小肠电刺激改变迷走传入神经可塑性影响肥胖大鼠胃肠动力的机制研究

Vagal afferent plasticity means that the basic changes in vagal afferent signaling in response to direct mechanical and chemical stimuli to modulation of these direct effects induced by a number of factors, including nutrients, hormones, circadian signals and the gut microbiota. This plasticity is very important for energy homeostasis. It's reported that the lose of vagal afferent neurons’ plasticity in chronic high fat feeding, resulting in altered gastrointestinal motility and promoted the obesity. It was related blunted sensitivity of VAN to cholecystokinin and leptin. Our preliminary data have suggested a therapeutic potential of intestinal electrical stimulation (IES) for obesity. The mechanism associated with delayed gastric emptying, accelerated intestinal transit and increased secretion of glucagon-like peptide-1(GLP-1). Furthermore GLP-1 is one of the important peptides of VAN plasticity. So, it's supposed that increased secretion of GLP-1, CCK and leptin induced anorexigenic signals were transit to the hypothalamus by VAN. We try to observe the changes of leptin receptors, cholecystokinin receptors and neurochemical phenotype of vagal afferent nerves after IES. We will further study the mechanism of IES to recuperate the plasticity of VAN, and provide theory basis for the clinical application of IES.

迷走传入神经可塑性是迷走传入神经元（vagal afferent neurons, VAN）对营养物质、激素和肠道微生物环境给与的机械和化学刺激做出的直接改变，它对于能量稳态调节至关重要。长期高脂饮食导致VAN失去可塑性，胃肠动力改变并促使肥胖发生发展。这种现象和VAN对胆囊收缩素(cholecystokinin, CCK)和廋素（leptin）反应钝化有关。前期研究中我们发现小肠电刺激能够改变肥胖大鼠摄食模式，抑制胃排空和促进小肠运输，这和胰高血糖素样肽-1（glucagon-like peptide-1, GLP-1）分泌增加有关。GLP-1是VAN可塑性调节的重要肠多肽。因此我们研究小肠电刺激改变GLP-1、CCK、leptin分泌致VAN传导“假”饱腹信号于下丘脑；改变VAN神经化学表型恢复可塑性，从而影响胃肠动力，减少肥胖大鼠摄食量。为小肠电刺激治疗肥胖提供理论依据。

一、项目背景.肥胖是全球性健康问题，病态肥胖是多种疾病的危险因素，但是肥胖的有效治疗方法非常有限。小肠电刺激（Intestinal electrical stimulation,IES）已经在多种动物模型中证明了减重潜能，但是具体机制还不清楚。迷走神经可塑性是迷走传入神经（vagal af erent neurons,VAN）在处理复杂能量信号时表现出的弹性反应，研究认为肥胖患者VAN可塑性出现了钝化导致了肥胖的发展,因此我们假设IES是通过恢复了VAN可塑性而达到减重的。.二、研究内容.1.观察IES对饮食诱导肥胖大鼠（Diet induced obesity，DIO）饮食模式、体重、平均摄食量、心率变异性以及胃排空和小肠运输的影响。验证IES对于DIO大鼠胃肠动力及迷走神经的影响。.2.观察IES对餐后脑肠肽CCK-1、GLP-1、Leptin及血糖的影响。探索IES干预了哪些脑肠肽的表达。.3.使用辣椒素选择性阻断颈部VAN，对比观察IES对脑肠肽GLP-1变化和胃排空，小肠运输变化。验证IES是否通过VAN发挥作用。.4.观察下丘脑孤束核部分中MCH1R的表达，观察中枢能量状态。.5.分离迷走神经结状神经节分别通过免疫组化观察GLP-1R以及免疫印迹法观察GLP-1受体蛋白表达水平，观察IES对大鼠末端回肠L细胞数目的影响。.6.分离大鼠十二指肠段观察IES干预对于离体肠段肌条的影响。.三、重要结果及数据.1.IES组大鼠4周平均体重下降5.2±1.8%，IES减少了摄食时间而不是进餐次数。IES减缓了11.2%，加快了小肠运输20.1%，但是在辣椒素阻断VAN后胃排空均减缓，但是IES不在进一步减慢胃排空，但是加速了约9.7%小肠运输速度，心率变异性测试提示IES增加了高频谱段约10.1%。.2.IES组餐后血清GLP-1水平明显增高，但是CCK-1及Leptin表达水平无明显差异，在VAN阻断后GLP-1表达下降但是仍较对照组水平增高。证明了IES加速小肠运输导致食物更快达到回肠是增加GLP-1表达的可能因素。.3.IES能增加餐后下丘脑中MCH1R表达水平。证明了大鼠表达了较高的饱腹信号。.四、意义. 首次证实了IES通过增加GLP-1来调节迷走传入神经可塑性来调节体重。