Factors Associated With Treatment and Control of Hypertension in a Healthy Elderly Population Free of Cardiovascular Disease: A Cross-sectional Study

BACKGROUND

Despite readily available treatments, control of blood pressure (BP) with population aging remains suboptimal. Further, there are gaps in the understanding of the management of high BP in the aged. We explored antihypertensive treatment and control among elderly hypertensive participants free from overt cardiovascular disease (CVD), and identified factors related to both "untreated" and "treated but uncontrolled" high BP.

METHODS

We analyzed baseline data from 19,114 individuals aged ≥65 years enrolled from Australia and United States (US) in the ASPirin in Reducing Events in the Elderly study. Hypertension was defined as an average systolic/diastolic BP ≥140/90 mm Hg and/or the use of any BP lowering medication. "Controlled hypertension" was defined if participants were receiving antihypertensive medication and BP <140 and 90 mm Hg. Descriptive analyses were used to summarize hypertension control rates; logistic regression was used to investigate relationships with treatment and BP control.

RESULTS

Overall, 74% (14,213/19,114) of participants were hypertensive; and of these 29% (4,151/14,213) were untreated. Among those treated participants, 53% (5,330/10,062) had BP ≥140/90 mm Hg. Participants who were untreated were more likely to be men, have higher educational status, and be in good physical health, and less likely to have significant comorbidities. The factors related to "treated but uncontrolled" BP included older age, male, Black race (vs. White), using antihypertensive monotherapy (vs. multiple) and residing in Australia (vs. US).

CONCLUSIONS

High levels of "untreated" and "treated but uncontrolled" BP occur in healthy elderly people without CVD, suggesting there are opportunities for better BP control in the primary prevention of CVD in this population.

CLINICAL TRIALS REGISTRATION

NCT01038583.

P4557Factors associated with treatment and control of hypertension in a healthy elderly population free of cardiovascular disease: a cross-sectional study

Introduction

Despite readily available treatments, control of high blood pressure (BP) in the ageing population remains suboptimal. Gaps in understanding the management of high BP amongst the elderly exist, as most studies have been in predominantly middle-aged populations.

Purpose

We explored pharmacological BP lowering treatment and control among elderly hypertensive participants free from overt cardiovascular disease (CVD), and identified factors related to both “untreated” and “treated but uncontrolled” high BP.

Methods

We analyzed baseline data from 19,114 individuals aged ≥65 years enrolled from Australia and the US in the ASPirin in Reducing Events in the Elderly (ASPREE) study. Hypertension was defined as an average systolic/diastolic BP ≥140/90 mmHg and/or use of any BP-lowering medication. `Controlled hypertensives” were those receiving BP-lowering medication and with BP <140/90 mmHg. Descriptive analyses were used to summarize hypertension control rates; logistic regression was used to investigate relationships with treatment and BP control.

Results

Overall, 74% (14,213/19,114) of participants were hypertensive, and of these 29% (4,151/14,213) were untreated. Among those treated, 47% (4,732/10,062) had BP <140/90 mmHg. Participants who were untreated were more likely to be men, have higher educational status, and be in good physical health, and less likely to have significant comorbidities. The factors related to “treated but uncontrolled” hypertension included older age, being men, Black race (versus White), using BP lowering monotherapy and residing in Australia (versus US) (Figure 1).

Conclusion(s)

There were high levels of “untreated” and “treated but uncontrolled” BP, in an otherwise healthy elderly population, suggesting that opportunities for better BP control exist through targeting intervention to high-risk individuals.

Acknowledgement/Funding

National Institute on Aging and the National Cancer Institute at NIH; NHMRC Australia, Monash University, Victorian Cancer Agency (Australia)

P6362Impact of the 2017 AHA/ACC hypertension guideline on hypertension prevalence and cardiovascular risk factors in a healthy older cohort

Background

The 2017 American Heart Association (AHA)/American College of Cardiology (ACC) hypertension guideline recommends a target blood pressure (BP) of <130/80 mmHg regardless of age, which is lower than previously recommended BP goals.

Purpose

We aimed to determine how much the updated classification for high BP would increase the overall prevalence of “hypertension” in an otherwise healthy elderly population. Additionally, we explored the cardiovascular disease (CVD) risk factor distribution in those newly classified “hypertensives” to determine whether the increased prevalence of hypertension was accompanied by an increase in other modifiable CVD risk factors.

Methods

We used baseline data from 19,114 participants (16,703 in Australia and 2,411 in the USA) aged ≥65 years who were enrolled in the ASPirin in Reducing Events in the Elderly (ASPREE) study between 2010 and 2014. Participants were classified as having hypertension using either: (a) pre-2017 thresholds (SBP ≥140 mmHg or mean DBP ≥90 mmHg and/or on anti-hypertensive) or (b) 2017 AHA/ACC guidelines (SBP ≥130 mmHg or DBP ≥80 mmHg and/or on anti-hypertensive). We assessed the presence of cardiovascular disease risk factors such as diabetes, hypercholesterolemia, smoking, obesity, reduced renal function among these hypertensive participants and also estimated their predicted risk over 10 years.

Results

Based on pre-2017 thresholds, 74% of the participants met the criteria for hypertension. Hypertension prevalence increased to 87% when the more stringent 2017 guideline was applied. 29% of this subset of newly classified hypertensive participants did not have any other identifiable traditional CVD risk factors. Further, a significantly lower 10-year predicted cardiovascular risk (22% versus 26%, p<0.001) among those newly classified hypertensive participants was observed in relation to those having hypertension based on pre-2017 guideline (Figure 1).

Figure 1. 10-year predicted CVD risk among hyoertensive and newly classified hypertensive ASPREE participants by presence of CVD risk factor

Conclusion

As expected, the prevalence of hypertension increased among the healthy elderly when applying the new AHA-2017 guideline; however, the increased prevalence occurs despite lack of an accompanying increase in additional CVD risk factors or predicted 10-year risk. Our findings suggest an individualized approach is needed in evaluating high BP among the healthy elderly.

Acknowledgement/Funding

National Institute on Aging and the National Cancer Institute at NIH; NHMRC Australia, Monash University, Victorian Cancer Agency (Australia)

Effect of Aspirin on All-Cause Mortality in the Healthy Elderly

BACKGROUND

In the primary analysis of the Aspirin in Reducing Events in the Elderly (ASPREE) trial, now published in the Journal, we report that the daily use of aspirin did not provide a benefit with regard to the primary end point of disability-free survival among older adults. A numerically higher rate of the secondary end point of death from any cause was observed with aspirin than with placebo.

METHODS

From 2010 through 2014, we enrolled community-dwelling persons in Australia and the United States who were 70 years of age or older (or ≥65 years of age among blacks and Hispanics in the United States) and did not have cardiovascular disease, dementia, or disability. Participants were randomly assigned to receive 100 mg of enteric-coated aspirin or placebo. Deaths were classified according to the underlying cause by adjudicators who were unaware of trial-group assignments. Hazard ratios were calculated to compare mortality between the aspirin group and the placebo group, and post hoc exploratory analyses of specific causes of death were performed.

RESULTS

Of the 19,114 persons who were enrolled, 9525 were assigned to receive aspirin and 9589 to receive placebo. A total of 1052 deaths occurred during a median of 4.7 years of follow-up. The risk of death from any cause was 12.7 events per 1000 person-years in the aspirin group and 11.1 events per 1000 person-years in the placebo group (hazard ratio, 1.14; 95% confidence interval [CI], 1.01 to 1.29). Cancer was the major contributor to the higher mortality in the aspirin group, accounting for 1.6 excess deaths per 1000 person-years. Cancer-related death occurred in 3.1% of the participants in the aspirin group and in 2.3% of those in the placebo group (hazard ratio, 1.31; 95% CI, 1.10 to 1.56).

CONCLUSIONS

Higher all-cause mortality was observed among apparently healthy older adults who received daily aspirin than among those who received placebo and was attributed primarily to cancer-related death. In the context of previous studies, this result was unexpected and should be interpreted with caution. (Funded by the National Institute on Aging and others; ASPREE ClinicalTrials.gov number, NCT01038583 .).

Effect of Aspirin on Cardiovascular Events and Bleeding in the Healthy Elderly

BACKGROUND

Aspirin is a well-established therapy for the secondary prevention of cardiovascular events. However, its role in the primary prevention of cardiovascular disease is unclear, especially in older persons, who have an increased risk.

