Effects of valsartan on mechanical properties of the carotid artery in spontaneously hypertensive rats under high-salt diet

Antihypertensive drug valsartan as a novel BDK inhibitor

Catabolism of branched-chain amino acids (BCAAs) is affected by various physiological conditions and its abnormality is associated with glucose metabolism, heart disease, and neurological dysfunction. The first two steps of the BCAA metabolic pathway are common to the three BCAAs (leucine, isoleucine, and valine). The second step is an irreversible rate-limited reaction catalyzed by branched-chain α-keto acid dehydrogenase (BCKDH), which is bound to a specific kinase, BCKDH kinase (BDK), and inactivated by phosphorylation. Here, we investigated potential new BDK inhibitors and discovered valsartan, an angiotensin II type 1 receptor (AT1R) blocker, as a new BDK inhibitor. BCKDH phosphorylation and the BCKDH-BDK interaction were inhibited by valsartan in vitro. Valsartan administration in rats resulted in increased BCKDH activity by decreasing the dephosphorylated level of BCKDH complex, bound forms of BDK from BCKDH complex as well as decreased plasma BCAA concentrations. Valsartan is a novel BDK inhibitor that competes with ATP, via a different mechanism from allosteric inhibitors. The BDK inhibitor has been shown to preserve cardiac function in pressure overload-induced heart failure mice and to attenuate insulin resistance in obese mice. Our findings suggest that valsartan is a potent seed compound for developing a powerful BDK inhibitor and useful medication for treating heart failure and metabolic diseases with suppressed BCAA catabolism.

Increase in Vascular Injury of Sodium Overloaded Mice May be Related to Vascular Angiotensin Modulation

This study aimed to analyzing the effect of chronic sodium overload upon carotid and femoral injury, and its relation to vascular angiotensin modulation. Male C57Bl6 mice were divided in: control (cont), receiving 1% NaCl solution for 2 weeks (salt-2) or 12 weeks (salt-12). Two-weeks before the end of the study, a 2mm catheter was implanted around the left femoral and carotid arteries to induce injury. Blood pressure (BP) and heart rate (HR) were measured at the end of the study by tail plethysmography. Arteries were collected and prepared for histological analysis to determine arterial thickening and perivascular collagen deposition. Angiotensin II and Ang(1-7) were quantified in fresh arteries using the HPLC method. There were no differences in body weight, BP and HR. Intima/media ratio had a similar increase in both injured arteries of cont and salt-2 mice, but a more pronounced increase was observed in salt-12 mice (31.1±6%). On the other hand, sodium overload modified perivascular collagen deposition, increasing thick fibers (cont: 0.5%; salt-2: 3.4%; salt-12: 0.6%) and decreasing thin fibers (cont: 7.4%; salt-2: 0.5%; salt-12: 6.8%) in non-injured arteries. Injured arteries presented similar collagen fiber distribution. Angiotensin quantification showed increased Ang(1-7) in salt treated mice (salt-2: +72%; salt-12: +45%) with a concomitant decrease in Ang II (salt-2: -54%; salt-12: -60%). Vascular injury increased significantly Ang(1-7) in salt-12 mice (+80%), maintaining Ang II reduction similar to that of a non-injured artery. The lack of changes in BP and HR suggests that the structural changes observed may be due to non-hemodynamic mechanisms such as local renin-angiotensin system. Collagen evaluation suggests that sodium overload induces time-related changes in vascular remodeling. The increase of artery injury with concomitant increase in Ang(1-7) in 12-week treated mice shows a direct association between the duration of salt treatment and the magnitude of vascular injury.

Cardioprotective effect of valsartan in mice with short-term high-salt diet by regulating cardiac aquaporin 1 and angiogenic factor expression

Hypertension is the most common risk factor for various cardiovascular and cerebrovascular diseases that affects approximately 61 million, or 25% of the population in United States. The dietary salt intake is one of the most important but modifiable factors for hypertension. In the current study, we aim to elucidate the role of aquaporin 1 in high-salt-induced hypertension and cardiac injuries and whether angiotensin II receptor blocker valsartan could ameliorate the effect of high salt on blood pressure. Mice were fed with normal diet, high-salt diet in the presence or absence of valsartan for 4 weeks. The body weight gain, feeding behavior, blood pressure, and cardiac pathology changes were monitored after 4 weeks. The expression of aquaporin 1, vascular endothelial growth factor, transforming growth factor β1, and basic fibroblast growth factor were analyzed using quantitative real-time polymerase chain reaction, Western blot, and immunohistochemical staining. Valsartan partially reversed the effects of high-salt diet on hypertension, cardiac injuries such as fibrosis and inflammatory cell infiltration, and inhibition of aquaporin 1 and angiogenic factors; valsartan alone did not exert such effects. The current data demonstrated that the reduction of cardiac aquaporin 1 and angiogenic factor expression level might be associated with high-salt-induced hypertension and cardiac injuries in mice, which could be ameliorated by angiotensin II receptor blocker treatment.

Comparative effectiveness of a fixed-dose combination of losartan + HCTZ versus bisoprolol + HCTZ in patients with moderate-to-severe hypertension: results of the 6-month ELIZA trial

Background

The aim of this study was to compare the antihypertensive efficacy of losartan 100 mg + hydrochlorothiazide (HCTZ) 25 mg versus bisoprolol 10 mg + HCTZ 25 mg and their influence on arterial stiffness and central blood pressure (BP).

Methods

Of 60 patients with a mean BP of 173.3 ± 1.7/98.4 ± 1.2 mmHg, 59 were random-ized to losartan + HCTZ (n = 32) or bisoprolol + HCTZ (n = 27). Amlodipine was added if target BP was not achieved at 1 month, and doxazosin was added if target BP was not achieved after 3 months. Body mass index, office and 24-hour ambulatory BP, pulse wave velocity (carotid-femoral [PWVE] and radial [PWVM]), noninvasive central systolic BP, augmentation index (AIx), laboratory investigations, and electrocardiography were done at baseline and after 6 months of treatment.

