Dual RAAS suppression: recent developments and implications in light of the ALTITUDE study

Effects of dual inhibition of renin-angiotensin-aldosterone system on cardiovascular and renal outcomes: balancing the risks and the benefits

Chronic kidney disease is a worldwide health problem often burdened by severe cardiovascular complications. Hypertension represents one of the most important risk factor in affecting cardiovascular profile of chronic kidney disease patients. Since renin-angiotensin-aldosterone system plays a major role in determining cardiovascular outcome, guidelines recommend the use of renin-angiotensin-aldosteron inhibitors in order to control hypertension.

Neprilysin inhibition and endothelin-1 elevation: Focus on the kidney

Increasing the degree of renin-angiotensin system (RAS) blockade by combining ≥2 RAS blockers marginally increases efficacy, but results in more side effects. Hence, interference with other systems is currently being investigated, like potentiation of natriuretic peptides with neprilysin inhibitors. However, the neprilysin inhibitor thiorphan was recently found to increase endothelin-1 when administered to TGR(mREN2)27 (Ren2) rats on top of RAS blockade. Here we investigated whether this effect is thiorphan-specific, by comparing the neprilysin inhibitors thiorphan and sacubitril, administered by osmotic minipumps at a low or high dose for 7 days, in Ren2 rats. Plasma and urinary levels of endothelin-1, atrial and brain natriuretic peptide (ANP, BNP) and their second messenger cyclic guanosine 3'5' monophosphate (cGMP) were monitored. No significant differences were found in the plasma concentrations of endothelin-1, cGMP, ANP and BNP after treatment, although plasma ANP tended to be higher in the high-dose thiorphan treatment group and the low- and high-dose sacubitril treatment groups, compared with vehicle. Urinary endothelin-1 increased in the low-dose thiorphan and high-dose sacubitril groups, compared with baseline, although significance was reached for the former only. Urinary cGMP rose significantly in the high-dose sacubitril treatment group compared with baseline. Both urinary endothelin-1 and cGMP were significantly higher in the high-dose sacubitril group compared with the low-dose sacubitril group. In conclusion, endothelin-1 upregulation occurs with both thiorphan and sacubitril, and is particularly apparent in neprilysin-rich organs like the kidney. High renal neprilysin levels most likely also explain why sacubitril increased cGMP in urine only.

Attitudes and preferences for the clinical management of hypertension and hypertension-related cerebrovascular disease in the general practice: results of the Italian hypertension and brain survey

Background

The aim of this survey was to evaluate attitudes and preferences for the clinical management of hypertension and hypertension-related cerebrovascular diseases (CVD) in Italy.

Methods

A predefined 16-item survey questionnaire was anonymously administered to a large community sample of general practitioners (GPs), trained by specialized physicians (SPs), who have been included in an educational program between January and November 2015.

Results

A total of 591 physicians, among whom 48 (8%) training SPs and 543 (92%) trained GPs, provided 12,258 valid answers to the survey questionnaire. Left ventricular hypertrophy was considered the most frequent marker of hypertension-related organ damage, whereas atrial fibrillation and carotid atherosclerosis were considered relatively not frequent (10–20%). The most appropriate blood pressure (BP) targets to be achieved in hypertensive patients with CVD were <140/90 mmHg for SPs and <135/85 mmHg for GPs. To achieve these goals, ACE inhibitors were considered the most effective strategies by GPs, whereas SPs expressed a preference for ARBs, both in monotherapies and in combination therapies with beta-blockers.

Conclusions

This survey demonstrates that Italian physicians considered left ventricular hypertrophy frequently associated to CVD and that drugs inhibiting the renin-angiotensin system the most appropriate therapy to manage hypertension and hypertension-related CVD.

Electronic supplementary material

The online version of this article (doi:10.1186/s40885-017-0066-0) contains supplementary material, which is available to authorized users.

