Effect of captopril on heavy proteinuria in azotemic diabetics

Angiotensin-converting enzyme inhibitors and type 2 diabetic nephropathy: a meta-analysis

OBJECTIVE

To perform a meta-analysis on studies evaluating the effect of angiotensin-converting enzyme (ACE) inhibitors on diabetic nephropathy in patients with type 2 diabetes mellitus.

METHODS

A computerized literature search was conducted for articles of studies comparing ACE inhibitors with a control in patients with diabetes, in which measurement of albuminuria or proteinuria was an outcome. Each article was abstracted by two of the authors. Data from the articles were presented as geometric or arithmetic means. The data were summarized separately by using standard techniques for meta-analysis.

MAIN RESULTS

Statistically significant reductions in albuminuria were observed regardless of whether data were described with geometric or arithmetic means. Both were associated with significant heterogeneity. When studies reporting geometric means were stratified and analyzed, the heterogeneity was lost and statistically significant reductions in albuminuria were observed. The same procedure was repeated for studies reporting arithmetic means, but heterogeneity remained.

CONCLUSION

The ACE inhibitors produce statistically significant reductions in albuminuria associated with significant heterogeneity of effect. Stratification reduces the heterogeneity and supports treatment with ACE inhibitors to reduce the progression of nephropathy in patients with type 2 diabetes mellitus.

Remission and regression of diabetic nephropathy

Diabetic nephropathy has become the single largest cause of end-stage renal disease (ESRD) worldwide. Until recently, it was thought that once a patient developed overt proteinuria, diabetic nephropathy was irreversible and inevitably progressed to ESRD. However, the reversal of lesions caused by diabetic nephropathy (e.g., glomerular basement membrane thickening and mesangial matrix increase) has been demonstrated in a series of patients who underwent a pancreas transplantation 10 years prior to the reversal. Remission of nephrotic range proteinuria has also been reported in some patients with type 1 diabetes from the Collaborative Study Group during a median follow-up of 3 years of angiotensin-converting enzyme (ACE) inhibitor administration; no deterioration of renal function was observed in these patients. Remission and regression in nephropathy of type 1 diabetes patients have also been reported when blood pressure was controlled aggressively. Recent clinical trials have demonstrated that angiotensin II receptor blocker (ARB) preserved renal function and slowed the progression of nephropathy to ESRD in patients with type 2 diabetes. Since many patients with type 2 diabetes manifest with a metabolic syndrome, multifactorial intensive treatment is necessary; such treatment includes behavior modifications, dietary intervention, exercise, and smoking cessation. In this population, pharmacological therapy targeting hyperglycemia, hypertension (including ARB/ACE inhibitor), and hyperlipidemia in cases of type 2 diabetes is also necessary.

Distinct time courses of renal protective action of angiotensin receptor antagonists and ACE inhibitors in chronic renal disease

Although the angiotensin receptor antagonist (ARB) shares the angiotensin-II-blocking activity with the angiotensin-converting enzyme inhibitor (ACE-I), pharmacological mechanisms of action of these agents differ. We evaluated the temporal profiles of action of ACE-I and ARB on urinary protein excretion and nitrate/nitrate (NO(x)) excretion in hypertensive (140 and/or 90 mmHg) patients with chronic renal disease (serum creatinine < 265 (range, 44-265) micromol/l or creatinine clearance > 30 (range, 30-121) ml/min). Patients with mild (<1 g/day; range, 0.4-1.0) and moderate proteinuria (>1 g/day; range, 1.1-6.9) were randomly assigned to ACE-I- and ARB-treated groups, and were treated with ACE-I (trandolapril or perindopril) or ARB(losartan or candesartan) for 48 weeks. In all groups, treatment with ACE-I or ARB decreased blood pressure to the same level, but had no effect on creatinine clearance. In patients with mild proteinuria, neither ACE-I nor ARB altered urinary protein excretion. In patients with moderate proteinuria, ACE-I caused 44 +/- 6% reduction in proteinuria (from 2.7 +/- 0.5 to 1.5 +/- 0.4 g/day, n = 14) at 12 weeks, and this beneficial effect persisted throughout the protocol (48 weeks, 1.2 +/- 0.2 g/day). In contrast, ARB did not produce a significant decrease in proteinuria at 12 weeks (23 +/- 8%, n = 13), but a 41 +/- 6% reduction in proteinuria was observed at 48 weeks. Similarly, although early (12 weeks) increases in urinary NO(x) excretion were observed with ACE-I (from 257 +/- 70 to 1111 +/- 160 micromol/day) and ARB (from 280 +/- 82 to 723 +/- 86 micromol/day), the ARB-induced increase in NO(x) excretion was smaller than that by ACE-I (P < 0.05). In conclusion, although both ACE-I and ARB reduce blood pressure similarly, the effect of these agents on proteinuria differs in chronic renal disease with moderate proteinuria. Relatively early onset of the proteinuria-reducing effect was observed with ACE-I, which paralleled the increase in urinary NO(x) excretion. Conversely, ARB decreased proteinuria and increased urinary NO(x) excretion gradually. These time course-dependent changes in proteinuria and urinary NO(x) may reflect the pharmacological property of ACE-I and ARB, with regard to the action on bradykinin.

Combination is better than monotherapy with ACE inhibitor or angiotensin receptor antagonist at recommended doses

OBJECTIVE

The combination of an angiotensin-converting enzyme (ACE) inhibitor and an angiotensin II (Ang II) receptor antagonist (ARB) could provide a higher degree of blockade of the renin-angiotensin system(RAS) than either agent alone. The primary aim of this study was to look at the effect of three therapeutic regimens (titrated ACE inhibitor (ACE-I) versus titrated ARB versus the combination of an ACE-I and an ARB) on the attainment of adequate blood pressure (BP) control and antiproteinuric effect. Both ACE-I and ARB were titrated as monotherapy up to the maximal recommended dose.

METHODS

A pilot randomised, parallel group open-label study was conducted in 36 patients with primary renal disease, proteinuria above 1.5 g/day and BP >140/90 mmHg while on therapy with an ACE-I. Patients were randomly assigned to (1) benazepril, n=12; (2) valsartan, n=12; or (3) benazepril plus valsartan, n=12. Other antihypertensive therapies could also be added to attain goal BP (<140/90 mmHg). The primary endpoint was the change in proteinuria during six months of follow-up.

