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

NT-proCNP levels predict higher atherosclerotic cardiovascular risk profile in patients with proliferative diabetic retinopathy

AIMS

In this study, we aimed to demonstrate the effectiveness of serum amino-terminal proCNP (NT-proCNP) levels in predicting coronary heart disease (CHD) and cardiovascular risk in type 2 diabetes mellitus (T2DM) patients.

METHODS

We recruited 73 patients with T2DM in the study. Additionally, we grouped the patients according to their status of diabetic retinopathy (DR) as no DR, non-proliferative DR, or proliferative DR. Serum NT-proCNP levels of the patients were measured and their atherosclerotic cardiovascular disease (ASCVD) risk scores were calculated.

RESULTS

There was no significant difference in terms of NT-proCNP levels between the groups (p = 0.3) and in terms of CHD and ASCVD risk scores (p = 0.4 and p = 0.4, respectively). In the correlation analysis, a significant correlation was observed between the NT-proCNP levels and the ASCVD risk score (r = 0.373; p = 0.008 among the entire cohort and r = 0.555; p = 0.01 in the non-proliferative-DR group), smoking status (r = 0.280; p = 0.03 among the entire cohort and r = 0.362; p = 0.035 in the non-proliferative-DR group), sBP (r = 0.278; p = 0.038 among the entire cohort), and dBP (r = 0.284; p = 0.034 among the entire cohort and r = 0.482; p = 0.004 in the proliferative-DR group). In the ROC analysis, we found that the NT-proCNP level predicted a high ASCVD risk score with 83.3% sensitivity and 70.8% specificity and a very high ASCVD risk score with 100% sensitivity and 69.2% specificity among the proliferative-DR patients. No cut-off value was calculated for the prediction of high and very-high ASCVD risk scores in patients with non-proliferative DR. Similarly, no cut-off value was revealed for the prediction of established coronary artery disease in all groups.

CONCLUSIONS

Our study revealed a significant association between NT-proCNP levels and high ASCVD risk scores in patients with proliferative DR.

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.

Review A State of Natriuretic Peptide Deficiency

Measurement of natriuretic peptides (NPs) has proven its clinical value as biomarker, especially in the context of heart failure (HF). In contrast, a state partial NP deficiency appears integral to several conditions in which lower NP concentrations in plasma presage overt cardiometabolic disease. Here, obesity and type 2 diabetes have attracted considerable attention. Other factors - including age, sex, race, genetics, and diurnal regulation - affect the NP "armory" and may leave some individuals more prone to development of cardiovascular disease. The molecular maturation of NPs has also proven complex with highly variable O-glycosylation within the biosynthetic precursors. The relevance of this regulatory step in post-translational propeptide maturation has recently become recognized in biomarker measurement/interpretation and cardiovascular pathophysiology. An important proportion of people appear to have reduced effective net NP bioactivity in terms of receptor activation and physiological effects. The state of NP deficiency, then, both entails a potential for further biomarker development and could also offer novel pharmacological possibilities. Alleviating the state of NP deficiency before development of overt cardiometabolic disease in selected patients could be a future path for improving precision medicine.

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.

Sex-specific mortality prediction by pro-C-type natriuretic peptide measurement in a prospective cohort of patients with ST-elevation myocardial infarction

OBJECTIVE

To determine the predictive value of pro-C-type natriuretic peptide (pro-CNP) measurement in plasma sampled on admission from patients presenting with ST-elevation myocardial infarction (STEMI).

DESIGN

Prospective cohort study.

SETTING

Two University Hospitals in Denmark.

PARTICIPANTS

1760 consecutive patients (470 females and 1290 males) with confirmed STEMI.

MAIN OUTCOMES AND MEASURES

The main outcome was all-cause mortality at 1 year after presentation and the primary measure was pro-CNP concentration in plasma at admission in all patients and longitudinal measurements in a consecutive subgroup of 287 patients. A reference population (n=688) defined cut-off values of increased pro-CNP concentrations.

