Mechanisms of Malnutrition in Cirrhosis with Portosystemic Shunting

肝硬化门体分流导致营养不良的机制

• 批准号: 8322007
• 负责人: Srinivasan Dasarathy
• 金额: $ 33.97万
• 依托单位: CLEVELAND CLINIC LERNER COM-CWRU
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-20 至 2016-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8322007
• 关键词: 70-kDa Ribosomal Protein S6 Kinases; Activin Receptor; Affect; Ammonia; Animal Model; Binding; Binding Sites; Cell Culture System; Cell Culture Techniques; Cell physiology; Cells; Cessation of life; Chemicals; Cirrhosis; Clinical; Complication; Data; Development; Drug Metabolic Detoxication; Follistatin; Foundations; Goals; Hepatic; Hyperammonemia; In Vitro; Inflammatory; Intervention; Knockout Mice; Liver; Liver diseases; Malnutrition; Mediating; Methodology; Methods; Modeling; Molecular; Morbidity - disease rate; Mus; Muscle; Muscle Cells; Muscle Proteins; Myoblasts; NF-kappa B; Nuclear; Nuclear Translocation; Outcome; Pathway interactions; Patients; Phosphorylation; Plasma; Process; Protein Biosynthesis; Proteins; Rattus; Regulation; Reporting; Signal Pathway; Signal Transduction; Signaling Molecule; Skeletal Muscle; Small Interfering RNA; Somatotropin; Staging; Surgical Portosystemic Shunt; System; TGF-beta type I receptor; Testing; Testosterone; Therapeutic Intervention; Time; Translating; Translations; United States; Up-Regulation; Work; abstracting; adenylate kinase; ammonium acetate; base; chemical genetics; clinical application; cytokine; deletion analysis; effective therapy; human FRAP1 protein; in vivo; innovation; kinase inhibitor; liver transplantation; mortality; muscle form; myostatin; novel; p65; promoter; response; sarcopenia; satellite cell; sensor; success; therapeutic target

DESCRIPTION (provided by applicant): Abstract End stage cirrhosis and its complications result in 27,000 deaths and 6,500 liver transplants annually in the United States. Reduced skeletal muscle mass or sarcopenia is one of the major complications of portosystemic shunting (PSS) that accompanies cirrhosis. Sarcopenia contributes significantly to the morbidity and mortality of these patients. There are no effective treatment options since the underlying mechanisms are currently unknown and most studies to date have been descriptive. Patients with cirrhosis and PSS as well as animal models have reduced muscle protein synthesis but the molecular mechanisms regulating this process are currently not known. Hyperammonemia is a consistent abnormality in cirrhosis and PSS due to impaired hepatic detoxification of ammonia. Our preliminary data in animal models of hyperammonemia and in muscle cell cultures exposed to ammonia showed an increased expression of myostatin. Myostatin inhibits skeletal muscle protein synthesis and results in lower muscle mass. The mechanism of increased myostatin induced by ammonia is not known. Our preliminary studies have demonstrated NFkB binding sites on the myostatin promoter and NFkB may be an upstream regulator of myostatin during hyperammonemia. In our preliminary studies in myoblast cells, NFkB was increased in response to ammonia and preceded the elevated expression of myostatin. Finally, in both our in vivo studies in PCA rat as well as cell cultures, we observed greater activation of a cellular energy sensor, AMP kinase when myostatin expression was elevated and these alterations were reversed by blocking myostatin in vivo. We therefore hypothesized that hyperammonemia induced increased expression of myostatin inhibits muscle protein synthesis and muscle mass constituting a liver muscle axis. To identify the underlying molecular mechanisms responsible for the reduced muscle protein synthesis with PSS we propose the following aims: 1) Establish that ammonia induced myostatin expression constitutes a liver-muscle axis in vivo, 2) Demonstrate that the mechanism of hyperammonemia mediated upregulation of myostatin expression is NFkB dependent and 3) Establish that the regulation of mTOR by myostatin is independent of Akt and is mediated by AMP kinase in hyperammonemia. Pharmacological, chemical and genetic approaches in animal models and cell culture systems will be used in these studies. The proposed studies are innovative because they will demonstrate the mechanism by which hyperammonemia inhibits muscle protein synthesis and identify a novel regulatory crosstalk between myostatin and mTOR, a critical signaling molecule that regulates protein synthesis. These studies are very significant because they will lay the foundation for understanding the mechanisms of sarcopenia in portosystemic shunting and identify potential therapeutic targets. Furthermore, the results from these studies have the potential to be rapidly translated to clinical application by using pharmacological methods to lower ammonia mediated increased myostatin expression.

在美国，终末期肝硬化及其并发症每年导致27，000例死亡和6，500例肝移植。骨骼肌质量减少或肌肉减少症是伴随肝硬化的门体分流术（PSS）的主要并发症之一。肌肉减少症对这些患者的发病率和死亡率有显著影响。由于目前尚不清楚潜在机制，因此没有有效的治疗方案，迄今为止的大多数研究都是描述性的。肝硬化和PSS患者以及动物模型的肌肉蛋白质合成减少，但调节这一过程的分子机制目前尚不清楚。高氨血症是肝硬化和PSS中由于氨的肝脏解毒受损而导致的一致异常。我们在高氨血症动物模型和暴露于氨的肌细胞培养物中的初步数据显示肌生长抑制素的表达增加。肌生长抑制素抑制骨骼肌蛋白质合成，导致肌肉质量降低。氨诱导的肌生长抑制素增加的机制尚不清楚。我们的初步研究表明，肌生成抑制素启动子上的NFkB结合位点和NFkB可能是高氨血症时肌生成抑制素的上游调节因子。在我们对成肌细胞的初步研究中，NFkB对氨的反应增加，并且先于肌生长抑制素的表达升高。最后，在我们在PCA大鼠以及细胞培养物中的体内研究中，我们观察到当肌生长抑制素表达升高时细胞能量传感器AMP激酶的更大激活，并且这些改变通过在体内阻断肌生长抑制素而逆转。因此，我们假设高氨血症诱导的肌生长抑制素表达增加抑制肌肉蛋白质合成和肌肉质量构成的肝肌肉轴。为了确定PSS降低肌肉蛋白质合成的潜在分子机制，我们提出了以下目标：1）确定氨诱导的肌生长抑制素表达在体内构成肝-肌轴，2）证明高氨血症介导的肌生长抑制素表达上调的机制是NFkB依赖性的，以及3）确定肌生长抑制素对mTOR的调节不依赖于Akt，并且在高氨血症中由AMP激酶介导。这些研究将采用动物模型和细胞培养系统中的药理学、化学和遗传学方法。拟议的研究是创新的，因为它们将证明高氨血症抑制肌肉蛋白质合成的机制，并确定肌肉生长抑制素和mTOR之间的一种新的调节串扰，mTOR是一种调节蛋白质合成的关键信号分子。这些研究将为了解门体分流术中肌肉减少症的发生机制和确定潜在的治疗靶点奠定基础，具有重要意义。此外，这些研究的结果有可能通过使用药理学方法来降低氨介导的肌生长抑制素表达增加而迅速转化为临床应用。