Regulation and significance of atrial and brain natriuretic peptides as cardiac hormones

Supersulfide catabolism participates in maladaptive remodeling of cardiac cells

The atrophic myocardium resulting from mechanical unloading and nutritional deprivation is considered crucial as maladaptive remodeling directly associated with heart failure, as well as interstitial fibrosis. Conversely, myocardial hypertrophy resulting from hemodynamic loading is perceived as compensatory stress adaptation. We previously reported the abundant presence of highly redox-active polysulfide molecules, termed supersulfide, with two or more sulfur atoms catenated in normal hearts, and the supersulfide catabolism in pathologic hearts after myocardial infarction correlated with worsened prognosis of heart failure. However, the impact of supersulfide on myocardial remodeling remains unclear. Here, we investigated the involvement of supersulfide metabolism in cardiomyocyte remodeling, using a model of adenosine 5'-triphosphate (ATP) receptor-stimulated atrophy and endothelin-1 receptor-stimulated hypertrophy in neonatal rat cardiomyocytes. Results revealed contrasting changes in intracellular supersulfide and its catabolite, hydrogen sulfide (H2S), between cardiomyocyte atrophy and hypertrophy. Stimulation of cardiomyocytes with ATP decreased supersulfide activity, while H2S accumulation itself did not affect cardiomyocyte atrophy. This supersulfide catabolism was also involved in myofibroblast formation of neonatal rat cardiac fibroblasts. Thus, unraveling supersulfide metabolism during myocardial remodeling may lead to the development of novel therapeutic strategies to improve heart failure.

Natriuretic peptides: Another tool for the management of cancer?

The connection between heart failure (HF) and cancer through multiple pathways such as inflammation, oxidative stress, and neurohormonal activation, among others, is well established. As a consequence, increases in plasma levels of several biomarkers have been described in both disorders. The most consistent information is related to natriuretic peptides (NPs). Although they are known to be produced in the ventricles as a response to myocardial distension, and thus can be useful for the diagnosis and prognosis of HF, and also for the management of chemotherapy-induced myocardial damage, they are also produced by tumour cells. In this regard, increased plasma levels of NPs have been described in patients with multiple malignancies in the absence of volume overload. Natriuretic peptide levels have been shown to correlate directly with the extension of tumours and with poorer outcomes. Moreover, some data indicate that they may help in the detection of subclinical tumours. Given that these peptides have been described to have anti-proliferative and anti-angiogenic effects, a plausible hypothesis is that they may be produced by tumours as a negative feed-back mechanism to avoid tumour progression. This would lead to increased levels of NPs in plasma that could be potentially useful for early detection of malignancies as well as for a prognostic assessment. Nevertheless, since the sample size of many studies published so far is limited, more data are needed to provide consistent data in order to confirm or rule out this hypothesis.

Do Heart Failure Biomarkers Influence Heart Failure Treatment Response?

PURPOSE OF REVIEW

Heart failure (HF) is one of the leading causes of cardiac morbidity and mortality around the world. Our evolving understanding of the cellular and molecular pathways of HF has led to the identification and evaluation of a growing number of HF biomarkers. Natriuretic peptides remain the best studied and understood HF biomarkers, with demonstrated clinical utility in the diagnosis and prognostication of HF. Less commonly understood is the utility of HF biomarkers for guiding and monitoring treatment response. In this review, we outline the current HF biomarker landscape and identify novel biomarkers that have potential to influence HF treatment response.

RECENT FINDINGS

An increasing number of biomarkers have been identified through the study of HF mechanisms. While these biomarkers hold promise, they have not yet been proven to be effective in guiding HF therapy. A more developed understanding of HF mechanisms has resulted in an increased number of available pharmacologic HF therapies. In the past, biomarkers have been useful for the diagnosis and prognostication of HF. Future evaluation on their use to guide pharmacologic therapy is ongoing, and there is promise that biomarker-guided therapy will allow clinicians to begin personalizing treatment for their HF patients.

Effect of Postnatal Epigallocatechin-Gallate Treatment on Cardiac Function in Mice Prenatally Exposed to Alcohol

Prenatal alcohol exposure affects the cardiovascular health of the offspring. Epigallocatechin-3-gallate (EGCG) may be a protective agent against it, but no data are available regarding its impact on cardiac dysfunction. We investigated the presence of cardiac alterations in mice prenatally exposed to alcohol and the effect of postnatal EGCG treatment on cardiac function and related biochemical pathways. C57BL/6J pregnant mice received 1.5 g/kg/day (Mediterranean pattern), 4.5 g/kg/day (binge pattern) of ethanol, or maltodextrin until Day 19 of pregnancy. Post-delivery, treatment groups received EGCG-supplemented water. At post-natal Day 60, functional echocardiographies were performed. Heart biomarkers of apoptosis, oxidative stress, and cardiac damage were analyzed by Western blot. BNP and Hif1α increased and Nrf2 decreased in mice prenatally exposed to the Mediterranean alcohol pattern. Bcl-2 was downregulated in the binge PAE drinking pattern. Troponin I, glutathione peroxidase, and Bax increased in both ethanol exposure patterns. Prenatal alcohol exposure led to cardiac dysfunction in exposed mice, evidenced by a reduced ejection fraction, left ventricle posterior wall thickness at diastole, and Tei index. EGCG postnatal therapy restored the physiological levels of these biomarkers and improved cardiac dysfunction. These findings suggest that postnatal EGCG treatment attenuates the cardiac damage caused by prenatal alcohol exposure in the offspring.

Role of Cardiac Natriuretic Peptides in Heart Structure and Function

Cardiac natriuretic peptides (NPs), atrial NP (ANP) and B-type NP (BNP) are true hormones produced and released by cardiomyocytes, exerting several systemic effects. Together with C-type NP (CNP), mainly expressed by endothelial cells, they also exert several paracrine and autocrine activities on the heart itself, contributing to cardiovascular (CV) health. In addition to their natriuretic, vasorelaxant, metabolic and antiproliferative systemic properties, NPs prevent cardiac hypertrophy, fibrosis, arrhythmias and cardiomyopathies, counteracting the development and progression of heart failure (HF). Moreover, recent studies revealed that a protein structurally similar to NPs mainly produced by skeletal muscles and osteoblasts called musclin/osteocrin is able to interact with the NPs clearance receptor, attenuating cardiac dysfunction and myocardial fibrosis and promoting heart protection during pathological overload. This narrative review is focused on the direct activities of this molecule family on the heart, reporting both experimental and human studies that are clinically relevant for physicians.

NRSF/REST-Mediated Epigenomic Regulation in the Heart: Transcriptional Control of Natriuretic Peptides and Beyond

Simple Summary

Reactivation of the fetal cardiac gene program, such as those encoding atrial and brain natriuretic peptides (ANP and BNP, respectively), is a characteristic feature of failing hearts. We previously revealed that a transcriptional repressor, neuron-restrictive silencer factor (NRSF), also called repressor element-1-silencing transcription factor (REST), plays a crucial role in the transcriptional control of ANP, BNP and other fetal cardiac genes through collaboration with various other transcription factors to maintain physiological cardiac function and electrical stability. Increased production of ANP and BNP prevents the progression of heart failure, but reactivation of Gα_o and fetal-type cardiac ion channels (T-type Ca²⁺ and HCN channels) leads to deteriorated cardiac function and lethal arrhythmias observed in mice with disturbed NRSF function. Epigenetic regulators with which NRSF forms a complex modify histone acetylation and methylation, thereby participating in NRSF-mediated transcriptional regulation. Further comprehensive studies will lead to clarification of the molecular mechanisms underlying the development of cardiac dysfunction and heart failure.

Abstract

Reactivation of fetal cardiac genes, including those encoding atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), is a key feature of pathological cardiac remodeling and heart failure. Intensive studies on the regulation of ANP and BNP have revealed the involvement of numerous transcriptional factors in the regulation of the fetal cardiac gene program. Among these, we identified that a transcriptional repressor, neuron-restrictive silencer factor (NRSF), also named repressor element-1-silencing transcription factor (REST), which was initially detected as a transcriptional repressor of neuron-specific genes in non-neuronal cells, plays a pivotal role in the transcriptional regulation of ANP, BNP and other fetal cardiac genes. Here we review the transcriptional regulation of ANP and BNP gene expression and the role of the NRSF repressor complex in the regulation of cardiac gene expression and the maintenance of cardiac homeostasis.

