基于GLP-1激活肠-脑-肝轴通路研究水飞蓟宾抗糖尿病作用及机制

Diabetes is a major public health problem that is approaching epidemic proportions globally, and the development of anti-diabetic drugs from natural sources has increased the prospects of achieving better control of hyperglycemia. Based on our preliminary research, administration of silibinin decreased the fasting blood glucose in type 2 diabetic rats with increased GLP-1 secretion from L cell, up-regulated GLP-1R expression in duodenum and activated NTS neurons in brain, while selective hepatic vagotomy revsersed the hypoglycemic effect of silibinin. These results indicate that gut-brain-liver axis mediates glucose homeostasis in therapeutic effect of silibinin. However, the initiation mechanism of gut-brain-liver axis in hypoglycemic effect of anti-diabetic drugs remains unclear. Based on the structural similarity of silibinin with phytoestrogens, in the proposed study, we aim to evaluate the effects of estrogen receptor on GLP-1 secretion from L cell under the stimulation of silibinin, and determine the role of GLP-1 in activation of gut-brain-liver axis in blood glucose control. These findings will help us elucidate the pharmacological mechanism of silibinin on diabetic control, provide new insight into the initiation mechanism of gut-brain-liver axis, and uncover potential target for the development of anti-diabetic drugs.

糖尿病已成为威胁人类健康的世界性公共卫生问题，抗糖尿病药物的开发受到医药学界越来越多的关注。天然来源是寻找具有降糖活性化合物的主要途径之一。申请人前期研究发现，水飞蓟宾能够有效降低2型糖尿病大鼠血糖，并在促进肠道L细胞分泌GLP-1及增加十二指肠GLP-1R表达的同时，促进脑孤束核区神经元兴奋，然而，肝支迷走神经的切断则显著逆转了水飞蓟宾的降糖作用。该研究结果表明，水飞蓟宾通过肠-脑-肝轴通路维持血糖稳定。然而，现有研究对该通路的启动机制尚不明晰。以前期实验为依据，以水飞蓟宾所具有的杂环多酚类植物性雌激素相似结构为基础，本项目拟考察L细胞雌激素受体是否介导了水飞蓟宾促进GLP-1的分泌，进而激活肠道神经元，最终活化肠-脑-肝轴以降低2型糖尿病动物血糖。这些研究有助于完善对肠-脑-肝轴信号通路的认识以及揭示水飞蓟宾抗糖尿病药理机制，为植物性雌激素类降糖药物的开发及设计提供新的实验依据。

世界范围内，糖尿病的发病率正逐年增加，寻找低毒副作用的天然降糖活性成分越来越受到关注。申请人前期研究发现，伴随着肠道L细胞GLP-1分泌水平的提高，天然产物水飞蓟宾可有效降低肥胖型2型糖尿病大鼠空腹血糖。为进一步探讨基于提高GLP-1分泌水平的水飞蓟宾抗糖尿病药理机制，本项目首先通过体外实验，考察了水飞蓟宾对棕榈酸诱导的GLUTag肠道L细胞脂毒性损伤的改善作用。研究显示，水飞蓟宾通过激活Nrf2-HO-1/SOD2抗氧化通路，逆转了棕榈酸提高的细胞凋亡与下调的GLP-1合成和分泌水平，然而，雌激素受体α或β拮抗剂的加入则抑制了水飞蓟宾的上述保护作用。蛋白质组学分析结果显示，雌激素受体α拮抗剂可逆转水飞蓟宾上调的抗氧化酶、胞吞及增殖相关蛋白表达，雌激素受体β拮抗剂也可逆转水飞蓟宾上调的胞吞相关蛋白表达。基于内质网应激对细胞存活与功能发挥潜在调控作用，项目进一步考察了水飞蓟宾对GLUTag细胞内质网应激的影响。结果显示，水飞蓟宾通过提高雌激素受体α与β表达，下调内质网应激介导的凋亡，抑制棕榈酸诱导的细胞损伤。体内实验结果显示，水飞蓟宾可能通过促进雌激素受体α与β表达，增加肥胖型2型糖尿病大鼠肠道L细胞数量与GLP-1分泌水平，进一步提高肠道神经元兴奋介导的肠-脑-肝轴通路，发挥血糖调节作用。这些研究有助于揭示水飞蓟宾抗糖尿病作用机制，并为降糖药物的开发与设计提供新的实验依据。