Txnip在京尼平苷拮抗高糖诱导胰腺β细胞损伤中的作用机制研究

Mounting evidence shows that reasonable insulin secretion from pancreatic β cells plays an essential role in keeping the homeostasis of glucose, β-cell functions, preventing the metabolic diseases, such as obesity and type 2 diabetes mellitus. Our previous work has been addressed that geniposide induces insulin secretion from pancreatic β cells with the activation of glucagons-like peptide 1 receptor(GLP-1R) directly, and enhances glucose-stimulated insulin secretion (GSIS) and glucose utilization in the presence of low and moderate concentrations of glucose in pancreatic INS-1 cells. But, in the presence of high concentration of glucose, the effect of geniposide on glucose-stimulated insulin secretion is totally opposite. But, geniposide preventing cell dysfunction of pancreatic beta cells from high concentration of glucose. Furthermore, geniposide attenuated blood glucose, improved lipid metabolism and insulin resistance in db/db transgenic mice. Unfortunately, the mechanisms of geniposide regulating GSIS and antagnizing cell damage from high concentration of glucose keep unknown. To study this point, we design to explore the role AMP-activated protein kinase (AMPK), a sensor of cellular energy, and Txnip, which plays s central role in glucose metabolism, in geniposide regulating GSIS and preventing cell dysfunction and their relative mechanisms in high concentration of glucose-treated pancreatic β cells. Additionally,to investigate the role of Txnip on the effects of geniposide in beta cells, the influence of geniposide on blood glucose, insulin and pancreatic β cells apoptosis will be probed in the current study in Txnip-/- mice. At the same time, the signal transduction of geniposide regulating the expression of UCP-2, an important mitochondrial protein will be probed in high concentration of glucose-treated pancreatic beta cells. All these work might be helpful to clarify the role of geniposide on GSIS and β-cell apoptosis and its mechanisms.

高血糖不仅是导致胰腺β细胞凋亡和功能障碍的元凶，也是引起多种糖尿病并发症的重要因素。我们研究证实，与其它的GLP-1受体激动剂只是增强β细胞分泌胰岛素不同，京尼平苷在高糖下抑制β细胞分泌胰岛素，而且还拮抗高糖诱导的胰腺β细胞损伤。由于京尼平苷可调节β细胞中能量传感器AMPK活性和线粒体功能蛋白UCP-2及Txnip蛋白水平，我们推测，京尼平苷抑制高糖诱导β细胞胰岛素分泌、拮抗高糖诱导的β细胞损伤可能与其调节细胞能量代谢有关。为验证我们的假说，本项目拟从细胞能量代谢的角度，在高糖诱导的胰腺β细胞损伤模型和高糖高脂喂养的Txnip-/-小鼠上，结合基因干扰和激酶抑制剂阻断的方法，考察AMPK和Txnip与京尼平苷拮抗高糖诱导的β细胞损伤的相关性及它们之间的调控机制。本课题将从全新的视角阐明Txnip和AMPK在京尼平苷拮抗高糖诱导β细胞损伤中的作用，为2型糖尿病的防治提供新的思路和靶点。

胰腺β细胞合理分泌胰岛素对于维持体内葡萄糖稳态、保持β细胞正常生理功能、防止肥胖和2型糖尿病等代谢性疾病都有十分重要的意义。本项目在前期研究证实京尼平苷能够抑制高糖诱导的β细胞胰岛素分泌和功能障碍的基础上，从细胞能量代谢的角度分析其中的分子机制，特别是京尼平苷对细胞能量传感器AMPK活性和Txnip蛋白水平的调控机制，并利用RNA干扰和酶抑制剂、激动剂分析它们与京尼平苷抑制高糖诱导的胰岛素分泌和β细胞功能障碍的相关性。研究结果表明，AMPK和Txnip在京尼平苷调节胰腺β细胞分泌胰岛素和细胞凋亡过程中具有十分重要的作用，京尼平苷可通过调节AMPK磷酸化状态、影响Txnip蛋白降解、进而调节细胞凋亡相关蛋白HO-1、Bcl-2、Bax和Casapse-3表达，并在体内外拮抗高糖高脂诱导的胰腺β细胞功能障碍和细胞凋亡。本项目的研究结果初步阐明了AMPK和Txnip与京尼平苷调节高糖高脂胰腺β功能障碍和细胞凋亡的相关性，为今后京尼平苷的临床应用提供科学依据，也为2型糖尿病的防治提供新的思路和靶点。