Effect of the angiotensin-converting-enzyme inhibitor benazepril on the progression of chronic renal insufficiency. The Angiotensin-Converting-Enzyme Inhibition in Progressive Renal Insufficiency Study Group

Successful treatment of radiation nephropathy with angiotensin II blockade

PURPOSE

The aim of this report is to document the successful treatment of radiation nephropathy.

METHODS

Clinical case report with statistical analysis of evolution of kidney function.

RESULTS

A case of radiation nephropathy was found in a kidney transplant recipient whose kidney transplant had been irradiated with 750 cGy 23 years previously. Use of the angiotensin II blocker, losartan, was associated with significant stabilization of the kidney function.

CONCLUSION

Radiation nephropathy can be successfully treated. Other normal-tissue radiation injuries may also be treatable.

Differing Anti-Proteinuric Action of Candesartan and Losartan in Chronic Renal Disease

It has becoming clear that angiotensin receptor blockers (ARBs) show varying levels of angiotensin II type 1 (AT1) receptor blocking activity. Although the duration of activity and the efficacy on blood pressure of ARB are reported to vary, depending on the agents used, it has not been examined whether the effects on proteinuria and urinary nitrite/nitrate (NOx) excretion differ in hypertensive patients with chronic renal disease. In the present study, patients with hypertension (> 140 and/or 90 mmHg) and chronic renal disease (proteinuria > 0.5g/day; serum creatinine < 265 micromol/l or creatinine clearance > 30 ml/min/1.72 m2) were randomly assigned to perindopril- (n = 15), trandolapril- (n = 15), candesartan- (n = 17), and losartan-treated groups (n = 15), and were followed up for 96 weeks. All agents decreased blood pressure to the same level, and none of them had any effect on creatinine clearance. Candesartan, perindopril, and trandolapril reduced proteinuria markedly (from 3.0 +/- 0.6 to 1.8 +/- 0.5 g/day, 2.7 +/- 0.5 to 1.6 +/- 0.4 g/day, and 2.7 +/- 0.5 to 1.7 +/- 0.4 g/day, respectively) at 12 weeks, and the beneficial effect persisted throughout the study. The effect of losartan, however, diminished over the study period. Whereas perindopril, trandolapril, and candesartan markedly increased urinary NOx excretion (from 257 +/- 23 to 1,011 +/- 150 micromol/day, 265 +/- 70 to 986 +/- 130 micromol/day, and 260 +/- 62 to 967 +/- 67 micromol/day at 12 weeks, respectively), a relatively blunted increase was observed with losartan (from 309 +/- 42 to 596 +/- 64 micromol/day). In conclusion, renal action of ARB varies, with relatively less proteinuria-sparing, as well as NOx-enhancing, effects observed with candesartan showing the greatest reduction of proteinuria and greatest enhancement of NOx. Furthermore, renal nitric oxide may contribute to the renal protective action of these agents when administered to patients with chronic renal disease.

Cell biology of the glomerular podocyte

Glomerular podocytes are highly specialized cells with a complex cytoarchitecture. Their most prominent features are interdigitated foot processes with filtration slits in between. These are bridged by the slit diaphragm, which plays a major role in establishing the selective permeability of the glomerular filtration barrier. Injury to podocytes leads to proteinuria, a hallmark of most glomerular diseases. New technical approaches have led to a considerable increase in our understanding of podocyte biology including protein inventory, composition and arrangement of the cytoskeleton, receptor equipment, and signaling pathways involved in the control of ultrafiltration. Moreover, disturbances of podocyte architecture resulting in the retraction of foot processes and proteinuria appear to be a common theme in the progression of acquired glomerular disease. In hereditary nephrotic syndromes identified over the last 2 years, all mutated gene products were localized in podocytes. This review integrates our recent physiological and molecular understanding of the role of podocytes during the maintenance and failure of the glomerular filtration barrier.

ACE Inhibition with moexipril: a review of potential effects beyond blood pressure control

ACE inhibitors induce metabolic changes and exert cardioprotective and vasoprotective properties, some of which cannot be attributed to their antihypertensive effect per se. Moexipril is an ACE inhibitor with a lipophilicity in the same range as quinapril, benazepril or ramipril, and so can readily penetrate lipid membranes and thus target tissue ACE in addition to plasma ACE. Evidence from animal studies shows similar and significant (p < 0.05) reductions in tissue ACE activity for moexipril and quinapril. Moexipril may improve endothelial dysfunction; moexiprilat and ramiprilat have demonstrated greater activity than captopril, enalaprilat and quinaprilat in isolated endothelium-denuded segments of the rabbit jugular vein where bradykinin elicits a constrictor response, mediated by activation of the bradykinin B(2) receptor. ACE inhibitors, including moexipril, may exert neuroprotective effects. Moexipril promoted neuronal survival in vitro and it is thought that this neuroprotective effect is due to free radical scavenging properties of the drug. ACE inhibitors can also decrease progression of renal insufficiency in patients with various underlying renal diseases. Moexipril may also have a renoprotective effect as it increased the ultrafiltration coefficient and normalized urinary protein excretion in rat models. Preclinical studies indicate that the renin-angiotensin-aldosterone system may play a role in the regulation of bone resorption and moexipril had no adverse effects on bone metabolism in animal models and the drug did not hamper the osteoprotective effects of estrogen. Reduction in left ventricular mass with moexipril in patients with hypertension was similar in magnitude to the effect of other ACE inhibitors. When investigated in hypertensive patients with an elevated cardiovascular risk, moexipril increased arterial distensibility and demonstrated antioxidative properties in addition to efficiently controlling blood pressure. Moexipril does not adversely affect serum levels of uric acid, lipids, blood glucose levels and plasma insulin levels and can be co-administered with hormone replacement therapy. Moreover, quality-of-life data suggest favorable effects of moexipril treatment in a patient population at high cardiovascular risk.

Treatment of high-risk African American patients: left ventricular dysfunction, heart failure, renal disease, and postmyocardial infarction

African Americans experience more mortality and morbidity from hypertension-related complications than other racial groups. Although angiotensin-converting enzyme (ACE) inhibitors have clearly been shown to reduce mortality and morbidity in hypertensive white patients with heart failure, renal dysfunction, stroke, and acute myocardial infarction, African American patients have been underrepresented in these trials. The lack of direct evidence of the benefit of ACE inhibitors in these individuals and the suggestion that ACE inhibitors are less efficacious in this group has resulted in a reluctance to use ACE inhibitors in African Americans. However, retrospective analyses in black patients with heart failure and a recent randomized clinical trial in African Americans with renal dysfunction suggest that a regimen based on ACE inhibitors is efficacious in this racial group. Although diuretics remain first-line therapy, data now suggest that ACE inhibitors provide additional benefit and should be considered for use in patients with high-risk complications regardless of race.

Blood pressure, antihypertensive therapy and risk for renal injury in African-Americans

PURPOSE OF REVIEW

African-Americans are more likely than Caucasians to develop hypertension-related end-stage renal disease. Elevations in blood pressure levels clearly potentiate pre-existing renal disease and also contribute to kidney injury independently of other primary renal diseases in this cohort. Until recently, data relevant to a full examination of the issue of blood pressure levels and end-stage renal disease in African-Americans have largely been from post-hoc analyses of clinical trials or from small, prospective, short-term studies.

RECENT FINDINGS

The most recent United States Renal Data Systems data show hypertension as the primary cause of end-stage renal disease in African-Americans until 1997, diabetes now being the most prevalent etiology. Data from post-hoc analyses of the Modification of Diet in Renal Disease study demonstrated that African-Americans with a mean arterial pressure above 98 mmHg had a higher risk of end-stage renal disease than Caucasians. The African-American Study of Kidney Disease tested the hypothesis that a blood pressure well below the usual recommended level will further reduce renal disease progression in African-Americans. The study concluded that a blood pressure lower than that needed to reduce cardiovascular events, as defined by the Sixth Joint National Committee Report on the Detection, Evaluation and Treatment of High Blood Pressure, i.e. 135-140/80-85 mmHg, will not further slow renal disease progression in African-Americans with hypertensive nephrosclerosis. Moreover, a regimen of blood pressure lowering anchored on angiotensin-converting enzyme inhibitors, antihypertensive agents that are touted as ineffective in African-Americans, was more effective than one based on either beta-blockers or dihydropyridine calcium-channel blockers in slowing the progression of renal injury.