RESULTS

In all patients, an increased pro-CNP concentration was associated with a higher all-cause mortality after 1 year (HR 1.6, 95% CI 1.1 to 2.4, P_logrank=0.009) including an interaction of sex (p=0.03). In separate sex-stratified analyses, female patients showed increased all-cause mortality (HR_{1 year} 2.6, 95% CI 1.5 to 4.6), P_logrank <0.001), whereas no differences were found in male patients (HR_{1 year} 1.1, 95% CI 0.7 to 1.9, P_logrank=0.66). After adjusting for potential risk factors, we found increased pro-CNP concentrations≥the median value to be independently associated with increased risk of mortality in female patients within 1 year (HR per 1 pmol/L increase: 1.04, 95% CI 1.01 to 1.06, p=0.007). Moreover, we found indications of sex differences in pro-CNP concentrations over time (higher pro-CNP in males (4.4, 95% CI -0.28 to 9.1 pmol/L, p=0.07) and interaction of sex and time (p=0.13)), and that hypertension was independently associated with higher pro-CNP (4.5, 95% CI 0.6 to 8.4 pmol/L, p=0.03).

CONCLUSIONS

In female but not male patients presenting with STEMI, high concentrations of pro-CNP (≥median) at admission independently indicate a higher risk of all-cause mortality. The findings are remarkably specific for female patients, suggesting a different vascular phenotype beyond traditional measures of coronary artery flow compared with male patients.

Fluorescent turn-on assay of C-type natriuretic peptide using a molecularly imprinted ratiometric fluorescent probe with high selectivity and sensitivity

A novel molecularly imprinted ratiometric fluorescent probe was fabricated by simple sol-gel polymerization for selective and sensitive assay of C-type natriuretic peptide (CNP) in biosamples. Both the nitrobenzoxadiazole (NBD) and carbon dots (CDs) were located on the surface of silica, used as the detection signal and reference signal, respectively. For the turn-on-based probe, the fluorescence intensity of NBD could be quantitatively enhanced by CNP based on the strategy of photo-induced electron transfer (PET), while the fluorescence of CDs remained unchanged. The obtained probe exhibited excellent recognition selectivity and fast kinetics to CNP templates, and also showed good stability. The linear range of CNP determination was 5-80 pg mL^-1 with a low detection limit of 2.87 pg mL^-1. Finally, the probe was successfully applied to determine CNP in human serum samples and attained high recoveries between 97.3 and 104% with precisions below 4.7%. The result indicates that the proposed method has promising potential for the assay of trace peptides in complex matrices. Schematic illustration for the formation and determination mechanism of the probe.

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.

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.

The effect of natriuretic C-type peptide and its change over time on mortality in patients on haemodialysis or haemodiafiltration

Background

C-type natriuretic peptide (CNP) and its co-product N-terminal proCNP (NTproCNP) have been associated with beneficial effects on the cardiovascular system. In prevalent dialysis patients, however, a relation between NTproCNP and mortality has not yet been investigated. Furthermore, as a middle molecular weight substance, its concentration might be influenced by dialysis modality.

Methods

In a cohort of patients treated with haemodialysis (HD) or haemodiafiltration (HDF), levels of NTproCNP were measured at baseline and 6, 12, 24 and 36 months. The relation between serum NTproCNP and mortality and the relation between the 6-month rate of change of NTproCNP and mortality were analysed using Cox regression models. For the longitudinal analyses, linear mixed models were used.

Results

In total, 406 subjects were studied. The median baseline serum NTproCNP was 93 pmol/L and the median follow-up was 2.97 years. No relation between baseline NTproCNP or its rate of change over 6 months and mortality was found. NTproCNP levels remained stable in HD patients, whereas NTproCNP decreased significantly in HDF patients. The relative decline depended on the magnitude of the convection volume.

Conclusions

In our study, levels of NTproCNP appear strongly elevated in prevalent dialysis patients. Second, while NTproCNP remains unaltered in HD patients, its levels decline in individuals treated with HDF, with the decline dependent on the magnitude of the convection volume. Third, NTproCNP is not related to mortality in this population. Thus NTproCNP does not seem to be a useful marker for mortality risk in dialysis patients.

Blood pressure in adults with short stature skeletal dysplasias

Hypertension, compounded by obesity, contributes to cardiovascular disease and mortality. Data describing hypertension prevalence in adults with short stature skeletal dysplasias are lacking, perhaps due to poor fit of typical adult blood pressure cuffs on rhizomelic or contracted upper extremities. Through health screening research, blood pressure was measured in short stature adults attending support group meetings and skeletal dysplasia clinics. Blood pressure was measured with a commercially available, narrower adult cuff on the upper and/or lower segment of the arm. Height, weight, age, gender, diagnosis, exercise, and medications were collected. Subjects were classified as normotensive, prehypertensive, or hypertensive for group analysis; no individual clinical diagnoses were made. In 403 short stature adults, 42% were hypertensive (systolic >140, diastolic >90 OR taking antihypertensive medications). For every BMI unit and 1 kg weight increase in males, there was a 9% and an 8% increase, respectively, in the odds of hypertension versus normotension. In females, the increase was 10% and 6%, respectively. In those with achondroplasia, the most common short stature dysplasia, males (n = 106) had 10% greater odds of hypertension versus normotension for every BMI unit and kilogram increase. In females with achondroplasia (n = 128), the odds of hypertension versus normotension was 8% greater for each BMI unit and 7% for each additional kilogram. These data suggest a high population prevalence of hypertension among short stature adults. Blood pressure must be monitored as part of routine medical care, and measuring at the forearm may be the only viable clinical option in rhizomelic short stature adults with elbow contractures.

