Recent advances on natriuretic peptide system: New promising therapeutic targets for the treatment of heart failure

From Snake Venoms to Therapeutics: A Focus on Natriuretic Peptides

Snake venom is a cocktail of multifunctional biomolecules that has evolved with the purpose of capturing prey and for defense. These biomolecules are classified into different classes based on their functions. They include three-finger toxins, natriuretic peptides, phospholipases and metalloproteinases. The focus for this review is on the natriuretic peptide (NP), which is an active component that can be isolated from the venoms of vipers and mambas. In these venoms, NPs contribute to the lowering of blood pressure, causing a rapid loss of consciousness in the prey such that its mobility is reduced, paralyzing the prey, and often death follows. Over the past 30 years since the discovery of the first NP in the venom of the green mamba, venom NPs have shown potential in the development of drug therapy for heart failure. Venom NPs have long half-lives, different pharmacological profiles, and may also possess different functions in comparison to the mammalian NPs. Understanding their mechanisms of action provides the strategies needed to develop new NPs for treatment of heart failure. This review summarizes the venom NPs that have been identified over the years and how they can be useful in drug development.

C-type natriuretic peptide in childhood obesity

According to the World Health Organization obesity is the result of an energy imbalance between calories assumed and expended and over the past 30 years its incidence has dramatically increased. Recently, the problem of obesity has drastically increased also in childhood, assuming a social relevance. Childhood obesity, in fact, increases the possibility to be obese in adulthood, representing a risk for cardiovascular morbidity and mortality. Aim of this review was to carry out a revision of the literature on childhood obesity focusing on natriuretic peptides (NPs) and in particular on the role of C-type natriuretic peptide (CNP). In obesity NPs play a fundamental role in the regulation of body weight and energy metabolism. Data on plasma CNP levels in children are scarce. The review of the literature relating to the role of CNP in adolescents showed a progressive reduction in the CNP plasma levels in overweight/obese adolescents compared to normal-weight subjects, as previously observed in obese adults, as well as a different modulation in CNP mRNA expression. An independent association between CNP levels and obesity as well as a significant association with the endothelial dysfunction index was reported, indicating that the peptide could play a very important role as a marker of risk of developing obesity. The results of these studies indicate the importance of adopting healthy lifestyles to improve glucometabolic control as well as to provide the rationale for designing and developing new drugs to modulate the NPs system.

Maternal plasma pro-atrial and C-type natriuretic peptide levels and their associations with cardiovascular and renal function in the second half of normal pregnancy: a longitudinal study

BACKGROUND

Physiological adaptation in pregnancy is characterized by remodeling of endocrine, cardiovascular and renal functions leading to fluid retention, volume expansion, altered cardiac loading conditions and hyperdynamic circulation. Natriuretic peptides have been used as biomarkers of cardiovascular function, but their associations with gestational age-related changes in maternal cardiac, endothelial and renal function have not been elucidated. The aim of this study was to establish longitudinal reference values for maternal plasma atrial natriuretic peptide (proANP) and C-type natriuretic peptide (CNP) and investigate their temporal association with cardiovascular and renal function in the second half of pregnancy.

METHODS

This study was a prospective longitudinal study of 53 low-risk pregnancies. Women were examined every 3-5 weeks during 22-40 weeks of gestation (252 observations). Fasting maternal blood samples were obtained to measure proANP, CNP, creatinine, cystatin C, uric acid, and fibrinogen levels. Cardiac function and systemic hemodynamics were assessed noninvasively by impedance cardiography (ICG) and vascular endothelial function by flow-mediated vasodilation of brachial artery (FMD).

