A Test in Context: Neprilysin

Soluble neprilysin does not correlate with prognosis in pulmonary hypertension

AIMS

It has been reported that circulating soluble neprilysin (sNEP), which catalyses the degradation of several vasodilator peptides such as natriuretic peptides, predicts prognosis in heart failure patients with reduced ejection fraction. Hypoxia-induced decrease in NEP expression in lungs has been reported. However, the associations between sNEP and haemodynamic parameters, as well as the prognostic impact of sNEP in pulmonary hypertension (PH), remain unclear. We aimed to clarify the relationships between sNEP and natriuretic peptide, haemodynamics (e.g. parameters of echocardiography and right heart catheter) or prognosis in PH patients.

METHODS AND RESULTS

First, we examined the associations between sNEP levels and natriuretic peptide, echocardiography, or right heart catheter in PH patients (mean pulmonary artery pressure ≥ 25 mmHg and pulmonary artery wedge pressure ≤ 15 mm Hg on the basis of right heart catheterization, n = 79). Next, we followed up the patients for all-cause mortality. Laboratory data revealed no significant correlations between sNEP and B-type natriuretic peptide (R = 0.022, P = 0.872), N-terminal proBNP (R = -0.018, P = 0.872), and high-sensitivity troponin I (R = 0.206, P = 0.107). Regarding the parameters of echocardiography and right heart catheter, there were no significant correlations between sNEP and left ventricular ejection fraction (R = -0.036, P = 0.764), right ventricular fractional area change (R = -0.259, P = 0.064), tricuspid valve pressure gradient (R = -0.037, P = 0.767), and any of the right heart catheter parameters. In the Kaplan-Meier analysis (mean follow-up, 1284 days, log-rank P = 0.531), all-cause mortality rates were comparable between the higher NEP group (sNEP ≥ median levels of 1.45 ng/mL, n = 39) and the lower NEP group (sNEP < 1.45 ng/mL, n = 40). In the Cox proportional hazard analysis, sNEP was not a predictor of all-cause mortality (hazard ratio 0.902, 95% CI 0.674-1.207, P = 0.487) in PH patients.

CONCLUSIONS

Circulating sNEP does not correlate with natriuretic peptide, haemodynamic parameters, or prognosis in patients with PH.

Sacubitril/Valsartan in Asian Patients with Heart Failure with Reduced Ejection Fraction

The Prospective comparison of Angiotensin Receptor-neprilysin inhibitor (ARNI) with Angiotensin converting enzyme inhibitor (ACEI) to Determine Impact on Global Mortality and morbidity in Heart Failure (HF) trial (PARADIGM-HF) showed that adding a neprilysin inhibitor (sacubitril) to a renin-angiotensin system blocker (and other standard therapy) reduced morbidity and mortality in ambulatory patients with chronic HF with reduced ejection fraction (HFrEF). In PARADIGM-HF, valsartan combined with sacubitril (a so-called ARNI) was superior to the current gold standard of an ACEI, specifically enalapril, reducing the risk of the primary composite outcome of cardiovascular (CV) death or first HF hospitalization by 20% and all-cause death by 16%. Following the results of PARADIGM-HF, sacubitril/valsartan was approved by American and European regulatory authorities for the treatment of HFrEF. The burden of HF in Asia is substantial, both due to the huge population of the region and as a result of increasing CV risk factors and disease. Both the prevalence and mortality associated with HF are high in Asia. In the following review, we discuss the development of sacubitril/valsartan, the prototype ARNI, and the available evidence for its efficacy and safety in Asian patients with HFrEF.

Neprilysin levels at the acute phase of ST-elevation myocardial infarction

BACKGROUND

Several preliminary analyses suggested an association between neprilysin (NEP) levels and myocardial infarction.

HYPOTHESIS

The objective was to assess whether NEP plasma levels following reperfusion might be a surrogate for infarct size (IS) or predict adverse outcomes in acute ST-segment elevation myocardial infarction (STEMI) patients.

METHODS

We measured NEP levels in a prospective cohort of 203 patients with STEMI referred for primary percutaneous coronary intervention. Circulating soluble NEP was measured by enzyme-linked immunosorbent assay at admission (t0) and 4 hours later (t4) following reperfusion and on 7 times points (t0, t4, t12, t24, t48, day 7 and day 30) in a subset of 21 patients. IS and left ventricular ejection fraction (LVEF) were measured at 1 month by cardiac magnetic resonance. Adverse cardiovascular outcomes were collected at 12-month follow-up.

