Effectively targetting the renin-angiotensin-aldosterone system in cardiovascular and renal disease: rationale for using angiotensin II receptor blockers in combination with angiotensin-converting enzyme inhibitors

Cardiomyocyte-specific deletion of TLR4 attenuates angiotensin II-induced hypertension and cardiac remodeling

Toll-like receptor 4 (TLR4) is an integral factor in the initiation of the innate immune response and plays an important role in cardiovascular diseases such as hypertension and myocardial infarction. Previous studies from our lab demonstrated that central TLR4 blockade reduced cardiac TLR4 expression, attenuated hypertension, and improved cardiac function. However, the contribution of cardiac specific TLR4 to the development of hypertension and cardiac remodeling is unknown. Therefore, we hypothesized that cardiomyocyte specific knockdown of TLR4 would have beneficial effects on hypertension, cardiac hypertrophy, and remodeling. To test this hypothesis, cardiomyocyte-specific TLR4 knockdown (cTLR4KO) mice were generated by crossing floxed TLR4 mice with Myh6-Cre mice, and subjected to angiotensin II (Ang II, 1 µg/kg/min or vehicle for 14 days) hypertension model. Blood pressure measurements using radio telemetry revealed no differences in baseline mean arterial pressure between control littermates and cTLR4KO mice (103 ± 2 vs. 105 ± 3 mmHg, p > 0.05). Ang II-induced hypertension (132 ± 2 vs. 151 ± 3 mmHg, p < 0.01) was attenuated and cardiac hypertrophy (heart/body weight; 4.7 vs. 5.8 mg/g, p < 0.01) was prevented in cTLR4KO mice when compared with control mice. In addition, the level of myocardial fibrosis was significantly reduced, and the cardiac function was improved in cTLR4KO mice infused with Ang II. Furthermore, cardiac inflammation, as evidenced by elevated gene expression of TNF, IL-6, and MCP-1 in the left ventricle, was attenuated in cTLR4KO mice infused with Ang II. Together, this data revealed a protective role for cardiomyocyte-specific deletion of TLR4 against Ang II-induced hypertension and cardiac dysfunction through inhibition of proinflammatory cytokines.

Efficacy and safety of supramaximal titrated inhibition of renin-angiotensin-aldosterone system in idiopathic dilated cardiomyopathy

Aims

The optimal dosing strategies for blocking the renin‐angiotensin‐aldosterone system in idiopathic dilated cardiomyopathy (IDCM) are poorly known. We sought to determine the long‐term efficacy and safety of supramaximal titration of benazepril and valsartan in patients with IDCM.

Methods and results

480 patients with IDCM in New York Heart Association functional class II–IV and with left ventricular ejection fraction ≤35% were randomly assigned to extended‐release metoprolol (mean 152 mg/day, range 23.75–190), low‐dose benazepril (20 mg/day), low‐dose valsartan (160 mg/day), high‐dose benazepril (mean 69 mg/day, range 40–80), and high‐dose valsartan (mean 526 mg/day, range 320–640). After a median follow‐up of 4.2 years, high‐dose benazepril and valsartan, compared with their respective low dosages, resulted in 41% and 52% risk reduction in the primary endpoint of all‐cause death or admission for heart failure (P = 0.042 and 0.002), promoted functional improvement, and reversed remodelling as assessed by New York Heart Association classes, quality‐of‐life scores, and echocardiographic recording of left ventricular ejection fraction, left ventricular end‐diastolic volume, mitral regurgitation, and wall motion score index. Compared with metoprolol, high‐dose valsartan reduced risk for the primary endpoint by 46% (P = 0.006), whereas high‐dose benazepril and both low‐dose groups showed no significant difference. Major adverse events involved hypotension and renal impairment but were largely tolerated.

Conclusions

Supramaximal doses of benazepril and valsartan were well tolerated and produced extra benefit than their low dosages in clinical outcome and cardiac reverse remodelling in patients with IDCM and modest‐severe heart failure. ClinicalTrials.gov identifier: NCT01917149.

