Chen, Horng H.

BACKGROUND: BNP is a cardiac peptide with vasodilatory, natriuretic and diuretic properties. Recent studies have suggested that its vasodilatory hypotensive properties may limit the renal actions of BNP, especially in patients with borderline low blood pressure. We have recently identified an alternatively spliced transcript for BNP (ASBNP) that includes a unique and distinct longer carboxyl-terminus consisting of 34 amino acids. Based upon preliminary studies, we generated a truncated form (ASBNP2.1) that contains the first 16 amino acids of the C-terminal of ASBNP. METHODS: We determined the cardiorenal and humoral actions of intravenous infusion of ASBNP2.1 at 2 pmol/Kg/min, 10 pmol/Kg/min and 100 pmol/Kg /min in 10 dogs with rapid ventricular pacing induced overt CHF (240 bpm for 10 days). * p<0.05 RESULTS: IV infusion of ASBNP 2.1 increased aquaresis (from 0.19±0.04 to 0.32±0.07, 0.46±0.11 and 0.39±0.09 ml/min*) without a significant change in urinary sodium excretion. Importantly, ASBNP 2.1 enhanced glomerular filtration rate (GFR), from 31±4 to 47±8, 69±10 and 56±9 ml/min*. These renal actions were associated with increases in urinary BNP*, ANP* and cGMP* excretion. BNP 2.1 did not have any systemic vasodilatory action resulting in no change in mean arterial blood pressure or cardiac-filling pressures even at the highest dose. There was not change in serum sodium concentration. CONCLUSION: We report for the first time that this novel peptide based upon ASBNP has potent aquaretic and GFR enhancing actions without the vasodilatory hypotensive properties in an experimental model of overt CHF. The lack of vasodilatation but with renal actions also suggest that the C-terminus plays a key role in the vascular actions of this peptide offering new insights into vascular-renal structure function of BNP and related peptides. This renal specific peptide may have potential therapeutic benefit in states of renal dysfunction with volume overload to enhance GFR and water excretion without the detrimental side effect of hypotension.

Background : Studies in human myocardial infarction (MI) suggest that even in the absence of heart failure (HF) alterations in renal function may occur and contribute to poor outcomes. After MI a decline in renal function may be seen acutely by mechanisms which are unclear. The long term consequences of MI upon renal function and structure remain poorly defined. We hypothesized that even without pre-existing renal disease, renal functional and structural changes would be present following MI. Methods : Cardiorenal function and structure were assessed in Wistar rats, Sham (S; n=10) and MI groups (n=9) 3 weeks after MI. GFR was determined by inulin clearance. Blood was obtained for PRA and aldosterone. Hearts and kidneys were harvested for histological analysis. Cardiac function was assessed by echo. Genome-wide microarray analysis was performed on kidney cortex (KC) and medulla (KM) (Affymetrix GeneChip® Rat Genome 230 2.0). Results : EF decreased after MI (S:62.8±2.3, MI:42.8±6.5 %, p<0.01) and LVEDd increased (p<0.005) PRA and aldosterone activation were absent. Blood pressure (BP) was not different between groups. There was no HF as sodium and water excretion was maintained. GFR tended to decrease (S:2.9±0.3, MI:2.4±0.2 ml/min, NS). Picrosirius Red staining for collagen in the KC and KM after MI showed greater fibrosis especially in the RM (KC S:1.1±0.2, MI:3.5±0.6 %, p<0.001 and KM S:1±0.2, MI:18.8±6 %, p<0.005). Microarray analysis revealed that 303 genes significantly changed in KM and 407 genes in the KC after MI (1.5 fold, P<0.05). Gene dysregulation was related to cell proliferation, metabolic processes and cell communication (Z value>2). Conclusion : We conclude that experimental MI results in renal structural remodeling characterized by renal cortical and medullary fibrosis with a mild reduction in GFR and extensive modulation of molecular pathways related to renal growth and metabolism. This investigation provides evidence for a heart-kidney connection after MI by mechanisms which remain to be defined. We also conclude that therapies for MI targeting the heart also should be evaluated for properties of renoprotection.

