Effects of atenolol and enalapril on kidney function in hypertensive diabetic patients

Dynamic tissue perfusion assessment reflects associations between antihypertensive treatment and renal cortical perfusion in patients with chronic kidney disease and hypertension

PURPOSE

Renal cortical perfusion measured in noninvasive, dynamic ultrasonic method is connected with the hemodynamic cardiac properties and renal function. Antihypertensive drugs affect the functioning of the heart and kidneys. The aim of the study was to evaluate the effect of a chronic use of antihypertensive drugs on ultrasound parameters of renal cortical perfusion.

METHODS

The study included 56 consecutive patients (49 M + 7 F, age 54.0 ± 13.3) with stable chronic kidney disease and hypertension. Color Doppler dynamic tissue perfusion measurement was used to assess renal cortical perfusion.

RESULTS

Patients were treated with a mean of 2.7 ± 1.4 antihypertensive drugs, of which diuretics accounted for 25%, angiotensin-converting enzyme inhibitors (ACE-I) together with angiotensin receptor blockers (ARB) 24%, beta-blockers (BB) 23%, calcium channel blockers 16%, alpha-1 blockers (α1B) 9% and centrally acting drugs 3%. All investigated groups of drugs correlated significantly with parameters of renal perfusion. In multivariable regression analyses adjusted to age, diuretics were connected with the decrease (r = - 0.473) and ACE-I + ARB (r = 0.390) with the improvement of proximal and whole renal cortex perfusion (R² = 0.28; p < 0.001), whereas BB (r = - 0.372) and α1B (r = - 0.280) independently correlated with worsened perfusion of renal distal cortex (R² = 0.21, p < 0.01).

CONCLUSIONS

The type of antihypertensive therapy had a significant influence on the ultrasound parameters of renal cortical perfusion. Noninvasive, ultrasonic dynamic tissue perfusion measurement method appears to be an adequate tool to assess the impact of drugs on renal cortical perfusion.

How Do Antihypertensive Drugs Work? Insights from Studies of the Renal Regulation of Arterial Blood Pressure

Though antihypertensive drugs have been in use for many decades, the mechanisms by which they act chronically to reduce blood pressure remain unclear. Over long periods, mean arterial blood pressure must match the perfusion pressure necessary for the kidney to achieve its role in eliminating the daily intake of salt and water. It follows that the kidney is the most likely target for the action of most effective antihypertensive agents used chronically in clinical practice today. Here we review the long-term renal actions of antihypertensive agents in human studies and find three different mechanisms of action for the drugs investigated. (i) Selective vasodilatation of the renal afferent arteriole (prazosin, indoramin, clonidine, moxonidine, α-methyldopa, some Ca(++)-channel blockers, angiotensin-receptor blockers, atenolol, metoprolol, bisoprolol, labetolol, hydrochlorothiazide, and furosemide). (ii) Inhibition of tubular solute reabsorption (propranolol, nadolol, oxprenolol, and indapamide). (iii) A combination of these first two mechanisms (amlodipine, nifedipine and ACE-inhibitors). These findings provide insights into the actions of antihypertensive drugs, and challenge misconceptions about the mechanisms underlying the therapeutic efficacy of many of the agents.

Effect of amlodipine and lisinopril on microalbuminuria in patients with essential hypertension: A prospective study

Microalbuminuria can be present in 25-100% of patients with essential hypertension and is associated with increased incidence of cardiovascular events. Our goal was to evaluate the effect of a commonly used calcium channel blocker, amlodipine, and an angiotensin converting enzyme inhibitor, lisinopril on urinary albumin excretion in patients with mild to moderate essential hypertension. We screened 324 patients with essential hypertension for microalbuminuria and documented it in 120 patients. These 120 patients with microalbuminuria were randomly divided into two groups of 60 each, matched for age, sex, arterial pressure, creatinine clearance, and urinary albumin excretion so as to receive amlodipine or lisinopril. We prospectively measured their urinary albumin excretion and creatinine clearance prior to treatment and, four and eight weeks after treatment with amlodipine or lisinopril. Mean arterial pressure (mean +/- SD) at baseline, after four weeks, and after eight weeks was 113.01 +/- 4.38,104.93 +/- 3.12, and 98.89 +/- 1.75 mmHg (P < 0.0000); and 114.13 +/- 7.11, 106.52 +/- 3.50, and 100.89 +/- 2.80 mmHg (P < 0.0000) in amlodipine and lisinopril groups, respectively. Urinary albumin excretion (mean +/- SEM) at baseline, after four, and after eight weeks was 79.30 +/- 3.74, 62.03 +/- 3.61, and 52.02 +/- 3.05 (P < 0.0000); and 73.96 +/- 4.10, 72.39 +/- 3.74, 66.12 +/- 3.94 (P = 0.1742) in lisinopril and amlodipine groups, respectively. Lisinopril but not amlodipine, reduced the urinary albumin excretion significantly despite their similar antihypertensive efficacy. The clinical and prognostic significance of these observations need to be established.

