FACTORS THAT MODIFY INSULIN ACTION

改变胰岛素作用的因素

• 批准号: 2850495
• 负责人: MARIA G BUSE
• 金额: $ 22.76万
• 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 2003-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2850495
• 关键词: 3T3 cells; N acetylglucosamine; amidophosphoribosyltransferase; biological signal transduction; carbohydrate biosynthesis; enzyme activity; genetically modified animals; glucose; glucose transport; glucose transporter; glycosylation; hexosamines; immunoprecipitation; insulin; insulin receptor; insulin sensitivity /resistance; intracellular transport; laboratory mouse; laboratory rat; matrix assisted laser desorption ionization; posttranslational modifications; protein kinase C; protein transport; protein tyrosine phosphatase; western blottings

"Glucose toxicity" accounts for insulin resistance in uncontrolled Type I diabetes (IDDM) and contributes to insulin resistance in Type II diabetes (NIDDM). Sustained hyperglycemia or hyperinsulinemia cause insulin resistance; glucose and insulin act synergistically in down- regulating insulin-stimulated glucose transport. A hypothesis to be tested in 3T3-Ll adipocytes is that glucose/insulin induced glucose transport desensitization reflects altered subcellular trafficking of the glucose transporter, GLUT4, which may involve impaired GLUT4 translocation and inappropriate association of GLUT4 containing vesicles (GCV) with the plasma membrane. Products of the hexosamine synthesis pathway (HNSP) have been implicated in glucose-induced insulin resistance; glutamine-fructose-6-P amidotransferase (GFAT) is the rate limiting enzyme and UDP-N-acetyl glucosamine (UDP-GlcNAc) the major product. The role of HNSP will be tested by examining whether conditions which increase or decrease flux via HNSP augment or mitigate, respectively, glucose induced insulin resistance. O-GlcNAcylation is a reversible process, involving O-glycosylation of proteins on Ser/Thr residues with monosaccharide GlcNAc. It usually involves phosphorylation sites and may be regulatory. Based on preliminary data in muscles of a mouse model of insulin resistance, over-expressing GLUTI in muscle, the hypothesis will be tested that increased flux via HNSP promotes O-GlcNAcylation of critical proteins involved in insulin- stimulated glucose transport. These may include GSV-associated proteins, possibly GLUT4 itself and/or proteins associated with GSV docking and fusion. Since adaptive regulation usually involves multiple sites,, we will test the hypothesis that glucose-induced insulin resistance represents in part down-regulation of the insulin receptor (IR) signaling cascade, attempt to identify the major regulatory sites and critically assess the possible contribution of HNSP to the glucose effect. If warranted, the involvement of modulators of IR signal transduction, I.E. protein kinase C (PKC) isoforms, and candidate protein tyrosine phosphatases (PTP-ases: PTP-1B, SH-PTP2 and LAR) will be examined. GFAT activity is allosterically regulated by UDP-GlcNAc, and is modulated in vivo in muscle by the hormonal and metabolic milieu. The pre- and post-translational regulation of GFAT expression will be studied in muscles of rodent models.

“葡萄糖毒性”导致不受控制的 I 型糖尿病 (IDDM) 中的胰岛素抵抗，并导致 II 型糖尿病 (NIDDM) 中的胰岛素抵抗。持续的高血糖或高胰岛素血症导致胰岛素抵抗；葡萄糖和胰岛素在下调胰岛素刺激的葡萄糖转运中协同作用。要在3T3-L1脂肪细胞中测试的假设是葡萄糖/胰岛素诱导的葡萄糖转运脱敏反映了葡萄糖转运蛋白GLUT4的亚细胞运输的改变，这可能涉及GLUT4易位受损以及含有GLUT4的囊泡(GCV)与质膜的不适当关联。己糖胺合成途径（HNSP）的产物与葡萄糖诱导的胰岛素抵抗有关；谷氨酰胺-果糖-6-P酰胺转移酶 (GFAT) 是限速酶，UDP-N-乙酰氨基葡萄糖 (UDP-GlcNAc) 是主要产物。 HNSP 的作用将通过检查通过 HNSP 增加或减少通量的条件是否分别增强或减轻葡萄糖诱导的胰岛素抵抗来测试。 O-GlcNAc 酰化是一个可逆过程，涉及单糖 GlcNAc 对 Ser/Thr 残基上的蛋白质进行 O-糖基化。它通常涉及磷酸化位点并且可能是调节性的。基于胰岛素抵抗小鼠模型肌肉中的初步数据，肌肉中过度表达 GLUTI，将测试以下假设：通过 HNSP 增加的流量促进参与胰岛素刺激的葡萄糖转运的关键蛋白质的 O-GlcNAc 酰化。这些可能包括 GSV 相关蛋白，可能是 GLUT4 本身和/或与 GSV 对接和融合相关的蛋白。由于适应性调节通常涉及多个位点，因此我们将测试葡萄糖诱导的胰岛素抵抗部分代表胰岛素受体（IR）信号级联下调的假设，尝试识别主要调节位点并严格评估其可能的贡献HNSP 对葡萄糖的影响。如果有必要，红外信号转导调制器的参与，即将检查蛋白激酶 C (PKC) 亚型和候选蛋白酪氨酸磷酸酶（PTP 酶：PTP-1B、SH-PTP2 和 LAR）。 GFAT 活性受 UDP-GlcNAc 变构调节，并在体内受激素和代谢环境调节。将在啮齿动物模型的肌肉中研究 GFAT 表达的翻译前和翻译后调节。