RESULTS

In the presence of similar BP decreases and stable creatinine clearance values, mean proteinuria decreases were 0.5+1.7, 1.2+2.0 and 2.5+1.8 g/day in groups 1, 2 and 3, respectively. When compared with baseline values, only the fall induced by the combination of ARB and ACE-I attained statistical significance (p<0.05).

CONCLUSION

The antiproteinuric capacity of monotherapy at recommended doses with either an ACE-I or an ARB is lower than that obtained with the combination of the two drugs.

Pathophysiology of proteinuria

Proteinuria is consequence of two mechanisms: the abnormal transglomerular passage of proteins due to increased permeability of glomerular capillary wall and their subsequent impaired reabsorption by the epithelial cells of the proximal tubuli. In the various glomerular diseases, the severity of disruption of the structural integrity of the glomerular capillary wall correlates with the area of the glomerular barrier being permeated by "large" pores, permitting the passage in the tubular lumen of high-molecular-weight (HMW) proteins, to which the barrier is normally impermeable. The increased load of such proteins in the tubular lumen leads to the saturation of the reabsorptive mechanism by the tubular cells, and, in the most severe or chronic conditions, to their toxic damage, that favors the increased urinary excretion of all proteins, including low-molecular-weight (LMW) proteins, which are completely reabsorbed in physiologic conditions. Recent clinical studies showed that in patients with glomerular diseases the urinary excretion of some HMW proteins [immunoglobulins G and M (IgG and IgM)] and of some LMW proteins, alpha1-microglobulin, beta2-microglobulin, correlates with the severity of the histologic lesions, and may predict, better than the quantity of proteinuria, the natural course, the outcome, and the response to treatment. It is suggested that some patients have already, at the time of clinical presentation, a structural damage of the glomerular capillary wall (injury of podocytes) and of the tubulointerstitium, the severity and scarce reversibility of which are reliably indicated by an elevated urinary excretion of HMW and LMW proteins.

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

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

Renal damage associated with proteinuria

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

Comorbidity and cardiovascular risk factors in patients with chronic kidney disease

The mortality rate among dialysis patients is high. Although guidelines have been in place to improve outcomes in dialysis patients, new emphasis is being placed on better management of patients who are pre-end-stage renal disease (pre-ESRD)-patients with chronic kidney disease (CKD). Spearheaded by the National Kidney Foundation, the National Institute of Health, and the nephrology community at large, an effort is underway to improve the care of patients with kidney disease. We hope that improvement in health and outcomes of patients with kidney disease will be optimized through attention to care before the development of advanced renal disease. Cardiovascular disease (CVD) is an important comorbidity of chronic kidney disease, and reducing cardiovascular events in this population is an important goal for the people who care for chronic kidney disease patients. In this article, we review the available literature regarding certain risk factors for cardiovascular disease: proteinuria, hyperglycemia, hypertension, homocysteine, hyperlipidemia, and inflammation. When possible, recommendations for treatment are provided based on the information reviewed.

ACEI/ATRA therapy decreases proteinuria by improving glomerular permselectivity in IgA nephritis

BACKGROUND

It has been postulated that angiotensin-converting enzyme inhibitor/angiotensin receptor antagonist (ACEI/ATRA) may decrease proteinuria in patients with glomerulonephritis by its action on the glomerular basement membrane. We therefore studied the relationship between the response of patients with IgA nephritis (IgAN) to ACEI/ATRA therapy by decreasing proteinuria and its effect on the selectivity index (SI) in these patients.

METHODS

Forty-one patients with biopsy-proven IgAN entered a control trial, with 21 in the treatment group and 20 in the control group. The entry criteria included proteinuria of 1 g or more and/or renal impairment. Patients in the treatment group received ACEI/ATRA or both with three monthly increases in dosage. In the control group, hypertension was treated with atenolol, hydrallazine, or methyldopa. The following tests were performed at three monthly intervals: serum creatinine, total urinary protein, SI, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and low molecular weight (LMW) proteinuria.

RESULTS

After a mean duration of therapy of 13 +/- 5 months, in the treatment group, there was no significant change in serum creatinine, proteinuria, or SI, but in the control group, serum creatinine deteriorated from 1.8 +/- 0.8 to 2.3 +/- 1.1 mg/dL (P < 0.05). Among the 21 patients in the treatment group, 10 responded to ACEI/ATRA therapy determined as a decrease in proteinuria by 30% (responders), and the other 11 did not respond (nonresponders). Among the responders, SI improved from a mean of 0.26 +/- 0.07 to 0.18 +/- 0. 07 (P < 0.001), indicating a tendency toward selective proteinuria. This was associated with an improvement in serum creatinine from mean 1.7 +/- 0.6 to 1.5 +/- 0.6 mg/dL (P < 0.02) and a decrease in proteinuria from a mean of 2.3 +/- 1.1 to 0.7 +/- 0.5 g/day (P < 0. 001). After treatment, proteinuria in the treatment group (1.8 +/- 1. 6 g/day) was significantly less than in the control group (2.9 +/- 1. 8 g/day, P < 0.05). The post-treatment SI in the responder group (0. 18 +/- 0.07) was better than that of the nonresponder group (0.33 +/- 0.11, P < 0.002). Eight out of 21 patients in the treatment group who had documented renal impairment had improved renal function compared with two in the control group (chi2 = 4.4, P < 0. 05). Of the eight patients in the treatment group who improved their renal function, three normalized their renal function compared with one from the control group.

CONCLUSION

Our data suggest that ACEI/ATRA therapy may be beneficial in patients with IgAN with renal impairment and nonselective proteinuria, as such patients may respond to therapy with improvement in protein selectivity, decrease in proteinuria, and improvement in renal function. ACEI/ATRA therapy probably modifies pore size distribution by reducing the radius of large unselective pores, causing the shunt pathway to become less pronounced, resulting in less leakage of protein into the urine.

Impact of angiotensin II on the kidney: does an angiotensin II receptor blocker make sense?

