Plasma C-type Natriuretic Peptide Research Articles

CNP Ameliorates Macrophage Inflammatory Response and Atherosclerosis.

CNP (C-type natriuretic peptide), an endogenous short peptide in the natriuretic peptide family, has emerged as an important regulator to govern vascular homeostasis. However, its role in the development of atherosclerosis remains unclear. This study aimed to investigate the impact of CNP on the progression of atherosclerotic plaques and elucidate its underlying mechanisms. Plasma CNP levels were measured in patients with acute coronary syndrome. The potential atheroprotective role of CNP was evaluated in apolipoprotein E-deficient (ApoE-/-) mice through CNP supplementation via osmotic pumps, genetic overexpression, or LCZ696 administration. Various functional experiments involving CNP treatment were performed on primary macrophages derived from wild-type and CD36 (cluster of differentiation 36) knockout mice. Proteomics and multiple biochemical analyses were conducted to unravel the underlying mechanism. We observed a negative correlation between plasma CNP concentration and the burden of coronary atherosclerosis in patients. In early atherosclerotic plaques, CNP predominantly accumulated in macrophages but significantly decreased in advanced plaques. Supplementing CNP via osmotic pumps or genetic overexpression ameliorated atherosclerotic plaque formation and enhanced plaque stability in ApoE-/- mice. CNP promoted an anti-inflammatory macrophage phenotype and efferocytosis and reduced foam cell formation and necroptosis. Mechanistically, we found that CNP could accelerate HIF-1α (hypoxia-inducible factor 1-alpha) degradation in macrophages by enhancing the interaction between PHD (prolyl hydroxylase domain-containing protein) 2 and HIF-1α. Furthermore, we observed that CD36 bound to CNP and mediated its endocytosis in macrophages. Moreover, we demonstrated that the administration of LCZ696, an orally bioavailable drug recently approved for treating chronic heart failure with reduced ejection fraction, could amplify the bioactivity of CNP and ameliorate atherosclerotic plaque formation. Our study reveals that CNP enhanced plaque stability and alleviated macrophage inflammatory responses by promoting HIF-1α degradation, suggesting a novel atheroprotective role of CNP. Enhancing CNP bioactivity may offer a novel pharmacological strategy for treating related diseases.

Abstract 15171: Endothelium-Derived C-Type Natriuretic Peptide Prevents the Development and Progression of Abdominal Aortic Aneurysm

Background: Abdominal aortic aneurysm (AAA) is a life-threatening disease characterised by dilatation, inflammation and structural weakness of the abdominal aorta. Since the only effective existing intervention is surgery, development of pharmacological therapies is desperately needed. C-type natriuretic peptide (CNP) is a key endothelium-derived molecule that possesses vasodilator, anti-inflammatory and anti-atherogenic activity. Thus, we explored the role and therapeutic potential of CNP in AAA pathogenesis. Methods: Suprarenal aortic diameter was assessed by ultrasonography at baseline and following Angiotensin II (AngII, 1.44mg/kg/day) infusion in wild type (WT) or endothelium-restricted CNP deficient (ecCNP -/- ) mice infected with an AAV-expressing proprotein convertase subtilisin/kexin type 9 gain-of-function mutation (D377Y) or backcrossed on an apolipoprotein E deficient (ApoE -/- ) background. At 28 days, aortas were harvested for qRT-PCR, pharmacological assessment of vasorelaxant activity and histological analysis; plasma CNP concentrations were also determined. In some studies, CNP (0.2mg/kg/day) was infused to rescue any adverse phenotype. Results: ecCNP -/- exhibited an aggravated AAA phenotype compared to WT, exemplified by greater dilation, fibrosis and elastin degradation (without changes in blood pressure). Whilst plasma CNP concentrations were reduced in murine AAA, CNP mRNA abundance was elevated within aneurysmal tissue of ecCNP -/- , accompanied by increased abundance of mRNA encoding markers of inflammation ( IL-6, Adgre1, VCAM-1, CCL-2 ), extracellular matrix remodelling/calcification ( MMP-2, Notch-1, BMPR2, smoothelin ), fibrosis ( fibronectin ) and apoptosis ( Bax ) . CNP-induced relaxations were enhanced in aortic rings from aneurysmal tissue compared to control; an effect possibly underpinned by upregulation of natriuretic peptide receptor expression. Prophylactic administration of CNP protected against the severity of AngII-induced AAA. Conclusions: Endothelial CNP plays an important role in attenuating AAA formation by preserving aortic structure and function. Therapeutic strategies aimed at mimicking CNP bioactivity may prevent the clinical progression of AAA.

