Low- and High-renin Heart Failure Phenotypes with Clinical Implications

Excess renin is attributed to the combination of forward and backward failure in HFrEF

AIMS

Regulation of the renin-angiotensin system (RAS) in heart failure (HF) with reduced ejection fraction (HFrEF) still raises questions, as a large proportion of patients show normal renin levels despite manifest disease. Experimental venous congestion results in reduced renal perfusion pressure and stimulates renin secretion. We hypothesized that excess renin levels are mainly a result of right ventricular failure as a sequalae of left ventricular dysfunction. The study aimed to link right ventricular function (RVF) with renin levels and to investigate further contributors to excess RAS activation.

METHODS AND RESULTS

Three hundred thirty-two chronic HFrEF patients undergoing routine ambulatory care were consecutively enrolled in a prospective, registry-based, observational study. Laboratory parameters, including cardiac-specific markers renin, aldosterone, and N-terminal pro-brain natriuretic peptide (NT-proBNP), echocardiographic examination (n = 247), and right heart catheterization (n = 85), were documented. The relationship between renin and its respective parameters was analysed. Renin concentration was not associated with the New York Heart Association class or NT-proBNP. Systolic blood pressure, systemic vascular resistance, serum sodium, aldosterone, and lactate dehydrogenase were associated with increased renin levels (P < 0.035 for all). Renin levels similarly increased with worsening of RVF parameters such as fractional area change, tricuspid annular plane systolic excursion, tissue Doppler imaging, and inferior vena cava diameter (P < 0.011 for all), but not with pulmonary pressure. Excess renin levels were observed when worsening RVF was combined with reduced renal perfusion {625 μIU/mL [interquartile range (IQR): 182-1761] vs. 67 μIU/mL [IQR: 16-231], P < 0.001}, which was associated with worse survival.

CONCLUSIONS

While unrelated to classical indices of HF severity, circulating renin levels increase with the worsening of RVF, especially in the combined presence of forward and backward failure. This might explain normal renin levels in HFrEF patients but also excess renin levels in poor haemodynamic conditions.

Effect of sacubitril/valsartan on the hypertensive heart in continuous light-induced and lactacystin-induced pre-hypertension: Interactions with the renin-angiotensin-aldosterone system

This study investigated whether sacubitril/valsartan or valsartan are able to prevent left ventricular (LV) fibrotic remodelling and dysfunction in two experimental models of pre-hypertension induced by continuous light (24 hours/day) exposure or by chronic lactacystin treatment, and how this potential protection interferes with the renin-angiotensin-aldosterone system (RAAS). Nine groups of three-month-old male Wistar rats were treated for six weeks as follows: untreated controls (C), sacubitril/valsartan (ARNI), valsartan (Val), continuous light (24), continuous light plus sacubitril/valsartan (24+ARNI) or valsartan (24+Val), lactacystin (Lact), lactacystin plus sacubitil/valsartan (Lact+ARNI) or plus valsartan (Lact+Val). Both the 24 and Lact groups developed a mild but significant systolic blood pressure (SBP) increase, LV hypertrophy and fibrosis, as well as LV systolic and diastolic dysfunction. Yet, no changes in serum renin-angiotensin were observed either in the 24 or Lact groups, though aldosterone was increased in the Lact group compared to the controls. In both models, sacubitril/valsartan and valsartan reduced elevated SBP, LV hypertrophy and fibrosis and attenuated LV systolic and diastolic dysfunction. Sacubitril/valsartan and valsartan increased the serum levels of angiotensin (Ang) II, Ang III, Ang IV, Ang 1-5, Ang 1-7 in the 24 and Lact groups and reduced aldosterone in the Lact group. We conclude that both continuous light exposure and lactacystin treatment induced normal-to-low serum renin-angiotensin models of pre-hypertension, whereas aldosterone was increased in lactacystin-induced pre-hypertension. The protection by ARNI or valsartan in the hypertensive heart in either model was related to the Ang II blockade and the protective Ang 1-7, while in lactacystin-induced pre-hypertension this protection seems to be additionally related to the reduced aldosterone level.

Effect of amlodipine on the circulating renin-angiotensin-aldosterone system in healthy cats

BACKGROUND

Systemic hypertension (SH) is a common cardiovascular disease in older cats that is treated primarily with the calcium channel blocker amlodipine besylate (AML). The systemic effect of AML on the classical and alterative arms of the renin-angiotensin-aldosterone system (RAAS) in cats is incompletely characterized.

HYPOTHESIS/OBJECTIVES

To determine the effect of AML compared to placebo on circulating RAAS biomarkers in healthy cats using RAAS fingerprinting.

ANIMALS

Twenty healthy client-owned cats.

METHODS

Cats were administered amlodipine besylate (0.625 mg in toto) or placebo by mouth once daily for 14 days in a crossover design with a 4-week washout period. Plasma AML concentrations and RAAS biomarker concentrations were measured at multiple timepoints after the final dose in each treatment period. Time-weighted averages for RAAS biomarkers over 24 hours after dosing were compared between treatment groups using Wilcoxon rank-sum testing.

RESULTS

Compared to placebo, AML treatment was associated with increases in markers of plasma renin concentration (median 44% increase; interquartile range [IQR] 19%-86%; P = .009), angiotensin I (59% increase; IQR 27-101%; P = .006), angiotensin II (56% increase; IQR 5-70%; P = .023), angiotensin IV (42% increase; -19% to 89%; P = .013); and angiotensin 1-7 (38% increase; IQR 9-118%; P = .015).

CONCLUSIONS AND CLINICAL IMPORTANCE

In healthy cats, administration of AML resulted in nonspecific activation of both classical and alternative RAAS pathways.

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.

Evaluation of Renin-Angiotensin-Aldosterone System Components and Enzymes in Systemically Hypertensive Cats Receiving Amlodipine

BACKGROUND

Chronic renin-angiotensin-aldosterone system (RAAS) activation is harmful. Amlodipine activates RAAS in humans and dogs, but contradictory data exist for systemically hypertensive (SHT) cats.

HYPOTHESIS

Cats with SHT and chronic kidney disease treated with amlodipine (SHT/CKD-A) are RAAS activated.

ANIMALS

Client-owned cats: unmedicated normotensive (NT) cats (n = 9); SHT/CKD-A cats (n = 5) with median systolic blood pressure of 170 mmHg (vs. 195 mmHg, pre-treatment), chronic kidney disease, and receiving no RAAS-suppressive therapy.

METHODS

Serum was frozen (-80 °C) until RAAS analysis via equilibrium analysis. The RAAS variables (reported as median (minimum-maximum)) were compared between groups, using Mann-Whitney U test.