SUMMARY

Systolic blood pressure reduction in the range 130-139 mmHg is appropriate to reduce risk of nephropathy progression and cardiovascular risk in African-Americans with hypertensive nephrosclerosis. Moreover, a regimen that is initiated with an angiotensin-converting enzyme inhibitor should be the antihypertensive treatment of choice in African-Americans with kidney disease.

Preventing renal dysfunction in patients with hypertension: clinical implications from the early AASK Trial results

Strategies to delay progression of established renal disease have primarily been directed at examining the class of antihypertensive therapy and/or the level of blood pressure control. In diabetic renal disease many trials have noted a protective role of ACE inhibitor-based therapy over non-ACE inhibitor-based therapy. This paper reviews recent clinical trials evaluating hypertension-related kidney disease including the interim results of the African-American Study of Kidney Diseases and Hypertension (AASK) Study, to date the largest prospective study of African-American patients with kidney disease due to hypertension. This trial reports a renoprotective effect of ACE inhibitor-based therapy over calcium-channel antagonist- based therapy. The renoprotective effect of ACE inhibitor-based therapy may, in part, be due to their antiproteinuric effect independent of blood pressure lowering.

ACE inhibition versus angiotensin type 1 receptor antagonism: differential effects on PAI-1 over time

ACE inhibition reduces plasminogen activator inhibitor-1 (PAI-1), a risk factor for myocardial infarction, whereas the effect of angiotensin receptor antagonism on PAI-1 is uncertain. The present study compares the time course of effects of ACE inhibition and angiotensin type 1 (AT1) receptor antagonism on morning plasma PAI-1 antigen. Blood pressure and endocrine, metabolic, and fibrinolytic variables were measured in 20 insulin-resistant (defined by fasting glucose >8.3 mmol/L, body mass index >28 kg/m2, or fasting serum triglyceride > or =2.8 mmol/L) hypertensive subjects (mean age, 47.9+/-2.1 years) (1) before and after 1 week of hydrochlorothiazide 12.5 mg/d, and (2) before and 1, 3, 4, and 6 weeks after addition of ramipril (escalated to 10 mg/d) or losartan (escalated to 100 mg/d). Hydrochlorothiazide decreased systolic (P=0.011) and diastolic (P=0.019) pressure. Ramipril (from 133.6+/-5.1/94.5+/-2.4 to 127.0+/-3.1/91.4+/-3.3 mm Hg) or losartan (from 137.0+/-3.9/93.1+/-2.9 to 123.7+/-2.6/86.4+/-2.1 mm Hg) further reduced systolic (P=0.009) and diastolic (P=0.037) pressure. The pressure effects of the 2 drugs were similar. Hydrochlorothiazide increased plasma PAI-1 (P=0.013) but not tissue-type plasminogen activator (tPA) (P=0.431) antigen. Addition of either ramipril or losartan significantly decreased plasma PAI-1 antigen (P=0.046). However, the effect of losartan on PAI-1 antigen was not sustained throughout the 6-week treatment period, such that there was a significant drugxtime interaction (P=0.043). tPA antigen decreased during either ramipril or losartan (P=0.032), but tPA activity decreased only during losartan (P=0.018). Short-term interruption of the renin-angiotensin-aldosterone system by either ACE inhibition or AT1 receptor antagonism decreases PAI-1 antigen, but the duration of this effect is greater for ACE inhibition than for AT1 receptor antagonism.

Between-patient differences in the renal response to renin-angiotensin system intervention: clue to optimising renoprotective therapy?

Renin-angiotensin-aldosterone system (RAAS) blockade with angiotensin-converting enzyme inhibitors (ACE-I) or angiotensin II (Ang II), AT(1)-receptor blockers (ARB) is the cornerstone of renoprotective therapy. Still, the number of patients with end-stage renal disease is increasing worldwide, prompting the search for improved renoprotective strategies. In spite of proven efficacy at group level, the long-term renoprotective effect of RAAS blockade displays a marked between-patient heterogeneity, which is closely linked to between-patient differences in the intermediate parameters of blood pressure, proteinuria and renal haemodynamics. Of note, the between-patient differences by far exceed the between-regimen differences, and thus may provide a novel target for exploration and intervention. The responsiveness to RAAS blockade appears to be an individual characteristic as demonstrated by studies applying a rotation-schedule design. The type and severity of renal disease, obesity, insulin-resistance, glycaemic control, and genetic factors may all be involved in individual differences in responsiveness, as well as dietary factors, such as dietary sodium and protein intake. Several strategies, such as dietary sodium restriction and diuretic therapy, dose-titration for proteinuria, and dual RAAS blockade with ACE-I and ARB, can improve the response to therapy at a group level. However, when analysed for their effect in individuals, it appears that these measures do not allow poor responders to catch up with the good responders, i.e. in spite of their efficacy at group level, the available measures are usually not sufficient to overcome individual resistance to RAAS blockade. We conclude that between-patient differences in responsiveness to renoprotective intervention should get specific attention as a target for intervention. Unravelling of the underlying mechanisms may allow development of specific intervention. Based on the currently available data, we propose that response-based treatment schedules, with a multidrug approach titrated and adapted at individual responses rather than fixed treatment schedules, may provide a fruitful strategy for more effective renoprotection.

Effects of dual blockade of the renin-angiotensin system in primary proteinuric nephropathies

BACKGROUND

Blockade of the renin-angiotensin system (RAS) with angiotensin converting enzyme (ACE) inhibitors or with angiotensin II type 1 (AT1) receptor blockers has been shown to reduce proteinuria and to slow down the progression of renal disease in diabetic and non-diabetic primary proteinuric nephropathies. Additionally, this beneficial effect is not dependent on blood pressure control.

METHODS

To assess and compare the effects of lisinopril (up to 40 mg/day), candesartan (up to 32 mg/day) and combination therapy (lisinopril up to 20 mg/day plus candesartan up to 16 mg/day) on urinary protein excretion, 45 patients with primary proteinuric nephropathies (urinary protein/creatinine ratio 3.8+/-2.4 g/g) and normal or slightly reduced renal function (CCr 95+/-33 mL/min) were enrolled in a six month multicenter, prospective, open, randomized, active-controlled and parallel-group trial with 1:1:1 allocation. Blood pressure goal was set at or below 125/75 mm Hg for all patients, with additional antihypertensive medication prescribed if required.

RESULTS

Renal function, estimated by creatinine clearance, remained stable throughout the study. Hyperkalemia (K>5.5 mmol/L) was detected in 3.1% of all measurements in follow-up, and was more frequent in patients treated with lisinopril alone or lisinopril plus candesartan (P<0.001) than in those on candesartan alone. No other relevant adverse event was recorded. The blood pressure goal (<125/75 mm Hg) was achieved by week 4 in all treatment groups (P<0.005 when compared to baseline), and afterwards the mean systolic and diastolic blood pressure remained below these values until the end of the trial with no statistically significant differences between groups. Urinary protein/creatinine ratio (percentage reduction 95% confidence intervals CI) decreased in patients treated with lisinopril alone to -33% (CI -12-56) to -31% (CI 0-68) and to -50% (CI -9-90), in patients treated with candesartan to -28% (CI -12-45), to -41% (CI -30-52) and to -48% (CI -32-63), in patients treated with the combination of both to -60% (CI -44-77) to -54% (CI -38-69) and to -70% (CI -57-83) at two, three, and six months, respectively. All comparisons with baseline achieved statistical significance and treatment with combination therapy was statistically more effective in proteinuria reduction than treatment with candesartan alone at two and six months (P=0.004 and P=0.023, respectively) and than treatment with lisinopril only at two months (P=0.03).

CONCLUSION

Dual blockade of the renin-angiotensin system with ACE inhibitors and AT1 receptor blockers produces a beneficial antiproteinuric effect that could not be explained only by the systemic blood pressure reduction. All treatments were well tolerated.