Candida krusei: biotechnological potentials and concerns about its safety

Yeasts have a tradition in biotechnological applications, and Saccharomyces species are the most dominating representatives. Among the yeast species, Candida krusei has been isolated from different habitats, and in recent years, it has gained increased interest because of its diverse biotechnological role. It is found in many fermented food items and dairy products and has also been exploited for production of biochemicals and enzymes. However, because of its opportunistic pathogenic nature, it draws scientific attention regarding the safety of its industrial exploitation. Candida krusei generally causes infections in immunocompromised patients, such as those suffering from Human immunodeficiency virus - acquired immune deficiency syndrome, and also in cancer patients. The recent increase in the use of immunosuppressive drugs has increased the chances of C. krusei infections. Candida krusei possesses an intrinsic resistance to many triazole antifungal drugs, especially fluconazole, which is a main drug used in antifungal therapy; therefore, there is serious concern regarding its safe industrial use.

Trilogy of ACE2: a peptidase in the renin-angiotensin system, a SARS receptor, and a partner for amino acid transporters

Angiotensin-converting enzyme (ACE) 2 is a homolog to the carboxypeptidase ACE, which generates angiotensin II, the main active peptide of renin-angiotensin system (RAS). After the cloning of ACE2 in 2000, three major ACE2 functions have been described so far. First ACE2 has emerged as a potent negative regulator of the RAS counterbalancing the multiple functions of ACE. By targeting angiotensin II ACE2 exhibits a protective role in the cardiovascular system and many other organs. Second ACE2 was identified as an essential receptor for the SARS coronavirus that causes severe acute lung failure. Downregulation of ACE2 strongly contributes to the pathogenesis of severe lung failure. Third, both ACE2 and its homologue Collectrin can associate with amino acid transporters and play essential role in the absorption of amino acids in the kidney and gut. In this review, we will discuss the multiple biological functions of ACE2.

Complementary effects of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers in slowing the progression of chronic kidney disease

Chronic kidney disease (CKD) and end-stage renal disease continue to pose major healthcare challenges. Early initiation of therapy aimed at slowing the progression of CKD is essential. Increased renin-angiotensin-aldosterone-system activity and, in particular, elevated levels of angiotensin II (AII) play important roles in the development and progression of CKD. Therefore, pharmacologic therapies that block the effects of AII and reduce its pathogenic effects are cornerstones of clinical management. Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) have been shown to have renoprotective effects in addition to their ability to control blood pressure. There is accumulating clinical evidence that the combination of an ACEI and an ARB provides greater renal protection, particularly in decreasing proteinuria, than does either agent alone.

Renoprotection of Optimal Antiproteinuric Doses (ROAD) Study: a randomized controlled study of benazepril and losartan in chronic renal insufficiency

The Renoprotection of Optimal Antiproteinuric Doses (ROAD) study was performed to determine whether titration of benazepril or losartan to optimal antiproteinuric doses would safely improve the renal outcome in chronic renal insufficiency. A total of 360 patients who did not have diabetes and had proteinuria and chronic renal insufficiency were randomly assigned to four groups. Patients received open-label treatment with a conventional dosage of benazepril (10 mg/d), individual uptitration of benazepril (median 20 mg/d; range 10 to 40), a conventional dosage of losartan (50 mg/d), or individual uptitration of losartan (median 100 mg/d; range 50 to 200). Uptitration was performed to optimal antiproteinuric and tolerated dosages, and then these dosages were maintained. Median follow-up was 3.7 yr. The primary end point was time to the composite of a doubling of the serum creatinine, ESRD, or death. Secondary end points included changes in the level of proteinuria and the rate of progression of renal disease. Compared with the conventional dosages, optimal antiproteinuric dosages of benazepril and losartan that were achieved through uptitration were associated with a 51 and 53% reduction in the risk for the primary end point (P = 0.028 and 0.022, respectively). Optimal antiproteinuric dosages of benazepril and losartan, at comparable BP control, achieved a greater reduction in both proteinuria and the rate of decline in renal function compared with their conventional dosages. There was no significant difference for the overall incidence of major adverse events between groups that were given conventional and optimal dosages in both arms. It is concluded that uptitration of benazepril or losartan against proteinuria conferred further benefit on renal outcome in patients who did not have diabetes and had proteinuria and renal insufficiency.

