胃转流术调节葡萄糖代谢平衡及其下丘脑调节机制的实验研究

It is very clear that the gastric bypass surgery is one of the most promising therapy to cure type 2 diabetes.However, the mechanisms are not yet understood. The previou study has shown that the hypothalamic leptin sensitivity plays an important role in insulin sensitivity and glucose homeostasis and the serum glucose and leptin level were dramatically decreased 24 hrs after gastric bypass surgery which indicate that the mechanism has closely related with hypothalamic leptin signaling. This project is aim to study the role of brain-peptic circuit in the regulation of glucose homeostas which to identify the relationship between hypothalamic leptin signaling and peptic signals,then explore the intracellular signaling transduction pathways as well as the mechanism of the peripheral glycemic control by using protein expression profiling and protein and the chips techniques on the basis that we have already identified 95 hypothalamic glucose and leptin related genes, transcription factors, peptides and ligands.The results of this project will produce new leptin feed back theory and improve the understanding of the neuroendocrinal mechanism of diabetes and the development of clinical implication of diabetes surgery.

胃转流术治疗2型糖尿病临床效果明确，是目前最有治愈前景的新疗法之一，但确切机理尚不明确。研究表明下丘脑瘦素敏感性在机体葡萄糖代谢平衡调控中起重要作用，而胃转流术后24小时内血糖降低伴随着血清瘦素水平的下降，提示治疗机制与下丘脑瘦素敏感性有重要关联。我们的前期实验提示下丘脑的瘦素受体表达增强，术后下丘脑NPY等基因均发生调节变化。为进一步了解术后瘦素水平下降的原因及其与相关下丘脑的调节机制，本研究拟建立2型糖尿病大鼠胃转流术模型，应用RtPCR和共聚焦显微镜技术观察下丘脑的基因和蛋白表达。用手术前后下丘脑和消化道粘膜组织进行蛋白质谱分析、基因蛋白芯片分析等方法，分析、筛选、鉴定出下丘脑瘦素传导信号的变化和引发下丘脑改变的消化道信号。探讨下丘脑神经元信号传导通路的机制，观察外周葡萄糖代谢指标的相应变化规律。以上成果将为深入了解糖尿病发病机理，阐明手术的中枢调节机制及临床推广提供科学依据。

糖尿病导致胰岛ß细胞功能障碍，但对糖尿病引起的下丘脑神经病变知之甚少，而胃转流手术治愈糖尿病外科效应的下丘脑机制也不甚清楚。为研究糖尿病下丘脑的病理生理变化并揭示下丘脑葡萄糖调节细胞、分子损伤-修复的中枢机制，我们选择非肥胖、糖耐量受损和轻度胰岛素抵抗的Goto-Kakizaki（GK）大鼠并实施Roux-en Y胃转流手术建立糖尿病治愈模型。采用术前和术后一个月的下丘脑RNA-seq分析技术，发现糖尿病大鼠下丘脑低表达基因涉及下丘脑葡萄糖代谢传递信号NAD/NADH导致的线粒体ATP产生, 脂肪酸合成通路中促进丙二酰辅酶A（Malonyl CoA）合成的乙酰辅酶A羧化酶(ACACA)，核糖体蛋白翻译过程以及神经元微管依赖动力蛋白（dynein）的信号运输和传递过程。高表达的基因包括糖异生的两个关键酶和载脂蛋白基因。同时，糖尿病性下丘脑慢性炎症因子，包括C反应蛋白（CRP）—补体（C1q）系统---肿瘤坏死因子（TNF）通路也呈现高表达状态。我们还发现，上述的大多数糖尿病相关异常表达基因可被胃转流手术的代谢效应逆转，并且最大的基因改变比例与糖有氧氧化和糖异生相关。因此，我们认为，糖尿病可导致炎性因子介导的下丘脑神经病变并以改变葡萄糖氧化代谢信号导致线粒体ATP产出不足引发的神经元细胞器功能障碍为主要特征，推断与糖尿病导致的细胞缺氧状态有关。但该病变可以通过某些外周肠道信号的改变逆转。这项手术代谢效应修复糖尿病下丘脑神经病变的研究揭示了治愈糖尿病的新治疗靶标，并为进一步研究开辟了新途径。