METHODS

From 2010 through 2014, we enrolled community-dwelling men and women in Australia and the United States who were 70 years of age or older (or ≥65 years of age among blacks and Hispanics in the United States) and did not have cardiovascular disease, dementia, or disability. Participants were randomly assigned to receive 100 mg of enteric-coated aspirin or placebo. The primary end point was a composite of death, dementia, or persistent physical disability; results for this end point are reported in another article in the Journal. Secondary end points included major hemorrhage and cardiovascular disease (defined as fatal coronary heart disease, nonfatal myocardial infarction, fatal or nonfatal stroke, or hospitalization for heart failure).

RESULTS

Of the 19,114 persons who were enrolled in the trial, 9525 were assigned to receive aspirin and 9589 to receive placebo. After a median of 4.7 years of follow-up, the rate of cardiovascular disease was 10.7 events per 1000 person-years in the aspirin group and 11.3 events per 1000 person-years in the placebo group (hazard ratio, 0.95; 95% confidence interval [CI], 0.83 to 1.08). The rate of major hemorrhage was 8.6 events per 1000 person-years and 6.2 events per 1000 person-years, respectively (hazard ratio, 1.38; 95% CI, 1.18 to 1.62; P<0.001).

CONCLUSIONS

The use of low-dose aspirin as a primary prevention strategy in older adults resulted in a significantly higher risk of major hemorrhage and did not result in a significantly lower risk of cardiovascular disease than placebo. (Funded by the National Institute on Aging and others; ASPREE ClinicalTrials.gov number, NCT01038583 .).

Effect of Aspirin on Disability-free Survival in the Healthy Elderly

BACKGROUND

Information on the use of aspirin to increase healthy independent life span in older persons is limited. Whether 5 years of daily low-dose aspirin therapy would extend disability-free life in healthy seniors is unclear.

METHODS

From 2010 through 2014, we enrolled community-dwelling persons in Australia and the United States who were 70 years of age or older (or ≥65 years of age among blacks and Hispanics in the United States) and did not have cardiovascular disease, dementia, or physical disability. Participants were randomly assigned to receive 100 mg per day of enteric-coated aspirin or placebo orally. The primary end point was a composite of death, dementia, or persistent physical disability. Secondary end points reported in this article included the individual components of the primary end point and major hemorrhage.

RESULTS

A total of 19,114 persons with a median age of 74 years were enrolled, of whom 9525 were randomly assigned to receive aspirin and 9589 to receive placebo. A total of 56.4% of the participants were women, 8.7% were nonwhite, and 11.0% reported previous regular aspirin use. The trial was terminated at a median of 4.7 years of follow-up after a determination was made that there would be no benefit with continued aspirin use with regard to the primary end point. The rate of the composite of death, dementia, or persistent physical disability was 21.5 events per 1000 person-years in the aspirin group and 21.2 per 1000 person-years in the placebo group (hazard ratio, 1.01; 95% confidence interval [CI], 0.92 to 1.11; P=0.79). The rate of adherence to the assigned intervention was 62.1% in the aspirin group and 64.1% in the placebo group in the final year of trial participation. Differences between the aspirin group and the placebo group were not substantial with regard to the secondary individual end points of death from any cause (12.7 events per 1000 person-years in the aspirin group and 11.1 events per 1000 person-years in the placebo group), dementia, or persistent physical disability. The rate of major hemorrhage was higher in the aspirin group than in the placebo group (3.8% vs. 2.8%; hazard ratio, 1.38; 95% CI, 1.18 to 1.62; P<0.001).

CONCLUSIONS

Aspirin use in healthy elderly persons did not prolong disability-free survival over a period of 5 years but led to a higher rate of major hemorrhage than placebo. (Funded by the National Institute on Aging and others; ASPREE ClinicalTrials.gov number, NCT01038583 .).

Baseline Characteristics of Participants in the ASPREE (ASPirin in Reducing Events in the Elderly) Study

BACKGROUND

There are no primary prevention trials of aspirin with relevant geriatric outcomes in elderly people. ASPirin in Reducing Events in the Elderly (ASPREE) is a placebo-controlled trial of low-dose aspirin that will determine whether 5 years of daily 100-mg enteric-coated aspirin extends disability-free and dementia-free life in a healthy elderly population and whether these benefits outweigh the risks.

METHODS

Set in primary care, this randomized double-blind placebo-controlled trial has a composite primary endpoint of death, incident dementia or persistent physical disability. Participants aged 70+ years (non-minorities) or 65+ years (U.S. minorities) were free of cardiovascular disease, dementia, or physical disability and without a contraindication to, or indication for, aspirin. Baseline data include physical and lifestyle, personal and family medical history, hemoglobin, fasting glucose, creatinine, lipid panel, urinary albumin:creatinine ratio, cognition (3MS, HVLT-R, COWAT, SDMT), mood (CES-D-10), physical function (gait speed, grip strength), Katz activities of daily living and quality of life (SF-12).

RESULTS

Recruitment ended in December 2014 with 16,703 Australian and 2,411 U.S. participants, a median age of 74 (range 65-98) years and 56% women. Approximately 55% of the U.S. cohort were from minority groups; 9% of the total cohort. Proportions with hypertension, overweight, and chronic kidney disease were similar to age-matched populations from both countries although lower percentages had diabetes, dyslipidemia, and osteoarthritis.

DISCUSSION

Findings from ASPREE will be generalizable to a healthier older population in both countries and will assess whether the broad benefits of daily low-dose aspirin in prolonging independent life outweigh the risks.

Short- and long-term survival in treated elderly hypertensive patients with or without diabetes: findings from the Second Australian National Blood Pressure study

BACKGROUND

We sought to determine the incidence of newly diagnosed diabetes in treated elderly hypertensive patients and the prognostic impact of diabetes on long-term survival.

METHODS

The Second Australian National Blood Pressure (ANBP2) study randomized 6,083 hypertensive patients aged 65-84 years to angiotensin-converting enzyme inhibitor (ACEI) or thiazide diuretic-based therapy and followed them for a median of 4.1 years. Long-term survival was determined in 5,678 patients over an additional median of 6.9 years after ANBP2 (post-trial).

RESULTS

After ANBP2, the cohort was classified into preexisting (7.2%), newly diagnosed (5.6%), and no diabetes (87.2%) groups. A 44% higher incidence of newly diagnosed diabetes was observed in patients randomized to thiazide diuretic compared with ACEI-based treatment. The other predictors of newly diagnosed diabetes were having a higher body mass index, having a higher random blood glucose, and living in a regional location compared to major cities (a geographical classification based on accessibility) at study entry. After completion of ANBP2, compared with those with no diabetes, the preexisting diabetes group experienced higher cardiovascular (hazards ratio (HR) = 1.65; 95% confidence interval (CI) = 1.03-2.65) and all-cause mortality (HR = 1.40; 95% CI = 1.02-1.92) when adjusted for age, sex, and treatment. A similar pattern was observed after including the post-trial period for cardiovascular (HR = 1.52; 95% CI = 1.20-1.93) and all-cause mortality (HR = 1.50; 95% CI = 1.29-1.73). However, when the newly diagnosed group was compared with the no diabetes group, no significant difference was observed in cardiovascular (HR = 0.33; 95% CI = 0.11-1.05) or all-cause mortality (HR = 0.76; 95% CI = 0.47-1.23) either during the ANBP2 trial or including post-trial follow-up (cardiovascular: HR = 0.82; 95% CI = 0.58-1.17; all-cause mortality: HR = 1.04; 95% CI = 0.85-1.27).

CONCLUSIONS

Long-term presence of diabetes reduces survival. Compared with thiazide diuretics, ACEI-based antihypertensives may delay the development of diabetes in those at risk and thus potentially improve cardiovascular outcome in the elderly.

Mulga snake (Pseudechis australis) envenoming: a spectrum of myotoxicity, anticoagulant coagulopathy, haemolysis and the role of early antivenom therapy - Australian Snakebite Project (ASP-19)

CONTEXT

Mulga snakes (Pseudechis australis) are venomous snakes with a wide distribution in Australia. Objective. The objective of this study was to describe mulga snake envenoming and the response of envenoming to antivenom therapy.

MATERIALS AND METHODS

Definite mulga bites, based on expert identification or venom-specific enzyme immunoassay, were recruited from the Australian Snakebite Project. Demographics, information about the bite, clinical effects, laboratory investigations and antivenom treatment are recorded for all patients. Blood samples are collected to measure the serum venom concentrations pre- and post-antivenom therapy using enzyme immunoassay.

