Renal hemodynamics and reduction of proteinuria by a vasodilating beta blocker versus an ACE inhibitor

ACE insertion/deletion polymorphism and diabetic nephropathy: clinical implications of genetic information

Approximately 20-40% of diabetic patients develop nephropathy which is the leading cause of ESRD in developed countries. The ACE I/D polymorphism is thought to be a marker for functional polymorphism which regulates circulating and tissue ACE activity. While the initial study found a protective effect of the II genotype on the development of nephropathy in IDDM patients, subsequent studies have addressed the role of ACE I/D polymorphism in the development and progression of diabetic nephropathy. RAAS blockers are the first line drugs for the treatment hypertension associated with diabetes and have been widely used in everyday clinical practice for the purpose of reducing proteinuria in patients with various renal diseases. However, the antiproteinuric effect of RAAS blockers is variable and the percentage of reducing proteinuria is in the range of 20-80%. The antiproteinuric effect of RAAS blockers may be related to a number of factors: the type or the dose of RAAS blockers, the duration of therapy, the level of sodium intake, and the type of patient's ACE I/D genotype. Besides the nongenetic factors, drug responses, can be influenced by ACE gene polymorphism. In this review, we discuss the relationship between ACE I/D polymorphism and diabetic nephropathy and therapeutic response of RAAS blockers.

Effect of zelandopam, a dopamine D1-like receptor agonist, in puromycin aminonucleoside nephrosis rats

The present experiment was designed to investigate the role of peripheral dopamine D1-like receptors and to evaluate the prophylactic effect of zelandopam, a dopamine D1-like receptor agonist, on puromycin aminonucleoside (PA)-induced nephrosis in rats. Rats were divided into six groups (n=10 per group): 0.9% saline-injected rats (control); PA-injected rats (PAN); PA-injected rats treated with the selective dopamine D1-like receptor agonist zelandopam (30, 100, 300 mg/kg p.o. twice a day); PA-injected rats treated with prednisolone (1 mg/kg p.o. once a day). Nephrosis was induced in rats with a single intravenous injection of PA at a dose of 50 mg/kg. The effects of zelandopam and prednisolone in PA nephrosis rats were evaluated before injection of PA and at 7 and 14 days after injection. PA-induced nephrosis was characterized by an increase in urinary protein excretion (proteinuria) and plasma total cholesterol. Zelandopam dose-dependently attenuated the increase in proteinuria and total cholesterol. Prednisolone significantly attenuated the increase in proteinuria and total cholesterol and resulted in a significant decrease in body weight. The present study demonstrates for the first time that zelandopam, a selective dopamine D1-like receptor agonist, is effective in blunting the development of PA-induced nephrosis, and that the effects of zelandopam are dose dependent.

ACE DD genotype is more susceptible than ACE II and ID genotypes to the antiproteinuric effect of ACE inhibitors in patients with proteinuric non-insulin-dependent diabetes mellitus

BACKGROUND

ACE polymorphism, especially genotype DD or D allele, may be involved in the progression of diabetic nephropathy. It may also have different effects on the reduction of proteinuria by ACE inhibitors in patients with proteinuria. We investigated the relationship between ACE gene polymorphism and antiproteinuric effect of ACE inhibitors (Benazepril 10 mg/day or Perindopril 4 mg/day) in 83 NIDDM patients with overt proteinuria (urinary protein excretion over 500 mg/day).

METHODS

We recruited NIDDM patients with overt proteinuria from our renal clinic. Before entry, previously used ACE inhibitors were withdrawn for at least 2 weeks and baseline proteinuria and albuminuria were measured. Patients were classified into three groups in accordance with ACE genotypes (17 DD; 33 ID; 33 II) and prospectively followed up for 3 months. Various clinical parameters including age, DM duration, body mass index (BMI), 24-h urine sodium, protein and albumin, BUN, serum creatinine, creatinine clearance (Ccr), mean arterial pressure (MAP), and HbA(1c) were measured in the pre- and post-treatment periods. ACE genotypes were determined by polymerase chain reaction.

RESULTS

There were no significant differences in the clinical parameters such as age, DM duration, BMI, BUN, serum creatinine, Ccr, MAP, HbA(1c), and daily urinary excretion of sodium, protein and albumin among three groups (P>0.05). After the 3-month treatment period using ACE inhibitors, there were no significant differences in the reduction of MAP and Ccr among the three groups (P>0.05). However, the percentage reductions in urinary excretion of protein and albumin for DD genotype were significantly higher than in ID and II genotypes (50.9+/-19.2% vs 19.2+/-16.0%, 20.2+/-20.4%; 52.6+/-23.6% vs. 13.5+/-51.8%, 24.8+/-23.9%, P<0.05). There were no statistically significant correlations between the levels of baseline proteinuria and albuminuria and the magnitudes of the reduction of proteinuria and albuminuria under ACE inhibition (P>0.05).

