Combination ACEI and ARB therapy: additional benefit in renoprotection?

The dilemma of dual renin-angiotensin system blockade in chronic kidney disease: why beneficial in animal experiments but not in the clinic?

Drugs interfering with the renin-angiotensin-aldosterone system (RAAS) improved the prognosis in patients with hypertension, heart failure, diabetes and chronic kidney disease. However, combining different drugs brought no further benefit while increasing the risk of hyperkalemia, hypotension and acute renal failure. This was so with combining angiotensin converting enzyme inhibitors (ACEi) and angiotensin II receptors type 1 antagonists (ARB). Dissimilarly, in animal disease models this dual therapy proved clearly superior to single drug treatment and became the optimal standard regime for comparison with other treatments. This review analyzes the causes of the discrepancy of effects of the dual therapy between animal experiments versus clinical studies, and is focused on the outcomes in chronic kidney disease. Discussed is the role of species differences in RAAS, of the variability of the disease features in humans versus relative stability in animals, of the genetic uniformity in the animals but not in humans, and of the biased publication habits of experimental versus clinical studies. We attempt to understand the causes and reconcile the discordant findings and suggest to what extent dual RAAS inhibition should be continued in animal experiments and why its application in the clinics should be limited to strictly selected groups of patients.

An additive effect of anti-PAI-1 antibody to ACE inhibitor on slowing the progression of diabetic kidney disease

While angiotensin II blockade slows the progression of diabetic nephropathy, current data suggest that it alone cannot stop the disease process. New therapies or drug combinations will be required to further slow or halt disease progression. Inhibition of plasminogen activator inhibitor type 1 (PAI-1) aimed at enhancing ECM degradation has shown therapeutic potential in diabetic nephropathy. Here, using a mouse model of type diabetes, the maximally therapeutic dose of the PAI-1-neutralizing mouse monoclonal antibody (MEDI-579) was determined and compared with the maximally effective dose of enalapril. We then examined whether addition of MEDI-579 to enalapril would enhance the efficacy in slowing the progression of diabetic nephropathy. Untreated uninephrectomized diabetic db/db mice developed progressive albuminuria and glomerulosclerosis associated with increased expression of transforming growth factor (TGF)-β1, PAI-1, type IV collagen, and fibronectin from weeks 18 to 22, which were reduced by MEDI-579 at 3 mg/kg body wt, similar to enalapril given alone from weeks 12 to 22 Adding MEDI-579 to enalapril from weeks 18 to 22 resulted in further reduction in albuminuria and markers of renal fibrosis. Renal plasmin generation was dramatically reduced by 57% in diabetic mice, a decrease that was partially reversed by MEDI-579 or enalapril given alone but was further restored by these two treatments given in combination. Our results suggest that MEDI-579 is effective in slowing the progression of diabetic nephropathy in db/db mice and that the effect is additive to ACEI. While enalapril is renal protective, the add-on PAI-1 antibody may offer additional renoprotection in progressive diabetic nephropathy via enhancing ECM turnover.

Nephroprotective action of renin-angiotensin-aldosterone system blockade in chronic kidney disease patients: the landscape after ALTITUDE and VA NEPHRON-D trails

The intervention in the renin-angiotensin-aldosterone system (RAAS) is currently the most effective strategy that combines blood pressure lowering and renoprotection. Several large, randomized, controlled trials evidenced the renoprotective potential of the angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) in nephropathies of almost any etiology. Mineralocorticoid receptor antagonists and direct renin inhibitor, aliskiren, as add-on treatments to standard therapy including the optimal dose of ACEIs or ARBs reduce albuminuria or proteinuria and slow development of renal dysfunction more than placebo. No clinical evidence is available however about whether these strategies may influence on long-term kidney outcome. Three recent trials suggested that aggressive RAAS blockade, that is, combination of 2 RAAS-blocking agents, does not decrease cardiovascular and renal morbidity and may carry an increased risk of serious complications. This article reviews an evidence-based approach on the use of RAAS-inhibiting agents in chronic kidney disease and considers the implementation of dual RAAS blockade with reference to the results of ALTITUDE and VA NEPHRON-D trails aiming to aid clinicians in their treatment decisions for patients with chronic kidney disease.

Losartan reverses glomerular podocytes injury induced by AngII via stabilizing the expression of GLUT1

Podocyte impairment is a key pathogenic even in the initiation and development of glomerular diseases associated with proteinuria. The type 2 diabetic patients is characterized by progressive increases in albuminuria which are associated with the development of characteristic histopathological features. Losartan had a benefit in decreasing albuminuria in type 2 diabetic patients,suggesting that losartan may have another effect other than blockade of the traditional renin-angiotensin system (RAS). However, the mechanism has remained undetermined. Glucose transporter 1 (GLUT1) is the predominant basal glucose transporter. In the kidney, GLUT1 was overexpressed predominantly in glomerular mesangial cells and in small vessels, rather than in podocytes. The increased glomerular GLUT1 mimicked diabetes-induced glomerular GLUT1 expression. In this study, we hypothesized that increased GLUT1 expression induced by angiotensinII (AngII) contributes to the progression of podocytes injury, losartan can block the effect of AngII and protect podocytes via stabilizing the expression of GLUT1, our results strongly suggest that losartan has a direct and protective effect on podocytes. This represents a novel mechanism by which losartan may protect podocyte from apoptotic death and improve podocyte function via stabilizing the expression of GLUT1. This finding underlines the crucial role of GLUT1 in the pathogenesis of podocyte injury and proteinuria.

Renoprotective trials completed with antihypertensive drugs also teach many other aspects

The author analyzes the applicability of the renin-angiotensin system blocking drugs in patients with chronic kidney disease emphasizing their renoprotective (blood pressure and albuminuria lowering) and cardiovascular risk decreasing effects. As opposed to a previously-published statement, the author believes that their application is fundamental, particularly in combination with calcium-antagonist drugs. Relying on many references the author suggests that combined treatment with different renin-angiotensin system blocking drugs cannot be entirely ruled out, although it is not yet recommended. Orv. Hetil., 2013, 154, 753–756.

