Natriuretic Hormones

C-type natriuretic peptide (CNP): The cardiovascular system and beyond

C-type natriuretic peptide (CNP) represents the 'local' member of the natriuretic peptide family, functioning in an autocrine or paracrine capacity to modulate a hugely diverse portfolio of physiological processes. Whilst the best-characterised of these regulatory roles are in the cardiovascular system, akin to its predominantly endocrine siblings atrial (ANP) and brain (BNP) natriuretic peptides, CNP governs many additional, unrelated mechanisms including bone growth, gamete maturation, auditory processing, and neuronal integrity. Furthermore, there is currently great interest in mimicking the biological activity of CNP for therapeutic gain in many of these disparate organ systems. Herein, we provide an overview of the physiology, pathophysiology and pharmacology of CNP in both cardiovascular and non-cardiovascular settings.

Biallelic NPR1 loss of function variants are responsible for neonatal systemic hypertension

BACKGROUND

Early-onset isolated systemic hypertension is a rare condition of unknown genetic origin. Renovascular, renal parenchymal diseases or aortic coarctation are the most common causes of secondary systemic hypertension in younger children and neonates. We investigated the genetic bases of early-onset isolated systemic hypertension.

METHODS

Whole-exome sequencing (WES) was followed by variant filtering and Sanger sequencing for validation and familial segregation of selected variants in a large consanguineous family. mRNA expression was performed to evaluate the impact of the predicted pathogenic variant on gene expression. WES or Sanger sequencing was performed in additional unrelated affected individuals.

RESULTS

In one consanguineous family with four children presenting with isolated neonatal-onset systemic hypertension, we identified homozygous stop-gain variant in the NPR1 gene (NM_000906.4:c.1159C>T (p.Arg387Ter)) in the affected individuals. This variant leads to a dramatic reduction of NPR1 RNA levels. NPR1 gene analysis of additional families allowed the identification of another family with two affected children carrying homozygous frameshift variant in NPR1 (NM_000906.4:c.175del (p.Val59TrpfsTer8)).

CONCLUSION

We show for the first time that biallelic loss of function of NPR1 is responsible for isolated neonatal-onset systemic hypertension in humans, which represents a new autosomal recessive genetic cause of infantile systemic hypertension or cardiogenic shock. This is consistent with studies reporting early-onset systemic hypertension and sudden death in Npr1-deficient mice. NPR1 gene analysis should be therefore investigated in infants with early-onset systemic hypertension with or without cardiogenic shock of unknown origin.

Prediction of gestational diabetes mellitus in the first trimester: comparison of maternal fetuin-A, N-terminal proatrial natriuretic peptide, high-sensitivity C-reactive protein, and fasting glucose levels

OBJECTIVE

We investigated the utility of maternal fetuin-A, N-terminal proatrial natriuretic peptide (pro-ANP), high-sensitivity C-reactive protein (hs-CRP), and fasting glucose levels at 11-14 gestation weeks for predicting pregnancies complicated by gestational diabetes mellitus (GDM).

SUBJECTS AND METHODS

This prospective cohort study included 327 low-risk pregnant women who completed antenatal follow-up at a tertiary research hospital between January and April 2014. Maternal blood samples were collected between 11-14 gestational weeks in the first trimester of pregnancy and then stored at -80 °C until further analyses. During follow-up, 29 (8.8%) women developed GDM. The study population was compared 1:2 with age- and body mass index-matched pregnant women who did not develop GDM (n = 59). Fasting plasma glucose (FPG) levels and serum fetuin-A, pro-ANP, and hs-CRP levels were measured using automated immunoassay systems.

RESULTS

There was a significant negative correlation between fetuin-A and hs-CRP (CC = -0.21, p = 0.047) and a positive correlation between FPG and hs-CRP (CC = 0.251, p = 0.018). The areas under the receiver operating characteristic curve for diagnosing GDM were 0.337 (p = 0.013), 0.702 (p = 0.002), and 0.738 (p < 0.001) for fetuin-A, hs-CRP, and FPG, respectively. The optimal cut-off values were > 4.65, < 166, and > 88.5 mg/dL for maternal hs-CRP, fetuin-A, and FPG, respectively.

CONCLUSION

Reduced fetuin-A, elevated hs-CRP, and FPG levels in women in the first trimester can be used for the early detection of GDM. Further research is needed before accepting these biomarkers as valid screening tests for GDM.

Localization profiles of natriuretic peptides in hearts of pre-hibernating and hibernating Anatolian ground squirrels (Spermophilus xanthoprymnus)

The Anatolian ground squirrel (Spermophilus xanthoprymnus) is a typical example of true mammalian hibernators. In order to adapt to extreme external and internal environments during hibernation, they lower their body temperatures, heart rates and oxygen consumption; however, pathological events such as ischemia and ventricular fibrillation do not occur in their cardiovascular systems. During the hibernation, maintenance of cardiac function is very important for survival of ground squirrels. Natriuretic peptides (NPs) are key factors in the regulation of cardiovascular hemostasis. Since NPs' role on the protection of heart during hibernation are less clear, the aim of this study was to investigate dynamic changes in NPs content in the cardiac chambers and to reveal the possible role of NPs on establishing cardiac function in ground squirrel during hibernation using immunohistochemistry. The immunohistochemical results indicate that cardiac NP expressions in atrial and ventricular cardiomyocytes were different from each other and were sex-independent. ANP and BNP were expressed in a chamber-dependent manner in female and male squirrel hearts. Furthermore, cardiac NPs expression levels in hibernation period were lower than those at the pre-hibernation period. During prehibernation period, ANP, BNP and CNP were expressed in the white and beige adipocytes of epicardial adipose tissue (EAT); while during hibernation period, the brown adipocytes of EAT were positive for BNP and CNP. These data suggest that the hibernation-dependent reduction in levels of NPs, particularly ANP, in cardiac chambers and EAT may be associated with low heart rate and oxygen consumption during hibernation. However, further studies are needed to better delineate the roles of NPs during the hibernation.

Immunolocalization of natriuretic peptides and their receptors in goat (Capra hircus) heart

Natriuretic peptides are structurally similar, but genetically distinct, hormones that participate in cardiovascular homeostasis by regulating blood and extracellular fluid volume and blood pressure. We investigated the distribution of natriuretic peptides and their receptors in goat (Capra hircus) heart tissue using the peroxidase-anti-peroxidase (PAP) immunohistochemical method. Strong staining of atrial natriuretic peptide (ANP) was observed in atrial cardiomyocytes, while strong staining for brain natriuretic peptide (BNP) was observed in ventricular cardiomyocytes. Slightly stronger cytoplasmic C-type natriuretic peptide (CNP) immunostaining was detected in the ventricles compared to the atria. Natriuretic peptide receptor-A (NPR-A) immunoreactivity was more prominent in the atria, while natriuretic peptide receptor-B (NPR-B) immunoreactivity was stronger in the ventricles. Cytoplasmic natriuretic peptide receptor-C (NPR-C) immunoreactivity was observed in both the atria and ventricles, although staining was more prominent in the ventricles. ANP immunoreactivity ranged from weak to strong in endothelial and vascular smooth muscle cells. Endothelial cells exhibited moderate to strong BNP immunoreactivity, while vascular smooth cells displayed weak to strong staining. Endothelial cells exhibited weak to strong cytoplasmic CNP immunoreactivity. Vascular smooth muscle cells were labeled moderately to strongly for CNP. Weak to strong cytoplasmic NPR-A immunoreactivity was found in the endothelial cells and vascular smooth muscle cells stained weakly to moderately for NPR-A. Endothelial and vascular smooth cells exhibited weak to strong cytoplasmic NPR-B immunoreactivity. Moderate to strong NPR-C immunoreactivity was observed in the endothelial and smooth muscle cells. Small gender differences in the immunohistochemical distribution of natriuretic peptides and receptors were observed. Our findings suggest that endothelial cells, vascular smooth cells and cardiomyocytes express both natriuretic peptides and their receptors.