The renin-angiotensin system (RAS) regulates blood pressure, volume, and electrolyte balance. Derangements of the RAS may contribute to hypertension and renal injury, particularly in patients with types 1 or 2 diabetes. Angiotensin-converting enzyme (ACE) inhibitors have been proven to be beneficial in patients with hypertension and diabetes by preventing or delaying the development and progression of proteinuria and glomerulosclerosis. Comparisons with other drug classes demonstrate renoprotective effects for ACE inhibitors that are independent of-and additive to-their systemic antihypertensive actions. These renal effects may derive from their preferential dilation of renal efferent arterioles, which further reduces intraglomerular pressure. Inhibition of angiotensin II (Ang II) synthesis is subtotal, however, because local non-ACE enzymes also convert Ang I to Ang II. The existence of alternative pathways for Ang II generation that are unaffected by ACE inhibitors raises questions about whether ACE is the optimal target for RAS suppression. Ang II receptor blockers (ARBs), which interrupt the RAS at the target-organ receptor level, will block the effect of angiotensin whether its production involved ACE or a non-ACE pathway. ARBs are currently undergoing clinical trials to assess their efficacy in hypertensive patients with nephropathy.

Pharmacologic Regulation of the Renin—Angiotensin System: Physiologic and Pathologic Effects

Objective:

To review the physiologic and pathologic roles of the renin-angiotensin system in maintaining blood pressure, glomerular filtration rate, and myocardial tissue growth. The pharmacologic regulations of the pathologic effects of the renin-angiotensin system are emphasized, with a comparison between angiotensin-converting enzyme (ACE) inhibitors and angiotensin1receptor (AT1) antagonists.

Data Sources:

English-language basic science, clinical studies, and review articles were identified using MEDLINE, IOWA, and a manual search from January 1966 through September 1999. References were also obtained from the reference section of relevant published articles.

Study Selection and Data Extraction:

All articles identified were evaluated for possible inclusion in this review. Evaluative and comparative data from basic science and controlled clinical studies were reviewed.

Data Synthesis:

The renin-angiotensin system has a plethora of physiologic and pathologic roles in the regulation of blood pressure, renal function, and cell growth. The cellular mechanisms involved in eliciting the responses to the renin-angiotensin system are discussed in detail, with an emphasis on the pharmacologic regulation of the cellular responses. The role of angiotensin II in maintaining blood pressure, glomerular filtration rate, and in regulating myocardial cell growth secondary to myocardial infarction or as a complication of congestive heart failure are all reviewed. The ACE inhibitors and AT1antagonists have comparable pharmacologic effects that can influence their therapeutic application. The ACE inhibitors and AT, antagonists are compared regarding clinically and experimentally observed differences that may affect their therapeutic application.

Conclusions:

The physiologic and pathologic roles of the renin-angiotensin system make the ACE inhibitors and AT1antagonists ideal candidates in treating many conditions. Presently, few studies have been conducted that directly compare ACE inhibitors and AT, antagonists. An understanding of the basic underlying pharmacologic principles is essential when attempting to apply the scientific and clinical information of the ACE inhibitors and AT1antagonists with the intention of extrapolating to therapeutic utility.

Short-term effect of captopril on microalbuminuria in children with glycogen storage disease type Ia

Early signs of renal dysfunction in glycogen storage disease type Ia (GSD Ia) are glomerular hyperfiltration and proteinuria. In a non-randomized study, the effect of captopril on the improvement of proteinuria in GSD Ia patients with microalbuminuria was investigated. A positive effect has been shown for the insulin-dependent diabetes mellitus patients. Microalbuminuria was defined as albumin/creatinine ratio (mg/mmol) more than 2.5 in spot urine. Nineteen (52.7%) out of 36 patients had microalbuminuria, and 8 patients received captopril at a dose of 1 mg/kg per day. Microalbuminuria was evaluated periodically during the follow-up period. Of the captopril-treated patients, one was lost to follow-up. In the remaining 7 patients, urinary albumin excretion normalized in 3 patients (42.9%) and decreased at least by 50% in another 3 patients (42.8%) after 6 months of treatment. One patient, who was the oldest, did not have any benefit. In untreated patients, only two patients had a decrease in microalbuminuria of more than 50%. Patients with microalbuminuria had significantly higher blood lactate (p < 0.05) and plasma triglyceride (p < 0.01) concentrations and significantly lower blood bicarbonate concentration (p < 0.05) than those patients without it. Additionally, the patients with microalbuminuria had been diagnosed earlier than those without microalbuminuria (p < 0.05). Patients with microalbuminuria have more severe clinical and laboratory findings than those without microalbuminuria. Captopril at a dose of 1 mg/kg per day seems to be effective in at least 50% of GSD Ia patients with microalbuminuria.

Antihypertensive drugs and diabetic nephropathy

Diabetic nephropathy is the most common cause of end-stage renal disease in the United States. Hypertension is a major risk factor that predisposes individuals with diabetes to the development of renal disease and is very common in patients with diabetes. The benefit of blood pressure control on the rate of progression of diabetic nephropathy is being increasingly demonstrated in both type 1 and type 2 diabetic patients. Angiotensin converting enzyme inhibitors have proven renoprotective benefits in human studies, but the results of studies with calcium channel blockers are somewhat inconclusive. The other classes of antihypertensives also may have certain indications in the population of patients with diabetic nephropathy. In this paper we will critically review current strategies for the treatment of hypertension in patients with established diabetic nephropathy.

Effects of antihypertensive therapy on progression of diabetic nephropathy

There is a clear relationship between hypertension and the microvascular complications of diabetes. Genetic predisposition to hypertension has been correlated to the risk of diabetic nephropathy in type I diabetes, and hypertension is a well known risk factor for developing nephropathy in patients with type II diabetes. Multiple studies have emphasized the importance of hypertension on renal disease progression, and blood pressure control with conventional antihypertensive drugs slows the rate of renal function loss in diabetic nephropathy. Furthermore, evidence of the role of renin-angiotensin system (RAS) on progression of renal damage has focused much interest on the therapeutic action of the RAS blockade. In patients with type I diabetes, blocking the RAS with angiotensin converting enzyme (ACE) inhibitors prevents progression from microalbuminuria to overt nephropathy, and in overt nephropathy decreases the gradual loss of renal function beyond its blood pressure lowering effect. Less clinical information is available in type II diabetic nephropathy, but our experience and some recent studies suggest that ACE inhibitors also have a renoprotective action in type II diabetes. The role of calcium channel blockers in diabetic nephropathy is not clear. Several short-term studies with the first generation dihydropyridine calcium antagonists showed a lower effect on urinary albumin excretion and a more rapid progression to renal failure than with ACE inhibitors. However, other calcium channel blockers, particularly of the non-dihydropyridine type, have been shown to have a beneficial effect on diabetic nephropathy, decreasing proteinuria and slowing progression.