Cyprinus carpio Decoction Improves Nutrition and Immunity and Reduces Proteinuria through Nephrin and CD2AP Expressions in Rats with Adriamycin-Induced Nephropathy

Cyprinus carpio decoction (CCD) is a well-known Chinese food medicine formula, accepted widely as a useful therapy in preventing edema and proteinuria caused by renal disease. However, the mechanism underlying this effect remains unclear. The current study investigated the potential mechanism of CCD in alleviating nephropathy induced by adriamycin (ADR) in rats. 70  eight-week-old Wistar rats were randomly divided into normal, model, fosinopril, YD, YG groups. All rats except for the normal group received 6.5 mg/kg·bw of ADR injection into the vena caudalis once. Different doses of CCD (11.3 and 22.5 g kg(-1)) were lavaged to rats in YD and YG groups, respectively. Then the serum biochemical values of the total protein (TP), albumin (ALB), blood urea nitrogen (BUN), creatinine (Cr), electrolyte levels, and the urinary protein (UP) content in 12 hr urine were measured. Interleukin-4 (IL-4) and interferon (INF-γ) were measured by enzyme-like immunosorbent assay (ELISA). The pathomorphological analysis was observed using light and electron microscopy, and the expressions of nephrin and CD2-associated protein (CD2AP) in renal tissues were determined by immunohistochemical assay. The results indicated that CCD can relieve ADR-induced nephropathy (ADN) by improving the nutrition status, regulating the immunity, and inhibiting proteinuria by increasing nephrin and CD2AP expressions.

Early treatment with everolimus exerts nephroprotective effect in rats with adriamycin-induced nephrotic syndrome

BACKGROUND

Nephrotic syndrome (NS) is a clinical state characterized by massive proteinuria and excessive fluid retention. The effects of early versus late treatment with low or high doses of oral everolimus, a mammalian target of rapamycin inhibitor, on proteinuria in NS have not been previously described.

METHODS

The effects of early treatment (2 days prior to NS induction) versus late treatment (beginning 2 weeks following the establishment of NS) with a low (20 mg/L) or high (100 mg/L) dose of everolimus for 5-7 weeks on proteinuria and nephrin/podocin abundance were assessed in male adult SD rats with adriamycin-induced NS.

RESULTS

Adriamycin caused a significant increase in daily and cumulative proteinuria throughout the experimental period. Early, and to a lesser extent late treatment, with a low dose of everolimus, significantly decreased both daily and cumulative proteinuria and improved renal function. The anti-proteinuric effects of low-dose everolimus were associated with restoration of the disruptive glomerular nephrin/podocin abundance. In contrast, administration of a high dose of everolimus resulted in a decrease in proteinuria in NS rats, subsequently to deterioration of renal function.

CONCLUSIONS

Early, and to a lesser extent late treatment, with a low but not a high dose of everolimus is effective in reducing proteinuria in nephrotic rats. The mechanism may be via nephrin/podocin protection.

Nephron-deficient Fvb mice develop rapidly progressive renal failure and heavy albuminuria involving excess glomerular GLUT1 and VEGF

Reduced nephron numbers may predispose to renal failure. We hypothesized that glucose transporters (GLUTs) may contribute to progression of the renal disease, as GLUTs have been implicated in diabetic glomerulosclerosis and hypertensive renal disease with mesangial cell (MC) stretch. The Os (oligosyndactyly) allele that typically reduces nephron number by approximately 50%, was repeatedly backcrossed from ROP (Ra/+ (ragged), Os/+ (oligosyndactyly), and Pt/+ (pintail)) Os/+ mice more than six times into the Fvb mouse background to obtain Os/+ and +/+ mice with the Fvb background for study. Glomerular function, GLUT1, signaling, albumin excretion, and structural and ultrastructural changes were assessed. The FvbROP Os/+ mice (Fvb background) exhibited increased glomerular GLUT1, glucose uptake, VEGF, glomerular hypertrophy, hyperfiltration, extensive podocyte foot process effacement, marked albuminuria, severe extracellular matrix (ECM) protein deposition, and rapidly progressive renal failure leading to their early demise. Glomerular GLUT1 was increased 2.7-fold in the FvbROP Os/+ mice vs controls at 4 weeks of age, and glucose uptake was increased 2.7-fold. These changes were associated with the activation of glomerular PKCbeta1 and NF-kappaB p50 which contribute to ECM accumulation. The cyclic mechanical stretch of MCs in vitro, used as a model for increased MC stretch in vivo, reproduced increased GLUT1 at 48 h, a stimulus for increased VEGF expression which followed at 72 h. VEGF was also shown to act in a positive feedback manner on MC GLUT1, increasing GLUT1 expression, glucose uptake and fibronectin (FN) accumulation in vitro, whereas antisense suppression of GLUT1 largely blocked FN upregulation by VEGF. The FvbROP Os/+ mice exhibited an early increase in glomerular GLUT1 leading to increased glomerular glucose uptake PKCbeta1, and NF-kappaB activation, with excess ECM accumulation. A GLUT1-VEGF-GLUT1 positive feedback loop may play a key role in contributing to renal disease in this model of nondiabetic glomerulosclerosis.

A comparative study of the prevalence of hyperkalemia with the use of angiotensin-converting enzyme inhibitors versus angiotensin receptor blockers

Background and objectives

Angiotensin-converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARB) are increasingly used in a variety of settings including heart failure, renal failure, arterial hypertension, and diabetic nephropathy. The objective of this study was to investigate the prevalence of hyperkalemia with ACEI and ARB use, in a population of the United States veterans.

Design, settings, material, and measurements

Retrospective observational cohort study of 1163 patients on ACEIs and 1168 patients on ARBs in a single Veterans Affairs Medical Center. Electronic medical records were reviewed over a 12-month period with data collected on various demographic, laboratory, comorbidity, and medication related variables.

Results

Hyperkalemia (>5 mEq/L) was observed in 20.4% of patients on ACEIs and 31.0% on ARBs. Severe hyperkalemia (6 mEq/L or higher), was observed in 0.8% of ACEI and 2.8% of ARB users. In univariate logistic regression analyses, diabetes mellitus; serum glucose, total carbon dioxide content, creatinine, and estimated glomerular filtration rate (GFR) were significantly associated with hyperkalemia. ARB use, when compared to ACEI, was associated with a 42% increase in odds of hyperkalemia (odds ratio [OR] = 1.42; p = 0.001) in a model including adjustment for GFR and a 56% increase in odds of hyperkalemia (OR = 1.56; p < 0.001) in a model including adjustment for serum creatinine.

Conclusions

Hyperkalemia, associated with the use of ACEIs and ARBs, is usually mild and severe hyperkalemia is rare. Hyperkalemia is more common with ARBs than ACEIs. ARB use, when compared to ACEI use, may significantly and independently be associated with increased odds of hyperkalemia.

Low-dose angiotensin II receptor antagonists and angiotensin II-converting enzyme inhibitors alone or in combination for treatment of primary glomerulonephritis

OBJECTIVE

The renin-angiotensin system is thought to be involved in the progression of chronic renal diseases of both diabetic and non-diabetic origin. It has been confirmed that angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) reduce urinary protein excretion and attenuate the development of renal injury. Clinical data comparing the renal effects of ACEIs and ARBs, either singly or in combination, are scarce and usually concern the use of standard or high doses.