Results

Losartan + HCTZ was as effective as bisoprolol + HCTZ, with target office BP achieved in 96.9% and 92.6% of patients and target 24-hour BP in 75% and 66.7% of patients, respectively, after 6 months. Effective treatment of BP led to significant lowering of central systolic BP, but this was decreased to a significantly (P < 0.05) greater extent by losartan + HCTZ (−23.0 ± 2.3 mmHg) than by bisoprolol + HCTZ (−15.4 ± 2.9 mmHg) despite equal lowering of brachial BP. Factors correlated with central systolic BP and its lowering differed between the treatment groups. Losartan + HCTZ did not alter arterial stiffness patterns significantly, but bisoprolol + HCTZ significantly increased AIx. We noted differences in ΔPWVE, ΔPWVM, and ΔAIx between the groups in favor of losartan + HCTZ. Decreased heart rate was associated with higher central systolic BP and AIx in the bisoprolol + HCTZ group, but was not associated with increased AIx in the losartan + HCTZ group.

Conclusion

Although both treatments decreased both office and 24-hour BP, losartan + HCTZ significantly decreased central systolic BP and had a more positive influence on pulse wave velocity, with a less negative effect of decreased heart rate on AIx and central systolic BP.

Effects of antihypertensive drugs on central blood pressure in humans: a preliminary observation

BACKGROUND

Central blood pressure (BP) is considered a better predictor of cardiovascular events than brachial BP. Modifications of central, beyond brachial BP, can be assessed by pressure amplification, a potential new cardiovascular risk factor. Comparison between drugs' effect on central hemodynamics has been poorly studied. Our aim was to assess the hemodynamic effect of a 12-week treatment with amlodipine 5mg, or candesartan 8mg, or indapamide sustained-release 1.5mg, in comparison with placebo.

METHODS

We analyzed 145 out-patients with essential hypertension in primary prevention enrolled in the Natrilix SR Versus Candesartan and Amlodipine in the Reduction of Systolic Blood Pressure in Hypertensive Patients (X-CELLENT) study, a multicenter, randomized, double-blinded, placebo-controlled trial. Arterial stiffness, central BP, pressure amplification, and wave reflection were measured by applanation tonometry.

RESULTS

Baseline characteristics of patients were homogeneous between groups. After treatment, we found that active drugs produced similar reduction of both central and peripheral BPs, with no significant interdrug differences (all P < 0.05; excluded peripheral pulse pressure, compared with placebo). Second, amlodipine (1.9% ± 15.3%), candesartan (3.0% ± 14.6%) and indapamide (4.1% ± 14.4%) all increased pulse pressure amplification, but only indapamide was statistically different from placebo (P = 0.02). Finally, no significant changes were observed on pulse wave velocity, heart rate, and augmentation index.

CONCLUSIONS

The 3 antihypertensive drugs similarly reduced peripheral and central BP, as compared with placebo, but a significant increase in pulse pressure amplification was obtained only with indapamide, independently of arterial stiffness modifications.

REGISTRATION NUMBER

3283161 by BIOPHARMA.

The effects of angiotensin-converting enzyme-inhibitory peptide LAP on the left common carotid artery remodeling in spontaneously hypertensive rats

OBJECTIVE

To investigate the protective effect of angiotensin-converting enzyme (ACE)-inhibitory peptide LAP on the left common carotid artery remodeling in spontaneously hypertensive rats (SHRs).

METHODS

A cohort of male SHRs were randomly divided into three groups (n = 10 for each group): pseudo-experimental group, enalapril-treated group as a positive control group, ACE-inhibitory peptide LAP-treated group. After the experiment, the left common carotid artery from each rat was removed for morphological evaluation.

RESULTS

It was observed that the vascular medial thickness, media thickness/lumen diameter, medial cross-sectional area and mean nuclear area of smooth muscle cells of the left common carotid artery in the LAP group or enalapril group were significantly lower than those in the pseudo-experimental group, while there was no significant difference in these parameters observed between the LAP group and enalapril group. Additionally, the vascular area percentage of collagen fibers of the left common carotid artery in the LAP group and enalapril group was significantly lower than that of the pseudo-experimental group.

CONCLUSIONS

The protective vessel remodeling effect in SHRs was observed with ACE-inhibitory peptide LAP in SHRs by decreasing blood pressure, inhibiting smooth muscle cell hypertrophy and reducing the proliferation of collagen fibers.

Large arteries and the kidney

In subjects with chronic renal disease, high systolic blood pressure (SBP) is the most modifiable cardiovascular (CV) risk factor that enables prevention of the progression of chronic kidney disease renal failure and the occurrence of CV events. Although large-artery stiffness and wave reflections are the principal hemodynamic determinants of SBP, their precise role in the progression of chronic renal disease has been poorly investigated. However, in subjects with mild to severe renal insufficiency, increased arterial stiffness and reduced creatinine clearance are closely related, independently of age; mean arterial pressure level; and presence of other traditional risk factors, including atherosclerotic plaques. Through inflammatory mechanisms, as well as through the development of arterial calcifications (including microscopic) and sodium-related alterations in extracellular matrix composition, arterial stiffness is associated with significant SBP and increased pulse pressure (PP). In the presence of renal dysfunction, frequently observed in elderly hypertensive or diabetic subjects, or even in some living donors, the resulting increase in PP may be transmitted toward and across glomeruli, even when peripheral blood pressure values are maintained. This alteration alone may initiate glomerulosclerosis and/or tubulointerstitial damage, eventually leading to CV events. In subjects with end-stage renal disease and high CV risk, pharmacological modulation of the renin-angiotensin system has been shown to prevent independently such complications.

