O-GlcNAc糖基转移酶OGT对胰岛α细胞胰高血糖素分泌的调控作用及机制研究

One of the major reasons of hyperglycemia of diabetes is the disorder of glucagon secretion from pancreatic alpha cells, however, the detailed mechanism is still unclear. Our previous study revealed that the loss of O-GlcNAc transferase OGT would lower the secretion of glucagon. The proposed project intend to study the regulation mechanism of OGT on glucose metabolism and islet function at the levels of tissue, cell and molecular by using islet α-cell tissue specific OGT knockout mouse model combined with diabetic animal model. Using the specific fluorescent probes of alpha cells and total internal reflection fluorescence microscope, we will explore the molecular mechanism of OGT regulation on glucagon secretion—— by O-GlcNAcylation of calcium signal and IR-PI3K pathway. Meanwhile, we knocked down the OGT expression of pancreatic islets in diabetic mice to investigate the possibility of targeted therapy for diabetes. The results of this project will help us to further illustrate the molecular mechanism of OGT in the regulation of glucagon secretion pathway, complete the knowledge of glucagon secretion and inhibition, and provide theoretical basis for the new therapeutic methods of diabetes.

糖尿病血糖紊乱的主要原因之一是胰岛α细胞胰高血糖素分泌异常，但调控机制未明。申请人前期研究发现O-GlcNAc糖基转移酶OGT的缺失会引起胰高血糖素分泌降低。本课题拟通过构建胰岛α细胞特异性OGT敲除小鼠结合成熟糖尿病动物模型，在组织、细胞和分子水平上研究OGT对糖代谢和胰岛功能的调控机制，并结合胰岛α细胞特异性荧光探针和全内角荧光显微镜技术来阐述OGT在调控胰高血糖素分泌过程中的具体分子机制——通过O-GlcNAc直接调控钙离子和胰岛素通路来完成。同时我们在糖尿病小鼠胰岛组织中敲低OGT表达来探讨靶向治疗糖尿病的可能性。本课题研究结果将进一步帮助我们阐明糖基化修饰调控胰高血糖素分泌通路的具体分子机制，完善目前对胰高血糖素分泌及抑制机制的认知，并为新型糖尿病药物的研制提供理论基础。

胰高血糖素（Glucagon）调控机制至今未明。本项目主要从细胞水平和动物模型两个层面对OGT/O-GlcNAc修饰调控胰高血糖素分泌展开研究。①体外实验证明糖基化转移酶OGT可在糖尿病环境下调控胰岛α细胞活性及胰高血糖素分泌；②转基因动物实验证明OGT对小鼠葡萄糖代谢及胰岛功能具有调控作用。除此之外，胰岛α细胞特异性探针的成功构建不但解决了基础研究中无法有效观测原代α细胞的问题，还为糖尿病靶点药物的研发提供了新的方向；而胰高血糖素与肿瘤之间关系的研究，为胰高血糖素作为一种新型化疗药物增敏剂应用于临床打下了坚实的基础。本项目还资助了1型糖尿病视网膜病变药物的研发及机制研究，为临床上治疗早期糖尿病视网膜病变提供了新的思路；同时研究了胰高血糖素靶向肿瘤纳米技术，为药物递送过程中全身副作用的降低提供了理论与实验基础。