Influence of ScaI and Natriuretic Peptide (NP) Clearance Receptor Polymorphisms of the NP System on NP Concentration in Chronic Heart Failure

Edema in childhood nephrotic syndrome: possible genes-hormones interplay

Background

The role of atrial natriuretic peptide (ANP) in edema formation in idiopathic nephrotic syndrome (INS) was studied before with conflicting results reported; however, the possible contribution of genes regulating ANP expression and receptors was never explored.

Methods

One hundred children (60 with active INS and 40 in remission) were studied for plasma atrial natriuretic peptide (ANP), urinary sodium, ANP gene A2843G and ScaI polymorphisms, and natriuretic peptide receptor clearance C (-55) A polymorphism. For comparative purposes, 20 healthy controls were studied for ANP levels.

Results

ANP was higher in active compared to remission patients (p<0.001). ANP in the healthy control group was significantly lower than the ANP level of active INS (during edema) group (p=0.009) but did not show significant differences when compared to ANP levels of either active INS group after resolution of edema or remission group (p= 0.42 and 0.56, respectively). Urinary sodium levels in edematous patients were significantly lower while ANP levels were significantly higher during edema than after resolution (p< 0.001 for both). Genotypes’ frequencies of studied polymorphisms did not differ between active and remission groups. Patients with the A1A1 genotype of ScaI polymorphism had higher ANP levels compared to other genotypes (p =0.01).

Conclusions

During edema, ANP levels are elevated in INS children however this increment is not associated with natriuresis suggesting a blunted renal response to ANP. Polymorphisms of genes regulating ANP levels and receptors don’t seem to be implicated in edema formation except for the A1A1 genotype of ScaI polymorphism however, its possible role needs further evaluation.

Structure and function of the Nppa-Nppb cluster locus during heart development and disease

Atrial natriuretic factor and brain natriuretic peptide are two important biomarkers in clinical cardiology. These two natriuretic peptide hormones are encoded by the paralogous genes Nppa and Nppb, which are evolutionary conserved. Both genes are predominantly expressed by the heart muscle during the embryonic and fetal stages, and in particular Nppa expression is strongly reduced in the ventricles after birth. Upon cardiac stress, Nppa and Nppb are strongly upregulated in the ventricular myocardium. Much is known about the molecular and physiological ques inducing Nppa and Nppb expression; however, the transcriptional regulatory mechanisms of the Nppa-Nppb cluster in vivo has proven to be quite complex and is not well understood. In this review, we will provide recent insights into the dynamic and complex regulation of Nppa and Nppb during heart development and hypertrophy, and the association of this gene cluster with the cardiomyocyte-intrinsic program of heart regeneration.

Identification of a regulatory domain controlling the Nppa-Nppb gene cluster during heart development and stress

The paralogous genes Nppa and Nppb are organized in an evolutionarily conserved cluster and provide a valuable model for studying co-regulation and regulatory landscape organization during heart development and disease. Here, we analyzed the chromatin conformation, epigenetic status and enhancer potential of sequences of the Nppa-Nppb cluster in vivo Our data indicate that the regulatory landscape of the cluster is present within a 60-kb domain centered around Nppb Both promoters and several potential regulatory elements interact with each other in a similar manner in different tissues and developmental stages. The distribution of H3K27ac and the association of Pol2 across the locus changed during cardiac hypertrophy, revealing their potential involvement in stress-mediated gene regulation. Functional analysis of double-reporter transgenic mice revealed that Nppa and Nppb share developmental, but not stress-response, enhancers, responsible for their co-regulation. Moreover, the Nppb promoter was required, but not sufficient, for hypertrophy-induced Nppa expression. In summary, the developmental regulation and stress response of the Nppa-Nppb cluster involve the concerted action of multiple enhancers and epigenetic changes distributed across a structurally rigid regulatory domain.

