Epigenetic Mechanisms of Diabetic Metabolic Memory as Studies in Adult Zebrafish

描述（由申请人提供）：糖尿病目前影响着2.85亿人，预计到2030年将增加到4.39亿人。来自实验室和大规模临床试验的证据表明，即使在药物控制血糖的情况下，糖尿病并发症的进展也不受代谢记忆现象的阻碍。表观基因组由包括DNA甲基化和组蛋白修饰在内的所有染色质修饰组成，表观遗传过程使细胞和生物体能够快速响应不断变化的环境刺激。这些过程不仅允许快速适应，而且赋予细胞“记忆”这些遭遇的能力。最近对表观基因组在代谢记忆中的作用的研究仅限于对特定组蛋白修饰的检查；然而，DNA甲基化在代谢记忆中的作用尚未报道。我们的长期目标是破译代谢记忆的分子机制，这些研究将导致识别和开发新的治疗靶点来控制糖尿病并发症的进展。为此，我们建立了1型糖尿病的成年斑马鱼模型，并对该模型进行了表征，表明糖尿病斑马鱼不仅表现出已知的继发性并发症，包括表皮伤口愈合受损，而且还表现出肢体再生受损（尾鳍再生）。在我们目前的研究中，我们证明了高血糖斑马鱼可以在药物去除后2周内恢复到正常的血糖水平，这是由于内源性胰腺β细胞的再生导致了生理上正常的血糖状态。然而，相比之下，这些鱼的体壁表皮伤口愈合和肢体再生仍然受到与急性糖尿病状态相同程度的损害，这表明这些并发症是持续存在的，并且易受代谢记忆的影响。此外，对高血糖后再生的子组织的检查也同样减少，揭示了代谢记忆现象的遗传传递。这些数据使我们假设：高血糖诱导异常DNA甲基化，有助于代谢记忆。这一假设将使用以下两个具体目标进行检验：1。正常、急性糖尿病和代谢记忆状态下DNA甲基化差异的测定。2 .确定高血糖诱导的DNA甲基转移酶和随后的DNA甲基化改变的时间过程。本课题实验的完成将建立高血糖诱导并维持在代谢记忆状态下的基因组甲基化模式。从长远来看，这些实验将为确定预防或逆转糖尿病并发症的新疗法的合适靶点提供基础。

DESCRIPTION (provided by applicant): Diabetes mellitus currently affects 285 million individuals and this is projected to increase to 439 million by 2030. Evidence from both the laboratory and large scale clinical trials has revealed that diabetic complications progress unimpeded via the phenomenon of metabolic memory even when glycemic control is pharmaceutically achieved. The epigenome is comprised of all chromatin modifications including DNA methylation and histone modifications and epigenetic processes allow cells and organisms to quickly respond to changing environmental stimuli. These processes not only allow for quick adaptation but also confer the ability of the cell to "memorize" these encounters. Investigation into the role of the epigenome in metabolic memory is recent and has been limited to the examination of specific histone modifications; however, the role of DNA methylation in metabolic memory has not been reported. Our long term objective is to decipher the molecular mechanisms of metabolic memory with a rationale that these studies will lead to the identification and development of novel therapeutic targets to control the progression of diabetic complications. To this end, we have developed an adult zebrafish model of type I diabetes mellitus and have characterized this model to show that diabetic zebrafish not only display the known secondary complications including impaired epidermal wound healing, but in addition, exhibit impaired limb regeneration (caudal fin regeneration). In our current studies, we demonstrate that hyperglycemic zebrafish can revert back to normal glycemia within 2 weeks of drug removal due to regeneration of endogenous pancreatic beta cells resulting in a physiologically normal glycemic state. However, in contrast, body wall epidermal wound healing and limb regeneration in these fish remains impaired to the same extent as in the acute diabetic state indicating these complications are persistent and are susceptible to metabolic memory. Moreover, examination of daughter tissue that was regenerated in the post hyperglycemia state was similarly reduced revealing the heritable transmission of the metabolic memory phenomenon. This data has led us to hypothesize that: hyperglycemia induces aberrant DNA methylation that contributes to metabolic memory. This hypothesis will be tested using the following two Specific Aims : 1. Determination of DNA methylation differences in the normal, acute diabetic, and metabolic memory states. and 2: Identification of the time course for hyperglycemia induced DNA methyltransferase and subsequent DNA methylation alterations. The completion of the experiments in this proposal will establish the genomic methylation patterns induced by hyperglycemia and maintained in the metabolic memory state. In the long term, these experiments will provide a foundation for the identification of appropriate targets for new treatments to prevent or reverse diabetic complications.