Assessing the outcomes of prescribing angiotensin converting enzyme inhibitors and angiotensin receptor blockers for COVID-19 patients

Background

Patients with heart failure were affected severely by COVID-19. Most heart failure patients are on guideline directed medical therapy, which includes ACE inhibitors (ACEI) and ARBs. These medications were controversial at the beginning of the pandemic due to their interplay with the receptor that SARS-CoV-2 binds in the lungs. We investigated the effect that ACEI and ARB had on patients with hypertension, coronary artery disease, and heart failure.

Methods

We recruited 176 patients with COVID-19 infection and cardiovascular comorbidities at the American University of Beirut Medical Center in Lebanon. Of these, 110 patients were taking ACEI or ARB and 66 were not. We collected clinical data and looked at inflammatory markers such as CRP and IL-6 and cardiac markers such as troponin T. We also reported the incidence of ARDS, sepsis, and death of each patient, and compared the 2 groups.

Results

We found that patients taking ACEI and ARB had a statistically significant decrease in levels of troponin T, IL-6, and CRP compared to patients not taking these medications (p < 0.05). We found no difference in rates of ARDS, sepsis, or death between the 2 groups.

Conclusion

Inhibition of the renin-angiotensin-aldosterone-system had no effect on the mortality of patients with COVID-19 and on their overall disease progression. However, it may be beneficial not to stop these medications as they decrease inflammation in the body and the levels of troponin, which are related to increased stress on the heart.

The Combination of Beta-Blockers and ACE Inhibitors Across the Spectrum of Cardiovascular Diseases

Cardiovascular disease is the leading cause of mortality worldwide, affecting a wide range of patients at different stages across the cardiovascular continuum. Hypertension is one of the earliest risk factors in this continuum and can be controlled in most patients with currently available antihypertensive agents. However, goals are often not met because treatments are not optimized in terms of tailoring therapy to individual patients based on their hypertension subclass and cardiovascular risk profile and initiating early use of adapted-dose, single-pill combinations. In this context, beta-blockers in combination with angiotensin-converting enzyme (ACE) inhibitors are of special interest as a result of their complementary actions on the sympathetic nervous system and renin-angiotensin-aldosterone system, two interlinked pathways that influence cardiovascular risk and disease outcomes. In addition to their antihypertensive actions, beta-blockers are used to manage arrhythmias and treat angina pectoris and heart failure, while ACE inhibitors provide cardioprotection in patients with acute coronary syndromes and treat congestive heart failure. A broad range of patients may therefore receive the combination in routine clinical practice. This paper examines the supporting evidence for beta-blockers and ACE inhibitors in each of the above indications and considers the rationale for combining these agents into a single pill, using data from bisoprolol and perindopril randomized controlled trials as supporting evidence. Combining these established antihypertensive agents into a single pill continues to provide effective blood pressure lowering and improved cardiovascular outcomes while allowing a greater proportion of patients to rapidly achieve treatment targets.

[Classical nephroprotection: Renin angiotensin aldosterone system inhibitors]

The role of the renin angiotensin aldosterone system (RAAS) in the pathophysiology of hypertension, cardiovascular disease and kidney disease has been known for years. RAAS inhibitors have been the mainstay of chronic kidney disease (CKD) treatment. Studies have shown that therapy with angiotensin-converting enzyme inhibitors (ACE inhibitors) or angiotensinII receptor blockers (ARBs) reduce the excretion of albuminuria and slow the progression of kidney disease in patients with and without diabetes. In clinical practice, RAAS inhibitors are recommended as the antihypertensive of choice in patients with CKD and albuminuria with or without diabetes. In addition, they have demonstrated cardiovascular benefits beyond blood pressure control. The use of RAAS inhibitors in non-proteinuric nephropathy and advanced CKD is not without controversy. Double blockade of the RAAS is contraindicated. On the other hand, it is essential to know how to titrate doses and avoid side effects, mainly hyperkalaemia.

