Adrenomedullin in experimental congestive heart failure: cardiorenal activation

Determinants of survival following hospitalization for acute heart failure

Heart failure constitutes a major public health concern in the United States and is one of the leading causes of hospitalization, readmission, and death. Due to an aging U.S. population, it is estimated that the prevalence of heart failure will increase by 25% over the coming decades, affecting approximately 3.5% of the population by the year 2030. The ability to discriminate patients admitted with acute heart failure syndromes who are at increased risk for poor post-hospitalization outcomes is thus critical to guide therapeutic decision making for healthcare providers. This review paper will discuss clinical, hemodynamic, as well as biochemical markers that have been demonstrated to predict post-discharge outcomes among patients hospitalized with acute heart failure.

Use of ivabradine and atorvastatin in emergent orthopedic lower limb surgery and computed tomography coronary plaque imaging and novel biomarkers of cardiovascular stress and lipid metabolism for the study and prevention of perioperative myocardial infarction: study protocol for a randomized controlled trial

Background

The incidence of perioperative myocardial infarction (PMI) globally is known to be around 2 to 3% and can prolong hospitalization, increased morbidity and mortality. Little is known about the pathophysiology and risk factors for PMI. We investigate the presence of elevated novel cardiac markers and preoperative coronary artery plaque through contemporary laboratory techniques to determine the correlation with PMI, as well as studying ivabradine and atorvastatin as protective pharmacotherapies against PMI in the context of orthopedic surgery.

Methods/Design

We aim to enroll 200 patients aged above 60 years who suffer from neck of femur fracture requiring surgery. Patients will be randomized to four arms (no study drugs, atorvastatin only, ivabradine only and ivabradine and atorvastatin). Our primary outcome is incidence of PMI. All patients will receive an electrocardiogram, cardiac echocardiography, measurement of novel cardiac biomarkers and computed tomography (CT) coronary angiography. A telephone interview post discharge will be conducted at 30 days, 60 days and 1 year.

Discussion

We postulate that ivabradine and atorvastatin will reduce the rate and magnitude of PMI following surgery by reducing heart rate and attenuating catecholamine-induced tachycardia postoperatively. Secondly, we postulate that postoperative reduction in heart rate and catecholamine-induced tachycardia with ivabradine will correlate with a reduction in cardiovascular novel biomarkers which will reduce atrial stretch and postoperative incidence of arrhythmia. We aim to demonstrate that treatment with ivabradine and atorvastatin will cause a reduction in the incidence and magnitude of PMI, the benefit of which is derived primarily in patients with greater atherosclerotic burden as measured by higher CT coronary calcium scores.

Trial registration

This study protocol has been listed in the Australia New Zealand Clinical Trial Registry (registration number: ACTRN12612000340831) on 23 March 2012.

Biomarkers in acute heart failure--state of the art

The role of biomarkers in the management of patients with acute heart failure (HF) has evolved rapidly in the past several years. Representing a major burden on health systems, acute HF has increased the need for earlier diagnosis, better risk stratification, and cost-effective treatment to reduce rates of hospitalization. Biomarker-guided diagnosis and treatment have become essential, especially in the acute setting to which the majority of the patients with acute HF initially present. Studies clearly demonstrate the complexity of these patients, who commonly have multiple comorbidities necessitating an integrative approach. Several groundbreaking studies conducted in the past decade have demonstrated how biomarkers, individually or in combination, can outperform conventional laboratory tests used in the emergency department as well as in hospitalized patients with acute HF. In this Review, we will provide an update on biomarkers considered state of the art in the diagnosis and management of patients with acute HF.

Plasma adrenomedullin concentration in dogs with myxomatous mitral valvular disease

Adrenomedullin (AM), a peptide identified to have vasodilating and natriuretic effects, is involved in the regulation of the cardiovascular system. To evaluate plasma AM concentration in dogs with myxomatous mitral valvular disease (MMVD), and to investigate the associations between the concentrations of plasma AM and natriuretic peptides and the echocardiographic data, we evaluated plasma AM concentrations in 31 healthy control dogs and 57 dogs with MMVD. Plasma AM concentrations in dogs with MMVD were higher than that in the control subjects. The plasma AM concentration increased in conjunction with the severity of heart failure according to the International Small Animal Cardiac Health Council (ISACHC). The AM concentrations were 25.1 ± 5.0 fmol/ml (ISACHC class Ia), 29.9 ± 11.0 fmol/ml (ISACHC class Ib), 43.4 ± 19.8 fmol/ml (ISACHC class II) and 73.5 ± 21.7 fmol/ml (ISACHC class III) and 7.5 ± 5.1 fmol/ml (control group), respectively. The receiver operating characteristic curve indicated an area of 0.93 (95% CI, 0.8801-0.9889; <0.0001), a cutoff value of 30.5 fmol/ml, a sensitivity of 87.1%, and a specificity of 82.5% for the determination of congestive heart failure. Plasma AM concentrations correlated with atrial natriuretic peptide concentrations, LA/Ao ratio, and left ventricular diameter. In conclusion, AM may be a potential diagnostic marker for canine MMVD and possibly plays a pathophysiological role in collaboration with the other neurohumoral factors such as natriuretic peptides.