Blood Pressure Control, Drug Therapy, and Kidney Disease

The African American Study of Kidney Disease and Hypertension examined the effect on renal function decline of 2 blood pressure (BP) goals (low mean arterial pressure [MAP] ≤92 versus usual MAP 102 to 107 mm Hg) and 3 antihypertensives (ramipril versus amlodipine versus metoprolol). We previously reported that in all drug groups combined the BP intervention had similar effects on the primary outcome of glomerular filtration rate (GFR) slope or the main secondary clinical composite outcome of end-stage renal disease (ESRD), death, or GFR decline by 50% or 25 mL/min per 1.73 m 2 . This report examines the effect of the BP intervention separately in the 3 drug groups. The BP effect was similar among the drug groups for either GFR slope or the main clinical composite. However, the BP effect differed significantly among the drug groups for the composite of ESRD or death ( P =0.035) and ESRD alone ( P =0.021). Higher event rates for amlodipine patients assigned to the usual BP goal (0.087 per patient-year for ESRD or death and 0.064 per patient-year for ESRD) were seen compared with the remaining groups of the factorial design (range, 0.041 to 0.050 for ESRD or death; and range, 0.027 to 0.036 for ESRD). The low BP goal was associated with reduced risk of ESRD or death (risk reduction 51%; 95% confidence interval, 13% to 73%) and ESRD (54%; 8% to 77%) for amlodipine patients, but not for patients assigned to the other drug groups. These secondary analyses suggest a benefit of the low BP goal among patients assigned to amlodipine, but they must be interpreted cautiously.

Design and statistical aspects of the African American Study of Kidney Disease and Hypertension (AASK)

The African American Study of Kidney Disease and Hypertension (AASK) is a multicenter randomized clinical trial designed to test the effectiveness of three anti-hypertensive drug regimens and two levels of BP control on the progression of hypertensive kidney disease. Participants include African-American men and women aged 18 to 70 yr who have hypertensive kidney disease and GFR between 20 and 65 ml/min per 1.73 m(2). The three anti-hypertensive drug regimens include an angiotensin converting enzyme inhibitor (ramipril), a dihydropyridine calcium channel blocker (amlodipine) or a beta-blocker (metoprolol) as initial therapy. The BP control levels are a lower goal (mean arterial pressure, Collapse

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MESH Headings

• Adolescent
• Adrenergic beta-Antagonists/administration & dosage
• Adult
• Black or African American/statistics & numerical data
• Aged
• Angiotensin-Converting Enzyme Inhibitors/administration & dosage
• Antihypertensive Agents/administration & dosage
• Calcium Channel Blockers/administration & dosage
• Dose-Response Relationship, Drug
• Drug Administration Schedule
• Drug Therapy, Combination
• Female
• Follow-Up Studies
• Humans
• Hypertension/complications
• Hypertension/diagnosis
• Hypertension/drug therapy
• Kidney Failure, Chronic/complications
• Kidney Failure, Chronic/diagnosis
• Kidney Failure, Chronic/therapy
• Male
• Middle Aged
• Pilot Projects
• Risk Assessment
• Treatment Outcome
• United States

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Grants

• U01 DK048643 NIDDK NIH HHS
• RR11145 NCRR NIH HHS
• U01 DK048648 NIDDK NIH HHS
• RR-00080 NCRR NIH HHS
• M01 RR000071 NCRR NIH HHS
• DK 2818 NIDDK NIH HHS
• M01 RR000052 NCRR NIH HHS
• M01 RR000032 NCRR NIH HHS
• K24 DK002818 NIDDK NIH HHS
• RR11104 NCRR NIH HHS
• RR-00071 NCRR NIH HHS
• P20 RR011104 NCRR NIH HHS
• P20 RR011145 NCRR NIH HHS
• U01 DK045381 NIDDK NIH HHS
• RR00827 NCRR NIH HHS
• U01 DK045386 NIDDK NIH HHS
• RR00052 NCRR NIH HHS
• M01 RR000827 NCRR NIH HHS
• M01 RR000080 NCRR NIH HHS
• RR00032 NCRR NIH HHS

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Affiliation(s)

Jennifer J Gassman Cleveland Clinic Department of Biostatistics, Ohio, 44195, USA.
Tom Greene
Jackson T Wright
Lawrence Agodoa
George Bakris
Gerald J Beck
Janice Douglas
Ken Jamerson
Julia Lewis
Michael Kutner
Otelio S Randall
Shin-Ru Wang

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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.