RESULTS

Median t0 and t4 NEP levels in 203 patients were respectively 88.3 pg/mL (interquartile range [IQR] [14; 375.4]) and 101.5 pg/mL (IQR [18.5; 423.8]). These levels remained unchanged over 1 month (P = 0.70). NEP levels did not correlate significantly with IS (P = 0.51) or LVEF (P = 0.34). There was no correlation between NEP and troponin, creatine kinase and interleukin-6 levels at h0 and h4. NEP levels above the median were not associated with adverse outcomes at follow-up (hazard ratio = 1.28, 95% confidence interval [0.69; 2.37]; P = 0.42).

CONCLUSIONS

NEP serum levels were widely distributed and did not change significantly in the first hours and 1-month period following reperfusion in STEMI patients. There was no significant relationship with markers of infarct size and inflammation, and 1-year adverse outcomes.

Effects of sacubitril/valsartan on neprilysin targets and the metabolism of natriuretic peptides in chronic heart failure: a mechanistic clinical study

AIM

This study aimed at evaluating the effects of sacubitril/valsartan on neprilysin (NEP), and the metabolism of natriuretic peptides in heart failure (HF) and providing additional mechanistic information on the mode of action of the drug.

METHODS AND RESULTS

We enrolled 73 chronic HF patients who were switched from angiotensin-converting enzyme inhibitor or angiotensin receptor blocker to sacubitril/valsartan. In addition to clinical and echocardiographic assessment, plasma biomarkers were measured at baseline, day 30 and day 90 after initiation of treatment. Sacubitril/valsartan led to decrease in New York Heart Association class and improvement of echocardiographic parameters, as well as a dose-dependent decrease in soluble NEP (sNEP) activity, while sNEP concentration remained unchanged. Neprilysin inhibition translated into an increase in its substrates such as atrial natriuretic peptide (ANP), substance P, and glucagon-like peptide 1, the latter translating into a decrease in fructosamine. Cardiac troponin and soluble ST2 levels, biomarkers of HF severity unrelated to NEP metabolism also decreased. While there was a ∼4-fold increase in ANP, we observed no change in plasma brain natriuretic peptide (BNP) and plasma BNP activity, and a mild decrease in N-terminal proBNP (NT-proBNP) concentrations. Finally, we found a progressive increase in the relationship between BNP and NT-proBNP, which strongly correlated with an increase in T71 proBNP glycosylation (R² = 0.94).

CONCLUSION

Sacubitril/valsartan rapidly and strongly reduced sNEP activity, leading to an increase in levels of NEP substrates. These data suggest a pleiotropic favourable impact of sacubitril/valsartan on the metabolism of HF patients with ANP rather than BNP as major effectors amongst natriuretic peptides.

Serum neprilysin and the risk of death in patients with out-of-hospital cardiac arrest of non-traumatic origin

BACKGROUND

Early risk stratification remains an unmet clinical need in patients with in out-of-hospital cardiac arrest. We hypothesised that soluble neprilysin may represent a promising biomarker in patients with out-of-hospital cardiac arrest of non-traumatic origin and provide new pathobiological insight.

METHODS

This pilot study was a biomarker analysis from the Heidelberg Resuscitation Registry. Serum soluble neprilysin levels on admission were measured in 144 patients with successful return of spontaneous circulation after out-of-hospital cardiac arrest of non-traumatic origin. The primary endpoint was time to all-cause mortality. KM Event Rates are reported. Cox models were adjusted for age, bystander resuscitation, initial ECG rhythm, baseline estimated glomerular filtration rate, baseline lactate, left ventricular function at baseline, and targeted temperature management.

RESULTS

In total, 90 (62.5%) patients died over a follow-up of at least 30 days. Soluble neprilysin correlated weakly with high-sensitivity troponin T (r=0.18, P=0.032) but did not correlate significantly with estimated glomerular filtration rate (r=-0.12) or lactate (r=0.11). Patients with elevated soluble neprilysin levels on admission were at significantly higher risk of all-cause mortality (Q4 69.1% vs. Q1 48.4%). After multivariable adjustment, soluble neprilysin in the top quartile (Q4) was significantly associated with all-cause mortality (Q4 vs. Q1: adjusted hazard ratio 2.48 (1.20-5.12)). In an adjusted multimarker model including high-sensitivity troponin T and high-sensitivity C-reactive protein, soluble neprilysin and high-sensitivity troponin T remained independently associated with all-cause mortality (soluble neprilysin: adjusted hazard ratio 2.27 (1.08-4.78); high-sensitivity troponin T: adjusted hazard ratio 3.40 (1.63-7.09)).

