Recent Advances in Serum Biomarkers for Risk Stratification and Patient Management in Cardio-Oncology

PURPOSE OF REVIEW

Following significant advancements in cancer therapeutics and survival, the risk of cancer therapy-related cardiotoxicity (CTRC) is increasingly recognized. With ongoing efforts to reduce cardiovascular morbidity and mortality in cancer patients and survivors, cardiac biomarkers have been studied for both risk stratification and monitoring during and after therapy to detect subclinical disease. This article will review the utility for biomarker use throughout the cancer care continuum.

RECENT FINDINGS

A recent meta-analysis shows utility for troponin in monitoring patients at risk for CTRC during cancer therapy. The role for natriuretic peptides is less clear but may be useful in patients receiving proteasome inhibitors. Early studies explore use of myeloperoxidase, growth differentiation factor 15, galectin 3, micro-RNA, and others as novel biomarkers in CTRC. Biomarkers have potential to identify subclinical CTRC and may reveal opportunities for early intervention. Further research is needed to elucidate optimal biomarkers and surveillance strategies.

Transcriptomics reveal stretched human pluripotent stem cell-derived cardiomyocytes as an advantageous hypertrophy model

Left ventricular hypertrophy, characterized by hypertrophy of individual cardiomyocytes, is an adaptive response to an increased cardiac workload that eventually leads to heart failure. Previous studies using neonatal rat ventricular myocytes (NRVMs) and animal models have revealed several genes and signaling pathways associated with hypertrophy and mechanical load. However, these models are not directly applicable to humans. Here, we studied the effect of cyclic mechanical stretch on gene expression of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) using RNA sequencing. hiPSC-CMs showed distinct hypertrophic changes in gene expression at the level of individual genes and in biological processes. We also identified several differentially expressed genes that have not been previously associated with cardiomyocyte hypertrophy and thus serve as attractive targets for future studies. When compared to previously published data attained from stretched NRVMs and human embryonic stem cell-derived cardiomyocytes, hiPSC-CMs displayed a smaller number of changes in gene expression, but the differentially expressed genes revealed more pronounced enrichment of hypertrophy-related biological processes and pathways. Overall, these results establish hiPSC-CMs as a valuable in vitro model for studying human cardiomyocyte hypertrophy.

Evaluation of left atrial dysfunction by speckle tracking echocardiography in systolic and diastolic heart failure

The study aimed to assess the accuracy of two-dimensional speckle tracking echocardiography (2DSTE) to evaluate the left atrial (LA) function in patients with heart failure. And can it differentiate accurately between heart failure preserved ejection fraction (HFpEF, HF with mid-range ejection fraction (HFmrEF=EF 41-49%) and heart failure with reduced ejection fraction (HFrEF= EF<40%)? It included 186 patients of heart failure who were classified into 74 patients with HFpEF (LVEF>50%), 56 patients with HFmrEF (LVEF 41-49%), 56 patients with HFrEF (LVEF<40%), and 50 normal matched subjects. B-type natriuretic peptide (BNP) was more than 35 pg/mL for all patients. The conventional echocardiography evaluated left ventricle systolic and diastolic functions. The 2DSTE evaluated the LV global strain (LVGS), and strain and strain rate (SR) in each phase of LA function. LVGS was -19.3±2.3%, -18.0±1.7%, -16.1±2.0%, and -14.3±2.2 in controls, HFpEF, and HFmrEF, and HFrEF, respectively (p<0.0001); GPALS was 34.1±6.7%, 27.5±4.7%, 21.7±4.8% and 16.9±4.9% in controls, HFpEF, HFmrEF, HFrEF, respectively (p<0.0001); The GPACS was 14.8±4.3%, 12.3±2.2%, 9.7±2.3%, and 7.5±2.6%  in controls, HFpEF, HFmrEF, and HFrEF, respectively (p<0.0001); The PALS-PACS was 19.4±3%, 15.1±4.4%, 12.0±3.4%, and  9.3±3.3% in controls, HFpEF, HFmrEF, and HFrEF (p<0.0001). Therefore, early LA dysfunction in heart failure can be detected accurately and easily by speckle tracking technique that could be a promising independent tool to better understand of heart failure and its classification.

Biomarkers in the clinical management of patients with atrial fibrillation and heart failure

Atrial fibrillation (AF) and heart failure (HF) are two cardiovascular diseases with an increasing prevalence worldwide. These conditions share common pathophysiologiesand frequently co-exit. In fact, the occurrence of either condition can 'cause' the development of the other, creating a new patient group that demands different management strategies to that if they occur in isolation. Regardless of the temproral association of the two conditions, their presence is linked with adverse cardiovascular outcomes, increased rate of hospitalizations, and increased economic burden on healthcare systems. The use of low-cost, easily accessible and applicable biomarkers may hasten the correct diagnosis and the effective treatment of AF and HF. Both AF and HF effect multiple physiological pathways and thus a great number of biomarkers can be measured that potentially give the clinician important diagnostic and prognostic information. These will then guide patient centred therapeutic management. The current biomarkers that offer potential for guiding therapy, focus on the physiological pathways of miRNA, myocardial stretch and injury, oxidative stress, inflammation, fibrosis, coagulation and renal impairment. Each of these has different utility in current clinincal practice.

Serum NT-proBNP levels and histopathological myocardial fibrosis in autopsied cases from a Japanese community: The Hisayama Study

BACKGROUND

natriuretic peptide is associated with myocardial fibrosis in animal models and among patients with heart disease. However, it remains unclear whether serum N-terminal pro-B-type peptide (NT-proBNP) levels are associated with histopathologically proven myocardial fibrosis among individuals without apparent heart disease. This study aimed to evaluate the association between serum NT-proBNP levels and the histopathologically estimated myocardial fibrotic area in autopsied samples from a community.

METHODS

we selected 63 cases without apparent heart disease with available data of serum NT-proBNP concentrations within six years before death (average age: 82 years; male: 52%) from autopsied cases in a community, and evaluated the percentage areas of myocardial fibrosis in four cardiac segments from each case (i.e. 252 cardiac segments in total). The association between serum NT-proBNP levels and the percentage area of myocardial fibrosis was estimated using a linear mixed model for repeated measures.

RESULTS

serum NT-proBNP levels were positively correlated with myocardial fibrotic area [Pearson's correlation coefficient: r = 0.49 (95% confidence interval: 0.28-0.66), p <0.001]. Serum NT-proBNP levels were significantly associated with the percentage areas of myocardial fibrosis after adjusting for potential confounding factors. There was no evidence of heterogeneity in the association between the subgroups with and without reduced estimated glomerular filtration rate (<60 mL/min/1.73 m²).

CONCLUSIONS

the present study demonstrated that elevated serum NT-proBNP levels were associated with the histopathologically measured myocardial fibrotic area in autopsied cases from a community. These findings may help clarify the association between elevated serum NT-proBNP levels and myocardial fibrosis and their influence on prognosis.

Association between platelet distribution width and prognosis in patients with heart failure

Background

The prognostic impact of platelet distribution width (PDW), which is a specific marker of platelet activation, has been unclear in patients with heart failure (HF).

Methods and results

We conducted a prospective observational study enrolling 1,746 hospitalized patients with HF. Patients were divided into tertiles based on levels of PDW: 1^st (PDW < 15.9 fL, n = 586), 2^nd (PDW 15.9–16.8 fL, n = 617), and 3^rd (PDW ≥ 16.9, n = 543) tertiles. We compared baseline patients’ characteristics and post-discharge prognosis: all-cause death; cardiac death; and cardiac events. The 3^rd tertile showed the highest age and levels of B-type natriuretic peptide compared to other tertiles (1^st, 2^nd, and 3^rd tertiles; age, 69.0, 68.0, and 70.0 years old, P = 0.038; B-type natriuretic peptide, 235.2, 171.9, and 241.0 pg/mL, P < 0.001). Left ventricular ejection fraction was equivalent among the tertiles. In the Kaplan-Meier analysis, rates of all endpoints were the highest in the 3^rd tertile (log-rank P < 0.001, respectively). The Cox proportional hazard analysis revealed that the 3^rd tertile was associated with adverse prognosis (all-cause death, hazard ratio [HR] 1.716, P < 0.001; cardiac death, HR 1.919, P < 0.001; cardiac event, HR 1.401, P = 0.002).

Conclusions

High PDW is a novel predictor of adverse prognosis in patients with HF.