BACKGROUND: AlbuBNP is a novel recombinant human BNP serum albumin fusion protein which possesses a significantly longer elimination half-life compared to BNP. To date, it remains unclear if this novel protein which represents a single molecule of BNP synthesized with the carrier protein albumin can enter the post glomerular/tubular system due to the fusion of BNP to albumin and mediate renal actions. We hypothesized that this fusion protein will have potent renal actions and possess prolonged renal hemodynamic enhancing and excretory properties based upon its unique structure as compared to native BNP. METHODS: We compared the cardiorenal and humoral actions of intravenous(IV) bolus of administration of AlbuBNP (Cardeva, CoGenesys, Rockville MD) (5 mg/kg, n=7) and Human BNP (Phoenix Pharmaceutical, Belmont CA) (25 μ g/Kg, n=5) in two groups of normal anesthetized dogs. * p<0.05 RESULTS: Single IV bolus of AlbuBNP resulted in a sustained increase in plasma cGMP (5±1 to 9±2 pmol/ml*) and urinary cGMP excretion (1136±113 to 2556±417 pmol/min*), markers of the biological activity of BNP, which remained elevated at the termination of the experiment at 270 minutes. In contrast, with human BNP, both plasma and urinary cGMP peaked at 30 minutes and returned to baseline by 150 minutes. In a similar fashion, there was a sustained increase in natriuresis (39±12 to 159±38 μEq/min*), diuresis (0.2±0.1 to 1.1±0.3 ml/min*), renal blood flow (220±22 to 301±33 ml/min*), and glomerular filtration rate (34±2 to 62±13 ml/min*) with AlbuBNP while with human BNP, these renal effects peaked at 30 minutes and returned to baseline by 150 minutes. Furthermore, there was a gradual and sustained suppression of plasma aldosterone (7.8±2 to 3.6±1 ng/dL*) with AlbuBNP. Likewise, there was a more sustained reduction of cardiac filling pressures with AlbuBNP as compared to human BNP. CONCLUSION: We report for the first time that this newly developed BNP/albumin fusion protein has a more prolonged and sustained renal enhancing properties compared to human BNP. Thus, AlbuBNP (Cardeva) represents a novel long-acting renal enhancing and aldosterone suppressing drug which has therapeutic potential for the management of cardiovascular and renal diseases that should be defined in further studies.

BACKGROUND: C-type natriuretic peptide (CNP) is a 22-amino-acid peptide produced mainly in the endothelium with potent cardiac unloading and modest blood pressure lowering actions, but minimal renal actions. Based on our previous knowledge, we recently fused a 6 aa sequence from BNP to the C-terminus and a 5 aa sequence from ANP to the N-terminus of CNP. This novel hybrid peptide, CBA-NP, has cardiac unloading actions and mild hypotensive effects similar to CNP. Importantly however, the N and C terminus alterations resulted in potent renal excretory actions. here we test the hypothesis that the 3 aa GSM 15–17 in the disulfide-ring mediate the vascular and hypotensive actions. We therefore mutated GSM 15–17 to REA 15–17 , which we named ABC-NP and compared its in vivo and in vitro actions to CBA-NP. METHODS: We determined the cardiorenal and humoral actions of intravenous bolus administration of CBA-NP (n=5) and ABC-NP (n=5) at 25 microgram/Kg in 2 separate group of normal anesthetized dogs. We also assessed the cGMP response of both peptides in human aortic endothelial cells (HAEC), human cardiac fibroblast (HCF) and isolated canine glomeruli. * p<0.05 RESULTS: IV bolus administration of CBA-NP and ABC-NP resulted in diuresis* and natriuresis*. There was a significant decrease in mean arterial blood (MAP) pressure with CBA-NP (126±6 to113±7 mmHg*) but no change with ABC-NP(126±8 to126±8 mmHg) . In addition, the reduction in pulmonary capillary wedge pressure (PCWP) and right atrial pressure (RAP) was significantly greater with CBA-NP as compared to ABC-NP. cGMP generation in HAEC and HCF was minimal with ABC-NP and was significantly higher with CBA-NP*. In contrast, cGMP generation was similar in isolated glomeruli between the two peptides. CONCLUSION: Our studies demonstrates that mutation of three amino acid (aa) residues within the CNP ring of CBA-NP from GSM 15–17 to REA alters the vascular but not the renal excretory properties. Hence by this strategic mutation within the ring of CBA-NP, we have designed a renal specific peptide ABC-NP resulting in new sequence specific functional information which can be used to design organ specific therapeutic peptides with unique properties tailored for a specific disease state.

