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Concept: Atrial natriuretic peptide

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Background Nitrates are commonly prescribed to enhance activity tolerance in patients with heart failure and a preserved ejection fraction. We compared the effect of isosorbide mononitrate or placebo on daily activity in such patients. Methods In this multicenter, double-blind, crossover study, 110 patients with heart failure and a preserved ejection fraction were randomly assigned to a 6-week dose-escalation regimen of isosorbide mononitrate (from 30 mg to 60 mg to 120 mg once daily) or placebo, with subsequent crossover to the other group for 6 weeks. The primary end point was the daily activity level, quantified as the average daily accelerometer units during the 120-mg phase, as assessed by patient-worn accelerometers. Secondary end points included hours of activity per day during the 120-mg phase, daily accelerometer units during all three dose regimens, quality-of-life scores, 6-minute walk distance, and levels of N-terminal pro-brain natriuretic peptide (NT-proBNP). Results In the group receiving the 120-mg dose of isosorbide mononitrate, as compared with the placebo group, there was a nonsignificant trend toward lower daily activity (-381 accelerometer units; 95% confidence interval [CI], -780 to 17; P=0.06) and a significant decrease in hours of activity per day (-0.30 hours; 95% CI, -0.55 to -0.05; P=0.02). During all dose regimens, activity in the isosorbide mononitrate group was lower than that in the placebo group (-439 accelerometer units; 95% CI, -792 to -86; P=0.02). Activity levels decreased progressively and significantly with increased doses of isosorbide mononitrate (but not placebo). There were no significant between-group differences in the 6-minute walk distance, quality-of-life scores, or NT-proBNP levels. Conclusions Patients with heart failure and a preserved ejection fraction who received isosorbide mononitrate were less active and did not have better quality of life or submaximal exercise capacity than did patients who received placebo. (Funded by the National Heart, Lung, and Blood Institute; ClinicalTrials.gov number, NCT02053493 .).

Concepts: Clinical trial, Myocardial infarction, Medical terms, Cardiology, Heart failure, Ejection fraction, Atrial natriuretic peptide, Isosorbide mononitrate

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Sildenafil, an inhibitor of the cGMP-degrading phosphodiesterase 5 that is used to treat erectile dysfunction, has been linked to an increased risk of melanoma. Here, we have examined the potential connection between cGMP-dependent signaling cascades and melanoma growth. Using a combination of biochemical assays and real-time monitoring of melanoma cells, we report a cGMP-dependent growth-promoting pathway in murine and human melanoma cells. We document that C-type natriuretic peptide (CNP), a ligand of the membrane-bound guanylate cyclase B, enhances the activity of cGMP-dependent protein kinase I (cGKI) in melanoma cells by increasing the intracellular levels of cGMP. Activation of this cGMP pathway promotes melanoma cell growth and migration in a p44/42 MAPK-dependent manner. Sildenafil treatment further increases intracellular cGMP concentrations, potentiating activation of this pathway. Collectively, our data identify this cGMP-cGKI pathway as the link between sildenafil usage and increased melanoma risk.

Concepts: Protein, Molecular biology, Signal transduction, Adenosine triphosphate, Cell membrane, Erectile dysfunction, Atrial natriuretic peptide, Cyclic guanosine monophosphate

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Fasting reduces glucose levels and protects mice against chemotoxicity, yet drugs that promote hyperglycemia are widely used in cancer treatment. Here, we show that dexamethasone (Dexa) and rapamycin (Rapa), commonly administered to cancer patients, elevate glucose and sensitize cardiomyocytes and mice to the cancer drug doxorubicin (DXR). Such toxicity can be reversed by reducing circulating glucose levels by fasting or insulin. Furthermore, glucose injections alone reversed the fasting-dependent protection against DXR in mice, indicating that elevated glucose mediates, at least in part, the sensitizing effects of rapamycin and dexamethasone. In yeast, glucose activates protein kinase A (PKA) to accelerate aging by inhibiting transcription factors Msn2/4. Here, we show that fasting or glucose restriction (GR) regulate PKA and AMP-activated protein kinase (AMPK) to protect against DXR in part by activating the mammalian Msn2/4 ortholog early growth response protein 1 (EGR1). Increased expression of the EGR1-regulated cardioprotective peptides atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) in heart tissue may also contribute to DXR resistance. Our findings suggest the existence of a glucose-PKA pathway that inactivates conserved zinc finger stress-resistance transcription factors to sensitize cells to toxins conserved from yeast to mammals. Our findings also describe a toxic role for drugs widely used in cancer treatment that promote hyperglycemia and identify dietary interventions that reverse these effects.

