Pyruvate Dehydrogenase kinase as Therapeutic Target for Hepatic Steatosis, Obesit

丙酮酸脱氢酶激酶作为肝脂肪变性、肥胖症的治疗靶点

基本信息

批准号：
8195602
负责人：
ROBERT A HARRIS
金额：
--
依托单位：
RLR VA MEDICAL CENTER
依托单位国家：
美国
项目类别：
财政年份：
2009
资助国家：
美国
起止时间：
2009-04-01 至 2012-09-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8195602
关键词：
Abbreviations Accounting Acetoacetates Acetyl-CoA Carboxylase Acyl Coenzyme A Adipose tissue Affect Alanine American Animal Feed Automobile Driving Back Benign Blood Blood Glucose Branched-Chain Amino Acids C-reactive protein Caprylates Carbon Carnitine O-Palmitoyltransferase Characteristics Cholesterol Cirrhosis Coenzyme A Coenzymes Commit Development Diabetes Mellitus Dichloroacetate Diet Dioxins Documentation Down-Regulation Dual-Energy X-Ray Absorptiometry Engineering Enzyme Activation Enzymes Esters Fasting Fatty Acids Fatty Liver Fatty acid glycerol esters Glucocorticoids Gluconeogenesis Glucose Glutamates Glycerol Goals Healthcare Hepatocyte Herbicides Hormonal Hormones Hospitals Hyperglycemia Inflammation Insulin Insulin Resistance Interleukin-6 Intervention Isoenzymes Ketone Bodies Knock-out Knockout Mice Laboratories Lead Learning Link Liver Liver Cirrhosis Liver Failure Liver diseases Malonyl Coenzyme A Metabolic Mitochondria Molecular Multienzyme Complexes Mus Muscle Non-Insulin-Dependent Diabetes Mellitus Nonesterified Fatty Acids Obesity Oxidative Stress PDH kinase Patients Pharmaceutical Preparations Pharmacologic Substance Phosphoenolpyruvate Carboxylase Phosphorylation Population Portal Hypertension Preparation Prevention Protein Biosynthesis Pyruvate Pyruvate Dehydrogenase Complex Regulation Relative (related person)Research Risk Risk Factors Role Shipping Ships Skeletal Muscle Starvation Testing Therapeutic Tissues Triglycerides United States Department of Veterans Affairs Veterans Vietnam Wild Type Mouse Work alpha-glycerophosphoric acid base beta-Hydroxybutyrate blood glucose regulation carbon compound diabetic patient fasting blood glucose level fatty acid oxidation feeding glucose metabolism glucose production glucose tolerance improved inflammatory marker inhibitor/antagonist insulin sensitivity ketogenesis killings kinase inhibitor knockout animal lipid metabolism meetings neuronal cell body non-alcoholic fatty liver nonalcoholic steatohepatitis novel oxidation preference prevent public health relevance response saturated fat small molecule therapeutic target transamination

