Natriuretic peptides in vascular physiology and pathology

Identification of natriuretic peptide receptor A-related gene expression signatures in podocytes in vivo reveals baseline control of protective pathways

Natriuretic peptide receptor-A (NPR-A) is the principal receptor for the natriuretic peptides atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP). Targeted deletion of NPR-A in mouse glomerular podocytes significantly enhances renal injury in vivo in the DOCA-salt experimental model. It was therefore hypothesized that natriuretic peptides exert a direct protective effect on glomerular barrier integrity through activation of NPR-A and modulation of gene expression patterns in podocytes. Green fluorescence-positive podocytes from mice with a conditional deletion of Npr1 encoding NPR-A were isolated by fluorescence-activated cell sorting (FACS). Differentially expressed genes (DEGs) in podocytes were identified by RNA sequencing of podocytes from wild-type and NPR-A-deleted mice. Enrichment analysis was performed on the DEGs using Gene Ontology (GO) terms. Identified transcripts were validated by real-time PCR and ELISA of cultured isolated human and mouse glomeruli. In addition, the effect of natriuretic peptides on podocyte migration was investigated by measuring the outgrowth of podocytes from cultured glomeruli. A total of 158 DEGs were identified with 81 downregulated DEGs and 77 upregulated DEGs in Npr1-deficient podocytes. Among the downregulated genes were protein S and semaphorin 3G, which are known to have protective effects in podocytes. Protein S was also expressed in and secreted from isolated human glomeruli. GO enrichment analysis revealed that the upregulated DEGs in NPR-A deficient podocytes were associated with cell migration and motility. In line, BNP significantly decreased podocyte outgrowth from cultured glomeruli. In conclusion, endogenous levels of natriuretic peptides in mice support baseline protective pathways at glomerular podocytes such as protein S and suppress podocyte migration.NEW & NOTEWORTHY A combination of fluorescence-activated cell sorting and RNA sequencing identified 158 changed gene products in adult mouse kidneys with and without podocyte-specific deletion of the natriuretic peptide receptor A. Downregulated products included protein S and semaphorin 3G, both with proven renoprotective impact, whereas upregulated products were related to mobility of podocytes. Protein S was produced and released from human and murine isolated glomeruli, and atrial natriuretic peptide (ANP) led to decreased migration of podocytes.

Safety and efficacy of angiotensin receptor neprilysin inhibitor in improving cardiac function and blood pressure in dialysis patients

Background

The efficacy of the angiotensin receptor neprilysin inhibitor (ARNI) sacubitril/valsartan (SV) in patients with chronic kidney disease (CKD) has been established. Two meta-analyses have demonstrated its significant role in enhancing ventricular remodeling. However, the effectiveness and safety of its use in patients with end-stage renal disease (ESRD) remain unclear.

Methods and results

Up to October 2023, we searched the PubMed, Embase, and Web of Science databases for studies involving ESRD patients treated with ARNI. The quality of the included studies was evaluated using the Newcastle-Ottawa Scale. Effect sizes were reported as mean differences (MD) with 95% confidence intervals (CIs). We included 10 studies, encompassing 649 patients. ARNI was associated with improvements in blood pressure and left ventricular (LV) function in ESRD patients, including systolic blood pressure (SBP) (MD -12.76 mmHg; 95% CI, -18.03 to -7.5 mmHg), diastolic blood pressure (DBP) (MD -6.41 mmHg; 95% CI, -8.10 to -4.72 mmHg), and left ventricular ejection fraction (LVEF) (MD, 4.61%; 95% CI, 1.78%-7.44%). Hemoglobin levels improved, but there were no significant statistical differences in other biomarkers for dialysis. Sacubitril/valsartan was generally well tolerated in ESRD patients. Improved indices of left ventricular function were noted at 6 months and were more pronounced at 12 months. A linear relationship between LVEF and left ventricular end-diastolic volume (LVEDV) was observed, as indicated by a high correlation coefficient (r-value).

Conclusion

ARNI effectively reduces blood pressure and enhances left ventricular function in dialysis patients, with early treatment associated with greater benefits. ARNI also demonstrates a favorable safety profile in this population. Further prospective studies are required to fully understand the long-term efficacy and safety of sacubitril/valsartan in dialysis patients.

Serum Biomarkers after Adenotonsillectomy for Pediatric OSA: A Systematic Review and Meta-Analysis

OBJECTIVE

To assess whether adenotonsillectomy improves levels of inflammatory and cardiometabolic markers in children with polysomnographically diagnosed obstructive sleep apnea (OSA).

DATA SOURCES

Two authors independently searched PubMed, Embase, and Cochrane databases up to August 16, 2022, for studies relating to pre- and post-operative levels of serum markers in pediatric patients undergoing adenotonsillectomy.

REVIEW METHODS

Data were extracted from included articles into a structured proforma. Meta-analyses of the standardized mean difference (SMD) were conducted in random-effects models. We calculated the probability of benefit (POB) and number needed to treat (NNT) for outcomes that demonstrated a statistically significant effect after adenotonsillectomy. The primary outcomes were changes in serum markers including C-reactive protein (CRP), high-sensitivity CRP (hs-CRP), Insulin-like growth factor 1 (IGF-1), interleukin-10 (IL-10), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), Brain natriuretic peptide (BNP), insulin, glucose, total cholesterol, triglyceride, low-density lipoprotein (LDL), high-density lipoprotein (HDL).

RESULTS

We screened 1616 studies and included 26 studies with 1331 participants. Meta-analysis was performed on 20 of the included studies. Adenotonsillectomy was associated with a significant decrease in insulin levels (SMD = -0.322, 95% Confidence Interval (CI) = -0.583 to -0.061), CRP (SMD = -0.946, 95% CI = -1.578 to -0.314), and BNP (SMD = -1.416, 95% CI = -2.355 to -0.477) and significant increase in levels of IGF-1 (SMD = 0.691, 95% CI = 0.207 to 1.176). There were no significant changes in levels of triglyceride, total cholesterol, TNF-α, LDL, HDL, glucose, IL-10, and IL-6.

CONCLUSION

In children with polysomnographically diagnosed OSA, adenotonsillectomy was associated with improvements in serum biomarkers, comprising lower CRP, insulin, and BNP, and higher IGF-1. Laryngoscope, 134:3030-3037, 2024.

Discovery of another mechanism for the inhibition of particulate guanylyl cyclases by the natriuretic peptide clearance receptor

The cardiac natriuretic peptides (NPs) control pivotal physiological actions such as fluid and electrolyte balance, cardiovascular homeostasis, and adipose tissue metabolism by activating their receptor enzymes [natriuretic peptide receptor-A (NPRA) and natriuretic peptide receptor-B (NPRB)]. These receptors are homodimers that generate intracellular cyclic guanosine monophosphate (cGMP). The natriuretic peptide receptor-C (NPRC), nicknamed the clearance receptor, lacks a guanylyl cyclase domain; instead, it can bind the NPs to internalize and degrade them. The conventional paradigm is that by competing for and internalizing NPs, NPRC blunts the ability of NPs to signal through NPRA and NPRB. Here we show another previously unknown mechanism by which NPRC can interfere with the cGMP signaling function of the NP receptors. By forming a heterodimer with monomeric NPRA or NPRB, NPRC can prevent the formation of a functional guanylyl cyclase domain and thereby suppress cGMP production in a cell-autonomous manner.

SYP-3343 drives abnormal vascularization in zebrafish through regulating endothelial cell behavior

SYP-3343 is a novel strobilurin fungicide with excellent and broad-spectrum antifungal activity, and its potential toxicity raises public health concerns. However, the vascular toxicity of SYP-3343 to zebrafish embryos is still not well understood. In the present study, we investigated the effects of SYP-3343 on vascular growth and its potential mechanism of action. SYP-3343 inhibited zebrafish endothelial cell (zEC) migration, altered nuclear morphology, and triggered abnormal vasculogenesis and zEC sprouting angiogenesis, resulting in angiodysplasia. RNA sequencing showed that SYP-3343 exposure altered the transcriptional levels of vascular development-related biological processes in zebrafish embryos including angiogenesis, sprouting angiogenesis, blood vessel morphogenesis, blood vessel development, and vasculature development. Whereas, the addition of NAC exerted an improvement effect on zebrafish vascular defects owing to SYP-3343 exposure. Additionally, SYP-3343 altered cell cytoskeleton and morphology, obstructed migration and viability, disrupted cell cycle progression, and depolarized mitochondrial membrane potential, as well as promoted apoptosis and reactive oxygen species (ROS) in HUVEC. SYP-3343 also caused an imbalance of the oxidation and antioxidant systems and irritated the alterations in the cell cycle- and apoptosis-related genes in HUVECs. Collectively, SYP-3343 has high cytotoxicity, possibly by up-regulating p53 and caspase3 expressions and bax/bcl-2 ratio via ROS, leading to malformed vascular development.

