Association of natriuretic peptides and receptor activity with cardio-metabolic health at middle age

Natriuretic peptides (NP) have multiple actions benefitting cardiovascular and metabolic health. Although many of these are mediated by Guanylyl Cyclase (GC) receptors NPR1 and NPR2, their role and relative importance in vivo is unclear. The intracellular mediator of NPR1 and NPR2, cGMP, circulates in plasma and can be used to examine relationships between receptor activity and tissue responses targeted by NPs. Plasma cGMP was measured in 348 participants previously recruited in a multidisciplinary community study (CHALICE) at age 50 years at a single centre. Associations between bio-active NPs and bio-inactive aminoterminal products with cGMP, and of cGMP with tissue response, were analysed using linear regression. Mediation of associations by NPs was assessed by Causal Mediation Analysis (CMA). ANP's contribution to cGMP far exceed those of other NPs. Modelling across three components (demographics, NPs and cardiovascular function) shows that ANP and CNP are independent and positive predictors of cGMP. Counter intuitively, findings from CMA imply that in specific tissues, NPR1 responds more to BNP stimulation than ANP. Collectively these findings align with longer tissue half-life of BNP, and direct further therapeutic interventions towards extending tissue activity of ANP and CNP.

Resveratrol‐induced suppression of CNP associates with increased vertebral bone density in post‐menopausal women

C-type natriuretic peptide (CNP) is a paracrine growth factor essential in driving endochondral bone growth in mammals including humans. Despite evidence from animal experiments and tissues that CNP signaling stimulates osteoblast proliferation and osteoclast activity, whether CNP participates in bone remodeling in the mature skeleton is unknown. Using stored plasma samples from a previous randomized controlled clinical trial (RESHAW) of resveratrol supplementation in postmenopausal women exhibiting mild osteopenia, we have studied changes in plasma aminoterminal proCNP (NTproCNP) and concurrent change in bone turnover markers of formation (osteocalcin [OC] and alkaline phosphatase [ALP]) and resorption (C-terminal telopeptide type 1 collagen [CTX]) with bone mineral density (BMD) over a 2-year period of study in 125 subjects. In year one, subjects received placebo or resveratrol, switching to resveratrol or placebo, respectively, in year two. Across all time points, there were no significant associations of NTproCNP with CTX, ALP, or OC. During year one, plasma NTproCNP declined significantly in both groups. In the crossover comparison, analysis of change within individuals showed that, compared with placebo, NTproCNP declined after resveratrol (p = 0.011) and ALP increased (p = 0.008), whereas CTX and OC were unchanged. Inverse association of NTproCNP (r = -0.31; p = 0.025) and positive association of OC (r = 0.32, p = 0.022) with BMD at the lumbar spine were identified after resveratrol but not found after placebo. Decline in NTproCNP was independently associated with resveratrol treatment. This is the first evidence that CNP is modulated during a period of increasing BMD in postmenopausal women. Further study of NTproCNP and associations with drivers of bone formation or resorption can be expected to clarify CNP's role during other interventions directed to bone health in adults. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

The Predictive Value of A, B, and C-Type Natriuretic Peptides in People at Risk of Heart Disease: Protocol for a Longitudinal Observational Study

BACKGROUND

Heart disease and stroke are major and often unheralded causes of serious morbidity and premature death in middle age. Early detection of those most at risk is an urgent unmet need for instituting preventative measures. In an earlier community study (Canterbury Health, Ageing and Life Course [CHALICE]) of healthy people aged 50 years, contrary to previous reports, low levels of the heart hormone B-type natriuretic peptide (BNP) were associated with reduced measures of heart function and higher markers of vascular risk. A specific gene variant (rs198358) was found to be an independent contributor to higher BNP levels. A closely related vascular hormone (C-type natriuretic peptide [CNP]) showed opposite associations-higher levels were correlated with higher vascular risk and reduced cardiac function. To determine whether these novel findings predict serious heart or vascular disease in later life, this proposal re-examines the same CHALICE participants 15 years later.

OBJECTIVE

The primary objective is to determine the predictive value of (1) low plasma concentrations of the circulating cardiac hormones (atrial natriuretic peptide [ANP] and BNP) and (2) high levels of the vascular hormone CNP at age 50 years in detecting impaired cardiac and vascular function 15 years later. Secondary objectives are to determine specific associations of individual analytes (ANP, BNP, CNP, cyclic guanosine monophosphate [cGMP]) with echo-derived changes in cardiac performance at ages 50 years and 65 years.

METHODS

All of the 348 participants (205/348, 58.9% female; 53/348, 15.2% Māori or Pacifica ethnicity) participating in the original CHALICE study-free of history of heart or renal disease at age 50 years and who consented to further study-will be contacted, recruited, and restudied as previously described. Data will include intervening health history, physical examination, heart function (speckle-tracking echocardiography), vascular status (carotid intimal thickness), and genetic status (genome-wide genotyping). Laboratory measures will include fasting blood sampling and routine biochemistry, ANP, BNP, CNP, their downstream effector (cGMP), and their bio-inactive products. Humoral metabolic-cardiovascular risk factors will be measured after an overnight fast. Primary outcomes will be analyzed using multiple linear regression.

RESULTS

The study will commence in 2022 and be completed in 2024.

CONCLUSIONS

Proving our hypothesis-that low BNP and high CNP at any age in healthy people predict premature aging of heart and blood vessels, respectively-opens the way to early detection and improved outcomes for those most at risk. Confirmation of our hypotheses would improve current methods of screening and, in appropriate cases, enable interventions aimed at increasing natriuretic hormones and reducing risk of serious cardiovascular complications using drugs already available. Such advances in detection, and from interventional corrections, have the potential to not only improve health in the community but also reduce the high costs inevitably associated with heart failure.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/37011.

Guanylyl Cyclase-B Dependent Bone Formation in Mice is Associated with Youth, Increased Osteoblasts, and Decreased Osteoclasts

C-type natriuretic peptide (CNP) activation of guanylyl cyclase-B (GC-B) catalyzes the synthesis of cGMP in chondrocytes and osteoblasts. Elevated cGMP stimulates long bone growth, and inactivating mutations in CNP or GC-B reduce cGMP, which causes dwarfism. GC-B^7E/7E mice that express a GC-B mutant that cannot be inactivated by dephosphorylation exhibit increased CNP-dependent GC-B activity, which increases bone length, as well as bone mass and strength. Importantly, how GC-B increases bone mass is not known. Here, we injected 12-week-old, wild type mice once daily for 28 days with or without BMN-111 (Vosoritide), a proteolytically resistant CNP analog. We found that BMN-111 treated mice had elevated levels of osteocalcin and collagen 1 C-terminal telopeptide (CTX) as well as increased osteoblasts and osteoclasts. In BMN-111 injected mice, tibial mRNAs for Rank ligand and osteoprotegrin were increased and decreased, respectively, whereas sclerostin mRNA was elevated 400-fold, consistent with increased osteoclast activity and decreased osteoblast activity. Mineral apposition rates and trabecular bone mass were not elevated in response to BMN-111. Because 9-week-old male GC-B^7E/7E mice have increased bone mass but do not exhibit increased mineral apposition rates, we examined 4-week-old male GC-B^7E/7E mice and found that these animals had increased serum osteocalcin, but not CTX. Importantly, tibias from these mice had 37% more osteoblasts, 26% fewer osteoclasts as well as 36% and 40% higher mineral apposition and bone formation rates, respectively. We conclude that GC-B-dependent bone formation is coupled to an early juvenile process that requires both increased osteoblasts and decreased osteoclasts.

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.

Broadening the spectrum of loss-of-function variants in NPR-C-related extreme tall stature

Context

Natriuretic peptide receptor-C (NPR-C, encoded by NPR3) belongs to a family of cell membrane–integral proteins implicated in various physiological processes, including longitudinal bone growth. NPR-C acts as a clearance receptor of natriuretic peptides, including C-type natriuretic peptide (CNP), that stimulate the cGMP-forming guanylyl cyclase-coupled receptors NPR-A and NPR-B. Pathogenic variants in CNP, NPR2, and NPR3 may cause a tall stature phenotype associated with macrodactyly of the halluces and epiphyseal dysplasia.

Objective

Here we report on a boy with 2 novel biallelic inactivating variants of NPR3.

Methods

History and clinical characteristics were collected. Biochemical indices of natriuretic peptide clearance and in vitro cellular localization of NPR-C were studied to investigate causality of the identified variants.

