【摘要】：阿爾茨海默癥(Alzheimer’s disease,AD)是一種表現(xiàn)為記憶和認(rèn)知功能退化的進(jìn)行性神經(jīng)退行疾病。大量研究表明AD與2型糖尿病存在聯(lián)系,共同致病機(jī)理有慢性炎癥、胰島素抵抗和線粒體功能異常。另一方面,腸道菌群能調(diào)節(jié)宿主的營養(yǎng)、代謝、免疫,并影響遠(yuǎn)端的中樞神經(jīng)系統(tǒng)。而高脂高糖的西式飲食可誘導(dǎo)腸道菌群失衡引起多種代謝性疾病。因此,本研究的目的是研究長期高糖飲食對AD發(fā)生發(fā)展,腸道菌群結(jié)構(gòu)和血漿代謝譜的影響,并探討它們背后的可能聯(lián)系。首先,我們以10%的蔗糖飲水(高糖組)和普通飼料飲水(正常飲食組)分別給予野生型和AD模型APP/PS1小鼠。6個月后,Morris水迷宮顯示高糖飲食促進(jìn)空間學(xué)習(xí)記憶能力的下降。免疫組化和免疫印跡分析發(fā)現(xiàn)APP/PS1鼠高糖組大腦的可溶性Aβ含量和沉積增多。進(jìn)一步實(shí)驗(yàn)顯示高糖組出現(xiàn)胰島素抵抗,同時血液中促炎因子(TNF-α和IL-6)及脂多糖結(jié)合蛋白水平上升,提示高糖飲食可能導(dǎo)致內(nèi)毒素血癥和慢性炎癥。另外,RT-qPCR檢測到高糖組小鼠結(jié)腸兩種緊密連接蛋白claudin-5和occludin mRNA轉(zhuǎn)錄水平下降。以上結(jié)果提示高糖飲食可能導(dǎo)致腸道通透性增加和內(nèi)毒素入血從而引發(fā)慢性炎癥和胰島素抵抗。而根據(jù)文獻(xiàn)報道,上述變化可能與腸道菌群失衡有關(guān)。隨后,我們對盲腸細(xì)菌進(jìn)行16S rRNA基因測序,有效序列聚類得到可操作分類單元(OTUs)�；诟鳂悠稯TU組成的PCA、PLS-DA等模型顯示高糖飲食明顯改變腸道菌群落的整體結(jié)構(gòu)。OTUs的物種注釋結(jié)果顯示:硬壁菌門/擬桿菌門的比值和疣微菌門相對豐度在高糖組下降,變形菌門則上升;屬水平上,多種有益菌Allobaculum,Akkermansia和乳桿菌屬豐度在高糖組下降,而擬桿菌屬,螺桿菌屬,Alloprevotella和Alistipes則上升。根據(jù)文獻(xiàn)報道,上述不同種類腸道菌含量的變化可能與腸道內(nèi)短鏈脂肪酸的產(chǎn)生異常,腸道屏障功能破壞,能量代謝失衡,慢性炎癥,胰島素抵抗和衰老等密切相關(guān)。此外,我們還通過UPLC-Q-TOF-MS代謝組學(xué)平臺,研究了高糖飲食對血漿代謝譜的影響,PLS-DA得分圖顯示高糖組和普通飲食組血漿代謝譜有明顯差異。經(jīng)鑒定的差異代謝物中,多種磷脂類、必需的多不飽和脂肪酸含量在APP/PS1高糖組中下降,而脂酰肉毒堿類和三種膽汁酸則上升。此外兩種腸道菌相關(guān)的代謝物p-cresol sulfate和p-cresol glucuronide在高糖組上升,它們是蛋白結(jié)合尿毒癥毒素。這些生物標(biāo)志物的變化表明:血脂異常、細(xì)胞膜破壞,以及腸道菌的有毒產(chǎn)物進(jìn)入體內(nèi)可能是高糖飲食促進(jìn)AD發(fā)展的致病機(jī)制之一�？傊�,本研究發(fā)現(xiàn)長期高糖飲食可促進(jìn)AD模型小鼠空間學(xué)習(xí)記憶能力下降和大腦淀粉樣變性。相關(guān)機(jī)制為高糖飲食可能導(dǎo)致腸壁屏障功能損壞,慢性炎癥,胰島素抵抗和血漿代謝譜異常,并可能與腸道菌群結(jié)構(gòu)失衡有關(guān),但需進(jìn)一步驗(yàn)證。本研究可能有助于為AD的致病機(jī)制研究提供新的視角,為疾病的預(yù)防和治療提供新的途徑。
[Abstract]:Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by memory and cognitive impairment. A large number of studies have shown that AD is associated with type 2 diabetes mellitus. The common pathogenesis of AD is chronic inflammation, insulin resistance and mitochondrial dysfunction. On the other hand, intestinal flora can regulate the nutrition and metabolism of the host. The aim of this study was to investigate the effects of a long-term high-glucose diet on the occurrence and development of AD, intestinal flora structure and plasma metabolic profiles, and to explore the possible links between them. Six months later, Morris water maze showed that high-sugar diet promoted the decline of spatial learning and memory. Immunohistochemistry and Western blot analysis showed that the soluble A beta content and deposition in the brain of APP/PS1 mice were increased in high-sugar diet group. In addition, RT-qPCR detected the transcriptional levels of claudin-5 and occludin mRNA in colon of mice in high glucose group. These results suggest that high-glucose diet may lead to increased intestinal permeability and endotoxin inflammation leading to chronic inflammation and insulin resistance. According to the literature, these changes may be related to the imbalance of intestinal flora. Subsequently, 16S rRNA gene sequencing of cecum bacteria, effective sequence clustering obtained operable taxon. (OTUs). PCA and PLS-DA models based on OTU composition of each sample showed that high-sugar diet significantly altered the overall structure of the intestinal bacterial community. The results of OTUs species annotation showed that the ratio of scleroderma to Bacteroides and the relative abundance of verrucous microflora decreased in the high-sugar group, while that of Proteus increased in the high-sugar group. The abundance of Lactobacillus spp. and Lactobacillus spp. decreased in the high glucose group, but increased in Bacillus spp., Helicobacter spp., Alloprevotella and Allistipes. In addition, we also studied the effects of high-sugar diet on plasma metabolic profiles using UPLC-Q-TOF-MS metabonomics platform. PLS-DA scores showed that there were significant differences in plasma metabolic profiles between high-sugar diet group and normal diet group. In addition, two intestinal bacteria-related metabolites, p-cresol sulfate and p-cresol glucuronide, increased in the high glucose group. They are protein-bound uremic toxins. Changes in these biomarkers indicate abnormal blood lipids, destruction of cell membranes, and entry of toxic products from intestinal bacteria into the body. In conclusion, this study found that long-term high-glucose diet could promote the decline of spatial learning and memory ability and amyloidosis in AD model mice. The mechanism is that high-glucose diet may lead to intestinal barrier dysfunction, chronic inflammation, insulin resistance and abnormal plasma metabolic profiles. This study may provide a new perspective for the pathogenesis of AD and provide a new way for the prevention and treatment of diseases.
【學(xué)位授予單位】：浙江工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：R749.16;R-332

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 趙虎;周庭銀;;脂多糖結(jié)合蛋白的結(jié)構(gòu)和功能[J];國外醫(yī)學(xué)(微生物學(xué)分冊);2000年03期

，

本文編號：2225842