Long-term effects of antihypertensive regimens on renal hemodynamics and proteinuria

Response and survival of dogs with proteinuria (UPC > 2.0) treated with angiotensin converting enzyme inhibitors

BACKGROUND

Angiotensin-converting enzyme inhibitors (ACEi) are a recommended treatment for glomerular proteinuria. Frequency of response to ACEi and the association of achieving proposed urine protein-to-creatinine ratio (UPC) targets on survival is unknown.

OBJECTIVES

To determine response rates to ACEi therapy and whether a positive response is associated with improved survival.

ANIMALS

Eighty-five dogs with proteinuria (UPC > 2.0).

METHODS

Retrospective study including dogs (UPC > 2.0) prescribed an ACEi for treatment of proteinuria. Baseline creatinine, albumin, cholesterol, UPC, and systolic blood pressure were recorded, and cases reviewed to track UPC. Treatment response was defined as achieving a UPC of <0.5 or reduction of ≥50% from baseline within 3 months. Outcome data were collected to determine overall and 12-month survival.

RESULTS

Thirty-five (41%) dogs responded to ACEi treatment. Treatment response was statistically associated with both median survival time (664 days [95% confidence interval (CI): 459-869] for responders compared to 177 [95% CI: 131-223] for non-responders) and 12-month survival (79% responders alive compared to 28% non-responders). Baseline azotemia or hypoalbuminemia were also associated with a worse prognosis, with odds ratios of death at 12 months of 5.34 (CI: 1.85-17.32) and 4.51 (CI: 1.66-13.14), respectively. In the 25 dogs with normal baseline creatinine and albumin, response to treatment was associated with 12-month survival (92% responders alive compared to 54% non-responders, P = .04).

CONCLUSIONS AND CLINICAL IMPORTANCE

When the UPC is >2.0, achieving recommended UPC targets within 3 months appears to be associated with a significant survival benefit. Response to treatment is still associated with survival benefit in dogs with less severe disease (no azotemia or hypoalbuminemia).

Slowing the Progression of Diabetic Kidney Disease

Diabetes is the most frequent cause of kidney disease that progresses to end-stage renal disease worldwide, and diabetic kidney disease is significantly related to unfavorable cardiovascular outcomes. Since the 1990s, specific therapies have emerged and been approved to slow the progression of diabetic kidney disease, namely, renin-angiotensin-aldosterone system blockers (including angiotensin-converting enzyme inhibitors (ACEi) angiotensin receptor blockers (ARBs), the non-steroidal mineralocorticoid receptor antagonist (NS-MRA), finerenone, and sodium-glucose cotransporter-2 (SGLT2) inhibitors). Mechanistically, these different classes of agents bring different anti-inflammatory, anti-fibrotic, and complementary hemodynamic effects to patients with diabetic kidney disease such that they have additive benefits on slowing disease progression. Within the coming year, there will be data on renal outcomes using the glucagon-like peptide-1 receptor agonist, semaglutide. All the aforementioned medications have also been shown to improve cardiovascular outcomes. Thus, all three classes (maximally dosed ACEi or ARB, low-dose SGLT-2 inhibitors, and the NS-MRA, finerenone) form the "pillars of therapy" such that, when used together, they maximally slow diabetic kidney disease progression. Ongoing studies aim to expand these pillars with additional medications to potentially normalize the decline in kidney function and reduce associated cardiovascular mortality.

Animal models of diabetic microvascular complications: Relevance to clinical features

Diabetes has become more common in recent years worldwide, and this growth is projected to continue in the future. The primary concern with diabetes is developing various complications, which significantly contribute to the disease's mortality and morbidity. Over time, the condition progresses from the pre-diabetic to the diabetic stage and then to the development of complications. Years and enormous resources are required to evaluate pharmacological interventions to prevent or delay the progression of disease or complications in humans. Appropriate screening models are required to gain a better understanding of both pathogenesis and potential therapeutic agents. Different species of animals are used to evaluate the pharmacological potentials and study the pathogenesis of the disease. Animal models are essential for research because they represent most of the structural, functional, and biochemical characteristics of human diseases. An ideal screening model should mimic the pathogenesis of the disease with identifiable characteristics. A thorough understanding of animal models is required for the experimental design to select an appropriate model. Each animal model has certain advantages and limitations. The present manuscript describes the animal models and their diagnostic characteristics to evaluate microvascular diabetic complications.

Effects of telmisartan on proteinuria and systolic blood pressure in dogs with chronic kidney disease

Renal proteinuria is associated with promoted renal dysfunction and a shorter survival period in dogs with chronic kidney disease (CKD). Renin angiotensin- aldosterone system inhibitors are primarily used to treat renal proteinuria. In this retrospective, open-label study, we aimed to evaluate the anti-proteinuric and anti-hypertensive effects of telmisartan (angiotensin II receptor blocker) in dogs with proteinuric CKD. A total of 28 dogs with proteinuric CKD were included in the study, all dogs received telmisartan 1 mg/kg q24h, PO. The urine protein-to-creatinine ratio (UPC), urine albumin-to-creatinine ratio (UAC) and systolic blood pressure (SBP) decreased significantly after telmisartan administration (P < 0.05). The median rate of change in UPC, UAC and SBP at Day 120 were - 65.1%, -75.9% and - 9.7%. Ten dogs (36.7%) achieved UPC < 1.0 at Day 120, of which six dogs had UPC < 0.5. A reduction of UPC to ≥50% was achieved in 10 dogs (36%) at Day 45 and 17 dogs (61%) at Day 120. Seventeen dogs (61%) had hypertension at baseline, of which 10 dogs (59%) had SBP < 160 mmHg at Day 120. Two-way repeated measures analysis of variance did not attribute the observed changes in SBP, UPC or UAC to feeding with a renal diet. In conclusion, telmisartan therapy provides anti-proteinuric and anti-hypertensive effects in dogs with proteinuric CKD.

The renin-angiotensin-aldosterone system and its suppression

Chronic activation of the renin-angiotensin-aldosterone system (RAAS) promotes and perpetuates the syndromes of congestive heart failure, systemic hypertension, and chronic kidney disease. Excessive circulating and tissue angiotensin II (AngII) and aldosterone levels lead to a pro-fibrotic, -inflammatory, and -hypertrophic milieu that causes remodeling and dysfunction in cardiovascular and renal tissues. Understanding of the role of the RAAS in this abnormal pathologic remodeling has grown over the past few decades and numerous medical therapies aimed at suppressing the RAAS have been developed. Despite this, morbidity from these diseases remains high. Continued investigation into the complexities of the RAAS should help clinicians modulate (suppress or enhance) components of this system and improve quality of life and survival. This review focuses on updates in our understanding of the RAAS and the pathophysiology of AngII and aldosterone excess, reviewing what is known about its suppression in cardiovascular and renal diseases, especially in the cat and dog.