CONCLUSIONS

Our results suggest that the ACE gene polymorphism might have a role in determining the responsiveness to the antiproteinuric effect of ACE inhibition in proteinuric NIDDM patients.

Angiotensin-converting enzyme in non-neoplastic kidney diseases

BACKGROUND

The angiotensin I-converting enzyme (ACE, CD143, kininase II) plays a critical role in controlling the level of vasoactive peptides such as angiotensins and kinins in the local circulations and tissue interstitium. Because recent work has documented a vessel-, organ-, and species-specific pattern of endothelial ACE expression in the vascular system, we have analyzed whether or not changes of this pattern occur in vessels, tubules, and interstitium of the human kidney that is affected by different non-neoplastic diseases.

METHODS

Using a set of well-characterized monoclonal antibodies (mAbs), ACE was assessed on renal tissue of 135 patients by immunohistochemistry, including an additional analysis at the ultrastructural level. A semiquantitative evaluation allowed the estimation and comparison of ACE content in different renal compartments. These data were compared with several clinical findings, diagnosis, therapeutic modalities, and histological features.

RESULTS

In contrast to the normal human kidney, where ACE is abundant in the brush border of the proximal tubule but is usually absent in endothelial cells of any vessel type, an endothelial neoexpression of ACE was observed in different diseases. In general, this neoexpression was associated with histological sites of interstitial fibrosis and showed some selectivity for glomerular endothelial cells in diabetes mellitus and chronic arterial hypertension. There was also a loss of epithelial ACE in the proximal tubule in certain pathological conditions, for example, in chronic fibroplastic processes, acute pyelonephritis, and different stages of acute renal failure.

CONCLUSIONS

Neoexpression of ACE by renal endothelial cells, as well as changes of the tubular ACE content, is a common finding in diseased human kidneys. As associated with certain tissue sites, clinical and/or morphological features, these changes may be involved in parenchymal remodeling and renal pathophysiology.

Efficacy and tolerability of tasosartan, a novel angiotensin II receptor blocker: results from a 10-week, double-blind, placebo-controlled, dose-titration study. Tasosartan Investigators Group

BACKGROUND

Angiotensin II receptor antagonists are selective blockers of the renin-angiotensin system and represent an alternative to angiotensin-converting enzyme inhibitors in the treatment of hypertension. Tasosartan is a newly developed nonpeptide AT1 receptor blocker.

METHODS AND RESULTS

In this double-blind, randomized, dose-titration, multicenter trial, tasosartan and placebo were compared in patients with stage I and stage II hypertension. A prequalification washout period (antihypertensive medications withdrawn) and a 2-week qualification period (patients received single-blind placebo) preceded a 10-week, double-blind treatment period. The patients received either 50 mg tasosartan (n = 132) or placebo (n = 130) once per day and were evaluated once per week. The dose of tasosartan was increased at 3-week intervals to 100 mg and then to 200 mg if the mean sitting diastolic blood pressure (SiDBP) exceeded 90 mm Hg. Compared with placebo, tasosartan produced significantly (P <.05) greater reductions in both SiDBP (-9.4 +/- 0.7 vs -2.0 +/- 0.7 mm Hg) and sitting systolic blood pressure (SBP) (-12.2 +/- 1.2 vs +0.4 +/- 1.2 mm Hg). The rate of response (SiDBP </=90 mm Hg or a decrease from baseline of >/=10 mm Hg) was significantly (P <.05) greater in the tasosartan group than in the placebo group (55% vs 19%). The mean 24-hour blood pressure reduction with tasosartan was -12.6 +/- 0. 9/-8.1 +/- 0.6, significantly greater (P <.05) than the reduction with placebo (+0.6 +/- 0.9/+0.5 +/- 0.6 mm Hg). The trough-to-peak ratio (determined from the ambulatory data) was 0.66 for DBP and 0. 72 for SBP for the tasosartan treatment group, demonstrating 24-hour efficacy with once-a-day administration. The safety profile of tasosartan was similar to placebo.

CONCLUSIONS

These results demonstrate that tasosartan at 50 to 200 mg given once a day over a titration period of 10 weeks was effective and safe in the treatment of essential hypertension.

