穹窿主体蛋白介导的巨噬细胞活性改变在肥胖相关性代谢紊乱中的作用及其机制研究

In recent years, the incidence of obesity is getting higher, which has increased the risk of obesity-related metabolic disorders such as type 2 diabetes, nonalcoholic fatty liver, and cardiovascular disease, and caused great harm to our people's health. Numerous studies have shown that macrophage-mediated metabolic inflammation is a key step in obesity-associated metabolic disorders. Macrophage phenotype is complicated in adipose tissue microenvironment, and the regulation mechanism of its activity has not been fully understood. In the pre-study, we found that macrophage major vault protein (MVP) can bind to TRAF6, inhibiting its ubiquitination and downstream IKK-NFkB phosphorylation. In obese mouse adipose tissues, MVP was overexpressed and predominantly distributed in macrophages. After MVP systemic deletion, the obesity, insulin resistance and hepatic steatosis in mice were exacerbated. Meanwhile, the accumulation of macrophages in adipose tissues was increased and the inflammatory response was significantly enhanced. In this project, we will further establish macrophage MVP-specific knockout mice and over-expression of MVP and its key fragments in macrophages in vivo. Further combined with cellular and molecular biology experiments, we are determined to study the role and molecular mechanisms of MVP in obesity-associated macrophage activity and metabolic disorders such as type 2 diabetes, hepatic steatosis, and vascular dysfunction.

近年来肥胖发生率增高，显著增加了II型糖尿病、非酒精性脂肪肝及心血管病等肥胖相关性代谢紊乱的发生风险，对我国人民健康造成极大危害。众多研究表明，巨噬细胞参与的代谢性炎症反应是肥胖相关性代谢紊乱的重要发病环节，但微环境中巨噬细胞表型复杂多变，其活性调控机制尚不明确。我们前期发现，巨噬细胞穹窿主体蛋白（MVP）可结合TRAF6，抑制其泛素化及下游IKK-NFkB活性。在肥胖小鼠脂肪组织中，MVP表达增加且主要分布于巨噬细胞。MVP全身性缺失后，小鼠肥胖加重，胰岛素抵抗增强，肝脏脂肪变性加剧，脂肪组织中巨噬细胞聚集增多、炎症反应增强。本项目拟在此基础上，进一步建立巨噬细胞MVP特异性敲除小鼠，及在体巨噬细胞特异性过表达MVP与其关键活性片段，并结合细胞分子生物实验，深入研究MVP在肥胖引起的巨噬细胞活性改变，与II型糖尿病、肝脏脂肪变性、血管功能紊乱等肥胖相关性代谢紊乱中的作用及其机制。

代谢性炎症是肥胖相关性代谢紊乱的重要发病机制，其是一种低烈度、持续且难以消除的慢性炎症反应，不仅不能有效清除感染与损伤，相反地却成为引起肥胖相关性代谢紊乱的关键环节，巨噬细胞的增多和炎性激活在其中发挥主导性作用。因此，深入研究巨噬细胞活性的调节机制，是阐明肥胖相关性代谢紊乱病变机制的关键，对于发现新的代谢性炎症干预靶点及防治代谢性疾病具有重要价值。穹窿主体蛋白（MVP）在巨噬细胞中高表达，可能在机体免疫炎症反应中发挥作用。本项目通过构建MVP全身性和髓系特异性敲除小鼠，发现MVP缺失可加重肥胖相关代谢紊乱及动脉粥样硬化病变。机制探究表明，MVP通过与TRAF6、ASK1等重要炎症调控节点分子相结合，抑制IKK-NFκB及ASK1-JNK信号通路，拮抗巨噬细胞炎症反应进而发挥保护性作用，进一步我们通过结构解析及分子生物学实验验证，找到其发挥作用的关键活性片段。本项目研究发现巨噬细胞MVP是代谢性炎症反应的重要内在负性调控节点，为肥胖相关性代谢紊乱及心血管疾病的防治提供了新的潜在干预靶标。本项目研究在Nat Commun，ATVB等重要学术期刊发表论文3篇，获得国家发明专利2项，累计培养研究生7人。