Renal damage associated with proteinuria

Experimental studies have demonstrated that proteins filtered by the glomerulus induce a proliferation of proximal tubular cells accompanied by an increased synthesis of many vasoactive and proinflammatory substances. The appearance of interstitial cellular infiltrates, a well-known finding in proteinuric diseases, precedes progressive tubulointerstitial fibrosis. Activation of the transcription factor kappaB (NF-kappaB) plays a pivotal role in the renal damage induced by proteinuria. In this scenario, any therapeutic intervention that reduces proteinuria should be beneficial for the kidney. Drugs that block the renin-angiotensin system [angiotensin converting enzyme (ACE) inhibitors and angiotensin II receptor antagonists (ARA)] have repeatedly shown striking antiproteinuric and renoprotective properties, both in experimental and clinical studies. Studies in patients with type 1 and type 2 diabetic nephropathy as well as in non-diabetic nephropathies have confirmed that the renoprotection obtained with ACEI/ARA is closely related with their antiproteinuric effect and is largely independent of blood pressure changes. However, resistance to the antiproteinuric effect of ACEI/ARA is a common clinical observation. Several therapeutic measures (that is, adequate blood pressure control, early introduction of ACEI/ARA, dietary protein restriction, low salt diets, weight loss in overweight patients, addition of a diuretic, increasing ACEI/ARA dose titrated against proteinuria levels, combined therapy ACEI plus ARA, addition of drugs with antiproteinuric effect such as non-dihydropiridine calcium channel blockers or NSAIDs) may increase the proteinuria reduction induced by ACEI and ARA.

Blood pressure-independent impact of antihypertensive agents on cardiovascular and renal disease

Reduction of elevated blood pressure clearly protects against target organ damage, but the different targets do not necessarily benefit to the same degree. There is considerable debate over whether or not there is a drug-specific benefit above and beyond that conferred by blood pressure reduction alone. We performed a Medline search to identify recent randomized clinical trials including 300 or more patients who were followed for at least 2 years. We critically reviewed these papers to find like trials for comparisons. There was too much dissimilarity to perform a meaningful meta-analysis. We found that the literature does not support a definitive conclusion either in favor of or against an overall drug-specific protective effect. However, by grouping like trials, it is possible to support an additional protective effect by angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers on reducing the rate of decline in renal function and in reducing proteinuria.

Role of combination therapy with ACE inhibitors and calcium channel blockers in renal protection

Over recent years, a target blood pressure of 125/75 mm Hg has been sought in order to reduce the rate of chronic renal disease (CKD) progression and cardiovascular mortality. Some antihypertensive agents, such as angiotensin converting enzyme (ACE) inhibitors, angiotensin II receptor antagonists and calcium channel blockers also may be capable of reducing CKD progression because they halt some of the pathogenetic mechanisms involved in renal damage. The possibility that combination treatments with ACE inhibitors and calcium-channel blockers may confer additive or even synergistic renoprotective effects other than blood pressure control is not only fascinating, but also particularly important because multidrug antihypertensive regimens are required to obtain adequate blood pressure in the majority of patients with CKD. This combination may provide better blood pressure control, appears to be better tolerated with fewer side effects than either drug alone, and may exert a greater renoprotective effect in patients at risk for renal failure than either an ACE inhibitors or a calcium channel blocker. However, the current available data are too few to confirm this hypothesis. Cardiovascular disease accounts for more than 50% of the deaths of hemodialysis patients. Thus, care must be taken to prevent and treat the cardiovascular risk factors optimally from the early phase of CKD, and for this reason effective antihypertensive therapy is the most important treatment, not only in order to delay CKD progression, but also to reduce the burden of cardiovascular disease. In this perspective combination therapy with ACE inhibitors and calcium channel blockers can give further advantages.

Protection of the cardiovascular system by imidapril, a versatile angiotensin-converting enzyme inhibitor

Imidapril hydrochloride (imidapril) is a long-acting, non-sulfhydryl angiotensin-converting enzyme (ACE) inhibitor, which has been used clinically in the treatment of hypertension, chronic congestive heart failure (CHF), acute myocardial infarction (AMI), and diabetic nephropathy. It has the unique advantage over other ACE inhibitors in causing a lower incidence of dry cough. After oral administration, imidapril is rapidly converted in the liver to its active metabolite imidaprilat. The plasma levels of imidaprilat gradually increase in proportion to the dose, and decline slowly. The time to reach the maximum plasma concentration (T(max)) is 2.0 h for imidapril and 9.3 h for imidaprilat. The elimination half-lives (t(1/2)) of imidapril and imidaprilat is 1.7 and 14.8 h, respectively. Imidapril and its metabolites are excreted chiefly in the urine. As an ACE inhibitor, imidaprilat is as potent as enalaprilat, an active metabolite of enalapril, and about twice as potent as captopril. In patients with hypertension, blood pressure was still decreased at 24 h after imidapril administration. The antihypertensive effect of imidapril was dose-dependent. The maximal reduction of blood pressure and plasma ACE was achieved with imidapril, 10 mg once daily, and the additional effect was not prominent with higher doses. When administered to patients with AMI, imidapril improved left ventricular ejection fraction and reduced plasma brain natriuretic peptide (BNP) levels. In patients with mild-to-moderate CHF [New York Heart Association (NYHA) functional class II-III], imidapril increased exercise time and physical working capacity and decreased plasma atrial natriuretic peptide (ANP) and BNP levels in a dose-related manner. In patients with diabetic nephropathy, imidapril decreased urinary albumin excretion. Interestingly, imidapril improved asymptomatic dysphagia in patients with a history of stroke. In the same patients it increased serum substance P levels, while the angiotensin II receptor antagonist losartan was ineffective. These studies indicate that imidapril is a versatile ACE inhibitor. In addition to its effectiveness in the treatment of hypertension, CHF, and AMI, imidapril has beneficial effects in the treatment of diabetic nephropathy and asymptomatic dysphagia. Good tissue penetration and inhibition of tissue ACE by imidapril contributes to its effectiveness in preventing cardiovascular complications of hypertension. The major advantages of imidapril are its activity in the treatment of various cardiovascular diseases and lower incidence of cough compared with some of the older ACE inhibitors.

Proteinuria: an underappreciated risk factor in cardiovascular disease

Changes in renal function produced by hypertension appear to be associated with higher cardiovascular morbidity and mortality. Indices of altered renal function (eg, microalbuminuria, increased serum creatinine concentrations, decrease in estimated creatinine clearance, or overt proteinuria) are independent predictors of cardiovascular morbidity and mortality. The Framingham Heart Study documented the relevance of proteinuria for cardiovascular prognosis in the community. The International Nifedipine GITS study: Intervention as a goal in Hypertension Treatment (INSIGHT) study assessed the role of proteinuria as a very powerful risk factor. Several studies demonstrated that microalbuminuria is a predictor of cardiovascular disease. It has been shown that the presence of microalbuminuria in primary hypertension carries an elevated cardiovascular risk. Furthermore, recent data indicate that even minor derangements of renal function are associated with an increase in cardiovascular risk factors, and promote progression of atherosclerosis. All these parameters should routinely be evaluated in clinical practice, and in the future must be considered in any stratification of cardiovascular risk in hypertensive patients.

Angiotensin AT-1 receptor antagonism: complementary or alternative to ACE inhibition in cardiovascular and renal disease?

Both angiotensin-converting enzyme (ACE) inhibitors and AT-1 receptor antagonists reduce the effects of angiotensin II, however they may have different clinical effects. This is because the ACE inhibitors, but not the AT-1 receptor antagonists, increase the levels of substance P, bradykinin and tissue plasminogen activator. The AT-1 receptor antagonists, but not the ACE inhibitors, are capable of inhibiting the effects of angiotensin II produced by enzymes other than ACE. On the basis of the present clinical trial evidence, AT-1 receptor antagonists, rather than the ACE inhibitors, should be used to treat hypertension associated with left ventricular (LV) hypertrophy. Both groups of drugs are useful when hypertension is not complicated by LV hypertrophy, and in diabetes. In the treatment of diabetes with or without hypertension, there is good clinical support for the use of either an ACE inhibitor or an AT-1 receptor antagonist. ACE inhibitors are recommended in the treatment of renal disease that is not associated with diabetes, after myocardial infarction when left ventricular dysfunction is present, and in heart failure. As the incidence of cough is much lower with the AT-1 receptor antagonists, these can be substituted for ACE inhibitors in patients with hypertension or heart failure who have persistent cough. Preliminary studies suggest that combining an AT-1 receptor antagonist with an ACE inhibitor may be more effective than an ACE inhibitor alone in the treatment of hypertension, diabetes with hypertension, renal disease without diabetes and heart failure. However, further trials are required before combination therapy can be recommended in these conditions.

