Comparative effects of chronic ACE inhibition and AT1 receptor blocked losartan on cardiac hypertrophy and renal function in hypertensive patients

Physical exercise is essential for increasing ventricular contractility in hypertensive rats treated with losartan

The treatment of hypertensive patients with losartan is very common. Despite the reduction in blood pressure, its effects on cardiac contractility and sympathetic autonomic drive are still controversial. In turn, aerobic physical training (APT) also presents an important therapeutic option, providing significant improvements in cardiovascular autonomic control, however little is known about its effects on cardiac contractility, especially when associated with losartan. Therefore, we investigated in spontaneously hypertensive rats (SHR) the effects of losartan and APT on cardiac hemodynamics and functionality, with emphasis on autonomic tonic balance and cardiac contractility. Sixty-four SHR (18 weeks old) were divided into four groups (N = 16): vehicle; vehicle submitted to APT through swimming for 12 weeks; treated with losartan (5 mg·kg-1·d-1) for 12 weeks; and treated with losartan associated with APT. The groups were submitted to cardiac morphological and functional analysis by echocardiography; double blockade of cardiac autonomic receptors with atropine and propranolol; and coronary bed reactivity and left ventricular contractility analyses by the Langendorff technique. APT improved functional parameters and autonomic balance by reducing sympathetic drive and/or increasing vagal drive. In contrast, it promoted a concentric remodeling of the left ventricle (LV). Treatment with losartan reduced sympathetic autonomic drive and cardiac morphological parameters, but there were no significant gains in cardiac functionality and contractility. When combined, the concentric remodeling of the LV to APT was abolished and gains in cardiac functionality and contractility were observed. Our findings suggest that the effects of losartan and APT are complementary and should be applied together in the treatment of hypertension. In spontaneously hypertensive rats, the combination of aerobic physical training with losartan treatment was crucial to greater blood pressure reductions and an increase in left ventricular contractility. Furthermore, losartan treatment prevented the concentric left ventricular remodeling caused by aerobic physical training.

The Effects of Salt and Glucose Intake on Angiotensin II and Aldosterone in Obese and Nonobese Patients with Essential Hypertension

Background

The exact mechanisms for the development of essential hypertension are not known. Activation of the renin-angiotensin-aldosterone system (RAAS) in adipose tissue may represent an important link between obesity and hypertension. This study investigates the effects of oral intake of glucose with and without NaCl on angiotensin II (AngII) and aldosterone in obese and nonobese patients with essential hypertension.

Methods

Twenty newly diagnosed untreated essential hypertensive patients and 15 normotensive control subjects matched for age, gender, and BMI were studied. Participants fasted overnight (8–10 hrs), and then each subject took 75 gm glucose alone and with 3 gm NaCl, each dissolved in 250 ml. Subjects were monitored for 2 hours. Half hourly BP, plasma glucose (PG), serum Na⁺, K⁺, insulin, AngII, and aldosterone were measured. Subjects were classified into obese (BMI >30 Kg/m²) (11 patients and 8 control) and nonobese (BMI <30 Kg/m²) (9 patients and 7 control).

Results

After intake of glucose with NaCl serum, AngII was significantly higher in obese hypertensive patients compared with nonobese patients (P = 0.016). Intake of glucose with NaCl resulted in a significantly higher serum Na in obese hypertensive patients compared with nonobese patients Na (P = 0.009). Serum aldosterone was significantly higher in obese patients (P = 0.03, after glucose; P = 0.003, after glucose with NaCl) and in nonobese patients (P = 0.000 and P = 0.000, respectively) compared with their respective normotensive control subjects. In obese and nonobese patients, intake of glucose and glucose with NaCl showed no significant change in the levels of serum AngII and aldosterone which was associated a significant increase in serum Na in obese patients (P = 0.03) and a highly significant reduction in serum K in nonobese patients (P = 0.001).

Conclusion

Failure of suppression or inappropriate maintenance of secretion of AngII and aldosterone in both hypertensive groups by intake of glucose with NaCl may indicate a possible mechanism of essential hypertension.

A systematic review and network meta-analysis of the comparative efficacy of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers in hypertension

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are drugs commonly used for the treatment of hypertension. However, studies on their comparative efficacy have not been extensively investigated. The current systematic review and network meta-analysis studied the comparative efficacy of the two antihypertensive treatment categories in reducing blood pressure, mortality, and morbidity in essential hypertension patients. A literature search was carried out in Medline and Cochrane Central Register of Controlled Trials for placebo- and active-controlled, double-blind randomized clinical trials, which had reported blood pressure effects, mortality, and/or morbidity. Blood pressure results were found in 30 studies with 7370 participants and 8 studies with 25,158 participants with mortality/morbidity results included in the analysis. The two drug classes had similar effectiveness in lowering systolic (weighted mean difference (WMD): 0.59, 95% CI: -0.21 to 1.38) and diastolic blood pressure (WMD: 0.62, 95% CI: -0.06 to 1.30), all-cause mortality (risk ratio (RR)): 0.96, 95% CI 0.80 to 1.14), cardiovascular mortality (RR: 0.87, 95% CI 0.67 to 1.14), fatal and non-fatal myocardial infarction (RR: 1.02, 95% CI 0.75 to 1.37) and stroke (RR: 1.13, 95% CI 0.87 to 1.46). Angiotensin-converting enzyme inhibitors were more helpful in the prevention and/or the hospitalization for heart failure than angiotensin receptor blockers (RR: 0.71, 95% CI 0.54 to 0.93). Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers were similarly effective in decreasing blood pressure, mortality, and morbidity in essential hypertension. Angiotensin-converting enzyme inhibitors were more protective in the advancement and/or hospitalization of the hypertensive patient for heart failure than angiotensin receptor blockers.