Results

We identified 2 novel compound heterozygous NPR3 variants c.943G>A p.(Ala315Thr) and c.1294A>T p.(Ile432Phe) in a boy with tall stature and macrodactyly of the halluces. In silico analysis indicated decreased stability of NPR-C, presumably resulting in increased degradation or trafficking defects. Compared to other patients with NPR-C loss-of-function, the phenotype seemed to be milder: pseudo-epiphyses in hands and feet were absent, biochemical features were less severe, and there was some co-localization of p.(Ile432Phe) NPR-C with the cell membrane, as opposed to complete cytoplasmic retention.

Conclusion

With this report on a boy with tall stature and macrodactyly of the halluces we further broaden the genotypic and phenotypic spectrum of NPR-C-related tall stature.

Evidence of feedback regulation of C-type natriuretic peptide during Vosoritide therapy in Achondroplasia

Evidence from genetic disorders of CNP signalling suggests that plasma concentrations of CNP are subject to feedback regulation. In subjects with Achondroplasia (Ach), CNP intracellular activity is suppressed and plasma concentrations are raised but the therapeutic impact of exogenous CNP agonists on endogenous CNP is unknown. In this exploratory dose finding and extension study of 28 Ach children receiving Vosoritide over a 5 year period of treatment, endogenous CNP production was assessed using measurements of plasma aminoterminal proCNP (NTproCNP) adjusted for age and sex and normalised as standard deviation score (SDS), and then related to skeletal growth. Before treatment NTproCNP SDS was raised. Within the first 3 months of accelerating growth, levels were significantly reduced. Across the 5 years of sustained growth, levels varied widely and were markedly increased in some subjects during adolescence. Plasma NTproCNP was suppressed at 4 h post-injection in proportion to the prevailing level of hormone resistance as reflected by SDS before injection. We conclude CNP remains subject to regulation during growth promoting doses of Vosoritide. Fall in CNP during accelerating growth is consistent with an indirect feedback whereas the fall at 4 h is likely to be a direct effect from removal of intra cellular CNP resistance.

Circulating products of C-type natriuretic peptide and links with organ function in health and disease

Paracrine actions of CNP and rapid degradation at source severely limit study of CNP's many roles in vivo. However provided sensitive and validated assays are used, there is increasing evidence that low concentrations of bioactive CNP in plasma, and the readily detectable concentrations of the bio-inactive processed product of proCNP (aminoterminal proCNP), can be used to advance understanding of the hormone's role in pathophysiology. Provided renal function is normal, concordant changes in both CNP and NTproCNP reflect change in tissue production of proCNP whereas change in CNP alone results from altered rates of bioactive CNP degradation and are reflected in the ratio of NTproCNP to CNP. As already shown in juveniles, where plasma concentration of CNP products are higher and are associated with concurrent endochondral bone growth, measurements of plasma CNP products in mature adults have potential to clarify organ response to stress and injury. Excepting the role of CNP in fetal-maternal welfare, this review examines evidence linking plasma CNP products with function of a wide range of tissues in adults, including the impact of extraneous factors such as nutrients, hormone therapy and exercise.

Hemodynamic, Hormonal, and Renal Actions of Phosphodiesterase-9 Inhibition in Experimental Heart Failure

BACKGROUND

Phosphodiesterase-9 (PDE9) reduces natriuretic peptide (NP) signaling and may be involved in the pathophysiology of heart failure (HF).

OBJECTIVES

This study investigated for the first time the integrated hemodynamic, endocrine, and renal effects of phosphodiesterase-9 inhibition (PDE9-I).

METHODS

A total of 8 normal sheep and 8 sheep with pacing-induced HF received incremental intravenous boluses of PDE9-I (30, 100, and 300 mg PF-04749982 at 1-h intervals).

RESULTS

PDE9-I dose-dependently increased plasma cyclic guanosine monophosphate (cGMP) in normal sheep (p < 0.05) while concurrently reducing circulating atrial natriuretic peptide levels (p < 0.01). Similar trends were evident in HF, resulting in significant elevations in the cGMP/NP ratio in both states (p < 0.001 and p < 0.05, respectively). PDE9-I also produced progressive falls in arterial pressure (HF: p < 0.001), atrial pressure (Normal: p < 0.001; HF: p < 0.001), and peripheral resistance (HF: p < 0.001), and transiently increased cardiac output at the top dose (Normal: p < 0.05; HF: p < 0.001). Inhibition of PDE9 had a negligible effect on circulating hormones at the lower doses, but post-high dose, acutely increased renin activity (Normal: p < 0.001; HF: p < 0.05), vasopressin (Normal: p < 0.001; HF: p < 0.01), and cyclic adenosine monophosphate (HF: p < 0.001). Plasma aldosterone increased briefly after high-dose PDE9-I in normal sheep, and fell following the top dose in HF. PDE9-I dose-dependently increased urinary cGMP in both states (both p < 0.001). In HF, this was associated with increases in urine volume (p < 0.01), sodium excretion (p < 0.01), and creatinine clearance (p < 0.001).

CONCLUSIONS

PDE9-I improves NP efficacy in conjunction with beneficial hemodynamic and renal effects in experimental HF. These results support a role for PDE9 in HF pathophysiology and suggest its inhibition may constitute a novel therapeutic approach to this disease.

Urinary Amino-Terminal Pro–C-Type Natriuretic Peptide: A Novel Marker of Chronic Kidney Disease in Diabetes

BACKGROUND

Chronic renal inflammation and fibrosis are common sequelae in diabetes mellitus (DM) and are major causes of premature mortality. Although upregulation of NPPC expression occurs in response to renal inflammation in experimental animals, nothing is known of the molecular forms of C-type natriuretic peptide (CNP) products in urine of people with DM or links with renal function.

METHODS

ProCNP products in urine were characterized with HPLC and a range of antisera directed to specific epitopes of amino-terminal proCNP (NTproCNP). The 5-kDa intact peptide was quantified in spot urine samples from healthy adults and 202 participants with DM selected to provide a broad range of renal function.

RESULTS

The predominant products of proCNP in urine were consistent with the 2-kDa fragment (proCNP 3–20) and a smaller peak of intact (5-kDa) fragment (proCNP 1–50, NTproCNP). No peaks consistent with bioactive forms (proCNP 82–103, 50–103) were identified. The urine NTproCNP to creatinine ratio (NCR) was more reproducible than the albumin to creatinine ratio (ACR) and strongly associated with the presence of chronic kidney disease. In models predicting independence, among 10 variables associated with renal function in DM, including plasma NTproCNP, only 3 (sex, ACR, and plasma creatinine) contributed to NCR.

CONCLUSIONS

Characterization of the products of proCNP in urine confirmed the presence of NTproCNP. In spot random urine from study participants with DM, NCR is inversely associated with estimated glomerular filtration rate. In contrast to ACR, NCR reflects nonvascular factors that likely include renal inflammation and fibrosis.

Contrasting signals of cardiovascular health among natriuretic peptides in subjects without heart disease

Natriuretic Peptides (NP) are important in maintaining normal cardiac and metabolic status and have been used to predict cardiovascular events. Whether plasma concentrations of NP products within the normal range reflect cardio-metabolic health is unknown. Plasma NTproANP, NTproBNP and NTproCNP and their bioactive counterparts were measured in a random sample of 348 community dwellers aged 49-51 yr without heart disease and associations sought with established vascular risk factors, echocardiographic indices and a genetic variant previously linked with BNP. Stratified by sex, each of ten vascular risk factors were positively associated with NTproCNP whereas associations with NTproBNP and NTproANP were all negative. In both sexes, higher plasma NTproCNP was associated with higher arterial elastance, lower LV stroke volume and lower LV end diastolic volume. Exactly opposite associations were found with plasma NTproBNP or NTproANP. Sex specific differences were identified: positive association of NTproBNP with LV end systolic volume and the negative association with LV elastance were found only in males. The genetic variant rs198358 was independently associated with NTproBNP but not with NTproANP. In conclusion, higher NTproCNP is likely to be an adaptive response to impaired LV relaxation whereas genetic factors likely contribute to higher NTproBNP and improved cardio-metabolic health at midlife.

