Comparative effects of antihypertensives on proteinuria: angiotensin-converting enzyme inhibitor versus alpha 1-antagonist

Understanding the complement-mediated glomerular diseases: focus on membranoproliferative glomerulonephritis and C3 glomerulopathies

An enhanced understanding of the role of complement in the pathogenesis of membranoproliferative glomerulonephritis has led to reclassification of the latter into immunoglobulin-mediated and non-immunoglobulin-mediated disease. The new classification schema resulted in improved diagnostic clinical algorithms, while it brought into light again the diseases, which are characterized by the presence of glomerular deposits, composed predominantly by C3, in the absence of significant amounts of immunoglobulins in renal biopsy, namely, C3 glomerulopathies (dense deposit disease and C3 glomerulonephritis). Despite the lack of randomized controlled trials following the advances in the understanding of the pathogenetic pathways involved in membranoproliferative glomerulonephritis, it is important that the new mechanistic approach has opened new roads for the exploration and discovery of targeted therapies.

The Combination of ACE Inhibition plus Sympathetic Denervation Is Superior to ACE Inhibitor Monotherapy in the Rat Renal Ablation Model

BACKGROUND

The blood pressure-independent renoprotective actions of the blockade of the renin-angiotensin and the sympathetic nervous system are well documented, but monotherapies fail to completely abrogate progression. We investigated whether combined inhibition of the two systems provides additive renoprotection.

METHODS

After subtotal nephrectomy (SNX) or sham operation, rats underwent resection of dorsal roots, i.e. rhizotomy or sham rhizotomy. Subsequently, they received tap water or quinapril in drinking water for 16 weeks (n = 18/group). Albuminuria, blood pressure and kidneys were assessed (morphometry, immunohistochemistry).

RESULTS

At the end of the study telemetric blood pressure in SNX was 118 +/- 16 mm Hg, in SNX + rhizotomy 110 +/- 10 mm Hg, in SNX + quinapril 103 +/- 9 mm Hg and in SNX + quinapril + rhizotomy 95 +/- 7 mm Hg. Albuminuria in the respective groups was 169 +/- 75, 86 +/- 45, 15 +/- 23 and 5 +/- 4 mg/24 h. The glomerulosclerosis index was 1.40 +/- 0.6, 0.80 +/- 0.23, 0.37 +/- 0.16 and 0.31 +/- 0.15 (p < 0.001). Only combined intervention caused significant reduction of the glomerular volume and podocyte hypertrophy. The lowest indices for nitrotyrosine, NOS-1 (nNOS), TGF-beta and interstitial collagen were seen with combined interventions (p < 0.05).

CONCLUSION

In angiotensin-converting enzyme inhibitor-treated SNX animals, abrogation of sympathetic overactivity provides additional renoprotection and less nitro-oxidative stress of podocytes than single interventions. The added benefits were partially blood pressure independent.

Renal and cardiovascular considerations for the nonpharmacological and pharmacological therapies of obesity-hypertension

Obesity-associated hypertension is a common disease that involves a complex pathogenesis. Failure to control hypertension (HTN) in obese subjects provides a great threat to their renal and cardiovascular functions. The treatment of obesity-associated HTN is often difficult, and requires nonpharmacological and/or pharmacological approaches. Weight reduction is the cornerstone of the therapies of obesity-HTN, as it reverses the multiple components of its pathogenesis. When weight loss cannot be sustained or fails, pharmacological means should then be used. Angiotensin-converting enzyme inhibitors (ACEI) are the drug of choice: they can reduce blood pressure, protect the kidney and heart, and improve the metabolic abnormalities in obese subjects. Angiotensin-2 type-1 receptor blockers have a renoprotective benefit similar to ACEI, and they provide an important alternative to the use of ACEI. Diuretics are very effective in African-American obese hypertensives, but small doses should be used to avoid adverse effects on metabolic profiles. Long-acting calcium channel blockers are also effective and have the advantage of no adverse metabolic effects. Nondihydropyridine calcium channel blockers may provide additional renal and cardiovascular protective effects. The beta-adrenergic receptor blockers can cause further weight gain and metabolic abnormalities in obese subjects; therefore, careful monitoring is needed. There are few clinical data that support the efficacy and benefit of centrally acting alpha-2 agonists and alpha-adrenergic receptor antagonists in the treatment of obesity-HTN.