Sex-specific long-term blood pressure regulation: Modeling and analysis

Hypertension is a global health challenge: it affects one billion people worldwide and is estimated to account for >60% of all cases or types of cardiovascular disease. In part because sex differences in blood pressure regulation mechanisms are not sufficiently well understood, fewer hypertensive women achieve blood pressure control compared to men, even though compliance and treatment rates are generally higher in women. Thus, the objective of this study is to identify which factors contribute to the sexual dimorphism in response to anti-hypertensive therapies targeting the renin angiotensin system (RAS). To accomplish that goal, we develop sex-specific blood pressure regulation models. Sex differences in the RAS, baseline adosterone level, and the reactivity of renal sympathetic nervous activity (RSNA) are represented. A novel aspect of the model is the representation of sex-specific vasodilatory effect of the bound angiotensin II type two receptor (AT2R-bound Ang II) on renal vascular resistance. Model simulations suggest that sex differences in RSNA are the largest cause of female resistance to developing hypertension due to the direct influence of RSNA on afferent arteriole resistance. Furthermore, the model predicts that the sex-specific vasodilatory effects of AT2R-bound Ang II on renal vascular resistance may explain the higher effectiveness of angiotensin receptor blockers in treating hypertensive women (but not men), compared to angiotensin converting enzyme inhibitors.

EndophilinA2 protects against angiotensin II-induced cardiac hypertrophy by inhibiting angiotensin II type 1 receptor trafficking in neonatal rat cardiomyocytes

Cardiac hypertrophy is one of the major risk factors for chronic heart failure. The role of endophilinA2 (EndoA2) in clathrin-mediated endocytosis and clathrin-independent endocytosis is well documented. In the present study, we tested the hypothesis that EndoA2 protects against angiotensin II (Ang II)-induced cardiac hypertrophy by mediating intracellular angiotensin II type 1 receptor (AT1-R) trafficking in neonatal rat cardiomyocytes (NRCMs). Cardiac hypertrophy was evaluated by using cell surface area and quantitative RT-PCR (qPCR) analyses. For the first time, we found that EndoA2 attenuated cardiac hypertrophy and fibrosis induced by Ang II. Moreover, EndoA2 inhibited apoptosis induced by excessive endoplasmic reticulum stress (ERS), which accounted for the beneficial effects of EndoA2 on cardiac hypertrophy. We further revealed that there was an interaction between EndoA2 and AT1-R.The expression levels of EndoA2, which inhibits AT1-R transport from the cytoplasm to the membrane, and the interaction between EndoA2 and AT1-R were obviously decreased after Ang II treatment. Furthermore, Ang II inhibited the co-localization of AT1-R with GRP-78, which was reversed by EndoA2 overexpression. In conclusion, our results suggested that EndoA2 plays a role in protecting against cardiac hypertrophy induced by Ang II, possibly by inhibiting AT1-R transport from the cytoplasm to the membrane to suppress signal transduction.

Losartan Reduces Left Ventricular Hypertrophy Proportionally to Blood Pressure Reduction in Hypertensives, but Does Not Affect Diastolic Cardiac Function

In contrast to the well-recognized salutary effects of angiotensin-converting enzyme inhibition, the value of angiotensin II type I (ATl)-receptor blockade on left ventricular hypertrophy (LVH) is controversial. In addition, the data on the influence of this therapy on cardiac diastolic function are scarce. Thirty-nine patients with moderate primary hypertension, LVH, and normal systolic function received losartan, 50 to 100 mg daily. Transthoracic echocardiography was performed at baseline and after 6 months of treatment. Thirty-one patients completed and were included in the study (16 males, 61.1 ±1.0 years). The patients were divided into responders if mean blood pressure (BP) decreased >5 mm Hg at the end of the study (20 patients) and non-responders (mean BP decrease ≤5 mm Hg, 11 patients). The BP and the LVH were significantly reduced (systolic BP by 10.0%, diastolic BP 6.5%, mean BP 8.2%, left ventricular mass index [LVMI] 6.2%, interventricular septum 5.8%, posterior wall 3.0%) (p≤0.02), attributed to the reduction of BP and LVH in responders; the LVH in non-responders did not alter with treatment. A significant correlation was noted between changes in BP and LVMI ( r =0.60, p<0.001). The systolic cardiac function remained normal. The Doppler parameters usually used to assess the diastolic function of the LV (early diastolic filling velocity [E wave], late diastolic filling velocity [A wave], ratio of E/A waves, isovolumic relaxation time), which were abnormal at baseline, did not change with treatment. The size of the left atrium increased (p<0.05) at the end of the study. In conclusion, a 6-month course with losartan decreased BP and LVH. However, the LVH regression was rather associated with the reduction of the hemodynamic stimulus per se, than any trophic effect of the drug in the myocardium. The diastolic cardiac function remained abnormal with treatment.