A Combination of an Angiotensin II Receptor and a Neprilysin Inhibitor Attenuates Liver Fibrosis by Preventing Hepatic Stellate Cell Activation.

The renin-angiotensin-aldosterone system has gained attention due to its role as a mediator of liver fibrosis and hepatic stellate cell (HSC) activation. Meanwhile, the natriuretic peptide (NP) system, including atrial NP (ANP) and C-type NP (CNP), is a counter-regulatory hormone regulated by neprilysin. Although the combination of an angiotensin receptor and a neprilysin inhibitor (sacubitril/valsartan: SAC/VAL) has shown clinical efficacy in patients with heart failure, its potential effects on hepatic fibrosis have not been clarified. This study assessed the effects of SAC/VAL in carbon tetrachloride (CCl4)-induced murine liver fibrosis as well as the in vitro phenotypes of HSCs. Treatment with SAC and VAL markedly attenuated CCl4-induced liver fibrosis while reducing α-SMA+-HSC expansion and decreasing hepatic hydroxyproline and mRNA levels of pro-fibrogenic markers. Treatment with SAC increased plasma ANP and CNP levels in CCl4-treated mice, and ANP effectively suppressed cell proliferation and TGF-β-stimulated MMP2 and TIMP2 expression in LX-2 cells by activating guanylate cyclase-A/cGMP/protein kinase G signaling. Meanwhile, CNP did not affect the pro-fibrogenic activity of LX-2 cells. Moreover, VAL directly inhibited angiotensin II (AT-II)-stimulated cell proliferation and the expression of TIMP1 and CTGF through the blockade of the AT-II type 1 receptor/protein kinase C pathway. Collectively, SAC/VAL may be a novel therapeutic treatment for liver fibrosis.

Is Plasma C-Type Natriuretic Peptide Level Suitable for Diagnosing and Typing Skeletal Dysplasia?

Objective: Skeletal dysplasia is a heterogeneous group of diseases that lead to abnormal enchondral ossification and typing of the disease is quite complex. C-type natriuretic peptide (CNP), one of the members of the natriuretic peptide family, has been implicated in bone development, and CNP levels are high in some types of skeletal dysplasia. The aim of this study was to evaluate the use of CNP as a marker for skeletal dysplasia types and to investigate its role in typing. Methods: Thirty-seven patients aged six months to 18 years [26 (70.3%) girls] were included in this cross-sectional study from among 75 skeletal dysplasia patients. All subjects were physically examined; anthropometric measurements were obtained, and bone surveys were evaluated. ELISA was used to assess CNP plasma levels. Forty-nine healthy children aged six months to 18 years [24 girls (49%)] comprised the control group. Results: The CNP concentration of the patient group (n=37) was 1.31±1.40 ng/mL which was similar to the control group (n=49) at 1.04±1.40 ng/mL (p=0.207). However, the CNP concentration of patients with achondroplasia (n=17) was significantly higher (1.79±1.64 ng/mL) than the control group (p=0.032). Conclusion: Our study contributes evidence concerning CNP values of both healthy children and children with skeletal dysplasia. Compared with healthy children, those with achondroplasia have elevated plasma levels of CNP. Further larger studies are necessary to assess the use CNP as a marker for the diagnosis and typing of skeletal dysplasia.

Collagen X Marker Levels are Decreased in Individuals with Achondroplasia.

Collagen X marker (CXM) is a degradation fragment of collagen type X. It is a real-time biomarker of height velocity with established norms. Plasma C-type natriuretic peptide (CNP) and NTproCNP levels have also been found to correlate with growth velocity in the general population and are elevated in individuals with achondroplasia compared with age- and sex-matched controls. Collagen X marker levels in people with fibroblast growth factor receptor 3 (FGFR3)-opathies have never been systematically measured. The objective of this study was to measure CXM in a population of dwarfism caused by FGFR3-opathies. Using the same cohort in which CNP and NTproCNP levels were previously measured, archived serum aliquots from 63 children with achondroplasia, six with hypochondroplasia, and two with thanatophoric dysplasia had CXM concentrations measured. Results were plotted against age- and sex-specific norms, and standard deviation scores were plotted for comparison between clinical diagnoses. CXM levels were significantly decreased (p < 0.0001) in children with achondroplasia compared with age- and sex-matched controls. Temporal patterns of change in CXM levels were sex-dependent. As the FGFR3 pathway was more constitutively active, CXM levels decreased. New tools are emerging to study impact of skeletal dysplasia on growth plate regulation and function.