ACVIM consensus statement: Guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats

An update to the 2007 American College of Veterinary Internal Medicine (ACVIM) consensus statement on the identification, evaluation, and management of systemic hypertension in dogs and cats was presented at the 2017 ACVIM Forum in National Harbor, MD. The updated consensus statement is presented here. The consensus statement aims to provide guidance on appropriate diagnosis and treatment of hypertension in dogs and cats.

Chronic Kidney Disease in Aged Cats: Clinical Features, Morphology, and Proposed Pathogeneses

Chronic kidney disease (CKD) is the most common metabolic disease of domesticated cats, with most affected cats being geriatric (>12 years of age). The prevalence of CKD in cats exceeds that observed in dogs, and the frequency of the diagnosis of CKD in cats has increased in recent decades. Typical histologic features include interstitial inflammation, tubular atrophy, and fibrosis with secondary glomerulosclerosis. In contrast to people and dogs, primary glomerulopathies with marked proteinuria are remarkably rare findings in cats. Although a variety of primary renal diseases have been implicated, the disease is idiopathic in most cats. Tubulointerstitial changes, including fibrosis, are present in the early stages of feline CKD and become more severe in advanced disease. A variety of factors-including aging, ischemia, comorbid conditions, phosphorus overload, and routine vaccinations-have been implicated as factors that could contribute to the initiation of this disease in affected cats. Factors that are related to progression of established CKD, which occurs in some but not all cats, include dietary phosphorus intake, magnitude of proteinuria, and anemia. Renal fibrosis, a common histologic feature of aged feline kidneys, interferes with the normal relationship between peritubular capillaries and renal tubules. Experimentally, renal ischemia results in morphologic changes similar to those observed in spontaneous CKD. Renal hypoxia, perhaps episodic, may play a role in the initiation and progression of this disease.

Comparison between Urine Protein: Creatinine Ratios of Samples Obtained from Dogs in Home and Hospital Settings

Background

The urine protein:creatinine ratio (UPC) is used to quantify urine protein excretion and guide recommendations for monitoring and treatment of proteinuria.

Hypothesis/Objectives

Home urine samples will have lower UPCs than hospital samples. The objectives were to compare UPCs of samples collected in each setting and to determine whether environment of sample collection might affect staging, monitoring or treatment recommendations.

Animals

Twenty‐four client‐owned dogs.

Methods

Prospective, nonmasked study. Clients collected a urine sample from their dog at home and a second sample was collected at the hospital. Dogs receiving corticosteroids or angiotensin‐converting enzyme inhibitors were excluded, as were those with urine samples of inadequate volume, no protein on dipstick analysis, or active urine sediment. Samples were refrigerated after collection, dipstick and sediment evaluations were completed and each sample was frozen at −80°C within 12 hours. UPCs were performed on frozen samples within 2 months.

Results

From 81 paired samples, 57 were excluded. Of the remaining 24, 12/24 (50%) had higher hospital sample UPCs, 9/24 (38%) had identical UPCs, and 3/24 (12%) had lower hospital UPCs. The UPCs of hospital samples were higher than home samples for the total population (P = .005) and the subset with UPC > 0.5 (P = .001).

Conclusions

Setting and related circumstances of urine collection in dogs is associated with UPC differences; results are usually higher in hospital than in home samples. This difference has the potential to affect clinical interpretation.

Prognostic Value of Microalbuminuria During Antihypertensive Treatment in Essential Hypertension

Whether changes over time of urinary albumin excretion have prognostic value is a matter of discussion. The objective was to assess the prognostic value of changes in urinary albumin excretion over time in cardiovascular risk during antihypertensive treatment. Follow-up study of 2835 hypertensives in the absence of previous cardiovascular disease (mean age 55 years, 47% men, BP 138/80 mm Hg, 19.1% diabetics, and calibrated systemic coronary risk estimation 5 or >10.6%). Usual-care of antihypertensive treatment was implemented to maintain blood pressure <140/90 mm Hg. Urinary albumin excretion was assessed yearly, and the values were expressed as the creatinine ratio. Incidence of cardiovascular events, fatal and nonfatal, was recorded during the follow-up. During a median follow-up of 4.7 years (17 028 patients-year), 294 fatal and first nonfatal cardiovascular events were recorded (1.73 CVD per 100 patients/year). Independently of blood pressure, estimated glomerular filtration rate, level of cardiovascular risk, and antihypertensive treatment, microalbuminuria at baseline and at any time during the follow-up resulted in higher risk for events, hazard ratio (HR) 1.35 (95% confidence interval [CI], 1.08–1.79) and HR 1.49 (95% CI, 1.14–1.94), respectively. Likewise, development of microalbuminuria (HR 1.60; 95% CI, 1.04–2.46) or persistence from the beginning (1.53; 95% CI, 1.13–2.06) had a significantly higher rate of events than if remained normoalbuminuric (HR 1) or regress to normoalbuminuria (HR 1.37; 95% CI, 0.92–2.06) with an 18%, 18%, 8%, and 11% events, respectively, P <0.001. The study supports the value of urinary albumin excretion assessment as a prognostic factor for cardiovascular risk, but also opens the way to consider it as an intermediate objective in hypertension.

Consensus recommendations for standard therapy of glomerular disease in dogs

Standard therapy forms the basic foundation for care of dogs with glomerular disease, as it is herein recommended for use in all affected animals regardless of causation of the disease. Consensus recommendations target the evaluation and management of proteinuria, inhibition of the renin-angiotensin-aldosterone system, modification in dietary intake with special consideration for those nutrients with renal effects, diagnosis and treatment of systemic hypertension, and evaluation and management of body fluid volume status in dogs with glomerular disease.

Longitudinal prevalence of hypertension, proteinuria, and retinopathy in dogs with spontaneous diabetes mellitus

Background

The prevalence and progression of vascular complications of spontaneous diabetes mellitus (DM) in dogs have not been described.

Objectives

To investigate the effects of duration of disease, as estimated by time since DM diagnosis, and glycemic control on prevalence of systemic hypertension, proteinuria, and diabetic retinopathy in dogs with spontaneous DM.

Animals

Seventeen client‐owned dogs with spontaneous DM.

Methods

Prospective, longitudinal observational study. Dogs with DM of less than 1 year's duration were recruited and evaluated once every 6 months for 24 months. Recorded measures included indirect BP, urine albumin, protein and creatinine concentrations, serial blood glucose and serum fructosamine concentrations, ophthalmic examination, and a standardized behavioral questionnaire.