Nephroprotective effect of antihypertensive drugs in essential hypertension

BACKGROUND

Effective antihypertensive treatment has prevented target-organ involvement in hypertension, markedly reducing morbidity and mortality from strokes, coronary heart disease, cardiac failure, and hypertensive emergencies. However, the incidence of hypertension-related end-stage renal disease continues to increase, suggesting that therapeutic reduction in arterial pressure by itself is not sufficient to prevent the development of hypertensive renal failure.

OBJECTIVE

To examine experimental and clinical data concerning the protective effect of reduction of arterial pressure on the progression of hypertension-related renal disease, and the evidence indicating that some antihypertensive agents may afford more nephroprotection, over and above that attributable to reduction of arterial pressure.

RESULTS

Results of numerous studies clearly indicate that adequate control of arterial pressure, irrespective of the antihypertensive agent used, slowed the progression of renal disease. Results of some studies suggest that lowering arterial pressure below the level that is usually considered adequate has an additional beneficial effect by slowing the progression of renal injury.

CONCLUSION

Results of a number of studies evaluating nephroprotective effects of various drugs and regimens have indicated that certain agents, most notably angiotensin converting enzyme inhibitors and their combination with calcium antagonists, afford more protection than do others at similar levels of reduction of arterial pressure. Results of still other studies suggest that certain agents that exert greater nephroprotection are more efficient at controlling arterial pressure. Therefore, further data are needed before any final conclusion can be drawn. However, it is clear that, in order to establish nephroprotection in patients with essential hypertension, the problem should not be further complicated by additional comorbid diseases such as diabetes mellitus.

Renal artery stenosis and unilateral focal and segmental glomerulosclerosis

Focal and segmental sclerosed lesions in the glomeruli are found in several pathological entities and more often are found in the corticomedullary junction where renal blood flow and filtration pressure is maximal. Experimental data suggest that hyperfiltration injury results in focal and segmental glomerulosclerosis (FSGS). In keeping with this concept, malignant hypertension is a known cause of nephrotic-range proteinuria and nephrotic syndrome pathalobically represented by FSGS. We report a case of unilateral renal artery stenosis associated with nephrotic syndrome and FSGS in the contralateral kidney only. The kidney with the stenosed renal artery showed normal glomeruli with juxtaglomerular hyperplasia, suggesting that protection from hyperfiltration injury was provided by the presence of high-grade stenosis. Serum creatinine concentration, blood pressure, and proteinuria normalized after aorto-renal bypass surgery. This case shows the importance of hemodynamic factors on the pathogenesis of secondary FSGS and the progression of renal disease.

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.

Contrasting effects of angiotensin converting inhibitor and alpha-1-antagonist on albuminuria in insulin-dependent diabetes mellitus patients with nephropathy

OBJECTIVE

The main aim of this study was to examine the effects of an angiotensin converting inhibitor, enalapril, and an alpha-1 (alpha-1) antagonist, doxazosin, on albumin excretion, renal haemodynamics and tubular function in insulin-dependent diabetes mellitus patients with nephropathy.

DESIGN

The study consisted of a four-week run-in period, a four-week active treatment period, a four-week wash-out period and a second four-week active treatment period.

SETTING

The study was performed in the out-patient clinic at a university hospital.

SUBJECTS

Ten patients with insulin dependent diabetes mellitus with macroalbuminuria (> 200 micrograms min-1), mild to moderate hypertension (diastolic blood pressure 85-115 mmHg) and serum creatinine level below 200 mumol L-1 were included in the study.

MAIN OUTCOME MEASURES

The effect of the drugs on albumin and total protein excretion, beta-2-microglobulin, proximal tubular enzyme markers and renal haemodynamics.