RESULTS

There were 17 patients with definite mulga snake bites. The median age was 37 years (6-70 years); 16 were male and six were snake handlers. Thirteen patients had systemic envenoming with non-specific systemic symptoms (11), anticoagulant coagulopathy (10), myotoxicity (7) and haemolysis (6). Antivenom was given to ten patients; the median dose was one vial (range, one-three vials). Three patients had systemic hypersensitivity reactions post-antivenom. Antivenom reversed the coagulopathy in all cases. Antivenom appeared to prevent myotoxicity in three patients with high venom concentrations, given antivenom within 2 h of the bite. Median peak venom concentration in 12 envenomed patients with samples was 29 ng/mL (range, 0.6-624 ng/mL). There was a good correlation between venom concentrations and the area under the curve of the creatine kinase for patients receiving antivenom after 2 h. Higher venom concentrations were also associated with coagulopathy and haemolysis. Venom was not detected after antivenom administration except in one patient who had a venom concentration of 8.3 ng/ml after one vial of antivenom, but immediate reversal of the coagulopathy.

DISCUSSION

Mulga snake envenoming is characterised by myotoxicity, anticoagulant coagulopathy and haemolysis, and has a spectrum of toxicity that is venom dose dependant. This study supports a dose of one vial of antivenom, given as soon as a systemic envenoming is identified, rather than waiting for the development of myotoxicity.

High-salt diet increases glomerular ACE/ACE2 ratio leading to oxidative stress and kidney damage

BACKGROUND

Angiotensin II (AngII) contributes to salt-driven kidney damage. In this study, we aimed at investigating whether and how the renal damage associated with a high-salt diet could result from changes in the ratio between angiotensin-converting enzyme (ACE) and angiotensin-converting enzyme 2 (ACE2).

METHODS

Forty-eight rats randomly allocated to three different dietary contents of salt were studied for 4 weeks after undergoing a left uninephrectomy. We focussed on kidney functional, structural and molecular changes. At the same time, we studied kidney molecular changes in 20 weeks old Ace2-knockout mice (Ace2KO), with and without ACE inhibition.

RESULTS

A high salt content diet significantly increased the glomerular ACE/ACE2 ratio. This was associated with increased oxidative stress. To assess whether these events were related, we measured renal oxidative stress in Ace2KO, and found that the absence of ACE2 promoted oxidative stress, which could be prevented by ACE inhibition.

CONCLUSION

One of the mechanisms by which a high-salt diet leads to renal damage seems to be the modulation of the ACE/ACE2 ratio which in turn is critical for the cause of oxidative stress, through AngII.

Who's really hypertensive? – Quality control issues in the assessment of blood pressure for randomized trials

The characterization of blood pressure in treatment trials assessing the benefits of blood pressure lowering regimens is a critical factor for the appropriate interpretation of study results. With numerous operators involved in the measurement of blood pressure in many thousands of patients being screened for entry into clinical trials, it is essential that operators follow pre-defined measurement protocols involving multiple measurements and standardized techniques. Blood pressure measurement protocols have been developed by international societies and emphasize the importance of appropriate choice of cuff size, identification of Korotkoff sounds, and digit preference. Training of operators and auditing of blood pressure measurement may assist in reducing the operator-related errors in measurement. This paper describes the quality control activities adopted for the screening stage of the 2nd Australian National Blood Pressure Study (ANBP2). ANBP2 is cardiovascular outcome trial of the treatment of hypertension in the elderly that was conducted entirely in general practices in Australia. A total of 54 288 subjects were screened; 3688 previously untreated subjects were identified as having blood pressure >140/90 mmHg at the initial screening visit, 898 (24%) were not eligible for study entry after two further visits due to the elevated reading not being sustained. For both systolic and diastolic blood pressure recording, observed digit preference fell within 7 percentage points of the expected frequency. Protocol adherence, in terms of the required minimum blood pressure difference between the last two successive recordings, was 99.8%. These data suggest that adherence to blood pressure recording protocols and elimination of digit preferences can be achieved through appropriate training programs and quality control activities in large multi-centre community-based trials in general practice. Repeated blood pressure measurement prior to initial diagnosis and study entry is essential to appropriately characterize hypertension in these elderly patients.

Smaller aortic dimensions do not fully account for the greater pulse pressure in elderly female hypertensives

This study examined the importance of aortic dimensions in determining pulse pressure in elderly hypertensives participating in the 2nd Australian National Blood Pressure Study, including a substantial number not previously receiving blood pressure lowering medication. Aortic dimensions were determined by ultrasound at the transverse arch and at the insertion of the aortic valve. Unadjusted data showed negative (P<0.001) correlations between central (carotid) and (brachial) peripheral pulse pressure and both arch (-0.200, -0.181) and outflow tract (-0.238, -0.238) diameters. Correlations were similar in those previously treated with blood pressure lowering medication and in the treatment naïve. Central pulse pressure (84+/-26 versus 75+/-28 mm Hg, P<0.001) was higher and aortic dimensions (transverse arch 2.56+/-0.31 versus 2.88+/-0.35 mm, P<0.001) smaller in women than men. Women had greater aortic stiffness (beta index 29.4+/-36.1 versus 22.1+/-21.3, P<0.03). Other bivariate correlates of central pulse pressure were age, mean arterial pressure, height, heart rate, augmentation index, aortic stiffness (all P<0.001), and weight (P=0.027). In multivariate analyses gender remained a predictor of central pulse pressure (P<0.001) even with inclusion of aortic dimensions (P=0.013) height and weight. Other significant terms were age, heart rate, mean blood pressure, and aortic stiffness (all P<0.001). These findings demonstrate an independent inverse relation between aortic size and pulse pressure in older hypertensive subjects. Differences in aortic dimensions and stiffness between genders do not fully account for the observed blood pressure differences, suggesting that a contributory factor to gender differences in pulse pressure is an increased age-related mismatch in ventricular function and aortic stiffness in women compared with men.

Similar Effects of Treatment on Central and Brachial Blood Pressures in Older Hypertensive Subjects in the Second Australian National Blood Pressure Trial

The Second Australian National Blood Pressure Trial reported better prognosis for hypertensive subjects randomly assigned to an angiotensin-converting enzyme inhibitor (ACE-I) compared with a diuretic-based regimen despite no difference in brachial blood pressure control. A possible explanation is that there was a difference in central aortic pressures despite similar brachial pressure reductions. We examined this hypothesis in a subset of the Second Australian National Blood Pressure Trial cohort evaluated both before and after 4 years of treatment. The average age of the 479 subjects was 71.6+/-4.7 years (mean+/-SD), and 56% were women. Brachial systolic and pulse pressures after treatment were 145+/-1 (mean+/-SEM), 143+/-1, 72+/-1, and 70+/-1 mm Hg for diuretic and ACE-I groups, respectively. The respective changes from pretreatment values were -17+/-2, -16+/-2, -9+/-1, and -7+/-1 mm Hg. None of the differences between diuretic and ACE-I groups were significant. Central arterial pressure waveforms were acquired from carotid tonometry and calibrated from brachial pressures. Central systolic and pulse pressures posttreatment were 144+/-2, 144+/-2, 71+/-2, and 72+/-2 mm Hg for diuretic and ACE-I groups, respectively. The respective changes from pretreatment values were -15+/-2, -17+/-2, -6+/-2, and -8+/-2 mm Hg. None of the differences between diuretic and ACE-I groups were significant. The similarity of central and brachial pressures in this cohort of older hypertensive subjects is most likely because of the influences of age and hypertension in increasing arterial stiffness. There is no evidence that the better prognosis for patients randomly assigned to ACE-I in Second Australian National Blood Pressure Trial resulted from a disproportionate lowering of central blood pressure.

Developmental expression of ACE2 in the SHR kidney: a role in hypertension?

The abnormal development of the intrarenal renin-angiotensin system (RAS) is thought contribute to adult-onset hypertension in the spontaneously hypertensive rat (SHR). Angiotensin-converting enzyme 2 (ACE2) is a novel enzyme with complementary actions to that of ACE. Recent studies have shown that ACE2 expression is reduced in the adult SHR. However, its regulation in pre-hypertensive animals is unknown. In this study, we examine the developmental expression of ACE2 in the rodent kidney and its temporal expression, as it relates to the development of hypertension in the SHR model. Kidneys from SHR and normotensive Wistar Kyoto (WKY) rats (n=8-12/group) at birth, 6 weeks of age, and adulthood (80 days) were examined. Gene expression and activity of ACE2 were determined by real-time reverse transcription-polymerase chain reaction and quenched fluorescence assays, respectively. Renal expression was localized by in situ hybridization and immunohistochemistry. The expression and ACE2 activity are significantly increased in the SHR kidney at birth. With the onset of hypertension, the tubular expression of ACE2 falls in SHR compared to WKY and remains reduced in the adult SHR kidney. Glomerular expression is paradoxically increased in the SHR glomerulus. The overall developmental pattern of ACE2 expression in the SHR kidney is also modified, with declining expression over the course of renal development. The developmental pattern of ACE2 expression in the SHR kidney is altered before the onset of hypertension, consistent with the key role of the RAS in the pathogenesis of adult-onset hypertension. Further research is required to distinguish the contribution of these changes to the development and progression of hypertension in this model.