Concepts: DNA, Protein, Signal transduction, Nutrition, Adenosine triphosphate, Enzyme, Brain natriuretic peptide, Atrial natriuretic peptide

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Aldosterone modulates the activity of the epithelial sodium channel (ENaC) through changes in its trafficking, membrane expression and open probability. Plasma levels of aldosterone are decreased in preeclampsia. Herein we postulated that if aldosterone regulates ENaC expression then its expression should be decreased in preeclampsia. We found a diminished expression of the three subunits of the ENaC in the membranes of preeclamptic placentas in comparison with the normal ones. Although the role of ENaC in placental tissues is poorly understood, these differences may have consequences for the ion transport involved in the pathophysiology of preeclampsia.

Concepts: Cell membrane, Aldosterone, Sodium, Placenta, Atrial natriuretic peptide, Amiloride, Epithelial sodium channel, Triamterene

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To evaluate the diagnostic performance of the mid-regional portion of the pro-atrial natriuretic peptide (MR-proANP) for heart failure (HF) in dyspnea patients.

Concepts: Heart failure, Atrial natriuretic peptide

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Cardiovascular hypertrophy is a common feature of hypertension and an important risk factor for heart damage. The regression of cardiovascular hypertrophy is currently considered an important therapeutic target in reducing the omplications of hypertension. The aim of this study was to investigate the inhibition of cardiac hypertrophy by probiotic-fermented purple sweet potato yogurt (PSPY) with high γ-aminobutyric acid (GABA) content in spontaneously hypertensive rat (SHR) hearts. Six-week-old male SHRs were separated randomly and equally into 4 experimental groups: sterile water, captopril and 2 PSPY groups with different doses (10 and 100%) for 8 weeks. The changes in myocardial architecture and key molecules of the hypertrophy-related pathway in the excised left ventricle from these rats were determined by histopathological analysis, hematoxylin and eosin staining and western blot analysis. Abnormal myocardial architecture and enlarged interstitial spaces observed in the SHRs were significantly decreased in the captopril and PSPY groups compared with the sterile water group. Moreover, the increases in atrial natriuretic peptide, B-type natriuretic peptide, phosphorilated protein kinase Cα and calmodulin-dependent protein kinase II levels in the left ventricle were accompanied by hypertension and increases in phosphorylated extracellular signal-regulated kinase 5 activities with enhanced cardiac hypertrophy. However, the protein levels of the hypertrophic-related pathways were completely reversed by the administration of PSPY. PSPY may repress the activation of ANP and BNP which subsequently inhibit the dephosphorylation of the nuclear factor of activated T-cells, cytoplasmic 3 and ultimately prevent the progression of cardiac hypertrophy.

Concepts: Signal transduction, Blood, Heart, Circulatory system, Ventricle, Atrium, Brain natriuretic peptide, Atrial natriuretic peptide

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BACKGROUND: Atrial fibrillation (AF) is highly prevalent in patients with ischemic stroke, but the diagnosis is often difficult. METHODS: This study consisted of 68 stroke patients in sinus rhythm without history of AF. All patients underwent P-wave signal-averaged electrocardiography (P-SAECG), echocardiography, 24-h Holter monitoring, and measurement of plasma B-type natriuretic peptide (BNP) concentrations at admission. RESULTS: An abnormal P-SAECG was found in 34 of 68 stroke patients. In the follow-up period of 11±4 months, AF developed in 17 patients (AF group). The remaining 51 patients were classified as the non-AF group. The prevalence of atrial late potentials (ALP) on P-SAECG, and the number of premature atrial contractions (PACs) were significantly higher in the AF group than those in the non-AF group (88.2% vs 37.3%; p<0.001, 149±120 vs 79±69; p=0.030, respectively). However, there were no significant differences in age, left atrial dimension, or BNP concentrations between both groups. Cox proportional hazards analysis revealed that the presence of ALP (risk ratio 11.15; p=0.002) and frequent PACs (more than 100/24h) (risk ratio 4.53; p=0.007) had significant correlation to the occurrence of AF. CONCLUSIONS: ALP may be a novel predictor of AF in stroke patients. P-SAECG should be considered in stroke of undetermined etiology.

