A Glucocorticoid Receptor-SETDB2 Co-Regulated Liver Metabolic Gene Program

过量的糖皮质激素有助于糖尿病和代谢综合征的发展，代谢综合征包括：肥胖症、高血糖症、高胆固醇血症、胰岛素抵抗和肝脏脂肪变性。糖皮质激素通过糖皮质激素受体（GR）发挥其生理作用，GR是一种在GRE基序处结合染色质的转录因子，导致基因激活或抑制。我们已发表的工作确定了一种以前未被认识的GR介导的基因调控机制，通过与含SET结构域的蛋白质SETDB 2合作，激活与糖尿病相关的肝脏中GR基因靶点的选择子集。我们发现SETDB 2缺陷小鼠的肝脏具有显著减弱的糖皮质激素反应，如通过空腹低血糖和缺乏关键GR靶基因的诱导所证明的。由于抑制肝脏中的糖皮质激素作用可以防止糖皮质激素诱导的糖尿病的负面代谢效应，我们假设肝脏特异性 当暴露于导致糖皮质激素升高的条件时，SETDB 2敲除（DB 2-LKO）小鼠将部分地免受代谢功能障碍。通过评价在升高的内源性糖皮质激素（饮食诱导的肥胖）或外源性糖皮质激素施用的条件下肝脏特异性DB2-LKO和肝脏特异性GR-LKO对葡萄糖/脂质稳态的影响来研究与糖皮质激素诱导的代谢疾病相关的基本机制。将测量与糖尿病相关的代谢参数：体重增加、葡萄糖不耐受、胰岛素抵抗、高脂血症和肝脂肪变性。此外，SETDB 2和GR联合作用的分子机制将在这些实验范例中表征，新的基因靶点和染色质靶向将通过RNA-seq、ChIP-seq和Hi-ChIP鉴定。整合所提出的实验将更好地了解SETDB 2如何影响与肝脏代谢疾病相关的GR的积极和消极作用。的 研究的基本机制可能为靶向SETDB 2在GR作用中的作用提供一种新的途径， 糖皮质激素诱导的糖尿病和代谢性疾病的治疗靶点。这些实验是在小鼠模型中进行的机制性和探索性研究的平衡，以研究与人类疾病直接相关的肝脏代谢过程的调节。这两个目标的结果将被整合在一起，以揭示SETDB 2-GR调节轴有助于肝脏适应急性营养（目标1），慢性营养和激素（目标2）代谢应激状态的重叠和独特机制。

Excess glucocorticoids contribute to the development of diabetes and metabolic syndrome, which includes: obesity, hyperglycemia, hypercholesterolemia, insulin resistance, and liver steatosis. Glucocorticoids exert their physiological effects via the glucocorticoid receptor (GR), a transcription factor that binds chromatin at GRE motifs leading to gene activation or repression. Our published work identified a previously unrecognized mechanism for GR-mediated gene regulation through its collaboration with the SET domain-containing protein, SETDB2, to activate a select subset of GR gene targets in the liver associated with diabetes. We showed livers of mice deficient in SETDB2 have a significantly blunted glucocorticoid response as demonstrated by fasting hypoglycemia and lack of induction of key GR target genes. Since inhibition of glucocorticoid action in liver can prevent the negative metabolic effects of glucocorticoid-induced diabetes, we hypothesize that liver-specific SETDB2-knockout (DB2-LKO) mice will be partially protected from metabolic dysfunction when exposed to conditions that lead to elevated glucocorticoids. Fundamental mechanisms associated with glucocorticoid-induced metabolic disease are studied by evaluating the effects of liver-specific DB2-LKO and liver-specific GR-LKO on glucose/lipid homeostasis under conditions of elevated endogenous glucocorticoids (diet- induced obesity) or exogenous glucocorticoid administration. Metabolic parameters associated with diabetes will be measured: weight gain, glucose-intolerance, insulin-resistance, hyperlipidemia, and hepatic steatosis. Additionally, the molecular mechanism for the combined action of SETDB2 and GR will be characterized within these experimental paradigms and novel gene targets and chromatin targeting will be identified by RNA-seq, ChIP-seq and Hi-ChIP. Integrating the proposed experiments will provide a better understanding of how SETDB2 affects the positive and negative actions of GR that are relevant to metabolic disease in the liver. The fundamental mechanism studied may provide a pathway to target SETDB2’s role in GR action as a new therapeutic target for glucocorticoid-induced diabetes and metabolic disease. The experiments a balance of mechanistic and exploratory studies in mouse models to investigate the regulation of hepatic metabolic processes that are directly relevant to human disease. The results from both aims will be integrated together to reveal the overlapping and unique mechanisms by which the SETDB2-GR regulatory axis contributes to the adaptation of the liver to acute nutritional (Aim 1), chronic nutritional and hormonal (Aim 2) states of metabolic stress.