Nephropathy and hypertension in diabetes

The treatment of the patient with diabetes, with or without hypertension, is complex and challenging. Hyperglycemic treatment should ideally not only control blood glucose, but also prevent the chronic complications and associated metabolic derangements that can lead to increased morbidity and mortality. Hypertensive treatment should not only decrease blood pressure, but also reduce the risk of macrovascular and microvascular disease. The use of antihypertensive agents that improve insulin resistance, dyslipidemia, glycemic control, and nephropathy is preferred whenever possible. The real key to success in the care of the hypertensive diabetic patient is adequate screening and appropriate, early treatment. Currently, there is ample evidence to support the use of intensive management with the goal of near-normalization of blood glucose levels in most patients with diabetes. Similarly, aggressive treatment of hypertension is the current standard. Accomplishing these goals helps to prevent the development of chronic diabetic complications, including nephropathy. ESRD need not be the inevitable outcome for individuals with early diabetic nephropathy. Interventions currently available that are targeted at the known modifiable risk factors underlying the development and progression of diabetic nephropathy offer the best hope for reducing the incidence and severity of this complication. Prevention of the complications of diabetes, including nephropathy, must be the goal for the future on behalf of all those who now have diabetes.

Is captopril-induced improvement of insulin sensitivity mediated via endothelin?

Angiotensin-converting enzyme (ACE) inhibitors have been reported to improve insulin sensitivity during either short-term or long-term administration. Recent studies indicate that endothelin-1 (ET-1) has potent glycogenolytic effects in rat hepatocytes and may cause insulin resistance in rat adipocytes. In addition, ET may also have a role in stimulation of the hypothalamic-pituitary-adrenal axis. To test the hypothesis that part of the effect of captopril in enhancing insulin sensitivity may be mediated via ET and/or by glucocorticoids, we measured 24-h urinary excretion of ET and free cortisol before and after short-term treatment with captopril. The 24-h urinary immunoreactive endothelin (IR-ET) excretion decreased significantly (p < 0.05) from 65 +/- 4 ng at baseline to 42 +/- 3 ng after captopril treatment, whereas no significant change in the 24-h urinary free cortisol excretion was observed. Moreover, no significant change in the 24-h urinary IR-ET and free cortisol excretions was noted in the placebo-treated group. We speculate that ACE inhibitors may exert their effect on insulin sensitivity not only by blocking the renin-angiotensin and kinin systems but also by inhibiting production and/or release of ET.

Interactions of transforming growth factor-beta and angiotensin II in renal fibrosis

Overproduction of transforming growth factor-beta clearly underlies tissue fibrosis in numerous experimental and human diseases. Transforming growth factor-beta's powerful fibrogenic action results from simultaneous stimulation of matrix protein synthesis, inhibition of matrix degradation, and enhanced integrin expression that facilitates matrix assembly. In animals, overexpression of transforming growth factor-beta by intravenous injection, transient gene transfer, or transgene insertion has shown that the kidney is highly susceptible to rapid fibrosis. The same seems true in human disease, where excessive transforming growth factor-beta has been demonstrated in glomerulonephritis, diabetic nephropathy, and hypertensive glomerular injury. A possible explanation for the kidney's particular susceptibility to fibrosis may be the recent discovery of biologically complex interactions between the renin-angiotensin system and transforming growth factor-beta. Alterations in glomerular hemodynamics can activate both the renin-angiotensin system and transforming growth factor-beta. Components of the renin-angiotensin system act to further stimulate production of transforming growth factor-beta and plasminogen activator inhibitor leading to rapid matrix accumulation. In volume depletion, transforming growth factor-beta is released from juxtaglomerular cells and may act synergistically with angiotensin II to accentuate vasoconstriction and acute renal failure. Interaction of the renin-angiotensin system and transforming growth factor-beta has important clinical implications. The protective effect of inhibition of the renin-angiotensin system in experimental and human kidney diseases correlates closely with the suppression of transforming growth factor-beta production. This suggests that transforming growth factor-beta, in addition to blood pressure, should be a therapeutic target. Higher doses or different combinations of drugs that block the renin-angiotensin system or entirely new drug strategies may be needed to achieve a greater antifibrotic effect.

Low dose angiotensin converting enzyme inhibition and glomerular permselectivity in renal transplant recipients

In this study, we determined the fractional clearance of neutral polydisperse dextrans (theta D) and monodisperse dextran sulfate (theta DS) to describe glomerular size and charge selectivity in 25 renal transplant recipients with proteinuria. Thirteen were treated with low dose lisinopril for six months (group 1) and 12 patients without ACE inhibitor therapy formed group 2. Mean arterial blood pressure was stable (group 1, 112 +/- 4; group 2, 109 +/- 2 mm Hg at baseline and after 6 months) whereas creatinine clearance, glomerular filtration rate and renal plasma flow decreased nonsignificantly but were comparable at any time. Lisinopril treatment lowered filtration fraction (22 +/- 2 vs. 19 +/- 2%, P = 0.07) whereas no change was seen in group 2 (20 +/- 2%). The fractional protein excretion (mg urinary protein per day/ml creatinine clearance per day) was stable in group 1, but significantly increased in group 2. The same pattern was found for theta D larger than 56 A. theta DS was stable and consistently elevated in both groups at any time. We conclude that low dose ACE inhibitor treatment in proteinuric renal transplant recipients stabilizes glomerular size selectivity independently of its systemic hemodynamic effects.

Effects of quinapril hydrochloride in patients with essential hypertension and impaired renal function

The short-term effects of administration of an angiotensin-converting enzyme (ACE) inhibitor, quinapril hydrochloride (quinapril) (5-10 mg/day), for 12 weeks on blood pressure and renal function were evaluated in 8 patients (60.5 +/- 7.3 years old, mean +/- SD) with mild to moderate essential hypertension and mild impairment of renal function due to nephrosclerosis. Systolic blood pressure and diastolic blood pressure were significantly reduced from 163.0 +/- 4.0 to 132.3 +/- 17.6 mmHg (p < 0.01) and from 98.3 +/- 4.6 to 81.5 +/- 6.4 mmHg (p < 0.001), respectively, before to after treatment. Both renal plasma flow (RPF) and glomerular filtration rate (GFR) were significantly increased in all patients, from 203.9 +/- 33.3 to 245.4 +/- 36.7 ml/min/1.73 m2 (p < 0.01), and from 43.4 +/- 6.4 to 53.5 +/- 4.6 ml/min/1.73 m2 (p < 0.05), respectively. Short-term quinapril administration was beneficial to renal function in patients with essential hypertension and impaired renal function.

