Late escape from the antiproteinuric effect of ace inhibitors in nondiabetic renal disease

Association between renal dysfunction and metalloproteinase (MMP)-9 activity in hypertensive patients

BACKGROUND AND OBJECTIVE

Matrix metalloproteinases (MMPs) are involved in deleterious tissue remodeling associated with target organ damage in renal disease. The aim of this study was to study the association between renal dysfunction and activity of the inflammatory metalloproteinase MMP-9 in hypertensive patients with mild-moderate chronic kidney disease (CKD).

MATERIAL AND METHODS

Plasmatic active MMP-9, total MMP-9, tissue inhibitor of MMP-9 (TIMP-1), MMP-9/TIMP-1 ratio and MMP-9-TIMP-1 interaction were analyzed in 37 hypertensive patients distributed by estimated glomerular filtration rate (eGFR) in 3 groups:>90, 90-60 y 60-30mL/min/1.73 m².

RESULTS

Total MMP-9 was not different as eGFR declines. TIMP-1 was significantly increased in hypertensive patients with eGFR 60-30mL/min/1.73 m² (P<.01 versus>90mL/min/1.73 m²). This relates to the significant decrease in the interaction between MMP-9-TIMP-1 observed in patients with eGFR 60-30mL/min/1.73 m² (P<.01 versus>90mL/min/1.73 m²). Despite the systemic elevation of TIMP-1, active MMP-9 was significantly increased in hypertensive patients with eGFR 60-30mL/min/1.73 m² (P<.05 and P<0.01 versus>90 and 90-60mL/min/1.73 m², respectively). TIMP-1, active MMP-9 and MMP-9-TIMP-1 interaction significantly correlate with the decline in renal function, which was not observed with total MMP-9.

CONCLUSIONS

The progression of CKD, even in stages where the decline of renal function is still moderate, is associated with an increase in MMP-9 activity, which could be considered as a potential therapeutic target.

Translational science in albuminuria: a new view of de novo albuminuria under chronic RAS suppression

The development of de novo albuminuria during chronic renin–angiotensin system (RAS) suppression is a clinical entity that remains poorly recognized in the biomedical literature. It represents a clear increment in global cardiovascular (CV) and renal risk that cannot be counteracted by RAS suppression. Although not specifically considered, it is clear that this entity is present in most published and ongoing trials dealing with the different forms of CV and renal disease. In this review, we focus on the mechanisms promoting albuminuria, and the predictors and new markers of de novo albuminuria, as well as the potential treatment options to counteract the excretion of albumin. The increase in risk that accompanies de novo albuminuria supports the search for early markers and predictors that will allow practising physicians to assess and prevent the development of de novo albuminuria in their patients.

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.

The role of aldosterone antagonism agents in diabetic kidney disease

BACKGROUND

Diabetic kidney disease is a common consequence of the development of diabetes. In the United Kingdom 18-30% of chronic kidney disease cases and 44% of end-stage renal disease cases in the United States have been attributed to complications of diabetic kidney disease. Angiotensin blockade using angiotensin converting enzyme inhibitors or angiotensin receptor blockers is the standard for slowing the progression of diabetic kidney disease. Evidence suggests that aldosterone antagonism added to standard therapy may be beneficial.

AIM OF REVIEW

This paper aims to explore the pathophysiological contribution of aldosterone in diabetic kidney disease and review available literature for aldosterone antagonism through mineralocorticoid receptor blockade.

METHODS

A comprehensive literature search was conducted. Results were analysed and summarised.

RESULTS

Nine trials evaluating a total of 535 patients with diabetic kidney disease were identified that evaluated the use of aldosterone antagonists for reducing the signs of diabetic kidney disease. All trials demonstrated a marked decrease in urinary protein excretion when compared to, or added to angiotensin converting enzyme inhibition or angiotensin receptor blockade. The most commonly reported side effect in all of the trials was hyperkalaemia, which occurred in 6.1% of all patients evaluated. Aldosterone antagonists were generally well tolerated in the evaluated patient populations.

CONCLUSION

Aldosterone antagonism may represent a safe and effective complimentary therapy to the use of angiotensin converting enzyme inhibition, or angiotensin receptor blockade, for slowing the progression of diabetic kidney disease.

