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Molecular mechanism of the novel oxidative stress in diabetes

糖尿病新型氧化应激的分子机制

基本信息

批准号：
16580109
负责人：
TAKENAKA Asako
金额：
$ 2.37万
依托单位：
Meiji University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16580109/
关键词：
α-tocopherol vitamin E α-TTP insulin lysosome proteasome insulin

项目摘要

It has bee reported that a-tocopherol (vitamin E) concentration in blood was reduced in diabetic patients and animals that could induce another oxidative stress by reducing anti-oxidative activity. It has been established that liver has the main role to secrete food-derived a-tocopherol to circulation through function of a-tocopherol transfer protein (a-TTP) and a-TTP was a major determinant of plasma a-tocopherol level by this mechanism. We have found that hepatic a-TTP level was reduced in streptozotocin-induced diabetic rats and reduction of a-TTP concentration was also observed in hepatocytes cultured with low concentration of insulin (<10^<-10>M). Therefore, the aim of this study was to investigate the molecular mechanism of the reduction of hepatic a-TTP concentration under insulin depleted condition. Primary cultured rat hepatocyte was incubated with/without cyclohexymide (inhibitor of protein synthesis) and with various concentration of insulin for various periods and a-TTP level was measured by Western blot analysis. The results showed that a-TTP level decreased with low concentrations of insulin (10^<-10>M, 0M) while a-TTP level was not changed with high concentrations of insulin (10^<-8>M, 10^<-6>M) for 12 and 24 hours incubation. Furthermore, the decrease of a-TTP disappeared by preventing protein synthesis. Therefore, the decrease of a-TTP might be due to degradation by protease activity induced by low insulin concentration. Next, we investigated whether concentration of a-TTP were influenced by lysosome or proteasome inhibitor. The results showed that a-TTP concentration was greatly reduced by addition of lysosome inhibitors but not influened by a proteasome inhibitor. In conclusion, hepatic a-TTP may be degraded under low concentration of insulin, and a-TTP protease may be rapidly procecced by lysosome.

据报道，在糖尿病患者和动物中，血液中的α-生育酚（维生素E）浓度降低，这可能通过降低抗氧化活性而诱导另一种氧化应激。已经确定，肝脏通过α-生育酚转移蛋白（α-TTP）的功能将食物来源的α-生育酚分泌到循环中具有主要作用，并且α-TTP通过该机制是血浆α-生育酚水平的主要决定因素。我们已经发现，在链脲佐菌素诱导的糖尿病大鼠中，肝脏a-TTP水平降低，并且在用低浓度胰岛素（<10 μ M）培养的肝细胞中也观察到a-TTP浓度的降低。<-10>因此，本研究的目的是探讨在胰岛素耗竭条件下肝脏a-TTP浓度降低的分子机制。将原代培养的大鼠肝细胞与/不与环己酰亚胺（蛋白质合成抑制剂）和不同浓度的胰岛素孵育不同的时间，并通过Western印迹分析测量α-TTP水平。结果表明，在12和24小时孵育期间，低浓度胰岛素（10 μ M，0 M）可降低a-TTP水平，而高浓度胰岛素（10 μ M，10 μ M）则无变化。<-10><-8><-6>此外，通过阻止蛋白质合成，a-TTP的减少消失。因此，α-TTP的降低可能是由于低胰岛素浓度诱导的蛋白酶活性的降解。接下来，我们研究了α-TTP的浓度是否受溶酶体或蛋白酶体抑制剂的影响。结果表明，溶酶体抑制剂能显著降低α-TTP浓度，而蛋白酶体抑制剂对α-TTP浓度无影响。结论：在低浓度胰岛素作用下，肝脏α-TTP可能被降解，α-TTP蛋白酶可能被溶酶体快速加工。