Brachial Blood Pressure But Not Carotid Arterial Waveforms Predict Cardiovascular Events in Elderly Female Hypertensives

Central arterial waveforms and related indices of large artery properties can be determined with relative ease. This would make them an attractive adjunct in the risk stratification for cardiovascular disease. Although they have been associated with some classical risk factors and the presence of coronary disease, their prospective value in predicting cardiovascular outcomes is unknown. The present study determined the relative predictive value for cardiovascular disease-free survival of large artery properties as compared with noninvasive brachial blood pressure alone in a population of elderly female hypertensive subjects. We measured systemic arterial compliance, central systolic pressure, and carotid augmentation index in a subset of female participants in the Second Australian National Blood Pressure Study (untreated blood pressure 169/88±12/8 mm Hg). There were a total of 53 defined events during a median of 4.1 years of follow-up in 484 women with complete measurements. Although baseline blood pressures at the brachial artery predicted cardiovascular disease-free survival (hazard ratio [HR], 2.3; 95% CI, 1.3 to 4.1 for pulse pressure ≥81 versus <81 mm Hg; P =0.01), no such relation was found for carotid augmentation index (HR, 0.80; 95% CI, 0.44 to 1.44; P value not significant) or systemic arterial compliance (HR, 1.25; 95% CI, 0.72 to 2.16; P value not significant). Blood pressure, but not noninvasively measured central arterial waveforms, predict outcome in the older female hypertensive patient. Thus, blood pressure measurement alone is superior to measurement of arterial waveforms in predicting outcome in this group.

Anti-atherosclerotic and renoprotective effects of combined angiotensin-converting enzyme and neutral endopeptidase inhibition in diabetic apolipoprotein E-knockout mice

OBJECTIVE

To investigate the effects of the combined angiotensin-converting enzyme (ACE)/neutral endopeptidase (NEP) inhibitor omapatrilat on atherosclerosis and renal injury in a model of diabetes-associated accelerated atherosclerosis and renal injury.

DESIGN

The study was performed using diabetic apolipoprotein E-knockout (apo E-KO) mice, a model combining hyperlipidemia and hyperglycemia, which leads to accelerated atherosclerosis and renal injury.

METHODS

Diabetes was induced by the injection of streptozotocin in 6-week old apo E-KO mice. Diabetic animals received no treatment (n = 12) or treatment with the ACE/NEP inhibitor omapatrilat (30 mg/kg per day, via gavage, n = 12) or quinapril (10 mg/kg per day, in drinking water, n = 12) for 20 weeks. Non-diabetic apo E-KO mice (n = 12) served as controls.

RESULTS

Omapatrilat reduced atherosclerosis and protected the mice from renal structural injury and albuminuria. The protective effects were associated with tissue inhibition of aortic and renal ACE and NEP as well as a significant reduction in blood pressure. Omapatrilat had similar anti-atherosclerotic effects compared with the ACE inhibitor quinapril in association with an almost complete inhibition of aortic ACE activity by both drugs. Omapatrilat conferred superior renoprotection in the diabetic apo E-KO mouse compared with quinapril in the context of greater renal ACE inhibition by omapatrilat than seen with quinapril, additional renal NEP inhibition and a modestly enhanced antihypertensive response.

CONCLUSIONS

These studies demonstrate the anti-atherosclerotic and renoprotective effects of omapatrilat in diabetic apo E-KO mice, a model of accelerated atherosclerosis and renal injury. These effects were observed in association with the local inhibition of ACE and NEP at the tissue level in the aorta and kidney. These results suggest that the anti-atherosclerotic effect conferred by omapatrilat treatment in the diabetic apo E-KO mouse is predominantly mediated by its capacity to inhibit local vascular ACE. By contrast, in the kidney, local renal ACE and NEP inhibition and the superior antihypertensive effect of omapatrilat all contribute to the renoprotective effect conferred by omapatrilat treatment in the diabetic apo E-KO mouse.

Predictors of failure to initiate randomized treatment in a large trial of antihypertensive drug therapy in the aged

BACKGROUND

The identification of factors that contribute to noncompliance with trial drug initiation where virtually complete compliance might be expected, may help identify patients whose management is least likely to comply with clinical guidelines and study protocols.

METHODS

Examination of cross-sectional and longitudinal data arising from the Second Australian National Blood Pressure Study. Prevalence rate ratios (RR) and 95% confidence intervals (CI) estimated from log-binomial models were used to assess associations between subject characteristics and whether the randomized drug was prescribed at trial randomization. The study population consisted of 6083 hypertensive Australians aged 65 to 84 years.

RESULTS

After adjusting for each variable in a multivariate model the following were significant predictors of failure to prescribe RR (95% CI): not previously prescribed antihypertensive drugs 2.89 (2.52-3.32); lower systolic blood pressure (BP) 1.51 (1.59-1.43) or diastolic BP 1.18 (1.22-1.13); younger age 80 to 84 v 65 to 79 years 0.75 (0.59-0.95); total cholesterol >or=6.6 v <or=5.0 mmol/L 1.27 (1.06-1.53); and not ever having had a raised cholesterol 1.20 (1.04-1.40). There was no difference in cardiovascular disease end points and death in those who were and were not initiated on drug therapy at randomization.

CONCLUSIONS

Failure to initiate antihypertensive therapy for patients at the randomization visit was associated with lower BP measurements, previous drug therapy, younger age, and a historic or current raised cholesterol, but not with overt cardiovascular disease or other risk factors. There was no difference in cardiovascular disease end points and death in those who were and were not initiated on drug therapy at randomization.

Identification of angiotensin converting enzyme 2 in the rodent retina

PURPOSE

An active renin-angiotensin system has been found in the retina of rats and humans. Angiotensin-converting enzyme 2 (ACE2) is a recently discovered enzymatic homologue of Angiotensin-converting enzyme (ACE) that may be an important new component of the renin-angiotensin system (RAS). This study assesses the involvement of ACE2 in the normal and diabetic rodent retina and its modulation by ACE inhibition.

METHODS

Sprague-Dawley rats were randomised into three groups, control, diabetes, and diabetes plus ramipril, with diabetes induced with the cell toxin streptozocin and the study run for 24 weeks. ACE2 and ACE gene levels were measured using quantitative real-time polymerase chain reaction (QRT-PCR), ACE2 protein expression was confirmed by Western blotting, and ACE and ACE2 catalytic activity were measured using specific activity assays in the rat retina. Localisation of ACE2 mRNA and protein were determined by in situ hybridisation and immunohistochemistry, respectively.

RESULTS

ACE mRNA levels were decreased to approximately 50% in the diabetic retina, but ACE2 mRNA levels were not significantly changed. ACE but not ACE2 gene expression was influenced by ramipril treatment. Following immunostaining, both ACE2 and ACE protein were localised predominantly to the inner nuclear layer (INL) but also to photoreceptors. In the diabetic retina, ACE enzyme activity was decreased, whereas ACE2 enzyme activity was increased.

CONCLUSIONS

This study has identified ACE2 gene and catalytically active protein in the rodent retina. In diabetes, the major changes were a decrease in ACE but an increase in ACE2 enzymatic activity. The ACE inhibitor ramipril did not reduce ACE2 enzymatic activity.

Why blockade of the renin–angiotensin system reduces the incidence of new-onset diabetes

Recent trials have suggested that inhibitors of the renin-angiotensin system (RAS), such as angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs), may reduce the incidence of new-onset diabetes in patients with or without hypertension and at high risk of developing diabetes. In this review, we critically evaluate the evidence from recent clinical trials for such a potential preventive effect of ACE inhibitors and ARBs, including a meta-analysis of these recent trials. The reduced incidence of diabetes in patients at high risk of developing diabetes by ACE inhibitors or ARBs has been explained by haemodynamic effects, such as improved delivery of insulin and glucose to the peripheral skeletal muscle, and non-haemodynamic effects, including direct effects on glucose transport and insulin signalling pathways, all of which decrease insulin resistance. There is now evidence that the pancreas may contain an in situ active RAS, which appears to be upregulated in an animal model of type 2 diabetes. Thus, ACE inhibitors and ARBs may act by attenuating the deleterious effect of angiotensin II on vasoconstriction, fibrosis, inflammation, apoptosis and beta-cell death in the pancreas, thereby protecting a critical beta-cell mass essential for insulin production. New evidence is presented that ACE inhibitors and ARBs may delay or prevent the development of insulin resistance and diabetes, for which novel mechanisms are suggested. The actions of agents that interrupt the RAS on insulin resistance, obesity and diabetes warrant further investigation in other animal models. Prospective clinical studies with the primary endpoint of the prevention of diabetes are now indicated to (i) further explore whether the inhibitors of the RAS are superior compared to other antihypertensive agents such as calcium channel blockers (CCBs) and (ii) to evaluate the potential beneficial effects of combination antihypertensive regimens on the development of diabetes.

