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    Abstract:
    Metabolic remodeling is an integral part of heart failure. Current studies are largely focusing on glucose and fatty acid metabolism, while little is known about the changes in amino acid homeostasis during heart failing process. Branched chain amino acids (BCAAs), including leucine, isoleucine, and valine, serve as not only essential building blocks for protein synthesis, but also important energy source and signaling molecules that have significant effects on cell growth and function. In this study, we demonstrated that the BCAA catabolic intermediate branched-chain keto acid (BCKA) accumulated in both mouse and human failing heart. BCAA catabolic genes were selectively and significantly down-regulated at both mRNA and protein levels in failing heart in mice, mimicking a similar expression pattern observed in neonatal heart. Using both in vitro and in vivo models, we established that BCAA catabolic genes were regulated by Krüppel-like factor 15 (KLF15), a key transcriptional regulator for glucose, fat, and amino acid nutrient homeostasis, suggesting that the KLF15-mediated BCAA catabolic regulation is part of the metabolic remodeling during heart failure. Genetic ablation of PP2Cm, a key regulator of BCAA catabolism, led to a significant impairment of BCAA catabolic activities and accumulation of BCKA in cardiac tissue. Importantly, PP2Cm deficiency accelerated heart failure under pressure overload. PP2Cm deficiency or elevated BCKA induced oxidative stress in cardiomyocytes and impairment of oxygen consumption and ATP production of mitochondria. Antioxidant treatment ameliorated the heart failure progression in PP2Cm deficient animals. Taken together, our data established for the first time that BCAA catabolic reprogramming is an integral component of metabolic remodeling during heart failure, and this remodeling can significantly contribute to heart failure progression.
    Keywords:
    Catabolism
    Branched-chain amino acid
    Homeostasis
    Energy homeostasis
    Metabolic remodeling is an integral part of heart failure. Current studies are largely focusing on glucose and fatty acid metabolism, while little is known about the changes in amino acid homeostasis during heart failing process. Branched chain amino acids (BCAAs), including leucine, isoleucine, and valine, serve as not only essential building blocks for protein synthesis, but also important energy source and signaling molecules that have significant effects on cell growth and function. In this study, we demonstrated that the BCAA catabolic intermediate branched-chain keto acid (BCKA) accumulated in both mouse and human failing heart. BCAA catabolic genes were selectively and significantly down-regulated at both mRNA and protein levels in failing heart in mice, mimicking a similar expression pattern observed in neonatal heart. Using both in vitro and in vivo models, we established that BCAA catabolic genes were regulated by Krüppel-like factor 15 (KLF15), a key transcriptional regulator for glucose, fat, and amino acid nutrient homeostasis, suggesting that the KLF15-mediated BCAA catabolic regulation is part of the metabolic remodeling during heart failure. Genetic ablation of PP2Cm, a key regulator of BCAA catabolism, led to a significant impairment of BCAA catabolic activities and accumulation of BCKA in cardiac tissue. Importantly, PP2Cm deficiency accelerated heart failure under pressure overload. PP2Cm deficiency or elevated BCKA induced oxidative stress in cardiomyocytes and impairment of oxygen consumption and ATP production of mitochondria. Antioxidant treatment ameliorated the heart failure progression in PP2Cm deficient animals. Taken together, our data established for the first time that BCAA catabolic reprogramming is an integral component of metabolic remodeling during heart failure, and this remodeling can significantly contribute to heart failure progression.
    Catabolism
    Branched-chain amino acid
    Homeostasis
    Energy homeostasis
    Significant evidence of the pharmacological and physiological effects of branched-chain amino acids (BCAA) has accumulated, attracting the interest of not only clinicians but also basic medical researchers. We summarize here the characteristic features of BCAA catabolism, focusing on the initial two enzymes in the pathway, branched-chain aminotransferase and branched-chain alpha-keto acid dehydrogenase complex. In addition, we describe a unique characteristic of the valine catabolic pathway. Finally, we present evidence obtained in animal studies that indicates that BCAA treatment may be appropriate for liver cirrhosis, but not acute liver failure.
    Chain (unit)
    Branched-chain amino acid
    In Brief Insulin-resistant or obese individuals have increased serum branched-chain amino acid (BCAA) levels. Recent findings relate increased BCAA catabolism to increased fatty acid oxidation and better metabolic health in physically active individuals. We hypothesize that, via glyceroneogenesis, BCAA catabolism mediates increased constitutive use of fatty acids for β-oxidation in subjects with increased inherent or acquired aerobic capacity both during exercise and at rest. This article presents the hypothesis that skeletal muscle BCAA catabolism mediates increased constitutive use of fatty acids for β-oxidation.
    Catabolism
    Branched-chain amino acid
    The hypothalamus is critical for the regulation of energy homeostasis. Genetic and pharmacologic studies have identified a number of key hypothalamic neuronal circuits that integrate signals controlling food intake and energy expenditure. Recently studies have begun to emerge demonstrating a role for non-neuronal cell types in the regulation of energy homeostasis. In particular the potential importance of different glial cell types is increasingly being recognized. A number of studies have described changes in the activity of hypothalamic macroglia (principally astrocytes and tanycytes) in response to states of positive and negative energy balance, such as obesity and fasting. This article will review these studies and discuss how these findings are changing our understanding of the cellular mechanisms by which energy homeostasis is regulated.
    Energy homeostasis
    Homeostasis
    Citations (14)