Results

Eleven dogs completed the 2‐year follow‐up period, during which the highest recorded prevalence of systolic and diastolic hypertension was 55 and 64%, respectively. Prevalence of microalbuminuria and elevated urine protein:creatinine ratio (UPC) ranged up to 73 and 55%, respectively. Prevalence of retinopathy ranged up to 20%. No significant effect of time since DM diagnosis or glycemic control was detected for any of the measures examined. Additionally, no significant associations between BP, urine albumin concentration, UPC and retinopathy were detected.

Conclusions and Clinical Relevance

With the exception of proteinuria, which was substantial in some cases, clinically deleterious diabetic vascular complications were not identified in dogs in this study.

Evaluation of the effects of a therapeutic renal diet to control proteinuria in proteinuric non-azotemic dogs treated with benazepril

BACKGROUND

Angiotensin-converting enzyme inhibitors (ACEIs) are currently used to control proteinuria in dogs with chronic kidney disease. Renal diets (RDs) have beneficial effects in the management of azotemic dogs, but its role in proteinuric non-azotemic (PNAz) dogs has been poorly documented.

HYPOTHESIS

Administration of a RD to PNAz dogs treated with benazepril (Be) improves proteinuria control compared with the administration of a maintenance diet (MD).

ANIMALS

Twenty-two PNAz (urine protein/creatinine ratio [UPC] >1) dogs.

METHODS

Randomized open label clinical trial design. Dogs were assigned to group-MD (5.5 g protein/100 kcal ME)/Be or to group-RD (3.7 g protein/100 kcal ME)/Be group during 60 days. Dogs with serum albumin (Alb) <2 g/dL received aspirin (1 mg/kg/12 hours). A physical examination, systolic blood pressure (SBP) measurement, complete blood count (CBC), biochemistry panel, urinalysis, and UPC were performed at day 0 (D0) and day 60 (D60).

RESULTS

At D0, there were no significant differences between groups in the evaluated variables. During the study, logUPC (geometric mean (95% CI) and SBP (mean±SD mmHg) significantly decreased (paired t-test, P = 0.001) in Group-RD (logUPC(D0) = 3.16[1.9-5.25]; UPC(D60) = 1.20 [0.59-2.45]; SBP(D0) = 160 ± 17.2; SBP(D60) = 151 ± 15.8), but not in Group-MD (UPC(D0) = 3.63[2.69-4.9]; UPC(D60) = 2.14 [0.76-6.17]; SBP(D0) = 158 ± 14.7; SBP(D60) = 153 ± 11.5). However, RM-ANOVA test did not confirm that changes were consequence of dietary modification. Weight and Alb concentration did not change significantly in any group.

CONCLUSION AND CLINICAL RELEVANCE

The administration of a RD to PNAz dogs treated with Be might help to control proteinuria and SBP compared with the administration of a MD, without inducing clinically detectable malnutrition, but more studies are warranted.

Renal pathophysiology: lessons learned from the canine remnant kidney model

OBJECTIVE

To review the pathophysiology of chronic kidney disease (CKD) in dogs and the contributions of the canine remnant kidney model to our understanding of this disease.

DATA SOURCES

Original studies in the human and veterinary medical fields.

DATA SYNTHESIS

Three of the fundamental principles of modern nephrology-the intact nephron hypothesis, the trade-off hypothesis, and the hyperfiltration theory were developed directly as a result of studies of the remnant kidney model. Most of the pivotal early studies were conducted in dogs. As a result, our understanding of CKD, and of the renal and systemic adaptations to CKD, is largely based on studies of this model.

CONCLUSIONS

Studies of the remnant kidney model have advanced our understanding of the pathophysiology of CKD. Nearly every therapeutic intervention used in CKD, by veterinarians and physicians alike, has its basis in studies of the remnant kidney model or in knowledge that was derived from studies of this model. A great debt is owed to the canine participants in these studies and to a small number of key scientists who conducted this important and insightful research.

Amlodipine Reduces Inflammation despite Promoting Albuminuria in the Streptozotocin-Induced Diabetic Rat

Amlodipine reduces blood pressure; however, its effect in the diabetic kidney irrespective of its blood pressure-lowering effects is unclear. This study examined the effects of amlodipine (0, 5, 10 and 20 mg/kg; D_A0, D_A5, D_A10 and D_A20, respectively) for 12 weeks on renal functional and structural changes in the streptozotocin-induced diabetic rat, a nonhypertensive model of diabetes-associated hyperfiltration. Compared with nondiabetic rats, diabetes (D) was associated with increased urine albumin excretion (UAE, 12.6 ± 3.40 vs. 3.73 ± 1.14 mg/day), glomerular filtration rate (2.17 ± 0.09 vs. 1.64 ± 0.12 ml/min/g kidney weight), glomerulosclerosis (0.21 ± 0.03 vs. 0.05 ± 0.01 AU) and infiltration of inflammatory cells (18.5 ± 2.78 vs. 6.92 ± 0.70 cells/cm²), but did not affect mean arterial pressure (MAP, 110 ± 4.70 vs. 109 ± 5.33 mm Hg). While D_A20 abolished glomerular hyperfiltration (1.49 ± 0.05 ml/min/g kidney weight) and inflammatory cell abundance (6.0 ± 0.79 cells/cm²), it exacerbated UAE (43.5 ± 8.49 mg/day) and increased MAP (132 ± 3.76 mm Hg), but had no effect on renal pathology. These data suggest that amlodipine reduces renal inflammation and abolished glomerular hyperfiltration, but increases blood pressure and exacerbates albuminuria in the rat model of normotensive diabetic kidney disease. We conclude that amlodipine may have limited renoprotective effects in the face of hyperfiltration and absence of elevated blood pressure.

Chronic sodium-retaining action of insulin in diabetic dogs

Insulin-mediated sodium retention is implicated as a mechanism for hypertension in metabolic syndrome and type II diabetes. However, there is no direct experimental evidence for a sustained antinatriuretic effect of insulin outside of rodents, and all previous studies in dogs have been negative. This study used a novel approach to test for a chronic sodium-retaining action of insulin in dogs, by testing the hypothesis that natriuresis in type I diabetes is dependent on the decrease in insulin, rather than being due solely to osmotic actions of hyperglycemia. Dogs were chronically instrumented and housed in metabolic cages. Fasting blood glucose in alloxan-treated dogs was maintained at ~65 mg/dl by continuous intravenous insulin infusion. Then, a 6-day diabetic period was induced by either 1) decreasing the insulin infusion to induce type I diabetes (D; blood glucose = 449 ± 40 mg/dl) or 2) clamping the insulin infusion and infusing glucose continuously (DG; blood glucose = 470 ± 56 mg/dl). Control urinary sodium excretion (UnaV) averaged 70 ± 5 (D) and 69 ± 5 (DG) meq/day and increased on day 1 in both groups. UnaV remained elevated in the D group (115 ± 15 meq/day days 2-6), but it returned to control in the DG group (69 ± 11 meq/day days 2-6) and was accompanied by decreased lithium clearance. Thus, insulin had a sustained antinatriuretic action that was triggered by increased glucose, and it was powerful enough to completely block the natriuresis caused by hyperglycemia. These data may reveal an unrecognized physiologic function of insulin as a protector against hyperglycemia-induced salt wasting in diabetes.