Effects of Recombinant Human Brain Natriuretic Peptide on Atrial Fibrillation After Coronary Artery Bypass Grafting

ABSTRACT

Previous studies reported that the use of natriuretic peptides (NPs) can effectively decrease arrhythmias. However, there is a lack of clinical evidence that recombinant human brain natriuretic peptide (rh-BNP) inhibits postoperative atrial fibrillation (POAF). This cohort aims to assess the effect of rh-BNP on POAF. This study retrospectively reviewed patients who underwent isolated coronary artery bypass grafting from January 2018 to January 2021. Patients were divided into 2 groups according to whether they received rh-BNP therapy within 5 days after surgery. A total of 1153 patients met the inclusion and exclusion criteria, of which 54 received rh-BNP therapy within 5 days. After propensity score matching, 53 patients were treated with rh-BNP, and 148 patients were not treated with rh-BNP. The incidence of POAF was lower in rh-BNP group than non-rh-BNP group (18.9% vs. 37.2%, odds ratio = 0.393, 95% confidence interval, 0.183-0.845, P = 0.017). There was no significant difference in the occurrence of ventricular arrhythmia ( P = 0.4), hypotension ( P = 0.763), and the risk of death ( P = 0.14). rh-BNP could significantly reduce the occurrence of POAF after coronary artery bypass grafting, and rh-BNP did not increase the risk of ventricular arrhythmia, hypotension, and death. Accordingly, rh-BNP could be a potential safe medicine for preventing POAF.

Sacubitril/Valsartan in Patients With Heart Failure and Concomitant End-Stage Kidney Disease

Background

Heart failure with reduced ejection fraction (HFrEF) is a chronic disease with substantial mortality. Management of HFrEF has seen significant breakthrough after the launch of neprilysin inhibitor. The PARADIGM‐HF (Prospective Comparison of ARNI with ACEI to Determine Impacton Global Mortality and Morbidity in Heart Failure) trial showed that sacubitril/valsartan significantly reduces HFrEF mortality and the heart failure hospitalization rate. However, in patients with advanced kidney disease, who have the highest prevalence of heart failure, the efficacy and safety of sacubitril/valsartan remains uncertain. We aim to study the efficiency of sacubitril/valsartan in patients with end‐stage kidney disease.

Methods and Results

Heart function was screened by echocardiogram among all patients with end‐stage kidney disease in 2 hospitals. Patients with HFrEF received either sacubitril/valsartan or conventional treatment. Fifteen echocardiographic parameters were compared before and after treatment. After 1‐year sacubitril/valsartan treatment, parameters of systolic (left ventricular ejection fraction 31.3% to 45.1%, P<0.0001; left ventricular end‐systolic volume 95.7 to 70.1 mL, P=0.006; left ventricular internal diameter at end‐systole phase 47.2 to 40.1 mm, P=0.005), and diastolic (E/A ratio 1.3 to 0.8, P=0.009; E/Med e' ratio 25.3 to 18.8, P=0.010) function improved in patients with HFrEF and end‐stage kidney disease. These parameters were unchanged in the conventional treatment group. Serum potassium did not increase in the sacubitril/valsartan group.

Conclusions

Sacubitril/valsartan improves left ventricular systolic and diastolic function in patients with HFrEF and end‐stage kidney disease.

Efficacy of angiotensin receptor neprilysin inhibitor in Asian patients with refractory hypertension

Sacubitril/valsartan, simultaneously inhibits neprilysin and angiotensin II receptor, showed an effect in reducing blood pressure (BP). The authors aimed to study whether it can be used as an antihypertensive agent in patients with refractory hypertension who have already been treated. A total of 66 Chinese patients with refractory hypertension were enrolled. Patients received sacubitril/valsartan  200 instead of angiotensin II receptor blocker or angiotensin converting enzyme inhibitor while other agents continued. If BP was uncontrolled after 4 weeks, sacubitril/valsartan was increased to 400 mg. The BP reduction was evaluated by office BP and ambulatory BP monitoring after 8‐week treatment. The baseline office BP and mean arterial pressure (MAP) were 150.0/95.0 mmHg and 113.3 mmHg. BP and MAP reduced to 130.6/83.2 mmHg and 99.0 mmHg at week 8. Office BP and MAP reductions were 19.4/11.8 mmHg and 14.3 mmHg at endpoint (all p < .001). The 24‐h, daytime and nighttime ambulatory BP were 146.2/89.1, 148.1/90.3, and 137.5/83.7 mmHg, respectively at baseline, and BP reduced to 129.6/79.8, 130.6/81.1, and 121.7/75.8 mmHg, respectively at week 8. The 24‐h, daytime and nighttime ambulatory BP reductions were 16.6/9.3, 17.5/9.2, and 15.8/7.9 mmHg, respectively at endpoint (all p < .001). Sacubitril/valsartan significantly reduced office and ambulatory BP in refractory hypertension patients. Our study provided new evidence for sacubitril/valsartan in refractory hypertension.

C-type natriuretic peptide in childhood obesity

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

A Contemporary View of Natriuretic Peptides in the SARS-CoV-2 Era

The heart releases natriuretic peptides (NPs) which represent an important hormonal axis with cardiorenal protective effects. In view of their properties, NPs have pathophysiologic, diagnostic and prognostic implications in several cardiovascular diseases (CVDs). Severe pulmonary inflammation, as induced by the SARS-COV2, may increase pulmonary pressure with potential influence on NPs release, whereby normal cardiovascular integrity becomes impaired. Moreover, pre-existing CVDs are strong negative prognostic factors since they exacerbate the effects of the viral infection and lead to worse outcomes. In this context, it may be expected that NPs exert a key protective role toward the virus infection whereas an impairment of NPs release contributes to the virus deleterious effects. In this review article we explore the potential involvement of NPs in the COVID-19 disease. To this aim, we will first focus on the interactions between NPs and the Ang II/ATIR arm of the renin-angiotensin-aldosterone system (RAAS) as well as with the protective ACE2/Ang (1-7) arm of the RAAS. Subsequently, we will review evidence that strongly supports the role of increased NT-proBNP level as a marker of cardiac damage and of worse prognosis in the COVID-19 affected patients. Finally, we will discuss the potential therapeutic benefits of these protective hormones toward the viral infection through their endothelial protective function, anti-inflammatory and anti-thrombotic effects. In conclusion, the potential implications of NPs in the SARS-CoV-2 infection, as discussed in our article, represent an important issue that deserves to be fully investigated.

N-Terminal Pro Brain, N-Terminal Pro Atrial Natriuretic Peptides, and Dynamic Cerebral Autoregulation

Background

Elevated natriuretic peptides (NP) are associated with adverse cerebrovascular conditions including stroke, cerebral small vessel disease, and dementia. However, the mechanisms underlying these associations remain unclear. In this study, we examined the relationship of NT‐proBNP (N‐terminal pro brain NP) and NT‐proANP (N‐terminal pro atrial NP) with cerebrovascular function, measured by cerebral autoregulation.

Methods and Results

We included 154 participants (mean age 56±4 years old) from the CARDIA (Coronary Artery Risk Development in Young Adults) cohort. NT‐proBNP and NT‐proANP were measured in blood samples from the year 25 examination using electrochemiluminescence Immunoassay and enzyme‐linked immunoassay, respectively. Dynamic cerebral autoregulation (dCA) was assessed at the year 30 examination by transcranial Doppler ultrasound, using transfer function analysis (phase and gain) of spontaneous blood pressure and flow velocity oscillations, where lower phase and higher gain reflect less efficient cerebral autoregulation. We used multivariable linear regression models adjusted for demographics, vascular risk factors, and history of kidney and cardiac diseases. Higher NT‐proBNP levels at year 25 were associated with lower phase (β [95% CI]=−5.30 lower degrees of phase [−10.05 to −0.54]) and higher gain (β [95% CI]=0.06 higher cm/s per mm Hg of gain [0.004–0.12]) at year 30. Similarly, higher NT‐proANP levels were associated with lower phase (β [95% CI]=−9.08 lower degrees of phase [−16.46 to −1.70]).

Conclusions

Higher circulating levels of NT‐proBNP and NT‐proANP are associated with less efficient dCA 5 years later. These findings link circulating NP to cerebral autoregulation and may be one mechanism tying NP to adverse cerebrovascular outcomes.