Concepts: Medical statistics, Cardiology, Stroke, Atrial fibrillation, Transient ischemic attack, Brain natriuretic peptide, Atrial natriuretic peptide, Holter monitor

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The main objective of this study was to investigate whether cardiac troponin (cTn) and N-terminal, protein B-type natriuretic peptide (NT-proBNP) can be useful as indicators for amitriptyline cardiotoxicity which is a known drug having sublethal toxic cardiac effects. At the same time, this study looked at detecting potential histopathological changes specific to irreversible cardiac injuries in a rat model of amitriptyline cardiotoxicity. Male Wistar rats were randomly divided into 2 groups, control (saline) group and amitriptyline group (100 mg/kg body weight intraperitoneally, equivalent for lethal dose at 50%). Blood was collected 30 minutes after the administration. The cTn was measured using 3 different methods (2 methods designed for human use and a sandwich enzyme immunoassay specific for rat cTnT). The brain natriuretic peptide was measured by 2 different methods (1 for human and 1 specific for rats). Electrocardiography showed that the QRS complex (P < .0001) and the QT interval (P = .002) were significantly prolonged for amitriptyline-treated animals. Troponin T and NT-proBNP had significantly increased levels in all the rats but showed positive results only when using rat-specific quantitative measurement. In certain rats, the histopathological examination identified a few small foci of acute myocardial necrosis. In conclusion, elevation of cTnT and NT-proBNP are early indicators of cardiotoxicity, yet the significance of irreversible myocardial damage in amitriptyline cardiotoxicity needs to be further understood.

Concepts: Protein, Myocardial infarction, Cardiology, Cardiac electrophysiology, Circulatory system, Toxicology, Troponin, Atrial natriuretic peptide

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AIMS: N-terminal pro brain natriuretic peptide (NT-proBNP) is an important biomarker in congestive heart failure. This has also been confirmed in congenital heart disease. However, its clinical value in patients with different types of Fontan circulation remains questionable. METHODS AND RESULTS: We prospectively analysed 124 patients with various types of Fontan surgery between October 2006 and February 2011. We included 49 patients with older Fontan modification [atriopulmonary connection (APC) and atrioventricular connection (AVC)] and 75 patients with total cavopulmonary connection (TCPC). The NT-proBNP levels of patients with APC/AVC were significantly higher than in patients with TCPC (P < 0.001), even after accounting for sex, age, ventricular function, atrioventricular regurgitation, ventricular morphology, and arrhythmia (P = 0.035). Levels of NT-proBNP positively correlated with atrioventricular valve regurgitation (r = 0.29, P = 0.013) and ventricular dysfunction (r = 0.23, P = 0.052) only in patients with TCPC, but not in patients with APC or AVC (r = 0.01, P = 0.509 and r = 0.10, P = 0.493, respectively). CONCLUSION: Levels of NT-pro BNP are related to the type of Fontan circulation. The older types (APC/AVC) that involve more atrial tissue in the systemic venous pathway show higher NT-proBNP levels independently of their cardiac status. Their NT-proBNP levels should be interpreted with care.

Concepts: Blood, Cardiology, Heart failure, Heart, Atrium, Brain natriuretic peptide, Atrial natriuretic peptide, Fontan procedure

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Blessed were the days when it all made sense and the apparent mechanism for edema formation in nephrotic syndrome was straightforward: the kidneys lost protein in the urine, which lowered the plasma oncotic pressure. Thus, fluid leaked into the interstitium, depleting the intravascular volume with subsequent activation of renin/aldosterone and consequent avid renal sodium retention. As simple as that! Unfortunately, a number of clinical and laboratory observations have raised serious concerns about the accuracy of this “underfill” hypothesis. Instead, an “overfill” hypothesis was generated. Under this assumption, the nephrotic syndrome not only leads to urinary protein wasting, but also to primary sodium retention with consequent intravascular overfilling, with the excess fluid spilling into the flood plains of the interstitium, leading to edema. Recently, an attractive mechanism was proposed to explain this primary sodium retention: proteinuria includes plasma proteinases, such as plasmin, which activate the epithelial sodium channel in the collecting duct, ENaC. In this edition, further evidence for this hypothesis is being presented by confirming increased plasmin content in the urine of children with nephrotic syndrome and demonstrating ENaC activation. If correct, this hypothesis would provide a simple treatment for the edema: pharmacological blockade of ENaC, for instance, with amiloride. Yet, how come clinicians have not empirically discovered the presumed power of ENaC blockers in nephrotic syndrome? And why is it that some patients clearly show evidence of intravascular underfilling? The controversy of over- versus underfilling demonstrates how much we still have to learn about the pathophysiology of nephrotic syndrome.

Concepts: Scientific method, Kidney, Nephrotic syndrome, Ureter, Aldosterone, Edema, Atrial natriuretic peptide, Epithelial sodium channel