treatment of HF. The mechanisms leading to improved outcomes include 1) treatment of diabetes, 2) osmodiuresis preventing volume overload, 3) enhancement of the cardio protective Angiotensin (Ang) 1–7 pathway, instead of Ang II. We aimed to characterize patients by factors which are modified by SGLT-2 inhibitors to identify individuals who may benefit from these drugs.

Methods

HFpEF patients were included in a single center registry. Baseline evaluation included assessment of HbA1c, fluid status measured by body composition monitor and plasma angiotensin concentration. A “SGLT-2 score” with a maximum of 3 points was calculated using the following parameters: 1) HbA1c &gt;6.5%, 2) overhydration, defined as a fluid overload of &gt;1,5L and 3) plasma renin activity (PRA) levels above the median as a parameter of over-all RAS activity. Primary outcome was defined as all-cause death or HF hospitalization. All parameters used in the “SGLT-2 score” were independently predictive for the chosen endpoint. Kaplan Meier analyses was used to show the association between the score and outcomes.

Results

90 patients were included in this registry. Median HbA1c was 6.0%, median fluid status was 1.2L and the median Ang II levels in the “high PRA-group” were 5.35.1 pmol/L. After a mean follow up time of 44.0±38.7 months, 60 patients (66.6%) reached the endpoint. Kaplan Meier analysis showed an association between SGLT-2 score and outcome (p=0.003).

Conclusion

Patients with HbA1c &gt;6.5%, overhydration and high RAS activity have poor outcomes. We propose the future use of this score to identify a subgroup of HFpEF patients who may benefit from SGLT-2 inhibitors.

Kaplan Meier analysis

Funding Acknowledgement

Type of funding source: None

Role of angiotensin peptides in risk stratification and prognostication for heart failure: focus on plasma Ang 1–7/Ang II ratio

Background

ACE2 and Ang 1–7 are endogenous negative regulators of the renin-angiotensin system (RAS) exerting cardioprotective effects in models of heart failure (HF). Recombinant ACE2 markedly increased plasma Ang 1–7 and lowered Ang II levels in clinical trials. Elevated plasma ACE2 activity is associated with adverse outcomes in HF patients. However, the direct effects of systemic and tissue ACE2 activation on angiotensin peptides in relation to long-term HF outcomes has yet to be examined.

Purpose

To generate insights into the ACE2 mediated cardioprotective arm through the relative levels of its substrates and products using the plasma Ang 1–7/Ang II ratio, and assess its prognostic utility in HF patients.

Methods

110 HF patients were prospectively enrolled from outpatient clinics and the emergency department. Comprehensive circulating and equilibrium levels of plasma angiotensin peptides were assessed using novel liquid chromatography-mass spectrometry/mass spectroscopy techniques. Plasma aldosterone, BNP, active renin activity and clinical profiles were captured at baseline. Patients were stratified into above and below median cohorts based on equilibrium and circulating levels of Ang 1–7/Ang II ratio, as a surrogate for ACE2 functionality. During a median follow-up of 5.1±0.8 years, composite clinical outcomes were assessed through all-cause in-patient hospitalizations and mortality.

Results

Circulating and equilibrium angiotensin peptide levels strongly correlated in our patient cohort. All-cause mortality for HF patients with equilibrium Ang 1–7/Ang II ratios above the median showed higher survival rates compared to below median patients (76.4% vs. 50.9%; p=0.004); similar results were observed for circulating Ang 1–7/Ang II ratios (72.7% vs. 54.5%; p=0.041). Adjusting for covariates, elevated equilibrium (HR: 0.24; 95% CI: 0.09 to 0.69; p=0.008) and circulating (HR: 0.35; 95% CI: 0.13 to 0.94; p=0.036) Ang 1–7/Ang II ratios was associated with improved survival. Lower hospitalization duration was also associated with elevated equilibrium (p&lt;0.001) and circulating (p=0.023) Ang 1–7/Ang II ratios. In nested models, net reclassification analysis showed considerable improvement in risk prediction for all-cause mortality at 5 years provided by both the equilibrium (+45.0% [95% CI: 7.3% to 82.7%]) and circulating Ang 1–7/Ang II ratios (+24.3% [95% CI: 0.4% to 59.6%]) respectively.

Conclusions

We extensively profiled plasma angiotensin peptides in HF patients and identified elevated ACE2 signature, reflected through the Ang 1–7/Ang II ratio, as an independent and incremental predictor of beneficial outcomes, higher survival rate, and decreased hospitalization duration. These findings provide important clinical evidence supporting strategies aiming to promote the beneficial ACE2/Ang 1–7/Mas receptor axis concurrent with RAS blockade therapies inhibiting the detrimental ACE/Ang II/AT1 receptor axis.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Alberta Innovates, Canadian Institute of Health Research

Associations of central and peripheral blood pressure with the renin-angiotensin-aldosterone system in healthy young adults: the African-PREDICT study