Biomarkers for Heart Failure Prognosis: Proteins, Genetic Scores and Non-coding RNAs

Heart failure (HF) is a complex disease in which cardiomyocyte injury leads to a cascade of inflammatory and fibrosis pathway activation, thereby causing decrease in cardiac function. As a result, several biomolecules are released which can be identified easily in circulating body fluids. The complex biological processes involved in the development and worsening of HF require an early treatment strategy to stop deterioration of cardiac function. Circulating biomarkers provide not only an ideal platform to detect subclinical changes, their clinical application also offers the opportunity to monitor disease treatment. Many of these biomarkers can be quantified with high sensitivity; allowing their clinical application to be evaluated beyond diagnostic purposes as potential tools for HF prognosis. Though the field of biomarkers is dominated by protein molecules, non-coding RNAs (microRNAs, long non-coding RNAs, and circular RNAs) are novel and promising biomarker candidates that encompass several ideal characteristics required in the biomarker field. The application of genetic biomarkers as genetic risk scores in disease prognosis, albeit in its infancy, holds promise to improve disease risk estimation. Despite the multitude of biomarkers that have been available and identified, the majority of novel biomarker candidates are not cardiac-specific, and instead may simply be a readout of systemic inflammation or other pathological processes. Thus, the true value of novel biomarker candidates in HF prognostication remains unclear. In this article, we discuss the current state of application of protein, genetic as well as non-coding RNA biomarkers in HF risk prognosis.

B-type natriuretic peptide is associated with post-discharge stroke in hospitalized patients with heart failure

Aims

Recently, B‐type natriuretic peptide (BNP) has been attracting attention as a predictor of stroke in patients with atrial fibrillation or those with prior stroke experience. However, the association between BNP and stroke has not been examined in patients with chronic heart failure (CHF). In the current study, we assessed whether BNP is associated with future occurrence of stroke in patients with CHF.

Methods and results

We prospectively studied 1803 consecutive patients who were admitted for decompensated HF and assessed the predictive value of circulating BNP levels for occurrence of post‐discharge stroke.

A total of 69 (3.8%) patients experienced a stroke (the stroke group) during the post‐discharge follow‐up period of a median of 1150 days. The stroke group showed a higher CHADS₂ score. With respect to past medical history, the stroke group had a higher prevalence of arterial hypertension, atrial fibrillation, prior stroke, and chronic kidney disease. Echocardiographic parameters showed no significant differences between the two groups. In contrast, BNP levels were significantly higher in the stroke group than in the non‐stroke group (452.1 vs. 222.7 pg/mL, P < 0.001). Multivariate Cox proportional hazard analysis indicated that BNP levels were independently associated with post‐discharge stroke (hazard ratio 2.636, 95% confidence interval 1.595–4.357, P < 0.001). The survival classification and regression tree analysis revealed that the accurate cut‐off point of BNP in predicting post‐discharge stroke was 187.7 pg/mL. We added high BNP level (BNP ≥ 180 pg/mL) as one point to CHADS₂ score. The BNP‐added CHADS₂ score was compared with CHADS₂ score alone by using c‐statistics. The areas under the curve of CHADS₂ score, BNP, and BNP‐added CHADS₂ score were 0.698, 0.616, and 0.723, respectively. The predictive value of BNP‐added CHADS₂ score was higher compared with those of CHADS₂ score (P = 0.026).

Conclusions

The assessment of BNP may predict the occurrence of stroke in CHF patients used alone or in combination with established CHADS₂ score.

Serum BNP Concentration and Left Ventricular Mass in CAPD and Automated Peritoneal Dialysis Patients

Objective

To compare ultrafiltration under continuous ambulatory peritoneal dialysis (CAPD) and automated PD (APD), disclosing potential effects on serum B-type natriuretic peptide (BNP) levels and echocardiographic findings.

Patients and Methods

This cross-sectional clinical study included 32 patients on CAPD and 30 patients on APD without clinical evidence of heart failure or hemodynamically significant valvular heart disease. Peritoneal equilibration tests, BNP levels, and echocardiographic measurements were performed in each subject. BNP measurements were also performed in 24 healthy control subjects.

Results

Patients on APD had lower ultrafiltration and higher values of BNP and left ventricular mass index (LVMI) compared with patients on CAPD (respectively: 775 ± 160 vs 850 ± 265 mL, p = 0.01; 253.23 ± 81.64 vs 109.42 ± 25.63 pg/mL, p = 0.001; 185.12 ± 63.50 vs 129.30 ± 40.95 g/m2, p = 0.001). This occurred despite higher mean dialysate glucose concentrations and far more extensive use of icodextrin in the APD group.

Conclusion

Treatment with APD is associated with higher plasma BNP levels and LVMI compared to CAPD. This may be the result of chronic fluid retention caused by lower ultra-filtration in APD patients.

The role of mechanotransduction in heart failure pathobiology-a concise review

This review evaluates the role of mechanotransduction (MT) in heart failure (HF) pathobiology. Cardiac functional and structural modifications are regulated by biomechanical forces. Exposing cardiomyocytes and the myocardial tissue to altered biomechanical stress precipitates changes in the end-diastolic wall stress (EDWS). Thereby various interconnected biomolecular pathways, essentially mediated and orchestrated by MT, are launched and jointly contribute to adapt and remodel the myocardium. This cardiac MT-mediated feedback decisively determines the primary cardiac cellular and tissue response, the sort (concentric or eccentric) of hypertrophy/remodeling, to mechanical and/or hemodynamic alterations. Moreover, the altered EDWS affects the diastolic myocardial properties independent of the systolic function, and elevated EDWS causes diastolic dysfunction. The close interconnection between MT pathways and the cell nucleus, the genetic endowment, principally allows for the wide variety of phenotypic appearances. However, demographic, environmental features, comorbidities, and also the genetic make-up may modulate the phenotypic result. Cardiac MT takes a fundamental and superordinate position in the myocardial adaptation and remodeling processes in all HF categories and phenotypes. Therefore, the effects of MT should be integrated in all our scientific, clinical, and therapeutic considerations.

Possible Mechanisms Underlying Elevated Serum N-Terminal Pro-Brain Natriuretic Peptide in Healthy Japanese Subjects

Background: The precise mechanisms underlying elevation of serum N-terminal pro-brain natriuretic peptide (NT-proBNP) in healthy subjects have not been fully clarified.

Methods and Results: In 2,844 Japanese healthy subjects with serum NT-proBNP <125 pg/mL, (1) brachial-ankle pulse wave velocity and (2) second peak of the peripheral systolic blood pressure minus diastolic blood pressure (pulse pressure 2 [PP2]), as markers of cardiac afterload; (3) fibrosis 4 score (FIB-4 score, a marker of liver fibrosis), as a marker of cardiac preload; and (4) ratio of the pre-ejection time to ejection time (PEP/ET), as a marker of cardiac systolic function, were measured. At the first examination, after the adjustments, log-transformed serum NT-proBNP was associated with PP2 and FIB-4 score, but not with PEP/ET. These parameters were successfully measured again after a 3-year interval in 1,978 subjects. On Pearson’s correlation analysis, change in PP2 and FIB-4 score during the study period was significantly correlated with change in serum NT-proBNP (r=0.05, 0.09, respectively; P<0.01).

Conclusions: In apparently healthy Japanese subjects, both increased cardiac preload and increased cardiac afterload, but not impaired cardiac systolic function, may be associated with elevated serum NT-proBNP.

Clinical Applications of Natriuretic Peptides in Heart Failure and Atrial Fibrillation

Natriuretic peptides (NPs) have become important diagnostic and prognostic biomarkers in cardiovascular diseases, particularly in heart failure (HF). Diagnosis and management of coronary artery disease and atrial fibrillation (AF) can also be guided by NP levels. When interpreting NP levels, however, the caveat is that age, sex, body mass index, renal dysfunction, and race affect the clearance of NPs, resulting in different cut-off values in clinical practice. In AF, NP levels have been associated with incident AF in the general population, recurrences after catheter ablation, prediction of clinical prognosis, and the risk of stroke. In this article, we first review and summarize the current evidence and the roles of B-type NP and atrial NP in HF and coronary artery disease and then focus on the increasing utility of NPs in the diagnosis and management of and the research into AF.

Prognostic impact of chronic obstructive pulmonary disease on adverse prognosis in hospitalized heart failure patients with preserved ejection fraction - A report from the JASPER registry

BACKGROUND

The prognostic impact of chronic obstructive pulmonary disease (COPD) on heart failure (HF) with preserved ejection fraction (HFpEF) patients and its clinical characteristics have not yet been fully examined.

METHODS

The Japanese Heart Failure Syndrome with Preserved Ejection Fraction (JASPER) registry is a nationwide, observational, prospective registration of consecutive Japanese hospitalized HFpEF patients with left ventricular ejection fraction (LVEF) of ≥50%. Among 535 patients enrolled in the registry, 10 lacking COPD data, and seven who died during the first hospitalization, were excluded. Finally, 518 patients were enrolled in this analysis. We divided these patients into two groups: the COPD group (n=40, 7.7%) and the non-COPD group (n=478, 92.3%). This analysis had two primary endpoints: (1) all-cause death and (2) all-cause death or rehospitalization for HF.