An evidence-based review of therapies for canine chronic kidney disease

Successful treatment and prevention of kidney disease in dogs requires a multi-dimensional approach to identify and eliminate causes or exacerbating factors, provide professional evaluation on a regular basis and implement a comprehensive treatment programme when necessary. Over the years, many therapeutic and preventive interventions have been developed or advocated for chronic kidney disease in dogs, but evidence of efficacy or effectiveness is often lacking or highly variable. Accordingly, the main objective of this systematic review was to identify and critically appraise the evidence supporting various aspects of managing canine chronic kidney disease.

Are differences in calcium antagonists relevant across all stages of nephropathy or only proteinuric nephropathy?

PURPOSE OF REVIEW

The main effects of classic calcium antagonists are mediated by the inhibition of L-type calcium channels broadly distributed within the renal vascular bed. Calcium antagonists act predominantly on the afferent arterioles, and dihydropyridines can favour the increase in glomerular hypertension and progression of kidney diseases, in particular when systemic blood pressure remains uncontrolled.

RECENT FINDINGS

Calcium antagonists have been widely used in clinical practice because of their antihypertensive capacity. The prevention of renal damage is a very important aim of antihypertensive therapy. This is particularly so taking into account the high prevalence of chronic kidney disease in the general population. Non-dihydropyridines such as verapamil have been shown to possess an antiproteinuric effect that could be particularly relevant.

SUMMARY

Recent data from clinical trials have confirmed that, in hypertensive patients with preserved renal function or with chronic kidney disease, calcium antagonists are effective antihypertensive drugs to be considered alone or in combination with an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. In those patients presenting with proteinuric kidney disease, non-dihydropyridines could reduce proteinuria to a greater degree than dihydropyridines.

Ca2+ channel subtypes and pharmacology in the kidney

A large body of evidence has accrued indicating that voltage-gated Ca(2+) channel subtypes, including L-, T-, N-, and P/Q-type, are present within renal vascular and tubular tissues, and the blockade of these Ca(2+) channels produces diverse actions on renal microcirculation. Because nifedipine acts exclusively on L-type Ca(2+) channels, the observation that nifedipine predominantly dilates afferent arterioles implicates intrarenal heterogeneity in the distribution of L-type Ca(2+) channels and suggests that it potentially causes glomerular hypertension. In contrast, recently developed Ca(2+) channel blockers (CCBs), including mibefradil and efonidipine, exert blocking action on L-type and T-type Ca(2+) channels and elicit vasodilation of afferent and efferent arterioles, which suggests the presence of T-type Ca(2+) channels in both arterioles and the distinct impact on intraglomerular pressure. Recently, aldosterone has been established as an aggravating factor in kidney disease, and T-type Ca(2+) channels mediate aldosterone release as well as its effect on renal efferent arteriolar tone. Furthermore, T-type CCBs are reported to exert inhibitory action on inflammatory process and renin secretion. Similarly, N-type Ca(2+) channels are present in nerve terminals, and the inhibition of neurotransmitter release by N-type CCBs (eg, cilnidipine) elicits dilation of afferent and efferent arterioles and reduces glomerular pressure. Collectively, the kidney is endowed with a variety of Ca(2+) channel subtypes, and the inhibition of these channels by their specific CCBs leads to variable impact on renal microcirculation. Furthermore, multifaceted activity of CCBs on T- and N-type Ca(2+) channels may offer additive benefits through nonhemodynamic mechanisms in the progression of chronic kidney disease.

Measurement, Interpretation, and Implications of Proteinuria and Albuminuria

Proteinuria is a common disorder in dogs and cats that can indicate the presence of chronic kidney disease (CKD) before the onset of azotemia or the presence of more severe CKD after the onset of azotemia. Although a direct pathogenetic link between glomerular disease, proteinuria, and progressive renal damage has not been established, attenuation of proteinuria has been associated with decreased renal functional decline in several studies. There is a need to continue to increase our understanding of the effects of proteinuria on the glomerulus, the tubule, and the interstitium in dogs and cats.

Microalbuminuria

Microalbuminuria, originally described more than 3 decades ago as a predictor of nephropathy in patients who had type 1 diabetes mellitus and associated with higher cardiovascular risk, is now linked with increased risk for cardiovascular events rather than progression to end-stage kidney disease. This article reviews the role of microalbuminuria in the context of atherosclerotic vascular disease. It presents the methods for microalbuminuria assessment in clinical practice, its relations with other cardiovascular risk factors, and the pathophysiologic associations between microalbuminuria and vascular damage. In addition, this article discusses the prognostic significance of microalbuminuria for cardiovascular disease as well as existing therapeutic interventions for reducing urine albumin excretion in patients who are at high cardiovascular risk.

Canine glomerulonephritis: new thoughts on proteinuria and treatment

Glomerular disease in the dog is not only a common form of renal disease but also an important cause of chronic renal failure. The presence of immune complexes in glomerular capillary walls is a major cause of canine glomerular disease and is commonly referred to as glomerulonephritis. Leakage of plasma proteins, principally albumin, across the damaged glomerular capillary walls results in persistent proteinuria--the clinicopathological hallmark of glomerulonephritis. Recent evidence suggests that, in addition to being a marker of disease, persistent proteinuria is associated with progressive glomerular and tubulointerstitial lesions and loss of additional nephrons. Perhaps the best treatment for glomerulonephritis is the identification and correction of any underlying inflammatory, immune-mediated or neoplastic disease that results in the deposition or formation of glomerular immune complexes. In cases of idiopathic glomerulonephritis, angiotensin-converting enzyme inhibitors have been shown to decrease proteinuria and potentially slow disease progression.

Renoprotective effect of diltiazem in hypertensive type 2 diabetic patients with persistent microalbuminuria despite ACE inhibitor treatment

The aim of the study was to evaluate the effects of the non-dihydropyridine calcium antagonist (NDCA) diltiazem on the development of urinary albumin excretion (UAE) in type 2 hypertensive diabetic patients with persistent microalbuminuria despite ACE inhibitor treatment. Thirty-six type 2 diabetic hypertensive patients with microalbuminuria persisting after at least 1 year of treatment with ACE inhibitors were randomized to receive captopril (n=22) or combined therapy with captopril and 120 mg diltiazem (n=14) for 2 years. Captopril dose was individualized according to blood pressure. Changes in UAE, blood pressure, and metabolic control were monitored to analyze the influence of the addition of diltiazem on progression of diabetic nephropathy. In patients treated with captopril and diltiazem, absolute UAE did not change during the study (baseline: 101 mg/24 h, range 39-298; 2 years after randomization: 74 mg/24 h, range 12-665). In contrast, UAE increased in patients treated with captopril monotherapy (baseline: 118 mg/24 h, range 32-282; 2 years after randomization: 164 mg/24 h, range 15-1161, p<0.05). In addition, fewer patients in the captopril/diltiazem group progressed to macroalbuminuria (eight patients in captopril group and one in captopril/diltiazem group, p<0.05). The beneficial effects of the addition of diltiazem were independent of blood pressure and metabolic control. We suggest that the combination of ACE inhibitors and NDCA should be considered in type 2 microalbuminuric patients at high risk for progression to established diabetic nephropathy.

