Rictor/mTORC2在老年肝脏再生中的作用及机制研究

The capacity of liver regeneration declines with age. mTORC1 is involved in the liver regeneration and aging, however, the function of mTORC2 in the liver regeneration and aging is still unclear. The survival of liver-specific deletion of Rictor (LiRiKO) mice (loss of mTORC2 activity) were significantly decreased after 70% partial hepatectomy (PH), the capacity of liver regeneration was also down, the liver triglyceride was increased, fatty acid oxidation was down，and these phenotypes were increased with age. The activity of FOXO1 and AMPK was comparable between LiRiKO mice and littermate control after PH, however, the activity of p53 was increased, and p53 inhibitor promoted the liver regeneration. It suggested that mTORC2 was involved in the liver regeneration during ageing by the reprograming of energy metabolism which could be regulated by p53. Sonar (sensor of NAD(H) redox） mouse is a new genetic fluorescent animal model, and it is very useful for monitoring the real-time and in vivo conditions of energy metabolism. NAD+/NADH ratio in the hepatocytes of Sonar mice was significantly down after PH during the liver regeneration, suggesting that glycolysis was increased during liver regeneration. Therefore, we hypothesize that mTORC2 has an effect on the liver regeneration by regulating the energy metabolism. Sonar-LiRiKO mice and liver-specific Rictor and p53 double knockout mice will be used in this study. Understanding the molecular mechanism of mTORC2-p53 in ageing and liver regeneration will be provided new evidences for the promotion of liver regeneration in ageing, and new targets for the prevention and treatment of hepatic diseases.

肝再生能力随着年龄增长而下降，mTORC1可调控衰老和肝再生，但mTORC2对衰老中肝再生的作用仍不清楚。我们发现Rictor肝特异敲除小鼠（mTORC2活性缺失）70%肝切除术后小鼠生存率显著下降，肝再生能力下降，肝脂质含量升高，脂肪酸氧化分解降低，以上表型随年龄增长而加剧。敲除小鼠肝再生时，FOXO1和AMPK活性无差异，p53显著激活，抑制p53能改善敲除小鼠肝再生，进一步研究提示mTORC2通过p53调控细胞能量代谢参与老年肝再生。新型遗传荧光探针模型Sonar小鼠能活体实时地监测机体能量代谢变化，肝再生时其肝细胞质内NAD+/NADH比值显著降低，提示肝再生时糖酵解活性增加。本项目拟利用Rictor敲除Sonar小鼠，Rictor和p53双基因敲除小鼠，深入解析mTORC2-p53在老年肝再生中的作用及机制，为改善老年肝再生的能力提供依据，为预防和治疗老年肝脏疾病提供新思路。

肝再生过程中有明显的脂滴积累，mTORC2参与脂类代谢，但mTORC2调控脂类代谢在肝再生中的作用及机制仍然未知。Rictor肝特异性敲除小鼠（R-LKO）导致肝mTORC2活性缺失。肝切除术后，R-LKO小鼠生存率显著下降，肝再生能力下降，切肝后肝脂质含量升高，脂肪酸氧化分解降低。肝脏再生时，R-LKO小鼠脂肪酸转运蛋白CD36, FABP4, Scl27a1和Scl27a5等表达升高。脂质组质谱发现，鞘磷脂中的GlcCer含量在R-LKO小鼠中明显的降低，我们发现GlcCer回补可以直接激活PPARα，改善肝脏再生能力。我们研究发现，mTORC2通过PPARα通路调控脂质代谢参与肝脏再生，GlcCer直接调控PPARα活性，为调控肝脏再生能力提供了新思路。目前研究结果，项目负责人（共同通讯）投稿到Cellular and Molecular Gastroenterology and Hepatology（IF=9.225）正在修回，Revision No：CMGH-D-21-00715。.miRNA在肝脏再生过程中有重要作用。小鼠肝脏切除术后，miR-126肝脏特异性敲除小鼠在术后肝脏再生能力明显降低。在miR-126肝脏特异性敲除小鼠中，抑制p53-p21 pathway能改善小鼠的肝脏再生能力。Cdkn2aip蛋白和mRNA水平在miR-126敲除条件下表达量有明显上升，在Cdkn2aip敲除后p53-p21pathway活性明显下降。miR-126通过调控Cdkn2aip调控p53-p21信号通路参与肝脏再生。此项研究内容，项目负责人以共同通讯发表在Signal Transduction and Targeted Therapy（2021年，标注基金支持））。另外培养2名硕士和1名博士研究生。