RESULTS

Angiotensin 1, angiotensin 1,7, angiotensin III, and angiotensin 1,5, and angiotensin-converting enzyme (ACE)-2 activity were higher in SHT/CKD-A cats compared to NT cats, while ACE activity was lower in SHT/CKD-A cats compared to NT cats (p < 0.05 all). A marker for alternative RAAS influence (ALT-S) was significantly higher (69; 58-73 pmol/pmol) in SHT/CKD-A cats compared to NT cats (35; 14-63 pmol/pmol; p = 0.001). Aldosterone concentrations were significantly higher (393; 137-564 pmol/L) in SHT/CKD-A cats compared to NT cats (129; 28-206 pmol/L; p = 0.007).

CONCLUSION AND CLINICAL IMPORTANCE

Circulating RAAS is activated in systemically hypertensive cats receiving amlodipine. Although this study did not parse out the individual contributions of SHT, chronic kidney disease, and amlodipine, the findings suggest that the use of concurrent RAAS-suppressant therapy, specifically aldosterone antagonism, in amlodipine-treated SHT cats with chronic kidney disease might be indicated.

Beyond Angiotensin-Converting Enzyme Inhibitors: Modulation of the Renin-Angiotensin-Aldosterone System to Delay or Manage Congestive Heart Failure

The renin-angiotensin-aldosterone system (RAAS) consists of bioactive angiotensin peptides, enzymatic pathways, receptors, and the steroid hormone aldosterone. The RAAS regulates blood pressure, sodium, and electrolyte homeostasis and mediates pathologic disease processes. Within this system is an alternative arm that counterbalances the vasoconstrictive, sodium and water retentive, and pro-fibrotic and inflammatory effects of the classical arm. Improved biochemical methodologies in RAAS quantification are elucidating how this complex system changes in health and disease. Future treatments for cardiovascular and kidney disease will likely involve a more nuanced manipulation of this system rather than simple blockade.

Renin Trajectories and Outcome in Stable Heart Failure with Reduced Ejection Fraction (HFrEF) on Contemporary Therapy: A Monocentric Study from an Austrian Tertiary Hospital Outpatient Clinic

Introduction

The renin-angiotensin system (RAS) is the main target of neurohumoral therapy in heart failure with reduced ejection fraction (HFrEF) effectively reducing mortality. Reasonably, renin might serve as a biomarker for risk prediction and therapy response. Renin indeed bears some additional value to clinical risk models, albeit the effect is not pronounced. Whether assessing renin trajectories can overcome the weaknesses of single renin measurements has not been reported.

Methods

A total of 505 patients with stable HFrEF were enrolled prospectively and followed through routine clinical visits. Active plasma renin concentration was documented up to 5 years. Changes in renin were analyzed throughout the disease course, and survival was compared for different renin trajectories within the first year.

Results

Baseline renin levels were not related to all-cause mortality (crude HR for an increase of 100 μiE/ml: 1.01 (95% CI: 0.99-1.02), p = 0.414) but associated with unplanned HF hospitalizations (crude HR: 1.01 (95% CI: 1.00-1.02), p = 0.015). Renin increased during the disease course from baseline to 1-year and 2-year FUP (122.7 vs. 185.6 μIU/ml, p = 0.039, and 122.7 vs. 258.5 μIU/ml, p = 0.001). Both survival and unplanned HF hospitalization rates were comparable for different renin trajectories at 1-year FUP (p = 0.546, p = 0.357).

Conclusions

Intriguingly, renin is not a good biomarker to indicate prognosis in HF, while renin trajectories over a 1-year period do not have an additional value. Rapid physiologic plasma renin variations, but also opposing effects of angiotensinogen-derived metabolites under presence of RAS blockade, might obscure the predictive ability of renin.

Dysregulation of intestinal epithelial electrolyte transport in canine chronic inflammatory enteropathy and the role of the renin-angiotensin-aldosterone-system

Chronic diarrhea is a hallmark sign of canine chronic inflammatory enteropathy (CIE), leading to fluid and electrolyte losses. Electrolyte homeostasis is regulated by the renin-angiotensin-aldosterone-system (RAAS), which might be involved in (counter-)regulating electrolyte losses in canine CIE. Whether and which electrolyte transporters are affected or if RAAS is activated in canine CIE is unknown. Thus, intestinal electrolyte transporters and components of the RAAS were investigated in dogs with CIE. Serum RAAS fingerprint analysis by mass spectrometry was performed in 5 CIE dogs and 5 healthy controls, and mRNA levels of intestinal electrolyte transporters and local RAAS pathway components were quantified by RT-qPCR in tissue biopsies from the ileum (7 CIE, 10 controls) and colon (6 CIE, 12 controls). Concentrations of RAAS components and mRNA expression of electrolyte transporters were compared between both groups of dogs and were tested for associations among each other. In dogs with CIE, associations with clinical variables were also tested. Components of traditional and alternative RAAS pathways were higher in dogs with CIE than in healthy controls, with statistical significance for Ang I, Ang II, and Ang 1-7 (all p < 0.05). Expression of ileal, but not colonic electrolyte transporters, such as Na+/K+-ATPase, Na+/H+-exchanger 3, Cl- channel 2, down-regulated in adenoma, and Na+-glucose-cotransporter (all p < 0.05) was increased in CIE. Our results suggest that the dys- or counter-regulation of intestinal electrolyte transporters in canine CIE might be associated with a local influence of RAAS. Activating colonic absorptive reserve capacities may be a promising therapeutic target in canine CIE.

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.

The effect of taurine supplementation on the renin-angiotensin-aldosterone system of dogs with congestive heart failure

The role of taurine in the treatment of congestive heart failure (CHF) in dogs without systemic deficiency is unexplored. Taurine might have beneficial cardiac effects aside from deficit replacement. We hypothesized that oral taurine supplementation administered to dogs with naturally-occurring CHF would suppress the renin-angiotensin aldosterone system (RAAS). Oral taurine was administered to 14 dogs with stable CHF. Serum biochemical variables, blood taurine concentrations, and comprehensive analysis of RAAS variables were compared before and 2 weeks after taurine supplementation added to background furosemide and pimobendan therapy for CHF. Whole blood taurine concentrations increased after supplementation (median 408 nMol/mL, range 248-608 before and median 493 nMol/mL, range 396-690 after; P = .006). Aldosterone to angiotensin II ratio (AA2) was significantly decreased after taurine supplementation (median 1.00, range 0.03-7.05 before and median 0.65, range 0.01-3.63 after; P = .009), but no other RAAS components significantly differed between timepoints. A subset of dogs showed marked decreases in RAAS metabolites after supplementation and these dogs were more likely to have been recently hospitalized for CHF treatment than dogs that did not show marked decreases in classical RAAS metabolites. Overall, taurine only lowered AA2 in this group of dogs, however, response heterogeneity was noted, with some dogs showing RAAS suppression.