Pharmacological modulation of arterial stiffness

Arterial stiffness has emerged as an important marker of cardiovascular risk in various populations and reflects the cumulative effect of cardiovascular risk factors on large arteries, which in turn is modulated by genetic background. Arterial stiffness is determined by the composition of the arterial wall and the arrangement of these components, and can be studied in humans non-invasively. Age and distending pressure are two major factors influencing large artery stiffness. Change in arterial stiffness with drugs is an important endpoint in clinical trials, although evidence for arterial stiffness as a therapeutic target still needs to be confirmed. Drugs that independently affect arterial stiffness include antihypertensive drugs, mostly blockers of the renin-angiotensin-aldosterone system, hormone replacement therapy and some antidiabetic drugs such as glitazones. While the quest continues for 'de-stiffening drugs', so far only advanced glycation endproduct cross-link breakers have shown promise.

Central Pressure and Biomarker Responses to Renin Inhibition with Hydrochlorothiazide and Ramipril in Obese Hypertensives: The ATTAIN Study

BACKGROUND/AIMS

In obese, hypertensive subjects, the renin-angiotensin system (RAS) is enhanced and natriuresis impaired, suggesting a role for combination RAS blockade with diuretics. Data suggest that renin inhibition may attenuate diuretic-induced RAS activation and oxidative stress.

METHODS

In this 8-week, double-blind study of 386 obese individuals (mean body mass index: 35.3) with stage 2 hypertension (mean age: 54.9 years; mean sitting systolic blood pressure, SBP: ≧160 but <200 mm Hg), we compared the efficacy of aliskiren + hydrochlorothiazide (HCTZ) in reducing blood pressure (BP), plasma renin activity (PRA), and a urinary marker of oxidative stress to ramipril. Subjects were randomized to aliskiren/HCTZ 150/12.5 mg or ramipril 5 mg for 1 week, and after the 1st week force titrated to aliskiren/HCTZ 300/25 mg or ramipril 10 mg for 7 weeks.

RESULTS

After 8 weeks, aliskiren/HCTZ provided greater reductions in office BP than ramipril (-28.1/-10.1 vs. -16.6/-3.6 mm Hg, p < 0.0001) as well as 24-hour ambulatory and central pressure measures. Aliskiren/HCTZ also lowered PRA (-45 vs. +83%) and the urinary F2-isoprostane/creatinine ratio (-18 vs. +7%) to a greater extent than ramipril. Adverse events (AEs) were similar in the two groups (35.8% with aliskiren/HCTZ vs. 37.3% on ramipril reporting at least one AE).

CONCLUSIONS

Our findings suggest that the aliskiren/HCTZ combination reduced BP, PRA, and isoprostanes to a greater extent than did ramipril in obese patients with stage 2 hypertension.

Effect of angiotensin II blockade on central blood pressure and arterial stiffness in subjects with hypertension

In hypertension, the blood pressure curve may be divided into two sets of components. The first set is mean arterial pressure, steady flow, and vascular resistance, thus acting on small arteries; the second set refers to large arteries, hence to pulse pressure, arterial stiffness, and wave reflections. The angiotensin-converting enzyme (ACE) inhibitor perindopril not only reduces mean arterial pressure but also acts specifically on pulse pressure. The effect on pulse pressure predominates on central rather than peripheral (brachial) large arteries, reducing aortic stiffness and most wave reflections. Such hemodynamic changes are not observed with standard β-blockade, which reduces aortic stiffness and brachial systolic and pulse pressure but not central pulse pressure and wave reflections. In hypertensive subjects, perindopril and other ACE inhibitors seem to predict more consistently the reduction of cardiovascular events, mainly of cardiac origin, than standard β-blockers alone. This effect is associated with the important biochemical finding that mechanotransductions of angiotensin and β-blockade are markedly different, acting in the former specifically on the α5β1 integrin complex and on the fibronectin ligand of arterial vessels.

Arterial aging--hemodynamic changes and therapeutic options

Arterial aging can be attributed to two different pathophysiological changes--increase in arterial stiffness and disturbed wave reflections. The capacity of the aorta to absorb the force exerted by the left ventricular ejection and dampen pulsatile flow becomes diminished with advancing age, owing to the progressive hardening of the arterial wall. These changes contribute to increase blood pressure, mainly systolic blood pressure and pulse pressure, which can trigger cardiovascular events. Understanding the pulsatile arterial hemodynamics that elevate cardiovascular risk has led to the use of pharmacological therapies, which prevent arterial stiffness and reduce wave reflections, and improve cardiovascular morbidity and mortality. Antifibrotic agents, such as those that block the renin-angiotensin-aldosterone pathway, are often given in association with diuretics, calcium-channel blockers, or both, but not with standard beta-blockers. Consistent reductions in cardiovascular outcomes obtained using these agents can be predicted through noninvasive measurements of central systolic blood pressure and pulse pressure.

Can antihypertensive treatment reverse large-artery stiffening?

In some controlled therapeutic trials for hypertension, a selective reduction of systolic blood pressure has been obtained with long-term treatment. The greatest effects on cardiovascular outcomes stem from a decrease of central blood pressure through a significant reduction of arterial stiffness, wave reflections, or both. Until now, all protocols have used angiotensin II blockade, mainly through angiotensin-converting enzyme inhibition. Cardiovascular outcomes have been significantly improved when compared with controls, but most of them have been treated with beta blockers. Such "de-stiffening" therapies are important to consider and require additional trials.