Arterial hypertension related to the injection of onabotulinumtoxinA in the detrusor

OBJECTIVE AND IMPORTANCE

We want to report on a first case reported of a 50-year-old female with repetitive and clinical significant hypertension after each injection of onabotulinumtoxinA. This is a retrospective chart review and prospective evaluation of the natriuresis and blood pressure at baseline and after injection therapy. The aim was to explore the mechanism of action of this apparent onabotulinumtoxinA related hypertension.

CASE PRESENTATION

Retrospectively hypertension appeared after 7 days and vanished after 4-5 months following injection of 300 units of onabotulinumtoxinA in the detrusor, bladder symptoms disappeared after 2 weeks and reoccurred after 5 months. Urological, nephrological, cardiological and endocrinological evaluations were normal.

INTERVENTION

In the prospective evaluation a 3-day bladder diary at baseline revealed a bladder capacity of 131 ± 57 ml and at 1 month when full effect was experienced 173 ± 50 ml. At 1 month there were no leakages with six episodes of intermittent catheterization per day. The 24-hour blood pressure registration demonstrated the onset of hypertension at day 7 together with a reversal of the urinary sodium/creatinine ratios on the renal function profile.

CONCLUSION

The increasing natriuresis coinciding with the hypertension is a normal compensatory mechanism suggesting that the hypertension has a central cause rather than it is caused by haematogenous spreading.

The role of neuroendocrine pathways in prognosis after stroke

A number of neuroendocrine changes have been described after stroke, which may serve adaptive or deleterious functions. The neuroendocrine changes include activation of the hypothalamo-pituitary-adrenal axis, sympathetic nervous system and alterations of several hormonal levels. Alterations of the HPA axis, increased catecholamines, natriuretic peptides and, decreased melatonin and IGF-1 levels are associated with poor post-stroke outcome, although there is no definitive proof of causality. Therefore, it remains to be established whether alteration of neuroendocrine responses could be used as a potential therapeutic target to improve stroke outcome. This article gives an overview of the major neuroendocrine pathways altered by stroke and highlights their potential for clinical use and further neurotherapeutic development by summarizing the evidence for their association with stroke outcome including functional outcome, post-stroke infection, delirium, depression and stroke-related myocardial injury.

N-Terminal proBNP Levels and Tissue Doppler Echocardiography in Acute Rheumatic Carditis

Background. Rheumatic heart disease (RHD) is a leading cause of heart failure in children and young adults worldwide. B-type natriuretic peptide (BNP) is a useful marker of critical pediatric heart disease, and its N-terminal peptide, NT-proBNP, is elevated in congenital and acquired heart disease in children. Aim. To measure NT-proBNP levels as a marker of carditis in children with acute rheumatic carditis, as compared to children with quiescent RHD and healthy controls. Methods. 16 children with acute rheumatic carditis, 33 children with quiescent RHD, and a cohort of 30 healthy children were studied. Transthoracic echocardiography was performed to assess valve and cardiac function. Tissue Doppler echocardiography was performed for E/E′ (ratio between mitral inflow E wave and lateral mitral annulus E′ wave) and systolic strain. Results. NT-proBNP levels were significantly higher in children with acute rheumatic carditis and dropped with its resolution. Strain and E/E′ values were comparable among the three groups. Conclusion. NT-proBNP is significantly elevated in children with acute rheumatic carditis in the acute stage compared to children with quiescent RHD and healthy subjects, in the presence of comparable echocardiographic indices of LV systolic and diastolic function.

Blood specimen biomarkers of inflammation, matrix degradation, angiogenesis, and cardiac involvement: a future useful tool in assessing clinical outcomes of COPD patients in clinical practice?

Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation that is not fully reversible; this airflow limitation is both progressive and associated with an abnormal inflammatory response of the lung to noxious particles or gasses. COPD is undoubtedly an umbrella term, and it seems unlikely that all patients with COPD have the same underlying disease processes; thus, there is a need for differential treatment of different subgroups. A potential solution is to find modifiable biomarkers that can assist in drug development and distinguish subgroups of COPD. With the exception of lung function tests, there are currently no well-validated biomarkers or surrogate endpoints that can be used to establish the efficacy of a drug for COPD. This article discusses biomarkers of inflammation (fibrinogen, C-reactive protein, pulmonary and activation-regulated chemokine/CC-chemokine ligand-18, serum surfactant protein D, interleukin (IL)-6, IL-8 and tumor necrosis factor α, complement factor C5a), angiogenesis factors as a part of the pathogenetic aspect in this disease (vascular endothelial growth factor, angiogenin, and IL-8), and matrix degradation biomarkers. Troponin and natriuretic peptides are presented as biomarkers of cardiac involvement in the light of COPD comorbidities. Trials based on research on known clinical variables such as FEV1, BODE, and 6MWT in combination with biomarkers from lung and blood specimens will probably clarify part of the prognosis and natural history of the disease. This will also represent an additional step in COPD phenotyping and new treatment possibilities.

[Correlations between B-type natriuretic peptide levels and non-geometric echocardiographic parameters in pediatric cardiomyopathies]

INTRODUCTION

B-type natriuretic peptide is a conventional cardiac biomarker in adult cardiology, however, it is not commonly used in pediatric cases.

AIMS

After introducing B-type natriuretic peptide measurements in pediatric patients for the evaluation of systemic right ventricular function, the authors wanted to evaluate the value of plasma B-type natriuretic peptide and compare the results with systolic and diastolic myocardial parameters obtained with conventional echocardiography and tissue Doppler imaging in children with cardiomyopathy.

METHODS

Between 2007 and 2010, 58 plasma B-type natriuretic peptide measurements were performed in 32 children (dilated cardiomyopathy in 20, hypertrophic cardiomyopathy in 10 and non-compacted cardiomyopathy in 2 cases). The age of the patients was 7.9±6.6 years (mean±SD). Plasma B-type natriuretic peptide was measured using an electrochemiluminescent assay within one day from echocardiographic evaluation.

RESULTS

As compared to normal values, children with the 3 types of cardiomyopathies showed significant differences in plasma B-type natriutretic peptide levels (dilated cardiomyopathy vs normal, p<0.001; hypertrophic cardiomyopathy vs. normal, p<0.01; non-compacted cardiomyopathy vs. normal, p<0.001). There was a significant negative correlation (r = -0,63; p<0,01) between B-type natriuretic peptide levels (range, 12-7002 ng/L; mean±SD, 1531±1750 ng/L) and linEF values (range, 4-50%; mean±SD, 22.5±13%). For B-type natriuteric peptide, a cut-off point of 1000 ng/L proved to differentiate significantly decreased linEF values (<17%). B-type natriuretic peptide levels significantly correlated with left ventricular end-diastolic diameter (r = 0.899; p<0.001), with left ventricular anular S wave parameters (r = 0.689; p<0.001) and with E/e ratio (r = 0.43; p<0.05).

CONCLUSIONS

B-type natriuretic peptide measurements are recommended in all types of cardiomyopathies.

C-type natriuretic peptide: a new cardiac mediator

Natriuretic peptides are endogenous hormones released by the heart in response to myocardial stretch and overload. While atrial and brain natriuretic peptides (ANP, BNP) were immediately considered cardiac hormones and their role was well-characterized and defined in predicting risk in cardiovascular disease, evidence indicating the role of C-type natriuretic peptide (CNP) in cardiovascular regulation was slow to emerge until about 8 years ago. Since then, considerable literature on CNP and the cardiovascular system has been published; the aim of this review is to examine current literature relating to CNP and cardiovascular disease, in particular its role in heart failure (HF) and myocardial infarction (MI). This review retraces the fundamental steps in research that led understanding the role of CNP in HF and MI; from increased CNP mRNA expression and plasmatic concentrations in humans and in animal models, to detection of CNP expression in cardiomyocytes, to its evaluation in human leukocytes. The traditional view of CNP as an endothelial peptide has been surpassed by the results of many studies published in recent years, and while its physiological role is still under investigation, information is now available regarding its contribution to cardiovascular function. Taken together, these observations suggest that CNP and its specific receptor, NPR-B, can play a very important role in regulating cardiac hypertrophy and remodeling, indicating NPR-B as a new potential drug target for the treatment of cardiovascular disease.