Combined Angiotensin Receptor Modulation in the Management of Cardio-Metabolic Disorders

Cardiovascular and metabolic disorders, such as hypertension, insulin resistance, dyslipidemia or obesity are linked with chronic low-grade inflammation and dysregulation of the renin–angiotensin system (RAS). Consequently, RAS inhibition by ACE inhibitors or angiotensin AT1 receptor (AT1R) blockers is the evidence-based standard for cardiovascular risk reduction in high-risk patients, including diabetics with albuminuria. In addition, RAS inhibition reduces the new onset of diabetes mellitus. Yet, the high and increasing prevalence of metabolic disorders, and the high residual risk even in properly treated patients, calls for additional means of pharmacological intervention. In the past decade, the stimulation of the angiotensin AT2 receptor (AT2R) has been shown to reduce inflammation, improve cardiac and vascular remodeling, enhance insulin sensitivity and increase adiponectin production. Therefore, a concept of dual AT1R/AT2R modulation emerges as a putative means for risk reduction in cardio-metabolic diseases. The approach employing simultaneous RAS blockade (AT1R) and RAS stimulation (AT2R) is distinct from previous attempts of double intervention in the RAS by dual blockade. Dual blockade abolishes the AT1R-linked RAS almost completely with subsequent risk of hypotension and hypotension-related events, i.e. syncope or renal dysfunction. Such complications might be especially prominent in patients with renal impairment or patients with isolated systolic hypertension and normal-to-low diastolic blood pressure values. In contrast to dual RAS blockade, the add-on of AT2R stimulation does not exert significant blood pressure effects, but it may complement and enhance the anti-inflammatory and antifibrotic/de-stiffening effects of the AT1R blockade and improve the metabolic profile. Further studies will have to investigate these putative effects in particular for settings in which blood pressure reduction is not primarily desired.

Effects of Minocycline on Urine Albumin, Interleukin-6, and Osteoprotegerin in Patients with Diabetic Nephropathy: A Randomized Controlled Pilot Trial

Background

We tested minocycline as an anti-proteinuric adjunct to renin-angiotensin-aldosterone system inhibitors (RAASi) in diabetic nephropathy (DN) and measured urinary biomarkers to evaluate minocycline’s biological effects.

Methods

Design: Prospective, single center, randomized, placebo-controlled, intention-to-treat pilot trial. Inclusion. Type 2 diabetes/DN; Baseline creatinine clearance > 30 mL/min; proteinuria ≥ 1.0 g/day; Age ≥30 years; BP <150/95 mm Hg; intolerant of/at maximum RAASi dose. Protocol. 3-wk screening; Baseline randomization; Urine and blood measures at months 1, 2, 4, and Month 6 study completion. Urine interleukin-6 (IL-6) and osteoprotegerin were measured in a subset. Primary outcome. Natural log of urine protein/creatinine (ln U P:Cr) ratio at Month 6 vs Baseline.

Results

30 patients completed the study. The 15% decline in U P: Cr in minocycline patients (6 month P:Cr ÷ Baseline P:Cr, 0.85 vs. 0.92) was not significant (p = 0.27). Creatinine clearance did not differ in the 2 groups. Urine IL-6:Cr (p = 0.03) and osteoprotegerin/Cr (p = 0.046) decrements were significant. Minocycline modified the relationship between urine IL-6 and proteinuria, suggesting a protective biological effect.

Conclusions

Although the decline in U P:Cr in minocycline patients was not statistically significant, the significant differences in urine IL-6 and osteoprotegerin suggest that minocycline may confer cytoprotection in patients with DN, providing a rationale for further study.

