Capturing the dynamics of systemic Renin-Angiotensin-Aldosterone System (RAAS) peptides heightens the understanding of the effect of benazepril in dogs

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.

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.

Management of Chronic Congestive Heart Failure Caused by Myxomatous Mitral Valve Disease in Dogs: A Narrative Review from 1970 to 2020

Simple Summary

Myxomatous mitral valve disease (MMVD) is the most common acquired cardiovascular disease in dogs. The progression of the disease and the increasing severity of valvular regurgitation cause a volume overload of the left heart, leading to left atrial and ventricular remodeling and congestive heart failure (CHF). The treatment of chronic CHF secondary to MMVD in dogs has not always been the same over time. In the last fifty years, the drugs utilized have considerably changed, as well as the therapeutic protocols. Some drugs have also changed their intended use. An analysis of the literature concerning the therapy of chronic heart failure in dogs affected by this widespread degenerative disease is not available; a synthesis of the published literature on this topic and a description of its current state of art are needed. To the authors’ knowledge, a review of this topic has never been published in veterinary medicine; therefore, the aim of this study is to overview the treatments of chronic CHF secondary to MMVD in dogs from 1970 to 2020 using the general framework of narrative reviews.

Abstract

The treatment of chronic congestive heart failure (CHF), secondary to myxomatous mitral valve disease (MMVD) in dogs, has considerably changed in the last fifty years. An analysis of the literature concerning the therapy of chronic CHF in dogs affected by MMVD is not available, and it is needed. Narrative reviews (NRs) are aimed at identifying and summarizing what has been previously published, avoiding duplications, and seeking new study areas that have not yet been addressed. The most accessible open-access databases, PubMed, Embase, and Google Scholar, were chosen, and the searching time frame was set in five decades, from 1970 to 2020. The 384 selected studies were classified into categories depending on the aim of the study, the population target, the pathogenesis of MMVD (natural/induced), and the resulting CHF. Over the years, the types of studies have increased considerably in veterinary medicine. In particular, there have been 43 (24.29%) clinical trials, 41 (23.16%) randomized controlled trials, 10 (5.65%) cross-over trials, 40 (22.60%) reviews, 5 (2.82%) comparative studies, 17 (9.60%) case-control studies, 2 (1.13%) cohort studies, 2 (1.13%) experimental studies, 2 (1.13%) questionnaires, 6 (3.40%) case-reports, 7 (3.95%) retrospective studies, and 2 (1.13%) guidelines. The experimental studies on dogs with an induced form of the disease were less numerous (49–27.68%) than the studies on dogs affected by spontaneous MMVD (128–72.32%). The therapy of chronic CHF in dogs has considerably changed in the last fifty years: in the last century, some of the currently prescribed drugs did not exist yet, while others had different indications.

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.

Mechanisms for the development of heart failure and improvement of cardiac function by angiotensin-converting enzyme inhibitors

Angiotensin-converting enzyme (ACE) inhibitors, which prevent the conversion of angiotensin I to angiotensin II, are well-known for the treatments of cardiovascular diseases, such as heart failure, hypertension and acute coronary syndrome. Several of these inhibitors including captopril, enalapril, ramipril, zofenopril and imidapril attenuate vasoconstriction, cardiac hypertrophy and adverse cardiac remodeling, improve clinical outcomes in patients with cardiac dysfunction and decrease mortality. Extensive experimental and clinical research over the past 35 years has revealed that the beneficial effects of ACE inhibitors in heart failure are associated with full or partial prevention of adverse cardiac remodeling. Since cardiac function is mainly determined by coordinated activities of different subcellular organelles, including sarcolemma, sarcoplasmic reticulum, mitochondria and myofibrils, for regulating the intracellular concentration of Ca2+ and myocardial metabolism, there is ample evidence to suggest that adverse cardiac remodelling and cardiac dysfunction in the failing heart are the consequence of subcellular defects. In fact, the improvement of cardiac function by different ACE inhibitors has been demonstrated to be related to the attenuation of abnormalities in subcellular organelles for Ca2+-handling, metabolic alterations, signal transduction defects and gene expression changes in failing cardiomyocytes. Various ACE inhibitors have also been shown to delay the progression of heart failure by reducing the formation of angiotensin II, the development of oxidative stress, the level of inflammatory cytokines and the occurrence of subcellular defects. These observations support the view that ACE inhibitors improve cardiac function in the failing heart by multiple mechanisms including the reduction of oxidative stress, myocardial inflammation and Ca2+-handling abnormalities in cardiomyocytes.