Introduction: The incidence of post-myocardial infarction (MI) heart failure (HF) is increasing in the elderly. Studies have demonstrated that B-type natriuretic peptide (BNP) mediates critical cardiorenal compensatory and protective actions through guanylyl cyclase receptor A and cGMP activation. Such actions include natriuresis, diuresis and suppression of adverse cardiorenal remodelling. Hypothesis: While the mechanism of this increased risk may be multifactorial, we hypothesized that an impairment of the compensatory protective BNP/cGMP axis in both the aged kidney and heart contributes to post-MI HF. Methods: 20 month old Fischer rats were randomized into two groups: Sham-operated (S) and MI(produced by left coronary artery ligation). Cardiorenal structure and function were assessed at 4 weeks and included mean arterial pressure(MAP), LV EF, LV chamber dimension, proteinuria, sodium (Na) excretion and fibrosis by picrosirius red staining. Plasma BNP and cGMP levels were assessed by RIA. Data presented as mean±SE,*P<0.05. Results: LV EF (S:78±2, MI:46±3 %*) was significantly reduced in aged MI rats, despite no difference in LV fibrosis in the remote region and no change in MAP compared to aged sham rats. Post-MI HF was evident and characterized by a significant reduction in Na excretion (S:0.20±0.03, MI:0.13±0.01 mEq/day*) as well as significant increases in LV dilatation (S:7.2±0.1, MI:8.3±0.2 mm*) and cardiac hypertrophy (S:2.78±0.06, MI:3.25±0.16 mg/g*) in aged MI rats. Notably, plasma BNP (S:9±1, MI:11±2 pg/ml) failed to increase and plasma cGMP (S:44±6, MI:27±3 mm*) was significantly reduced in the MI group. Importantly, MI in the aged rat resulted in a significant loss in total renal mass (S:2739±83, MI:2351±68 mg*), consistent with renal atrophy, while no changes in proteinuria or renal fibrosis were observed. Conclusions: Post-MI dysfunction of the protective BNP/cGMP axis in the aged rat was associated with various cardiorenal abnormalities including renal atrophy, which may contribute to the pathophysiology of HF. This pre-clinical model provides new insights into post-MI HF and may be used to examine therapeutic strategies using natriuretic peptides to protect the heart and kidney in the elderly post-MI population.