Applied Healthspan engineering

According to the Homeric Hymn to Aphrodite, when Eos asked Zeus for Tithonus to be granted immortality, she forgot to ask for eternal youth. Applied Healthspan Engineering (AHE) seeks to address this problem. All organisms have a minimal level of functional reserve required to sustain life that eventually declines to a point incompatible with survival at death. AHE seeks to maintain or restore optimal functional reserve of critical tissues and organs. Tissue reserve correlates with well being. Diet, physical exercise, and currently available small-molecule-based therapeutics may attenuate the rate of decline of specific organs or organ systems, but are unlikely to restore lost reserve. Inherent evolutionary-derived limitations in tissue homeostasis and cell maintenance necessitate the development of therapies to enhance regenerative processes and possibly replace whole organs or tissues. AHE supports the study of cell, tissue, and organ homeostatic mechanisms to derive new regenerative and tissue replacement therapies to extend the period of human health.

Cardiovascular effects of inhibition of renin-angiotensin-aldosterone system components in hypertensive rats given salt excess

This study examined the role of the renin-angiotensin-aldosterone system (RAAS) in mediating cardiovascular and renal damage in spontaneously hypertensive rats (SHR) given salt excess. Since the circulating RAAS is inhibited in this model, it permits examination of the role of local tissue RAASs in mediating this injury. To this end, male 8-wk SHR were divided into 7 groups. The control group (C) received normal NaCl (0.6%) diet. All other groups were given 8% NaCl chow. In addition, group 2 was given placebo, group 3 the mineralocorticoid receptor blocker eplerenone (100 mg·kg−1·day−1), group 4 the angiotensin converting enzyme inhibitor quinapril (3 mg·kg−1·day−1), group 5 the angiotensin II type 1 receptor blocker candesartan (10 mg·kg−1·day−1), and groups 6 and 7 eplerenone and either quinapril or candesartan. The treatments lasted 8 wk. Compared with controls, mean arterial pressure (MAP), renal blood flow, coronary flow reserve, minimal coronary vascular resistance, diastolic time constant, and maximal rate of ventricular pressure fall were all adversely affected by salt loading. Left ventricular mass and fibrosis as well as proteinuria were also markedly increased by salt overload. Eplerenone induced only slight changes, whereas quinapril and candesartan normalized all indexes except MAP. Combination therapy also normalized all indexes, including MAP. These data suggest that 1) cardiovascular and renal damage induced by salt excess in the SHR were not pressure dependent; 2) mineralocorticoids were only marginally involved in this model; and 3) local tissue generation of angiotensin II may be, at least in part, responsible for the other adverse effects.

The Renin-Angiotensin System in the Development of Salt-Sensitive Hypertension in Animal Models and Humans

Hypertension is still one of the major causes of death from cardiovascular failure. Increased salt intake may aggravate the rise in blood pressure and the development of consequential damage of the heart, the vessels and other organs. The general necessity of restricted salt intake regardless of blood pressure or salt sensitivity has been a matter of debate over the past decades. This review summarizes the main pathogenic mechanisms of hypertension and salt sensitivity in rat models, particularly in the spontaneously hypertensive rat (SHR), and in patients with essential hypertension (EH). Although SHRs are commonly considered to be salt-resistant, there is much evidence that salt loading may deteriorate blood pressure and cardiovascular function even in these animals. Similarly, EH is not a homogenous disorder - some patients, but not all, exhibit pronounced salt sensitivity. The renin-angiotensin system (RAS) plays a key role in the regulation of blood pressure and salt and fluid homeostasis and thus is one of the main targets of antihypertensive therapy. This review focuses on the contribution of the RAS to the pathogenesis of salt-sensitive hypertension in SHRs and patients with EH.

De-stiffening drug therapy and blood pressure control

In hypertensive subjects, cardiovascular risk reduction is critically related to the decrease of systolic blood pressure (SBP). De-stiffening therapy means that, in a controlled therapeutic trial of long duration, a selective reduction of SBP has been obtained in the studied group by comparison with the control group, and that this SBP reduction is due to a decrease of either arterial stiffness, or wave reflections, or both. Central SBP reduction and cardiovascular remodeling are specifically involved. Most protocols require the presence of an angiotensin II blocker, potentially associated with a diuretic compound and/or a calcium-channel blocker. Cardiovascular outcomes are significantly reduced by comparison with the control group, particularly when this latter group involves administration of a beta-blocking agent.

Angiotensin II, mechanotransduction, and pulsatile arterial hemodynamics in hypertension

The aortic blood pressure curve involves two components: a steady component, the mean arterial pressure (MAP), which is dependent on cardiac output and vascular resistance, and a pulsatile component pulse pressure (PP), which is dependent on arterial stiffness and pulse wave reflections. The transduction mechanisms of MAP and PP differ markedly, involving focal adhesion kinase for MAP and oxygen free radicals for PP. Angiotensin II (ANG II) and its blockade are associated with changed vascular resistance and MAP; however, their effects on PP (peripheral and mostly central PP) have been inadequately investigated. In hypertensive rats, when compared with their normotensive controls, ANG II blockade normalizes central PP (<50 mmHg) but not MAP when the same drug dosage is used for each. In hypertensive patients, ANG II blockade reduces arterial stiffness and pulse wave reflections, but with the same reduction in MAP, there is a greater reduction in central than peripheral PP, thereby increasing carotid-brachial PP amplification. With long-term ANG II blockade, the hypertensive arteriolar hypertrophy observed at baseline is corrected in association with reduced arteriolar reflection coefficients, reduced carotid arterial attachments linking alpha(5)-integrin to its ligand fibronectin, and decreased circulating C-reactive protein. When given a normal salt diet, each of these factors contributes separately in reducing arterial stiffness and wave reflections. These responses disappear with a high-salt diet, a condition that usually involves the activation of the local vascular renin-angiotensin-aldosterone system and can be prevented by its selective blockade. Thus ANG II inhibition seems to contribute independently in reducing central PP and aortic stiffness.

