Heublein, Denise M.

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.

Rationale: The role of cardiac natriuretic peptides (NPs) in peripheral arterial disease (PAD) or thromboangiitis obliterans (TA) is unknown. Recent studies in mice suggested that BNP may be produced outside the heart in the ischemic limbs contributing to peripheral angiogenesis. Objective: Determine if synthesis or consumption/degradation of NPs occur in the ischemic legs of patients with PAD or TA. Methods: 32 patients with critical limb ischemia (CLI) or claudication (PAD n=31; TA n=1; 20 males; mean age 72.9 years) underwent diagnostic angiography or revascularization. We determined differences of concentrations of BNP, NT-proBNP, and CNP in the blood of proximal veins and arteries of both legs. Concentrations differences were then compared between the more ischemic target and the contralateral self-control legs. Results: Values are means ± SD. P values <0.05 were considered significant. In the PAD group, in the target extremity, concentration step-ups of NT-proBNP (11±68; p=0.40) and CNP (0.45±6.22; p=0.71) were not significant from the arterial to venous blood. In the contralateral self-control legs, NT-proBNP and CNP concentrations drops were also not significant (-37±160, p=0.7; -0.89±4.09, p=0.23). Venous BNP concentrations were significantly lower than arterial both in the target (-66±153, p<0.001) and self-control legs (-59±107, p<0.001). BNP concentrations drops were greater in the CLI than claudication cases driving the overall significance. In the patient with TA, whose only identifiable PAD risk factor was smoking, arterial concentrations of NPs were generally low (NT-proBNP 81; BNP 46; CNP 8.2), but higher than venous concentrations (80; 41; 6.7). Conclusion: Significantly lower venous BNP concentrations suggest possible BNP consumption/degradation in the ischemic legs. Concentrations of NT-proBNP, that has a longer half-life than BNP, were more stable suggesting no significant local production or conversion to BNP. CNP concentrations were stable. Recognizing the angiogenic properties of NPs and lack of evidence of peripheral production, studies are warranted in humans with PAD to determine the potential angiogenic properties of exogenous NPs supplementation in what could be considered a local NPs deficiency state.

Background: Renal dysfunction has emerged as an important independent prognostic factor in patients with heart failure (HF). Cardiac resynchronization therapy (CRT) improves functional status and left ventricular (LV) function in HF patients with ventricular dyssynchrony. We hypothesized that CRT would also improve glomerular filtration rate as estimated by the abbreviated MDRD equation (eGFR) in patients with reduced eGFR. Methods: This is a retrospective analysis of the Multicenter InSync Randomized Clinical Evaluation (MIRACLE) study, which evaluated CRT in HF patients with NYHA class III–IV, ejection fraction ≤35%, QRS ≥130 ms, and stable medical regimen. Patients were evaluated before implantation and 6 months after randomization to control (CRT device OFF, n=225) or CRT (n=228). Patients were categorized according to their baseline eGFR: ≥90 (category A), 60≤eGFR<90 (category B), and 30≤eGFR<60 (category C) mL/min per 1.73m 2 . Changes in eGFR were also correlated with changes in other parameters in univariate analysis. Results: At baseline, reduced eGFR was associated with ischemic etiology, increased age, mitral regurgitation, and neurohumoral activation. CRT increased LV ejection fraction and decreased LV volumes and mitral regurgitation in all categories. Importantly, CRT improved eGFR (p=0.003) and reduced blood urea nitrogen (p=0.008) compared to control in category C, but not A (p=0.75/p=0.41) and B (p=0.43/p=0.89). In addition, only in category C did atrial natriuretic peptide decrease, suggesting reduced atrial distention and filling pressures with CRT in this group with impaired eGFR. In univariate analysis, changes in eGFR correlated weakly but significantly with changes in aldosterone (r=−0.22), plasma renin activity (r=−0.19, norepinephrine (r=−0.16), and mean blood pressure (r=+0.14), a pattern consistent with reduced neurohumoral activation due to increased systemic and renal perfusion pressure. Conclusions: CRT increased eGFR and reduced blood urea nitrogen in HF patients with reduced baseline eGFR. By improving cardiac function, CRT can indirectly improve renal function, underscoring the importance of cardiorenal interaction and providing another mechanism for the beneficial effects of CRT.

Introduction: ProANP is a 108 amino acid (AA) prohormone which is produced in the atria and processed to the mature 28 AA ANP which activates the guanylyl cyclase receptor-A (GC-A) and its second messenger cGMP. ProANP is found in the human circulation but its bioavailability is undefined. Hypothesis: ProANP represents a novel cardiac peptide with more sustained natriuretic actions than either carperitide (ANP) or nesiritide (BNP). ProANP itself can activate GC-A in vitro and the proANP can be processed in human serum from normals and in patients with heart failure (HF). Methods: We examined the in vivo cardiorenal actions of proANP compared to ANP, BNP, or placebo in normal canines (667 pmol/kg, n=5/group). We determined cGMP activation of proANP, ANP and BNP in GC-A expressing HEK293 cells. ProANP processing and degradation was also defined in serum from normal subjects (n=13) and patients with HF (n=14) ex vivo. Results: ProANP had significantly greater diuretic and natriuretic properties with increased renal blood flow and sustained renal tubular actions compared to ANP or BNP in canines. ProANP also resulted in greater and more prolonged cardiac unloading than ANP, and much less hypotensive effects than BNP. The plasma half-life of proANP was 4.5 times longer than ANP and 3.8 times longer than BNP. ProANP itself stimulated cGMP generation in GC-A expressing HEK cells which was equal to ANP. ProANP was processed to ANP in fresh serum from normals as well as HF patients ex vivo and the processed peptide activated cGMP in GC-A expressing HEK cells. Conclusions: ProANP represents a novel GC-A activator with a longer half-life and greater natriuresis and diuresis than ANP and BNP and less hypotensive effects than BNP. The bioactivity of exogenous proANP may be through direct stimulation of GC-A, as well as through processing into ANP, as proANP is processed in the circulation of both normal and HF. As proANP circulates in the human circulation, proANP may represent a key circulating hormone in cardiorenal and blood pressure homeostasis as well as a potential innovative therapeutic beyond ANP (carperitide) or BNP (nesiritide) for cardiorenal diseases including HF.