CONCLUSION

Soluble neprilysin, measured as early as on hospital admission, was independently associated with all-cause mortality in patients with out-of-hospital cardiac arrest of non-traumatic origin and may prove to be useful in the estimation of risk in these patients.

A Novel Paradigm for Sacubitril/Valsartan: Beta-Endorphin Elevation as a Contributor to Exercise Tolerance Improvement in Rats With Preexisting Heart Failure Induced by Pressure Overload

BACKGROUND

Simultaneous angiotensin receptor (AT1) blockade and neprilysin inhibition with the use of sacubitril/valsartan has been recently approved to treat patients with heart failure (HF). Therapeutic benefits of this therapy have been attributed to natriuretic peptide elevation and AT1 receptor blockade. However, that pharmacologic picture may not be complete. The aims of this study were to investigate the pharmacology of sacubitril/valsartan compared with sacubitril and valsartan alone and to examine their impact on peptides up-regulated by neprilysin inhibition, such as beta-endorphin.

METHODS AND RESULTS

An HF model was induced by pressure overload via constriction of the suprarenal abdominal aorta in rats. Sacubitril/valsartan (68 mg/kg), valsartan (31 mg/kg), sacubitril (31 mg/kg), or placebo was administered by daily oral gavage (starting 4 weeks after pressure overload onset and continued for 4 additional weeks; n = 8 in each group). Exercise tolerance testing was conducted using a rodent treadmill and hemodynamic assessments were conducted under anesthesia with the use of Millar left ventricular (LV) conductance technology. Pressure overload led to exercise intolerance by 4 weeks and to hypertension and LV dysfunction and remodeling by 8 weeks. Both sacubitril/valsartan and sacubitril elevated beta-endorphin levels, by 40% and 54%, respectively, and improved exercise tolerance, by 93% and 112%, whereas valsartan did not. Indices of LV dysfunction persisted with the use of sacubitril/valsartan and valsartan therapies and even deteriorated in sacubitril group.

CONCLUSIONS

When added to valsartan, sacubitril increases beta-endorphin concentrations and improves exercise tolerance. These data suggest beta-endorphin elevation as a potential mechanism of action leading to improvement in exercise tolerance that is seen with sacubitril/valsartan. This therapeutic benefit is potentially independent from LV function.

Sacubitril/valsartan and short-term changes in the 6-minute walk test: A pilot study

BACKGROUND

Impaired exercise capacity is the most disabling symptom in patients with heart failure with reduced ejection fraction (HFrEF). Despite sacubitril/valsartan showing reduced long-term morbidity and mortality over enalapril in HFrEF, its effects on short-term functional capacity remain uncertain. We sought to evaluate the effects of sacubitril/valsartan on a 30-day six-minute walk test in eligible patients with HFrEF.

METHODS AND RESULTS

From November 1, 2016 to February 1, 2017, a total of 58 stable symptomatic patients with HFrEF were eligible for sacubitril/valsartan and underwent 6-MWT before and 30days after initiation of sacubitril/valsartan therapy. A mixed-effects model for repeated-measures was used to analyze the changes. Mean age was 70±11years. 72.4% males, 46.6% with ischemic heart disease, and 51.7% on NYHA functional class III were included. The mean (SD) values of baseline LVEF and 6MWT were 30±7%, and 300±89m, respectively. The median (IQR) of NT-proBNP at baseline was 2701pg/ml (1087-4200). Compared with baseline, the 6-MWT distance increased significantly at 30days by 13.9% (+∆=41.8m (33.4-50.2); p<0.001).

CONCLUSIONS

In this pilot study, sacubitril/valsartan was associated with an improvement in exercise tolerance in symptomatic patients with HFrEF.

Possible Enzymatic Downregulation of the Natriuretic Peptide System in Patients with Reduced Systolic Function and Heart Failure: A Pilot Study

Background

In patients with reduced systolic function, the natriuretic peptide system affects heart failure (HF) progression, but the expression of key activating (corin) and degrading enzymes (neprilysin) is not well understood.

