Search

Aims Chronic heart failure is becoming increasingly prevalent and is still associated with a high mortality rate. Myocardial hypertrophy and fibrosis drive cardiac remodelling and heart failure, but they are not sufficiently inhibited by current treatment strategies. Furthermore, despite increasing knowledge on cardiomyocyte intracellular signalling proteins inducing pathological hypertrophy, therapeutic approaches to target these molecules are currently unavailable. In this study, we aimed to establish and test a therapeutic tool to counteract the 22 kDa calcium and integrin binding protein (CIB) 1, which we have previously identified as nodal regulator of pathological cardiac hypertrophy and as activator of the maladaptive calcineurin/NFAT axis. Methods and results Among three different sequences, we selected a shRNA construct (shCIB1) to specifically down-regulate CIB1 by 50% upon adenoviral overexpression in neonatal rat cardiomyocytes (NRCM), and upon overexpression by an adeno-associated-virus (AAV) 9 vector in mouse hearts. Overexpression of shCIB1 in NRCM markedly reduced cellular growth, improved contractility of bioartificial cardiac tissue and reduced calcineurin/NFAT activation in response to hypertrophic stimulation. In mice, administration of AAV-shCIB1 strongly ameliorated eccentric cardiac hypertrophy and cardiac dysfunction during 2 weeks of pressure overload by transverse aortic constriction (TAC). Ultrastructural and molecular analyses revealed markedly reduced myocardial fibrosis, inhibition of hypertrophy associated gene expression and calcineurin/NFAT as well as ERK MAP kinase activation after TAC in AAV-shCIB1 vs. AAV-shControl treated mice. During long-term exposure to pressure overload for 10 weeks, AAV-shCIB1 treatment maintained its anti-hypertrophic and anti-fibrotic effects, but cardiac function was no longer improved vs. AAV-shControl treatment, most likely resulting from a reduction in myocardial angiogenesis upon downregulation of CIB1. Conclusions Inhibition of CIB1 by a shRNA-mediated gene therapy potently inhibits pathological cardiac hypertrophy and fibrosis during pressure overload. While cardiac function is initially improved by shCIB1, this cannot be kept up during persisting overload. [ABSTRACT FROM AUTHOR]

Pathological cardiac overload induces myocardial protein synthesis and hypertrophy, which predisposes to heart failure. To inhibit hypertrophy therapeutically, the identification of negative regulators of cardiomyocyte protein synthesis is needed. Here, we identified the tumor suppressor protein TIP30 as novel inhibitor of cardiac hypertrophy and dysfunction. Reduced TIP30 levels in mice entailed exaggerated cardiac growth during experimental pressure overload, which was associated with cardiomyocyte cellular hypertrophy, increased myocardial protein synthesis, reduced capillary density, and left ventricular dysfunction. Pharmacological inhibition of protein synthesis improved these defects. Our results are relevant for human disease, since we found diminished cardiac TIP30 levels in samples from patients suffering from end‐stage heart failure or hypertrophic cardiomyopathy. Importantly, therapeutic overexpression of TIP30 in mouse hearts inhibited cardiac hypertrophy and improved left ventricular function during pressure overload and in cardiomyopathic mdx mice. Mechanistically, we identified a previously unknown anti‐hypertrophic mechanism, whereby TIP30 binds the eukaryotic elongation factor 1A (eEF1A) to prevent the interaction with its essential co‐factor eEF1B2 and translational elongation. Therefore, TIP30 could be a therapeutic target to counteract cardiac hypertrophy. Synopsis: How overshooting protein synthesis and growth are prevented in the heart during pathological overload or in cardiomyopathy is not known. The tumor suppressor protein TIP30 is shown here to act as an endogenous brake on cardiac hypertrophy by inhibiting translational elongation. TIP30 binds the eukaryotic elongation factor (eEF1A), thereby interfering with binding of the guanine exchange factor eEF1B and inhibiting reconstitution of inactive into active, GTP‐bound eEF1A.Endogenous TIP30 levels are downregulated in the myocardium of patients suffering from hypertrophic cardiomyopathy or end‐stage heart failure, while the levels of eEF1A remain unchanged.Reduced myocardial TIP30 with unchanged eEF1A levels in mice lead to exaggerated cardiac protein synthesis and growth as well as cardiac dysfunction during pathological overload.Exaggerated cardiac growth in mice with reduced TIP30 levels is normalized by pharmacological inhibition of eEF1A as well as by cardiomyocyte specific expression of TIP30.Overexpression of TIP30 effectively inhibits pathological cardiac hypertrophy and dysfunction during pathological overload or in cardiomyopathy. [ABSTRACT FROM AUTHOR]