Prevention and slowing down the progression of the diabetic nephropathy through antihypertensive therapy

Diabetic nephropathy is the major cause of illness and premature death in people with diabetes, largely through accompanying cardiovascular disease and end-stage renal failure. Diabetic patients are several times as prone to kidney disease as nondiabetic people and the accumulative risk of diabetic nephropathy in insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM) is about 30%-50% after 25 years of disease. Diabetic nephropathy is a progressive disease that takes several years to develop, ending in chronic renal insufficiency. Proteinuria heralds the onset of diabetic nephropathy, and the worsening of proteinuria parallels the progression of renal disease. The main risk factors for the frequency, severity, and progression of diabetic nephropathy are the degree of hyperglycemia and associated metabolic disturbances, hypertension, protein overload, cigarette smoking, as well as the duration of diabetes. Interventional strategies for primary, secondary, and tertiary prevention of diabetic nephropathy therefore include meticulous glycemic control, appropriate treatment of associated lipid abnormalities, rigorous control of the blood pressure, reduction in dietary protein intake, in particular animal protein, and of fat intake, and stopping cigarette smoking. Randomized clinical trials indicate that antihypertensive therapy is beneficial in preventing and slowing down the progression of diabetic nephropathy. There is now increasing evidence that angiotensin-converting enzyme inhibitors and certain calcium antagonists produce a more beneficial effect on diabetic nephropathy in terms of reducing proteinuria and slowing the progression to diabetic renal failure. These drugs are attributed nephroprotective capacity beyond their blood pressure lowering capacity and initial clinical trials with combinations have revealed even additive protective effects on end organs.

Can we further slow down the progression to end-stage renal disease in diabetic hypertensive patients?

HYPERTENSION AND DIABETES

Hypertension occurs about twice as frequently in diabetics compared with the general population, with a prevalence of approximately 25% in young patients with insulin-dependent diabetes mellitus (IDDM) and 50% in newly diagnosed non-IDDM (NIDDM) patients. Studies strongly suggest that hypertensions is involved in the progression and perhaps the onset of diabetic nephropathy, which is a major cause of illness and premature death in diabetic patients, largely through accompanying cardiovascular disease and end-stage renal failure.

TREATMENT

A large body of evidence has accumulated which emphasizes the beneficial effects of antihypertensive treatment in reducing proteinuria and preserving renal function in both IDDM and NIDDM. It appears that angiotensin converting enzyme inhibitors and certain calcium antagonists, notably the non-dihydropyridine type and second-generation dihydropyridine calcium antagonists, produce a more beneficial effect on nephropathy in terms of reducing proteinuria and slowing progression in renal failure. These drugs have displayed a nephroprotective capacity beyond their systemic blood pressure-lowering effects, and initial clinical trials with combinations of different antihypertensive drug classes have revealed additive effects in reducing albuminuria together with the lowest rate of decline in glomerular filtration rates with the lowest incidence of adverse effects.

AVAILABLE STUDIES

The studies available on antihypertensive treatment in IDDM and NIDDM patients with incipient or overt diabetic nephropathy are mainly prospective. There have also been some preliminary trials with antihypertensive combinations in diabetic patients.

ACE inhibitors and proteinuria

This review discusses the clinical consequences of urinary protein loss and the effects of inhibitors of the angiotensin converting enzyme (ACE) on this clinical finding. Proteinuria appears to be an important risk factor for renal function deterioration and for cardiovascular mortality. ACE inhibitors have been shown to reduce proteinuria more effectively than other antihypertensives. Their antiproteinuric effect seems to be independent of the underlying renal disease, and is mediated by a specific, not yet fully elucidated mechanism. Urinary protein loss related phenomena, such as hypoalbuminemia and aberrant lipoprotein profile, tend to improve also during ACE inhibitor treatment. Furthermore, ACE inhibition has been shown to prevent the renal function deterioration that is frequently observed in patients with renal disease. Interestingly, it has recently been shown that in proteinuric patients with renal disease the initial proteinuria lowering response to ACE inhibition predicts long-term renal function outcome during this treatment the more proteinuna is lowered during the first months, the better renal function will be preserved over the following years. Because of these favorable effects ACE inhibitors have become a widely used class of agents in nephrology. They are not only prescribed for lowering blood pressure in the hypertensive renal patient, but also as symptomatic treatment of patients with proteinuria, and to prevent renal function loss in patients with both diabetic and non-diabetic renal disease.

Proteinuria and albumin homeostasis in the nephrotic syndrome: effect of dietary protein intake

Nephrotic syndrome is analyzed in the light of interventions designed to decrease proteinuria and renal injury. The effect of dietary protein intake on urinary protein losses and albumin homeostasis are discussed on the basis of the pathophysiologic mechanisms known to account for changes in renal function of nephrotic patients. In addition, the effect of angiotensin-converting enzyme inhibitors for reduction of proteinuria is discussed in terms of the modulation of glomerular permselectivity and hemodynamics.

Effect of 2,3-dimercaptosuccinic acid on nephrosclerosis in the Dahl rat. I. Role of reactive oxygen species

2,3-Dimercaptosuccinic acid (DMSA), a sulfhydryl-containing chelator, has previously been shown to reduce mean blood pressure in lead-treated rats. In the present study we have demonstrated that DMSA (0.5% for 5 days every 2 weeks) also reduces mean blood pressure in the Dahl salt-sensitive (SS) rat. Six-week-old Dahl SS and salt resistant (SR) rats were placed on a 0.3% NaCl diet for two weeks, followed by an 8% NaCl diet for four weeks. Eight SS and 8 SR rats remained untreated while 8 SS and 8 SR rats were treated with DMSA. DMSA treatment ameliorated the mean blood pressure rise in the Dahl SS rats (141 +/- 5 vs. 120 +/- 4 mm Hg at 6 weeks, P < 0.001). Nephrosclerosis was severe in untreated SS rats but absent in treated SS rats as well as in both treated and untreated SR rats. Reactive oxygen species formation, as assessed by kidney cortex content of malondialdehyde (MDA) and immunohistochemical demonstration of nitrotyrosine (a byproduct of peroxynitrite) in interlobular arteries, was increased in Dahl SS rats, but abolished by DMSA (MDA 9.65 +/- 0.33 nmol/g wet wt, untreated SS, vs. 6.46 +/- 0.51, treated SS, P < 0.001). The anti-nephrosclerotic action of DMSA was clearly disproportionate to the reduction in blood pressure. We conclude that the effect of DMSA was related instead to the reactive oxygen species scavenging properties of the thiol groups.