The plasma B-type natriuretic peptide levels are low in males with stable ischemic heart disease (IHD) compared to those observed in patients with non-IHD: a retrospective study

Objective

Although the plasma B-type natriuretic peptide (BNP) level is a marker of heart failure, it is unclear whether BNP per se plays a pivotal role for pathogenic mechanisms underlying the development of ischemic heart disease (IHD). In this study, we retrospectively examined the plasma BNP levels in stable patients with IHD and compared to stable patients with cardiovascular diseases other than IHD.

Methods

The study population was 2088 patients (1698 males and 390 females) who were admitted to our hospital due to IHD (n = 1,661) and non-IHD (n = 427) and underwent cardiac catheterization. Measurements of the hemodynamic parameters and blood sampling were performed.

Results

The plasma BNP levels were significantly lower in the IHD group than in the non-IHD group (p<0.001). The multiple regression analysis examining the logBNP values showed that age, a male gender, low left ventricular ejection fraction, low body mass index, serum creatinine, atrial fibrillation and IHD per se were significant explanatory variables. When the total study population was divided according to gender, the plasma BNP levels were found to be significantly lower in the IHD group than in the non-IHD group among males (p<0.001), but not females (p = NS). Furthermore, a multiple logistic regression analysis of IHD showed the logBNP value to be a significant explanatory variable in males (regression coefficient: −0.669, p<0.001), but not females (p = NS).

Conclusions

The plasma BNP levels were relatively low in stable patients with IHD compared with those observed in stable patients with non-IHD; this tendency was evident in males. Perhaps, the low reactivity of BNP is causally associated with IHD in males. We hope that this study will serve as a test of future prospective studies.

Atrial natriuretic peptide gene variants and circulating levels: implications in cardiovascular diseases

ANP (atrial natriuretic peptide), discovered 30 years ago in rat cardiac atria, has been extensively investigated with regard to physiology, pathophysiology, cardiovascular disease therapeutics and molecular genetic aspects. Besides its diuretic, natriuretic and vasorelaxant effects, novel properties of this hormone have been described. Thus anti-hypertrophic, anti-fibrotic, anti-proliferative and anti-inflammatory actions suggest that ANP contributes not only to haemodynamic homoeostasis and adjustments, but has also a role in cardiovascular remodelling. Circulating ANP levels represent a valuable biomarker in cardiovascular diseases. ANP structure is highly conserved among species, indicating a key role in cardiovascular health. Thus an abnormal ANP structure may contribute to an increased risk of disease due to altered functions at either the vascular or cardiac level. Among others, the 2238T>C exon 3 variant has been associated with endothelial cell damage and dysfunction and with an increased risk of acute cardiovascular events, a frameshift mutation within exon 3 has been related to increased risk of atrial fibrillation, and ANP gene variants have been linked to increased risk of hypertension in different ethnic groups. On the other hand, the rs5068 variant, falling within the 3' UTR and associated with higher circulating ANP levels, has been shown to have a beneficial cardioprotective and metabolic effect. Dissecting out the disease mechanisms dependent on specific ANP molecular variants may reveal information useful in the clinical setting for diagnostic, prognostic and therapeutic purposes. Furthermore, insights from molecular genetic analysis of ANP may well integrate advancing knowledge on the role of ANP as a significant biomarker in patients affected by cardiovascular diseases.

Association of 2238T>C polymorphism of the atrial natriuretic peptide gene with coronary artery disease in Afro-Caribbeans with type 2 diabetes

BACKGROUND

The atrial natriuretic peptide (ANP) is known mainly for its effects on kidney function and blood pressure homeostasis. We investigated the association between two ANP polymorphisms and pre-existing coronary artery disease (CAD) in patients of African descent with type 2 diabetes (T2D).

METHODS

We conducted a cross-sectional and retrospective study of 218 volunteer Afro-Caribbean patients with T2D. Two polymorphisms (rs5064, 708C>T; and rs5065, 2238T>C) of ANP were genotyped using PCR-restriction fragment length polymorphism analysis. ANCOVA, χ2-test, and logistic regression were used for statistical analysis.