Methods and Results

This pilot study (n=48) compared plasma levels of corin, neprilysin, ANP, BNP, and cGMP in control patients with normal ejection fractions (mean EF 63 ± 3%) versus patients with systolic dysfunction, with (EF 24 ± 8%) and without (EF 27 ± 7%) decompensated HF (dHF), as defined by Framingham and BNP criteria. Mean ages, use of beta blockers, and ACE-inhibitors-angiotensin receptor blockers were similar between the groups. Corin levels were depressed in systolic dysfunction patients (797 ± 346 pg/ml) versus controls (1188 ± 549, p<0.02), but levels were not affected by dHF (p=0.77). In contrast, levels of neprilysin (p<0.01), cGMP (p<0.001), and ANP (p<0.001) were higher in systolic dysfunction patients than controls and were the highest in patients with dHF.

Conclusions

Levels of neprilysin, ANP, BNP, and cGMP increased in patients with reduced systolic function and were the highest in dHF patients. Conversely, corin levels were low in patients with reduced EF with or without dHF. This pattern suggests possible enzymatic downregulation of natriuretic peptide activity in patients with reduced EF, which may have diagnostic and prognostic implications.

Genetics of guanylyl cyclase pathways in the cochlea and their influence on hearing

Although hearing loss is the most common sensory deficit in Western societies, there are no successful pharmacological treatments for this disorder. Recent experiments have demonstrated that manipulation of intracellular cyclic guanosine monophosphate (cGMP) concentrations can have both beneficial and harmful effects on hearing. In this review, we will examine the role of cGMP as a key second messenger involved in many aspects of cochlear function and discuss the known functions of downstream effectors of cGMP in sound processing. The nitric oxide-stimulated soluble guanylyl cyclase system (sGC) and the two natriuretic peptide-stimulated particulate GCs (pGCs) will be more extensively covered because they have been studied most thoroughly. The cochlear GC systems are attractive targets for medical interventions that improve hearing while simultaneously representing an under investigated source of sensorineural hearing loss.

Angiotensin receptor-neprilysin inhibitors: A new paradigm in heart failure with reduced ejection fraction

Despite significant advances in the last 30 years in reducing morbidity and mortality from heart failure with reduced ejection fraction (HFrEF) with pharmacological and device-based therapies, patients remain at a high risk of adverse cardiovascular outcomes. Sacubitril/valsartan, a first-in-class angiotensin receptor-neprilysin inhibitors (ARNI), has been shown to reduce the risk of cardiovascular death or heart failure hospitalisation and improve symptoms in patients with chronic, ambulatory, symptomatic HFrEF in a large, phase 3, multicentre, international, randomised controlled trial, PARADIGM-HF, when compared to the gold-standard angiotensin converting enzyme inhibitor, enalapril. This article will review the development of sacubitril/valsartan, the evidence for its use and its current and future role in the management of HFrEF.

MicroRNA-143 modulates the expression of Natriuretic Peptide Receptor 3 in cardiac cells

Natriuretic Peptide Receptor 3 (NPR3), the clearance receptor for extracellular bio-active natriuretic peptides (NPs), plays important roles in the homeostasis of body fluid volume and vascular tone. Using luciferase reporter and antagomir-based silencing assays, we demonstrated that the expression of NPR3 could be modulated by microRNA-143 (miR-143-3p), a microRNA species with up-regulated circulating concentrations in clinical heart failure. The regulatory effect of miR-143 on NPR3 expression was further evidenced by the reciprocal relationship between miR-143 and NPR3 levels observed in hypoxia-treated human cardiac cells and in left ventricular tissue from rats undergoing experimental myocardial infarction. Further analysis indicated elevation of miR-143 in response to hypoxic challenge reflects transcriptional activation of the miR-143 host gene (MIR143HG). This was corroborated by demonstration of the induction of host gene promoter activity upon hypoxic challenge. Moreover, miR-143 was shown to enhance its own expression by increasing MIR143HG promoter activity, as well as targeting the expressions of NPPA, NPPC, NR3C2, and CRHR2 in cardiac cells. Taken together, these findings suggest that the elevation of miR-143 upon hypoxic insult may be part of a microRNA-based feed forward loop that results in fine tuning the levels of NPs and neurohormonal receptors in cardiac cell lineages.

N-Terminal B-type Natriuretic Peptide in Heart Failure

Plasma amino-terminal pro-B-type natriuretic peptide (NT-proBNP) is a guideline-mandated biomarker in heart failure (HF). Used as an inclusion criterion for therapeutic trials, NT-proBNP enriches trial populations and is a valid surrogate endpoint. Its diagnostic performance is best validated in acute decompensated HF (ADHF). NT-proBNP offers prognostic information independent of standard clinical predictors and refines risk stratification. With the advent of combined angiotensin 2 type 1 receptor blockade and neprilysin inhibition (ARNI) NT-proBNP retains its relationship to cardiac status and is the marker of choice in assessment of possible ADHF and in serial monitoring of HF patients receiving ARNI treatment.