This study investigated associations of brachial and central blood pressure (BP) with detailed renin-angiotensin-aldosterone system (RAAS) components in a healthy young population stratified according to ethnicity and sex. We included healthy black men (n = 285) and women (n = 304) and white men (n = 278) and women (n = 305) aged 20-30 years old. We derived central systolic BP (cSBP), measured clinic and 24-h systolic and diastolic BP. Aldosterone and equilibrium angiotensin levels were assessed and used for calculating angiotensin-derived markers for plasma renin activity (PRA-S, Angiotensin I + Angiotensin II), angiotensin-converting enzyme (ACE-S, Angiotensin II/Angiotensin I), and two markers for adrenal effects of angiotensin II, the aldosterone-to-renin ratio (ARR-S, Aldosterone/PRA-S) and the aldosterone-to-angiotensin II-ratio (AA2-R, Aldosterone/Angiotensin II)_. Young black men and women presented with lower RAAS components and higher cSBP compared to their white counterparts (all p ≤ 0.001). In multivariable-adjusted regression analyses, positive associations of cSBP with ARR-S and AA2-R and negative associations with PRA-S and angiotensin II were found for black women (all p ≤ 0.001); this pattern was also observed for 24-h and clinic BP (p ≤ 0.045). A similar trend of RAAS associations was present in black men but only for clinic BP (all p ≤ 0.047). In white men, negative associations between clinic SBP and PRA-S, angiotensin II and aldosterone were detected (all p ≤ 0.048). No associations were observed in white women. Positive associations of central and peripheral BP with the ratio of aldosterone to PRA-S and angiotensin II only in healthy, young black adults suggest that relative aldosterone excess may contribute to early hypertension development in this group.

Measurement of Equilibrium Angiotensin II in the Diagnosis of Primary Aldosteronism

BACKGROUND

Many medications (including most antihypertensives) and physiological factors affect the aldosterone/renin ratio (ARR) when screening for primary aldosteronism (PA). We sought to validate a novel equilibrium angiotensin II (eqAngII) assay and compare correlations between the aldosterone/angiotensin II ratio (AA2R) and the current ARR under conditions affecting the renin-angiotensin system.

METHODS

Among 78 patients recruited, PA was excluded in 22 and confirmed in 56 by fludrocortisone suppression testing (FST). Peripheral levels of eqAngII, plasma renin activity (PRA) and direct renin concentration (DRC) were measured.

RESULTS

EqAngII showed good consistency with DRC and PRA independent of PA diagnosis, posture, and fludrocortisone administration. EqAngII showed close (P < 0.01) correlations with DRC (r = 0.691) and PRA (r = 0.754) during FST. DRC and PRA were below their assays' functional sensitivity in 43.9% and 15.1%, respectively, of the total 312 samples compared with only 7.4% for eqAngII (P < 0.01). Bland-Altman analysis revealed an overestimation of PRA and DRC compared with eqAngII in a subset of samples with low renin levels. The AA2R showed not only consistent changes with the ARR but also close (P < 0.01) correlations with the ARR, whether renin was measured by DRC (r = 0.878) or PRA (r = 0.880).

CONCLUSIONS

Dynamic changes of eqAngII and the AA2R show good consistency and close correlations with renin and the ARR. The eqAngII assay shows better sensitivity than DRC and PRA assays, especially at low concentrations. Whether the AA2R can reduce the impact of some factors that influence the diagnostic power of the ARR warrants further study.

Elevated Angiotensin 1-7/Angiotensin II Ratio Predicts Favorable Outcomes in Patients With Heart Failure

BACKGROUND

ACE2 (angiotensin-converting enzyme 2) and Ang 1-7 (angiotensin 1-7) are endogenous negative regulators of the renin-angiotensin system exerting cardioprotective effects in models of heart failure. Recombinant human ACE2 markedly increased plasma Ang 1-7 and lowered Ang II levels in phase II clinical trials. We hypothesize that the dynamic state of this renin-angiotensin system protective arm could influence long-term outcomes in patients with heart failure.

METHODS

One hundred ten patients with heart failure were prospectively enrolled from our outpatient clinic and the emergency department. Comprehensive circulating and equilibrium levels of plasma angiotensin peptide profiles were assessed using novel liquid chromatography-mass spectrometry/mass spectroscopy techniques. Plasma aldosterone, B-type natriuretic peptide, active renin concentration, and clinical profiles were captured at baseline. During a median follow-up of 5.1 years (interquartile range, 4.7-5.7 years), composite clinical outcomes were assessed using all-cause in-patient hospitalizations and mortality.

RESULTS

Circulating and equilibrium angiotensin peptide levels strongly correlated in our patient cohort. Adjusting for covariates, elevated equilibrium (hazard ratio, 0.38 [95% CI, 0.18-0.81] P=0.012), and circulating (hazard ratio, 0.38 [95% CI, 0.18-0.80] P=0.011) Ang 1-7/Ang II ratios were associated with improved survival. Lower hospitalization duration was also associated with elevated equilibrium (P<0.001) and circulating (P=0.023) Ang 1-7/Ang II ratios. Importantly, individual Ang 1-7 and Ang II peptide levels failed to predict all-cause mortality or hospitalization duration in our patient cohort.

CONCLUSIONS

We extensively profiled plasma angiotensin peptides in patients with heart failure and identified elevated Ang 1-7/Ang II ratio, as an independent and incremental predictor of beneficial outcomes, higher survival rate, and decreased hospitalization duration. These findings provide important clinical evidence supporting strategies aiming to promote the beneficial Ang 1-7/Mas axis concurrent with renin-angiotensin system blockade therapies inhibiting the detrimental Ang II/AT₁ receptor axis.

