Angiotensin converting enzyme inhibitors and angiotensin II receptor blockers: evidence for and against the combination in the treatment of hypertension and proteinuria

Effect of Dual Blockade of Renin-Angiotensin System on Proteinuria

Aim: Aim of the study was the evaluation of the effect of dual blockade of the renin-angiotensin system (RAS) on proteinuria. Material and Methods: Sixty patients, included in the study, were treated with angiotensin-converting enzyme inhibitor and angiotensin receptor blocker for a period of 3 months. Results: The dual blockade of RAS resulted with decrease of proteinuria, a slight increase of serum creatinine and was not associated with a lowering of blood pressure.Conclusion: Combined therapy with ACE-I and ARB results in a more complete blockade of the RAS than monotherapy. In proteinuric nephropathies it reduces significantly baseline proteinuria.

Combination Angiotensin-Converting Enzyme Inhibitor and Angiotensin Receptor Blocker Therapy: Its Role in Clinical Practice

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are commonly prescribed for the management of hypertension. In addition, each of these drug classes has been shown to be effective in the treatment of congestive heart failure, proteinuric chronic kidney disease, and most recently the high-cardiac-risk profile patient. The individual success of each of these drug classes has fueled the theory that given together, the overall biologic effect of both would surpass that of either given alone. The foundation of this premise, although biologically plausible, has yet to be proven in a compelling enough fashion to support the everyday use of these two drug classes in combination. Additional clarifying studies are required to establish whether specific patient subsets exist that might benefit from such combination therapy.

Combination ACE Inhibitor and Angiotensin Receptor Blocker Therapy-Future Considerations

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are regularly prescribed for the management of hypertension. Each of these drug classes has also been shown to provide survival benefits for patients with heart failure, proteinuric chronic kidney disease, and/or a high cardiac risk profile. The individual gains seen with each of these drug classes have led to speculation that their combination might offer additive if not synergistic outcome benefits. The foundation of this hypothesis, although biologically possible, has thus far not been sufficiently well proven to support the everyday use of these 2 drug classes in combination. Additional outcomes trials, which are currently proceeding to their conclusion, may provide the necessary proof to support an expanded use of these 2 drug classes in combination.

High glucose concentration stimulates intracellular renin activity and angiotensin II generation in rat mesangial cells

Increased intrarenal renin-angiotensin system activity contributes to diabetic nephropathy. ANG II generation in mesangial cells (MC) is increased by high-glucose (HG) exposure. This study assessed the mechanisms involved in the glucose-induced ANG II generation in rat MC. Under basal conditions, MC mainly secreted prorenin. HG decreased prorenin secretion and induced a striking 30-fold increase in intracellular renin activity. After 72 h of HG exposure, only the mRNA levels for angiotensinogen and angiotensin-converting enzyme (ACE) were significantly elevated. However, after shorter periods of 24 h of HG stimulation the mRNA levels of the enzymes prorenin and cathepsin B, besides that for ACE, were significantly increased. The results suggest that the HG-induced increase in ANG II generation in MC results from an increase in intracellular renin activity mediated by at least three factors: a time-dependent stimulation of (pro)renin gene transcription, a reduction in prorenin enzyme secretion, and an increased rate of conversion of prorenin to active renin, probably mediated by cathepsin B. The increase in angiotensinogen mRNA in parallel to increased renin activity indicates that HG also increased the availability of the renin substrate. The consistent upregulation of ACE mRNA suggests that, besides renin, ACE is directly involved in the increased mesangial ANG II generation induced by HG.

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.

Microalbuminuria and hypertension with focus on type 1 and type 2 diabetes

Microalbuminuria and hypertension with Over the past decade, there has been considerable focus on the concept of microalbuminuria, not only because it predicts renal disease in type 1 and type 2 diabetes, but also because it relates to premature mortality in the diabetic and in the general population. More importantly, intervention at this stage is now possible with the perspective of preserving glomerular filtration rate (GFR) and ameliorating cardiovascular disease and ensuing strong end-points. INITIAL STUDIES: The concept of microalbuminuria was introduced about 20 years ago and since then there has been a multitude of studies and papers on this subject using the original definition, but not always, in the US. Before that time it was suggested, mainly from the US, that diabetic renal disease was an untreatable relentlessly progressive condition.