Aldosterone blockade in chronic kidney disease

Although blockade of the renin-angiotensin-aldosterone system with angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers has become standard therapy for chronic kidney disease (CKD), renewed interest in the role of aldosterone in mediating the injuries and progressive insults of CKD has highlighted the potential role of treatments targeting the mineralocorticoid receptor (MR). Although salt restriction is an important component of mitigating the profibrotic effects of MR activation, a growing body of literature has shown that MR antagonists, spironolactone and eplerenone, can reduce proteinuria and blood pressure in patients at all stages of CKD. These agents carry a risk of hyperkalemia, but this risk likely can be predicted based on baseline renal function and mitigated using dietary modifications and adjustments of concomitant medications. Data on hard outcomes, such as progression to end-stage renal disease and overall mortality, still are lacking in patients with CKD.

Proteinuria and its relation to cardiovascular disease

Chronic kidney disease (CKD) and its associated morbidity pose a worldwide health problem. As well as risk of endstage renal disease requiring renal replacement therapy, cardiovascular disease is the leading cause of premature death among the CKD population. Proteinuria is a marker of renal injury that can often be detected earlier than any tangible decline in glomerular filtration rate. As well as being a risk marker for decline in renal function, proteinuria is now widely accepted as an independent risk factor for cardiovascular morbidity and mortality. This review will address the prognostic implications of proteinuria in the general population as well as other specific disease states including diabetes, hypertension and heart failure. A variety of pathophysiological mechanisms that may underlie the relationship between renal and cardiovascular disease have been proposed, including insulin resistance, inflammation, and endothelial dysfunction. As proteinuria has evolved into a therapeutic target for cardiovascular risk reduction in the clinical setting we will also review therapeutic strategies that should be considered for patients with persistent proteinuria.

Effect of aldosterone breakthrough on albuminuria during treatment with a direct renin inhibitor and combined effect with a mineralocorticoid receptor antagonist

We have reported observing aldosterone breakthrough in the course of relatively long-term treatment with renin-angiotensin (RA) system inhibitors, where the plasma aldosterone concentration (PAC) increased following an initial decrease. Aldosterone breakthrough has the potential to eliminate the organ-protective effects of RA system inhibitors. We therefore conducted a study in essential hypertensive patients to determine whether aldosterone breakthrough occurred during treatment with the direct renin inhibitor (DRI) aliskiren and to ascertain its clinical significance. The study included 40 essential hypertensive patients (18 men and 22 women) who had been treated for 12 months with aliskiren. Aliskiren significantly decreased blood pressure and plasma renin activity (PRA). The PAC was also decreased significantly at 3 and 6 months; however, the significant difference disappeared after 12 months. Aldosterone breakthrough was observed in 22 of the subjects (55%). Urinary albumin excretion differed depending on whether breakthrough occurred. For the subjects in whom aldosterone breakthrough was observed, eplerenone was added. A significant decrease in urinary albumin excretion was observed after 1 month, independent of changes in blood pressure. In conclusion, this study demonstrated that aldosterone breakthrough occurs in some patients undergoing DRI therapy. Aldosterone breakthrough affects the drug's ability to improve urinary albumin excretion, and combining a mineralocorticoid receptor antagonist with the DRI may be useful for decreasing urinary albumin excretion. When the objective is organ protection in hypertensive patients, a two-pronged approach using combination therapy to inhibit both the RA system and aldosterone may be highly effective.

Sodium intake, ACE inhibition, and progression to ESRD

High sodium intake limits the antihypertensive and antiproteinuric effects of angiotensin-converting enzyme (ACE) inhibitors in patients with CKD; however, whether dietary sodium also associates with progression to ESRD is unknown. We conducted a post hoc analysis of the first and second Ramipril Efficacy in Nephropathy trials to evaluate the association of sodium intake with proteinuria and progression to ESRD among 500 CKD patients without diabetes who were treated with ramipril (5 mg/d) and monitored with serial 24-hour urinary sodium and creatinine measurements. Urinary sodium/creatinine excretion defined low (<100 mEq/g), medium (100 to <200 mEq/g), and high (≥200 mEq/g) sodium intake. During a follow-up of >4.25 years, 92 individuals (18.4%) developed ESRD. Among those with low, medium, and high sodium intakes, the incidence of ESRD was 6.1 (95% confidence interval [95% CI], 3.8-9.7), 7.9 (95% CI, 6.1-10.2), and 18.2 (95% CI, 11.3-29.3) per 100 patient-years, respectively (P<0.001). Patients with high dietary sodium exhibited a blunted antiproteinuric effect of ACE inhibition despite similar BP among groups. Each 100-mEq/g increase in urinary sodium/creatinine excretion associated with a 1.61-fold (95% CI, 1.15-2.24) higher risk for ESRD; adjusting for baseline proteinuria attenuated this association to 1.38-fold (95% CI, 0.95-2.00). This association was independent from BP but was lost after adjusting for changes in proteinuria. In summary, among patients with CKD but without diabetes, high dietary salt (>14 g daily) seems to blunt the antiproteinuric effect of ACE inhibitor therapy and increase the risk for ESRD, independent of BP control.