Therapeutic implications and new perspectives for essential hypertension and renal damage

The kidney can suffer the consequences of a persistently elevated blood pressure. In fact end-stage renal failure caused by essential hypertension appears to be one of the most prevalent etiologies in patients entering a dialysis program. Blood pressure control is needed in order to prevent the progressive loss of renal function. Target blood pressure control has been established at values as low as 125/75 mm Hg for patients with proteinuria above 1 g/day. Attainment of this target level usually requires the combination of two or more drugs. However, the possibility that differences exist among the different classes of antihypertensive drugs beyond their capacity to simply lower blood pressure remains to be clearly elucidated. The fact that the presence of chronic renal failure is also accompanied by an enhanced cardiovascular risk potentiates the need to explore the renoprotective and cardiovascular protective capacity of the different classes of antihypertensive drugs, in patients with essential hypertension and some degree of renal involvement, characterized by the presence of microalbuminuria, proteinuria and/or an elevated serum creatinine.

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.

Achievement and safety of a low blood pressure goal in chronic renal disease. The Modification of Diet in Renal Disease Study Group

The Modification of Diet in Renal Disease Study showed a beneficial effect of a lower-than-usual blood pressure (BP) goal on the progression of renal disease in patients with proteinuria. The purpose of the present analyses was to examine the achieved BP, baseline characteristics that helped or hindered achievement of the BP goals, and safety of the BP interventions. Five hundred eighty-five patients with baseline glomerular filtration rate between 13 and 55 mL/min per 1.73 m2 (0.22 to 0.92 mL/s per 1.73 m2) were randomly assigned to either a usual or low BP goal (mean arterial pressure < or = 107 or < or = 92 mm Hg, respectively). Few patients had a history of cardiovascular disease. All antihypertensive agents were permitted, but angiotensin-converting enzyme inhibitors (with or without diuretics) followed by calcium channel blockers were preferred. The mean (+/- SD) of the mean arterial pressures during follow-up in the low and usual BP groups was 93.0 +/- 7.3 and 97.7 +/- 7.7 mm Hg, respectively. Follow-up BP was significantly higher in subgroups of patients with preexisting hypertension, baseline mean arterial pressure > 92 mm Hg, a diagnosis of polycystic kidney disease or glomerular diseases, baseline urinary protein excretion > 1 g/d, age > or = 61 years, and black race. The frequency of medication changes and incidence of symptoms of low BP were greater in the low BP group, but there were no significant differences between BP groups in stop points, hospitalizations, or death. When data from both groups were combined, each 1-mm Hg increase in follow-up systolic BP was associated with a 1.35-times greater risk of hospitalization for cardiovascular or cerebrovascular disease. Lower BP than usually recommended for the prevention of cardiovascular disease is achievable by several medication regimens without serious adverse effects in patients with chronic renal disease without cardiovascular disease. For patients with urinary protein excretion > 1 g/d, target BP should be a mean arterial pressure of < or = 92 mm Hg, equivalent to 125/75 mm Hg.

Effect of ramipril on blood pressure and protein excretion rate in normotensive nondiabetic patients with proteinuria

Angiotensin-converting enzyme inhibitors reduce proteinuria in both normotensive and hypertensive patients with proteinuric renal disease. However, the mechanism of the antiproteinuric effect has not been clarified. We performed a prospective, double-blind, placebo-controlled, randomized crossover trial to test the hypothesis that the antiproteinuric effect of ramipril was due to an improvement in glomerular permselectivity independent of blood pressure and glomerular filtration rate. The effect of low-dose (1.25 mg/d) and high-dose (5 mg/d) ramipril was assessed in 15 normotensive nondiabetic patients with proteinuria (> 150 mg/d). The study was divided into four 12-week periods: placebo, high- or low-dose ramipril, crossover to low- or high-dose ramipril, and placebo. Blood pressure, glomerular filtration rate, renal plasma flow rate, urinary protein excretion rate, and plasma angiotensin II levels were measured at the end of each period. Mean arterial pressure, urine protein to creatinine ratio, and albumin excretion rate decreased significantly during low- and high-dose ramipril. Glomerular filtration rate and renal plasma flow rate were not changed significantly. Plasma angiotensin II levels decreased with both low- and high-dose ramipril. There were no episodes of hypotension and only one subject developed cough during ramipril that did not require discontinuation of the study drug. In conclusion, administration of ramipril in both low and high doses lowered blood pressure and reduced proteinuria in this cohort of normotensive patients with a variety of proteinuric renal diseases. The antiproteinuric effect of ramipril is probably mediated by a reduction in glomerular capillary pressure.