Mechanism and prevention of atrial remodeling and their related genes in cardiovascular disorders

Atrial fibrillation (AF) is associated with profound structural and functional changes in the atrium. Inflammation mediated atrial fibrosis is one of the key mechanisms in the pathogenesis of AF. The collagen deposition in extracellular matrix (ECM) is mainly mediated by transforming growth factor β1 (TGF-β1) which promotes AF via controlling smads mediated-collagen gene transcription and regulating the balance of metalloproteinases (MMPs)/ tissue inhibitor of metalloproteinases (TIMPs). Although many processes can alter atrial properties and promote AF, animal models and clinical studies have provided insights into two major forms of atrial remodeling: Atrial tachycardia remodeling (ATR), which occurs with rapid atrial tachyarrhythmia's such as AF and atrial flutter, and atrial structural remodeling (ASR), which is associated with CHF and other fibrosis-promoting conditions. The mechanism of atrial remodeling such as atrial enlargement, ultra structural changes of atrial muscle tissue and myocardial interstitial fibrosis in AF is still unclear. At present, many studies focus on calcium overload, renin angiotensin aldosterone system and transforming growth factor β1, that effect on atrial structural remodeling. Recent experimental studies and clinical investigations have provided structural remodeling is important contributor to the AF. This paper reviews the current understanding of the progresses about mechanism of atrial structural remodeling, and highlights the potential therapeutic approaches aimed at attenuating structural remodeling to prevent AF. Now some recent advancements of this area are reviewed in this paper.

Evaluating the effects of sodium glucose co-transporter -2 inhibitors from a renin-angiotensin-aldosterone system perspective in patients infected with COVID-19: contextualizing findings from the dapagliflozin in respiratory failure in patients with COVID-19 study

Numerous studies demonstrate parallels between CVD, type 2 diabetes mellitus (T2DM) and COVID-19 pathology, which accentuate pre-existing complications in patients infected with COVID-19 and potentially exacerbate the infection course. Antidiabetic drugs such as sodium-glucose transporter-2 (SGLT-2) inhibitors have garnered substantial attention recently due to their efficacy in reducing the severity of cardiorenal disease. The effect of SGLT-2 inhibitors in patients with COVID-19 remains unclear particularly since SGLT-2 inhibitors contribute to altering the RAAS cascade activity, which includes ACE-2, the major cell entry receptor for SARS-CoV2. A study, DARE-19, was carried out to unveil the effects of SGLT-2 inhibitor treatment on comorbid disease complications and concomitant COVID-19 outcomes and demonstrated no statistical significance. However, the need for further studies is essential to provide conclusive clinical findings.

Renin angiotensin aldosterone system in pulmonary fibrosis: Pathogenesis to therapeutic possibilities

Pulmonary fibrosis is a devastating lung disease with multifactorial etiology characterized by alveolar injury, fibroblast proliferation and excessive deposition of extracellular matrix proteins, which progressively results in respiratory failure and death. Accumulating evidence from experimental and clinical studies supports a central role of the renin angiotensin aldosterone system (RAAS) in the pathogenesis and progression of idiopathic pulmonary fibrosis. Angiotensin II (Ang II), a key vasoactive peptide of the RAAS mediates pro-inflammatory and pro-fibrotic effects on the lungs, adversely affecting organ function. Recent years have witnessed seminal discoveries in the field of RAAS. Identification of new enzymes, peptides and receptors has led to the development of several novel concepts. Of particular interest is the establishment of a protective axis of the RAAS comprising of Angiotensin converting enzyme 2 (ACE2), Angiotensin-(1-7) [Ang-(1-7)], and the Mas receptor (the ACE2/Ang-(1-7)/Mas axis), and the discovery of a functional role for the Angiotensin type 2 (AT₂) receptor. Herein, we will review our current understanding of the role of RAAS in lung fibrogenesis, provide evidence on the anti-fibrotic actions of the newly recognized RAAS components (the ACE2/Ang-(1-7)/Mas axis and AT₂ receptor), discuss potential strategies and translational efforts to convert this new knowledge into effective therapeutics for PF.