Dose-response of benazepril on biomarkers of the classical and alternative pathways of the renin-angiotensin-aldosterone system in dogs

Angiotensin-converting enzyme inhibitors (ACEI) such as benazepril are commonly prescribed in both humans and dogs with heart disease to mitigate the renin-angiotensin-aldosterone system (RAAS); however, the dose-dependent effects of benazepril on comprehensive RAAS components remain unknown. In this study, nine purpose-bred healthy dogs received three different dosages of oral benazepril (0.125 mg/kg, 0.25 mg/kg, or 0.5 mg/kg) in a randomized crossover design following induction of RAAS activation by consuming a low-sodium diet. Blood samples were collected at serial time intervals after benazepril dosing to measure plasma benazeprilat (active metabolite of benazepril) and serum RAAS biomarkers. Blood pressure and echocardiogram were performed at baseline and after each benazepril administration. Time-weighted averages for RAAS biomarkers for 12 h post-dose and hemodynamic variables were compared between dosing groups using Wilcoxon rank-sum testing. Compared to the lowest dosage of benazepril (0.125 mg/kg), the highest dosage (0.5 mg/kg) resulted in lower time-weighted average values of angiotensin (Ang) II (- 38%, P = 0.004), Ang1-5 (- 53%, P = 0.001), ACE-S (surrogate for ACE activity; - 59%, P = 0.0002), and ALT-S (surrogate for alternative RAAS activity; - 22%, P = 0.004), and higher values of AngI (+ 78%, P = 0.014) and PRA-S (surrogate for plasma renin activity; + 58%, P = 0.040). There were no relevant differences between dosing groups for blood pressure or echocardiographic variables. Knowledge of dose-dependent alterations in biomarkers of the classical and alternative RAAS pathways could help inform clinical trials for dosage optimization in both dogs and humans.

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.

The systemic renin-angiotensin system in COVID-19

SARS-CoV-2 gains cell entry via angiotensin-converting enzyme (ACE) 2, a membrane-bound enzyme of the "alternative" (alt) renin-angiotensin system (RAS). ACE2 counteracts angiotensin II by converting it to potentially protective angiotensin 1-7. Using mass spectrometry, we assessed key metabolites of the classical RAS (angiotensins I-II) and alt-RAS (angiotensins 1-7 and 1-5) pathways as well as ACE and ACE2 concentrations in 159 patients hospitalized with COVID-19, stratified by disease severity (severe, n = 76; non-severe: n = 83). Plasma renin activity (PRA-S) was calculated as the sum of RAS metabolites. We estimated ACE activity using the angiotensin II:I ratio (ACE-S) and estimated systemic alt-RAS activation using the ratio of alt-RAS axis metabolites to PRA-S (ALT-S). We applied mixed linear models to assess how PRA-S and ACE/ACE2 concentrations affected ALT-S, ACE-S, and angiotensins II and 1-7. Median angiotensin I and II levels were higher with severe versus non-severe COVID-19 (angiotensin I: 86 versus 30 pmol/L, p < 0.01; angiotensin II: 114 versus 58 pmol/L, p < 0.05), demonstrating activation of classical RAS. The difference disappeared with analysis limited to patients not taking a RAS inhibitor (angiotensin I: 40 versus 31 pmol/L, p = 0.251; angiotensin II: 76 versus 99 pmol/L, p = 0.833). ALT-S in severe COVID-19 increased with time (days 1-6: 0.12; days 11-16: 0.22) and correlated with ACE2 concentration (r = 0.831). ACE-S was lower in severe versus non-severe COVID-19 (1.6 versus 2.6; p < 0.001), but ACE concentrations were similar between groups and correlated weakly with ACE-S (r = 0.232). ACE2 and ACE-S trajectories in severe COVID-19, however, did not differ between survivors and non-survivors. Overall RAS alteration in severe COVID-19 resembled severity of disease-matched patients with influenza. In mixed linear models, renin activity most strongly predicted angiotensin II and 1-7 levels. ACE2 also predicted angiotensin 1-7 levels and ALT-S. No single factor or the combined model, however, could fully explain ACE-S. ACE2 and ACE-S trajectories in severe COVID-19 did not differ between survivors and non-survivors. In conclusion, angiotensin II was elevated in severe COVID-19 but was markedly influenced by RAS inhibitors and driven by overall RAS activation. ACE-S was significantly lower with severe COVID-19 and did not correlate with ACE concentrations. A shift to the alt-RAS axis because of increased ACE2 could partially explain the relative reduction in angiotensin II levels.

Influence of sex on renin-angiotensin-aldosterone system metabolites and enzymes in Doberman Pinschers

BACKGROUND

Estrogen modulates the renin-angiotensin-aldosterone system (RAAS) in women, but sex differences have not been fully explored in dogs.

OBJECTIVE

We hypothesized that the RAAS profile of intact female (IF) Doberman Pinschers (DP) would differ from spayed female (SF) and intact male (IM) DP.

ANIMALS

Eighteen healthy DP (6 IF, 6 SF, 6 IM).

METHODS

Absolute and indexed RAAS metabolites, angiotensin-converting enzyme (ACE) and ACE2 activities, and genotypes (pyruvate kinase dehydrogenase 4, titin, and ACE variants) were compared among sex groups using Kruskal-Wallis or chi-square tests, and linear regression controlling for age. Data are expressed as median (minimum, maximum) and P < .05 was considered significant.

RESULTS

The ACE activity was higher in IF DP (656 pmol/L; 436, 784) compared to SF DP (411 pmol/L; 287, 451; P = .01) and IM DP (365 pmol/L; 276, 1200; P = .04) after controlling for age. Angiotensin II, angiotensin I, and plasma renin activity marker (PRA-S) were higher in IF DP compared to SF DP, but not significantly (P ≤ .25). After controlling for age, angiotensin 1-7/angiotensin I was lower in IF DP compared to SF DP (P = .01). Genotypes did not differ among groups. Most DP (94%) were ACE variant positive.

CONCLUSIONS AND CLINICAL SIGNIFICANCE

Sex and reproductive status influenced the RAAS of DP, with IF DP showing genotype-independent higher ACE activity. These findings hold implications for sterilization practices in female dogs, and support sex and reproductive status as a source of variability in RAAS studies. Additionally, the frequency of the ACE gene variant was very high in this group of DP.