RESULTS

Systolic and diastolic blood pressure were equally reduced by both drugs. Enalapril reduced albumin excretion from 1090 +/- 281 micrograms min-1 to 742 +/- 246 micrograms min-1 (P < 0.01) and total protein excretion from 2.0 +/- 0.4 g per 24 h to 1.3 +/- 0.4 per 24 h whereas doxazosin was without effect. Glomerular filtration rate and effective renal plasma flow were unchanged by either drug. Doxazosin increased filtration fraction from 0.21 +/- 0.02 to 0.23 +/- 0.01 (P < 0.05). The urinary excretion of the proximal enzyme markers N-acetyl-beta-glucosaminidase and alkaline phosphatase were elevated as well as urinary excretion of beta-2-microglobulin. However, neither the excretion of beta-2-microglobulin nor the enzyme markers were affected by either drug.

CONCLUSIONS

Enalapril, but not doxazosin, reduces albuminuria in insulin dependent diabetes mellitus patients with nephropathy. The drugs exert differential effects on renal haemodynamics.

Low-protein diets and angiotensin-converting enzyme inhibition in progressive renal failure

Both protein restriction and administration of angiotensin-converting enzyme (ACE) inhibitors have been reported to slow the progression of chronic renal failure. Protein intake conditions the activity of the renin-angiotensin system and the renal production and excretion in the urine of eicosanoids. Both dietary protein restriction and ACE inhibitors decrease proteinuria. The effects of ACE inhibitors on the progression of renal disease may be due to hemodynamic effects (lowering of systemic or intraglomerular pressures) or to decreased activity of growth factors as a result of blockade or angiotensin II production.

Comparison between carvedilol and captopril in rats with partial ablation-induced chronic renal failure

1. The effect of the novel beta-adrenoceptor antagonist and vasodilator, carvedilol (SK&F 105517, approximately 70 mg kg-1 daily in the food), and captopril (approximately 38 mg kg-1 daily in the drinking fluid) on the progression of chronic renal failure in rats was studied. 2. Six weeks following partial renal ablation, the urinary protein excretion of the carvediol- (60 +/- 21 mg day-1) and captopril-treated (35 +/- 9 mg day-1) animals was less than 50% that of control rats (133 +/- 27 mg d-1). 3. Serum creatinine (Scr) and urea nitrogen (SUN) concentrations of the carvedilol-(Scr, 0.63 +/- 0.09 mg dl-1; SUN, 11.3 +/- 1.2 mg dl-1) and captopril-treated (Scr, 0.82 +/- 0.05 mg dl-1; SUN, 14.1 +/- 1.5 mg dl-1) animals were also significantly (P < 0.05) lower than that observed in control animals (Scr, 1.4 +/- 0.3 mg dl-1; SUN, 19.2 +/- 3.9 mg dl-1), indicating that glomerular filtration rate was improved by both drugs. Plasma renin activity was significantly (P < 0.05) higher in captopril-treated rats (24.7 +/- 4.6 ng angiotensin I ml-1 h-1) than in either carvedilol-treated (7.9 +/- 1.4 ng angiotensin I ml-1 h-1) or control animals (7.4 +/- 1.0 ng angiotensin I ml-1 h-1). 4. Histological examination of the kidneys demonstrated a significantly reduced glomerular hypertrophy and glomerulosclerosis in those animals receiving carvedilol or captopril compared to controls. 5. Serum carvedilol concentration measured every 6 h for 24 h was variable and ranged on average from 57 +/- 13 ng ml-1 at 16 h 00 min to 121 +/- 31 ng ml-1 at 03 h 00 min. These data indicate that the rats probably had 24 h systemic exposure to carvedilol.6. The present study indicates that carvedilol is effective in attenuating the progression of chronic renal failure in rats.

Hemodynamic alterations and urinary albumin excretion in patients with essential hypertension

Salt-sensitive animals as well as patients with essential hypertension appear to have a greater propensity to develop renal disease as a consequence of hypertension. They also manifest an abnormal renal hemodynamic adaptation to changes in dietary sodium intake and blood pressure. This suggests that the two may be related. Some patients with essential hypertension manifest an increase in urinary albumin excretion (UAE). It is uncertain whether this is more common in salt-sensitive patients and whether it represents a marker for progressive renal disease. The effect of antihypertensive agents on UAE varies substantially depending on the agent used, and it is not necessarily related to the antihypertensive action. Whether antihypertensive agents that more effectively reduce UAE may also result in greater renal protective effects remains to be established.