Retrospective evaluation of a dose-dependent effect of angiotensin-converting enzyme inhibitors on long-term outcome in dogs with cardiac disease

Background

Angiotensin‐converting enzyme inhibitors (ACEIs) are commonly prescribed in dogs, but the ideal dosage is unknown.

Hypothesis/Objectives

In dogs with cardiac disease, a dose‐response relationship exists for ACEIs with respect to long‐term outcome.

Animals

One hundred forty‐four dogs with cardiac disease, 63 with current or prior congestive heart failure.

Methods

Retrospective medical record review. Cox proportional hazards models were used to determine variables associated with 2‐year survival or survival from first‐onset congestive heart failure (CHF).

Results

Median initial ACEI dosage was 0.84 (interquartile range [IQR], 0.56‐0.98) mg/kg/day, and 108/144 (75%) of dogs received q12h dosing. No clinically relevant changes in renal function test results, serum electrolyte concentrations, or blood pressure occurred between initial prescription of ACEI and first reevaluation (median, 14 days later). In univariable analysis, higher ACEI dose was associated with increased survival from first‐onset CHF (P = .005), and within the subgroup of dogs in CHF at the time of ACEI prescription, higher ACEI dose was associated with improved survival at 2 years (P = .04). In multivariable analysis, q12h dose frequency of ACEI (hazard ratio [HR], 0.30; 95% CI, 0.10‐0.88; P = .03) and higher serum potassium concentration at visit 1 (HR, 0.39; 95% CI, 0.16‐0.97; P = .04) were predictive of 2‐year survival. The ACEIs were well‐tolerated, with only 8/144 (5.6%) dogs having ACEI dose decreased or discontinued because of adverse effects.

Conclusions and Clinical Importance

Twice daily dose frequency might optimize the cardioprotective benefit of ACEIs.

Evaluation of the diagnostic value of the renal resistive index as a marker of the subclinical development of cardiorenal syndrome in MMVD dogs

Introduction:

Myxomatous mitral valve disease (MMVD) in dogs inevitably causes renal dysfunction. These interactions are known as the cardiorenal syndrome (CRS). The main aims of the study were to evaluate whether renal resistive index (RRI) may be useful as a non-invasive marker in subclinical stage of kidney injury in dogs with MMVD and to compare RRI with SDMA and Cyst C.

Methods:

Forty-four dogs were divided into two groups: control—15 healthy dogs and the heart group—29 dogs with MMVD (ACVIM class Cc). Study protocol included: anamnesis, clinical examination, electrocardiography, echocardiography, chest radiography, abdominal ultrasonography with measurements of the renal resistive index (RRI), urine, and blood analysis.

Results:

The RRI in the heart group was significantly higher 0.725 ± 0.035 versus control group 0.665 ± 0.028 (p < 0.00085). The RRI cut-off point in dogs with stable chronic heart failure (CHF) under 8 years is 0.775, in older 0.64. RRI was similar in MMVD dogs treated with ACE-I + furosemide and dogs treated ACE-I + torasemide + pimobendan + spironolactone. There was no correlation between RRI and SDMA or Cyst C.

Conclusion:

RRI is more sensitive than creatinine, SDMA and Cyst C to reveal kidney injury in MMVD dogs class Cc younger than 8 years.

The renin-angiotensin-aldosterone system and its suppression

Chronic activation of the renin-angiotensin-aldosterone system (RAAS) promotes and perpetuates the syndromes of congestive heart failure, systemic hypertension, and chronic kidney disease. Excessive circulating and tissue angiotensin II (AngII) and aldosterone levels lead to a pro-fibrotic, -inflammatory, and -hypertrophic milieu that causes remodeling and dysfunction in cardiovascular and renal tissues. Understanding of the role of the RAAS in this abnormal pathologic remodeling has grown over the past few decades and numerous medical therapies aimed at suppressing the RAAS have been developed. Despite this, morbidity from these diseases remains high. Continued investigation into the complexities of the RAAS should help clinicians modulate (suppress or enhance) components of this system and improve quality of life and survival. This review focuses on updates in our understanding of the RAAS and the pathophysiology of AngII and aldosterone excess, reviewing what is known about its suppression in cardiovascular and renal diseases, especially in the cat and dog.

