Postprandial insulin regulation of B100 and importance to VLDL1 secretion

餐后胰岛素对 B100 的调节及其对 VLDL1 分泌的重要性

• 批准号: 8718737
• 负责人: JANET DEHOFF SPARKS
• 金额: $ 30.7万
• 依托单位: UNIVERSITY OF ROCHESTER
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-04-11 至 2016-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8718737
• 关键词: Address; Apolipoproteins; Apolipoproteins B; Atherosclerosis; Autophagocytosis; Autophagosome; Binding; Binding Proteins; Chylomicrons; Code; Complex; Confocal Microscopy; Data; Development; Dietary Fats; Endoplasmic Reticulum; Enzymes; Equilibrium; Event; Face; Fasting; Fatty Acids; Generations; Genetic Translation; Goals; Golgi Apparatus; Hepatic; High Density Lipoproteins; Human; Hypertriglyceridemia; Immunoelectron Microscopy; Immunofluorescence Immunologic; Insulin; Insulin Resistance; Lipids; Lipolysis; Lipoproteins; Liver; Low-Density Lipoproteins; Lysosomes; Mediating; Membrane; Messenger RNA; Metabolic syndrome; Metabolism; Modeling; Molecular; Movement; Muscle; Non-Insulin-Dependent Diabetes Mellitus; Nuclear; Pathway interactions; Peripheral; Phosphorylation; Phosphotransferases; Process; Production; Protein Binding; Proteins; Proteolysis; Recycling; Regulation; Resistance; Role; Techniques; Therapeutic; Tissues; Transcript; Translating; Translations; Triglycerides; Very low density lipoprotein; Vesicle; base; crosslink; feeding; insulin secretion; insulin sensitivity; luminal membrane; messenger ribonucleoprotein; novel; particle; public health relevance; sortilin; therapeutic target; tripolyphosphate

DESCRIPTION (provided by applicant): The goal of the proposal is to define mechanisms responsible for insulin suppression of hepatic secretion of very low density lipoproteins (VLDL) containing apolipoprotein B100 (B100). Postprandial insulin increases B100 degradation and reduces B100 synthesis limiting VLDL secretion. Resistance to insulin results in continuous secretion of large VLDL1 causing hypertriglyceridemia. We were first to observe insulin effects on B100 and recently demonstrated that degradation is mediated by sortilin and directed to autophagy. We plan to further define mechanisms for this novel insulin action. Insulin dependent apo B degradation decreases B100 availability by enhancing post endoplasmic reticulum (ER) presecretory B100 proteolysis. Little is known about how insulin reduces apo B synthesis. Our previous studies established that insulin suppression requires activation of Class IA phosphatidylinositide 3-kinase (PI3K) and product PI (3,4,5) triphosphate (PIP3) in the ER. Aim 1 is to determine the role of sortilin in insulin-mediated B100 degradation based on evidence showing insulin increases sortilin interaction with B100. We propose that this process involves binding of PIP3 to B100, movement to the Golgi, interaction with sortilin, and stimulation of autophagy leading to degradation of both sortilin and B100 through insulin initiated p110¿ induced autophagy. In Aim 2, we propose studies on how PIP3 generation causes downstream effects on B100. These studies are novel as they propose translocation of B100 associated with PIP3 from the cytoplasmic face of the ER membrane where PIP3 is generated during translation of B100. Transient cytoplasmic orientation of B100 occurs as a result of pause-transfer sequences allowing exposure of B100 to PIP3 and incorporation into primordial lipoproteins. A model is presented where B100-PIP3 complexes on immature VLDL are transported and released into Golgi by specific vesicles followed by increased B100 interaction with sortilin. Aim 3 is to further define insulin effects on B100 synthesis. Insulin dependent B100 silencing involves movement of B100 mRNA into processing bodies (P-bodies) as shown by our collaborator, Dr. Khosrow Adeli. Our studies will define initiating events that are reversible preceding formation of P-bodies. We hypothesize that B100 mRNA binding proteins that interact with coding regions resist movement of B100 transcripts into inactive mRNPs. Preliminary data support a role for insulin-dependent phosphorylation of apobec-1 complementation factor (A1CF) induced nuclear retention which reduces cytoplasmic availability of A1CF for stabilization of B100 mRNA translation thereby favoring formation of inactive B100 mRNPs. Resistance to insulin-regulated hepatic B100 secretion is one of the earliest events in development of metabolic syndrome and results in postprandial hypertriglyceridemia which enhances formation of small easily oxidizable LDL and destabilization of HDL. Defining mechanisms involved in insulin regulation of hepatic VLDL secretion will allow focused therapeutic strategies to be developed to restore lipoprotein balance and reduce atherogenic lipoprotein profile during the postprandial transition.

描述（由适用提供）：该提案的目的是定义负责抑制含有载脂蛋白B100（B100）的非常低密度脂蛋白（VLDL）胰岛素分泌的机制。餐后胰岛素会增加B100降解并减少B100合成限制VLDL分泌。对胰岛素的耐药性导致大型VLDL1的连续分泌，从而导致高甘油三酯血症。我们首先观察到对B100的胰岛素作用，并最近证明降解是由托硅蛋白介导的，并针对自噬。我们计划进一步定义这种新型胰岛素作用的机制。胰岛素依赖性的APO B降解通过增强内质网（ER）预偏b100蛋白水解来降低B100的可用性。关于胰岛素如何减少APO B合成的知之甚少。我们先前的研究表明，胰岛素抑制需要激活ER中的IA类磷脂酰肌醇3-激酶（PI3K）和产物Pi（3,4,5）的产物Pi（3,4,5）（PIP3）。目的1是根据表明胰岛素增加与B100相互作用的证据，确定甲硅素在胰岛素介导的B100降解中的作用。我们建议该过程涉及PIP3与B100的结合，与高尔基体运动，与Tortilin的相互作用以及自噬的刺激，从而导致通过胰岛素通过p110启动P110诱导的自噬，从而导致Tortilin和b100降解。在AIM 2中，我们提出了有关PIP3生成如何对B100产生下游影响的研究。这些研究是新颖的，因为它们提出了与ER膜细胞质面的B100翻译与PIP3相关的翻译，其中PIP3在B100翻译过程中产生。 B100的瞬时细胞质取向是由于暂停转移序列的结果，允许B100暴露于PIP3和工业中，并将其引入原始脂蛋白中。提出了一个模型，其中B100-PIP3复合物在未成熟的VLDL上被运输并通过特定的蔬菜释放到高尔基体中，然后增加了B100与Tortilin的相互作用。目的3是进一步定义胰岛素对B100合成的影响。胰岛素依赖的B100沉默涉及将B100 mRNA运动转化为加工体（P-Bodies），如我们的合作者Khosrow Adeli博士所示。我们的研究将定义启动事件，这些事件是P体的可逆形成。我们假设B100 mRNA结合蛋白与编码区域相互作用的B100转录物在非活动性mRNP中相互作用。初步数据支持APOBEC-1完成因子（A1CF）诱导的核保留率胰岛素依赖性磷酸化的作用，该核保留率降低了A1CF的细胞质可用性，以稳定B100 mRNA翻译，从而有利于形成不活跃的B100 mRNP的形成。对胰岛素调节的肝B100分泌的耐药性是代谢综合征发展中最早的事件之一，并导致餐后高糖性血症，从而增强了小易于氧化的LDL的形成，而HDL的不稳定。定义肝素VLDL分泌胰岛素调节的机制将允许在餐后过渡期间开发出重点的治疗策略以恢复脂蛋白平衡并减少动脉粥样硬化的脂蛋白谱。