MATERIAL AND METHODS

This was a prospective, randomized, 9-month study of the effects of low doses of losartan (25 mg; n = 18) versus enalapril (10 mg; n = 18) versus the combination of losartan (25 mg) and enalapril (10 mg) (n = 16) on proteinuria, kidney function and metabolic profile in 54 patients with biopsy-proven chronic glomerulonephritis, hypertension and normal or slightly impaired kidney function. The clinical evaluation and laboratory tests were performed before treatment (baseline) and after 3 and 9 months of therapy.

RESULTS

After 3 months, significant decreases in proteinuria were observed in all groups: losartan, 22.6% (p = 0.02); enalapril, 43% (p = 0.012); and combined therapy, 63% (p = 0.001). This anti-proteinuric effect was even greater after 9 months of therapy: losartan, 44.2% (p = 0.02); enalapril, 49.6% (p = 0.02); and combined therapy, 51% (p = 0.003). There was no significant difference between losartan and enalapril with respect to their impact on proteinuria level. Proteinuria reduction was significantly greater in patients receiving combined therapy in comparison with losartan treatment after 3 months of therapy (p = 0.02). Creatinine clearance and serum creatinine were stable during the entire study period in all patients. No significant changes in lipids, serum uric acid or protein levels were observed.

CONCLUSIONS

These results indicate that proteinuria is reduced by low doses of losartan or enalapril. The combination of these drugs seems to be beneficial and may offer an additional renoprotective effect. This needs to be confirmed in a study with a larger sample size.

Low-dose dual blockade of the renin–angiotensin system improves tubular status in non-diabetic proteinuric patients

OBJECTIVE

Treatment with agents that inhibit the renin-angiotensin system is commonly regarded as a gold standard renoprotective strategy in patients with chronic kidney diseases. For maximum antiproteinuric effect, the dose titration of these agents is recommended. This therapeutic strategy is not used for proteinuric patients who are not able to receive high doses of angiotensin-converting enzyme inhibitor or angiotensin II receptor antagonists.

MATERIAL AND METHODS

In patients with primary glomerulonephritis (n=24), a randomized, triple-treatment, triple-period, cross-over study was performed to compare the effects of combined therapy with benazepril 5 mg and losartan 25 mg and monotherapy with either agent alone at a two-fold higher dose on the extent of tubular injury as assessed by alpha1-microglobulin (alpha1-m) excretion and the plasma level of transforming growth factor-beta1 (TGF-beta1).

RESULTS

Combination therapy significantly reduced alpha1-m excretion compared to either agent used alone: 178.29+/-27.36 to 99.63+/-13.03 mg/g creatinine for losartan + benazepril vs 178.29+/-27.36 to 161.59+/-23.22 mg/g creatinine for benazepril alone (p<0.05; ANOVA) and 178.29+/-27.36 to 99.63+/-13.03 mg/g creatinine for losartan + benazepril vs 178.29+/-27.36 to 173.45+/-27.69 mg/g creatinine for losartan alone (p<0.05; ANOVA). There was a significant correlation between change in alpha1-m excretion and reduction in proteinuria (r=0.704; p=0.023). There were no differences in TGF-beta1 level between the studied treatments. Systemic blood pressure reduction did not differ among the therapies.

CONCLUSIONS

Combination therapy with angiotensin-converting enzyme inhibitor and angiotensin II subtype 1 receptor antagonists at very small doses may be superior to monotherapy with these agents at higher doses as far as tubular injury is concerned. We speculate that such a therapeutic strategy may be a useful approach for patients who are known not to be capable of receiving optimal renoprotective doses of these regimens.

Dual blockade of the renin-angiotensin-aldosterone system with high-dose angiotensin-converting enzyme inhibitor for nephroprotection: an open, controlled, randomized study

OBJECTIVE

Despite the proven effectiveness of combination therapy with an angiotensin I-converting enzyme inhibitor (ACEI) and angiotensin II-receptor blockers (ARBs) for the prevention and treatment of kidney disease, it has not proved possible to inhibit the progress of chronic nephropathies completely. To improve renal outcome one may consider using increased dosages of ACEI above those usually recommended for hypertension.

MATERIAL AND METHODS

A randomized, open, controlled study was conducted to evaluate the influence of two combination therapies on proteinuria, markers of tubular injury and renal fibrosis. A total of 18 patients with a creatinine level of 109+/-36 micromol/l and proteinuria of 0.97+/-0.76 g/24 h were enrolled in the study. In the 8-week run-in period, an ACEI (cilazapril 5 mg once-daily) and an ARB (telmisartan 80 mg once-daily) were administered to achieve the target blood pressure of < or = 130/80 mmHg. Next, the patients were randomly assigned to either an increased dose of cilazapril (10 mg) or the previous dose (5 mg) in two active-treatment periods, each lasting 8 weeks.

RESULTS

A significant increase in renin activity was observed after administration of cilazapril 10 mg (6.46+/-1.12 vs 4.67+/-0.7 ng/ml/h; p=0.028). Proteinuria, urine excretion of N-acetyl-beta-D-glucosaminidase, and alpha1-microglobulin and amino-terminal propeptide of type III procollagen were unchanged.

CONCLUSION

An increased dosage of cilazapril (twice the maximum recommended dose) in addition to combination therapy with telmisartan was associated with increased blockade of the renin-angiotensin-aldosterone system, with no additional effect on proteinuria, markers of tubular injury or renal fibrosis.

Present and future drug treatments for chronic kidney diseases: evolving targets in renoprotection

At present, there are no specific cures for most of the acquired chronic kidney diseases, and renal transplantation is limited by organ shortage, therefore present efforts are concentrated on the prevention of progression of renal diseases. There is robust experimental and clinical evidence that progression of chronic nephropathies is multifactorial; however, intraglomerular haemodynamic changes and proteinuria play a key role in this process. With a focus on renoprotection, we first examine more established therapies--such as those that modulate the renin-angiotensin-aldosterone system--that can be used for the treatment of proteinuric renal diseases. We then discuss examples of novel drugs and biologics that might be used to target the inflammatory and profibrotic process, and glomerular injury, highlighting results from recent clinical trials.

New therapeutic strategies with combined renin-angiotensin system inhibitors for pediatric nephropathy

Renin-angiotensin system (RAS) inhibitors may delay progression of several chronic kidney diseases in adults. Two classes of RAS inhibitors--angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs)--have been shown to have renoprotective abilities. Despite their different mechanisms of action, these two drug classes appear to have comparable antiproteinuric and renoprotective properties. Preliminary investigations suggest that combination therapy with an ACE inhibitor and ARB offers additional benefit. Only a few studies with these drugs for treatment of pediatric nephrology have been conducted; however, their results are encouraging. Additional clinical trials are needed to confirm these results.