B-Type Natriuretic Peptide (BNP) Revisited—Is BNP Still a Biomarker for Heart Failure in the Angiotensin Receptor/Neprilysin Inhibitor Era?

Simple Summary

Active BNP-32, less active proBNP-108, and inactive N-terminal proBNP-76 all circulate in the blood. The circulating protease neprilysin has lower substrate specificity for BNP than ANP, while proBNP and N-terminal proBNP are not degraded by neprilysin. Currently available BNP immunoassays react with both mature BNP and proBNP; therefore, measured plasma BNP is mature BNP + proBNP. Because ARNI administration increases mature BNP, measured plasma BNP initially increases with ARNI administration by the amount of the increase in mature BNP. Later, ARNI administration reduces myocardial wall stress, and the resultant reduction in BNP production more than offsets the increase of mature BNP due to inhibition of degradation by neprilysin, resulting in lower plasma BNP levels. In the ARNI era, BNP remains a useful biomarker for heart failure, though mild increases early during ARNI administration should be taken into consideration.

Abstract

Myocardial wall stress, cytokines, hormones, and ischemia all stimulate B-type (or brain) natriuretic peptide (BNP) gene expression. Within the myocardium, ProBNP-108, a BNP precursor, undergoes glycosylation, after which a portion is cleaved by furin into mature BNP-32 and N-terminal proBNP-76, depending on the glycosylation status. As a result, active BNP, less active proBNP, and inactive N-terminal proBNP all circulate in the blood. There are three major pathways for BNP clearance: (1) cellular internalization via natriuretic peptide receptor (NPR)-A and NPR-C; (2) degradation by proteases in the blood, including neprilysin, dipeptidyl-peptidase-IV, insulin degrading enzyme, etc.; and (3) excretion in the urine. Because neprilysin has lower substrate specificity for BNP than atrial natriuretic peptide (ANP), the increase in plasma BNP after angiotensin receptor neprilysin inhibitor (ARNI) administration is much smaller than the increase in plasma ANP. Currently available BNP immunoassays react with both mature BNP and proBNP. Therefore, BNP measured with an immunoassay is mature BNP + proBNP. ARNI administration increases mature BNP but not proBNP, as the latter is not degraded by neprilysin. Consequently, measured plasma BNP initially increases with ARNI administration by the amount of the increase in mature BNP. Later, ARNI reduces myocardial wall stress, and the resultant reduction in BNP production more than offsets the increase in mature BNP mediated by inhibiting degradation by neprilysin, which lowers plasma BNP levels. These results suggest that even in the ARNI era, BNP can be used for diagnosis and assessment of the pathophysiology and prognosis of heart failure, though the mild increases early during ARNI administration should be taken into consideration.

Beta-blockers are associated with increased B-type natriuretic peptide levels differently in men and women in heart failure with preserved ejection fraction

Beta-blocker (BB) use is a mainstay for treatment of heart failure (HF) with reduced ejection fraction (HFrEF), whereas its efficacy for heart failure with preserved ejection fraction (HFpEF) remains controversial. Women outnumber men in HFpEF, whereas men outnumber women in HFrEF. Plasma B-type natriuretic peptide (BNP) is established as a biomarker for HF. We examined whether BB use is associated with plasma BNP levels differently in men and women with HFpEF. The study subjects comprised 721 patients with HFpEF (LVEF≥50%) (184 men, mean age 78.2±9.2 and 537 women, mean age 83.1±8.8), 179 on BB (66 men and 113 women) and 542 (118 men and 424 women) not, 583 in sinus rhythm (SR) and 138 in atrial fibrillation (AF). Multivariable logistic regression test was utilized. Plasma BNP levels were higher (P=0.0005), systolic blood pressure and LVEF lower (P=0.0003, and P=0.0059, respectively) on BBs than on no-BBs in women, whereas in men plasma BNP levels, systolic blood pressure, and LVEF were not altered significantly (P=0.0849, P=0.9129, and P=0.4718, respectively) on BBs compared to no-BBs in patients with SR. Multivariable logistic regression analysis revealed that BB use and women were a positive and a negative predictor for high BNP levels (P=0.003 and P=0.032, respectively) in SR but not in AF. BB use was associated with high plasma BNP levels and lower LVEF in women but not in men with HFpEF and SR, suggesting that the pathogenesis and of HFpEF may differ in men and women in SR.

The effect of subclinical thyroid dysfunction on B- type natriuretic peptide level

Thyroid hormones (THs) have a significant effect on the cardiovascular system. THs increase myocardium stretch, leading to the release of B-type Natriuretic Peptide (BNP), which is considered a diagnostic biomarker of heart failure (HF). Thyroid dysfunctions (subclinical hypothyroidism; SCH and subclinical hyperthyroidism; SCHyper) stimulate several changes in the heart by causing either diastolic or systolic left ventricular dysfunctions leading to HF. This study aims to measure the changes of B- type NP levels in cases of subclinical hypo and hyperthyroidism. The present study aims to measure the changes in B-type Natriuretic Peptide (BNP) levels in subclinical hypo and hyperthyroidism (SCH and SCHyper). A theoretical study was also conducted using a docking program to find the effectiveness of some drugs in inhibiting or promoting B-type Natriuretic Peptide (BNP). A case study was conducted in a private clinic, Mosul- Iraq, from (April 1st – Sep 1) 2021, with 25 healthy participants with normal functioning thyroids as a control group (EU). A newly diagnosed 25 SCH and 17 SCHyper patients participated in this study, considering that none of them have thyroid dysfunctions taking medicine, hypertension, heart diseases, renal failure, and pregnant women. They all were checked for Thyroid Function Tests (TFTs), Free Triiodothyronine (FT3), Free Thyroxin (FT4) and Thyroid Stimulating Hormone (TSH). The plasma level of BNP was measured in all participants of the three groups. The results showed that the plasma level of BNP was higher in SCHyper patients (10.97 pg/ml) as compared to that of SCH patients (8.09 pg/ml) and EU subjects (8.27 pg/ml). Hereby, we could state that subclinical hyperthyroidism, SCHyper, triggers BNP release. Therefore, it should be kept in mind that any high BNP levels due to SCHyper should be considered a reliable diagnostic biomarker of heart failure (HF). Keywords. Thyroid hormone(TH), Subclinical hypothyroidism(SCH), Subclinical hyperthyroidism(SCHyper), Chronic heart disease(CHD), Heart failure(HF), B-type natriuretic peptide(BNP), Docking Study.

N-Terminal Pro-Brain Natriuretic Peptide Plasma Levels Are Associated with Intermediate-Term Follow-Up Cancer in Coronary Patients

N-terminal pro-brain natriuretic peptide (NT-proBNP) plasma levels are increased in patients with cancer. In this paper, we test whether NT-proBNP may identify patients who are going to receive a future cancer diagnosis (CD) in the intermediate-term follow-up. We studied 962 patients with stable coronary artery disease and free of cancer and heart failure at baseline. This sample represents a re-analysis of a previous work expanding the sample size and the follow-up. NT-proBNP, galectin-3, monocyte chemoattractant protein-1, high-sensitivity C-reactive protein, high-sensitivity cardiac troponin I (hsTnI), and calcidiol (vitamin D) plasma levels were assessed. The primary outcome was new CD. After 5.40 (2.81–6.94) years of follow-up, 59 patients received a CD. NT-proBNP [HR 1.036 CI (1.015–1.056) per increase in 100 pg/mL; p = 0.001], previous atrial fibrillation (HR 3.140 CI (1.196–8.243); p = 0.020), and absence of previous heart failure (HR 0.067 CI (0.006–0.802); p = 0.033) were independent predictors of receiving a CD in the first three years of follow-up. None of the variables analyzed predicted a CD beyond this time. The number of patients developing heart failure during follow-up was 0 (0.0%) in patients receiving CD in the first three years of follow-up, 2 (6.9%) in those receiving a CD diagnosis beyond this time, and 40 (4.4%) in patients not developing cancer (p = 0.216). These numbers suggest that future heart failure was not a confounding factor. In patients with coronary artery disease, NT-proBNP was an independent predictor of CD in the first three years of follow-up but not later, suggesting that it could be detecting subclinical undiagnosed cancers.