Evaluation of multiple biomarkers of cardiovascular stress for risk prediction and guiding medical therapy in patients with stable coronary disease

BACKGROUND

Circulating biomarkers can offer insight into subclinical cardiovascular stress and thus have the potential to aid in risk stratification and tailoring of therapy.

METHODS AND RESULTS

We measured plasma levels of 4 cardiovascular biomarkers, midregional pro-atrial natriuretic peptide (MR-proANP), midregional pro-adrenomedullin (MR-proADM), C-terminal pro-endothelin-1 (CT-proET-1), and copeptin, in 3717 patients with stable coronary artery disease and preserved left ventricular ejection fraction who were randomized to trandolapril or placebo as part of the Prevention of Events With Angiotensin Converting Enzyme (PEACE) trial. After adjustment for clinical cardiovascular risk predictors and left ventricular ejection fraction, elevated levels of MR-proANP, MR-proADM, and CT-proET-1 were independently associated with the risk of cardiovascular death or heart failure (hazard ratios per 1-SD increase in log-transformed biomarker levels of 1.97, 1.48, and 1.47, respectively; P≤0.002 for each biomarker). These 3 biomarkers also significantly improved metrics of discrimination when added to a clinical model. Trandolapril significantly reduced the risk of cardiovascular death or heart failure in patients who had elevated levels of ≥2 biomarkers (hazard ratio, 0.53; 95% confidence interval, 0.36-0.80), whereas there was no benefit in patients with elevated levels of 0 or 1 biomarker (hazard ratio, 1.09; 95% confidence interval, 0.74-1.59; P(interaction)=0.012).

CONCLUSIONS

In patients with stable coronary artery disease and preserved left ventricular ejection fraction, our results suggest that elevated levels of novel biomarkers of cardiovascular stress may help identify patients who are at higher risk of cardiovascular death and heart failure and may be useful to select patients who derive significant benefit from angiotensin-converting enzyme inhibitor therapy.

Cloning of prepro-adrenomedullin and mRNA expression in cats

The objective of this paper was to evaluate the sequence of feline prepro-adrenomedullin (AM) and its tissue distribution and to investigate whether expression of feline AM mRNA increases in association with spontaneous cardiomyopathy. The feline prepro-AM cDNA sequence and deduced amino acids were 564 base pairs and 188 residues, respectively. The cDNA sequences of feline prepro-AM including AM and proadrenomedullin N-terminal 20 peptide showed high homology with those of other mammalian species. The mRNA expression of AM was detectable in various normal tissues. The mRNA levels of AM were elevated in hearts with cardiomyopathy compared with normal hearts. This study suggests that AM has an important role as a neurohumoral factor in cats with spontaneous heart diseases.

Gene expression of adrenomedullin in canine normal tissues and diseased hearts

The purposes of this study were to determine the tissue distribution of canine adrenomedullin (AM) and to determine whether increased canine AM mRNA expression is associated with congestive heart failure (CHF) due to mitral regurgitation (MR). Canine AM mRNA expression was detectable in various normal tissues, including cardiovascular tissues. In addition, the AM mRNA expression in the left atrium of dogs with MR was significantly higher than that in normal subjects. In conclusion, AM is a potential neurohumoral factor in dogs with CHF due to MR.

Atrial myocardium is the predominant inotropic target of adrenomedullin in the human heart

Adrenomedullin (ADM) is an endogenous peptide with favorable hemodynamic effects in vivo. In this study, we characterized the direct functional effects of ADM in isolated preparations from human atria and ventricles. In electrically stimulated human nonfailing right atrial trabeculae, ADM (0.0001–1 μmol/l) increased force of contraction in a concentration-dependent manner, with a maximal increase by 35 ± 8% (at 1 μmol/l; P < 0.05). The positive inotropic effect was accompanied by a disproportionate increase in calcium transients assessed by aequorin light emission [by 76 ± 20%; force/light ratio (ΔF/ΔL) 0.58 ± 0.15]. In contrast, elevation of extracellular calcium (from 2.5 to 3.2 mmol/l) proportionally increased force and aequorin light emission (ΔF/ΔL 1.0 ± 0.1; P < 0.05 vs. ADM). Consistent with a cAMP-dependent mechanism, ADM (1 μmol/l) increased atrial cAMP levels by 90 ± 12%, and its inotropic effects could be blocked by the protein kinase A (PKA) inhibitor H-89. ADM also exerted positive inotropic effects in failing atrial myocardium and in nonfailing and failing ventricular myocardium. The inotropic response was significantly weaker in ventricular vs. atrial myocardium and in failing vs. nonfailing myocardium. In conclusion, ADM exerts Ca2+-dependent positive inotropic effects in human atrial and less-pronounced effects in ventricular myocardium. The inotropic effects are related to increased cAMP levels and stimulation of PKA. In heart failure, the responsiveness to ADM is reduced in atria and ventricles.