RESULTS

Among these patients (92 men; 128 women), 67 (30.7%) had CAD, of whom 75% had had myocardial infarction. The frequency of rs5065-C carriers (TC/CC) was significantly lower in patients with CAD than in those without CAD (24 vs. 41%, P = 0.01). The frequency of hypertension did not differ significantly according to genotype. Univariate logistic regression revealed that male sex, age, dyslipidemia, hypertension, and rs5065-C carrier status were associated significantly with CAD. After adjustment for the variables of interest, the odds ratio (ORs) of CAD for rs5065-C carriers (TC/CC) was 0.50 (0.26-0.96; P = 0.038). No association was found between the rs5064 (708C>T) single-nucleotide polymorphisms (SNPs) and pre-existing CAD or cardiovascular risk factors.

CONCLUSIONS

The ANP rs5065 (2238T>C) C allele seems to exert a protective effect against CAD in T2D patients of African descent. The relevance of ANP polymorphisms for CAD should be determined in different populations.

[Recent advances in natriuretic peptide family genes and cardiovascular diseases]

Natriuretic peptide family consists of several hormones produced by cardiomyocyte, including atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP). They possess similar gene structures and protective effects of cardiovascular physiology, such as anti-hypertrophy, anti-fibrosis, myocardial relaxation and blood pressure regulation. The corresponding natriuretic peptide receptor A, B and C mediate multiple effects of natriuretic peptides to maintain cardiovascular homeostasis. Specially, natriuretic peptide receptor-A preferentially binds ANP and BNP, while natriuretic peptide receptor-B is more selective for C-type natriuretic peptides. Natriuretic peptide receptor-C(NPR-C), binding all kinds of natriuretic peptides, clears natriuretic peptides from the circulation through receptor-mediated internalization and degradation. BNP levels were reported to be a good predictor of left ventricular dysfunction and decompensated heart failure from a clinical standpoint. BNP infusion is an effective treatment for acute heart failure. Investigations on natriuretic peptides' single nucleotide polymorphisms and biological function suggested that they could be associated with several cardiovascular diseases, such as atrial fibrillation, cardiomyopathy, heart failure and so on. Transgenic mice with natriuretic peptides and their receptors gene deletion display myocardial hypertrophy and fibrosis, which are associated with the development of hypertension, cardiomyopathy and heart failure. Certain stimuli triggering cardiac hypertrophy and ischemic injuries may be involved in regulating gene expression of natriuretic peptides and their receptors. Therefore, advances in understanding of natriuretic peptide family genes and their regulatory mechanisms will lead to greater insight into the pathogenesis of cardiovascular diseases and blaze a new trail in clinical treatment.

Potential association between frequent nonsynonymous variant of NPPA and cardioembolic stroke

Atrial natriuretic peptide (ANP, also known as NPPA) and brain natriuretic peptide (BNP, also known as NPPB) have been determined as genetic factors for several diseases, including stroke and myocardial infarction, in human and rat models. To investigate the potential association between polymorphisms of the NPPA gene and stroke in a Korean population, nine single-nucleotide polymorphisms (SNPs) of NPPA and NPPB genes were genotyped in a total of 941 Korean subjects, including 674 stroke patients (109 hemorrhagic and 565 ischemic) and 267 unaffected controls. Genotype comparisons of the targeted alleles revealed that there were no significant associations between stroke patients and control subjects, or among hemorrhagic, ischemic, and control groups. However, in logistic analysis for Trial of Org 10172 in Acute Stroke Treatment (TOAST) classification of ischemic stroke, nonsynonymous rs5065 (STOP152Arg) and rs5067 in 3'UTR of NPPA, which were in complete linkage disequilibrium, showed significant associations with cardioembolic stroke. These two SNPs showed higher frequencies in cardioembolic stroke patients than those in controls and ischemic patients with small-vessel occlusion (p=0.002, adjusted p=0.02). It was also found that NPPA rs5065C allele in all of the Korean subjects existed as heterozygous compared with Caucasian and African populations. Although further replications in larger cardioembolic stroke subjects are required, our preliminary findings suggest that the nonsynonymous rs5065C of the NPPA gene, which could produce a new or dysfunctional transcript, is possibly associated with cardioembolism.