The changing course of diabetic nephropathy: low-density lipoprotein cholesterol and blood pressure correlate with regression of proteinuria

Diabetic nephropathy (DN) as manifested by persistent and clinically evident proteinuria, has long been considered an irreversible process that predicts a rapid decline in renal function. The observation of reversal of DN in several individuals enrolled in a prospective study of the natural course of diabetes complications challenged this view and led to the current investigation into the correlates of such regression of proteinuria. DN was defined as a median albumin excretion rate (AER) over 200 microg/min in two or three urine collections obtained at baseline, and again at 2 and 4 years of follow-up. Among 658 individuals with childhood-onset insulin-dependent diabetes mellitus (IDDM), 146 had DN at baseline. Nine subsequently died without renal failure, and 13 were lost to follow-up. Of the 124 subjects with at least survey follow-up data, 32 (24%) developed renal failure, and 78 of the remaining 92 provided full quantitative data. AER decreased by > or = 10-fold into the microalbuminuric (20 to 200 microg/min) or normal range (<20 microg/min) in 7 of these individuals and are called "regressors of proteinuria." Compared with the remaining 71 subjects, the strongest correlate of regression of proteinuria was an improvement in fasting plasma low-density lipoprotein cholesterol (LDL-C) in the 7 regressors (P < 0.008). Improved glycemic control was not a significant predictor of improved AER. Five of the 7 individuals with improved AER had a baseline median AER below 500 microg/min. When the 7 regressors of proteinuria were combined with an additional 38 individuals who also experienced smaller decreases in median AER, such improvement was associated with a more favorable systolic (or diastolic) blood pressure (BP) change (P < 0.01), and a decrease in plasma LDL-C level (P = 0.01). These data suggest that proteinuria in DN may substantially regress in approximately 6% and improve in at least 34% of individuals with IDDM over a 4-year period, often in association with a decrease in plasma LDL-C concentration or stabilization or improvement in BP. Furthermore, the data suggest that the nonreversibility threshold for diabetic nephropathy may be higher (500 mg/min) than previously reported (200 microg/min).

Hypertension in diabetes mellitus

Hypertension should be detected and treated early in diabetic patients. It has a marked contribution to the morbidity and mortality of diabetic individuals due to both atherosclerosis and microvascular disease. Antihypertensive treatment is an effective tool in slowing the progression of early and advanced diabetic nephropathy. Prospective studies addressing the effects of antihypertensive regimens on the incidence of CHF, stroke, and coronary artery disease in the diabetic population are not available. We assume that the beneficial effects of therapy apply to both diabetic and nondiabetic subjects. Glycemic control and the lipid profile are major concerns when selecting an antihypertensive drug. Because hyperinsulinemia and insulin resistance have been advocated as hypertensive and atherosclerotic risk factors, the effects of antihypertensive drugs on insulin action and plasma insulin levels may also become an important element in the selection of an antihypertensive agent. ACE inhibitors, calcium channel blockers, and alpha-adrenergic blockers probably offer the most favorable metabolic profile when compared with diuretics and beta-blockers and should be used as the initial drugs in most clinical settings.

Prevention and Treatment of Diabetic Nephropathy: Role of Angiotensin-Converting Enzyme Inhibitors

OBJECTIVE

To discuss the role of angiotensin-converting enzyme inhibitors in the management of diabetes-related renal disease.

METHODS

We review the published data from animal studies and clinical trials and outline the adverse effects that may limit the use of these drugs.

RESULTS

Diabetic nephropathy is the most common cause of end-stage renal disease and dialysis in the United States. With improving measures to optimize blood glucose control and blood pressure, the progression from mild proteinuria to overt renal insufficiency can now be retarded or even arrested. Studies of therapeutic interventions have shown that angiotensin-converting enzyme inhibitors have a superior beneficial effect on nephropathy. Few adverse effects are associated with use of these drugs: a nonproductive cough is the most frequent side effect, and angioedema and agranulocytosis are the most serious (albeit rarely reported) effects.

CONCLUSION

Angiotensin-converting enzyme inhibitors should be considered as first-line therapy for patients with diabetes who have microalbuminuria or macroalbuminuria.

Decrease of exercise-induced microalbuminuria in patients with type I diabetes by means of an angiotensin-converting enzyme inhibitor

Taking into account both the importance of microalbuminuria (MA) as a predictive parameter of clinical nephropathy in diabetic patients and the efficiency of exertion to show and/or to increase MA in both diabetic patients and normal individuals, we studied 37 type I diabetic patients divided into two groups: group A, with no MA at rest (n = 19), and group B, with MA at rest (n = 18). Group C comprised 10 healthy volunteers as controls. Changes of basal MA during exercise and postexercise were studied in all three groups. Normotensive patients with no metabolic disorders, normal renal function, and no proteinuria underwent an ergometric test up to 600 kg. This test was repeated after the administration of 20 mg enalapril in a single daily dose for 60 days. Body weight, systolic and diastolic arterial pressure, creatinine, and creatinine clearance were determined and showed no significant variations either between groups or with treatment. Microalbuminuria was studied in the three groups with and without administration of enalapril throughout the 2 months of the study. Determinations were performed under conditions of rest, exercise, and postexercise. Mean baseline MA values +/- SEM were as follows: at rest, 5.22 +/- 0.49, 58.36 +/- 13.24, and 4.73 +/- 0.45 micrograms/min for groups A, B, and C, respectively; with exercise, 15.19 +/- 4.43, 74.70 +/- 14.89, and 16.76 +/- 4.62 micrograms/min for groups A, B, and C, respectively; and postexercise, 32.04 +/- 6.64, 253.15 +/- 63.88, and 9.23 +/- 3.25 micrograms/min, respectively. The geometric means of the baseline to posttreatment MA ratio were as follows: at rest, 0.95, 1.59 (P < 0.01), and 1.03 for groups A, B, and C, respectively; with exercise, 1.53 (P < 0.01), 1.91 (P < 0.01), and 1.69 for groups A, B, and C, respectively; and postexercise, 2.94 (P < 0.01), 3.24 (P < 0.01), and 1.03 for groups A, B, and C, respectively. In conclusion, in the early diagnostic suspicion of diabetic nephropathy, the screening of postexercise MA during an ergometric test could be of help. Treatment with enalapril decreased MA in diabetic groups A (no MA at rest) and B (MA at rest) during exercise and postexercise, and also decreased MA in group B while at rest.