Introduction: Cardiac cachexia is a strong independent risk factor for mortality in patients with chronic heart failure. However, the mechanism how skeletal muscle wasting adversely affects the course of heart failure during cardiac cachexia remains elusive. Here, we aim to determine whether skeletal muscle derived myokines are involved and whether they might be a therapeutic target to treat aggravated heart failure associated with cachexia. Methods Results: Transaortic constriction (TAC) for 12 weeks was used to induce severe long-term pressure overload and transition to heart failure with cardiac cachexia in C57/Bl6J mice. By RNAseq from quadriceps femoris muscle of cachectic mice, we identified a strongly reduced expression of Ostn , encoding the skeletal muscle derived and secreted protein musclin, which has been implicated in the control of natriuretic peptide (NP) signaling through binding to the NP clearance receptor Npr3. Compared to wild-type mice, skeletal muscle-restricted and tetracycline-inducible Ostn knock-out mice (Ostn flflHSA-rtTA/TRE-Cre) exhibited a marked deterioration of cardiac function and aggravated cardiac fibrosis after TAC. In turn, AAV6-mediated musclin overexpression in the quadriceps muscle and therefore restoration of musclin levels during wasting, ameliorated myocardial fibrotic remodeling, pulmonary congestion and LV-dysfunction compared to AAV6-control treated mice 12 weeks after TAC. Mechanistically, musclin enhanced C-type natriuretic peptide (CNP)- augmented contractility via a cGMP mediated inhibition of phosphodiesterase 3 (PDE3) and a subsequent rise in cAMP in isolated cardiomyocytes. Strikingly, the cardioprotective effects of musclin were blunted by administration of a selective Npr3 inhibitor, indicating that musclin mediates its effects at least in part via Npr3. Conclusions: Our data show that skeletal muscle-secreted musclin potently attenuates LV dysfunction following pressure overload through enhancement of CNP-cGMP-PDE3 dependent augmentation of cAMP signaling in the heart. Inter-tissue communication via AVV6-mediated overexpression of the myokine musclin could be a promising therapeutic strategy for treating heart failure progression during cardiac cachexia. [ABSTRACT FROM AUTHOR]

Perturbed vitamin-A metabolism is associated with type 2 diabetes and mitochondrial dysfunction that are pathophysiologically linked to the development of diabetic cardiomyopathy (DCM). However, the mechanism, by which vitamin A might regulate mitochondrial energetics in DCM has previously not been explored. To test the hypothesis that vitamin-A deficiency accelerates the onset of cardiomyopathy in diet-induced obesity (DIO), we subjected mice with lecithin retinol acyltransferase (Lrat) germline deletion, which exhibit impaired vitamin-A stores, to vitamin A-deficient high-fat diet (HFD) feeding. Wild-type mice fed with a vitamin A-sufficient HFD served as controls. Cardiac structure, contractile function, and mitochondrial respiratory capacity were preserved despite vitamin-A deficiency following 20 wk of HFD feeding. Gene profiling by RNA sequencing revealed that vitamin A is required for the expression of genes involved in cardiac fatty acid oxidation, glycolysis, tricarboxylic acid cycle, and mitochondrial oxidative phosphorylation in DIO as expression of these genes was relatively preserved under vitamin A-sufficient HFD conditions. Together, these data identify a transcriptional program, by which vitamin A preserves cardiac energetic gene expression in DIO that might attenuate subsequent onset of mitochondrial and contractile dysfunction. NEW & NOTEWORTHY The relationship between vitamin-A status and the pathogenesis of diabetic cardiomyopathy has not been studied in detail. We assessed cardiac mitochondrial respiratory capacity, contractile function, and gene expression by RNA sequencing in a murine model of combined vitamin-A deficiency and diet-induced obesity. Our study identifies a role for vitamin A in preserving cardiac energetic gene expression that might attenuate subsequent development of mitochondrial and contractile dysfunction in diet-induced obesity.