Dipeptidyl peptidase 3 modulates the renin-angiotensin system in mice

Dipeptidyl peptidase 3 (DPP3) is a zinc-dependent hydrolase involved in degrading oligopeptides with 4-12 amino acid residues. It has been associated with several pathophysiological processes, including blood pressure regulation, pain signaling, and cancer cell defense against oxidative stress. However, the physiological substrates and the cellular pathways that are potentially targeted by DPP3 to mediate these effects remain unknown. Here, we show that global DPP3 deficiency in mice (DPP3^-/-) affects the renin-angiotensin system (RAS). LC-MS-based profiling of circulating angiotensin peptides revealed elevated levels of angiotensin II, III, IV, and 1-5 in DPP3^-/- mice, whereas blood pressure, renin activity, and aldosterone levels remained unchanged. Activity assays using the purified enzyme confirmed that angiotensin peptides are substrates for DPP3. Aberrant angiotensin signaling was associated with substantially higher water intake and increased renal reactive oxygen species formation in the kidneys of DPP3^-/- mice. The metabolic changes and altered angiotensin levels observed in male DPP3^-/- mice were either absent or attenuated in female DPP3^-/- mice, indicating sex-specific differences. Taken together, our observations suggest that DPP3 regulates the RAS pathway and water homeostasis by degrading circulating angiotensin peptides.

Effects of Ramipril on the Aldosterone/Renin Ratio and the Aldosterone/Angiotensin II Ratio in Patients With Primary Aldosteronism

The aldosterone/renin ratio (ARR) is currently considered the most reliable approach for case detection of primary aldosteronism (PA). ACE (Angiotensin-converting enzyme) inhibitors are known to raise renin and lower aldosterone levels, thereby causing false-negative ARR results. Because ACE inhibitors lower angiotensin II levels, we hypothesized that the aldosterone/equilibrium angiotensin II (eqAngII) ratio (AA2R) would remain elevated in PA. Receiver operating characteristic curve analysis involving 60 patients with PA and 40 patients without PA revealed that the AA2R was not inferior to the ARR in screening for PA. When using liquid chromatography-tandem mass spectrometry to measure plasma aldosterone concentration, the predicted optimal AA2R cutoff for PA screening was 8.3 (pmol/L)/(pmol/L). We then compared the diagnostic performance of the AA2R with the ARR among 25 patients with PA administered ramipril (5 mg/day) for 2 weeks. Compared with basally, plasma levels of equilibrium angiotensin I (eqAngI) and direct renin concentration increased significantly (P<0.01 or P<0.05) after ramipril treatment, whereas eqAngII and ACE activity (eqAngII/eqAngI) decreased significantly (P<0.01). The changes of plasma renin activity and plasma aldosterone concentration in the current study were not significant. On day 14, 4 patients displayed false-negative results using ARR_direct renin concentration (plasma aldosterone concentration/direct renin concentration), 3 of whom also showed false-negative ARR_plasma renin activity (plasma aldosterone concentration/plasma renin activity). On day 15, 2 patients still demonstrated false-negative ARR_plasma renin activity, one of whom also showed a false-negative ARR_direct renin concentration. No false-negative AA2R results were observed on either day 14 or 15. In conclusion, compared with ARR which can be affected by ACE inhibitors causing false-negative screening results, the AA2R seems to be superior in detecting PA among subjects receiving ACE inhibitors.

IL (Interleukin)-1 Receptor Antagonist Increases Ang (Angiotensin [1–7]) and Decreases Blood Pressure in Obese Individuals

IL (Interleukin)-1 antagonism decreases blood pressure in obese individuals. The underlying mechanisms are unknown. Based on experimental data, we hypothesized an effect of IL-1 antagonism via modulation of the renin-angiotensin-aldosterone system. In this explorative study, we examined shorter- (2 days) and longer-term effects (4 weeks) of IL-1 antagonism (anakinra/Kineret) on renin-angiotensin system peptide profiles and on hemodynamic parameters assessed by noninvasive measurement in obese (body mass index ≥30 kg/m 2 ) individuals from 2 interventional trials (a prospective interventional trial [n=73] and a placebo controlled-double blinded interventional trial [n=67]). A total of 140 patients were included. Systolic blood pressure decreased after short-term (absolute difference −5.2 mm Hg [95% CI, −8.5 to −1.8]; P =0.0006) and after longer-term treatment with anakinra (absolute difference −3.9 mm Hg [95% CI, −7.59 to −0.21]; P =0.04), with no change in blood pressure in the placebo group. Upon IL-1 antagonism, equilibrium levels of Ang II (angiotensin II), Ang I, aldosterone, and renin remained unchanged. In contrast, Ang (1–7) peptide levels increased after 4 weeks (between-group difference 16.35 pmol/L [95% CI, 1.22–30.17], P =0.03), as well as the Ang (1–7)/Ang II ratio (between-group difference 0.42 [95% CI, 0.17–0.67], P =0.02) in comparison to placebo. Consistently, the stroke systemic vascular resistance index significantly decreased in the anakinra group (between-group difference of −62.65 dyn/sec per cm −5 per m 2 [95% CI, −116.94 to −18.36], P =0.008, consistent with a 25% decrease). IL-1 antagonism increased the vasodilatory Ang (1–7) peptide after 4 weeks of treatment in obese individuals, paralleled by a decrease in peripheral vascular resistance. These findings point to an IL-1 mediated blood pressure-lowering mechanism via modulation of Ang (1–7).

