TGR5-GLP-1信号通路在石胆酸调控妊娠期胰岛素抵抗中的作用及机制

Bile acids were recently shown to be a new kind of endocrine regulators, and they improved insulin sensitivity and enhance glucose metabolism by activating G protein-coupled receptor (TGR5). Our preliminary data indicated that first-trimester total bile acid(TBA) levels were significantly elevated and independently associated with the incidence of gestational diabetes mellitus (GDM). Then our metabolomics analysis by a cohort study in pregnant women with or without GDM firstly revealed that the increase in the levels of lithocholic acid (LCA), known as the strongest agonist of TGR5, was greatest in GDM women. Furthermore, we found in the animal model that after treatment with LCA, the levels of TGR5 in placenta and adipose tissue from pregnant mice were significantly increased, at the same time, the expressions of GLUT-1 and GLUT-4 in adipose tissue were significantly increased, and the serum TNF-α levels decreased..However, how does LCA alleviate the insulin resistance in pregnancy? It is not clear till now. To answer this scientific question, we designed the present study to clarify the effect of TGR5-GLP-1 signaling in the mechanism of LCA to induce insulin resistance alleviation during pregnancy by:1) in vivo study with the systemic insulin sensitivity, glucose uptake, inflammation and TGR5-GLP-1 signaling after LCA and TGR5 activated or inhibited intervention; 2)in vitro study with the TGR5-GLP-1 signaling and inflammatory response in target cells of insulin and intestine L cells treated with LCA or its inhibitor. .This program will reveal the molecular mechanism of TGR5-GLP-1 signal activation in the improvement of insulin sensitivity induced by LCA. And these results will provide the scientific basis of exploring a novel molecular target and new potential stratgies for GDM prevention through improving insulin sensitivity.

胆汁酸是一种重要内分泌调节因子，可通过激活G蛋白偶联受体-5（TGR5）提高胰岛素敏感性，改善糖代谢。我们的前期研究表明，妊娠糖尿病（GDM）孕妇孕早期总胆汁酸水平显著升高，进一步代谢组学分析显示：GDM患者石胆酸（已知最强的TGR5激动剂）水平升高幅度最大。给孕鼠喂养添加石胆酸的饲料，其胎盘和脂肪TGR5表达明显增加，脂肪GLUT-1和GLUT-4表达上调，血清TNF-α水平下降。但石胆酸如何改善孕期胰岛素抵抗？其分子机制仍不清楚。为回答此科学问题，本项目拟通过石胆酸或TGR5 激活或TGR5抑制治疗后孕鼠胰岛素抵抗及其受体后胰岛素信号传导、葡萄糖摄取等通路和TGR5-GLP-1通路变化的体内研究，及石胆酸对胰岛素靶组织和细胞的TGR5-GLP-1信号通路变化等体外研究，多层次阐明TGR5-GLP-1通路在石胆酸减轻妊娠期胰岛素抵抗的分子机制，为有效防治GDM提供全新的思路和分子靶点。

妊娠期糖尿病（GDM）是指在妊娠期发生或首次发现的不同程度的糖耐量异常。胆汁酸是一种重要内分泌调节因子，可通过激活G蛋白偶联受体-5（TGR5）提高改善糖代谢。本课题研究GDM危险因素、TGR5激活后对GDM发病的作用及调控机制。. 临床研究部分，建立前瞻性队列，在孕早中期做生化指标检测，孕24-28周随访行OGTT筛查GDM，而后进行血糖监测和产后结局随访。结果发现：1.妊娠期胰岛功能缺陷和胰岛素抵抗存在异质性，早期合并胰岛素抵抗和胰岛功能障碍的GDM孕妇较糖耐量正常的孕妇更易发生LGA（P=0.008）和围产期不良结局（P=0.005）。但校正了孕前BMI等混杂因素后，这种差异就消失。2.补体因子H因子（CFH），白介素IL-6, TNF-a, CRP与BMI和HOMA-IR呈正相关(all P ＜0.05)，但校正BMI等后CFH与GDM无独立相关关系；提示这些炎症因子在GDM中的改变受BMI影响，间接参与GDM疾病的发生。3.补体系统炎症因子Ba（Ba）与GDM独立相关，校正BMI后Ba与GDM关系仍存在，提示其可作为GDM预测因子，但Ba是否参与GDM发病有待研究。. 基础研究部分，对孕鼠构建STZ和高脂饮食两种GDM动物模型，并进行细胞研究。首先，分离提取孕鼠骨髓来源的细胞，诱导分化为成熟原代巨噬细胞，观察激活TGR5后对其极化、迁移功能和炎症影响。其次，TGR5激动剂灌胃处理后GDM小鼠整体炎症因子、糖代谢和GLP-1变化。最后，体外培养胎盘滋养细胞系，用棕榈酸诱导出炎症，观察TGR5激动对细胞功能和其炎症的影响。结果发现：1.TGR5激活后，GDM小鼠血清GLP-1水平升高；IL-6等炎症因子下降，糖代谢改善。2.激活巨噬细胞TGR5受体可抑制巨噬细胞向M1类型极化、M2/M1比值升高、趋化因子表达及其迁移能力，且此效应通过上调PC1/3的表达实现。3.高脂刺激物棕榈酸可抑制胎盘滋养细胞活性，且促进其炎症因子分泌，而TGR5激活后，通过抑制NF-κB通路改善其炎症反应。. 总之，TGR5激活可能通过提高GLP-1、调控巨噬细胞极化和功能而抑制其炎症介导作用、改善胎盘细胞慢性炎症，改善孕鼠整体和胎盘的糖代谢和妊娠不良结局。本研究为从激活TGR5、抑制巨噬细胞介导的炎症等角度防治GDM提供思路。