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Does aldosterone upregulate the brain renin-angiotensin system in rats with heart failure?

ABSTRACT: The brain renin-angiotensin system (RAS) contributes to increased sympathetic drive in heart failure (HF). The factors upregulating the brain RAS in HF remain unknown. We hypothesized that aldosterone (ALDO), a downstream product of the systemic RAS that crosses the blood-brain barrier, signals the brain to increase RAS activity in HF. We examined the relationship between circulating and brain ALDO in normal intact rats, in adrenalectomized rats receiving subcutaneous infusions of ALDO, and in rats with ischemia-induced HF and sham-operated controls. Brain ALDO levels were proportional to plasma ALDO levels across the spectrum of rats studied. Compared with sham-operated controls rats, HF rats had higher plasma and hypothalamic tissue levels of ALDO. HF rats also had higher expression of mRNA and protein for angiotensin-converting enzyme and angiotensin type 1 receptors in the hypothalamus, increased reduced nicotinamide-adenine dinucleotide phosphate oxidase activity and superoxide generation in the paraventricular nucleus of the hypothalamus, increased excitation of paraventricular nucleus neurons, and increased plasma norepinephrine. HF rats treated for 4 weeks with intracerebroventricular RU28318 (1 microg/h), a selective mineralocorticoid receptor antagonist, had less hypothalamic angiotensin-converting enzyme and angiotensin type 1 receptor mRNA and protein, less reduced nicotinamide-adenine dinucleotide phosphate-induced superoxide in the paraventricular nucleus, fewer excited paraventricular nucleus neurons, and lower plasma norepinephrine. RU28318 had no effect on plasma ALDO or on angiotensin-converting enzyme or angiotensin type 1 receptor expression in brain cortex. The data demonstrate that ALDO of adrenal origin enters the hypothalamus in direct proportion to plasma levels and suggest that ALDO contributes to the upregulation of hypothalamic RAS activity and sympathetic drive in heart failure.

SUBMITTER: Yu Y

PROVIDER: S-EPMC2790402 | biostudies-literature | 2008 Mar

REPOSITORIES: biostudies-literature

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Does aldosterone upregulate the brain renin-angiotensin system in rats with heart failure?

Yu Yang Y Wei Shun-Guang SG Zhang Zhi-Hua ZH Gomez-Sanchez Elise E Weiss Robert M RM Felder Robert B RB

Hypertension (Dallas, Tex. : 1979) 20080128 3

The brain renin-angiotensin system (RAS) contributes to increased sympathetic drive in heart failure (HF). The factors upregulating the brain RAS in HF remain unknown. We hypothesized that aldosterone (ALDO), a downstream product of the systemic RAS that crosses the blood-brain barrier, signals the brain to increase RAS activity in HF. We examined the relationship between circulating and brain ALDO in normal intact rats, in adrenalectomized rats receiving subcutaneous infusions of ALDO, and in r ...[more]

PMID: 18227408

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Project description:ObjectivesThe purpose of this study was to assess the relationship between biomarkers of renin-angiotensin-aldosterone system (RAAS) activation and decongestion strategies, worsening renal function, and clinical outcomes.BackgroundHigh-dose diuretic therapy in patients with acute heart failure (AHF) is thought to activate the RAAS; and alternative decongestion strategies, such as ultrafiltration (UF), have been proposed to mitigate this RAAS activation.MethodsThis study analyzed 427 AHF patients enrolled in the DOSE-AHF (Diuretic Optimization Strategies in Acute Heart Failure) and CARRESS-HF (Cardiorenal Rescue Study in Acute Decompensated Heart Failure) trials. We assessed the relationship between 2 markers of RAAS activation (plasma renin activity [PRA] and aldosterone) from baseline to 72 h and 96 h and decongestion strategy: high- versus low-dose and continuous infusion versus bolus furosemide for DOSE-AHF and UF versus stepped pharmacologic care for CARRESS-HF. We determined the relationships between RAAS biomarkers and 60-day outcomes.ResultsPatients with greater RAAS activation at baseline had lower blood pressures, lower serum sodium levels, and higher blood urea nitrogen (BUN) concentration. Continuous infusion furosemide and UF were associated with greater PRA increases (median: +1.66 vs. +0.66 ng/ml/h with continuous vs. bolus infusion, respectively, p = 0.021; +4.05 vs. +0.56 ng/ml/h with UF vs. stepped care, respectively, p = 0.014). There were no significant differences in RAAS biomarker changes with high- versus low-dose diuretic therapy (both: p > 0.5). Neither baseline log PRA nor log aldosterone was associated with increased death or HF hospitalization (hazard ratio [HR] for a doubling of 1.05; 95% confidence interval [CI]: 0.98 to 1.13; p = 0.18; and HR: 1.13; 95% CI: 0.99 to 1.28; p = 0.069, respectively). The change in RAAS biomarkers from baseline to 72 and 96 h was not associated with outcomes (both: p > 0.5).ConclusionsHigh-dose loop diuretic therapy did not result in RAAS activation greater than that with low-dose diuretic therapy. UF resulted in greater PRA increase than stepped pharmacologic care. Neither PRA nor aldosterone was significantly associated with short-term outcomes in this cohort. (Determining Optimal Dose and Duration of Diuretic Treatment in People With Acute Heart Failure [DOSE-AHF]; NCT00577135; Effectiveness of Ultrafiltration in Treating People With Acute Decompensated Heart Failure and Cardiorenal Syndrome [CARRESS]; NCT00608491).

Project description:Rationale & objectiveHeart failure treatment relies on loop diuretics to induce natriuresis and decongestion, but the therapy is often limited by diuretic resistance. We explored the association of renin-angiotensin-aldosterone system (RAAS) activation with diuretic response.Study designObservational cohort.Setting & populationEuvolemic ambulatory adults with chronic heart failure were administered torsemide in a monitored environment.PredictorsPlasma total renin, active renin, angiotensinogen, and aldosterone levels. Urine total renin and angiotensinogen levels.OutcomesSodium output per doubling of diuretic dose and fractional excretion of sodium per doubling of diuretic dose.Analytical approachRobust linear regression models estimated the associations of each RAAS intermediate with outcomes.ResultsThe analysis included 56 participants, and the median age was 65 years; 50% were women, and 41% were Black. The median home diuretic dose was 80-mg furosemide equivalents. In unadjusted and multivariable-adjusted models, higher levels of RAAS measures were generally associated with lower diuretic efficiency. Higher plasma total renin remained significantly associated with lower sodium output per doubling of diuretic dose (β = -0.41 [-0.76, -0.059] per SD change) with adjustment; higher plasma total and active renin were significantly associated with lower fractional excretion of sodium per doubling of diuretic dose (β = -0.48 [-0.83, -0.14] and β = -0.51 [-0.95, -0.08], respectively) in adjusted models. Stratification by RAAS inhibitor use did not substantially alter these associations.LimitationsSmall sample size; highly selected participants; associations may not be causal.ConclusionsAmong multiple measures of RAAS activation, higher plasma total and active renin levels were consistently associated with lower diuretic response. These findings highlight the potential drivers of diuretic resistance and underscore the need for high-quality trials of decongestive therapy enhanced by RAAS blockade.

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Does aldosterone upregulate the brain renin-angiotensin system in rats with heart failure?

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Does aldosterone upregulate the brain renin-angiotensin system in rats with heart failure?

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