Evaluation of the association between initial proteinuria and morbidity rate or death in dogs with naturally occurring chronic renal failure

OBJECTIVE

To determine whether urine protein-to-creatinine ratio (UP:C) > or = 1.0 at initial diagnosis of chronic renal failure (CRF) is associated with greater risk of development of uremic crises, death, and progression of renal failure in dogs.

DESIGN

Prospective cohort study.

ANIMALS

45 dogs with CRF PROCEDURE: Dogs were prospectively assigned to 2 groups on the basis of initial UP:C < 1.0 or 2 > or = 1.0. The association between magnitude of proteinuria and development of uremic crises and death was determined before and after dogs with initial UP:C > or =1.0 were assigned to 3 subgroups and compared with dogs with initial UP:C < 1.0. Changes in reciprocal serum creatinine concentration were used to estimate decrease in renal function.

RESULTS

Initially, dogs had similar clinical characteristics with the exception of systolic blood pressure and UP:C. Relative risks of development of uremic crises and death were approximately 3 times higher in dogs with UP:C > or =1.0, compared with dogs with UP:C < 1.0. Relative risk of adverse outcome was approximately 1.5 times higher for every 1-unit increment in UP:C. The decrease in renal function was of greater magnitude in dogs with UP:C > or =1.0, compared with dogs with UP:C < 1.0.

CONCLUSIONS AND CLINICAL RELEVANCE

Initial UP:C > or =1.0 in dogs with CRF was associated with greater risk of development of uremic crises and death, compared with dogs with UP:C < 1.0. Initial determinations of UP:C in dogs with naturally occurring CRF may be of value in refining prognoses.

Angiotensin-converting enzyme inhibitors in the therapy of renal diseases

Renal diseases, especially chronic renal failure (CRF), are common in canine and feline medicine. The renin-angiotensin-aldosterone system (RAAS) plays a pivotal role in these conditions in the development of renal lesions and the progression of kidney dysfunction. Angiotensin-converting enzyme inhibitors (ACEI) are currently considered as the most efficient agents in therapeutic strategies. The benefit of an ACEI treatment can be explained by at least three mechanisms: ACEI limit systemic and glomerular capillary hypertension, have an antiproteinuric effect, and retard the development of glomerulosclerosis and tubulointerstitial lesions. These effects have been studied in dogs and cats, and there is now some evidence to support the recommendation of ACEI therapy in dogs and cats with CRF. Nevertheless the prescription of ACEI in such patients should take into account the potential influence of renal impairment on ACEI disposition, and adverse effects on the renal function itself (especially hypotension and acute reductions in glomerular filtration rate). The risk of drug interaction with diuretics, nonsteroidal anti-inflammatory drugs and anesthetics, should not be overestimated. Furthermore, hypotension may occur in patients on a low sodium diet.

Differential effects of calcium antagonist subclasses on markers of nephropathy progression

BACKGROUND

Numerous studies suggest that the dihydropyridine calcium antagonists (DCAs) and nondihydropyridine calcium antagonists (NDCAs) have differential antiproteinuric effects. Proteinuria reduction is a correlate of the progression of renal disease. In an earlier systematic review, calcium antagonists were shown as effective antihypertensive drugs, but there was uncertainty about their renal benefits in patients with proteinuria and renal insufficiency.

METHODS

A systematic review was conducted to assess the differential effects of DCAs and NDCAs on proteinuria in hypertensive adults with proteinuria, with or without diabetes, and to determine whether these differential effects translate into altered progression of nephropathy. Studies included in the review had to be randomized clinical trials with at least 6 months of treatment, include a DCA or NDCA treatment arm, have one or more renal end points, and have been initiated after 1986. Summary data were extracted from 28 studies entered into two identical but separate databases, which were compared and evaluated by independent reviewers. The effects of each drug class on blood pressure (N= 1338) and proteinuria (N= 510) were assessed.

RESULTS

After adjusting for sample size, study length, and baseline value, there were no statistically significant differences in the ability of either class of calcium antagonist to decrease blood pressure. The mean change in proteinuria was +2% for DCAs and -30% for NDCAs (95% CI, 10% to 54%, P= 0.01). Consistently greater reductions in proteinuria were associated with the use of NDCAs compared with DCAs, despite no significant differences in blood pressure reduction or presence of diabetes.

CONCLUSION

This analysis supports (1) similar efficacy between subclasses of calcium antagonists to lower blood pressure, and (2) greater reductions in proteinuria by NDCAs compared to DCAs in the presence or absence of diabetes. Based on these findings, NDCAs, alone or in combination with an angiotensin-converting enzyme (ACE) inhibitor or an angiotensin receptor blocker (ARB), are suggested as preferred agents to lower blood pressure in hypertensive patients with nephropathy associated with proteinuria.

The role of calcium antagonists in chronic kidney disease

PURPOSE OF REVIEW

To review goals of antihypertensive treatment in chronic kidney disease in the context of what role calcium antagonists play toward reducing progression of kidney disease.

RECENT FINDINGS

All recently published guidelines recommend a blood pressure goal of less than 130/80 mmHg in patients with chronic kidney disease. Use of calcium antagonists is not recommended as part of the initial armamentarium. Angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers, when used in concert with diuretics reduce blood pressure as well as both proteinuria and the rate of decline in the glomerular filtration rate. The evidence for calcium antagonists in this regard is more divergent. Dihydropyridine calcium antagonists, e.g. amlodipine, felodipine, help achieve blood pressure goals and reduce stroke risk. When used with a renin-angiotensin system blocker they do not detract from the benefits of this blockade on slowing progression of kidney disease. Non-dihydropyridine calcium antagonists, e.g. verpamil or diltiazem, decrease proteinuria and in studies with 5 to 6 years follow-up preserve kidney function similarly to angiotensin-converting enzyme inhibitors. The reason for this outcome difference between calcium antagonists is partial preservation of renal autoregulation compared to its obliteration by the dihydropyridine subclass.

