Do plasma neprilysin activity and plasma neprilysin concentration predict cardiac events in chronic kidney disease patients?

Relevance of Neutrophil Neprilysin in Heart Failure

Significant expression of neprilysin (NEP) is found on neutrophils, which present the transmembrane integer form of the enzyme. This study aimed to investigate the relationship of neutrophil transmembrane neprilysin (mNEP) with disease severity, adverse remodeling, and outcome in HFrEF. In total, 228 HFrEF, 30 HFpEF patients, and 43 controls were enrolled. Neutrophil mNEP was measured by flow-cytometry. NEP activity in plasma and blood cells was determined for a subset of HFrEF patients using mass-spectrometry. Heart failure (HF) was characterized by reduced neutrophil mNEP compared to controls (p < 0.01). NEP activity on peripheral blood cells was almost 4-fold higher compared to plasma NEP activity (p = 0.031) and correlated with neutrophil mNEP (p = 0.006). Lower neutrophil mNEP was associated with increasing disease severity and markers of adverse remodeling. Higher neutrophil mNEP was associated with reduced risk for mortality, total cardiovascular hospitalizations, and the composite endpoint of both (p < 0.01 for all). This is the first report describing a significant role of neutrophil mNEP in HFrEF. The biological relevance of neutrophil mNEP and exact effects of angiotensin-converting-enzyme inhibitors (ARNi) at the neutrophil site have to be determined. However, the results may suggest early initiation of ARNi already in less severe HF disease, where effects of NEP inhibition may be more pronounced.

Sacubitril/valsartan in chronic kidney disease: From pharmacological mechanism to clinical application

Chronic kidney disease (CKD) is an irreversible, progressive disease characterized by persistent kidney damage, and significantly increased risks of cardiovascular event. However, therapeutic strategies to prevent or slow the progression of CKD remain limited. Sacubitril/valsartan (LCZ696), the representative of the first novel angiotensin receptor-neprilysin inhibitor, has been incorporated into clinical practice guidelines for improving outcomes as a milestone in patients with heart failure. Considering the complex and close relationship between CKD and heart failure, LCZ696 may be beneficial in the treatment of CKD. This review summarizes the pharmacological mechanism and clinical application of LCZ696 in patients with CKD, including its effect on cardiovascular risk and renal outcome, together with potential adverse events. Additionally, due to the influence of serum creatinine and estimated glomerular filtration rate on LCZ696 in patients with heart failure, we also discussed the effects of LCZ696 in patients with advanced CKD and end-stage renal disease. It should be noted that, current clinical studies on LCZ696 are mostly carried out in patients with heart failure, and renal indicators are selected as secondary outcomes. Therefore, more researches should be conducted in patients with CKD alone in the future, to determine the efficacy and safety of LCZ696 in patients with CKD.

Reduced serum protease activity in Complex Regional Pain Syndrome: The impact of angiotensin-converting enzyme and carboxypeptidases

Complex Regional Pain Syndrome (CRPS) occurs in about 2% of patients after fracture of the limbs. In an earlier clinical study with 102 probands we have shown that the serum protease network in CRPS might be less effective. Based on these results we hypothesized that angiotensin-converting enzyme (ACE) and carboxypeptidase N (CPN) activity contribute to the differences of labeled bradykinin (DBK) degradation by patients' sera. Details of the enzymatic processes remained however unclear. The contributions of ACE and CPN in the serum degradation of DBK were studied using specific inhibitors. CPN1-ELISA was performed in serum. It was confirmed that the majority of DBK was degraded by ACE and CPN. The data delivered proof that the ACE serum activity was lowered in CRPS. High-resolution mass spectrometry was additionally used for protein expression analysis of sera of above study cohort (CRPS vs. healthy probands). According to principal component analysis of these data, significant differences between CRPS and control samples only occurred in sera of females younger than 46 years. In these CRPS patients, a number of defence / immunity-related proteins and members of the renin-angiotensin system (RAS) protein network were regulated. The impact of CPN in CRPS pathophysiology is subject to further investigation. The data support the hypothesis that both the RAS and the innate immune system might be affected in CRPS. A database of regulated serum proteins was established for future research.

Circulating Neprilysin Level Predicts the Risk of Cardiovascular Events in Hemodialysis Patients

Background: Neprilysin inhibition has demonstrated impressive benefits in heart failure treatment, and is the current focus of interest in cardiovascular (CV) and kidney diseases. However, the role of circulating neprilysin as a biomarker for CV events is unclear in hemodialysis (HD) patients.

