Heart failure-induced diaphragm myopathy.

BACKGROUND: Intracellular signaling pathways involved in skeletal myosin heavy chain (MyHC) isoform alterations during heart failure (HF) are not completely understood. We tested the hypothesis that diaphragm expression of mitogen-activated protein kinases (MAPK) and myogenic regulatory factors is changed in rats with myocardial infarction (MI) induced HF. METHODS: Six months after MI rats were subjected to transthoracic echocardiography. After euthanasia, infarcted rats were subdivided in MI/HF- group (with no HF evidence; n=10), and MI/HF+ (with right ventricular hypertrophy and lung congestion; n=10). Sham-operated rats were used as controls (n=10). MyHC isoforms were analyzed by electrophoresis. STATISTICAL ANALYSIS: ANOVA and Pearson correlation. RESULTS: MI/HF- had left cardiac chambers dilation with systolic and diastolic left ventricular dysfunction. Cardiac injury was more intense in MI/HF+ than MI/HF-. MyHC I isoform percentage was higher in MI/HF+ than MI/HF-, and IIb isoform lower in MI/HF+ than Sham. Left atrial diameter-to-body weight ratio positively correlated with MyHC I (p=0.005) and negatively correlated with MyHC IIb (p=0.02). TNF-α serum concentration positively correlated with MyHC I isoform. Total and phosphorylated ERK was lower in MI/HF- and MI/HF+ than Sham. Phosphorylated JNK was lower in MI/HF- than Sham. JNK and p38 did not differ between groups. Expression of NF-κB and the myogenic regulatory factors MyoD, myogenin, and MRF4 was similar between groups. CONCLUSION: Diaphragm MyHC fast-to-slow shift is related to cardiac dysfunction severity and TNF-α serum levels in infarcted rats. Reduced ERK expression seems to participate in MyHC isoform changes. Myogenic regulatory factors and NF-κB do not modulate diaphragm MyHC distribution during chronic HF.

Diabetes mellitus activates fetal gene program and intensifies cardiac remodeling and oxidative stress in aged spontaneously hypertensive rats.

BACKGROUND: The combination of systemic arterial hypertension and diabetes mellitus (DM) induces greater cardiac remodeling than either condition alone. However, this association has been poorly addressed in senescent rats. Therefore, this study aimed to analyze the influence of streptozotocin-induced DM on ventricular remodeling and oxidative stress in aged spontaneously hypertensive rats (SHR). METHODS: Fifty 18 month old male SHR were divided into two groups: control (SHR, n = 25) and diabetic (SHR-DM, n = 25). DM was induced by streptozotocin (40 mg/kg, i.p.). After nine weeks, the rats underwent echocardiography and myocardial functional study in left ventricular (LV) isolated papillary muscle preparations. LV samples were obtained to measure myocyte diameters, interstitial collagen fraction, and hydroxyproline concentration. Gene expression of atrial natriuretic peptide (ANP) and α- and ß-myosin heavy chain (MyHC) isoforms was evaluated by RT-PCR. Serum oxidative stress was assessed by measuring lipid hydroperoxide concentration and superoxide dismutase and glutathione peroxidase activities. STATISTICS: Student's t test or Mann-Whitney test, p < 0.05. RESULTS: SHR-DM presented higher blood glucose (487 ± 29 vs. 89.1 ± 21.1 mg/dL) and lower body weight (277 ± 26 vs. 339 ± 38 g). Systolic blood pressure did not differ between groups. Echocardiography showed LV and left atrial dilation, LV diastolic and relative wall thickness decrease, and LV systolic and diastolic function impairment in SHR-DM. Papillary muscle study showed decreased myocardial contractility and contractile reserve in SHR-DM. Myocyte diameters and myocardial interstitial collagen fraction and hydroxyproline concentration did not differ between groups. Increased serum pro-oxidant activity and gene expression of ANP and ß/α-MyHC ratio were observed in DM. CONCLUSION: Diabetes mellitus induces cardiac dilation and functional impairment, increases oxidative stress and activates fetal gene program in aged spontaneously hypertensive rats.

Efeitos do bloqueio precoce da aldosterona na estrutura e função cardíaca e na composição da matriz colágena miocárdica de ratos espontaneamente hipertensos / Early blockad effects of aldosterone on cardiac structure and function and composition of collagenase myocardial array of spontaneously hypertensive rats

A hipertensão arterial sistêmica é uma das principais causas de insuficiência cardíaca (IC). Durante o desenvolvimento de hipertrofia miocárdica e a evolução para IC, ocorre ativação dos sistemas nervoso simpático e reninaangiotensina- aldosterona. Estudos clínicos e experimentais mostraram que a aldosterona exerce diversos efeitos deletérios sobre o sistema cardiovascular e que o bloqueio de sua ação melhora a sobrevida e atenua o remodelamento ventricular na IC avançada. Entretanto, poucos estudos avaliaram as consequências de seu bloqueio na hipertensão arterial, antes do surgimento de sinais de IC. Assim, o objetivo deste estudo foi avaliar o efeito da administração precoce de espironolactona sobre variáveis estruturais e funcionais cardíacas de ratos espontaneamente hipertensos (SHR) e, adicionalmente, investigar os componentes responsáveis pela remodelação da matriz extracelular. Ratos SHR com 13 meses de idade foram divididos em dois grupos: um grupo SHR controle (SHR-C, n=20) e outro grupo SHR tratado com espironolactona (20 mg/kg/dia) (SHR-ESP, n=24) por seis meses. Ratos Wistar-Kyoto (WKY-C, n=15) de mesma idade foram utilizados como controle. A pressão arterial sistólica (PAS) foi medida no início e no final do experimento. A avaliação estrutural e funcional in vivo do coração foi realizada por meio de ecocardiograma. A função miocárdica in vitro foi avaliada em preparações de músculo papilar isolado do ventrículo esquerdo (VE). As análises séricas de eletrólitos e creatinina foram realizadas por kits bioquímicos específicos. Para análise de variáveis anatômicas foram medidos os pesos úmidos e secos do VE, ventrículo direito (VD), átrios e amostras de fígado e pulmão...