Anti-inflammatory HDL effects are impaired in atrial fibrillation

High-density lipoprotein (HDL), best known for cholesterol transport, also has anti-inflammatory effects. Previous studies suggest involvement of myeloperoxidase (MPO) in modification of HDL. HDL bound Sphingosine-1-phosphate (S1P) has been implied to be an essential protein regarding beneficial HDL effects. In this study, we analyzed anti-inflammatory HDL properties in patients with atrial fibrillation (AF), a disease involving atrial inflammation, compared to non-AF controls and whether anti-inflammatory properties improve upon catheter ablation. Additionally, association with serum concentrations of MPO and S1P were assessed. We isolated HDL from 25 AF patients, 13 non-AF individuals and 14 AF patients at follow-up (FU) after catheter ablation. S1P was measured in a cohort of 141 AF and 21 FU patients. Following preincubation with HDL from either group, bovine aortic endothelial cells were stimulated using tumor necrosis factor α and expression of pro-inflammatory genes intercellular adhesion molecule 1 (ICAM1), vascular cell adhesion molecule 1 (VCAM1), E-selectin (SELE) and P-selectin (SELP) was assessed using qPCR. Concentrations of circulating protein of these genes as well as MPO and S1P were measured in serum samples. Compared to non-AF individuals HDL from AF patients suppressed gene expression of the pro-inflammatory adhesion molecules ICAM1, VCAM1, SELE and SELP 27%, 18%, 21% and 57% less, respectively (p < 0.05 for all except SELE p = 0.06). In FU patients, the anti-inflammatory HDL activity was improved (suppression of ICAM1 + 22%, VCAM1 + 10%, SELE + 38% and SELP + 75%, p < 0.05 for all except VCAM1 p = 0.08). AF patients using angiotensin converting enzyme inhibitors or angiotensin receptor blockers had better anti-inflammatory HDL properties than non-users (gene expression suppression at least 28% more, p < 0.05 for all except ICAM1 p = 0.051). Circulating protein concentrations were not correlated with in vitro gene-expression, but circulating P-selectin was generally elevated in AF and FU patients compared to non-AF patients. MPO plasma concentration was positively associated with gene-expression of ICAM1, VCAM1 and SELP (r² > 0.4, p < 0.05). Serum concentrations of S1P were increased in FU patients {1.201 µM [1.077–1.543]} compared to AF patients {0.953 µM [0.807–1.135], p < 0.01} but not correlated with ICAM1, VCAM1 and SELP gene expression. We conclude that the anti-inflammatory activity of HDL is impaired in AF patients, which might promote AF progression and AF-associated complications.

Rationale and methods of a randomized trial evaluating the effect of neprilysin inhibition on left ventricular remodelling

AIMS

In patients at high risk of heart failure following myocardial infarction (MI) as a result of residual left ventricular systolic dysfunction (LVSD), the angiotensin receptor neprilysin inhibitor sacubitril/valsartan may result in a greater attenuation of adverse left ventricular (LV) remodelling than renin angiotensin aldosterone system inhibition alone, due to increased levels of substrates for neprilysin with vasodilatory, anti-hypertrophic, anti-fibrotic, and sympatholytic effects.

METHODS

We designed a randomized, double-blinded, active-comparator trial to examine the effect of sacubitril/valsartan to the current standard of care in reducing adverse LV remodelling in patients with asymptomatic LVSD following MI. Eligible patients were ≥3 months following MI, had an LV ejection fraction ≤40% as measured by echocardiography, were New York Heart Association functional classification I, tolerant of an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker at equivalent dose of ramipril 2.5 mg twice daily or greater, and taking a beta-blocker unless contraindicated or intolerant. Patients were randomized to sacubitril/valsartan (target dose 97/103 mg twice daily) or valsartan (target dose 160 mg twice daily). The primary endpoint will be change in LV end-systolic volume indexed for body surface area measured using cardiac magnetic resonance imaging over 52 weeks from randomization. Secondary endpoints include other magnetic resonance imaging-based metrics of LV remodelling, biomarkers associated with LV remodelling and neurohumoral activation, and change in patient well-being assessed using a patient global assessment questionnaire.

CONCLUSIONS

This trial will investigate the effect of neprilysin inhibition on LV remodelling and the neurohumoral actions of sacubitril/valsartan in patients with asymptomatic LVSD following MI.

Comparison of Severity of COVID-19 Infection among Patients Using RAAS Inhibitors and Non-RAAS Inhibitors

Aims and objectives

The aim of the article was to study the safety profile of renin-angiotensin-aldosterone system (RAAS) inhibitor in COVID-19-affected Indian patients.

Introduction

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for COVID-19 infection. There has been uncertainty about use of RAAS inhibitors in COVID-19. The association of RAAS inhibitors with severity of infection and clinical outcomes was addressed in this study.

Materials and methods

This is a single-center retrospective study from Indian intensive care unit (ICU). A total of 138 were included, who were divided into group A (RAAS inhibitor) and group B (non-RAAS inhibitor). They are followed up till ICU stay during which peak levels of ferritin, D dimer, interleukin-6 were noted (primary outcome). The number of ventilator days, ICU length of stay, and ICU outcome also compared.