Mechanisms of Systolic Cardiac Dysfunction in PP2A, PP5 and PP2AxPP5 Double Transgenic Mice

As part of our ongoing studies on the potential pathophysiological role of serine/threonine phosphatases (PP) in the mammalian heart, we have generated transgenic mice with cardiac muscle cell-specific overexpression of PP2Acα (PP2A) and PP5 (PP5). For further studies we crossbred PP2A and PP5 mice to obtain PP2AxPP5 double transgenic mice (PP2AxPP5, DT) and compared them with littermate wild-type mice (WT) serving as a control. The mortality of DT mice was greatly enhanced vs. other genotypes. Cardiac fibrosis was noted histologically and mRNA levels of collagen 1α, collagen 3α and fibronectin 1 were augmented in DT. DT and PP2A mice exhibited an increase in relative heart weight. The ejection fraction (EF) was reduced in PP2A and DT but while the EF of PP2A was nearly normalized after β-adrenergic stimulation by isoproterenol, it was almost unchanged in DT. Moreover, left atrial preparations from DT were less sensitive to isoproterenol treatment both under normoxic conditions and after hypoxia. In addition, levels of the hypertrophy markers atrial natriuretic peptide and B-type natriuretic peptide as well as the inflammation markers interleukin 6 and nuclear factor kappa B were increased in DT. PP2A enzyme activity was enhanced in PP2A vs. WT but similar to DT. This was accompanied by a reduced phosphorylation state of phospholamban at serine-16. Fittingly, the relaxation times in left atria from DT were prolonged. In summary, cardiac co-overexpression of PP2A and PP5 were detrimental to animal survival and cardiac function, and the mechanism may involve dephosphorylation of important regulatory proteins but also fibrosis and inflammation.

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020)

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020), a Japanese-specific set of clinical practice guidelines for sepsis and septic shock created as revised from J-SSCG 2016 jointly by the Japanese Society of Intensive Care Medicine and the Japanese Association for Acute Medicine, was first released in September 2020 and published in February 2021. An English-language version of these guidelines was created based on the contents of the original Japanese-language version. The purpose of this guideline is to assist medical staff in making appropriate decisions to improve the prognosis of patients undergoing treatment for sepsis and septic shock. We aimed to provide high-quality guidelines that are easy to use and understand for specialists, general clinicians, and multidisciplinary medical professionals. J-SSCG 2016 took up new subjects that were not present in SSCG 2016 (e.g., ICU-acquired weakness [ICU-AW], post-intensive care syndrome [PICS], and body temperature management). The J-SSCG 2020 covered a total of 22 areas with four additional new areas (patient- and family-centered care, sepsis treatment system, neuro-intensive treatment, and stress ulcers). A total of 118 important clinical issues (clinical questions, CQs) were extracted regardless of the presence or absence of evidence. These CQs also include those that have been given particular focus within Japan. This is a large-scale guideline covering multiple fields; thus, in addition to the 25 committee members, we had the participation and support of a total of 226 members who are professionals (physicians, nurses, physiotherapists, clinical engineers, and pharmacists) and medical workers with a history of sepsis or critical illness. The GRADE method was adopted for making recommendations, and the modified Delphi method was used to determine recommendations by voting from all committee members.As a result, 79 GRADE-based recommendations, 5 Good Practice Statements (GPS), 18 expert consensuses, 27 answers to background questions (BQs), and summaries of definitions and diagnosis of sepsis were created as responses to 118 CQs. We also incorporated visual information for each CQ according to the time course of treatment, and we will also distribute this as an app. The J-SSCG 2020 is expected to be widely used as a useful bedside guideline in the field of sepsis treatment both in Japan and overseas involving multiple disciplines.

The natriuretic peptide system in heart failure: Diagnostic and therapeutic implications

Natriuretic peptides, which are activated in heart failure, play an important cardioprotective role. The most notable of the cardioprotective natriuretic peptides are atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), which are abundantly expressed and secreted in the atrium and ventricles, respectively, and C-type natriuretic peptide (CNP), which is expressed mainly in the vasculature, central nervous system, and bone. ANP and BNP exhibit antagonistic effects against angiotensin II via diuretic/natriuretic actions, vasodilatory actions, and inhibition of aldosterone secretion, whereas CNP is involved in the regulation of vascular tone and blood pressure, among other roles. ANP and BNP are of particular interest with respect to heart failure, as their levels, most notably BNP and N-terminal proBNP-a cleavage product produced when proBNP is processed to mature BNP-are increased in patients with heart failure. Furthermore, the identification of natriuretic peptides as sensitive markers of cardiac load has driven significant research into their physiological roles in cardiovascular homeostasis and disease, as well as their potential use as both biomarkers and therapeutics. In this review, I discuss the physiological functions of the natriuretic peptide family, with a particular focus on the basic research that has led to our current understanding of its roles in maintaining cardiovascular homeostasis, and the pathophysiological implications for the onset and progression of heart failure. The clinical significance and potential of natriuretic peptides as diagnostic and/or therapeutic agents are also discussed.

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020)

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020), a Japanese-specific set of clinical practice guidelines for sepsis and septic shock created as revised from J-SSCG 2016 jointly by the Japanese Society of Intensive Care Medicine and the Japanese Association for Acute Medicine, was first released in September 2020 and published in February 2021. An English-language version of these guidelines was created based on the contents of the original Japanese-language version. The purpose of this guideline is to assist medical staff in making appropriate decisions to improve the prognosis of patients undergoing treatment for sepsis and septic shock. We aimed to provide high-quality guidelines that are easy to use and understand for specialists, general clinicians, and multidisciplinary medical professionals. J-SSCG 2016 took up new subjects that were not present in SSCG 2016 (e.g., ICU-acquired weakness [ICU-AW], post-intensive care syndrome [PICS], and body temperature management). The J-SSCG 2020 covered a total of 22 areas with four additional new areas (patient- and family-centered care, sepsis treatment system, neuro-intensive treatment, and stress ulcers). A total of 118 important clinical issues (clinical questions, CQs) were extracted regardless of the presence or absence of evidence. These CQs also include those that have been given particular focus within Japan. This is a large-scale guideline covering multiple fields; thus, in addition to the 25 committee members, we had the participation and support of a total of 226 members who are professionals (physicians, nurses, physiotherapists, clinical engineers, and pharmacists) and medical workers with a history of sepsis or critical illness. The GRADE method was adopted for making recommendations, and the modified Delphi method was used to determine recommendations by voting from all committee members. As a result, 79 GRADE-based recommendations, 5 Good Practice Statements (GPS), 18 expert consensuses, 27 answers to background questions (BQs), and summaries of definitions and diagnosis of sepsis were created as responses to 118 CQs. We also incorporated visual information for each CQ according to the time course of treatment, and we will also distribute this as an app. The J-SSCG 2020 is expected to be widely used as a useful bedside guideline in the field of sepsis treatment both in Japan and overseas involving multiple disciplines.

Marein ameliorates Ang II/hypoxia-induced abnormal glucolipid metabolism by modulating the HIF-1α/PPARα/γ pathway in H9c2 cells

The objectives of this study were to investigate the effects of marein, a major bioactive compound in functional food Coreopsis tinctoria, in hypertrophic H9c2 cells. Treating angiotensin II/hypoxia-stimulated H9c2 cells with marein led to decreasing cell surface area, intracellular total protein, atrial natriuretic peptide, and free fatty acids levels, but increasing glucose level. Marein treatment decreased hypoxia inducible factor-1α (HIF-1α), peroxisome proliferator activated receptor γ (PPARγ), medium chain acyl-coenzyme A dehydrogenase, glucose transporter-4, and glycerol-3-phosphate acyltransferase protein expressions, and increased PPARα, fatty acid transport protein-1, carnitine palmitoyltransferase-1, and pyruvate dehydrogenase kinase-4 protein expressions. Similar results were observed in HIF-1α-overexpressing H9c2 cells, whereas these effects were abolished in siRNA-HIF-1α-transfected H9c2 cells. It was concluded that marein could ameliorate abnormal glucolipid metabolism in hypertrophic H9c2 cells, and the effects could be attributable to reduction of HIF-1α expression and subsequent regulation PPARα/γ-mediated lipogenic gene expressions.