Nocturia, sleep-disordered breathing, and cardiovascular morbidity in a community-based cohort

Background

Nocturia has been independently associated with cardiovascular morbidity and all-cause mortality, but such studies did not adjust for sleep-disordered breathing (SDB), which may have mediated such a relationship. Our aims were to determine whether an association between nocturia and cardiovascular morbidity exists that is independent of SDB. We also determined whether nocturia is independently associated with SDB.

Methodology/Principal Findings

In order to accomplish these aims we performed a cross-sectional analysis of the Sleep Heart Health Study that contained information regarding SDB, nocturia, and cardiovascular morbidity in a middle-age to elderly community-based population. In 6342 participants (age 63±11 [SD] years, 53% women), after adjusting for known confounders such as age, body mass index, diuretic use, diabetes mellitus, alpha-blocker use, nocturia was independently associated with SDB (measured as Apnea Hypopnea index >15 per hour; OR 1.3; 95%CI, 1.2–1.5). After adjusting for SDB and other known confounders, nocturia was independently associated with prevalent hypertension (OR 1.23; 95%CI 1.08–1.40; P = 0.002), cardiovascular disease (OR 1.26; 95%CI 1.05–1.52; P = 0.02) and stroke (OR 1.62; 95%CI 1.14–2.30; P = 0.007). Moreover, nocturia was also associated with adverse objective alterations of sleep as measured by polysomnography and self-reported excessive daytime sleepiness (P<0.05).

Conclusions/Significance

Nocturia is independently associated with sleep-disordered breathing. After adjusting for SDB, there remained an association between nocturia and cardiovascular morbidity. Such results support screening for SDB in patients with nocturia, but the mechanisms underlying the relationship between nocturia and cardiovascular morbidity requires further study. MeSH terms: Nocturia, sleep-disordered breathing, obstructive sleep apnea, sleep apnea, polysomnography, hypertension.

Genome-wide association analysis and fine mapping of NT-proBNP level provide novel insight into the role of the MTHFR-CLCN6-NPPA-NPPB gene cluster

High blood concentration of the N-terminal cleavage product of the B-type natriuretic peptide (NT-proBNP) is strongly associated with cardiac dysfunction and is increasingly used for heart failure diagnosis. To identify genetic variants associated with NT-proBNP level, we performed a genome-wide association analysis in 1325 individuals from South Tyrol, Italy, and followed up the most significant results in 1746 individuals from two German population-based studies. A genome-wide significant signal in the MTHFR-CLCN6-NPPA-NPPB gene cluster was replicated, after correction for multiple testing (replication one-sided P-value = 8.4 × 10⁻¹⁰). A conditional regression analysis of 128 single-nucleotide polymorphisms in the region of interest identified novel variants in the CLCN6 gene as independently associated with NT-proBNP. In this locus, four haplotypes were associated with increased NT-proBNP levels (haplotype-specific combined P-values from 8.3 × 10⁻⁰³ to 9.3 × 10⁻¹¹). The observed increase in the NT-proBNP level was proportional to the number of haplotype copies present (i.e. dosage effect), with an increase associated with two copies that varied between 20 and 100 pg/ml across populations. The identification of novel variants in the MTHFR-CLCN6-NPPA-NPPB cluster provides new insights into the biological mechanisms of cardiac dysfunction.

Genetic Polymorphisms of the Natriuretic Peptide System in the Pathogenesis of Cardiovascular Disease: What Lies on the Horizon?

Background: The natriuretic peptide hormone family includes various proteins characterized by similar chemical structure and shared biological functions, with important effects on the cardiovascular system. Accordingly, these molecules are widely recognized as key clinical biomarkers in the diagnosis and monitoring of heart failure, hypertension, and coronary heart disease.