Benefits of the RAS blockade: clinical evidence before the ONTARGET study

Activation of the AT1 angiotensin II (Ang II) receptors has various effects including vasoconstriction, hypertrophy, and possibly hyperplasia of vascular smooth muscle cells and cardiomyocytes and increase in extracellular collagen matrix synthesis. These actions lead to the development of cardiovascular hypertrophy and fibrosis, as well as arterial stiffness, which are some key factors in the development of the cardiovascular and renal complications. In clinical studies, it has been shown that renin-angiotensin blockade has direct and specific implications in the evolution of heart failure, coronary disease, stroke, and hypertensive and diabetic renal disease. The beneficial cardiovascular and renal effects of blocking the renin-angiotensin-aldosterone system reported in numerous clinical trials may be at least partially related to the actions of these drugs on cardiovascular and renal fibrosis, and arterial stiffness. These effects are now well-established and lead the international medical societies to propose the use of the renin-angiotensin system (RAS) blockers as initial treatment (both angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers) in several cardiovascular, metabolic, and renal disorders such as hypertension, heart failure, and proteinuria.

Selective reduction of central pulse pressure under angiotensin blockage in SHR: role of the fibronectin-alpha5beta1 integrin complex

BACKGROUND

Meta-analyses of antihypertensive therapy suggest that, independently of blood pressure (BP) level, stroke prevention is influenced mainly by calcium-entry blockers (CEB) and cardiac risk prevention by angiotensin-converting enzyme inhibitors (ACEIs). The possibility that central systolic and pulse pressure (PP) reduction differs between the two drug classes for the same mean BP (MBP) has never been explored. Our aim was to compare carotid PP at the same MBP obtained with the CEB, amlodipine, and the ACEI, trandolapril, in spontaneously hypertensive rats (SHR), and to evaluate the resulting changes of fibronectin (Fn) and its integrin alpha5beta1 receptor on central PP and arterial stiffness.

METHODS

Amlodipine and trandolapril were administered chronically to achieve the same MBP. Carotid arterial systolic BP (SBP) and PP, diameter and incremental elastic modulus (E(inc)) were determined using echo Doppler techniques, and complemented with vascular histomorphometry, and Fn and alpha5beta1-integrin immunolabeling.

RESULTS

Both drugs produced the same MBP, carotid wall thickness, and stress. Trandolapril reduced PP and E(inc) significantly more than amlodipine, while both agents comparably lowered EIIIA-Fn. Total Fn and alpha-subunit were lowered significantly by trandolapril, but unaffected by amlodipine, indicating that ACEI alone contributed to both diminished carotid stiffness and decrease of the Fn-integrin complex.

CONCLUSIONS

Results showed that amlodipine and trandolapril have different effects on carotid mechanical properties for comparable MBP reduction. Changes in Fn-integrin complex not only modify consistently ACEI mechanotransduction but also are associated with selective central PP reduction. Whether this property has consequences on cardiovascular (CV) risk remains to be investigated.

Hypertension, systolic blood pressure, and large arteries

This article discusses the following: (1) factors modulating central and peripheral SBP and PP in hypertensive subjects; (2) mechanisms enhancing PP variations in this population; (3) Analysis of pulsatile arterial hemodynamics as predictors of CV risk; and (4) Pulsatile hemodynamics and strategies lowering CV risk in the treatment of hypertension.

Central blood pressure and hypertension: role in cardiovascular risk assessment

Although the differences between central and peripheral BP (blood pressure) have been known for decades, the consequences of decision-making based on peripheral rather than central BP have only recently been recognized. The influence of cyclic stretch (owing to cyclic changes in BP) on the aortic wall in atherosclerosis has been documented at every stage of its development. Apart from mediating atherosclerosis progression and plaque instability, the pulsatile component of BP is the main mechanism leading to plaque rupture and, consequently, to acute coronary syndromes and other vascular complications. The principal goal of the present review is to evaluate the role of central BP measurements, principally systolic and pulse pressure, for cardiovascular risk assessment. Recent findings suggest that the pulsatile component of BP (when represented by central pulse pressure or central pulsatility) is one of the most important factors determining event-free survival. Results of several prospective studies (using both invasive and non-invasive measurements of central BP) indicate not only an independent predictive value of central pulse pressure, but also its advantage over brachial pressure. Recent evidence suggests that some antihypertensive drugs can influence central BP more consistently when compared with peripheral BP. This is especially true for agents acting on the renin–angiotensin system. Nevertheless, large prospective studies aiming at the comparison of the predictive value of peripheral and central BP in the general population, as well as studies comparing the effectiveness of hypertension management based on peripheral compared with central BP measurements, are needed before algorithms based on central BP can be recommended for clinical practice.

Mechanical properties of rat thoracic and abdominal aortas

Mechanical properties of abdominal and thoracic arteries of 2mm in diameter were determined from adults Wistar rats. A tensile testing instrument was used to obtain stress/strain curves with arteries immersed in physiological buffer at 37 degrees C. A displacement was applied on all arteries with various frequencies (1-7.5Hz) and strains (5-60%). From each curve a Young modulus was obtained using a mathematical model based on a nonlinear soft tissue model. No influence of frequency on modulus was evidenced in the tested range. Abdominal aortas, which were found slightly thicker than thoracic aortas, were characterized by a higher modulus. Due to the interest of decellularized biological materials, we also used SDS/Triton treated arteries, and found that the chemical treatment increased modulus of thoracic arteries. Tensile tests were also performed on thoracic aortas in the longitudinal and transversal directions. Longitudinal moduli were found higher than transversal moduli and the difference could be related to the longitudinal orientation of collagen fibers. These data and mathematical model seem useful in the design of new vascular synthetic or biological prostheses for the field of tissue engineering.

