多形拟杆菌合成短链脂肪酸促进肠道GLP-1合成分泌从而改善宿主肥胖的机制研究

Obesity has become a pandemic metabolic disease with high global concentration and a major risk factor for a number of co-occurring diseases, including type 2 diabetes, nonalcoholic fatty liver, cardiovascular diseases and certain cancers. Gut hormones regulate metabolism through the coordination of digestion, absorption, nutrient disposal and appetite. Glucagon-like peptide-1 (GLP-1) produced by enteroendocrine L cells may has transient postprandial increase and multifaceted beneficial effects on food intake, including inhibition of gastric emptying and an increased feeling of satiety, which result in weight loss. Association between the gut microbiota and obesity has been validated, whereas the underlying molecular mechanisms remain largely to be elucidated. Our recent study showed that Bacteroides thetaiotaomicron could alleviate diet-induced body-weight gain and adiposity in mice, however which signaling pathways mediated the interaction between B.thetaiotaomicron and the host need to be deeply investigated. Previous evidence demonstrated that short chain fatty acids (SCFAs) derived from fermentation of fibre triggered GLP-1 secretion in vitro. Hence, the aim of this project is to identify the metabolic pathway that B.thetaiotaomicron adopted to synthesize SCFAs by gene knockout method, to analyze the effect of B.thetaiotaomicron on host enteric GLP-1 level using Gcg-iCre transgenic reporter mice model, to illuminate whether B.thetaiotaomicron exerted the anti-obesity effect through producing SCFAs and stimulating GLP-1 secretion in host. Overall, this study would offer novel research ideas on obesity development mechanisms and individualized obesity intervention and therapy targeting the gut microbiota.

肥胖已成为一类全球关注的慢性代谢疾病，同时也是罹患其他慢性非传染性疾病的重要风险因素。肠内分泌细胞能产生一系列肠道激素，其中L细胞产生的胰高血糖素样肽1（GLP-1）在进食后迅速分泌，减缓胃排空，增强饱腹感，从而有效减缓体重增加。近期文献证实，肠道菌群与肥胖密切相关，但因果关系及背后的机制尚未明确。课题组前期结果显示：肠道多形拟杆菌（Bt）可改善宿主肥胖病症，但通过何种信号通路与宿主互作存在未知。体外实验证实膳食纤维发酵产生的短链脂肪酸（SCFAs）可诱导肠道GLP-1的产生。本项目拟通过同源重组基因敲除技术研究Bt菌发酵碳水化合物产生SCFAs的代谢途径；通过CRISP Cas9构建的Gcg-iCre小鼠分析Bt菌对GLP-1表达水平的影响；结合基因测序技术深入探究Bt菌是否通过SCFAs-GLP-1通路介导对宿主肥胖改善的调控，为肥胖症发生机制研究及个体化精准治疗提供理论支持。

肥胖已成为一类全球关注的慢性代谢疾病，同时也是罹患其他慢性非传染性疾病的重要风险因素 。肠内分泌细胞能产生一系列肠道激素，其中L细胞产生的胰高血糖素样肽1(GLP-1)在进食后迅速分泌，减缓胃排空，增强饱腹感，从而有效减缓体重增加。近期文献证实，肠道菌群与肥胖密切相关，但因果关系及背后的机制尚未明确。课题组前期结果显示:肠道多形拟杆菌(Bt)可改善宿主肥胖病症，但通过何种信号通路与宿主互作存在未知。体外实验证实膳食纤维发酵产生的短链脂肪酸(SCFAs )可诱导肠道GLP-1的产生。本项目利用序列比对鉴定到Bt丙酸合成中的关键酶甲基丙酰辅酶A异位酶，通过构建敲除菌株证实了MCM参与Bt菌丙酸合成的生物学功能；利用抗生素处理小鼠及无菌小鼠灌胃模型初步探究了MCM介导的丙酸合成对宿主肠道GLP-1合成分泌的促进作用；基于BtMCM的保守性分析筛选获得人源性拟杆菌株库，后续将通过Gcg-iCre报告小鼠分析候选菌对GLP-1表达水平的影响，为肥胖症发生机制研究及个体化精准治疗提供理论支持和靶向菌株开发。