C-type natriuretic peptide in childhood obesity

According to the World Health Organization obesity is the result of an energy imbalance between calories assumed and expended and over the past 30 years its incidence has dramatically increased. Recently, the problem of obesity has drastically increased also in childhood, assuming a social relevance. Childhood obesity, in fact, increases the possibility to be obese in adulthood, representing a risk for cardiovascular morbidity and mortality. Aim of this review was to carry out a revision of the literature on childhood obesity focusing on natriuretic peptides (NPs) and in particular on the role of C-type natriuretic peptide (CNP). In obesity NPs play a fundamental role in the regulation of body weight and energy metabolism. Data on plasma CNP levels in children are scarce. The review of the literature relating to the role of CNP in adolescents showed a progressive reduction in the CNP plasma levels in overweight/obese adolescents compared to normal-weight subjects, as previously observed in obese adults, as well as a different modulation in CNP mRNA expression. An independent association between CNP levels and obesity as well as a significant association with the endothelial dysfunction index was reported, indicating that the peptide could play a very important role as a marker of risk of developing obesity. The results of these studies indicate the importance of adopting healthy lifestyles to improve glucometabolic control as well as to provide the rationale for designing and developing new drugs to modulate the NPs system.

Prognostic Value of Urinary and Plasma C-Type Natriuretic Peptide in Acute Decompensated Heart Failure

ObjectivesThis study sought to characterize urinary and plasma C-type natriuretic peptide (CNP) in acute decompensated heart failure (ADHF) to define their relationship with clinical variables and to determine whether urinary and plasma CNP together add prognostic value. BackgroundCNP is a protective hormone that is synthesized in the kidney and endothelium and possesses antiremodeling properties. Urinary and plasma CNP levels are elevated in pathophysiological conditions; however, their regulation and prognostic value in heart failure (HF) is unclear. MethodsUrinary and plasma CNP were measured in 109 healthy subjects and 208 patients with ADHF; the 95th percentile of CNP values from healthy subjects established the normal contemporary cutoffs. Patients with ADHF were stratified based on urinary and plasma CNP levels for clinical characterization and the assessment of risk for adverse outcomes. ResultsThere was no significant correlation between urinary and plasma CNP in both cohorts. Urinary and plasma CNP were significantly elevated in patients with ADHF, and both increased with disease severity and were positively correlated with plasma N-terminal pro–B-type natriuretic peptide (NT-proBNP). Of the patients with ADHF, 23% had elevations in both urinary and plasma CNP, whereas 24% had normal CNP levels. During a median follow-up of 3 years, patients with elevated urinary and plasma CNP had a significantly higher risk of rehospitalization and/or death (HR: 1.79; P = 0.03) and rehospitalization (HR: 2.16; P = 0.01) after adjusting for age, sex, left ventricular ejection fraction, renal function, and plasma NT-proBNP. The C-statistic and integrated discrimination analyses further supported that the addition of urinary and plasma CNP to established risk models improved the prediction of adverse outcomes in patients with ADHF. ConclusionsUrinary and plasma CNP are differentially regulated in ADHF, and elevations in both provided independent prognostic value for predicting adverse outcomes.

Prenatal Particulate Matter (PM) Exposure and Natriuretic Peptides in Newborns from Mexico City.

(1) Background: The aim of this study was to assess associations between particulate matter (PM) exposure and natriuretic peptide concentrations in cord blood from newborns. (2) Methods: we conducted a cross-sectional study in Mexico City with 101 pregnant women from CIMIGEN Hospital. Atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) were measured in plasma from cord blood in 51 newborns by ELISA. We estimated PM exposure (PM2.5 and PM10) at first, second and third trimester of pregnancy. (3) Results: The median and interquartile range for ANP, BNP and CNP plasma concentrations were 66.71 (46.92–80.23), 98.23 (73.64–112.30) and 1129.11 (944.10–1452.02) pg/mL, respectively. PM2.5 and PM10 levels for the whole pregnancy period were 22.2 µg/m3 and 41.63 µg/m3, respectively. Employing multivariable linear regression models adjusted for maternal age, newborn sex, smoking before pregnancy, maternal occupation and newborns’ length and height, we observed a 2.47 pg/mL (95%CI: −4.67, −0.27) decrease in BNP associated with PM2.5 exposure during second trimester. Adjusted for the same set of confounders, third trimester PM10 exposure was inversely associated with ANP concentrations (beta estimate: −0.90; 95% CI: −1.80, −0.03). Neither PM10 nor PM2.5 were associated with CNP at any trimester of pregnancy. (4) Conclusions: Prenatal exposure to particulate matter was associated with ANP and BNP decrease in newborns.