Pulse pressure lowering effect of dual blockade with candesartan and lisinopril vs. high-dose ACE inhibition in hypertensive type 2 diabetic subjects: a CALM II study post-hoc analysis

BACKGROUND

Elevated pulse pressure (PP) is strongly associated with micro- and macrovascular complications in type 2 diabetic patients. We examined the effect of 12 months of dual blockade with candesartan and lisinopril vs. high-dose lisinopril monotherapy on ambulatory PP in hypertensive type 2 diabetic patients from the CALM (Candesartan and Lisinopril Microalbuminuria Trial) II study.

METHODS

The CALM II study was a 12-month prospective, randomized, parallel-group, double-masked study that included 75 type 1 and type 2 diabetic subjects with hypertension. Participants were randomized for treatment with either high-dose lisinopril (40 mg once daily (o.d.)) or for dual blockade treatment with candesartan (16 mg o.d.) and lisinopril (20 mg o.d.). In this article, we present data from the post-hoc subgroup of 51 type 2 diabetic subjects who completed the full 12-month study period with successful ambulatory blood pressure (BP) measurements at both baseline and follow-up visits.

RESULTS

Baseline 24-h BP values were similar in the two groups (24-h systolic BP (SBP) 130 +/- 12 vs. 127 +/- 9, 24-h diastolic BP (DBP) 77 +/- 8 vs. 74 +/- 7, and 24-h PP 53 +/- 8 vs. 53 +/- 7 mm Hg, for the lisinopril and dual blockade groups, respectively, P > 0.2 for all). Compared with lisinopril monotherapy, dual blockade treatment caused a highly significant reduction in 24-h PP levels (-5 +/- 5 mm Hg, P = 0.003), albeit the difference in the BP lowering effect between the treatment groups did not differ significantly for 24-h systolic (P = 0.21) or diastolic (P = 0.49) BP. Dual blockade treatment significantly lowered 24-h SBP (-5 +/- 11 mm Hg, P = 0.03), but not 24-h DBP (-2 +/- 7 mm Hg, P = 0.29), whereas in the lisinopril group, the opposite effect was observed (24-h SBP -1 +/- 9 mm Hg, P = 0.45, 24-h SBP -3 +/- 7 mm Hg, P = 0.03).

CONCLUSIONS

Twelve months of dual blockade with candesartan and lisinopril significantly reduced PP when compared with high-dose monotherapy with lisinopril. Larger studies are needed to confirm this observation, and to evaluate whether this effect translates into a greater degree of end-organ protection from dual blockade treatment than from conventional angiotensin-converting enzyme (ACE) inhibition.

AT1 receptor antagonism attenuates target organ effects of salt excess in SHRs without affecting pressure

Our recent studies have demonstrated that salt excess in the spontaneously hypertensive rat (SHR) produces a modestly increased arterial pressure while promoting marked myocardial fibrosis and structural damage associated with altered coronary hemodynamics and ventricular function. The present study was designed to determine the efficacy of an angiotensin II type 1 (AT(1)) receptor blocker (ARB) in the prevention of pressure increase and development of target organ damage from high dietary salt intake. Eight-week-old SHRs were given an 8% salt diet for 8 wk; their age- and gender-matched controls received standard chow. Some of the salt-loaded rats were treated concomitantly with ARB (candesartan; 10 mg kg(-1) day(-1)). The ARB failed to reduce the salt-induced rise in pressure, whereas it significantly attenuated left ventricular (LV) remodeling (mass and wall thicknesses), myocardial fibrosis (hydroxyproline concentration and collagen volume fraction), and the development of LV diastolic dysfunction, as shown by longer isovolumic relaxation time, decreased ratio of peak velocity of early to late diastolic waves, and slower LV relaxation (minimum first derivative of pressure over time/maximal LV pressure). Without affecting the increased pulse pressure by high salt intake, the ARB prevented the salt-induced deterioration of coronary and renal hemodynamics but not the arterial stiffening or hypertrophy (pulse wave velocity and aortic mass index). Additionally, candesartan prevented the salt-induced increase in kidney mass index and proteinuria. In conclusion, the ARB given concomitantly with dietary salt excess ameliorated salt-related structural and functional cardiac and renal abnormalities in SHRs without reducing arterial pressure. These data clearly demonstrated that angiotensin II (via AT(1) receptors), at least in part, participated importantly in the pressure-independent effects of salt excess on target organ damage of hypertension.

Disturbance of macro- and microcirculation: relations with pulse pressure and cardiac organ damage

Whereas large arteries dampen oscillations resulting from intermittent ventricular ejection, small arteries steadily deliver optimal blood flow to various organs as the heart. The transition from pulsatile to steady pressure is influenced by several factors as wave travel, damping, and reflections, which are mainly determined by the impedance mismatch between large vessels and arteriolar bifurcations. The mechanism(s) behind the dampening of pressure wave in the periphery and the links between central and peripheral pulsatile pressure (PP) may determine cardiac damage. Active pathways participate to pulse widening and changes in pulse amplitude in microvessels. Steady and cyclic stresses operate through different transduction mechanisms, the former being focal adhesion kinase and the latter being free radicals and oxidative stress. Independently of mechanics, calcifications and attachment molecules contribute to enhance vessel wall stiffness through changes in collagen cross-links, proteoglycans, integrins, and fibronectin. Enhanced PP transmission may thus occur and precipitate organ damage at each time that autoregulatory mechanisms, normally protecting the heart from vascular injury, are blunted. Such circumstances, observed in old subjects with systolic hypertension and/or Type 2 diabetes mellitus, particularly under high-sodium diet, cause cardiac damage and explain why increased PP and arterial stiffness are significant predictors of morbidity and mortality in the elderly.

