乳酸菌SL001对AD模型小鼠胆固醇代谢及Aβ生成的影响及作用机制研究

The dysfunction of cholesterol metabolism is closely related with Alzheimer’s disease (AD). Although many cholesterol lowering drugs have certain beneficial effects on curing of AD, but most of them are expensive and have side effects. The probiotics have been proved of possessing the ability of cholesterol-lowering effect. The intestinal microflora balance is disrupted easily when people get to their ageing time, and the probiotics' number is decreased greatly than ever. There is no evidence indicating that there has any relationship between probiotics, cholesterol metabolism and AD developing. Combined with our previous research results, we provide the hypothesis that when people get to their ageing time, the intestinal probiotics decreased and hindered brain cholesterol metabolism and transportation, which lead to the increasing production and accumulation of Aβ. We proposed that if the AD patient was treated with probiotics, by which intestinal microflora balance will be reconstructed. It will not only promote cholesterol metabolism and transportation, but also it can prevent the development of alzheimer’s disease. Based on this hypothesis, we decided to use the cholesterol-lowering lactic acid bacteria Lactobacillus reuteri SL001 and APPswe/PS1DE9 double transgenic AD mouse model as the research object. The cholesterol-lowering lactobacillus strain will be orally treated to the AD model mice. We will use many methods like PCR-DGGE, LDR, Immunohistochemistry, ELISA and water maze technique to detect the relationship between intestinal micro ecological balance, cholesterol metabolism and the development of alzheimer's disease.

胆固醇代谢异常与阿尔茨海默病（alzheimer’s disease, AD）密切相关，虽降胆固醇药物对AD有一定治疗作用，但大多昂贵且副作用大。益生菌具有降胆固醇作用，老年人肠道菌群易发生菌群失调，特别是益生菌数量下降显著。目前还不清楚益生菌、胆固醇代谢与AD发生之间是否存在关联。结合他人及前期研究结果，我们推测：老年人肠道菌群失调引起胆固醇代谢异常，导致脑内Aβ生成增多；如采用口服益生菌，重塑肠道微生态平衡，不仅促进胆固醇代谢，还有可能对AD起到预防及治疗作用。基于此假说，本课题拟以APPswe/PS1DE9双转基因AD模型小鼠为研究对象，使用本研究小组分离的具有分解胆固醇作用的罗伊氏乳酸菌SL001对AD模型小鼠进行乳酸菌灌胃处理，然后采用PCR-DGGE、LDR、免疫组化、ELISA及行为学观察等技术，系统研究益生菌、肠道微生态平衡、胆固醇代谢及AD发生之间关系及分子机制。

胆固醇代谢异常与阿尔茨海默病（alzheimer’s disease, AD）密切相关，虽降胆固醇药物对AD有一定治疗作用，但大多昂贵且副作用大。益生菌具有降胆固醇作用，老年人肠道菌群易发生菌群失调，特别是益生菌数量下降显著。我们推测：老年人肠道菌群失调引起胆固醇代谢异常，导致脑内Aβ生成增多；如采用口服益生菌，重塑肠道微生态平衡，不仅促进胆固醇代谢，还有可能对AD起到预防及治疗作用。本项目利用分离得到的一株在体外具有降解胆固醇能力的罗伊式乳酸杆菌SL001对益生菌、胆固醇代谢与AD发生之间是否存在关联进行了研究。结果显示，L. reuteri SL001耐酸、耐胆盐，在体外具有很强的降解胆固醇能力，可在小鼠肠道内定植并具有改善小鼠肠道微生态平衡的作用，添食该菌可以改善小鼠肠道细菌群落结构组成，对AD模型小鼠能够起到一定程度的积极调整作用；L. reuteri SL001添食后能影响小鼠肝脏、肠和脑中胆固醇代谢相关基因（Lxrα，Hmgcr，Ldlr，ApoE、Abcg1等）的表达，进而影响脑组织中胆固醇的代谢；L. reuteri SL001添食可显著降低AD小鼠脑组织中BACE1蛋白的表达，海马和血清中的Aβ总含量下降，脑部皮层区域Aβ斑块沉积减少。另外，不同添食周期（45d, 100d, 150d）的结果比较发现，小鼠6月龄时的脑部病变改善效果要优于8月龄时期，这表明添食乳酸菌SL001可以在AD病变早期起到一定的延缓作用，但却不能改善中后期的病变。Morris水迷宫检测结果显示，L. reuteri SL001添食未能改善AD小鼠的学习记忆能力。本研究揭示了益生菌、胆固醇代谢与AD发生三者之间的关系，其结果为延缓AD的发生提供了新的理论依据。此外，我们还尝试了将该菌给AA白羽健康肉鸡添食，结果显示SL001处理组日增重和终体重显著高于对照组和抗生素添食组（P＜0.05）；SL001添食组与抗生素组相比，肉鸡的平均日采食量和料重比显著性降低（P＜0.05），显示出该菌在畜牧业有非常好的应用前景。