Blood pressure and long-term mortality in United States hemodialysis patients: USRDS Waves 3 and 4 Study

BACKGROUND

The long-term prognostic associations of pre- and post-dialysis blood pressures, interdialytic weight gain, and antihypertensive use in hemodialysis patients are unclear.

METHODS

The United States Renal Data System (USRDS) Dialysis Morbidity and Mortality Waves 3 and 4 Study, a randomly generated sample of 11,142 subjects receiving hemodialysis on December 31, 1993, was examined, with vital status followed until May 2000.

RESULTS

Pre- and post-dialysis blood pressure values, interdialytic weight gain and number of antihypertensives averaged 151.8/79.7, 137.0/74, 3.6% and 0.76, respectively. Prognostic discrimination was maximized by considering pre- and post-systolic and diastolic blood pressure values simultaneously, in a pattern suggesting that wide pulse pressures were associated with mortality (P < 0.0001). Comorbidity adjustment markedly affected associations, with low pre-dialysis diastolic (P < 0.05), low post-dialysis dialysis diastolic pressure (P < 0.05), high post-dialysis dialysis systolic pressure (P < 0.05), and high interdialytic weight gains (P = 0.005) associated with mortality. Each class of antihypertensive drug, except angiotensin-converting enzyme (ACE)-inhibitors, was associated with lower mortality in unadjusted models, an effect most pronounced for beta-blockers (hazards ratio 0.72, 95% CI 0.66 to 0.79, P < 0.0001). Comorbidity adjustment eliminated survival associations for each antihypertensive class except beta-blockers.

CONCLUSIONS

Pre- and post-dialysis blood pressure values have independent associations with mortality, in a way that implicates wide pulse pressures. Much of the adverse prognosis of wide pulse pressures probably reflects older age and cardiovascular comorbidity. Large interdialytic weight gains are associated with shorter survival when comorbidity is taken into account. Beta-blocker use shows a robust association with survival, and may be protective.

Ongoing trials involving angiotensin-converting enzyme inhibitors

Angiotensin-converting enzyme inhibitors (ACEIs) are an important class of drugs in cardiovascular disease. As their name suggests, they act by blocking angiotensin converting enzyme, thereby limiting the production of angiotensin II, the most active component of the renin-angiotensin- aldosterone system. This system plays an important role in maintenance of blood pressure and electrolyte and fluid balance. Therefore, by blocking this system, the ACEIs have wide ranging effects. Recent trials have reaffirmed their place in the management of hypertension, congestive cardiac failure, in the prevention of renal complications in diabetes and the prevention of strokes in 'at risk' patients. There are still many ongoing trials using the ACEIs. These trials are mainly aimed at comparing their efficacy with 'older' drugs (such as betablockers) and 'newer' drugs such as the angiotensin receptor blockers and calcium antagonists in different indications, such as heart failure and diabetic nephropathy. The impact of these drugs on the prevention of macro- and micro vascular complications in diabetes is also being investigated. The results of all these trials, when available, are expected to reaffirm the important role of this class of drugs in our modern day medical armamentarium. In this review, the ongoing clinical trials involving ACEIs, the rationale behind these trials and what impact they hope to have on our current understanding of the role of this important class of drug in medical practice, will be discussed.

Does type 2 diabetes mellitus delay renal failure in autosomal dominant polycystic kidney disease?

Autosomal dominant polycystic kidney disease (ADPKD) is a common renal disease without an effective therapeutic intervention to delay renal failure. Within kindreds, renal dysfunction often develops at a similar age in affected individuals, although there are known modifying factors. Two kindreds with ADPKD have shown a striking pattern of delayed onset of renal insufficiency in those individuals also suffering from type 2 diabetes mellitus. Eight nondiabetic patients with ADPKD had onset of dialysis or renal death at ages 38-52 years, (mean +/- SEM 46 +/- 1.9, n = 7) as compared with four diabetics who started dialysis or are still off dialysis at the age of 61 +/- 2.8 years (p < 0.01). Two of the four diabetics still have reasonable renal function at age 61 and 66. The diabetes was diagnosed at age 32 +/- 2 years and was treated with oral hypoglycemics for 19 +/- 2 years before institution of insulin. Cardiovascular disease dominated the clinical picture in the diabetics. In conclusion, onset of renal failure in ADPKD was delayed for over 15 years in individuals who also suffered from type 2 diabetes mellitus, in two ADPKD kindreds. Possible mechanisms are discussed, including glibenclamide inhibition of the cystic fibrosis transmembrane conductance regulator. The striking delay associated with type 2 diabetes mellitus in ADPKD induced renal failure should be evaluated further.

Chronic renal ischemia: pathophysiologic mechanisms of cardiovascular and renal disease

Chronic renal ischemia caused by renal artery stenosis (RAS) elicits a complex biologic response. Although the traditional pathophysiologic pathways underlying renal ischemia have been well studied, there is emerging evidence that additional mechanisms may be responsible for producing many of the hemodynamic alterations and end-organ injury seen in patients with RAS, including persistent hypertension, renal insufficiency, and cardiac disturbance syndromes. A better understanding of these mechanisms may allow earlier identification of RAS, provide markers to predict the response to revascularization, or allow unique therapeutic targets for drug development. This and a subsequent article will explore the pathophysiologic and clinical implications of chronic renal ischemia.

Renoprotection: a matter of blood pressure reduction or agent-characteristics?

Data from recent clinical trials show that lowering of BP reduces the rate of renal function loss in chronic renal disease. There is evidence supporting the assertion that BP lowering obtained by intervention in the renin-angiotensin-aldosterone system (RAAS) has an additive renoprotective effect in both diabetic and nondiabetic renal diseases. However, to dissociate BP-dependent and non-BP-dependent action of RAAS blockade, the relevant trials are in many cases flawed by design, resulting in BP differences between the comparative antihypertensive strategies. This review discusses whether the relevant literature allows for the conclusion that RAAS intervention has renoprotective effects in addition to its effects on BP. In particular, the main evidence for a specific renoprotective action of RAAS blockade is provided by its consistent antiproteinuric action, which cannot completely be attributed to the reduction in BP. Indeed, other strategies that lower proteinuria without having an antihypertensive effect, such as lowering dietary protein intake or the use of non-steroidal antiinflammatory drugs, appear to have a renoprotective effect as well. Interestingly, a consistent finding across different intervention studies is that the more proteinuria is reduced the better the kidney appears to be protected. Therefore, it is concluded that agent-characteristics of RAAS intervention (i.e., antiproteinuric properties) independently influence renal function loss in addition to its BP-lowering effect. Future studies should further explore the renoprotective benefit of non-antihypertensive intervention measures, alone and in combination with antihypertensive strategies.

Selection of the dose of angiotensin converting enzyme inhibitor for patients with diabetic nephropathy depends on the presence or absence of left ventricular hypertrophy

The coexistence of hypertension increases cardiovascular risks and the rate of deterioration of renal function for diabetic patients. For patients with left ventricular hypertrophy (LVH), the use of an angiotensin converting enzyme (ACE) inhibitor is known to be effective and well tolerated and to be protective against chronic renal insufficiency (CRI). However, serious adverse reactions to ACE inhibitors, such as the rapid deterioration of renal function, have been reported, making physicians hesitant to use these agents. To resolve this dilemma, we compared changes in renal function and left ventricular function and the safety and effectiveness of benazepril, an ACE inhibitor, in patients with diabetic nephropathy, with or without LVH. The age, sex, duration of diabetes, levels of blood pressure and blood glucose and rates of creatinine clearance (CrCl) were compared between 36 diabetic patients with LVH and 36 matched diabetic patients without LVH. The rates of CrCl in all patients were between 14 and 35 ml/min, and all patients received an ACE inhibitor before enrollment. The group comprised 43 men and 29 women, with a mean age of 56 +/- 4 years. These patients were divided into three groups, each of which was subdivided into a group with and a group without LVH. Group I (without LVH) or I-L (with LVH) received a half dose of benazepril (2.5 mg daily), Group II (without LVH) or II-L (with LVH) received a normal daily dose of 5 mg benazepril, and Group III (without LVH) or III-L (with LVH) discontinued the administration of the ACE inhibitor. The follow-up period was 1 year and, during the study, blood pressure was maintained at less than 140/90 mmHg. If the blood pressure control was not satisfactory, benidipine, a calcium antagonist, and/or furosemide, a loop diuretic, and/or guanabenz, a central acting antihypertensive agent, were administered. In the diabetic patients with LVH, the administration of a normal dose of benazepril inhibited the decline of renal function and cardiac function (CrCl: 24.2 +/- 1.5 to 22.0 +/- 2.5 ml/min; EF (ejection fraction): 56 +/- 3 to 54 +/- 6%) compared to the other two groups. In patients without LVH, a half dose of benazepril preserved renal function (23.4 +/- 2.6 to 22.0 +/- 3.1 ml/min; EF: 54 +/- 3 to 56 +/- 3%). Discontinuation of the administration of ACE inhibitor led to the further progression of renal dysfunction and decreases in EF in patients with or without LVH. Our results provide some indications for the use of ACE inhibitors in diabetic patients when renal dysfunction and/or cardiac hypertrophy are present.

