猪STEAP4对巨噬细胞浸润脂肪组织引发炎症反应的调控机制

Excessive fat deposition (Obesity) is one of the most important issues for animal and medical researchers. A major advance in recent metabolic research is the finding of the relationship between inflammation and obesity, which provides academic foundation to demonstrate the role of inflammation in mediating obesity-induced metabolic diseases. STEAP4 is thought to be a counter-regulator controlling obesity-induced inflammation and metabolic diseases, and plays an important role in maintaining cellular metabolic homeostasis. Based on our previous studies on functional analysis and transcriptional regulations of porcine STEAP4, we intend to further carry out the following studies in the present proposal: 1) to assess the expression of porcine steap4 and other related genes, lipid synthesis pathway and insulin signal pathway in visceral adipose tissue of the pigs injected by clodronate liposomes to deplete macrophages; 2) to explore the coordinated roles and mechanism of porcine STEAP4, MIF and resistin during porcine primary macrophages migration to adipocytes in vitro models; 3) to determine porcine STEAP4 can block which one of inflammatory signal pathways by microarray and inhibition analysis; 4) to evaluate whether porcine STEAP4 controls ER stress by UPR pathway; 5) to explore whether porcine STEAP4 can rescue the damages of mitochondrial number and function elicited by FFAs. The goal of our investigation is to clarify the regulation and mechanism of porcine STEAP4 in inflammatory response and metabolic diseases elicited by macrophages infiltration into adipose tissue, which could provide experimental evidences for improving the meat quality of animals as well as new molecular academic foundation for combating obesity-associated metabolic diseases in humans/animals.

脂肪过度沉积（肥胖）是动物界和医学界关注的焦点之一。炎症与肥胖的关联是近年来代谢研究的重要发现，为证明炎症介导肥胖引发的各种代谢疾病提供了理论基础。STEAP4是控制炎症和代谢疾病的反调节子，对维护细胞代谢稳态发挥重要作用。本项目在前期研究猪STEAP4基因功能和转录调控的基础上，将深入研究：1）体内靶向剔除猪腹腔巨噬细胞对STEAP4等基因表达、脂质合成通路、胰岛素信号通路的影响；2）STEAP4、MIF和resistin在体外巨噬细胞向脂肪细胞迁移过程中的协调作用；3）利用基因芯片和抑制剂，确定猪STEAP4阻断的具体炎症信号途径；4）猪STEAP4对内质网应激的调控；5）猪STEAP4能否挽救FFAs引起的线粒体数量及功能的损伤。旨在弄清STEAP4对巨噬细胞浸润脂肪组织并引发炎症反应的调控机制，为猪肉品质的改良提供实验依据，也为动物或人肥胖相关的代谢疾病控制提供新的分子理论基础。

代谢与炎症是动物或人存活的两大基本需求。炎症与代谢疾病的关联是近年来代谢研究的重要发现。STEAP4被看作是一个处于代谢和炎症交叉路口的关键基因，对维护细胞代谢稳态和调节各种代谢性炎症疾病中发挥着重要作用。本研究以HepG2肝细胞为细胞模型，以遗传性肥胖的通城猪、高脂诱导的肥胖小鼠以及Sirt1或FGF21敲除小鼠为动物模型，研究了猪STEAP4对脂肪沉积、脂肪异位沉积的调控以及对营养过剩或LPS刺激引起的细胞氧化应激、内质网应激、自噬的调控，探究了STEAP4、Twist2、FTO等对肥胖引起的非酒精性脂肪肝疾病（NAFLD）、胰岛素抵抗及代谢性炎症等的调控及机制，分析了肥胖状态下巨噬细胞浸润脂肪组织并引发炎症反应的原因及机制。研究结果表明，STEAP4和Twist2对脂肪沉积、肝脏脂肪异位沉积、炎症以及胰岛素抵抗等具有很好的控制作用，其机制主要是因为它们对细胞稳态（包括内质网应激、线粒体氧化应激和自噬）或动物机体的稳态具有非常重要的调控作用。本项目的研究结果具有潜在的应用价值，可为动物或人相关的代谢疾病控制提供了新的分子理论基础和治疗策略，也为猪肉品质的改良提供了实验依据。