Eplerenone potentiates the antiproteinuric effects of enalapril in experimental nephrotic syndrome

Nephrotic syndrome (NS) is a clinical state characterized by massive proteinuria and edema. It is believed that nephrin and podocin are involved in the development of proteinuria. The proteinuria and effects of eplerenone alone or combined with enalapril on nephrin/podocin abundance in rats with NS have not yet been studied. Therefore, the present study was designed to examine the early (beginning 2 days before NS induction) and late (beginning 2 wk after NS induction) effects of eplerenone and enalapril, alone or combined, on proteinuria and nephrin/podocin abundance in rats with adriamycin-induced NS. Adriamycin caused a significant increase in daily protein excretion (UprV; from 26.96 ± 3.43 to 958.57 ± 56.7 mg/day, P < 0.001) and cumulative proteinuria [from 900.33 ± 135.5 to 22,490.62 ± 931.26 mg ( P < 0.001)] during 6 wk. Early treatment with enalapril significantly decreased UprV from 958.6 ± 56.7 to 600.31 ± 65.13 mg/day ( P < 0.001) and cumulative proteinuria to 12,842.37 ± 1,798.17 mg/6 wk ( P < 0.001). Similarly, early treatment with eplerenone produced a profound antiproteinuric effect: UprV decreased from 958.57 ± 56.7 to 593.38 ± 21.83 mg/day, P < 0.001, and cumulative proteinuria to 16,601.84 ± 1,334.31 mg/6 wk; P < 0.001. An additive effect was obtained when enalapril and eplerenone were combined: UprV decreased from 958.57 ± 56.69 to 424.17 ± 38.54 mg/day, P < 0.001, and cumulative protein excretion declined to 10,252.88 ± 1,011.3 mg/6 wk, P < 0.001. These antiproteinuric effects were associated with substantial preservation of glomerular nephrin and podocin. In contrast, late treatment with either enalapril or eplerenone alone or combined mildly decreased UprV and cumulative proteinuria. Thus pretreatment with eplerenone or enalapril is effective in reducing daily and cumulative protein excretion and preservation of nephrin/podocin. More profound antiproteinuric effects were obtained when enalapril and eplerenone were combined.

Norcantharidin ameliorates proteinuria, associated tubulointerstitial inflammation and fibrosis in protein overload nephropathy

Norcantharidin (NCTD), the demethylated analog of cantharidin isolated from Mylabris, is an anticancer drug routinely used against various human cancers in China. The aims of this study are to learn if NCTD has a protective action against severe proteinuria and consequent interstitial inflammation and fibrosis, and if the inhibition of nuclear factor-kappaB (NF-kappaB) and connective tissue growth factor (CTGF) by NCTD might be involved. Male Sprague-Dawley rats with protein overload nephropathy induced by intraperitoneally injected bovine serum albumin were used as a model. The histopathological examination of kidney tissue in the 9th week by light microscopy and scanning electron microscopy revealed that inflammatory cells had extensively infiltrated into the tubulointerstitial areas with interstitial fibrosis. The administration of NCTD at 0.1 mg/kg/day to the bovine-serum-albumin-injected animal models effectively reduced the proteinuria, and prevented the proteinuria-induced interstitial inflammation and fibrosis. Expressions of the NF-kappaB p65 subunit and CTGF, detected by immunohistochemistry, Western blotting and reverse-transcription polymerase chain reaction, were upregulated in protein overload nephropathy and were attenuated by NCTD. Inhibition of the expressions of the NF-kappaB p65 subunit and CTGF was one beneficial effect of NCTD. These results suggest that in addition to the antiproteinuric action of NCTD, due to its anti-inflammatory and antifibrotic effects as shown in the present study, it may become a therapeutic agent for proteinuria and its associated chronic inflammatory and fibrotic nephropathy.

Novel insights in the treatment of diabetic nephropathy

Diabetes is currently one of the leading causes of end-stage renal failure requiring renal replacement therapy in the Western World. About 15% to 20% of type 1 diabetic patients and 30% to 40% of type 2 diabetic patients will eventually develop end-stage renal failure. To prevent the development or progression of diabetic kidney disease, good glycaemic control remains the cornerstone in the management of diabetic patients. Beyond glycaemic control, other metabolic factors have been shown to be involved in the development of diabetic kidney disease, i.e. advanced glycation endproducts (AGEs) and the aldose reductase pathway. Furthermore, an adequate control of high blood pressure and treatment of microalbuminuria are major therapeutic targes. To achieve adequate blood pressure control, a combination therapy with different classes of antihypertensive agents is often necessary, especially including angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. Other vasoactive factors involved in diabetic nephropathy such as endothelin and nitric oxide will be covered briefly. Besides hyperglycaemia and high blood pressure, other risk factors have been identified in the development or progression of diabetic kidney disease: smoking, hyperlipidaemia, obesity and high protein intake. Their impact on renal function will be highlighted. Finally, recent research has also identified intracellular pathways such as the diacylglycerol-protein kinase C pathway and several growth factors, such as growth hormone, insulin-like growth factor, transforming growth factor-beta, vascular endothelial growth factor, and platelet derived growth factor as players in diabetic kidney disease.

Determinants of progression from microalbuminuria to proteinuria in patients who have type 1 diabetes and are treated with angiotensin-converting enzyme inhibitors

The aims of this study were to assess the frequency and determinants of (1) treatment with angiotensin-converting enzyme inhibitors (ACE-I) and (2) progression to proteinuria in the presence of ACE-I treatment in patients with type 1 diabetes and microalbuminuria. A clinic-based cohort study of patients with type 1 diabetes was begun in 1991. The patients who were included in this study (n = 373) are the cohort members who received a diagnosis of microalbuminuria during a 2-yr baseline observation and were followed for 10 yr with frequent assessments of urinary albumin excretion and biennial examinations. Progression to proteinuria occurred when the median urinary albumin excretion during a 2-yr interval exceeded 299 mug/min. During the decade-long study, the proportion of patients who had a history of microalbuminuria and were treated with ACE-I rose from 17 to 67%. Patients who started this treatment had (on average) higher BP, higher urinary albumin excretion, and longer diabetes duration than those who did not. Microalbuminuria often progressed to proteinuria (6.3/100 person-years) in those who were treated. Poor glycemic control and elevated serum cholesterol were the major determinants/predictors of this progression. Although treatment with ACE-I increased during the past decade, it was not completely effective, because microalbuminuria progressed to proteinuria in many treated patients. Poor glycemic control and elevated serum cholesterol were the major determinants/predictors for progression while on ACE-I treatment. The mechanisms that are responsible for the frequent failure of ACE-I to prevent progression of microalbuminuria to proteinuria in a clinical setting are not clear.