Diabetic renal disease: the quest for normotension--and beyond

Over the past two decades there has been an increasing interest in hypertension as a risk factor for diabetic renal disease and in particular for the possibility of early antihypertensive intervention. Therefore, it would seem timely to review the history of hypertension in diabetes, with special reference to renal disease and the need for normotension, in a manner resembling glycaemic control. Elevated blood pressure (BP) associated with diabetes mellitus has been recognized since the beginning of the century and was initially particularly documented in association with the demonstration of the striking histological lesion in glomeruli, starting with the observation of Kimmelstiel and Wilson in 1936. These patients in many cases also showed hypertension, as confirmed in several subsequent reports, very similar to the studies of Kimmelstiel and Wilson. However, the development was hampered by the lack of effective antihypertensive agents and also by some who believed that elevated BP could be of importance to preserve renal function in these individuals. Indeed, it was suggested that reduction of BP could mean permanent deterioration in renal function. BP remained very high in the standard care of diabetic patients up to the middle 1970s. At this time it was documented that elevated BP was very closely related to development of diabetic renal disease in Type 1 (insulin-dependent) diabetic (IDDM) patients, and studies also showed a correlation between blood pressure and rate of progression. This correlation stimulated research in intervention, and indeed in the 1980s and 1990s several long-term studies reported that antihypertensive treatment can reduce the rate of decline in glomerular filtration rate (GFR) from about 12 ml min-1 yr-1 down to about 2 ml min-1 yr-1 in the most optimistic reports; usually a mean level of 2-5 ml min-1 yr-1 is achievable by antihypertensive treatment, in clinical situations where glycaemic control often is far from perfect. Many studies have also documented that BP starts to rise in the early phase of incipient diabetic nephropathy characterized by microalbuminuria. This is a stage with well-preserved GFR and therefore probably an ideal stage for intervention in these at risk patients. Many studies, in particular those employing angiotensin converting enzyme (ACE) inhibitors based on important pathophysiological concepts proposed by Brenner, have shown that microalbuminuria can be reduced or stabilized by early antihypertensive treatment, just as we see with optimized glycaemic control. ACE inhibitors have also been widely used in patients with overt nephropathy and the rate of decline in GFR has been reduced considerably.(ABSTRACT TRUNCATED AT 400 WORDS)

Glomerular permselectivity in proteinuric patients after kidney transplantation

To characterize the defect in glomerular permselectivity responsible for proteinuria after renal transplantation, we studied 10 patients with moderate proteinuria (median 0.37 g/d, range 0.20-0.79), 16 patients with the nephrotic syndrome (6.73 g/d, 3.9-14.6), 8 living related donor transplant recipients without any history of rejection (median proteinuria 0.26 g/d, 0.06-0.58), and 12 healthy volunteers. The fractional clearance of neutral dextrans > 54 A was significantly higher in nephrotic patients, demonstrating a defect in glomerular size selectivity. Using a log-normal model of glomerular pore size distribution, r*(5%) and r*(1%), indices for the presence of large pores, were increased in the nephrotic patients. The fractional clearance of negatively charged dextran sulfate was significantly higher in all patient groups, indicating a loss of glomerular charge selectivity. Biopsy findings showed more prominent glomerular lesions in the nephrotic group compared with the moderately proteinuric group. We conclude that mild proteinuria late after renal transplantation is associated with a defect in glomerular charge selectivity. The development of nephrotic range proteinuria is associated also with a defect of glomerular size selectivity, which correlates with prominent glomerular pathology.

Effects of fosinopril on exercise tolerance and clinical deterioration in patients with chronic congestive heart failure not taking digitalis. Fosinopril Heart Failure Study Group

A total of 241 men and women with mild to moderately severe chronic heart failure (New York Heart Association functional class II [90%] or III) and a mean (+/- SD) left ventricular ejection fraction of 25 +/- 7%, entered a 24-week, prospective, double-blind, placebo-controlled trial of 10 or 20 mg/day of fosinopril, a phosphinic acid angiotensin-converting enzyme inhibitor. Patients received concomitant diuretic therapy but not digitalis. Primary end points were mean change in maximal treadmill exercise time and occurrence of prospectively defined clinical events indicative of worsening heart failure (most to least severe): death, withdrawal for worsening heart failure, hospitalization for worsening heart failure, need for supplemental diuretic or emergency room visit for worsening heart failure, and no event. At study end point, treadmill exercise time had improved in the fosinopril versus the placebo group (+28.4 vs -13.5 seconds, p = 0.047). New York Heart Association functional class had improved at end point more frequently (24% vs 13%) and deteriorated less frequently (18% vs 32%) in the fosinopril group (p = 0.003). More patients treated with fosinopril (66% vs 50%) remained free of clinical events indicative of worsening heart failure, and fosinopril-treated patients had less severe clinical events (p = 0.004). Dyspnea, fatigue, and paroxysmal nocturnal dyspnea improved more often and worsened less often in this group (p < or = 0.002), and edema showed a trend toward improvement (p = 0.088). These clinical benefits did not require concomitant digitalis therapy. Fosinopril was associated with an acceptable safety profile.

The pattern of diabetic nephropathy among Saudi patients with noninsulin-dependent diabetes mellitus

There were no studies on the different stages of diabetic nephropathy in Saudi Arabia, particularly the earliest stages. We have therefore investigated the frequency of occurrence of varying degrees of proteinuria including microalbuminuria in noninsulin-dependent diabetes mellitus (NIDDM) Saudi patients as well as the correlation of varying degrees of proteinuria with other diabetic complications and risk factors. One hundred and twenty-five NIDDM patients were studied. Fifty-seven were males and 68 were females. Their mean age was 49.8 +/- 10 years with a mean duration of diabetes of 9.48 +/- 6 years. The mean of HbA1c was 10.3 +/- 2.6%, serum creatinine was 76.7 +/- 23 mmol/L, creatinine clearance 94.3 mL/min, glomerular filtration rate 129.7 +/- 44 and effective renal plasma flow was 496.5 +/- 153. The pattern of proteinuria group was as follows: nephrotic range proteinuria 5.6%, clinical proteinuria 30.4%, microalbuminuria 16.8%. Hypertension and retinopathy were present in 36.8% and 37% of the patients respectively. A significant correlation was found between the presence of hypertension, duration of diabetes and development of diabetic nephropathy. Similarly, a significant correlation was found between retinopathy and the degree of proteinuria. In conclusion, the pattern of diabetic nephropathy in the Saudi NIDDM patients is similar to that in the Western world. Hypertension and duration of diabetes mellitus are important risk factors in the development of diabetic nephropathy. There is a good correlation between retinopathy and the degree of proteinuria.

