鲑鱼不饱和脂肪酸改善胰岛素抵抗过程中调控GLUT4囊泡运输和脂肪棕色化的协同机制研究

Mechanistic studies on the improvement of insulin resistance and maintenance of glucose and lipid homeostasis have attracted wide concern in the field of life sciences. This project will systematically investigate the amelioration effect of salmon unsaturated fatty acids (UFA) on insulin resistance and their dynamic mechanisms for the regulation of glucose transporter 4 (GLUT4) based on the achievements of "vesicular trafficking regulation" awarded by Nobel Prize in Physiology or Medicine and "adipose browning" recognized as a novel target for the prevention and control of metabolic syndromes. The specific aims are to: (i) investigate the amelioration effect of salmon UFA on the glucose and lipid metabolism and energy balance in insulin resistance mice; (ii) study the regulation effect of UFA on the GLUT4 vesicle trafficking and signal transduction pathway and the translocation trajectory of plasmid-transfected GLUT4, and investigate the effect of UFA on the regulation of mitochondria generation and adipose browning marker genes in adipose cells; and (iii) study the amelioration rule of UFA on the insulin resistance to various extent, and demonstrate the molecular mechanism of synergistic dynamic regulation effect of UFA on the GLUT4 vesicular trafficking and adipose browning in GLUT4-specific deficiency mice according to soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) and irisin hypotheses, respectively. The outcomes of this project will significantly contribute to: (i) laying foundations for the molecular mechanism of dynamic regulation effect of UFA on the glucose and lipid metabolism; (ii) expanding the use of UFA functional foods for the amelioration of insulin resistance; (iii) promoting the development and utilization of marine bioresources; and (iv) facilitating national strategy of developing marine science and technology in the field of food science.

改善胰岛素抵抗和维持糖脂稳态的机制研究受到生命科学界的广泛关注。本项目依托诺贝尔奖获奖成果——囊泡运输调控和代谢综合症防控新靶点——脂肪棕色化，以鲑鱼不饱和脂肪酸（UFA）为对象，系统研究其改善胰岛素抵抗作用及葡萄糖转运蛋白4（GLUT4）动态调控机制。采用胰岛素抵抗小鼠模型，研究鲑鱼UFA改善糖脂代谢和能量平衡的作用；采用脂肪细胞模型，研究UFA对GLUT4囊泡及信号转导通路和质粒转染后GLUT4转位轨迹的调控机制，探索其调控线粒体生成和脂肪棕色化标志基因的机制；采用GLUT4特异性缺陷小鼠模型，研究UFA改善不同程度胰岛素抵抗的规律，根据SNARE和irisin学说论证其动态调控囊泡运输和脂肪棕色化的协同分子机制。为阐释鲑鱼UFA动态调控糖脂稳态的分子机制奠定基础，对拓展UFA功能性食品在改善胰岛素抵抗方面的新用途，促进海洋生物资源的开发利用及推动食品领域海洋科技发展战略具有重要意义。

本项目以鲑鱼不饱和脂肪酸（UFA）为对象，系统研究其改善胰岛素抵抗作用及葡萄糖转运蛋白4（GLUT4）动态调控机制。采用脂肪细胞模型，研究UFA对GLUT4囊泡及信号转导通路和质粒转染后GLUT4转位轨迹的调控机制，探索其调控线粒体生成和脂肪棕色化标志基因的机制；采用胰岛素抵抗小鼠模型，研究鲑鱼UFA改善糖脂代谢和能量平衡的作用。细胞试验结果表明，鲑鱼UFA的主要成分EPA和DHA能促进正常脂肪细胞和胰岛素抵抗脂肪细胞中葡萄糖消耗和摄取。在基础状态下，EPA和DHA通过GLUT1蛋白转运葡萄糖，影响糖代谢；在胰岛素刺激下，两者通过改变胰岛素信号通路AKT磷酸化，影响GLUT4蛋白转运葡萄糖。通过活细胞显微动态成像和间接免疫荧光染色技术观察GLUT4囊泡运输过程中表征变化，发现EPA和DHA能促使正常脂肪细胞和胰岛素抵抗脂肪细胞中GLUT4囊泡往细胞膜转移靠近，并能促进GLUT4囊泡和细胞膜锚定、融合。基于SNARE学说的分子机制研究表明，EPA和DHA不改变和囊泡聚集栓系有关的Rab4、Rab10和Rab14基因表达水平；不改变目标SNARE syntaxin4和SNAP23基因表达水平；不改变和控制SNARE复合物装配有关的Munc18c基因表达水平；但能上调正常脂肪细胞囊泡SNARE VAMP2基因和蛋白表达水平，促进囊泡膜和细胞膜的锚定、融合从而促进GLUT4囊泡转运葡萄糖，提高细胞中葡萄糖摄取和消耗。动物试验结果表明，鲑鱼UFA的主要成分EPA和DHA对脂代谢并无显著作用，但是明显改善了雌雄肥胖小鼠的糖代谢，包括提高糖耐量和胰岛素敏感性，可能通过下调TLR4-NFkb通路发挥抗炎作用，降低脂肪组织炎症水平，促进GLUT4表达，其次还能通过上调胰岛素信号通路PI3K/Akt中Akt磷酸化来促进GLUT4转运，从而改善胰岛素抵抗。本课题所取得的研究结果为阐释鲑鱼UFA动态调控糖脂稳态的分子机制奠定基础，对拓展UFA功能性食品在改善胰岛素抵抗方面的新用途和促进海洋生物资源的开发利用具有重要意义。共发表SCI论文4篇，其中IF>5的论文2篇；做国际会议口头报告1次，墙报展示5次，培养博士生和硕士生各2人。