Cardiovascular Outcomes with Sacubitril-Valsartan in Heart Failure: Emerging Clinical Data

One of the defining features of heart failure (HF) is neurohormonal activation. The renin-angiotensin-aldosterone-system (RAAS) and sympathetic nervous system (SNS) cause vasoconstriction and fluid retention and, in response, the secretion of natriuretic peptides (NPs) from volume and pressure-overloaded myocardium promotes vasodilation and diuresis. Inhibition of the RAAS with either angiotensin-converting enzyme inhibitors (ACEI) or angiotensin receptor blockers (ARB) has been the cornerstone of medical treatment for HF with a reduced ejection fraction (HFrEF) but, until recently, it was unclear how the beneficial effects of NPs may be augmented in patients with HF. Neprilysin, a metalloproteinase widely distributed throughout the body, plays a role in degrading the gross excess of circulating NPs in patients with HF. Early studies of neprilysin inhibition suggested possible physiological benefits. In 2014, the PARADIGM-HF trial found that sacubitril-valsartan, a combination of the ARB valsartan, and the neprilysin inhibitor sacubitril, was superior to enalapril in patients with HFrEF, reducing the relative risk of cardiovascular (CV) death or first hospitalisation with HF by 20%. Almost half of the patients with HF symptoms have a “preserved” ejection fraction (HFpEF); however, the PARAGON-HF study found that sacubitril-valsartan in patients with LVEF ≥45% had no effect on CV death or first and recurrent hospitalisations with HF compared to valsartan. Guidelines across the world have changed to include sacubitril-valsartan for patients with HFrEF yet, nearly 6 years after PARADIGM-HF, there is still uncertainty as to when and in whom sacubitril-valsartan should be started. Furthermore, there may yet be subsets of patients with HFpEF who might benefit from treatment with sacubitril-valsartan. This review will describe the mechanisms behind the outcome benefit of sacubitril-valsartan in patients with HFrEF and to consider its future role in the management of patients with HF.

An evaluation of the fixed-dose combination sacubitril/valsartan for the treatment of arterial hypertension

INTRODUCTION

Essential hypertension is a significant risk factor for cardiovascular disease, renal disease, and mortality with increasing prevalence. Despite the availability of various antihypertensive agents, hypertension is still poorly controlled. Therefore, new chemical compounds with antihypertensive efficacy need to be developed. The dual angiotensin II receptor-neprilysin inhibitor LCZ696 is a single molecule synthesized by co-crystallization of valsartan and the neprilysin inhibitor prodrug sacubitril (1:1 molar ratio).

AREAS COVERED

This review includes an overview of hypertension and the current pharmacotherapy. The authors summarize the LCZ696 drug chemistry, pharmacodynamics, pharmacokinetics, metabolism, randomized control trials (RCTs), and safety concerns. Databases searched included PubMed, Google Scholar, Embase, and ClinicalTrials.gov.

EXPERT OPINION

LCZ696 is effective in hypertension treatment. Short-term RCTs have shown that the highest doses of LCZ696 (200 and 400 mg [q.d.]) were more effective at lowering office and ambulatory blood pressure than angiotensin II receptor blockers (ARB) alone while having a similar tolerability profile. The effects of LCZ696 on hypertensive organ damage are only sparsely investigated and so far no studies have established the impact of LCZ696 on cardiovascular event rates. Future studies should focus on the comparison of LCZ696 and combination therapies already in use such as ARB and calcium channel blockers.

Elevated MR-proANP plasma concentrations are associated with sepsis and predict mortality in critically ill patients

Background and aims

Mid-regional pro atrial natriuretic peptide (MR-proANP) is an established biomarker for heart failure, based on its key role in regulating homeostasis of water balance and blood pressure. The aim of the study was to determine the value of MR-proANP as a clinical biomarker in critical illness and/or sepsis. Upon admission to the medical intensive care unit (ICU), we investigated MR-proANP plasma concentrations in 217 critically ill patients (144 with sepsis, 73 without sepsis). Results were compared with 65 healthy controls.

Results

MR-proANP plasma levels were significantly elevated in critically ill patients, when compared to healthy controls. Notably, MR-proANP levels were significantly higher in ICU patients with sepsis. MR-proANP levels were not associated with metabolic comorbidities like diabetes or obesity. In critically ill patients, MR-proANP plasma concentrations correlated with inflammatory cytokines, markers of organ dysfunction and several adipocytokines, such as resistin, retinol-binding protein 4 (RBP4) and adiponectin. Importantly, high MR-proANP plasma levels were associated with mortality, as MR-proANP levels above 227.0 pmol/l indicated a particularly increased mortality risk in ICU patients. The association between MR-proANP and mortality was independent of single organ failure and inflammation markers.

Conclusion

Our study emphasizes the role of circulating MR-proANP as a biomarker in critically ill patients, in which high MR-proANP indicates organ dysfunction, sepsis and mortality risk. The association between high MR-proANP and inflammatory as well as adipose tissue-derived endocrine mediators warrants further pathophysiological investigations.

Expression patterns of natriuretic peptides in pre-hibernating and hibernating Anatolian ground squirrel (Spermophilus xanthoprymnus) kidney

Hibernation is characterized by marked suppression of renal function. Natriuretic peptides (NPs) are involved in the regulation of renal function. However, the role of NPs in the renal function during hibernation remains unclear. We aimed to investigate the distribution patterns of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) in Anatolian ground squirrel (Spermophilus xanthoprymnus) kidneys during pre-hibernation and hibernation periods. Cortical proximal tubules showed weak ANP immunoreactivity, with moderate staining on the brush border during the pre-hibernation period. In the hibernation period, moderate ANP immunoreactivity was seen in cortical proximal tubules, with very weak reaction in hibernating cortical distal tubules, medullary proximal and collecting tubules. Cortical proximal and distal tubules of both periods had strong and weak BNP immunoreactivity, respectively. Medullary proximal, distal and Henle's loop segments showed very weak BNP immunoreactivity during pre-hibernation. Medullary distal, proximal and collecting tubules and Henle's loop segments had moderate staining during hibernation. In both periods, cortical proximal tubules displayed strong immunoreactivity to CNP. Distal tubules had moderate CNP staining during pre-hibernation, albeit weak staining during hibernation. Medullary proximal tubules exhibited moderate to strong immunoreactivity during pre-hibernation. Medullary distal and proximal tubules had weak and moderate CNP staining, respectively, during pre-hibernation. In both periods, Henle's loop segments displayed moderate CNP immunoreactivity. Glomeruli had similar weak ANP, BNP and CNP staining in both periods. These results suggest that heterothermic conditions differently affected the expression of NPs in the squirrel kidney. This different expression of NPs may contribute to the renal adaptation during hibernation.

The Clinical Value of N-Terminal Pro B-Type Natriuretic Peptide in Evaluating Obstructive Sleep Apnea in Patients With Coronary Artery Disease

STUDY OBJECTIVES

Natriuretic peptides have been identified as biomarkers of increased myocardial wall stress in the context of obstructive sleep apnea (OSA) in the general population. However, the relationship between N-terminal pro B-type natriuretic peptide (NT-proBNP) and OSA remains unclear in patients with coronary artery disease (CAD). Hence, we aimed to investigate the clinical value of NT-proBNP in evaluating OSA in a large population of patients with CAD.

METHODS

Consecutive patients with CAD were prospectively enrolled between February 2015 and March 2018. Portable respiratory monitoring was applied to facilitate the diagnosis of sleep apnea. Patients were as assigned to the non-OSA (when the respiratory events index [REI] or 3% oxygen desaturation index [ODI] < 15 events/h) and OSA (when the REI or 3% ODI ≥ 15 events/h) groups. Multivariate analyses were used to explore the independent association between NT-proBNP levels and OSA.

RESULTS

A total of 1,292 consecutive patients were included with a mean NT-proBNP value of 826.57 μg/L. Patients with high levels of NT-proBNP experienced increasing severity of OSA in those with CAD (P = .0004). Univariate analysis demonstrated that NT-proBNP was a risk factor for OSA (odds ratio [OR] 1.10, 95% confidence interval [CI] 1.03-1.18, P = .005). In addition, multivariate analysis revealed that NT-proBNP was independently associated with the presence of OSA (OR 1.11, 95% CI 1.02-1.20, P = .012) even after adjusting for other cofounding factors.

CONCLUSIONS

Elevated levels of NT-proBNP were independently associated with a higher likelihood of OSA in patients with CAD. Periodically screening for NT-proBNP levels may provide early identification of OSA.