Introduction: Plasma aldosterone (Aldo) increases Na and water reabsorption and mediates inflammation. Our recent findings in a general population cohort showed Aldo strongly associated with hypertension (HTN), obesity, chronic kidney disease (CKD) and lower natriuretic peptide levels (NPs) during a first visit (V1), even when Aldo was within the normal range. It is undefined whether Aldo itself (V1) and/or its increase after 4-year (second visit, V2) can predict new onset cardiovascular and metabolic diseases. Hypotheses: We hypothesized that: 1) Aldo-V1 predicts new onset disease at V2; 2) The increase of Aldo between V1 and V2 predicts new onset disease-V2; and 3) Aldo-V2 remains associated with cardiovascular and metabolic disease-V2. Methods: We defined the correlations between Aldo-V1 and Aldo-V2 with cardiometabolic diseases and medications at V2, in a general community cohort (N=1368) from Olmsted County, MN. Associations were adjusted for age, sex and BMI; Aldo was analyzed as continuous variable and according to tertiles. Results: After 4 years, Aldo-V1 continuous variable predicted new onset of central obesity (p=0.0113, OR=1.36, CI=1.07-1.73), HTN (p=0.0012, OR=1.36, CI=1.13-1.63) and use of antilipemic drugs (p=0.0119, OR=1.25, CI=1.05-1.48); while Aldo-V1 in the 3 rd tertile predicted new onset of type 2 diabetes (T2DM) (p=0.0392, OR=1.96, CI=1.03-3.70), use of antilipemic therapy (p=0.0162, OR=1.59, CI=1.09-2.31) and HTN (p=0.049, OR1.44, CI=1.00-2.08) at V2. Secondly, we observed that the increase in Aldo between V1 and V2 predicted new HTN-V2. Finally, we found higher Aldo-V2, but still within the normal range and Aldo-V2 remained associated with HTN, obesity and CKD, when analyzed as continuous variable and when in the 3 rd tertile. Conclusions: In the general community, Aldo-V1 predicts new onset HTN, central obesity, T2DM and use of antilipemic therapy. Importantly, the increase of aldosterone between V1 and V2 also predicts new onset HTN. Finally, Aldo-V2 correlates with HTN, obesity and CKD as we found at V1. Further studies are warranted to evaluate aldosterone as therapeutic target to delay disease progression, and to support its role as prognostic biomarker to identify high-risk subjects.

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. We hypothesized that even without preexisting renal disease, renal functional, structural and molecular changes would be present following MI. Wistar rats were used, Sham(S;n=10) and MI(n=9). 3 weeks after MI, GFR was determined by inulin clearance. Blood was obtained for PRA and aldosterone. Cardiac function was assessed by echo. Genomewide microarray analysis was performed on kidney cortex (KC) and medulla (KM) (Affymetrix). EF decreased after MI (S:63±2, MI:43±6%, p<0.01) and LVEDd increased. PRA, aldosterone and blood pressure (BP) did not change. There was no HF as Na and water excretion was maintained. GFR tended to decrease. Pic Red staining in the KC and KM after MI showed greater fibrosis (KC S:1±0.2, MI:3±0.6%, p<0.001 and KM S:1±0.2, MI:19±6%, p<0.005). Microarray analysis showed that 303 genes changed in KM and 407 genes in KC after MI (1.5 fold, P<0.05) related to structure morphogenesis and metabolic processes(Z value>2). We conclude that experimental MI results in renal structural remodeling characterized by cortical and medullary fibrosis with a mild reduction in GFR and extensive modulation of molecular pathways related to renal growth and morphogenesis underscoring a heart‐kidney connection after MI.

Despite optimal current therapies, cardiovascular disease remains the leading cause for death worldwide. Importantly, advances in peptide engineering have accelerated the development of innovative therapeutics for diverse human disease states. Additionally, the advancement of bispecific therapeutics targeting >1 signaling pathway represents a highly innovative strategy for the treatment of cardiovascular disease. We, therefore, engineered a novel, designer peptide, which simultaneously targets the pGC-A (particulate guanylyl cyclase A) receptor and the MasR (Mas receptor), potentially representing an attractive cardiorenoprotective therapeutic for cardiovascular disease. We engineered a novel, bispecific receptor activator, NPA7, that represents the fusion of a 22-amino acid sequence of BNP (B-type natriuretic peptide; an endogenous ligand of pGC-A) with Ang 1–7 (angiotensin 1–7)—the 7-amino acid endogenous activator of MasR. We assessed NPA7’s dual receptor activating actions in vitro (second messenger production and receptor interaction). Further, we performed an intravenous peptide infusion comparison study in normal canines to study its biological actions in vivo, including in the presence of an MasR antagonist. Our in vivo and in vitro studies demonstrate the successful synthesis of NPA7 as a bispecific receptor activator targeting pGC-A and MasR. In normal canines, NPA7 possesses enhanced natriuretic, diuretic, systemic, and renal vasorelaxing and cardiac unloading properties. Importantly, NPA7’s actions are superior to that of the individual native pGC-A or MasR ligands. These studies advance NPA7 as a novel, bispecific designer peptide with potential cardiorenal therapeutic benefit for the treatment of cardiovascular disease, such as hypertension and heart failure.