Mechanisms of progression of chronic kidney disease

Chronic kidney disease (CKD) occurs in all age groups, including children. Regardless of the underlying cause, CKD is characterized by progressive scarring that ultimately affects all structures of the kidney. The relentless progression of CKD is postulated to result from a self-perpetuating vicious cycle of fibrosis activated after initial injury. We will review possible mechanisms of progressive renal damage, including systemic and glomerular hypertension, various cytokines and growth factors, with special emphasis on the renin-angiotensin-aldosterone system (RAAS), podocyte loss, dyslipidemia and proteinuria. We will also discuss possible specific mechanisms of tubulointerstitial fibrosis that are not dependent on glomerulosclerosis, and possible underlying predispositions for CKD, such as genetic factors and low nephron number.

The Role of Angiotensin II Type 1 Receptor Antagonists in Elderly Patients with Hypertension

Hypertension is a major risk factor for stroke and coronary events in elderly people and clinical trials have shown that treatment of hypertension with various drugs can result in a substantial reduction in cerebrovascular and cardiovascular events. The angiotensin II type 1 (AT1) receptor antagonists are the newest class of antihypertensive agents to be used widely in clinical practice. AT1 receptor antagonists can generally be given once-daily. They are also extremely well tolerated with minimal first-dose hypotension and an incidence of adverse effects similar to that seen with placebo. Adverse event rates are significantly lower than with other classes of antihypertensive drugs including ACE inhibitors. These factors result in improved compliance and increased rates of continuance on therapy. AT1 receptor antagonists show similar efficacy in lowering blood pressure to other classes of antihypertensive agents and their antihypertensive effect is potentiated when they are given concomitantly with low-dose thiazide diuretics. AT1 receptor antagonists are eliminated predominantly by the hepatic route but most are not subject to extensive metabolism and interactions with other drugs are uncommon. This is an advantage in the elderly, who are often receiving multiple medications which increases the risk for adverse drug interactions. Dose adjustments are not usually required in the elderly unless there is plasma volume depletion. Although plasma AT1 receptor antagonist concentrations are generally higher in the elderly than in younger subjects, this pharmacokinetic difference may be balanced by decreased activation of the circulating renin-angiotensin-aldosterone system in the elderly. Recent clinical studies in high-risk hypertensive patients with left ventricular hypertrophy or in patients with diabetic nephropathy or heart failure have demonstrated that AT1 receptor antagonists can improve clinical outcomes to a similar or sometimes greater extent than other antihypertensive agents. Many of these studies have included large numbers of older patients and have confirmed the excellent tolerability profile of these drugs. Thus, AT1 receptor antagonists should be considered as a possible first-line treatment or as a component of combination therapy in patients with type 2 diabetes mellitus and microalbuminuria or nephropathy and as an alternative or additional treatment to ACE inhibitors in patients with heart failure or left ventricular dysfunction. AT1 receptor antagonists also appear to reduce the onset of new diabetes compared with some other antihypertensive drugs. The benefits in terms of organ protection have mainly been seen in studies using higher doses of particular AT1 receptor antagonists and it is not certain at present whether these results can be extrapolated to other members of the class. As the elderly are more likely to have developed organ damage related to hypertension or to have heart failure or diabetes as concomitant conditions, AT1 receptor antagonists represent an appropriate option for many elderly patients. The main disadvantage of these drugs is the cost of the medication but this may be offset by their improved tolerability with fewer adverse reactions and thus increased compliance, resulting in better blood pressure control and fewer clinical events. Overall, AT1 receptor antagonists are well tolerated and efficacious for blood pressure-lowering when given as a single daily dose in elderly patients and have many potential benefits in high-risk hypertensive subjects.

Renal Protective Effects of the Renin-Angiotensin-Aldosterone System Blockade: From Evidence-Based Approach to Perspectives

The renin-angiotensin-aldosterone system (RAAS) blockade is currently the best-documented treatment strategy to delay the progression of chronic nephropathies. Angiotensin-converting enzyme inhibitors (CEIs) or angiotensin II type 1 receptor antagonists (ARBs) should be used in every normotensive and hypertensive patient with chronic proteinuric nephropathy of both diabetic and non-diabetic origin. The therapy should be initiated as early as possible, bearing in mind that the renoprotection is more effective if used before overt proteinuria or a reduction in kidney function is present. The therapy should be offered to all patients, regardless of renal function, as well as to subjects with severely impaired glomerular filtration. CEIs and ARBs should be administered in therapeutic doses as high as possible to achieve maximal possible proteinuria reduction and systemic blood pressure target <130/80 mm Hg, and 125/75 mm Hg in those subjects with renal insufficiency who present with proteinuria above 1 g/24 h. The combined therapy with the concomitant use of CEIs and ARBs should be offered to all patients with proteinuric non-diabetic chronic nephropathies who do not achieve full and persistent remission of proteinuria with CEI or ARB alone. The article reviews an evidence-based approach on the use of RAAS-inhibiting agents in kidney diseases, considers treatment strategies in different clinical situations and discusses some perspectives related to the implementation of the RAAS blockade in renal protection.

Glomerular abundance of nephrin and podocin in experimental nephrotic syndrome: different effects of antiproteinuric therapies

Nephrotic syndrome (NS) is a clinical state characterized by massive proteinuria, hypoalbuminemia, and eventual edema formation. Although the mechanisms underlying this phenomenon are not yet fully clarified, it is well accepted that nephrin and podocin are involved in the development of proteinuria. The effects of early treatment with various antiproteinuric therapies on proteinuria and glomerular staining of nephrin and podocin in rats with experimental NS have not been previously studied. Proteinuria and glomerular nephrin and podocin immunofluorescence were examined in rat kidneys with adriamycin-induced NS and the effects of antiproteinuric drug therapies during 5 wk with enalapril, losartan, alone or in combination, omapatrilat, and mycophenolate mofetil on these parameters were assessed. Injection of adriamycin caused a significant increase in daily (from 21.8 ± 1.4 to 983.1 ± 45.8 mg/day, P < 0.01) and cumulative protein excretion (from negligible values to 22,490 ± 931 mg, P < 0.001) during 5 wk. Early treatment with enalapril significantly decreased the daily (641.7 ± 82.4 mg/day, P < 0.0023) and cumulative proteinuria (15,727 ± 2,204 mg, P < 0.001). A similar effect, although to a lesser extent, was obtained after omapatrilat treatment: cumulative proteinuria was reduced to 18,706 ± 1,042 mg, P < 0.001. In contrast, losartan treatment did not significantly influence the cumulative proteinuria that remained comparable (20,351 ± 1,360 mg, P > 0.05) to that observed in untreated NS rats. Unexpectedly, when losartan was given in combination with enalapril, it abolished the beneficial effects of the latter. Pretreatment with mycophenolate mofetil exerted a moderate antiproteinuric effect, which appeared only during the last week of the experimental treatment. Nephrotic rats exhibited severe disruption of slit diaphragm structure as seen by rapid and profound loss of nephrin and podocin. Beneficial effects of enalapril, omapatrilat, and mycophenolate mofetil paralleled the preservation of nephrin, as determined immunohistochemically, and enabled prediction of significant antiproteinuric responses. Enalapril alone or in combination with losartan resulted in significant preservation of podocin. Pretreatment with enalapril, and to a lesser extent omapatrilat, is superior to losartan in reducing proteinuria in NS rats. A combination of ACE inhibitors with ANG II receptor blockers does not provide any advantageous antiproteinuric therapy in these animals. Nephrin loss is an indication of proteinuria in NS and the antiproteinuric effects of ACE inhibitors, vasopeptidase inhibitors, and mycophenolate mofetil attenuate this reduction. Not all the drugs which restore podocin reduce urinary protein in NS.

