马齿苋多糖改善胰岛β细胞自身胰岛素抵抗的分子机制研究

从天然食物资源中筛选降糖因子指导研制新型降糖食品，成为食品功能因子关注的焦点之一。马齿苋粗提液或多糖对糖尿病模型动物的降糖调脂作用已被我们和其他学者报道，但细胞分子水平的作用机制尚未揭示。本项目拟在前期基础上，以胰岛β细胞（HIT-T15）胰岛素抵抗模型和T2DM动物模型为研究对象，用免疫荧光、Western blotting、实时荧光定量PCR等技术，研究马齿苋多糖对胰岛β细胞自身胰岛素抵抗及与胰岛素抵抗相关的信号转导通路中InsR、IRS、PKB、PI-3K、GLUT-2、PDX-1等关键靶基因和蛋白表达水平的影响，并结合多糖对T2DM动物模型的生理生化、胰岛素抵抗相关靶基因和蛋白表达的影响，从分子、细胞和整体水平综合分析马齿苋多糖改善胰岛β细胞胰岛素抵抗的分子机制，揭示马齿苋多糖作用新靶点，为阐明基于马齿苋多糖的新型降糖因子提供理论支持，对研发马齿苋降糖功能食品具有重要理论指导价值。

Type II diabetes mellitus (T2DM) is major health concern worldwide and its prevalence has increased dramatically in the past few decades. Screening of hypoglycemic functional factors has been extensively investigated in the past few decades. Eespecially plants-derived products, serving as a major source of functional foods, have been recommended for the prevention of T2DM. Portulaca oleracea L. has been used as a kind of food and medicinal plant for thousands of years in China. Previous studies of our team and other researchers have shown that crude extract of Portulaca oleracea L. and polysaccharides from Portulaca oleracea L. (POP) can remarkably decrease the incidence of T2DM, reduce fasting blood glucose concentration, improve glucose tolerance and regulate the blood lipid profile in patients and model animal with T2DM (in vivo). However, the molecular mechanism of its anti-T2DM function remains unclear. In the present study, the effects of refined POP or purified POPI, POPII and POPIII will be investigated on panereatic central insulin resistance in pancreatic β-cell model (HIT-T15 cells) and T2DM animal model, which are induced with high-concentration glucose and/or high-concentration free ratty acid or alloxan. Furthermore, the potential molecular mechanisms of POP, the expression of key molecular targets such as InsR, IRS-1/-2, PI-3K, GLUT-2 in HIT-T15 cells and T2DM diabetic mice, which are strongly associated with insulin signaling transduction pathways in insulin resistance, will be determined by applying the methods such as immunofluorescence, Western blotting and RT-PCR. The molecular mechanisms of improvement of insulin resistance in pancreatic β-cells by POP will be studied on the molecular, cellular, and animal level. The results will provide scientific evidences for development of POP as a potential natural hypoglycemic functional factors or functional foods.