Expression patterns of natriuretic peptides in pre-hibernating and hibernating anatolian ground squirrel (Spermophilus xanthoprymnus) lung

Anatolian ground squirrel (Spermophilus xanthoprymnus) is a true hibernator. This animal transiently reduces pulmonary function during hibernation. Continuance of pulmonary function is very important to survive ground squirrels during the hibernation. Natriuretic peptides may be key players in the modulation of pulmonary hemostasis. However, NPs' role in pulmonary function during hibernation remains unclear. We aimed to investigate the localization and distribution of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) in squirrel lungs during pre-hibernation and hibernation periods using immunohistochemistry. Our immunohistochemical data indicate that ANP, BNP, and CNP were produced by the mucosal epithelium of terminal and respiratory bronchioles, smooth muscle cells in the lamina propria of terminal bronchioles and vascular smooth muscle cells, alveolar type II cells, and macrophages. ANP immunoreactivity was weaker than BNP and CNP immunoreactivities in these cells. The results also demonstrate that the number of ANP, BNP and CNP positive alveolar type II cells tended to increase, although statistically non-significant, during the hibernation period, but the expression of NPs in other pulmonary cells is unaffected by hibernation. This study firstly investigates ANP, BNP and CNP distribution in the Anatolian ground squirrel lung. However, further studies are required to dissect their functional roles during the hibernation.

Understanding the pathobiology in patent ductus arteriosus in prematurity-beyond prostaglandins and oxygen

The ductus arteriosus (DA) is probably the most intriguing vessel in postnatal hemodynamic transition. DA patency in utero is an active state, in which prostaglandin E₂ (PGE₂) and nitric monoxide (NO), play an important role. Since the DA gets programmed for postnatal closure as gestation advances, in preterm infants the DA frequently remains patent (PDA). PGE₂ exposure programs functional postnatal closure by inducing gene expression of ion channels and phosphodiesterases and anatomical closure by inducing intimal thickening. Postnatally, oxygen inhibits potassium and activates calcium channels, which ultimately leads to a rise in intracellular calcium concentration consequently inducing phosphorylation of the myosin light chain and thereby vasoconstriction of the DA. Since ion channel expression is lower in preterm infants, oxygen induced functional vasoconstriction is attenuated in comparison with full term newborns. Furthermore, the preterm DA is more sensitive to both PGE₂ and NO compared to the term DA pushing the balance toward less constriction. In this review we explain the physiology of DA patency in utero and subsequent postnatal functional closure. We will focus on the pathobiology of PDA in preterm infants and the (un)intended effect of antenatal exposure to medication on both fetal and neonatal DA vascular tone.

Normotensive patients with obstructive sleep apnoea: changes in 24-h ambulatory blood pressure monitoring with continuous positive airway pressure treatment

BACKGROUND

Continuous positive airway pressure (CPAP) treatment reduces blood pressure (BP) in obstructive sleep apnoea (OSA) and hypertensive patients, but there is a lack of data about the effects of CPAP on the BP in normotensive patients.

OBJECTIVE

The aim of the study was to evaluate BP changes in normotensive OSA individuals receiving CPAP treatment.

METHODS

We selected 131 normotensive outpatients with an apnoea/hypopnoea index (AHI) greater than 15 events/hour who required CPAP treatment. All patients underwent a sleep study and 24-h ambulatory BP monitoring (ABPM) at baseline and after 6 months. In addition, the patients were assessed for the presence of baseline masked hypertension, defined as office BP less than 140/90 mmHg and increased BP on 24-h ABPM (mean 24-h BP ≥130/80 mmHg).

RESULTS

After 6 months of CPAP treatment, a mild reduction in all 24-h ABPM variables was observed, but only the mean 24-h DBP [-1.39 mmHg, 95% confidence interval (95% CI), -2.50 to -0.27], mean daytime DBP (-1.39 mmHg, 95% CI -2.56 to -0.22) and the mean 24-h ambulatory BP (-1.80 mmHg, 95% CI, -3.16 to -0.44) reached statistical significance. The reduction was primarily due to BP changes in individuals with masked hypertension who displayed a mean BP reduction of -4.78 mmHg (-7.25 to -2.30 mmHg). Consistent with a circadian BP pattern, a reduction in mean nocturnal BP of -4.73 mmHg (-7.39 to -2.06 mmHg) was observed at 6 months in nondippers; in contrast, the mean nocturnal BP in dippers increased by 2.61 mmHg (0.60-4.62 mmHg).

CONCLUSION

Our findings suggest that the CPAP effects may be different in normotensive outpatients depending on the presence of undiagnosed masked hypertension and the dipping pattern. Therefore, it is important to consider measuring ABPM in this type of patient.

Localization profiles of natriuretic peptides in hearts of pre-hibernating and hibernating Anatolian ground squirrels (Spermophilus xanthoprymnus)

The Anatolian ground squirrel (Spermophilus xanthoprymnus) is a typical example of true mammalian hibernators. In order to adapt to extreme external and internal environments during hibernation, they lower their body temperatures, heart rates and oxygen consumption; however, pathological events such as ischemia and ventricular fibrillation do not occur in their cardiovascular systems. During the hibernation, maintenance of cardiac function is very important for survival of ground squirrels. Natriuretic peptides (NPs) are key factors in the regulation of cardiovascular hemostasis. Since NPs' role on the protection of heart during hibernation are less clear, the aim of this study was to investigate dynamic changes in NPs content in the cardiac chambers and to reveal the possible role of NPs on establishing cardiac function in ground squirrel during hibernation using immunohistochemistry. The immunohistochemical results indicate that cardiac NP expressions in atrial and ventricular cardiomyocytes were different from each other and were sex-independent. ANP and BNP were expressed in a chamber-dependent manner in female and male squirrel hearts. Furthermore, cardiac NPs expression levels in hibernation period were lower than those at the pre-hibernation period. During prehibernation period, ANP, BNP and CNP were expressed in the white and beige adipocytes of epicardial adipose tissue (EAT); while during hibernation period, the brown adipocytes of EAT were positive for BNP and CNP. These data suggest that the hibernation-dependent reduction in levels of NPs, particularly ANP, in cardiac chambers and EAT may be associated with low heart rate and oxygen consumption during hibernation. However, further studies are needed to better delineate the roles of NPs during the hibernation.

Maternal pregnancy-induced hypertension increases the subsequent risk of transient tachypnea of the newborn: A nationwide population-based cohort study

OBJECTIVE

To determine the association between pregnancy-induced hypertension (PIH) and transient tachypnea of the newborn (TTN) and to identify the predictive risk factors.

MATERIALS AND METHODS

Pregnant women with a newly diagnosed PIH (between 2000 and 2013) from the Taiwan National Health Insurance Research Database (NHIRD) were compared with a matched (with respect to age and year of delivery) cohort of pregnant women without PIH. The occurrence of TTN was evaluated in both cohorts.

RESULTS

Among the 23.3 million individuals registered in the NHIRD, 29,013 patients with PIH and 116,052 matched controls were identified. According to a multivariate analysis, PIH (odds ratio [OR] = 1.85, 95% confidence interval [CI] = 1.69-2.03, p < 0.0001), age ≥ 30 years (OR = 1.38, 95% CI = 1.26-1.51, p < 0.0001), primiparity (OR = 1.37, 95% CI = 1.24-1.5, p < 0.0001), preterm birth (OR = 3.4, 95% CI = 3.09-3.75, p < 0.0001), multiple births (OR = 2.54, 95% CI = 2.24-2.89, p < 0.0001), and cesarean section (OR = 1.71, 95% CI = 1.56-1.88, p < 0.0001) were independent risk factors for the development of TTN.

CONCLUSION

Women with PIH have an increased risk of having infants who develop TTN compared with those without PIH. Additionally, age ≥30 years, primiparity, preterm birth, multiple births, and cesarean section were independent risk factors for the development of TTN.

Immunolocalization of natriuretic peptides and their receptors in goat (Capra hircus) heart

Natriuretic peptides are structurally similar, but genetically distinct, hormones that participate in cardiovascular homeostasis by regulating blood and extracellular fluid volume and blood pressure. We investigated the distribution of natriuretic peptides and their receptors in goat (Capra hircus) heart tissue using the peroxidase-anti-peroxidase (PAP) immunohistochemical method. Strong staining of atrial natriuretic peptide (ANP) was observed in atrial cardiomyocytes, while strong staining for brain natriuretic peptide (BNP) was observed in ventricular cardiomyocytes. Slightly stronger cytoplasmic C-type natriuretic peptide (CNP) immunostaining was detected in the ventricles compared to the atria. Natriuretic peptide receptor-A (NPR-A) immunoreactivity was more prominent in the atria, while natriuretic peptide receptor-B (NPR-B) immunoreactivity was stronger in the ventricles. Cytoplasmic natriuretic peptide receptor-C (NPR-C) immunoreactivity was observed in both the atria and ventricles, although staining was more prominent in the ventricles. ANP immunoreactivity ranged from weak to strong in endothelial and vascular smooth muscle cells. Endothelial cells exhibited moderate to strong BNP immunoreactivity, while vascular smooth cells displayed weak to strong staining. Endothelial cells exhibited weak to strong cytoplasmic CNP immunoreactivity. Vascular smooth muscle cells were labeled moderately to strongly for CNP. Weak to strong cytoplasmic NPR-A immunoreactivity was found in the endothelial cells and vascular smooth muscle cells stained weakly to moderately for NPR-A. Endothelial and vascular smooth cells exhibited weak to strong cytoplasmic NPR-B immunoreactivity. Moderate to strong NPR-C immunoreactivity was observed in the endothelial and smooth muscle cells. Small gender differences in the immunohistochemical distribution of natriuretic peptides and receptors were observed. Our findings suggest that endothelial cells, vascular smooth cells and cardiomyocytes express both natriuretic peptides and their receptors.