项目摘要

DESCRIPTION (provided by applicant): PROJECT SUMMARY The primary goal of our research is to establish whether the pyruvate dehydrogenase kinases (PDKs) should be considered therapeutic targets for the treatment of hepatic steatosis, obesity, and type 2 diabetes. The long-term objective is to find inhibitors of the PDKs that will lead to development of effective drugs for the treatment of these conditions. The immediate objective is to perform proof-of- principle studies with PDK knockout mice generated in my laboratory. Two lines of evidence support our hypothesis that the PDKs are viable targets for the treatment of these conditions. First, down regulation of the expression of PDKs is a critical component of the mechanism by which insulin controls blood glucose. Second, PDK knock out mice maintained on a high-fat, diabetogenic diet accumulate less fat in their livers, are less obese, and have lower blood glucose levels, better glucose tolerance, and greater insulin sensitivity than wild type mice. The activity of the pyruvate dehydrogenase complex (PDC) is tightly regulated by phosphorylation by the PDKs. The phosphorylation state of PDC is controlled by changes in expression level of the PDKs. PDC is inactivated in starvation and diabetes because of induction of PDK2 and 4 by high levels of glucocorticoids and fatty acids and low levels of insulin. That glucose homeostasis depends upon regulation of PDC, which in turn depends upon hormonal control of the amounts of the PDKs, was the original hypothesis for this work. Studies with knockout mice for PDK2 and PDK4 have confirmed this hypothesis. Preliminary studies indicate that knocking out both PDK2 and PDK4 in the same mouse results in an even greater improvement in glucose tolerance and insulin sensitivity than knocking out PDK4 alone. The specific objectives of the proposal are: (a) determine the effects that knocking out both PDK2 and PDK4 in the same mouse has upon fasting blood glucose levels, glucose tolerance, insulin sensitivity, hepatic steatosis, adiposity, branched chain amino acids (BCAAs), free fatty acids (FFAs), ketone bodies, triacylglcyerols (TAG), cholesterol, blood pH, and markers of inflammation and oxidative stress in mice fed a high saturated fat diet; (b) determine the molecular mechanisms responsible for the increases in blood levels of ketone bodies in PDK knockout mice; and (c) determine whether knocking out PDK2 and PDK4 inhibits glyceroneogenesis by reducing the availability of lactate, pyruvate, and alanine. Following completion of these proof-of-principle studies, we hope to shift our goal to the identification of small molecule inhibitors of PDKs for the treatment of hepatic steatosis, obesity, and type 2 diabetes. PUBLIC HEALTH RELEVANCE: PROJECT NARRATIVE Hepatic steatosis, the accumulation of fat in the liver, is a common feature of nonalcoholic fatty liver disease (NAFLD) that occurs in 14 to 20% of the US population [63]. Once considered benign, NAFLD is now known to be a risk factor for nonalcoholic steatohepatitis (NASH), a serious condition in which inflammation kills liver cells, ultimately culminating in liver cirrhosis, portal hypertension, and liver failure. Although NASH is less prevalent (about a quarter of the population with NAFLD have NASH), the number is growing in parallel with the increase in NAFLD. 27,000 Americans die each year from cirrhosis. Hepatic steatosis, obesity, insulin resistance, and type 2 diabetes mellitus are all closely linked [64]. Indeed the majority of obese, type 2 diabetic patients also have hepatic steatosis. Since a fourth of patients treated at Veteran Administration hospitals have type 2 diabetes [65], many veterans have NAFLD and are at risk of developing NASH and dying of cirrhosis. Furthermore, veterans exposed to dioxin- contaminated herbicides in Vietnam are particularly prone to the development of type 2 diabetes and therefore hepatic steatosis, NASH, and cirrhosis [66]. Learning how to prevent NAFLD and its progression to NASH depends upon a better understanding of why fat accumulates in tissues and why the amount of fat that accumulates usually correlates with the degree of insulin resistance. Fatty acids synthesized in the liver in the absorptive state should be esterified to glycerol and shipped to the adipose tissue for storage, never retained in the liver. Fatty acids delivered to the liver from the adipose tissue in the postabsorptive state should be either oxidized or re-esterified to glycerol and shipped back to the adipose tissue. The reason why fatty acids are retained in the liver as TAG in NAFLD is poorly understood. Part of what needs further clarification is the role of PDC in regulation of relative rates of fatty acid and glucose oxidation. A better understanding of how regulation of PDC affects fat accumulation and insulin sensitivity of the liver could help in the effort to develop pharmaceuticals for the prevention of NAFLD and NASH. Our hope is that work on this enzyme complex will lead to the development of novel drugs for the treatment of hepatic steatosis, obesity, and type 2 diabetes. We therefore believe the proposed work has the potential to have a significant impact on the health care of Veterans.