Methods: A total of 439 HD patients from the K-cohort were enrolled from June 2016 to April 2019. The plasma neprilysin level and echocardiographic findings at baseline were examined. The patients were prospectively followed up to assess the primary endpoint (composite of CV events and cardiac events).

Results: Plasma neprilysin level was positively correlated with left ventricular (LV) mass index, LV end-systolic volume, and LV end-diastolic volume. Multivariate linear regression analysis revealed that neprilysin level was negatively correlated with LV ejection fraction (β = −2.14; p = 0.013). The cumulative event rate of the composite of CV events was significantly greater in neprilysin tertile 3 (p = 0.049). Neprilysin tertile 3 was also associated with an increased cumulative event rate of cardiac events (p = 0.016). In Cox regression analysis, neprilysin tertile 3 was associated with a 2.61-fold risk for the composite of CV events [95% confidence interval (CI), 1.37–4.97] and a 2.72-fold risk for cardiac events (95% CI, 1.33–5.56) after adjustment for multiple variables.

Conclusions: Higher circulating neprilysin levels independently predicted the composite of CV events and cardiac events in HD patients. The results of this study suggest the importance of future studies on the effect of neprilysin inhibition in reducing CV events.

Neprilysin as a Biomarker: Challenges and Opportunities

Neprilysin (NEP) inhibition is a successful novel therapeutic approach in heart failure with reduced ejection fraction. Assessing individual NEP status might be important for gathering insights into mechanisms of disease and optimising individualised patient care. NEP is a zinc-dependent multisubstrate-metabolising oligoendopeptidase localised in the plasma membrane with the catalytic site facing the extracellular space. Although NEP activity in vivo is predominantly tissue-based, NEP can be released into the circulation via ectodomain shedding and exosomes. Attempts to determine circulating NEP concentrations and activity have not yet resulted in convincingly coherent results relating NEP biomarkers to heart failure disease severity or outcomes. NEP is naturally expressed on neutrophils, opening up the possibility of measuring a membrane-associated form with integrity. Small studies have linked NEP expression on neutrophils with inflammatory state and initial data might indicate its role in heart failure with reduced ejection fraction. Future studies need to assess the regulation of systemic NEP activity, which is assumed to be tissue-based, and the relationship of NEP activation with disease state. The relationship between tissue NEP activity and easily accessible circulating NEP biomarkers and the impact of the latter remains to be established.

Heart Failure With Reduced Ejection Fraction Is Characterized by Systemic NEP Downregulation

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The kidneys might play a crucial role in regulating systemic NEP actions based on 20 to 100 higher NEP content and activity of the kidneys compared with any other organ.

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Tissue NEP expression seems to be downregulated and translates into reduced tissue protein concentrations and activity in HF.

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Neither plasma or liquor NEP concentrations and activities reflect tissue NEP regulation; therefore, using NEP as a circulating biomarker seems to be questionable.

Based on the investigation of neprilysin (NEP) regulation in a translational porcine model of chronic heart failure (HF), this study concluded: 1) that kidneys might play a crucial part in systemic NEP regulation based on 20 to 100 higher NEP content and/or activity compared with any other organ; 2) NEP seems to be downregulated under HF conditions; and 3) that the value of plasma NEP concentrations and activity as biomarkers is questionable. For the first time, these data provide basic knowledge on HF-related pathophysiological alterations of the NEP system and contribute to understanding the mechanism of action of angiotensin-receptor neprilysin-inhibitors, which remains elusive despite broad clinical applications.

Plasma Neprilysin Displays No Relevant Association With Neurohumoral Activation in Chronic HFrEF

Background

Neprilysin is a transmembrane endopeptidase involved in the breakdown of a variety of vasoactive peptides and serves as a therapeutic target in heart failure with reduced ejection fraction (HFrEF). This study aimed to investigate the relationship of circulating neprilysin with neurohumoral activation and the impact of plasma neprilysin activity on prognosis in HFrEF.