Sacubitril/Valsartan and Ivabradine Attenuate Left Ventricular Remodelling and Dysfunction in Spontaneously Hypertensive Rats: Different Interactions with the Renin–Angiotensin–Aldosterone System

This study investigated whether sacubitril/valsartan and ivabradine are able to prevent left ventricular (LV) fibrotic remodelling and dysfunction in a rat experimental model of spontaneous hypertension (spontaneously hypertensive rats, SHRs) and whether this potential protection is associated with RAAS alterations. Five groups of three-month-old male Wistar rats and SHRs were treated for six weeks as follows: untreated Wistar controls, Wistar plus sacubitril/valsartan, SHR, SHR plus sacubitril/valsartan, and SHR plus ivabradine. The SHRs developed a systolic blood pressure (SBP) increase, LV hypertrophy and fibrosis, and LV systolic and diastolic dysfunction. However, no changes in serum RAAS were observed in SHRs compared with the controls. Elevated SBP in SHRs was decreased by sacubitril/valsartan but not by ivabradine, and only sacubitril/valsartan attenuated LV hypertrophy. Both sacubitril/valsartan and ivabradine reduced LV collagen content and attenuated LV systolic and diastolic dysfunction. Sacubitril/valsartan increased the serum levels of angiotensin (Ang) II, Ang III, Ang IV, Ang 1-5, Ang 1-7, and aldosterone, while ivabradine did not affect the RAAS. We conclude that the SHR is a normal-to-low serum RAAS model of experimental hypertension. While the protection of the hypertensive heart in SHRs by sacubitril/valsartan may be related to an Ang II blockade and the protective Ang 1-7, the benefits of ivabradine were not associated with RAAS modulation.

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.

Circulating renin‐angiotensin‐aldosterone system activity in cats with systemic hypertension or cardiomyopathy

Background

Activity of the circulating renin‐angiotensin‐aldosterone system (RAAS) has not been comprehensively characterized in cats with systemic hypertension (SH) or cardiomyopathy (CM), and the effects of furosemide or amlodipine treatment on the RAAS have not been fully evaluated in cats.

Hypothesis/Objectives

To document RAAS activity in cats with SH or CM compared to healthy cats and determine how RAAS profiles change with furosemide or amlodipine treatment.

Animals

Sixty‐six client‐owned cats: 15 with SH (7 amlodipine‐treated, 8 untreated), 17 with advanced CM (7 furosemide‐treated, 10 not furosemide‐treated), and 34 healthy cats.

Methods

Equilibrium concentrations of RAAS peptides and aldosterone were quantified in serum samples by liquid chromatography‐mass spectrometry. Variables were compared between groups using Kruskal‐Wallis analysis with post hoc Holms‐corrected Dunn's testing.

Results

Compared with healthy cats, cats with CM had higher concentrations of angiotensin I, aldosterone, and plasma renin activity (all P < .01), and these differences remained significant (P < .03) after considering subgroups of untreated or furosemide‐treated cats. Compared with healthy cats, untreated cats with SH showed no differences in RAAS biomarkers, whereas amlodipine‐treated cats had higher concentrations of angiotensins I, II, III, IV, and 1‐7, aldosterone, and plasma renin activity (all P < .03). Multivariable analysis determined that furosemide and amlodipine treatments were independent predictors of increased RAAS biomarker concentrations.

Conclusions and Clinical Importance

Cats with CM had increased RAAS activity, whereas cats with untreated SH did not. Furosemide and amlodipine both led to nonspecific activation of both classical and alternative RAAS pathways in cats.

Changes in renin-angiotensin-aldosterone system during cardiac remodeling after mitral valvuloplasty in dogs

BACKGROUND

Information regarding changes in renin-angiotensin-aldosterone system (RAAS) during cardiac remodeling after mitral valvuloplasty (MVP) in dogs remains lacking.

HYPOTHESIS/OBJECTIVES

To assess the longitudinal effects of MVP on circulating RAAS activity.

ANIMALS

Eight client-owned dogs receiving MVP for myxomatous mitral valve disease (MMVD).

METHODS

This is a cohort study. Plasma renin activity (PRA), angiotensin II (AT2), aldosterone (PAC), blood urea nitrogen (BUN), and creatinine concentrations, were measured in these dogs before (baseline) and at 3 consecutive monthly follow-ups (Post-1M, Post-2M, Post-3M). Echocardiography was concomitantly used to assess the process of cardiac recovery after MVP.

RESULTS

The echocardiography revealed a significant decrease in LVIDDN, LA/Ao, FS, E velocity, E/A, E' sep, S' lat, E' lat, and A' lat after MVP compared with baseline (P < .05). There was a significant reduction in the PRA (2.45, 3.05, 2.74 vs 8.8 ng/mL/h; P = .002), AT2 (466, 315, 235 vs 1200 pg/mL; P = .009), and PAC (39.88, 47, 54.62 vs 179.5 pg/mL; P = .01), respectively at Post-1M, Post-2M, Post-3M compared to the baseline. Additionally, BUN and creatinine concentrations decreased from Post-1M. The RAAS variables showed significant, weak to moderate, relationship with selected echocardiographic variables.

CONCLUSIONS AND CLINICAL IMPORTANCE

Mitral valvuloplasty contributes to decreased RAAS activity in MMVD dogs, which paralleled the process of cardiac reverse remodeling up to Post-3M. This information facilitates formulating strategies to optimize clinical outcomes for dogs after MVP.

Suspected primary hyperreninism in a cat with malignant renal sarcoma and global renin-angiotensin-aldosterone system upregulation

A 14-year-old male castrated domestic medium-hair cat with diabetes mellitus was evaluated for vomiting, diarrhea, and anorexia. Two weeks before presentation, the cat had been diagnosed with congestive heart failure and started on furosemide. Initial diagnostic testing identified hypokalemia, systemic hypertension, and hypertrophic cardiomyopathy phenotype, and plasma aldosterone concentration was moderately increased. Abdominal ultrasound examination disclosed bilateral adrenomegaly and a right renal mass, and cytology of a needle aspirate of the mass was consistent with malignant neoplasia. The cat was treated with amlodipine and spironolactone. Because of the unusual presentation for hyperaldosteronism, a comprehensive profile of renin-angiotensin-aldosterone system (RAAS) peptides was performed. Results from multiple timepoints indicated persistently and markedly increased plasma renin activity and generalized RAAS upregulation. In addition to the lack of adrenal tumor, the markedly increased plasma renin activity was atypical for primary hyperaldosteronism. These clinical findings are suggestive of primary hyperreninism, a condition previously unreported in cats. The concurrent presence of a renal neoplasm suggests the possibility of a renin-secreting tumor.