Myocardial fibrosis, impaired coronary hemodynamics, and biventricular dysfunction in salt-loaded SHR

Arterial pressure in most experimental and clinical hypertensions is exacerbated by salt. The effects of salt excess on right and left ventricular (RV and LV, respectively) functions and their respective coronary vasodilatory responses have been less explored. We therefore examined the effects of 8 wk of NaCl excess (8% in food) on arterial pressure, RV and LV functions (maximal rate of increase and decrease of ventricular pressure; dP/dt(max) and dP/dt(min)), coronary hemodynamics (microspheres), and collagen content (hydroxyproline assay and collagen volume fraction) in young adult normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR), aged 16 wk by the end of the study. Prolonged salt excess in WKY and SHR elevated pressure only modestly, but it markedly increased LV mass, especially in SHR. Moreover, salt excess significantly impaired RV and LV diastolic function in SHR but only LV diastolic function in WKY rats. However, salt loading affected neither RV nor LV contractile function in both strains. Interstitial and perivascular collagen deposition was increased, whereas coronary vasodilatory responses to dipyridamole diminished in both ventricles in the salt-loaded SHR but not in WKY rats. Therefore, accumulation of ventricular collagen as well as altered myocardial perfusion importantly contributed to the development of salt-related RV and LV dysfunctions in this model of naturally occurring hypertension. The unique effects of salt loading on both ventricles in SHR, but not WKY rats, strongly suggest that nonhemodynamic mechanisms in hypertensive disease participate pathophysiologically with salt-loading hypertension. These findings point to the conclusion that the concept of "salt sensitivity" in hypertension is far more complex than simply its effects on arterial pressure or the LV.

Systolic hypertension in the elderly: arterial wall mechanical properties and the renin-angiotensin-aldosterone system

BACKGROUND

Systolic hypertension in the elderly involves an increase of arterial stiffness and early wave reflections, both of them causing a predominant or selective increase of systolic blood pressure. The mechanisms for such alterations remain largely unknown.

DESCRIPTION AND RESULTS

The development of systolic hypertension includes constantly an age-related increase of sodium sensitivity and of endothelial dysfunction, both responsible for phenotypic changes of aortic smooth muscle cells with collagen accumulation and increased stiffness. In the presence of a high sodium diet and under the influence of angiotensin II and aldosterone, a higher number of attachments between vascular smooth muscle cells and collagen fibers develop, causing a supplementary increase in stiffness independent of the mean blood pressure together with the occurrence of early wave reflections. Gene polymorphisms related to the renin-angiotensin system may participate in this evolution.

CONCLUSION

This process contributes to accelerating the increase in pulse pressure and arterial stiffness with age, and therefore to the development of cardiovascular risk.

Angiotensin II AT1 receptors regulate ACE2 and angiotensin-(1-7) expression in the aorta of spontaneously hypertensive rats

When increased in vascular tissues, angiotensin-converting enzyme 2 (ACE2), a carboxypeptidase that hydrolyzes angiotensin II to angiotensin-(1-7), may augment the growth inhibitory and vasodilatory effects of the heptapeptide. We investigated the regulation of ACE2 and angiotensin-(1-7) expression in aortas and carotid arteries of 12-wk-old male spontaneously hypertensive rats (SHR) by determining the effect of sustained angiotensin type 1 (AT(1)) receptor blockade with olmesartan (10 mg.kg(-1).day(-1), n = 13) compared with those that received atenolol (30 mg.kg(-1).day(-1), n = 13), hydralazine (10 mg.kg(-1).day(-1), n = 13), or vehicle (n = 21). Systolic blood pressures were approximately 30% lower (P < 0.05) in rats treated for 2 wk with olmesartan compared with vehicle-treated rats. Both atenolol and hydralazine produced similar decreases in systolic blood pressure. ACE2 mRNA in the thoracic aorta of olmesartan-treated rats (n = 8) was fivefold greater (P < 0.05) than that in vehicle-treated rats (n = 16), whereas atenolol (n = 8) or hydralazine (n = 8) had no effect. Immunostaining intensities in rats treated with olmesartan (n = 5) were also associated with increased (P < 0.05) ACE2 and angiotensin-(1-7) in thoracic aorta media compared with vehicle-treated rats. In contrast, immunostaining intensities for both ACE2 and angiotensin-(1-7) were not different from vehicle (n = 5) in carotid arteries of SHR medicated with either atenolol (n = 5) or hydralazine (n = 5). A comparison of vessel wall dimensions showed that olmesartan selectively reduced the thoracic aorta media-to-lumen ratio (P < 0.05) and media thickness (P < 0.05) without an effect on carotid artery morphometry. Compared with vehicle-treated SHR, vascular hypertrophy determined from media and lumen measurements was not changed in SHR given either atenolol or hydralazine. These data represent the first report of ACE2 and angiotensin-(1-7) expression in the aorta and carotid arteries of SHR. Increased ACE2 and angiotensin-(1-7) in association with altered dimensions of the thoracic aorta but not carotid arteries in response to olmesartan treatment provides evidence that this pathway is regulated by AT(1) receptors and may be important in mediating the pressure-independent vascular remodeling effects of angiotensin peptides.

Marinobufagenin may mediate the impact of salty diets on left ventricular hypertrophy by disrupting the protective function of coronary microvascular endothelium