Trial Registration

Clinicaltrials.gov NCT01779089

Attitudes and preferences for the clinical management of patients with hypertension and hypertension with chronic obstructive pulmonary disease in Italy: main results of a survey questionnaire

Hypertension treatment and control represent a clinical challenge, particularly in case of concomitant risk factors and comorbidities, including chronic obstructive pulmonary disease (COPD). To evaluate attitudes and preferences for the clinical management of hypertension and hypertension associated with COPD by a large community sample of physicians in Italy. A predefined 18-item survey questionnaire was anonymously administered to both specialised physicians (SPs) and general practitioners (GPs), who have been included in an educational programme, performed between January and June 2014. A total of 1181 physicians (767 males, mean age 55.8 ± 7.3 years, average age of medical activity 27.6 ± 8.3 years), among whom 64 (5.4 %) SPs and 1117 (94.6 %) GPs, provided 21,809 valid answers to the survey questionnaire. Concomitant presence of hypertension and COPD was frequently associated (21-40 %) with hypertension-related organ damage and comorbidities. Concomitant presence of hypertension and COPD was able to affect physicians' ability to achieve the recommended therapeutic targets. To achieve the recommended BP goals, ACE inhibitors or ARBs were considered the most effective antihypertensive strategies, both in monotherapies and in combination therapies with either diuretics or calcium-channel blockers. This observational, cross-sectional survey provides useful information on physicians' attitudes and preferences for the clinical management of patients with hypertension and hypertension associated with COPD.

Understanding and treating hypertension in diabetic populations

Hypertension and diabetes frequently occurs in the same individuals in clinical practice. Moreover, the presence of hypertension does increase the risk of new-onset diabetes, as well as diabetes does promote development of hypertension. Whatever the case, the concomitant presence of these conditions confers a high risk of major cardiovascular complications and promotes the use integrated pharmacological interventions, aimed at achieving the recommended therapeutic targets. While the benefits of lowering abnormal fasting glucose levels in patients with hypertension and diabetes have been consistently demonstrated, the blood pressure (BP) targets to be achieved to get a benefit in patients with diabetes have been recently reconsidered. In the past, randomized clinical trials have, indeed, demonstrated that lowering BP levels to less than 140/90 mmHg was associated to a substantial reduction of the risk of developing macrovascular and microvascular complications in hypertensive patients with diabetes. In addition, epidemiological and clinical reports suggested that "the lower, the better" for BP in diabetes, so that levels of BP even lower than 130/80 mmHg have been recommended. Recent randomized clinical trials, however, designed to evaluate the potential benefits obtained with an intensive antihypertensive therapy, aimed at achieving a target systolic BP level below 120 mmHg as compared to those obtained with less stringent therapy, have challenged the previous recommendations from international guidelines. In fact, detailed analyses of these trials showed a paradoxically increased risk of coronary events, mostly myocardial infarction, in those patients who achieved the lowest BP levels, particularly in the high-risk subsets of hypertensive populations with diabetes. In the light of these considerations, the present article will briefly review the common pathophysiological mechanisms, the potential sites of therapeutic interactions and the currently recommended BP targets to be achieved under pharmacological treatment in hypertension and diabetes.

Dual renin-angiotensin-aldosterone blockade: promises and pitfalls

Single renin-angiotensin-aldosterone system (RAAS) blockade has been shown to be effective and safe for the treatment of hypertension, coronary heart disease (CHD), heart failure (HF), diabetes, and chronic kidney disease (CKD) with proteinuria. Due to the action of RAAS blockers at various levels of the RAAS cascade, it was hypothesized that dual RAAS blockade would result in more complete inhibition of angiotensin II (Ang II) production and be more effective in blocking its detrimental cardiovascular remodeling effects. Unfortunately, several clinical trials in patients with hypertension, CHD, HF, and CKD with proteinuria have demonstrated no superiority of dual versus single RAAS blockade, but a higher incidence of adverse events. Based on these findings, dual RAAS blockade is no longer recommended for the routine treatment of various cardiovascular diseases, except diabetic nephropathy with proteinuria and HF with reduced ejection fraction. All the new information gathered from studies within the last 3 years will be presented in this review.

Renin-angiotensin system phenotyping as a guidance toward personalized medicine for ACE inhibitors: can the response to ACE inhibition be predicted on the basis of plasma renin or ACE?

