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Concept: Angiotensin-converting enzyme

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Angiotensin-converting enzyme (ACE) is a zinc-dependent peptidase responsible for converting angiotensin I into the vasoconstrictor angiotensin II. However, ACE is a relatively nonspecific peptidase that is capable of cleaving a wide range of substrates. Because of this, ACE and its peptide substrates and products affect many physiologic processes, including blood pressure control, hematopoiesis, reproduction, renal development, renal function, and the immune response. The defining feature of ACE is that it is composed of two homologous and independently catalytic domains, the result of an ancient gene duplication, and ACE-like genes are widely distributed in nature. The two ACE catalytic domains contribute to the wide substrate diversity of ACE and, by extension, the physiologic impact of the enzyme. Several studies suggest that the two catalytic domains have different biologic functions. Recently, the X-ray crystal structure of ACE has elucidated some of the structural differences between the two ACE domains. This is important now that ACE domain-specific inhibitors have been synthesized and characterized. Once widely available, these reagents will undoubtedly be powerful tools for probing the physiologic actions of each ACE domain. In turn, this knowledge should allow clinicians to envision new therapies for diseases not currently treated with ACE inhibitors.

Concepts: DNA, Evolution, Enzyme, Physiology, Blood pressure, Angiotensin, Renin-angiotensin system, Angiotensin-converting enzyme

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ACE Inhibitors (ACE-I) and Angiotensin-Receptor Antagonists (ARAs) are commonly prescribed but can cause acute kidney injury (AKI) during intercurrent illness. Rates of hospitalization with AKI are increasing. We aimed to determine whether hospital AKI admission rates are associated with increased ACE-I/ARA prescribing.

Concepts: Surgery, Diabetic nephropathy, Angiotensin-converting enzyme, Angiotensin II receptor antagonist, ACE inhibitor, Bradykinin, Hyperkalemia, Captopril

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We aimed to characterize different cellular effects of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin 1 (AT1) receptor blockers (ARBs) as mono- or combination therapy in cardiac pressure overload. Methods and

Concepts: Hypertension, Enzyme inhibitor, Angiotensin-converting enzyme, Angiotensin II receptor antagonist, ACE inhibitor, Differential, Ramipril

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Renin-angiotensin-aldosterone system (RAAS) inhibitors are well established for the reduction in cardiovascular morbidity, but their impact on all-cause mortality in hypertensive patients is uncertain. Our objective was to analyse the effects of RAAS inhibitors as a class of drugs, as well as of angiotensin-converting enzyme (ACE) inhibitors and AT1 receptor blockers (ARBs) separately, on all-cause mortality.

Concepts: Pharmacology, Epidemiology, Hypertension, Blood pressure, Renin-angiotensin system, Angiotensin-converting enzyme, Angiotensin II receptor antagonist, Captopril

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Dietary fats and sodium are both palatable and are hypothesized to synergistically contribute to ingestive behavior and thereby obesity. Contrary to this hypothesis, C57BL/6J mice fed a 45% high fat diet exhibited weight gain that was inhibited by increased dietary sodium content. This suppressive effect of dietary sodium upon weight gain was mediated specifically through a reduction in digestive efficiency, with no effects on food intake behavior, physical activity, or resting metabolism. Replacement of circulating angiotensin II levels reversed the effects of high dietary sodium to suppress digestive efficiency. While the AT1 receptor antagonist losartan had no effect in mice fed low sodium, the AT2 receptor antagonist PD-123,319 suppressed digestive efficiency. Correspondingly, genetic deletion of the AT2 receptor in FVB/NCrl mice resulted in suppressed digestive efficiency even on a standard chow diet. Together these data underscore the importance of digestive efficiency in the pathogenesis of obesity, and implicate dietary sodium, the renin-angiotensin system, and the AT2 receptor in the control of digestive efficiency regardless of mouse strain or macronutrient composition of the diet. These findings highlight the need for greater understanding of nutrient absorption control physiology, and prompt more uniform assessment of digestive efficiency in animal studies of energy balance.

Concepts: Protein, Nutrition, Fat, Angiotensin, Renin-angiotensin system, Angiotensin-converting enzyme, Angiotensin II receptor antagonist, Angiotensin receptor

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AIMS: Although the focus of therapeutic intervention has been on neurohormonal pathways thought to be harmful in heart failure (HF), such as the renin-angiotensin-aldosterone system (RAAS), potentially beneficial counter-regulatory systems are also active in HF. These promote vasodilatation and natriuresis, inhibit abnormal growth, suppress the RAAS and sympathetic nervous system, and augment parasympathetic activity. The best understood of these mediators are the natriuretic peptides which are metabolized by the enzyme neprilysin. LCZ696 belongs to a new class of drugs, the angiotensin receptor neprilysin inhibitors (ARNIs), which both block the RAAS and augment natriuretic peptides.MethodsPatients with chronic HF, NYHA class II-IV symptoms, an elevated plasma BNP or NT-proBNP level, and an LVEF of ≤40% were enrolled in the Prospective comparison of ARNI with ACEI to Determine Impact on Global Mortailty and morbidity in Heart Failure trial (PARADIGM-HF). Patients entered a single-blind enalapril run-in period (titrated to 10 mg b.i.d.), followed by an LCZ696 run-in period (100 mg titrated to 200 mg b.i.d.). A total of 8436 patients tolerating both periods were randomized 1:1 to either enalapril 10 mg b.i.d. or LCZ696 200 mg b.i.d. The primary outcome is the composite of cardiovascular death or HF hospitalization, although the trial is powered to detect a 15% relative risk reduction in cardiovascular death.PerspectivesPARADIGM-HF will determine the place of the ARNI LCZ696 as an alternative to enalapril in patients with systolic HF. PARADIGM-HF may change our approach to neurohormonal modulation in HF.Trial registrationNCT01035255.

