Hepatic Rictor Knockout Mouse Model and the Metabolic Syndrome

肝 Rictor 敲除小鼠模型和代谢综合征

• 批准号: 8110032
• 负责人: Jennifer Marie Rojas
• 金额: $ 2.62万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-01 至 2013-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8110032
• 关键词: 1-Phosphatidylinositol 3-Kinase; 3-Phosphoinositide Dependent Protein Kinase-1; ADD-1 protein; Albumins; Alleles; Animal Model; Apolipoproteins B; Atherosclerosis; Cardiovascular Diseases; Complex; Couples; Coupling; Defect; Diabetes Mellitus; Dilution Techniques; Dyslipidemias; Enzymes; Epidemic; Euglycemic Clamping; Failure; Fatty Liver; Functional disorder; Gene Dosage; Gene Expression; Genes; Genetic; Genomics; Gluconeogenesis; Glucose Clamp; Glycogen Synthase Kinase 3; Healthcare Systems; Hepatic; Hepatocyte; High Density Lipoprotein Cholesterol; High Density Lipoproteins; Hyperglycemia; Hyperlipidemia; Hypertriglyceridemia; Insulin; Insulin Resistance; Knockout Mice; LDL Cholesterol Lipoproteins; Lipids; Lipoproteins; Liver; Low-Density Lipoproteins; Mediating; Mediator of activation protein; Metabolic; Metabolic syndrome; Modeling; Molecular; Morbidity - disease rate; Mus; Neuropathy; Obesity; Pathogenesis; Peripheral; Phosphorylation; Phosphorylation Site; Play; Preventive; Production; Protein-Serine-Threonine Kinases; Proteins; Proto-Oncogene Proteins c-akt; Radiolabeled; Regulation; Retinal Diseases; Risk Factors; Role; Serine; Signal Transduction; Signaling Molecule; Testing; Therapeutic; Threonine; Tissues; Tracer; Triglycerides; Vascular Diseases; Very low density lipoprotein; design; genetic regulatory protein; glucose disposal; glucose metabolism; glucose production; improved; insulin mediators; insulin sensitivity; insulin signaling; lipid biosynthesis; lipid metabolism; loss of function; mTOR protein; mortality; mouse Cre recombinase; mouse model; radiotracer; very low density lipoprotein triglyceride

Concomitant with the parallel obesity and diabetes epidemics, an increasing burden on our healthcare system is due to the complications of hyperglycemia (nephropathy, neuropathy, retinopathy and vascular disease) and hyperlipidemia (atherosclerosis and cardiovascular disease). Insulin resistance is a common contributor to the pathophysiology of obesity, diabetes and metabolic syndrome, and many of their associative complications. The liver is central to glucose and lipid metabolism and insulin plays a key regulatory role. Elevated hepatic glucose production contributes to hyperglycemia; whereas, increased very low-density lipoproteins (VLDL)- Triglyceride (TG) production contributes to atherogenic dyslipidemia (elevated TGs, small and dense low- density lipoproteins (LDL) and reduced high-density lipoproteins (HDL)). The resultant hyperglycemia and dyslipidemia are attributed to altered insulin action in the liver. "Selective" insulin resistance in liver is characterized by inability of insulin to suppress gluconeogenesis (impaired FOXO1 regulation) while continuing to stimulate de novo lipogenesis and VLDL-TG secretion (intact regulation of SREBP1c). Thus, selective insulin resistance is a potential mechanism by which hyperglycemia and hyperlipidemia can ensue; however, the molecular defect involved is not known. I hypothesize that "selective" insulin resistance is due to partial AKT activation that results from the uncoupling of Serine473 (S473) and Threonine308 (T308) phosphorylation sites on AKT; loss of S473 phosphorylation results in the failure of AKT to phosphorylate FOXO1 and suppress expression of key gluconeogenic enzymes, whereas partially activated AKT (only T308) is sufficient to phosphorylate and inhibit GSK3, leading to SREBP1c activation and hypertriglyceridemia. I will test this hypothesis by studying a mouse model in which the mTORC2 regulatory protein, rictor, has been genetically deleted in hepatocytes leading to impaired S473 phosphorylation with intact T308 phosphorylation. I will validate genetic loss of rictor in the liver, gene dosage specific effects of rictor gene expression and rictor/mTORC2 function (AKT phosphorylation). Euglycemic clamp and tracer dilution techniques will be employed to quantify the ability of insulin to suppress hepatic glucose production. Hypertriglyceridemia will be assessed by utilizing tyloxapol and radiolabeled lipid studies to quantify the rate of VLDL-TG production and clearance, and effects on the lipoprotein profile (VLDL, LDL, HDL and apoB). The possibility of hepatic steatosis will be assessed by liver lipid quantification.

伴随着肥胖和糖尿病的流行，高血糖（肾病、神经病、视网膜病和血管疾病）和高脂血症（动脉粥样硬化和心血管疾病）的并发症给我们的医疗保健系统带来了越来越大的负担。胰岛素抵抗是导致肥胖、糖尿病和代谢综合征及其许多相关并发症的病理生理学的常见因素。肝脏是葡萄糖和脂质代谢的中心，胰岛素起着关键的调节作用。肝葡萄糖生成增加导致高血糖；然而，极低密度脂蛋白（VLDL）-甘油三酯（TG）的产生增加会导致动脉粥样硬化性血脂异常（TG升高、小而密的低密度脂蛋白（LDL）和高密度脂蛋白（HDL）减少）。由此产生的高血糖和血脂异常归因于肝脏中胰岛素作用的改变。 肝脏中“选择性”胰岛素抵抗的特征是胰岛素无法抑制糖异生（FOXO1 调节受损），同时继续刺激从头脂肪生成和 VLDL-TG 分​​泌（SREBP1c 的完整调节）。因此，选择性胰岛素抵抗是导致高血糖和高脂血症的潜在机制。然而，所涉及的分子缺陷尚不清楚。我假设“选择性”胰岛素抵抗是由于 AKT 部分激活所致，而该激活是由于 AKT 上丝氨酸 473 (S473) 和苏氨酸 308 (T308) 磷酸化位点解偶联所致； S473 磷酸化的缺失导致 AKT 无法磷酸化 FOXO1 并抑制关键糖异生酶的表达，而部分激活的 AKT（仅 T308）足以磷酸化并抑制 GSK3，导致 SREBP1c 激活和高甘油三酯血症。我将通过研究小鼠模型来检验这一假设，在该模型中，mTORC2 调节蛋白 rictor 在肝细胞中被基因删除，导致 S473 磷酸化受损，而 T308 磷酸化完整。我将验证肝脏中 rictor 的遗传损失、rictor 基因表达和 rictor/mTORC2 功能（AKT 磷酸化）的基因剂量特异性影响。将采用正常血糖钳和示踪剂稀释技术来量化胰岛素抑制肝葡萄糖产生的能力。高甘油三酯血症将通过利用泰洛沙泊和放射性标记的脂质研究来评估，以量化 VLDL-TG 的产生和清除率，以及对脂蛋白谱（VLDL、LDL、HDL 和 apoB）的影响。通过肝脏脂质定量来评估肝脂肪变性的可能性。