RESULTS

The COPD group showed a higher prevalence of male sex (70.0% vs. 48.1%, p=0.008), history of prior hospitalization for HF (63.2% vs. 35.1%, p=0.001), smoking history (71.8% vs. 43.3%, p=0.001), and a higher usage of loop diuretics (70.0% vs. 50.0%, p=0.015). In the follow-up period after discharge (median 733 days), there were 82 all-cause deaths and 127 rehospitalizations for HF. In the Kaplan-Meier analysis, the COPD group showed higher all-cause death and reached the composite endpoint more often than in the non-COPD group (all-cause death, log-rank 0.035; all-cause death or rehospitalization for HF, log-rank 0.025). In the Cox proportional hazard analysis, COPD was a predictor of all-cause death (hazard ratio 1.957, 95% confidence interval 1.037-3.694, p=0.038) and the composite endpoint (hazard ratio 1.694, 95% confidence interval 1.064-2.697, p=0.026).

CONCLUSIONS

COPD is associated with adverse prognosis in hospitalized patients with HFpEF.

Hyponatremia at discharge is associated with adverse prognosis in acute heart failure syndromes with preserved ejection fraction: a report from the JASPER registry

INTRODUCTION

Hyponatremia predicts adverse prognosis in patients with heart failure in particular with reduced ejection fraction. In contrast, it has recently been reported that hyponatremia on admission is not a predictor of post-discharge mortality in patients with heart failure with preserved ejection fraction. We investigated the prognostic impact of hyponatremia at discharge in patients with heart failure with preserved ejection fraction and its clinical characteristics.

METHODS AND RESULTS

The Japanese Heart Failure Syndrome with Preserved Ejection Fraction (JASPER) registry is a nationwide, observational, prospective registration of consecutive Japanese patients hospitalised with heart failure with preserved ejection fraction and left ventricular ejection fraction of 50% or greater. Five hundred consecutive patients were enrolled in this analysis. We divided the patients into two groups based on their sodium serum levels at discharge: hyponatremia group (sodium <135 mEq/L, n=50, 10.0%) and control group (sodium ⩾135 mEq/L, n=450, 90.0%). This present analysis had two primary endpoints: all-cause death and all-cause death or rehospitalisation for heart failure. At discharge, the hyponatremia group had lower systolic blood pressure (110.0 mmHg vs. 114.5 mmHg, P=0.014) and higher levels of urea nitrogen (31.9 mg/dL vs. 24.2 mg/dL, P=0.032). In the Kaplan-Meier analysis, more patients in the hyponatremia group reached the primary endpoints than those in the control group (log rank <0.01, respectively). In the Cox proportional hazard analysis, hyponatremia at discharge was a predictor of the two endpoints (all-cause death, hazard ratio 2.708, 95% confidence interval 1.557-4.708, P<0.001; all-cause death or rehospitalisation for heart failure, hazard ratio 1.829, 95% confidence interval 1.203-2.780, P=0.005).

CONCLUSIONS

Hyponatremia at discharge is associated with adverse prognosis in hospitalised patients with heart failure with preserved ejection fraction.

Involvement of brain natriuretic peptide signaling pathway in the cardioprotective action of sitagliptin

BACKGROUND

The current study is focusing on the role of brain natriuretic peptide (BNP), a substrate of dipeptidyl peptidase-4 (DPP-4) enzyme, and its signaling survival pathway in the cardioprotective mechanism of sitagliptin, a DPP-4 inhibitor.

METHODS

Male Wistar rats were randomized into 7 groups, sham, I/R, KT-5823 (selective protein kinase (PK) G inhibitor), 5-HD (selective mito-KATP channel blocker), sitagliptin (300mg/kg, po), sitagliptin+KT-5823, and sitagliptin+5-HD. Sitagliptin was administered for 3 days prior to induction of coronary I/R, while either KT-5823 or 5-HD was administered intravenously 5min before coronary ligation.

RESULTS

Pretreatment with sitagliptin provided significant protection against I/R injury as manifested by decreasing, percentage of infarct size, suppressing the elevated ST segment, reducing the increased cardiac enzymes, as well as DPP-4 activity and elevating both heart rate (HR) and left ventricular developed pressure (LVDP). However, the addition of either blocker to sitagliptin regimen reversed partly its cardioprotective effects. Although I/R increased BNP content, it unexpectedly decreased that of cGMP; nevertheless, sitagliptin elevated both parameters, an effect that was not affected by the use of the two blockers. On the molecular level, sitagliptin decreased caspase-3 activity and downregulated the mRNA levels of BNP, Bax, and Cyp D, while upregulated that of Bcl2. The use of either KT-5823 or 5-HD with sitagliptin hindered its effect on the molecular markers tested.

CONCLUSIONS

The results of the present study suggest that the cardioprotective effect of sitagliptin is mediated partly, but not solely, through the BNP/cGMP/PKG survival signaling pathway.

Mechanical stretch induced transcriptomic profiles in cardiac myocytes

Mechanical forces are able to activate hypertrophic growth of cardiomyocytes in the overloaded myocardium. However, the transcriptional profiles triggered by mechanical stretch in cardiac myocytes are not fully understood. Here, we performed the first genome-wide time series study of gene expression changes in stretched cultured neonatal rat ventricular myocytes (NRVM)s, resulting in 205, 579, 737, 621, and 1542 differentially expressed (>2-fold, P < 0.05) genes in response to 1, 4, 12, 24, and 48 hours of cyclic mechanical stretch. We used Ingenuity Pathway Analysis to predict functional pathways and upstream regulators of differentially expressed genes in order to identify regulatory networks that may lead to mechanical stretch induced hypertrophic growth of cardiomyocytes. We also performed micro (miRNA) expression profiling of stretched NRVMs, and identified that a total of 8 and 87 miRNAs were significantly (P < 0.05) altered by 1-12 and 24-48 hours of mechanical stretch, respectively. Finally, through integration of miRNA and mRNA data, we predicted the miRNAs that regulate mRNAs potentially leading to the hypertrophic growth induced by mechanical stretch. These analyses predicted nuclear factor-like 2 (Nrf2) and interferon regulatory transcription factors as well as the let-7 family of miRNAs as playing roles in the regulation of stretch-regulated genes in cardiomyocytes.

Hypoxia exposure and B-type natriuretic peptide release from Langendorff heart of rats

Aim

We studied whether available oxygen without induced mechanical stretch regulates the release of the biologically active B‐type natriuretic peptide (BNP) from Langendorff heart.

Methods

Rat hearts were isolated and perfused with a physiological Krebs–Henseleit solution at a constant hydrostatic pressure in Langendorff set‐up. The basal O₂ level of perfusate (24.4 ± 0.04 mg L⁻¹) was gradually lowered to 3.0 ± 0.01 mg L⁻¹ over 20 min using N₂ gas (n = 7). BNP and O₂ level were measured from coronary flow. During control perfusions (n = 5), the O₂ concentration was kept at 26.6 ± 0.3 mg L⁻¹.

Results

A low oxygen concentration in the perfusate was associated with a significant increase in BNP release (F = 40.4, P < 0.001). Heart rate decreased when the oxygen concentration in the perfusate reached 9.1 ± 0.02 mg L⁻¹ and continued to fall in lower oxygen concentrations (F = 14.8, P < 0.001). There was also a significant but inverse correlation between BNP and oxygen in the coronary flow (R² = 0.27, P < 0.001).

Conclusion

In the spontaneously beating Langendorff rat heart, a decreasing concentration of oxygen in the ingoing perfusion increased the secretion of BNP. The effect of oxygen was independent of mechanical stretch of the heart as it occurred even when the heart rate decreased but the pressure conditions remained constant. The difference in the oxygen capacitance of blood and Krebs–Henseleit solution appears to be a major factor affecting secretion of BNP, which is correlated with the oxygen tension of myocardial cells and affected both by the oxygen concentration and capacitance of solution perfusing the heart and by the coronary flow.

B-type natriuretic peptide levels normalise in preterm infants without a patent ductus arteriosus by the fifth postnatal day

AIM

Few published reports have established B-type natriuretic peptide (BNP) levels in preterm infants without a patent ductus arteriosus (PDA). This study addressed that gap in our knowledge by establishing a reference range for BNP levels during the first two weeks of life in preterm infants without a PDA.

METHODS

We enrolled 36 preterm infants between 24 and 32 weeks of gestation in this prospective, noninterventional study. Infants with a PDA, congenital heart disease, possible or confirmed sepsis and, or, meningitis, or perinatal depression requiring chest compressions were excluded. BNP levels were measured on postnatal days one, five, 10 and 15, with an echocardiogram on day five. Statistical analyses were performed using the ANOVA and Mann-Whitney U-tests.

RESULTS

BNP levels were significantly higher on day one than on days five, 10 and 15, and there was no statistical difference between days five, 10 and 15. The levels were not statistically different between infants of less than and greater than 29 weeks of gestation.

CONCLUSION

BNP levels were significantly elevated on postnatal day one in preterm infants without a PDA, but then decreased by day five and continued to stay low after that. Gestational age did not have an effect on BNP levels.