Bi-allelic Loss-of-Function Mutations in the NPR-C Receptor Result in Enhanced Growth and Connective Tissue Abnormalities

The natriuretic peptide signaling pathway has been implicated in many cellular processes, including endochondral ossification and bone growth. More precisely, different mutations in the NPR-B receptor and the CNP ligand have been identified in individuals with either short or tall stature. In this study we show that the NPR-C receptor (encoded by NPR3) is also important for the regulation of linear bone growth. We report four individuals, originating from three different families, with a phenotype characterized by tall stature, long digits, and extra epiphyses in the hands and feet. In addition, aortic dilatation was observed in two of these families. In each affected individual, we identified a bi-allelic loss-of-function mutation in NPR3. The missense mutations (c.442T>C [p.Ser148Pro] and c.1088A>T [p.Asp363Val]) resulted in intracellular retention of the NPR-C receptor and absent localization on the plasma membrane, whereas the nonsense mutation (c.1524delC [p.Tyr508^∗]) resulted in nonsense-mediated mRNA decay. Biochemical analysis of plasma from two affected and unrelated individuals revealed a reduced NTproNP/NP ratio for all ligands and also high cGMP levels. These data strongly suggest a reduced clearance of natriuretic peptides by the defective NPR-C receptor and consequently increased activity of the NPR-A/B receptors. In conclusion, this study demonstrates that loss-of-function mutations in NPR3 result in increased NPR-A/B signaling activity and cause a phenotype marked by enhanced bone growth and cardiovascular abnormalities.

Environmental Enrichment Elicits a Transient Rise of Bioactive C-Type Natriuretic Peptide in Young but Not Aged Rats

Beneficial molecular and neuroplastic changes have been demonstrated in response to environmental enrichment (EE) in laboratory animals across the lifespan. Here, we investigated whether these effects extend to C-type Natriuretic Peptide (CNP), a widely expressed neuropeptide with putative involvement in neuroprotection, neuroplasticity, anxiety, and learning and memory. We determined the CNP response in 36 young (8-9 months) and 36 aged (22-23 months) male PVGc hooded rats that were rehoused with new cage mates in either standard laboratory cages or EE for periods of 14 or 28 days. Tissues were rapidly excised from four brain regions associated with memory formation (dorsal hippocampus, retrosplenial cortex, medial prefrontal cortex, and mammillary bodies) plus the occipital cortex and hypothalamus, and immediately frozen. Radioimmunoassay was used to measure bioactive CNP and the amino-terminal fragment of proCNP, NTproCNP. Because CNP but not NTproCNP is rapidly degraded at source, NTproCNP reflects CNP production whereas the ratio NTproCNP:CNP is a biomarker of CNP's local degradation rate. EE increased CNP at 14 days in all brain regions in young, but not old rats; this effect in young rats was lost at 28 days in all regions of interest. NTproCNP:CNP ratio, but not NTproCNP, was reduced in all regions by EE at 14 days in young rats, but not in old rats, which suggests a period of reduced degradation or receptor mediated clearance, rather than increased production of CNP in these young EE rats. Aged rats tended to show reduced NTproCNP:CNP ratios but this did not occur in dorsal hippocampus or mammillary bodies. This is the first study demonstrating modulation of CNP protein concentrations, and the effect of age, in response to environmental stimulation. Furthermore, it is the first to show that changes in degradation rate in vivo may be an important component in determining CNP bioactivity in neural tissues.

New Insights into Cardiac and Vascular Natriuretic Peptides: Findings from Young Adults Born with Very Low Birth Weight

BACKGROUND

In community studies, plasma B-type natriuretic peptide (BNP) is positively associated with cardiovascular disorders. Those born with very low birth weight (VLBW) have increased risk of metabolic and vascular disorders in later life, but plasma concentrations of natriuretic peptides have not been studied. The objectives here were to evaluate BNP and C-type natriuretic peptide (CNP)—a putative marker of vascular risk—in young adults born with VLBW.

METHODS

In all, 220 VLBW cases and 97 matched controls were studied 28 years after birth during a 2-day period at 1 research center. Aminoterminal (NT) products (NTproBNP, NTproCNP) and a range of conventional vascular risk factors including echocardiographic indices were measured along with genetic polymorphisms known to increase plasma NTproBNP.

RESULTS

VLBW individuals were smaller, had smaller hearts, reduced stroke volume and endothelial function, and higher systolic blood pressure and arterial elastance. Of the many humoral vascular and metabolic risk factors measured, including NTproBNP, only plasma NTproCNP (higher in VLBW individuals) differed significantly. Across all individuals, associations of NTproCNP with each of 7 conventional risk factors, as well as with arterial elastance, were positive, whereas associations of NTproBNP with risk were all inverse. In multivariate analysis, the genetic variant rs198358 was independently associated with NTproBNP.

CONCLUSIONS

In young adults at increased risk of cardiovascular disease, higher NTproCNP likely reflects a compensatory vascular response to vascular stress, whereas the negative link with NTproBNP likely reflects beneficial genetic mutations. The ratio of NTproBNP to NTproCNP may provide a novel index of ideal cardiovascular health.

Molecular forms of C-type natriuretic peptide in cerebrospinal fluid and plasma reflect differential processing in brain and pituitary tissues

C-type natriuretic peptide (CNP) is a paracrine growth factor widely expressed within tissues of the central nervous system. Consistent with this is the high concentration of CNP in cerebrospinal fluid (CSF), exceeding levels in the systemic circulation. CNP abundance is high in hypothalamus and especially enriched in pituitary tissue where - in contrast to hypothalamus - processing to CNP-22 is minimal. Recently we have shown that dexamethasone acutely raises CNP peptides throughout the brain as well as in CSF and plasma. Postulating that molecular forms of CNP would differ in central tissues compared to forms in pituitary and plasma, we have characterized the molecular forms of CNP in tissues (hypothalamus, anterior and posterior pituitary gland) and associated fluids (CSF and plasma) using size-exclusion high performance liquid chromatography (SE-HPLC) and radioimmunoassay in control (saline-treated) and dexamethasone-treated adult sheep. Three immunoreactive-CNP components were identified which were consistent with proCNP (1-103), CNP-53 and CNP-22, but the presence and proportions of these different fragments differed among tissues. Peaks consistent with CNP-53 were the dominant form in all tissues and fluids. Peaks consistent with proCNP, conspicuous in hypothalamic extracts, were negligible in CSF whereas proportions of low molecular weight immunoreactivity (IR) consistent with CNP-22 were similar in hypothalamus, posterior pituitary gland and CSF. In contrast, in both plasma and the anterior pituitary gland, proportions of higher molecular weight IR, consistent with CNP-53 and proCNP, predominated, and low molecular weight IR consistent with CNP-22 was very low. After dexamethasone, proCNP like material - but not other forms - was increased in all samples except CSF, consistent with increased synthesis and secretion. In conclusion, immunoreactive forms of CNP in central tissues differ from those identified in anterior pituitary tissue and plasma - suggesting that the anterior pituitary gland may contribute to systemic levels of CNP in some physiological settings.

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.

Nutrient restriction in early ovine pregnancy stimulates C-type natriuretic peptide production

C-type natriuretic peptide (CNP), a paracrine growth factor promoting vasodilation and angiogenesis, is upregulated in human and ovine pregnancy in response to vascular stress or nutrient restriction (NR) in late gestation. Postulating that maternal plasma CNP products are increased by modest NR (50% of metabolisable energy requirement) early in pregnancy, and further enhanced by litter size, we studied serial changes of maternal plasma CNP in pregnant ewes receiving a normal (NC, n=12) or restricted (NR, n=13) diet from Day 30 to Day 93 or 94 of gestation. Liveweight of NR ewes was 10kg less than that of NC ewes at slaughter. Plasma CNP products increased progressively after Day 40 and were higher in NR (P<0.05) ewes after Day 60; they were also enhanced by litter size (P<0.01) and were positively associated with increased placental efficiency. In contrast, whereas fetal and placental weight were reduced by NR, fetal plasma CNP products (Day 93/94) were not affected. We conclude that increases in CNP during rapid placental growth are further enhanced by both increasing nutrient demands and by reduced supply, presumably as part of an adaptive response benefitting placental-fetal exchange.

C-Type Natriuretic Peptides in Coronary Disease

AIMS

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.

METHODS AND RESULTS

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.

CONCLUSIONS

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.

Dynamic response of C-type natriuretic peptide and its aminoterminal propeptide (NTproCNP) to growth hormone treatment in children with short stature

OBJECTIVE

C-type natriuretic peptide (CNP) and its aminoterminal propeptide (NTproCNP) are potential biomarkers of recombinant human growth hormone (rhGH) efficacy. The objective of this study was to describe the pharmacodynamics of plasma CNP and NTproCNP levels in response to rhGH treatment and to identify the optimal time of sampling after starting rhGH.

DESIGN

This was a prospective, observational study. Subjects were treated with rhGH for 1 year, with blood sampled at regular intervals.