Prevention of progression and remission/regression strategies for chronic renal diseases: Can we do better now than five years ago?

The prevalence of chronic renal diseases is increasing worldwide. There is a great need to identify therapies that arrest disease progression to end-stage renal failure. Inhibition of renin-angiotensin system both by ACE inhibitors and angiotensin II receptor antagonists is probably the best therapeutic option available. Several large, multicenter studies have indeed shown a significant reduction in the risk of doubling baseline serum creatinine or progression toward end-stage renal failure in diabetic and nondiabetic patients with chronic nephropathies treated with ACE inhibitors or angiotensin II receptor antagonists. However, the number of patients that reach end-stage renal failure is still considerably high. Significant reduction of the incidence of end-stage renal disease is likely to be achieved in the next future for chronic nephropathies, provided that we can improve the degree of renoprotection. This goal may be attainable with a more complex strategy than with a single or dual pharmacologic intervention on the renin-angiotensin system. Strict control of blood pressure and protein excretion rate, lowering of blood lipids, tight glucose control for diabetics, and lifestyle changes form part of the future multimodal protocol for management of patients with chronic nephropathies.

Losartan renography for the detection of renal artery stenosis: comparison with captopril renography and evaluation of dose and timing

PURPOSE

Radionuclide renography with angiotensin converting enzyme (ACE) inhibition plays an important role in the diagnosis of haemodynamically significant renal artery stenosis. Angiotensin receptor antagonists inhibit the renin angiotensin system at different levels from ACE inhibitors by selectively blocking the binding of angiotensin II to AT1 receptors. The AT1 angiotensin receptor antagonist losartan has recently been used clinically in the treatment of hypertension. However, the available data on the use of losartan with renography for the detection of renovascular hypertension are limited and contradictory. The purpose of this prospective study was to compare the effectiveness of losartan renography and captopril scintigraphy in revealing renal artery stenosis.

METHODS

A total of 61 renal units in 32 patients with hypertension were studied in two groups based on the losartan dosage (50 mg in group A and 100 mg in group B). Group A consisted of 17 patients, in whom 19 renal units had angiographically proven renal artery stenosis (>or=50%). In group B, there were 15 patients, in whom 20 renal arteries were stenotic. All of the patients underwent three renographies (baseline, captopril renography and early losartan renography). Early losartan renography was performed at 1 h after oral losartan administration in both groups. In group B, seven patients underwent additional losartan renography (late losartan) performed 3 h after oral losartan administration; these patients composed group B1.

RESULTS

The sensitivities of captopril and losartan studies were 63.2% and 42% in group A, 65% and 65% in group B and 55.6% and 66.6% in group B1, respectively.

CONCLUSION

From our preliminary results, we conclude that losartan is not superior to captopril renography for the detection of haemodynamically significant renal artery stenosis. However, a high dose (100 mg) of losartan provided higher sensitivity than the lower dose (50 mg). Late losartan scintigraphy provided similar diagnostic efficacy to early losartan renography.

Emerging drugs for renal failure

Renal failure involves a significant impairment of the essential functions of the kidney, which can be either acute with sudden and rapid onset (acute renal failure [ARF]) or chronic with gradual onset (chronic renal failure [CRF]). ARF, if detected early, may be halted or reversed, whereas CRF is generally irreversible. Without treatment or intervention, both forms of renal failure lead to end stage renal failure (ESRF) or end stage renal disease (ESRD), requiring renal replacement therapy (RRT) in the form of dialysis or renal transplantation for survival. However, provision of RRT requires expert teams working in specialised units, making therapy of patients with renal failure expensive; furthermore, RRT is complex, with its own complications. Although pharmacological interventions have shown promise in experimental models, these have not been as successful in the clinical setting (e.g., administration of atrial natriuretic peptide, low-dose dopamine). At present, drugs are administered during CRF to either reduce one of the many risk factors of CRF (e.g., angiotensin-converting enzyme inhibitors, statins) or to deal with the consequences of CRF (e.g., erythropoietin, calcitriol). Recent evidence suggests that some of these interventions may provide further direct beneficial effects via reduction of renal inflammation. Although these interventions have greatly improved the prospects for patients suffering ESRF, the development of novel drugs and therapies with which to reduce the consequences of renal failure and ESRD remain topics of great interest. This article reviews the therapies available for the prevention and management of renal failure in adults and describes, in detail, emerging drugs and novel interventions that may soon become available for the treatment or prevention of ESRF.

Stabilization and regression of albuminuria in Chinese patients with type 2 diabetes: a one-year randomized study of valsartan versus enalapril

This study was designed to compare the short-term (1-y) tolerability and antiproteinuric efficacy of enalapril and valsartan in patients with type 2 diabetes. Forty-two patients with normal renal function or early-stage nephropathy were recruited in Hong Kong and randomized to valsartan 80 mg/day or enalapril 5 mg/day; the doses were increased to 160 mg and 10 mg daily, respectively, as tolerated. Early-morning urine was analyzed for albumin and creatinine and 24-hour urinary albumin excretion at baseline and 1 year after therapy began. Twenty-two patients were randomized to valsartan and 20 to enalapril. The 2 treatment groups were similar in terms of age, sex distribution, and duration of diabetes or hypertension. Blood pressure decreased to a similar extent (-2.5% to -5.0%) with each drug. Similarly, the 24-hour urinary albumin excretion decreased by 5% to 6% with each drug. The albumin-creatinine ratio in early-morning urine samples and plasma creatinine levels decreased in the valsartan group and increased in the enalapril group, but the difference was not significant. Plasma potassium levels were stable in both groups at the end of study. Cough was reported by 7 (35%) patients receiving enalapril and none of those receiving valsartan (P=.003). In conclusion, enalapril and valsartan both reduced blood pressure and albuminuria to a similar extent with 1 year of therapy in Chinese patients with type 2 diabetes and normal renal function or early-stage nephropathy. Fewer adverse events were reported with valsartan, but both drugs appear to be relatively safe.