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

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

Updated report on comparative effectiveness of ACE inhibitors, ARBs, and direct renin inhibitors for patients with essential hypertension: much more data, little new information

OBJECTIVES

A 2007 systematic review compared angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) in patients with hypertension. Direct renin inhibitors (DRIs) have since been introduced, and significant new research has been published. We sought to update and expand the 2007 review.

DATA SOURCES

We searched MEDLINE and EMBASE (through December 2010) and selected other sources for relevant English-language trials.

STUDY ELIGIBILITY CRITERIA, PARTICIPANTS, AND INTERVENTIONS

We included studies that directly compared ACE inhibitors, ARBs, and/or DRIs in at least 20 total adults with essential hypertension; had at least 12 weeks of follow-up; and reported at least one outcome of interest. Ninety-seven (97) studies (36 new since 2007) directly comparing ACE inhibitors versus ARBs and three studies directly comparing DRIs to ACE inhibitor inhibitors or ARBs were included.

STUDY APPRAISAL AND SYNTHESIS METHODS

A standard protocol was used to extract data on study design, interventions, population characteristics, and outcomes; evaluate study quality; and summarize the evidence.

RESULTS

In spite of substantial new evidence, none of the conclusions from the 2007 review changed. The level of evidence remains high for equivalence between ACE inhibitors and ARBs for blood pressure lowering and use as single antihypertensive agents, as well as for superiority of ARBs for short-term adverse events (primarily cough). However, the new evidence was insufficient on long-term cardiovascular outcomes, quality of life, progression of renal disease, medication adherence or persistence, rates of angioedema, and differences in key patient subgroups.

LIMITATIONS

Included studies were limited by follow-up duration, protocol heterogeneity, and infrequent reporting on patient subgroups.

CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

Evidence does not support a meaningful difference between ACE inhibitors and ARBs for any outcome except medication side effects. Few, if any, of the questions that were not answered in the 2007 report have been addressed by the 36 new studies. Future research in this area should consider areas of uncertainty and be prioritized accordingly.

Losartan therapy and hyperuricemia correction in patients with metabolic syndrome and arterial hypertension

Aim. To assess the potential of the angiotensin II receptor antagonist losartan for the correction of hyperuricemia (HU) in patients with arterial hypertension (AH) and metabolic syndrome (MS). Material and methods. This open, randomised, controlled comparative study in parallel groups included 60 AH patients with MS and HU. The patients received losartan or standard therapy for 12 weeks. Results. Throughout the follow-up period, no significant difference in antihypertensive effect was observed between the losartan and standard therapy groups. Losartan group patients demonstrated a more pronounced decrease in uric acid levels (-34,7 % vs. -7,8 % in the standard therapy group; p<0,05). In addition, losartan therapy, compared to the standard treatment, was associated with improved vascular elasticity, as manifested by the pulse wave velocity decrease (-27,8 % vs. -8,1 % for carotid-femoral index, and -30,2 % vs. -12,6 % for carotidradial index, respectively; both p<0,05).

Health-related quality of life in hypertension, chronic kidney disease, and coexistent chronic health conditions

With the increasing prevalence of hypertension, there has been a growing interest in understanding the health-related quality of life (HRQOL) of patients with hypertension. Although hypertension is often perceived as asymptomatic, it is associated with impaired HRQOL because of complications or comorbidities, awareness of the diagnosis, and adverse effects from antihypertensive medications. This article focuses on the literature published since 2000, on HRQOL in elderly hypertensive individuals as well as hypertensives with co-existent diseases, including chronic kidney disease, cardiovascular disease, and diabetes mellitus. Most of the studies found that hypertensive individuals with co-existent co-morbidities tend to have lower HRQOL than those with hypertension alone, and identified the number of co-morbid illnesses as an independent determinant of HRQOL. The most pronounced effect was noted in the physical function domains of HRQOL. Studies have also examined the effects on HRQOL of specific classes of antihypertensive drugs without specific demonstration of superiority of one drug class over another in terms of HRQOL measures. Although there is evidence in favor of angiotensin-converting enzyme-inhibition for improving renal and cardiovascular outcomes in hypertensive patients, its role in ameliorating HRQOL outcomes remains to be established.

Fifteen years of losartan: what have we learned about losartan that can benefit chronic kidney disease patients?

Losartan, the first AT1 receptor blocker (ARB), was FDA approved 15 years ago. During those years, researchers and clinicians have developed a growing base of knowledge on the benefits of losartan, particularly for hypertension and renal disease. These benefits include decreasing proteinuria, slowing the progression of diabetic nephropathy, controlling hypertension, and decreasing stroke risk in patients with left ventricular hypertrophy. Although many of the benefits of losartan represent a class effect for ARBs, losartan has pharmacokinetic and pharmacodynamic characteristics and effects that are unique and are not a class effect. For example, a shorter duration of action is seen with this first ARB compared with other more recently approved ARBs. Losartan also has a uricosuric effect not seen in other ARBs and attenuates platelet aggregation, which is not seen or is seen to a lesser extent with the other ARBs. This review presents the physiological effects of losartan on the kidney and discusses relevant clinical outcomes.