Therapeutic hypothermia after cardiac arrest increases the plasma level of B-type natriuretic peptide

Natriuretic peptides (NPs) regulate blood pressure and fluid homeostasis and exert various effects on the cardiovascular system. Recently, the relationship between NPs and the energy metabolism has been reported, and using a cell culture experiment system, we previously showed that NP activated brown cells in a low temperature environment while also suppressing a decrease in the cell temperature. However, few reports have described the secretion of NPs in cold environments, and there have been almost no studies of B-type natriuretic peptide (BNP) in humans. We investigated how NPs respond to cold environments in 21 patients who underwent therapeutic hypothermia (TH) after cardiac arrest. The plasma BNP levels were significantly increased (more than fivefold) during TH (logarithmically from 1.98 ± 0.79 to 2.63 ± 0.59, P < 0.01). During TH, diastolic pulmonary artery pressure (PAP) significantly decreased, and there were no significant changes in the stroke volume index (SVI). This increase of BNP was not associated with any hemodynamic changes. In contrast to our findings for BNP, the change in A-type NP (ANP) was quite small. We detected a significant increase in the plasma BNP levels during TH, unrelated to hemodynamics. This elevation of BNP levels seems to be potential influenced by hypothermia.

Gaining insight into cellular cardiac physiology using single particle tracking

Single particle tracking (SPT) is a robust technique to monitor single-molecule behaviors in living cells directly. By this approach, we can uncover the potential biological significance of particle dynamics by statistically characterizing individual molecular behaviors. SPT provides valuable information at the single-molecule level, that could be obscured by simple averaging that is inherent to conventional ensemble measurements. Here, we give a brief introduction to SPT including the commonly used optical implementations, fluorescence labeling strategies, and data analysis methods. We then focus on how SPT has been harnessed to decipher myocardial function. In this context, SPT has provided novel insight into the lateral diffusion of signal receptors and ion channels, the dynamic organization of cardiac nanodomains, subunit composition and stoichiometry of cardiac ion channels, myosin movement along actin filaments, the kinetic features of transcription factors involved in cardiac remodeling, and the intercellular communication by nanotubes. Finally, we speculate on the prospects and challenges of applying SPT to future questions regarding cellular cardiac physiology using SPT.

Luteolin improves myocardial cell glucolipid metabolism by inhibiting hypoxia inducible factor-1α expression in angiotensin II/hypoxia-induced hypertrophic H9c2 cells

Luteolin, a natural flavonoid, can attenuate hepatic lipid accumulation and insulin resistance in obese mice. Therefore, we hypothesized that luteolin may also improve the abnormal glucolipid metabolism of hypertrophic myocardial cells. This study aimed to investigate the effect and possible molecular mechanisms of luteolin. Hypertrophic H9c2 cells were induced by angiotensin II/hypoxia and simultaneously treated with 2 to 8 μg/mL luteolin for 24 h. Luteolin might dose-dependently decrease intracellular total protein, atrial natriuretic peptide, and free fatty acid levels, and increase supernatant glucose levels. Western blot assay showed that luteolin could inhibit the expressions of intracellular hypoxia inducible factor-1α (HIF-1α) and glucose transporter-4 (GLUT-4) proteins, and increase the expressions of intracellular peroxisome proliferator-activated receptor α (PPARα), carnitine palmitoyltransferase-1A (CPT-1A), and pyruvate dehydrogenase kinase-4 (PDK-4) proteins. These findings demonstrate that luteolin can improve abnormal glucolipid metabolism in angiotensin II/hypoxia-induced hypertrophic H9c2 cells, and its mechanisms are related to the inhibition of HIF-1α expression and subsequent modulation of PPARα-mediated target genes, including CPT-1A, PDK-4, and GLUT-4.

Low-dose atrial natriuretic peptide for prevention or treatment of acute kidney injury: a systematic review and meta-analysis

Background

Theoretically, atrial natriuretic peptide (ANP), especially low-dose ANP, is beneficial in acute kidney injury (AKI). In this study, we examined whether low-dose ANP is effective in preventing or treating AKI by conducting an updated systematic review for randomized controlled trials (RCTs).

Method

We searched the Excerpta Medica database (EMBASE), PubMed, and Cochrane CENTRAL databases for RCTs that compare the effects of low-dose ANP (≤ 50 ng/kg/min) with a placebo or conventional therapy in at-risk patients or patients with AKI. The primary outcome was the incidence of new AKI (in prevention RCTs), while the secondary outcomes were in-hospital mortality rate, renal replacement therapy (RRT) requirement, length of hospital and intensive care unit (ICU) stay, incidence of hypotension, and peak serum creatinine levels. The risk-of-bias was evaluated using the Cochrane Collaboration risk-of-bias tool. Trial sequential analysis (TSA) was used for each outcome of interest.

Results

A total of 18 RCTs (16 prevention and two treatment trials) fulfilled our inclusion criteria. In prevention RCTs, the incidence of new AKI was significantly low in the low-dose ANP group (relative risk [RR] = 0.51; 95% confidence interval [CI] = 0.36–0.72; P = 0.0001) compared to the control group. In addition, the low-dose ANP group showed a significantly reduced RRT requirement in both prevention (RR = 0.17; 95% CI = 0.04–0.64; P = 0.009) and treatment (RR = 0.43; 95% CI = 0.20–0.93; P = 0.03) RCTs. Among secondary outcomes, in some cases, low-dose ANP was associated with a reduction in ICU and in-hospital stay. The risk-of-bias assessment and TSA results indicated that the sample sizes and qualities of the RCTs were insufficient to conclude the efficacy of low-dose ANP.

Conclusion

Low-dose ANP might be effective in preventing or treating AKI. However, the evidence accumulated so far is not strong enough to demonstrate ANP’s beneficial effects. The next step is to elucidate the effects of low-dose ANP by conducting multicenter, high-quality, large-sample RCTs.

Trial registration

PROSPERO registry CRD42017068568. Registered 20 June 2017.

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2330-z) contains supplementary material, which is available to authorized users.

Atrial and brain natriuretic peptides: Hormones secreted from the heart

The natriuretic peptide family consists of three biologically active peptides: atrial natriuretic peptide (ANP), brain (or B-type) natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). Among these, ANP and BNP are secreted by the heart and act as cardiac hormones. Both ANP and BNP preferentially bind to natriuretic peptide receptor-A (NPR-A or guanylyl cyslase-A) and exert similar effects through increases in intracellular cyclic guanosine monophosphate (cGMP) within target tissues. Expression and secretion of ANP and BNP are stimulated by various factors and are regulated via multiple signaling pathways. Human ANP has three molecular forms, α-ANP, β-ANP, and proANP (or γ-ANP), with proANP predominating in healthy atrial tissue. During secretion proANP is proteolytically processed by corin, resulting in secretion of bioactive α-ANP into the peripheral circulation. ProANP and β-ANP are minor forms in the circulation but are increased in patients with heart failure. The human BNP precursor proBNP is proteolytically processed to BNP_1-32 and N-terminal proBNP (NT-proBNP) within ventricular myocytes. Uncleaved proBNP as well as mature BNP_1-32 and NT-proBNP is secreted from the heart, and its secretion is increased in patients with heart failure. Mature BNP, its metabolites including BNP_3-32, BNP_4-32, and BNP_5-32, and proBNP are all detected as immunoreactive-BNP by the current BNP assay system. We recently developed an assay system that specifically detects human proBNP. Using this assay system, we observed that miR30-GALNTs-dependent O-glycosylation in the N-terminal region of proBNP contributes to regulation of the processing and secretion of proBNP from the heart.

Natriuretic peptides in human heart: Novel insight into their molecular forms, functions, and diagnostic use

Among the three natriuretic peptides, atrial/A-type natriuretic peptide (ANP) and brain/B-type natriuretic peptide (BNP) are primarily produced by, and secreted from, heart tissue. They maintain cardiovascular homeostasis by binding to natriuretic peptide receptor-A. Since plasma ANP and BNP concentrations, as well as expression, are elevated in response to increased body fluid volume and pressure load on the heart wall, these peptides are widely utilized as diagnostic biomarkers for evaluating heart failure. Regardless of their high utility, differences in their molecular forms between healthy and diseased subjects and how these relate to pathophysiology have not well been examined. Recent studies have shown that the circulating molecular forms of ANP and BNP are not uniform; bioactive α-ANP is the major ANP form, whereas the weakly active proBNP is the major BNP form. The relative ratios of the different molecular forms are altered under different pathophysiological conditions. These facts indicate that detailed measurements of each form may provide useful information on the pathophysiological state of heart tissue. Here, we revisit the relationship between the molecular forms of, and pathophysiological alterations in, human ANP and BNP and discuss the possible utility of the measurement of each of the molecular forms. The third peptide, C-type natriuretic peptide, activates natriuretic peptide receptor-B, but little is known about its production and function in the heart because of its extremely low levels. However, through recent studies, its role in the heart is gradually becoming clear. Here, we summarize its molecular forms, assay systems, and functions in the heart.

