One of the major manifestations of obesity is increased production of the adipocyte-derived 16-kDa peptide leptin, which is also elevated in heart disease, including congestive heart failure. However, whether leptin can directly alter the cardiac phenotype is not known. We therefore studied the effect of leptin as a potential hypertrophic factor in cultured myocytes from 1-to 4-day-old neonatal rat heart ventricles. Using RT-PCR, we demonstrate that these cells express the short-form (OB-Ra) leptin receptor. Twenty-four hours of exposure to leptin (0.31 to 31.3 nmol/L) produces a significantly increased cell surface area that peaked at 0.63 nmol/L. Subsequent experiments were done with 3.1 nmol/L leptin, which significantly increased cell area by 42%, protein synthesis by 32%, and ␣-skeletal actin and myosin light chain-2 expression by 250% and 300%, respectively. These events occurred in the absence of any increased cell death. Hypertrophy was preceded by rapid activation of the mitogen-activated protein kinase system including p38 and p44/42 as early as 5 minutes after leptin addition, whereas hypertrophy was inhibited by the p38 inhibitor SB203580 but not by the p44/42 inhibitor PD98059. Our results demonstrate a direct hypertrophic effect of leptin and may offer a biological link between hypertrophy and hyperleptinemic conditions such as obesity.O besity is associated with increased production of leptin, a 16-kDa peptide that is a product of the obesity gene (ob) and produced primarily by adipocytes. 1 The effects of leptin are mediated by distinct receptors (OB-R) belonging to the class I cytokine receptor family. It has been suggested that leptin may contribute to cardiovascular disease, independently of obesity such as in hypertension, 2 where elevated levels of the peptide could be a contributing factor due to its ability to stimulate the sympathetic nervous system. 3 Recent clinical evidence has implicated leptin as a potential independent risk factor for coronary heart disease, 4 and increased plasma leptin levels have been found in patients with congestive heart failure. 5 Heart failure is generally preceded by myocardial remodeling, involving cardiomyocyte hypertrophy and other maladaptive responses, 6 although whether leptin contributes to these events has not been studied. Accordingly, we examined leptin's effects in cultured cardiomyocytes and sought to identify potential mechanisms underlying these effects. Materials and MethodsExperiments were done on primary cultures of rat neonatal cardiomyocytes exposed to leptin for 24 hours in the absence or presence of mitogen-activated protein kinase (MAPK) inhibitors. Hypertrophy was determined by measuring cell area, leucine incorporation, and gene expression of molecular markers. Cell viability was determined by vital staining and MAPK activation with Western blotting.An expanded Materials and Methods section can be found in the online data supplement available at http://www.circresaha.org. ResultsThe leptin receptors are generally classified into two...

Background-Probiotics are extensively used to promote gastrointestinal health, and emerging evidence suggests that their beneficial properties can extend beyond the local environment of the gut. Here, we determined whether oral probiotic administration can alter the progression of postinfarction heart failure. Methods and Results-Rats were subjected to 6 weeks of sustained coronary artery occlusion and administered the probiotic Lactobacillus rhamnosus GR-1 or placebo in the drinking water ad libitum. Culture and 16s rRNA sequencing showed no evidence of GR-1 colonization or a significant shift in the composition of the cecal microbiome. However, animals administered GR-1 exhibited a significant attenuation of left ventricular hypertrophy based on tissue weight assessment and gene expression of atrial natriuretic peptide. Moreover, these animals demonstrated improved hemodynamic parameters reflecting both improved systolic and diastolic left ventricular function. Serial echocardiography revealed significantly improved left ventricular parameters throughout the 6-week follow-up period including a marked preservation of left ventricular ejection fraction and fractional shortening. Beneficial effects of GR-1 were still evident in those animals in which GR-1 was withdrawn at 4 weeks, suggesting persistence of the GR-1 effects after cessation of therapy. Investigation of mechanisms showed a significant increase in the leptin:adiponectin plasma concentration ratio in rats subjected to coronary ligation, which was abrogated by GR-1. Metabonomic analysis showed differences between sham control and coronary artery ligated hearts particularly with respect to preservation of myocardial taurine levels. Conclusions-The study suggests that probiotics offer promise as a potential therapy for the attenuation of heart failure.(Circ Heart Fail. 2014;7:491-499.)