Therapeutic efficacy of renin—angiotensin blockade in patients receiving dialysis

Observational data in dialysis patients has indicated an increased cardiovascular mortality. One pathophysiological cause of this cardiovascular mortality in these patients is volume overload. In addition, an inappropriately activated renin—angiotensin system (RAS) has been proposed as another possible mechanism for the increased cardiovascular mortality. With these possible causes in mind, blockade of the RAS with an angiotensin-converting enzyme (ACE) inhibitor or an angiotensin receptor blocker (ARB) have both emerged as means of preventing cardiovascular events in this population. This review focuses on clinical evidence of the beneficial effects of ACE inhibitors and ARBs in dialysis patients with regard to the improvement of cardiovascular events as well as blood pressure control and maintenance of dialysis therapy.

Effect of Dominant-Negative Epidermal Growth Factor Receptors on Cardiomyocyte Hypertrophy

Angiotensin II (AngII) induces heart growth via cardiomyocyte hypertrophy, and central to this is the capacity of the type 1 AngII receptor (AT1R) to "transactivate" epidermal growth factor receptors (EGFRs)--a family with four main subtypes (HER1-4)--although the exact molecular mechanism remains unresolved. In this study, the pharmacological inhibition of AngII-stimulated ERK1/2 activation and cardiomyocyte hypertrophy by increasing concentrations of an EGFR inhibitor, AG1478, indicated that other EGFR subtypes, in addition to HER1, may be involved. We constructed expression vectors and adenoviruses expressing truncated mutant versions of HER1, HER2, and HER4 and determined their capacity to act as dominant-negative inhibitors when co-transfected with full-length EGFRs. It is surprising that adenoviral-mediated expression of these truncated EGFRs in cardiomyocytes led to paradoxical, ligand-independent increases in cardiomyocyte hypertrophy and unusual morphological changes. These results challenge our perception of AT1R-mediated EGFR transactivation and imply that truncated EGFRs may affect cell function through unconventional mechanisms.

Adaptation to high altitude in Sherpas: association with the insertion/deletion polymorphism in the Angiotensin-converting enzyme gene

OBJECTIVE

Sherpas are well-known for their physical strength at high altitudes. They adapt to high altitude so well that little acute or chronic mountain sickness has been documented in them. The possible genetic basis for this adaptation is, however, unclear. The objective of this study was to elucidate the genetic background underlying this characteristic among Sherpas with respect to the angiotension-converting enzyme (ACE) gene.

METHODS

We enrolled 105 Sherpa volunteers in Namche Bazaar (3440 meters) and 111 non-Sherpa Nepalese volunteers in Kathmandu Valley (1330 meters) in Nepal. Information about high-altitude exposure and physiological phenotypes was obtained via fieldwork investigation. The genotype of the insertion/deletion (I/D) polymorphism in the ACE gene was identified by polymerase chain reaction. Serum ACE activity was also measured.

RESULTS

The distribution of the I dominant genotype (II & ID) and the I allelic frequency were significantly more prevalent in Sherpas (II & ID: 94.3%, I allele: 73.3%) than in non-Sherpas (II & ID: 85.6%, P = .035; I allele: 64.0%, P = .036). Moreover, despite residing at high altitude, the circulating ACE levels of Sherpas were statistically similar to those of non-Sherpas at low altitudes (Sherpas: 14.5 +/- 0.4 IU/L/37 degrees C; non-Sherpas: 14.7 +/- 0.4 IU/L/37 degrees C; P = .755).

CONCLUSIONS

These findings suggest that the overrepresented I allele of the ACE gene in Sherpas might be one of the fundamental genetic factors responsible for maintaining physiological low-altitude ACE activity at high altitude, which may have an advantageous physiological role in adapting to a high-altitude environment.

Studies on left ventricular hypertrophy regression in arterial hypertension: a clear message for the clinician?

BACKGROUND

Evidence-based medicine should provide clear and unbiased information to clinicians. We conducted an analysis on published randomized trials evaluating the effects of antihypertensive therapy on left ventricular (LV) morphology assessed by echocardiography to investigate (i) the consistency of criteria used for definition of LV hypertrophy (LVH) and (ii) the consistency of the way LVH regression and blood pressure (BP) control were reported.

METHODS

Studies identified by a PubMed search were eligible for inclusion in the analysis, if they fulfilled the following criteria: (i) publication in a peer-reviewed journal within the last 12 years; (ii) double blind, randomized, controlled, parallel-group design; (iii) numerosity of at least 50 adult hypertensive subjects; (iv) follow-up duration of at least 6 months; (v) comparison between single-drugs or association regimens; (vi) LV mass (LVM) or wall thickness measured by echocardiography.

RESULTS

Thirty-nine trials, including 9,162 hypertensive subjects of both genders in 78 active treatment arms or in 6 placebo arms were identified. Definition of LVH was provided by 34 studies (87.1%) according to 19 different criteria. All trials evaluated LVH regression as the absolute or relative changes of continuous variables such as LVM index (LVMI) or LV wall thickness. Data concerning prevalence rates of LVM normalization were reported in 12 studies (30.7%). The percentage of patients reaching BP target (<140/90 mm Hg) was reported in 11 studies (28.2%).

CONCLUSIONS

Our findings indicate that (i) definition of hypertensive LVH phenotype is extremely variable, and (ii) no precise information on LVH regression rates or changes in LV geometrical patterns, as well as on target BP, is provided by the majority of papers.