Microarray analysis of long non-coding RNA and mRNA expression profiles in diabetic cardiomyopathy using human induced pluripotent stem cell-derived cardiomyocytes

AIM

This study aims to investigate the altered expression signature of long non-coding RNAs, mRNAs and deregulated pathways related to diabetic cardiomyopathy disease pathogenesis.

METHOD

We utilize the previously established in vitro diabetic cardiomyopathy model of human induced pluripotent stem cell-derived human cardiomyocytes to perform long non-coding RNA and mRNA expression analysis on glucose (11 mM), endothelin-1 (10 nM) and cortisol (1 µM) stimulated human induced pluripotent stem cell-derived human cardiomyocytes to interrogate diabetic cardiomyopathy associated RNA expression profile.

RESULT

Out of 20,730 mRNAs and 40,173 long non-coding RNAs being screened, 2046 long non-coding RNAs and 1582 mRNAs were differentially regulated (fold change > 2, p < 0.05) between diabetic cardiomyopathy and control group, of which more than half were intergenic and antisense long non-coding RNAs. Most of the coding transcripts were associated with processes like inflammation, structural reorganization, metabolism, smooth muscle contraction, focal adhesion and repair contributing towards the development of diabetic cardiomyopathy. The subgroup analysis further revealed 411 long non-coding RNAs being co-expressed with neighbouring genes. However, our coding-non-coding co-expression analysis showed an overall 48,155 co-expression network connections. In addition to that, the long non-coding RNAs with highest network connections were profoundly enriched for focal adhesion, cell-matrix adhesion and muscle contraction.

CONCLUSION

These results provide comprehensive data about the pathways and regulatory mechanisms associated with diabetic cardiomyopathy and indicate that long non-coding RNAs may play a crucial role in diabetic cardiomyopathy.

PIMT/NCOA6IP Deletion in the Mouse Heart Causes Delayed Cardiomyopathy Attributable to Perturbation in Energy Metabolism

PIMT/NCOA6IP, a transcriptional coactivator PRIP/NCOA6 binding protein, enhances nuclear receptor transcriptional activity. Germline disruption of PIMT results in early embryonic lethality due to impairment of development around blastocyst and uterine implantation stages. We now generated mice with Cre-mediated cardiac-specific deletion of PIMT (csPIMT^−/−) in adult mice. These mice manifest enlargement of heart, with nearly 100% mortality by 7.5 months of age due to dilated cardiomyopathy. Significant reductions in the expression of genes (i) pertaining to mitochondrial respiratory chain complexes I to IV; (ii) calcium cycling cardiac muscle contraction (Atp2a1, Atp2a2, Ryr2); and (iii) nuclear receptor PPAR- regulated genes involved in glucose and fatty acid energy metabolism were found in csPIMT^−/− mouse heart. Elevated levels of Nppa and Nppb mRNAs were noted in csPIMT^−/− heart indicative of myocardial damage. These hearts revealed increased reparative fibrosis associated with enhanced expression of Tgfβ2 and Ctgf. Furthermore, cardiac-specific deletion of PIMT in adult mice, using tamoxifen-inducible Cre-approach (TmcsPIMT^−/−), results in the development of cardiomyopathy. Thus, cumulative evidence suggests that PIMT functions in cardiac energy metabolism by interacting with nuclear receptor coactivators and this property could be useful in the management of heart failure.

Cardiac-specific ablation of the E3 ubiquitin ligase Mdm2 leads to oxidative stress, broad mitochondrial deficiency and early death

The maintenance of normal heart function requires proper control of protein turnover. The ubiquitin-proteasome system is a principal regulator of protein degradation. Mdm2 is the main E3 ubiquitin ligase for p53 in mitotic cells thereby regulating cellular growth, DNA repair, oxidative stress and apoptosis. However, which of these Mdm2-related activities are preserved in differentiated cardiomyocytes has yet to be determined. We sought to elucidate the role of Mdm2 in the control of normal heart function. We observed markedly reduced Mdm2 mRNA levels accompanied by highly elevated p53 protein expression in the hearts of wild type mice subjected to myocardial infarction or trans-aortic banding. Accordingly, we generated conditional cardiac-specific Mdm2 gene knockout (Mdm2^f/f;mcm) mice. In adulthood, Mdm2^f/f;mcm mice developed spontaneous cardiac hypertrophy, left ventricular dysfunction with early mortality post-tamoxifen. A decreased polyubiquitination of myocardial p53 was observed, leading to its stabilization and activation, in the absence of acute stress. In addition, transcriptomic analysis of Mdm2-deficient hearts revealed that there is an induction of E2f1 and c-Myc mRNA levels with reduced expression of the Pgc-1a/Ppara/Esrrb/g axis and Pink1. This was associated with a significant degree of cardiomyocyte apoptosis, and an inhibition of redox homeostasis and mitochondrial bioenergetics. All these processes are early, Mdm2-associated events and contribute to the development of pathological hypertrophy. Our genetic and biochemical data support a role for Mdm2 in cardiac growth control through the regulation of p53, the Pgc-1 family of transcriptional coactivators and the pivotal antioxidant Pink1.

The neural basis of homeostatic and anticipatory thirst

Water intake is one of the most basic physiological responses and is essential to sustain life. The perception of thirst has a critical role in controlling body fluid homeostasis and if neglected or dysregulated can lead to life-threatening pathologies. Clear evidence suggests that the perception of thirst occurs in higher-order centres, such as the anterior cingulate cortex (ACC) and insular cortex (IC), which receive information from midline thalamic relay nuclei. Multiple brain regions, notably circumventricular organs such as the organum vasculosum lamina terminalis (OVLT) and subfornical organ (SFO), monitor changes in blood osmolality, solute load and hormone circulation and are thought to orchestrate appropriate responses to maintain extracellular fluid near ideal set points by engaging the medial thalamic-ACC/IC network. Thirst has long been thought of as a negative homeostatic feedback response to increases in blood solute concentration or decreases in blood volume. However, emerging evidence suggests a clear role for thirst as a feedforward adaptive anticipatory response that precedes physiological challenges. These anticipatory responses are promoted by rises in core body temperature, food intake (prandial) and signals from the circadian clock. Feedforward signals are also important mediators of satiety, inhibiting thirst well before the physiological state is restored by fluid ingestion. In this Review, we discuss the importance of thirst for body fluid balance and outline our current understanding of the neural mechanisms that underlie the various types of homeostatic and anticipatory thirst.

The cardiac calsequestrin gene transcription is modulated at the promoter by NFAT and MEF-2 transcription factors

Calsequestrin-2 (CASQ2) is the main Ca²⁺-binding protein inside the sarcoplasmic reticulum of cardiomyocytes. Previously, we demonstrated that MEF-2 and SRF binding sites within the human CASQ2 gene (hCASQ2) promoter region are functional in neonatal cardiomyocytes. In this work, we investigated if the calcineurin/NFAT pathway regulates hCASQ2 expression in neonatal cardiomyocytes. The inhibition of NFAT dephosphorylation with CsA or INCA-6, reduced both the luciferase activity of hCASQ2 promoter constructs (-3102/+176 bp and -288/+176 bp) and the CASQ2 mRNA levels in neonatal rat cardiomyocytes. Additionally, NFATc1 and NFATc3 over-expressing neonatal cardiomyocytes showed a 2-3-fold increase in luciferase activity of both hCASQ2 promoter constructs, which was prevented by CsA treatment. Site-directed mutagenesis of the -133 bp MEF-2 binding site prevented trans-activation of hCASQ2 promoter constructs induced by NFAT overexpression. Chromatin Immunoprecipitation (ChIP) assays revealed NFAT and MEF-2 enrichment within the -288 bp to +76 bp of the hCASQ2 gene promoter. Besides, a direct interaction between NFAT and MEF-2 proteins was demonstrated by protein co-immunoprecipitation experiments. Taken together, these data demonstrate that NFAT interacts with MEF-2 bound to the -133 bp binding site at the hCASQ2 gene promoter. In conclusion, in this work, we demonstrate that the Ca²⁺-calcineurin/NFAT pathway modulates the transcription of the hCASQ2 gene in neonatal cardiomyocytes.