Diuretic and Enhanced Sodium Restriction Results in Improved Antiproteinuric Response to RAS Blocking Agents

Angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and diuretics may exert synergistic antiproteinuric effects. Eighteen patients with a proteinuria >1 g/24 h after 6 mo of treatment with ramipril at 5 mg/d were assigned to receive in random order ramipril at 10 mg/d, valsartan at 160 mg/d, or combined ramipril at 5 mg/d and valsartan at 80 mg/d in addition to their antihypertensive treatment. The treatment periods lasted 4 wk and were separated by a 4-wk washout with ramipril at 5 mg/d. At the end of this crossover sequence, patients received combined ramipril at 5 mg/d, valsartan at 80 mg/d, and an increased furosemide dosage for an additional 4-wk period. The primary end point was the urinary protein/creatinine ratio for two 24-h urine collections at the end of each treatment period. No significant differences were noted between the study end points of the ramipril 10, valsartan 160, and combined ramipril 5 and valsartan 80 treatment groups. However, the urinary protein/creatinine ratio was lower with combined ramipril 5 and valsartan 80-increased furosemide dosage than with valsartan 160 and combined ramipril 5 and valsartan 80, with a similar tendency compared with ramipril 10. Combined ramipril 5 and valsartan 80-increased furosemide dosage decreased systolic home BP and increased serum creatinine but did not significantly increase the number of symptomatic hypotension cases compared with the other three treatments. Thus, in patients with severe proteinuria and hypertension, a cautious increase in diuretic dosage in addition to combined angiotensin-converting enzyme inhibitors and angiotensin receptor blockers decreases proteinuria and BP but may expose the patient to prerenal failure.

Angiotensin-converting enzyme inhibition and angiotensin II antagonism in nondiabetic chronic nephropathies

Angiotensin II (A II), the main effector of the renin angiotensin system (RAS), plays a central role in the hemodynamic and nonhemodynamic mechanisms of chronic renal disease and is currently the main target of interventions aimed to prevent the onset and progression of chronic nephropathies to end-stage renal disease (ESRD). In addition, to ameliorate glomerular hyperfiltration and size selectivity, reduce protein traffic and prevent glomerular and tubulointerstitial toxicity of ultrafiltered proteins, RAS inhibitors also limit the direct nephrotoxic effects of A II. Thus, both angiotension-converting enzyme (ACE) inhibitors (ACEi) and A II antagonists (ATA) exert a specific nephroprotective effect in both experimental and human chronic renal disease. This effect is time-dependent and is observed across degrees of renal insufficiency. Forced ACEi or ATA uptitration above doses recommended to control arterial hypertension and combined treatment with both agents allow optimization of A II inhibition and maximization of renoprotection. Multifactorial interventions combining RAS inhibition to treatments targeted also to non-RAS mechanisms could even achieve regression of glomerulosclerosis and chronic tubulointerstitial injury. Studies are needed to assess whether renal damage can be reverted to such a point that renal function could be fully prevented from worsening, and possibly improvement. The economic impact of even a partial improvement would be enormous. Moreover, chronic renal insufficiency is an independent risk factor for cardiovascular disease, and effective nephroprotection could also decrease the excess cardiovascular morbidity and mortality associated with chronic nephropathies. In patients with renal insufficiency, ACEi are even more cardioprotective than in those without and are well tolerated. Thus, RAS inhibitor therapy should be offered to all renal patients without specific contraindications, including those closer to renal replacement therapy.

From hyperglycemia to diabetic kidney disease: the role of metabolic, hemodynamic, intracellular factors and growth factors/cytokines

At present, diabetic kidney disease affects about 15-25% of type 1 and 30-40% of type 2 diabetic patients. Several decades of extensive research has elucidated various pathways to be implicated in the development of diabetic kidney disease. This review focuses on the metabolic factors beyond blood glucose that are involved in the pathogenesis of diabetic kidney disease, i.e., advanced glycation end-products and the aldose reductase system. Furthermore, the contribution of hemodynamic factors, the renin-angiotensin system, the endothelin system, and the nitric oxide system, as well as the prominent role of the intracellular signaling molecule protein kinase C are discussed. Finally, the respective roles of TGF-beta, GH and IGFs, vascular endothelial growth factor, and platelet-derived growth factor are covered. The complex interplay between these different pathways will be highlighted. A brief introduction to each system and description of its expression in the normal kidney is followed by in vitro, experimental, and clinical evidence addressing the role of the system in diabetic kidney disease. Finally, well-known and potential therapeutic strategies targeting each system are discussed, ending with an overall conclusion.

Evaluation of a technique of inducing hypertensive renal insufficiency in cats

OBJECTIVE

To compare 2 techniques of inducing combined renal insufficiency and systemic hypertension in cats.

ANIMALS

22 cats 6 to 12 months of age.

PROCEDURES

Cats were randomly assigned to 1 of 3 groups. Control (C) group cats had 2 intact kidneys, remnant kidney (RK) group cats underwent unilateral partial renal infarction and contralateral nephrectomy, and remnant-wrap (W) group cats underwent unilateral partial renal infarction and partial abtation and wrapping of the contralateral kidney. Systemic arterial blood pressure (BP) was measured continuously by use of implanted radiotelemetric devices. Renal function was assessed via determination of glomerular filtration rate, measurement of serum creatinine and BUN concentrations, and determination of urine protein-to-creatinine ratio (UP/C). Serum aldosterone concentration and plasma renin activity were measured on day 75.

RESULTS

Systolic BP was significantly higher in groups RK and W than in group C, and systolic BP was significantly higher in group W than in group RK. Serum aldosterone concentration and plasma renin activity were significantly higher in group W, compared with groups C and RK. Glomerular filtration rate was significantly lower in groups RK and W, compared with group C. Histologic indices of renal injury and UP/C were significantly higher in group W, compared with groups C and RK.

CONCLUSIONS AND CLINICAL RELEVANCE

Hypertensive renal insufficiency in group W was characterized by marked sustained systemic hypertension, decreased renal function, proteinuria, activation of the renin-angiotensin-aldosterone axis, and renal structural injury. Results support the hypothesis that marked systemic hypertension, activation of the renin-angiotensin-aldosterone axis, and proteinuria may damage the kidney of cats with preexisting renal insufficiency.