The impact of sleep apnoea syndrome on nocturia according to age in men

Study Type--Symptom prevalence (cohort) Level of Evidence 2b. What's known on the subject? and What does the study add? Sleep apnoea syndrome (SAS) can be a risk factor for nocturia, although whether the relationship between nocturia and SAS changes according to age remains to be addressed. SAS has a modest impact on nocturia frequency and the prevalence of pathological nocturia in young adults and middle-aged men. However, SAS may not be a risk factor for nocturia in the elderly, and age-related urinary diseases and voiding dysfunctions could over-ride the influence of SAS on nocturia in the elderly.

OBJECTIVE

• To assess the association between nocturia and sleep apnoea syndrome (SAS) according to age, as well as to determine the factors related to nocturia.

PATIENTS AND METHODS

• A total of 1757 men who had been referred to a sleep laboratory underwent polysomnography. • Nocturia frequency was assessed using a questionnaire, and pathological nocturia was defined as the need to void two or more times per night. • The Pittsburgh Sleep Quality Index (PSQI) and Beck Depression Inventory (BDI) were applied to all study subjects.

RESULTS

• Nocturia frequency was significantly correlated with age (r = 0.405, P < 0.001) and the apnoea-hypopnoea index (AHI) (r = 0.065, P < 0.01). • In those men aged <65 years, significant correlations were found between nocturic frequency and age, AHI, BDI and PSQI. • Multiple regression analysis showed that age (β = 0.303, P < 0.001), AHI (β = 0.107 P < 0.001) and benign prostatic hypertrophy (BPH; β = 0.069, P < 0.01) were associated with nocturia, and that the presence of pathological nocturia was predicted by BPH (odds ratio [OR], 2.77; P < 0.01), age (OR, 1.09; P < 0.001) and AHI (OR, 1.02; P < 0.001). • However, in men aged >65 years, nocturia frequency was significantly associated with BDI and PSQI, although no relationship was found between nocturia frequency and SAS parameters. • BPH was more frequently observed in elderly men with pathological nocturia than in those without pathological nocturia (OR, 2.18; P < 0.05).

CONCLUSIONS

• In the elderly, SAS may not be a risk factor for nocturia. • Age-related urinary diseases and voiding dysfunction may over-ride the influence of SAS.

Plasma C-type natriuretic peptide levels in healthy children

C-type natriuretic peptide (CNP) is assuming increasing importance in cardiovascular disease, and in adults its plasma levels are related to clinical and functional disease severity. Data are scarce regarding the reference values for CNP in infancy. Aim of this study was to assess the reference intervals for CNP in human healthy newborns and infants. Plasma CNP was measured in 121 healthy children divided into: 41 newborns (age 0-3 days), 24 newborns (4-30 days), 22 infants (1-12 months) and 32 children (1-12 years). A group of 32 healthy adult subjects (age 64 ± 1 years) was also studied. CNP was measured by a specific radioimmunoassay. Between- and within-assay variability resulted ≤ 30 and 20%, respectively and analytical sensitivity 0.77 ± 0.05 pg/tube. Plasma CNP resulted significantly higher in children than in adult subjects (13.6 ± 1.2 pg/ml vs. 7.4 ± 1.0 pg/ml, p=0.030). When the results were analyzed as a function of the age the reference intervals for plasma CNP resulted: 11.6 ± 2.1 pg/ml for newborns (0-3 days), 16.4 ± 3.7 pg/ml for newborns (4-30 days), 15.4 ± 2.7 pg/ml for infants (1-12 months), 13.6 ± 2.3 pg/ml for children (1-12 years) [p=0.01 newborns (4-30 days) vs. adults; p=0.03 infants (1-12 months) vs. adults]. CNP showed the highest concentrations after 12h of life with a peak between 4 and 5 days of life and with a progressive decline afterwards. According to these data at least five different reference intervals for CNP determinations should be used. These observations may be helpful for future clinical application of CNP in human children.

Expression of C-type natriuretic peptide and its receptor NPR-B in cardiomyocytes

C-type natriuretic peptide (CNP) was recently found in myocardium at the mRNA and protein levels, but it is not known whether cardiomyocytes are able to produce CNP. The aim of this study was to determine the expression of CNP and its specific receptor NPR-B in cardiac cells, both in vitro and ex vivo. CNP, brain natriuretic peptide (BNP) and natriuretic peptide receptor (NPR)-B mRNA expression were examined by RT-PCR in the H9c2 rat cardiac myoblast cell line, in neonatal rat primary cardiomyocytes and in human umbilical vein endothelial cells (HUVECs) as control. CNP protein expression was probed in cardiac tissue sections obtained from adult male minipigs by immunohistochemistry, and in H9c2 cells both by immunocytochemistry and by specific radioimmunoassay. The results showed that cardiac cells as well as endothelial cells were able to produce CNP. Unlike cardiomyocytes, as expected, in endothelial cells expression of BNP was not detected. NPR-B mRNA expression was found in both cell types. Production of CNP in the heart muscle cells at protein level was confirmed by radioimmunological determination (H9c2: CNP=0.86 ± 0.083 pg/mg) and by immunocytochemistry studies. By immunostaining of tissue sections, CNP was detected in both endothelium and cardiomyocytes. Expression of CNP in cardiac cells at gene and protein levels suggests that the heart is actively involved in the production of CNP.

The effects of delivery route and anesthesia type on early postnatal weight loss in newborns: the role of vasoactive hormones

OBJECTIVE

To investigate the effects of delivery route and maternal anesthesia type and the roles of vasoactive hormones on early postnatal weight loss in term newborns.

METHODS

Ninety-four term infants delivered vaginally (group 1, n=31), cesarean section (C/S) with general anesthesia (GA) (group 2, n=29), and C/S with epidural anesthesia (EA) (group 3, n=34) were included in this study. All infants were weighed at birth and on the second day of life and intravenous (IV) fluid infused to the mothers for the last 6 h prior to delivery was recorded. Serum electrolytes, osmolality, N-terminal proANP (NT-proANP), brain natriuretic peptide (BNP), aldosterone and plasma antidiuretic hormone (ADH) concentrations were measured at cord blood and on the second day of life.

RESULTS

Our research showed that postnatal weight loss of infants was higher in C/S than vaginal deliveries (5.7% vs. 1.3%) (p < 0.0001) and in EA group than GA group (6.8% vs. 4.3%) (p < 0.0001). Postnatal weight losses were correlated with IV fluid volume infused to the mothers for the last 6 h prior to delivery (R = 0.814, p = 0.000) and with serum NT-proANP (R = 0.418, p = 0.000), BNP (R = 0.454, p = 0.000), and ADH (R = 0.509, p = 0.000) but not with aldosterone concentrations (p > 0.05).

CONCLUSION

Large amounts of IV fluid given to the mothers who were applied EA prior to the delivery affect their offsprings' postnatal weight loss via certain vasoactive hormones.

Midregional proatrial natriuretic peptide predicts survival in exacerbations of COPD

BACKGROUND

Recently, the use of systemic biomarkers to monitor and assess the clinical evolution of respiratory disease has gained interest. We investigated whether midregional proatrial natriuretic peptide (MR-proANP) predicts survival in patients with COPD when they are admitted to the hospital for exacerbation.

METHODS

One hundred sixty-seven patients (mean age 70 years old, 75 men) admitted to the hospital for exacerbation were followed up for 2 years. MR-proANP was measured on admission, after 14 days, and at 6 months. The predictive value of clinical, functional, and laboratory parameters on admission were assessed by Cox regression analyses. The time to death was analyzed by Kaplan-Meier survival curves.