Neprilysin Deficiency Is Associated With Expansion of Islet β-Cell Mass in High Fat-Fed Mice

Neprilysin (NEP) is an endopeptidase known to modulate nervous, cardiovascular, and immune systems via inactivation of regulatory peptides. In addition, it may also contribute to impaired glucose homeostasis as observed in type 2 diabetes (T2D). Specifically, we and others have shown that NEP is upregulated under conditions associated with T2D, whereas NEP deficiency and/or inhibition improves glucose homeostasis via enhanced glucose tolerance, insulin sensitivity, and pancreatic β-cell function. Whether increased β-cell mass also occurs with lack of NEP activity is unknown. We sought to determine whether NEP deficiency confers beneficial effects on β- and α-cell mass in a mouse model of impaired glucose homeostasis. Wild-type and NEP^-/- mice were fed low- or high-fat diet for 16 weeks, after which pancreatic β- and α-cell mass were assessed by immunostaining for insulin and glucagon, respectively. Following low-fat feeding, NEP^-/- mice exhibited lower β- and α-cell mass compared with wild-type controls. A high-fat diet had no effect on these parameters in wild-type mice, but in NEP^-/- mice, it resulted in the expansion of β-cell mass. Our findings support a role for NEP in modulating β-cell mass, making it an attractive T2D drug target that acts via multiple mechanisms to affect glucose homeostasis.

Sustained Activation of Rho GTPases Promotes a Synthetic Pulmonary Artery Smooth Muscle Cell Phenotype in Neprilysin Null Mice

OBJECTIVE

Pulmonary artery smooth muscle cells (PASMCs) from neprilysin (NEP) null mice exhibit a synthetic phenotype and increased activation of Rho GTPases compared with their wild-type counterparts. Although Rho GTPases are known to promote a contractile SMC phenotype, we hypothesize that their sustained activity decreases SM-protein expression in these cells.

APPROACH AND RESULTS

PASMCs isolated from wild-type and NEP-/- mice were used to assess levels of SM-proteins (SM-actin, SM-myosin, SM22, and calponin) by Western blotting, and were lower in NEP-/- PASMCs compared with wild-type. Rac and Rho (ras homology family member) levels and activity were higher in NEP-/- PASMCs, and ShRNA to Rac and Rho restored SM-protein, and attenuated the enhanced migration and proliferation of NEP-/- PASMCs. SM-gene repressors, p-Elk-1, and Klf4 (Kruppel lung factor 4), were higher in NEP-/- PASMCs and decreased by shRNA to Rac and Rho. Costimulation of wild-type PASMCs with PDGF (platelet-derived growth factor) and the NEP substrate, ET-1 (endothelin-1), increased Rac and Rho activity, and decreased SM-protein levels mimicking the NEP knock-out phenotype. Activation of Rac and Rho and downstream effectors was observed in lung tissue from NEP-/- mice and humans with chronic obstructive pulmonary disease.

CONCLUSIONS

Sustained Rho activation in NEP-/- PASMCs is associated with a decrease in SM-protein levels and increased migration and proliferation. Inactivation of RhoGDI (Rho guanine dissociation inhibitor) and RhoGAP (Rho GTPase activating protein) by phosphorylation may contribute to prolonged activation of Rho in NEP-/- PASMCs. Rho GTPases may thus have a role in integration of signals between vasopeptides and growth factor receptors and could influence pathways that suppress SM-proteins to promote a synthetic phenotype.

Potential and Limitations of Atrial Natriuretic Peptide as Biomarker in Pediatric Heart Failure-A Comparative Review