PATIENTS

Eighteen prepubertal children, eight with low levels of GH on biochemical testing and ten with idiopathic short stature, completed the study.

MEASUREMENTS

Blood levels of CNP, NTproCNP, GH, insulin-like growth factor-I, leptin and bone-specific alkaline phosphatase were measured. Anthropometrics were obtained.

RESULTS

Plasma levels of both CNP and NTproCNP reached peak levels 7-28 days after starting rhGH treatment and then declined to intermediate levels through the first year. Plasma NTproCNP levels after 14 days trended towards a correlation with height velocity after 6 and 12 months of treatment. Unexpectedly, serum GH levels measured 2 and 28 days after starting rhGH correlated strongly with height velocity after 6 and 12 months of treatment.

CONCLUSIONS

This study identified 14 days after starting rhGH treatment as the optimal time for assessing CNP and NTproCNP levels as biomarkers of rhGH efficacy. Additionally, we identified GH levels as a potential biomarker. Larger, prospective studies are now needed to test the clinical utility of these biomarkers.

The New Zealand 1986 very low birth weight cohort as young adults: mapping the road ahead

Background

Very low birth weight (less than 1500 g) is associated with increased morbidity and costs of health care in childhood. Emerging evidence suggests these infants face a range of health and social problems as young adults. We studied all New Zealand very low birth weight infants born in 1986 (when 58 % were exposed to antenatal corticosteroids) in infancy, with later follow-up at 7 to 8 years and 23 to 24 years. We now aim to assess the cohort at 26–28 years compared with controls.

Methods/design

The case sample will comprise a minimum of 250 members of the 1986 New Zealand national very low birth weight cohort (77 % of survivors). Outcomes will be compared with a control group of 100 young adults born at term in 1986. Following written informed consent, participants will travel to Christchurch for 2 days of assessments undertaken by experienced staff. Medical assessments include growth measures, vision, respiratory function, blood pressure and echocardiogram, renal function, dental examination and blood tests. Cognitive and neuropsychological functioning will be assessed with standard tests, and mental health and social functioning by participant interview. A telephone interview will be conducted with a parent or significant other person nominated by the respondent to gain a further perspective on the young person’s health and functioning. All those born at less than 28 weeks’ gestation, plus a random subset of the cohort to a total of 150 cases and 50 controls, will be offered cranial magnetic-resonance imaging. Statistical analysis will examine comparison with controls and long-term trajectories for the very low birth weight cohort.

Discussion

The research will provide crucial New Zealand data on the young adult outcomes for very low birth weight infants and address gaps in the international literature, particularly regarding cardiovascular, respiratory, visual and neurocognitive outcomes. These data will inform future neonatal care, provide evidence-based guidelines for care of preterm graduates transitioning to adult care, and help shape health education and social policies for this high risk group.

Trial registration

Australian New Zealand Clinical Trials Registry ACTRN12612000995875. Registered 1 October 2012

Electronic supplementary material

The online version of this article (doi:10.1186/s12887-015-0413-9) contains supplementary material, which is available to authorized users.

Sustained increases in plasma C-type natriuretic peptides fail to increase concentrations in cerebrospinal fluid: Evidence from pregnant sheep

C-type natriuretic peptide (CNP) is a paracrine growth factor with high abundance in CNS tissues and cerebrospinal fluid (CSF). Consistent with findings of CNP transcripts in the cerebral microvasculature and hypothalamus, CNP increases the permeability of the blood-brain barrier and reduces food intake when administered intracerebroventricularly in rodents. Whether high concentrations of CNP in plasma can affect CSF levels is unknown. Accordingly we have studied changes (days 4, 87 and 116) in concurrent plasma and CSF concentrations of CNP peptides in pregnant sheep - a physiologically unique setting in which plasma CNP is elevated for prolonged periods. Preliminary studies in non pregnant sheep showed stable CNP levels in CSF during repetitive sampling. Compared with values in non pregnant controls, plasma concentrations of CNP peptides were markedly raised (30-fold) at days 87 and 116 in pregnant sheep, yet CSF levels in the two groups did not differ. CNP peptides in CSF decreased from day 4 to day 87 in pregnant sheep, possibly reflecting an adaptive response of the cerebral vasculature to increased hemodynamic load. We conclude that sustained high concentrations of CNP - far exceeding levels encountered in human pathophysiology - fail to affect CNP peptide levels in CSF.

C-type natriuretic peptide plasma levels are elevated in subjects with achondroplasia, hypochondroplasia, and thanatophoric dysplasia

CONTEXT

C-type natriuretic peptide (CNP) is a crucial regulator of endochondral bone growth. In a previous report of a child with acromesomelic dysplasia, Maroteaux type (AMDM), caused by loss-of-function of the CNP receptor (natriuretic peptide receptor-B [NPR-B]), plasma levels of CNP were elevated. In vitro studies have shown that activation of the MAPK kinase (MEK)/ERK MAPK pathway causes functional inhibition of NPR-B. Achondroplasia, hypochondroplasia, and thanatophoric dysplasia are syndromes of short-limbed dwarfism caused by activating mutations of fibroblast growth factor receptor-3, which result in overactivation of the MEK/ERK MAPK pathway.

OBJECTIVE

The purpose of this study was to determine whether these syndromes exhibit evidence of CNP resistance as reflected by increases in plasma CNP and its amino-terminal propeptide (NTproCNP).

DESIGN

This was a prospective, observational study.

SUBJECTS

Participants were 63 children and 20 adults with achondroplasia, 6 children with hypochondroplasia, 2 children with thanatophoric dysplasia, and 4 children and 1 adult with AMDM.

RESULTS

Plasma levels of CNP and NTproCNP were higher in children with achondroplasia with CNP SD scores (SDSs) of 1.0 (0.3-1.4) (median [interquartile range]) and NTproCNP SDSs of 1.4 (0.4-1.8; P < .0005). NTproCNP levels correlated with height velocity. Levels were also elevated in adults with achondroplasia (CNP SDSs of 1.5 [0.7-2.1] and NTproCNP SDSs of 0.5 [0.1-1.0], P < .005). In children with hypochondroplasia, CNP SDSs were 1.3 (0.7-1.5) (P = .08) and NTproCNP SDSs were 1.9 (1.8-2.3) (P < .05). In children with AMDM, CNP SDSs were 1.6 (1.4-3.3) and NTproCNP SDSs were 4.2 (2.7-6.2) (P < .01).

CONCLUSIONS

In these skeletal dysplasias, elevated plasma levels of proCNP products suggest the presence of tissue resistance to CNP.

Differential response of C-type natriuretic peptide to estrogen and dexamethasone in adult bone

C-type natriuretic peptide (CNP) is crucial in promoting endochondral bone growth in mammals including humans but whether this paracrine hormone participates in maintaining bone integrity in the mature skeleton is unknown. Accordingly we studied changes in plasma and bone tissue CNP in anoestrus adult ewes receiving short term anabolic (estrogen) or catabolic (dexamethasone) treatment for 7days. CNP and the aminoterminal fragment of the CNP prohormone (NTproCNP) were measured in plasma and extracts of cancellous bone excised from vertebral, iliac, tibial and marrow tissues. Concentrations of CNP peptides were much higher in vertebral and iliac extracts than those of tibial or marrow. Both plasma CNP and NTproCNP increased rapidly after estrogen followed by a later rise in bone alkaline phosphatase. Vertebral and iliac (but not tibial or marrow) CNP peptide content were significantly increased by estrogen. Consistent with a skeletal source, plasma NTproCNP was significantly associated with vertebral tissue CNP. In contrast, bone tissue CNP peptide content was unaffected by dexamethasone despite suppression of plasma CNP peptides and bone alkaline phosphatase. We postulate that increases in trabecular bone CNP reflect new endosteal bone formation in these estrogen responsive tissues whereas reduced plasma CNP peptides after dexamethasone, without change in cancellous bone content, reflects reductions in cortical bone turnover.

C-type natriuretic peptide in complicated pregnancy: increased secretion precedes adverse events

CONTEXT

C-type natriuretic peptide (CNP), a vasoactive product of the endothelium, is markedly increased during placentation in ovine pregnancy and is further stimulated by nutrient restriction. Whether CNP products change in human pregnancy is unknown.

OBJECTIVES

The objective of the study was to compare serial changes in maternal plasma CNP peptides during normal pregnancy with changes in pregnancy complicated by adverse events and relate these to fetal growth and placental CNP content.

DESIGN

This was a prospective observational study undertaken in a tertiary care center.