Brain natriuretic peptide: Much more than a biomarker

Brain natriuretic peptide (BNP) modulates several biological processes by activating the natriuretic peptide receptor A (NPR-A). Atria and ventricles secrete BNP. BNP increases natriuresis, diuresis and vasodilatation, thus resulting in a decreased cardiac workload. BNP and NT-proBNP, which is the biologically inactive N-terminal portion of its pro-hormone, are fast and sensitive biomarkers for diagnosing heart failure. The plasma concentrations of both BNP and NT-proBNP also correlate with left ventricular function in patients with acute exacerbation of COPD, even without history of heart failure. Several studies have been conducted in vitro and in vivo, both in animals and in humans, in order to assess the potential role of the NPR-A activation as a novel therapeutic approach for treating obstructive pulmonary disorders. Unfortunately, these studies have yielded conflicting results. Nevertheless, further recent specific studies, performed in ex vivo models of asthma and COPD, have confirmed the bronchorelaxant effect of BNP and its protective role against bronchial hyperresponsiveness in human airways. These studies have also clarified the intimate mechanism of action of BNP, represented by an autocrine loop elicited by the activation of NPR-A, localized on bronchial epithelium, and the relaxant response of the surrounding ASM, which does not expresses NPR-A. This review explores the teleological activities and paradoxical effects of BNP with regard to chronic obstructive respiratory disorders, and provides an excursus on the main scientific findings that explain why BNP should be considered much more than a biomarker.

Bone morphogenetic protein-2--a potential autocrine/paracrine factor in mediating the stretch activated B-type and atrial natriuretic peptide expression in cardiac myocytes

Hemodynamic overload exposes the heart to variety of neural, humoral and mechanical stresses. Even without the neurohumoral control of the entire organism cardiac myocytes have the ability to sense mechanical stretch and convert it into adaptive intracellular signals. This process is controlled by several growth factors. Here we show that mechanical stretch in vitro and hemodynamic overload in vivo activated the expression of bone morphogenetic protein-2 (BMP-2), while expression of BMP-4 was temporarily attenuated by stretch. BMP-2 and BMP-4 alone stimulated B-type and atrial natriuretic peptide (BNP and ANP) expression and protein synthesis, and activated transcription factor GATA-4 resembling the effects of mechanical stretch of cultured cardiac myocytes. Further, BMP antagonist Noggin was able to inhibit stretch and hypertrophic agonist induced BNP and ANP expression. Together these data provide evidence for BMP-2 as a new autocrine/paracrine factor that regulates cardiomyocyte mechanotransduction and adaptation to increased mechanical stretch.

Different implication of elevated B-type natriuretic peptide level in patients with heart failure with preserved ejection fraction and in those with reduced ejection fraction

BACKGROUND

There have been no reports that show significant direct relationship between echocardiographic parameters and B-type natriuretic peptide (BNP) level. This could be due to the heterogeneous pathophysiology of heart failure and a lack of appropriate echocardiographic parameters. We sought to determine the best echocardiographic parameter that described elevated BNP level in patients with heart failure with and without systolic dysfunction.

METHODS AND RESULTS

We studied 111 consecutive heart failure patients. They were divided into patients with heart failure and preserved ejection fraction (HFPEF, n = 61) and that with heart failure and reduced ejection fraction (HFREF, n = 50). Conventional and new echocardiographic parameters including myocardial strains were measured. BNP did not reflect any single echocardiographic parameter in patients with heart failure in total. The ratio of early diastolic transmitral flow velocity and mitral annular velocity had strong positive correlation with BNP level in the HFPEF group but not in the HFREF group. In the group of HFREF, global longitudinal and circumferential strains were positively correlated. Multivariate analysis revealed that predicted factors for BNP value in HFPEF and in HFREF were different.

CONCLUSION

High BNP level may indicate high filling pressure when ejection fraction is preserved and may indicate myocardial dysfunction when it is reduced.

B-type natriuretic peptide and C-reactive protein in the prediction of atrial fibrillation risk: the CHARGE-AF Consortium of community-based cohort studies

AIMS

B-type natriuretic peptide (BNP) and C-reactive protein (CRP) predict atrial fibrillation (AF) risk. However, their risk stratification abilities in the broad community remain uncertain. We sought to improve risk stratification for AF using biomarker information.

METHODS AND RESULTS

We ascertained AF incidence in 18 556 Whites and African Americans from the Atherosclerosis Risk in Communities Study (ARIC, n=10 675), Cardiovascular Health Study (CHS, n = 5043), and Framingham Heart Study (FHS, n = 2838), followed for 5 years (prediction horizon). We added BNP (ARIC/CHS: N-terminal pro-B-type natriuretic peptide; FHS: BNP), CRP, or both to a previously reported AF risk score, and assessed model calibration and predictive ability [C-statistic, integrated discrimination improvement (IDI), and net reclassification improvement (NRI)]. We replicated models in two independent European cohorts: Age, Gene/Environment Susceptibility Reykjavik Study (AGES), n = 4467; Rotterdam Study (RS), n = 3203. B-type natriuretic peptide and CRP were significantly associated with AF incidence (n = 1186): hazard ratio per 1-SD ln-transformed biomarker 1.66 [95% confidence interval (CI), 1.56-1.76], P < 0.0001 and 1.18 (95% CI, 1.11-1.25), P < 0.0001, respectively. Model calibration was sufficient (BNP, χ(2) = 17.0; CRP, χ(2) = 10.5; BNP and CRP, χ(2) = 13.1). B-type natriuretic peptide improved the C-statistic from 0.765 to 0.790, yielded an IDI of 0.027 (95% CI, 0.022-0.032), a relative IDI of 41.5%, and a continuous NRI of 0.389 (95% CI, 0.322-0.455). The predictive ability of CRP was limited (C-statistic increment 0.003). B-type natriuretic peptide consistently improved prediction in AGES and RS.

CONCLUSION

B-type natriuretic peptide, not CRP, substantially improved AF risk prediction beyond clinical factors in an independently replicated, heterogeneous population. B-type natriuretic peptide may serve as a benchmark to evaluate novel putative AF risk biomarkers.

Quercetin inhibits left ventricular hypertrophy in spontaneously hypertensive rats and inhibits angiotensin II-induced H9C2 cells hypertrophy by enhancing PPAR-γ expression and suppressing AP-1 activity

BACKGROUND

Quercetin is the most abundant flavonoid in fruit and vegetables and is believed to attenuate cardiovascular disease. We hypothesized that quercetin inhibits cardiac hypertrophy by blocking AP-1 (c-fos, c-jun) and activating PPAR-γ signaling pathways.

METHODOLOGY/PRINCIPAL FINDINGS

The aim of this study was to identify the mechanism underlying quercetin-mediated attenuation of cardiac hypertrophy. Quercetin therapy reduced blood pressure and markedly reduced the ratio of left ventricular to body weight (LVW/BW) (P<0.05, vs. spontaneously hypertensive rats (SHRs)). In vitro, quercetin also significantly attenuated Ang II-induced H9C2 cells hypertrophy, as indicated by its concentration dependent inhibitory effects on [³H]leucine incorporation into H9C2 cells (64% reduction) and by the reduced hypertrophic surface area in H9C2 cells compared with the Ang II group (P<0.01, vs. Ang II group). Concurrently, we found that PPAR-γ activity was significantly increased in the quercetin-treated group both in vivo and in vitro when analyzed using immunofluorescent or immunohistochemical assays (P<0.05, vs. SHRs or P<0.01, vs. the Ang II group). Conversely, in vivo, AP-1 (c-fos, s-jun) activation was suppressed in the quercetin-treated group, as was the downstream hypertrophy gene, including mRNA levels of ANP and BNP (P<0.05, vs. SHRs). Additionally, both western blotting and real time-PCR demonstrated that PPAR-γ protein and mRNA were increased in the myocardium and AP-1 protein and mRNA were significantly decreased in the quercetin-treated group (P<0.05, vs. SHRs). Furthermore, western blotting and real time-PCR analyses also showed that transfection with PPAR-γ siRNA significantly increased AP-1 signaling and reversed the effects of quercetin inhibition on mRNA expression levels of genes such as ANP and BNP in hypertrophic H9C2 cells.

CONCLUSIONS

Our data indicate that quercetin may inhibit cardiac hypertrophy by enhancing PPAR-γ expression and by suppressing the AP-1 signaling pathway.

Role of B-type natriuretic peptide as a marker of mortality in acute kidney injury patients treated with continuous renal replacement therapy

OBJECTIVES

Acute kidney injury (AKI) treated with continuous renal replacement therapy (CRRT) is associated with poor outcome. Plasma B-type natriuretic peptide (BNP) is a biomarker related to fluid volume overload, and is elevated in AKI patients. The purpose of the study was to assess whether BNP levels at the time of starting CRRT could be used as a predictor of mortality in patients with AKI receiving CRRT.

METHODS

We conducted a prospective observational cohort study enrolling 149 patients with AKI receiving CRRT. The primary outcome was mortality during CRRT.

RESULTS

The median BNP level of 84 (56.3%) patients who expired was significantly higher than that of those who survived (1812.5 vs. 475.0 pg/mL; p = 0.01). Receiver operating characteristic curves demonstrated BNP levels as a predictor of mortality during CRRT with an area under the curve of 0.77 (p = 0.000), and the optimal threshold for BNP was 1054 pg/mL. Patients with BNP levels above 1054 pg/mL had a significantly higher mortality (76.6 vs. 34.7%; p = 0.01).