Sodium/hydrogen exchange (NHE) inhibitors show promise as potential therapeutic agents for the treatment of heart failure, but it is not known whether they can reverse the maladaptive remodeling that results in heart failure. We sought to determine the effect of the NHE-1-specific inhibitor EMD-87580 (EMD) on heart failure produced by myocardial infarction in the rat and to assess whether up to 4 wk of treatment delay results in beneficial effects. Male Sprague-Dawley rats were subjected to coronary artery ligation (or a sham procedure) and followed for up to 3 mo, at which time hypertrophy and hemodynamics were determined. EMD was provided in the diet, and treatment commenced immediately or 2-4 wk after ligation. EMD significantly reduced hemodynamic abnormalities, including the elevation in left ventricular end-diastolic pressure, and diminished the loss of systolic function with all treatment protocols. Left ventricular dilatation and hypertrophy, as assessed by heart weight, cell size, and atrial natriuretic peptide (ANP) expression, were similarly reversed to sham or near-sham levels. In addition, the increased plasma ANP and pro-ANP values were reversed to levels not significantly different from sham. Surprisingly, virtually all beneficial effects were identical with all treatment protocols. These effects were observed in the absence of infarct size reduction or blood pressure-lowering effects. Our results suggest that NHE-1 inhibition attenuates and reverses postinfarction remodeling and heart failure with a treatment delay of up to 4 wk after infarction. The effect is independent of infarct size or afterload reduction, indicating a direct effect on the myocardium.

Abstract-We determined the effect of 24-hour aldosterone (100 nmol/L) treatment on hypertrophic responses in rat neonatal ventricular myocytes and the possible role of Na ϩ -H ϩ exchange isoform 1 (NHE-1). Aldosterone significantly increased cell size by 61% and expression of atrial natriuretic peptide by 2-fold. NHE-1 mRNA expression and protein abundance were significantly increased, and intracellular Na ϩ levels were elevated. Both hypertrophy and elevated Na ϩ levels were prevented by the NHE-1-specific inhibitor EMD87580 as well as the aldosterone antagonist spironolactone, although the increased NHE-1 levels were prevented only by spironolactone. Aldosterone transiently (within 5 minutes) stimulated p44/42 phosphorylation, which decreased thereafter for the remaining 24 hours, whereas p38 phosphorylation was reduced. Neither a p38 nor a p44/42 inhibitor had any effect on aldosterone-induced hypertrophy or NHE-1 regulation. Our results therefore demonstrate a direct hypertrophic effect of aldosterone on cultured myocytes, which is dependent on NHE-1 activity. (Hypertension. 2003;42:1171-1176.)Key Words: aldosterone Ⅲ sodium-proton exchange Ⅲ kinase Ⅲ rats Ⅲ hypertrophy, cardiac Ⅲ myocytes C ardiac hypertrophy represents a major component of myocardial remodeling contributing to heart failure. 1 Hypertrophy is mediated by endocrine, paracrine, and autocrine growth factors acting via complex cell-signaling processes. 2,3 Aldosterone might contribute to heart failure independently of its renal effects (reviewed in Slight et al 4 ). Aldosterone is produced in cardiac tissue, and aldosterone receptors have been identified in the cardiac cell. 5,6 The aldosterone antagonist spironolactone has been shown to reduce mortality in patients with severe heart failure, although the precise mechanism is unknown. 7 Aldosterone infusion into uninephrectomized rats produces cardiac hypertrophy, which is attenuated by the angiotensin II type 1 receptor antagonist losartan as well by 2 calcineurin inhibitors. 8 Moreover, aldosterone failed to directly produce hypertrophy in cultured neonatal rat ventricular myocytes, although a synergistic hypertrophic effect with endothelin-1 was reported. 9 The preceding 2 studies suggest an indirect cardiac hypertrophic influence of aldosterone. However, in view of the demonstration of cardiac aldosterone receptors, 5,6 we hypothesized that direct aldosterone receptor-mediated actions on the cardiac cell could be predicted and therefore, determined whether it exerts direct hypertrophic effects. We focused on the potential role of the Na ϩ -H ϩ exchanger isoform 1 (NHE-1) in this response, because inhibition of the antiporter has been shown to attenuate myocardial hypertrophy and heart failure. 10 -13 Moreover, aldosterone activates NHE-1, including that in cardiac cells, 14,15 although with respect to the latter, this occurred only after 9 days of treatment. 15 Patients with primary aldosteronism have increased erythrocyte NHE activity. 16 In the present study, we examined the direct e...