RESULTS

The plasma proANP (R2adj = 0.79; P = 0.007), CNP (R2adj = 0.54; P = 0.005) decreased between 22 and 40 weeks. The creatinine (R2adj = 0.90; P < 0.001), cystatin C (R2adj = 0.93; P = < 0.001) and uric acid (R2adj = 0.83; P < 0.001) increased significantly, whereas the estimated glomerular filtration rate (R2adj = 0.93; P < 0.001) decreased with gestational age. The FMD did not change significantly but fibrinogen (R2adj = 0.79; P < 0.001) increased with advancing gestation. The maternal systemic vascular resistance index (R2adj = 0.50; P < 0.001) increased, stroke index (R2adj = 0.62; P < 0.001) decreased, whereas the cardiac index (R2adj = 0.62; P = 0.438) and thoracic fluid content (R2adj = 0.72; P = 0.132) did not change significantly with gestation. The proANP was associated with thoracic fluid content (R2adj = 0.74; P < 0.001) and fibrinogen (R2adj = 0.78; P = 0.034) but not with other variables of systemic hemodynamics, endothelial function, or renal function. The CNP was not associated significantly with parameters of cardiovascular or renal function.

CONCLUSION

Longitudinal reference values for maternal plasma proANP and CNP were established. These natriuretic peptides decreased slightly with advancing gestation, but they did not reflect the temporal physiological changes in maternal systemic hemodynamics, vascular endothelial function and renal function during the second half of pregnancy. The proANP correlated with the thoracic fluid content reflecting volume load in pregnancy.

C-type natriuretic peptide plasma levels and whole blood mRNA expression show different trends in adolescents with different degree of endothelial dysfunction

C-type natriuretic peptide (CNP) is an endogenous adipogenesis regulator whose plasma levels in childhood are known, while no data are available on its expression. Our aim was to evaluate both CNP plasma levels and CNP system expression in whole blood obtained from normal-weight (N, n = 24) and obese (O, n = 16) adolescents (age:13.5 ± 0.4 years). Endothelial function was assessed measuring reactive hyperemia index (RHI). CNP plasma levels, evaluated with specific RIA, resulted significantly lower in O than in N (6.1 ± 0.8 vs.15.2 ± 1.3 pg/mL; p < 0.0001), while CNP/NPR-B/NPR-C mRNA, measured by Real-Time PCR, resulted similar in N (4.1 ± 1.7; 5.0 ± 1.6; 2.2 ± 0.9) and in O (4.3 ± 1.6; 3.5 ± 1.1; 2.3 ± 0.8). RHI was significantly lower in O than in N (1.4 ± 0.08 vs.2.1 ± 0.04, p < 0.0001). Dividing all subjects according to the RHI median value, irrespective of the presence or absence of obesity (Group 1 > 1.9, n = 23, Group 2 < 1.9, n = 17), CNP plasma concentrations resulted significantly (p = 0.014) higher in Group 1 (14.6 ± 1.6) than in Group 2 (7.5 ± 1.0), showing a significant correlation with RHI (p = 0.0026), while CNP mRNA expression was, surprisingly, higher in Group 2 (7.0 ± 2.3) than in Group 1 (1.8 ± 0.4; p = 0.02). NPR-B mRNA resulted similar in both Groups (4.3 ± 1.6; 4.7 ± 1.3) and NPR-C significantly higher in Group 2 (p = 0.02). Our data suggest different trends between CNP plasma levels and expression, assessed for the first time in whole blood, that could reflect changes occurring both at CNP transcriptional level in activated leukocytes due to inflammation, and at circulating levels, due to CNP paracrine/autocrine activities. This could represent an interesting area for new therapies able to modulate endothelial dysfunction.

Tuscany Sangiovese grape juice imparts cardioprotection by regulating gene expression of cardioprotective C-type natriuretic peptide

PURPOSE

A regular intake of red grape juice has cardioprotective properties, but its role on the modulation of natriuretic peptides (NPs), in particular of C-type NP (CNP), has not yet been proven. The aims were to evaluate: (1) in vivo the effects of long-term intake of Tuscany Sangiovese grape juice (SGJ) on the NPs system in a mouse model of myocardial infarction (MI); (2) in vitro the response to SGJ small RNAs of murine MCEC-1 under physiological and ischemic condition; (3) the activation of CNP/NPR-B/NPR-C in healthy human subjects after 7 days' SGJ regular intake.