CONCLUSION

Elevated BNP level is associated with mortality in patients with AKI receiving CRRT.

N-terminal pro-B-type natriuretic peptide, left ventricular mass, and incident heart failure: Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Elevated N-terminal pro-B-type natriuretic peptide (NT-proBNP) is associated with clinically overt heart failure (HF). However, whether it provides additive prognostic information for incident HF beyond traditional risk factors and left ventricular (LV) mass index among multi-ethnic asymptomatic individuals has not yet been determined. We studied the associations of plasma NT-proBNP and magnetic resonance imaging defined LV mass index with incident HF in an asymptomatic multi-ethnic population.

METHODS AND RESULTS

A total of 5597 multi-ethnic participants without clinically apparent cardiovascular disease underwent baseline measurement of NT-proBNP and were followed for 5.5±1.1 years. Among them, 4163 also underwent baseline cardiac magnetic resonance imaging. During follow-up, 111 participants experienced incident HF. Higher NT-proBNP was significantly associated with incident HF, independent of baseline age, sex, ethnicity, systolic blood pressure, diabetes mellitus, smoking, estimated glomerular filtration rate, medications (anti-hypertensive and statin), LV mass index, and interim myocardial infarction (hazard ratio: 1.95 per 1U log NT-proBNP increment, 95% CI 1.54-2.46, P<0.001). This relationship held among different ethnic groups, non-Hispanic whites, African-Americans, and Hispanics. Most importantly, NT-proBNP provided additive prognostic value beyond both traditional risk factors and LV mass index for predicting incident HF (integrated discrimination index=0.046, P<0.001; net reclassification index; 6-year risk probability categorized by <3%, 3-10%, >10% =0.175, P=0.019; category-less net reclassification index=0.561, P<0.001).

CONCLUSIONS

Plasma NT-proBNP provides incremental prognostic information beyond traditional risk factors and the magnetic resonance imaging-determined LV mass index for incident symptomatic HF in an asymptomatic multi-ethnic population.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00005487.

M-CAT element mediates mechanical stretch-activated transcription of B-type natriuretic peptide via ERK activation

The muscle-CAT (M-CAT) promoter element is found on promoters of most muscle-specific cardiac genes, but its role in cardiac pathology is poorly understood. Here we studied whether the M-CAT element is involved in hypertrophic process activated by mechanical stretch, and identified the intracellular pathways mediating the response. When an in vitro stretch model of cultured neonatal rat cardiomyocytes and luciferase reporter construct driven by rat B-type natriuretic peptide (BNP) promoter were used, mutation of M-CAT element inhibited not only the basal reporter activity (88%), but also the stretch-activated BNP transcription (58%, p < 0.001). Stretch-induced BNP promoter activation was associated with an increase in transcriptional enhancer factor-1 (TEF-1) binding activity after 24 h mechanical stretch (p < 0.05). Inhibition of mitogen-activated protein kinases ERK, JNK, or p38 attenuated stretch-induced BNP activation. Interestingly, as opposed to p38 and JNK, inhibition of ERK had no additional effect on transcriptional activity of BNP promoter harboring the M-CAT mutation, suggesting a pivotal role for ERK in regulating stretch-induced BNP transcription via M-CAT binding site. Finally, immunoprecipitation studies showed that mechanical stretch induced myocyte enhancer factor-2 (MEF-2) binding to TEF-1. These data suggest a central role for M-CAT element in regulation of mechanical stretch-induced hypertrophic response via ERK activation.

NT-ProBNP levels, water and sodium homeostasis in healthy men: effects of 7 days of dry immersion

Immersion is a useful tool for studying fluid-volume homeostasis. Natriuretic peptides play a vital role in renal, humoral, and cardiovascular regulation under changing environmental conditions. We hypothesized that dry immersion would rapidly induce a new steady state for water and sodium metabolism, and that serum NT-proBNP levels, a proxy measure for brain natriuretic peptide (BNP), would decrease during long-term dry immersion and increase during recovery. Eight healthy young men were studied before, during, and after 7 days of dry immersion. Body weight, water balance, and plasma volume changes were evaluated. Plasma and serum samples were analyzed for active renin, NT-proBNP, aldosterone, electrolytes, osmolality, total protein, and creatinine. Urine samples were analyzed to determine levels of electrolytes, osmolality, creatinine, and free cortisol. A stand test was performed before and after dry immersion to evaluate cardiovascular deconditioning. Long-term dry immersion induced acute changes in water and sodium homeostasis on day 1, followed by a new steady state. Plasma volume decreased significantly during dry immersion. The serum levels of NT-proBNP increased significantly in recovery (10 ± 3 ng/L before dry immersion vs. 26 ± 5 ng/L on the fourth recovery day). Heart rate in the standing position was significantly greater after immersion. Results suggest that chronic dry immersion rapidly induced a new level of water-electrolyte homeostasis. The increase in NT-proBNP levels during the recovery period may be related to greater cardiac work and might reflect the degree of cardiovascular deconditioning.

Upregulation of ANP and NPR-C mRNA in the kidney and heart of eNOS knockout mice

OBJECTIVES

The aim of the present studywas to examine the question of whether the atrial natriuretic peptide (ANP) system is altered by endothelial nitric-oxide synthase (eNOS).

METHODS

Male eNOS-deficient mice (eNOS-/-) and wild type control mice (eNOS+/+, C57B1/6J) were used. Blood pressure was measured in anesthetized mice by tail cuff plethysmography and renal function was measured. Expression of ANP, natriuretic peptide receptor (NPR)-A, NPR-C, and tonicity-responsive enhancer binding protein (TonEBP) mRNA was determined by real-time PCR. Localization of (125)I-ANP binding sites was measured using in vitro autoradiography.

RESULTS

In eNOS-/- mice, systolic blood pressure increased and left ventricular hypertrophy was observed. Urine volume and osmolarity did not change. Expression of ANP markedly increased in the heart and kidney of eNOS-/- mice. Expression of NPR-A and NPR-C increased in the heart and tended to increase in the kidney of eNOS-/- mice. In the renal medulla in particular, increased expression of NPR-C was more prominent. Expression of TonEBP mRNA was markedly decreased in the renal medulla, but not in the renal cortex. Maximum binding capacity (B(max)) of ANP and C-ANP increased in the renal medulla in eNOS-/- mice.

CONCLUSION

These results suggest that the eNOS-NO system may be partly involved in regulation of ANP, NPR-A, -C, and TonEBP mRNA expression in the kidney.

The mixed-lineage kinase 1-3 signalling pathway regulates stress response in cardiac myocytes via GATA-4 and AP-1 transcription factors

BACKGROUND AND PURPOSE

The mixed-lineage kinases (MLKs) act upstream of mitogen-activated protein kinases, but their role in cardiac biology and pathology is largely unknown.

EXPERIMENTAL APPROACH

We investigated the effect of a MLK1-3 inhibitor CEP-11004 on G protein-coupled receptor agonist-induced stress response in neonatal rat cardiac myocytes in culture.

KEY RESULTS

CEP-11004 administration dose-dependently attenuated phenylephrine and endothelin-1 (ET-1)-induced c-Jun N-terminal kinase activation. MLK inhibition also reduced ET-1- and phenylephrine-induced phosphorylation of p38 mitogen-activated protein kinase. In contrast, phenylephrine-induced extracellular signal-regulated kinase phosphorylation was further up-regulated by CEP-11004. ET-1 increased activator protein-1 binding activity 3.5-fold and GATA-binding protein 4 (GATA-4) binding activity 1.8-fold, both of which were attenuated with CEP-11004 administration by 59% and 63% respectively. Phenylephrine induced activator protein-1 binding activity by 2.6-fold, which was decreased by 81% with CEP-11004 administration. Phenylephrine also induced a 3.7-fold increase in the transcriptional activity of B-type natriuretic peptide (BNP), which was attenuated by 41% with CEP-11004 administration. In agreement, MLK inhibition also reduced hypertrophic agonist-induced secretion of immunoreactive atrial natriuretic peptide and BNP.

CONCLUSIONS AND IMPLICATIONS

These results showed that inhibition of the MLK1-3 signalling pathway was sufficient for suppressing the activity of key nuclear effectors (GATA-4 and activator protein-1 transcription factors) in cardiac hypertrophy, and attenuated the agonist-induced atrial natriuretic peptide secretion and activation of BNP gene transcription.