SUMMARY

Use of calcium antagonists is safe and necessary to achieve blood pressure goals in people with chronic kidney disease. While both subclasses are safe and necessary to achieve blood pressure goals, dihydropyridine calcium antagonists fail to significantly slow the progression of kidney disease among patients with established nephropathy and macroalbuminuria when compared to agents that block the renin-angiotensin system.

Calcium channel blockers in the prevention of end stage renal disease: a review

Hypertension and high levels of proteinuria are independent risk factors for accelerated progression of renal failure. There is increasing evidence that strict control of both blood pressure (BP) and proteinuria are beneficial in slowing the rate of progression of chronic renal disease in diabetic as well as non-diabetic nephropathy. The angiotensin-converting enzyme inhibitors (ACE-I) and angiotensin 2 receptor blockers (ARB) have clearly demonstrated their beneficial effect on both reduction of BP and proteinuria. The calcium channel blockers (CCB) have individual pharmacological and therapeutic properties that may vary, but as a group they are effective antihypertensive agents in patients with renal disease. Their effects on the kidney may extend beyond BP reduction alone. Current studies suggest that CCB do not worsen the progression of renal disease but may rather provide benefit when systemic BP has been tightly normalised. The non-dihydropyridine calcium channel blockers (NDHP), diltiazem and verapamil, slow the progression of type 2 diabetic nephropathy with overt proteinuria almost to a similar extent as observed with ACE-I. The dihydropyridine calcium channel blockers (DHP) have a variable effect on proteinuria. Pharmaceutical compounds, which inhibit the renin-angiotensin system (RAAS), remain the drugs of first choice in the treatment of hypertension and/or proteinuria in chronic nephropathy. However, a combination of two or more drugs is almost always required to attain sufficient BP reduction. CCB may have an advantage in combination with ACE-I and/or ARB.

The BErgamo NEphrologic DIabetes Complications Trial (BENEDICT): design and baseline characteristics

Microalbuminuria is an early marker of diabetic nephropathy and its prevention is considered key for the primary prevention of diabetic nephropathy. Angiotensin-converting enzyme (ACE) inhibitors and nondihydropyridine calcium channel blockers (CCBs) have specific renoprotective properties in diabetes, and preliminary evidence is available that they are more effective in combination than either of the two agents alone in limiting albuminuria either in micro- or macroalbuminuric type 2 diabetic patients. The BErgamo NEphrologic DIabetes Complications Trial (BENEDICT) is a prospective, randomized, double-blind parallel-group study primarily aimed at evaluating the possibility of preventing the progression to microalbuminuria (urinary albumin excretion [UAE] rate 20-200 microg/min, i.e., incipient nephropathy) in 1209 hypertensive, type 2 diabetic patients with a normal UAE rate (<20 microg/min). During phase A of the study, patients are randomized to a 3-year treatment with one of the following: (1) a nondihydropyridine CCB (verapamil SR 240 mg/day); (2) an ACE inhibitor (trandolapril 2 mg/day); (3) the combination of the above study drugs (verapamil SR 180 mg/day plus trandolapril 2 mg/day); or (4) placebo. Phase B of the study evaluates the progression to macroalbuminuria (UAE> or =200 microg/min) in patients who progress to microalbuminuria in phase A or are found with microalbuminuria during the screening phase; these patients are randomized to a 2-year treatment with either trandolapril (2 mg/day) alone or verapamil SR (180 mg/day) plus trandolapril (2 mg/day). BENEDICT final results are expected to be available by the end of 2003 for phase A and 2 years later for phase B. The BENEDICT study, in addition to exploring whether primary prevention of diabetic nephropathy is an achievable goal, will also offer an opportunity to study prospectively risk factors of nephropathy and other chronic complications of type 2 diabetes. Here we provide an overview of the protocol and summarize the main baseline demographic, biochemical, and clinical characteristics of randomized participants.

Evaluation of the effects of inhibition of angiotensin converting enzyme with enalapril in dogs with induced chronic renal insufficiency

OBJECTIVE

To determine whether the angiotensin converting enzyme inhibitor enalapril would lower systemic arterial and glomerular capillary pressure and reduce the magnitude of renal injury in a canine model of renal insufficiency.

ANIMALS

18 adult dogs that had renal mass reduced by partial nephrectomy.

PROCEDURE

After surgical reduction of renal mass and baseline measurements, dogs in 2 equal groups received either placebo (group 1) or enalapril (0.5 mg/kg, PO, q 12 h; group 2) for 6 months.

RESULTS

Values for systemic mean arterial blood pressure determined by indirect and direct measurement after 3 and 6 months of treatment, respectively, were significantly lower in group 2 than in group 1. During treatment, monthly urine protein-to-creatinine ratios were consistently lower in group 2 than in group 1, although values were significantly different only at 3 months. At 6 months, significant reduction in glomerular capillary pressure in group 2 was detected, compared with group 1, but glomerular filtration rate in group 2 was not compromised. Glomerular hypertrophy, assessed by measurement of planar surface area of glomeruli, was similar in both groups. Glomerular and tubulointerstitial lesions were significantly less in group 2, compared with group 1.

CONCLUSIONS AND CLINICAL RELEVANCE

Data suggest that inhibition of angiotensin converting enzyme was effective in modulating progressive renal injury, which was associated with reduction of glomerular and systemic hypertension and proteinuria but not glomerular hypertrophy. Inhibition of angiotensin converting enzyme may be effective for modulating progression of renal disease in dogs.

Association between initial systolic blood pressure and risk of developing a uremic crisis or of dying in dogs with chronic renal failure

OBJECTIVE

To determine whether high systolic blood pressure (SBP) at the time of initial diagnosis of chronic renal failure in dogs was associated with increased risk of uremic crisis, risk of dying, or rate of decline in renal function.

DESIGN

Prospective cohort study.

ANIMALS

45 dogs with spontaneous chronic renal failure.

PROCEDURE

Dogs were assigned to 1 of 3 groups on the basis of initial SBP (high, intermediate, low); Kaplan-Meier and Cox proportional hazards methods were used to estimate the association between SBP and development of a uremic crisis and death. The reciprocal of serum creatinine concentration was used as an estimate of renal function.

RESULTS

Dogs in the high SBP group were more likely to develop a uremic crisis and to die than were dogs in the other groups, and the risks of developing a uremic crisis and of dying increased significantly as SBP increased. A greater decrease in renal function was observed in dogs in the high SBP group. Retinopathy and hypertensive encephalopathy were detected in 3 of 14 dogs with SBP > or = 180 mm Hg. Systolic blood pressure remained high in 10 of 11 dogs treated with antihypertensive drugs.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that initial high SBP in dogs with chronic renal failure was associated with increased risk of developing a uremic crisis and of dying. Further studies are required to determine whether there is a cause-and-effect relationship between high SBP and progressive renal injury and to identify the risks and benefits of antihypertensive drug treatment.