Three molecular forms of atrial natriuretic peptides: quantitative analysis and biological characterization

Atrial natriuretic peptide (ANP) is primarily produced in the heart tissue and plays a pivotal role in maintaining cardiovascular homeostasis in endocrine and autocrine/paracrine systems and has clinical applications as a biomarker and a therapeutic agent for cardiac diseases. ANP is synthesized by atrial cardiomyocytes as a preprohormone that is processed by a signal peptidase and stored in secretory granules as a prohormone. Subsequent proteolytic processing of ANP by corin during the secretion process results in a bioactive form consisting of 28 amino acid residues. Mechanical stretch of the atrial wall and multiple humoral factors directly stimulates the transcription and secretion of ANP. Secreted ANP elicits natriuretic and diuretic effects via cyclic guanosine monophosphate produced through binding to the guanylyl cyclase-A/natriuretic peptide receptor-A. Circulating ANP is subjected to rapid clearance by a natriuretic peptide receptor-C-mediated mechanism and proteolytic degradation by neutral endopeptidase. In humans, ANP is present as three endogenous molecular forms: bioactive α-ANP, a homodimer of α-ANP designated as β-ANP, and an ANP precursor designated as proANP (also referred to as γ-ANP). The proANP and especially β-ANP, as minor forms in circulation, are notably increased in patients with cardiac diseases, suggesting the utility of monitoring the pathophysiological conditions that result in abnormal proANP processing that cannot be monitored by inactive N-terminal proANP-related fragments. Emerging plate-based sandwich immunoassays for individual quantitation of the three ANP forms enables evaluation of diagnostic implications and net ANP bioactivity. This new tool may provide further understanding in the pathophysiology of cardiac diseases. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Brain Natriuretic Peptide Counteracting the Renin-angiotensin-aldosterone System in Accelerated Malignant Hypertension

We describe 2 patients, a 52-year-old woman and a 57-year-old man, with rapidly progressive hypertension and marked elevation of brain natriuretic peptide who exhibited polyuria, natriuresis, hypokalemia, posterior reversible encephalopathy syndrome and left ventricular dysfunction together with retinopathy and nephropathy, which were attenuated in a short time span of 1-2 months with normalization of blood pressure after the antihypertensive treatment. The possible role of brain natriuretic peptide in the pathophysiology of accelerated malignant hypertension was discussed and a review of the literature was completed.

Cardiomyocyte-Specific Ablation of Med1 Subunit of the Mediator Complex Causes Lethal Dilated Cardiomyopathy in Mice

Mediator, an evolutionarily conserved multi-protein complex consisting of about 30 subunits, is a key component of the polymerase II mediated gene transcription. Germline deletion of the Mediator subunit 1 (Med1) of the Mediator in mice results in mid-gestational embryonic lethality with developmental impairment of multiple organs including heart. Here we show that cardiomyocyte-specific deletion of Med1 in mice (csMed1-/-) during late gestational and early postnatal development by intercrossing Med1fl/fl mice to α-MyHC-Cre transgenic mice results in lethality within 10 days after weaning due to dilated cardiomyopathy-related ventricular dilation and heart failure. The csMed1-/- mouse heart manifests mitochondrial damage, increased apoptosis and interstitial fibrosis. Global gene expression analysis revealed that loss of Med1 in heart down-regulates more than 200 genes including Acadm, Cacna1s, Atp2a2, Ryr2, Pde1c, Pln, PGC1α, and PGC1β that are critical for calcium signaling, cardiac muscle contraction, arrhythmogenic right ventricular cardiomyopathy, dilated cardiomyopathy and peroxisome proliferator-activated receptor regulated energy metabolism. Many genes essential for oxidative phosphorylation and proper mitochondrial function such as genes coding for the succinate dehydrogenase subunits of the mitochondrial complex II are also down-regulated in csMed1-/- heart contributing to myocardial injury. Data also showed up-regulation of about 180 genes including Tgfb2, Ace, Atf3, Ctgf, Angpt14, Col9a2, Wisp2, Nppa, Nppb, and Actn1 that are linked to cardiac muscle contraction, cardiac hypertrophy, cardiac fibrosis and myocardial injury. Furthermore, we demonstrate that cardiac specific deletion of Med1 in adult mice using tamoxifen-inducible Cre approach (TmcsMed1-/-), results in rapid development of cardiomyopathy and death within 4 weeks. We found that the key findings of the csMed1-/- studies described above are highly reproducible in TmcsMed1-/- mouse heart. Collectively, these observations suggest that Med1 plays a critical role in the maintenance of heart function impacting on multiple metabolic, compensatory and reparative pathways with a likely therapeutic potential in the management of heart failure.

Pharmacological Therapy in the Heart as an Alternative to Cellular Therapy: A Place for the Brain Natriuretic Peptide?

The discovery that stem cells isolated from different organs have the ability to differentiate into mature beating cardiomyocytes has fostered considerable interest in developing cellular regenerative therapies to treat cardiac diseases associated with the loss of viable myocardium. Clinical studies evaluating the potential of stem cells (from heart, blood, bone marrow, skeletal muscle, and fat) to regenerate the myocardium and improve its functional status indicated that although the method appeared generally safe, its overall efficacy has remained modest. Several issues raised by these studies were notably related to the nature and number of injected cells, as well as the route and timing of their administration, to cite only a few. Besides the direct administration of cardiac precursor cells, a distinct approach to cardiac regeneration could be based upon the stimulation of the heart's natural ability to regenerate, using pharmacological approaches. Indeed, differentiation and/or proliferation of cardiac precursor cells is controlled by various endogenous mediators, such as growth factors and cytokines, which could thus be used as pharmacological agents to promote regeneration. To illustrate such approach, we present recent results showing that the exogenous administration of the natriuretic peptide BNP triggers “endogenous” cardiac regeneration, following experimental myocardial infarction.

N-Terminal Pro-Brain Natriuretic Peptide Is Associated with a Future Diagnosis of Cancer in Patients with Coronary Artery Disease

Objective

Several papers have reported elevated plasma levels of natriuretic peptides in patients with a previous diagnosis of cancer. We have explored whether N-terminal pro-brain natriuretic peptide (NT-proBNP) plasma levels predict a future diagnosis of cancer in patients with coronary artery disease (CAD).

Methods

We studied 699 patients with CAD free of cancer. At baseline, NT-proBNP, galectin-3, monocyte chemoattractant protein-1, soluble tumor necrosis factor-like weak inducer of apoptosis, high-sensitivity C-reactive protein, and high-sensitivity cardiac troponin I plasma levels were assessed. The primary outcome was new cancer diagnosis. The secondary outcome was cancer diagnosis, heart failure requiring hospitalization, or death.

Results

After 2.15±0.98 years of follow-up, 24 patients developed cancer. They were older (68.5 [61.5, 75.8] vs 60.0 [52.0, 72.0] years; p=0.011), had higher NT-proBNP (302.0 [134.8, 919.8] vs 165.5 [87.4, 407.5] pg/ml; p=0.040) and high-sensitivity C-reactive protein (3.27 [1.33, 5.94] vs 1.92 [0.83, 4.00] mg/L; p=0.030), and lower triglyceride (92.5 [70.5, 132.8] vs 112.0 [82.0, 157.0] mg/dl; p=0.044) plasma levels than those without cancer. NT-proBNP (Hazard Ratio [HR]=1.030; 95% Confidence Interval [CI]=1.008-1.053; p=0.007) and triglyceride levels (HR=0.987; 95%CI=0.975-0.998; p=0.024) were independent predictors of a new cancer diagnosis (multivariate Cox regression analysis). When patients in whom the suspicion of cancer appeared in the first one-hundred days after blood extraction were excluded, NT-proBNP was the only predictor of cancer (HR=1.061; 95%CI=1.034-1.088; p<0.001). NT-proBNP was an independent predictor of cancer, heart failure, or death (HR=1.038; 95%CI=1.023-1.052; p<0.001) along with age, and use of insulin and acenocumarol.