Epigenetic control of cardiomyocyte production in response to a stress during the medaka heart development

The size and morphology of organs are largely determined by a genetic program. However in some cases, an epigenetic mechanism influences the process of organ development. Particularly, epigenetic factors such as hemodynamic stress and blood pressure affect the morphogenesis of cardiac chambers and valves. Here, we report that the epigenetic influences affect the cardiomyocyte production. Taking advantage of longer developmental period of medaka fish, we could examine the later emerging tissue responses to the defect of ventricular beating, which occurred in the hozuki (hoz) mutant that harbors the mutated ventricular myosin heavy chain (vmhc) gene. The mutant showed a remarkable ventricular enlargement, and we showed that this enlargement was due to an excess production of ventricular cardiomyocytes in addition to the lack of concentric chamber growth. By experimental blockade of blood flow, we demonstrated that an elevated cardiac pressure was responsible for the aberrant cardiomyocyte production. From these data, we propose that the epigenetic tissue response to a stressed situation controls the production of cardiomyocytes to attain a fine tuning of heart formation.

Early left ventricular gene expression profile in response to increase in blood pressure

The heart adapts to increased pressure overload by hypertrophic growth of terminally differentiated cardiomyocytes. At the genetic level, the hypertrophic response is characterized by the reprogramming of gene expression, i.e. upregulation of immediate early genes, natriuretic peptide genes and genes encoding structural proteins. In the present study, we characterized the early changes in gene expression with cDNA expression arrays in response to increase in blood pressure produced by arginine8-vasopressin infusion (0.05 microg/kg/min, i.v.) for 30 min and 4 h in conscious normotensive rats. Expression profiling revealed differential expression of 14 genes in the left ventricle, and several novel factors of immediate early genetic response to pressure overload were identified, such as growth arrest and DNA damage inducible protein 45 (GADD45alpha), epidermal fatty acid-binding protein (E-FABP) and Bcl-X. Administration of angiotensin II (Ang II) for 6 h by osmotic minipumps also increased left ventricular GADD45alpha, E-FABP and Bcl-X gene expression. Furthermore, the induction of GADD45alpha and Bcl-X gene expression by Ang II was blocked by angiotensin II type 1 receptor antagonist losartan. In summary, our analysis provided new insights into the pathogenesis of pressure overload-induced hypertrophy by suggesting the existence of novel regulators of the immediate early gene expression program.

Osmoregulation of natriuretic peptide receptors in bromoethylamine-treated rat kidney

Extracellular osmolarity is known as an important factor for the regulation of natriuretic peptide receptors (NPRs). We investigated the intra-renal osmoregulation of NPRs using renal medullectomized rats with bromoethylamine hydrobromide (BEA, 200mg/kg). The administration of BEA caused the decreased food intake and body weight. Water intake was decreased on the first day and then increased from the second day. Urine volume was persistently increased from the first day and free water clearance was also increased from the second day. Urinary excretions of sodium and potassium were decreased on the second day and then recovered to control level. Plasma levels of atrial natriuretic peptide (ANP) and Dendroaspis natriuretic peptide (DNP) in BEA-treated rats were not different from control rats. The inactive renin was increased. The maximum binding capacities of (125)I-ANP as well as (125)I-DNP decreased in glomeruli and medulla of BEA-treated rat kidneys but the binding affinity was not changed. In renal cortex, the gene expressions of ANP, NPR-A, and NPR-B were not changed but that of NPR-C decreased. In renal medulla, the gene expressions of NPR-A, -B, and -C decreased without change in ANP mRNA. Both renal medullary osmolarity and sodium concentration by BEA treatment were lower than those in control kidney. The cGMP concentrations in renal medulla and urine in BEA-treated rats were higher than those in control rats. These results suggest that the increased cGMP production may be partly involved in the decrease in NPRs mRNA expression and their binding capacities by BEA-induced medullectomy.

Role of B-type natriuretic peptide in epoxyeicosatrienoic acid-mediated improved post-ischaemic recovery of heart contractile function

AIMS

This study examined the functional role of B-type natriuretic peptide (BNP) in epoxyeicosatrienoic acid (EET)-mediated cardioprotection in mice with targeted disruption of the sEH or Ephx2 gene (sEH null).

METHODS AND RESULTS

Isolated mouse hearts were perfused in the Langendorff mode and subjected to global no-flow ischaemia followed by reperfusion. Hearts were analysed for recovery of left ventricular developed pressure (LVDP), mRNA levels, and protein expression. Naïve hearts from sEH null mice had similar expression of preproBNP (Nppb) mRNA compared with wild-type (WT) hearts. However, significant increases in Nppb mRNA and BNP protein expression occurred during post-ischaemic reperfusion and correlated with improved post-ischaemic recovery of LVDP. Perfusion with the putative EET receptor antagonist 14,15-epoxyeicosa-5(Z)-enoic acid prior to ischaemia reduced the preproBNP mRNA in sEH null hearts. Inhibitor studies demonstrated that perfusion with the natriuretic peptide receptor type-A (NPR-A) antagonist, A71915, limited the improved recovery in recombinant full-length mouse BNP (rBNP)- and 11,12-EET-perfused hearts as well as in sEH null mice. Increased expression of phosphorylated protein kinase C epsilon and Akt were found in WT hearts perfused with either 11,12-EET or rBNP, while mitochondrial glycogen synthase kinase-3beta was significantly lower in the same samples. Furthermore, treatment with the phosphoinositide 3-kinase (PI3K) inhibitor wortmannin abolished improved LVDP recovery in 11,12-EET-treated hearts but not did significantly inhibit recovery of rBNP-treated hearts.

CONCLUSION

Taken together, these data indicate that EET-mediated cardioprotection involves BNP and PI3K signalling events.

Responses of the trout cardiac natriuretic peptide system to manipulation of salt and water balance

Natriuretic peptides (NPs) are evolutionarily conserved hormones that affect blood pressure and fluid volume through membrane-bound guanylate cyclase (GC)-linked natriuretic peptide receptors-A and -B (NPR-A and NPR-B, respectively) in a variety of vascular, renal, and other tissues. The principal physiological stimulus for cardiac NPs in fish is somewhat debated between two prominent theories: regulation of salt balance (osmoregulatory hypothesis) or prevention of volume expansion (cardioprotective hypothesis). In the present study, we examined atrial and ventricular expression of trout NPs, atrial (ANP), brain (BNP), and ventricular (VNP) using Northern (mRNA), Western (NP pro-hormone), and qPCR (GC-NPR-A and -B mRNA) blot analysis following independent manipulation of plasma salt and volume levels after chronic exposure to freshwater (FW; volume loaded, salt depleted), saltwater (SW; volume depleted, salt loaded), or freshwater trout fed a high-salt diet (FW-HSD; volume and salt loaded). We also measured NP transcriptional response to acute (2 h) volume expansion with dialyzed plasma (VE; 80% blood vol) or volume depletion by hemorrhage (VD, 20% blood volume every 30 min for 2 h) with real-time PCR. In essentially all instances, increased expression of the NP system was associated with FW-HSD or plasma expansion. There were no differences in NP expression between chronically adapted FW and SW fish, and hemorrhage decreased atrial ANP and VNP mRNA. These results indicate that rainbow trout cardiac NPs and cardiovascular GC-NPRs respond principally to volume, not salt overload, and this suggests that the primary function of trout cardiac NP system is to protect the heart.

B-type natriuretic peptide and wall stress in dilated human heart

Background Although B-type natriuretic peptide (BNP) is used as complimentary diagnostic tool in patients with unknown thoracic disorders, many other factors appear to trigger its release. In particular, it remains unresolved to what extent cellular stretch or wall stress of the whole heart contributes to enhanced serum BNP concentration. Wall stress cannot be determined directly, but has to be calculated from wall volume, cavity volume and intraventricular pressure of the heart. The hypothesis was, therefore, addressed that wall stress as determined by cardiac magnetic resonance imaging (CMR) is the major determinant of serum BNP in patients with a varying degree of left ventricular dilatation or dysfunction (LVD). Methods A thick-walled sphere model based on volumetric analysis of the LV using CMR was compared with an echocardiography-based approach to calculate LV wall stress in 39 patients with LVD and 21 controls. Serum BNP was used as in vivo marker of a putatively raised wall stress. Nomograms of isostress lines were established to assess the extent of load reduction that is necessary to restore normal wall stress and related biochemical events. Results Both enddiastolic and endsystolic LV wall stress were correlated with the enddiastolic LV volume (r = 0.54, P < 0.001; r = 0.81, P < 0.001). LV enddiastolic wall stress was related to pulmonary pressure (capillary: r = 0.69, P < 0.001; artery: r = 0.67, P < 0.001). Although LV growth was correlated with the enddiastolic and endsystolic volume (r = 0.73, P < 0.001; r = 0.70, P < 0.001), patients with LVD exhibited increased LV wall stress indicating an inadequately enhanced LV growth. Both enddiastolic (P < 0.05) and endsystolic (P < 0.01) wall stress were increased in patients with increased BNP. In turn, BNP concentration was elevated in individuals with increased enddiastolic wall stress (>8 kPa: 587 +/- 648 pg/ml, P < 0.05; >12 kPa: 715 +/- 661 pg/ml, P < 0.001; normal < or =4 kPa: 124 +/- 203 pg/ml). Analysis of variance revealed LV enddiastolic wall stress as the only independent hemodynamic parameter influencing BNP (P < 0.01). Using nomograms with "isostress" curves, the extent of load reduction required for restoring normal LV wall stress was assessed. Compared with the CMR-based volumetric analysis for wall stress calculation, the echocardiography based approach underestimated LV wall stress particularly of dilated hearts. Conclusions In patients with LVD, serum BNP was increased over the whole range of stress values which were the only hemodynamic predictors. Cellular stretch appears to be a major trigger for BNP release. Biochemical mechanisms need to be explored which appear to operate over this wide range of wall stress values. It is concluded that the diagnostic use of BNP should primarily be directed to assess ventricular wall stress rather than the extent of functional ventricular impairment in LVD.

