Neu1介导肝脏胰高血糖素受体去唾液酸化调节糖异生的机制研究

Type 2 diabetes, characterized by hyperglycemia attributed to insulin resistance and hepatic gluconeogenesis, is a serious hazard to human health. Studies have shown that sialidase Neu1 can mediate insulin receptor (IR) desialyation, reverse insulin resistance, regulate blood glucose homeostasis, but but few investigations on the function of Neu1 in regulating glucose metabolism mention gluconeogenesis. In our preliminary data, we found that: Activity and protein expression of Neu1 both reduced under glucagon induction, and molecular weight of GCGR increased; Neu1 can interact with GCGR in vitro; Liver Neu1 deficiency mice show elevated blood glucose and enhanced glucagon sensitivity, reduced pyruvate tolerance. Thus, we hypothesize that Neu1 inhibited gluconeogenesis by desialyation of GCGR. To validate this, we used liver specific Neu1 knockout mice model and diabetic mice model, in vivo and in vitro experiments will be set up to demonstrate the special role of Neu1 in gluconeogenesis regulation. Together, the novel function of Neu1 in treatment of T2DM will be added to the bibliography and hints the clinical therapy.

由胰岛素抵抗和肝糖异生过度激活引起的以高血糖为特征的2型糖尿病，严重危害人类健康。已有研究表明唾液酸酶Neu1可介导胰岛素受体（IR）去唾液酸化，逆转胰岛素抵抗，调节血糖稳态，但Neu1对糖代谢调控的研究忽视了其对糖异生的调节作用。本项目前期研究表明：细胞水平激活糖异生时，Neu1的活性和表达量均显著下调，细胞表面糖蛋白胰高血糖素受体（GCGR）分子量增大； Neu1可与GCGR结合；肝脏特异性Neu1敲除小鼠表现为：血糖和胰高血糖素敏感性升高，丙酮酸耐受性下降。鉴于此，我们提出假设：Neu1可通过介导肝脏GCGR去唾液酸化，抑制肝糖异生。本项目将使用肝脏特异性Neu1敲除小鼠模型和糖尿病小鼠模型，从细胞和动物水平设计实验，揭示Neu1调节肝糖异生的分子机制，阐释Neu1在肝脏糖代谢过程中的生物效应，为2型糖尿病的防治提供新的视点。

肝脏葡萄糖生成是维持人体葡萄糖稳态的关键，肝糖异生失衡可显著加速2型糖尿病的发生和进展。虽已有研究表明唾液酸酶Neu1是肝脏糖脂代谢的重要调控因子，但其在肝糖异生中的调节作用尚未报道。本项目中，我们使用Alb-cre在肝脏细胞选择性的敲除Neu1基因，从而研究Neu1在肝脏糖异生中的功能。研究发现：肝脏特异性的Neu1敲除小鼠表现为晚期肥胖和糖代谢紊乱，高脂诱导可加剧青年小鼠的糖脂代谢异常。通过分子生物检测发现，肝脏特异性的Neu1敲除，可诱导糖异生关键基因的上调，Neu1-GCGR-Akt-FoxO1信号通路的活化可能是促进其糖异生水平异常上升的原因。此外转录组学分析显示：老年肝脏特异性的Neu1敲除小鼠肝脏中脂质代谢异常与炎症信号通路激活密切相关。本研究为临床采用Neu1为靶点治疗肝脏糖脂代谢异常提供潜在靶点。