Complications of hypertension and the role of angiotensin receptor blockers in hypertension trials

Hypertension is a high-prevalence disease that may affect several organs. In recent years, data have accumulated indicating that angiotensin II receptor blockers (ARBs) may have a supplementary effect beyond lowering blood pressure. The aim of this review is to evaluate the impact of ARBs on the most important complications of hypertension--heart, cerebrovascular and renal diseases, and metabolic complications--based on the findings from large clinical hypertension trials. The results may indicate that ARBs have a superior effect compared with placebo or other antihypertensive drugs in order to prevent left ventricular hypertrophy, atrial fibrillation, stroke, renal disease and diabetes mellitus, while there appears to be no blood pressure-independent superior effect of ARBs regarding prevention of myocardial infarction or heart failure.

Beneficial effects of losartan on vascular injury induced by advanced glycosylation end products and their receptors in spontaneous hypertension rats

This study was designed to explore the role of losartan, an angiotensin II receptor blocker, in hypertensive injuries of blood vessels and the potential mechanisms related to the vascular advanced glycosylation end product (AGE)/receptor (RAGE) system, oxidative stress and endothelial proinflammatory factors. Spontaneously hypertensive rats (SHR) were employed for our study, and age-matched Wistar-Kyoto rats (WKY) were used for control experiments. After losartan treatment for 12 weeks, we observed by immunofluorescence that the vascular AGE level in the losartan group was significantly lower than that of the SHR group and that the vascular mRNA expression of RAGE, NF-kappaB, NADPH oxidase p47phox and ET-1, as detected by RT-PCR, was significantly lower in losartan group than in the SHR group. Meanwhile, we found that the expression of RAGE and NF-kappaB proteins in the losartan group and the WKY group was remarkably lower than that of the SHR group. Compared with the SHR group, the activities of plasma superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) and the NO level were robustly increased, while the plasma malondialdehyde (MDA) and ET-1 were substantially reduced. These findings suggest that losartan decreases the vascular AGE level, suppresses RAGE and NF-kappaB activation, and enhances the antioxidant capacity thereby improving the endothelial function, which induce hypertensive vascular remodeling.

Review of the molecular pharmacology of Losartan and its possible relevance to stroke prevention in patients with hypertension

BACKGROUND

The Losartan Intervention For End-point reduction in hypertension (LIFE) study found that a losartan-based regimen, compared with an atenolol-based regimen, resulted in a significantly lower risk of stroke in hypertensive patients with left ventricular hypertrophy, despite similar reductions in blood pressure.

OBJECTIVE

The purpose of this review was to examine the molecular and pharmacologic mechanisms that may be associated with the different outcomes observed in the LIFE study.

METHODS

A PubMed/MEDLINE search of English-language articles (1990 to February 2006) with the terms angiotensin II antagonists or AIIAs or angiotensin receptor blockers or losartan or atenolol or beta blocker and terms including, but not limited to, atherosclerosis, left ventricular hypertrophy, carotid artery hypertrophy, fatty streaks, atrial fibrillation, arrhythmias, endothelial function, myocyte hypertrophy, myocardial fibrosis, platelet aggregation, tissue factor, plasminogen activator inhibitor-1, PAI-1, anti-inflammatory, uric acid, or oxidative stress.

RESULTS

Losartan's significant effect on stroke may be related to several possible mechanisms that are independent of blood-pressure reductions. These include improvements in endothelial function and vascular structure; decreases in vascular oxidative stress; reductions in left ventricular hypertrophy, reductions in myocardial fibrosis, or both; and modulation of atherosclerotic disease progression. Although some of these effects may be shared by other angiotensin II receptor antagonists (AIIAs), and perhaps other anti-hypertensive classes (eg, angiotensin-converting enzyme inhibitors), the ability of losartan to lower serum uric acid levels-a proposed independent risk factor for cardiovascular disease-appears to be a molecule-specific effect. Alternative explanations of the results of the LIFE study have also been hypothesized, including inappropriate choice of atenolol as an active comparator and differences in central pulse pressures between study groups.

CONCLUSIONS

This review of the literature suggests that losartan (and perhaps other AIIAs) may possess a number of properties, independent of its antihypertensive effects, that may be associated with decreased vulnerability of the plaque, myocardium, and blood.

Mechanism of Angiotensin II Type 1 Receptor Blocker Action in the Regression of Left Ventricular Hypertrophy

Left ventricular hypertrophy refers to a pathologic increase in left ventricular mass and is associated with an increased risk of subsequent cardiovascular morbidity and mortality from any cause. In the development of left ventricular hypertrophy there is growth of cardiomyocytes and accumulation of extracellular matrix and fibrosis. The actions are partly induced by angiotensin II, the principal effector of the renin-angiotensin-aldosterone system, binding to the AT1 receptor. Biochemical markers, some implicated in inflammatory changes, correlate with changes in left ventricular mass. The reduction in left ventricular mass brought about with angiotensin-converting enzyme inhibitor or angiotensin receptor blocker (ARB) therapy correlates with a reduction in these inflammatory changes, monitored by brain natriuretic peptide. Recent studies incorporating trials of ARBs have found ARBs to be more effective in reducing left ventricular mass than beta blockers and possibly more effective than calcium antagonists. Initial studies suggest that ARBs and angiotensin-converting enzyme inhibitors may have similar effects in terms of reducing left ventricular hypertrophy, and the combination of angiotensin-converting enzyme inhibitors and ARBs is thought to be synergistic due to a more complete inhibition of the renin-angiotensin-aldosterone system. In conclusion, these agents are efficacious in antihypertensive therapy and can play an important role in the prevention or regression of left ventricular hypertrophy due to hypertension.