Hypertension

Systemic arterial hypertension is the most important modifiable risk factor for all-cause morbidity and mortality worldwide and is associated with an increased risk of cardiovascular disease (CVD). Fewer than half of those with hypertension are aware of their condition, and many others are aware but not treated or inadequately treated, although successful treatment of hypertension reduces the global burden of disease and mortality. The aetiology of hypertension involves the complex interplay of environmental and pathophysiological factors that affect multiple systems, as well as genetic predisposition. The evaluation of patients with hypertension includes accurate standardized blood pressure (BP) measurement, assessment of the patients' predicted risk of atherosclerotic CVD and evidence of target-organ damage, and detection of secondary causes of hypertension and presence of comorbidities (such as CVD and kidney disease). Lifestyle changes, including dietary modifications and increased physical activity, are effective in lowering BP and preventing hypertension and its CVD sequelae. Pharmacological therapy is very effective in lowering BP and in preventing CVD outcomes in most patients; first-line antihypertensive medications include angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, dihydropyridine calcium-channel blockers and thiazide diuretics.

cGMP Signaling in the Cardiovascular System-The Role of Compartmentation and Its Live Cell Imaging

The ubiquitous second messenger 3′,5′-cyclic guanosine monophosphate (cGMP) regulates multiple physiologic processes in the cardiovascular system. Its intracellular effects are mediated by stringently controlled subcellular microdomains. In this review, we will illustrate the current techniques available for real-time cGMP measurements with a specific focus on live cell imaging methods. We will also discuss currently accepted and emerging mechanisms of cGMP compartmentation in the cardiovascular system.

Cardiac Natriuretic Peptides, Hypertension and Cardiovascular Risk

Prevalence of cardiovascular (CV) disease is increasing worldwide. One of the most important risk factors for CV disease is hypertension that is very often related to obesity and metabolic syndrome. The search for key mechanisms, linking high blood pressure (BP), glucose and lipid dysmetabolism together with higher CV risk and mortality, is attracting increasing attention. Cardiac natriuretic peptides (NPs), including ANP and BNP, may play a crucial role in maintaining CV homeostasis and cardiac health, given their impact not only on BP regulation, but also on glucose and lipid metabolism. The summa of all metabolic activities of cardiac NPs, together with their CV and sodium balance effects, may be very important in decreasing the overall CV risk. Therefore, in the next future, cardiac NPs system, with its two receptors and a neutralizing enzyme, might represent one of the main targets to treat these multiple related conditions and to reduce hypertension and metabolic-related CV risk.

Vascular Tone Regulation Induced by C-Type Natriuretic Peptide: Differences in Endothelium-Dependent and -Independent Mechanisms Involved in Normotensive and Spontaneously Hypertensive Rats

Given that the role of C-type natriuretic peptide (CNP) in the regulation of vascular tone in hypertensive states is unclear, we hypothesized that impaired response of the nitric oxide system to CNP in spontaneously hypertensive rats (SHR) could affect vascular relaxation induced by the peptide in this model of hypertension, and that other endothelial systems or potassium channels opening could also be involved. We examined the effect of CNP on isolated SHR aortas, and the hindlimb vascular resistance (HVR) in response to CNP administration compared to normotensive rats. Aortas were mounted in an isometric organ bath and contracted with phenylephrine. CNP relaxed arteries in a concentration-dependent manner but was less potent in inducing relaxation in SHR. The action of CNP was diminished by removal of the endothelium, inhibition of nitric oxide synthase by N^ω-nitro-L-arginine methyl ester, and inhibition of soluble guanylyl cyclase by 1H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one in both groups. In contrast, blockade of cyclooxygenase or subtype 2 bradykinin receptor increased CNP potency only in SHR. In both Wistar and SHR, CNP relaxation was blunted by tetraethylammonium and partially inhibited by BaCl₂ and iberiotoxin, indicating that it was due to opening of the Kir and BKCa channels. However, SHR seem to be more sensitive to Kir channel blockade and less sensitive to BKCa channel blockade than normotensive rats. In addition, CNP decreases HVR in Wistar and SHR, but the effect of CNP increasing blood flow was more marked in SHR. We conclude that CNP induces aorta relaxation by activation of the nitric oxide system and opening of potassium channels, but the response to the peptide is impaired in conductance vessel of hypertensive rats.

The effect of surgical and non-surgical weight loss on N-terminal pro-B-type natriuretic peptide and its relation to obstructive sleep apnea and pulmonary function

Background

Obesity is a major risk factor for obstructive sleep apnea, impaired pulmonary function and heart failure, but obesity is also associated with paradoxically low levels of serum N-terminal pro-B-type natriuretic peptide (NT-proBNP). In subjects with severe obesity undergoing weight loss treatment, we assessed the associations between changes in severity of obstructive sleep apnea, pulmonary function and serum NT-proBNP levels.

Methods

One-year non-randomized controlled clinical trial. Participants, 69.6 % women, mean (SD) age 44.6 (10.8) years and body mass index (BMI) 45.1 (5.6) kg/m², underwent gastric bypass surgery (n = 76) or intensive lifestyle intervention (n = 63), resulting in 30 (8) % and 8 (9) % weight loss, respectively. The reference group included 30 normal weight, healthy, gender and age matched controls. Sleep recordings, arterial blood gases, pulmonary function and blood tests were assessed before and 1 year after the interventions.

Results

NT-proBNP concentrations increased significantly more after surgery than after lifestyle intervention. The post intervention values in both groups were significantly higher than in a normal weight healthy reference group. In the whole study population changes (∆) in NT-proBNP correlated significantly with changes in both BMI (r = −0.213) and apnea hypopnea index (AHI, r = −0.354). ∆NT-proBNP was, independent of age, gender and ∆BMI, associated with ∆AHI (beta −0.216, p = 0.021). ∆AHI was, independent of ∆BMI, significantly associated with changes in pO₂ (beta −0.204), pCO₂ (beta 0.199), forced vital capacity (beta −0.168) and forced expiratory volume first second (beta −0.160).

Conclusions

Gastric bypass surgery was associated with a greater increase in NT-proBNP concentrations than non-surgical weight loss treatment. Reduced AHI was, independent of weight loss, associated with increased NT-proBNP levels and improved dynamic lung volumes and daytime blood gases.

Clinical Trial Registration ClinicalTrials.gov NCT00273104, retrospectively registered Jan 5, 2006 (study start Dec 2005)

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-016-2241-x) contains supplementary material, which is available to authorized users.

How does serum brain natriuretic peptide level change under nasal continuous positive airway pressure in obstructive sleep apnea-hypopnea syndrome?

BACKGROUND

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is associated with cardiovascular morbidity and mortality, which can be improved by using continuous positive airway pressure (CPAP) therapy. However, the pathophysiological links between the two kinds of disease and the mechanism of the CPAP effect remain incompletely understood. We aimed to inquire into the myocardial involvement in this relationship. We suggested that serum brain natriuretic peptide (BNP) is sensitive enough to detect myocardial stress caused by OSAHS.

DESIGN AND METHODS

Sixty-four subjects without cardiovascular disease (21 controls, 24 normotensive OSAHS patients, and 19 hypertensive OSAHS patients) were analyzed for serum BNP at baseline and serially over 6 months. CPAP was applied to 23 patients with severe OSAHS.