Amplifying effect of chronic lisinopril therapy on diastolic function and the angiotensin-(1-7) Axis by the G1 agonist in ovariectomized spontaneously hypertensive rats

G protein-coupled estrogen receptor (GPER) activation by G1 attenuates diastolic dysfunction from estrogen loss, which may be partly due to suppression of angiotensin II pathological actions. We aimed to determine the independent effects of 8 weeks of G1 (100 µg/kg/d, subcutaneous pellet), ACE-inhibition (ACEi; lisinopril 10 mg/kg, drinking water), or combination therapy versus vehicle in the ovariectomized (OVX) spontaneously hypertensive rat (SHR) on cardiac function and morphometrics (echocardiography), serum equilibrium of angiotensins (mass spectroscopy) and cardiac components of the RAS (Western blotting). G1 alone and when combined with ACEi enhanced myocardial relaxation (é: 30 and 17%) and diastolic wall strain (DWS: 76 and 68%) while reducing relative wall thickness (RWT: 20 and 33%) and filling pressures (E/é: 30 and 37%). Cardiac expression levels of Mas receptor (Mas-R) and ACE2 also increased in the presence of G1. Strong antihypertensive effects of lisinopril monotherapy were associated with reductions in RWT, collagen deposition and E/é without overtly altering é or DWS. Chronic ACEi also increased cardiac levels of Mas-R and AT₁-R and tilted the circulating RAS toward the formation of Ang-(1-7), which was amplified in the presence of G1. In vitro studies further revealed that an inhibitor to prolyl endopeptidase (PEP), but not to neprilysin, significantly reduced serum Ang-(1-7) levels in G1-treated rats, suggesting that G1 might be increasing Ang-(1-7) formation via PEP. We conclude that activating GPER with G1 augments components of the cardiac RAS and improves diastolic function without lowering blood pressure, and that lisinopril-induced blood pressure control and cardiac alterations in OVX SHR are permissive in facilitating G1 to augment Ang-(1-7) in serum, thereby strengthening its cardioprotective benefits.

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.

Renin-angiotensin-aldosterone system peptide profiles in patients with COVID-19

OBJECTIVE

While evidence on the interface between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the renin-angiotensin-aldosterone-system (RAAS) is accumulating, clinical data on RAAS peptide alteration among coronavirus disease-19 (COVID-19) patients is missing.

DESIGN AND METHODS

In this exploratory study, we prospectively included adult patients (aged ≥ 18 years) admitted between February 26 and April 30, 2020 to a tertiary care hospital in Switzerland. We assessed the association of an underlying SARS-CoV-2 infection and equilibrium serum levels of RAAS peptides in hospitalized COVID-19 patients 1:1 propensity-score matched with patients suffering from SARS-CoV-2-negative respiratory infections. Subgroup analyses involved stratification for taking RAAS inhibitors.

RESULTS

COVID-19 patients had about 50% lower equilibrium serum RAAS peptide levels as compared with matched controls (angiotensin I: 31.6 vs 66.8 pmol/L, -52.7% (95%CI: -68.5% to -36.9%); angiotensin II: 37.7 vs 92.5 pmol/L, -59.2% (95%CI: -72.1% to -46.3%); angiotensin (1-5): 3.3 vs 6.6 pmol/L, -49.7% (95%CI: -59.2% to -40.2%); angiotensin (1-7): 4.8 vs 7.6 pmol/L, -64.9% (95%CI: -84.5% to -45.3%)). While the plasma renin activity was lower in COVID-19 patients (88.6 vs 207.9 pmol/L, -58.5% (95%CI: -71.4% to -45.6%)), there was no difference of angiotensin-converting enzyme (ACE) and ACE2 plasma activity between the groups. Subgroup analyses revealed a pronounced RAAS peptide profile depression in COVID-19 patients among those not on RAAS inhibitors.

CONCLUSIONS

As compared with SARS-CoV-2-negative patients, we found a downregulated RAAS in presence of a SARS-CoV-2 infection. Whether the lower levels of the protective angiotensin (1-5) and (1-7) are linked to adverse outcomes in COVID-19 warrants further investigation.

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.

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.

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.

The renin-angiotensin-system and left ventricular mass in young adults: the African-PREDICT study

PURPOSE

Raised blood pressure, with the renin-angiotensin system (RAS) as a central regulatory component, is one of the most important contributors to early development of left ventricular hypertrophy. Factors such as increased age, sex, black ethnicity and a low socio-economic status also contribute to left ventricular remodelling. To better understand early contributors to left ventricular mass, we investigated the relationship between left ventricular mass index (LVMi) and the components of the RAS in young healthy adults while considering ethnicity, sex and socio-economic status.

MATERIALS AND METHODS

Black and white women and men (N = 1186) between the ages of 20-30 years were included. By using standard echocardiography, we determined LVMi. Ultra-pressure-liquid chromatography tandem-mass spectrometry (LC-MS/MS) was used to measure the RAS-fingerprint^®.

RESULTS

Components of the RAS such as plasma renin activity (PRA-S), angiotensin I (Ang I), angiotensin II (Ang II) and aldosterone were suppressed in the black compared to the white group (all p < 0.001). No associations between LVMi and the RAS were evident in the total, black or white groups. With additional grouping according to sex and socio-economic status, inverse associations between LVMi and PRA-S (β= -0.168;  p = 0.017), Ang I (β= -0.155; p = 0.028) and Ang II (β= -0.172; p = 0.015) were found only in low socio-economic black women.

CONCLUSION

Despite a suppressed RAS in the black compared to the white group, components of the RAS were not associated with LVMi in this young cohort. The low socio-economic black women of this study population may be vulnerable to future RAS-related increases in left ventricular mass.

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.

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.

Plasma Neprilysin Displays No Relevant Association With Neurohumoral Activation in Chronic HFrEF

Background

Neprilysin is a transmembrane endopeptidase involved in the breakdown of a variety of vasoactive peptides and serves as a therapeutic target in heart failure with reduced ejection fraction (HFrEF). This study aimed to investigate the relationship of circulating neprilysin with neurohumoral activation and the impact of plasma neprilysin activity on prognosis in HFrEF.

Methods and Results

A total of 369 chronic HFrEF patients were enrolled prospectively. Plasma neprilysin concentration and activity were determined by a specific ELISA and a fluorometric method. The association between plasma neprilysin and heart failure (HF) severity, neurohumoral activation, ie norepinephrine and absolute renin concentration, as well as all‐cause mortality was assessed. Median plasma neprilysin concentrations and activity levels were 413 pg/mL (interquartile range 0–4111) and 2.36 nmol/mL per minute (interquartile range 1.16–4.59). No correlation could be shown between plasma neprilysin concentrations and activity (r_s=0.09, P=0.088). Plasma neprilysin activity correlated with HF severity reflected by New York Heart Association stage (P=0.003) and tertiles of N‐terminal pro‐B‐type natriuretic peptide (P<0.001), whereas neprilysin concentrations did not (P=0.220; P=0.849). There was no relevant relationship between plasma neprilysin concentrations and activity, with neurohumoral activation reflected by absolute renin concentration (r_s=−0.02, P=0.648; r_s=0.03, P=0.574) or norepinephrine levels (r_s=−0.06, P=0.248; r_s=0.20, P<0.001). Neither circulating neprilysin concentrations nor activity were associated with outcome.