Results

Of 138 patients, 18 are included in group A and 120, in group B. There is no difference in peak levels (mean) D dimer [5,893 vs 7,710, p 0.46], ferritin [2,388 vs 3,635, p 0.56], interleukin-6 [9,597 vs 3,625, p 0.06]. There is no difference in number of ventilator days (2.2 vs 1.78, p 0.53) and ICU length of stay (6.5 vs 6.1, p 0.74).

Conclusion

RAAS inhibitors can be safely continued in COVID-19 infection. It is not associated with an increase in severity of infection, ICU length of stay, and mortality.

How to cite this article

Reddy PR, Samavedam S, Aluru N, Rajyalakshmi B. Comparison of Severity of COVID-19 Infection among Patients Using RAAS Inhibitors and Non-RAAS Inhibitors. Indian J Crit Care Med 2021;25(4):366–368.

Is hypertension in African-descent populations contributed to by an imbalance in the activities of the ACE2/Ang-(1-7)/Mas and the ACE/Ang II/AT1 axes?

Introduction:

Low plasma renin activity hypertension is prevalent in Afro-Caribbean persons. Reduced angiotensin converting enzyme 2 activity from the counter angiotensin converting enzyme 2 /angiotensin-(1-7)/Mas receptor axis of the renin angiotensin aldosterone system has been reported in people with pre-hypertension, type 2 diabetes mellitus and chronic renal disease. This study investigates whether an imbalance in the regulatory mechanisms between the pressor arm of the renin angiotensin aldosterone system (angiotensin converting enzyme/angiotensin II/AT1 receptor) and the depressor axis (angiotensin converting enzyme 2/angiotensin-(1-7)/Mas receptor) predisposes persons of African descent to hypertension.

Methods:

In total, 30 normotensives and 30 recently diagnosed hypertensives aged 18–55 of Afro-Caribbean origin who are naïve to antihypertensive treatment will be recruited from public sector polyclinics in Barbados. Demographic and anthropometric data, clinical blood pressure readings, 24-hour urine collections and venous blood samples will be collected. Biological samples will be analysed for renin angiotensin aldosterone system peptide markers using radioimmunoassay.

Conclusion:

We describe the design, methods and rationale for the characterization of renin angiotensin aldosterone system mechanisms that may contribute to hypertension predisposition in persons of African descent. Our findings will characterize any imbalance in the counter axes of the renin angiotensin aldosterone system in hypertensive Afro-Caribbeans with a potential view of identifying novel approaches with the use of renin angiotensin aldosterone system and mineralocorticoid blockers to manage the condition.

Improvement in Angiotensin 1-7 precedes and correlates with improvement in Arterial stiffness and endothelial function following Renin-Angiotensin system inhibition in type 2 diabetes with newly diagnosed hypertension

BACKGROUND AND AIM

Studies in cell cultures and animal models have revealed the possible pathophysiological factors associated with vascular endothelial dysfunction. However, the same in human subjects has not been clearly established. The current study uses a novel approach to identify the factors associated with endothelial function and arterial function by altering these vascular parameters using Angiotensin-Converting-Enzyme (ACE) inhibition.

METHODS

Diabetic patients with newly diagnosed hypertension (n = 60) were recruited for the study. Flow-mediated-dilation (FMD), carotid-femoral (cf), carotid-radial (cr) Pulse-wave-velocity (PWV), Augmentation-Index, Carotid-Intima-Media-Thickness (CIMT), serum levels of Renin, Angiotensin II (AngII), Angiotensin-Converting-Enzyme2 (ACE2), Angiotensin1-7 (Ang1-7), E-selectin, Vascular-Cell-Adhesion-Molecule-1 (VCAM-1), Highly-sensitive-C-Reactive-Protein (hsCRP) and Interleukin-10 were measured at baseline (V1), after 1 week (V2) and 3 months (V3) of ACE inhibition in patients of diabetes with newly diagnosed hypertension. The amplitude of change after 1 week (V₂-V₁) and 3 months (V₃-V₁) for the clinical and various parameters were correlated with the change in endothelial function and arterial stiffness.

RESULTS

Carotid radial-PWV_V2-V1 (p = 0.001) and Ang1-7_V2-V1 (p = 0.01) emerged as independent predictors of FMD_V2-V1. Renin_V2-V1 and VCAM-1_V2-V1 independently predicted E-selectin_V2-V1 [(p = 0.01) and (p = 0.001), respectively]. ACE 2_V2-V1 was the only independent predictor of cf-PWV_V2-V1. The same parameters remained as independent predictors of the respective vascular factors after 3 months of ACE inhibition.