Methods and Results

A total of 369 chronic HFrEF patients were enrolled prospectively. Plasma neprilysin concentration and activity were determined by a specific ELISA and a fluorometric method. The association between plasma neprilysin and heart failure (HF) severity, neurohumoral activation, ie norepinephrine and absolute renin concentration, as well as all‐cause mortality was assessed. Median plasma neprilysin concentrations and activity levels were 413 pg/mL (interquartile range 0–4111) and 2.36 nmol/mL per minute (interquartile range 1.16–4.59). No correlation could be shown between plasma neprilysin concentrations and activity (r_s=0.09, P=0.088). Plasma neprilysin activity correlated with HF severity reflected by New York Heart Association stage (P=0.003) and tertiles of N‐terminal pro‐B‐type natriuretic peptide (P<0.001), whereas neprilysin concentrations did not (P=0.220; P=0.849). There was no relevant relationship between plasma neprilysin concentrations and activity, with neurohumoral activation reflected by absolute renin concentration (r_s=−0.02, P=0.648; r_s=0.03, P=0.574) or norepinephrine levels (r_s=−0.06, P=0.248; r_s=0.20, P<0.001). Neither circulating neprilysin concentrations nor activity were associated with outcome.

Conclusions

Plasma neprilysin concentrations and activity are not directly related to neurohumoral activation, indicating that neprilysin regulation is either more complex or not correctly mirrored by circulating neprilysin as a biomarker. Circulating neprilysin concentrations and activity were not associated with overall survival, implicating limited prognostic value of plasma neprilysin measurements in HFrEF patients.

Soluble neprilysin, NT-proBNP, and growth differentiation factor-15 as biomarkers for heart failure in dialysis patients (SONGBIRD)

Background

Dialysis patients are at increased risk of HF. However, diagnostic utility of NT-proBNP as a biomarker is decreased in patients on dialysis. GDF-15 and cNEP are biomarkers of distinct mechanisms that may contribute to HF pathophysiology in such cohorts. The aim of this study was to determine whether growth differentiation factor-15 (GDF-15) and circulating neprilysin (cNEP) improve the diagnosis of congestive heart failure (HF) in patients on dialysis.

Methods and results

We compared circulating concentrations of NT-proBNP, GDF-15, and cNEP along with cNEP activity in patients on chronic dialysis without (n = 80) and with HF (n = 73), as diagnosed by clinical parameters and post-dialysis echocardiography. We used correlation, linear and logistic regression as well as receiver operating characteristic (ROC) analyses. Compared to controls, patients with HF had higher median values of NT-proBNP (16,216 [interquartile range, IQR = 27739] vs. 2883 [5866] pg/mL, p < 0.001), GDF-15 (7512 [7084] vs. 6005 [4892] pg/mL, p = 0.014), but not cNEP (315 [107] vs. 318 [124] pg/mL, p = 0.818). Median cNEP activity was significantly lower in HF vs. controls (0.189 [0.223] vs. 0.257 [0.166] nmol/mL/min, p < 0.001). In ROC analyses, a multi-marker model combining clinical covariates, NT-proBNP, GDF-15, and cNEP activity demonstrated best discrimination of HF from controls (AUC = 0.902, 95% CI 0.857–0.947, p < 0.001 vs. base model AUC = 0.785).

Conclusion

We present novel comparative data on physiologically distinct circulating biomarkers for HF in patients on dialysis. cNEP activity but not concentration and GDF-15 provided incremental diagnostic information over clinical covariates and NT-proBNP and may aid in diagnosing HF in dialysis patients.

Graphic abstract

Electronic supplementary material

The online version of this article (10.1007/s00392-020-01597-x) contains supplementary material, which is available to authorized users.

Burden and challenges of heart failure in patients with chronic kidney disease. A call to action

Patients with the dual burden of chronic kidney disease (CKD) and chronic congestive heart failure (HF) experience unacceptably high rates of symptom load, hospitalization, and mortality. Currently, concerted efforts to identify, prevent and treat HF in CKD patients are lacking at the institutional level, with emphasis still being placed on individual specialty views on this topic. The authors of this review paper endorse the need for a dedicated cardiorenal interdisciplinary team that includes nephrologists and renal nurses and jointly manages appropriate clinical interventions across the inpatient and outpatient settings. There is a critical need for guidelines and best clinical practice models from major cardiology and nephrology professional societies, as well as for research funding in both specialties to focus on the needs of future therapies for HF in CKD patients. The implementation of cross-specialty educational programs across all levels in cardiology and nephrology will help train future specialists and nurses who have the ability to diagnose, treat, and prevent HF in CKD patients in a precise, clinically effective, and cost-favorable manner.

