Regulation of de novo lipogenesis through BAD-dependent glucose signaling

通过 BAD 依赖性葡萄糖信号传导调节从头脂肪生成

• 批准号: 9244778
• 负责人: Elizabeth Lane
• 金额: $ 3.15万
• 依托单位: HARVARD MEDICAL SCHOOL
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-01 至 2018-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9244778
• 关键词: Acetates; Acetylation; Active Sites; Acute; Affect; Amphipathic Alpha Helix; BCL2 gene; BH3 Domain; Bad protein; Binding; Binding Proteins; Biochemical; Carbohydrates; Cardiovascular Diseases; Cells; Charge; Cues; DNA Binding; Data; Disease; Enzymes; Equilibrium; Fasting; Fatty acid glycerol esters; Fructose; Gene Expression; Genes; Genetic; Genetic Transcription; Glucokinase; Gluconeogenesis; Glucose; Glucose-6-Phosphate; Glycogen; Glycolysis; Hepatic; Hepatocyte; Hormonal; Lead; Learning; Link; Lipids; Liver; Measurement; Mediating; Metabolic; Modification; Molecular; Mus; Non-Insulin-Dependent Diabetes Mellitus; Nuclear Translocation; Nutrient; Obesity; Organ; Pathway interactions; Pharmacology; Phosphorylation; Post-Translational Protein Processing; Production; Protein Family; Proteins; Regulation; Response Elements; Role; Serine; Signal Transduction; Testing; Transcription Alteration; activating transcription factor; blood glucose regulation; extracellular; glucose metabolism; glucose production; inorganic phosphate; insight; lipid biosynthesis; liquid chromatography mass spectrometry; new therapeutic target; programs; protein activation; public health relevance; reaction rate; response; small hairpin RNA; transcription factor

 DESCRIPTION (provided by applicant): Regulation of de novo lipogenesis through BAD-dependent glucose signaling The homeostatic balance between hepatic utilization, storage, and production of glucose and fat in fed and fasted states is exquisitely controlled by hormonal and nutrient cues. In the fed state, the liver stores excess glucose first as glycogen then as fat through de novo lipogenesis. How the liver senses glucose to determine its utilization and storage is not fully understood at the molecular level. Emerging evidence indicates that glucose-derived metabolites, including the activity of glucokinase (GK), which catalyzes the first step of hepatic glycolysis, influence de novo lipogenesis by both providing metabolic precursors for lipid synthesis as well as triggering the expression of lipogenic genes. Glucose regulation of de novo lipogenesis is dependent, at least in part, on the Carbohydrate Response Element Binding Protein (ChREBP), a transcription factor that is activated by certain glucose-derived metabolites. My proposed studies test the role of the BCL-2 family protein BAD as an upstream regulator of hepatic glucose signaling and de novo lipogenesis through ChREBP. BAD's modulation of glucose metabolism is mediated by phosphorylation of Ser155, which leads to direct activation of GK. The functional relevance of this interaction is evident from the observations that BAD deficiency or interference with its phosphorylation is associated with reduced hepatic GK activity and glycolysis. I have found that glucose induction of ChREBP activity and lipogenic gene expression is diminished in Bad -/- hepatocytes. These data, together with the known capacity of BAD to activate GK and GK's relevance in ChREBP activation, give rise to the hypothesis that BAD modulates hepatic ChREBP activity and de novo lipogenesis through its ability to regulate GK activity. I will test this hypothesis through the following specific aims: Aim 1 will interrogate the acute and cell autonomous effect of BAD modifications in primary hepatocytes and the attendant changes in GK on stimulation of ChREBP transcriptional activity by glucose. Aim 2 will determine the functional and metabolic correlates of BAD-dependent changes in lipogenic gene expression by biochemical measurement of de novo lipogenesis and glucose-dependent changes in lipid profiles in primary hepatocytes following genetic or pharmacologic modification of BAD. Aim 3 will dissect the mechanistic link between BAD modifications and ChREBP activity by examining alterations in defined post translational modifications of ChREBP in response to glucose, including phosphorylation and acetylation known to modulate ChREBP transcriptional activity. In the fullness of time, these studies will provide an integrated picture of the pathway connecting BAD and GK- dependent glucose metabolism with ChREBP activity and the lipogenic program. Understanding this pathway should yield useful molecular insights into hepatic glucose sensing, nutrient utilization and storage.

 描述（由申请人提供）：通过BAD依赖性葡萄糖信号传导调节从头脂肪生成在进食和禁食状态下，肝脏利用、储存以及产生葡萄糖和脂肪之间的稳态平衡是由激素和营养信号精确控制的。在进食状态下，肝脏首先将多余的葡萄糖储存为糖原，然后通过从头脂肪生成储存为脂肪。肝脏如何感知葡萄糖以确定其利用和储存在分子水平上尚未完全了解。新的证据表明，葡萄糖衍生的代谢物，包括催化肝糖酵解第一步的葡萄糖激酶 (GK) 的活性，通过为脂质合成提供代谢前体以及触发脂肪生成基因的表达来影响从头脂肪生成。从头脂肪生成的葡萄糖调节至少部分依赖于碳水化合物反应元件结合蛋白（ChREBP），这是一种被某些葡萄糖衍生代谢物激活的转录因子。我提出的研究测试了 BCL-2 家族蛋白 BAD 作为肝葡萄糖信号传导和通过 ChREBP 从头脂肪生成的上游调节剂的作用。 BAD 对葡萄糖代谢的调节是通过 Ser155 磷酸化介导的，这会导致 GK 的直接激活。这种相互作用的功能相关性从以下观察结果中可以明显看出：BAD 缺乏或对其磷酸化的干扰与肝脏 GK 活性和糖酵解降低有关。我发现在 Bad -/- 肝细胞中葡萄糖对 ChREBP 活性和脂肪生成基因表达的诱导减弱。这些数据，加上已知的 BAD 激活 GK 的能力以及 GK 在 ChREBP 激活中的相关性，得出这样的假设：BAD 通过其调节 GK 活性的能力来调节肝脏 ChREBP 活性和从头脂肪生成。我将通过以下具体目标来检验这一假设：目标 1 将探讨原代肝细胞中 BAD 修饰的急性和细胞自主效应以及 GK 对葡萄糖刺激 ChREBP 转录活性的随之变化。目标 2 将通过对 BAD 进行遗传或药理学修饰后原代肝细胞中脂肪从头生成的生化测量和脂质谱中葡萄糖依赖性变化的生化测量，确定脂肪生成基因表达中 BAD 依赖性变化的功能和代谢相关性。目标 3 将通过检查 ChREBP 响应葡萄糖而定义的翻译后修饰的变化（包括已知调节 ChREBP 转录活性的磷酸化和乙酰化）来剖析 BAD 修饰和 ChREBP 活性之间的机制联系。随着时间的推移，这些研究将提供 BAD 和 GK 依赖性葡萄糖代谢与 ChREBP 活性和脂肪生成程序之间的连接途径的综合图景。了解这一途径应该会对肝葡萄糖传感、营养利用和储存产生有用的分子见解。