Content: Several single-nucleotide polymorphisms have been recently identified in genes associated with the natriuretic system. This review provides an overview of new insights into the functional role of these genetic variants, as well as their impact on cardiovascular physiopathology and drug response.

Conclusions: Noteworthy relationships between some specific polymorphisms and clinical correlates of cardiovascular disease have emerged. Nevertheless, future confirming studies are needed to substantiate the clinical relevance of such variants.

Natriuretic peptide system gene variants are associated with ventricular dysfunction after coronary artery bypass grafting

BACKGROUND

Ventricular dysfunction (VnD) after primary coronary artery bypass grafting is associated with increased hospital stay and mortality. Natriuretic peptides have compensatory vasodilatory, natriuretic, and paracrine influences on myocardial failure and ischemia. The authors hypothesized that natriuretic peptide system gene variants independently predict risk of VnD after primary coronary artery bypass grafting.

METHODS

A total of 1,164 patients undergoing primary coronary artery bypass grafting with cardiopulmonary bypass at two institutions were prospectively enrolled. After prospectively defined exclusions, 697 patients of European descent (76 with VnD) were analyzed. VnD was defined as need for at least 2 new inotropes and/or new mechanical ventricular support after coronary artery bypass grafting. A total of 139 haplotype-tagging single nucleotide polymorphisms (SNPs) within 7 genes (NPPA, NPPB, NPPC, NPR1, NPR2, NPR3, CORIN) were genotyped. SNPs univariately associated with VnD were entered into logistic regression models adjusting for clinical covariates predictive of VnD. To control for multiple comparisons, permutation analyses were conducted for all SNP associations.

RESULTS

After adjusting for clinical covariates and multiple comparisons within each gene, seven NPPA/NPPB SNPs (rs632793, rs6668352, rs549596, rs198388, rs198389, rs6676300, rs1009592) were associated with decreased risk of postoperative VnD (additive model; odds ratios 0.44-0.55; P = 0.010- 0.036) and four NPR3 SNPs (rs700923, rs16890196, rs765199, rs700926) were associated with increased risk of postoperative VnD (recessive model; odds ratios 3.89-4.28; P = 0.007-0.034).

CONCLUSIONS

Genetic variation within the NPPA/NPPB and NPR3 genes is associated with risk of VnD after primary coronary artery bypass grafting. Knowledge of such genotypic predictors may result in better understanding of the molecular mechanisms underlying postoperative VnD.

Genetic variation in the natriuretic peptide system and heart failure

Heart failure (HF) is a modern epidemic and is one of the few cardiovascular diseases which is increasing in prevalence. The growing importance of the Natriuretic Peptide (NP) system in HF is well recognized. Laboratory tests for B-type Natriuretic Peptide (BNP) have proven value as diagnostic and prognostic tools in HF and are now part of routine clinical care. Furthermore, recombinant atrial natriuretic peptide (ANP) (carperitide) and BNP (nesiritide) and are approved HF therapies in Japan and the US, respectively and additional natriuretic peptides (e.g., CNP, urodilatin, and designer NPs) are under investigation for use in HF. Common genetic sequence variants are increasingly being recognized as determinants of disease risk or drug response and may help explain a portion of the inter-individual variation in the human NP system. This review describes current knowledge of NP system genetic variation as it pertains to HF as well as ongoing studies and where the field is expected to progress in the near future. To briefly summarize, NP system genetic variants have been associated with alterations in gene expression, NP levels, and cardiovascular disease. The next step forward will include specific investigations into how this genetic variation can advance 'Personalized Medicine', such as whether they impact the utility of diagnostic BNP testing or effectiveness of therapeutic NP infusion. This is already in progress, with pharmacogenetic studies of nesiritide currently underway. We expect that within 5 years there should be a reasonable idea of whether NP system genetic variation will have important clinical implications.