Novel Chemiluminescent Enzyme Immunoassays for Individual Quantification of 3 Endogenous Molecular Forms of Atrial Natriuretic Peptide in Human Plasma

Association between left ventricular reverse remodelling and the B-type natriuretic peptide-cGMP cascade after anterior acute myocardial infarction

BACKGROUND

The role of cyclic guanosine 3',5'-monophosphate (cGMP) after acute myocardial infarction (AMI) is not well understood despite its significance as a second messenger of natriuretic peptides (NPs) in cardiovascular disease. We investigated the association between the NP-cGMP cascade and left ventricular reverse remodelling (LVRR) in anterior AMI.

METHODS

67 patients with their first anterior AMI (median age, 64 years; male, 76%) underwent prospective evaluation of plasma concentrations of the molecular forms of A-type and B-type natriuretic peptide (BNP) and cGMP from immediately after primary percutaneous coronary intervention (PPCI) to 10 months post-AMI. The estimated mature BNP (emBNP) concentration was calculated as the difference between total BNP and prohormone of BNP (proBNP) concentrations. Patients were divided into LVRR and non-LVRR groups on the basis of residuals between observed change in left ventricular end-systolic volume index on MR during the first 11 months after AMI and change adjusted for proBNP concentration immediately post-PPCI, which was calculated with regression. The LVRR group (n=33) had residuals below the median; the non-LVRR group (n=34) had residuals at or above the median.

RESULTS

The LVRR group had higher freedom from major adverse cardiac and cerebrovascular events (MACCEs) than the non-LVRR group during a median follow-up of 9.9 years (p=0.008). The presence of LVRR (HR 0.256; 95% CI 0.081 to 0.809; p=0.028) and peak creatine phosphokinase-myocardial band level (per 100 IU/L) (HR 1.22; 95% CI 1.02 to 1.46; p=0.027) were independent predictors of MACCE after adjusting for age, male sex, infarct size and hypertension. Multivariable analyses identified logarithmic proBNP and emBNP concentrations from 12 hours to 5 days post-AMI and logarithmic cGMP concentration from immediately post-PPCI to 3 days post-AMI as independent predictors of LVRR (p<0.05).

CONCLUSIONS

Early-phase BNP-cGMP cascade activation might play a crucial role in LVRR in anterior AMI.

N-terminal pro atrial natriuretic peptide as a prognostic marker of cardiac resynchronization therapy recipients

Background

Although the dynamic changes of atrial natriuretic peptide (ANP) expressions in a failing heart are well-documented, the clinical implications of detailed measurements of each ANP molecular form processed from proANP remain unclear.

Methods

Patients screening was conducted on patients who were eligible for cardiac resynchronization therapy (CRT) between 2014 and 2019 in our institution. Blood samples and echocardiographic parameters were collected on the day before and six months after implantation. Total ANP, proANP, and N-terminal fragment of proANP (NT-proANP) were examined as predictive biomarkers for cardiac death, left ventricular assist device implantation, and heart failure hospitalization following CRT implantation.

Results

A total of 86 subjects (mean age 70 years, 64 males) who underwent successful CRT implantation were enrolled. Plasma levels of total ANP, proANP, and NT-proANP were not normally distributed [25.8 pM (interquartile range: 11.1-53.1), 2.2 pM (1.0-5.4), and 4.1 nM (2.4-7.1), respectively]. Over a median follow-up of 2.7 years, 31 patients (2 deaths and 29 heart failure hospitalizations) reached the endpoints. Among the different ANP forms, only NT-proANP emerged as an independent predictor of the composite outcome (adjusted odds ratio of 2.542 in those with levels above vs. below the median, 95 % confidence interval 1.151-5.615, p = 0.021). NT-proANP levels were associated with left atrial volume and left diastolic functional parameters and decreased in response to echocardiographic improvements at six months post-implantation (16 ± 44 % decrease in responders vs 18 ± 60 % increase in non-responders, p = 0.005).

Conclusion

Pre-implantation NT-proANP levels could serve as a predictive factor for clinical outcomes in recipients of CRT.