Antiproteinuric effects of combined antihypertensive therapies in patients with overt type 2 diabetic nephropathy

Combined antihypertensive therapy plays a crucial role in achieving targeted blood pressure reductions and renoprotection. We therefore compared the antihypertensive and antiproteinuric effects of combined therapy with either a calcium channel blocker (CCB) plus an angiotensin II receptor blocker (ARB) or an angiotensin converting enzyme inhibitor (ACE-I) plus an ARB in patients with type 2 diabetes mellitus complicated by overt nephropathy and mild to moderate hypertension. After a 12-week dietary control period, diabetic patients with mildly to moderately impaired renal function were randomly assigned to either a CCB (amlodipine 5 mg once daily) or an ACE-I (temocapril 2 mg once daily) for 12 weeks (monotherapy period). Both groups then received add-on therapy with an ARB (candesartan 4 mg once daily) for an additional 12 weeks. During the monotherapy period, blood pressure was decreased equally well in both groups. Daily urinary protein excretion remained unchanged in the CCB-treated group (control period, 4.0 +/- 1.8 g/day vs. CCB period, 4.1 +/- 1.9 g/day; ns; n = 8), but decreased in the ACE-I-treated group (control period, 4.3 +/- 1.8 g/day vs. ACE-I period, 3.5 +/- 1.7 g/day; p < 0.05; n = 9). After the combined therapy period, blood pressure was decreased to the same degree in both groups. Although ARB plus CCB significantly reduced urinary protein excretion (to 3.5 +/- 1.5 g/day; p < 0.05 vs. control period; n = 8), a more profound reduction was achieved with ARB plus ACE-I (to 2.6 +/- 1.3 g/day; p < 0.01 vs. control period; n = 9). Monotherapy with the ACE-I increased the serum potassium concentration, and this elevation was sustained after addition of the ARB. In contrast, the serum potassium concentration was not influenced by monotherapy with the CCB, but was significantly increased after addition of the ARB. A decreased hematocrit was observed in the ARB plus ACE-I group. The present study suggests that combined antihypertensive therapy with either a CCB plus an ARB or an ACE-I plus an ARB exerts an antiproteinuric effect in patients with type 2 diabetic nephropathy with mildly impaired renal function. Although the latter combination had a more profound effect, it was associated with an increased serum potassium concentration and worsening of renal anemia. Thus, the combination of a CCB and an ARB should be the first line antihypertensive therapy in those with overt diabetic nephropathy. The long-term efficacy of these combined antihypertensive therapies will need to be further addressed in a future study.

Is it the agent or the blood pressure level that matters for renal protection in chronic nephropathies?

Some antihypertensive agents may be capable of reducing chronic renal insufficiency (CRI) progression because they halt some of the pathogenic mechanisms involved in renal damage. Although this effect seems to be partially independent of BP reduction, it is still unclear whether these drugs are really superior to other antihypertensive agents when the BP values recommended by the present guidelines are actually achieved. This is particularly true when considering that, in published trials, target and achieved BP values were constantly higher than those nowadays recommended. Furthermore, in the majority of these studies, patients treated with ACE-inhibitors (ACE-I) or Angiotensin II receptor antagonists (ATIIRA) achieved lower BP values than those in control groups and BP values during 24 h were not recorded. Anyway, taking into account the role of baseline and follow-up BP values, the treatment effect remained significant in almost all of the multivariate models. These findings suggest that the renoprotective effect of these agents (ACE-I, ATIIRA) is partially independent of better BP control. However, caution should be paid in attributing true biologic renoprotective properties to drugs just on the basis of statistical adjustments of BP values, although robustly performed, without being aware of what those BP values actually reflect.

The role of angiotensin II receptor blockers in preventing the progression of renal disease in patients with type 2 diabetes

Diabetes mellitus is the most common cause of end-stage renal disease in the United States, accounting for about 50% of all new cases. Although we previously established the renoprotective benefits of angiotensin converting enzyme (ACE) inhibitors in patients with coexisting hypertension and type 1 diabetes, evidence of the renoprotective effect of ACE inhibitors in patients with type 2 diabetes is less clear. We conducted the Irbesartan Diabetic Nephropathy Trial (IDNT) to determine whether the angiotensin II receptor blocker (ARB) irbesartan slows the progression of nephropathy in patients with type 2 diabetes independently of its blood pressure (BP)-lowering effect. In this randomized, controlled trial, we found that irbesartan was associated with a 20% reduction in the risk for the primary composite end point (doubling of the baseline serum creatinine concentration, development of end-stage renal disease, or death from any cause) compared with placebo (P =.02) and a 23% reduction compared with amlodipine therapy (P =.006). These results were not explained by differences in the BP that was achieved. In a separate study, losartan was shown to reduce the risk for progression of renal disease in patients with type 2 diabetic nephropathy. Angiotensin II receptor blocker therapy has also been demonstrated to slow the progression to overt nephropathy when initiated early in the course of type 2 diabetic renal disease (ie, in patients with microalbuminuria). Based on these studies, ARBs are clearly effective in protecting against the progression of nephropathy due to type 2 diabetes. This protection is independent of their BP-lowering effect. Preclinical studies with the newest ARB, olmesartan medoxomil, suggest that this agent may provide renoprotective benefits as well.

Angiotensin II and progressive renal insufficiency

The inhibition of angiotensin II through angiotensin converting enzyme inhibitors or angiotensin receptor blockers has become the foundation of medical treatment of progressive chronic renal disease. Although these drugs provide a significant improvement over earlier treatments, they only slow the progression of renal disease, implying the need for additional drugs that could be combined with antiangiotensin treatment. Potentially valuable novel drug targets include downstream mediators of angiotensin II such as transforming growth factor-b, plasminogen activator inhibitor-1, and endothelin-1. In addition, recent evidence points to aldosterone as a major player in progressive renal disease, indicating that multiple points of the renin-angiotensin-aldosterone system might have to be targeted. This paper reviews the experimental and clinical evidence indicating that targeting these cytokines and hormones could provide additional benefits to antiangiotensin treatment in chronic renal disease.

Effect of renal insufficiency on the pharmacokinetics and pharmacodynamics of benazepril in cats

The effect of renal insufficiency was studied on the pharmacokinetics (PK) and pharmacodynamics (PD) of the angiotensin-converting enzyme (ACE) inhibitor benazepril in cats. The active metabolite of benazepril, benazeprilat, is eliminated principally ( approximately 85%) via biliary excretion in cats. A total of 20 control animals and 32 cats with moderate renal insufficiency induced by partial nephrectomy were used. Assessments were made at steady state after treatment with placebo or benazepril (0.25-2 mg/kg) once daily for a minimum of 10 days. The PK endpoint was the AUC (0-->24 h) of total plasma benazeprilat. The PD endpoints were systolic, diastolic and mean blood pressures (respectively SBP, DBP and MBP) measured by telemetry, and plasma ACE activity, assessed by an ex vivo assay. Renal function was assessed by glomerular filtration rate (GFR), measured by inulin clearance, and plasma creatinine concentrations (1/PCr). As compared with control animals, the renal insufficient cats had a 78% reduction in GFR (0.57 +/- 0.41 mL/min kg), increased plasma creatinine (2.7 +/- 1.0 mg/dL), urea (44.0 +/- 11.9 mg/dL) and ACE activity, and moderately increased blood pressure (SBP 171.8 +/- 5.1 mmHg) (all parameters P < 0.05). Renal insufficient cats receiving benazepril had significantly (P < 0.05) lower SBP, DBP, MBP and ACE, and higher GFR values as compared with placebo-treated animals. There were no significant differences in SBP, DBP, MBP, benazeprilat or ACE values according to the degree of renal insufficiency in cats receiving benazepril. It is concluded that no dose adjustment of benazepril is necessary in cats with moderate renal insufficiency.

