Cataliotti, Alessandro

Introduction: Aldosterone (Aldo) increases sodium and water reabsorption and mediates inflammatory processes. Its relationship to co-morbidities has not been well defined in the general population. Hypothesis: We addressed the hypothesis that plasma aldosterone concentration (PAC) is associated with metabolic and cardiorenal diseases in the general community. Methods: We determined PAC in a general community-based cohort from Olmsted County, MN (n=1,674), and defined correlations with cardiorenal, metabolic diseases and myocardial function and structure. Results: PAC was detected in all subjects and ranged from 2.5 to 91 ng/dl (mean value 6.7 ng/dl, +/- SD 6.6). Multivariate analysis adjusted for age, gender, BMI, ANP and BNP showed highly significant correlations between PAC and hypertension (HTN) (p<.0001, OR=2.28, CI:1.91-2.71), atrial fibrillation (p<.01), chronic kidney disease (CKD) (p<.0001, OR=1.64, CI:1.33-2.02), central obesity (p<.0001, OR=1.61, CI:1.27-2.05), hypertriglyceridemia (p<.003), prevalence of metabolic syndrome (MetS) (p<.0007, OR=1.40, CI=1.15-1.71), obesity (p<.0001, OR=1.48, CI:1.27-1.73), and concentric left ventricular hypertrophy (cLVH) (p=.01). Recognizing that ANP and BNP are known inhibitors of Aldo, we defined the relationship between these cardiac hormones (NTpro-ANP and NT-proBNP) and PAC and observed highly significant inverse relationships with NTpro-ANP (p=0.0009), NTpro-BNP (p=0.0003) in the general population. Conclusions: In conclusion, in the general community, PAC is strongly correlated with renal, metabolic and cardiovascular diseases as well as cardiac remodeling. Specifically, increasing PAC is strongly associated with HTN, CKD, obesity, MetS, cLVH, and lower levels of natriuretic peptides. Our data suggest a key role of Aldo as a possible biomarker and/or mediator of human cardiorenal and metabolic diseases even in the general adult population, prior to overt disease. This study also supports a possible counter regulatory relationship between cardiac natriuretic peptides and PAC. Further studies are warranted to evaluate possible therapeutic interventions targeting Aldo as a strategy to delay disease progression.

Background Sustained Acting Atrial Natriuretic Peptide (SA-ANP) is a 40 AA peptide consisting of native ANP (1–28) with a 12 AA C-terminus extension which we synthesized based upon a familial ANP gene frameshift mutation. SA-ANP possesses markedly greater and more sustained mean arterial pressure (MAP) lowering, diuretic/natriuretic, angiotensin-aldosterone suppressing, and cGMP activating properties compared to ANP in normal dogs consistent with a super agonist of the ANP receptor (NPR-A) ( JACC in press ). Here we evaluated SA-ANP in a model of acute hypertension with the hypothesis that SA-ANP would have potent MAP lowering and renal enhancing properties. Methods Integrated physiological studies were performed in a canine model of ANG induced hypertension (20 ng/kg/min continuous infusion) before, during, and up to 3 hours following a 45 minute infusion of SA-ANP (30 pmol/kg/min) (n=6) or vehicle (n=6). Results MAP is shown in Figure 1 . SVR significantly decreased and despite a significant reduction in MAP both renal blood flow (RBF) and GFR were significantly increased following SA-ANP infusion. There were significant reductions in proximal and distal tubule sodium reabsorption resulting in a significant increase (>50 fold) in diuresis and natriuresis with SA-ANP. These renal actions were associated with significant increases in plasma and urine cGMP and a significant inhibition of aldosterone activation. Discussion We report for the first time in an acute model of hypertension that SA-ANP reduced MAP while enhancing RBF, GFR, and sodium/water excretion and thus may serve as a potential therapeutic agent in the treatment of hypertension in the setting of volume overload.