Long-term safety of high-dose angiotensin receptor blocker therapy in hypertensive patients with chronic kidney disease

BACKGROUND

Reducing urinary protein excretion in patients with renal disease is an important therapeutic target to prevent the progression of renal and cardiovascular disease. Drugs such as angiotensin-converting enzyme inhibitors and angiotensin receptor blockers (ARBs), which block the actions of the renin-angiotensin-aldosterone system, are recommended because they reduce blood pressure and proteinuria. Recently, the use of higher doses of ARBs, up to three times the maximal approved dose, resulted in further reductions in protein excretion. Despite the effectiveness of this therapeutic approach, no long-term safety analysis has been conducted in patients receiving high-dose ARB treatment.

OBJECTIVE

To study the long-term safety of high-dose ARB treatment.

METHODS

We observed 48 patients [44 men and 4 women; ages 64 +/- 15 years (mean +/- SD), weight 88 +/- 28 kg, estimated glomerular filtration rate 53 +/- 23 ml/min] receiving treatment with high doses (1.5-5 times greater than the maximum approved dose) of ARBs, for 40 +/- 24 months (range 6-98 months).

RESULTS

The average ARB dose tended to increase over time and was 3.2 +/- 1.2 times greater at the end of the study than that at the start. Systolic blood pressure was similar at the beginning and end of the study period (132 +/- 20 and 125 +/- 20 mmHg, respectively), but diastolic blood pressure showed a decrease throughout the study and was significantly reduced (P < 0.05) in association with 1.5x and 2x the maximum ARB dose (73 +/- 11 and 72 +/- 10 mmHg, respectively) when compared with baseline (78 +/- 11 mm Hg). There was a trend (P > 0.05) for increases in concentrations of serum potassium (0.2 +/- 0.9 mmol/l) and creatinine (0.3 +/- 0.7 mg/dl) with increases in dose from baseline to the end of the study. Serum creatinine concentration was greater (P < 0.05) at the periods of 3x and 4x the maximum dose, but this represented increases of only 12 and 20% from baseline, respectively.

CONCLUSIONS

High-dose ARB treatment in patients with chronic renal disease is not associated with any clinically significant long-term negative effects on serum creatinine or potassium and is thus a important therapeutic modality with which to achieve further reductions in urinary protein excretion.

Long-Term Renoprotective Effects of Standard Versus High Doses of Telmisartan in Hypertensive Nondiabetic Nephropathies

BACKGROUND

This report describes an open randomized study intended to evaluate the long-term renoprotective effects of "standard" (80 mg once daily) versus "high" (80 mg twice daily) doses of telmisartan in hypertensive patients without diabetes with biopsy-proven chronic proteinuric nephropathies.

METHODS

We included 78 patients (age, 43.5 +/- 13.2 years; 71.8% men). After a 4-week wash-out period, patients were randomly assigned to telmisartan, 80 mg once daily (n = 40) or 80 mg twice daily (n = 38), during a mean follow-up of 24.6 +/- 2.2 months.

RESULTS

Baseline characteristics were similar in both groups, including blood pressure, renal function, and proteinuria. Blood pressure control did not differ between groups during follow-up. In the group administered telmisartan, 80 mg once daily, serum creatinine level increased from 1.6 +/- 0.6 to 2.7 +/- 0.9 mg/dL (141 +/- 52 to 239 +/- 80 micromol/L), and estimated creatinine clearance declined from 68 +/- 30 to 50 +/- 34 mL/min (1.13 +/- 0.50 to 0.83 +/- 0.57 mL/s), whereas in those administered 80 mg twice daily, serum creatinine (1.6 +/- 0.7 to 1.6 +/- 0.8 mg/dL [141 +/- 62 to 141 +/- 71 micromol/L]) and estimated creatinine clearance values (67 +/- 38 to 74 +/- 38 mL/min [1.12 +/- 0.63 to 1.23 +/- 0.63 mL/s]) did not change during the study. The decrease in proteinuria was more pronounced (P < 0.01) in patients administered the high dose of telmisartan compared with those treated with the standard dose. Serum potassium levels and lipid profiles did not change significantly in either group.