RESULTS

At baseline, the serum BNP levels were significantly higher (p=0.0001) in the OSAHS group (22.3±14.79 pg/ml) than in the control group (9.2±6.75 pg/ml). Increased serum BNP levels were significantly associated with mean transcutaneous oxygen saturation (SpO2) (p<0.0001), minimal SpO2 (p=0.002), oxygen desaturation index (p=0.001), and total sleep time spent with SpO2 lower than 90% (p=0.002). All patients with elevated BNP levels (≥37 pg/ml) had moderate or severe OSAHS (11/43 OSAHS patients). The more severe the OSAHS, the higher the BNP levels were. However, only the difference between severe and mild OSAHS was statistically significant (p=0.029). Hypertensive OSAHS patients had the highest baseline BNP levels (27.7±16.74 pg/ml). They were significantly higher (p=0.001) than in normotensive OSAHS patients (18±11.72 pg/ml) (p=0.039) and the controls (9.2±6.75 pg/ml). As compared with baseline, treatment with CPAP significantly decreased BNP levels in both hypertensive and normotensive OSAHS patients (respectively, from 36±16.10 to 29.7±14.29 pg/ml, p<0.001, and from 20±10.09 to 16±8.98 pg/ml, p<0.001). In contrast, the BNP levels slightly increased in the controls (from 9.2±6.75 to 9.5±7.02 pg/ml, p=0.029), but there was no statistically significant difference in comparison with the baseline value. The effect of CPAP on BNP levels was more marked in patients with higher baseline BNP levels and those with the most prolonged nocturnal desaturation (p=0.001, r=0.65). It was also more marked in hypertensive OSHAS patients (p=0.015, r=0.72) in comparison with normotensive OSAHS patients (p=0.03, r=0.62).

CONCLUSION

BNP seems to be sensitive enough to detect myocardial stress caused by OSAHS. As such, it is a potential marker for screening of preclinical cardiovascular damage in patients with untreated OSAHS. Application of CPAP decreases levels significantly in normotensive and particularly in hypertensive OSAHS. These findings are consistent with previous results suggesting the potential benefits of CPAP on cardiovascular outcome in OSAHS patients.

Relaxation Induced by Atrial Natriuretic Peptide Is Impaired in Carotid but Not Renal Arteries from Spontaneously Hypertensive Rats Due to Reduced BKCa Channel Activity

Atrial natriuretic peptide (ANP) plays an important role in vascular functions such as blood pressure regulation and relaxant activity. Individual vascular beds exhibit differences in vascular reactivity to various ligands, however, the difference in responsiveness to ANP between carotid and renal arteries and the molecular mechanisms of its vasorelaxant activity in a pathophysiological state, including hypertension, remain unclear. We therefore investigated this issue by exposing carotid and renal artery rings obtained from spontaneously hypertensive rats (SHR) to ANP. In the SHR artery (vs. control WKY artery), the ANP-induced relaxations were reduced in carotid artery but not renal artery. Acetylcholine-induced relaxations were reduced in both arteries in SHR (vs. WKY). Sodium nitroprusside-induced relaxation was similar in both arteries between the groups. In carotid arteries, the ANP-induced relaxation was not affected by endothelial denudation or by treatment with inhibitors of nitric oxide synthase, cyclooxygenase, the voltage-dependent potassium channel, or ATP-sensitive potassium channel in arteries from both SHR and WKY. In the carotid artery from WKY but not SHR, the ANP-induced relaxation was significantly reduced by inhibition of the large-conductance calcium-activated potassium channel (BKCa). The BKCa activator-induced relaxation was reduced in the SHR artery (vs. WKY). These results suggest that ANP-induced relaxation is impaired in the carotid artery from SHR and this impairment may be at least in part due to the reduction of BKCa activity rather than endothelial components.

Brain natriuretic peptide: Much more than a biomarker

Brain natriuretic peptide (BNP) modulates several biological processes by activating the natriuretic peptide receptor A (NPR-A). Atria and ventricles secrete BNP. BNP increases natriuresis, diuresis and vasodilatation, thus resulting in a decreased cardiac workload. BNP and NT-proBNP, which is the biologically inactive N-terminal portion of its pro-hormone, are fast and sensitive biomarkers for diagnosing heart failure. The plasma concentrations of both BNP and NT-proBNP also correlate with left ventricular function in patients with acute exacerbation of COPD, even without history of heart failure. Several studies have been conducted in vitro and in vivo, both in animals and in humans, in order to assess the potential role of the NPR-A activation as a novel therapeutic approach for treating obstructive pulmonary disorders. Unfortunately, these studies have yielded conflicting results. Nevertheless, further recent specific studies, performed in ex vivo models of asthma and COPD, have confirmed the bronchorelaxant effect of BNP and its protective role against bronchial hyperresponsiveness in human airways. These studies have also clarified the intimate mechanism of action of BNP, represented by an autocrine loop elicited by the activation of NPR-A, localized on bronchial epithelium, and the relaxant response of the surrounding ASM, which does not expresses NPR-A. This review explores the teleological activities and paradoxical effects of BNP with regard to chronic obstructive respiratory disorders, and provides an excursus on the main scientific findings that explain why BNP should be considered much more than a biomarker.

Computerized tomography measured liver fat is associated with low levels of N-terminal pro-brain natriuretic protein (NT-proBNP). Multi-Ethnic Study of Atherosclerosis

BACKGROUND AND AIMS

N-terminal pro B-type natriuretic peptide (NT-proBNP) is inversely associated with diabetes mellitus, obesity and metabolic syndrome. We aim to characterize the association between NT-proBNP and nonalcoholic fatty liver disease (NAFLD), a condition strongly associated with metabolic syndrome.

METHODS

4529 participants from the Multi-Ethnic Study of Atherosclerosis (MESA) free of cardiovascular disease, without self-reported liver disease and not diabetic at their baseline visit in 2000-2002 were included in this analysis. NAFLD was defined by a liver attenuation <40 HU. Relative prevalence (RP) for NAFLD was assessed adjusted for age, race, and sex, percentage of dietary calories derived from fat, total intentional exercise, alcoholic drinks per week, and interleukin-6 by quintiles of NT-proBNP. Adjusted linear spline model was used to characterize a non-linear association between NT-proBNP and liver fat. The inflection point (IP) was the NT-proBNP concentration where there was a change in slope in the association between liver attenuation and NT-proBNP.

RESULTS

RP for NAFLD decreased by 30% from the lowest to the highest quintile of NT-proBNP, p=0.01. We observed an inverse linear association between NT-proBNP and liver fat, which plateaued (IP) at an NT-proBNP concentration of 45pg/mL. Linear regression coefficient (SE) per unit of NT-proBNP less than and greater than or equal to IP was of 0.05 (0.02), p=0.001 and 0.0006 (0.0008), p=0.5, respectively; differences between slopes, p<0.0001.

CONCLUSIONS

In this cross-sectional study of a community based multiethnic sample of non-diabetic adults, low levels of NT-proBNP are associated with greater prevalence of NAFLD.

Development and Validation of Risk Prediction Models for Cardiovascular Events in Black Adults: The Jackson Heart Study Cohort

IMPORTANCE

Cardiovascular risk assessment is a fundamental component of prevention of cardiovascular disease (CVD). However, commonly used prediction models have been formulated in primarily or exclusively white populations. Whether risk assessment in black adults is dissimilar to that in white adults is uncertain.

OBJECTIVES

To develop and validate risk prediction models for CVD incidence in black adults, incorporating standard risk factors, biomarkers, and subclinical disease.

DESIGN, SETTING, AND PARTICIPANTS

The Jackson Heart Study (JHS), a longitudinal community-based study of 5301 black adults in Jackson, Mississippi. Inclusive study dates were the date of a participant's first visit (September 2000 to March 2004) to December 31, 2011. The median (75th percentile) follow-up was 9.1 (9.7) years. The dates of the analysis were August 2013 to May 2015. Measurements included standard risk factors, including age, sex, body mass index, systolic and diastolic blood pressure, ratio of fasting total cholesterol to high-density lipoprotein cholesterol, estimated glomerular filtration rate, antihypertensive therapy, diabetes mellitus, and smoking; blood biomarkers; and subclinical disease measures, including ankle-brachial index, carotid intimal-medial thickness, and echocardiographic left ventricular hypertrophy and systolic dysfunction.

MAIN OUTCOMES AND MEASURES

Incident CVD event was defined as the first occurrence of myocardial infarction, coronary heart disease death, congestive heart failure, stroke, incident angina, or intermittent claudication. Model performance was compared with the American College of Cardiology/American Heart Association (ACC/AHA) CVD risk algorithm and the Framingham Risk Score (FHS) refitted to the JHS data and evaluated in the Atherosclerosis Risk in Communities (ARIC) and Multi-Ethnic Study of Atherosclerosis cohorts.

RESULTS

The study cohort comprised 3689 participants with mean (SD) age at baseline was 53 (11) years, and 64.8% (n = 2390) were female. Over a median of 9.1 years, 270 participants (166 women) experienced a first CVD event. A simple combination of standard CVD risk factors, B-type natriuretic peptide, and ankle-brachial index (model 6) yielded modest improvement over a model without B-type natriuretic peptide and ankle-brachial index (C statistic, 0.79; 95% CI, 0.75-0.83 [relative integrated discrimination improvement, 0.22; 95% CI, 0.15-0.30]). However, the reclassification improvement was not substantially different between model 6 and the ACC/AHA CVD Pooled Cohort risk equations or between model 6 and the FHS. The models discriminated reasonably well in the ARIC and Multi-Ethnic Study of Atherosclerosis data (C statistic range, 0.70-0.77).