Pharmacology of irbesartan

Despite the introduction of new antihypertensive agents such as angiotensin-converting enzyme inhibitors and calcium channel antagonists, the blood pressure of fewer than 30% of hypertensive patients is controlled with current therapies; compliance and continuation with medication are poor. The renin-angiotensin system is important in the pathophysiology of hypertension, end-organ damage and congestive cardiac failure. Irbesartan is an angiotensin II receptor antagonist that provides dose-dependent, specific, insurmountable blockade of the AT1 receptor both in vivo and in vitro. It is rapidly absorbed after oral administration, has a bioavailability of 60-80% with no food effect, does not require metabolism to a bioactive compound, and is excreted by both biliary and renal routes so that dosage adjustments are unnecessary in patients with renal or hepatic disease. Irbesartan produces dose-dependent blood pressure reductions, with 24 h activity confirmed by ambulatory blood pressure monitoring. Irbesartan is effective in the elderly and non-elderly, men and women and in cases of mild and severe hypertension. The recommended starting dosage is 150 mg once daily (o.d.), which can be increased to 300 mg. Its antihypertensive effect is accentuated by diuretic co-administration. In controlled clinical trials, irbesartan was at least as effective as atenolol, hydrochlorothiazide, amlodipine and enalapril. In a double-blind study, irbesartan 300 mg was more effective than losartan 100 mg, and in a dose-titration study, irbesartan 150-300 mg produced significantly greater blood pressure reductions than losartan 50-100 mg. In pooled data from nine placebo-controlled studies, adverse event and discontinuation rates for irbesartan were similar to those for placebo, and there was no relationship between dose and adverse effects. Preliminary clinical data suggest positive haemodynamic effects in heart failure and renoprotective effects in diabetic nephropathy.

Myocardial infarction increases ACE2 expression in rat and humans

AIMS

Angiotensin converting enzyme (ACE) 2 catalyses the cleavage of angiotensin (Ang) I to Ang 1-9 and of Ang II to Ang 1-7. ACE2 deficiency impairs cardiac contractility and upregulates hypoxia-induced genes, suggesting a link with myocardial ischaemia. We studied the expression of ACE2 after myocardial infarction (MI) in the rat as well as in human failing hearts.

METHODS AND RESULTS

Rats were killed at days 1, 3, and 28 after MI, or treated for 4 weeks with the ACE inhibitor ramipril (1 mg/kg). Cardiac gene and protein expression of ACE and ACE2 were assessed by quantitative real-time reverse transcriptase-polymerase chain reaction and immunohistochemistry/activity assays/in vitro autoradiography, respectively. Both ACE (P = 0.022) and ACE2 (P = 0.015) mRNA increased in the border/infarct area compared with the viable area at day 3 after MI. By day 28, increases in ACE (P = 0.005) and ACE2 (P = 0.006) mRNA were also seen in the viable myocardium of MI rats compared with myocardium of control rats. ACE2 protein localized to macrophages, vascular endothelium, smooth muscle, and myocytes. Ramipril attenuated cardiac hypertrophy and inhibited cardiac ACE. In contrast, ramipril had no effect on cardiac ACE2 mRNA, which remained elevated in all areas of the MI rat heart. Immunoreactivity of both ACE and ACE2 increased in failing human hearts.

CONCLUSION

The increase in ACE2 after MI suggests that it plays an important role in the negative modulation of the renin angiotensin system in the generation and degradation of angiotensin peptides after cardiac injury.

ACE2, a new regulator of the renin-angiotensin system

Angiotensin-converting enzyme (ACE) is a zinc metalloproteinase and a key regulator of the renin-angiotensin system (RAS). ACE2 is a newly described enzyme identified in rodents and humans with a more restricted distribution than ACE, and is found mainly in heart and kidney. ACE2 cleaves a single residue from angiotensin I (Ang I) to generate Ang 1-9, and degrades Ang II, the main effector of the RAS, to the vasodilator Ang 1-7. The importance of ACE2 in normal physiology and pathophysiological states is largely unknown. ACE2 might act in a counter-regulatory manner to ACE, modulating the balance between vasoconstrictors and vasodilators within the heart and kidney, and playing a significant role in regulating cardiovascular and renal function.

Differential tissue and enzyme inhibitory effects of the vasopeptidase inhibitor omapatrilat in the rat

Vasopeptidase inhibitors simultaneously inhibit angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP). The present study characterized the tissue distributions of ACE and NEP, and assessed the effects of the vasopeptidase inhibitor omapatrilat on ACE and NEP in rat tissues. In vivo ACE and NEP inhibition was studied by in vitro autoradiography and using the ACE inhibitor radioligand (125)I-MK351A and the NEP inhibitor radioligand (125)I-RB104 in rats that received oral omapatrilat (40 mg x day(-1) x kg(-1)) for 3 days. In vitro autoradiography was used to examine the distribution of ACE and NEP in the kidney, aorta, heart, adrenal gland, lung, intestine, liver, spleen and brain, and to assess enzyme inhibition after oral omapatrilat. Omapatrilat inhibited plasma ACE and increased plasma renin activity (P <0.01). Tissue ACE was inhibited by 70-95% (P <0.01), except in the brain, where ACE was not inhibited. NEP was inhibited by 87% in the kidney and by 20-40% in atria, aorta, adrenal gland, lung, liver and intestine; it was not inhibited in the brain, the ventricle or the spleen. Omapatrilat is a potent vasopeptidase inhibitor that significantly inhibits tissue ACE and NEP, with the degree of inhibition varying according to the enzyme and the tissue under assessment. The degree and site of tissue enzyme inhibition by vasopeptidase inhibitors may be relevant to end-organ protection as well as to the side-effect profiles of these agents.

Renoprotective effects of vasopeptidase inhibition in an experimental model of diabetic nephropathy

AIMS

Although ACE inhibitors slow progression of diabetic renal disease, the mortality and morbidity is still high. As other hormonal factors are involved, inhibition of vasopeptidases could further reduce progression. We studied dual inhibition of angiotensin converting enzyme and neutral endopeptidase in a model of progressive diabetic renal injury. The major endpoints were reductions in systemic blood pressure, albuminuria and renal structural injury.

METHODS

Diabetic spontaneously hypertensive rats were treated with the ACE inhibitor perindopril (mg.kg(-1).day(-1)) or the vasopeptidase inhibitor omapatrilat at doses of 10 (oma10) and 40 (oma40) mg.kg(-1).day(-1) for 32 weeks. In vivo ACE and NEP inhibition was quantitated by in vitro autoradiography. Renal structural injury was assessed by measurement of the glomerulosclerotic (GS) index and tubulointerstitial area (TI). The expression of transforming growth factor beta, beta-inducible gene-h3 and nephrin were also quantitated.

RESULTS

Despite a similar reduction in blood pressure by perindopril and oma10, greater attenuation of albuminuria was afforded by oma10, with a complete amelioration observed with oma40. Oma40 lead to a 33% reduction in renal NEP binding and this was associated with less albuminuria and prevention of GS, TI area and overexpression of TGFbeta and betaig-h3. Diabetes-associated reduction in nephrin expression was restored by both drugs.

CONCLUSION/INTERPRETATION

These findings suggest that other vasoactive mechanisms in addition to angiotensin II are important in the prevention of diabetic nephropathy, and that vasopeptidase inhibition might confer an advantage over blockade of the RAS alone in the treatment of diabetic renal disease.