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.

Plasma C-Type Natriuretic Peptide: Emerging Applications in Disorders of Skeletal Growth

Although studies in experimental animals show that blood levels of C-type natriuretic peptide (CNP) and its bioinactive aminoterminal propeptide (NTproCNP) are potential biomarkers of long bone growth, a lack of suitable assays and appropriate reference ranges has limited the application of CNP measurements in clinical practice. Plasma concentrations of the processed product of proCNP, NTproCNP - and to a lesser extent CNP itself - correlate with concurrent height velocity throughout all phases of normal skeletal growth, as well as during interventions known to affect skeletal growth in children. Since a change in levels precedes a measurable change in height velocity during interventions, measuring NTproCNP may have predictive value in clinical practice. Findings from a variety of genetic disorders affecting CNP signaling suggest that plasma concentrations of both peptides may be helpful in diagnosis, provided factors such as concurrent height velocity, feedback regulation of CNP, and differential changes in peptide clearance are considered when interpreting values. An improved understanding of factors affecting plasma levels, and the availability of commercial kits enabling accurate measurement using small volumes of plasma, can be expected to facilitate potential applications in growth disorders including genetic causes -affecting the CNP signaling pathway.

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.

Natriuretic Peptides and Normal Body Fluid Regulation

Natriuretic peptides are structurally related, functionally diverse hormones. Circulating atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are delivered predominantly by the heart. Two C-type natriuretic peptides (CNPs) are paracrine messengers, notably in bone, brain, and vessels. Natriuretic peptides act by binding to the extracellular domains of three receptors, NPR-A, NPR-B, and NPR-C of which the first two are guanylate cyclases. NPR-C is coupled to inhibitory proteins. Atrial wall stress is the major regulator of ANP secretion; however, atrial pressure changes plasma ANP only modestly and transiently, and the relation between plasma ANP and atrial wall tension (or extracellular volume or sodium intake) is weak. Absence and overexpression of ANP-related genes are associated with modest blood pressure changes. ANP augments vascular permeability and reduces vascular contractility, renin and aldosterone secretion, sympathetic nerve activity, and renal tubular sodium transport. Within the physiological range of plasma ANP, the responses to step-up changes are unimpressive; in man, the systemic physiological effects include diminution of renin secretion, aldosterone secretion, and cardiac preload. For BNP, the available evidence does not show that cardiac release to the blood is related to sodium homeostasis or body fluid control. CNPs are not circulating hormones, but primarily paracrine messengers important to ossification, nervous system development, and endothelial function. Normally, natriuretic peptides are not powerful natriuretic/diuretic hormones; common conclusions are not consistently supported by hard data. ANP may provide fine-tuning of reno-cardiovascular relationships, but seems, together with BNP, primarily involved in the regulation of cardiac performance and remodeling. © 2017 American Physiological Society. Compr Physiol 8:1211-1249, 2018.

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.

Clinical Application of Biomarkers in Heart Failure with a Preserved Ejection Fraction: A Review

Heart failure with a preserved ejection fraction (HFpEF) is increasingly prevalent and a leading cause of morbidity and mortality worldwide. HFpEF has a complex pathophysiology, with recent evidence suggesting that an interaction of cardiovascular and noncardiovascular comorbidities (e.g. obesity, hypertension, diabetes, coronary artery disease, and chronic kidney disease) induces an inflammatory state that eventually leads to myocardial structural and functional alterations. Current ACCF/AHA guidelines suggest incorporation of biomarkers along with clinical and imaging tools to establish the diagnosis and disease severity in heart failure (HF). However, the majority of data on biomarkers relating to their levels, or their role in accurate diagnosis, prognostication, and disease activity, has been derived from studies in undifferentiated HF or HF with a reduced EF (HFrEF). As the understanding of the mechanisms underlying HFpEF continues to evolve, biomarkers reflecting different pathways including neurohormonal activation, myocardial injury, inflammation, and fibrosis have a clinical utility beyond the diagnostic scope. Accordingly, in this review article we describe the various established and novel plasma biomarkers and their emerging value in diagnosis, prognosis, response, and guiding of targeted therapy in patients with HFpEF.

