羊肚菌多糖PMEP调控胆固醇代谢的分子机制及构效关系研究

Hyperlipidaemia and hypercholeslerolemia are closely related to the occurrence as well as development of atherosclerosis（AS）and coronary heart diseases. Controlling and reducing excess cholesterol in vivo has important significance to prevent heart cerebrovascular diseases. One of the most effective ways is to regulate cholesterol metabolism and reduce cholesterol content in vivo through nutrition intervention. Many researches confirmed that natural plant polysaccharides play a vital role in preventing and ameliorating heart cerebrovascular diseases. Among them, edible mushrooms are good polysaccharide sources. Morchella esculenta (L.)Pers polysaccharide PMEP-1 is a hetero-polysaccharide which consists of glucose, mannose, galactose and arabinose. It is isolated and purified from fruiting body of wild Morchella and has a health function of antiatheroscloresis. However, due to its complex chemical structure, the structure-activity relationship and molecular biology mechanism of regulating cholesterol metabolism is still unclear. In this project, polysaccharide PMEP-1 from Morchella was used as materials and modified with sulphating, carboxymethylation, acetylation, and methylation. The influence of Morchella polysaccharide on the regulation effect, structure-activity relationship and related genes expression of cholesterol metabolism was investigated to ascertain the unclear molecular mechanism. Therefore, the project could provide a theoretical basis for deep exploitation of polysaccharide health foods and medicines.

高脂血症和高胆固醇血症是动脉粥样硬化（AS）和冠心病的发生、发展密切相关，控制和降低体内过量胆固醇对预防心脑血管疾病具有重要的意义，最有效的方法之一是通过营养干预来调节胆固醇代谢、降低体内胆固醇含量。大量研究证实天然植物多糖对预防和改善心脑血管疾病有重要作用，而食用菌又是天然植物中较好的多糖来源。羊肚菌多糖PMEP-1是从野生羊肚菌子实体中分离纯化出的一种由葡萄糖、甘露糖、半乳糖和阿拉伯糖构成的杂多糖，具有降血脂保健功能，但由于其化学结构非常复杂，其调控胆固醇代谢的构效关系和分子生物学机制还不清楚。本项目拟以羊肚菌多糖PMEP-1为材料，进行硫酸酯化、羧甲基化、乙酰化、甲基化修饰，考察羊肚菌多糖对体内胆固醇代谢的调控效果、构效关系、胆固醇合成代谢相关基因表达的影响，进而探明羊肚菌多糖调控胆固醇代谢的分子机制，为多糖类保健食品或药物的深度开发提供理论依据。

高脂血症和高胆固醇血症是动脉粥样硬化（AS）和冠心病的发生、发展密切相关，控制和降低体内过量胆固醇对预防心脑血管疾病具有重要的意义，最有效的方法之一是通过营养干预来调节胆固醇代谢、降低体内胆固醇含量。本项目以羊肚菌多糖（Polysaccharide of Morchella angusticepes Peck, PMEP）为材料，分别进行羊肚菌多糖的羧甲基化、硫酸化、乙酰化等化学修饰，并通过核磁共振（NMR）、红外光谱（IR）、圆二色谱（CD）、X-射线衍射分析、原子力显微镜（AFM）、扫描电镜（SEM）等对羊肚菌多糖进行了结构表征；研究了羊肚菌多糖对高脂血症大鼠胆固醇代谢关键酶、细胞膜受体、胆固醇及胆汁酸吸收排泄、胆固醇合成代谢相关基因表达的影响，初步探明羊肚菌多糖对高血脂症大鼠胆固醇代谢调控的分子生物学机制。研究结果表明，化学修饰（羧甲基化和硫酸化）羊肚菌多糖对高胆固醇血症大鼠胆固醇代谢有一定的调控作用。在胆固醇合成代谢方面，羊肚菌多糖通过显著下调肝脏HMG-CoA蛋白和HMG-CoA R mRNA的表达，抑制大鼠体内胆固醇的合成，使细胞内胆固醇合成减少。在胆固醇体内转运方面，羊肚菌多糖能显著激活SR-B1 mRNA和LDL-R蛋白的表达，将蓄积于末梢组织的游离胆固醇运输到肝脏，加速胆固醇的逆转运（RCT），最终转化为胆汁胆固醇、胆汁酸盐排泄。在胆固醇分解代谢方面，羊肚菌多糖能显著上调CYP7A1蛋白的表达，加速胆固醇转化为胆汁酸，减少胆汁酸的重吸收并促进排泄。同时，羊肚菌多糖具有较好的抗氧化活性、抗增殖活性及调节免疫活性。这对于深入挖掘羊肚菌多糖的功能活性和功能食品开发具有重要的意义。.