PURPOSE & METHODS

Not all hypertensive patients respond well to ACE inhibition. Here we determined whether renin-angiotensin system (RAS) phenotyping, i.e., the measurement of renin or ACE, can predict the individual response to RAS blockade, either chronically (enalapril vs. enalapril + candesartan) or acutely (enalapril ± hydrochlorothiazide, HCT).

RESULTS

Chronic enalapril + candesartan induced larger renin rises, but did not lower blood pressure (BP) more than enalapril. Similar observations were made for enalapril + HCT vs. enalapril when given acutely. Baseline renin predicted the peak changes in BP chronically, but not acutely. Baseline ACE levels had no predictive value. Yet, after acute drug intake, the degree of ACE inhibition, like Δrenin, did correlate with ΔBP. Only the relationship with Δrenin remained significant after chronic RAS blockade. Thus, a high degree of ACE inhibition and a steep renin rise associate with larger acute responses to enalapril. However, variation was large, ranging >50 mm Hg for a given degree of ACE inhibition or Δrenin. The same was true for the relationships between Δrenin and ΔBP, and between baseline renin and the maximum reduction in BP in the chronic study.

CONCLUSIONS

Our data do not support that RAS phenotyping will help to predict the individual BP response to RAS blockade. Notably, these conclusions were reached in a carefully characterized, homogenous population, and when taking into account the known fluctuations in renin that relate to gender, age, ethnicity, salt intake and diuretic treatment, it seems unlikely that a cut-off renin level can be defined that has predictive value.

Optimum AT1 receptor-neprilysin inhibition has superior cardioprotective effects compared with AT1 receptor blockade alone in hypertensive rats

Neprilysin inhibitors prevent the breakdown of bradykinin and natriuretic peptides, promoting vasodilation and natriuresis. However, they also increase angiotensin II and endothelin-1. Here we studied the effects of a low and a high dose of the neprilysin inhibitor thiorphan on top of AT1 receptor blockade with irbesartan versus vehicle in TGR(mREN2)27 rats with high renin hypertension. Mean arterial blood pressure was unaffected by vehicle or thiorphan alone. Irbesartan lowered blood pressure, but after 7 days pressure started to increase again. Low- but not high-dose thiorphan prevented this rise. Only during exposure to low-dose thiorphan plus irbesartan did heart weight/body weight ratio, cardiac atrial natriuretic peptide expression, and myocyte size decrease significantly. Circulating endothelin-1 was not affected by low-dose thiorphan with or without irbesartan, but increased after treatment with high-dose thiorphan plus irbesartan. This endothelin-1 rise was accompanied by an increase in renal sodium-hydrogen exchanger 3 protein abundance, and an upregulation of constrictor vascular endothelin type B receptors. Consequently, the endothelin type B receptor antagonist BQ788 no longer enhanced endothelin-1-induced vasoconstriction (indicative of endothelin type B receptor-mediated vasodilation), but prevented it. Thus, optimal neprilysin inhibitor dosing reveals additional cardioprotective effects on top of AT1 receptor blockade in renin-dependent hypertension.

Novel effective drugs for diabetic kidney disease? or not?

INTRODUCTION

Diabetes mellitus is increasingly common worldwide and is expected to affect 592 million people by 2035. The kidney is often involved. A key goal in treating diabetes is to reduce the risk of development of kidney disease and, if kidney disease is already present, to delay the progression to end-stage renal disease (ESRD). This represents a social and ethical issue, as a significant proportion of patients reaching ESRD in developing countries do not have access to renal replacement therapy.

AREAS COVERED

The present review focuses on novel therapeutic approaches for diabetic nephropathy (DN), implemented on the basis of recent insights on its pathophysiology, which might complement the effects of single inhibition of the renin-angiotensin-aldosterone system (RAAS), the cornerstone of renoprotective interventions in diabetes, along with glycemic and blood pressure control.