Conclusions

NT-proBNP is an independent predictor of malignancies in patients with CAD. New studies in large populations are needed to confirm these findings.

Natriuretic peptide receptor 3 (NPR3) is regulated by microRNA-100

Natriuretic peptide receptor 3 (NPR3) is the clearance receptor for the cardiac natriuretic peptides (NPs). By modulating the level of NPs, NPR3 plays an important role in cardiovascular homeostasis. Although the physiological functions of NPR3 have been explored, little is known about its regulation in health or disease. MicroRNAs play an essential role in the post-transcriptional expression of many genes. Our aim was to investigate potential microRNA-based regulation of NPR3 in multiple models. Hypoxic challenge elevated levels of NPPB and ADM mRNA, as well as NT-proBNP and MR-proADM in human left ventricle derived cardiac cells (HCMa), and in the corresponding conditioned medium, as revealed by qRT-PCR and ELISA. NPR3 was decreased while NPR1 was increased by hypoxia at mRNA and protein levels in HCMa. Down-regulation of NPR3 mRNA was also observed in infarct and peri-infarct cardiac tissue from rats undergoing myocardial infarction. From microRNA microarray analyses and microRNA target predictive databases, miR-100 was selected as a candidate regulator of NPR3 expression. Further analyses confirmed up-regulation of miR-100 in hypoxic cells and associated conditioned media. Antagomir-based silencing of miR-100 enhanced NPR3 expression in HCMa. Furthermore, miR-100 levels were markedly up-regulated in rat hearts and in peripheral blood after myocardial infarction and in the blood from heart failure patients. Results from this study point to a role for miR-100 in the regulation of NPR3 expression, and suggest a possible therapeutic target for modulation of NP bioactivity in heart disease.

RNA expression profiling of human iPSC-derived cardiomyocytes in a cardiac hypertrophy model

Cardiac hypertrophy is an independent risk factor for cardiovascular disease and heart failure. There is increasing evidence that microRNAs (miRNAs) play an important role in the regulation of messenger RNA (mRNA) and the pathogenesis of various cardiovascular diseases. However, the ability to comprehensively study cardiac hypertrophy on a gene regulatory level is impacted by the limited availability of human cardiomyocytes. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) offer the opportunity for disease modeling. Here we utilize a previously established invitro model of cardiac hypertrophy to interrogate the regulatory mechanism associated with the cardiac disease process. We perform miRNA sequencing and mRNA expression analysis on endothelin 1 (ET-1) stimulated hiPSC-CMs to describe associated RNA expression profiles. MicroRNA sequencing revealed over 250 known and 34 predicted novel miRNAs to be differentially expressed between ET-1 stimulated and unstimulated control hiPSC-CMs. Messenger RNA expression analysis identified 731 probe sets with significant differential expression. Computational target prediction on significant differentially expressed miRNAs and mRNAs identified nearly 2000 target pairs. A principal component analysis approach comparing the invitro data with human myocardial biopsies detected overlapping expression changes between the invitro samples and myocardial biopsies with Left Ventricular Hypertrophy. These results provide further insights into the complex RNA regulatory mechanism associated with cardiac hypertrophy.

Incomplete recovery of mechanical and endocrine left atrial functions one month after electrical cardioversion for persistent atrial fibrillation: a pilot study

Background

Restoration of the mechanical and endocrine functions of the left atrium remains controversial after electrical cardioversion treatment for persistent atrial fibrillation. The objective of the prospective study was to describe the recovery of the endocrine and mechanical functions of the left atrium.

Methods

Evaluation of left atrium recovery after electrical cardioversion by the new speckle-tracking echocardiography technique and proANP measurement.

Results

Twenty patients suffering from persistent atrial fibrillation with no alteration of left ventricular ejection fraction were prospectively evaluated at baseline and then one month later by echocardiography, measuring left atrial volume and left atrial deformation (MPALS), as well as the proANP and BNP concentrations. One month after cardioversion 10 patients remained in sinus rhythm and 10 showed recurrent atrial fibrillation. No significant differences between the two groups in terms of clinical, echocardiographic and endocrine parameters were observed at baseline evaluation. We observed a significant reduction of left atrial volume only in the sinus group, whereas restoration of the left atrial deformation was only partial (18%) in that group. By contrast, we registered no significant changes in ANP concentration at one month in either the sinus or the atrial fibrillation groups.

Conclusion

These results suggest that restoration of left atrium mechanical function is only partial one month after treatment of persistent atrial fibrillation by electrical cardioversion, whereas a significant reduction of left atrial volume was noted, explaining the remaining high level of ANP in the sinus group.

Plasma natriuretic peptides in children and adolescents with obstructive sleep apnea and their changes following intervention

OBJECTIVE

This study aimed to evaluate circulating natriuretic peptides (NP) concentration in obese and non-obese children and adolescents with and without obstructive sleep apnea (OSA), and their levels following OSA treatment.

METHODS

Subjects with habitual snoring and symptoms suggestive of OSA were recruited. They underwent physical examination and overnight polysomnography (PSG). OSA was diagnosed if obstructive apnea-hypopnea index (OAHI) was ≥1/h. Fasting serum atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were taken after overnight PSG. The subjects were divided into obese, non-obese, with and without OSA groups for comparisons.

RESULTS

One hundred fourteen children (77 were boys) with a median [interquartile range (IQR)] age of 10.8 (8.3-12.7) years (range: 2.4-11.8 years) were recruited. Sixty-eight subjects were found to have OSA. NP levels did not differ between subjects with and without OSA in both obese and non-obese groups. Stepwise multiple linear regressions revealed that body mass index (BMI) z-score was the only independent factor associated with NP concentrations. Fifteen children with moderate-to-severe OSA (OAHI >5/h) underwent treatment and there were no significant changes in both ANP and BNP levels after intervention.

CONCLUSION

Body mass index rather than OSA was the main determinant of NP levels in school-aged children and adolescents.

Cardiac production of B-type natriuretic peptide is inversely related to the plasma level of free fatty acids in obese individuals - possible involvement of the insulin resistance -

B-type natriuretic peptide (BNP) is produced by the heart and its plasma level is increased with the severity of left ventricular (LV) dysfunction/hypertrophy. The normal heart preferentially utilizes fatty acids as energy substrates. Plasma BNP levels are reported to be lower in obese individuals. We examined the relationship between BNP production and plasma free fatty acids (FFA), homeostasis model assessment of insulin resistance (HOMA-IR), and LV dysfunction/ hypertrophy. We examined the plasma BNP levels and FFA at the aortic root (AO) and coronary sinus (CS) as well as hemodynamic parameters in 62 patients (38 men and 24 women, 62.5±11.7 yrs) who underwent cardiac catheterization. Log BNP (AO) had a significant positive correlation with log BNP (CS-AO) (r=0.877, P<0.001). Log BNP(CS-AO) had a significant negative correlation with BMI (r=-0.558, P<0.001), waist circumference (WC) (r=-0.574, P<0.001), log FFA(AO) (r=-0.643, P<0.001), log triglyceride (r=-0.431, P<0.001), and log HOMA-IR (r=-0.463, P<0.001) and a significant positive correlation with left ventricular mass index (LVMI) (r=0.403, P=0.001). The multivariable regression analyses including log HOMA-IR, LVMI, and age as an independent variable revealed that HOMA-IR and LVMI were significant predictors of log BNP (CS-AO) or BNP production (P=0.001 and 0.004, respectively). We conclude that plasma BNP levels are determined primarily by cardiac production and that insulin resistance is a significant predictor of cardiac BNP production independent of LV hypertrophy in obese individuals.

[The heart as an endocrine organ]

The discovery of cardiac hormone production significantly changed the evaluation of the function of the heart, which is rather regarded as a determining factor of the electrolyte and hemodynamic homeostasis cooperating with other organ systems instead of a mechanical pump. The most important hormones produced by the heart are the natriuretic peptides that have the primary role of protection against volume overload through natriuretic, diuretic, vasodilator and antiproliferative effects. They are integrative markers of the cardiac, vascular and renal functions and marking cardiorenal distress. Brain natriuretic peptide and the N-terminal pro-hormone (NT-proBNP) became generally accepted markers of heart failure exceeding traditional pathophysiological significance of those. They are useful in the diagnosis, estimation of prognosis and therapy guidance and their therapeutic administration is also available. Although the detection of extraadrenal aldosterone production is an exciting new discovery, intracardial aldosterone production is not significant in human beings. The intracardial thyroid hormone production is regulated by deiodinase activity. The role of elevated T3 concentration was suggested in the development of cardiac hypertrophy, while low T3 is assumed to be important in adaptation to hypoxia. An unexpected, complex relation can be determined between epicardial adipose tissue and coronary artery diseases, cytokine and adipokine production of adipocytes might be a part of the self-enhancing process of atherosclerosis.