Although B-type Natriuretic Peptide (BNP), N-terminal-proBNP (NT-proBNP), and mid-regional-proANP (MR-proANP) are included in current guidelines on heart failure in adults, no guideline considering these biomarkers in pediatric heart failure is available. A new drug class of neprilysin inhibitors as fixed-dose combination (Sacubitril/valsartan) has been introduced and is currently being investigated in children suffering from heart failure. Atrial Natriuretic Peptide (ANP) is discussed as a more useful alternative to BNP because it may grants better insights into the effects of this treatment. Thus, this review aimed to provide an overview of the current knowledge concerning ANP in pediatric heart failure and compares its suitability regarding diagnosis and prognosis of heart failure. A literature search using PubMed resulted in 147 publications of which 22 studies were classified as relevant. The review presents available ANP, NT-proANP, and MR-proANP level data in children (0-18 years). Summarizing, ANP shows only minor differences as marker for diagnosing and monitoring pediatric heart failure if compared to BNP. Due to its fast release, ANP offers the advantage of displaying rapid changes during therapy or operation. ANP is -like the other natriuretic peptides- influenced by age, presenting with the highest levels in very young infants. ANP also correlates with atrial pressure and volume overload in children. In addition, ANP determination in saliva appears to be a promising alternative to blood sampling. Similarly to NT-proBNP, NT-proANP, and MR-proANP offer better stability but only few data has been published in children and thus their potential is only presumable so far.

Evolving Role of Natriuretic Peptides from Diagnostic Tool to Therapeutic Modality

Natriuretic peptides (NP) are widely recognized as key regulators of blood pressure, water and salt homeostasis. In addition, they play a critical role in physiological cardiac growth and mediate a variety of biological effects including antiproliferative and anti-inflammatory effects in other organs and tissues. The cardiac release of NPs ANP and BNP represents an important compensatory mechanism during acute and chronic cardiac overload and during the pathogenesis of heart failure where their actions counteract the sustained activation of renin-angiotensin-aldosterone and other neurohormonal systems. Elevated circulating plasma NP levels correlate with the severity of heart failure and particularly BNP and the pro-peptide, NT-proBNP have been established as biomarkers for the diagnosis of heart failure as well as prognostic markers for cardiovascular risk. Despite activation of the NP system in heart failure it is inadequate to prevent progressive fluid and sodium retention and cardiac remodeling. Therapeutic approaches included administration of synthetic peptide analogs and the inhibition of NP-degrading enzyme neutral endopeptidase (NEP). Of all strategies only the combined NEP/ARB inhibition with sacubitril/valsartan had shown clinical success in reducing cardiovascular mortality and morbidity in patients with heart failure.

A novel chemical inducer of Streptococcus quorum sensing acts by inhibiting the pheromone-degrading endopeptidase PepO

Bacteria produce chemical signals (pheromones) to coordinate behaviors across a population in a process termed quorum sensing (QS). QS systems comprising peptide pheromones and their corresponding Rgg receptors are widespread among Firmicutes and may be useful targets for manipulating microbial behaviors, like suppressing virulence. The Rgg2/3 QS circuit of the human pathogen Streptococcus pyogenes controls genes affecting resistance to host lysozyme in response to short hydrophobic pheromones (SHPs). Considering that artificial activation of a QS pathway may be as useful in the objective of manipulating bacteria as inhibiting it, we sought to identify small-molecule inducers of the Rgg2/3 QS system. We report the identification of a small molecule, P516-0475, that specifically induced expression of Rgg2/3-regulated genes in the presence of SHP pheromones at concentrations lower than typically required for QS induction. In searching for the mode of action of P516-0475, we discovered that an S. pyogenes mutant deficient in pepO, a neprilysin-like metalloendopeptidase that degrades SHP pheromones, was unresponsive to the compound. P516-0475 directly inhibited recombinant PepO in vitro as an uncompetitive inhibitor. We conclude that this compound induces QS by stabilizing SHP pheromones in culture. Our study indicates the usefulness of cell-based screens that modulate pathway activities to identify unanticipated therapeutic targets contributing to QS signaling.

NT-proBNP: When is it useful in Obstetric Medicine?

Pregnancy, viewed as a stress test of the haemodynamic system, may unmask underlying cardiac disease. Pregnancy may also induce de novo cardiac disease. N-terminal pro brain-type natriuretic peptide (NT-proBNP) is a useful biomarker in all clinical conditions in which the ventricle is stressed and especially stretched in the general population. In hypertensive diseases of pregnancy, increased levels of NT-proBNP in preeclampsia are associated with increased cardiac filling pressures and diastolic dysfunction. Increased levels of NT-proBNP in pregnant women with known cardiac disease may lead to earlier diagnosis of impending heart failure. Similarly, elevated levels of NT-proBNP assist with the diagnosis of peripartum cardiomyopathy and are increasingly used in follow-up. Women with known congenital heart disease who are pregnant can be screened for risk of cardiac events such as heart failure by the use of NT-proBNP levels. There is a paucity of data in pregnancy with the use of NT-proBNP and more research is needed.