CONCLUSION

Long-term administration of high doses of telmisartan seems to improve the efficacy of the drug to decrease proteinuria and slow the progression to end-stage renal failure in nondiabetic hypertensive renal disease.

Diabetic nephropathy: recent insights into the pathophysiology and the progression of diabetic nephropathy

Diabetes has become the single most frequent comorbid condition in patients admitted for renal replacement therapy. This is the result of a greater prevalence of type 2 diabetes and better survival of diabetic patients. Progress has been made in pinpointing the predisposition to diabetes on metabolic abnormalities of muscle mitochondrial metabolism, but the long sought genes predisposing to diabetes and to diabetic nephropathy have not yet been identified. Of great concern are experimental studies documenting that maternal hyperglycemia causes nephron underdosing in the offspring. Relevant to pathogenesis and treatment of diabetic nephropathy are, among others, recent insights that hyperglycemia sensitizes target organs to blood pressure-induced damage, and that local renin-angiotensin systems play an important role in genesis and progression of diabetic nephropathy.

Renal failure and ACE inhibition: how much is too much?

The dose-response relationship between pharmacological blockade of the renin-angiotensin system (RAS) and angiotensin II concentration in the circulation, on the one hand, and decrease of blood pressure, on the other hand, has been well established. In contrast it is currently unclear which dose of ACE inhibitors and/or angiotensin receptor blockers is optimal for nephroprotection. Clinical studies are rendered quite complex by an early decrease of glomerular filtration after RAS blockade and by side effects at higher doses such as renal sodium loss, hyperkalemia, anemia, etc. Animal experiments and recent clinical studies suggest that the doses of ACE inhibitors or angiotensin receptor blockers required for maximal reduction of proteinuria (as a surrogate marker) and for optimal nephroprotection (retardation of the loss of glomerular filtration) exceed those required for maximal lowering of blood pressure. Ongoing studies try to define the relative merits of high dose monotherapy (ACE inhibitors or angiotensin receptor blockers) versus a combination therapy of the two.

Antihypertensive efficacy of candesartan-lisinopril in combination vs. up-titration of lisinopril: the AMAZE trials

The AMAZE (A Multicenter Trial Using Atacand and Zestril vs. Zestril to Evaluate the Effects on Lowering Blood Pressure) program included two identical studies sponsored by AstraZeneca LP. The oral form of candesartan is candesartan cilexetil; for simplicity, the term "candesartan" is used throughout this manuscript. Two identical multicenter, randomized, double-blind studies were performed to determine if addition of the angiotensin receptor blocker candesartan was more effective in lowering blood pressure than up-titration of lisinopril. Hypertensive patients (N=1,096) who were uncontrolled on lisinopril 20 mg daily were randomized (1:1) to receive either 8 weeks of high-dose lisinopril (40 mg) or the addition of candesartan (16 mg) for 2 weeks followed by 32 mg for 6 weeks. Study 1 (n=538) demonstrated decreases in trough sitting systolic/diastolic blood pressures at Week 8 by 6.2/5.9 mm Hg, respectively, for the lisinopril up-titration treatment group and by 11.6/8.3 mm Hg, respectively, for the lisinopril plus candesartan treatment group (p<0.01 in comparing both blood pressures reductions between the two treatment groups). Corresponding results for Study 2 (n=558) are reductions of 8.7/6.2 mm Hg and 9.5/7.4 mm Hg, respectively, for each of the two treatment groups. For Study 2, comparisons of systolic/diastolic blood pressures between the two treatment groups were not statistically significantly different (p=0.51/p=0.08, respectively). Post hoc pooled analysis (N=1,096) demonstrated a slightly greater blood pressure reduction with lisinopril plus candesartan compared with lisinopril (3.1/1.7 mm Hg). A 95% confidence interval limit for the difference in least squares mean change from baseline in systolic blood pressure between the two treatment groups is -4.8 to -1.5 and is -2.8 to -0.7 in mm Hg for diastolic blood pressure. The blood pressure control rates (<140/<90 mm Hg) were 42.7% and 36.9%, respectively. Both treatment regimens were well tolerated in all groups. In conclusion, for hypertensive patients not controlled by lisinopril 20 mg once daily, addition of candesartan (32 mg once daily) or doubling the dose of lisinopril provides safe, additional reduction of blood pressure.