Insulin Infusion Is Linked to Increased NPPC Expression in Muscle and Plasma C-type Natriuretic Peptide in Male Dogs.

The purpose of this study was to assess insulin-stimulated gene expression in canine skeletal muscle with a particular focus on NPPC, the gene that encodes C-type natriuretic peptide, a key hormonal regulator of cardiometabolic function. Four conscious canines underwent hyperinsulinemic, euglycemic clamp studies. Skeletal muscle biopsy and arterial plasma samples were collected under basal and insulin-stimulated conditions. Bulk RNA sequencing of muscle tissue was performed to identify differentially expressed genes between these 2 steady-state conditions. Our results showed that NPPC was the most highly expressed gene in skeletal muscle in response to insulin infusion, rising 4-fold between basal and insulin-stimulated conditions. In support of our RNA sequencing data, we found that raising the plasma insulin concentration 15-fold above basal elicited a 2-fold (P = 0.0001) increase in arterial plasma concentrations of N-terminal prohormone C-type natriuretic peptide. Our data suggest that insulin may play a role in stimulating secretion of C-type natriuretic peptide by skeletal muscle. In this context, C-type natriuretic peptide may act in a paracrine manner to facilitate muscle–vascular bed crosstalk and potentiate insulin-mediated vasodilation. This could serve to enhance insulin and glucose delivery, particularly in the postprandial absorptive state.

Maternal plasma pro-atrial and C-type natriuretic peptide levels and their associations with cardiovascular and renal function in the second half of normal pregnancy: a longitudinal study

BackgroundPhysiological adaptation in pregnancy is characterized by remodeling of endocrine, cardiovascular and renal functions leading to fluid retention, volume expansion, altered cardiac loading conditions and hyperdynamic circulation. Natriuretic peptides have been used as biomarkers of cardiovascular function, but their associations with gestational age-related changes in maternal cardiac, endothelial and renal function have not been elucidated. The aim of this study was to establish longitudinal reference values for maternal plasma atrial natriuretic peptide (proANP) and C-type natriuretic peptide (CNP) and investigate their temporal association with cardiovascular and renal function in the second half of pregnancy.MethodsThis study was a prospective longitudinal study of 53 low-risk pregnancies. Women were examined every 3–5 weeks during 22–40 weeks of gestation (252 observations). Fasting maternal blood samples were obtained to measure proANP, CNP, creatinine, cystatin C, uric acid, and fibrinogen levels. Cardiac function and systemic hemodynamics were assessed noninvasively by impedance cardiography (ICG) and vascular endothelial function by flow-mediated vasodilation of brachial artery (FMD).ResultsThe plasma proANP (R2adj = 0.79; P = 0.007), CNP (R2adj = 0.54; P = 0.005) decreased between 22 and 40 weeks. The creatinine (R2adj = 0.90; P < 0.001), cystatin C (R2adj = 0.93; P = < 0.001) and uric acid (R2adj = 0.83; P < 0.001) increased significantly, whereas the estimated glomerular filtration rate (R2adj = 0.93; P < 0.001) decreased with gestational age. The FMD did not change significantly but fibrinogen (R2adj = 0.79; P < 0.001) increased with advancing gestation. The maternal systemic vascular resistance index (R2adj = 0.50; P < 0.001) increased, stroke index (R2adj = 0.62; P < 0.001) decreased, whereas the cardiac index (R2adj = 0.62; P = 0.438) and thoracic fluid content (R2adj = 0.72; P = 0.132) did not change significantly with gestation. The proANP was associated with thoracic fluid content (R2adj = 0.74; P < 0.001) and fibrinogen (R2adj = 0.78; P = 0.034) but not with other variables of systemic hemodynamics, endothelial function, or renal function. The CNP was not associated significantly with parameters of cardiovascular or renal function.ConclusionLongitudinal reference values for maternal plasma proANP and CNP were established. These natriuretic peptides decreased slightly with advancing gestation, but they did not reflect the temporal physiological changes in maternal systemic hemodynamics, vascular endothelial function and renal function during the second half of pregnancy. The proANP correlated with the thoracic fluid content reflecting volume load in pregnancy.