METHODS

We studied changes in maternal plasma aminoterminal proCNP (NTproCNP) and CNP at monthly intervals, fetal growth, and placental and umbilical plasma CNP peptides in 51 women, 28 of whom experienced an adverse event and 23 were uneventful. Age matched healthy nonpregnant women served as a reference range for NTproCNP.

RESULTS

Compared with nonpregnant women, maternal plasma NTproCNP in an uneventful pregnancy was significantly reduced from first sampling (16 wk gestation) until 36 weeks. In contrast, in complicated pregnancy, levels did not decline and were significantly higher (P < .001 by ANOVA) than in normal pregnancy from 20 weeks. Highest values occurred in women later developing hypertension and fetal growth disorders. Placental concentration of NTproCNP was unrelated to maternal NTproCNP but strongly correlated with cord plasma levels.

CONCLUSIONS

Maternal NTproCNP is significantly raised in women who later exhibit a range of obstetric adverse events. Lack of association with placental concentrations suggests that these changes represent an adaptive response within the maternal circulation to a threatened nutrient supply to the fetus.

Impact of age, phenotype and cardio-renal function on plasma C-type and B-type natriuretic peptide forms in an adult population

CONTEXT

In contrast to the cardiac hormones, atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP), variations in plasma concentrations of C-type natriuretic peptide (CNP) in healthy adults are ill-defined, limiting their clinical application.

OBJECTIVE

Our objective was to define the effect of age, phenotype (gender, height, BMI), and cardiac and renal function on plasma CNPs in an adults population without renal or cardiovascular disease.

DESIGN AND SETTING

This was a prospective cross-sectional observational study of adult volunteers, aged 21-80 years, randomly selected from the electoral roll.

SUBJECTS AND METHODS

Plasma CNP and its associated aminoterminal propeptide (NTproCNP) were measured in 258 subjects and related to age, gender, height and plasma creatinine. Subgroup analyses seeking associations with cardiac function (plasma BNP and NTproBNP) and bone turnover bone-specific alkaline phosphatase (bALP) were also determined.

RESULTS

Plasma concentrations of CNPs in men continued to decline from adolescent values to reach a nadir in the 5th decade after which values increased. Similar but less marked changes occurred in women. In both sexes, NTproCNP was inversely and independently correlated with height. In contrast to B-type natriuretic peptides (BNPs), NTproCNP was higher in men, significantly related to creatinine and positively related to bALP.

CONCLUSIONS

Gender- and age-specific changes affect CNPs in adults. Inverse associations of NTproCNP with adult height, positive correlation with creatinine - and in contrast to CNP - no association with BNP are further unique findings distinguishing NTproCNP, which need to be considered in future studies.

C-Type Natriuretic Peptide (CNP) levels are altered in boys with Klinefelter syndrome

CONTEXT

B-type natriuretic peptide (BNP) expression in vitro is up-regulated by the protein coded by the short stature homeobox gene (SHOX). C-type natriuretic peptide (CNP) is a paracrine regulatory factor of the growth plate that plays a key role in endochondral growth and shares clearance pathways with BNP. We explored the possibility that alterations in natriuretic peptide regulation may play a role in the overgrowth of boys with Klinefelter syndrome.

OBJECTIVE

The objectives of the study were to document the blood levels of amino-terminal propeptide of B-type natriuretic peptide (NTproBNP), CNP, and its amino-terminal propeptide (NTproCNP) in boys with Klinefelter syndrome and compare values with age- and height-matched control subjects.

DESIGN

This was a prospective, case-controlled, observational study.

SUBJECTS

Participants were 24 healthy boys with Klinefelter syndrome between 4 and 14 yr of age. Data from sex-, age-, and height-matched healthy controls were obtained from subjects participating in a previously described study.

RESULTS

Plasma levels of NTproBNP and CNP were lower, whereas levels of NTproCNP were higher in boys with Klinefelter syndrome compared with published reference ranges. In addition, CNP levels were lower and NTproCNP levels higher than in sex-, age-, and height-matched controls.

CONCLUSIONS

In contrast to plasma NTproBNP, CNP production and clearance are increased in boys with Klinefelter syndrome. Together these findings argue against an interaction between BNP with CNP in the growth plate. Why CNP peptide levels are altered in Klinefelter syndrome remains to be explored.

Amino-terminal propeptide of C-type natriuretic peptide (NTproCNP) predicts height velocity in healthy children

OBJECTIVE

C-type natriuretic peptide (CNP) is a paracrine regulatory factor of the growth plate and plays a key role in endochondral growth. Its amino-terminal propeptide (NTproCNP) is an equimolar product of CNP biosynthesis and is easily measured in plasma. Preliminary studies suggest that NTproCNP levels correlate with height velocity in sheep and children. The objectives of the study were to correlate NTproCNP levels with height velocity and to define the reference range for plasma CNP and NTproCNP across childhood.

DESIGN

This was a prospective, cross-sectional, observational study of healthy children.

PATIENTS

Participants were 258 healthy children between 2 months and 20 years of age.

MEASUREMENTS

Anthropometrics were obtained and CNP and NTproCNP levels were determined by radioimmunoassay.

RESULTS

For both sexes, CNP and NTproCNP levels were high in infancy, lower in early childhood, rising during puberty, then falling to low adult levels. Levels of NTproCNP peaked at 14·1 years in boys and 11·9 years in girls, coincident with the age of peak height velocity. Levels of NTproCNP varied with pubertal status, peaking at genital Tanner stage IV in boys and III in girls. There was a highly significant correlation between NTproCNP and height velocity.

CONCLUSIONS

C-type natriuretic peptide plays an integral role in endochondral growth. We show here that CNP synthesis (as measured by NTproCNP levels in plasma) is closely related to linear growth in healthy children at all ages. We propose NTproCNP as a biomarker of linear growth.

C-type Natriuretic Peptide: a novel biomarker of steroid induced bone toxicity in children with acute lymphoblastic leukemia (ALL)

Impaired bone growth and mineralization, and osteonecrosis are significant and common long-term sequelae of chemotherapy for childhood acute lymphoblastic leukemia (ALL). Here we have evaluated the relationship between linear bone growth during chemotherapy for ALL and bone derived C-type Natriuretic Peptide (CNP). CNP is known to be critical to normal endochondral bone growth in both rodents and humans, and plasma concentration of the amino terminal pro CNP (NTproCNP) is strongly correlated with concurrent height velocity in children. Plasma NTproCNP and CNP were measured by radio-immunoassay in 12 children aged 2-9 years during induction and maintenance chemotherapy for children with ALL. Height velocity was calculated from stadiometer readings at intervals of 3-12 months and related to plasma NTproCNP during each growth interval. Plasma NTproCNP was markedly suppressed in all subjects during induction chemotherapy. Brief periods of NTproCNP decline and rapid rebound during maintenance treatment coincided with the use of dexamethasone but not with other chemotherapeutics. Height velocity was markedly reduced during ALL induction but unaffected in maintenance phase, and these changes in growth were strongly correlated with plasma NTproCNP concentration. Plasma NTproCNP has potential use as a biomarker of glucocorticoid-induced bone toxicity.

C-type natriuretic peptide forms in adult hyperthyroidism: correlation with thyroid hormones and markers of bone turnover

CONTEXT

Plasma C-type natriuretic peptide (CNP) forms correlate with linear growth velocity in juveniles. In hyperthyroid children, plasma CNP products fall in parallel with height velocity and thyroid hormones (TH) as euthyroidism is restored. The effect of TH on CNP forms after completion of endochondral growth is unknown.

OBJECTIVE

To determine the effect of restoring euthyroidism on plasma CNP forms and bone turnover markers (BTMs) in hyperthyroid adults.

DESIGN AND SETTING

We performed a prospective observational study in 20 adults (19 women) with acquired hyperthyroidism before and during carbimazole treatment. INTERVENTION AND MAIN OUTCOMES: Blood levels of CNP, amino-terminal propeptide of CNP (NTproCNP), TH and BTMs - bone-specific alkaline phosphatase, osteocalcin, procollagen type 1 amino-terminal propeptide and type 1 collagen C-telopeptide (CTx) - were measured before and during the first 6 months of carbimazole treatment and correlations determined.

RESULTS

Both CNP and NTproCNP were significantly correlated with TH at baseline. As in children, decreases in CNP forms were closely associated with fall in TH. Significant associations were found between CNP forms and CTx.

CONCLUSIONS

CNP production from tissues other than endochondral cartilage is responsive to TH. Strong temporal links with markers of bone resorption suggest that CNP may also participate in bone remodelling in the adult skeleton.

