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(T2D)与肥胖受试者肝脏DNA甲基化的变化有关。然而，糖尿病肝脏中DNA甲基化如何调节基因表达的确切机制，以及这些变化是否导致肝脏胰岛素抵抗，目前大多尚不清楚。我的项目提案旨在识别肝脏中重要代谢基因的动态表观遗传调节，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。第六年的发现增加了新的目标：新颖1.1。2型糖尿病肥胖者和DIO小鼠的肝脏microRNA表达和WGBS。Galnt18-/-小鼠的初步代谢特征在第一个资助期间，收集了肥胖、2型糖尿病和非糖尿病受试者的肝活检。此外，还进行了一项纵向小鼠研究，在高脂喂养开始后1、2、4、5、6、7、8和12周采集饮食诱导的肥胖小鼠的肝脏。在AIMS 1.1中，将对这些人和小鼠的肝脏样本进行microRNA和全基因组二硫化物测序(WGBS)数据的分析，以寻找2TD中表观遗传失调的基因，并追踪这些变化是否动态和导致胰岛素抵抗的发展。在第一个资助期间，我们已经发现基因组和表观遗传学的改变与肝脏转录因子结合和T2D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，导致DNA甲基化改变的分子机制将在扩大的资助期内详细研究。将描述Galnt18缺陷小鼠(Galnt18-/-)的葡萄糖和能量代谢。GALNT18对糖蛋白的形成是重要的，但GALNT18的代谢功能目前尚不清楚。Galnt18-/-小鼠目前正在当地扩大群体的动物设施中繁殖，第一批数据显示Galnt18-/-小鼠降低了血糖和血浆胰岛素浓度。这些小鼠的体重、摄食量、身体成分、葡萄糖和胰岛素耐量以及能量代谢将在正常和高脂肪饲养条件下在全身水平上进行表征。寻找新的糖尿病疾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.