Aktivnost' renin-angiotenzinovoy sistemy (RAS) zhirovoy tkani: metabolicheskie effekty blokady RAS

The review presents data confirming that fat tissue is a significant source of synthesis of all components of renin-angiotensin system (RAS). It is proposed that activation of fat tissue RAS components have a local paracrine and autocrine actions on adipocytes, regulates their growth and differentiation, induces subclinical inflammation and insulin resistance (IR). Thus, hyperactivity of local RAS in fat tissue is one of the mechanisms of visceral obesity, IR and metabolic syndrome. Use of traditional RAS blocking medications (angiotensin converting enzyme inhibitors, angiotensin receptor blockers) is followed by IR decrease and prevents from development of type 2 diabetes mellitus. The perspectives of use of a new RAS blocker from a group of direct rennin inhibitors - aliskiren - for correction of metabolic abnormalities in visceral obesity are considered.

The potential of small chemical functional groups for directing the differentiation of kidney stem cells

In the future, stem-cell-based therapies could offer new approaches to treat kidney disease and reduce the incidence of ESRD (end-stage renal disease), but, as yet, research in this area is only being conducted in rodents and it is not clear whether or when it could be applied to human patients. Drug therapies, on the other hand, have been very effective at delaying the progression of kidney disease, but, for various reasons, current drug regimes are not suitable for all patients. A greater understanding of the molecular mechanisms that underlie disease progression in chronic kidney disease could help to identify novel drug targets. However, progress in this area is currently hindered due to the lack of appropriate in vitro culture systems for important renal cell types, such as proximal tubule cells and podocytes. This problem could be overcome if it were possible to direct the differentiation of kidney stem cells to renal cell types in vitro. In the present review, we highlight the potential of surface gradients of small chemical functional groups to direct the differentiation of kidney stem cells.

Role of aldosterone in the progression of chronic kidney disease and potential use of aldosterone blockade in children

Much focus has been placed on the role of the renin-angiotensin system as a mediator of the progression of chronic kidney disease. Novel therapeutic strategies to inhibit the negative impact of renin-angiotensin activation, including dual therapy with an angiotensin-converting enzyme inhibitor and an angiotensin-receptor blocker, have been suggested to achieve more complete disruption of the renin-angiotensin system. The role played by aldosterone, a target of angiotensin II, in the progression of chronic kidney disease has become a subject of significant interest over the past decade. Experimental studies in animals have shown that persistently elevated aldosterone levels lead to pathohistological changes in the kidney, along with renal and cardiac fibrosis. Incomplete suppression of aldosterone may, therefore, contribute to the deleterious effects of the renin-angiotensin system in the setting of chronic kidney disease. Clinical trials in adults have shown a potential role for mineralocorticoid receptor blockers to delay further the development of end-stage renal disease by completing renin-angiotensin blockade. In adults, mineralocorticoid receptor blockade produces a significant anti-proteinuric effect and has minimal risk of causing hyperkalemia if the condition of the patients is closely monitored. Further studies will need to be conducted to determine whether mineralocorticoid receptor blockers are equally effective and safe for the treatment of chronic kidney disease in children.

Proteinuria and clinical outcomes in hypertensive patients

This narrative review focuses on outcomes related to proteinuria in hypertension (HT), and also examines the role of current and future therapeutic strategies. Proteinuria is an independent marker of renal and cardiovascular (CV) disease in hypertensive populations, particularly in high-risk groups such as diabetic patients. Effective blood pressure (BP) control and proteinuria management are associated with significant improvements in the risk of key adverse outcomes, although a causative relationship needs careful assessment. Available antihypertensives have varying effects on proteinuria reduction. Drugs affecting the renin system offer antiproteinuric and renoprotective effects that are probably at least partially independent of their BP effects. Economic evaluations of these interventions confirm their cost-saving benefits relative to other antihypertensives, but outcomes-based research is needed in some settings.