Possible effect of angiotensin-converting enzyme inhibition on glomerular charge selectivity

Angiotensin-converting enzyme (ACE) inhibitors are known to reduce urinary albumin excretion (UAE) in diabetic patients. Animal studies have shown that, besides diminishing the glomerular capillary pressure, ACE inhibitors might reduce albuminuria by influencing glomerular charge selectivity through glomerular preservation of heparan sulphate proteoglycan. In humans, an indirect measurement of glomerular charge selectivity can be obtained by calculating the glomerular charge selectivity index (SI), a clearance ratio of IgG/IgG4, two identically sized but differently charged molecules. The aim of the present study was to evaluate the effect of ACE inhibition on charge selectivity by comparing SI in type I (insulin-dependent) diabetic patients with microalbuminuria after 6 years of treatment either with or without captopril. Thirty-five of 45 patients participating in a prospective randomized study evaluating the effect of captopril in preventing the development of diabetic nephropathy were included in the present study, 17 being treated with captopril, 18 left as untreated controls. The selectivity index was calculated after measuring s-IgG, u-IgG, s-IgG4, and u-IgG4. The results demonstrated a higher selectivity index in the captopril-treated group [1.21 (0.51-1.94) median (range)] compared to the control group [0.94 (0.31-1.87)], however, the difference was not statistically significant (p = 0.16). A negative correlation between the selectivity index and UAE was demonstrated in the captopril-treated group (r = -0.77; p = 0.0004), whereas the correlation in the control group did not reach statistical significance (r = -0.3; p = 0.2).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of intensive treatment on diabetic nephropathy in patients with type I diabetes

We evaluated the long-term effect of an intensive treatment of diabetic nephropathy (anti-hypertensive drugs, low protein diet, multiple insulin injections to achieve a good metabolic control) on glomerular filtration rate (GFR) and albumin excretion rate (AER). Fourteen type I diabetic patients (mean age 45 +/- 9.5 years, mean duration of diabetes 23.5 +/- 7.3 years, 8 males/6 females) with glomerular filtration rate < 70 ml/min-1/1.73 m2 and albumin excretion rate > 30 micrograms/min were treated intensively for 36 months. This intensive treatment consisted of multiple insulin injections, antihypertensive therapy with ACE inhibitors and a low-protein diet (0.8 g/kg body wt/day.) Renal function was evaluated as GFR and AER. HbA1c mean value decreased significantly from 8.7 +/- 0.8% to 6.5 +/- 0.5% (P < 0.0002). GFR rose from 58 +/- 12 ml/min-1/1.73 m2 to 84 +/- 11 ml/min-1/1.73 m2 (P < 0.0008). AER decreased from 208 micrograms/min (range: 73 to 500) to 63.8 micrograms/min (range 15 to 180; P < 0.05). Systolic and diastolic blood pressure decreased respectively from 144 +/- 26 mm Hg to 120 +/- 15 mm Hg and from 89 +/- 9 mm Hg to 75 +/- 8 mm Hg (P < 0.01). We obtained a rise of GFR and a reduction of proteinuria after three years of this treatment. We suggest that this intensive treatment in all patients with early stage diabetic nephropathy may be effective in slowing the progression to renal failure.

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.

Hypertension in diabetic patients: an update of interventional studies to preserve renal function

Hypertension and diabetes mellitus are a malignant combination of diseases for the kidney. They markedly increase the risk for progressive renal injury and are the largest single cause of renal failure. Strategies to reduce the risk for renal injury in hypertensive diabetics are very important. Although Type I and Type II diabetes are different diseases, they may be associated with similar mechanisms of renal injury in hypertensive patients. Reduction of elevated systemic arterial pressure is of proven benefit in limiting progressive renal injury in diabetic hypertensives. However, converting enzyme inhibitors and possibly the nondihydropyridine calcium antagonists may possess antiproteinuric abilities independent of blood pressure reduction which, in addition to their antihypertensive effects, may be important in limiting the progression of human diabetic renal disease. Long-term clinical trials have evaluated the impact of these and other agents on progression of diabetic renal disease. This paper reviews these trials and focuses on renal effects of antihypertensive agents independent of blood pressure reduction.

