Glycemic Control and Progession of Diabetic Retinopathy

摘要 糖尿病视网膜病变仍然是劳动年龄成年人失明的主要原因。具有里程碑意义的临床研究 已经证明，即使在实现并保持良好的血糖控制多年后，损害 先前糟糕的血糖控制所灌输的东西变得难以撤销，结果表明 既往的高血糖会留下后遗症。这种“新陈代谢” 记忆现象在体外和体内也被复制。 糖尿病视网膜病变的活体实验模型。大鼠高血糖的终止不能逆转 线粒体功能障碍和DNA(MtDNA)损伤， DNA修复酶MutL同源物1(MLH1)残留 线粒体DNA异常和受损 抄写继续危及 电子传输链(等)。 基因组和结构/生理的稳定性对线粒体的动态平衡很重要； 即使在高血糖停止后，融合酶丝裂原2(Mfn2)也仍然低于正常水平。近期 研究已经证明，基因组功能也受到表观遗传修饰的调节，即 在不改变DNA序列的情况下调节基因表达的修饰。我们最近的研究表明 研究表明，糖尿病会激活视网膜及其毛细血管细胞中的DNA甲基化机制，而这 激活不会因高血糖逆转而终止。因此，中心假设是由于持续的 表观遗传修饰、线粒体DNA和结构/功能仍然受损。功能失调 线粒体继续进入自由基的恶性循环，而高血糖的停止未能 阻止早期糖尿病视网膜病变的进展。 目的1研究表观遗传修饰在线粒体基因组稳定性中的作用。我们的模型预测 由于持续的MLH1启动子DNA超甲基化，线粒体基因组保持稳定 线粒体DNA转录受损，继续破坏ETC系统，进入线粒体 损坏。目标2将确定表观遗传修饰如何调节线粒体结构/生理 动态平衡，并将研究Mfn2启动子的表观遗传修饰在继续 线粒体受损。目的3将确定线粒体动态平衡的保护作用 糖尿病视网膜病变在正常血糖期间通过直接抑制表观遗传修饰而抵抗停止， 这是伴随着高血糖而来的。该计划将使用体外(视网膜内皮细胞)和体内(视网膜 来自啮齿动物的微血管维持在不同的血糖控制中)代谢记忆模型，并将利用 充分优化分子生物学和药理学方法。我们的总体目标是了解 糖尿病进展过程中线粒体持续损伤的分子机制 视网膜病变。该提案基于一个可验证的中心假说，这些创新研究带有 显著的翻译影响，因为它们有望定义表观遗传学在持续线粒体中的作用 此外，它还可以抑制这种损害，并确定新的治疗靶点，以抑制这种威胁视力的疾病的进展。

ABSTRACT Diabetic retinopathy remains the leading cause of blindness in working-age adults. Landmark clinical studies have documented that even after achieving and maintaining good glycemic control for many years, damage instilled by the prior poor glycemic control becomes difficult to undo, and the results have suggested that the prior hyperglycemia leaves a legacy. This `metabolic memory' phenomenon is also duplicated in vitro and in vivo experimental models of diabetic retinopathy. Termination of hyperglycemia in rats does not reverse mitochondrial dysfunction and DNA (mtDNA) damage, DNA repair enzyme MutL homolog 1 (Mlh1) remains subnormal, and impaired mtDNA transcription continues to compromise the electron transport chain (ETC). Stability of both genomic and structure/physiology are important for mitochondrial homeostasis; mitochondrial fusion enzyme mitofusin 2 (Mfn2) also remains subnormal even after cessation of hyperglycemia. Recent studies have documented that genomic functions are also modulated by epigenetic modifications, the modifications that regulate gene expression without changing the DNA sequence. Our recent research has shown that diabetes activates DNA methylation machinery in the retina and its capillary cells, and this activation is not terminated by reversal of hyperglycemia. Thus, the central hypothesis is that due to sustained epigenetic modifications, mitochondrial DNA and structure/function remain damaged. Dysfunctional mitochondria continues to fuel into the vicious cycle of free radicals, and cessation of hyperglycemia fails to arrest the progression of incipient diabetic retinopathy. Aim 1 will investigate the role of epigenetic modification in mitochondrial genomic stability. Our model predicts that due to sustained Mlh1 promoter DNA hypermethylation, mitochondrial genomic stability remains compromised, and impaired mtDNA transcription continues to damage ETC system, fueling into mitochondrial damage. Aim 2 will determine how epigenetic modifications regulate mitochondrial structural/physiological homeostasis, and will investigate the role of epigenetic modifications of Mfn2 promoter in continued mitochondrial damage. Aim 3 will determine the effect of protection of mitochondrial homeostasis in the resistance of diabetic retinopathy to halt by directly inhibiting epigenetic modifications during normal glycemia, which has followed hyperglycemia. The plan will employ in vitro (retinal endothelial cells) and in vivo (retinal microvessels from rodents maintained in varied glycemic control) models of metabolic memory, and will utilize fully optimized molecular biological and pharmacological approaches. Our overall goal is to understand the molecular mechanism responsible for continued mitochondrial damage in the progression of diabetic retinopathy. The proposal is based on a testable central hypothesis, and these innovative studies carry a significant translational impact as they are expected to define the role of epigenetics in continued mitochondrial damage, and identify novel therapeutic targets to inhibit the progression of this sight-threatening disease.