Acute and chronic renal failure

Renal failure is defined as a deterioration of kidney function that results in the retention of nitrogenous waste products. It is increasingly prevalent in older populations, individuals with diabetes or hypertension, and postoperative patients. Therefore, podiatric physicians caring for these populations can expect to encounter this condition frequently. This article describes the epidemiology, causes, complications, and appropriate evaluation of renal failure relevant to a practicing podiatric physician. Also highlighted are treatment considerations, renal dosing of medications, and prevention of contrast nephropathy.

How high should an ACE inhibitor or angiotensin receptor blocker be dosed in patients with diabetic nephropathy?

Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), two drug classes that effectively block the actions of the renin-angiotensin system (RAS), have unique capabilities as antihypertensive agents. Recent landmark clinical trials have demonstrated their important roles as primary therapy for the prevention of renal disease in diabetes. The optimal dosage of these RAS blockers required to slow the progression of renal disease or impair the development of cardiovascular risk is not known. However, data from many studies strongly support the use of the higher doses of ACE inhibitors or ARBs to reduce proteinuria. All studies of kidney disease progression demonstrate benefit on slowing only when blood pressure is reduced when using higher doses. In order to accrue the optimum benefit from ACE inhibitors and ARBs, the dose-response relationship for diabetic renal disease will have to be determined. The best strategy, ie, supramaximal doses of ACE inhibitors or ARBs or combining them, is still a matter of debate but may be resolved soon by results of ongoing studies.

How to titrate ACE inhibitors and angiotensin receptor blockers in renal patients: according to blood pressure or proteinuria?

The inhibition of the effects of angiotensin II is necessary to ensure the best degree of renal protection by the simultaneous control of blood pressure (BP) and the achievement of the maximal antiproteinuric capacity. The inhibition can be attained through the administration of either an angiotensin-converting enzyme (ACE) inhibitor or an angiotensin II receptor blocker (ARB). Uptitration of antihypertensive therapy is frequently required to achieve the desired BP goal in patients presenting with renal disease, with or without proteinuria. Control of BP is good for both cardiovascular and renal protection. Sometimes, in particular when BP levels are high in the absence of therapy, the simple control of BP without inhibiting the renin- angiotensin system can be accompanied by a significant drop in proteinuria. On the other hand, the possibility that an ACE inhibitor or an ARB diminishes protein excretion in urine in the absence of changes in BP has been considered after the known evidence that these classes of drugs are renoprotective independently of their effect on BP control. The aim of this paper is to briefly review the evidence in favor of uptitration of either class of inhibitors of the renin-angiotensin system as compared with the combination of the two for the control of either BP or proteinuria.

Just the beginning: novel functions for angiotensin-converting enzymes

Cardiovascular disease is predicted to be the commonest cause of death worldwide by the year 2020. Diabetes, smoking and hypertension are the main risk factors. The renin-angiotensin system plays a key role in regulating blood pressure and fluid and electrolyte homeostasis in mammals. The discovery of specific drugs that block either the key enzyme of the renin-angiotensin system, angiotensin-converting enzyme (ACE), or the receptor for its main effector angiotensin II, was a major step forward in the treatment of hypertension and heart failure. In recent years, however, the renin-angiotensin system has been shown to be a far more complex system than initially thought. It has become clear that additional peptide mediators are involved. Furthermore, a new ACE, angiotensin-converting enzyme 2 (ACE2), has been discovered which appears to negatively regulate the renin-angiotensin system. In the heart, ACE2 deficiency results in severe impairment of cardiac contractility and upregulation of hypoxia-induced genes. We shall discuss the interplay of the various effector peptides generated by angiotensin-converting enzymes ACE and ACE2, highlighting the role of ACE2 as a negative regulator of the renin-angiotensin system.