EXPERT OPINION

Although a plethora of new treatment options has arisen from experimental studies, the number of novel renoprotective molecules successfully implemented in clinical practice over the last two decades is disappointingly low. Thus, new investigational strategies and diagnostic tools - including the appropriate choice of relevant renal end points and the study of urinary proteome of patients - will be as important as new therapeutic interventions to fight DN. Finally, in spite of huge financial interests in replacing the less expensive ACE inhibitors and angiotensin II receptor blockers with newer drugs, any future therapeutic approach has to be tested on top of - rather than instead of - optimal RAAS blockade.

Contemporary treatment strategies for Type 2 diabetes-related macrovascular disease

Type 2 diabetes mellitus poses a major challenge to healthcare providers in the coming years as its prevalence increases across the globe. The disease doubles the risk of cardiovascular morbidity and mortality, with 70% of sufferers dying from a cardiac cause. Large clinical trials of current glucose-lowering therapies for Type 2 diabetes have shown no benefit in reducing the risk of macrovascular events. Blood pressure control, angiotensin-converting enzyme inhibitor therapy and improvement of dyslipidemia with statins have proven benefit in reducing cardiovascular risk in Type 2 diabetes. A growing understanding of the importance of pathological processes including endothelial dysfunction, abnormal growth factor biology, oxidative stress, dysregulation of adipokines and deficient vascular repair and regeneration in insulin-resistant states promises new treatments to combat the problem.

Deterioration of kidney function by the (pro)renin receptor blocker handle region peptide in aliskiren-treated diabetic transgenic (mRen2)27 rats

Dual renin-angiotensin system (RAS) blockade in diabetic nephropathy is no longer feasible because of the profit/side effect imbalance. (Pro)renin receptor [(P)RR] blockade with handle region peptide (HRP) has been reported to exert beneficial effects in various diabetic models in a RAS-independent manner. To what degree (P)RR blockade adds benefits on top of RAS blockade is still unknown. In the present study, we treated diabetic TGR(mREN2)27 rats, a well-established nephropathy model with high prorenin levels [allowing continuous (P)RR stimulation in vivo], with HRP on top of renin inhibition with aliskiren. Aliskiren alone lowered blood pressure and exerted renoprotective effects, as evidenced by reduced glomerulosclerosis, diuresis, proteinuria, albuminuria, and urinary aldosterone levels as well as diminished renal (P)RR and ANG II type 1 receptor expression. It also suppressed plasma and tissue RAS activity and suppressed cardiac atrial natriuretic peptide and brain natriuretic peptide expression. HRP, when given on top of aliskiren, did not alter the effects of renin inhibition on blood pressure, RAS activity, or aldosterone. However, it counteracted the beneficial effects of aliskiren in the kidney, induced hyperkalemia, and increased plasma plasminogen activator-inhibitor 1, renal cyclooxygenase-2, and cardiac collagen content. All these effects have been linked to (P)RR stimulation, suggesting that HRP might, in fact, act as a partial agonist. Therefore, the use of HRP on top of RAS blockade in diabetic nephropathy is not advisable.

Sequential RAAS blockade: is it worth the risk?

Soon after the emergence of the renin-angiotensin-aldosterone system (RAAS) blocking treatment as the cornerstone of renoprotective treatment in the prevention and treatment of diabetic and nondiabetic CKD, it was investigated if a higher degree of achievable RAAS blockade by combining more than one compound is feasible and advantageous. Regardless of the benefits from using monotherapy for diabetic kidney disease, there is still much improvement to wish for in terms of kidney prognosis in these populations. A great deal of research has gone into evaluating combinations of the RAAS blocking treatments in different populations and with different drugs and doses. Studies have mostly been short-term and use surrogate endpoints such as albuminuria. Side effects have been well known and expected in terms of increasing potassium levels and hypotension, but to an acceptable extent. With recent disappointing results from major hard endpoint trials using dual RAAS blockade the concept is now under scrutiny. In this review we will discuss the pros and cons of dual RAAS blockade, with facts and findings from smaller studies, endpoint trials, and meta-analyses.