Autoregulation of glomerular filtration rate in patients with type 2 diabetes during isradipine therapy

OBJECTIVE

Calcium-channel blockade impairs renal autoregulation in animals. Impaired renal autoregulation leads to transmission of the systemic blood pressure (BP) into the glomerulus, resulting in capillary hypertension. Information on the impact of calcium antagonist treatment on renal autoregulation in humans is lacking. This study examines the effect of isradipine treatment on the autoregulation of the glomerular filtration rate (GFR).

RESEARCH DESIGN AND METHODS

We performed a randomized double-blind crossover study with 5 mg o.d. isradipine retard and matching placebo in 16 hypertensive patients with type 2 diabetes. Each treatment arm lasted 4 weeks. On the last day of each treatment period, GFR (single-shot 51Cr-EDTA plasma clearance technique for 4 h) was measured twice between 8:00 A.M. and 5:00 P.M., first without clonidine and then after intravenous injection of 75 micro g clonidine. BP was measured every 10 min (Takeda TM2420; A&D, Tokyo).

RESULTS

Clonidine reduced mean arterial BP (MABP) by 15 +/- 1 vs. 11 +/- 1 mmHg (means +/- SE) during placebo and isradipine treatment, respectively (P < 0.05). GFR was reduced from 102 +/- 4 to 99 +/- 4 ml. min(-1). 1.73 m(-2) with placebo (P < 0.01) and from 106 +/- 5 to 98 +/- 5 ml. min(-1). 1.73 m(-2) during treatment with isradipine (P < 0.01). Mean difference (95% CI) between changes in GFR with placebo and isradipine was -4.6 ml. min(-1). 1.73 m(-2) (-10.0 to 0.6) (P = 0.08). Six patients had a reduction in GFR >13% (exceeding the normal limit of autoregulation) combined with a complete pressure-passive vasculature (defined as DeltaMABP% < or = DeltaGFR%) during isradipine treatment versus none during the placebo treatment (P < 0.05).

CONCLUSIONS

Isradipine impairs GFR autoregulation in a sizeable proportion of hypertensive type 2 diabetic patients.

Role of diltiazem in pregnant women with chronic renal disease

OBJECTIVE

To determine whether diltiazem therapy decreases proteinuria during pregnancy in women with chronic renal disease, resulting in decreased risk of pre-eclampsia, preterm delivery and intrauterine fetal growth restriction.

METHODS

We undertook retrospective data collection by chart review of pregnant women with chronic renal disease. Women treated with and without diltiazem were compared by independent t test analysis.

RESULTS

Seven women were eligible for inclusion in the study. Individual patient trends revealed decreased or attenuated increase in proteinuria across gestation with diltiazem therapy. Mean arterial pressure was also decreased in the therapy group compared to increased pressure in the third trimester in the group with no therapy. The incidence of fetal growth restriction and need for labor induction were lower in the diltiazem-treated group.

CONCLUSIONS

Diltiazem, a non-dihydropyridine calcium channel antagonist, decreases proteinuria and preserves renal structure and function and should be considered an alternative to angiotensin converting enzyme inhibitors in pregnancy in women with chronic renal disease.

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

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

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

OBJECTIVE

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

ANIMALS

20 cats with partial nephrectomy.

PROCEDURE

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

RESULTS

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

CONCLUSIONS AND CLINICAL RELEVANCE

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

Angiotensin converting enzyme inhibitors or angiotensin receptor blockers in nephropathy from type 2 diabetes

Type 2 diabetes is the most common cause of end-stage renal disease in the United States, and type 2 diabetes has been shown to be a myocardial infarction equivalent in regard to risk of death from a cardiovascular event. Proteinuria is a surrogate marker for renal disease progression, and although data favor both the angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) in reducing proteinuria, data for renal outcomes, such as time to dialysis, only exist for the ARBs, which clearly increase the duration to dialysis. Conversely, ACE inhibitors have overwhelming data that show substantial risk reduction from cardiovascular events and death in people with type 2 diabetes. Similar data on cardiovascular risk reduction are not yet available with ARBs, although two trials of renal disease progression did have cardiovascular endpoints as secondary outcomes. There were no significant differences between the ARB and control group except for first hospitalization with heart failure, where losartan reduced the risk by 32%, but there was a trend, albeit not significant, toward reduction of myocardial infarction. The first information regarding ARB effects on cardiovascular events as primary outcomes will come from the Losartan Intervention for Endpoint (LIFE) Reduction in Hypertension study. Therefore, as of this writing, all patients with type 2 diabetes and no evidence of nephropathy, ie, proteinuria and an elevated creatinine > 1.5 mg/dL, should be placed on an ACE inhibitor for cardiovascular risk reduction. If nephropathy is present, the evidence would support an ARB for therapy in concert with a b-blocker for cardiovascular risk reduction and renoprotection.

Effects of the angiotensin converting enzyme inhibitor benazepril in cats with induced renal insufficiency

OBJECTIVE

To determine effects of the angiotensin converting enzyme inhibitor benazepril in cats with induced renal insufficiency.

ANIMALS

32 cats.

PROCEDURE

Renal mass was surgically reduced, and cats were assigned to 1 of 4 eight-cat groups. Group 1 received placebo, whereas groups 2, 3, and 4 received benazepril hydrochloride orally once daily for approximately 6.5 months at the following doses: group 2, 0.25 to 0.50 mg/kg of body weight; group 3, 0.50 to 1.00 mg/kg; and group 4, 1.00 to 2.00 mg/kg. Arterial blood pressures, glomerular filtration rate (GFR), and renal plasma flow were determined before treatment and during the treatment period. Other determinants of renal hemodynamics were measured by use of micropuncture techniques. Renal biopsy specimens were examined microscopically.

RESULTS

Compared with cats that received placebo, mean systolic arterial blood pressure was significantly less and GFR significantly greater in cats that received benazepril. Glomerular capillary pressure and the ratio of efferent to afferent arteriolar vascular resistance were also significantly less in treated cats. However, histologic differences in renal specimens were not detected.

CONCLUSIONS AND CLINICAL RELEVANCE

Treatment with benazepril sustained single nephron GFR in remnant nephrons of cats with induced renal insufficiency. Administration of benazepril was also associated with a small but significant reduction in degree of systemic hypertension and an increase in whole kidney GFR. Benazepril may be an effective treatment to slow the rate of progression of renal failure in cats with renal disease.