Serum Neprilysin and Recurrent Admissions in Patients With Heart Failure

BACKGROUND

Our aim was to evaluate the association between the soluble form of neprilysin (sNEP) levels and long-term all-cause, cardiovascular, and acute heart failure (AHF) recurrent admissions in an ambulatory cohort of patients with heart failure. sNEP has emerged as a new biomarker with promising implications for prognosis and therapy in patients with heart failure. Reducing the recurrent admission rate of heart failure patients has become an important target of public health planning strategies.

METHODS AND RESULTS

We measured sNEP levels in 1021 consecutive ambulatory heart failure patients. End points were the number of all-cause, cardiovascular, and AHF hospitalizations during follow-up. We used covariate-adjusted incidence rate ratios to identify associations. At a median follow-up of 3.4 years (interquartile range: 1.8-5.7), 391 (38.3%) patients died, 477 (46.7%) patients had 1901 all-cause admissions, 324 (31.7%) patients had 770 cardiovascular admissions, and 218 (21.4%) patients had 488 AHF admissions. The medians for sNEP and amino-terminal pro-brain natriuretic peptide were 0.64 ng/mL (interquartile range: 0.39-1.22) and 1248 pg/mL (interquartile range: 538-2825), respectively. In a multivariate setting, the adjusted incidence rate ratios for the top (>1.22 ng/mL) versus the bottom (≤0.39 ng/mL) quartiles of sNEP were 1.37 (95% confidence interval: 1.03-1.82), P=0.032; 1.51 (95% confidence interval: 1.10-2.06), P=0.010; and 1.51 (95% confidence interval: 1.05-2.16), P=0.026 for all-cause, cardiovascular, and AHF admissions, respectively.

CONCLUSIONS

Elevated sNEP levels predicted an increased risk of recurrent all-cause, cardiovascular, and AHF admissions in ambulatory patients with heart failure.

Subclinical Atherosclerosis, Cardiac and Kidney Function, Heart Failure, and Dementia in the Very Elderly

BACKGROUND

Heart failure (HF) and dementia are major causes of disability and death among older individuals. Risk factors and biomarkers of HF may be determinants of dementia in the elderly. We evaluated the relationship between biomarkers of cardiovascular disease and HF and risk of dementia and death. Three hypotheses were tested: (1) higher levels of high-sensitivity cardiac troponin T, N-terminal of prohormone brain natriuretic peptide, and cystatin C predict risk of death, cardiovascular disease, HF, and dementia; (2) higher levels of cardiovascular disease biomarkers are associated with increased risk of HF and then secondary increased risk of dementia; and (3) risk of dementia is lower among participants with a combination of lower coronary artery calcium, atherosclerosis, and lower high-sensitivity cardiac troponin T (myocardial injury).

METHODS AND RESULTS

The Cardiovascular Health Study Cognition Study was a continuation of the Cardiovascular Health Study limited to the Pittsburgh, PA, center from 1998-1999 to 2014. In 1992-1994, 924 participants underwent magnetic resonance imaging of the brain. There were 199 deaths and 116 developed dementia before 1998-1999. Of the 609 participants eligible for the Pittsburgh Cardiovascular Health Study Cognition Study, 87.5% (n=532) were included in the study. There were 120 incident HF cases and 72% had dementia. In 80 of 87, dementia preceded HF. A combination of low coronary artery calcium score and low high-sensitivity cardiac troponin T was significantly associated with reduced risk of dementia and HF.

CONCLUSIONS

Most participants with HF had dementia but with onset before HF. Lower high-sensitivity cardiac troponin T and coronary artery calcium was associated with low risk of dementia based on a small number of events.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00005133.

Mechanisms of action of sacubitril/valsartan on cardiac remodeling: a systems biology approach