METHODS

(1) C57BL/6J male and female mice (n = 33) were randomly subdivided into: SHAM (n = 7), MI (n = 15) and MI fed for 4 weeks with a normal chow supplemented with Tuscany SGJ (25% vol/vol, 200 µl/per day) (MI + SGJ, n = 11). Echocardiography and histological analyses were performed. Myocardial NPs transcriptional profile was investigated by Real-Time PCR. (2) MCEC-1 were treated for 24 h with a pool of SGJ small RNAs and cell viability under 24 h exposure to H₂O₂ was evaluated by MTT assay. (3) Human blood samples were collected from seven subjects before and after the 7 days' intake of Tuscany SGJ. NPs and miRNA transcriptional profile were investigated by Real-Time PCR in MCEC-1 and human blood.

RESULTS

Our experimental data, obtained in a multimodal pipeline, suggest that the long-term intake of SGJ promotes an adaptive response of the myocardium to the ischemic microenvironment through the modulation of the cardiac CNP/NPR-B/NPR-C system.

CONCLUSIONS

Our results open new avenue in the development of functional foods aimed at enhancing cardioprotection of infarcted hearts through action on the myocardial epigenome.

Brain Natriuretic Peptide and Its Biochemical, Analytical, and Clinical Issues in Heart Failure: A Narrative Review

Heart failure (HF) is a primary cause of morbidity and mortality worldwide. As the most widely studied and commonly applied natriuretic peptide (NP), B-type natriuretic peptide (BNP) has the effects of diuresis, natriuresis, vasodilation, anti-hypertrophy, and anti-fibrosis and it inhibits the renin-angiotensin-aldosterone and sympathetic nervous systems to maintain cardiorenal homeostasis and counteract the effects of HF. Both BNP and N-terminal pro B-type natriuretic peptide (NT-proBNP) are applied as diagnostic, managing, and prognostic tools for HF. However, due to the complexity of BNP system, the diversity of BNP forms and the heterogeneity of HF status, there are biochemical, analytical, and clinical issues on BNP not fully understood. Current immunoassays cross-react to varying degrees with pro B-type natriuretic peptide (proBNP), NT-proBNP and various BNP forms and cannot effectively differentiate between these forms. Moreover, current immunoassays have different results and may not accurately reflect cardiac function. It is essential to design assays that can recognize specific forms of BNP, NT-proBNP, and proBNP to obtain more clinical information. Not only the processing of proBNP (corin/furin) and BNP (neprilysin), but also the effects of glycosylation on proBNP processing and BNP assays, should be targeted in future studies to enhance their diagnostic, therapeutic, and prognostic values.

New issues on measurement of B-type natriuretic peptides

The measurement of the active hormone of B-type natriuretic peptide (BNP) system actually has several analytical limitations and difficulties in clinical interpretations compared to that of inactive peptide N-terminal proBNP (NT-proBNP) because of the different biochemical and pathophysiological characteristics of two peptides and quality specifications of commercial immunoassay methods used for their measurement. Because of the better analytical characteristics of NT-proBNP immunoassays and the easier pathophysiological and clinical interpretations of variations of NT-proBNP levels in patients with heart failure (HF), some authors claimed to measure the inactive peptide NT-proBNP instead of the active hormone BNP for management of HF patients. The measurement of the active peptide hormone BNP gives different, but complementary, pathophysiological and clinical information compared to inactive NT-proBNP. In particular, the setup of new more sensitive and specific assays for the biologically active peptide BNP1-32 should give better accurate information on circulating natriuretic activity. In conclusion, at present time, clinicians should accurately consider both the clinical setting of patients and the analytical characteristics of BNP and NT-proBNP immunoassays in order to correctly interpret the variations of natriuretic peptides measured by commercially available laboratory methods, especially in patients treated with the new drug class of angiotensin receptor-neprilysin inhibitors.

Combined Assessment of Relaxin and B-Type Natriuretic Peptide Improves Diagnostic Value in Patients With Congestive Heart Failure

BACKGROUND

To improve the poor prognosis of congestive heart failure (CHF), early and accurate diagnosis is necessary. Relaxin is an endogenous cardiovascular peptide, and its plasma level is usually increased in patients with CHF. In this pilot study, we aimed to determine the diagnostic value of relaxin and B-type natriuretic peptide (BNP) in patients with and without CHF.