Registration—

URL: https://www.clinicaltrials.gov . Unique identifiers: NCT02227420 and NCT02672592.

Critical Role of Neprilysin in Kidney Angiotensin Metabolism

RATIONALE

Kidney homeostasis is critically determined by the coordinated activity of the renin-angiotensin system (RAS), including the balanced synthesis of its main effector peptides Ang (angiotensin) II and Ang (1-7). The condition of enzymatic overproduction of Ang II relative to Ang (1-7) is termed RAS dysregulation and leads to cellular signals, which promote hypertension and organ damage, and ultimately progressive kidney failure. ACE2 (angiotensin-converting enzyme 2) and NEP (neprilysin) induce the alternative, and potentially reno-protective axis by enhancing Ang (1-7) production. However, their individual contribution to baseline RAS balance and whether their activities change in chronic kidney disease (CKD) has not yet been elucidated.

OBJECTIVE

To examine whether NEP-mediated Ang (1-7) generation exceeds Ang II formation in the healthy kidney compared with diseased kidney.

METHODS AND RESULTS

In this exploratory study, we used liquid chromatography-tandem mass spectrometry to measure Ang II and Ang (1-7) synthesis rates of ACE, chymase and NEP, ACE2, PEP (prolyl-endopeptidase), PCP (prolyl-carboxypeptidase) in kidney biopsy homogenates in 11 healthy living kidney donors, and 12 patients with CKD. The spatial expression of RAS enzymes was determined by immunohistochemistry. Healthy kidneys showed higher NEP-mediated Ang (1-7) synthesis than Ang II formation, thus displaying a strong preference towards the reno-protective alternative RAS axis. In contrast, in CKD kidneys higher levels of Ang II were recorded, which originated from mast cell chymase activity.

CONCLUSIONS

Ang (1-7) is the dominant RAS peptide in healthy human kidneys with NEP rather than ACE2 being essential for its generation. Severe RAS dysregulation is present in CKD dictated by high chymase-mediated Ang II formation. Kidney RAS enzyme analysis might lead to novel therapeutic approaches for CKD.

SUN-LB98 RAAS Triple-A Analysis for the Screening of Primary Aldosteronism

Primary aldosteronism (PA) is recognized as the most frequent cause of secondary hypertension, and its screening is expected to become a routine evaluation in most patients with hypertension. The interference of antihypertensive therapies with the aldosterone-to-renin ratio (ARR) during screening process is a major confounder. Renin-Angiotensin-Aldosterone System Triple-A (RAAS Triple-A) testing is a novel mass-spectrometry based assay for quantification of Angiotensin I (Ang I), Angiotenisn II (Ang II) and Aldosterone in a single sample of serum by RAAS equilibrium analysis. Obtained hormone levels are used to calculate markers for plasma-renin-activity (PRA-S, Ang I + Ang II), plasma angiotensin-converting-enzyme activity (ACE-S, Ang II-to-Ang I ratio) and adrenal function (AA2-Ratio, Aldosterone-to-Ang II ratio), with the latter being useful to screen for PA in hypertension. We performed a comparative evaluation of the diagnostic performance of the AA2-Ratio and 5 renin-based diagnostic ratios, differing in methods to determine aldosterone levels and renin activity in a cohort of 110 patients with hypertension (33 patients with confirmed primary aldosteronism and 77 with essential hypertension). All ratios showed comparable areas under the curves ranging between 0.924 and 0.970 without significant differences between each other. The evaluation of the ACE-S revealed persistent drug intake in some patients as cause for suppressed renin-based diagnostic ratios, while the AA2-Ratio remained unaffected. The Youden index optimal cutoff value for the AA2-Ratio was 6.6 ([pmol/L]/[pmol/L]) with a sensitivity of 90% and a specificity of 93%, proving non-inferiority compared with the ARR while pointing to the potential for an interference-free application in patients under ACE inhibitor therapy. This study shows for the first time the accuracy and reliability of RAAS Triple-A analysis for the screening of primary aldosteronism that can be applied in clinical routine.