CONCLUSION

The study highlights the role of AngII/Ang1-7 balance in alteration of endothelial function and central arterial stiffness in humans in addition to identifying the interrelationship between the renin-angiotensin-aldosterone-system components and clinically ascertainable parameters.

Folic acid and RAAS blockers in ischemia/reperfusion-induced hepatic injury: A current mechanistic concept for understanding the incidence, significance & outcome

Hepatic ischemia-reperfusion injury (IRI) is not only one of the pathophysiological process involving the liver, but also a complex systemic process affecting multiple tissues and organs. IRI after liver transplant occurs due to in major resections and occlusion of vessels, or during the perioperative period, leads to acute liver failure which shows the dynamic process that involves two interrelated phases of local ischemic insult and inflammation-mediated reperfusion injury and has an impact on morbidity and mortality. The renin-angiotensin-aldosterone system (RAAS) is activated locally in the injured cells by the occurrence of I/R, which plays an essential role in the fate of the damaged tissue. However, a preclinical study explores the protective role of RAAS inhibitor in acute liver injury in a model of inflammation caused by ischemia and reperfusion. In-addition to RAAS blockers in monotherapy does not effectively block the complete pathway. Thus, the present study is designed to explore the effect of combined folic acid with RAAS blockers in combination, produce a synergistic effect. Moreover, in this review, we will describe the understanding of the possible incidence of downregulatory molecular mechanisms associated with renin-angiotensin-aldosterone system and the significance & outcome of the combination of folic acid and RAAS blockers in liver injury due to ischemia/reperfusion.

Should Angiotensin-Converting Enzyme Inhibitors ever Be Used for the Management of Hypertension?

Purpose of Review

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are commonly used anti-hypertensive medications in a number of clinical settings. They are often used interchangeably, but we pose the provocative question as to whether they should be. We review the literature to evaluate for any differences in efficacy between the two classes in order to determine if the greater side effects associated with angiotensin-converting enzyme inhibitors are offset by any advantageous effects on outcomes to warrant their use over angiotensin receptor blockers.

Recent Findings

In many clinical scenarios, the data supports similar efficacy between ACE inhibitors and ARBs, while in a minority of others, there are murky signals from previous trials that suggest ACE inhibitors may be better. However, when reviewing the literature in its entirety, and taking into account recently published pooled analysis and head to head trials, it is reasonable to conclude that ACE inhibitors and ARBs have similar efficacy. This is in contrast to data on adverse effects, which consistently favors the use of ARBs.

Summary

From the available data, it is reasonable to conclude that ACE inhibitors and ARBs have equal efficacy yet unequal adverse effects. It is in this context that we take the provocative stance that ACE inhibitors should not be used to treat hypertension.

Impact of sex and gender on COVID-19 outcomes in Europe

BACKGROUND

Emerging evidence from China suggests that coronavirus disease 2019 (COVID-19) is deadlier for infected men than women with a 2.8% fatality rate being reported in Chinese men versus 1.7% in women. Further, sex-disaggregated data for COVID-19 in several European countries show a similar number of cases between the sexes, but more severe outcomes in aged men. Case fatality is highest in men with pre-existing cardiovascular conditions. The mechanisms accounting for the reduced case fatality rate in women are currently unclear but may offer potential to develop novel risk stratification tools and therapeutic options for women and men.

CONTENT

The present review summarizes latest clinical and epidemiological evidence for gender and sex differences in COVID-19 from Europe and China. We discuss potential sex-specific mechanisms modulating the course of disease, such as hormone-regulated expression of genes encoding for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) entry receptors angiotensin converting enzyme (ACE) 2 receptor and TMPRSS2 as well as sex hormone-driven innate and adaptive immune responses and immunoaging. Finally, we elucidate the impact of gender-specific lifestyle, health behavior, psychological stress, and socioeconomic conditions on COVID-19 and discuss sex specific aspects of antiviral therapies.

CONCLUSION

The sex and gender disparities observed in COVID-19 vulnerability emphasize the need to better understand the impact of sex and gender on incidence and case fatality of the disease and to tailor treatment according to sex and gender. The ongoing and planned prophylactic and therapeutic treatment studies must include prospective sex- and gender-sensitive analyses.