Conclusions

Plasma neprilysin concentrations and activity are not directly related to neurohumoral activation, indicating that neprilysin regulation is either more complex or not correctly mirrored by circulating neprilysin as a biomarker. Circulating neprilysin concentrations and activity were not associated with overall survival, implicating limited prognostic value of plasma neprilysin measurements in HFrEF patients.

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.

Clinical determinants and prognostic implications of renin and aldosterone in patients with symptomatic heart failure

Aims

Activation of the renin–angiotensin–aldosterone system plays an important role in the pathophysiology of heart failure (HF) and has been associated with poor prognosis. There are limited data on the associations of renin and aldosterone levels with clinical profiles, treatment response, and study outcomes in patients with HF.

Methods and results

We analysed 2,039 patients with available baseline renin and aldosterone levels in BIOSTAT‐CHF (a systems BIOlogy study to Tailored Treatment in Chronic Heart Failure). The primary outcome was the composite of all‐cause mortality or HF hospitalization. We also investigated changes in renin and aldosterone levels after administration of mineralocorticoid receptor antagonists (MRAs) in a subset of the EPHESUS trial and in an acute HF cohort (PORTO). In BIOSTAT‐CHF study, median renin and aldosterone levels were 85.3 (percentile_25–75 = 28–247) μIU/mL and 9.4 (percentile_25–75 = 4.4–19.8) ng/dL, respectively. Prior HF admission, lower blood pressure, sodium, poorer renal function, and MRA treatment were associated with higher renin and aldosterone. Higher renin was associated with an increased rate of the primary outcome [highest vs. lowest renin tertile: adjusted‐HR (95% CI) = 1.47 (1.16–1.86), P = 0.002], whereas higher aldosterone was not [highest vs. lowest aldosterone tertile: adjusted‐HR (95% CI) = 1.16 (0.93–1.44), P = 0.19]. Renin and/or aldosterone did not improve the BIOSTAT‐CHF prognostic models. The rise in aldosterone with the use of MRAs was observed in EPHESUS and PORTO studies.

Conclusions

Circulating levels of renin and aldosterone were associated with both the disease severity and use of MRAs. By reflecting both the disease and its treatments, the prognostic discrimination of these biomarkers was poor. Our data suggest that the “point” measurement of renin and aldosterone in HF is of limited clinical utility.

Renin-angiotensin aldosterone profile before and after angiotensin-converting enzyme-inhibitor administration in dogs with angiotensin-converting enzyme gene polymorphism

BACKGROUND

An angiotensin-converting enzyme (ACE) gene polymorphism occurs in dogs; however, functional importance is not well studied.

HYPOTHESIS

We hypothesized that dogs with the polymorphism would show alternative renin-angiotensin aldosterone system (RAAS) pathway activation and classical RAAS pathway suppression before and after ACE-inhibitor administration, as compared to dogs without the polymorphism that would show this pattern only after ACE-inhibitor administration.

ANIMALS

Twenty-one dogs with mitral valve disease that were genotyped for the ACE gene polymorphism.

METHODS

This retrospective study utilized stored samples from 8 ACE gene polymorphism-negative (PN) dogs and 13 ACE gene polymorphism-positive (PP) dogs before and after enalapril administration. Equilibrium analysis was performed to evaluate serum RAAS metabolites and enzyme activities. Results were compared before and after enalapril, and between groups.

RESULTS

The classical RAAS pathway was suppressed and the alternative RAAS pathway was enhanced for both genotypes after administration of enalapril, with no differences before enalapril administration. Aldosterone breakthrough occurred in both PN (38%) and PP (54%) dogs despite angiotensin II suppression. Aldosterone was significantly higher (P = .02) in ACE gene PP dogs (median, 92.17 pM; IQR, 21.85-184.70) compared to ACE gene PN dogs (median, 15.91 pM; IQR, <15.00-33.92) after enalapril.

CONCLUSIONS AND CLINICAL IMPORTANCE

The ACE gene polymorphism did not alter baseline RAAS activity. Aldosterone breatkthrough in some dogs suggests nonangiotensin mediated aldosterone production that might be negatively influenced by genotype. These results support the use of aldosterone receptor antagonists with ACE-inhibitors when RAAS inhibition is indicated for dogs, especially those positive for the ACE gene polymorphism.

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.

Role of electrolyte concentrations and renin-angiotensin-aldosterone activation in the staging of canine heart disease

Background

Refractory congestive heart failure (CHF) and associated diuretic resistance are not well defined.

Objectives

To characterize renal function, electrolyte concentrations, indices of diuretic efficacy, and renin‐angiotensin‐aldosterone system (RAAS) activation in dogs with naturally occurring heart disease (HD) in American College of Veterinary Internal Medicine stages B1, B2, C, and D and to determine their usefulness in defining HD stages.

Animals

Group 1:149 dogs with HD stages B1, B2, C, and D. Group 2:22 dogs with HD stages C and D.

Methods

Group 1: Renal parameters, serum and urine electrolyte and diuretic concentrations, and urine aldosterone concentrations were measured. Medication dosages and measured variables were compared among stages. Correlation of furosemide dosages to serum concentrations was explored. Group 2: Angiotensin‐converting enzyme activity and RAAS components were measured and compared among CHF stages.

Results

Serum chloride concentration was the best differentiator of HD stage. Furosemide PO dosages (≤6 mg/kg/day) were weakly correlated with serum furosemide concentrations, whereas higher dosages were not significantly correlated. Angiotensin‐converting enzyme inhibitor dosage and RAAS inhibition were greater in stage D, compared to stage C dogs.

Conclusions and Clinical Importance

Hypochloremia is a useful marker for stage D HD in dogs. Poor furosemide dosage correlation to serum concentration may indicate variable and poor absorption, especially at higher dosages, advanced disease, or both. A small number of stage D dogs met proposed criteria for diuretic resistance. Greater RAAS inhibition in stage D versus stage C indicates effectiveness of RAAS‐suppressive treatments in this group of dogs with refractory CHF.

Cardiac Pathophysiology and the Future of Cardiac Therapies in Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a devastating disease featuring skeletal muscle wasting, respiratory insufficiency, and cardiomyopathy. Historically, respiratory failure has been the leading cause of mortality in DMD, but recent improvements in symptomatic respiratory management have extended the life expectancy of DMD patients. With increased longevity, the clinical relevance of heart disease in DMD is growing, as virtually all DMD patients over 18 year of age display signs of cardiomyopathy. This review will focus on the pathophysiological basis of DMD in the heart and discuss the therapeutic approaches currently in use and those in development to treat dystrophic cardiomyopathy. The first section will describe the aspects of the DMD that result in the loss of cardiac tissue and accumulation of fibrosis. The second section will discuss cardiac small molecule therapies currently used to treat heart disease in DMD, with a focus on the evidence supporting the use of each drug in dystrophic patients. The final section will outline the strengths and limitations of approaches directed at correcting the genetic defect through dystrophin gene replacement, modification, or repair. There are several new and promising therapeutic approaches that may protect the dystrophic heart, but their limitations suggest that future management of dystrophic cardiomyopathy may benefit from combining gene-targeted therapies with small molecule therapies. Understanding the mechanistic basis of dystrophic heart disease and the effects of current and emerging therapies will be critical for their success in the treatment of patients with DMD.