RESULTS

MR-proANP level was significantly higher on admission for exacerbation, compared with recovery and stable state (P = .004 for the comparison among all time points). MR-proANP correlated with the Charlson condition and age-related score (P < .0001), left ventricular ejection fraction (P < .0001), C-reactive protein (P = .037), and FEV(1)% predicted (P = .004). MR-proANP levels were similar in patients requiring ICU treatment and in those treated in the medical ward (P = .086). Thirty-seven patients (22%) died within 2 years. MR-proANP levels were higher in nonsurvivors compared with survivors (median [interquartile range] 185 pmol/L [110-286] vs 92 pmol/L [56-158], P < .001). Mortality was higher across MR-proANP quartiles (log rank P < .0001). Charlson condition and age-related score (P = .001), Paco(2) (P < .0001), and MR-proANP (P = .001) predicted mortality in the univariate Cox-regression model. Both MR-proANP and Paco(2) were independent predictors of mortality in the multivariate Cox regression model.

CONCLUSIONS

MR-proANP at exacerbation is associated with 2-year long-term survival in patients with exacerbation of COPD.

A new use for B-type natriuretic peptide: to detect myocardial ischaemia in non-heart failure patients

B-type natriuretic peptide (BNP) is a natriuretic peptide released primarily by ventricular myocytes in response to various physiological and pathological stimuli. In addition to its established diagnostic role in patients with heart failure, a growing body of evidence suggests that raised levels of BNP in the absence of heart failure can indicate myocardial ischaemia. This appears to be the case in patients with symptomatic, and even asymptomatic coronary artery disease (CAD). In this review, we discuss the current evidence supporting the role of BNP as a simple marker of cardiac ischaemia and CAD. We also propose some therapeutic interventions that may be useful when BNP detects silent myocardial ischaemia.

Transcriptomic analysis of the venom gland of the red-headed krait (Bungarus flaviceps) using expressed sequence tags

Background

The Red-headed krait (Bungarus flaviceps, Squamata: Serpentes: Elapidae) is a medically important venomous snake that inhabits South-East Asia. Although the venoms of most species of the snake genus Bungarus have been well characterized, a detailed compositional analysis of B. flaviceps is currently lacking.

Results

Here, we have sequenced 845 expressed sequence tags (ESTs) from the venom gland of a B. flaviceps. Of the transcripts, 74.8% were putative toxins; 20.6% were cellular; and 4.6% were unknown. The main venom protein families identified were three-finger toxins (3FTxs), Kunitz-type serine protease inhibitors (including chain B of β-bungarotoxin), phospholipase A₂ (including chain A of β-bungarotoxin), natriuretic peptide (NP), CRISPs, and C-type lectin.

Conclusion

The 3FTxs were found to be the major component of the venom (39%). We found eight groups of unique 3FTxs and most of them were different from the well-characterized 3FTxs. We found three groups of Kunitz-type serine protease inhibitors (SPIs); one group was comparable to the classical SPIs and the other two groups to chain B of β-bungarotoxins (with or without the extra cysteine) based on sequence identity. The latter group may be functional equivalents of dendrotoxins in Bungarus venoms. The natriuretic peptide (NP) found is the first NP for any Asian elapid, and distantly related to Australian elapid NPs. Our study identifies several unique toxins in B. flaviceps venom, which may help in understanding the evolution of venom toxins and the pathophysiological symptoms induced after envenomation.

Skeletal contributions to plasma CNP forms: evidence from regional sampling in growing lambs

Unlike the cardiac circulating hormones, atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP), C-type natriuretic peptide (CNP) appears to be largely tissue-based and circulates at concentrations considered insufficient to affect organ function. Consistent with CNP's crucial role in regulating skeletal growth, serial studies in juveniles show that both plasma CNP and aminoterminal proCNP (NTproCNP) are highly correlated with growth velocity raising the possibility that skeletal tissues contribute to circulating concentrations of CNP forms during the growing period. Hypothesizing that venous blood draining from bone dense regions is relatively enriched in CNP, we have performed trans-organ regional blood sampling for measurement of CNP forms in 4-week-old lambs and compared the findings to simultaneous levels of ANP and BNP. Because bone growth and CNP synthesis are inhibited by glucocorticoids, identical studies were also undertaken in lambs pretreated with dexamethasone. Highly significant positive arterio-venous gradients of CNP were found across the head, heart, leg and foot. Dexamethasone significantly reduced the CNP arterio-venous gradient across the head and leg but not heart, liver or kidney. In contrast, there was no evidence of tissue secretion of ANP or BNP except across the heart, and no effect on these gradients from dexamethasone. These findings of CNP enrichment in samples from bone dense regions in growing lambs, and their selective reduction by dexamethasone, provide in vivo evidence linking plasma and skeletal tissue concentrations of CNP and further support the use of plasma CNP forms as markers of bone growth.

Influence of natriuretic peptide receptor-1 on survival and cardiac hypertrophy during development

The heart adapts to an increased workload through the activation of a hypertrophic response within the cardiac ventricles. This response is characterized by both an increase in the size of the individual cardiomyocytes and an induction of a panel of genes normally expressed in the embryonic and neonatal ventricle, such as atrial natriuretic peptide (ANP). ANP and brain natriuretic peptide (BNP) exert their biological actions through activation of the natriuretic peptide receptor-1 (Npr1). The current study examined mice lacking Npr1 (Npr1(-/-)) activity and investigated the effects of the absence of Npr1 signaling during cardiac development on embryo viability, cardiac structure and gene and protein expression. Npr1(-/-)embryos were collected at embryonic day (ED) 12.5, 15.5 and neonatal day 1 (ND 1). Npr1(-/-)embryos occurred at the expected Mendelian frequency at ED 12.5, but knockout numbers were significantly decreased at ED 15.5 and ND 1. There was no indication of cardiac structural abnormalities in surviving embryos. However, Npr1(-/-)embryos exhibited cardiac enlargement (without fibrosis) from ED 15.5 as well as significantly increased ANP mRNA and protein expression compared to wild-type (WT) mice, but no concomitant increase in expression of the hypertrophy-related transcription factors, Mef2A, Mef2C, GATA-4, GATA-6 or serum response factor (SRF). However, there was a significant decrease in Connexin-43 (Cx43) gene and protein expression at mid-gestation in Npr1(-/-)embryos. Our findings suggest that the mechanism by which natriuretic peptide signaling influences cardiac development in Npr1(-/-) mice is distinct from that seen during the development of pathological cardiac hypertrophy and fibrosis. The decreased viability of Npr1(-/-)embryos may result from a combination of cardiomegaly and dysregulated Cx43 protein affecting cardiac contractility.

Gene expression of natriuretic peptides and their receptors type-A and-C after myocardial infarction in rats

The purpose of this study was to investigate myocardial mRNA expression of brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) in different regions of the heart at three different time points after induction of myocardial infarction (MI) in rats. Furthermore, we examined putative changes in mRNA expression of natriuretic peptide receptors (NPRs), NPR-A and NPR-C, in myocardium and peripheral organs. Substantial increase in the mRNA levels of both BNP and ANP in the infarcted as well as non-infarcted regions were observed after induction of MI. These findings were paralleled by elevated circulating concentrations of ANP, BNP and N-terminal proANP (Nt-proANP). In addition, the mRNA levels of the clearance receptor, NPR-C, were augmented in the infarcted and non-infarcted regions of the left ventricular wall (LV), while it was decreased in the kidneys and lungs 28 days post-MI. Based on these data, we propose that, in addition to increased myocardial secretion of BNP and ANP, reduced peripheral clearance by NPR-C may contribute to the observed increase in circulating plasma concentrations of the natriuretic peptides after induction of MI in rats.

Gated myocardial perfusion scintigraphy in children with myocarditis: can it be considered as an indicator of clinical outcome?

PURPOSE

Myocarditis is an inflammation of the heart muscle and represents a challenge for diagnosis and treatment. On account of the lack of sensitivity and specificity of routine cardiac tests, there is a need for accurate diagnostic imaging. The aim of this study is to review the role of gated 99Tc-methoxyisobutylisonitrile myocardial perfusion scintigraphy (G-MPS) in the diagnosis and follow-up of the patients with myocarditis in comparison with gallium scintigraphy.