Intraoperative hemodynamic, renin, and catecholamine responses after prophylactic and intraoperative administration of intravenous enalaprilat

This study was designed to evaluate effects of enalaprilat, an angiotensin-converting enzyme inhibitor, on hemodynamic and hormonal responses during surgery at endotracheal intubation, incision, and limb-tourniquet inflation. Thirty patients undergoing limb procedures with general anesthesia (N2O/narcotic technique) and a pneumatic tourniquet were randomized to receive either preoperative enalaprilat (1.25 mg intravenously [i.v.] 20 min prior to induction) or intraoperative enalaprilat (0.625 mg i.v. at the onset of tourniquet-associated hypertension), with appropriate placebo controls. Arterial blood pressure and heart rate increased significantly in response to intubation in the placebo group. Although there were no significant differences in catecholamine levels, plasma renin activity was significantly increased at postincision in the preoperative-enalaprilat group versus the placebo group. This suggests that activation of the renin-angiotensin system may play a key role in mediation of intraoperative hemodynamic responses to endotracheal intubation. With respect to tourniquet hypertension, preoperative or intraoperative treatment with enalaprilat reduced neither the pressor response to tourniquet inflation nor the amount of enflurane subsequently required to control arterial blood pressure. These findings suggest that this response is mediated by pain pathways, and may be treated more effectively with anesthesia/analgesia.

Successful treatment of Finnish congenital nephrotic syndrome with captopril and indomethacin

Two infants with biopsy-proven microcystic Finnish congenital nephrotic syndrome (onset at birth) were treated with a combination of captopril and indomethacin for 2 1/2 and 2 years, respectively; they had a marked reduction of urinary protein excretion without further need for albumin infusions. One infant has end-stage renal disease; the other infant's glomerular filtration rate has remained within normal limits.

Selected aspects of ACE inhibitor therapy for patients with renal disease: impact on proteinuria, lipids and potassium

Overt proteinuria is often accompanied by hypercholesterolemia and is associated with increased lipoprotein(a) levels. These lipid abnormalities are probably involved in the high incidence of macrovascular complications associated with diabetic nephropathy and possibly other kinds of non-diabetic proteinuric renal disease. Over the last decade many studies have shown that ACE inhibitors can reduce urinary protein excretion but little attention was paid to the impact of this form of therapeutic intervention on the lipid profile. In this article we review our recent data showing that fosinopril administration was associated with significant decreases in both urinary protein excretion, serum total cholesterol levels, and plasma lp(a) levels. The use of ACE inhibitors in patients with renal impairment can result in the development of hyperkalemia as a result of suppression of angiotensin II-driven aldosterone secretion by the adrenal gland. Inhibition of aldosterone secretion may depend on the degree of inhibition of angiotensin II formation in the circulation and also locally in the adrenal gland. Because the various ACE inhibitors exhibit different degrees of ACE inhibition at the tissue level, we have postulated that angiotensin II-dependent aldosterone production will be inhibited to a lesser degree by agents that have low tissue affinity for the adrenal gland. The implication of this theoretical concept for the development of hyperkalemia in patients with impaired renal function treated with ACE inhibitors is discussed.

Angiotensin II in cell growth and matrix production

Glomerular mesangial cells and cardiac fibroblasts have been called "myofibroblasts" because of their phenotypic characteristics (resembling both the fibroblast and muscle cells). Thus, it is not surprising that AII would have similar effects on both cell types, which play critical roles in target organ stress response and wound healing, ultimately leading to remodeling changes. These effects are primarily mediated by the AT1 receptor and include: 1) growth: hyperplasia in cardiac fibroblasts and hypertrophy in normal adult mesangial cells and 2) matrix production: there appears to be an early upregulation of fibronectin message which is later followed by an increase in collagens. It is likely that elevated production of fibronectin may activate signal transduction pathways which lead to increased expression of collagen genes, and which may be critical for the organization and laying down of collagens. Thus, an overall theme that emerges is the impact of AII on both growth and wound repair. Other potential important cellular effects of AII in these systems include: 1) stimulation of growth factors, cytokines, and arachidonic acid products that could have autocrine or paracrine effects, 2) regulation of cell migration and adhesion, 3) alteration of responses to neurohormones, 4) development and maintenance of a differentiated phenotype, and others. Molecular techniques including subtraction hybridization, differential display, antisense knockout, and development of transgenic and embryonic stem cell models will be important in defining the specific role of AII in cardiovascular and renal disease.

Efficacy of captopril treatment in children with steroid-resistant nephrotic syndrome

We studied the efficacy of captopril, an angiotensin-converting enzyme inhibitor in treating persistent moderate or severe proteinuria in children with various glomerular diseases other than minimal-change nephrotic syndrome. Captopril was administered for 3 months to 15 normotensive and nonazotemic or mildly azotemic patients (12 boys, 3 girls) in whom corticosteroid and cytotoxic treatment had failed to induce remission. Urinary protein excretion decreased from 2873.14 +/- 1937.50 (mean +/- s.e.m.) to 1684.71 +/- 1463.13 mg/day (P < 0.05). The reduction in proteinuria was not related to a significant fall in systemic blood pressure or a change in renal function. Serum albumin did not rise and side effects due to captopril were not observed. We concluded that, in the short term, captopril can be used safely and effectively for decreasing the proteinuria of nephrotic children unresponsive to conventional therapy.

Therapeutic progress. III: Diabetic nephropathy

Diabetic nephropathy is a common cause of end stage renal failure. Patients ultimately require dialysis or transplantation and endure a poor quality of life in association with increased mortality. Due to the quantitative significance of this problem there is also a considerable financial burden. It has been generally accepted that once nephropathy is established it is irreversible although aggressive anti-hypertensive treatment can delay its progression. More recently there have been numerous reports proposing a specific renal protective role of certain drugs. In this article we review the current literature on the use of angiotensin converting enzyme inhibitors in diabetic nephropathy. There is strong evidence that the use of ACE inhibitors in diabetic nephropathy (in the presence or absence of hypertension) slows the progression of deterioration in renal function and may even arrest its progression if detected at the microproteinuric stage.