Normalizing Plasma Renin Activity in Experimental Dilated Cardiomyopathy: Effects on Edema, Cachexia, and Survival

Heart failure (HF) patients frequently have elevated plasma renin activity. We examined the significance of elevated plasma renin activity in a translationally-relevant model of dilated cardiomyopathy (DCM), which replicates the progressive stages (A–D) of human HF. Female mice with DCM and elevated plasma renin activity concentrations were treated with a direct renin inhibitor (aliskiren) in a randomized, blinded fashion beginning at Stage B HF. By comparison to controls, aliskiren treatment normalized pathologically elevated plasma renin activity (p < 0.001) and neprilysin levels (p < 0.001), but did not significantly alter pathological changes in plasma aldosterone, angiotensin II, atrial natriuretic peptide, or corin levels. Aliskiren improved cardiac systolic function (ejection fraction, p < 0.05; cardiac output, p < 0.01) and significantly reduced the longitudinal development of edema (extracellular water, p < 0.0001), retarding the transition from Stage B to Stage C HF. The normalization of elevated plasma renin activity reduced the loss of body fat and lean mass (cachexia/sarcopenia), p < 0.001) and prolonged survival (p < 0.05). In summary, the normalization of plasma renin activity retards the progression of experimental HF by improving cardiac systolic function, reducing the development of systemic edema, cachexia/sarcopenia, and mortality. These data suggest that targeting pathologically elevated plasma renin activity may be beneficial in appropriately selected HF patients.

Plasma and tissue angiotensin-converting enzyme 2 activity and plasma equilibrium concentrations of angiotensin peptides in dogs with heart disease

Background

Angiotensin‐converting enzyme 2 (ACE2) is a homologue of angiotensin‐converting enzyme (ACE) and produces angiotensin peptides (APs), such as angiotensin 1‐9 and 1‐7 that are vasodilatory and natriuretic, and act to counterbalance angiotensin II.

Hypothesis

Evidence of ACE2 can be found in tissues and plasma of dogs. Equilibrium concentrations of renin angiotensin aldosterone system (RAAS) APs differ in dogs with heart disease compared to healthy dogs and recombinant human ACE2 (rhACE2) alters relative concentrations of APs.

Animals

Forty‐nine dogs with and 34 dogs without heart disease.

Methods

Immunohistochemistry and assays for tissue and plasma ACE2 activity and equilibrium concentrations of plasma RAAS APs were performed.

Results

Immunolabeling for ACE2 was present in kidney and myocardial tissue. Median plasma ACE2 activity was significantly increased in dogs with congestive heart failure (CHF; 6.9 mU/mg; interquartile range [IQR], 5.1‐12.1) as compared to control (2.2 mU/mg; IQR, 1.8‐3.0; P = .0003). Plasma equilibrium analysis of RAAS APs identified significant increases in the median concentrations of beneficial APs, such as angiotensin 1‐7, in dogs with CHF (486.7 pg/mL; IQR, 214.2‐1168) as compared to those with preclinical disease (41.0 pg/mL; IQR, 27.4‐45.1; P < .0001) or control (11.4 pg/mL; IQR, 7.1‐25.3; P = .01). Incubation of plasma samples from dogs with CHF with rhACE2 increased beneficial APs, such as angiotensin 1‐9 (preincubation, 10.3 pg/mL; IQR, 4.4‐37.2; postincubation, 2431 pg/mL; IQR, 1355‐3037; P = .02), while simultaneously decreasing maladaptive APs, such as angiotensin II (preincubation, 53.4 pg/mL; IQR, 28.6‐226.4; postincubation, 2.4 pg/mL; IQR, 0.50‐5.8; P = .02).

Conclusions and Clinical Importance

Recognition of the ACE2 system expands the conventional view of the RAAS in the dog and represents an important potential therapeutic target.

Renin Activity in Heart Failure with Reduced Systolic Function-New Insights

Regardless of the cause, symptomatic heart failure (HF) with reduced ejection fraction (rEF) is characterized by pathological activation of the renin–angiotensin–aldosterone system (RAAS) with sodium retention and extracellular fluid expansion (edema). Here, we review the role of active renin, a crucial, upstream enzymatic regulator of the RAAS, as a prognostic and diagnostic plasma biomarker of heart failure with reduced ejection fraction (HFrEF) progression; we also discuss its potential as a pharmacological bio-target in HF therapy. Clinical and experimental studies indicate that plasma renin activity is elevated with symptomatic HFrEF with edema in patients, as well as in companion animals and experimental models of HF. Plasma renin activity levels are also reported to be elevated in patients and animals with rEF before the development of symptomatic HF. Modulation of renin activity in experimental HF significantly reduces edema formation and the progression of systolic dysfunction and improves survival. Thus, specific assessment and targeting of elevated renin activity may enhance diagnostic and therapeutic precision to improve outcomes in appropriate patients with HFrEF.

Angs (Angiotensins) of the Alternative Renin-Angiotensin System Predict Outcome in Patients With Heart Failure and Preserved Ejection Fraction

The renin-angiotensin system plays an important role in the development and progression of heart failure (HF). In addition to the classical renin-angiotensin pathway, an alternative pathway produces Angs (angiotensins), which counteract the negative effects of Ang II. We hypothesized that Ang profiling could provide insights into the pathogenesis and prognosis of HF with preserved ejection fraction. We aimed to investigate the effects of Angs on outcome in HF with preserved ejection fraction. Consecutive patients were included into a prospective single-center registry. Clinical, laboratory, and imaging parameters were assessed and serum samples were taken at baseline and measured by mass spectroscopy. Serum equilibrium levels were analyzed in regard to the combined clinical end point of cardiovascular death or HF hospitalization. In total, 155 patients were included during a median follow-up time of 22.5 (interquartile range, 4.0-61.0) months, 52 individuals (34%) reached the combined end point. We identified higher levels of Ang 1-7 and Ang 1-5 as predictors for poor outcome. After adjusting for potential confounding factors, Ang 1-5 remained predictive for poor outcome. In addition to Ang 1-7 and Ang 1-5, the novel ACE (angiotensin-converting enzyme) independent Ang composite marker [Ang 1-7+Ang 1-5] was shown to predict adverse events. We conclude that Angs of the alternative renin-angiotensin system seem to play a role in HF with preserved ejection fraction and are linked to outcome in patients with HF and preserved ejection fraction. Ang 1-5 and the alternative renin-angiotensin system composite marker [Ang 1-7+Ang 1-5] are independent predictors of outcome.