MATERIALS AND METHODS

Thirteen patients with a clinical diagnosis of myocarditis were included in the study. All underwent rest G-MPS and the images were then evaluated by quantitative perfusion single-photon emission computed tomography and quantitative gated single photon emission computed tomography software program. Visual evaluation of perfusion was performed as well as analysis of motion with thickening function [expressed as summed rest score, summed motion score, and summed thickening score (STS)] with calculation of ejection fraction (EF) and lung-to-heart (L/H) ratio. Eight patients underwent 67Ga scintigraphy. Clinical, echocardiography, and cardiac enzymes (creatinine kinase-MB, myoglobulin, troponin T, brain natriuretic peptide) data were gathered from the patients' charts. Clinical outcome was grouped according to prognosis. Spearman's correlation (SC) test was used for comparison analysis.

RESULTS

Myocardial perfusion defects were observed in eight patients. Perfusion defects in the left ventricle involve a mean of 7.25% (range: 1-11%), whereas wall motion abnormality on G-MPS was more prominent, which showed to be a better marker for myocardial inflammation and necrosis. The 67Ga scintigraphy findings were normal in all, but two. The G-MPS EF (33+/-21%) was slightly lower than the echocardiography EF (40+/-15%), but with close correlation (SC coefficient: 0.635). Comparison of scintigraphic findings with clinical parameters showed that summed motion score with G-MPS EF and STS with L/H ratios were highly correlated (0.932 and 0.622, respectively). The maximum brain natriuretic peptide and L/H ratio with STS were highly correlated with the patients' outcomes (SC coefficient: -0.621, 0.821, and 0.579, respectively), as well.

CONCLUSION

Tc-methoxyisobutylisonitrile G-MPS is therefore helpful in providing additional diagnostic and prognostic information in patients with myocarditis.

Expression of natriuretic peptide-activated guanylate cyclases by cholinergic and dopaminergic amacrine cells of the rat retina

Recently, the natriuretic peptides were detected in the cholinergic and dopaminergic amacrine cells of the retina. We performed immunofluorescence labeling of rat retinal sections to examine the immunoreactivity of natriuretic peptide-activated guanylate cyclases (NPR-A and NPR-B) in the rat retina, in particular whether they were localized to dopaminergic and cholinergic amacrine cells. NPR-A and NPR-B immunoreactivity was detected in several layers of the retina including amacrine cells. In amacrine cells, both NPR-A and NPR-B were co-localized with tyrosine hydroxylase, a marker of dopaminergic cells. NPR-B, but not NPR-A, was localized to amacrine cells expressing choline acetyltransferase (ChAT), a marker of cholinergic cells. These findings suggest that natriuretic peptides have different regulatory systems in dopaminergic and cholinergic amacrine cells in rat retina.

Advances in congestive heart failure management in the intensive care unit: B-type natriuretic peptides in evaluation of acute heart failure

BACKGROUND

Circulating concentrations of B-type natriuretic peptide (BNP) and the aminoterminal fragment (NT-proBNP) of its prohormone (proBNP) are increased in congestive heart failure in proportion to the severity of symptoms, the degree of left ventricular dysfunction, and cardiac filling pressures. Following the introduction of rapid, automated assays for determination of BNP and NT-proBNP, these peptides are increasingly used for diagnostic and prognostic purposes.

OBJECTIVE

To review studies evaluating the diagnostic and prognostic value of BNP and NT-proBNP, with special emphasis on their performance as indicators of acute heart failure in the intensive care unit.

RESULTS

In patients presenting with acute dyspnea, both BNP and NT-proBNP are accurate indicators of acute heart failure and provide prognostic information above and beyond conventional risk markers. Increased plasma levels of BNP and NT-proBNP are not specific for heart failure and may be influenced by a variety of cardiac and noncardiac conditions commonly seen in the intensive care unit, including myocardial ischemia, cardiac arrhythmias, sepsis, shock, anemia, renal failure, hypoxia, acute pulmonary embolism, pulmonary hypertension, and acute respiratory distress syndrome.

CONCLUSIONS

The diagnostic performance of BNP and NT-proBNP as indicators of acute heart failure depends on the clinical setting. In the intensive care unit, particular caution should be used in the interpretation of elevated BNP and NT-proBNP levels.

Elevation of plasma placental growth factor in the patients with ischemic cardiomyopathy

BACKGROUND

Placental growth factor (PlGF), which is a member of the vascular endothelial growth factor family, stimulates angiogenesis and collateral growth in ischemic tissues. In addition, PlGF has been known to be a useful biomarker of vascular inflammation. This study was undertaken to examine whether plasma PlGF levels were increased in patients with congestive heart failure (CHF).

METHODS

Ninety-eight patients with systolic heart failure (ejection fraction <40%) and twenty control subjects were enrolled. The patients were divided into four subgroups according to the criteria of NYHA functional class. Plasma PlGF, tumor necrosis factor (TNF)-alpha, brain natriuretic peptide (BNP), norepinephrine, high-sensitive C-reactive protein (hs-CRP) were determined.

RESULTS

In analysis of all the subjects, there was no significant difference in plasma PlGF levels among the subgroups of NYHA classes and the controls. In the ischemic cardiomyopathy (ICM) patients, however, plasma PlGF levels were significantly increased according to the severity of NYHA class; control: 8.9+/-0.5; NYHA I: 9.4+/-1.1, NYHA II: 9.7+/-1.9, NYHA III: 14.6+/-1.2, NYHA IV: 17.9+/-1.9 pg/ml (p=0.0006). Plasma PlGF levels correlated positively with BNP (r=0.53, p=0.0003) and hs-CRP (r=0.23, p=0.02) in the ICM patients, whereas there was not any correlation between plasma PlGF levels and other variable values in the non-ICM patients.

CONCLUSIONS

In the ICM patients, plasma PlGF levels are increased according to the severity of heart failure. These results may indicate that augmented release of PlGF is involved in the pathogenesis of cardiomyopathy derived from chronic myocardial ischemia.

Response of plasma CNP forms to acute anabolic and catabolic interventions in growing lambs

Using a novel marker of C-type natriuretic peptide (CNP) synthesis [amino-terminal pro-CNP (NT-proCNP)], we have recently shown that plasma NT-proCNP is strongly correlated with skeletal growth and markers of bone formation and is reversibly reduced by glucocorticoids. The effects on CNP of other catabolic or anabolic factors, known to affect skeletal growth, are unknown. Accordingly, we have studied the response of plasma CNP forms to acute catabolic (caloric restriction) and anabolic [growth hormone (GH) stimulation] interventions in lambs and related the findings to circulating IGF-I levels, growth velocity, and markers of bone formation. Lambs fed a reduced caloric intake (25% of normal) for 6 days exhibited reduced live weight, plasma urea, and IGF-I (P < 0.001 for all) compared with control lambs. Basal levels of NT-proCNP (40.1 +/- 0.9 pmol/l) fell promptly to a nadir (28.1 +/- 0.8 pmol/l, P < 0.001) on day 6, returning rapidly to basal levels upon refeeding. Although plasma alkaline phosphatase (ALP) fell (P < 0.001), reductions in metacarpal growth velocity were not significant within the 12-day period of study. In contrast to caloric restriction, long-acting bovine recombinant GH (2.5 mg/kg on days 0 and 6), as expected, increased plasma IGF-I more than twofold above control for 12 days (P < 0.001). Growth velocity did not differ during the 30 days of observation, and, consistent with unchanged growth velocity, plasma NT-proCNP and ALP were also unaffected. In conclusion, CNP synthesis and markers of bone formation are acutely sensitive to catabolism but unaffected by doses of GH that fail to stimulate skeletal growth.

Diagnostic accuracy of serum B-type natriuretic peptide for myocardial ischemia detection during exercise testing with Spect perfusion imaging

OBJECTIVE

To determine whether serum B-type natriuretic peptide measured at rest and peak exercise and DeltaBNP contribute to the predictive value and diagnostic accuracy of exercise test in the diagnosis of myocardial ischemia.

BACKGROUND

Ventricular myocytes release BNP in response to increased wall stress that occurs in acute ischemia. During exercise testing, transient myocardial ischemia could also cause acute myocardial stress and changes in circulating BNP.