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.

Biomarkers for Heart Failure in Asia

Contributions from the Asian biomedical community to knowledge of biomarkers in heart failure have grown rapidly since 2000. Japan has made world-leading contributions in the discovery and application of cardiac natriuretic peptides as biomarkers in heart failure, but there has been rapid growth in reports from China. Contributions also come from Taiwan, South Korea, Singapore, and Hong Kong. Centers in Asia have established clinical cohorts providing powerful platforms for the discovery and validation of biomarkers in heart failure. This century, Asian enquiry into biomarkers in heart failure will include peptides, cytokines, metabolites, nucleic acids, and other analytes.

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.

N-terminal pro-C-type natriuretic peptide in serum associated with bone destruction in patients with multiple myeloma

Aim: To examine whether N-terminal proCNP concentrations in serum is associated with bone destruction in patients with multiple myeloma. Materials & methods: N-terminal proCNP and biochemical bone markers were measured in 153 patients. Radiographic bone disease and skeletal-related events were evaluated at specific time-points. Results: N-terminal proCNP concentrations increased with age. High N-terminal proCNP concentrations were associated with high-risk disease and renal impairment. Renal function explained 22% of the variation. N-terminal proCNP concentrations correlated with serum bone ALP and serum PINP, but lacked association with bone resorption markers, radiographic bone disease and skeletal-related events. Conclusion: Serum N-terminal proCNP are associated with bone formation activity in patients with multiple myeloma, but should be interpreted with caution in patients with renal impairment.

Circulating C-type natriuretic peptide and its relationship to cardiovascular disease in the general population

C-type natriuretic peptide (CNP) is an endothelium-derived peptide that is released as a protective mechanism in response cardiovascular injury or disease. However, no studies have investigated circulating CNP, identifying clinical factors that may influence CNP and its relationship to cardiovascular disease in the general population. We studied 1841 randomly selected subjects from Olmsted County, MN (mean age, 63±11 years; 48% men). Plasma CNP was measured by a well-established radioimmunoassay and echocardiography, clinical characterization, and detailed medical record review were performed. We report that CNP circulates at various concentrations (median, 13 pg/mL), was unaffected by sex, was weakly associated by age, and that highest quartile of CNP identified a high-risk phenotype. Subjects with CNP in the highest quartile were associated with increased risk of myocardial infarction (multivariable-adjusted hazard ratio, 1.51; 95% confidence interval, 1.09-2.09; P=0.01) but not heart failure, cerebrovascular accidents, or death during a follow-up of 12 years. Addition of the highest quartile of CNP to clinical variables led to a modest increase in the integrated discrimination improvement for risk of myocardial infarction. In a large community-based cohort, elevated circulating CNP identified a high-risk phenotype that included cardiovascular comorbidities and left ventricular dysfunction, and provided evidence that highest concentrations of CNP potentially has prognostic value in predicting future risk of myocardial infarction. Together, these data from the general population highlight the potential value of CNP and support the need for additional studies to evaluate whether mechanisms regulating CNP could improve outcomes.

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.

Role of C-type natriuretic peptide signalling in maintaining cartilage and bone function

C-type natriuretic peptide (CNP) has been demonstrated in human and mouse models to play critical roles in cartilage homeostasis and endochondral bone formation. Indeed, targeted inactivation of the genes encoding CNP results in severe dwarfism and skeletal defects with a reduction in growth plate chondrocytes. Conversely, cartilage-specific overexpression of CNP was observed to rescue the phenotype of CNP deficient mice and significantly enhanced bone growth caused by growth plate expansion. In vitro studies reported that exogenous CNP influenced chondrocyte differentiation, proliferation and matrix synthesis with the response dependent on CNP concentration. The chondroprotective effects were shown to be mediated by natriuretic peptide receptor (Npr)2 and enhanced synthesis of cyclic guanosine-3',5'-monophosphate (cGMP) production. Recent studies also showed certain homeostatic effects of CNP are mediated by the clearance inactivation receptor, Npr3, highlighting several mechanisms in maintaining tissue homeostasis. However, the CNP signalling systems are complex and influenced by multiple factors that will lead to altered signalling and tissue dysfunction. This review will discuss the differential role of CNP signalling in regulating cartilage and bone homeostasis and how the pathways are influenced by age, inflammation or sex. Evidence indicates that enhanced CNP signalling may prevent growth retardation and protect cartilage in patients with inflammatory joint disease.

