Carbohydrate Regulation of Hepatic Gene Expression

碳水化合物对肝基因表达的调节

• 批准号: 7787585
• 负责人: KOSAKU UYEDA
• 金额: $ 23.78万
• 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 2011-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7787585
• 关键词: 14-3-3 Proteins; Binding; Binding Proteins; Binding Sites; Carbohydrates; Carbon; Cell Nucleus; Consumption; Cyclic AMP; DNA; DNA Binding; Development; Diabetes Mellitus; Diet; Dietary Carbohydrates; Disease; Eating; Elements; Enzyme Gene; Enzymes; Epidemic; Famines; Fasting; Fatty Acids; Fatty acid glycerol esters; Food; Food Supply; Gene Expression; Genes; Genetic Transcription; Glucose; Glycolysis; Goals; Health; Hepatic; Hormonal; Human; Ingestion; Knowledge; Laboratories; Life Style; Liver; Malignant Neoplasms; Measurement; Mediating; Molecular; N-terminal; Nuclear; Nuclear Import; Nutrient; Obesity; Organ; Overweight; Pharmacotherapy; Phosphoric Monoester Hydrolases; Phosphorylation; Phosphorylation Site; Phosphotransferases; Physiological; Play; Population; Prevention strategy; Process; Protein Binding; Protein Biosynthesis; Protein Dephosphorylation; Protein Export Pathway; Protein Inhibition; Protein Phosphatase 2A Regulatory Subunit PR53; Protein phosphatase; Proteins; Rattus; Reaction; Regulation; Response Elements; Role; Signal Transduction; Site; Source; Specificity; Starvation; Structure; Time; Tissues; Triglycerides; Work; X-Ray Crystallography; base; carbohydrate binding protein; carbohydrate receptor; design; hypertensive heart disease; insight; lead-binding proteins; lipid biosynthesis; novel; obesity treatment; pressure; promoter; protein complex; public health relevance; response; three dimensional structure; transcription factor

DESCRIPTION (provided by applicant): Evolutionary pressure has favored mechanisms that allow the body to efficiently store nutrients as fat when food is abundant as a safeguard against occasional famine. With the dramatic changes in modern lifestyle including consumption of high carbohydrate and high fat foods, these mechanisms may now be contributing to a major epidemic of obesity in the US where the majority of the population is overweight. Glucose is not only a major fuel of all mammalian tissues but also a source of carbon for fat and protein synthesis. The liver is the principal organ responsible for the conversion of excess dietary carbohydrate into triglycerides. Ingestion of a high carbohydrate diet induces transcription of more than 15 genes involve in the conversion of glucose to storage fat. A transcription factor, purified from rat liver, with specificity for carbohydrate responsive elements (ChRE) found in the promoters of multiple genes required for lipogenesis and which displayed appropriate dietary responsive regulation was first identified in this laboratory and termed "carbohydrate response element binding protein, ChREBP". The complete process by which ChREBP is activated in response to excess carbohydrate in order to induce the transcription of lipogenesis enzyme genes, and then is turned off, is not yet fully understood. We have shown that glucose and cAMP have opposing activities in the regulation of lipogenesis, in part through dephosphorylation/phosphorylation of multiple sites on ChREBP. Glucose stimulates dephosphorylation of at least some of these sites by activating a Xu5P-stimulated protein phosphatase, Xu5P-PP2A. We recently found that the interaction of ChREBP with 14-3-3 is one of the most important steps regulating the nuclear localization of ChREBP. Phosphorylation of ChREBP activates its binding to 14-3-3 and is essential for ChREBP export out of the nucleus under starvation conditions. In addition, we found more recently that a specific metabolite in liver promotes the interaction of ChREBP with 14-3-3. To characterize the metabolite further we propose to (1) isolate the metabolite in pure form and determine the structure, (2) determine the mechanism by which it activates the interaction between ChREBP and 14-3-3, (3) determine how the metabolite is synthesized and degraded, what enzymes are responsible for these reactions and how they are regulated, (4) investigate whether the metabolite might be a signaling compound for regulation of the subcellular localization of ChREBP in response to nutrients and starvation, and (5) elucidate how Xu5P activates ChREBP and the bifunctional enzyme, Fru6P, 2kinase/Fru2,6 bisPase, using X-ray crystallography. PUBLIC HEALTH RELEVANCE: Obesity and its associated diseases, diabetes, hypertension, heart disease and some cancers are among the most serious health problems now facing the US. The efficient conversion of excess carbohydrates to fat for long-term storage, which until modern times it would appear was an evolutionary advantage in adapting to uncertain food supplies, now appears to contribute significantly to development of obesity. Carbohydrate response element binding protein (ChREBP) is a transcription factor that becomes active when carbohydrates are eaten and increases the expression of genes required for synthesis of fatty acids. The results of the work proposed in this application will elucidate the mechanisms involved both in activation and termination of ChREBP dependent increases in enzymes needed to make fatty acids. This knowledge will provide information that may be useful in developing strategies for the prevention and treatment of obesity.