Introduction: Blood pressure (BP) control remains low despite combination therapy in resistant hypertension (RH). Thus, there is an unmet need for novel strategies targeting RH. Recently we have reported that M-ANP, a novel Mayo engineered ANP-based peptide, possesses greater and more sustained biological actions compared to ANP and is more resistant to neprilysin degradation. The current study was designed to investigate for the first time the efficacy of a single daily subcutaneous (SQ) injection of M-ANP using a chronic canine model of hypertension induced by angiotensin II (Ang-II). Hypothesis: We hypothesize that a daily SQ M-ANP injection would have potent BP lowering and renal enhancing properties in our chronic hypertensive canine model. Methods: We induced hypertension in canines (n=5) by continuous Ang II (80 ng/kg/min) osmotic mini-pump administration for 24 days. Continuous 24 hour mean BP (MBP) was measured by telemetry and a 24 hour urine collection was used to assess urinary volume, sodium (Na) and cGMP, the second messenger for the ANP system. M-ANP was administered SQ for 5 days (10μg/kg/day). Data are mean±SE. ΨP<0.05 Ang II Day 16 vs. baseline; *P<0.05 Ang II Day 16 vs. M-ANP (Table 1). Results: Chronic Ang II administration resulted in model of severe hypertension, with an increase in MBP from 112±2 to 157±2 mmHg (day 16). As seen in Table 1, M-ANP significantly reduced MBP, significantly increased plasma cGMP as well as urinary cGMP excretion, urinary volume rate (UV) and urinary Na excretion (UNa), without significant changes in heart rate (HR). Furthermore, there was a trend for plasma ANP to increase and plasma aldosterone to decrease with SQ M-ANP injection. Conclusions: This study demonstrates for the first time that chronic SQ administration of M-ANP reduces BP, activates plasma cGMP, and increases UV and UNa, without significant changes in HR in an experimental model of chronic hypertension.

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: Chronic renal insufficiency (CRI) is a strong predictor of increased mortality in the presence of heart failure (HF) and its prevalence has been increasing in the US. In addition, CRI is a major contributing factor to the progression of HF as it is associated with chronic volume overload, accelerated atherosclerosis and hypertension (HTN). The first aim of the current study was to evaluate the prevalence of CRI in an adult general population. The second aim was to address whether calculated glomerular filtration rate (cGFR) adds value to the cardiac biomarkers BNP and NT-proBNP in detecting early cardiac structural and functional impairments in the general population. Methods: From 1997 to 1999 medical history, physical examination, echocardiography, BNP (Biosite) and NT-proBNP (Roche) and serum creatinine (SCr) were obtained in 1,982 randomly selected residents of Olmsted County, MN >= 45 years (range 45 – 96 years). GFR was calculated using the Cockroft Gault equation. CRI was defined as a GFR < 60 ml/min. Cardiac structure and function were evaluated by in-depth echocardiographic examination. Results: The prevalence of cardiovascular co-morbidities was coronary atherosclerosis 12%, HTN 29.5% and diabetes mellitus 7.5%. The prevalence of CRI was 22.8% when cGFR was used for its detection. Importantly, by Chi-Square model, cGFR significantly increased the ability of BNP in detecting left ventricular hypertrophy (LVH) (p=0.004), increased relative wall thickness (p=0.0036), diastolic dysfunction (DDF) (p=0.0001) and HTN (p=0.0002). Similarly, when combined with NT-proBNP, cGFR increased the predictive power of detecting DDF (p=0.0001) and HTN (p=0.0366). Conclusion: This study reports a higher than predicted prevalence of CRI in this general US population equal to 23% and closely associated with the prevalence of HTN (29.5%). Importantly, this study also demonstrates that cGFR has additive predictive power when used in combination with two cardiac biomarkers of cardiac dysfunction and remodeling, BNP and NT-proBNP. These studies underscore the increasing burden of CRI in the general population and the utility of assessing cardiorenal function by combining renal and cardiac biomarkers in assessment of cardiac structure and function.

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.

