Mitochondrial-Derived Superoxide in Type 2 Diabetic Kidney Disease

 描述(由申请人提供)： 在美国，每年有超过10万人被诊断为肾衰竭。糖尿病是慢性肾脏疾病和肾衰竭的最常见原因。在过去的几年里，我们的研究工作集中在识别糖尿病肾病并发症的分子机制和潜在的生物标志物上。我们的研究确定了促纤维化细胞因子转化生长因子在糖尿病肾病中的核心作用。我们还发现，在肥胖的非裔美国人中，脂联素激素与蛋白尿呈负相关，非裔美国人是退伍军人中肾脏疾病发病率较高的人群。这一观察直接使我们认识到，主要的能量感受器，AMP激活的蛋白激酶(AMPK)，是由脂联素调节的，在肾脏疾病中发挥着重要作用。在VA Merit基金的支持下，我们最近的研究进一步表明，1型糖尿病肾脏疾病和肥胖相关肾脏疾病的特征都是AMPK活性降低。AMPK活性的恢复阻断了基质的积累和转化生长因子的产生和活性。此外，我们最近发现，AMPK的激活可以降低炎症和过氧化氢水平，这可能是通过调节NAPDH氧化酶来实现的。通过使用基于GC-MS的代谢组学分析，我们最近发现糖尿病和慢性肾脏疾病患者中13种代谢物显著减少，这些代谢物是潜在的肾功能生物标志物。在13个差异表达的代谢物中，有12个与线粒体代谢有关，这表明线粒体活性有缺陷。最近的另一个重大突破是，通过使用新的实时成像技术，我们发现1型糖尿病动物模型的肾脏和心脏中线粒体超氧化物减少，这与目前认为线粒体超氧化物增加是器官损伤的观点相反。用AMPK激动剂刺激后，线粒体含量增加，线粒体复合体活性增加，线粒体超氧化物歧化生成增加，炎症和纤维化减轻。因此，我们推测底物氧化和线粒体活性的改变可能在早期糖尿病中起关键作用。 肾脏疾病和线粒体含量的长期减少可能导致器官衰竭。然而，类似的研究还没有在2型糖尿病中进行。尽管我们发现了2型糖尿病和慢性肾脏病患者线粒体功能降低的证据，但我们还没有用动物模型建立这些发现的基础。由于2型糖尿病的发展与1型糖尿病的发病机制有很大的不同，因此可能会对代谢和线粒体功能产生不同的影响。然而，在初步研究中，我们发现在2型糖尿病db/db小鼠模型的肾脏中线粒体超氧化物也减少。目前的提案将集中于了解线粒体衍生的超氧化物在2型糖尿病肾脏疾病模型中的机制和后果。我们将分析与线粒体和细胞代谢相关的具体变化，以及改善线粒体功能的方法，以确定治疗干预的目标。

 DESCRIPTION (provided by applicant): Each year in the United States, more than 100,000 people are diagnosed with kidney failure. Diabetes is the most common cause of chronic kidney disease and kidney failure. From the last several years, our research efforts are focused on identifying molecular mechanisms and potential biomarkers involved in the complications of diabetic kidney disease. Our research established a central role for the pro-fibrotic cytokine Transforming Growth Factor- (TGF) in diabetic nephropathy. We also showed that the hormone adiponectin negatively correlates with albuminuria in obese African Americans, a portion of the VA population that has a high incidence of kidney disease. This observation directly led us to the recognition that the master energy sensor, the enzyme AMP activated protein kinase (AMPK), is regulated by adiponectin and plays a major role in kidney disease. Our recent studies, supported by VA Merit funding, further demonstrated that both type 1 diabetic kidney disease and obesity-related kidney disease are characterized by reduced AMPK activity. Restoration of AMPK activity blocked matrix accumulation and TGF- production and activity. In addition, we recently found that AMPK activation reduces inflammation and hydrogen peroxide levels, likely via regulation of NAPDH oxidase. By using GC-MS based metabolomic analysis we recently identified a significant reduction in 13 metabolites, potential biomarkers of kidney function, in patients with diabetes and chronic kidney disease. Twelve of the 13 differentially expressed metabolites are linked to mitochondrial metabolism, suggesting defective mitochondrial activity. Another major recent breakthrough was that by using novel real-time imaging techniques, we found that mitochondrial superoxides are reduced in the kidneys and heart of animal models with type 1 diabetes, which is in contrast to the current belief that increased mitochondrial superoxide is responsible for organ damage. Stimulation with AMPK activators resulted in an increase in mitochondrial content, an increase in mitochondrial complex activity, an increase in mitochondrial superoxide production and resolution of inflammation and fibrosis. Therefore, we hypothesize that alterations in substrate oxidation and mitochondrial activity may play a key role in early diabetic kidney disease and prolonged reduction of mitochondrial content may lead to organ failure. However, similar studies have not been performed in type 2 diabetes. Although we find evidence of reduced mitochondrial function in patients with type 2 diabetes and CKD, we have not established the basis of these findings using animal models. As type 2 diabetes development is very different than pathogenesis of type 1 diabetes, there could be different effects on metabolism and mitochondrial function. However, in preliminary studies we find that mitochondrial superoxide is also reduced in the kidney of the db/db mouse model of type 2 diabetes. The current proposal will be focused to understand the mechanisms and consequences of mitochondrial derived superoxides in type 2 models of diabetic kidney disease. We will analyze specific changes associated with mitochondrial and cellular metabolism and approaches to improve mitochondrial function with the aim of identifying targets for therapeutic intervention.