Strategies to meet lower blood pressure goals with a new standard in angiotensin II receptor blockade

The continued poor rates of blood pressure (BP) control to the recommended target BP of <140/90 mm Hg in patients with hypertension indicate a persistent need for improved antihypertensive therapy. Angiotensin II receptor blockers (ARBs) constitute the newest approved class of antihypertensive agents. As with angiotensin converting enzyme inhibitors, ARBs block the renin-angiotensin-aldosterone system, but do so through a more specific mechanism. Angiotensin converting enzyme inhibitors block the conversion of angiotensin I to angiotensin II, but angiotensin II may be produced by several alternate pathways. Angiotensin II receptor blockers, by contrast, inhibit the binding of angiotensin II to the angiotensin II type 1 (AT1) receptor, independent of the pathway of angiotensin II production. Comparative safety and efficacy trials indicate that ARBs are similar to other antihypertensive drugs in terms of BP-lowering effectiveness and have superior tolerability. Olmesartan medoxomil is the newest and one of the most effective of the ARBs. In controlled trials, it has been shown to provide 24-h BP control with antihypertensive efficacy at least as good as that of the calcium channel blockers amlodipine besylate and felodipine and the beta-blocker atenolol. In a comparative study, olmesartan medoxomil demonstrated significantly greater reductions in diastolic BP than did three other leading ARBs-losartan potassium, irbesartan, and valsartan. With the convenience of placebo-like tolerability and once-daily dosing, combined with excellent antihypertensive efficacy, olmesartan medoxomil may be a useful addition to our management of hypertension.

Antiproteinuric effect of candesartan cilexetil in patients with chronic glomerulonephritis

A prospective, randomised, double-blind, parallel-group, dose-response trial was conducted to investigate the antiproteinuric effect of candesartan cilexetil, the angiotensin II type 1 receptor blocker, in patients with chronic glomerulonephritis. Patients (n=280) were treated for 12 weeks with candesartan cilexetil 2, 4, or 8 mg given orally once-daily (o.d.). The improvement in urinary protein excretion observed at the end of the treatment period was 15.9% in the 2 mg group, 25.6% in the 4 mg group, and 34.6% in the 8 mg group, respectively, showing a clear dose-response (2 mg <4 mg <8 mg; p=0.003). The mean reduction in urinary protein excretion was 11.3% in the 2 mg group, 26.3% in the 4 mg group, and 26.0% in the 8 mg group, showing a dose-response pattern, in that the effect of 4 mg and 8 mg was greater than that of 2 mg (2 mg <4 mg asymptotically equal to 8 mg; p=0.010). As the observed reduction in urinary protein excretion failed to correlate with changes in mean blood pressure, it could not be attributed to the antihypertensive effect of the study drug alone. This suggests that candesartan cilexetil, 4 8 mg o.d., has antiproteinuric effects in patients with chronic glomerulonephritis.

Antiproteinuric versus antihypertensive effects of high-dose ACE inhibitor therapy

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors effectively reduce proteinuria; however, the optimal antiproteinuric dose is still unknown. We conducted this study to determine whether an increase in ACE-inhibitor dose above the maximal antihypertensive effect has additional antiproteinuric potential.

METHODS

Twenty-three proteinuric patients were administered the ACE inhibitor spirapril at a starting dose of 3 to 6 mg/d. The dose was increased every 6 weeks until the maximal antihypertensive effect, assessed by 24-hour ambulatory blood pressure (ABP) monitoring, was achieved (spir(max)), then increased to a supramaximal dose (spir(supramax)). Renal parameters, urinary protein excretion, and systemic activity of the renin-angiotensin system were compared between baseline, spir(max), and spir(supramax). Glomerular filtration rate and renal plasma flow were determined before the administration of spirapril and after administration of the supramaximal dose.

RESULTS

Median ABP and proteinuria decreased significantly between baseline and spir(max) (median, 102 mm Hg; range, 82 to 122 mm Hg versus 97 mm Hg; range, 82 to 113 mm Hg; median protein, 2.56 g/d; range, 1.05 to 22.1 g/d versus 1.73 g/d; range, 0.42 to 4.7 g/d). Both creatinine level and creatinine clearance remained unchanged. Suppression of angiotensin II formation led to a significant increase in renin and angiotensin I concentrations and a nonsignificant decrease in aldosterone levels. The increase in spirapril to a supramaximal dose had no further effect on serum renin or angiotensin I levels or proteinuria. There was an additional slight decrease in aldosterone levels and, subsequently, a significantly lower level than at baseline.

CONCLUSION

Our results show that the antiproteinuric effect of spirapril is associated with its antihypertensive effect. Although high-dose ACE-inhibitor therapy has no additional influence on proteinuria, a possible beneficial long-term effect cannot be ruled out.

Effects of long-term administration of enalapril on clinical indicators of renal function in dogs with compensated mitral regurgitation

OBJECTIVE

To determine the effect of long-term administration of enalapril on renal function in dogs with severe, compensated mitral regurgitation.

DESIGN

Randomized controlled trial.

ANIMALS

139 dogs with mitral regurgitation but without overt signs of heart failure.

PROCEDURE

Dogs were randomly assigned to be treated with enalapril (0.5 mg/kg [0.23 mg/lb], PO, q 24 h) or placebo, and serum creatinine and urea nitrogen concentrations were measured at regular intervals for up to 26 months.

RESULTS

Adequate information on renal function was obtained from 132 dogs; follow-up time ranged from 0.5 to 26 months (median, 12 months). Mean serum creatinine and urea nitrogen concentrations were not significantly different between dogs receiving enalapril and dogs receiving the placebo at any time, nor were concentrations significantly different from baseline concentrations. Proportions of dogs that developed azotemia or that had a +/- 35% increase in serum creatinine or urea nitrogen concentration were also not significantly different between groups.

CONCLUSIONS

And Clinical Relevance: Results suggest that administration of enalapril for up to 2 years did not have any demonstrable adverse effects on renal function in dogs with severe, compensated mitral regurgitation.

Clinical profiles and outcomes of end-stage renal failure patients with late initiation of renal replacement therapy based on uremic symptoms under intensive renoprotective therapies

AIM

This study describes the clinical profiles and outcomes of renal failure patients with late initiation of renal replacement therapies (RRT) based on uremic symptoms under intensive treatment prior to the start of RRT (IT).

METHODS

Thirteen patients (male 10, female 3) with end-stage renal disease who preferred to wait for the initiation of RRT until uremic symptoms appeared regardless of serum creatinine (s-Cr) and 24-hour creatinine clearance (24-hour Ccr) were chosen. All patients received IT including a low-protein diet, antihypertensive drugs including enalapril, erythropoietin and others to prevent and manage uremic states until the initiation of RRT. Clinical findings at the initiation of RRT and the outcomes after the start of RRT were examined.

RESULTS

RRT was initiated 23.6 +/- 16.9 months after IT without any complication in all patients when mild uremic symptoms appeared. Uremic symptoms, blood pressure, serum albumin, potassium, calcium and urinary Cr excretion were well controlled except inorganic phosphate, hemoglobin and cardiac size. 24-hour Ccr and s-Cr were 3.4 +/- 0.7 ml/min and 17.4 +/- 3.8 mg/dl at initiation of RRT. The outcomes of all the patients were all well during chronic RRT.

CONCLUSION

Intensive treatment prior to the start of RRT can diminish uremic symptoms and complications so that RRT might be initiated safely and with fewer problems, even in the face of lower 24-hour Ccr and markedly higher s-Cr.

Five preventable causes of kidney graft loss in the 1990s: a single-center analysis

BACKGROUND

Despite improvements in immunosuppressive protocols and patient care, kidney allografts continue to fail. We studied causes of graft loss for primary kidney transplants in the 1990s to determine major causes and potential interventions.