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

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

Aldosterone and progression of kidney disease

Experimental evidence indicates that aldosterone, besides its mineralcorticoid properties, directly contributes to accelerate renal damage through promotion of cell growth, fibrosis and inflammation. As a consequence, attenuation of growth-promoting and fibroproliferative effects of aldosterone might contribute to slow progression of chronic renal injury. Preliminary clinical observations have documented that aldosterone blockers added to angiotensin-converting enzyme inhibitor- and/or angiotensin receptor blocker-based regimens exerted significant antiproteinuric effects in patients with diabetic and nondiabetic nephropathies. Further studies in larger cohorts are now required to definitively address the safety and efficacy of aldosterone antagonism in patients with chronic kidney diseases.

Economic burden of chronic kidney disease

OBJECTIVES

To define the cost of care and evaluate interventions associated with improving outcomes and delaying the progression of chronic kidney disease (CKD).

METHODS

Using the PubMed database, a systematic review of the literature was conducted describing (i) the cost of care associated with treating earlier stages of CKD, and (ii) the role of early referral, erythropoiesis-stimulating proteins and anti-hypertensive agents in improving clinical outcomes and reducing the cost of CKD.

RESULTS

The higher costs associated with treatment of the CKD population are largely due to higher rates and duration of comorbidity-driven hospitalizations. Studies suggest that early referral to a nephrologist, use of erythropoiesis-stimulating proteins and anti-hypertensive agents may be associated with better outcomes and lower costs. In some instances, however, higher target haemoglobin levels could have harmful effects in CKD patients.

CONCLUSION

The substantial costs incurred during earlier stages of CKD increase markedly during the transition to renal replacement and remain elevated thereafter. An increase in awareness among health care providers may result in more timely interventions. More proactive management, in turn, can lead to improved clinical and economic outcomes through the slowing of disease progression and prevention of comorbidities.

Therapeutic strategies to slow chronic kidney disease progression

Childhood chronic kidney disease commonly progresses toward end-stage renal failure, largely independent of the underlying disorder, once a critical impairment of renal function has occurred. Hypertension and proteinuria are the most important independent risk factors for renal disease progression. Therefore, current therapeutic strategies to prevent progression aim at controlling blood pressure and reducing urinary protein excretion. Renin-angiotensin-system (RAS) antagonists preserve kidney function not only by lowering blood pressure but also by their antiproteinuric, antifibrotic, and anti-inflammatory properties. Intensified blood pressure control, probably aiming for a target blood pressure below the 75th percentile, may exert additional renoprotective effects. Other factors contributing in a multifactorial manner to renal disease progression include dyslipidemia, anemia, and disorders of mineral metabolism. Measures to preserve renal function should therefore also comprise the maintenance of hemoglobin, serum lipid, and calcium-phosphorus ion product levels in the normal range.

Aldosterone and end-organ damage

Aldosterone concentrations are inappropriately high in many patients with hypertension, as well as in an increasing number of individuals with metabolic syndrome and sleep apnoea. A growing body of evidence suggests that aldosterone and/or activation of the MR (mineralocorticoid receptor) contributes to cardiovascular remodelling and renal injury in these conditions. In addition to causing sodium retention and increased blood pressure, MR activation induces oxidative stress, endothelial dysfunction, inflammation and subsequent fibrosis. The MR may be activated by aldosterone and cortisol or via transactivation by the AT(1) (angiotenin II type 1) receptor through a mechanism involving the EGFR (epidermal growth factor receptor) and MAPK (mitogen-activated protein kinase) pathway. In addition, aldosterone can generate rapid non-genomic effects in the heart and vasculature. MR antagonism reduces mortality in patients with CHF (congestive heart failure) and following myocardial infarction. MR antagonism improves endothelial function in patients with CHF, reduces circulating biomarkers of cardiac fibrosis in CHF or following myocardial infarction, reduces blood pressure in resistant hypertension and decreases albuminuria in hypertensive and diabetic patients. In contrast, whereas adrenalectomy improves glucose homoeostasis in hyperaldosteronism, MR antagonism may worsen glucose homoeostasis and impairs endothelial function in diabetes, suggesting a possible detrimental effect of aldosterone via non-genomic pathways.

Aldosterone breakthrough during therapy with angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers in proteinuric patients with immunoglobulin A nephropathy

BACKGROUND

We are investigating whether aldosterone breakthrough negatively impacts on the antiproteinuric effects of angiotensin-converting enzyme (ACE) inhibitors and/or angiotensin II receptor blockers (ARB).