MATERIALS AND METHODS

The plasma level of relaxin was measured by enzyme-linked immunosorbent assay and plasma level of BNP by fluorescence immunoassay. The area under the receiver operating characteristic curve was used to assess the diagnostic value of relaxin and BNP.

RESULTS

We included 81 patients with decompenstated CHF and 36 controls. Plasma levels of relaxin and BNP were both higher in CHF patients than in controls. The correlation between plasma levels of relaxin and BNP and between relaxin or BNP and cardiac function was nonlinear. Relaxin had medium diagnostic value, and BNP had higher value for cardiac function and CHF. At a cutoff of 39.76pg/mL relaxin, sensitivity was 82.7%, specificity 55.6%, sum of the highest positive predictive value 80.5% and negative predictive value 58.8%. Although the diagnostic value was not better for relaxin than BNP, their combined assessment improved the sensitivity and specificity of diagnosis for CHF as compared with BNP alone.

CONCLUSIONS

Combined assessment of relaxin and BNP may improve the diagnosis of decompensated CHF, which may have potential application in the clinic.

Resetting the neurohormonal balance in heart failure (HF): the relevance of the natriuretic peptide (NP) system to the clinical management of patients with HF

The natriuretic peptide (NP) system, which includes atrial natriuretic peptide, B-type natriuretic peptide, and C-type natriuretic peptide, has an important role in cardiovascular homeostasis, promoting a number of physiological effects including diuresis, vasodilation, and inhibition of the renin-angiotensin-aldosterone system. Heart failure (HF) is associated with defects in NP processing and synthesis, and there is a strong relationship between NP levels and disease state. NPs are useful biomarkers in HF, and their use in diagnosis and evaluation of prognosis is well established, particularly in patients with HF with reduced ejection fraction (HFrEF). There has also been interest in their use to guide disease management and therapeutic decision making. An understanding of NPs in HF has also resulted in interest in synthetic NPs for the treatment of HF and in treatments that target neprilysin, a protease that degrades NPs. A novel drug, the angiotensin receptor neprilysin inhibitor sacubitril/valsartan (LCZ696), which simultaneously inhibits neprilysin and blocks the angiotensin II type I receptor, was shown to have a favorable efficacy and safety profile in patients with HFrEF and has been approved for use in such patients in Europe and the USA. In light of the development of treatments that target neprilysin and of recent data in relation to synthetic NPs, it is timely to review the current understanding of the role of NPs in HF and their use in diagnosis, evaluating prognosis and guiding treatment, as well as their place in HF therapy.

Natriuretic peptides as biomarkers of cardiac endocrine function in heart failure: new challenges and perspectives

Several studies indicated that B-type natriuretic peptide (BNP) assay is able to detect patients even in the early phases of heart failure (HF), when the myocardial remodeling process may be still reversible. BNP assay may assist the physician to initiate appropriate and prompt pharmacological treatments. However, clinical relevance and result interpretation of BNP assay for the guide of therapy or in particular clinical conditions, such as renal failure or treatment with inhibitors of enzymes degrading BNP in HF patients, are still debated. The aim of this article is to discuss some still controversial issues concerning the clinical use of measurement of cardiac natriuretic peptides, and also to provide a general overview and some perspectives related to pathophysiological mechanisms of HF.

Relaxation Induced by Atrial Natriuretic Peptide Is Impaired in Carotid but Not Renal Arteries from Spontaneously Hypertensive Rats Due to Reduced BKCa Channel Activity

Atrial natriuretic peptide (ANP) plays an important role in vascular functions such as blood pressure regulation and relaxant activity. Individual vascular beds exhibit differences in vascular reactivity to various ligands, however, the difference in responsiveness to ANP between carotid and renal arteries and the molecular mechanisms of its vasorelaxant activity in a pathophysiological state, including hypertension, remain unclear. We therefore investigated this issue by exposing carotid and renal artery rings obtained from spontaneously hypertensive rats (SHR) to ANP. In the SHR artery (vs. control WKY artery), the ANP-induced relaxations were reduced in carotid artery but not renal artery. Acetylcholine-induced relaxations were reduced in both arteries in SHR (vs. WKY). Sodium nitroprusside-induced relaxation was similar in both arteries between the groups. In carotid arteries, the ANP-induced relaxation was not affected by endothelial denudation or by treatment with inhibitors of nitric oxide synthase, cyclooxygenase, the voltage-dependent potassium channel, or ATP-sensitive potassium channel in arteries from both SHR and WKY. In the carotid artery from WKY but not SHR, the ANP-induced relaxation was significantly reduced by inhibition of the large-conductance calcium-activated potassium channel (BKCa). The BKCa activator-induced relaxation was reduced in the SHR artery (vs. WKY). These results suggest that ANP-induced relaxation is impaired in the carotid artery from SHR and this impairment may be at least in part due to the reduction of BKCa activity rather than endothelial components.