Renin-Angiotensin-Aldosterone System Triple-A Analysis for the Screening of Primary Aldosteronism

Primary aldosteronism is recognized as the most frequent cause of secondary hypertension, and its screening is expected to become a routine evaluation in most patients with hypertension. The interference of antihypertensive therapies with the aldosterone-to-renin ratio during screening process is a major confounder. Renin-angiotensin-aldosterone system Triple-A analysis is a novel liquid chromatography/tandem mass spectrometry diagnostic assay that allows simultaneous quantification of aldosterone, equilibrium Ang I (angiotensin I), and Equilibrium Ang II in a single sample of serum. We performed a comparative evaluation of the diagnostic performance of the aldosterone-to-Ang II ratio and 5 renin-based diagnostic ratios, differing in methods to determine aldosterone levels and renin activity in a cohort of 110 patients with hypertension (33 patients with confirmed primary aldosteronism and 77 with essential hypertension). All ratios showed comparable areas under the curves ranging between 0.924 and 0.970 without significant differences between each other. The evaluation of the Ang II-to-Ang I ratio revealed persistent drug intake in some patients as cause for suppressed renin-based diagnostic ratios, while aldosterone-to-Ang II ratio remained unaffected. The Youden index optimal cutoff value for the aldosterone-to-Ang II ratio was 6.6 ([pmol/L]/[pmol/L]) with a sensitivity of 90% and a specificity of 93%, proving noninferiority compared with the aldosterone-to-renin ratio while pointing to the potential for an interference-free application in patients under ACE (angiotensin-converting enzyme) inhibitor therapy. This study shows for the first time the accuracy and reliability of renin-angiotensin-aldosterone system triple-A analysis for the screening of primary aldosteronism that can be applied in clinical routine.

Aldosterone Stimulates Its Biosynthesis Via a Novel GPER-Mediated Mechanism

CONTEXT

The G protein-coupled estrogen receptor (GPER) mediates an aldosterone secretagogue effect of 17β-estradiol in human HAC15 adrenocortical cells after estrogen receptor β blockade. Because GPER mediates mineralocorticoid receptor-independent aldosterone effects in other cell types, we hypothesized that aldosterone could modulate its own synthesis via GPER activation.

METHODS

HAC15 cells were exposed to aldosterone in the presence or absence of canrenone, a mineralocorticoid receptor antagonist, and/or of the selective GPER antagonist G36. Aldosterone synthase (CYP11B2) mRNA and protein levels changes were the study end points. Similar experiments were repeated in strips obtained ex vivo from aldosterone-producing adenoma (APA) and in GPER-silenced HAC15 cells.

RESULTS

Aldosterone markedly increased CYP11B2 mRNA and protein expression (vs untreated samples, P < 0.001) in both models by acting via GPER, because these effects were abolished by G36 (P < 0.01) and not by canrenone. GPER-silencing (P < 0.01) abolished the aldosterone-induced increase of CYP11B2, thus proving that aldosterone acts via GPER to augment the step-limiting mitochondrial enzyme (CYP11B2) of its synthesis. Angiotensin II potentiated the GPER-mediated effect of aldosterone on CYP11B2. Coimmunoprecipitation studies provided evidence for GPER-angiotensin type-1 receptor heterodimerization.

CONCLUSION

We propose that this autocrine-paracrine mechanism could enhance aldosterone biosynthesis under conditions of immediate physiological need in which the renin-angiotensin-aldosterone system is stimulated as, for example, hypovolemia. Moreover, as APA overexpresses GPER this mechanism could contribute to the aldosterone excess that occurs in primary aldosteronism in a seemingly autonomous fashion from angiotensin II.

A primary aldosteronism-like phenotype identified with the aldosterone-to-angiotensin II ratio in black men: the SABPA study

INTRODUCTION

Black populations may be more likely to have primary aldosteronism (PA) due to adrenal hyperplasia or other forms of adrenal hyperactivity, with suppressed renin levels and high levels of aldosterone, which may contribute to the development of hypertension.

METHODS

This sub-study involved 35 black men matched for age, gender and race, and aged 20-65 years, living in the North West Province of South Africa. RAAS triple-A analysis was carried out with LC-MS/MS quantification. Blood pressure, electrocardiography and other variables were determined with known methods.

RESULTS

Hypertensive subjects with higher aldosterone levels showed an increased aldosterone-angiotensin II ratio (AA2 ratio) compared to the hypertensive subjects with low aldosterone levels (10.2 vs 3.0 pmol/l; p = 0.003). The serum potassium concentration was significantly lower in the high-aldosterone group and the serum sodium-potassium ratio was significantly higher compared to the low-aldosterone group (3.9 vs 4.5, p = 0.016, 34.8 vs 31.8, p = 0.032, respectively). Furthermore, aldosterone was positively associated with both left ventricular hypertrophy (Cornell product) (Spearman R = 0.560; p = 0.037) and kidney function [albumin-to-creatinine ratio (ACR) ] (Spearman R = 0.589, p = 0.021) in the hypertensive high-serum aldosterone group.

CONCLUSIONS

The AA2 ratio, a novel screening test that is currently being validated for PA case detection, was used to identify a PA-like phenotype in black men. Excess aldosterone was associated with endothelial dysfunction and left ventricular hypertrophy, independent of blood pressure.

Comparison between the effects of torsemide and furosemide on the renin-angiotensin-aldosterone system of normal dogs

INTRODUCTION/OBJECTIVES

We hypothesized that torsemide and furosemide, at approximately equipotent dosages (similar diuresis), would have comparable effects on the circulating renin-angiotensin-aldosterone system.

ANIMALS, MATERIALS AND METHODS

Six, healthy, middle-aged, male Beagles were randomized to receive torsemide (0.1 mg/kg PO q 12 h), furosemide (2.0 mg/kg PO q 12 h), or placebo for 10 days during three separate periods, separated by a 10-day washout period, in a crossover design. Blood was collected on days 1, 5, and 9 and 24-h urine collection ended on days 2, 6, and 10. After repeated measures analysis and Bonferonni correction, variables with an adjusted p<0.05 were investigated further, using Tukey's method.