METHODS

We examine the role of aldosterone breakthrough in 43 normotensive, proteinuric (0.7 +/- 0.3 g/day) outpatients (aged 41.5 +/- 10.9 years) with immunoglobulin A nephropathy (IgAN) accompanied by stable renal function (creatinine clearance >50 mL/min). The patients were treated with temocapril (1 mg; n = 14), losartan (12.5 mg; n = 16), or a combination therapy (n = 13) for 12 months. We prospectively evaluated blood pressure (BP), urinary protein excretion (UPE), biochemical parameters and the renin-angiotensin-aldosterone system before and after 12 months of treatment.

RESULTS

Although the overall plasma aldosterone concentrations values did not change after any of the treatments administered for 12 months, they eventually increased in 23 (temocapril, seven patients; losartan, eight patients; combination, seven patients) of the 43 patients (53.4%; aldosterone breakthrough), and fell in the remainder (46.6%). Blood pressure and renal function did not differ among the three groups at 12 months. In contrast, UPE was significantly higher in patients with, than without aldosterone breakthrough during temocapril and losartan administration. However, combination therapy induced a more remarkable reduction in UPE regardless of aldosterone breakthrough.

CONCLUSIONS

A combination of ACE inhibitors and ARB in normotensive patients with IgAN produces a more profound decrease in proteinuria than either monotherapy. This additive antiproteinuric effect is not dependent on aldosterone breakthrough. Additional larger, prospective, randomized studies will be needed for general acceptance of this strategy.

Add-on therapy with angiotensin II receptor 1 blocker in children with chronic kidney disease already treated with angiotensin-converting enzyme inhibitors

The standard renoprotection is based on the inhibition of the renin-angiotensin system (RAS) by angiotensin convertase inhibitors (ACEi) or angiotensin II receptor 1 blockers (AT1B). The aim of our study was to analyze the effects of the addition of AT1B to ACEi-based renoprotection in children with chronic kidney disease. We examined 11 children with a mean age of 10.5 years (range, 0.5-18 years) with a mean glomerular filtration rate (GFR) of 61+/-61 ml/min/1.73 m(2). In four patients, the primary renal disease was hemolytic uremic syndrome, in three congenital nephrotic syndrome (CNS), in two reflux nephropathy, prune-belly syndrome in one and acute cortical necrosis in one. All patients were treated with complex hypotensive ACEi-based therapy. AT1B losartan was added in a mean dose of 0.9 mg/kg/day. The change in GFR, proteinuria and blood pressure at two 12-month intervals before and after adding AT1B was compared. The results showed that during the 12 months preceding AT1B therapy, there was no change in blood pressure and proteinuria, but the GFR declined in 7 of 11 patients. After the 12th month of add-on therapy with AT1B, there was a significant decrease in both absolute and indexed blood pressure values. Proteinuria decreased in eight patients, did not change in one and increased in two, including one with CNS. The GFR stabilized or increased in eight patients and decreased in three patients with CNS. In 7 of 11 patients, there was a significant, but not threatening increase in serum potassium. In conclusion, add-on renoprotection with AT1B added to ACEi is safe and significantly improves the renoprotective effects of ACEi treatment in children with progressive nephropathies, including patients with advanced CKD.

Long-term effects of spironolactone on proteinuria and kidney function in patients with chronic kidney disease

Experimental evidence suggests that aldosterone contributes to progressive kidney disease. Angiotensin-converting enzyme inhibitors and angiotensin type 1 receptor antagonists suppress the renin-angiotensin system but they do not effectively reduce plasma aldosterone. Hence, administration of aldosterone receptor antagonists may provide additional renal protection. In the present prospective randomized open-label study, we evaluated the effects of spironolactone (25 mg/day for 1 year) on proteinuria and estimated glomerular filtration rate in 83 patients with chronic kidney disease already treated with angiotensin-converting enzyme inhibitors and/or angiotensin type 1 receptor antagonists. Eighty-two patients were treated with angiotensin-converting enzyme inhibitors and/or angiotensin type 1 receptor antagonists alone and served as controls. After 1 year of therapy, proteinuria decreased from 2.1+/-0.08 to 0.89+/-0.06 g/g creatinine (P<0.001) in patients treated with spironolactone, but it did not change in control patients. Baseline aldosterone levels were significantly correlated with proteinuria (r=0.76, P<0.0001), and predicted the degree of reduction in proteinuria with spironolactone (r=0.42, P<0.0002). Baseline estimated glomerular filtration rate was similar in patients treated with spironolactone and controls (62.4+/-2.4 and 62.2+/-2.1 ml/min/1.73 m(2), respectively). After 1 month of therapy with spironolactone, estimated glomerular filtration rate decreased more in patients treated with spironolactone than in controls. However, by the end of 1 year the monthly rate of decrease in estimated glomerular filtration rate from baseline was lower in patients treated with spironolactone than in controls (0.323+/-0.044 vs 0.474+/-0.037 ml/min/1.73 m(2), P<0.01). Spironolactone caused a significant rise in serum potassium levels (from 4.2+/-0.04 at baseline to 5.0+/-0.05 mEq/l after 12 months of treatment, P<0.001). In conclusion, this study has shown that spironolactone may reduce proteinuria and retard renal progression in chronic kidney disease patients.

