ACE inhibition and cardiovascular mortality and morbidity in essential hypertension: the end of the search or a need for further investigations?

Targeting the renin-angiotensin system for the reduction of cardiovascular outcomes in hypertension: angiotensin-converting enzyme inhibitors and angiotensin receptor blockers

Agents that counteract the negative impact of the renin-angiotensin-aldosterone system (RAAS) are effective antihypertensives and reduce the risk of developing Type 2 diabetes. Contrary to common perception, angiotensin-converting enzyme inhibitors do not share the apparent benefit of angiotensin II receptor blockers (ARBs) in reducing risk of cardiovascular-disease outcomes, particularly stroke, in randomised clinical trials. RAAS agents, especially ARBs, are well tolerated. Use of ARBs alone or in combination with other classes of antihypertensive agents to lower blood pressure and/or medications to control other conditions (e.g., insulin sensitivity) reduces risk of cardiovascular disease outcomes and Type 2 diabetes with excellent tolerability. Selected issues related to use of RAAS agents as antihypertensive therapies (e.g., Type 2 diabetes, global risk management, multiple drug therapy and coronary heart disease) are addressed.

Angiotensin II-receptor antagonist in the treatment of hypertension

Effective treatment of high blood pressure levels represents a crucial point in reducing global cardiovascular risk, and several studies have clearly demonstrated a significant reduction in cardiovascular and renal morbidity and mortality with a more intensive blood pressure-lowering treatment. Other factors beyond blood pressure control may be important in reducing the risk related to hypertension. Pharmacologic agents blocking the renin-angiotensin system, in particular the angiotensin II-receptor blocker (ARB), a novel class of antihypertensive agents, represent an important addition to the therapeutic options for hypertension management, and recent large, international, randomized, trials have demonstrated that ARBs have clinical benefits across the spectrum of disease severity. In this article, we provide some evidence derived from these trials, supporting a role for ARBs in primary and secondary prevention of cardiovascular and renal disease, beyond blood pressure control.

Vasopeptidase inhibition has beneficial cardiac effects in spontaneously diabetic Goto–Kakizaki rats

In this study we examined diabetes- and hypertension-induced changes in cardiac structure and function in an animal model of type 2 diabetes, the Goto-Kakizaki (GK) rat. We hypothesized that treatment with omapatrilat, a vasopeptidase inhibitor, which causes simultaneous inhibition of angiotensin converting enzyme and neutral endopeptidase, provides additional cardioprotective effects, during normal- as well as high sodium intake, compared to treatment with enalapril, a selective inhibitor of angiotensin converting enzyme. Fifty-two GK rats were randomized into 6 groups to receive either normal-sodium (NaCl 0.8%) or high-sodium (NaCl 6%) diet and enalapril, omapatrilat or vehicle for 12 weeks. The GK rats developed hypertension, cardiac hypertrophy and overexpression of cardiac natriuretic peptides and profibrotic connective tissue growth factor compared to nondiabetic Wistar rats. The high dietary sodium further increased the systolic blood pressure, and changed the mitral inflow pattern measured by echocardiography towards diastolic dysfunction. Enalapril and omapatrilat equally decreased the systolic blood pressure compared to the control group during normal- as well as high-sodium diet. Both drugs had beneficial cardioprotective effects, which were blunted by the high dietary sodium. Compared to enalapril, omapatrilat reduced the echocardiographically measured left ventricular mass during normal-sodium diet and improved the diastolic function during high-sodium diet in GK rats. Furthermore, omapatrilat reduced relative cardiac weight more effectively than enalapril during high sodium intake. Our results suggest that both the renin-angiotensin and the neutral endopeptidase system are involved in the pathogenesis of diabetic cardiomyopathy since vasopeptidase inhibition was shown to provide additional benefits in comparison with selective angiotensin converting enzyme inhibition alone.

Angiotensin-II receptor blockers: benefits beyond blood pressure reduction?