C-type natriuretic peptide is closely associated to obesity in Caucasian adolescents

CNP is a natural regulator of adipogenesis playing a role in the development of obesity in childhood. Aim of the study was to evaluate CNP plasma levels in normal-weight (N), overweight (OW) and obese adolescents (O). Eighty two subjects (age:12.8±2.4, years) without cardiac dysfunction were enrolled and CNP plasma levels were measured by RIA. NT-proBNP, MR-proANP, AGEs, reactive hyperemia index (RHI) and standard clinical chemistry parameters were also measured. O and OW adolescents had higher values of BMI and fat mass than N. CNP levels were significantly lower in OW:4.79[3.29-21.15] and O:3.81[1.55-13.4] than in N:13.21[7.6-37.8]; p<0.0001N vs O, p=0.0003N vs OW). LogCNP values correlated significantly and inversely with BMI z-score, FM%, TF% and circulating levels of CRP, insulin, total cholesterol, LDL, and triglycerides, in addition to an inverse relationship with skin AGEs and a direct correlation with RHI. LogCNP was also inversely associated with LogNT-proBNP and LogMR-proANP values. Using ROC analysis the risk of obesity resulted significantly (p≪0.0001) associated with CNP values (AUC=0.9724). These results suggest that CNP may play a more important role than BNP and ANP related peptides, as risk marker of obesity, in addition to its involvement in adipogenesis and endothelial dysfunction.

N-Terminal Pro-B Type Natriuretic Peptide as a Marker of Bronchopulmonary Dysplasia or Death in Very Preterm Neonates: A Cohort Study

Background

Bronchopulmonary dysplasia (BPD) is a serious complication of preterm birth. Plasma N-terminal pro-B type natriuretic peptide (NT-proBNP) has been suggested as a marker that may predict BPD within a few days after birth.

Objectives

To investigate the association between NT-proBNP day three and bronchopulmonary dysplasia (BPD) or death and further to assess the impact of patent ductus arteriosus (PDA) on this association in neonates born before 32 gestational weeks.

Methods

A cohort study of 183 neonates born before 32 gestational weeks consecutively admitted to the Neonatal Intensive Care Unit, Aarhus University Hospital, Denmark. On day three plasma samples were collected and echocardiography carried out. NT-proBNP was measured by routine immunoassays. The combined outcome BPD or death was assessed at 36 weeks of postmenstrual age. Receiver operator characteristic (ROC) analysis was performed to determine the discrimination ability of NT-proBNP by the natural log continuous measure to recognize BPD or death. The association of BPD or death was assessed in relation to natural log NT-proBNP levels day three.

Results

The risk of BPD or death increased 1.7-fold with one unit increase of natural log NT-proBNP day three when adjusted for gestational age at birth (OR = 1.7, 95% CI 1.3; 2.3). The association was found both in neonates with and without a PDA. Adjusting for GA, PDA diameter, LA:Ao-ratio, or early onset sepsis did not change the estimate.

Conclusion

We found NT-proBNP to be associated with BPD or death in very preterm neonates. This association was not only explained by the PDA. We speculate that NT-proBNP may help the identification of neonates at risk of BPD as early as postnatal day three.

Diagnostic Accuracy of Natriuretic Peptides for Heart Failure in Patients with Pleural Effusion: A Systematic Review and Updated Meta-Analysis

Background

Previous studies have reported that natriuretic peptides in the blood and pleural fluid (PF) are effective diagnostic markers for heart failure (HF). These natriuretic peptides include N-terminal pro-brain natriuretic peptide (NT-proBNP), brain natriuretic peptide (BNP), and midregion pro-atrial natriuretic peptide (MR-proANP). This systematic review and meta-analysis evaluates the diagnostic accuracy of blood and PF natriuretic peptides for HF in patients with pleural effusion.