METHODS

Causes of graft loss were reviewed for 1467 primary kidney transplants done at our institution between January 1, 1990, and December 31, 1999. Graft loss for that entire population was studied and then the causes of loss selectively examined at <1 year, 1 to 5 years, and>5 years post-transplant. Finally, causes of loss in the 1990s versus the 1980s were compared.

RESULTS

Five major causes of graft loss were noted in the 1990s: thrombosis, acute rejection (either alone or combined with delayed graft function or infection), chronic rejection, death with function, and noncompliance. In the first year post-transplant, thrombosis (25%) and death with function (41%) were the major causes of graft loss. After the first year, chronic rejection and death with function predominated. For recipients dying with graft function, cardiovascular disease was the major cause of death.

CONCLUSIONS

This study identified the five major causes of kidney graft loss in the 1990s. Different interventions are required to decrease loss from each of these causes. Future research needs to be directed at such interventions.

ACE genotype and ACE inhibitor response in kidney disease: a perspective

Angiotensin-converting enzyme (ACE) inhibitors have been shown to reduce blood pressure and slow the progression of renal diseases. However, a substantial interindividual variability in treatment response also has been noted. The activity of ACE is partially dependent on the presence or absence of a 287-bp element in intron 16, and this insertion/deletion (I/D) polymorphism accounts for 47% of the total phenotypic variance in plasma ACE; DD subjects have the highest; ID subjects, intermediate; and II individuals, the lowest concentrations. Data suggest that genotype also determines tissue enzyme activity, and, at least under certain conditions, ACE activity is a rate-limiting step for angiotensin II formation. It therefore has been speculated that the ACE polymorphism also might affect therapeutic effects of ACE inhibitors. Unfortunately, clinical studies performed to date do not allow us to draw definite conclusions. Nonetheless, the rapidly evolving area of pharmacogenomics soon will also affect therapeutic decisions in the field of nephrology and hypertension.

Are clinical endpoint benefits of angiotensin converting enzyme inhibitors independent of their blood pressure effects?

Both basic and experimental data indicate that the renin-angiotensin system through angiotensin II mediates its classic hemodynamic role, but also has a significant deleterious role in a number of cardiac, vascular, and renal disorders. Indeed, evidence indicates that angiotensin II negatively impacts endothelial function, cardiac remodeling, vessel wall hypertrophy, atherosclerosis, and progressive renal disease. Newer data point to a significant role for angiotensin II in inflammation and in inducing plasminogen activator inhibitor. This widespread negative effect can be countered by newer antihypertensive drugs, angiotensin converting enzyme inhibitors, and angiotensin receptor blockers. Both small and large clinical trials suggest a large benefit of such drugs on not only organ-specific endpoints such as renal disease or proteinuria, but on global cardiovascular events. It does appear that when blood pressure is significantly elevated, lowering blood pressure does indeed provide protection for larger endpoints such as stroke. However, at lower blood pressure levels, a hemodynamically independent effect is likely to be contributing to the positive effects. We should embrace these effects and champion them for our patients.

Quality of prereferral care in patients with chronic renal insufficiency

BACKGROUND

Appropriate care in chronic renal insufficiency (CRI) includes blood pressure and diabetes control, as well as the investigation and management of anemia, acidosis, and bone disease. There is a lack of data on the control of these parameters at the time of referral to a nephrologist. Similarly, early referral has been emphasized in the literature, yet very little published has examined current referral patterns.

METHODS

A single-center retrospective/prospective review of all new outpatient referrals to nephrologists in Halifax, Canada, in 1998 and 1999 was conducted to identify patients with CRI (serum creatinine > 1.6 mg/dL [141 micromol/L] for men or >1.2 mg/dL [106 micromol/L] for women). Quality of prereferral care was based on data from the initial clinic visit.

RESULTS

Of 1,050 charts reviewed, 411 patients met the study criteria. Twenty-six percent of patients had diabetes mellitus, 18% were referred with a calculated glomerular filtration rate less than 15 mL/min, and blood pressure was optimally controlled (<130 mm Hg systolic and <80 mm Hg diastolic) in only 24%. Only 44% of patients were administered an angiotensin-converting enzyme inhibitor. Patients were administered an average of 1.9 antihypertensive agents. Significant anemia (hemoglobin < 10 g/dL) was present in 21%, and appropriate investigations were performed in only 35% of these patients. Calcium levels less than 8.6 mg/dL (2.15 mmol/L) were found in 19% of patients, and only 14% of these patients were started on calcium supplement therapy. Phosphate levels greater than 5.0 mg/dL (1.6 mmol/L) were seen in 20% of patients, and 14% of these patients were on phosphate-binder therapy. Parathyroid hormone levels were more than five times normal values in 18% of patients, and 25% of patients had bicarbonate levels less than 23 mmol/L.

CONCLUSIONS

A significant proportion of patients referred with CRI receive inadequate prereferral care. Continuing education programs and referral guidelines must not only emphasize the importance of early referral, but also address the related consequences of CRI to delay the progression of renal disease and avoid complications.

Comparative effects on dynamic renal potassium excretion of ACE inhibition versus angiotensin receptor blockade in hypertensive patients with type II diabetes mellitus

Both ACE inhibitors (ACEI) and angiotensin receptor blockers (ARB) are renoprotective beyond their effects on blood pressure (BP), but their widespread use is limited by their tendency to provoke hyperkalemia. The comparative effects of ACEI and ARB on potassium handling have not been investigated. The objective of this study was to determine whether there are differences in dynamic renal potassium handling between ACEI and ARB in response to an oral potassium challenge. This was a randomized crossover study of candesartan versus lisinopril titrated to control BP followed by an inpatient study of renal potassium handling in 24 hypertensive patients with type II diabetes mellitus (DMII) and preserved renal function. Following an oral potassium challenge (0.75 mmol/kg), differences in hourly serum K (mmol/L), rate of urinary potassium excretion (UkV, micromol/min), and fractional excretion of potassium (FEK) were assessed by repeated-measures ANOVA. Hourly UkV(p = .45) and FEK (p = .19) were similar for candesartan and lisinopril, although FEK at 2 hours for candesartan tended to exceed that for lisinopril (.34 [.04] vs. .26 [.03]) and approached significance (p = .096). UkVfor candesartan at hour 2 was 177 (26) and 121 (21) for lisinopril and also approached significance (p = .10). Serial serum potassium did not differ (p = .70). No statistical differences were discovered in renal potassium handling between candesartan and lisinopril in patients with DMII and preserved renal function. Whether there are differences between the drug classes in renal impairment remains to be determined.

Renoprotective effect of small doses of losartan and enalapril in patients with primary glomerulonephritis. Short-term observation

BACKGROUND

The renin-angiotensin system is thought to be involved in progression of chronic renal diseases of both diabetic and nondiabetic origin. It is confirmed that angiotensin-converting enzyme inhibitors reduce urinary protein excretion (UPE) and attenuate the development of renal injury. The angiotensin II receptor blockers are an alternative class of drugs inhibiting the renin-angiotensin system activity with preliminarily confirmed renoprotective activity. However, there is lack of data concerning renoprotective action of very small doses of these drugs.

METHODS

Prospective, randomized, 3-month study of the effects of losartan 25 mg (n = 17) vs. enalapril 10 mg (n = 17) vs. combination of losartan 25 mg and enalapril 10 mg (n = 15) on proteinuria, kidney function and metabolic profile in 51 patients with biopsy proven chronic glomerulonephritis with normal or slightly declined kidney function [creatinine clearance (CRCL) between 36 and 93 ml/min] was performed. Clinical evaluation and laboratory tests were estimated before treatment (basal), during the first week and after 3 months of therapy.

RESULTS

Both, monotherpy with losartan and enalapril significantly reduced proteinuria by 25.35 and 45.07%, respectively. There was no significant difference between groups. Combined therapy induced a more remarkable reduction of proteinuria (65.96%) than either of the drugs administered alone. This antiproteinuric effect was significantly more pronounced only in comparison with the losartan group (p = 0.009). Decreasing of blood pressure was most pronounced in the combined group. In all groups, no correlation between fall of UPE and reducing the systolic or diastolic blood pressure was found. Significant decline in CRCL was observed with enalapril treatment just after 1 week of therapy (p = 0.039) and at the end of observation (p = 0.043). CRCL remained stable in losartan-treated subjects. No changes in serum creatinine level, metabolic profile and sodium excretion were observed during therapy in studied groups.

