Prolonged Diabetic Damage to Cardiac Mitochondria

描述(由申请人提供)： 糖尿病患者的并发症，如心肌病，会在多年的高血糖状态下发生。我们认为，延长的时间过程源于线粒体产生的活性氧物种(ROS)和活性氮物种(RNS)增加而对线粒体DNA造成的损伤逐渐积累。由于几个原因，线粒体DNA特别容易受到损伤，某些类型的损伤修复得很差。我们假设线粒体DNA损伤是糖尿病状态下细胞和器官功能障碍的原因。我们实验室开发了OVE26小鼠I型糖尿病模型，最适合于跟踪慢性并发症的发展。长期糖尿病OVE26小鼠的心肌线粒体出现形态退化，谷胱甘肽含量降低，DNA损伤增加。以心脏为目标的线粒体抗氧化剂MnSOD活性增加的转基因小鼠，当与OVE26背景杂交时，表现出较少的收缩功能障碍，改善了线粒体形态，并显著改善了线粒体呼吸。我们认为，MnSOD的过度表达抑制了线粒体基因组的损伤，这是改善心肌细胞功能的原因。为了验证ROS或RNS的进行性线粒体DNA损伤在糖尿病心肌病发生发展中的作用这一假说，我们将进行以下具体目标：目的1：评估线粒体DNA的突变和缺失，并将这些变化与线粒体呼吸功能、电子ROS的产生和心肌细胞的收缩能力相关联。目的2：探讨线粒体DNA损伤与糖尿病心肌病之间是否存在因果关系。在OVE26糖尿病的背景下，线粒体DNA将受到心肌过表达MnSOD和线粒体靶向OGG1的保护。我们还将确定，将现有的OGG1基因敲除动物与我们的糖尿病小鼠杂交，是否会加剧DNA损伤和糖尿病心肌病。目的3：评估与自由过渡金属结合的药物的系统治疗是否可以防止超氧化物形成更多破坏线粒体DNA的活性物种。这些研究的结果可能直接适用于开发最大限度地减少或绝对预防某些糖尿病并发症的新疗法。

DESCRIPTION (provided by applicant): In diabetic patients complications such as cardiomyopathy develop over many years of hyperglycemia. We are proposing that the prolonged time course stems from the gradual accumulation of damage to mitochondrial DNA caused by increased mitochondrial generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). For several reasons, mitochondrial DNA is especially vulnerable to damage and some types of damage are poorly repaired. We hypothesize that mitochondrial DNA damage is causal for cellular and organ dysfunction in the diabetic state. Our laboratory developed the OVE26 mouse model of Type I diabetes, optimal for following chronic development of complications. Cardiac mitochondria from long-term diabetic OVE26 mice exhibit morphological degeneration, decreased glutathione content and increased DNA damage. Transgenic mice with increased activity of the mitochondrial antioxidant MnSOD, targeted to the heart, when crossed onto the OVE26 background, show less contractile dysfunction, improved mitochondrial morphology and a significant improvement in mitochondrial respiration. We propose that MnSOD overexpression suppresses damage to the mitochondrial genome and that this accounts for improved cardiomyocyte function. To test the hypothesis that progressive mitochondrial DNA damage by ROS or RNS contributes to the development of diabetic cardiomyopathy we will carry out the following Specific Aims: Aim 1: Evaluate mutations and deletions in mitochondrial DNA and correlate these changes with mitochondrial respiratory function, electron ROS generation and cardiomyocyte contractility. Aim 2: Determine if there is a cause and effect relationship between mitochondrial DNA damage and diabetic cardiomyopathy. On the OVE26 diabetic background mitochondrial DNA will be protected by cardiac overexpression of MnSOD and mitochondrial targeted OGG1. We will also determine whether both DNA damage and diabetic cardiomyopathy are exacerbated by crossing existing OGG1 knockout animals to our diabetic mice. Aim 3: Assess whether systemic therapy with agents that bind free transition metals can prevent superoxide from forming more reactive species that damage mitochondrial DNA. Results of these investigations may be directly applicable to the development of new therapies which minimize or absolutely prevent certain diabetic complications.