Factors that modify insulin action

改变胰岛素作用的因素

• 批准号: 6611828
• 负责人: MARIA G BUSE
• 金额: $ 30.69万
• 依托单位: MEDICAL UNIVERSITY OF SOUTH CAROLINA
• 依托单位国家: 美国
• 财政年份: 1978
• 资助国家: 美国
• 起止时间: 1978-05-01 至 2007-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6611828
• 关键词: 3T3 cells; SDS polyacrylamide gel electrophoresis; acylation; adipocytes; amidophosphoribosyltransferase; carbohydrate biosynthesis; enzyme activity; genetically modified animals; glucose; glucose transport; glucose transporter; green fluorescent proteins; hexosamines; high performance liquid chromatography; immunoprecipitation; insulin; insulin receptor; insulin sensitivity /resistance; intracellular transport; laboratory mouse; mass spectrometry; noninsulin dependent diabetes mellitus; pancreatic islet function; striated muscles; two dimensional gel electrophoresis; western blottings

DESCRIPTION (provided by applicant): "Glucose toxicity" accounts for insulin resistance in uncontrolled Type 1 diabetes and contributes to it in Type 2 diabetes. In 3T3-L1 adipocytes, preincubation in high glucose + 0.6 nM insulin synergistically down-regulate insulin stimulation of glucose transport and Akt/PKB activation distal to phosphatidyl inositol-3- kinase (PI(3)K) activation. The hexosamine synthesis pathway has been implicated in insulin resistance; its major product is UDP-N-acetylglucosamine (UDP-GIcNAc), the substrate of O-GIcNAc-transferase (OGT). OGT catalyzes the addition of single O-GIcNAc to specific Ser/Thr residues. O-GIcNAcylation and O-phosphorylation are often reciprocal. Chronic increased glucose flux enhances protein O-GIcNAcylation in cells and in muscle, in vivo. The role of enhanced O-GIcNAcylation in insulin resistance will be studied in 3T3-L1 adipocytes, L-6 myotubes and in skeletal muscle of insulin-resistant mouse models. Glucose/insulin-responsive O-GIcNAcylated proteins will be identified by mass spectrometry combined with immunological methods. Of special interest are proteins involved in GLUT4 trafficking. O-GIcNAcylation site(s) will be identified and the functional significance of the modification evaluated. The effect of O-GIcNAc-ase overexpression will be studied to test whether preventing excessive O-GIcNAcylation mitigates or prevents glucose-induced insulin resistance. Akt is a downstream target of PI(3)K involved in insulin's metabolic effects, including glucose transport. The mechanism of impaired Akt activation in glucose-induced insulin resistance will be studied. If insulin-stimulated 3-phosphoinositides at the plasma membrane (PM) are decreased, their dephosphorylation may be accelerated, e.g. by SHIP2 or PTEN, or PI(3)K may be mistargeted. If insulin normally stimulates 3-phosphoinositides at the PM in insulin-resistant cells, the activity of phosphoinositide dependent kinase-1 (PDK-1) or effects on Akt itself (e.g., accelerated dephosphorylation or protein interactions) will be examined. The possible role of altered O-GIcNAcylation in the identified defect(s) will be assessed. Defining mechanisms of insulin resistance may lead to the development of novel therapeutic targets.

描述（由申请人提供）：“葡萄糖毒性”是不受控制的 1 型糖尿病中胰岛素抵抗的原因，也是 2 型糖尿病中胰岛素抵抗的原因之一。在 3T3-L1 脂肪细胞中，在高葡萄糖 + 0.6 nM 胰岛素中预孵育可协同下调胰岛素对葡萄糖转运的刺激以及磷脂酰肌醇 3-激酶 (PI(3)K) 激活远端的 Akt/PKB 激活。己糖胺合成途径与胰岛素抵抗有关；其主要产品是UDP-N-乙酰氨基葡萄糖(UDP-GlcNAc)，O-GlcNAc-转移酶(OGT)的底物。 OGT 催化单个 O-GlcNAc 添加到特定的 Ser/Thr 残基上。 O-GlcNAcNA酰化和O-磷酸化通常是相互的。长期增加的葡萄糖通量可增强体内细胞和肌肉中蛋白质 O-GlcNAcNA 酰化。将在胰岛素抵抗小鼠模型的 3T3-L1 脂肪细胞、L-6 肌管和骨骼肌中研究增强的 O-GlcNAcNAc 化在胰岛素抵抗中的作用。葡萄糖/胰岛素反应性 O-GlcNAcNA 酰化蛋白将通过质谱结合免疫学方法进行鉴定。特别令人感兴趣的是参与 GLUT4 运输的蛋白质。将鉴定 O-GlcNAcNA 酰化位点并评估修饰的功能意义。将研究 O-GlcNAc 酶过度表达的影响，以测试防止过度的 O-GlcNAc 酰化是否可以减轻或预防葡萄糖诱导的胰岛素抵抗。 Akt 是 PI(3)K 的下游靶标，参与胰岛素的代谢作用，包括葡萄糖转运。将研究葡萄糖诱导的胰岛素抵抗中 Akt 激活受损的机制。如果质膜 (PM) 上胰岛素刺激的 3-磷酸肌醇减少，它们的去磷酸化可能会加速，例如SHIP2 或 PTEN 或 PI(3)K 可能会被误定位。如果胰岛素通常刺激胰岛素抵抗细胞中 PM 的 3-磷酸肌醇，则将检查磷酸肌醇依赖性激酶 1 (PDK-1) 的活性或对 Akt 本身的影响（例如，加速去磷酸化或蛋白质相互作用）。将评估改变的 O-GlcNAcylation 在已识别缺陷中的可能作用。明确胰岛素抵抗机制可能会导致新治疗靶点的开发。