Sacubitril/valsartan (LCZ696) significantly reduces aldosterone and increases cGMP circulating levels in a canine model of RAAS activation

Simultaneous blockade of angiotensin receptors and enhancement of natriuretic peptides (NP) by the first-in-class angiotensin receptor neprilysin (NEP) inhibitor sacubitril/valsartan constitutes an effective approach to treating heart failure. This study examined the effects of sacubitril/valsartan (225 and 675 mg/day) vs. placebo, sacubitril (360 mg/day), valsartan (900 mg/day), and benazepril (5 mg/day) on the dynamics of the renin-angiotensin-aldosterone system (RAAS) and the NP system in dogs. Beagle dogs (n = 18) were fed a low-salt diet (0.05% Na) for 15 days to model RAAS activation observed in clinical heart failure. Drugs were administered once daily during the last 10 days, while the effects on the RAAS and NPs were assessed on Day 1, 5, and 10. Steady-state pharmacokinetics of the test agents were evaluated on Day 5. Compared with placebo, sacubitril/valsartan (675 mg) substantially increased cGMP circulating levels, while benazepril and valsartan showed no effect. Additionally, sacubitril/valsartan (675 mg) and valsartan significantly increased plasma renin activity, angiotensin I and angiotensin II concentrations. Finally, sacubitril/valsartan (both doses), and valsartan significantly decreased plasma aldosterone vs. placebo. Systemic exposure to valsartan following sacubitril/valsartan 675 mg administration was similar to that observed with valsartan 900 mg administration alone. Sacubitril/valsartan favorably modulates the dynamics of the renin and NP cascades through complementary NEP and RAAS inhibition.

Evaluation of a fixed-dose combination of benazepril and pimobendan in dogs with congestive heart failure: a randomized non-inferiority clinical trial

A fixed-dose combination tablet of benazepril and pimobendan (Fortekor Plus; Elanco Animal Health) was tested in dogs with congestive heart failure (CHF) caused by myxomatous mitral valve disease (MMVD) in a three-arm, masked, randomized, non-inferiority clinical trial in Japan. The test group (n = 34) received Fortekor Plus twice daily. Two control groups received registered formulations of benazepril (Fortekor; Elanco Animal Health) and pimobendan (Vetmedin; Boehringer Ingelheim Vetmedica) with administration of Vetmedin twice daily and Fortekor twice (Control I, n = 14) or once (Control II, n = 19) daily. Diuretics were used in 22 dogs (32.8%). Global clinical scores decreased significantly from baseline in all groups; there were no significant differences between groups, and non-inferiority of Fortekor Plus compared to Control I, Control II, and combined Control I + II groups was demonstrated. There were no significant differences between groups for relevant clinical chemistry and hematology variables or frequency of all adverse events. Frequency of emesis was significantly (p = 0.0042) lower in the Fortekor Plus (8.8%) group than in the Control I + II (39.4%) group. In conclusion, Fortekor Plus had non-inferior efficacy and was associated with significantly less emesis compared to Fortekor and Vetmedin in dogs with CHF caused by MMVD.

Effect of benazepril, robenacoxib and their combination on glomerular filtration rate in cats

Background

Combined use of angiotensin-converting enzyme inhibitors and nonsteroidal anti-inflammatory drugs may induce acute kidney injury in humans, especially when combined with diuretics. The objective of this investigation was to evaluate the effects of benazepril, robenacoxib and their combination in healthy cats.

In each of two studies (study 1 followed by study 2), 32 healthy cats were randomised to one of four groups (n = 4 male and 4 female cats per group) in a parallel-group design. The groups received orally once daily for 7 days either placebo (control group), benazepril, robenacoxib or benazepril plus robenacoxib. In study 2, all groups received in addition 0.5 mg/kg furosemide twice daily by subcutaneous injection for 7 days.

Results

Benazepril, robenacoxib and their combination were well tolerated as evidenced from lack of clinical signs and no negative effects on body weight, feed consumption and clinical chemistry, haematology and urinalysis variables.

The primary endpoint of the study was the glomerular filtration rate (GFR), which was estimated from the plasma clearance of iohexol. In the absence of furosemide, GFR was significantly higher in cats receiving the combination of benazepril plus robenacoxib compared to the other three groups, and was also significantly higher in females receiving only benazepril compared to the control.