METHODS

BNP was measured before and immediately after exercise testing with radionuclide imaging in 203 consecutive subjects referred for chest pain evaluation. Tested subjects were classified as ischemic and non-ischemic based on exercise results, and no ischemia, mild-moderate, and severe ischemia according to perfusion scan results. A logistic regression model, constructed of an ROC and an AUC (area under the curve), was used.

RESULTS

Ischemic ECG changes (> or =1 mm, horizontal S-T shift) were detected in the treadmill exercise test in 127 subjects (62.6%), and 76 (37.4%) had neither ST segment shift nor chest pain. Baseline BNP was higher in the ischemic group compared to the non-ischemic group (p=0.044); peak BNP was also higher in the ischemic group (p=0.025), as was DeltaBNP (p=0.0126). Of these 127 subjects, 106 (52% of all) had abnormal perfusion scan results. In the ischemic group, the median baseline, peak exercise BNP, and DeltaBNP values from baseline to peak were higher than in the non-ischemic group. In the severe ischemic group these variables were approximately three-fold higher than in the mild-moderate ischemic group (p<0.0001 for baseline; p<0.0001 for peak; and p<0.0001 for DeltaBNP). Rest, peak exercise, and DeltaBNP values were significantly higher in patients with previous myocardial infarction (p<0.001) and in patients treated with beta blockers; peak exercise BNP was higher in hypertensives and diabetics (p<0.05). The ROC convergence model showed that the AUC for peak-exercise BNP was best able to discriminate and predict severe ischemia and no ischemia, while DeltaBNP from rest to peak exercise discriminated best between mild-moderate and severe ischemia.

CONCLUSIONS

Peak exercise BNP and DeltaBNP improved the sensitivity, specificity, positive likelihood ratio, predictive value, and diagnostic accuracy of severe ischemia detection during an exercise test. The contribution of BNP determination during exercise was, however, less impressive than previously reported by others.

Alterations in atrial natriuretic peptide and its receptor levels in long-term, streptozotocin-induced, diabetes in rats

Diabetes mellitus (DM) shows a markedly increased incidence of cardiovascular pathology that leads to hypertension, endothelial macro- and microangiopathy, diabetic nephropathy, and myocardial infarction. Atrial natriuretic peptide (ANP), is a 28 amino acid peptide hormone synthesized mainly by the heart atria and ventricles. It has potent diuretic and natriuretic properties. In this article the effect of long-term DM on blood plasma, kidney, and heart atrial and ventricular ANP concentrations were evaluated in streptozotocin (STZ)-induced 8-month diabetic and control rats by using radioimmunoassay (RIA). Moreover, ANP receptors in STZ-induced, 8-month diabetic rat kidneys were studied by receptor autoradiography. In addition, the expression of ANP concentrations in the kidney of diabetic and control rats was evaluated by means of immunohistochemistry. Body weight loss and increased blood glucose levels were used as indices of DM in the STZ-induced diabetic rats. Our results showed significantly higher ANP concentrations in diabetic plasma (P < 0.05), kidney (P < 0.01), heart atria (P < 0.05), and ventricles (P < 0.01) compared to controls. We also demonstrated a significant decrease in ANP receptors in the outer cortex (P < 0.05), juxtaglomerular medulla (P < 0.05), and papilla (P < 0.05) of 8-month diabetic rat kidneys compared to controls. The observed increase in ANP levels in plasma and kidney could play a role in the development of diabetic nephropathy: probably by reducing the levels of ANP receptors in diabetic kidney. Furthermore, the role of ANP in the STZ-induced diabetic heart merits additional study.

Comparison of infarct-derived and control ovine cardiac myofibroblasts in culture: response to cytokines and natriuretic peptide receptor expression profiles

This study investigated whether gene expression profiles of myofibroblasts derived from infarcted myocardium differ from normal cardiac fibroblasts. We compared the expression of cytoskeletal proteins in cultured ovine cardiac fibroblasts derived from infarcted (ID) and noninfarcted ovine myocardium (NID) and the levels of expression of the natriuretic peptide receptors (NPR)-A and NPR-B in response to treatment with transforming growth factor (TGF)-β1 and/or platelet-derived growth factor (PDGF). Transformation of cultured cardiac fibroblasts to myofibroblasts, as indicated by α-smooth muscle actin and vimentin expression, was independent of the presence of TGF-β1, PDGF, or cell origin. ID fibroblasts had higher basal levels than NID fibroblasts of NPR-A (ID: 58.0 ± 32.2 arbitrary density units, NID: undetectable), NPR-B (ID: 780 ± 155, NID: 330 ± 38 arbitrary density units) and collagen I (ID: 17.2 ± 0.5, NID: 10.5 ± 1.7 pg mRNA/μg total RNA, P < 0.05) but lower levels of α-SMa expression (ID: 50.2 ± 7.9, NID: 76.9 ± 3.2 fluorescence units, P < 0.05). NPR-A mRNA in ID fibroblasts showed a rapid fourfold increase in response to TGF-β1 and/or PDGF at 4 and 2 h, respectively, followed by a profound decline; in NID cells, NPR-A mRNA was undetectable. In ID fibroblasts, cytokines reduced NPR-B mRNA below control levels; in NID fibroblasts, TGF-β1 and PDGF elicited prompt increments in expression: a fourfold increase with TGF-β1 at 8 h and a twofold increase with PDGF at 4 h ( P < 0.05). In summary, transformation of cardiac fibroblasts to myofibroblasts in culture is independent of cytokine treatment. Moreover, whether the cultured cardiac fibroblasts are from infarct tissue is a major determinant of NPR expression levels and cytokine responses, even after four to five passages.

C-type natriuretic peptide and heart failure

C-type natriuretic peptide (CNP) is a peptide produced by the vascular endothelium with vasodilative properties. It shares structural and physiological properties with the atrial and brain natriuretic peptides (ANP and BNP), whose central role in the pathophysiology of heart failure (CHF) is firmly established. The role of CNP, first isolated from porcine brain, has not been yet completely determined. The transcription of the gene, that in man is located on chromosome 2, is regulated by factors such as tumor necrosis factor and interleukin-1. Two mature forms of the peptide exist: CNP-53, that predominates in tissues and CNP-22, found mainly in plasma. As recently found, CNP is produced directly in the myocardium and an increase in plasma levels of this peptide and of its precursor was observed in CHF. The aim of this review was to examine the current literature relating to cardiovascular functions of CNP and in particular to its role in CHF. In fact, CNP may represent an important new local autocrine and endocrine mediator in CHF although further evaluations are required to define its full pathophysiological role in this disease.

A metabolic study of patients with lung cancer and hyponatremia of malignancy

PURPOSE

One-third of patients with lung cancer and hyponatremia have no evidence of ectopic arginine vasopressin (AVP) production and the cause of their hyponatremia is not conclusively established. We sought to distinguish patients with hyponatremia caused by elevated AVP versus those with ectopic atrial natriuretic peptide (ANP) via this detailed metabolic study.

EXPERIMENTAL DESIGN

We enrolled 24 patients recently diagnosed with lung cancer in a metabolic study in which patients were placed on sodium and fluid restriction for 4 days. Serum electrolytes, osmolality, urine electrolytes and osmolality, plasma AVP, ANP, aldosterone, urinary cyclic AMP and cyclic guanosine 3',5'-monophosphate were measured daily and tumor tissue was obtained to measure ectopic hormone production. We attempted to characterize the pathophysiology of hyponatremia caused by ectopic ANP production in patients with small cell lung cancer (SCLC) and to determine its effect on the aldosterone axis.

RESULTS

Seven of the nine patients with SCLC presented with hyponatremia and three had elevated ANP levels at presentation without elevation of AVP. All three patients who presented with hyponatremia and elevated ANP showed a decline in serum sodium following fluid restriction, whereas two patients with SCLC and elevated AVP had normalized serum sodium levels. The combination of hyponatremia and elevated ANP was associated with a persistent natriuresis and inappropriately low aldosterone levels despite sodium restriction, suggesting ANP suppression of the aldosterone axis.

CONCLUSIONS

Management of patients with hyponatremia and SCLC should be guided by the knowledge that some patients with SCLC have ectopic production of ANP as the cause of their hyponatremia.