Blockade of the renin-angiotensin-aldosterone system: a key therapeutic strategy to reduce renal and cardiovascular events in patients with diabetes

Diabetes (particularly type 2 diabetes) represents a global health problem of epidemic proportions. Individuals with diabetes are not only more likely to develop hypertension, dyslipidemia, and obesity, but are also at a significantly higher risk for coronary heart disease, peripheral vascular disease, and stroke. Angiotensin II plays a key pathophysiological role in the progression of diabetic renal disease, and blockade of the renin-angiotensin system with angiotensin-converting enzyme inhibitors (ACEi) or angiotensin II antagonists has therefore become an important therapeutic strategy to reduce renal and cardiovascular events in patients with diabetes. Several studies have demonstrated the effects of angiotensin II antagonists on the reduction of albuminuria and the progression of renal disease from microalbuminuria to macroalbuminuria. More importantly, several endpoint trials have shown that the antiproteinuric effects of losartan and irbesartan translate into cardiovascular and renoprotective benefits beyond blood pressure lowering, thereby delaying the need for dialysis or kidney transplantation by several years. These and other studies indicate that angiotensin II antagonists not only improve survival and quality of life of patients with diabetic nephropathy, but also have the potential to reduce the substantial healthcare burden associated with managing these patients. ACEi also appear to exert similar beneficial effects in diabetic patients, but whether clinically significant differences in renoprotection or mortality exist between angiotensin II antagonists and ACEi in patients with type 2 diabetes remains to be fully investigated in appropriate head-to-head studies.

Genetic variations of tubular sodium reabsorption leading to “primary” hypertension: from gene polymorphism to clinical symptoms

The definition of the most appropriate strategy to demonstrate causation of a given genetic-molecular mechanism in a complex multifactorial polygenic disease like hypertension is hampered by the underestimation of the complexity arising from the genetic and environmental interactions. To disentangle this complexity, we developed a strategy based on six steps: 1) isolation of a rodent model of hypertension (Milan hypertensive strain and Milan normotensive strain) that shares some pathophysiological abnormalities with human primary hypertension; 2) definition in the model of the sequence of events linking these abnormalities to a genetic molecular mechanism; 3) determination of the polymorphism of the three adducin genes discovered in the model both in rats and in humans; 4) comparison at biochemical and physiological levels between the rodent models and the hypertensive carriers of the “mutated” gene variants; 5) evaluation of the impact of the adducin genes in hypertension and its organ complications with association and linkage studies in humans, also considering the genetic and environmental interactions; and 6) development of a pharmacogenomic approach aimed at establishing the therapeutic benefit of a drug interfering with the sequence of events triggered by adducin and their effect's size. The bulk of data obtained demonstrates the importance of a multidisciplinary approach considering a variety of genetic and environmental interactions. Adducin functions within the cells as a heterodimer composed of a combination of three subunits. Each of these subunits is coded by genes mapping to different chromosomes. Therefore, the interaction among these genes, taken together with the interactions with other modulatory genes or with the environment, is indispensable to establish the adducin clinical impact. The hypothesis that adducin polymorphism favors the development of hypertension via an increased tubular sodium reabsorption is well supported by a series of consistent experimental and clinical data. Many mechanistic aspects, underlying the link between these genes and clinical symptoms, need to be clarified. The clinical effect size of adducin must be established also with the contribution of pharmacogenomics with a drug that selectively interferes with the sequence of events triggered by the mutated adducin.

Angiotensin II receptor antagonists alone and combined with hydrochlorothiazide: potential benefits beyond the antihypertensive effect

Angiotensin II receptor antagonists (angiotensin receptor blockers; ARBs) and thiazide diuretics have an accepted place in the management of hypertension. Most patients require combination therapy with two or more drugs to adequately control blood pressure to targets recommended by European and international guidelines. ARBs and the thiazide diuretic hydrochlorothiazide have complementary modes of action. Fixed-dose combinations of an ARB and low-dose hydrochlorothiazide provide a convenient and effective treatment option for patients who do not achieve blood pressure targets on monotherapy, without compromising the placebo-like tolerability of ARBs. In Europe, fixed-dose combinations with hydrochlorothiazide currently are available for the ARBs candesartan, eprosartan, irbesartan, losartan, telmisartan, and valsartan. Recently, a number of studies have focused on the use of ARBs in monotherapy and in combination therapy, in conditions including congestive heart failure, post-myocardial infarction management, hypertension with cardiovascular risk factors, and diabetic and non-diabetic nephropathy. Evidence from these studies suggests a beneficial role beyond the antihypertensive effect of these therapies in providing protection against cardiovascular, renovascular, and cerebrovascular events.

Angiotensin converting enzyme inhibition for cardiac hypertrophy in patients with end-stage renal disease: what is the evidence?