Serum endotrophin levels in patients with heart failure with reduced and mid-range ejection fraction

BACKGROUND

Endotrophin, a type VI collagen cleavage product, has fibrosis, and insulin resistance effects. Type VI collagen also plays a role in cardiac fibrosis. In this study, we aimed to investigate the role of endotrophin in the pathogenesis of cardiac fibrosis by determining its levels in patients with heart failure with reduced and mid-range ejection fraction (EF). We also aimed to determine the possible association between endotrophin and treatment that prevents ventricular fibrosis.

METHODS

Sixty patients with heart failure with reduced and mid-range EF and 27 volunteers with no cardiac failure were included in this study. In both groups, biochemical tests, EF, and endotrophin levels were measured. ELISA was performed for the determination of endotrophin levels.

RESULTS

When compared with the control group, there was no significant difference for endotrophin levels in the patient group (p = .35). Participants in the study were divided into two groups according to their EFs, 40% and less, and 40-49%. They were classified according to their use of renin-angiotensin-aldosterone system (RAAS) blocking drugs. Endotrophin levels were significantly lower in patients with mid-range EFs between 40 and 49% (p = .03) using RAAS blockers.

CONCLUSION

This study is the first to evaluate the relationship between endotrophin and heart failure. Endotrophin levels were found to be low in patients with heart failure with mid-range EF who were using RAAS blockers. This suggests that RAAS blockers may influence endotrophin levels and thus could have a role in the prevention of remodelling.

Imbalance between Angiotensin II - Angiotensin (1-7) system is associated with vascular endothelial dysfunction and inflammation in type 2 diabetes with newly diagnosed hypertension

AIM

Diabetes is associated with Renin-angiotensin-aldosterone-system (RAAS) activation. Protective role of Angiotensin (1-7) has been recently identified. The study aims to identify associations between imbalance in RAAS components with vascular endothelial dysfunction and inflammation in diabetics with newly diagnosed hypertension.

METHODS

Brachial Flow-mediated-dilation (FMD), Carotid Intima-media-thickness (CIMT), pulse-wave-velocity (PWV), Serum E-selectin, Vascular-Cell-Adhesion-Molecule-1 (VCAM-1), high-sensitivity C-Reactive Protein (hsCRP), Interleukin-10 (IL-10), Renin, AngiotensinII, Angiotensin-Converting-Enzyme 2 (ACE2) and Angiotensin1-7 were measured in 60 diabetic patients with newly diagnosed hypertension. Patients with AngiotensinII/Angiotensin1-7 ratio <1 were classified as Favourable-Axis (FA) group (n = 22) and those with ratio >1 were classified as Unfavourable-Axis (UA) group (n = 38).

RESULTS

hsCRP was higher [9.52 (4.64-16.19) vs 3.62 (1.77-13.09) (mg/l), p = 0.04], IL-10 was lower [2.26 (1.34-12.05) vs 10.98 (4.44-17.78) (pg/ml),p = 0.006], %FMD was lower [(5.51 ± 2.97) vs (7.66 ± 3.38) (%), p = 0.01] and CIMT was higher in UA compared to FA group [0.7 (0.55-0.79) vs 0.51 (0.49-0.65) (mm), p = 0.001]. Renin correlated positively with pressure, PWV, E-selectin and VCAM-1, opposing associations were obtained for Angiotensin1-7 and ACE2.

CONCLUSION

Imbalance between AngiotensinII - Angiotensin1-7 is associated with increased inflammation and vascular dysfunction in diabetics and can contribute to development of hypertension in these patients.

Autonomic nervous system involvement in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a chronic pulmonary vascular disease characterized by increased pulmonary vascular resistance (PVR) leading to right ventricular (RV) failure. Autonomic nervous system involvement in the pathogenesis of PAH has been demonstrated several years ago, however the extent of this involvement is not fully understood. PAH is associated with increased sympathetic nervous system (SNS) activation, decreased heart rate variability, and presence of cardiac arrhythmias. There is also evidence for increased renin-angiotensin-aldosterone system (RAAS) activation in PAH patients associated with clinical worsening. Reduction of neurohormonal activation could be an effective therapeutic strategy for PAH. Although therapies targeting adrenergic receptors or RAAS signaling pathways have been shown to reverse cardiac remodeling and improve outcomes in experimental pulmonary hypertension (PH)-models, the effectiveness and safety of such treatments in clinical settings have been uncertain. Recently, novel direct methods such as cervical ganglion block, pulmonary artery denervation (PADN), and renal denervation have been employed to attenuate SNS activation in PAH. In this review, we intend to summarize the multiple aspects of autonomic nervous system involvement in PAH and overview the different pharmacological and invasive strategies used to target autonomic nervous system for the treatment of PAH.

