Epigenetic regulation of hepatic gene expression in the pathogenesis of insulin resistance

以前我和其他人表明，2型糖尿病（T2 D）与肥胖受试者肝脏中DNA甲基化的变化有关。然而，糖尿病肝脏中基因表达如何受DNA甲基化调控的确切机制以及这些改变是否有助于肝脏胰岛素抵抗仍然是未知的。我的项目提案旨在确定肝脏中重要代谢基因的动态表观遗传调控，以增加我们对胰岛素抵抗的理解，并确定新的治疗方法来逆转与肥胖和T2 DM相关的表观遗传改变的基因表达程序。2型糖尿病肥胖受试者和DIO小鼠肝脏中的microRNA表达和WGBS Galnt 18-/-小鼠的初始代谢特征在第一个资助期间，收集来自肥胖的T2糖尿病和非糖尿病受试者的肝活检。此外，进行了一项纵向小鼠研究，其中在高脂肪喂养开始后1、2、4、5、6、7、8和12周从饮食诱导的肥胖小鼠收获肝脏。在目标1.1中，将在这些人类和小鼠肝脏样本中进行microRNA和全基因组二硫键测序（WGBS）数据分析，以发现2 TD中表观遗传失调的基因，并跟踪这些变化是否是胰岛素抵抗发展的动态和因果关系。在第一个资助期间，我们已经确定基因组和表观遗传学改变与肝脏中转录因子结合和T2 D的改变有关。增加更多的全基因组数据将提升该项目，并保证更有效地识别导致肝脏胰岛素抵抗的表观遗传机制。此外，将在扩大供资期间详细研究导致DNA甲基化改变的分子机制。将表征Galnt 18缺陷小鼠（Galnt 18-/-）的葡萄糖和能量代谢。GALNT 18对于糖蛋白的形成是重要的，但GALNT 18的代谢功能目前尚不清楚。Galnt 18-/-小鼠目前正在当地动物设施中繁殖以进行群体扩增，第一批数据显示Galnt 18-/-小鼠具有降低的血糖和血浆胰岛素浓度。将在正常和高脂肪饲养条件下，在这些小鼠中在全身水平上表征体重、食物摄入、身体组成、葡萄糖和胰岛素耐受性以及能量代谢。发现新的糖尿病致病基因对于了解糖尿病的发病机制和制定未来的治疗策略具有重要意义。

Previously I and others showed that type 2 diabetes (T2D) is associated with changes in DNA methylation in liver of obese subjects. However, the precise mechanism how gene expression is regulated by DNA methylation in the diabetic liver and whether these alterations contribute to hepatic insulin resistance remain mostly unknown. My project proposal aims to identify dynamic epigenetic regulation of important metabolic genes in the liver to increase our understanding of insulin resistance and to identify novel therapeutic approaches to reverse the epigenetically altered gene expression programs associated with obesity and T2DM.New aims that are added for the sixth year of finding are:novel 1.1. microRNA expression and WGBS in liver of T2-diabetic obese subjects and DIO micenovel 2.4. Initial metabolic characterization of Galnt18-/- miceDuring the first funding period liver biopsies form obese T2-diabetic and non-diabetic subjects were collected. Furthermore, a longitudinal mouse study was performed in which liver from diet-induced obese mice was harvested 1, 2, 4, 5, 6, 7, 8 and 12 weeks after onset of high-fat feeding. In aims 1.1 analysis of microRNA and whole-genome bisulfide sequencing (WGBS) data will be performed in these human and mouse liver samples to find genes that are epigenetically dysregulated in 2TD and to track if these changes are dynamic and causal for the development of insulin resistance. During the first funding period we already identified that genomic and epigenetic alterations are associated with altered transcription factor binding and T2D in liver. Adding more genome-wide data will elevate the project and guarantee a more efficient identification of epigenetic mechanisms leading to hepatic insulin resistance. Moreover, molecular mechanisms leading to altered DNA methylation will be studied in detail in the expended funding period.Aim 2.4. will characterize the glucose and energy metabolism of Galnt18-deficient mice (Galnt18-/-). GALNT18 is important for formation of glycoproteins but metabolic functions of GALNT18 are currently unknown. Galnt18-/- mice are currently breeding at the local animal facility for colony expansion and first data show that Galnt18-/- mice have reduced blood glucose and plasma-insulin concentrations. The body-weight, food intake, body composition, glucose- and insulin tolerance and energy metabolism will be characterized in these mice under normal and high-fat feeding conditions on a whole-body level. Finding novel diabetes disease genes is of high importance for understanding and diabetes pathogenesis and to develop future treatment strategies.