Hypertensive patients and diabetes: a high-risk population

Rising worldwide rates of diabetes mellitus heighten the need to maintain adequate metabolic control in diabetic patients and to control for other cardiovascular risk factors, such as lipid profile disturbances, high blood pressure, and smoking habits. This is especially the case in diabetic patients who also present with hypertension, a co-morbid state that is present in at least 50% of Type 1 and Type 2 diabetic patients. Cardiovascular disease is present in 75% of all diabetes-related deaths, and the concomitant condition of diabetes and hypertension is believed to act synergistically on elevating the risk for cardiovascular disease. A number of trials have demonstrated a greater incidence of cardiovascular disease end points in diabetic hypertensive patients than in diabetic normotensive patients. Furthermore, hypertension is associated not only with an increased risk for cardiovascular mortality but also for microvascular complications in patients with diabetes. Adequate treatment of high blood pressure is imperative in these patients. The effectiveness of antihypertensive treatment can be measured not only by the degree of reduction in blood pressure but also by assessment of the effects on urinary albumin excretion rate. It is assumed that the greater the reduction in urinary albumin excretion rate, the greater the renoprotective effect. Treatment choices should be evidence-based, i.e., physicians should concentrate not only on the treatment of hypertension but also on improving glycemic control and lipid profile disorders, when necessary. When viewed in this regard, angiotensin-converting enzyme inhibitors, low-dose diuretics, and in some cases beta-blockers, should be considered agents of choice in hypertensive diabetic patients.

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.

Effects of benazepril and nicardipine on microalbuminuria in normotensive and hypertensive patients with diabetes

Diabetic nephropathy is the most frequent cause of chronic renal failure. The onset of microalbuminuria in patients with diabetes mellitus, which seems to be related to blood pressure and the control of glycemia, is predictive of the development of true proteinuria. This multicenter, single-blind, randomized study examined the effects of benazepril and nicardipine on overnight microalbuminuria in 57 normotensive and 46 hypertensive diabetic patients. At the end of a 3-month placebo run-in period, the patients were stratified on the basis of the presence or absence of arterial hypertension and, within each stratum, randomized to receive one daily tablet of 10 mg benazepril or one tablet of 20 mg nicardipine twice daily for 6 months. Renal hemodynamics was investigated in 25 patients. Both drugs decreased overnight microalbuminuria throughout the study period, but benazepril was more effective than nicardipine (p = 0.025); in the patients with hypertension, both drugs led to a similar marked reduction in systolic and diastolic blood pressure. This study shows that benazepril was more effective than nicardipine in reducing overnight microalbuminuria in patients with diabetes mellitus, independently of their antihypertensive properties.

The diabetic patient with hypertension

Hypertension and diabetes co-exist more commonly than would be expected from their individual prevalences. Elevated blood pressure is most commonly due to coexisting essential hypertension, or diabetic renal disease. Early stages of diabetic renal disease can be identified by detecting microalbuminuria. Standard measures of blood pressure are not necessarily raised, but 24-hour ambulatory measures frequently identify a loss of nocturnal drop in blood pressure. Treating hypertension aggressively is important in slowing the inexorable decline in glomerular filtration rate. In diabetes there appears to be no 'J'-shaped relationship between blood pressure and cardiovascular events, thus removing any concern about attaining low blood pressures as long as the patient is asymptomatic. Morbidity and mortality in these patients is usually associated with cardiovascular events, and it is important to assess the effect of drugs on left ventricular hypertrophy and metabolic parameters. Many drugs are effective at lowering blood pressure, but angiotensin-converting enzyme inhibitors may have an additional renoprotective action. alpha-Adrenergic antagonists may improve lipid profiles and calcium antagonists are probably lipid neutral, making these drugs useful alternatives. Dihydropyridine calcium antagonists (eg, nifedipine) may augment protein-uria, and hence non-dihydropyridine calcium antagonists (eg, verapamil, diltiazem) would be preferred. beta-Blockers and thiazide diuretics have the disadvantage of causing a deterioration in glycaemic and lipid profiles, but can be useful on occasions.