RESULTS

Twenty-four-hour urine production differed significantly between the diuretics only on day 10, with torsemide causing a 38% greater diuresis than furosemide. There was, however, no significant difference in average 3-day diuresis. There were no significant differences between diuretics in the 24-h urinary excretion of sodium, chloride, or potassium, though furosemide caused less kaliuresis than torsemide. Serum renin, angiotensin II, and aldosterone and the urine aldosterone-to-creatinine ratio were significantly increased in the diuretic groups, as compared to placebo on days 5/6 and 9/10. There were no significant differences in these values between diuretics. Creatinine and blood urea nitrogen concentrations rose comparably in the diuretic groups, remaining within reference intervals in all dogs.

CONCLUSIONS

At approximately equipotent dosages (20:1), torsemide and furosemide produced comparable renin-angiotensin-aldosterone system activation. Torsemide's similar potassium excretion profile to furosemide decreases support for a hypothesized mineralocorticoid-receptor blocking capability.

P5448Enzymatic regulation of the myocardial tissue renin-angiotensin-system of the failing heart

Background

In heart failure with reduced ejection fraction (HFrEF) the renin-angiotensin-system (RAS) is dysregulated and serves as therapeutic target. Research has been focusing on plasma RAS. Information on tissue RAS is scarce although assumedly more crucial for myocardial function. Among known angiotensins, only AngII and AngIII are detectable in the failing heart. Plasma samples in HFrEF show high AngI and AngII levels with clearly distinguishable AngI/AngII ratios for different RAS-inhibitors. AngII and AngIII levels in the myocardium were comparable for different RAS-inhibitors, i.e. no RAS-blocker, ACE-inhibitor, ARB or angiotensin-receptor neprilysin-inhibitor (ARNI). Here we aimed to elucidate the metabolic regulation of tissue RAS enzymes for these four different modalities of RAS-inhibition.

Methods

Enzyme regulation and metabolic activities were investigated in myocardial samples of end-stage HFrEF patients undergoing heart transplantation with a mass-spectrometry based method. Concentrations of respective angiotensin metabolites AngI, AngII, Ang1–7, AngIII, Ang1–5 and AngIV (RAS-fingerprints) were investigated after adding AngI or AngII and incubation to display metabolic patterns of the main plasma angiotensins. Metabolic activities of distinct enzymes have been assessed for the no therapy and ACE-I subgroups. Patients were stratified according to background therapy with RAS-inhibitors.

Results

A total of 30 patients were included (n=6 without RAS-blockade, n=16 with ACE-I, n=6 with ARB, n=2 with ARNI). Median age was 55 (IQR 45–63) years, 87%were male. Etiology of HF was ischemic in 40%, median NT-proBNP levels were 3498pg/ml (IQR 1761–8400). Patterns for tissue RAS metabolism of AngI and AngII was visually similar for all groups, indicating comparable regulation of tissue RAS enzymes independent from therapy (Figure 1). The formation of AngII from AngI was mainly chymase dependent with conversion rates of 99.4 (IQR 77.0–254.1) (pg/μg protein)/h for ACE-I and 141.8 (IQR 67.9–369.2) (pg/μg protein)/h for no RAS-blockade, whereas ACE-related generation of AngII was under the detection limit. The formation of Ang1–7 from AngI was mediated by NEP and PEP. The contribution of NEP was significantly higher [5022 (IQR 5002–5286) (pg/μg)/h vs 3555 (IQR 3351–3849) (pg/μg)/h, p=0.005 for the ACE-I group and 4729 (IQR 4438–6135) (pg/μg)/h vs 3601 (IQR 3052–4182) (pg/μg)/h, p=0.012 for no RAS-blockade]. No differences in tissue enzymatic activities between ACE-I and no therapy, as already indicated by the metabolization patterns occurred.

Figure 1

Conclusions

Enzymatic tissue RAS regulation in end-stage HF seems to be independent from the mode of established RAS-inhibitor therapy.In contrast to plasma, AngII formation of the tissue is mainly chymase dependent, whereas ACE seems to play an unsignificant role. NEP has a substantial role in generating beneficial Ang1–7 from AngI. The impact of NEP inhibition by ARNI on tissue RAS and mechanism of action have to be further investigated.

P1661The myocardial tissue Renin-Angiotensin-System (RAS) of the failing heart

Background

Prognosis of patients with HFrEF remains poor despite recent advances in pharmacologic therapy as the introduction of the angiotensin-receptor neprilysin-inhibitor (ARNI). The Renin-Angiotensin-System (RAS) is dysregulated in HF with elevated AngII levels as a central driver of disease progression. The myocardium is capable of synthesizing all RAS components resulting in tissue specific angiotensin levels. Neprilysin (NEP) catalyzes the generation of Ang1–7 which counteracts the deleterious effects of AngII. Myocardial tissue angiotensins of the failing heart and the role of long-lasting RAS-inhibitor therapy and particularly NEP inhibition on tissue RAS have not been investigated yet.