Brain natriuretic peptide and its relationship to left ventricular hypertrophy in patients on peritoneal dialysis or hemodialysis less than 3 years

An increase of brain natriuretic peptide (BNP) levels is commonly observed in patients on dialysis. Increased circulating levels of BNP are related to future cardiac events and associated with shorter survival in patients on chronic hemodialysis (HD). During the first 1 or 2 years on dialysis, patients on peritoneal dialysis (PD) have been shown to have an improvement in left ventricular hypertrophy, blood pressure, and volume status. This study compares BNP levels and cardiac status of PD and HD patients without cardiovascular disease and on dialysis for less than 36 months. The correlation between plasma BNP concentration and findings of echocardiography before HD scans were examined and compared with findings of PD. Twenty-two HD patients (15 men, 7 women; mean age, 52.5 +/- 13.9 years) and 19 PD patients (10 men, 9 women; mean age, 47.6 +/- 11.3 years) were studied. There were no significant differences between HD and PD patients with regard to age, gender, duration of dialysis, left ventricular mass, left ventricular mass index (p > 0.05). Plasma BNP levels were markedly greater in HD patients (467.8 +/- 466.5 pg/ mL) than those of PD patients (143.1 +/- 165.2 pg/mL). Urine output was significantly higher in PD patients compared with HD patients (p < 0.05). A positive correlation between systolic blood pressure, diastolic blood pressure, and plasma BNP in HD patients (r: 0.653, p: 0.001; r: 0.493, p: 0.023, respectively) was detected. Additional studies are needed to investigate whether lower BNP level in PD patients is an advantage.

B-type natriuretic peptide in pediatrics

OBJECTIVES

There has been growing interest in the use of serum B-type natriuretic peptide (BNP) and the N-terminal segment of its pro-hormone (NT-proBNP) as biomarkers for cardiac disease. The aim of this review is to summarize the current state of knowledge regarding BNP and NT-proBNP measurement in the pediatric population.

DESIGN AND METHODS

A computerized literature search on the National Library of Medicine was done and all articles including BNP and pediatrics were selected and discussed.

RESULTS

The data from several studies suggest that the measurement of BNP may be useful in diagnosing and managing pediatric heart failure, congenital heart disease, cardiac transplantation and patients on chemotherapy. There are difficulties in establishing appropriate reference ranges in children.

CONCLUSION

There is insufficient evidence for the routine use of BNP or NT-proBNP. Further research to clearly define the clinical utility in the pediatric age group is eagerly anticipated.

Influence of atrial fibrillation on cardiac brain natriuretic peptide release during haemodynamic stress in heart failure

BACKGROUND

The determinants of release of brain natriuretic peptide (BNP) in heart failure (HF) are incompletely understood, particularly, the effect of heart rhythm and haemodynamic stress.

AIMS

To investigate the effect of haemodynamic stress on cardiac BNP release in HF and differentiate this response for atrial fibrillation (AF) and sinus rhythm (SR).

METHODS

In 18 HF patients (ejection fraction<40%, 9 in AF and 9 in SR) haemodynamics and BNP levels were measured from arterial and coronary sinus samples at baseline, after 10 min of 20 degrees passive head up tilt (HUT) and after 10 min of isometric handgrip (IHG) exercise. From these data, we calculated a transcardiac BNP gradient and compared results between the AF and SR cohort.

RESULTS

During haemodynamic stress in both groups, there were no significance differences in left sided filling pressures. At baseline, there were no differences in BNP measurements between the SR and AF group. The transcardiac BNP gradient increased significantly in the SR (p=0.02) but not the AF cohort, after HUT. During IHG exercise, there was a significant decrease in cardiac BNP release in the AF cohort (p=0.03) but not the SR cohort.

CONCLUSION

These data imply in HF, cardiac rhythm influences cardiac BNP release in response to haemodynamic stress.

Association of Hyperadiponectinemia With Severity of Ventricular Dysfunction in Congestive Heart Failure

BACKGROUND

Adiponectin, which is a collagen-like plasma protein produced by adipose tissue, has anti-atherogenic and anti-inflammatory effects. Plasma adiponectin levels in patients with congestive heart failure (CHF) were determined, as well as relationships between the plasma levels of adiponectin and other hormones.

METHODS AND RESULTS

The study group comprised 90 patients with CHF and 20 control subjects, who were divided into 4 subgroups according to New York Heart Association (NYHA) functional class. Plasma levels of adiponectin, tumor necrosis factor (TNF)-alpha and brain natriuretic peptide (BNP) and cardiac hemodynamics were determined. Plasma adiponectin levels were significantly increased according to the severity of NYHA class in the patients with CHF; control: 6.2+/-1.0; NYHA I: 8.5+/-1.9, NYHA II: 12.0+/-2.2, NYHA III: 13.0+/-2.7, NYHA IV: 14.9+/-2.7 microg/ml (p=0.0008). Similarly, plasma BNP levels were significantly increased in accordance with the NYHA class. Plasma adiponectin levels correlated positively with BNP (r=0.40, p=0.0002) and TNF-alpha (r=0.49, p=0.0001), and correlated negatively with cardiac index (r=-0.27, p=0.05). In 24 of 46 patients in the NYHA III and IV subgroups, according to the prompt improvement in cardiac function, levels of both plasma adiponectin and BNP were significantly reduced (p<0.0001).

CONCLUSION

Plasma adiponectin levels increased according to the severity of CHF and, moreover, they correlated with the plasma levels of BNP and TNF-alpha. These results indicate that augmented release of adiponectin is involved in the pathogenesis of CHF and further study is needed to elucidate its exact role.

NT-proBNP as a marker for persistent cardiac disease in children with history of dilated cardiomyopathy and myocarditis

Children with myocarditis and dilated cardiomyopathy may recover clinically and echocardiographically. Plasma levels of the N-terminal segment of B-type natriuretic peptide prohormone (NT-proBNP), a sensitive marker for cardiac dysfunction, may reflect residual cardiac damage in these patients. The purpose of this study was to evaluate NT-proBNP status in pediatric patients with a history of myocarditis and dilated cardiomyopathy. Cardiac evaluation was performed and the levels of NT-proBNP were measured in 23 children who had a history of myocarditis or dilated cardiomyopathy. NT-proBNP levels were also measured in 56 age-matched control children. Nine of the 23 patients had evidence of left ventricular dysfunction (DCM group), whereas 14 had none (recovery). NT-proBNP levels were higher in the DCM group (3154 +/- 2858 pg/ml) than in the recovery group (122 +/- 75 pg/ml, p < 0.001) and the control group (113 +/- 96 pg/ml, p < 0.001). There was no difference between the recovery and the control groups (p = 0.45), and none of the recovered patients had a NT-proBNP level higher than the upper limit of normal. The area under the receiver operating characteristics curve for the diagnosis of persistent left ventricular dysfunction was 0.984. NT-proBNP levels correlated with echocardiographically derived shortening fraction and with clinical score. NT-proBNP is a good marker for persistent left ventricular dysfunction in children who have had myocarditis or cardiomyopathy. In this group of patients, NT-proBNP levels are normal in children who recover echocardiographically, suggesting no residual hemodynamic abnormalities.

Possible vascular role of increased plasma arginine vasopressin in congestive heart failure

BACKGROUND

The present study was undertaken to determine the relation of cardiac dysfunction with hormonal release in patients with congestive heart failure.

METHODS

Seventy-two patients with congestive heart failure were examined, who were divided into four subgroups classified by the criteria of the New York Heart Association (NYHA). Also, 10 age-matched subjects were served as a control. Plasma arginine vasopressin (AVP), norepinephrine, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were determined. Cardiac index and pulmonary capillary wedge pressure (PCWP) were measured in 51 of 72 patients.