Methods

PubMed and EMBASE databases were searched to identify articles published in English that investigated the diagnostic accuracy of BNP, NT-proBNP, and MR-proANP for HF. The last search was performed on 9 October 2014. The quality of the eligible studies was assessed using the revised Quality Assessment of Diagnostic Accuracy Studies tool. The diagnostic performance characteristics (sensitivity, specificity, and other measures of accuracy) were pooled and examined using a bivariate model.

Results

In total, 14 studies were included in the meta-analysis, including 12 studies reporting the diagnostic accuracy of PF NT-proBNP and 4 studies evaluating blood NT-proBNP. The summary estimates of PF NT-proBNP for HF had a diagnostic sensitivity of 0.94 (95% confidence interval [CI]: 0.90–0.96), specificity of 0.91 (95% CI: 0.86–0.95), positive likelihood ratio of 10.9 (95% CI: 6.4–18.6), negative likelihood ratio of 0.07 (95% CI: 0.04–0.12), and diagnostic odds ratio of 157 (95% CI: 57–430). The overall sensitivity of blood NT-proBNP for diagnosis of HF was 0.92 (95% CI: 0.86–0.95), with a specificity of 0.88 (95% CI: 0.77–0.94), positive likelihood ratio of 7.8 (95% CI: 3.7–16.3), negative likelihood ratio of 0.10 (95% CI: 0.06–0.16), and diagnostic odds ratio of 81 (95% CI: 27–241). The diagnostic accuracy of PF MR-proANP and blood and PF BNP was not analyzed due to the small number of related studies.

Conclusions

BNP, NT-proBNP, and MR-proANP, either in blood or PF, are effective tools for diagnosis of HF. Additional studies are needed to rigorously evaluate the diagnostic accuracy of PF and blood MR-proANP and BNP for the diagnosis of HF.

Admission hypoxia-inducible factor 1α levels and in-hospital mortality in patients with acute decompensated heart failure

BACKGROUND

Hypoxia-inducible factor 1 (HIF-1) is a critical regulator for cellular oxygen balance. Myocardial hypoxia can induce the increased expression of HIF-1α. Our goals were to evaluate the value of HIF-1α in predicting death of patients with acute decompensated heart failure (ADHF) and describe the in vivo relationship between serum HIF-1α and N-terminal-pro-brain natriuretic peptide (NT-proBNP) levels.

METHOD

We included 296 patients who were consecutively admitted to the emergency department for ADHF. The primary end point was in-hospital death. The patients were categorized as HFrEF (patients with reduced systolic function) and HFpEF (patients with preserved systolic function) groups.

RESULTS

In our patients, the median admission HIF-1α level was 2.95 ± 0.85 ng/ml. The HIF-1α level was elevated significantly in HFrEF patients and deceased patients compared with HFpEF patients and patients who survived. The HIF-1α level was positively correlated with NT-proBNP and cardiac troponin T levels, and negatively correlated with left ventricular ejection fraction and systolic blood pressure. Kaplan-Meier curves revealed a significant increase in in-hospital mortality in ADHF patients with higher HIF-1α levels. Multivariable Cox regression analysis showed that HIF-1α levels were not correlated with the short-term prognosis of ADHF patients.

CONCLUSIONS

This is the first study to evaluate the circulating levels of HIF-1α in ADHF patients. Serum HIF-1α levels may reflect a serious state in patients with ADHF. Due to the limitations of the study, serum HIF-1α levels were not correlated with the in-hospital mortality based on regression analysis. Further studies are needed to demonstrate the diagnostic and/or prognostic role of HIF-1α as a risk biomarker in patients with ADHF.