Pharmacodynamic responses of plasma and tissue C-type natriuretic peptide to GH: correlation with linear growth in GH-deficient rats

Studies from genetic modification and spontaneous mutations show that C-type natriuretic peptide (CNP) signalling plays an essential part in postnatal endochondral growth, but measurement of CNP proteins and changes in their abundance in tissues and plasma during normal growth has not been reported. Using rodent pups with GH deficiency, we now describe the pharmacodynamic response of CNP and rat amino-terminal proCNP (NTproCNP) in plasma and tissues, and relate these to changes in linear growth (nose-tail length, tibial length and tibial growth plate width) during the course of 1 week of GH or saline (control) administration. Compared with saline, significant increases in plasma and tissue CNP forms were observed after 24 h in GH-treated pups and before any detectable change in linear growth. Whereas CNP abundance was increased in most tissues (muscle, heart and liver) by GH, enrichment was the greatest in extracts from growth plates and kidney. Plasma and tissue concentrations in GH-treated pups were sustained or further increased at 1 week when strong positive associations were found between plasma NTproCNP and linear growth or tissue concentrations. High content of NTproCNP in kidney tissue strongly correlated with plasma concentrations, which is consistent with previous data showing renal extraction of the peptide. In showing a prompt and significant increase in CNP in tissues driving normal endochondral growth, these findings provide further rationale for CNP agonists in the treatment of growth disorders resistant to current therapies and support the use of CNP concentrations as biomarkers of linear growth.

Plasma C-type natriuretic peptide forms and thyroid status in prepubertal children with acquired thyroid disease

OBJECTIVE

C-type natriuretic peptide (CNP) and thyroid hormone (TH) are essential for normal skeletal growth. Plasma CNP peptides correlate with growth velocity, but the relationship between thyroid status and CNP production is unknown. This study examined the impact of restoring normal TH levels on CNP and height velocity (HV) in children with acquired hypo- and hyperthyroidism.

DESIGN

We performed a prospective, observational study in prepubertal children with acquired hypothyroidism (n = 15) and hyperthyroidism (n = 12).

MEASUREMENTS

Blood levels of CNP, amino-terminal proCNP (NTproCNP), bone-specific alkaline phosphatase (BSAP), IGF-I and TH levels were measured before and during the first 6 months of standard treatment for hypo- and hyperthyroidism, and correlations were determined.

RESULTS

At baseline, HV, CNP, NTproCNP and BSAP were significantly higher in hyper- than in hypothyroid subjects. Changes in TH after treatment were closely coupled to change in CNP and NTproCNP in hyperthyroid, but not in hypothyroid, children. In addition, a positive association of HV with CNP peptides was found during treatment of hyperthyroidism. Normalizing TH did not correlate with changes in BSAP or IGF-I in either group.

CONCLUSIONS

Plasma CNP peptides are higher in children with hyperthyroidism than in those with hypothyroidism at diagnosis and, in hyperthyroid children, change concordantly with TH and HV during treatment. Differential responses of CNP in the two groups suggest CNP production is dependent on growth plate activity and not a direct effect of TH on CNP gene expression. Our findings suggest novel mechanisms underlying changes in skeletal response during treatment in children with acquired thyroid disease.

Central and peripheral forms of C-type natriuretic peptide (CNP): evidence for differential regulation in plasma and cerebrospinal fluid

Aminoterminal proCNP (NTproCNP), a stable product of CNP gene expression and readily measured in human plasma, provides a new approach to studies of CNP which is rapidly degraded at source. CNP is detectable in human CSF but the presence and proportions of NTproCNP in CSF are unknown. Since CNP is widely expressed throughout the CNS, we hypothesized that the ratio of NTproCNP to CNP in CSF is greatly increased when compared to plasma and that CSF CNP peptides may contribute to their concentrations in the systemic circulation. Concurrent plasma and CSF concentrations of CNP forms were measured in 51 subjects undergoing spinal anesthesia for arranged orthopedic procedures. Elevated concentrations of NTproCNP (1045 ± 359 pmol/L), characterized by HPLC-RIA, were found in CSF and greatly exceeded those of CNP (7.9 ± 3.2 pmol/L). The ratio of NTproCNP to CNP in CSF (145 ± 55) was much higher than in plasma (31 ± 27). A significant inverse relation was found between plasma and CSF CNP concentrations (r = -0.29, p < 0.05). cGMP and neprilysin were unrelated to CNP levels in CSF. We conclude that CNP is differentially regulated across the brain in normal health. Despite markedly elevated levels of NTproCNP in CSF, it is unlikely that these contribute to systemic levels in healthy adults. Identifying NTproCNP as the dominant CNP form in CSF opens up the possibility of its use in future studies exploring CNP regulation within the CNS and possible applications in the diagnosis and monitoring of subjects with central neural disorders.

Effect of cortisol on C-type natriuretic peptide in ovine pregnancy: differential responses in fetal and placental tissues

We have used aminoterminal pro C-type natriuretic peptide (NTproCNP)--a stable marker of CNP secretion--to study the effect of cortisol on CNP secretion and fetal growth. In ovine pregnancy, maternal plasma NTproCNP (largely sourced from the placenta) increases at the end of the first trimester and then decreases abruptly preterm during the phase of fetal surge in cortisol secretion. Postulating that increases in cortisol, as occurs in the fetal or maternal circulation in late pregnancy, will reduce CNP secretion, we studied the fetal and maternal responses in NTproCNP to sustained low-dose infusions of cortisol (1.2 mg/d/kg for 11 d) delivered to the fetus from d 117 gestation. Fetal plasma NTproCNP was progressively reduced during fetal cortisol infusions, whereas fetal girth growth was unchanged. In contrast, maternal NTproCNP was unaffected by cortisol. We conclude that fetal but not placental tissue production of CNP is reduced by small increments in fetal cortisol. Failure to reduce maternal NTproCNP may relate to the continuing presence of the placental barrier to cortisol at this stage of pregnancy.

Effect of nutrition on plasma C-type natriuretic peptide forms in adult sheep: evidence for enhanced C-type natriuretic peptide degradation during caloric restriction

Previous studies in lambs and children show that the plasma concentration of amino terminal pro-C-type natriuretic peptide (NTproCNP), a stable product of proCNP, is strongly correlated with skeletal growth and markers of bone formation. Consistent with these findings, CNP expression is sensitive to nutritional status and is reduced by caloric restriction (CR) in both the fetus and the postnatal lamb. However, the effect of nutritional status on CNP in the adult, once linear growth is complete, is unknown. Hypothesizing that reduced CNP synthesis during CR is contingent on the presence of active growth plates, we studied the effect of CR ( 25% of maintenance) or loading (CL, 200% of maintenance) on CNP forms and alkaline phosphatase (ALP) in adult ewes and compared the findings to responses in a control group (C) fed a maintenance diet of 10.6 MJ of metabolizable energy. Live body weight was reduced (17%) in the CR group and increased (10%) in the CL group after 16 days of intervention. Plasma CNP concentration and ALP both fell in CR sheep and were significantly lower than C (P < .05 for both), returning toward basal levels 1 week after refeeding. In contrast, plasma NTproCNP did not differ (CR vs C). There were no significant changes in CNP forms and ALP in CL sheep compared with C. Fall in plasma CNP but not in NTproCNP in CR adult sheep suggests that CNP degradation (not synthesis) is altered, and contrasts with previous findings in growing lambs where CR reduces both CNP forms.

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

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

C-type natriuretic peptide forms in pregnancy: maternal plasma profiles during ovine gestation correlate with placental and fetal maturation

Circulating concentrations of C-type natriuretic peptide (CNP) and a related amino terminal fragment (NTproCNP) were measured at weekly intervals from preconception to 3 wk postpartum in ewes with twins (n = 8) and nonpregnant ewes (n = 8). In contrast to low and stable values in nonpregnant ewes (CNP, 0.75 +/- 0.08; NTproCNP, 22 +/- 2 pmol/liter), CNP forms increased abruptly at 40-50 d of gestation and rose to peak values (CNP, 31 +/- 5, NTproCNP, 270 +/- 16 pmol/liter) at about d 120. Approximately 7 d prepartum, the concentration of both CNP forms fell precipitously to preconception values immediately postpartum. In separate studies, circulating maternal CNP forms were positively related to fetal number at d 120. Consistent with a major contribution from the placenta to circulating levels, the concentrations of CNP forms were elevated in the placentome (cotyledon: CNP, 18 +/- 4, NTproCNP, 52 +/- 10 pmol/g; caruncle: CNP, 13 +/- 3, NTproCNP, 31 +/- 6 pmol/g) and much higher than those of intercaruncular uterine tissue (CNP, 0.19 +/- 0.05, NTproCNP, 0.98 +/- 0.2 pmol/g) in late-gestation ewes (P < 0.001, n = 4). These distinctive patterns of maternal plasma CNP forms, positive relation with fetal number, and greatly elevated protein concentrations in the placentome demonstrate the hormone's strong relation to placental and fetal maturation. The findings provide a firm basis for future studies of the functional role of CNP in fetal-maternal welfare.