描述(申请人提供)：进化压力有利于机制，允许身体有效地储存营养物质，当食物充足时，作为对偶尔发生的饥荒的保障。随着现代生活方式的戏剧性变化，包括高碳水化合物和高脂肪食物的消费，这些机制现在可能会导致美国肥胖的主要流行，因为美国大多数人都超重。葡萄糖不仅是所有哺乳动物组织的主要燃料，也是脂肪和蛋白质合成的碳源。肝脏是负责将过量的饮食碳水化合物转化为甘油三酯的主要器官。摄入高碳水化合物饮食会诱导15个以上的基因转录，这些基因涉及将葡萄糖转化为储存脂肪。本实验室首次从大鼠肝脏中鉴定出一种转录因子，命名为“碳水化合物反应元件结合蛋白”，该转录因子对脂肪生成所需的多个基因启动子中的碳水化合物反应元件(CHRE)具有特异性，并具有适当的饮食反应调节作用。ChREBP被激活以响应过量碳水化合物以诱导脂肪生成酶基因转录，然后被关闭的完整过程尚不完全清楚。我们已经证明，葡萄糖和cAMP在调节脂肪生成方面具有相反的活性，部分是通过ChREBP上多个位点的去磷酸化/磷酸化。葡萄糖通过激活X5P刺激的蛋白磷酸酶X5P-PP2A来刺激至少其中一些位点的去磷酸化。我们最近发现，ChREBP与14-3-3的相互作用是调控ChREBP核定位的重要步骤之一。ChREBP的磷酸化激活了其与14-3-3的结合，是饥饿条件下ChREBP输出到细胞核外所必需的。此外，我们最近发现，肝脏中的一种特定代谢物促进了ChREBP与14-3-3的相互作用。为了进一步确定代谢产物的性质，我们建议(1)分离纯形式的代谢物并确定其结构，(2)确定它激活ChREBP与14-3-3之间相互作用的机制，(3)确定代谢物是如何合成和降解的，哪些酶负责这些反应以及它们是如何被调控的，(4)研究代谢物是否可能是调节ChREBP在营养和饥饿下的亚细胞定位的信号化合物，以及(5)利用X射线结晶学来阐明XX5P如何激活ChREBP和双功能酶Fru6P，2Kinase/Fru2，6 BisPase。 与公共健康相关：肥胖及其相关疾病、糖尿病、高血压、心脏病和一些癌症是美国目前面临的最严重的健康问题。将多余的碳水化合物有效地转化为脂肪以供长期储存，直到现代，这似乎是适应不确定的食物供应的一种进化优势，现在似乎对肥胖的发展做出了重大贡献。碳水化合物反应元件结合蛋白(ChREBP)是一种转录因子，在摄入碳水化合物时变得活跃，并增加合成脂肪酸所需基因的表达。本申请中提出的工作结果将阐明ChREBP激活和终止所涉及的机制，这些机制依赖于生成脂肪酸所需酶的增加。这些知识将提供可能有助于制定预防和治疗肥胖症的战略的信息。