An in-depth review of the evidence linking dietary salt intake and progression of chronic kidney disease

BACKGROUND

Dietary salt has been debated for decades as having a potentially deleterious influence on human health.

OBJECTIVES

To determine the quality of research and the relationship between dietary salt and markers for progression of kidney disease.

METHODS

Data sources included 7 electronic databases comprehensively searched for literature published between January 1, 1966, and August 31, 2004, and a manual search of bibliographies of relevant papers, and consultation with experts in the field. Differences between the paired reviewers were reconciled through consensus or by a content expert.

RESULTS

Sixteen studies met the inclusion-exclusion criteria and were identified for review; however, the study methodologies were extremely heterogeneous. Conclusions commonly cited in the studies include: variations in salt consumption are directly correlated with albuminuria, and an increase in salt consumption is associated with an acute increase in glomerular filtration rate, while a reduction in salt consumption may slow the rate of renal function loss.

CONCLUSIONS

The available published information, while highly variable in methods and quality, suggests that variations in dietary salt consumption directly influence albuminuria, with increasing salt intake associated with worsening albuminuria; however, results are inadequate and conflicting on the effects of dietary salt consumption on renal function, especially over a prolonged time. There was no evidence of a detrimental effect of reduced salt intake. On the other hand, there is consistent experimental evidence to link increased salt exposure with kidney tissue injury. On the basis of these data, we believe that dietary salt restriction should be considered in patients with chronic kidney disease.

Does dietary salt increase the risk for progression of kidney disease?

Due to the inconsistent observations and suboptimal quality of the study designs, there is insufficient clinical evidence to suggest that increased salt intake may adversely modify the rate of progression of kidney disease. However, there is experimental evidence to suggest a link between increased salt exposure and kidney tissue injury. Further clinical trials are needed to evaluate the relationship between dietary salt and risk for progression of chronic kidney disease.

Differential effects of antihypertensive drugs on renal and glomerular hemodynamics and injury in the chronic nitric-oxide-suppressed rat

BACKGROUND/AIMS

Prolonged nitric oxide synthase (NOS) inhibition with N(omega)-nitro-L-arginine methylester in normotensive and hypertensive rats has been demonstrated to produce severe systemic and glomerular hypertension with glomerular sclerosis, and these changes have become a useful experimental model of hypertensive nephrosclerosis. This review summarizes data from our serial studies as well as work of others who are also investigating the effects of the commonly used antihypertensive drugs (including calcium antagonist, angiotensin-converting enzyme inhibitor, angiotensin II type 1 receptor blocker, aldosterone antagonist and thiazide diuretic) on renal and glomerular hemodynamics, renal function and glomerular histopathology using this model.

METHODS

A Medline search was performed to identify the relevant literature describing renal effects of antihypertensive drugs in models of hypertension and nephrosclerosis produced or exacerbated by NOS inhibition.

RESULTS

Existing data have indicated that most of these drug classes have produced dramatic renoprotective effects, structurally or functionally, on nephrosclerosis induced by prolonged NOS inhibition.

CONCLUSION

This review of experimental studies has provided strong evidence supporting the clinical benefits of antihypertensive drugs for hypertensive patients with renal impairment particularly those with endothelial dysfunction associated with NOS deficiency.

Antihypertensive and antiproteinuric efficacy of ramipril in children with chronic renal failure

BACKGROUND

While the antihypertensive and renoprotective potency of angiotensin-converting enzyme (ACE) inhibitors is well-established in adults with hypertension and/or chronic renal failure, little experience exists in pediatric chronic kidney disease.