Methods

Concentrations of AngI, AngII, Ang1–7, AngIII, Ang1–5 and AngIV (RAS-fingerprints) were investigated in myocardial samples of end-stage HFrEF patients undergoing heart transplantation with a mass-spectrometry based method. Patients were stratified according to background therapy with RAS-inhibitors and variables were compared by a non-parametrical test.

Results

A total of 30 patients were included (n=6 without RAS-blockade, n=16 with ACE-I, n=6 with ARB and n=2 with ARNI). Median age was 55 (IQR 45–63) years and 87% of patients were male. 40% of patients had an ischemic etiology of HF, median NT-proBNP levels were 3498pg/ml (IQR 1761–8400). Tissue RAS patterns were visually similar between all groups (Figure 1). Myocardial AngI, Ang1–7, Ang1–5 and AngIV levels were below the detection limit for all samples. Median tissue AngII and AngIII concentrations across all samples were 83.1pg/ml (IQR 29.3–196.6) and 26.4pg/ml (IQR 5.0–64.5). Despite different background RAS-inhibitor therapy, AngII and AngIII levels were comparable between all groups [median (IQR) in pg/ml – AngII: 51.5 (41.5–123.8) vs. 72.4 (28.5–177.6) vs. 176.1 (22.4–286.8) vs. 266.0 (108.2–423.8); p=ns and 26.4 (5.0–89.2) vs. 23.2 (5.0–59.3) vs. 39.4 (5.0–94.3) vs. 105.9 (46.5–165.3); p=ns for no therapy, ACE-I, ARB and ARNI respectively].

Figure 1. RAS-fingerprints of the failing heart according to RAS-inhibiton. Numbers in brackets indicate the specific angiotensin peptides. Side of spheres and numbers beside represent absolute concentrations of angiotensins (pg/ml, median value).

Conclusions

Although in the plasma of HFrEF patients only AngI and AngII are detectable at substantial concentrations, the predominant angiotensins of the failing heart are AngII and AngIII. AngII levels are high in the failing heart supporting the hypothesis that excess AngII is involved in disease progression. AngIII similarly increases cardiac sympathetic activity assumedly potentiating further deteoriation. The modality of long established RAS-inhibitor therapy in end-stage HF, particularly the inhibition of NEP, seems to have no (more) influence on myocardial tissue RAS regulation. The impact of NEP inhibition by ARNI on tissue RAS enzymes and mechanism of action need to be further investigated.

Novel Therapeutic Approaches Targeting the Renin-Angiotensin System and Associated Peptides in Hypertension and Heart Failure

Despite the success of renin-angiotensin system (RAS) blockade by angiotensin-converting enzyme (ACE) inhibitors and angiotensin II type 1 receptor (AT1R) blockers, current therapies for hypertension and related cardiovascular diseases are still inadequate. Identification of additional components of the RAS and associated vasoactive pathways, as well as new structural and functional insights into established targets, have led to novel therapeutic approaches with the potential to provide improved cardiovascular protection and better blood pressure control and/or reduced adverse side effects. The simultaneous modulation of several neurohumoral mediators in key interconnected blood pressure-regulating pathways has been an attractive approach to improve treatment efficacy, and several novel approaches involve combination therapy or dual-acting agents. In addition, increased understanding of the complexity of the RAS has led to novel approaches aimed at upregulating the ACE2/angiotensin-(1-7)/Mas axis to counter-regulate the harmful effects of the ACE/angiotensin II/angiotensin III/AT1R axis. These advances have opened new avenues for the development of novel drugs targeting the RAS to better treat hypertension and heart failure. Here we focus on new therapies in preclinical and early clinical stages of development, including novel small molecule inhibitors and receptor agonists/antagonists, less conventional strategies such as gene therapy to suppress angiotensinogen at the RNA level, recombinant ACE2 protein, and novel bispecific designer peptides.

Abstract P2030: DOCA-Salt Diminishes Brain RAS Activity In Parallel With Plasma And Renal RAS Activity - No Evidence For Selective Brain RAS Activation