Clinical efficacy of mouse nerve growth factor plus nimodipine in neonatal intracranial hemorrhage and its effect on plasma PAF, CNP, MMP-2, and neurological function.

To investigate the clinical efficacy of combination of mouse nerve growth factor (NGF) and nimodipine in the treatment of neonatal intracranial hemorrhage (NICH) and its effect on plasma platelet-activating factor (PAF), C-type natriuretic peptide (CNP), matrix metalloproteinase-2 (MMP-2), and neurological function. A total of 90 infants with severe ICH admitted to our hospital from December 2016 to December 2018 were enrolled for retrospective study. According to different treatment schemes, they were assigned into 2 groups: group A (n=40) treated with mouse NGF plus nimodipine; group B (n=50) treated with nimodipine. The recovery time, serum indexes (PAF, MMP-2, CNP), neurological function (neonatal behavioral neurological assessment (NBNA) score), complications, and total effective rate of patients were recorded, and the satisfaction degree of family members was statistically analyzed. Patients in group A showed shorter recovery time, down-regulated PAF and MMP-2, evidently up-regulated CNP, and significantly increased NBNA score after one/two weeks of treatment, as well as fewer complications, higher total effective rate and higher satisfaction of family members. To sum up, the combination of mouse NGF and nimodipine achieves good clinical efficacy in NICH, which down-regulates plasma PAF and MMP-2, up-regulates CNP, and improves neurological function. Therefore, it is suitable for clinical promotion.

Prognostic Implications of Urinary and Plasma C-type Natriuretic Peptide in Human Acute Decompensated Heart Failure

Introduction C-type natriuretic peptide (CNP) is a cardiorenal-derived hormone that possesses potent anti-fibrotic, anti-hypertrophic, anti-apoptotic and cardiac unloading properties. While plasma and urinary CNP have been shown to be elevated in heart failure (HF) patients, limited studies have simultaneously characterized and evaluated the clinical utility of plasma and urinary CNP in acute decompensated HF (ADHF). Hypothesis We hypothesize that plasma and urinary CNP are elevated and distinctly regulated in ADHF and elevation of both are a marker of disease severity and will have additional prognostic value for adverse outcomes. Methods ADHF patients (n=208) and healthy subjects (n=109) were prospectively recruited and urinary and plasma CNP, plasma NT-proBNP, eGFR and urinary protein/creatinine were determined. The 95th percentile (%) of CNP values from healthy subjects were used to establish normal cutoffs. ADHF patients were stratified based on whether their CNP levels were considered as elevated (> 95th % of normal) or normal (≤ 95th % of normal). The adverse outcomes were all-cause rehospitalization and/or death over 3.0 (1.0, 4.9) years of follow-up. Results ADHF patients had elevated plasma and urinary CNP levels compared to healthy subjects [plasma CNP: 18.2 (10.7-30.3) vs 11.8 (9.5-15.0) pg/mL; urinary CNP: 43.1 (27.9-74.7) vs 15.8 (12.1-20.2) ng/g Cr; P Conclusions This study is the largest to date to provide novel pathophysiological insights into plasma and urinary CNP. We report for the first time that elevations of both CNP indices are associated with disease severity and have prognostic utility beyond robust clinical risk models in ADHF.

Effect of statin therapy on plasma C-type Natriuretic Peptides and Endothelin-1 in males with and without symptomatic coronary artery disease

C-type Natriuretic Peptide (CNP) and Endothelin-1 (ET-1) have reciprocal roles in maintaining vascular homeostasis and are acutely modulated by statins in human cultured endothelial cells. Whether these actions of statins in vitro are reflected in studies in vivo is unknown. In a prospective study of 66 subjects with or without post- acute coronary syndrome (ACS), plasma concentrations of bioactive CNP and bio-inactive aminoterminal proCNP (NTproCNP), ET-1, B-type Natriuretic Peptide (BNP) and high sensitivity C Reactive Protein (hsCRP) were measured together with lipids before and at intervals of 1, 2 and 7 days after commencing atorvastatin 40 mg/day - and for a further period of 6months in those with ACS. Plasma lipids fell significantly in all subjects but plasma CNP, NTproCNP and ET-1 were unchanged by atorvastatin. In ACS, baseline hsCRP, BNP and CNP but not NTproCNP or ET-1 were significantly raised compared to values in age-matched controls. The ratio of NTproCNP to CNP was significantly lower in ACS throughout the study and was unaffected by statin therapy. We conclude that conventional doses of atorvastatin do not affect plasma CNP products or ET-1. Elevated CNP after cardiac injury likely results from regulated changes in clearance, not enhanced production.