Targets, trends, excesses, and deficiencies: refocusing clinical investigation to improve patient outcomes

Clinical trials in nephrology have focused on achieving targets, supplementing deficiencies, and correcting excesses in order to improve patient outcomes. The majority of interventions have failed to demonstrate benefit and some have caused harm. It may be that therapies aiming to 'normalize' parameters may actually disturb evolutionary adaptation, thus causing harm. By refocusing on the physiology of disease, and complexity of adaptation, we may design better trials. We review successful and unsuccessful trials in nephrology and other disciplines and suggest a set of principles by which to design future clinical trials:(1) acknowledge heterogeneity of chronic kidney disease populations and appropriately characterize populations for studies; (2) develop better validated biomarkers (through proteomics, genomics, and metabolomics) to identify responders and nonresponders to interventions; (3) design interventions that mimic physiological processes without collateral detrimental effects; (4) reconsider the status of the randomized-controlled trial as the only 'gold standard' and perform large-scale pragmatic trials comparing current care with the intervention(s) of interest, and (5) broaden nephrology research culture so that the majority of patients are enrolled into observational cohorts and intervention studies, which foster greater knowledge acquisition and dissemination. Improved understanding of pathophysiological mechanisms, in conjunction with more innovative but stringent clinical trial design, will ultimately lead to improved patient outcomes.

Targeting the renin-angiotensin-aldosterone system in heart failure

The renin-angiotensin-aldosterone system is a well-established therapeutic target in the treatment of heart failure (HF). Substantial advances have been made with existing agents--angiotensin-converting enzyme (ACE) inhibitors, angiotensin II-receptor blockers (ARBs), and mineralocorticoid-receptor antagonists (MRAs)--and new data continue to emerge. The indication for the use of MRAs has been broadened to include potentially all patients who have HF with reduced ejection fraction (HFrEF), and ACE inhibitors might have a novel application in patients who are at risk of left ventricular dysfunction (those with aortic valvular disease or pacing-induced heart disease). ARBs have been shown to be a beneficial alternative to ACE inhibitors in HFrEF, but their value when added to ACE inhibitors has been questioned. Upstream, direct renin blockade with aliskiren is being pursued in two large trials of HF, despite the premature halting of a third study. A substantial, unmet need remains in patients who have HF with preserved ejection fraction (HFpEF). New data on spironolactone and LCZ696 (a combined ARB and neprilysin inhibitor) show promise for these patients. Results of the TOPCAT study of spironolactone in patients with HFpEF are awaited, and LCZ696 is now being tested in a large trial in patients with HFrEF.

Key developments in renin-angiotensin-aldosterone system inhibition

The renin-angiotensin-aldosterone system (RAAS) was initially thought to be fairly simple. However, this idea has been challenged following the development of RAAS blockers, including renin inhibitors, angiotensin-converting-enzyme (ACE) inhibitors, type 1 angiotensin II (AT(1))-receptor blockers and mineralocorticoid-receptor antagonists. Consequently, new RAAS components and pathways that might contribute to the effectiveness of these drugs and/or their adverse effects have been identified. For example, an increase in renin levels during RAAS blockade might result in harmful effects via stimulation of the prorenin receptor (PRR), and prorenin-the inactive precursor of renin-might gain enzymatic activity on PRR binding. The increase in angiotensin II levels that occurs during AT(1)-receptor blockade might result in beneficial effects via stimulation of type 2 angiotensin II receptors. Moreover, angiotensin 1-7 levels increase during ACE inhibition and AT(1)-receptor blockade, resulting in Mas receptor activation and the induction of cardioprotective and renoprotective effects, including stimulation of tissue repair by stem cells. Finally, a role of angiotensin II in sodium and potassium handling in the distal nephron has been identified. This finding is likely to have important implications for understanding the effects of RAAS inhibition on whole body sodium and potassium balance.