Background CD‐NP is a novel chimeric natriuretic peptide (NP) consisting of the full‐length human C‐type natriuretic peptide (CNP), a NP receptor (NPR)‐B agonist, and the C‐terminus of Dendroaspis NP (DNP), a NPR‐A agonist. In the first‐in‐human clinical trial, CD‐NP activated plasma and urinary cGMP, the second messenger for the NPs, and increased Na + excretion in normal subjects. Here we report for the first time plasma aldosterone (ALDO) and angiotensin II (ANG II) levels. Methods In the double‐blind, PLB‐controlled phase of this trial, adults received CD‐NP 17.5 ng/kg/min (n = 6) or PLB (n = 4) i.v. for 4 hours. Plasma ALDO and ANG II were quantified by RIA. Data were analyzed by 2‐tailed paired t‐test and signed‐rank (S‐R) test (SAS v9). Results In subjects who received CD‐NP, plasma ALDO (mean±SD) decreased from a baseline of 21.9±2.7 to 9.5±3.2 ng/dL (P<0.001 t‐test, P<0.05 S‐R test) at the end of infusion. Plasma ANG II tended to decrease (29.2±5.2 to 23.0±3.5 ng/L, P=0.086 t‐test, P=0.69 S‐R test). In the PLB group, ALDO (20.3±4.2 to 13.6±4.5 ng/dL) and ANG II (23.3±2.2 to 19.8±8.2 ng/L) did not change. Conclusion CD‐NP suppressed plasma ALDO in normal subjects, consistent with NPR‐A activation by a novel NP with dual NPR‐A and NPR‐B activating properties. CD‐NP may be of therapeutic potential in disease states that are characterized by ALDO activation, such as in heart failure warranting further studies. Sources of funding: Mayo Foundation and Nile Therapeutics, Inc.

Decreased renal function is associated with increased CV morbidity and mortality. The changes mild renal impairment may cause structurally/molecularly in the heart remain unclear. We hypothesized that mild renal dysfunction produced by unilateral nephrectomy(UNX)results in changes in ventricular structure and gene expression in the absence of hypertension or vol overload. Wistar rats were used[sham (S; n=10) and UNX; n=9]. At 4 weeks, GFR was determined by inulin clearance and RBF by PAH. Hearts and kidneys were harvested for histological analysis. Cardiac function assessed by echo. Genomewide microarray analysis was performed on LV myocardium (Affymetrix). Glomerular hypertrophy was observed in UNX. GFR tended to decrease with a reduction in RBF (S:8±1, Nx:5±1 ml/min, p<0.005). Blood pressure (BP), Na and water excretions were maintained without activation of PRA, aldo or BNP. LVEF and LV diameters were normal. Microarray analysis of LV revealed that 278 genes changed with UNX (1.5 fold, P<0.05) related to cell growth, bone remodeling and muscle contraction (Z value>2). Importantly, Pic Red staining in the LV of UNX revealed greater fibrosis (S:2±0.1, Nx:4±0.4 %, p<0.001). We conclude that mild renal insufficiency initiates myocardial gene responses and fibrosis independent of alterations in the circulating RAAS, BNP, BP, vol overload or systolic dysfunction.

Background: The aims of this study are to evaluate the rate of progression of preclinical (Stage A and B) heart failure, identify associated characteristics, and evaluate long-term outcomes. Methods: Retrospective review of the Olmsted County Heart Function Study. Individuals categorized as Stage A or B heart failure at initial visit that returned for a second visit 4 years later were included. Logistic regression analyses evaluated group differences with adjustment for age and sex. Results: At visit 1, 413 (32%) individuals were classified as Stage A and 413 (32%) as Stage B. By visit 2, 146 (35%) individuals from Stage A progressed with the vast majority (n=142) progressing to Stage B. In comparison, a total of 23 (6%) individuals progressed from Stage B. A greater rate of progression was seen for Stage A compared with Stage B (8.7 per 100 person-years [95% CI, 7.4–10.2] versus 1.4 per 100 person-years [95% CI, 0.9–2.1]; P <0.001). NT-proBNP correlated with progression for Stage B ( P =0.01), but not for Stage A ( P =0.39). A multivariate model found female sex (odds ratio, 1.65 [95% CI, 1.05–2.58]; P =0.03), increased E/e’ (odds ratio, 1.13 [95% CI, 1.02–1.26], P =0.02), and beta blocker use (odds ratio, 2.19 [95% CI, 1.25–3.82], P =0.006) were associated with progression for Stage A. There was a signal that cardiovascular mortality was higher in individuals who progressed, although not statistically significant ( P =0.06 for Stage A and P =0.05 for Stage B). Conclusions: There is significant progression of preclinical heart failure in a community population, with progression rates higher for Stage A. NT-proBNP correlated with progression for Stage B, but not for Stage A. No statistically significant differences in long-term outcomes were seen. Study results have clinical implications important to help guide future heart failure screening and prevention strategies.