Altered myocardial structure and function, secondary to chronically elevated blood pressure, are leading causes of heart failure and death. B-type natriuretic peptide (BNP), a guanylyl cyclase A agonist, is a cardiac hormone integral to cardiovascular regulation. Studies have demonstrated a causal relationship between reduced production or impaired BNP release and the development of human hypertension. However, the consequences of BNP insufficiency on blood pressure and hypertension-associated complications remain poorly understood. Therefore, the goal of this study was to create and characterize a novel model of BNP deficiency to investigate the effects of BNP absence on cardiac and renal structure, function, and survival. Genetic BNP deletion was generated in Dahl salt-sensitive rats. Compared with age-matched controls, BNP knockout rats demonstrated adult-onset hypertension. Increased left ventricular mass with hypertrophy and substantially augmented hypertrophy signaling pathway genes, developed in young adult knockout rats, which preceded hypertension. Prolonged hypertension led to increased cardiac stiffness, cardiac fibrosis, and thrombi formation. Significant elongation of the QT interval was detected at 9 months in knockout rats. Progressive nephropathy was also noted with proteinuria, fibrosis, and glomerular alterations in BNP knockout rats. End-organ damage contributed to a significant decline in overall survival. Systemic BNP overexpression reversed the phenotype of genetic BNP deletion. Our results demonstrate the critical role of BNP defect in the development of systemic hypertension and associated end-organ damage in adulthood.

Although effective in relieving symptoms of edema in congestive heart failure (CHF), diuretic-induced natriuresis may be associated with reductions in glomerular filtration rate (GFR) and effective renal plasma flow (ERPF), which subsequently may reduce the duration of natriuresis. Moreover, recent studies have reported that the preservation of GFR is an important predictor of survival in human CHF. We hypothesized that the acute detrimental renal hemodynamic and tubular responses to furosemide in symptomatic human CHF will be attenuated by AT1 receptor blockade with losartan. We defined the renal hemodynamic and tubular actions and aldosterone responses to furosemide (40 mg, orally) in the presence of acute AT1 receptor antagonism (losartan, MSD, 50 mg orally) vs. placebo in 10 subjects with CHF (New York Heart Association II-III) in a double-blind, placebo-controlled crossover study. Furosemide with placebo increased sodium excretion and reduced ERPF and GFR ( P < 0.05 vs. baseline). After 4 h, sodium excretion compared with baseline was decreased ( P < 0.05). In contrast, furosemide with losartan resulted in a greater increase in sodium excretion but without reductions in ERPF and GFR ( P < 0.05 vs. placebo). After 4 h, sodium excretion was greater compared with the placebo group. Importantly, plasma aldosterone tended to increase in the placebo group, whereas it was decreased ( P < 0.05 vs. baseline) only in the losartan group. These studies underscore the pathophysiological role of the AT1 receptor in mediating detrimental renal and adrenal properties of diuretics in human CHF. AT1 receptor antagonism preserves GFR and renal blood flow and enhances sodium excretion during acute diuretic therapy in addition to inhibiting aldosterone secretion. These findings support the use of AT1 receptor blockade for human CHF requiring acute diuretics to improve renal hemodynamic and tubular function and to suppress aldosterone.

C-type natriuretic peptide (CNP) possesses well-established cardiovascular properties. Although present in the mammalian kidney, CNP production in human kidney and its modulation in human renal disease remain less defined. We investigated the presence of CNP in normal human kidney and in patients with nephrotic syndrome (NS). We also addressed whether or not a low-protein diet (LPD) alters plasma CNP and urinary CNP excretion in NS. In situ hybridization studies demonstrated CNP mRNA expression in tubular cells and glomeruli of normal human kidneys. CNP immunoreactivity was positive in proximal, distal, and medullary collecting duct tubular cells in both controls and patients with NS. The ratios of plasma CNP and urinary CNP to creatinine were significantly higher in patients with NS compared with controls. Urinary CNP, but not plasma CNP, was significantly lowered in patients with NS after an LPD. Similarly, the ratios of urinary protein to creatinine and urinary albumin to creatinine, but not urinary guanosine 3′,5′-cyclic monophosphate to creatinine, decreased significantly with an LPD. These data confirm and extend previous reports and demonstrate for the first time the presence of CNP in human kidney with NS. We also report increased plasma CNP concentration and urinary CNP excretion in NS patients and a significant reduction of CNP excretion with an LPD. Our findings demonstrate that CNP metabolism is altered in patients with NS and support the hypothesis that activation of renal CNP can be partially offset by an LPD. These results underscore that the beneficial effect of an LPD on protein excretion is paralleled by a substantial reduction in intrarenal CNP release.