OGA调控肝细胞损伤与巨噬细胞介导免疫应答的协同效应在NASH中的作用和机制研究

NASH is an inflammatory-related metabolic disorder and about 30% of NASH patients eventually develop to liver cirrhosis. O-GlcNAc glycosylation, an important type of post-translational modifications (PTMs) mediated by OGA/OGT, plays key roles in regulating hepatic gluconeogenesis and lipid metabolism. In our previous studies, OGA-liver-specific-knockout (OGA-LKO) mice, which were established for the first time in our laboratory, displayed insulin resistance, gluconeogenesis disorder, increased fatty acid synthesis and retardant ß-oxidation. Moreover, the absence of OGA in hepatocyte aggravated NASH induced by high fat diet (HFD), suggesting that OGA may be involved in NASH via negative regulation of liver immune inflammatory response. Given that glycolysis and fatty acid synthesis can modulate macrophage (Mφ) activation, and Mφ plays an important role in NSAH progression. However, the molecular mechanism whereby OGA regulates hepatic steatosis and macrophage immune responses remains to be further explored. In this study, we aim to: (1) reveal the underlying molecular mechanism whereby OGA regulates gluconeogenesis, fat synthesis and β-oxidation in the liver; (2) investigate the role of OGA in cooperatively regulating hepatocellular injury and Mφ-mediated immune response in NASH; (3) determine the gut microbiota profiling that is specific to NAFL or NASH and explore its clinical value.

NASH是一种炎症相关的代谢紊乱性疾病，临床上约30%的NASH患者最终进展为肝硬化。OGA/OGT介导的O-GlcNAc糖基化修饰在调节肝脏糖脂代谢中发挥重要的作用。课题组在率先建立的肝细胞特异敲除OGA小鼠中观察到胰岛素抵抗、糖异生紊乱、脂肪酸合成增加和β-氧化减弱，且在HFD诱导下促进NASH发生，提示OGA可能通过负向调控肝脏免疫炎性反应而参与NASH发生，但其核心机制尚未见报道。已知糖酵解和脂肪酸合成可调控巨噬细胞(Mφ)活化，且Mφ在NASH进展中发挥重要作用。因此，通过本项目的研究，我们有望揭示：(1)OGA调控肝细胞糖异生、脂肪合成和脂肪β-氧化的具体分子机制；(2)明确在NAFL发展为NASH过程中OGA促进肝细胞损伤、以及与巨噬细胞介导免疫应答发挥协同效应的分子机制；(3)建立准确的NAFL和NASH肠道微生态指纹谱并探究其临床应用价值。

NASH是一种炎症相关的代谢紊乱性疾病，临床上约30%的NASH患者最终进展为肝硬化。OGA/OGT介导的O-GlcNAc糖基化修饰在调节肝脏糖脂代谢中发挥重要的作用。.项目组主要聚焦OGA在NASH发生中的作用和机制研究。阐明(1)OGA在肝脏糖异生、脂肪合成和脂肪氧化等代谢过程中发挥重要的调控作用和机制；(2) OGA 直接或间接调控巨噬细胞系统促进 NAFL 向 NASH 进展的作用及机制；(3) OGA 直接或间接影响肠道微生态特征谱，通过“肝-肠轴”的调控 NASH 的发生发展的作用和机制。.课题组在率先建立的肝细胞OGA敲除小鼠（OGA-LKO）发现正常饮食下自发脂肪肝形成，并加剧HFD诱导的脂肪肝和肥胖。结合转录组和O-GlcNAc修饰蛋白质组学鉴定并发现OGA-LKO通过升高脂肪水解酶HSL蛋白含量，降低p-HSL（S563），导致HSL脂解活性下降。HSL S565位点的O-GlcNAc糖基化修饰抑制S563位点的磷酸化和HSL的泛素化降解，增强其稳定性。进一步发现OGA-LKO通过抑制肝脏PPARa-FGF21通路，进而引起肝脏脂肪酸氧化代谢减弱和肝-脂肪对话异常。此外，我们还发现OGA-LKO促进MCD饮食诱导的肝脂肪变、炎症和纤维化，而且Kupffer细胞OGA敲除也促进了MCD诱导的肝脏炎症相关表型。O-GlcNAc糖基化修饰的HMGB1可能通过介导肝细胞与Kupffer细胞对话，促进了NASH进展。我们在肥胖伴NAFLD人群中，获得此类患者的肠道细菌特征谱，并筛选出一组以Bacteroides和Streptococcus为代表的，与代谢改变相关的肠道细菌。此外，我们在胰岛β细胞特异性OGA敲除小鼠中发现，OGA可通过调控DRP1引起β细胞损伤、诱导糖耐量受损胰岛素水平下降。肠上皮OGA敲除通过调控S82、T87为CUL5的糖基化修饰影响其稳定性，继而促进炎症相关性肠癌(CAC)发生发展。.项目组兼顾“肝-脂肪”、“肝-肠”、“肝-胰”器官的crosstalk，阐明了OGA调控HSL、AIMP2、YTHDF1、HMGB1、DRP1、CUL5等分子的O-糖基化修饰在NAFLD发生发展、糖脂代谢紊乱及肠道炎癌中的关键机制。