Natriuretic peptides, heart, and adipose tissue: new findings and future developments for diabetes research

Natriuretic peptides (NPs) play a key role in cardiovascular homeostasis, counteracting the deleterious effects of volume and pressure overload and activating antibrotic and antihypertrophic pathways in the heart. N-terminal B-type NP (NT-proBNP) also is a promising biomarker of global cardiovascular risk in the general population, and there is increasing interest on its potential use in diabetic patients for screening of silent cardiovascular abnormalities, cardiovascular risk stratification, and guided intervention. Recently, both atrial NP (ANP) and B-type NP (BNP) have emerged as key mediators in the control of metabolic processes including the heart in the network of organs that regulate energy usage and metabolism. Epidemiological studies have shown that ANP and BNP are reduced in people with obesity, insulin resistance, and diabetes, and this deficiency may contribute to enhance their global cardiovascular risk. Moreover, ANP and BNP have receptors in the adipose tissue, enhance lipolysis and energy expenditure, and modulate adipokine release and food intake. Therefore, low ANP and BNP levels may be not only a consequence but also a cause of obesity, and recent prospective studies have shown that low levels of NT-proBNP and midregional proANP (MR-proANP) are a strong predictor of type 2 diabetes onset. Whether ANP and BNP supplementation may result in either cardiovascular or metabolic benefits in humans remains, however, to be established.

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.

Serum atrial natriuretic peptide level inversely associates with metabolic syndrome in older adults

AIM

Atrial natriuretic peptide (ANP) is a potent lipolytic agent that acts in adipose tissue. Low levels of ANP might lead to reduced lipolysis and excessive weight gain, which could be one of the biological alterations that contribute to the development of obesity. The aim of the present study was to evaluate the relationship between metabolic syndrome and fasting serum ANP concentrations in older adults.

METHODS

Fasting blood samples were obtained from 90 older adults. Metabolic syndrome and its components were defined using diagnostic criteria from the International Diabetes Federation.

RESULTS

A total of 40 older adults (44.4%) had metabolic syndrome. Fasting ANP level was negatively correlated with metabolic syndrome (P = 0.015). Univariate linear regression analysis showed that high-density lipoprotein cholesterol (P < 0.001) was positively correlated with serum logANP levels, whereas waist circumference (P = 0.001) and body fat mass (P = 0.002) were negatively correlated with fasting serum logANP levels. Multivariate forward stepwise linear regression analysis of the significant variables showed that high-density lipoprotein cholesterol (β = 0.419, R(2) = 0.268, P < 0.001) and body fat mass (β = -0.396, R(2) = 0.154, P = 0.002) were independent predictors of fasting serum logANP levels in geriatric persons.

CONCLUSIONS

Serum ANP levels were reduced in geriatric persons affected by metabolic syndrome. Body fat mass and high-density lipoprotein cholesterol were independent predictors of fasting serum ANP levels in older adults.

Acute inflammation in young children inhibits C-type natriuretic peptide

BACKGROUND

C-type natriuretic peptide (CNP) is a paracrine growth factor critical in endochondral bone growth. Amino-terminal CNP (NTproCNP), measurable in plasma, correlates with growth-plate activity and can be used as a biomarker of growth velocity in children. Because severe inflammation in adults increases CNP, we studied CNP peptides and inflammatory markers in children with acute illness.

METHODS

Forty-two children aged 2 mo to 5 y with acute illness warranting admission to an acute assessment unit were studied. Fifteen age-matched healthy children attending an outpatient clinic served as controls. Venous CNP concentrations were measured at admission, along with markers of acute inflammation (body temperature, C-reactive protein (CRP), and white blood cell count) in children with acute illness.

RESULTS

NTproCNP and CNP SD scores (SDSs) in the acutely ill group were significantly suppressed (P < 0.001) as compared with those of healthy children or healthy population norms. NTproCNP SDS was significantly inversely related to body temperature (r = -0.42, P < 0.01) and CRP (r = -0.56, P < 0.001).

CONCLUSION

Acute inflammation in young children potently reduces CNP production, which needs to be considered when screening for growth disorders. Our data raise the possibility that the adverse effects of inflammatory cytokines on skeletal growth may be mediated in part by reduced CNP.