Regional release and clearance of C-type natriuretic peptides in the human circulation and relation to cardiac function

Production and clearance of plasma C-type natriuretic peptide (CNP) and amino terminal (NT)-proCNP immunoreactivity in the human circulation remain poorly characterized. Accordingly, we have measured arterial and venous concentrations of CNP and NT-proCNP across multiple tissue beds during cardiac catheterization in 120 subjects (age: 64.2+/-9.0 years; 73% men) investigated for cardiovascular disorders. The heart, head and neck, and musculoskeletal tissues made the clearest contributions to both plasma CNP and NT-proCNP (P<0.05). Net release of NT-proCNP was also observed from hepatic tissue (P<0.001). Negative arteriovenous gradients for CNP were observed across renal, hepatic, and pulmonary tissue (P<0.05), indicating net clearance, whereas no tissue-specific site of NT-proCNP clearance was identified. Age, mean pulmonary artery pressure, left ventricular end diastolic pressure, Brandt score of myocardial jeopardy, and troponin I were independent predictors of circulating CNP levels in multivariable analysis. Sex and kidney function were independently predictive of arterial NT-proCNP. The proportional step-up of CNP (+60%) across the heart was less than for brain natriuretic peptide (+123%) but greater than for NT-pro-brain natriuretic peptide (NT-proBNP) (+36%) and NT-proCNP (+42%; P<0.001 for all). We conclude that cardiac and head and neck tissue are important sources of CNP. Circulating CNP but not NT-proCNP concentrations are related to cardiac hemodynamic load and ischemic burden. Although cardiac release is most evident, multiple additional tissues release NT-proCNP immunoreactivity without evidence for an organ-specific site for NT-proCNP degradation. Taken together, differences in magnitude and direction of transorgan gradients for CNP compared with NT-proCNP suggest net generalized cosecretion with differing mechanisms of clearance.

Effect of sex steroids on plasma C-type natriuretic peptide forms: stimulation by oestradiol in lambs and adult sheep

Although C-type natriuretic peptide (CNP) is crucial to post-natal endochondral growth, roles for the hormone in pubertal bone growth and the physiological effects of sex steroid substitution on CNP synthesis are not known. Using a plasma marker of CNP tissue synthesis (amino-terminal proCNP, NTproCNP), we have studied the effect of exogenous oestrogen (E(2)) or testosterone (T) on plasma CNP forms and bone alkaline phosphatase (bALP) in pre-pubertal lambs. Responses to E(2) in non-cycling adult ewes were also studied. In 15-week-old intact ewe lambs, E(2) promptly increased plasma NTproCNP and CNP (P<0.001) to peak on day 2, and bALP (P<0.001 peaking on day 7), whereas no significant stimulation in response to T was observed in male lambs. Linear bone growth and live weight were unaffected. In adult anoestrous ewes, basal concentrations of CNP forms and bALP were lower than in ewe lambs, in keeping with skeletal maturity, but adults responded similarly to E(2). Prompt and sustained increases in NTproCNP and CNP, and a later threefold rise in bALP (all P<0.001), were induced by E(2). Possible contributions to these increases in plasma CNP forms by reproductive tissues (a known site of E(2)-induced CNP expression) were excluded by showing similar E(2)-induced CNP responses in adult ewes after surgical removal of reproductive tissues. These results are the first to show that E(2) stimulates plasma CNP forms and bALP in lambs and adult sheep and raise the possibility that CNP also participates in bone formation in the mature skeleton.

Plasma amino-terminal pro C-type natriuretic Peptide in the neonate: relation to gestational age and postnatal linear growth

CONTEXT

C-type natriuretic peptide (CNP) plays an essential role in endochondral bone growth. Insight into CNP's paracrine actions is possible using plasma measurements of the amino-terminal pro C-type natriuretic peptide (NTproCNP). Whether correlations of NTproCNP with linear growth, as found in children and lambs, apply in neonates is unknown.

OBJECTIVES

Our objective was to determine the effects of prematurity, gender, and antenatal steroids on plasma NTproCNP at birth, and serial changes in hormone concentrations, linear growth, and markers of bone turnover in the first month of postnatal life.

DESIGN AND SETTING

This is a prospective study of newborn infants admitted to an intensive care unit.

SUBJECTS

A total of 48 infants (four gestation groups) were enrolled. Umbilical cord samples were also obtained from 39 healthy term infants.

MAIN OUTCOME MEASURES

Plasma NTproCNP and CNP were measured in cord plasma. In enrolled neonates, serial measurements of hormone concentrations and markers of bone turnover were related to tibial growth velocity as measured by knemometry.

RESULTS

Cord plasma NTproCNP was inversely related to gestational age (r = -0.35; P = 0.003) and was higher in males (P < 0.001). Plasma NTproCNP (P = 0.016) and CNP (P < 0.001) increased within the first week of life, the increase relating inversely to gestational age (r = -0.64; P < 0.001). Plasma NTproCNP at 1 wk was strongly correlated with linear growth velocity (r = 0.49; P < 0.001), and also at 2-4 wk, the relation being stronger than observed between bone turnover markers and growth velocity.

CONCLUSIONS

In neonates with diverse disorders affecting growth and nutrition, plasma NTproCNP was strongly correlated with linear growth during the first 4 wk of postnatal life and may prove to be a novel marker of growth plate activity in neonates.

Amino-terminal propeptide of C-type natriuretic peptide and linear growth in children: effects of puberty, testosterone, and growth hormone

CONTEXT

C-type natriuretic peptide (CNP), a paracrine factor of the growth plate, plays a key role in stimulating bone growth. The amino-terminal propeptide of CNP (NTproCNP) is produced in equimolar amounts with CNP and is measurable in plasma, providing a potential biomarker for growth plate activity and, hence, linear growth.

OBJECTIVE

We explored the effects of puberty, testosterone, and GH treatment on NTproCNP levels in normal and short-statured children.

DESIGN

This was a retrospective analysis of samples obtained during previous studies.

SETTING

The study was conducted at a pediatric clinical research center.

SUBJECTS

Children with short stature due to GH deficiency, idiopathic short stature (ISS), or constitutional delay of growth and maturation (CDGM) were studied (n = 37). A cohort of normal-statured adolescent boys was also studied (n = 23).

INTERVENTIONS

Children with GH deficiency and ISS were studied before and during testosterone and/or GH treatment. Boys with CDGM and healthy controls were studied once.

MAIN OUTCOME MEASURES

The main outcomes were NTproCNP levels before and during growth-promoting therapy and during pubertal growth.

RESULTS

Children with short stature due to GH deficiency, ISS, or CDGM had comparable baseline levels of NTproCNP, and levels increased markedly in response to GH or testosterone treatment. In boys with CDGM, levels were comparable with height-matched controls but were less than those from age-matched controls. In healthy boys, NTproCNP appears to peak with the pubertal growth spurt.

CONCLUSIONS

NTproCNP levels increase during growth-promoting therapy and are increased during puberty in boys. This novel biomarker of growth may have clinical utility in the evaluation of children with short stature and for monitoring growth-promoting therapy.