RESULTS

Plasma AVP levels were significantly increased according to the severity of NYHA classes; control: 1.7 +/- 0.2; NYHA I: 4.9 +/- 0.8, NYHA II: 5.5 +/- 0.9, NYHA III: 13.4 +/- 2.6 (p < 0.05), NYHA IV: 26.9 +/- 5.6 pmol/l (p < 0.001). Similar results were obtained with plasma norepinephrine, ANP and BNP. Plasma AVP levels had negative correlation with cardiac index (r = -0.36, p < 0.01), but did not with PCWP and plasma osmolality. Plasma BNP levels positively correlated with PCWP (r = 0.44, p < 0.001), but did not with cardiac index. There was no correlation between plasma AVP and BNP. Intensive therapy profoundly reduced all the hormones according to the improvement of cardiac index in the patients with NYHA class III and IV. The percent decrease in plasma AVP was 60.0%, a value greater than that in plasma BNP.

CONCLUSION

The present study indicates that increased AVP may deteriorate cardiac function through V(1a) as well as V(2) action, and that plasma AVP level is also a proper marker for the presence and severity of congestive heart failure.

Molecular evolution of the natriuretic peptide system as revealed by comparative genomics

The natriuretic peptide (NP) family is a group of peptides involved in cardiovascular and body fluid regulation in vertebrates. While only C-type NP (CNP) has been found in elasmobranchs, atrial NP (ANP), B-type NP (BNP) and CNP have been found in mammals, and ventricular NP (VNP) instead of BNP in teleosts. Thus, it was once hypothesized that CNP is the ancestral NP, from which ANP and BNP/VNP were generated. However, the discovery of hfNP in the hagfish, and CNP in the lamprey suggested that the ancestral NP had characteristics common to these two peptides. Genomic studies in ray-finned fish revealed multiplication processes of NP genes: The ancestral gene was duplicated into four CNP genes before the divergence of elasmobranchs, and ANP, BNP and VNP genes were generated from one of the four CNP genes by tandem duplications. From up to seven NP genes thus generated, tetrapods are supposed to have lost some of them. Concerning NP receptors, teleosts also have more subtypes (three guanylyl cyclase-coupled receptors and two clearance receptors) than mammals. It is of interest to examine how the complicated NP system in teleosts compared with tetrapods, is involved in the adaptation to a wide variety of osmotic environments.

Plasma atrial natriuretic peptide in fetuses with cardiac disease

OBJECTIVE

To investigate atrial natriuretic peptide (ANP) levels in fetuses with cardiac defects and to evaluate the relationships between plasma ANP levels and the presence of polyhydramnios.

METHODS

Plasma ANP levels were measured by radioimmunoassay in 27 fetuses with cardiac abnormalities and in 14 normal healthy fetuses.

RESULTS

Fetal plasma ANP levels were similar in the two studied groups (p = 0.18) but they were significantly higher in a subset of cases with cardiac disease and polyhydramnios (n = 7) than in those with cardiac disease and normal amniotic fluid (n = 20; p = 0.036) and controls (p = 0.01).

CONCLUSION

Polyhydramnios in fetuses with heart conditions might be explained by increased fetal diuresis secondary to increased ANP production.

Amino-terminal proCNP: a putative marker of cartilage activity in postnatal growth

Recent evidence from rodents and humans shows that C-type natriuretic peptide (CNP) plays an essential role in endochondral bone growth. We recently identified a stable product of proCNP, amino-terminal proCNP (NT-proCNP), which unlike CNP is readily measurable in human and ovine plasma. Hypothesizing that plasma NT-proCNP concentrations reflect in part CNP synthesis within growth plates of rapidly growing cartilage, we studied levels of CNP forms in both children and lambs and related these to age, growth velocity, and biochemical markers of bone turnover. Plasma NT-proCNP levels were elevated at birth and fell progressively with age. Significant associations between plasma NT-proCNP and height velocity, alkaline phosphatase, and type 1 collagen C telopeptide were identified in children (aged 5-18 y). In longitudinal animal studies, elevated plasma concentration of NT-proCNP in 1-wk-old lambs fell progressively to mature adult levels at age 27 wk. Plasma NT-proCNP showed a highly significant association with alkaline phosphatase and metacarpal growth velocity. Glucocorticoids, a treatment known to inhibit cartilage proliferation, reduced metacarpal growth elongation in 4-wk-old lambs and markedly lowered circulating NT-proCNP levels during the treatment period. In summary, NT-proCNP levels in blood show a strong association with growth velocity and markers of bone formation and may well serve as a useful marker of growth plate activity in humans and other mammals.

Can Exercise-Induced Changes in B-Type Natriuretic Peptides Be Used to Detect Cardiac Ischemia?

BACKGROUND

We reviewed the current medical literature that pertained to the question of whether myocardial ischemia triggers the release of B-type natriuretic peptides (BNPs) and, in particular, whether transient exercise-induced ischemia can be detected by the measurement of changes in these biomarkers. BNPs are well-established as markers of left ventricular dysfunction, particularly heart failure. There is accumulating evidence that various conditions with the common denominator of myocardial ischemia are also associated with increased circulating levels of these peptides.

METHODS AND RESULTS

Recently published methods and results, which includes our published and unpublished data, were reviewed.

CONCLUSION

The results show that exercise-induced ischemia or its associated regional wall-motion abnormalities trigger the release of BNPs and that the measurement of plasma levels of N-terminal pro brain natriuretic peptide and BNP before and immediately after symptom-limited exercise can distinguish patients with and without ischemia with a high degree of accuracy.

Cardioprotective functions of atrial natriuretic peptide and B-type natriuretic peptide: a brief review

1. If one was to design a hormone to protect the heart, it would have a number of features shown by the cardiac natriuretic peptides atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP). These hormones are made in cardiomyocytes and are released into the circulation in response to atrial and ventricular stretch, respectively. Atrial natriuretic peptide and BNP can reduce the preload and after-load in normal and failing hearts. They reduce blood volume over the short term by sequestering plasma and over the longer term by promoting renal salt and water excretion and by antagonizing the renin-angiotensin-aldosterone system at many levels. Each of these actions affords indirect benefit to a volume- or pressure-threatened heart. 2. Recent studies have identified additional modes of action of the natriuretic peptides that may also confer cardioprotective benefits, especially in heart disease. The emerging findings are: (i) that ANP and BNP antagonize the cardiac hypertrophic action of angiotensin II and continue working under conditions where endothelial nitric oxide (NO) function is compromised, such as in the presence of high glucose in diabetes; (ii) they potentiate the bradycardia caused by inhibitory ('autoprotective') cardio-cardiac reflexes; and, furthermore, (iii) BNP can suppress cardiac sympathetic nerve activity in humans, including those with heart failure. Thus, it appears that natriuretic peptides can shift sympathovagal balance in a beneficial direction (away from the sympathetic). The vagal reflex and antihypertrophic actions of the peptides are mediated by particulate guanylyl cyclase (pGC) natriuretic peptide receptors. 3. The multiple synergistic actions of the natriuretic peptides make them and their pGC receptors attractive targets for therapy in heart disease. Encouragingly, exogenous natriuretic peptides remain effective even when endogenous peptide levels are raised, as is the case in heart failure. They also remain effective in disease states where other protective mechanisms, such as the NO system, have become ineffective, offering yet further encouragement for the therapeutic use of the natriuretic peptides.

Determinants of B-type natriuretic peptide plasma levels in the chronic phase after heart transplantation*

Determinants of B-type natriuretic peptide (BNP) plasma levels in the chronic phase after heart transplantation remain unclear. BNP was measured in 105 stable long-term heart transplant recipients with normal left ventricular function by echocardiography and correlated with clinical, demographic and hemodynamic parameters. Multivariate analysis revealed a significant correlation of BNP with female recipient gender (P = 0.006), time post-transplant (P =0.006), donor age (P = 0.007), angiographic signs of transplant vasculopathy (TVP) (P = 0.03), serum creatinine level (P = 0.04), and a strong trend for diastolic dysfunction (P = 0.09). Donor gender, recipient age, cyclosporin A blood levels, rejection history, and pulmonary artery pressure had no independent effect on BNP. BNP after heart transplantation appears to be influenced both by established general determinants (female gender, renal function) and transplant-specific determinants such as time post-transplant, donor age and potentially also TVP. In order to determine the value of BNP as a potential surrogate marker of TVP serial intraindividual measurements appear appropriate.