Effective treatment of hypertension is essential to reduce the risk of renal and cardiovascular (CV) morbidity. The risks associated with hypertension are modulated by the presence of other factors. This has prompted the quest for agents that have benefits beyond blood pressure (BP) lowering. The angiotensin II receptor blocker (ARB) class of antihypertensive agents represents an important addition to the therapeutic options for elevated BP. Their ability to control BP is equivalent to existing therapies and there is a considerable and mounting evidence-base for their ability to reduce hypertension-associated target organ damage and comorbidities. Studies show that ARBs have clinical benefits across the spectrum of disease severity. In particular, recent large studies have demonstrated that these benefits extend to patients with conditions predisposing to CV events, such as diabetes, left ventricular hypertrophy and microalbuminuria, and where risk factors coexist. Data from these studies suggest that the CV protective effects of ARBs are at least, in part, independent from the BP lowering action. In addition, ARBs are extremely well tolerated, and strong evidence suggests that compliance with therapy--a key factor in achieving adequate BP control--with ARBs is higher than with other antihypertensive agents. Furthermore, flexible dosing and good tolerability profile mean that, where necessary, ARBs can be combined with other classes of antihypertensive agents to achieve adequate BP control and reduce the risk of hypertension-associated morbidity.

Pharmacological Inhibition and Genetic Deficiency of Plasminogen Activator Inhibitor-1 Attenuates Angiotensin II/Salt-Induced Aortic Remodeling

OBJECTIVE

To test the hypothesis that pharmacological plasminogen activator inhibitor (PAI)-1 inhibition protects against renin-angiotensin-aldosterone system-induced cardiovascular injury, the effect of a novel orally active small-molecule PAI-1 inhibitor, PAI-039, was examined in a mouse model of angiotensin (Ang) II-induced vascular remodeling and cardiac fibrosis.

METHODS AND RESULTS

Uninephrectomized male C57BL/6J mice were randomized to vehicle subcutaneus, Ang II (1 mug/h) subcutaneous, vehicle+PAI-039 (1 mg/g chow), or Ang II+PAI-039 during high-salt intake for 8 weeks. Ang II caused significant medial, adventitial, and aortic wall thickening compared with vehicle. PAI-039 attenuated Ang II-induced aortic remodeling without altering the pressor response to Ang II. Ang II increased heart/body weight ratio and cardiac fibrosis. PAI-039 did not attenuate the effect of Ang II on cardiac hypertrophy and increased fibrosis. The effect of PAI-039 on Ang II/salt-induced aortic remodeling and cardiac fibrosis was comparable to the effect of genetic PAI-1 deficiency. Ang II increased aortic mRNA expression of PAI-1, collagen I, collagen III, fibronectin, osteopontin, monocyte chemoattractant protein-1, and F4/80; PAI-039 significantly decreased the Ang II-induced increase in aortic osteopontin expression at 8 weeks.

CONCLUSIONS

This study demonstrates that pharmacological inhibition of PAI-1 protects against Ang II-induced aortic remodeling. Future studies are needed to determine whether the interactive effect of Ang II/salt and reduced PAI-1 activity on cardiac fibrosis is species-specific. In this study, the effect of pharmacological PAI-1 inhibition in a mouse model of Ang II-induced vascular remodeling and cardiac fibrosis was examined. PAI-1 inhibition significantly attenuated Ang II-induced aortic medial and wall thickening, but not cardiac hypertrophy, and enhanced Ang II/salt-induced cardiac fibrosis.

Hypertension mega-trials with cardiovascular end points: effect of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers

BACKGROUND

The renin-angiotensin-aldosterone system has a pivotal role in the short- and long-term regulation of blood pressure through its principal mediator, angiotensin II. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II-receptor blockers (ARBs) decrease the deleterious effects of angiotensin II on the vasculature and heart, but have different mechanisms of action. Although the blood pressure-lowering effect of ACE inhibitors and ARBs is equivalent to that of most other antihypertensive agents, emerging data suggest that these drug classes may have a greater effect on decreasing cardiovascular morbidity and mortality rates in specific patient populations.

METHODS

We reviewed large (approximately > or =5000 patients) hypertension clinical trials using ACE inhibitors and ARBs and with cardiovascular morbidity/mortality end points.

RESULTS

Six trials of ACE inhibitors and 5 trials of ARBs (3 completed, 2 ongoing) were selected for this analysis. Data from these hypertension mega-trials suggest that ACE inhibitors and ARBs may decrease cardiovascular morbidity and mortality rates, especially in patients with diabetes mellitus, renal dysfunction, and left ventricular hypertrophy. However, some trials showed important blood-pressure differences and are therefore partly inconclusive for particular drug effects.