Remission of nephrotic range proteinuria in type I diabetes. Collaborative Study Group

The present study assessed the extent to which remission of nephrotic-range proteinuria occurred in patients with Type I diabetes enrolled in the Captopril Study, a placebo controlled multicenter clinical trial of captopril therapy in diabetic nephropathy. Of the 409 patients recruited into the Captopril Study, 108 had nephrotic-range proteinuria (> 3.5 g/24 hr) at entry in the Study (baseline). This group was the subject of the present study. Remission of nephrotic-range proteinuria was defined as follows: (1) Onset of the remission was taken as the date when proteinuria was first noted to be < or = 1.0 g/24 hr. (2) The reduction in proteinuria had to be sustained for a minimum of six months and until the end of the Captopril Study. (3) During the remission, the average of all 24 hour proteinuria measurements could not exceed 1.5 g. (4) Decline in renal function could not explain the reduced proteinuria. That is, the patient's serum creatinine during the entire period of observation in the Captopril Study had to remain at less than a doubling of the baseline serum creatinine. Remission of nephrotic-range proteinuria occurred in 7 of 42 patients assigned to captopril (16.7%, mean follow-up 3.4 +/- 0.8 years) and in 1 of 66 patients assigned to placebo (1.5%, mean follow-up 2.3 +/- 1.1 years; P = 0.005, comparing remission rate in captopril vs. placebo-treated patients).(ABSTRACT TRUNCATED AT 250 WORDS)

Captopril and atenolol are equally effective in retarding progression of diabetic nephropathy. Results of a 2-year prospective, randomized study

The progression of diabetic nephropathy can be positively influenced by maintaining a low blood pressure level. This has been shown in studies with conventional antihypertensive treatment as well as with ACE inhibitors. Whether the latter group of drugs is more effective remains to be proven and was the aim of our study. In a prospective randomized study we compared the effects of ACE inhibition and beta-blockade on retarding progression of renal function in IDDM patients with an early stage of overt diabetic nephropathy. Twenty-nine patients were studied for 2 years, 15 were randomized for treatment with captopril and 14 for atenolol. Every 6 weeks blood pressure and urinary albumin and total protein excretion were measured. GFR was measured every 6 months as 51Cr-EDTA clearance. Baseline values for blood pressure, renal function and albuminuria were identical in the two groups. The effect of both drugs on blood pressure was not significantly different. In the captopril-treated patients MAP before and after 2 years was 110 +/- 3 (SEM) and 100 +/- 2 mm Hg, respectively and in the atenolol-treated patients 105 +/- 2 vs 101 +/- 2 mm Hg. Both drugs reduced albuminuria and total proteinuria to the same extent. With captopril albuminuria decreased from 1549 (989-2399) to 851 (537-1380) mg/24 h and proteinuria from 2.5 (1.6-3.8) to 1.2 (0.8-1.8) g/24 h. With atenolol albuminuria decreased from 933 (603-1445) to 676 (437-1047) mg/24 h and proteinuria from 1.5 (1.0-2.4) to 0.9 (0.6-1.5) g/24 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Dissociation between the course of the hemodynamic and antiproteinuric effects of angiotensin I converting enzyme inhibition

Angiotensin I converting enzyme inhibition (ACEi) has been shown to lower urinary protein excretion in human renal disease. The mechanism of this antiproteinuric effect is hypothesized to be mediated by changes in renal hemodynamics. However, clinical studies suggest that the effect on renal hemodynamics is fully established immediately after the start of treatment, whereas others show the antiproteinuric effect to reach maximum only after several weeks. To clarify this issue we studied the course of renal hemodynamics, blood pressure and proteinuria during 28 days of ACEi (enalapril 10 mg oid) in nine patients with proteinuria due to non-diabetic renal disease. The effect of ACEi on blood pressure and renal hemodynamics was already maximal within few hours after start of treatment, and remained stable thereafter: MAP was lowered with 8.6 +/- 1.9%, 10.6 +/- 2.1%, 12.8 +/- 2.3% and 12.9 +/- 2.5%, while FF fell 23.0 +/- 2.0%, 17.0 +/- 2.6%, 16.8 +/- 2.8% and 15.9 +/- 4.0% on days 1, 7, 14 and 28 of ACEi, respectively. However, the antiproteinuric effect only gradually reached its maximum on day 28. Urinary protein excretion decreased with 10.9 +/- 6.1%, 32.7 +/- 6.2%, 46.3 +/- 2.5% and 54.0 +/- 2.5% on days 1, 7, 14 and 28 of ACEi, respectively. After drug withdrawal all parameters returned towards baseline. We conclude that a dissociation occurs in the course of the ACEi induced effects on hemodynamics and urinary protein excretion.(ABSTRACT TRUNCATED AT 250 WORDS)