CONCLUSIONS AND RELEVANCE

Our findings using the JHS data in the present study are valuable because they confirm that current FHS and ACC/AHA risk algorithms work well in black individuals and are not easily improved on. A unique risk calculator for black adults may not be necessary.

The pathophysiological role of natriuretic peptide-RAAS cross talk in heart failure

Chronic Heart Failure (HF) is still a disease state characterized by elevated morbidity and mortality and represents an unresolved problem for its socio-economic impact. Besides many of the pathophysiological events leading to advanced HF have been widely disclosed in the past decades, the role of neuro-hormonal dysregulation accompanying HF has to be clearly assessed with the objective of better therapeutic approaches in treating such a disease. In the present review article, alongside with a brief re-evaluation of general aspects of HF physiopathology, we summarize recent advances in the cross talk between renin-angiotensin-aldosterone system (RAAS) with natriuretic peptides (NPs) which have been shown to play a relevant role in the development of severe HF. The role of RAAS-NPs interplay has been shown to be crucial in both hemodynamic and tissue remodeling associated to cardiomyocyte dysfunction, leading to advanced impairment of left ventricular performance. On the basis of these results, the development of drugs resetting both RAAS and NPs system seems to be promising for a successful long term treatment of chronic HF.

Recent advances in treatment of heart failure

With the total cases and economic burden of heart failure continuing to rise, there is an overwhelming need for novel therapies. Several drugs for heart failure have succeeded in preclinical and early-phase clinical trials, but most of them failed to show the real benefit in pivotal clinical trials. Meanwhile, the US Food and Drug Administration recently approved two promising new drugs to treat heart failure: ivabradine and sacubitril/valsartan. Furthermore, some of the newer agents in testing offer the potential for significant progress in addition to these drugs. Patiromer and zirconium cyclosilicate are attractive agents that are expected to prevent hyperkalemia during renin-angiotensin-aldosterone system inhibition, and serelaxin and urodilatin are promising drugs in the treatment of acute heart failure. Future clinical trials with more appropriate study designs, optimal clinical endpoints, and proper patient selection are mandatory to assess the true efficacy of these attractive compounds in clinical practice.

Detection by ELISA of C-terminal proBNP in plasma from cats with cardiomyopathy

The B-type natriuretic peptide prohormone (proBNP) is enzymatically cleaved into an inactive N-terminal peptide and a biologically active C-terminal peptide with many beneficial cardiorenal effects. The purpose of this study was to develop and test in cats with cardiomyopathy an immunoassay to quantify the concentrations of C-terminal proBNP in feline plasma. An anti-canine proBNP monoclonal antibody (UI-1021) was shown to have adequate binding affinity to proBNP 80-106 for use in a solid-phase immunoassay, and by epitope mapping to bind within positions 84-87 of feline proBNP. UI-1021 was paired with an affinity-purified rabbit polyclonal detection antibody to feline proBNP 100-106, in a sandwich ELISA with feline proBNP 80-106 standard. The linearity and analytical range and sensitivity of the assay were confirmed from 1.4 to 85 pmol/L. Spike recovery averaged 106.5% (95% confidence interval 78-135%). Within run and intra-assay coefficients of variation were <12%. A protease inhibitor mixture preserved proBNP 80-106 immunoreactivity for at least 5 days in plasma. Clinical verification of the ELISA was done using plasma from 13 cats with cardiomyopathy, whose C-terminal proBNP concentrations ranged from 1.7 to 78.8 pmol/L vs. <1.4-1.8 pmol/L in plasma from 18 healthy cats. Concentrations were found to be substantially lower than reported N-terminal proBNP concentrations, and similar to those of human heart failure patients where relative C-terminal BNP deficiencies have been proposed as contributory to the progression of the disease.

In vivo Evaluation of Cenderitide-Eluting Stent (CES) II

The use of drug-eluting coronary stents has led to significant reduction in in-stent restenosis (ISR), but led to delayed endothelialization, necessitating the prolonged use of expensive anti-thrombotic drugs with their side-effects. Cenderitide (CD-NP) is a novel anti-proliferative chimeric peptide of semi-endothelial origin. Our previous work in vitro has demonstrated; that the smooth muscle cells were inhibited significantly more than endothelial cells which is the desirable feature of an anti-restenosis drug. This work reports the effects of implantation of a centeritide-eluting stent (CES) on ISR and endothelialization in an in vivo model. CESs were produced by coating bare metallic stents with CD-NP entrapped in biodegradable poly(ε-caprolactone) using an ultrasonic spray coater. A total of 32 stents were successfully implanted into 16 pigs, and all animal survived for 28 days. The plasma levels of CD-NP were significantly higher in the CES group than in the control group (bare metal stents and polymer-coated stent) at post-stenting, indicating the successful release of CD-NP from the stent in vivo. Furthermore, SEM analysis results showed the greater endothelial coverage of the stent struts, as well as between the struts in CES group. Moreover, histological results showed mild inflammation, and low fibrin score at 28 days. However, plasma cGMP (second messenger, cyclic 3',5' guanosine monophosphate) does not show a significant difference, and the CES is also unable to show significant difference in terms on neointimal area and stenosis, in comparison to BMS at 28 days.

In vitro evaluation of cenderitide-eluting stent I -an antirestenosis and proendothelization approach

Despite the success that drug-eluting stents (DESs) have achieved for minimizing in-stent restenosis (ISR), the antirestenotic agents used in DES have been implicated in delayed endothelial healing and impairment of endothelial functions. Cenderitide (CD-NP) is a novel antiproliferation chimeric peptide of semiendothelial origin; thus, this paper aims to demonstrate the selectivity aspect of this new peptide via in vitro evaluation on key players in ISR-smooth muscle cells (SMCs) and endothelial cells. The microbicinchoninic acid protein assay was used to investigate the CD-NP release from films and stents. Cenderitide-containing films blended with poly(ethylene glycol) and its copolymer exhibited higher release kinetics compared with neat poly(ε-caprolactone) (PCL) formulation. Cenderitide-eluting stents (CES) was produced by coating bare metallic stents with CD-NP entrapped PCL using an ultrasonic spray coater. The investigation of CD-NP on in vitro cells revealed that CD-NP inhibits human coronary smooth muscle cells (HCaSMCs) proliferation but exhibits no effects on human umbilical vein endothelial cells (HUVECs) proliferation. Moreover, CD-NP released up to 7 days displayed inhibitory effects on SMCs proliferation. The CES produced in this work shows that the released CD-NP inhibits HCaSMCs proliferation but did not hamper HUVECs proliferation in vitro, suggesting that it has potential to reduce ISR without retarding the endothelialization healing in vivo.

Natriuretic peptides and cardio-renal disease

The natriuretic peptide (NP) system is an important endocrine, autocrine and paracrine system, consisting of a family of peptides which provide cardiac, renal and vascular effects that, through their beneficial physiological actions, play a key role in maintaining overall cardiovascular health. Traditionally, the pathophysiological origins of cardio-renal disease have been viewed as the domain of the renin-angiotensin-aldosterone system (RAAS) and the sympathetic nervous system (SNS), with inappropriate activation of both systems leading to deleterious changes in cardio-renal function and structure. Therapies designed to suppress the RAAS and the SNS have been routinely employed to address the consequences of cardio-renal disease. However, it is now becoming increasingly apparent that enhancing the beneficial physiological effects of the NP system may represent an attractive alternative therapeutic approach to counter the pathophysiological effects of disease. In particular, innovative therapeutic strategies aimed at enhancing the physiological benefits afforded by NPs while simultaneously suppressing the RAAS are generating increasing interest as potential treatment options for the management of cardio-renal disease.

Vascular relaxation induced by C-type natriuretic peptide involves the ca2+/NO-synthase/NO pathway

AIMS

C-type natriuretic peptide (CNP) and nitric oxide (NO) are endothelium-derived factors that play important roles in the regulation of vascular tone and arterial blood pressure. We hypothesized that NO produced by the endothelial NO-synthase (NOS-3) contributes to the relaxation induced by CNP in isolated rat aorta via activation of endothelial NPR-C receptor. Therefore, the aim of this study was to investigate the putative contribution of NO through NPR-C activation in the CNP induced relaxation in isolated conductance artery.

MAIN METHODS

Concentration-effect curves for CNP were constructed in aortic rings isolated from rats. Confocal microscopy was used to analyze the cytosolic calcium mobilization induced by CNP. The phosphorylation of the residue Ser1177 of NOS was analyzed by Western blot and the expression and localization of NPR-C receptors was analyzed by immunohistochemistry.