Natriuretic peptides in vascular physiology and pathology

Four major natriuretic peptides have been isolated: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), C-type natriuretic peptide (CNP), and Dendroaspis-type natriuretic peptide (DNP). Natriuretic peptides play an important role in the regulation of cardiovascular homeostasis maintaining blood pressure and extracellular fluid volume. The classical endocrine effects of natriuretic peptides to modulate fluid and electrolyte balance and vascular smooth muscle tone are complemented by autocrine and paracrine actions that include regulation of coronary blood flow and, therefore, myocardial perfusion; modulation of proliferative responses during myocardial and vascular remodeling; and cytoprotective anti-ischemic effects. The actions of natriuretic peptides are mediated by the specific binding of these peptides to three cell surface receptors: type A natriuretic peptide receptor (NPR-A), type B natriuretic peptide receptor (NPR-B), and type C natriuretic peptide receptor (NPR-C). NPR-A and NPR-B are guanylyl cyclase receptors that increase intracellular cGMP concentration and activate cGMP-dependent protein kinases. NPR-C has been presented as a clearance receptor and its activation also results in inhibition of adenylyl cyclase activity. The wide range of effects of natriuretic peptides might be the base for the development of new therapeutic strategies of great benefit in patients with cardiovascular problems including coronary artery disease or heart failure. This review summarizes current literature concerning natriuretic peptides, their receptors and their effects on fluid/electrolyte balance, and vascular and cardiac physiology and pathology, including primary hypertension and myocardial infarction. In addition, we will attempt to provide an update on important issues regarding natriuretic peptides in congestive heart failure.

Cardiac BNP gene activation by angiotensin II in vivo

The transcription factors involved in the activation of cardiac gene expression by angiotensin II (Ang II) in vivo are not well understood. Here we studied the contribution of transcriptional elements to the activation of the cardiac B-type natriuretic peptide (BNP) gene promoter by Ang II in conscious rats and in angiotensin II type 1 receptor (AT1R) transgenic mice. Rat BNP luciferase reporter gene constructs were injected into the left ventricular wall. The mean luciferase activity was 1.8-fold higher (P<0.05) in the ventricles of animals subjected to 2-week Ang II infusion as compared with vehicle infusion. Our results indicate that GATA binding sites at -90 and -81 in the rat BNP promoter are essential for the in vivo response to Ang II. The GATA factor binding to these sites is GATA-4. BNP mRNA levels and GATA-4 binding activity are also increased in the hypertrophied hearts of aged AT1R transgenic mice.

Calcium-calmodulin kinase II is the common factor in calcium-dependent cardiac expression and secretion of A- and B-type natriuretic peptides

Peptides derived from the precursor of A- and B-type natriuretic peptides (ANP and BNP) are powerful clinical markers of cardiac hypertrophy and dysfunction. It is known that many stimuli affecting the intracellular calcium concentration also induce ANP and BNP secretion. It was our intention to study the mechanisms by which calcium regulates the secretion of ANP and BNP. The effects of pacing and calcium-calmodulin kinase II activity on natriuretic peptide secretion were studied in isolated perfused rat atria and cultured rat neonatal cardiomyocytes. In isolated rat atrium pacing induced an increase in diastolic, systolic, and averaged intracellular free calcium concentration and a frequency-dependent increase in the secretion of both ANP and BNP. The molar ratio of the secreted natriuretic peptides (ANP to BNP) remained nearly constant ( approximately 1000) at all the pacing frequencies tested (1, 3, 6, and 8 Hz). Calmodulin kinase II inhibitor KN-93 (3 mum) did not affect intracellular free calcium concentration but showed a frequency-dependent inhibitory effect on ANP and BNP secretion without a change in ANP to BNP ratio. In the neonatal cardiomyocytes, KN-93 (3 mum) suppressed the secretion and gene expression of both ANP and BNP. Overexpression of constitutively active (T286D) or nuclear (delta(B)) calcium-calmodulin kinase II induced an increase in ANP and BNP gene expression. The results indicate that the calcium-dependent secretion and gene expression of A- and B-type natriuretic peptides are similarly regulated by calmodulin kinase II-dependent mechanisms. This is a plausible mechanism contributing to exercise-induced natriuretic peptide secretion and the augmented secretion in heart dysfunction due to impaired calcium handling.

Cardiovascular hemodynamics and umbilical artery N-terminal peptide of proB-type natriuretic peptide in human fetuses with growth restriction

OBJECTIVE

To test our hypothesis that human fetal N-terminal peptide of proB-type natriuretic peptide (NT-proBNP) secretion is increased in proportion to the severity of fetal cardiovascular compromise in intrauterine growth restriction.

METHODS

This prospective cross-sectional study consisted of 42 growth-restricted fetuses who underwent Doppler ultrasonographic examination of cardiovascular hemodynamics within 7 days before delivery. Group 1 fetuses (n = 13) had normal umbilical artery (UA) velocimetry. Group 2 fetuses (n = 15) had abnormal UA and normal ductus venosus (DV) velocimetry. In Group 3 fetuses (n = 14), both UA and DV velocimetries were abnormal. At delivery, an UA blood sample was obtained for assessment of NT-proBNP. Normal values for UA NT-proBNP were determined in 49 neonates (control group) with uncomplicated pregnancy and delivery.

RESULTS

Group 3 fetuses demonstrated greater (P < 0.05) UA and descending aorta pulsatility indices (PIs) and greater DV, left hepatic vein (LHV) and inferior vena cava PIs for veins (PIVs) than fetuses in Groups 1 and 2. Weight-indexed cardiac outputs and ventricular ejection forces were similar among the groups. Group 3 fetuses had higher (P < 0.05) UA NT-proBNP concentration than fetuses in Groups 1 and 2. In the control group, the 95(th) percentile value of UA NT-proBNP was 518 pmol/L. In Group 3, 13/14 neonates demonstrated abnormal UA NT-proBNP levels. The corresponding incidences were 4/13 and 7/15 in Groups 1 and 2. Significant positive correlations were found between UA, DV and LHV PIVs and UA NT-proBNP concentrations.

CONCLUSION

In human fetal growth restriction, increased cardiac afterload and pulsatility in DV blood velocity waveform pattern are associated with elevated UA NT-proBNP concentrations.

Reduction of N terminal-pro-brain (B-type) natriuretic peptide levels with exercise-based cardiac rehabilitation in patients with left ventricular dysfunction after myocardial infarction

INTRODUCTION

N-terminal-pro-brain (B-type) natriuretic peptide (NT-pro-BNP) is a peptide hormone released from ventricles in response to myocyte stretch. The aim of the study was to investigate the influence of exercise training on plasma NT-pro-BNP to verify if this parameter could be used as a biological marker of left ventricular remodelling in myocardial infarction patients undergoing an exercise training programme.

METHODS

Forty-four patients after myocardial infarction were enrolled into a cardiac rehabilitation programme, and were randomized in two groups of 22 patients each. Group A patients followed a 3-month exercise training programme, while group B patients received only routine recommendations. All patients underwent NT-pro-BNP assay, and cardiopulmonary exercise test before hospital discharge and after 3 months.

RESULTS

In Group A, exercise training reduced NT-pro-BNP levels (from 1498+/-438 to 470+/-375 pg/ml, P=0.0026), increased maximal (VO2peak+4.3+/-2.9 ml/kg per min, P<0.001; Powermax+38+/-7, P<0.001) exercise parameters and work efficiency (Powermax/VO2peak+1.3+/-0.4 Power/ml per kg per min, P<0.001); there was also an inverse correlation between changes in NT-pro-BNP levels and in VO2peak (r=-0.72, P<0.001), E-wave (r=-0.51, P<0.001) and E/A ratio (r=0.59, P<0.001). In group B, at 3 months, no changes were observed in NT-pro-BNP levels, exercise and echocardiographic parameters.

CONCLUSION

Three months exercise training in patients with moderate left ventricular systolic dysfunction after myocardial infarction induced a reduction in NT-pro-BNP levels, an improvement of exercise capacity and early left ventricular diastolic filling, without negative left ventricular remodelling. Whether the reduction of NT-pro-BNP levels could be useful as a surrogate marker of favourable left ventricular remodelling at a later follow-up remains to be further explored.