Dialysis patients show a high prevalence of cardiovascular complications among which left ventricular hypertrophy is one of the most frequent and is independently predictive of mortality. A recent study indicates that partial regression of left ventricular hypertrophy improves mortality and reduces cardiovascular events in end-stage renal disease (ESRD) patients, suggesting the importance of targeting therapeutic strategies to reduce cardiac hypertrophy and improve the outcome in these patients. The pathogenesis of left ventricular hypertrophy in ESRD patients is multifactorial and includes hypertension, activation of the renin-angiotensin system, increased sympathetic activity, chronic volume overload, chronic anaemia and hyperparathyroidism. In this paper, we review the available experimental and clinical evidence showing the important contribution of the renin-angiotensin system as well as its interaction with the sympathetic nervous system in the pathogenesis of left ventricular hypertrophy in ESRD patients. Furthermore, we summarize the results of currently available clinical studies that examined the effects of angiotensin-converting enzyme inhibition or angiotensin receptor antagonism on left ventricular hypertrophy in ESRD patients, and review evidences that support the use of angiotensin-converting enzyme inhibitors or angiotensin receptor antagonists in the ESRD population.

Regulation of the Cell Surface Expression and Function of Angiotensin II Type 1 Receptor by Rab1-mediated Endoplasmic Reticulum-to-Golgi Transport in Cardiac Myocytes

Rab1 GTPase coordinates vesicle-mediated protein transport specifically from the endoplasmic reticulum (ER) to the Golgi apparatus. We recently demonstrated that Rab1 is involved in the export of angiotensin II (Ang II) type 1 receptor (AT1R) to the cell surface in HEK293 cells and that transgenic mice overexpressing Rab1 in the myocardium develop cardiac hypertrophy. To expand these studies, we determined in this report whether the modification of Rab1-mediated ER-to-Golgi transport can alter the cell surface expression and function of endogenous AT1R and AT1R-mediated hypertrophic growth in primary cultures of neonatal rat ventricular myocytes. Adenovirus-mediated gene transfer of wild-type Rab1 (Rab1WT) significantly increased cell surface expression of endogenous AT1R in neonatal cardiomyocytes, whereas the dominant-negative mutant Rab1N124I had the opposite effect. Brefeldin A treatment blocked the Rab1WT-induced increase in AT1R cell surface expression. Fluorescence analysis of the subcellular localization of AT1R revealed that Rab1 regulated AT1R transport specifically from the ER to the Golgi in HL-1 cardiomyocytes. Consistent with their effects on AT1R export, Rab1WT and Rab1N124I differentially modified the AT1R-mediated activation of ERK1/2 and its upstream kinase MEK1. More importantly, adenovirus-mediated expression of Rab1N124I markedly attenuated the Ang II-stimulated hypertrophic growth as measured by protein synthesis, cell size, and sarcomeric organization in neonatal cardiomyocytes. In contrast, Rab1WT expression augmented the Ang II-mediated hypertrophic response. These data strongly indicate that AT1R function in cardiomyocytes can be modulated through manipulating AT1R traffic from the ER to the Golgi and provide the first evidence implicating the ER-to-Golgi transport as a regulatory site for control of cardiomyocyte growth.

A meta-analysis of the effects of treatment on left ventricular mass in essential hypertension

PURPOSE

Antihypertensive medications have different effects on left ventricular mass. We conducted a meta-analysis of double-blind trials that measured the effects of antihypertensive therapy on left ventricular mass.

METHODS

Medical databases and review articles were screened for double-blind, randomized controlled trials (through September 2002) that reported the effects of diuretics, beta-blockers, calcium antagonists, angiotensin-converting enzyme (ACE) inhibitors, or angiotensin II receptor antagonists on echocardiographic left ventricular mass in essential hypertension. Treatment arms of the same drug class, weighted for the number of patients, were combined. Analysis of covariance was performed to detect differences among drug classes in effects on left ventricular structure.

RESULTS

Eighty trials with 146 active treatment arms (n = 3767 patients) and 17 placebo arms (n = 346 patients) were identified. Adjusted for treatment duration and change in diastolic blood pressure, there was a significant difference (P = 0.004) among medication classes: left ventricular mass index decreased by 13% with angiotensin II receptor antagonists (95% confidence interval [CI]: 8% to 18%), by 11% with calcium antagonists (95% CI: 9% to 13%), by 10% with ACE inhibitors (95% CI: 8% to 12%), by 8% with diuretics (95% CI: 5% to 10%), and by 6% with beta-blockers (95% CI: 3% to 8%). In pairwise comparisons, angiotensin II receptor antagonists, calcium antagonists, and ACE inhibitors were more effective at reducing left ventricular mass than were beta-blockers (all P <0.05 with Bonferroni correction).

CONCLUSIONS

Antihypertensive drug classes have different effects on left ventricular mass reduction. Whether a greater reduction of left ventricular mass results in better clinical outcomes remains to be determined.