C-type natriuretic peptide forms in the ovine fetal and maternal circulations: evidence for independent regulation and reciprocal response to undernutrition

C-type natriuretic peptide (CNP) has a crucial role in postnatal endochondral bone growth and is rapidly responsive to changes in nutrition. Although CNP is expressed in the placenta, little is known about the regulation and role of CNP in fetal-maternal health. We hypothesized that CNP may be similarly responsive to undernutrition in the growing fetus, in which maternal nutrition is crucial to normal growth and development. We therefore studied maternal and fetal CNP and the aminoterminal (bioinactive) fragment of proCNP (NTproCNP) in 39 chronically catheterized pregnant sheep before and after a 3-d maternal fast from 121 d gestation. Maternal CNP and NTproCNP levels were higher than in the fetus (CNP 12-fold, NTproCNP 1.5-fold, both P < 0.001). The ratio of NTproCNP to CNP was higher in the fetus than the mother (53 +/- 3 vs. 8.7 +/- 0.6, P < 0.001), suggesting enhanced synthesis and/or degradation of CNP in the fetus. As in postnatal lambs, fetal plasma CNP forms fell promptly during maternal fasting. In contrast, maternal levels exhibited reciprocal and contemporaneous increase, which was reversed by refeeding. Uteroplacental production of CNP was suggested by a high venoarterial concentration gradient across the gravid uterus, and a correlation between maternal NTproCNP levels and placental weight (r(2) = 0.26, P = 0.01). These studies provide the first evidence that CNP is regulated independently in the fetus. Reciprocal increases in maternal CNP forms may reflect the response of the uteroplacental unit to substrate deficiency. CNP may have a role in maintaining fetal welfare and provides a possible marker of uteroplacental nutrient supply.

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

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

Heterozygous mutations in natriuretic peptide receptor-B (NPR2) are associated with short stature

CONTEXT

C-type natriuretic peptide (CNP) is an important regulator of skeletal growth. Loss-of-function mutations affecting the CNP receptor natriuretic peptide receptor-B (gene NPR2) cause the autosomal recessive skeletal dysplasia, acromesomelic dysplasia, Maroteaux type (AMDM). The phenotype of heterozygous carriers of NPR2 mutations is less clear.

OBJECTIVE

The objective of the study was to determine the phenotypic features of heterozygous carriers of NPR2 mutations.

DESIGN AND SETTING

This was a case-control study from the general community.

SUBJECTS

Thirty-nine members of a family in which one member has AMDM were studied.

INTERVENTION

This was an observational study.

MAIN OUTCOME MEASURE

The primary measure was stature, with the hypothesis that carriers have reduced stature compared with noncarriers.

RESULTS

Sixteen family members were NPR2 mutation carriers. Height z-scores of these carriers were -1.8 +/- 1.1 (mean +/- sd), which was significantly less than the 23 noncarrier family members (-0.4 +/- 0.8, P < 0.0005) and the general population (P < 0.0005). However, there was no difference in body proportion between carriers and noncarriers. The proband with AMDM had low IGF-I levels and evidence of GH resistance, as well as very high plasma levels of CNP and its amino-terminal propeptide. Levels of these peptides were normal in the heterozygous carriers.

CONCLUSIONS

We have shown that heterozygous mutations in NPR2 are associated with short stature. Assuming one in 700 people unknowingly carry an NPR2 mutation, our data suggest that approximately one in 30 individuals with idiopathic short stature are carriers of NPR2 mutations.

Regional sampling and the effects of experimental heart failure in sheep: differential responses in A, B and C-type natriuretic peptides

While regional plasma concentrations of the endocrine hormones atrial and brain natriuretic peptide (ANP and BNP) have been studied, there are few reports of regional changes in the largely paracrine C-type natriuretic peptide (CNP) and its amino terminal fragment NT-CNP. Accordingly, we have performed trans-organ arteriovenous sampling for measurement of plasma ANP, BNP, CNP and NT-CNP in anesthetized sheep before and after induction of experimental heart failure. ANP and BNP plasma concentrations are sourced from a single organ (the heart) and are subject to substantial extraction across most tissue beds. In contrast, our data demonstrate that multiple tissues including liver, heart, hind limb and kidney contribute to circulating CNP. Given that arteriovenous gradients for NT-CNP were similar, this is likely to represent de novo secretion. Circulating levels of CNP and NT-CNP were raised in heart failure but to a much lesser degree than ANP and BNP. There was no evidence of net extraction of CNP or NT-CNP across any tissue bed.

Comparison of B-Type Natriuretic Peptides for Assessment of Cardiac Function and Prognosis in Stable Ischemic Heart Disease

In 1,049 patients with stable ischemic heart disease (IHD), brain natriuretic peptide (BNP) and amino terminal pro-brain natriuretic peptide (NTproBNP) correlated closely (r = 0.09, p < 0.001) and were similarly related to left ventricular ejection fraction (LVEF) (r = -0.50 and -0.46, respectively), age (0.44 and 0.47), and creatinine clearance (-0.51 and -0.51). Receiver-operating characteristic curves for detection of LVEF <30% were similar (area under the curves = 0.83 and 0.80, both p < 0.001), and both peptides had strong negative predictive value (95% and 94%). Both independently predicted all-cause mortality and/or heart failure with closely overlapping event-free survival curves; BNP and NTproBNP display strong, near-identical test performance in ruling about severely reduced LVEF and in prediction of all-cause mortality or heart failure in stable IHD.

OBJECTIVES

The aim of this work was to test B-type natriuretic peptides for assessment of function and prognosis in stable ischemic heart disease (IHD) and to compare brain natriuretic peptide (BNP) with amino terminal pro-brain natriuretic peptide (NTproBNP), including the relative effects of age and renal function on test performance.

BACKGROUND

Brain natriuretic peptide and NTproBNP are emerging diagnostic and prognostic markers in heart failure and acute coronary syndromes. Their performance in assessing function and prognosis in stable IHD is unknown. Whether one marker is superior and the relative effects of age and renal function on test performance are uncertain.

METHODS

In 1,049 patients with stable IHD, left ventricular ejection fraction (LVEF) was measured by radionuclide scanning and creatinine clearance estimated by the Cockroft-Gault equation. Age, gender, and body mass index were recorded. Twelve-month all-cause mortality or admission with heart failure was prospectively recorded; BNP and NTproBNP were measured by radioimmunoassay.

RESULTS

Brain natriuretic peptide and NTproBNP correlated closely (r = 0.90, p < 0.001) and had similar relationships to LVEF (r = -0.50 and -0.46, respectively, both p < 0.001), age (0.44 and 0.47, both p < 0.001), and creatinine clearance (-0.51 and -0.51, both p < 0.001). Areas under receiver-operating characteristic curves for detection of LVEF <30% were similar (0.83 and 0.80, both p < 0.001) with strong negative predictive values for both (95% and 94%). Both markers independently predicted the clinical end point with closely overlapping event-free survival curves.

CONCLUSIONS

In stable IHD, BNP and NTproBNP display strong and near-identical test performance in ruling out severely reduced LVEF and in prediction of all-cause mortality or heart failure despite significant effects of age, gender, and renal function on levels of both markers.

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

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

Four-day urocortin-I administration has sustained beneficial haemodynamic, hormonal, and renal effects in experimental heart failure

AIMS

To investigate the subacute effects of a sustained intravenous infusion of urocortin-I (Ucn-I) in experimental heart failure (HF).

METHODS AND RESULTS

In eight sheep with pacing-induced HF, a 4-day infusion of Ucn-I (0.3 microg/kg/h) induced prompt (30 min) and sustained (4-day) increases in cardiac output (CO, Day 4: 1.8+/-0.2 vs. 2.3+/-0.2 L/min, P<0.001) and stroke volume (7.8+/-0.8 vs. 10.2+/-1.0 mL/beat, P=0.0011), and reductions in mean arterial pressure (MAP, 72+/-3 vs. 70+/-3 mmHg, P=0.0305), left atrial pressure (26+/-1 vs. 11+/-2 mmHg, P<0.001), and total calculated peripheral resistance (43+/-6 vs. 32+/-4 mmHg/L/min, P<0.001). Ucn-I also induced persistent falls in plasma renin (1.34+/-0.23 vs. 0.77+/-0.10 nmol/L/min, P=0.048), aldosterone (3273+/-1172 vs. 382+/-44 pmol/L, P=0.0098), endothelin-1 (4.6+/-0.3 vs. 2.7+/-0.3 pmol/L, P<0.001), vasopressin (24+/-4 vs. 14+/-2 pmol/L, P=0.0028) and atrial (184+/-14 vs. 154+/-29 pmol/L, P=0.0226) and brain (43+/-5 vs. 32+/-6 pmol/L, P=0.0016) natriuretic peptides. Plasma adrenocorticotrophic hormone and cortisol rose transiently on Day 0. Ucn-I enhanced urinary sodium excretion (5.3-fold, P=0.0001) and creatinine clearance (1.3-fold, P=0.0055) long-term, and tended to increase urine output (P=0.0748). Food intake was attenuated over the first 2 days of treatment (P=0.0283).

CONCLUSION

Four-day administration of Ucn-I induces sustained reductions in cardiac preload and MAP, improvements in CO and renal function, and inhibition of a range of vasoconstrictor/volume-retaining factors. These findings support Ucn-I's therapeutic potential in HF.