A microanalytical capillary electrophoresis mass spectrometry assay for quantifying angiotensin peptides in the brain

The renin-angiotensin system (RAS) of the brain produces a series of biologically active angiotensinogen-derived peptides involved in physiological homeostasis and pathophysiology of disease. Despite significant research efforts to date, a comprehensive understanding of brain RAS physiology is lacking. A significant challenge has been the limited set of bioanalytical assays capable of detecting angiotensin (Ang) peptides at physiologically low concentrations (2-15 fmol/g of wet tissue) and sufficient chemical specificity for unambiguous molecular identifications. Additionally, a complex brain anatomy calls for microanalysis of specific tissue regions, thus further taxing sensitivity requirements for identification and quantification in studies of the RAS. To fill this technology gap, we here developed a microanalytical assay by coupling a laboratory-built capillary electrophoresis (CE) nano-electrospray ionization (nano-ESI) platform to a high-resolution mass spectrometer (HRMS). Using parallel reaction monitoring, we demonstrated that this technology achieved confident identification and quantification of the Ang peptides at approx. 5 amol to 300 zmol sensitivity. This microanalytical assay revealed differential Ang peptide profiles between tissues that were micro-sampled from the subfornical organ and the paraventricular nucleus of the hypothalamus, important brain regions involved in thirst and water homeostasis and neuroendocrine regulation to stress. Microanalytical CE-nano-ESI-HRMS extends the analytical toolbox of neuroscience to help better understand the RAS.

Acute AT1R blockade prevents isoproterenol-induced injury in mdx hearts

BACKGROUND

Duchenne muscular dystrophy (DMD) is an X-linked disease characterized by skeletal muscle degeneration and a significant cardiomyopathy secondary to cardiomyocyte damage and myocardial loss. The molecular basis of DMD lies in the absence of the protein dystrophin, which plays critical roles in mechanical membrane integrity and protein localization at the sarcolemma. A popular mouse model of DMD is the mdx mouse, which lacks dystrophin and displays mild cardiac and skeletal pathology that can be exacerbated to advance the disease state. In clinical and pre-clinical studies of DMD, angiotensin signaling pathways have emerged as therapeutic targets due to their adverse influence on muscle remodeling and oxidative stress. Here we aim to establish a physiologically relevant cardiac injury model in the mdx mouse, and determine whether acute blockade of the angiotensin II type 1 receptor (AT₁R) may be utilized for prevention of dystrophic injury.

METHODS AND RESULTS

A single IP injection of isoproterenol (Iso, 10 mg/kg) was used to induce cardiac stress and injury in mdx and wild type (C57Bl/10) mice. Mice were euthanized 8 h, 30 h, 1 week, or 1 month following the injection, and hearts were harvested for injury evaluation. At 8 and 30 h post-injury, mdx hearts showed 2.2-fold greater serum cTnI content and 3-fold more extensive injury than wild type hearts. Analysis of hearts 1 week and 1 month after injury revealed significantly higher fibrosis in mdx hearts, with a more robust and longer-lasting immune response compared to wild type hearts. In the 30-hour group, losartan treatment initiated 1 h before Iso injection protected dystrophic hearts from cardiac damage, reducing mdx acute injury area by 2.8-fold, without any significant effect on injury in wild type hearts. However, both wild type and dystrophic hearts showed a 2-fold reduction in the magnitude of the macrophage response to injury 30 h after Iso with losartan.

CONCLUSIONS

This work demonstrates that acute blockade of AT₁R has the potential for robust injury prevention in a model of Iso-induced dystrophic heart injury. In addition to selectively limiting dystrophic cardiac damage, blocking AT₁R may serve to limit the inflammatory nature of the immune response to injury in all hearts. Our findings strongly suggest that earlier adoption of angiotensin receptor blockers in DMD patients could limit myocardial damage and subsequent cardiomyopathy.

Effect of Ivabradine on a Hypertensive Heart and the Renin-Angiotensin-Aldosterone System in L-NAME-Induced Hypertension

Ivabradine, the selective inhibitor of the If current in the sinoatrial node, exerts cardiovascular protection by its bradycardic effect and potentially pleiotropic actions. However, there is a shortage of data regarding ivabradine's interaction with the renin-angiotensin-aldosterone system (RAAS). This study investigated whether ivabradine is able to protect a hypertensive heart in the model of L-NAME-induced hypertension and to interfere with the RAAS. Four groups (n = 10/group) of adult male Wistar rats were treated as follows for four weeks: control, ivabradine (10 mg/kg/day), L-NAME (40 mg/kg/day), and L-NAME plus ivabradine. L-NAME administration increased systolic blood pressure (SBP) and left ventricular (LV) weight, enhanced hydroxyproline concentration in the LV, and deteriorated the systolic and diastolic LV function. Ivabradine reduced heart rate (HR) and SBP, and improved the LV function. The serum concentrations of angiotensin Ang 1⁻8 (Ang II), Ang 1⁻5, Ang 1⁻7, Ang 1⁻10, Ang 2⁻8, and Ang 3⁻8 were decreased in the L-NAME group and ivabradine did not modify them. The serum concentration of aldosterone and the aldosterone/Ang II ratio were enhanced by L-NAME and ivabradine reduced these changes. We conclude that ivabradine improved the LV function of the hypertensive heart in L-NAME-induced hypertension. The protective effect of ivabradine might have been associated with the reduction of the aldosterone level.

Effect of Melatonin on the Renin-Angiotensin-Aldosterone System in l-NAME-Induced Hypertension

The renin-angiotensin-aldosterone system (RAAS) is a dominant player in several cardiovascular pathologies. This study investigated whether alterations induced by l-NAME, (NLG)-nitro-l-arginine methyl ester, a nitric oxide synthase inhibitor, and the protective effect of melatonin are associated with changes in the RAAS. Four groups of 3-month-old male Wistar rats (n = 10) were treated as follows for four weeks: untreated controls, rats treated with melatonin (10 mg/kg/day), rats treated with l-NAME (40 mg/kg/day), and rats treated with l-NAME + melatonin. l-NAME administration led to hypertension and left ventricular (LV) fibrosis in terms of enhancement of soluble, insoluble and total collagen concentration and content. Melatonin reduced systolic blood pressure enhancement and lowered the concentration and content of insoluble and total collagen in the LV. The serum concentration of angiotensin (Ang) 1–8 (Ang II) and its downstream metabolites were reduced in the l-NAME group and remained unaltered by melatonin. The serum aldosterone level and its ratio to Ang II (AA2-ratio) were increased in the l-NAME group without being modified by melatonin. We conclude that l-NAME-hypertension is associated with reduced level of Ang II and its downstream metabolites and increased aldosterone concentration and AA2-ratio. Melatonin exerts its protective effect in l-NAME-induced hypertension without affecting RAAS.