Regulation of angiotensin II receptors in the prostate of the transgenic (mRen-2)27 rat: effect of angiotensin-converting enzyme inhibition

We examined the regulation/expression of angiotensin II (Ang II) receptors in the transgenic (TG) (mRen-2)27 rat compared to the normal Sprague-Dawley (SD) rat. Ang II receptor binding and mRNA expression were determined by quantitative autoradiography and real-time PCR, respectively. Ang II receptors in the rat prostate rat were of the AT(1) receptor subtype and were significantly reduced in the prostate of the TG rat compared to the normal SD rat. However, AT(1) receptor binding was significantly higher in the prostate of the TG rat treated with the ACE inhibitor lisinopril compared to the untreated TG rat and comparable to the control SD rat. In contrast to the protein, AT(1) receptor mRNA expression was not reduced in the prostate of the TG rat compared to the SD rat. However, AT(1) receptor mRNA was markedly reduced in the prostate of the lisinopril-treated TG rat compared to the untreated TG rat or control SD rat. In conclusion, the findings suggest that AT(1) receptors are present in the rat prostate at a protein level and are subject to down-regulation in the TG rat which may be due to receptor internalisation as a consequence of receptor hyper-stimulation by increased local tissue levels of Ang II. Moreover, AT(1) receptor protein and mRNA expression in the prostate may be inversely modulated.

Characterization of renal angiotensin-converting enzyme 2 in diabetic nephropathy

ACE2, initially cloned from a human heart, is a recently described homologue of angiotensin-converting enzyme (ACE) but contains only a single enzymatic site that catalyzes the cleavage of angiotensin I to angiotensin 1-9 [Ang(1-9)] and is not inhibited by classic ACE inhibitors. It also converts angiotensin II to Ang(1-7). Although the role of ACE2 in the regulation of the renin-angiotensin system is not known, the renin-angiotensin system has been implicated in the pathogenesis of diabetic complications and in particular in diabetic nephropathy. Therefore, the aim of this study was to assess the possible involvement of this new enzyme in the kidney from diabetic Sprague-Dawley rats to compare and contrast it to ACE. ACE2 and ACE gene and protein expression were measured in the kidney after 24 weeks of streptozocin diabetes. ACE2 and ACE mRNA levels were decreased in diabetic renal tubules by approximately 50% and were not influenced by ACE inhibitor treatment with ramipril. By immunostaining, both ACE2 and ACE protein were localized predominantly to renal tubules. In the diabetic kidney, there was reduced ACE2 protein expression that was prevented by ACE inhibitor therapy. The identification of ACE2 in the kidney, its modulation in diabetes, and the recent description that this enzyme plays a biological role in the generation and degradation of various angiotensin peptides provides a rationale to further explore the role of this enzyme in various pathophysiological states including diabetic complications.

A comparison of outcomes with angiotensin-converting--enzyme inhibitors and diuretics for hypertension in the elderly

BACKGROUND

Treatment of hypertension with diuretics, beta-blockers, or both leads to improved outcomes. It has been postulated that agents that inhibit the renin-angiotensin system confer benefit beyond the reduction of blood pressure alone. We compared the outcomes in older subjects with hypertension who were treated with angiotensin-converting-enzyme (ACE) inhibitors with the outcomes in those treated with diuretic agents.

METHODS

We conducted a prospective, randomized, open-label study with blinded assessment of end points in 6083 subjects with hypertension who were 65 to 84 years of age and received health care at 1594 family practices. Subjects were followed for a median of 4.1 years, and the total numbers of cardiovascular events in the two treatment groups were compared with the use of multivariate proportional-hazards models.

RESULTS

At base line, the treatment groups were well matched in terms of age, sex, and blood pressure. By the end of the study, blood pressure had decreased to a similar extent in both groups (a decrease of 26/12 mm Hg). There were 695 cardiovascular events or deaths from any cause in the ACE-inhibitor group (56.1 per 1000 patient-years) and 736 cardiovascular events or deaths from any cause in the diuretic group (59.8 per 1000 patient-years; the hazard ratio for a cardiovascular event or death with ACE-inhibitor treatment was 0.89 [95 percent confidence interval, 0.79 to 1.00]; P=0.05). Among male subjects, the hazard ratio was 0.83 (95 percent confidence interval, 0.71 to 0.97; P=0.02); among female subjects, the hazard ratio was 1.00 (95 percent confidence interval, 0.83 to 1.21; P=0.98); the P value for the interaction between sex and treatment-group assignment was 0.15. The rates of nonfatal cardiovascular events and myocardial infarctions decreased with ACE-inhibitor treatment, whereas a similar number of strokes occurred in each group (although there were more fatal strokes in the ACE-inhibitor group).

CONCLUSIONS

Initiation of antihypertensive treatment involving ACE inhibitors in older subjects, particularly men, appears to lead to better outcomes than treatment with diuretic agents, despite similar reductions of blood pressure.

Angiotensin-converting enzyme inhibition in adult hypertensive rats: a stereological study of renal filtration surface area

1. Angiotensin-converting enzyme (ACE) inhibitor treatment leads to beneficial effects on kidney function. The aim of the present study was to determine whether ACE inhibition at high or low doses affects glomerular capillary surface area and length, glomerular number or total renal filtration surface area in rats with established hypertension and, if so, to determine whether these effects are mediated through bradykinin potentiation. 2. Spontaneously hypertensive rats (SHR) were treated with the ACE inhibitor perindopril at either 3 or 0.1 mg/kg per day (high and low doses, respectively) from 16 to 24 weeks of age. Some rats were concomitantly treated with the bradykinin B2 receptor antagonist S16118 (10 nmol/kg per day). Blood pressure was measured twice weekly during the treatment period. At 24 weeks of age, rats were perfusion fixed at 140 mmHg, the kidneys removed, embedded in resin and examined stereologically to estimate glomerular number and volume, length and surface area of glomerular capillaries and total renal filtration surface area. 3. High- and low-perindopril treatment significantly reduced systolic blood pressure compared with control SHR. However, the rats treated with low-dose perindopril were still considered hypertensive. Neither low-dose nor high-dose perindopril treatment had any observable effect on glomerular number (23 876 +/- 1201 vs 26 240 +/- 1465 glomeruli/kidney, respectively) or volume (2.25 +/- 0.21 and 1.96 +/- 0.06 x 10-3 mm3, respectively) compared with controls (glomerular number 25866 +/- 1210 glomeruli/kidney; glomerular volume 2.24 +/- 0.21 x 10-3 mm3). As a result, there was no significant difference in total renal filtration surface area between any of the experimental groups (8161.6 +/- 550.9, 8699.7 +/- 427.6, 9081.9 +/- 453.6, 8830.2 +/- 521.2 and 8559.4 +/- 341.4 mm2 for SHR, SHR low-dose perindopril, SHR low-dose perindopril + B2 antagonist, SHR high-dose perindopril and SHR high-dose perindopril + B2 antagonist, respectively). Coadministration of the bradykinin antagonist had no observable effect on any of the parameters studied. 4. In conclusion, because neither high-dose nor low-dose perindopril had any effect on total renal filtration surface area, the observed beneficial effects of ACE inhibition on kidney function are not the result of enhancement in glomerular capillary surface area.

Combined inhibition of neutral endopeptidase with angiotensin converting enzyme or endothelin converting enzyme in experimental diabetes

OBJECTIVE

The effects of combined inhibition of neutral endopeptidase (NEP) with either angiotensin-converting enzyme (ACE), or endothelin-converting enzyme (ECE) on blood pressure, urinary albumin excretion and heart weight were explored in experimental diabetes.

DESIGN

Streptozotocin-induced diabetic Sprague-Dawley rats were treated with vehicle, the NEP/ACE inhibitor S 21402, the NEP/ECE inhibitor CGS 26303, the NEP inhibitor SCH 42495, the ACE inhibitor captopril or the endothelin receptor antagonist bosentan for 4 weeks.

METHODS

Blood pressure was measured by tail-cuff method and radiotelemetry. Albuminuria, plasma renin activity and plasma atrial natriuretic peptide (ANP) were determined by radioimmunoassay. NEP binding was assessed by in vitro quantitative autoradiography. Metabolic and biochemistry parameters including food intake, 24-h urine volume, plasma glucose, glycated hemoglobin, glomerular filtration rate (GFR) and urinary sodium excretion were also determined.

RESULTS

Mean blood pressure over the 4-week study period after commencement of treatment was reduced to a similar extent by a range of treatments including the ACE inhibitor, NEP/ACE inhibitor, endothelin receptor antagonist, NEP/ECE inhibitor, but not the NEP inhibitor, compared with vehicle-treated diabetic rats. Heart to body weight ratio in diabetic rats was only reduced by the NEP/ACE and the NEP/ECE inhibitor. Increased albuminuria in diabetic rats (1.1 times/divided by 1.2 mg/day) was reduced by the NEP/ACE (0.6 times/divided by 1.2 mg/day) and the NEP/ECE inhibitors (0.4 times/divided by 1.2 mg/day). Renal NEP was reduced by the NEP/ACE inhibitor (35 +/- 4%) or NEP/ECE inhibitor (38 +/- 4%) as well as by the pure NEP inhibitor (27 +/- 4%) compared with the untreated diabetic group. Other abnormal metabolic and biochemical parameters in diabetic rats were not influenced by any drug treatment.

