Hepatic TGFbeta1 in Control of Type 2 Diabetes and NASH via FoxO1 Signaling

项目摘要 营养过剩诱导胰岛素抵抗，这是T2 D和NASH的高危因素。的 胰岛素抵抗诱导的肝脏脂肪生成、纤维化、凋亡和炎症的机制 对于NASH，尚不清楚。血液和组织中高水平的转化生长因子-β1（TGFβ1）， 在患有T2 D和NASH的人和小鼠中观察到。TGF-β1在多种肿瘤的发生、发展中起着关键作用。 细胞反应，包括细胞外基质（ECM）合成和细胞凋亡，这是必不可少的， 组织稳态，但TGFβ1调节葡萄糖代谢和肝脏的分子机制 功能不完全理解。 叉头转录因子Foxo 1是胰岛素→ PI 3 K →蛋白的关键下游靶点 激酶B（Akt）信号通路和胰高血糖素→cAMP→蛋白激酶A（PKA）信号通路。Akt 磷酸化Foxo 1-Ser 253，触发Foxo 1核输出和细胞质隔离， 泛素化相比之下，PKA磷酸化Foxo 1-Ser 273以促进Foxo 1核转位， 肝细胞中的蛋白稳定性。在代谢应激如营养过剩、Foxo 1过度激活时， 促进肝葡萄糖生成（HGP）和高血糖症。在本提案中，PI假设， 肝TGFβ1通过S273磷酸化（Foxo 1-pS273）在控制Foxo 1中起关键作用， Foxo 1核活性，并诱导高血糖症、肝纤维化和炎症，并促进T2 D和 纳什在目标1中，PI和他的团队将使用遗传方法1）删除肝脏中的TGFβ1基因 具有或不具有活性Foxo 1-S273 D/D突变的小鼠（L-TGFβ 1 KO），或2）产生肝特异性 TGFβ1过表达小鼠（L-TGFβ 1 OE），有或没有失活Foxo 1-S273 A/A突变，研究 肝TGFβ1是否是Foxo 1-pS273促进HGP、凋亡、肝纤维化和 NASH饮食喂养后的炎症。目的2是使用小鼠原代肝细胞，骨髓- 来源的巨噬细胞和肝星状细胞（HSC），以确定TGFβ1 通过Foxo 1-pS273在肝细胞中促进巨噬细胞去极化和HSC活化。具体的- Smad 3和Foxo 1的结构域相互作用以及相关靶基因在肝细胞中的表达将进一步被研究。 研究了目的3是研究系统性或肝脏TGFβ1信号转导的抑制是否是 足以以Foxo 1依赖性方式预防小鼠中的T2 D和NASH。总的来说，使用 遗传学、基因组学、生物信息学和药理学方法，PI和他的团队完全有能力 探讨肝TGF-β1→ Foxo 1-pS273→TGFβ1环系统在肝纤维化中的新的病理生理作用。 控制T2 D和NASH，这将为糖尿病和NASH的机制提供新的见解。

Project Summary Overnutrition induces insulin resistance, which is a high-risk factor for T2D and NASH. The mechanism underlying insulin resistance-induced hepatic lipogenesis, fibrosis, apoptosis, and inflammation for NASH is unclear. High levels of transforming growth factor-β1 (TGFβ1) in blood and tissues were observed in both human and mice with T2D and NASH. TGF-β1 plays a pivotal role in a diverse range of cellular responses, including extracellular matrix (ECM) synthesis and apoptosis which are essential for tissue homeostasis, but the molecular mechanism by which TGFβ1 regulates glucose metabolism and liver function is incompletely understood. The forkhead transcription factor Foxo1 is a key downstream target of the insulin→ PI3K→protein kinase B (Akt) signaling pathway and the glucagon→cAMP→protein kinase A (PKA) signaling pathway. Akt phosphorylates Foxo1-Ser253, triggering Foxo1 nuclear export and cytoplasmic sequestration for ubiquitination. By contrast, PKA phosphorylates Foxo1-Ser273 to promote Foxo1 nuclear translocation and protein stability in hepatocytes. Upon metabolic stress such as overnutrition, Foxo1 hyperactivation promotes hepatic glucose production (HGP) and hyperglycemia. In this proposal, the PI hypothesizes that hepatic TGFβ1 plays key role in control of Foxo1 via phosphorylation at S273 (Foxo1-pS273), enhancing Foxo1 nuclear activity, and inducing hyperglycemia, liver fibrosis and inflammation, and promoting T2D and NASH. In Aim 1, PI and his team will use genetic approaches to 1) delete the TGFβ1 gene in the liver of mice (L-TGFβ1KO) with or without active Foxo1-S273D/D mutation, or 2) generate liver-specific overexpression TGFβ1 mice (L-TGFβ1OE) with or without inactive Foxo1-S273A/A mutation, investigating whether hepatic TGFβ1 is a key controller for Foxo1-pS273 in promoting HGP, apoptosis, liver fibrosis and inflammation following the NASH diet feeding. Aim2 is to use mouse primary hepatocytes, bone marrow- derived macrophages, and hepatic stellate cells (HSC) to determine the mechanisms by which TGFβ1 promotes macrophage depolarization and HSC activation via Foxo1-pS273 in hepatocytes. The specific- domain interactions of Smad3 and Foxo1 and related target genes expression in hepatocytes will be further investigated. Aim 3 is to investigate whether suppression of systematic or hepatic TGFβ1 signaling is sufficient for the prevention of T2D and NASH in mice, in a Foxo1 dependent manner. Overall, using the genetic, genomic, bioinformatic, and pharmacological approaches, the PI and his team are fully equipped to investigate the new pathophysiological role of hepatic TGF-β1→Foxo1-pS273→TGFβ1 looping system in control of T2D and NASH, which will provide novel insights on mechanism of diabetes and NASH.