The role of renin-angiotensin-aldosterone system inhibition in chronic kidney disease

Chronic kidney disease (CKD) is emerging as a new health pandemic. Underlying the global rise in CKD is an increase in diabetes, hypertension and other cardiovascular risk factors leading to progressive renal dysfunction. Emerging evidence strongly suggests that achieving target blood pressure goals via inhibition of the renin-angiotensin-aldosterone system confers significant renal and cardioprotection for patients with CKD. Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) lower blood pressure, reduce proteinuria and reduce both the progression of CKD and adverse cardiovascular events. The role of aldosterone inhibition and combination therapy, such as ACEI/ARB, in CKD are under investigation. As our understanding of the basic mechanisms underlying CKD progression advances, novel therapies targeting post-translational endothelial and mesangial messengers downstream from angiotensin II and aldosterone may become available for clinical use.

Diabetic nephropathy and transforming growth factor-beta: transforming our view of glomerulosclerosis and fibrosis build-up

The manifestations of diabetic nephropathy may be a consequence of the actions of certain cytokines and growth factors. Prominent among these is transforming growth factor beta (TGF-beta) because it promotes renal cell hypertrophy and stimulates extracellular matrix accumulation, the 2 hallmarks of diabetic renal disease. In tissue culture studies, cellular hypertrophy and matrix production are stimulated by high glucose concentrations in the culture media. High glucose, in turn, appears to act through the TGF-beta system because high glucose increases TGF-beta expression, and the hypertrophic and matrix-stimulatory effects of high glucose are prevented by anti-TGF-beta therapy. In experimental diabetes mellitus, several reports describe overexpression of TGF-beta or TGF-beta type II receptor in the glomerular and tubulointerstitial compartments. As might be expected, the intrarenal TGF-beta system is triggered, evidenced by activity of the downstream Smad signaling pathway. Treatment of diabetic animals with a neutralizing anti-TGF-beta antibody prevents the development of mesangial matrix expansion and the progressive decline in renal function. This antibody therapy also reverses the established lesions of diabetic glomerulopathy. Finally, the renal TGF-beta system is significantly up-regulated in human diabetic nephropathy. Although the kidney of a nondiabetic subject extracts TGF-beta1 from the blood, the kidney of a diabetic patient actually elaborates TGF-beta1 protein into the circulation. Along the same line, an increased level of TGF-beta in the urine is associated with worse clinical outcomes. In concert with TGF-beta, other metabolic mediators such as connective tissue growth factor and reactive oxygen species promote the accumulation of excess matrix. This fibrotic build-up also occurs in the tubulointerstitium, probably as the result of heightened TGF-beta activity that stimulates tubular epithelial and interstitial fibroblast cells to overproduce matrix. The data presented here strongly support the consensus that the TGF-beta system mediates the renal hypertrophy, glomerulosclerosis, and tubulointerstitial fibrosis of diabetic kidney disease.

Enalapril in children with Alport syndrome

Ten pediatric patients with Alport syndrome received enalapril for 5 years. There were nine boys. Eight patients have the X-linked form of the disease and two the autosomal recessive form. The median age at the start of treatment was 10.25 years. Only one patient was hypertensive. The starting dose of enalapril was 0.05 mg/kg; the target dose was 0.5 mg/kg per day. The median dose given effectively was 0.24, 0.37, 0.45, 0.43, and 0.49 mg/kg per day at years of study 1, 2, 3, 4, and 5, respectively. The median urinary protein/creatinine ratio was 1.58 g/g (range 0.49-4.60) before treatment. This decreased to 0.98, 1.09, 1.35, 1.11, and 1.38 g/g after 1, 2, 3, 4, and 5 years, respectively. The median creatinine clearance at baseline was 100 ml/min per 1.73 m2 (range 82-133) and after 5 years 92 ml/min per 1.73 m2 (range 22-115). Three patients did not reach the target dose of enalapril because of orthostatic hypotension. One of them was the only patient to develop chronic renal failure within 5 years. The present study indicates that enalapril reduces urinary protein excretion and preserves glomerular filtration in Alport patients as a group. However, there was individual variation, as in most studies of patients with proteinuric nephropathies given inhibitors of the angiotensin-converting enzyme.

Low-dose dual blockade of the renin-angiotensin system in patients with primary glomerulonephritis

BACKGROUND

Treatment with agents interfering with the renin-angiotensin system retards the progressive course of proteinuric chronic renal disease. However, because of unwanted effects associated with such therapy, some patients cannot be treated with these drugs at all or may be administered only very small doses. To find an optimal nephroprotective strategy for these patients, we compared antiproteinuric effects of combination therapy with an angiotensin-converting enzyme inhibitor and angiotensin II type 1 receptor antagonist in very small doses with treatment with either agent alone at greater, but not maximal, doses. We compared the concomitant use of benazepril, 5 mg, and losartan, 25 mg, and monotherapy with these agents in doses 2-fold greater.

METHODS

This is a randomized, open, crossover study of 3 treatments in 3 periods of 4 months each. Twenty-four patients with primary glomerulonephritis and nonnephrotic proteinuria, recognized previously as not able to be administered high doses of drugs from these classes, completed the protocol.

RESULTS

Combined therapy decreased 24-hour proteinuria (-45.54% versus baseline) more effectively than either losartan (-28.17%; analysis of variance, P < 0.01) or benazepril (-20.19%; analysis of variance, P < 0.001) alone. Subgroup analysis showed that antiproteinuric effects of combination therapy, as well as losartan or benazepril alone, were significantly greater in patients with basal proteinuria greater than 2 g/24 h than in those with proteinuria less than this value (P < 0.001, P < 0.01, and P < 0.05, respectively). All therapies significantly decreased blood pressure (BP) compared with baseline, but there were no differences between treatments in BP changes.

CONCLUSION

The study shows that combination therapy with very small doses of losartan and benazepril was more effective in reducing proteinuria than greater doses of either agent in monotherapy, and this greater antiproteinuric efficacy was independent of changes in BP.

Diabetic nephropathy

As the epidemic of diabetes spreads so does the number of patients at risk for developing diabetic nephropathy, which occurs in 20% to 40% of all diabetic patients. Indeed, diabetes is the most common cause of end-stage renal disease (ESRD) in the United States, accounting for > 40% of patients starting renal replacement therapy each year. Unfortunately, the outcome for diabetic patients with ESRD is worse than that for nondiabetic patients because of comorbid conditions in the diabetic population. However, with early and intensive blood glucose and blood pressure control--including the use of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers--the development and progression of diabetic kidney disease can be slowed.