Aldosterone breakthrough in dogs with naturally occurring myxomatous mitral valve disease

INTRODUCTION

Aldosterone breakthrough (ABT) is the condition in which angiotensin converting enzyme inhibitors (ACEIs) and/or angiotensin receptor blockers fail to effectively suppress the activity of the renin angiotensin aldosterone system. The objective of this study was to determine if ABT occurs in dogs with naturally occurring myxomatous mitral valve disease receiving an ACEI, using the urine aldosterone to creatinine ratio (UAldo:C) as a measure of renin angiotensin aldosterone system activation.

ANIMALS, MATERIALS AND METHODS

This study includes 39 dogs with myxomatous mitral valve disease. A UAldo:C cut-off definition (derived from a normal population of healthy, adult, and client-owned dogs) was used to determine the prevalence of ABT in this population. Spearman analysis and univariate logistic regression were used to evaluate the relationship between UAldo:C and ABT (yes/no) and eight variables (age, serum K⁺ concentration, serum creatinine concentration, ACEI therapy duration and ACEI dosage, furosemide therapy duration and furosemide dosage, and urine sample storage time). Finally, the UAldo:C in dogs receiving spironolactone, as part congestive heart failure (CHF) therapy, was compared to dogs with CHF that were not receiving spironolactone.

RESULTS

The prevalence of ABT was 32% in dogs with CHF and 30% in dogs without CHF. There was no relationship between either the UAldo:C or the likelihood of ABT and the eight variables. Therapy with spironolactone lead to a significant elevation of the UAldo:C.

DISCUSSION

Using the UAldo:C and a relatively stringent definition of ABT, it appears that incomplete RAAS blockade is common in dogs with MMVD receiving an ACEI. The prevalence of ABT in this canine population mirrors that reported in humans. While the mechanism of ABT is likely multifactorial and still poorly understood, the proven existence of ABT in dogs offers the potential to improve the prognosis for MMVD with the addition of a mineralocorticoid receptor blocker to current therapeutic regimens.

CONCLUSIONS

Approximately 30% of dogs being treated for heart disease and CHF satisfied the definition of ABT. Identifying patient subpopulations experiencing ABT may help guide future study design and clinical decision-making.

The Gut, Its Microbiome, and Hypertension

PURPOSE OF THE REVIEW

Evidence is rapidly accumulating implicating gut dysbiosis in hypertension (HTN). However, we are far from understanding whether this is a cause or consequence of HTN, and how to best translate this fundamental knowledge to advance the management of HTN. This review aims to summarize recent advances in the field, illustrate the connections between the gut and hypertension, and establish that the gut microbiota (GM)-gut interaction is centrally positioned for consideration as an innovative approach for HTN therapeutics.

RECENT FINDINGS

Animal models of HTN have shown that gut pathology occurs in HTN, and provides some clues to mechanisms linking the dysbiosis, gut pathology, and HTN. Circumstantial evidence links gut dysbiosis and HTN. Gut pathology, apparent in animal HTN models, has not been fully investigated in hypertensive patients. Objective evidence and an understanding of mechanisms could have a major impact for new antihypertensive therapies and/or improved applications of current ones.

The renin-angiotensin-aldosterone-system and right heart failure in congenital heart disease

Adults with congenital heart disease represent a rapidly growing patient group. Dysfunction of the right ventricle is often present, and right heart failure constitutes the main cause of death. Heart failure therapies used in acquired left heart failure are often initiated in adults with right heart failure due to congenital heart disease, but the right ventricle differs substantially from the left ventricle, and the clinical evidence for this treatment strategy is lacking.

In this review, we identified existing clinical studies evaluating the effects of ACE inhibitors, angiotensin II receptor blockers and aldosterone antagonists in adults with congenital heart disease by a systematic literature search. From 13 identified studies no clear evidence of beneficial effects was found, but the design of the studies limits the validity of the results. The studies in general include low numbers of patients, have short follow-up periods and evaluate surrogate endpoints instead of hard clinical endpoints. Specific evaluation of symptomatic patients with a systemic right ventricle indicates that these patients may benefit from RAAS inhibitory treatments, but this requires further investigation.

To conclude, existing studies do not support the use of RAAS inhibitory treatments in right heart failure due to congenital heart disease but contain important limitations. Hence, there is a need for new well-designed trials including higher numbers of patients and validated endpoints to optimize and guide future treatment of this patient group.