METHODS

As part of a prospective assessment of the renoprotective efficacy of ACE inhibition and intensified blood pressure (BP) control, 397 children (ages 3 to 18 years) with chronic renal failure [CRF; glomerular filtration rate (GFR) 11 to 80 mL/min/1.73 m2] and elevated or high-normal BP received ramipril (6 mg/m2) following a 6-month run-in period including a two-month washout of any previous ACE inhibitors. Drug efficacy was assessed by two monthly office BP and proteinuria assessments, and by ambulatory BP monitoring at start and after 6 months of treatment.

RESULTS

In the 352 patients completing six months of treatment, 24-hour mean arterial pressure (MAP) had decreased by a mean of 11.5 mm Hg (-2.2 SDS) in initially hypertensive subjects, but only by 4.4 mm Hg (-0.8 SDS) in patients with initially normal BP. A linear correlation was found between MAP at baseline and the change of MAP during treatment (r= 0.51; P < 0.0001). The antihypertensive response was independent of changes in concomitant antihypertensive medication or underlying renal disease. BP was reduced with equal efficacy during day- and nighttime. Urinary protein excretion was reduced by 50% on average, with similar relative efficacy in patients with hypo/dysplastic nephropathies and glomerulopathies. The magnitude of proteinuria reduction depended on baseline proteinuria (r= 0.32, P < 0.0001), and was correlated with the antihypertensive efficacy of the drug (r= 0.22, P < 0.001). The incidence of rapid rises in serum creatinine and progression to end-stage CRF during treatment did not differ from the pretreatment observation period. Mean serum potassium increased by 0.3 mmol/L. Ramipril was discontinued in three patients due to symptomatic hypotension or hyperkalemia. Hemoglobin levels decreased by 0.6 g/dL in the first two treatment months and remained stable thereafter.

CONCLUSION

Ramipril appears to be an effective and safe antihypertensive and antiproteinuric agent in children with CRF-associated hypertension. The BP lowering and antiproteinuric effects are greatest in severely hypertensive and proteinuric children.

Immunologic risk factors and glomerular C4d deposits in chronic transplant glomerulopathy

BACKGROUND

Chronic transplant glomerulopathy is an uncommon cause of chronic transplant dysfunction of unknown pathogenesis. We evaluated the epidemiologic, clinical, and histologic features of chronic transplant glomerulopathy. To determine the possible contribution of humoral immune responses, we assessed glomerular deposition of C4d.

METHODS

From a cohort of 1111 kidney transplants (1983 to 2001) with at least 6 months of graft function, we identified 18 cases with chronic transplant glomerulopathy (1.6%) showing double contours of the glomerular basement membrane (GBM) on light microscopy. To assess the risk factors, this group was compared with 739 patients with stable function using multivariate Cox regression analysis. Paraffin sections of 11/18 biopsies were stained with polyclonal C4d antibodies. Sera of 13/18 patients could be tested for antidonor human leukocyte antigen (HLA) antibodies by enzyme-linked immunosorbent assay (ELISA). Patients with chronic allograft nephropathy without chronic transplant glomerulopathy or predominant cyclosporine nephrotoxicity were used as controls.

RESULTS

Chronic transplant glomerulopathy was diagnosed at a median of 8.3 (range 2.6-12.5) years posttransplantation. Panel reactive antibodies at time of transplantation, RR 1.23 (1.05-1.45) per 10% increase, and late acute rejection episodes, RR 7.6 (1.8-31.7), were independently associated with chronic transplant glomerulopathy. We found glomerular C4d deposits in 10/11 biopsies showing chronic transplant glomerulopathy and in only 2/13 controls. Peritubular capillary C4d deposits and donor-specific anti-HLA antibodies were demonstrated in 4 and 3 of the 10 patients with glomerular C4d deposits, respectively.

CONCLUSION

Presensitization and late acute rejection episodes were the risk factors identified. Glomerular C4d deposits suggest that chronic transplant glomerulopathy emerges from in situ humoral rejection. Chronic transplant glomerulopathy should be considered as a manifestation of immune-mediated injury.

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.