GENETIC STUDIES

There is an overwhelming number of studies on genetics and diabetes and also covering the genetics of diabetic complications including nephropathy. However, so far the results are extremely disappointing. Patients at risk cannot be identified and genetic analyses are of no value as a guide to treatment. The notion that the development of complications is controlled mainly by a special genetic pattern is increasingly doubtful. In genetic studies, it is rather phenotypic well-accepted risk factors that dominate. STRUCTURAL BASIS OF MICROALBUMINURIA: Patients with microalbuminuria have significant abnormalities in the kidney, including glomeruli. This is quite clear in patients with type 1 diabetes, but is also seen in type 2 diabetes, where on the other hand, other risk factors such as hypertension and dyslipidaemia also seem to be of importance, including loss of autoregulation. Renal biopsies are generally not indicated in the management of diabetic patients. MICROALBUMINURIA AND EARLY MORTALITY: It is quite clear that microalbuminuria predicts early mortality both in type 1 and type 2 diabetes. The association to other risk factors may partly explain this--but this does not account for the whole picture. Endothelial dysfunction as well as inflammatory and arteriosclerotic abnormalities in blood vessels may be a relevant hypothesis that needs to be further explored along with other possibilities. CLINICAL COURSE AND ASSOCIATED ABNORMALITIES: The risk factor for progression in normoalbuminuric patients to microalbuminuria is higher than normal albumin excretion (strongest factor), poor glycaemic control, elevated blood pressure, and to some extent smoking. The clinical course of microalbuminuria is usually progressive, but with the more effective intervention now available we encounter that the so-called natural history (without intervention) is increasingly difficult to study. Microalbuminuria is clearly associated with a number of abnormalities, almost in all organs, but GFR is generally well preserved in spite of more advanced structural lesions. Therefore, microalbuminuria is an important marker for more pronounced diabetic vascular disease in general as well as for nephropathy. Regression to normoalbuminuria only rarely occurs during standard unchanged nonintensive treatment. TREATMENT STRATEGIES: The best possible glycaemic control is important in preventing and ameliorating the course of normo- and micro-albuminuria. Another major treatment strategy, especially in microalbuminuric patients, is antihypertensive treatment including inhibition of the renal angiotensin aldosterone system. Numerous new studies are available, both in type 1 and type 2 diabetes, documenting that not only microalbuminuria but also renal and cardiovascular complications in these patient are also far better controlled by early detection and treatment. Therefore, screening for microalbuminuria should be a strategy in all diabetes management followed by effective intervention as outlined in this paper.

Microalbuminuria in hypertension

A body of evidence indicates that microalbuminuria is a well-recognized marker of cardiovascular complications and increased cardiovascular risk in hypertension. However, the prognostic significance of microalbuminuria remains controversial because only the results of a few prospective studies performed in small groups of hypertensive subjects without diabetes mellitus are available. Several factors can affect the prevalence of microalbuminuria in hypertension including age, sex, race, severity of the disease, and concomitant risk factors. This accounts for the large differences in the prevalence of microalbuminuria that can be found in the literature, with prevalence rates going from a low of 4.7% to a high of 46%. The main determinant of albumin excretion rate in subjects with mild hypertension and no cardiovascular complications seems to be the hemodynamic load, whereas in subjects with more severe hypertension and associated target organ damage, the augmented urinary albumin leak is probably the consequence of glomerular damage. Inhibition of the renin-angiotensin system with angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists is particularly effective at reducing the albumin excretion rate, but whether these classes of drugs are more beneficial in patients with microalbuminuria remains to be determined. There is general consensus that evaluation of microalbuminuria is useful for the assessment of overall cardiovascular risk in hypertension, since albumin excretion rate appears to be a cost-effective way to identify patients at higher risk for whom additional preventive and therapeutic measures are advisable.