Administration of furosemide induced diuresis, reduced GFR and activated the renin-aldosterone-angiotensin system, evidenced from increased plasma renin activity and plasma aldosterone concentrations. Compared to the control group in cats treated with furosemide, GFR was increased by benazepril (females only) but decreased by robenacoxib (males only). Benazepril, robenacoxib and their combination significantly inhibited the increase in plasma aldosterone induced by furosemide.

Conclusions

The combination of benazepril and robenacoxib was well tolerated and either increased or had a neutral effect on GFR in healthy cats without or with concomitant furosemide. The combination of benazepril and robenacoxib reduced plasma aldosterone concentrations increased by furosemide. It is recommended to test the efficacy and safety of the combined use of benazepril and robenacoxib in cats with clinical disease, notably proteinuric chronic kidney disease.

Effect of benazepril and robenacoxib and their combination on glomerular filtration rate in dogs

Combined use of angiotensin-converting enzyme inhibitors and nonsteroidal anti-inflammatory drugs may induce acute kidney injury, especially when combined with diuretics. The objective of this investigation was to evaluate the effect of benazepril, robenacoxib and their combination in healthy dogs. In each of two studies (studies 1 and 2), 32 beagle dogs were randomized into one of four groups in a parallel-group design. Groups received once-daily oral treatment for 7 days with placebo, benazepril, robenacoxib or benazepril plus robenacoxib. In study 2, all dogs received additionally 2 mg/kg furosemide orally twice daily. The primary endpoint was the glomerular filtration rate (GFR) estimated from the plasma clearance of iohexol. Secondary endpoints included standard clinical monitoring and, in study 2, plasma renin activity, urine volume, specific gravity and aldosterone concentration and water intake. Administration of furosemide induced diuresis, reduced GFR and activated the renin-aldosterone-angiotensin system. Benazepril and robenacoxib, administered alone or in combination, were tolerated well, did not decrease GFR with or without co-administration of furosemide and significantly reduced urinary aldosterone concentrations. No increased risk of acute kidney injury was identified with the combination of benazepril and robenacoxib in healthy dogs. Different effects might occur in dogs with heart or renal disease.

Short-term hemodynamic and neuroendocrine effects of pimobendan and benazapril in dogs with myxomatous mitral valve disease and congestive heart failure

BACKGROUND

Pimobendan and benazepril are frequently used with diuretics to treat dogs in congestive heart failure (CHF) caused by myxomatous mitral valve disease (MMVD).

AIM

To compare the short-term effects of pimobendan versus benazepril on pump function, heart size, and neuroendocrine profile in dogs with CHF caused by MMVD.

ANIMALS

Sixteen client-owned dogs.

MATERIAL AND METHODS

Seven-day prospective single-blinded study of dogs stabilized on furosemide monotherapy, randomized to pimobendan (0.4-0.6 mg/kg/day) or benazepril (0.25-1.0 mg/kg/day). Dogs had first-pass radionuclide angiocardiography, and heart size was measured by radiography and echocardiography. Circulating neuroendocrine hormones were measured.

RESULTS

Baseline variables did not differ between treatment groups. Greater decreases in the pimobendan than in the benazepril group were found for heart rate (P = .001), heart rate-normalized pulmonary transit time (P = .02), left atrial size (P = .03), and systolic and diastolic left ventricular diameters (P < .001 and P = .03, respectively) and volumes (P < .001 and P = .02, respectively), whereas ejection fraction increased more (P = .02) in the pimobendan group. Of the neuroendocrine hormones, only N-terminal proatrial natriuretic peptide (NT-ProANP) differed (P = .04) between groups. Within groups, plasma aldosterone increased (P = .01), and NT-proANP (P = .01) and NT-proB-type (P = .02) natriuretic peptide decreased in the pimobendan group, and NT-proANP (P = .02) and plasma vasopressin (P = .01) decreased in the benazepril group.

CONCLUSIONS AND CLINICAL IMPORTANCE

Pimobendan improves short-term cardiac function more than benazepril in dogs with CHF caused by MMVD. Pimobendan treatment enables the heart to work at smaller end-systolic and diastolic dimensions while maintaining adequate forward stroke volume. Some of the treatment responses found in neuroendocrine profile might have therapeutic relevance.