Oral acetylcysteine does not protect renal function from moderate to high doses of intravenous radiographic contrast

The use of radiographic contrast during cardiac catheterization can cause acute renal failure with an increase in morbidity and mortality. Prophylactic acetylcysteine plus intravenous hydration have been shown to prevent contrast-induced nephropathy (CIN) in patients with chronic renal failure undergoing computed tomography scan, who receive low doses of intravenous contrast. Whether the use of prophylactic acetylcysteine can decrease the incidence of CIN when larger doses of contrast are used remains to be determined. We sought to evaluate whether the prophylactic administration of acetylcysteine plus intravenous hydration is superior to intravenous hydration alone in prevention of CIN in patients with chronic renal failure undergoing cardiac catheterization and receiving moderate to high doses of intravenous contrast (> 1 cc/kg). Seventy-three consecutive patients with renal insufficiency who received intravenous hydration and 600 mg of acetylcysteine twice a day 24 hr before and the day of the cardiac catheterization were compared with 106 consecutive patients who received hydration alone. Baseline and 48-hr serum creatinine concentrations were compared between the two groups before and after cardiac catheterization. Multivariate and univariate analysis were performed to assess the effects of acetylcysteine and other clinical variables in the change of serum creatinine after the procedure. Both groups had comparable clinical characteristics and received similar volumes of intravenous hydration. The volume of contrast used was similar for the two groups (2.2 +/- 1.7 vs. 2.3 +/- 1.5 cc/kg; P = 0.67). A mean change in serum creatinine of 0.17 +/- 0.54 mg/dl for the acetylcysteine group vs. 0.19 +/- 0.40 mg/dl for the control group (P = 0.77) was observed at 48 hr. The incidence CIN was 13% in the acetylcysteine vs. 12% in the control group (P = 0.84). Acetylcysteine, whether analyzed with multivariate or univariate analysis, failed to demonstrate a significant effect in the change of serum creatinine after cardiac catheterization. In patients with chronic renal insufficiency, acetylcysteine in a dose of 600 mg twice a day before and after cardiac catheterization, along with intravenous fluids, is as effective as fluids alone in the prevention of CIN when moderate to high doses of contrast are used.

Angiotensin AT-1 receptor antagonism: complementary or alternative to ACE inhibition in cardiovascular and renal disease?

Both angiotensin-converting enzyme (ACE) inhibitors and AT-1 receptor antagonists reduce the effects of angiotensin II, however they may have different clinical effects. This is because the ACE inhibitors, but not the AT-1 receptor antagonists, increase the levels of substance P, bradykinin and tissue plasminogen activator. The AT-1 receptor antagonists, but not the ACE inhibitors, are capable of inhibiting the effects of angiotensin II produced by enzymes other than ACE. On the basis of the present clinical trial evidence, AT-1 receptor antagonists, rather than the ACE inhibitors, should be used to treat hypertension associated with left ventricular (LV) hypertrophy. Both groups of drugs are useful when hypertension is not complicated by LV hypertrophy, and in diabetes. In the treatment of diabetes with or without hypertension, there is good clinical support for the use of either an ACE inhibitor or an AT-1 receptor antagonist. ACE inhibitors are recommended in the treatment of renal disease that is not associated with diabetes, after myocardial infarction when left ventricular dysfunction is present, and in heart failure. As the incidence of cough is much lower with the AT-1 receptor antagonists, these can be substituted for ACE inhibitors in patients with hypertension or heart failure who have persistent cough. Preliminary studies suggest that combining an AT-1 receptor antagonist with an ACE inhibitor may be more effective than an ACE inhibitor alone in the treatment of hypertension, diabetes with hypertension, renal disease without diabetes and heart failure. However, further trials are required before combination therapy can be recommended in these conditions.

Are all antihypertensive drug classes equal in reducing left ventricular hypertrophy?

Left ventricular hypertrophy (LVH) is a major cardiovascular risk factor for morbidity and mortality. It is caused by arterial hypertension, although various hemodynamic and nonhemodynamic factors contribute to its development. Especially, the renin-angiotensin-aldosterone system is involved in the pathophysiology of LVH. The Treatment of Mild Hypertension study demonstrated that in mild essential hypertension, nonpharmacologic treatment is an effective tool for treating LVH. There are at least three major meta-analyses with several thousand patients examining the ability of antihypertensive drugs on the reversal of LVH. The results of these meta-analyses are very consistent. Angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers achieve significantly better results than b-blockers. The most recently published Losartan Intervention For Endpoint reduction in hypertension study confirmed the superiority of angiotensin receptor blockers against b-blockers in a large-scale prospective trial. It also proves for the first time that regression of LVH is associated with better cardiovascular outcome.

Part 1. Uric acid and losartan

PURPOSE OF REVIEW

To characterize the mechanism and clinical impact of the angiotensin-receptor blocker losartan on both renal uric acid handling and thereby serum uric acid.

RECENT FINDINGS

Losartan effect on serum uric acid has been demonstrated at various stages of renal failure including most recently observations obtained in end-stage renal disease patients. Other angiotensin-receptor blockers do not alter renal handling of uric acid. The uricosuria, which accompanies losartan administration, has not been associated with adverse renal consequences, in part, because of the increase in urinary pH that follows its administration.

SUMMARY

Hyperuricemia is closely linked to both hypertension and cardiovascular disease. The development of hyperuricemia and its persistence are clearly renal processes. Likewise, the correction of hyperuricemia is often accomplished by increasing its renal excretion. A number of medications, by way of varying mechanisms, can alter renal urate handling and thereby influence serum uric acid values. Most recently, the angiotensin-receptor blocker losartan has been shown to reduce serum uric acid. The mechanism of this process relates to losartan alone and does not involve the E-3174 metabolite of this compound. This probenecid-like effect of losartan occurs shortly after drug administration, and is both transient and dose-dependent. This property of losartan, touted by some as a meaningful pharmacological distinction among the angiotensin-receptor blockers, remains to be proved, since, to date, the hypothesis that a reduction in serum uric acid alters the natural history of cardiovascular disease has not been formally tested.