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Abstract-Chronic elevation of plasma aldosterone contributes to heart failure. Mineralocorticoid receptor (MR) antagonism is cardioprotective in such a setting, but whether such protection occurs in the presence of low-aldosterone concentrations remains unclear. We investigated whether MR blockade attenuates cardiac hypertrophy and failure in rats with salt-sensitive hypertension. Dahl salt-sensitive (DS) rats fed a high-salt diet from 7 weeks develop concentric left ventricular (LV) hypertrophy secondary to hypertension at 12 weeks followed by heart failure at 19 weeks (DS-CHF).DS rats on such a diet were treated with a non-antihypertensive dose of the selective MR antagonist eplerenone from 12 to 19 weeks. Renin activity and aldosterone concentration in plasma were decreased in DS-CHF rats compared with controls. LV hypertrophy and fibrosis, as well as macrophage infiltration around coronary vessels, were apparent in DS-CHF rats. The amounts of mRNAs for 11␤-hydroxysteroid dehydrogenase type 1, MR, monocyte chemoattractant protein 1, and osteopontin were increased in these hearts. Treatment of DS-CHF rats with eplerenone inhibited these changes in gene expression, as well as coronary vascular inflammation and heart failure. Eplerenone attenuated both the decrease in the ratio of reduced to oxidized glutathione and the increase in NADPH oxidase activity apparent in DS-CHF rat hearts. MR blockade with eplerenone thus resulted in attenuation of LV hypertrophy and failure, without an antihypertensive effect, in rats with low-aldosterone hypertension.

Background— Mineralocorticoid receptor antagonism reduces mortality associated with heart failure by mechanisms that remain unclear. The effects of the mineralocorticoid receptor antagonist spironolactone on left ventricular (LV) function and chamber stiffness associated with myocardial fibrosis were investigated in mildly symptomatic patients with idiopathic dilated cardiomyopathy (DCM). Methods and Results— Twenty-five DCM patients with a New York Heart Association functional class of I or II were examined before and after treatment with spironolactone for 12 months. LV pressures and volumes were measured simultaneously, and LV endomyocardial biopsy specimens were obtained. Serum concentrations of the carboxyl-terminal propeptide (PIP) and carboxyl-terminal telopeptide (CITP) of collagen type I were measured. The patients were divided into 2 groups on the basis of the serum PIP/CITP ratio (≤35, group A, n=12; >35, group B, n=13), an index of myocardial collagen accumulation. LV diastolic chamber stiffness, the collagen volume fraction, and abundance of collagen type I and III mRNAs in biopsy tissue were greater and the LV early diastolic strain rate (tissue Doppler echocardiography) was smaller in group B than in group A at baseline. These differences and the difference in PIP/CITP were greatly reduced after treatment of patients in group B with spironolactone, with treatment having no effect on these parameters in group A. The collagen volume fraction was significantly correlated with PIP/CITP, LV early diastolic strain rate, and LV diastolic chamber stiffness for all patients before and after treatment with spironolactone. Conclusions— Spironolactone ameliorated LV diastolic dysfunction and reduced chamber stiffness in association with regression of myocardial fibrosis in mildly symptomatic patients with DCM. These effects appeared limited, however, to patients with increased myocardial collagen accumulation.