【作者】 刘伟；

【导师】 黄小丹； 李斌；

【作者基本信息】 兰州大学 ， 公共卫生与预防医学·营养与食品卫生学， 2024， 硕士

【摘要】 高海拔地区低压低氧环境可致肠道屏障功能损伤,引起肠道微生态失衡和全身性炎症反应,严重者还可诱发高原多器官功能障碍综合征。益生元作为对机体有益的活性分子,能够有效调节肠道菌群、促进肠道稳态、改善宿主健康,在缓解低压低氧条件造成的肠道损伤方面具有巨大的潜力。其中,植物多糖被证实可有效调节肠道紊乱,改善氧化应激相关疾病,可为以膳食为导向的高原肠道损伤治疗和预防提供新的见解。基于此,本研究首先对芫根粗多糖的分子量及结构特征进行解析,并明确其体外抗氧化特性;继而构建低压低氧及粪菌移植(FMT)小鼠模型,联合动物生理、组织评价、宏基因组学等多技术手段,探索芫根粗多糖对低压低氧小鼠诱导肠道损伤的保护作用及肠道菌群响应机制。研究结果发现:1)芫根粗多糖重均分子量为42.47 k Da,傅里叶红外光谱分析显示其含有β-吡喃糖和糖醛酸结构,具有典型的多糖结构特征。体外抗氧化实验结果表明,芫根粗多糖具有较好的体外抗氧化特性,当其浓度为5.0 mg/m L时,对羟自由基(OH~-)的清除率高达91.40%;2)低压低氧小鼠模型实验发现,芫根粗多糖干预可增加低压低氧条件下小鼠血清中T-AOC、SOD和GSH-Px的含量,降低血清MDA、回肠组织DAO、MPO及炎症因子IL-6、IL-1β和TNF-α的水平,有效缓解低压低氧导致的小鼠氧化应激、肠道损伤和炎症反应;3)芫根粗多糖干预有助于回肠对营养物质的消化和吸收,刺激血管形成和肠绒毛生长,逆转回肠组织杯状细胞减少和上皮细胞凋亡,增加紧密连接蛋白claudin-1、occludin、ZO-1表达,缓解低压低氧诱导的肠道损伤,恢复肠道屏障功能;4)芫根粗多糖干预显著降低了低压低氧模型小鼠肠道中潜在有害菌Chlamydia和Alistipes的丰度,增加了Leuconostoc lactis和Enterococcus faecium等有益菌的丰度,提升了肠道短链脂肪酸中乙酸和丁酸的含量,有效调节肠道菌群结构,促进肠道健康;且基于粪菌移植的FMT组表现出与干预组一致的肠道菌群、代谢调节动态;5)基于宏基因组学的功能基因富集分析显示,芫根粗多糖可通过富集肠道菌群中的Leuconostoc lactis、Enterococcus faecium和Akkermansia muciniphila,上调精氨酸、蛋氨酸合成,促进谷胱甘肽等抗氧化物酶合成,缓解机体氧化损伤。综上,芫根粗多糖可在Leuconostoc lactis、Enterococcus faecium和Akkermansia muciniphila等关键肠道微生物的介导下,调节精氨酸、蛋氨酸和磷酸戊糖途径,提高机体的抗氧化水平,维持肠道稳态,改善肠道屏障功能,进而有效缓解低压低氧小鼠的氧化应激和肠道损伤。本研究可为缓解高原氧化应激和肠道损伤提供有效的治疗方案,对于高原地区人群健康维系意义重大,具有广阔的应用前景。更多还原

【Abstract】 The impaired intestinal barrier function induced by low pressure and hypoxia in high-altitude regions leads to dysbiosis of the intestinal microbiota and systemic inflammatory responses,which can further trigger high-altitude multiple organ dysfunction syndrome.Prebiotics,as active molecules capable of modulating the gut microbiota and exerting beneficial effects on the host,hold significant potential in promoting intestinal homeostasis and ameliorating host health under conditions of low pressure and hypoxia.Among them,plant polysaccharides have been demonstrated to effectively regulate intestinal dysbiosis and ameliorate oxidative stress-related diseases.These findings offer novel insights into the dietary-based treatment and prevention of high-altitude intestinal injury.In this study,we first elucidated the structural characteristics of Brassica rapa L.polysaccharide and clarified its in vitro antioxidant properties.Subsequently,utilizing a hypoxic mouse model,we employed a combination of physiological,histological,and metagenomic techniques to investigate the protective effect of Brassica rapa L.polysaccharide on intestinal injury in hypoxic mice and the associated gut microbiota response mechanisms.The research findings are as follows:1.The average molecular weight of Brassica rapa L.crude polysaccharides was42.47 k Da,with Fourier transform infrared spectroscopy showing typical polysaccharide structural characteristics,containing β-pyranose and uronic acid structures.In vitro antioxidant activity experiments demonstrated that Brassica rapa L.crude polysaccharides exhibited good antioxidant properties,with a hydroxyl radical clearance rate of up to 91.40% at a concentration of 5.0 mg/m L;2.Intervention with Brassica rapa L.crude polysaccharides increased the levels of T-AOC,SOD,and GSH-Px in the serum of mice under hypobaric hypoxia conditions,while reducing the levels of MDA,intestinal tissue DAO,MPO,and inflammatory factors IL-6,IL-1β,and TNF-α,effectively alleviating oxidative stress,intestinal damage,and inflammatory responses induced by hypobaric hypoxia in mice;3.Brassica rapa L.crude polysaccharide intervention facilitated the digestion and absorption of nutrients in the ileum,stimulated vascular formation and villi growth,reduced the decrease of goblet cells and apoptosis of epithelial cells in the ileum tissue,increased the expression of tight junction proteins claudin-1,Occludin,and ZO-1,alleviated hypobaric hypoxia-induced intestinal damage,and restored intestinal barrier function in mice under hypobaric hypoxia conditions;4.Brassica rapa L.crude polysaccharide intervention significantly reduced the abundance of potentially harmful bacteria Chlamydia and Alistipes in the intestines of mice in the hypobaric hypoxia model,increased the abundance of beneficial bacteria such as Leuconostoc lactis,Enterococcus faecium and Akkermansia muciniphila enhanced the content of acetic acid and butyric acid in intestinal short-chain fatty acids,effectively regulating the structure and homeostasis of gut microbiota,and promoting intestinal health;5.Functional gene enrichment analysis based on metagenomics showed that Brassica rapa L.crude polysaccharides,acting as prebiotics,could enrich Leuconostoc lactis,Enterococcus faecium and Akkermansia muciniphila in the gut microbiota,upregulate the synthesis of amino acids,such as arginine and tryptophan,and the phosphotransferase pathway,promote the synthesis of antioxidant enzymes such as glutathione,and alleviate oxidative damage in the body.In conclusion,Brassica rapa L.crude polysaccharides,mediated by key intestinal microbiota,regulate the pathways of arginine,tryptophan,and phosphotransferase,enhance the body’s antioxidant level,maintain intestinal homeostasis,improve intestinal barrier integrity and function,and effectively alleviate oxidative stress and intestinal damage in mice under hypobaric hypoxia.This study provides an effective therapeutic approach for alleviating oxidative stress and intestinal damage in high-altitude regions,which is of great significance for the health maintenance of populations living in high-altitude areas and holds promising prospects for future applications.更多还原