Is C-type natriuretic peptid level can be an early indicator for acute kidney injury?

Acute kidney injury (AKI) is defined as a reduction of renal function in hours, including both structural damage and loss of function. There are limited number of biomarkers for early detection and staging of severity. C-type natriuretic peptide (CNP) has been detected in at several tissues. We aimed to evaluate plasma CNP and creatinine levels correlated with duration of ischemia in an experimentally induced AKI rat model. Forty male Sprague-Dawley type rats (aged 8 to 12 weeks, weighing 250-350 g) were used. The animals were randomly seperated into 4 groups: Group 1(n:10): Only laparotomy was performed. The left renal artery was clamped for 3, 6 and 9 hours in groups 2 ( n:10), 3 (n:10) and 4 (n:10) respectively. CNP and creatinine levels were measured in serum samples from rats. A significant increase in creatinine levels was determined in group 2 according to group 1 (p=0.006). The mean plasma creatinine values in group 3 and 4 were decreased compared to group 2 but this difference was not statistically significant (p=0.0862). The mean CNP level in Group 2 (39.5 ± 7.93 mg/dl) was found numerically higher than group 1 (37.90 ± 5.38mg/dl). There was a statistically insignificant decrease in mean CNP levels in group 3 and 4 compared with group 2. Renal ischemia increases the level of CNP. Although the increase in CNP levels is not significant, it can be said that clinical and experimental studies evaluating the timing of ischemia involving different durations should be performed.

C-type natriuretic peptide plasma levels and whole blood mRNA expression show different trends in adolescents with different degree of endothelial dysfunction

C-type natriuretic peptide (CNP) is an endogenous adipogenesis regulator whose plasma levels in childhood are known, while no data are available on its expression. Our aim was to evaluate both CNP plasma levels and CNP system expression in whole blood obtained from normal-weight (N, n = 24) and obese (O, n = 16) adolescents (age:13.5 ± 0.4 years). Endothelial function was assessed measuring reactive hyperemia index (RHI). CNP plasma levels, evaluated with specific RIA, resulted significantly lower in O than in N (6.1 ± 0.8 vs.15.2 ± 1.3 pg/mL; p < 0.0001), while CNP/NPR-B/NPR-C mRNA, measured by Real-Time PCR, resulted similar in N (4.1 ± 1.7; 5.0 ± 1.6; 2.2 ± 0.9) and in O (4.3 ± 1.6; 3.5 ± 1.1; 2.3 ± 0.8). RHI was significantly lower in O than in N (1.4 ± 0.08 vs.2.1 ± 0.04, p < 0.0001). Dividing all subjects according to the RHI median value, irrespective of the presence or absence of obesity (Group 1 > 1.9, n = 23, Group 2 < 1.9, n = 17), CNP plasma concentrations resulted significantly (p = 0.014) higher in Group 1 (14.6 ± 1.6) than in Group 2 (7.5 ± 1.0), showing a significant correlation with RHI (p = 0.0026), while CNP mRNA expression was, surprisingly, higher in Group 2 (7.0 ± 2.3) than in Group 1 (1.8 ± 0.4; p = 0.02). NPR-B mRNA resulted similar in both Groups (4.3 ± 1.6; 4.7 ± 1.3) and NPR-C significantly higher in Group 2 (p = 0.02). Our data suggest different trends between CNP plasma levels and expression, assessed for the first time in whole blood, that could reflect changes occurring both at CNP transcriptional level in activated leukocytes due to inflammation, and at circulating levels, due to CNP paracrine/autocrine activities. This could represent an interesting area for new therapies able to modulate endothelial dysfunction.

Postnatal effects of intrauterine treatment of the growth-restricted ovine fetus with intra-amniotic insulin-like growth factor-1.

