Control of cAMP Mediated Glucagon Response by Bile Acids

胆汁酸控制 cAMP 介导的胰高血糖素反应

• 批准号: 7867913
• 负责人: Norman H Lee
• 金额: $ 32.92万
• 依托单位: GEORGE WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-01 至 2012-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7867913
• 关键词: 1,2-diacylglycerol; Accounting; Age; Animal Model; Animals; Area; Ascites; Attenuated; Bile Acids; Binding; Calcium; Cartoons; Catalytic Domain; Cause of Death; Cell Nucleus; Cell membrane; Cessation of life; Chenodeoxycholic Acid; Cholestasis; Chronic; Cirrhosis; Common bile duct structure; Complication; Cyclic AMP; Data; Diabetes Mellitus; Diagnosis; Diglycerides; Disease; Docking; Dominant-Negative Mutation; Drug Design; Encephalopathies; Equilibrium; Event; Fatigue; Genomics; Glucagon; Glucagon Receptor; Glucose Intolerance; Hamsters; Hemorrhage; Hepatic; Hepatobiliary; Hepatocyte; Hormonal; Hormones; Human; In Vitro; Incidence; Individual; Inositol; Knowledge; Ligation; Liver; Liver Cirrhosis; Liver Failure; Liver diseases; Malnutrition; Mediating; Modeling; Molecular; Molecular Target; Muscle; National Institute of Diabetes and Digestive and Kidney Diseases; OGTT; Organelles; Patients; Peritonitis; Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositols; Phosphatidylserines; Phosphorylation; Phosphorylation Site; Phosphotransferases; Physiological; Production; Protein Isoforms; Protein Kinase C; Protein Kinase C Inhibitor; Proteins; Proteomics; Receptor Activation; Regulation; Research; Resistance; Role; Severities; Signal Transduction; Site; Specificity; Staging; Testing; United States; aged; attenuation; base; citrate carrier; clinically significant; glucose metabolism; glucose production; glucose uptake; human tissue; in vivo; inhibitor/antagonist; insight; mortality; novel; outcome forecast; prevent; protein protein interaction; public health relevance; receptor; receptor function; response; wasting

DESCRIPTION (provided by applicant): Chronic liver disease and cirrhosis in particular, is the 12th leading cause of mortality in the United States and the 4th leading cause of death for individuals aged 45 to 54 years. The prognosis is poor, generally irreversible, and marked by progressive destruction of the liver cells. Around 50% of patients with liver disease and 80% of cirrhotic patients display glucose intolerance associated with a decreased gluconeogenic response to glucagon. This decreased glucagon-induced hepatocellular glucose production is due to a significant hepatic resistance to glucagon and attenuation of glucagon-induced cAMP production. Our early studies showed glucagon responsiveness to be significantly attenuated in hepatocytes isolated from cholestatic hamsters, and this effect was mimicked by submicellar concentrations of bile acids including chenodeoxycholic acid (CDCA) in hepatocytes isolated from control hamsters. Our data suggested the attenuated cAMP response induced by bile acids to be PKCalpha and/or PKCdelta-mediated. Our overarching hypothesis is that in hepatocytes, phosphorylation of PKC by CDCA leads to activation of this kinase, which in turn phosphorylates the glucagon receptor and attenuates glucagon responsiveness, which is one of the events associated to the progression of liver disease during cholestasis. The aims of the proposed study are: 1) Identification in vitro by a proteomic approach of the PKC residues that are phosphorylated in the presence of CDCA, and the consequences that the phosphorylation has on PKC stability and activity. 2) Determination in vivo the sites and the mechanism responsible for the PKC phosphorylation and the consequences on the localization, stability and activity of this kinase. 3) The impact that the activation of this kinase has on glucagon receptor function in cholestasis. Findings from our proposed studies will have direct clinical significance and add new insight to the understanding of the attenuation of glucagon responsiveness in cholestatic liver diseases. These studies will define molecular mechanisms regulating both PKC and glucagon receptor activation by bile acids. Furthermore, the delineation of the molecular balance between phosphorylation and activation of PKC may have the added benefit of identifying novel molecular targets for rational drug design in the treatment of cholestatic hepatobiliary disorders, as well as diabetes. Public Health Relevance: This study will highlight novel mechanisms by which physiological control of signal transduction is attenuated in cholestasis. The knowledge gained from these studies could in turn impact both the diagnosis and treatment of cholestatic hepatobiliary disorders, as well as diabetes.

描述(申请人提供)：慢性肝病，尤其是肝硬变，在美国是第12大致死原因，在45至54岁的人群中是第4大致死原因。预后很差，一般不可逆，以肝细胞进行性破坏为特征。大约50%的肝病患者和80%的肝硬变患者表现出葡萄糖不耐受，这与对胰高血糖素的糖异生反应降低有关。这种减少高血糖素诱导的肝细胞葡萄糖产生是由于肝脏对高血糖素有明显的抵抗力，并减弱了高血糖素诱导的cAMP产生。我们早期的研究表明，在胆汁淤积症仓鼠的肝细胞中，胰高血糖素的反应性显著减弱，这种作用被对照仓鼠肝细胞中包括鹅去氧胆酸(CDCA)在内的胆汁酸的亚胶束浓度所模拟。我们的数据表明胆汁酸诱导的减弱的cAMP反应是由PKCalpha和/或PKC Delta介导的。我们的主要假设是，在肝细胞中，CDCA对PKC的磷酸化导致该激酶的激活，进而使胰高血糖素受体磷酸化，减弱胰高血糖素的反应性，这是胆汁淤积期与肝病进展相关的事件之一。本研究的目的是：1)用蛋白质组学方法在体外鉴定在CDCA存在下被磷酸化的PKC残基，以及磷酸化对PKC稳定性和活性的影响。2)体内测定PKC磷酸化的部位和机制，以及对其定位、稳定性和活性的影响。3)胆汁淤积症中该激酶的激活对胰升糖素受体功能的影响。我们建议的研究结果将具有直接的临床意义，并为理解胆汁淤积性肝病中胰高血糖素反应性的减弱提供新的见解。这些研究将确定胆汁酸激活PKC和胰高血糖素受体的分子机制。此外，描绘PKC的磷酸化和活化之间的分子平衡可能具有额外的好处，为合理设计治疗淤胆性肝胆疾病和糖尿病的药物寻找新的分子靶点。公共卫生相关性：这项研究将强调在胆汁淤积症中信号转导的生理控制减弱的新机制。从这些研究中获得的知识反过来可以影响胆汁淤积性肝胆疾病以及糖尿病的诊断和治疗。