Neutral Endopeptidase (Neprilysin) in Therapy and Diagnostics: Yin and Yang

Neprilysin (NEP) is a zinc-dependent metalloproteinase that exists in organisms in both transmembrane and soluble forms. NEP substrates are involved in regulating the cardiovascular and nervous systems. In this review, we discuss some of the biochemical characteristics and physiological functions of this enzyme with special emphasis on the use of NEP as a therapeutic target. The history and various physiological aspects of applying NEP inhibitors for treating heart failure and attempts to increase NEP activity when treating Alzheimer's disease using gene and cell therapies are described. Another important issue discussed is the role of NEP as a potential marker for predicting the risk of cardiovascular disease complications. The diagnostic and prognostic performance of soluble NEP in various types of heart failure is analyzed and presented. We also discuss the methods and approaches for measuring NEP activity for prognosis and diagnosis, as well as a possible new role of natriuretic peptides (NEP substrates) in cardiovascular diagnostics.

Cardiorenal Interactions Revisited: How to Improve Heart Failure Outcomes in Patients With Chronic Kidney Disease

PURPOSE OF THE REVIEW

To summarize current advances in the understanding and management of heart failure (HF) in patients with advanced chronic kidney disease (CKD).

RECENT FINDINGS

Diagnosis of HF and treatment of congestion are crucial in the management of patients with advanced CKD to reduce symptoms, preserve organ function, and improve outcomes. Echocardiography and cardiovascular biomarkers may help to differentiate cardiac from non-cardiac components of overhydration. Renal replacement therapy or ultrafiltration may be required to treat congestion. Furthermore, patients with advanced CKD are frequently undertreated with disease-modifying HF therapies, but the use of beta-blockers and ACEi should be considered under close monitoring of kidney function and serum potassium. The use of the new oral potassium binders may translate into improved outcomes. The treatment of HF in patients with advanced CKD requires a multi-disciplinary approach. New diagnostic and therapeutic strategies are under evaluation and may contribute to improved outcomes.

The circulating form of neprilysin is not a general biomarker for overall survival in treatment-naïve cancer patients

The transmembrane zink-metalloendopeptidase neprilysin (NEP) is implicated in cardiovascular disease but also tumor biology. The aim of the study was to investigate the relationship of circulating NEP (cNEP) levels with established cardiovascular biomarkers and its effect on overall survival in an unselected cohort of treatment-naïve cancer patients. 555 consecutive cancer patients prior anticancer therapy were enrolled prospectively. NEP levels were determined alongside routine laboratory parameters, established cardiac biomarkers, i.e. NT-proBNP, hsTnT, MR-proANP, MR-proADM, CT-proET-1 and Copeptin, and inflammatory parameters, i.e. CRP, IL-6 and SAA, in venous plasma samples. All-cause mortality was the primary endpoint. cNEP levels of 276 pg/ml (IQR: 0–5981) displayed a weak inverse correlation with age [r = −0.12, p = 0.023] and inflammatory status [r = −0.14, p = 0.007 CRP; r = −0.20, p < 0.001 IL-6 and r = −0.18, p < 0.001 SAA]. cNEP was comparable between different tumor entities and stages and not related to functional parameters of other organ systems as kidney, liver or especially the heart. Moreover, cNEP was not associated with overall survival in the total cohort [adj.HR for ln (cNEP) 1.00, 95% CI: 0.94–1.06, p = 0.887] but in myelodysplatic malignancies [adj.HR for ln (cNEP) 1.27, 95% CI: 1.01–1.61, p = 0.044]. In conclusion, cNEP lacks association with outcome but for myelodysplastic disease. cNEP shows no correlation with established cardiovascular biomarkers related to prognosis, thereby holding a limited potential as a biomarker in cardio-oncology.

Neprilysin Inhibitors: Filling a Gap in Heart Failure Management, Albeit Amidst Controversy and at a Significant Cost

Dual angiotensin and neprilysin inhibition using the combination drug sacubitril-valsartan has ushered in a new era in the treatment of heart failure (HF). The randomized controlled PARADIGM-HF trial, which randomized 8399 patients with HF to enalapril or sacubitril-valsartan, showed a 20% reduction in mortality and HF hospitalization with the new drug. This has been heralded as a step toward filling a crucial gap in HF management by providing strong evidence that combined inhibition of the angiotensin receptor and neprilysin is superior to inhibition of the renin-angiotensin system alone in stable patients with chronic HF as it negates the deleterious effects of angiotensin while concomitantly augmenting the beneficial effects of the endogenous natriuretic peptide system. This new therapy is costly, and other confirmatory studies have been lacking for over 2 years since its approval by major regulatory authorities. As such, controversy and heated discussions have amassed, as has detailed information from a plethora of secondary analyses of this pivotal trial about the pros and cons of this promising new therapeutic strategy in HF management. The aim of this review was to provide a critical assessment of all these aspects.