Fetal growth restriction increases the risk of fetal and neonatal mortality and morbidity, and contributes to increased risk of chronic disease later in life. Intra-amniotic insulin-like growth factor-1 (IGF1) treatment of the growth-restricted ovine fetus improves fetal growth, but postnatal effects are unknown. Here we report that intra-amniotic IGF1 treatment of the growth-restricted ovine fetus alters size at birth and mechanisms of early postnatal growth in a sex-specific manner. We also show that maternal plasma C-type natriuretic peptide (CNP) products are related to fetal oxygenation and size at birth, and hence may be useful for non-invasive monitoring of fetal growth restriction. Intrauterine IGF1 treatment in late gestation is a potentially clinically relevant intervention that may ameliorate the postnatal complications of fetal growth restriction. Placental insufficiency-mediated fetal growth restriction (FGR) is associated with altered postnatal growth and metabolism, which are, in turn, associated with increased risk of adult disease. Intra-amniotic insulin-like growth factor-1 (IGF1) treatment of ovine FGR increases growth rate in late gestation, but the effects on postnatal growth and metabolism are unknown. We investigated the effects of intra-amniotic IGF1 administration to ovine fetuses with uteroplacental embolisation-induced FGR on phenotypical and physiological characteristics in the 2 weeks after birth. We measured early postnatal growth velocity, amino-terminal propeptide of C-type natriuretic peptide (NTproCNP), body composition, tissue-specific mRNA expression, and milk intake in singleton lambs treated weekly with 360μg intra-amniotic IGF1 (FGRI; n=13 females, 19 males) or saline (FGRS; n=18 females, 12 males) during gestation, and in controls (CON; n=15 females, 22 males). There was a strong positive correlation between maternal NTproCNP and fetal oxygenation, and size at birth in FGR lambs. FGR lambs were ∼20% lighter at birth and demonstrated accelerated postnatal growth velocity. IGF1 treatment did not alter perinatal mortality, partially abrogated the reduction in newborn size in females, but not males, and reduced accelerated growth in both sexes. IGF1-mediated upregulation of somatotrophic genes in males during the early postnatal period could suggest that treatment effects are associated with delayed axis maturation, whilst treatment outcomes in females may rely on the reprogramming of nutrient-dependent mechanisms of growth. These data suggest that the growth-restricted fetus is responsive to intra-amniotic intervention with IGF1, and that sex-specific somatotrophic effects persist in the early postnatal period.

C53: A Novel CNP-Based Therapeutic Strategy Targeting Cardiac Fibrosis and Heart Failure

Background: Cardiac fibrosis is a characteristic feature of the failing heart for which there is an unmet need of fibro-inhibiting therapies targeting heart failure (HF). C-type natriuretic peptide (CNP), a human endothelial derived 22 amino acid (AA) peptide, is a guanylyl cyclase B (GC-B) activator that mediates potent anti-fibrotic actions via its second messenger, cGMP. However, the endogenous anti-fibrotic actions of CNP are limited, in part, due to its rapid metabolic clearance by the clearance receptor (NPRC), which has been reported to be up regulated in HF patients. Considering the fibro-suppressing properties of GC-B activation, we engineered a novel 53 AA peptide (C53) based upon the CNP and proCNP sequence with the goal of advancing C53‘s therapeutic potential including reduced NPRC binding. Hypothesis: We hypothesized C53 would have enhanced cGMP generating actions in vivo due to reduced NPRC binding compared to CNP and C53 would activate cGMP in human cardiac fibroblasts (hCFs). Methods: Therapeutic dose of CNP, equimolar dose of C53 and vehicle were IV infused into normal anesthetized rats (n = 12) and in vivo CNP and cGMP levels were assessed. NPRC binding with C53 and CNP were assessed using a modified AlphaScreen luminescent proximity assay (ALPA). In vitro cGMP activating property of C53 (10−8M and 10−6M) compared to no treatment in hCFs was assessed. Data are mean ± SE and significance was achieved with P < .05. Results: In vivo, C53 significantly increased plasma and urinary cGMP compared to equimolar CNP and vehicle (P < .05), which correlated with higher plasma CNP levels with C53 IV infusion (P < .05). Binding studies using the ALPA demonstrated that C53 had reduced binding to NPRC compared to CNP. In hCFs, C53 generated cGMP at 10−8M and markedly activated cGMP at 10−6M compared to no treatment (no treatment: 0.00 ± 0.00; 10−8M: 0.17 ± 0.03; 10−6M: 1.79 ± 0.02, pmol/well, P < .05). Conclusion: We report a newly engineered CNP-based peptide, C53, has cGMP activating actions in hCFs and has superior in vivo cGMP generation than CNP which may, in part, be related to reduced binding to the metabolic clearance receptor NPRC. These studies suggest that C53 may be a novel therapeutic strategy for the prevention and treatment of cardiac fibrosis in HF and further investigations are warranted.

