糖尿病肾病中MC-1/MC-3差异性表达的作用及调节机制研究

Mitochondrial dysfunction plays an important role in diabetes and diabetic complications. Substantial evidence suggests that ROS generation from the mitochondrial complexes I（MC-1） and III（MC-3） is a major contributor to oxidative stress in the diabetic kidney. It was found that the development of diabetic nephropathy as indicated by hyperfiltration and histopathological lesions in the kidney of db/db mice is associated with diminished induced ROS generation and MC-3 activity. The MC-3 protein level in the renal mitochondria was equivalent in db/db and the non-diabetic db/m mice whereas MC-1 protein was dramatically upregulated in db/db mice. However, does this nonunified upregulation among individual mitochondrial complexes alter the equilibrium of the electron transport chain in renal mitochondria and contribute to ROS overproduction and oxidative stress? What is the mechanism of the nonconcordant regulation in the expression of individual electron transport chain components? In the current work, we will focus on the mechanism of the diabetic mitochondrial dysfunction and the nonconcordant regulation in the expression of individual electron transport chain components by modern biological technologies. This study may provide one mechanism of diabetic nephropathy and a new target for diabetic complications therapy.

线粒体功能障碍在糖尿病及其并发症中扮演着重要角色。线粒体复合体Ⅰ（MC-1）和MC-3生成的过量ROS是糖尿病肾病中氧化应激的主要责任者。我们发现：在db/db小鼠中，糖尿病肾病的发展与诱导性ROS生成减弱及MC-3活性减弱相关（与肾脏滤过损伤和病理组织学损伤的结果一致）；而MC-1表达的增高与内源性ROS呈正相关。那么，电子传递链上各MC非"和谐一致"的调节是否是线粒体功能异常、电子漏增加和ROS过度生成的原因呢？糖尿病时电子传递链上MC之间差异性表达的调节机制又是什么呢？本研究拟利用db/db小鼠和原代肾细胞，采用多种生物医学技术，研究MC差异性表达与线粒体功能及ROS的关系、以及MC差异性表达的调节机制，揭示糖尿病时线粒体功能障碍的分子机制，阐明线粒体功能障碍在糖尿病肾损伤中的作用。本研究结果不仅有助于认识糖尿病肾病的病理发生机制，同时对糖尿病肾病的防治也具有重要意义。

本项目对糖尿病线粒体复合物差异性表达在糖尿病并发症中的作用及机制进行了研究。研究发现：（1）db/db小鼠肾脏线粒体中，线粒体复合物Ⅰ（MC-1）表达增加，而线粒体复合物Ⅲ（MC-3）的活性减低，Maletonin诱发的ROS生成显著减低。（2）Maletonin是通过MC-3上抗霉素A敏感的位点（即MC-3还原中心）诱发快速ROS生成的，并且这一过程不依赖/不伴随线粒体钙离子活动。（3）提高MC-3活性，可增加Melatonin诱发的不伴随线粒体Ca2+活动的ROS生成，这一过程对高糖引发的线粒体损伤具有一定抑制效应。（4）NF-κB抑制剂QNZ可以显著抑制缓激肽所引发的线粒体钙离子活动，NF-κB对线粒体钙离子活动的影响可能参与了线粒体复合物差异性表达对ROS生成的影响这一过程之中。本研究不仅有助于我们认识线粒体功能在糖尿病中的作用，而且有助于我们更深刻的理解糖尿病与其并发症之间的病理发生机制，同时对糖尿病肾病的防治也具有重要意义。