Individuals who eat salty diets and who are "salt-sensitive" tend to have increased left ventricular mass, independent of blood pressure; this phenomenon awaits an explanation. It is clear that local up-regulation of angiotensin II (AngII) production and activity play a key role in the induction of left ventricular hypertrophy (LVH). Recent evidence suggests that a healthy coronary microvascular endothelium opposes this effect by serving as a paracrine source of nitric oxide (NO), a natural antagonist of AngII activity, and that up-regulation of this mechanism can account for the protective role of bradykinin with respect to LVH. The coronary microvasculature also possesses NAD(P)H oxidase activity that can generate superoxide, inimical to the bioactivity of endothelial NO. There is now good reason to believe that the triterpenoid marinobufagenin (MBG), a selective inhibitor of the alpha-1 isoform of the sodium pump, mediates the impact of salty diets on blood pressure; production of MBG by the adrenal cortex is boosted when salt-sensitive animals are fed salty diets. It is hypothesized that coronary microvascular endothelium expresses the alpha-1 isoform of the sodium pump, and that MBG thus can target this endothelium. If that is the case, MBG would be expected to decrease membrane potential in these cells; as a consequence, superoxide production would be up-regulated, NO synthase activity would be down-regulated, and myocardial NO bioactivity would thus be suppressed. This would offer a satisfying explanation for the impact of salt and salt-sensitivity on risk for LVH. If expression of the alpha-1 isoform of the sodium pump is a more general property of vascular endothelium, MBG may suppress NO bioactivity in other regions of the vascular tree, thereby contributing to other adverse effects elicited by salty diets: reduced arterial compliance, medial hypertrophy, impaired endothelium-dependent vasodilation, hypertensive/diabetic glomerulopathy, increased risk for stroke, and hypertension.

Marinobufagenin may mediate the impact of salty diets on left ventricular hypertrophy by disrupting the protective function of coronary microvascular endothelium

Individuals who eat salty diets and who are "salt-sensitive" tend to have increased left ventricular mass, independent of blood pressure; this phenomenon awaits an explanation. It is clear that local up-regulation of angiotensin II (AngII) production and activity play a key role in the induction of left ventricular hypertrophy (LVH). Recent evidence suggests that a healthy coronary microvascular endothelium opposes this effect by serving as a paracrine source of nitric oxide (NO), a natural antagonist of AngII activity, and that up-regulation of this mechanism can account for the protective role of bradykinin with respect to LVH. The coronary microvasculature also possesses NAD(P)H oxidase activity that can generate superoxide, inimical to the bioactivity of endothelial NO. There is now good reason to believe that the triterpenoid marinobufagenin (MBG), a selective inhibitor of the alpha-1 isoform of the sodium pump, mediates the impact of salty diets on blood pressure;production of MBG by the adrenal cortex is boosted when salt-sensitive animals are fed salty diets. It is hypothesized that coronary microvascular endothelium expresses the alpha-1 isoform of the sodium pump, and that MBG thus can target this endothelium. If that is the case, MBG would be expected to decrease membrane potential in these cells;as a consequence, superoxide production would be up-regulated, NO synthase activity would be down-regulated, and myocardial NO bioactivity would thus be suppressed. This would offer a satisfying explanation for the impact of salt and salt-sensitivity on risk for LVH. If expression of the alpha-1 isoform of the sodium pump is a more general property of vascular endothelium, MBG may suppress NO bioactivity in other regions of the vascular tree, thereby contributing to other adverse effects elicited by salty diets: reduced arterial compliance, medial hypertrophy, impaired endothelium-dependent vasodilation, hypertensive/diabetic glomerulopathy, increased risk for stroke, and hypertension.

Hypertension and the elderly: more than just blood pressure control

Hypertension is a major risk factor for cardiovascular disease in both young and elderly persons; therefore, good blood pressure control is at the center of improved cardiovascular health. The recently issued seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure and the European Society of Hypertension/European Society of Cardiology 2003 guidelines for hypertension management emphasize the importance of treatment efficacy rather than age in treating elderly persons with hypertension. Most hypertension clinical trials have been carried out with younger hypertensives, but this is changing with trials such as the Systolic Hypertension in the Elderly Program, the first Swedish Trial of Old Patients With Hypertension, and the Systolic Hypertension in Europe trial. These trials have clearly demonstrated the benefits of good blood pressure control in reducing the risk of stroke in elderly persons. With many safe and effective antihypertensive drugs on the market, the question becomes how elderly persons should be treated. Elderly patients often have isolated systolic hypertension, which is related to loss of arterial elasticity or compliance with aging and is more recalcitrant to treatment than essential hypertension. In addition, with advancing age there is the likelihood that other disease states are present in addition to hypertension. The newer antihypertensive drugs that interfere with the renin angiotensin system, such as angiotensin-converting enzyme inhibitors and angiotensin-receptor blockers, have the potential of improving cardiovascular outcomes in elderly persons in addition to offering effective blood pressure reduction. Their use should be considered within a comprehensive risk assessment that includes individualized risk-benefit considerations.

Gender influence on the dose-ranging of a low-dose perindopril-indapamide combination in hypertension: effect on systolic and pulse pressure

BACKGROUND

Dose-ranging of antihypertensive agents have been done to optimize diastolic blood pressure (DBP) reduction, but with little information on systolic (SBP), mean (MBP), or pulse (PP) pressures. A low-dose combination of perindopril (Per) and indapamide (Ind) has been shown to reduce more SBP than atenolol for the same DBP reduction. However, the possible influence of gender on this finding has never been tested.

PURPOSE

A database of five randomized, double-blind, dose-ranging studies was established to determine the optimal dose of the Per/Ind combination in hypertensive men and women. A total of 2907 patients were treated by either placebo or various combinations associating Per (2, 4, 8 mg) and Ind (0.625, 1.25, 2.5 mg).

RESULTS

In the overall population, there was a significant dose-response relationship (P < 0.001) for doubling the dose of Per 2/Ind 0.625 mg up to Per 8/Ind 2.5 mg with a progressive fall in SBP, DBP, MBP. When men and women were analyzed by dose, SBP, DBP and MBP (but not PP) decreased significantly more in women than in men until the Per 4/Ind 1.25 dosage was reached. Thereafter, with higher dosages, generating a slight but significant hypokalemia, the finding was reversed, resulting in a gender interaction in the overall population.

CONCLUSION

In hypertensive subjects, the low-dose combinations Per 2/Ind 0.625 and Per 4/Ind 1.25 are the most effective in reducing blood pressure and avoiding hypokalemia. This effect is more pronounced in women, in which increased SBP and PP are predominant hemodynamic features.