Deoxycorticosterone acetate (DOCA)-salt is suggested to increase blood pressure via selective upregulation of the brain renin-angiotensin system (RAS), while suppressing the circulating RAS. Yet, we have observed parallel downregulation of plasma and brain renin in mice. Here, we quantified brainstem angiotensinogen (AGT) and angiotensin (Ang) levels in rats exposed to DOCA (200mg; 60-day release) and 0.9% NaCl as drinking water for 7 weeks. To determine the contribution of AGT (liver vs. kidney/brain), Ang II type 1 receptors (AT1R) and blood pressure to tissue Ang II content, rats received vehicle, liver-targeted AGT siRNA (10 mg/kg fortnightly; s.c.), valsartan (31 mg/kg/day; s.c.) or spironolactone (80 mg/kg/day; s.c.) during the final 3 weeks, the latter fully normalizing blood pressure (n=3-9 per group). Plasma renin and AGT were determined by enzyme-kinetic assay, tissue AGT by western blotting, and Ang I and II by LC-MS/MS. Plasma renin, AGT, Ang I and II in rats not exposed to DOCA-salt were 24±8ng Ang I/mL per h, 731±51nM, 123±38pM and 109±43pM. AGT was present in liver, kidney and brainstem. Kidney Ang I and II were 540±135and 510±97fmol/g, while brainstem Ang I and II were undetectable in all and 50% of the rats, respectively (<6 and <12±4 fmol/g). DOCA-salt lowered plasma and renal Ang I and II by ≈90%, while brainstem Ang II became undetectable in 70% of the rats. AGT siRNA reduced plasma AGT by 97±1%, with similar reductions in the liver and kidney, while brain AGT was unaltered. Neither valsartan nor spironolactone affected AGT at any site. Spironolactone increased plasma renin, and hence plasma, renal and brain Ang I and II also rose modestly. Both siRNA and valsartan tended to further lower renal Ang levels, while neither drug affected plasma renin or Ang I and II in plasma and brain. In conclusion, DOCA-salt suppresses plasma, renal and brain Ang II in parallel. Renal Ang II is determined by hepatic AGT and relies on AT1R-mediated internalization. Although brain AGT is liver-independent, it is unaltered by DOCA-salt and does not permit selective brain RAS upregulation. The RAS upregulation induced by spironolactone, combined with its blood pressure-normalizing effect, argues against the (brain) RAS as a major blood pressure determinant in this model.

Abstract P2074: Improving Hypertension Control By Molecular Stratification Of First-Line Non-Responders Using RAAS Triple-A Testing

According to new European guidelines, first-line anti-hypertensive therapies include either an ACE inhibitor (ACEi) or an angiotensin receptor blocker (ARB) in a single pill combination with a calcium channel blocker (CCB) or a diuretic. Insufficient therapeutic effects could be caused by various factors ranging from compliance issues, patient specific PK/PD profiles, or secondary forms of hypertension resulting in blood pressure control rates in the range of 50% of patients on therapy. RAAS Triple-A testing is based on a high-throughput mass-spectrometry assay for quantification of Angiotensin I (Ang I), Angiotenisn II (Ang II) and Aldosterone in standard serum or plasma samples by RAAS equilibrium analysis. Obtained hormone levels are used to calculate markers for plasma-renin-activity (PRA-S), plasma angiotensin-converting-enzyme activity (ACE-S) and adrenal function (AA2-Ratio). The diagnostic performance of the AA2-Ratio in screening for primary aldosteronism (PA) has been compared to the aldosterone-to-renin ratio (ARR) as putative gold standard in resistant hypertensive patients, revealing major advantages of the AA2-Ratio especially in terms of usability and drug interference. A diagnostic scheme for the stratification of first-line non-responding hypertensive patients has been developed to improve the control rates for hypertension and to provide an easy-to-handle diagnostic tool for physicians involved in first-line treatment of hypertension. RAAS Triple-A analysis for the first time provides insights into a patient’s RAAS at the level of effector hormones, molecular regulation and patient specific pharmacologic responses to anti-hypertensive therapies and has the potential to result in significant changes in hypertension care in clinical practice by introducing personalized treatments based on an easy and effective diagnostic tool.

Abstract P3059: ACE S: A NOVEL ANGIOTENSIN BASED MARKER FOR MONITORING PHARMACOLOGIC ACTIVITY OF ACE INHIBITORS IN HYPERTENSIVE PATIENTS

Angiotensin-converting-enzyme-inhibitors (ACEi) are widely used for treating hypertension and cardiovascular diseases and block Angiotensin-II (Ang-II) formation from Angiotensin-I (Ang-I). The therapeutic response to ACE inhibition critically depends on in vivo pharmacologic efficacy and affected by dosing, patient compliance and patient specific compensatory mechanisms, all being relevant topics for the clinical management of hypertension.

Samples were collected from 19 hypertensive patients and 7 confirmed primary aldosteronism (PA) patients. Hypertensive patients were investigated at baseline and after 4 weeks on therapy with a single daily dose of perindopril. PA patients were sampled before and after 14 day administration of ramipril. All samples were analysed by LC-MS/MS based RAAS Triple-A testing which involves the calculation of ACE-S, the ratio between plasma equilibrium levels of Ang-II and Ang-I as a novel marker for circulating ACE activity. ACE activity was further measured by analyzing the time dependent conversion of spiked Ang-I (LC-MS/MS) and by performing a clinical colorimetric ACE assay. Treatment adherence was confirmed by quantification of plasma drug levels.

ACE-S was significantly lower in all patients on perindopril or ramipril therapy compared to baseline (MEDIANS: 0.35 vs. 2.75 pM/pM, p<0.001). While eqAng-II levels were increased up to 5-fold compared to baseline levels in a subset of patients due to renin up-regulation, ACE-S stayed significantly suppressed in all samples investigated. In contrast, ACE inhibition appeared to be less effective using classical enzymatic approaches assessing ACE activity.

The novel angiotensin based marker ACE-S can be used to monitor pharmacologic efficacy of ACE inhibitors independent of their chemical structure. As part of the RAAS Triple-A test that is currently validated in screening for secondary forms of hypertension, ACE-S has the potential to support the clinical management of first-line non-responders in terms of optimizing ACEi dosing and visualizing patient specific compensatory mechanisms, thereby improving the overall control rates in hypertension.