CONCLUSIONS

Combined inhibition of NEP/ACE or NEP/ECE confers beneficial effects on blood pressure, albuminuria and heart to body weight ratio in experimental diabetes.

Neurohormonal antagonism in heart failure; beneficial effects of vasopressin V(1a) and V(2) receptor blockade and ACE inhibition

OBJECTIVE

To assess the long-term efficacy of vasopressin (AVP) V(1a) and V(2) receptor blockade with conivaptan, alone and in combination with angiotensin converting enzyme (ACE) inhibition on blood pressure, metabolic and neurohormonal parameters, and cardiovascular structure in a rat model of congestive heart failure (CHF).

METHODS

CHF was induced by left coronary artery ligation. CHF rats received conivaptan (1 mg/kg/day), ACE inhibition (captopril, 50 mg/kg/day), conivaptan and captopril (Combination) or vehicle for 4 weeks. Blood pressure was measured weekly, metabolic caging studies performed at 25 days, and rats killed and blood and tissue collected after 4 weeks treatment.

RESULTS

Combination treatment lowered blood pressure (P<0.01), and conivaptan and Combination caused an aquaresis (P<0.01). Combination decreased plasma natriuretic peptide (P<0.05), reduced left and right ventricular mass (P<0.01) and lung mass (P<0.05).

CONCLUSIONS

In CHF, blockade of vasopressin V(1a) and V(2) receptors was associated with increased water excretion, and the combination of conivaptan with ACE inhibition was the only treatment to reduce blood pressure, natriuretic peptide and pulmonary congestion. These results suggest conivaptan may be a useful addition to ACE inhibitors in the management of vasoconstriction and fluid retention that characterizes CHF.

Evidence for activation of the renin-angiotensin system in the human prostate: increased angiotensin II and reduced AT(1) receptor expression in benign prostatic hyperplasia

The expression and cellular localization of angiotensin II (Ang II) and AT(1) receptor proteins were examined in the normal human prostate and benign prostatic hyperplasia (BPH) by immunohistochemistry. In the normal prostate, Ang II immunoreactivity was localized to the basal layer of the epithelium and AT(1) receptor immunostaining was found predominantly on stromal smooth muscle and also on vascular smooth muscle of prostatic blood vessels. Ang II immunoreactivity was markedly increased in hyperplastic acini in BPH compared with acini in the normal prostate (normal: 7.4+/-0.2%, n=5 vs. BPH: 22.7+/-1.9%, n=5, p<0.001). However, AT(1) receptor immunoreactivity was significantly decreased in BPH compared with the normal prostate [normal: 16.4+/-2.2%, n=4 vs. BPH: 9.4+/-1.3%, n=5, p<0.05 (p=0.025)]. The present study demonstrates the presence of Ang II peptide in the basal layer of the epithelium and AT(1) receptors on stromal smooth muscle, suggesting that Ang II may mediate paracrine functions on cellular growth and smooth muscle tone in the human prostate. Furthermore, AT(1) receptor down-regulation in BPH may be due to receptor hyperstimulation by increased local levels of Ang II in BPH. These data extend previous findings in support of the novel concept that overactivity of the renin-angiotensin system (RAS) may be involved in the pathophysiology of BPH.

Evidence for cardioprotective, renoprotective, and vasculoprotective effects of vasopeptidase inhibitors in disease

In both the natriuretic peptide and renin-angiotensin systems, peptidases play an important role in the inactivation or activation of the system. Angiotensin-converting enzyme is responsible for the conversion of angiotensin I to angiotensin II, while neutral endopeptidase is one of the pathways involved in the degradation of the natriuretic peptides. The vasopeptidase inhibitors, which simultaneously inhibit neutral endopeptidase and angiotensin-converting enzyme, appear to offer distinct therapeutic advantages in treating hypertension, heart failure, and endothelial dysfunction.

Localization of angiotensin-converting enzyme in the human prostate: pathological expression in benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is the most common hyperplastic disease in man and it is characterized by increased cellular growth (stromal and epithelial hyperplasia) and enhanced local sympathetic tone, both of which are known to be augmented by activation of the renin-angiotensin system (RAS) in other tissues. Angiotensin-converting enzyme (ACE) is an integral component of the RAS that is responsible for the production of the active peptide angiotensin II from the inactive precursor angiotensin I. The present study was undertaken to map the anatomical localization of ACE protein and messenger ribonucleic acid (mRNA) in the normal human prostate and to establish whether their expression is pathologically altered in BPH. Human prostate samples were obtained at post-mortem and histologically defined as normal or hyperplastic. ACE protein binding/expression was determined by in vitro autoradiography and immunohistochemistry using the ACE-specific radioligand [125I]-MK351A and a mouse anti-ACE polyclonal antibody, respectively, whereas the spatiotemporal distribution of ACE mRNA was determined by in situ hybridization using 35S-labelled oligonucleotide probes. ACE protein was localized to the glandular epithelium in the human prostate. ACE binding and immunostaining were increased in BPH compared with normal (non-hyperplastic) prostate specimens [X-ray film autoradiography: normal 873+/-48 dpm/mm2 (n=8) vs. BPH 1631+/-274 dpm/mm2 (n=6), p<0.05; emulsion autoradiography: normal 3.1+/-0.5 grains/mm2 (n=6) vs. BPH 32.8+/-8.6 grains/mm2 (n=5), p<0.01]. ACE mRNA was also localized to glandular epithelial cells in the human prostate with a significant increase in ACE mRNA expression in BPH compared with the normal prostate [normal 11.04+/-2.03 grains/cell (n=220 cells total) vs. BPH 22.29+/-1.34 grains/cell (n=198 cells total), p<0.05]. The findings of the present study suggest that ACE is localized to the glandular epithelium of the human prostate and that its expression, at both protein and mRNA level, is aberrantly increased in BPH. These data support the concept that hyperactivity of the local RAS in the prostate may be involved in the pathogenesis of BPH.

Angiotensin AT(4) receptors in the normal human prostate and benign prostatic hyperplasia

The cellular localisation and expression of angiotensin AT(4) receptors was examined in the normal human prostate and benign prostatic hyperplasia (BPH) by quantitative in vitro autoradiography using [(125)I]-Ang IV. In the normal human prostate, AT(4) receptors were localised to the glandular epithelium. Interestingly, specific AT(4) receptor binding was significantly reduced in BPH compared to the normal prostate, as quantitated macroscopically (normal: 5038+/-476 dpm/mm(2), n=6 vs BPH: 2701+/-176 dpm/mm(2), n=6, P<0.001) and microscopically (normal: 7.28+/-0.36 grains/mm(2), n=6 vs BPH: 2.50+/-0.47 grains/mm(2), n=6, P<0.001). The findings of the present study demonstrate the presence of AT(4) receptors in the human prostate, being localised to the glandular epithelium, which suggest that the Ang IV/AT(4) system may play a role in the regulation of ionic transport and glandular secretion in the human prostate. The observation that AT(4) receptors appear reduced in BPH suggests that the AT(4) receptor may undergo agonist-induced receptor internalisation, possibly due to increased local tissue levels of Ang IV in BPH.

Angiotensin II enhances noradrenaline release from sympathetic nerves of the rat prostate via a novel angiotensin receptor: implications for the pathophysiology of benign prostatic hyperplasia

The renin-angiotensin system (RAS) is present in the human prostate and may be activated in benign prostatic hyperplasia (BPH), possibly contributing to the pathophysiology of this disorder by enhancing local sympathetic tone and cell growth. The functional role of the RAS in the prostate, however, is unknown. The present study was undertaken to determine whether angiotensin (Ang) II enhances sympathetic transmission in the prostate. The neuronal stores of the rat prostate were labelled with [(3)H]noradrenaline (NA). Ang II and Ang I enhanced [(3)H]NA release in a concentration-dependent manner. The Ang II receptor subtype 1 (AT(1) receptor) antagonist losartan and the AT(2) receptor antagonist PD123319 inhibited this facilitatory effect of Ang II and Ang I, whereas the other AT(2) receptor antagonist, CGP42112, was without effect. Bradykinin also increased [(3)H]NA release, which was inhibited by the B(2) receptor antagonist Hoe140. The angiotensin-converting enzyme inhibitor captopril inhibited the effect of Ang I, but potentiated that of bradykinin. Interestingly, captopril alone produced an increase in [(3)H]NA release which was inhibited by Hoe140. Losartan, but not PD123319 or CGP42112, inhibited [(125)I]-Ang II binding in Chinese hamster ovary cells transfected with the AT(1a) or AT(1b) receptor. In contrast, in cells expressing the AT(2) receptor, PD123319 and CGP42112, but not losartan, inhibited [(125)I]-Ang II binding. In conclusion, Ang II enhances the release of NA from sympathetic nerves of the rat prostate via a novel functional receptor distinct from the cloned AT(1a), AT(1b) or AT(2). These data provide direct evidence in support of a functional role for the local RAS in modulating sympathetic transmission in the prostate, which may have important implications for the pathophysiology of BPH.