Hypertension is a leading cause of heart failure (HF). During the development of myocardial hypertrophy and progression to heart failure there is activation of sympathetic nervous and renin-angiotensin-aldosterone systems. Clinical and experimental studies have shown that aldosterone exerts several deleterious effects on cardiovascular system and that blocking its action improves survival and attenuates ventricular remodeling in advanced HF. However, few studies have evaluated the consequences of aldosterone blockade in hypertensive cardiopathy before clinical evidence of HF. The purpose of this study was to evaluate the effects of early spironolactone (SPR) administration on cardiac structure and function in spontaneously hypertensive rats (SHR) and to investigate extracellular matrix remodeling. Forty-four 13 month old SHR were divided into two groups: control SHR (SHR-C, n=20) and SHR treated with SPR 20 mg/kg/day (SHR-SPR, n=24) for six months. Age-matched Wistar- Kyoto rats (WKY-C, n=15) were used as controls. Systolic blood pressure (SBP) was measured at the beginning and end of the experiment. Echocardiogram was performed to evaluate in vivo cardiac structures and left ventricular (LV) function. Myocardial function was analyzed in LV papillary muscle preparations. Serum electrolytes and creatinine levels were determined by specific biochemical kits. Wet and dry weights of LV, right ventricle, atria, and liver and lung samples were measured. LV tissue samples were obtained for histological analysis, determination of hydroxyproline and total and soluble collagen concentration, and evaluation of types I and III collagen, and lysyl oxidase gene and protein expressions...

Miostatina e redução da massa muscular em doenças crônicas / Myostatin and muscle mass in chronic diseases

JUSTIFICATIVA E OBJETIVOS: A miostatina, também conhecida como fator de crescimento e diferenciação-8 (GDF-8), regula o crescimento de músculos esqueléticos durante o desenvolvimento embrionário e na vida adulta. Foi descoberta em pesquisas para identificar novos membros da superfamília fator transformador do crescimento-Beta (TGF-Beta) de fatores de diferenciação e crescimento celular. Os objetivos deste estudo consistiram em descrever o histórico e as características da miostatina, resumo de estudos sobre mecanismo de ação em condições fisiológicas e patológicas, por meio de estudos em humanos e modelos experimentais em animais, bem como as perspectivas futuras de utilização terapêutica de antagonistas da miostatina. CONTEÚDO: Estudos sobre os efeitos da miostatina mostraram correlação negativa entre sua expressão e massa muscular, sugerindo que possa estar envolvida na indução de hipotrofia e inibição do crescimento da musculatura esquelética. O mecanismo de ação da miostatina também foi avaliado, experimentalmente, em várias doenças como insuficiência cardíaca, neoplasias, cirrose, distrofias musculares, uremia e denervação. Os resultados sugerem que amiostatina exerce ações relevantes na redução da musculatura esquelética associada a estas condições. Também em humanos, os estudos realizados com indivíduos saudáveis e em pacientes com doenças crônicas reforçam este conceito. Entre as perspectivas para o futuro, ainda em fase de investigação experimental, há possibilidades terapêuticas que permitam antagonizar a ação da miostatina e reverter ou impedir a perda de massa muscular associada a doenças crônicas. Entre elas incluem-se anticorpos monoclonais anti-miostatina, propeptídeo da miostatina resistente à clivagem, forma solúvel do receptor activina tipo IIB e folistatina...

BACKGROUND AND OBJECTIVES: Myostatin, or GDF-8 (growth and differentiation factor-8), regulates muscle growth during development and adult life. Myostatin was originally identified in a screen for novel members of the transforming growth factor-Beta (TGF-Beta) superfamily of growth and differentiation factors. In this short review we describe myostatin characteristics, summary of studies on myostatin during physiological and pathological settings in human and experimental animal?s studies and future directions on myostatin antagonism.CONTENTS: Studies about the myostatin effects have shown a negative correlation between myostatin expression and muscle mass suggesting its involvement on muscle growth inhibition and atrophy. Myostatin has also been experimentally evaluated in several diseases such as heart failure, cancer, cirrhosis, muscular dystrophy, uremia, and denervation. The results suggest that myostatin can play an important role on chronic disease-associated skeletal muscle wasting. Although human studies are sparse, evaluation performed in healthy individuals and chronically diseased patients reinforces this hypothesis. Considering future perspectives, there is therapeutic potential to inhibit myostatin activity and treat or prevent muscle loss associated with chronic diseases. This includes myostatin neutralizing antibodies, protease resistant form of the myostatin propeptide, soluble version of the activin RIIB receptor, and follistatin. CONCLUSION: Experimental studies validate myostatin inhibition as a therapeutic approach to muscular dystrophy and chronic disease-associated muscle wasting.