Association of angiotensin converting enzyme gene insertion/deletion polymorphism with essential hypertension in south Indian population

Genetic, environmental and demographic factors contribute to the development of essential hypertension. Genetic polymorphism of Rennin-angiotensin-aldosterone system (RAAS) has been extensively studied to determine the genetic susceptibility to hypertension. The insertion/deletion (I/D) angiotensin converting enzyme (ACE) polymorphism has been established as a cardiovascular risk factor in some population, but its association with essential hypertension is controversial. This study sought to determine the association of I/D polymorphism of the ACE gene in south Indian essential hypertensive subjects. A total of 208 clinically diagnosed essential hypertensive patients without any associated diseases and 220 healthy control subjects were included in this study. Distribution and allelic frequency of Insertion (I) and Deletion (D) polymorphism at the 287 base pair Alu repeat sequence in the intron 16 of ACE gene were analyzed. The distribution of II, ID, DD genotypes of ACE gene was 28.3%, 32.6% and 38.9% respectively in essential hypertensive patients and to 53.6%, 26.3% and 20% in controls. The allele frequency for D allele is 0.58 in essential hypertension as compared to 0.34 of control subjects. The genotype and allele frequency of ACE gene polymorphism is significantly differed in patients when compared to controls. In conclusion, the I/D polymorphism of ACE gene is associated with Indian essential hypertension.

RAAS inhibition and the course of Alport syndrome

Alport syndrome (AS) is a hereditary progressive glomerulonephritis with a high life-time risk for end-stage renal disease (ESRD). Most patients will reach ESRD before the age of 30 years, while a subset of them with milder mutations will do so at older ages, even after 50 years. Frequent extrarenal manifestations are hearing loss and ocular abnormalities. AS is a genetically heterogeneous collagen IV nephropathy, with 85% of the cases caused by mutations in the X-linked COL4A5 gene and the rest by homozygous or compound heterozygous mutations in either the COL4A3 or the COL4A4 gene on chromosome 2q36-37. There is no radical cure for the disease and attempts to use various stem cell therapies in animal models have been met with ambiguous success. However, effective treatment has been accomplished with pharmacological intervention at the renin-angiotensin-aldosterone system (RAAS), first in animal models of AS and more recently in humans. Angiotensin converting enzyme inhibitors (ACEis) and angiotensin receptor blockers (ARBs) have been shown to significantly delay the progression of chronic kidney disease and the onset of ESRD. Also, renin inhibitors and aldosterone blockade were used with positive results, while the combination of ACEis and ARBs was met with mixed success. An important study, the EARLY-PROTECT, aims at evaluating the efficacy of ACEis when administered very early on in children with AS. Novel therapies are also tested experimentally or are under design in animal models by several groups, including the use of amniotic fluid stem cells and synthetic chaperones.

Recent Update of Renin-angiotensin-aldosterone System in the Pathogenesis of Hypertension

The activation of renin-angiotensin-aldosterine system(RAAS) is one of the main pathogenesis of hypertension. All the components of RAAS are present in the kidneys at higher concentrations compared to plasma levels, and intrarenal formation of angiotensin II (Ang II) is independent of the systemic RAAS. There are some unique features in intrarenal RAAS compared to systemic RAAS. Unlike JG cells where Ang II inhibits renin release via the AngII type 1 (AT1) receptor by negative feedback, in the collecting duct Ang II stimulates renin expression via the AT1 receptor. Upregulated renin produced in the distal nephron may be able to support continued intrarenal Ang II formation leading to amplification or maintenance of the hypertensive state.The recently discovered angiotensin-converting enzyme-related carboxypeptidase 2 (ACE2)-Angiotensin-(1-7) Ang-(1-7)-Mas receptor axis has an opposing function to that of the ACE-Ang II-AT1 receptor axis.The ACE2 deficiency was associated with an increase in blood pressure, and ACE2 knockout mice have highlighted hypertensive response to Ang II infusion associated with exaggerated accumulation of Ang II in the kidney. Recently, several numbers of patients have been evaluated as the activators of ACE2-Ang-(1-7)-Mas receptor axis, which can be divided into two main classes: aimed to increase the activity of ACE2, and directed to stimulate the Ang-(1-7) receptor Mas. In order to investigate new targets for hypertension and kidney disease, further research on the function of the ACE-Ang-(1-7)-Mas receptor axis is required.