Concepts: Hypertension, Blood pressure, Enzyme inhibitor, Angiotensin, Renin-angiotensin system, Angiotensin-converting enzyme, Autonomic nervous system, ACE inhibitor

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To examine adherence to serum creatinine and potassium monitoring and discontinuation guidelines following initiation of treatment with ACE inhibitors (ACEI) or angiotensin receptor blockers (ARBs); and whether high-risk patients are monitored.

Concepts: Hypertension, Blood pressure, Angiotensin, Renin-angiotensin system, Angiotensin-converting enzyme, Angiotensin II receptor antagonist, Angiotensin receptor, Captopril

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We describe a case where a patient presented with acute angiotensin-converting enzyme inhibitor (ACE-I) induced angioedema without signs or symptoms of upper airway edema beyond lip swelling. Point-of-care ultrasound (POCUS) was used as an initial diagnostic test and identified left-sided subglottic upper airway edema that was immediately confirmed with indirect fiberoptic laryngoscopy. ACE-I induced angioedema and the historical use of ultrasound in evaluation of the upper airway is briefly discussed. To our knowledge, POCUS has not been used to identify acute upper airway edema in the emergency setting. Further investigation is needed to determine if POCUS is a sensitive and specific-enough tool for the identification and evaluation of acute upper airway edema.

Concepts: Inflammation, Medical terms, Enzyme inhibitor, Angiotensin-converting enzyme, Angiotensin II receptor antagonist, Angioedema, ACE inhibitor, Bradykinin

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IMPORTANCE Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) may have different effects on cardiovascular (CV) events in patients with diabetes mellitus (DM). OBJECTIVE To conduct a meta-analysis to separately evaluate the effects of ACEIs and ARBs on all-cause mortality, CV deaths, and major CV events in patients with DM. DATA SOURCES Data sources included MEDLINE (1966-2012), EMBASE (1988-2012), the Cochrane Central Register of Controlled Trials, conference proceedings, and article reference lists. STUDY SELECTION We included randomized clinical trials reporting the effects of ACEI and ARB regimens for DM on all-cause mortality, CV deaths, and major CV events with an observation period of at least 12 months. Studies were excluded if they were crossover trials. DATA EXTRACTION AND SYNTHESIS Dichotomous outcome data from individual trials were analyzed using the risk ratio (RR) measure and its 95% CI with random-effects models. We estimated the difference between the estimates of the subgroups according to tests for interaction. We performed meta-regression analyses to identify sources of heterogeneity. MAIN OUTCOMES AND MEASURES Primary end points were all-cause mortality and death from CV causes. Secondary end points were the effects of ACEIs and ARBs on major CV events. RESULTS Twenty-three of 35 identified trials compared ACEIs with placebo or active drugs (32 827 patients) and 13 compared ARBs with no therapy (controls) (23 867 patients). When compared with controls (placebo/active treatment), ACEIs significantly reduced the risk of all-cause mortality by 13% (RR, 0.87; 95% CI, 0.78-0.98), CV deaths by 17% (0.83; 0.70-0.99), and major CV events by 14% (0.86; 0.77-0.95), including myocardial infarction by 21% (0.79; 0.65-0.95) and heart failure by 19% (0.81; 0.71-0.93). Treatment with ARBs did not significantly affect all-cause mortality (RR, 0.94; 95% CI, 0.82-1.08), CV death rate (1.21; 0.81-1.80), and major CV events (0.94; 0.85-1.01) with the exception of heart failure (0.70; 0.59-0.82). Both ACEIs and ARBs were not associated with a decrease in the risk for stroke in patients with DM. Meta-regression analysis showed that the ACEI treatment effect on all-cause mortality and CV death did not vary significantly with the starting baseline blood pressure and proteinuria of the trial participants and the type of ACEI and DM. CONCLUSIONS AND RELEVANCE Angiotensin-converting enzyme inhibitors reduced all-cause mortality, CV mortality, and major CV events in patients with DM, whereas ARBs had no benefits on these outcomes. Thus, ACEIs should be considered as first-line therapy to limit excess mortality and morbidity in this population.

Concepts: Epidemiology, Myocardial infarction, Hypertension, Medical statistics, Angiotensin, Renin-angiotensin system, Angiotensin-converting enzyme, Angiotensin II receptor antagonist