Impact of AT2 receptor deficiency on postnatal cardiovascular development

BACKGROUND

The angiotensin II receptor subtype 2 (AT2 receptor) is ubiquitously and highly expressed in early postnatal life. However, its role in postnatal cardiac development remained unclear.

METHODOLOGY/PRINCIPAL FINDINGS

Hearts from 1, 7, 14 and 56 days old wild-type (WT) and AT2 receptor-deficient (KO) mice were extracted for histomorphometrical analysis as well as analysis of cardiac signaling and gene expression. Furthermore, heart and body weights of examined animals were recorded and echocardiographic analysis of cardiac function as well as telemetric blood pressure measurements were performed. Moreover, gene expression, sarcomere shortening and calcium transients were examined in ventricular cardiomyocytes isolated from both genotypes. KO mice exhibited an accelerated body weight gain and a reduced heart to body weight ratio as compared to WT mice in the postnatal period. However, in adult KO mice the heart to body weight ratio was significantly increased most likely due to elevated systemic blood pressure. At postnatal day 7 ventricular capillarization index and the density of α-smooth muscle cell actin-positive blood vessels were higher in KO mice as compared to WT mice but normalized during adolescence. Echocardiographic assessment of cardiac systolic function at postnatal day 7 revealed decreased contractility of KO hearts in response to beta-adrenergic stimulation. Moreover, cardiomyocytes from KO mice showed a decreased sarcomere shortening and an increased peak Ca(2+) transient in response to isoprenaline when stimulated concomitantly with angiotensin II.

CONCLUSION

The AT2 receptor affects postnatal cardiac growth possibly via reducing body weight gain and systemic blood pressure. Moreover, it moderately attenuates postnatal vascularization of the heart and modulates the beta adrenergic response of the neonatal heart. These AT2 receptor-mediated effects may be implicated in the physiological maturation process of the heart.

Transcriptional regulation of the fetal cardiac gene program

Reactivation of the fetal cardiac gene program in adults is a reliable marker of cardiac hypertrophy and heart failure. Normally, genes within this group are expressed in the fetal ventricles during development, but are silent after birth. However, their expression is re-induced in the ventricular myocardium in response to various cardiovascular diseases, and potentially plays an important role in the pathological process of cardiac remodeling. Thus, analysis of the molecular mechanisms that govern the expression of fetal cardiac genes could lead to the discovery of transcriptional regulators and signaling pathways involved in both cardiac differentiation and cardiac disease. In this review we will summarize what is currently known about the transcriptional regulation of the fetal cardiac gene program.

DelK32-lamin A/C has abnormal location and induces incomplete tissue maturation and severe metabolic defects leading to premature death

The LMNA gene encodes lamin A/C intermediate filaments that polymerize beneath the nuclear membrane, and are also found in the nucleoplasm in an uncharacterized assembly state. They are thought to have structural functions and regulatory roles in signaling pathways via interaction with transcription factors. Mutations in LMNA have been involved in numerous inherited human diseases, including severe congenital muscular dystrophy (L-CMD). We created the Lmna(ΔK32) knock-in mouse harboring a L-CMD mutation. Lmna(ΔK32/ΔK32) mice exhibited striated muscle maturation delay and metabolic defects, including reduced adipose tissue and hypoglycemia leading to premature death. The level of mutant proteins was markedly lower in Lmna(ΔK32/ΔK32), and while wild-type lamin A/C proteins were progressively relocated from nucleoplasmic foci to the nuclear rim during embryonic development, mutant proteins were maintained in nucleoplasmic foci. In the liver and during adipocyte differentiation, expression of ΔK32-lamin A/C altered sterol regulatory element binding protein 1 (SREBP-1) transcriptional activities. Taken together, our results suggest that lamin A/C relocation at the nuclear lamina seems important for tissue maturation potentially by releasing its inhibitory function on transcriptional factors, including but not restricted to SREBP-1. And importantly, L-CMD patients should be investigated for putative metabolic disorders.

Differential role of Nkx2-5 in activation of the atrial natriuretic factor gene in the developing versus failing heart

Atrial natriuretic factor (ANF) is abundantly expressed in atrial cardiomyocytes throughout ontogeny and in ventricular cardiomyocytes in the developing heart. However, during cardiac failure and hypertrophy, ANF expression can reappear in adult ventricular cardiomyocytes. The transcription factor Nkx2-5 is one of the major transactivators of the ANF gene in the developing heart. We identified Nkx2-5 binding at three 5' regulatory elements (kb -34, -31, and -21) and at the proximal ANF promoter by ChIP assay using neonatal mouse cardiomyocytes. 3C analysis revealed close proximity between the distal elements and the promoter region. A 5.8-kb fragment consisting of these elements transactivated a reporter gene in vivo recapitulating endogenous ANF expression, which was markedly reduced in tamoxifen-inducible Nkx2-5 gene knockout mice. However, expression of a reporter gene was increased and expanded toward the outer compact layer in the absence of the transcription repressor Hey2, similar to endogenous ANF expression. Functional Nkx2-5 and Hey2 binding sites separated by 59 bp were identified in the -34 kb element in neonatal cardiomyocytes. In adult hearts, this fragment did not respond to pressure overload, and ANF was induced in the absence of Nkx2-5. These results demonstrate that Nkx2-5 and its responsive cis-regulatory DNA elements are essential for ANF expression selectively in the developing heart.

Cellular Interplay between Cardiomyocytes and Nonmyocytes in Cardiac Remodeling

Cardiac hypertrophy entails complex structural remodeling involving rearrangement of muscle fibers, interstitial fibrosis, accumulation of extracellular matrix, and angiogenesis. Many of the processes underlying cardiac remodeling have features in common with chronic inflammatory processes. During these processes, nonmyocytes, such as endothelial cells, fibroblasts, and immune cells, residing in or infiltrating into the myocardial interstitium play active roles. This paper mainly addresses the functional roles of nonmyocytes during cardiac remodeling. In particular, we focus on the communication between cardiomyocytes and nonmyocytes through direct cell-cell interactions and autocrine/paracrine-mediated pathways.

[Physiology and clinical role of natriuretic peptides]

In the last three decades many members of the natriuretic peptide family was isolated. The function and physiological role of these peptides are pleiotropic. All natriuretic peptides are synthesized from polypeptide precursors. Together with the sympathetic nervous system and other hormones they play key roles, like an endogenous system in the regulation of the body fluid homeostasis and blood pressure. Changes in this balance lead to dysfunction in the endothel and left ventricle, which can cause severe complications. In many cardiovascular diseases natriuretic peptides serve not only as marker for diagnosis and prognosis but they have therapeutic importance. In the last years the potential use of the elevated BNP levels for diagnosis of pre-eclampsia was examined. In our review we discuss the current understanding of molecular biology, biochemistry and clinical relevance of natriuretic peptides.

Natriuretic peptides: ready for prime-time in hypertension?

Over the past years, natriuretic peptides have been recognised not only as important contributors to cardiovascular regulation but also as valuable markers in overt cardiac disease, including heart failure or coronary disease. More recently, these markers have shown their ability to detect preclinical cardiac alterations in different settings. In this respect, natriuretic peptides offer a new perspective for risk stratification in hypertension. They are correlated to various features of cardiac remodelling provoked by hypertension. They also depend on vascular properties, including blood pressure level and aortic stiffness. In addition to being integrative markers of cardiovascular alterations, several studies have shown their value in predicting all-cause mortality or cardiovascular mortality and morbidity in the general population. At least three consistent studies are now available in hypertension also showing this prognostic value. This performance, together with the ease of measurement, low cost and widespread availability, should prompt the wide use of natriuretic peptides for risk stratification in hypertension, at least in patients with normal electrocardiography, but also in most hypertensive patients.