Sacubitril/Valsartan, proved superiority over other conventional heart failure management treatments, but its mechanisms of action remains obscure. In this study, we sought to explore the mechanistic details for Sacubitril/Valsartan in heart failure and post-myocardial infarction remodeling, using an in silico, systems biology approach. Myocardial transcriptome obtained in response to myocardial infarction in swine was analyzed to address post-infarction ventricular remodeling. Swine transcriptome hits were mapped to their human equivalents using Reciprocal Best (blast) Hits, Gene Name Correspondence, and InParanoid database. Heart failure remodeling was studied using public data available in gene expression omnibus (accession GSE57345, subseries GSE57338), processed using the GEO2R tool. Using the Therapeutic Performance Mapping System technology, dedicated mathematical models trained to fit a set of molecular criteria, defining both pathologies and including all the information available on Sacubitril/Valsartan, were generated. All relationships incorporated into the biological network were drawn from public resources (including KEGG, REACTOME, INTACT, BIOGRID, and MINT). An artificial neural network analysis revealed that Sacubitril/Valsartan acts synergistically against cardiomyocyte cell death and left ventricular extracellular matrix remodeling via eight principal synergistic nodes. When studying each pathway independently, Valsartan was found to improve cardiac remodeling by inhibiting members of the guanine nucleotide-binding protein family, while Sacubitril attenuated cardiomyocyte cell death, hypertrophy, and impaired myocyte contractility by inhibiting PTEN. The complex molecular mechanisms of action of Sacubitril/Valsartan upon post-myocardial infarction and heart failure cardiac remodeling were delineated using a systems biology approach. Further, this dataset provides pathophysiological rationale for the use of Sacubitril/Valsartan to prevent post-infarct remodeling.

The new wonder drug in heart failure management, Sacubitril/Valsartan, rejuvenates the heart by preventing its dilation. Using data from myocardial infarction and heart failure samples, we generated a mathematical model to better understand how Sacubitril/Valsartan modulates pathological heart resize and the combined effect of the drug. Our analysis revealed that Sacubitril/Valsartan mainly acts by blocking both, cell death and the pathological makeover of the outer-membrane of the cardiac cells. These two major processes occur after a heart attack. Most importantly, we discovered a core of 8 proteins that emerge as key players in this process. A better understanding of the mechanism of novel cardiovascular drugs at the most basic level may help decipher future therapies and indications.

Improved glycaemia in high-fat-fed neprilysin-deficient mice is associated with reduced DPP-4 activity and increased active GLP-1 levels

AIM/HYPOTHESIS

Neprilysin, a widely expressed peptidase, is upregulated in metabolically altered states such as obesity and type 2 diabetes. Like dipeptidyl peptidase-4 (DPP-4), neprilysin can degrade and inactivate the insulinotropic peptide glucagon-like peptide-1 (GLP-1). Thus, we investigated whether neprilysin deficiency enhances active GLP-1 levels and improves glycaemia in a mouse model of high fat feeding.

METHODS

Nep ^+/+ and Nep ^-/- mice were fed a 60% fat diet for 16 weeks, after which active GLP-1 and DPP-4 activity levels were measured, as were glucose, insulin and C-peptide levels during an OGTT. Insulin sensitivity was assessed using an insulin tolerance test.

RESULTS

High-fat-fed Nep ^-/- mice exhibited elevated active GLP-1 levels (5.8 ± 1.1 vs 3.5 ± 0.8 pmol/l, p < 0.05) in association with improved glucose tolerance, insulin sensitivity and beta cell function compared with high-fat-fed Nep ^+/+ mice. In addition, plasma DPP-4 activity was lower in high-fat-fed Nep ^-/- mice (7.4 ± 1.0 vs 10.7 ± 1.3 nmol ml^-1 min^-1, p < 0.05). No difference in insulin:C-peptide ratio was observed between Nep ^-/- and Nep ^+/+ mice, suggesting that improved glycaemia does not result from changes in insulin clearance.

CONCLUSIONS/INTERPRETATION

Under conditions of increased dietary fat, an improved glycaemic status in neprilysin-deficient mice is associated with elevated active GLP-1 levels, reduced plasma DPP-4 activity and improved beta cell function. Thus, neprilysin inhibition may be a novel treatment strategy for type 2 diabetes.

Neprilysin inhibition in heart failure: mechanisms and substrates beyond modulating natriuretic peptides

The autonomic nervous system, the renin-angiotensin-aldosterone system, and the natriuretic peptide system represent critical regulatory pathways in heart failure and as such have been the major targets of pharmacological development. The introduction and approval of angiotensin receptor neprilysin inhibitors (ARNi) have broadened the available drug treatments of patients with chronic heart failure with reduced ejection fraction. Neprilysin catalyses the degradation of a number of vasodilator peptides, including the natriuretic peptides, bradykinin, substance P, and adrenomedullin, as well as vasoconstrictor peptides, including endothelin-1 and angiotensin I and II. We review the multiple, potentially competing, substrates for neprilysin inhibition, and the resultant composite clinical effects of ARNi therapy. A mechanistic understanding of this novel therapeutic class may provide important insights into the expected on-target and off-target effects when this agent is more widely prescribed.