KEY FINDINGS

CNP was less potent in inducing relaxation in denuded endothelium aortic rings than in intact ones. L-NAME attenuated the potency of CNP and similar results were obtained in the presence of hydroxocobalamin, an intracellular NO0 scavenger. CNP did not change the phosphorylation of Ser1177, the activation site of NOS-3, when compared with control. The addition of CNP produced an increase in [Ca2+]c in endothelial cells and a decrease in [Ca2+]c in vascular smooth muscle cells. The NPR-C-receptors are expressed in endothelial and adventitial rat aortas.

SIGNIFICANCE

These results suggest that CNP-induced relaxation in intact aorta isolated from rats involves NO production due to [Ca2+]c increase in endothelial cells possibly through NPR-C activation expressed in these cells. The present study provides a breakthrough in the understanding of the close relationship between the vascular actions of nitric oxide and CNP.

The effects of 17-methoxyl-7-hydroxy-benzene-furanchalcone on the pressure overload-induced progression of cardiac hypertrophy to cardiac failure

We investigated the effects of 17-methoxyl-7-hydroxy-benzene-furanchalcone (MHBFC), which was isolated from the roots of Millettia pulchra (Benth.) Kurz var. Laxior (Dunn) Z.Wei (Papilionaceae) (MKL), on the progression of cardiac hypertrophy to failure in a rat model of abdominal aortic banding (AAB)-induced pressure overloading. Endothelial dysfunction is central to pressure overload-induced cardiac hypertrophy and failure. It would be useful to clarify whether MHBFC could prevent this dysfunction. The effects of pressure overload were assessed in male Sprague-Dawley rats 6 weeks after AAB using the progression of cardiac hypertrophy to heart failure as the endpoint. The AAB-treated rats exhibited a greater progression to heart failure and had significantly elevated blood pressure, systolic and diastolic cardiac dysfunction, and evidence of left ventricular hypertrophy (LVH). LVH was characterized by increases in the ratios of heart and left ventricular weights to body weight, increased myocyte cross-sectional areas, myocardial and perivascular fibrosis, and elevated cardiac hydroxyproline. These symptoms could be prevented by treatment with MHBFC at daily oral doses of 6 and 12 mg/kg for 6 weeks. The progression to cardiac failure, which was demonstrated by increases in relative lung and right ventricular weights, cardiac function disorders and overexpression of atrial natriuretic peptide (ANP) mRNA, could also be prevented. Furthermore, MHBFC partialy rescued the downregulated nitric oxide signaling system, whereas inhibited the upregulated endothelin signaling system, normalizing the balance between these two systems. MHBFC protected the endothelium and prevented the pressure overload-induced progression of cardiac hypertrophy to cardiac failure.

Investigation of cenderitide controlled release platforms for potential local treatment of cardiovascular pathology

In this work, we focused on the development and investigation of controlled release matrices for a novel cardiotherapeutic peptide, cenderitide (CD-NP) that has shown to be useful for control of ventricular remodeling. To circumvent the hydrophilicity disparity between CD-NP and hydrophobic polymer matrix, a cosolvent system (water/dichloromethane) was selected for investigation. The effect of emulsification conditions, addition of poly(ethylene glycol) (PEG) and its copolymer on the release mechanism and profile were investigated. To verify the retention of bioactivity of entrapped CD-NP in different formulations, the generation of 3',5' cyclic guanosine monophospate (cGMP) and the inhibition of human cardiac fibroblast (HCF) were evaluated. The results showed that neat poly(ε-caprolactone) matrices carried out via two distinct emulsification conditions had either an unacceptably high burst or incomplete release of CD-NP; and the addition of PEG and its copolymer obtained intermediate profiles. Our confocal laser scanning microscopy and surface morphological investigations showed that the copolymer excipient was superior in playing stabilizer role by colocalizing and redistributing peptide throughout the matrix, making the release less sensitive to emulsification conditions. Furthermore, the released CD-NP is able to generate the cGMP and inhibit the HCF proliferation. Our investigations showed that CD-NP-loaded platforms can be a feasible option to provide sustained antifibrotic moderation of fibrotic scar formation and be potentially used to alleviate the adverse effects of cardiac remodeling.

Plasma volume expansion by 0.9% NaCl during sepsis/systemic inflammatory response syndrome, after hemorrhage, and during a normal state

OBJECTIVE

The objective of this study was to determine the degree of plasma volume expansion by 0.9% NaCl in relation to the infused volume, in sepsis/systemic inflammatory response syndrome (SIRS), after a standardized hemorrhage, and in a normal condition.

DESIGN

Prospective, randomized animal study.

SETTING

The study was performed at a university hospital laboratory.

SUBJECTS

Thirty anesthetized adult male rats were included in the study.

INTERVENTIONS

The study was performed in three groups: a sepsis/SIRS group (the S group), in which sepsis/SIRS was induced by cecal ligation and incision; a hemorrhage group (the H group), in which the rats were left without intervention for 4 h and bled 8 mL/kg thereafter; and a group that was left without intervention (the N group). Then, 4 h after baseline, all three groups were given an infusion of 0.9% NaCl (32 mL/kg) for 15 min. Baseline was defined as the time point when the surgical preparation was finished.

MEASUREMENTS AND MAIN RESULTS

Plasma volumes were measured using I-albumin dilution technique at baseline, after 4 h, and 20 min after the end of infusion. The plasma volume-expanding effect 20 min after end of infusion was 0.6% ± 2.9% in the S group, 20% ± 6.4% in the H group, and 12% ± 11% in the N group, compared with just before start of infusion.

CONCLUSIONS

The present study in rats showed that the plasma volume-expanding effect after an infusion of 0.9% NaCl was smaller in a septic/SIRS state than after hemorrhage and in a normal state. This indicates that the plasma volume-expanding effect of a crystalloid is dependent on pathophysiologic changes in sepsis/SIRS.

Infusion rate and plasma volume expansion of dextran and albumin in the septic guinea pig

BACKGROUND

Intravenous fluid treatment of hypovolaemia in states of increased capillary permeability, e.g. sepsis, is often accompanied by adverse oedema formation. A challenge is therefore to achieve and maintain normovolaemia using as little plasma volume substitution as possible to minimise interstitial oedema. In the present study, we evaluated the importance of infusion rate for the plasma volume expanding effects of 6% dextran 70 and 5% human albumin in a guinea pig sepsis model.

METHODS

In this prospective, randomised study, 50 anaesthetised adult male Dunkin-Hartley guinea pigs were used. After laparotomy, sepsis was induced by caecal ligation and incision. Three hours later, an infusion (12 ml/kg) of one of the studied fluids was given either over 15 min (bolus group) or over 3 h (continuous group). A sham group underwent the same surgical procedure but did not receive any fluid.

RESULTS

At the end of the experiment 3 h after the start of infusion, plasma volumes in the continuous group and the bolus group, respectively, were: 47.2 ± 5.3 ml/kg and 36.5 ± 3.9 ml/kg (P < 0.001) for 6% dextran 70, and 47.3 ± 7.5 ml/kg and 39.7 ± 2.8 ml/kg (P < 0.01) for 5% albumin. Plasma volume for the sham group at the same time point was 29.9 ± 3.3 ml/kg.

CONCLUSIONS

The study performed on a guinea pig sepsis model showed that the plasma volume expanding effects of fixed volumes of 6% dextran 70 and 5% albumin were greater when given at a slow than at a fast infusion rate.

The NO/ONOO-cycle as the central cause of heart failure

The NO/ONOO-cycle is a primarily local, biochemical vicious cycle mechanism, centered on elevated peroxynitrite and oxidative stress, but also involving 10 additional elements: NF-κB, inflammatory cytokines, iNOS, nitric oxide (NO), superoxide, mitochondrial dysfunction (lowered energy charge, ATP), NMDA activity, intracellular Ca(2+), TRP receptors and tetrahydrobiopterin depletion. All 12 of these elements have causal roles in heart failure (HF) and each is linked through a total of 87 studies to specific correlates of HF. Two apparent causal factors of HF, RhoA and endothelin-1, each act as tissue-limited cycle elements. Nineteen stressors that initiate cases of HF, each act to raise multiple cycle elements, potentially initiating the cycle in this way. Different types of HF, left vs. right ventricular HF, with or without arrhythmia, etc., may differ from one another in the regions of the myocardium most impacted by the cycle. None of the elements of the cycle or the mechanisms linking them are original, but they collectively produce the robust nature of the NO/ONOO-cycle which creates a major challenge for treatment of HF or other proposed NO/ONOO-cycle diseases. Elevated peroxynitrite/NO ratio and consequent oxidative stress are essential to both HF and the NO/ONOO-cycle.