FoxO1表达与表观遗传修饰在胰岛β细胞衰老和功能障碍中的作用及其机制

Degenerative disorder of pancreatic β cells is a major cause of type 2 diabetes. It has been shown that FoxO1 plays an important role in the regulation of pancreatic β cell function. Our preliminary study showed that abnormal glucose metabolism and decreased expression of FoxO1 in islets were found in aged mice. Furthermore, we innovatively found that FoxO1 could be epigenetically regulated by lysine methylation. Based on these observations, we hypothesize that FoxO1 can be dynamically regulated by epigenetic modification to maintain its expression and activity at different levels in pancreatic β cells, and that FoxO1 could directly regulate aging-related target genes in pancreatic β cells, inhibit β cell senescence and thus delay the occurrence and progression of diabetes. In this research project, we intend to detect the changes of pancreatic β cell senescence and function as well as the level and activity of FoxO1 in mice at different ages or under different metabolic stress statuses. We will also identify the effects of FoxO1 on pancreatic β cell senescence and dysfunction in both systemic FoxO1 knockout mice and β cell-specific FoxO1 knockout mice. Next, we will verify the effects of FoxO1 on pancreatic β cell senescence and function by overexpression and knockdown of FoxO1 in the mouse pancreatic β cell line Min6 and isolated primary mouse islets. Then, we will clarify the direct modification of (de)methyltransferase and deacetylase on FoxO1 and the direct regulation of FoxO1 on aging-related target genes in pancreatic β cells. Our project is not only helpful for elucidating the roles and mechanism of FoxO1 in pancreatic β cell senescence and dysfunction, but also provides a new clue for the prevention and treatment of type 2 diabetes.

胰岛β细胞退行性变是导致糖尿病的重要原因。研究表明，FoxO1在β细胞功能调控中发挥重要作用。我们的预实验显示，老年小鼠具有糖代谢异常，胰岛FoxO1表达下调，且FoxO1存在赖氨酸甲基化修饰的全新方式。据此我们假设：FoxO1经由表观遗传修饰进行动态调节，维持不同的表达水平和活性，FoxO1进而调控衰老相关基因，抑制β细胞衰老，延缓糖尿病发生发展。本项目拟在不同年龄、不同代谢应激状态下的小鼠中观察β细胞衰老、功能及FoxO1的变化；在全身性和β细胞特异性FoxO1基因敲除小鼠中明确FoxO1对β细胞衰老和功能的影响；在β细胞系和原代小鼠胰岛中过表达或敲减FoxO1，验证FoxO1对β细胞衰老和功能的调控作用；明确（去）甲基转移酶、去乙酰化酶对FoxO1的直接调控及FoxO1对衰老相关基因的直接作用。本项目有助于阐明FoxO1在β细胞衰老和功能障碍中的作用及其机制，为糖尿病防治提供新思路。

胰岛β细胞退行性病变是2型糖尿病的重要病理生理机制之一，已有报道发现，FoxO1在β细胞功能调控中发挥作用。本课题明确FoxO1在胰岛细胞衰老和胰岛功能障碍中的作用及其潜在机制，并探讨FoxO1在胰高糖素受体单克隆抗体（一种已进入2/3期临床试验的新型降糖药物）调控β细胞功能中的作用。结果显示，在代谢应激状态下，胰岛β细胞抗衰老基因表达显著降低，β细胞特异性标志物表达也可显著下降，提示胰岛β细胞衰老和去分化在糖尿病发生发展中发挥重要作用。在衰老和代谢应激状态下，胰岛β细胞中FoxO1表达降低并发生核内转位，β细胞特异性敲除FoxO1基因的衰老小鼠在葡萄糖负荷后血糖显著升高，提示FoxO1在胰岛β细胞衰老及衰老小鼠血糖调节中发挥重要作用。此外，本课题还发现，在胰腺癌细胞系中，FoxO1存在赖氨酸甲基化修饰方式，其可与赖氨酸甲基转移酶SET7/9及赖氨酸去甲基化酶LSD1结合并具有相互作用，提示FoxO1的甲基化调节可能调控FoxO1表达水平和活性进而影响胰岛β细胞功能。另一方面，本课题还发现，胰高糖素受体单抗干预正常小鼠可改善其空腹及负荷后血糖，降低血浆胰岛素水平，使胰岛FoxO1由胞浆转位到胞核。在衰老的β细胞特异性FoxO1基因敲除小鼠中，药物干预并不能降低小鼠空腹及负荷后血糖，小鼠血浆胰岛素水平也未见显著降低，提示FoxO1参与介导胰高糖素受体单克隆抗体治疗所致的血糖控制和胰岛β细胞功能改善效应，其在衰老小鼠的血糖稳态调节中发挥重要作用。本课题有助于阐明FoxO1在胰岛细胞衰老和胰岛功能障碍中的作用及其机制，为研发2型糖尿病治疗的新策略提供实验依据及理论基础。本课题共发表论著17篇，其中SCI论文13篇，中文核心4篇。研究成果在全国性大型学术会议上做大会报告、特邀报告或口头发言10余次。培养研究生7名（其中博士6名，硕士1名），出站博士后1名。