Expressions of adrenomedullin mRNA and protein in rats with hypobaric hypoxia-induced pulmonary hypertension

Experimental pulmonary hypertension induced in a hypobaric hypoxic environment (HHE) is characterized by structural remodeling of the heart and pulmonary arteries. Adrenomedullin (AM) has diuretic, natriuretic, and hypotensive effects. To study the possible effects of HHE on the AM synthesis system, 150 male Wistar rats were housed in a chamber at the equivalent of a 5,500-m altitude level for 21 days. After 14 days of exposure to HHE, pulmonary arterial pressure (PAP) was significantly increased (compared with control rats). The plasma AM protein level was significantly increased on day 21 of exposure to HHE. In the right ventricle (RV), right atrium, and left atrium of the heart, the expressions of AM mRNA and protein were increased in the middle to late phase (5–21 days) of HHE, whereas in the brain and lung they were increased much earlier (0.5–5 days). In situ hybridization and immunohistochemistry showed AM mRNA and protein staining to be more intense in the RV in animals in the middle to late phase of HHE exposure than in the controls. During HHE, these changes in AM synthesis, which occurred strongly in the RV, occurred alongside the increase in PAP. Conceivably, AM may play a role in modulating pulmonary hypertension in HHE.

Adrenomedullin functions as an important tumor survival factor in human carcinogenesis

Adrenomedullin (AM) is a pluripotent regulatory peptide initially isolated from a human pheochromocytoma (adrenal tumor) and subsequently shown to play a critical role in cancer cell division, tumor neovascularization, and circumvention of programmed cell death, thus it is an important tumor cell survival factor underlying human carcinogenesis. A variety of neural and epithelial cancers have been shown to produce abundant amounts of AM. Recent findings have implicated elevation of serum AM with the onset of malignant expression. In addition, patients with tumors producing high levels of this peptide have a poor prognostic clinical outcome. Given that most human epithelial cancers display a microenvironment of reduced oxygen tension, it is interesting to note that AM and several of its receptors are upregulated during hypoxic insult. The existence of such a regulatory pathway has been implicated as the basis for the overexpression of AM/AM-R in human malignancies, thereby generating a subsequent autocrine/paracrine growth advantage for the tumor cell. Furthermore, AM has been implicated as a potential immune suppressor substance, inhibiting macrophage function and acting as a newly identified negative regulator of the complement cascade, protective properties which may help cancer cells to circumvent immune surveillance. Hence, AM's traditional participation in normal physiology (cited elsewhere in this issue) can be extended to a primary player in human carcinogenesis and may have clinical relevance as a biological target for the intervention of tumor progression.

Effects of adrenomedullin on load and myocardial performance in normal and heart-failure dogs

Myocardial actions of the vasodilator peptide adrenomedullin (ADM) in the intact animal are unknown. Negative and positive inotropic actions have been reported in ex vivo experiments. Myocardial and load-altering actions of ADM in dogs before and after development of heart failure were studied. With controlled heart rate (atrial pacing) and after beta-blockade, ADM was administered to five normal dogs in doses of 20 ng. kg(-1). min(-1) iv, 100 ng. kg(-1). min(-1) iv, and 200 ng. kg(-1). min(-1) into the left ventricle (LV). LV peak systolic pressure and end-systolic volume decreased with each dose of ADM. End-systolic pressure decreased with the two higher doses. At the highest dose, arterial elastance and the time constant of LV isovolumic relaxation (tau) decreased, and LV end-systolic elastance (E(es)) increased. LV end-diastolic pressure and volume were unchanged. In five additional normal dogs receiving only the highest dose of ADM (200 ng. kg(-1). min(-1) intra-LV), to control for increased heart rate and sympathetic activation observed with the cumulative infusion, ADM produced arterial vasodilation but no change in E(es) or tau. In four dogs with pacing-induced heart failure, ADM (200 ng. kg(-1). min(-1) intra-LV) was without effect on tau, E(es), and systolic or diastolic pressure and volume. In vivo, ADM appears to be a selective arterial dilator without inotropic or lusitropic effects. The vasodilatory actions are attenuated in heart failure.