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

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

RAAS escape: a real clinical entity that may be important in the progression of cardiovascular and renal disease

Interruption of the renin-angiotensin-aldosterone system (RAAS) at different levels is target-organ protective in several disease states; however, complete blockade is unlikely to be achieved due to escape mechanisms whenever blockade is attempted, incomplete knowledge of the role of all elements of the RAAS, and lack of pharmacotherapy against some elements that have been shown to contribute to disease states. Aldosterone has been overlooked as a mediator of RAAS escape and a key factor in target-organ injury despite the use of available RAAS blockers. Aldosterone is thought to play a role in the development of hypertension, alteration in vascular structure, vascular smooth muscle hypertrophy, endothelial dysfunction, structural renal injury, proteinuria, left ventricular remodeling, collagen synthesis, and myocardial fibrosis. Aldosterone receptor antagonists have been shown to antagonize all these effects in experimental models. Clinical trials with aldosterone antagonists showed an improvement in survival and left ventricular mass index in patients with congestive heart failure, and a reduction in urinary protein excretion and left ventricular mass index in patients with type 2 diabetes and early nephropathy who developed aldosterone synthesis escape. Consequently, aldosterone receptor antagonists may have specific benefits for reducing target-organ injury, particularly if there is evidence of RAAS escape.

Combination treatment of angiotensin-II receptor blocker and angiotensin-converting-enzyme inhibitor in non-diabetic renal disease (COOPERATE): a randomised controlled trial

BACKGROUND

Present angiotensin-converting-enzyme inhibitor treatment fails to prevent progression of non-diabetic renal disease. We aimed to assess the efficacy and safety of combined treatment of angiotensin-converting-enzyme inhibitor and angiotensin-II receptor blocker, and monotherapy of each drug at its maximum dose, in patients with non-diabetic renal disease.

METHODS

336 patients with non-diabetic renal disease were enrolled from one renal outpatient department in Japan. After screening and an 18-week run-in period, 263 patients were randomly assigned angiotensin-II receptor blocker (losartan, 100 mg daily), angiotensin-converting-enzyme inhibitor (trandolapril, 3 mg daily), or a combination of both drugs at equivalent doses. Survival analysis was done to compare the effects of each regimen on the combined primary endpoint of time to doubling of serum creatinine concentration or end-stage renal disease. Analysis was by intention to treat.

FINDINGS

Seven patients discontinued or were otherwise lost to follow-up. Ten (11%) of 85 patients on combination treatment reached the combined primary endpoint compared with 20 (23%) of 85 on trandolapril alone (hazard ratio 0.38, 95% CI 0.18-0.63, p=0.018) and 20 (23%) of 86 on losartan alone (0.40, 0.17-0.69, p=0.016). Covariates affecting renal survival were combination treatment (hazard ratio 0.38, 95% CI 0.18-0.63, p=0.011), age (1.30, 1.03-2.29, p=0.009), baseline renal function (1.80, 1.02-2.99, p=0.021), change in daily urinary protein excretion rate (0.58, 0.24-0.88, p=0.022), use of diuretics (0.80, 0.30-0.94, p=0.043), and antiproteinuric response to trandolapril (0.81, 0.21-0.91, p=0.039). Frequency of side-effects with combination treatment was the same as with trandolapril alone.

INTERPRETATION

Combination treatment safely retards progression of non-diabetic renal disease compared with monotherapy. However, since some patients reached the combined primary endpoint on combined treatment, further strategies for complete management of progressive non-diabetic renal disease need to be researched.

Effectiveness of aldosterone blockade in patients with diabetic nephropathy

It has been reported that continuous ACE inhibitor therapy does not necessarily produce a maintained decrease in plasma aldosterone levels, which may remain high or increase eventually during long-term use (aldosterone escape). We have examined the role of aldosterone escape in 45 patients with type 2 diabetes and early nephropathy treated with an ACE inhibitor for 40 weeks. With treatment, there was a 40% reduction in average urinary albumin excretion, although urinary albumin excretion in patients with aldosterone escape (18 patients) was significantly higher than that in patients without escape (27 patients). In the 18 patients with escape, spironolactone (25 mg/d) was added to ACE inhibitor treatment in 13. After a 24-week study period, urinary albumin excretion and left ventricular mass index were significantly reduced without blood pressure change. In conclusion, the present study demonstrates that aldosterone escape is observed in 40% of patients with type 2 diabetes with early nephropathy despite the use of ACE inhibitors. Our study suggests the possibility that aldosterone blockade may represent optimal therapy for patients with early diabetic nephropathy who show aldosterone escape during ACE inhibitor treatment and who no longer show maximal antiproteinuric effects of ACE inhibition. Additional, larger, prospectively randomized, double-blind studies will be needed before adaptation of this strategy.