Elevated NT-pro-brain natriuretic peptide level is independently associated with all-cause mortality in HIV-infected women in the early and recent HAART eras in the Women's Interagency HIV Study cohort

BACKGROUND

HIV-infected individuals are at increased risk of right and left heart dysfunction. N-terminal-pro-brain natriuretic peptide (NT-proBNP), a marker of cardiac ventricular strain and systolic dysfunction, may be associated with all-cause mortality in HIV-infected women. The aim of this study was to determine if elevated levels of NT-proBNP is associated with increased mortality in HIV-infected women.

DESIGN

Prospective cohort study.

METHODS AND RESULTS

We measured NT-proBNP in 936 HIV-infected and 387 age-matched HIV-uninfected women early (10/11/94 to 7/17/97) and 1082 HIV-infected and 448 HIV-uninfected women late (4/1/08 to 10/7/08) in the highly active antiretroviral therapy (HAART) periods in the Women's Interagency HIV Study. An NT-proBNP >75th percentile was more likely in HIV-infected persons, but only statistically significant in the late period (27% vs. 21%, unadjusted p = 0.03). In HIV-infected participants, NT-proBNP>75th percentile was independently associated with worse 5-year survival in the early HAART period (HR 1.8, 95% CI 1.3-2.4, p<0.001) and remained a predictor of mortality in the late HAART period (HR 2.8, 95% CI 1.4-5.5, p = 0.002) independent of other established risk covariates (age, race/ethnicity, body mass index, smoking, hepatitis C serostatus, hypertension, renal function, and hemoglobin). NT-proBNP level was not associated with mortality in HIV-uninfected women.

CONCLUSION

NT-proBNP is a novel independent marker of mortality in HIV-infected women both when HAART was first introduced and currently. As NT-proBNP is often associated with both pulmonary hypertension and left ventricular dysfunction, these findings suggest that these conditions may contribute significantly to adverse outcomes in this population, requiring further definition of causes and treatments of elevated NT-proBNP in HIV-infected women.

State of the art of immunoassay methods for B-type natriuretic peptides: An update

The aim of this review article is to give an update on the state of the art of the immunoassay methods for the measurement of B-type natriuretic peptide (BNP) and its related peptides. Using chromatographic procedures, several studies reported an increasing number of circulating peptides related to BNP in human plasma of patients with heart failure. These peptides may have reduced or even no biological activity. Furthermore, other studies have suggested that, using immunoassays that are considered specific for BNP, the precursor of the peptide hormone, proBNP, constitutes a major portion of the peptide measured in plasma of patients with heart failure. Because BNP immunoassay methods show large (up to 50%) systematic differences in values, the use of identical decision values for all immunoassay methods, as suggested by the most recent international guidelines, seems unreasonable. Since proBNP significantly cross-reacts with all commercial immunoassay methods considered specific for BNP, manufacturers should test and clearly declare the degree of cross-reactivity of glycosylated and non-glycosylated proBNP in their BNP immunoassay methods. Clinicians should take into account that there are large systematic differences between methods when they compare results from different laboratories that use different BNP immunoassays. On the other hand, clinical laboratories should take part in external quality assessment (EQA) programs to evaluate the bias of their method in comparison to other BNP methods. Finally, the authors believe that the development of more specific methods for the active peptide, BNP1-32, should reduce the systematic differences between methods and result in better harmonization of results.

Obesity and natriuretic peptides, BNP and NT-proBNP: mechanisms and diagnostic implications for heart failure

Many advances have been made in the diagnosis and management of heart failure (HF) in recent years. Cardiac biomarkers are an essential tool for clinicians: point of care B-type natriuretic peptide (BNP) and its N-terminal counterpart (NT-proBNP) levels help distinguish cardiac from non-cardiac causes of dyspnea and are also useful in the prognosis and monitoring of the efficacy of therapy. One of the major limitations of HF biomarkers is in obese patients where the relationship between BNP and NT-proBNP levels and myocardial stiffness is complex. Recent data suggest an inverse relationship between BNP and NT-proBNP levels and body mass index. Given the ever-increasing prevalence of obesity world-wide, it is important to understand the benefits and limitations of HF biomarkers in this population. This review will explore the biology, physiology, and pathophysiology of these peptides and the cardiac endocrine paradox in HF. We also examine the clinical evidence, mechanisms, and plausible biological explanations for the discord between BNP levels and HF in obese patients.