The Emerging Role of Atrial Natriuretic Peptide in Psychiatry

INTRODUCTION

Atrial natriuretic peptide (ANP), composed by 28 amino-acids, is well known to modulate fluid and electrolyte homeostasis, the hypothalamic-pituitary-adrenal (HPA) axis activity and the immune system. Since ANP is produced in both heart and in the central nervous system (CNS), in the last years, increasing attention has been devoted to its possible role in neuropsychiatric disorders. Indeed, scattered data would indicate its possible role in anxiety, major depression, addictive behaviors, post-traumatic stress disorder and other stress-related disorders. Further, ANP has been hypothesized to represent one of the factors linking depression to cardiovascular health and the immune system.

AIMS

Given the paucity of available information, the aim of this paper was to review the current literature on the role of ANP in the CNS and in the pathophysiology of different neuropsychiatric and stress-related conditions.

DISCUSSION

Supporting data on ANP in psychiatric disorders are still limited to animal studies, or to a few "real" findings in patients gathered some decades ago that should be replicated in larger clinical samples.

CONCLUSION

Further studies are necessary to understand the possible implications of ANP in neuropsychiatry, because potentially it might represent a new way for innovative psychopharmacological treatments in different conditions, all underlaid by hyperactive HPA axis.

Natriuretic peptides in human heart: Novel insight into their molecular forms, functions, and diagnostic use

Among the three natriuretic peptides, atrial/A-type natriuretic peptide (ANP) and brain/B-type natriuretic peptide (BNP) are primarily produced by, and secreted from, heart tissue. They maintain cardiovascular homeostasis by binding to natriuretic peptide receptor-A. Since plasma ANP and BNP concentrations, as well as expression, are elevated in response to increased body fluid volume and pressure load on the heart wall, these peptides are widely utilized as diagnostic biomarkers for evaluating heart failure. Regardless of their high utility, differences in their molecular forms between healthy and diseased subjects and how these relate to pathophysiology have not well been examined. Recent studies have shown that the circulating molecular forms of ANP and BNP are not uniform; bioactive α-ANP is the major ANP form, whereas the weakly active proBNP is the major BNP form. The relative ratios of the different molecular forms are altered under different pathophysiological conditions. These facts indicate that detailed measurements of each form may provide useful information on the pathophysiological state of heart tissue. Here, we revisit the relationship between the molecular forms of, and pathophysiological alterations in, human ANP and BNP and discuss the possible utility of the measurement of each of the molecular forms. The third peptide, C-type natriuretic peptide, activates natriuretic peptide receptor-B, but little is known about its production and function in the heart because of its extremely low levels. However, through recent studies, its role in the heart is gradually becoming clear. Here, we summarize its molecular forms, assay systems, and functions in the heart.

Three molecular forms of atrial natriuretic peptides: quantitative analysis and biological characterization

Atrial natriuretic peptide (ANP) is primarily produced in the heart tissue and plays a pivotal role in maintaining cardiovascular homeostasis in endocrine and autocrine/paracrine systems and has clinical applications as a biomarker and a therapeutic agent for cardiac diseases. ANP is synthesized by atrial cardiomyocytes as a preprohormone that is processed by a signal peptidase and stored in secretory granules as a prohormone. Subsequent proteolytic processing of ANP by corin during the secretion process results in a bioactive form consisting of 28 amino acid residues. Mechanical stretch of the atrial wall and multiple humoral factors directly stimulates the transcription and secretion of ANP. Secreted ANP elicits natriuretic and diuretic effects via cyclic guanosine monophosphate produced through binding to the guanylyl cyclase-A/natriuretic peptide receptor-A. Circulating ANP is subjected to rapid clearance by a natriuretic peptide receptor-C-mediated mechanism and proteolytic degradation by neutral endopeptidase. In humans, ANP is present as three endogenous molecular forms: bioactive α-ANP, a homodimer of α-ANP designated as β-ANP, and an ANP precursor designated as proANP (also referred to as γ-ANP). The proANP and especially β-ANP, as minor forms in circulation, are notably increased in patients with cardiac diseases, suggesting the utility of monitoring the pathophysiological conditions that result in abnormal proANP processing that cannot be monitored by inactive N-terminal proANP-related fragments. Emerging plate-based sandwich immunoassays for individual quantitation of the three ANP forms enables evaluation of diagnostic implications and net ANP bioactivity. This new tool may provide further understanding in the pathophysiology of cardiac diseases. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.