Endothelin-1 and angiotensin II contribute to BNP but not c-fos gene expression response to elevated load in isolated mice hearts

The early events in the cardiac hypertrophic process induced by hemodynamic load include activation of B-type natriuretic peptide (BNP) and c-fos gene expression. However, it is unknown whether stretch acts directly or through local paracrine factors to trigger changes in cardiac gene expression. Herein we studied the involvement of endothelin-1 (ET-1) and angiotensin II (Ang II) in load-induced activation of left ventricular BNP and c-fos gene expression using an in vitro stretch model in isolated perfused adult mice hearts. Two-hour stretch induced by increasing coronary flow rate from 2 to 5 ml/min increased the expression of BNP and c-fos genes by 1.9- and 1.5-fold, respectively (P<0.001 and P<0.05). A mixed ET(A/B) receptor antagonist bosentan attenuated the BNP gene expression response to load by 58% (P<0.005). A similar 53% inhibition was observed with the selective ET(A) receptor blocker BQ-123 (P<0.05). Type 1 Ang II receptor antagonist CV-11974 decreased the activation of BNP gene expression by 50% (P<0.05). In contrast, the activation of c-fos gene expression was not inhibited by antagonists of ET(A/B) and AT(1) receptors. Our results show that ET-1 and Ang II play a key role in the induction of BNP, but not c-fos gene expression in response to load in intact adult murine hearts.

Fetal cardiac natriuretic peptide expression and cardiovascular hemodynamics in endotoxin-induced acute cardiac dysfunction in mouse

We hypothesized that, in acute endotoxin-induced fetal cardiac dysfunction, atrial (ANP) and B-type (BNP) natriuretic peptide mRNA expressions are increased in proportion to the severity of fetal cardiovascular compromise in mouse. To investigate in vitro the effect of endotoxin-induced inflammation on cardiac natriuretic peptide expression, fetal hearts were harvested at 15-16 d of gestation and incubated for 6 h with lipopolysaccharide (LPS). To examine the relationship between fetal cardiovascular compromise and cardiac natriuretic peptide expression in endotoxin-induced cardiac dysfunction in the in vivo model, fetuses received intra-amniotically 25 microL LPS (10 microg/mL) or 25 microL of 0.9% saline. Fetal Doppler ultrasonography was performed before and six hours after the injections. In in vitro cultured fetal hearts, LPS induced the production of proinflammatory cytokines without affecting the basal expressions of natriuretic peptides. In the in vivo model, Doppler ultrasonography revealed severe cardiac dysfunction after LPS injection. No significant changes in ANP or atrial BNP mRNA were found. The fetal ventricular BNP mRNA levels were about 2.6-fold in the LPS group compared with the control group. Decreased fetal cardiac outflow mean velocity, increased proportion of isovolumetric contraction time of the cardiac cycle, and increased pulsatility indices of the descending aorta and inferior vena cava were related to elevated ventricular BNP mRNA levels. Our results show that LPS did not increase the mRNA expression of natriuretic peptides in cultured fetal hearts. In contrast, fetal ventricular BNP gene expression was increased in proportion to the severity of the hemodynamic compromise in vivo.

B-type natriuretic peptide strongly reflects diastolic wall stress in patients with chronic heart failure: comparison between systolic and diastolic heart failure

OBJECTIVES

We explored the stimulus for B-type natriuretic peptide (BNP) secretion in the clinical setting of heart failure (HF).

BACKGROUND

Increasingly, plasma BNP levels are being incorporated into the clinical assessment and management of systolic heart failure (SHF) as well as diastolic heart failure (DHF). However, heterogeneity in BNP levels among individuals with HF can cause some confusion in interpreting results.

METHODS

In 160 consecutive patients presenting with HF, we measured plasma BNP levels and performed echocardiography and cardiac catheterization. Systolic and diastolic meridional wall stress was calculated from echocardiographic and hemodynamic data.

RESULTS

Although plasma BNP had a significant correlation (r2 = 0.296 [p < 0.001]) with left ventricular end-diastolic pressure (EDP) as previously reported, the correlation between plasma BNP and end-diastolic wall stress (EDWS) (r2 = 0.887 [p < 0.001]) was more robust. In a subanalysis of 62 patients with DHF, a similar result was obtained (r2 = 0.143 for EDP and r2 = 0.704 for EDWS). In a comparison between SHF and DHF, the BNP level was significantly higher in SHF (p < 0.001). Although EDP did not show any difference, EDWS was significantly higher in SHF than in DHF (p < 0.001).

CONCLUSIONS

The present study shows that plasma BNP levels reflect left ventricular EDWS more than any other parameter previously reported, not only in patients with SHF, but also in patients with DHF. The relationship of left ventricular EDWS to plasma BNP may provide a better fundamental understanding of the interindividual heterogeneity in BNP levels and their clinical utility in the diagnosis and management of HF.

Posttranscriptional activation of BNP gene expression in response to increased left ventricular wall stress: role of calcineurin and PKC

To study the molecular mechanisms for load-induced activation of BNP gene expression, increased wall stress was imposed on isolated isovolumetrically beating adult rat hearts by distension of a fluid filled balloon within the left ventricle. The wall stress for 2 h resulted in a 1.6-fold increase in the expression of BNP gene and a 2.0-fold increase of the c-fos gene. The inhibition of transcription by actinomycin D significantly decreased the baseline BNP mRNA levels but the wall stretch-induced increase of the gene expression remained unaffected. In contrast, the protein synthesis inhibitor cycloheximide increased baseline BNP mRNA levels and abolished the load-induced activation of gene expression. Furthermore, we studied the effects of protein kinase C (PKC), calcineurin and protein phosphatase 2A (PP2A) inhibition to characterize the role of intracellular pathways in the stretch-induced gene expression in the left ventricle. The expression of BNP and c-fos genes were not influenced by calcineurin, PP2A and PKC inhibition. In conclusion, we showed that the stretch-induced activation of BNP gene expression by increased left ventricular wall stress is independent of transcriptional mechanisms and dependent on protein synthesis. Moreover, our results suggest that the load-induced activation of BNP gene expression is independent of calcineurin, PKC and PP2A.

Prognostic value of plasma brain natriuretic peptide combined with left ventricular dimensions in predicting sudden death of patients with chronic heart failure

BACKGROUND

We evaluated a combined assessment of brain natriuretic peptide (BNP) with left ventricular dimensions as a prognostic marker for sudden death in patients with chronic heart failure (CHF). Ventricular dimensions and BNP are separately recognized as prognostic markers for sudden death in patients with CHF.

METHODS AND RESULTS

CHF patients at Stage C and B were registered for a prospective study. From the database, we analyzed 417 patients with coronary arterial disease (CAD) or primary/secondary dilated cardiomyopathy (DCM). Main effects of BNP, left ventricular ejection fraction (EF), LV diastolic dimension (LVDD), and interaction of BNP with the EF and LVDD were tested with Cox's proportional hazard model. BNP in sudden death patients was significantly higher than that in event-free patients. Although multivariate analysis revealed that BNP by itself was not an independent risk factor for sudden death after adjustments, it was revealed that BNP entered the model via interaction with EF as a risk factor associating with sudden death. On the other hand, BNP was an independent risk factor associating with heart failure events (death and hospitalization), and BNP did not enter the model via an interaction with EF.

CONCLUSION

BNP by itself was an independent risk factor for the heart failure events, but not for sudden death in CHF patients of the present study. However, BNP should be important in predicting sudden death when measured with EF.

Wall stress modulates brain natriuretic peptide production in pressure overload cardiomyopathy

OBJECTIVES

We postulated that both diastolic and systolic load modulate B-type natriuretic peptide (BNP) production in human pressure overload hypertrophy/failure.

BACKGROUND

In isolated myocytes, diastolic stretch induces BNP messenger ribonucleic acid expression. However, the mechanism of the BNP release in human hypertrophy remains controversial.

METHODS

In 40 patients with symptomatic aortic stenosis (AS), left ventricular (LV) performance and systolic and diastolic wall stress were calculated from combined invasive and echocardiographic data. Plasma BNP was determined by the rapid point-of-care bedside analyzer (Biosite Triage, Biosite Diagnostics Inc., San Diego, California).

RESULTS

A significant relationship was observed between plasma BNP and pulmonary capillary wedge pressure (p < 0.001), fractional shortening (p = 0.001), and aortic valve area (p = 0.006). Furthermore, a significant correlation was noted between BNP and LV mass index (p = 0.005) as well as between BNP and markers of diastolic load such as LV end-diastolic wall stress (p = 0.011), indexed LV end-diastolic volume (p < 0.001), and isovolumic relaxation time (p = 0.02). Preoperative BNP levels were elevated in patients with AS compared with patients without AS. Plasma BNP was higher in AS patients with impaired versus normal preload reserve (297 +/- 56 pg/ml vs. 168 +/- 44 pg/ml; p = 0.017) and in AS patients with clinical deterioration after valve replacement compared with those without (399 +/- 82 pg/ml vs. 124 +/- 41 pg/ml; p = 0.011).

CONCLUSIONS

In patients with AS, BNP appears to be regulated not only by systolic but also by diastolic load. This supports the hypothesis that myocardial stretch modulates BNP production in human pressure overload hypertrophy/failure.