Abstract Aims Heart failure with preserved ejection fraction (HFpEF) is a heterogeneous condition, and tissue congestion manifested by oedema is not present in all patients. We compared clinical characteristics, exercise capacity, and outcomes in patients with HFpEF with and without oedema. Methods and results This study was a post hoc analysis of pooled data of patients with left ventricular ejection fraction of ≥50% enrolled in the DOSE, CARRESS-HF, RELAX, ATHENA, ROSE, INDIE, and NEAT trials. Patients were dichotomized by the severity of oedema. Cox proportional hazard regression and generalized linear regression models were used to assess associations between oedema, symptoms, and clinical outcomes. The ambulatory cohort included 393 patients (228 with and 165 without oedema), and the hospitalized cohort included 338 patients (249 with ≥moderate oedema and 89 with mild or none). Among ambulatory patients, patients with oedema had a higher body mass index (35.2 kg/m2 [inter-quartile range, IQR 30.5, 41.6] vs. 31.6 kg/m2 [IQR 27.9, 36.3], P &lt; 0.001), greater burden of co-morbidities, higher intravascular pressures estimated on physical examination (elevated jugular venous pressure: 50% vs. 24.7%, P &lt; 0.001), poorer renal function (creatinine: 1.2 mg/dL [IQR 0.9, 1.5] vs. 1 mg/dL [IQR 0.8, 1.3], P = 0.003), and lower peak VO2 (adjusted mean difference −1.04 mL/kg/min, 95% confidence interval [−1.71, −0.37], P &lt; 0.003). Among hospitalized patients, despite greater in-hospital fluid/weight loss in the ≥moderate oedema group, there was no difference in the improvement in dyspnoea by the visual analogue scale or well-being visual analogue scale from baseline to 3–4 days and no statistically significant difference in the rate of 60 day rehospitalization/death (adjusted hazard ratio 1.44, 95% confidence interval [0.87, 2.39], P = 0.156). Conclusions Patients with HFpEF and oedema display higher body mass, greater burden of co-morbidities, and more severe exercise intolerance, but clinical responses to treatment appear similar. Further research is required to better understand the nature of volume distribution in different HFpEF phenotypes.

Objective B-type natriuretic peptide (BNP) has favourable effects on left ventricular remodelling, including antifibrotic and antiapoptotic properties. We tested the hypothesis that infusion of BNP after an acute myocardial infarction would reduce left ventricular systolic and diastolic volumes and improve left ventricular ejection fraction compared with placebo. Methods A total of 58 patients who underwent successful revascularisation for an acute ST elevation anterior myocardial infarction were randomised to receive 72-hour infusion of BNP at 0.006 µg/kg/min or placebo. Left ventricular end diastolic and systolic volumes and left ventricular ejection fraction were measured at baseline and at 30 days by multigated acquisition scan. Left ventricular infarction size was measured by cardiac MRI. Results BNP infusion led to significantly higher BNP levels and plasma cyclic guanosine monophosphate at 72 hours. No significant difference in change of left ventricular volumes or ejection fraction from baseline to 30 days was observed between groups. Although left ventricular infarction size measured by cardiac MRI was not significantly different between BNP infusion versus placebo (p=0.39), there was a trend towards reduced infarction size in patients with a baseline ejection fraction of <40% (p=0.14). Conclusions Infusion of BNP in patients with an anterior myocardial infarction did not affect parameters of left ventricular remodelling. Patients treated with BNP who had a baseline left ventricular ejection fraction of <40% had a trend towards reduced left ventricular infarction size compared with placebo. These results do not support the use of intravenous BNP in patients after recent myocardial infarction. Trial registration number NCT00573144.