CONCLUSIONS

Analysis of recently reported and ongoing mega-trials of renin-angiotensin-aldosterone system inhibitors may support the notion that their vasculoprotective properties confer greater benefit by virtue of their effects beyond blood-pressure reduction. Results from trials that will be completed in the next few years may provide further support of blocking the renin-angiotensin-system in cardiovascular protection in the management of hypertension.

Cerebrovascular protection and antihypertensive therapy

PURPOSE OF REVIEW

Our aim is to review the association between blood pressure and stroke and analyse data from randomized controlled trials involving diverse therapies, especially those regarding the renin-angiotensin system. In addition, an overview of stroke pathogenesis is given and its relationship with treatment action mechanisms reviewed.

RECENT FINDINGS

Stroke is a leading cause of death worldwide. In addition, many survivors of stroke suffer different degrees of disability. Because of the ageing of the global population, especially in regions of rapid economic growth, stroke will remain the second leading cause of death and in terms of disability it will be among the five most important causes in both developing and developed countries. High blood pressure is the most important risk factor for stroke, either ischemic or haemorrhagic, and established hypertension is the most prevalent modifiable risk factor. Data from controlled trials of blood-pressure-lowering treatment have demonstrated that treatment considerably lowers the risk of stroke within a few years of starting treatment. However, there exists controversy about the most efficient treatment regimen for primary and secondary prevention of stroke among the different blood-pressure-lowering treatments.

SUMMARY

Debate rages as to whether the benefits of treating high blood pressure are simply determined by the quality of blood-pressure control, or whether the choice of drug therapy adds or detracts from the expected benefits of blood-pressure reduction. The desirable future interventional comparative studies should consent to determine specific effects of drug classes on cardiovascular risk in the absence of the confounding effect of a relevant blood-pressure reduction that may counteract the potential blood-pressure-independent benefits of specific drug classes.

Novel antihypertensive agents

Coronary heart disease and cerebrovascular disease continue to be the leading causes of illness and death among adults from developed countries. Their prevalence is strongly related to the effects of many different risk factors, including high blood pressure, cigarette smoking, dyslipidaemia and diabetes. The management of cardiovascular (CV) risk factors should be viewed as an integrated strategy of intervention aimed at correcting as many of the underlying causes of CV disease as possible. Blocking the renin-angiotensin-aldosterone system with new, well-tolerated antihypertensive drugs, and blood pressure regulation by means of new drugs that also reduce plasma cholesterol levels or improve insulin resistance and glucose tolerance, could lead to a reduction of CV diseases.

ACE inhibition or angiotensin receptor blockade: which should we use in diabetic patients?

Blockade of the effects of angiotensin II (Ang II) by using an angiotensin-converting enzyme (ACE) inhibitor has been proven to be of value in Type 1 diabetic nephropathy and in non-diabetic renal disease. Evidence in favour of Ang II blockade in Type 2 diabetic patients with renal damage is still lacking for ACE inhibitors (ACE-Is), while recent data indicate that angiotensin receptor blockers (ARBs) could be the drugs of choice in this situation. On the other hand, renal damage from the onset of disease is accompanied by a very significant increment in global cardiovascular risk. This fact, as well as that of simultaneous renal and cardiovascular protection, have to be considered for drug selection. In this sense, ACE-Is have been shown to be the drugs of choice when secondary cardiovascular prevention is required, while the evidence in primary prevention in hypertensive patients has been shown with losartan in the Losartan Intervention For Endpoint reduction in hypertension (LIFE) study. All these facts led to the conclusion that both ACE-Is and ARBs can be considered when both renal and cardiovascular protection are aimed for in Type 2 diabetic patients.

Obesity-associated activation of angiotensin and endothelin in the cardiovascular system

The renin-angiotensin system (RAS) and the endothelin system have been implicated in the pathogenesis of human cardiovascular and renal diseases, and inhibition of the RAS markedly improves morbidity and survival. Obesity in humans is associated with an increased risk for the development of hypertension, atherosclerosis and focal-segmental glomerulosclerosis, however the exact mechanisms underlying these pathologies in obese individuals are not known. This article discusses the clinical importance of obesity and the current evidence for local activation of the renin-angiotensin system and its interactions with the endothelin system in obesity and the cardiovascular pathologies associated with it.