Carbohydrate Regulation of Hepatic Gene Expression

碳水化合物对肝基因表达的调节

• 批准号: 6984777
• 负责人: KOSAKU UYEDA
• 金额: $ 26.02万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-01-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6984777
• 关键词: DNA binding protein; biological signal transduction; carbohydrate metabolism; enzyme activity; gene deletion mutation; gene expression; gene targeting; genetic transcription; genetically modified animals; glucose; glucose metabolism; laboratory mouse; laboratory rat; lipid biosynthesis; liver; mass spectrometry; molecular cloning; phosphoprotein phosphatase; phosphorylation; protein transport; steroid biosynthesis; transcription factor

DESCRIPTION (provided by applicant): Evolutional pressure has favored the ability to efficiently store nutrients as fat during abundant food supply as a safeguard against occasional famine. Due to the abundance of the food supply and dramatic changes in modern lifestyle, these genes may now contribute to major epidemic of obesity, especially in the US where over a half of population is overweight. This is predicted to be a major public health problem in the near future. The liver is the principal organ responsible for the conversion of excess dietary carbohydrate into triglycerides. Ingestion of high carbohydrate diet induces transcription of more than 15 genes involved in the metabolic conversion of glucose to storage fat. Until recently, it was thought that insulin and glucagons regulate the transcription of these genes. However, it has been shown that nutrients themselves play an important role in the regulation of transcription independent of insulin. The mechanism by which excess carbohydrate generates a signal to induce the transcription of lipogenesis enzyme gene is not known. We have identified and characterized a new transcription factor termed "Carbohydrate response element binding protein, ChREBP" which responds to high glucose and induce the liver pyruvate kinase (LPK) gene and lipogenic genes. Our goal is to understand how excess glucose, independent of insulin, activates the transcription. We have shown that glucose and cAMP are adversary in the lipognesis, cAMP and AMP inhibit ChREBP by phosphorylation at the specific sites which are mediated by protein kinase A and AMPprotein kinase. Glucose reverses the inhibition and activates ChREBP to favor triglycerides synthesis. We propose that glucose activates the transcription of these genes by dephosphorylation catalyzed by a specific protein phosphatase that is activated by a glucose-signaling compound. Our specific objectives for the current application are: (1) identify the specific protein phosphatases (PPase) in cytosol and in nucleus that are responsible for the nuclear import and the DNA binding activity of ChREBP. (2) Detect and identify a glucose signaling compound which activates the PPases and the transcription. (3) Investigate the mechanism of import and export of ChREBP. The important question is whether the import and export of ChREBP are regulated only by phosphorylation and dephosphorylation. Determine the genes altered by the ChREBP gene knockout and characterize the resulting physiological and biochemical changes in these mice in order to understand the roles of ChREBP in vivo. Produce other crosses with ChREBP-/- such as ob/ob mice by breeding our knockout mice with the ob/ob animals for potential elimination of obesity. Other possibility is to produce a combination of ChREBP-/- and SREBP-/- that inhibit the major portion of lipogenesis in liver.

描述（由申请人提供）：进化压力有利于在食物供应中有效地将营养作为脂肪的脂肪作为偶尔偶然饥荒的保障能力。由于粮食供应​​的丰富和现代生活方式的巨大变化，这些基因现在可能有助于肥胖症的主要流行，尤其是在美国超过一半的人口超重的美国。预计在不久的将来，这将是一个主要的公共卫生问题。肝脏是负责将过量饮食碳水化合物转化为甘油三酸酯的主要器官。摄入高碳水化合物饮食可诱导葡萄糖代谢转化为储存脂肪的15个以上基因的转录。直到最近，人们认为胰岛素和葡萄糖会调节这些基因的转录。但是，已经表明，营养本身在独立于胰岛素的转录调节中起着重要作用。多余的碳水化合物产生信号以诱导脂肪生成酶基因转录的机制尚不清楚。 我们已经确定并表征了一种称为“碳水化合物响应元件结合蛋白Chrebp”的新转录因子，该因子对高葡萄糖的反应并诱导肝丙酮酸激酶（LPK）基因和脂源基因。我们的目标是了解多余的葡萄糖如何独立于胰岛素激活转录。我们已经表明，葡萄糖和cAMP在脂肪认知，cAMP和AMP中是对手，通过磷酸化在特定位点抑制CHREBP，这是由蛋白激酶A和增强蛋白激酶介导的特定位点。葡萄糖逆转抑制作用，并激活Chrebp以有利于甘油三酸酯的合成。我们提出，葡萄糖通过由特定蛋白磷酸酶催化的去磷酸化激活这些基因的转录，该蛋白磷酸酶被葡萄糖信号化合物激活。 我们对当前应用程序的具体目标是： （1）在细胞质和核中确定特定的蛋白磷酸酶（PPase），这些蛋白质磷酸酶（PPase）负责CHREBP的核进口和DNA结合活性。 （2）检测并识别激活PPases和转录的葡萄糖信号传导化合物。 （3）研究Chrebp进口和出口的机理。重要的问题是，Chrebp的进口和出口是否仅受磷酸化和去磷酸化的调节。 确定Chrebp基因敲除改变的基因，并表征这些小鼠的生理和生化变化，以了解Chrebp在体内的作用。通过用ob/ob动物繁殖我们的基因敲除小鼠，以消除肥胖症来生产其他十字架，例如ob/ob小鼠。另一种可能性是生成Chrebp - / - 和Srebp - / - 的组合，从而抑制肝脏中脂肪形成的主要部分。