Chronic heart failure in Australian general practice. The Cardiac Awareness Survey and Evaluation (CASE) Study

OBJECTIVES

To investigate the frequency and general practitioner awareness of patients with chronic heart failure (CHF), and to evaluate a cardiac algorithm and document cardiac investigations performed in establishing this diagnosis.

DESIGN AND SETTING

Between March and August 1998, consecutive patients aged 60 years and older presenting to their GP were assessed. In patients previously diagnosed with CHF, aetiology and diagnostic assessments were documented. In patients with suspected CHF (by a standardised algorithm, based on World Health Organization guidelines), further investigations and GP diagnosis were recorded.

PATIENTS

80 consecutive patients were assessed by each of 341 GPs throughout Australia, reflecting the Australian metropolitan/rural population mix of 1996. This provided a total of 22060 evaluable patients.

MAIN OUTCOME MEASURES

Estimated numbers of patients with CHF in general practice (previously and newly diagnosed); major aetiological factors; use of ancillary diagnostic tests; drugs prescribed.

RESULTS

CHF was diagnosed in 2905 of 22060 patients (13.2%) (2485 previously diagnosed and 420 newly diagnosed). Major aetiological factors were ischaemic heart disease and hypertension. Echocardiography had been performed in 64% of previously diagnosed patients, but was performed in only 22% of possible CHF patients. Angiotensin-converting enzyme (ACE) inhibitors were prescribed in 58.1% of patients with CHF. Patients with evidence of left ventricular dysfunction were more likely to have received ACE inhibitors.

CONCLUSIONS

CHF appears to be very common in the elderly, based on GP diagnosis of the condition. Of 100 patients aged 60 years and over presenting to their GP, two new cases of CHF will be detected using a simple clinical algorithm in conjunction with appropriate diagnostic tests. ACE inhibitors appear to be underutilised.

Angiotensin receptors: distribution, signalling and function

Angiotensin II (Ang II) is a multi-functional hormone that plays a major role in regulating blood pressure and cardiovascular homoeostasis. The actions of Ang II are mediated by at least two receptor subtypes, designated AT(1) and AT(2). In addition, other angiotensin receptors have been identified which may recognize other angiotensin peptide fragments; however, until now only the AT(1) and AT(2) receptor have been cloned in animals or humans. Most of the well-described actions of Ang II, such as vasoconstriction, facilitation of sympathetic transmission, stimulation of aldosterone release and promotion of cellular growth are all mediated by the AT(1) receptor. Much less is known about the function of the AT(2) receptor, but recent studies suggest that it may play a role in mediating anti-proliferation, cellular differentiation, apoptosis and vasodilatation. In this review, we discuss recent advances in our understanding of Ang II receptors, in particular, their distribution, signalling and function.

In-vitro and in-vivo inhibition of rat neutral endopeptidase and angiotensin converting enzyme with the vasopeptidase inhibitor gemopatrilat

OBJECTIVES

Vasopeptidase inhibitors are single molecules that simultaneously inhibit neutral endopeptidase (NEP) and angiotensin converting enzyme (ACE). The aim of this study was to characterize in-vitro and in-vivo inhibition of NEP and ACE in the rat with the vasopeptidase inhibitor gemopatrilat.

DESIGN AND METHODS

In-vitro NEP and ACE inhibition was studied by radioinhibitory binding assay using rat renal membranes and the specific NEP inhibitor radioligand 125I-RB104 and the specific ACE inhibitor radioligand 125I-MK351A, respectively (n = 3 per curve). In-vivo NEP and ACE inhibition was studied using in-vitro autoradiography in rats that received oral gemopatrilat (1, 3, 10 mg/kg; n = 4 per dose) and were killed 1 h later, or received oral gemopatrilat (3, 10 mg/kg) and were killed at time points 1, 2, 4, 8, 18, 24 and 48 h (n = 4 per time point).

RESULTS

Gemopatrilat caused a concentration-dependent displacement of specific radioligands from renal membrane NEP (IC50 305 +/- 5.4 nmol/I) and ACE (IC50 3.6 +/- 0.02 nmol/). In the dose-response study gemopatrilat (1, 3 and 10 mg/kg) caused significant inhibition of plasma ACE (P< 0.01), and renal ACE and NEP (3, 10 mg/kg, P < 0.01). In the time course experiment, gemopatrilat (10 mg/kg) increased plasma renin activity for 8 h (P< 0.01) and inhibited plasma ACE (P< 0.05), renal NEP (P< 0.01) and renal ACE (P< 0.05) for 48 h.

CONCLUSIONS

Gemopatrilat is a potent in-vitro vasopeptidase inhibitor that also causes prolonged inhibition of circulating and renal ACE and renal NEP after a single oral dose. The data suggest that gemopatrilat may be a useful addition to existing vasopeptidase inhibitors in the treatment of cardiovascular disease.

Effect of angiotensin-converting enzyme inhibition on myocardial vascularization in the adolescent and adult spontaneously hypertensive rat

OBJECTIVE

To determine whether angiotensin-converting enzyme (ACE) inhibition treatment enhances myocardial vascularization in adolescent and adult spontaneously hypertensive rats (SHRs).

METHODS

Male SHRs were treated from 7 to 14 or from 16 to 24 weeks of age with the ACE inhibitor, perindopril, in either a low dose (0.1 mg/kg per day) or a high dose (1 mg/kg per day). Some rats were concomitantly treated with a bradykinin antagonist. At termination of treatment, the left ventricular wall was extensively sampled and the surface area density and length density of myocardial blood vessels stereologically determined.

RESULTS

High-dose perindopril treatment prevented the development of hypertension and left ventricular hypertrophy in adolescent SHRs and markedly reduced blood pressure and left ventricular size in adult SHRs. SHRs treated with the low dose of perindopril remained hypertensive, although there were significant reductions in blood pressure and left ventricular growth. High-dose perindopril treatment in adolescent SHRs led to a significant increase in the surface area density of blood vessels in the left ventricle after 4 weeks of treatment and an increase in both the surface area density and length density of blood vessels after 7 weeks of treatment Co-administration with the bradykinin antagonist did not reverse these effects. In contrast, ACE inhibitor treatment had no effect on myocardial vascularization in adult rats with established hypertension.

CONCLUSION

ACE inhibitor treatment enhances vascularization in the adolescent heart through reductions in myocardial mass, but not capillary growth. ACE inhibition in the adult heart with established hypertension reduces left ventricular hypertrophy, but does not enhance myocardial capillarization.

Identification, distribution, and expression of angiotensin II receptors in the normal human prostate and benign prostatic hyperplasia

The tissue distribution, cellular localization, and level of expression of angiotensin II (Ang II) receptors were examined in the normal human prostate and benign prostatic hyperplasia (BPH) by in vitro autoradiography, immunohistochemistry, and radioligand binding studies. In the normal human prostate, Ang II receptors were of the AT(1) subtype and localized predominantly to periurethral stromal smooth muscle. The AT(1) receptor antagonist losartan totally displaced specific [(125)I]-[Sar(1),Ile(8)]Ang II binding, in a concentration-dependent manner, whereas the AT(2) receptor antagonist PD123319 was without effect. There was no significant difference in receptor affinity, but AT(1) receptor density was markedly reduced in BPH compared with that in normal prostate. In rat prostate, Ang II (0.01-1 microM) produced a concentration-dependent increase in [(3)H]-noradrenaline release from sympathetic nerves. The findings of the present study suggest that angiotensin AT(1) receptors predominate in the human prostate. The high concentration of AT(1) receptors in the periurethral region suggests a role for Ang II in modulating cell growth, smooth muscle tone, and possibly micturition. Furthermore, down-regulation of AT(1) receptors in BPH may be due to receptor hyperstimulation by increased local levels of Ang II in BPH. Finally, Ang II may play a functional role in modulating sympathetic transmission in the prostate. These data support the novel concept that activation of the renin-angiotensin system may be involved in the pathophysiology of BPH.