Dexamethasone increases production of C-type natriuretic peptide in the sheep brain.

Although C-type natriuretic peptide (CNP) has high abundance in brain tissues and cerebrospinal fluid (CSF), the source and possible factors regulating its secretion within the central nervous system (CNS) are unknown. Here we report the dynamic effects of a single IV bolus of dexamethasone or saline solution on plasma, CSF, CNS and pituitary tissue content of CNP products in adult sheep, along with changes in CNP gene expression in selected tissues. Both CNP and NTproCNP (the amino-terminal product of proCNP) in plasma and CSF showed dose-responsive increases lasting 12-16 h after dexamethasone, whereas other natriuretic peptides were unaffected. CNS tissue concentrations of CNP and NTproCNP were increased by dexamethasone in all of the 12 regions examined. Abundance was highest in limbic tissues, pons and medulla oblongata. Relative to controls, CNP gene expression (NPPC) was upregulated by dexamethasone in 5 of 7 brain tissues examined. Patterns of responses differed in pituitary tissue. Whereas the abundance of CNP in both lobes of the pituitary gland greatly exceeded that of brain tissues, neither CNP nor NTproCNP concentration was affected by dexamethasone, despite an increase in NPPC expression. This is the first report of enhanced production and secretion of CNP in brain tissues in response to a corticosteroid. Activation of CNP secretion within CNS tissues by dexamethasone, not exhibited by other natriuretic peptides, suggests an important role for CNP in settings of acute stress. Differential findings in pituitary tissues likely relate to altered processing of proCNP storage and secretion.

C-Type Natriuretic Peptides in Coronary Disease.

C-type natriuretic peptide (CNP) is a paracrine growth factor expressed in the vascular endothelium. Although upregulated in atheromatous arteries, the predictive value of plasma CNP products for outcome in coronary disease is unknown. This study aimed to compare the prognostic value of plasma CNP products with those of other natriuretic peptides in individuals with coronary artery disease, and investigate their associations with cardiac and renal function. Plasma concentrations of CNP and amino-terminal proCNP (NT-proCNP) were measured at baseline in 2129 individuals after an index acute coronary syndrome admission and related to cardiac and renal function, other natriuretic peptides [atrial NP (ANP) and B-type NP (BNP)] and prognosis (primary end point, mortality; secondary end point, cardiac readmission). Median follow-up was 4 years. At baseline, and in contrast to CNP, ANP, and BNP, plasma NT-proCNP was higher in males and weakly related to cardiac function but strongly correlated to plasma creatinine. All NPs were univariately associated with mortality. Resampling at 4 and 12 months in survivors showed stable concentrations of NT-proCNP whereas all other peptides declined. When studied by diagnosis (myocardial infarction, unstable angina) at index admission using a multivariate model, NT-proBNP predicted mortality and readmission in myocardial infarction. In unstable angina, only NT-proCNP predicted both mortality and cardiac readmission. In contrast to the close association of NT-proBNP with cardiac function, and predictive value for outcome after myocardial infarction, plasma NT-proCNP is highly correlated with renal function and is an independent predictor of mortality and cardiac readmission in individuals with unstable angina.

Elevated C-type natriuretic peptide elicits exercise preconditioning-induced cardioprotection against myocardial injury probably via the up-regulation of NPR-B.

To evaluate exercise preconditioning (EP)-induced cardioprotective effects against exercise-induced acute myocardial injury and investigate the alterations of C-type natriuretic peptide (CNP) and its specific receptor, natriuretic peptide receptor B (NPR-B), during EP-induced cardioprotection. Rats were subjected to treadmill exercise as an EP model (4 periods of 10min each at 30m/min with intervening periods of rest lasting 10min). High-intensity exercise was performed 0.5 and 24h after the EP. EP attenuated high-intensity exercise-induced myocardial injury in both the early and late phases. After EP and high-intensity exercise, CNP and NPR-B levels increased robustly, but no alterations in the plasma CNP were observed. The enhanced NPR-B, plasma and tissue CNP, and its mRNA levels after high-intensity exercise were significantly elevated by EP. These results suggest that cardiac CNP and NPR-B play an important role in EP-mediated cardioprotection against high-intensity exercise-induced myocardial injury in rats.