CONCLUSIONS

These results indicated that even very small doses of losartan and enalapril reduce proteinuria in patients with primary glomerulonephritis. Combination of these drugs could cause significantly greater antiproteinuric effect than either of the agents in monotherapy. It is likely that the treatment with losartan, compared to enalapril, is associated with less risk of acute fall of glomerular filtration at the beginning of therapy.

Angiotensin type 2 receptor antagonism confers renal protection in a rat model of progressive renal injury

The role of the angiotensin type 2 (AT(2)) receptor in the pathogenesis of progressive renal injury has not been previously elucidated. The renal expression of the AT(1) and AT(2) receptors in subtotally nephrectomized rats (STNx) and the effects of AT(2) receptor blockade on renal injury were explored. Reduced renal expression of the AT(1) but not the AT(2) receptor was observed in STNx by reverse transcription-PCR, by in vitro autoradiography, and by immunohistochemical staining. The STNx rats were randomly assigned to AT(1) receptor antagonist valsartan, AT(2) receptor antagonist PD123319, or the combination of both for 4 wk. Increased proteinuria in STNx rats was reduced by PD123319 but to a lesser degree when compared with valsartan. Reduced gene and protein expression of the slit diaphragm protein nephrin was prevented by either valsartan or PD123319. Expression of osteopontin, proliferating cell nuclear antigen, and monocyte/macrophage infiltration was increased in STNx rats and was reduced by both AT(1) and AT(2) receptor antagonists. These effects of AT(2) receptor antagonism were observed in the presence of increased BP in STNx rats. These findings suggest that blockade of the AT(2) receptor alone confers a degree of renal protection; in particular, it seems that the combination of the AT(1) and AT(2) receptor antagonists may confer additive renal effects than either receptor antagonist as monotherapy.

Hypertensive emergencies: diagnosis and management

The treatment of hypertension is preventive medicine. This principle applies in the emergency room as well as the clinic. However, there are crucial contrasts between these two care settings related to specific goals of management for real emergencies and nonemergency conditions. In the emergency room, rapid triage is necessary to separate those who can safely be sent home for future clinic assessment from those who require immediate interventions including short stays in 24-hour observation units or hospitalization for more serious problems. This review focuses on decisions related to hypertension management in the emergency room and over brief periods of observation and treatment. Strategy is supported by evidence-based considerations whenever possible. Where outcome studies are not available, we rely on the rationale derived from relevant clinical research.

Calcium channel blockade in combination with angiotensin-converting enzyme inhibition or angiotensin II (AT(1)-receptor) antagonism in hypertensive diabetics and patients with renal disease and hypertension

Effective reduction in blood pressure (BP) improves survival and morbidity in hypertensive patients. Combination therapy with multiple antihypertensive agents is frequently required in clinical practice and therapeutic trials to achieve target BP. Patients at elevated cardiovascular risk achieve the greatest benefit from equivalent reduction in BP and also require more stringent BP control. In patients with hypertension and diabetes mellitus or renal disease, BP control is of primary importance and blockade of the renin-angiotensin system (RAS) should be the initial therapeutic intervention. Choice of combination therapy has been insufficiently studied in major clinical cardiovascular endpoint trials. Diuretic therapy remains the logical addition to RAS blockade. Despite previous debate, the available evidence suggests long-acting calcium-channel blockers are also a safe and very effective addition to improve BP control further. The choice of antihypertensive combination therapy should not override the fundamental necessity of lowering BP to target levels.

Combination therapy of amlodipine/benazepril versus monotherapy of amlodipine in a practice-based setting

BACKGROUND

Community-based studies are conducted to determine the degree to which therapeutic interventions will succeed in real world settings. This large practice-based clinical trial assessed the efficacy and tolerability of fixed-dose combination therapy with amlodipine/benazepril, compared with amlodipine monotherapy, in patients with mild-to-moderate hypertension.

METHODS

Hypertensive patients currently taking amlodipine were selected based on one of two criteria: inadequate blood pressure (BP) control on amlodipine (diastolic BP [DBP] > or = 90 mm Hg; group 1), or inability to tolerate amlodipine (DBP < or = 90 mm Hg, but with edema; group 2). Eligible patients were switched from 5 or 10 mg of amlodipine to 5/10 mg or 5/20 mg of amlodipine/benazepril for 4 weeks. In group 1 (n = 6410), primary efficacy outcome was change in mean sitting DBP. A secondary efficacy outcome was change in mean sitting systolic BP (SBP). In group 2 (n = 1502), primary efficacy outcome was the percentage of patients whose edema improved during therapy with amlodipine/benazepril when compared with amlodipine monotherapy.

RESULTS

In group 1, mean sitting DBP declined from 96.5 mm Hg at baseline to 84.9 mm Hg at week 4, a mean reduction of 11.5 mm Hg (95% confidence interval [CI] -11.8 to -11.3 mm Hg; P < .001). From baseline to week 4, mean sitting SBP declined from 152.9 mm Hg to 137.3 mm Hg, a mean reduction of 15.6 mm Hg (95% CI -16.0 to -15.2 mm Hg; P < .001). In group 2, 85% (95% CI 83%-87%) experienced some improvement in edema compared with baseline levels.

CONCLUSIONS

Fixed-dose combination antihypertensive agent amlodipine/benazepril was safe and effective for patients who experienced either inadequate BP control or edema with amlodipine monotherapy.

Effects of the calcium channel antagonist amlodipine in cats with surgically induced hypertensive renal insufficiency

OBJECTIVE

To determine whether amlodipine besylate decreases systemic arterial blood pressure (BP) and reduces the prevalence of complications in cats with induced hypertensive renal insufficiency.

ANIMALS

20 cats with partial nephrectomy.

PROCEDURE

Following reduction in renal mass, 10 cats were administered 0.25 mg of amlodipine/kg, PO, q 24 h (group A). Ten cats served as a control group (group C). Systolic BP (SBP), diastolic BP (DBP), and mean BP (MBP), physical activity, and pulse rate were measured continuously for 36 days by use of radiotelemetric devices.

RESULTS

Compared with values for clinically normal cats, SBP, DBP, and MBP were significantly increased in cats of group C. Cats in group A had significant reductions in SBP, DBP, and MBP, compared with values for cats in group C. Albuminuria but not urine protein-to-creatinine ratio was significantly correlated (R2 = 0.317) with SBP in hypertensive cats. Prevalence of ocular lesions attributable to systemic hypertension in group C (7 cats) was greater than that observed in group A (2). Two cats in group C were euthanatized on day 16 because of nuerologic complications attributed to systemic hypertension. One normotensive cat in group A was euthanatized because of purulent enteritis of unknown cause on day 27.

CONCLUSIONS AND CLINICAL RELEVANCE

Amlodipine had an antihypertensive effect in cats with coexistent systemic hypertension and renal insufficiency. Its use may improve the prognosis for cats with systemic hypertension by decreasing the risk of ocular injury or neurologic complications induced by high BP.

Carcinogenicity of antihypertensive therapy

Several studies have suggested that antihypertensive treatment may promote cancer through unknown mechanisms. Early retrospective studies implicated reserpine in breast cancer, but data from prospective studies and meta-analysis of several case-controlled studies showed only a weak association between reserpine and breast cancer which, although statistically significant, is of little clinical concern. Data from case-controlled studies and several cohort studies suggested an association between the use of a diuretic and the occurrence of renal cell cancer, particularly in women. A recent study showed an association between the use of a diuretic and the occurrence of colon cancer. Several prospective studies showed that treatment with atenolol may increase mortality from malignancy. However, other studies that analyzed data from several thousand patients could not confirm this association. In three prospective and a few case-controlled studies, angiotensin converting enzyme inhibitors were not associated with increased mortality from malignancy. In addition, a recent retrospective study showed that long-term use of angiotensin converting enzyme inhibitors had a protective effect against malignancy. Data from three large case-controlled studies and the combined data from eight randomized controlled studies and seven longitudinal studies showed a similar risk for malignancy among users and nonusers of calcium antagonists. Until further data from prospective clinical trials are available, we advise caution about long-term diuretic therapy in women. With regard to other antihypertensive drug classes, we suggest continuing the management of hypertension according to current treatment guidelines with little fear of any substantial cancer risk.