Effect of nitrendipine and nisoldipine on renal structure and function in long-term experimental diabetes in rats

This study investigates the efficacy of late intervention with the calcium channel blockers (CCBs) nitrendipine and nisoldipine in preventing development of albuminuria and glomerular hypertrophy in experimental diabetes. Streptozotocin (STZ)-induced diabetic rats were treated with nitrendipine or nisoldipine for 6 weeks after 3 or 6 months of untreated diabetes. The CCBs were administered in the fodder in a concentration of 250 mg/kg. After 3 months of untreated diabetes, nitrendipine treatment for 6 weeks significantly reduced urinary albumin excretion (UAE; P < 0.05) and glomerular hypertrophy. Nitrendipine also prevented an increase in systemic blood pressure compared with untreated diabetes. Nisoldipine showed no significant effect on UAE or glomerular hypertrophy despite systemic blood pressures similar to those of the diabetic nitrendipine-treated group. After 6 months of untreated diabetes, treatment with nitrendipine or nisoldipine for 6 weeks did not show effects on UAE, glomerular hypertrophy, or systemic blood pressure. No effect was found on renal growth in the treatment groups, and neither nitrendipine nor nisoldipine had any effect on body weight, blood glucose level, or food intake.

Influence of the timing of initiating antihypertensive therapy in hypertensive rats with renal failure

The important contribution of hypertension to the progression of renal failure is well realized. However, it have been less discussed which drugs are suitable for the different stages of progressive renal failure. The present study examined the effects of timing of antihypertensive therapy using calcium channel blocker and angiotensin converting enzyme inhibitor in 5/6 nephrectomized spontaneously hypertensive rats (SHRs). Forty male 6 week old SHRs were divided into 5 groups (n=8 in each group), and they were placed on a high salt diet after 5/6 nephrectomy. Group 1, high salt diet without any drug. Group 2 received 0.2 mg/kg/day of amlodipine and group 3 received 0.2 mg/kg/day of enalapril mixed in the high salt diet from week 6 respectively. Similarly group 4 received the same doses of amlodipine, and group 5 received the same doses of enalapril from week 10. Each drug protected from increasing blood pressure in 4 groups, and no significant difference was observed between the effects of amlodipine and enalapril. Proteinuria was reduced with both drugs. In histopathological evaluation, glomerulosclerosis was controlled only in group 2, and arterio/olosclerosis was significantly suppressed in all treated groups except group 5. From these results, both amlodipine and enalapril are renal protective in early stage of renal failure with hypertension. However, in advanced stage of renal failure, amlodipine is superior in its renal protective effect.

Effects of dietary polyunsaturated fatty acid supplementation in early renal insufficiency in dogs

Dietary supplementation with polyunsaturated fatty acids (PUFAs) alters the course of experimental kidney disease in dogs. In particular, supplementation with omega-6 PUFAs hastens the decline of kidney function, and omega-3 PUFAs are renoprotective. We investigated the early stages of renal insufficiency to determine whether PUFA supplementation altered the magnitude of hypercholesterolemia or glomerular hemodynamics. Two months after 11/12 nephrectomy, dogs were randomly divided into three groups of 6 animals each. Each group of dogs was then fed a low-fat basal diet supplemented with one of three sources of lipid to achieve a final concentration of 15% added fat. Fat sources were rich in omega-3 PUFAs (menhaden fish oil, group FO), omega-6 PUFAs (safflower oil, group SO), or saturated fatty acids (beef tallow, group C). Early in renal insufficiency, before significant kidney damage, group FO had a lower (P<.05) serum cholesterol concentration and tended to have a lower urinary prostaglandin E2 (PGE2) and thromboxane A2 (TxA2) excretion than group C. In contrast, group SO had a higher mean glomerular capillary pressure (P<.05) and more glomerular enlargement (P<.05) and tended to have higher eicosanoid excretion rates than group C. These differences in lipid metabolism, glomerular hypertension and hypertrophy, and urinary eicosanoid metabolism could explain, in part, the beneficial effects of omega-3 PUFAs and the detrimental effects of omega-6 PUFAs when administered on a long-term basis in this model of renal insufficiency.

The case for combining angiotensin-converting enzyme inhibitors and calcium-channel blockers

Tight blood pressure control among diabetic and nondiabetic patients with hypertension is perhaps the single most effective intervention used to delay progression to end-stage renal disease (ESRD). The renoprotective actions of angiotensin-converting enzyme (ACE) inhibitors in patients with diabetic and hypertensive nephropathy is well established. Drugs of this class fairly uniformly reduce glomerulosclerosis, delay the deterioration in renal function, and improve proteinuria, a predictive surrogate marker for renal injury. Calcium- channel blockers (CCBs) in the phenylalkylamine (verapamil) and benzothiazepine (diltiazem) classes also improve proteinuria and delay the progression of renal disease in diabetic and nondiabetic hypertensive nephropathy beyond that attributable to blood pressure control. The short-acting dihydropyridine CCBs worsen proteinuria and accelerate renal injury in both animal models and humans with hypertension or diabetes. A very limited number of studies in animals or humans with hypertension or diabetes have demonstrated at least an additive renoprotective effect when the combination of ACE inhibitors and nondihydropyridine CCBs has been compared with each agent administered as monotherapy. Because patients with impaired renal function and either hypertension or diabetes appear to benefit from aggressive blood pressure reduction, many of these patients will require two or more drugs to achieve the currently recommended blood pressure goals. Combinations of ACE inhibitor and CCB are attractive because they may provide better blood pressure control, appear to be better tolerated with fewer side effects than either drug alone, and may exert a greater renoprotective effect in patients at risk for renal failure than either an ACE inhibitor or a CCB.

Effect of the calcium channel blocker nitrendipine in normotensive and spontaneously hypertensive, diabetic rats on kidney morphology and urinary albumin excretion

OBJECTIVE

To investigate the effect of nitrendipine on the development of renal changes in experimental diabetes.

DESIGN

Streptozotocin (STZ)-induced diabetic normotensive Wistar rats (WIS) and spontaneously hypertensive rats (SHR) were randomly allocated to nitrendipine treatment (250 mg/kg fodder) or placebo treatment for 6 months.

METHODS

Blood pressure was assessed by the tail-cuff method, urinary albumin excretion (UAE) was determined, and glomerular basement membrane (GBM) thickness, mesangial volume, and mean glomerular volume (MGV) were estimated by morphometric measurements.

RESULTS

In diabetic WIS, nitrendipine significantly reduced UAE after 2 months of treatment (P< 0.05), while no effect was was seen after 4-6 months. In diabetic SHR, no effect on UAE was seen at any time. Nitrendipine was unable to inhibit the renal and glomerular enlargement in diabetic WIS and SHR. Diabetes plus hypertension was associated with significant increase in GBM thickness, while diabetes or hypertension alone showed no significant increase in GBM. Nitrendipine treatment was unable to prevent increased GBM in diabetic SHR.

CONCLUSION

Nitrendipine inhibits an early increase in UAE in normotensive, diabetic rats, but fails to sustain this effect in long-term diabetes. No effect of nitrendipine was observed in SHR.