描述（由申请人提供）：项目总结我们研究的主要目的是确定丙酮酸脱氢酶激酶（PDK）是否应视为治疗肝脂肪变性，肥胖和2型糖尿病的治疗靶标。长期目标是找到PDK的抑制剂，这些抑制剂将导致有效的药物治疗这些疾病。直接目标是通过我的实验室中产生的PDK敲除小鼠进行原则研究。两条证据支持我们的假设，即PDK是治疗这些疾病的可行目标。首先，调节PDK的表达是胰岛素控制血糖的机制的关键组成部分。其次，在高脂糖尿病饮食上保持的PDK敲除小鼠的肝脏脂肪含量较少，肥胖较少，血糖水平较低，葡萄糖耐受性较低，胰岛素敏感性更高，而胰岛素敏感性比野生型小鼠更高。丙酮酸脱氢酶复合物（PDC）的活性受PDK磷酸化的严格调节。 PDC的磷酸化状态受PDK表达水平的变化控制。由于PDK2诱导PDC和糖尿病，PDC被高水平的糖皮质激素和脂肪酸以及低水平的胰岛素诱导。葡萄糖稳态取决于PDC的调节，这又取决于PDK量的激素控制，是这项工作的原始假设。对PDK2和PDK4的基因敲除小鼠的研究证实了这一假设。初步研究表明，在同一小鼠中淘汰PDK2和PDK4会导致葡萄糖耐受性和胰岛素敏感性的提高比单独淘汰PDK4更大。 The specific objectives of the proposal are: (a) determine the effects that knocking out both PDK2 and PDK4 in the same mouse has upon fasting blood glucose levels, glucose tolerance, insulin sensitivity, hepatic steatosis, adiposity, branched chain amino acids (BCAAs), free fatty acids (FFAs), ketone bodies, triacylglcyerols (TAG), cholesterol, blood pH，以及喂养高饱和脂肪饮食的小鼠炎症和氧化应激的标记；（b）确定负责PDK敲除小鼠血液水平增加的分子机制；（c）确定敲除PDK2和PDK4是否通过降低乳酸，丙酮酸和丙氨酸的可用性来抑制甘油发生。完成这些原则研究后，我们希望将我们的目标转移到对PDK的小分子抑制剂的鉴定，以治疗肝脂肪变性，肥胖和2型糖尿病。公共卫生相关性：项目叙事肝脂肪变性是肝脏中脂肪的积累，是非酒精性脂肪肝病（NAFLD）的共同特征，在14％至20％的美国人群中发生[63]。曾经被认为是良性的，NAFLD现在被称为非酒精性脂肪性肝炎（NASH）的危险因素，这种炎症会杀死肝脏细胞，最终导致肝硬化，门静脉高血压和肝衰竭。尽管纳什（Nash）的流行程度较低（大约是NAFLD人口的四分之一），但与NAFLD的增加相同。每年有27,000名美国人死于肝硬化。肝脂肪变性，肥胖，胰岛素抵抗和2型糖尿病均紧密联系[64]。实际上，大多数肥胖，2型糖尿病患者也患有肝脂肪变性。由于在资深管理医院接受治疗的患者中有四分之一患有2型糖尿病[65]，因此许多退伍军人患有NAFLD，并且有发展NASH和死于肝硬化的风险。此外，在越南暴露于二恶英污染的除草剂的退伍军人特别容易发生2型糖尿病的发展，因此肝脂肪变性，纳什和肝硬化[66]。学习如何防止NAFLD及其向NASH的发展取决于更好地理解脂肪在组织中积累的原因以及为什么积累的脂肪量通常与胰岛素抵抗程度相关。应在吸收态下在肝脏中合成的脂肪酸应酯化至甘油并运送到脂肪组织中以储存，从不保留在肝脏中。在吸收后状态下从脂肪组织中输送到肝脏的脂肪酸应被氧化或重新溶解至甘油，然后运回脂肪组织。人们理解的NAFLD中脂肪酸作为NAFLD中的标签保留在肝脏中的原因。需要进一步澄清的一部分是PDC在调节脂肪酸和葡萄糖氧化相对速率中的作用。更好地理解PDC的调节如何影响肝脏的脂肪积累和胰岛素敏感性可以帮助开发用于预防NAFLD和NASH的药物。我们的希望是，这种酶复合物的工作将导致新的药物开发用于治疗肝脂肪变性，肥胖和2型糖尿病。因此，我们认为拟议的工作有可能对退伍军人的医疗保健产生重大影响。