蛋白磷酸酶2A在肠外营养相关肝损伤中的作用机制研究

Parenteral nutrition is the main method of nutritional support in intestinal failure patients, but the complication called parenteral nutrition related liver injury limits the application of parenteral nutrition. We have established stable parenteral nutrition model in mice, and found that liver fat deposition and elevated PP2A expression occurred together during parenteral nutrition. We also found that the level of phosphorylated LKB1/AMPK decreased. It was reported that PP2A may lead to LKB1 / AMPK dephosphorylation in literature. It is still unclear that how does PP2A work on the role of PNALD. We thus hypothesize that the inhibition of LKB1/AMPK phosphorylation mediated by PP2A may affect the liver fat metabolism which induces liver fat deposition and plays a crucial role in the development of PNALD. We establish the PN model and investigate the changes and relationship among the level of PP2A, the LKB1/AMPK signaling pathway and the levels of key molecules in lipid metabolism, using liver specific PP2A knockout mice and molecular biological techniques such as Western Blot, qRT - PCR, adenovirus infection in vitro cell, to explore the the mechanism of PNALD. It will provide theoretical basis and new ideas to prevent PN related complications in early phase and improve the treatment effects.

肠外营养是肠功能衰竭病人的主要营养支持方式，但其并发症肠外营养相关性肝脏损伤限制了肠外营养在肠衰竭病人中的应用。我们前期已建立稳定的肠外营养小鼠模型，并在研究中发现肠外营养时肝脏脂肪沉积与PP2A表达升高相伴发生，且与脂肪代谢密切相关的LKB1/AMPK磷酸化水平降低，同时文献报道，PP2A可诱导LKB1/AMPK去磷酸化的作用。但PP2A在肠外营养相关肝脂肪变性中的作用及机制尚不清楚。因此我们提出假设肠外营养时PP2A通过LKB1/AMPK去磷酸化作用，影响肝脏脂肪代谢从而诱导肝脏脂肪沉积，参与PNALD的发生发展。本课题采用肝脏特异性PP2A基因敲除小鼠，通过建立PN模型、Western Blot、qRT-PCR、体外细胞腺病毒感染等方法，探讨PN刺激下肝脏PP2A水平、LKB1/AMPK信号通路、脂肪代谢途径关键分子表达变化及其相关性，明确PNALD发生机制，为临床早期预防PN相关。

肠外营养是挽救肠功能衰竭病人生命的主要治疗手段，但其并发症肠外营养相关性肝脏脂肪变是限制肠外营养长期使用并导致不良结局的重要因素。课题组首先从临床病例出发，通过病人肝脏组织标本的蛋白质组学研究，探讨肠外营养相关肝脏脂肪病变的蛋白表达水平的变化及潜在分子机制。同时通过建立稳定的肠外营养肝脏脂肪病变的动物模型，确定了蛋白磷酸酶2A（protein phophastase 2A, PP2A）在肠外营养相关肝脏脂肪病变中的保护作用，并分别应用肝脏组织特异性 PP2A 敲除小鼠及构建PP2A过表达腺病毒转染，通过qPCR、western blot等方法探讨PP2A在肠外营养肝脏脂肪变中的潜在作用机制，发现DGAT在其中起到了重要作用。上述研究结果为预防或减轻肠外营养肝脏脂肪变提供理论基础，为后续肠外营养长期临床应用提供新的干预靶点。