金线莲苷衍生物降糖活性和作用机制研究

New therapies are demanded for type 2 diabetes mellitus (T2DM) which is rapidly increasing with severe socioeconomic impacts. New findings suggest that lipid accumulation in peripheral tissues and lipid-induced insulin resistance are closely associated with the pathology of T2DM, furthermore, targeted inhibition of vascular endothelial growth factor receptor 1 (VEGFR1) could prevent lipid accumulation in extra-adipose tissues and improve peripheral insulin sensitivity. Nowadays, natural products and derivatives continue to play a highly significant role in the drug discovery and development process. Our previous study found a novel nature product derivative, 6′-O-cinnamoyloxy-kinsenoside, has a significant hypoglycemic activity, and provide a potential mechanistic of direct combination with VEGFR1. The purpose of the current study is to assess the hypoglycemic effects and verify the molecular mechanisms of kinsenoside derivatives, using modern pharmacology, cell biology, molecular biology, proteomics and structural biology approaches. Based on these, we can analysis the structure-activity relationship of kinsenoside derivatives; it will helpful to the further research or clinic use of these natural product derivatives, it will also provide an insight into the pharmacological research of other potent and safe hypoglycemic agents.

糖尿病的发病率在全国乃至全球范围内不断增加，给当今社会带来极其沉重的社会和经济负担，因此新型降糖药物的研发已迫在眉睫。本课题组前期基于“结构拼合”理论，对降糖活性天然产物金线莲苷进行一系列结构修饰，发现一个活性更佳的衍生物，其作用机制可能是通过靶向抑制血管内皮生长因子受体1（VEGFR1），有效控制外周组织对脂肪酸的摄取，抑制过度的脂质沉积，恢复其胰岛素敏感性，最终达到降糖效果。作为第一个降糖活性的VEGFR1小分子抑制剂，本研究拟在前期研究的基础上，结合现代药理学、细胞生物学、分子生物学、蛋白质组学和结构生物学等学科的方法，着重评价金线莲苷衍生物的降糖活性并验证其机理，深入评价该类化合物作为先导化合物和成药的可能性；并以此为基础，对其衍生物进行构效关系分析，为这一类化合物的进一步结构优化提供科学依据。

金线莲苷衍生物C6可显著降低STZ诱导的2型糖尿病大鼠的血糖水平，改善其各项生理指标。为深入探明其作用机制，本课题采用计算机反向虚拟筛选技术，发现其可能的作用靶点为VEGFR1。外周组织中过度的脂质沉积可损害组织胰岛敏感性及对葡萄糖的摄取，是2型糖尿病形成的病理因素之一。针对这一筛选结果，本文采用分子生物学技术，成功重组、表达并纯化VEGFb与其受体VEGFR1结合结构域，并通过微量热泳动技术，C6抑制二者结合率的EC50为5.37±0.79 M，抑制能力远强于其他同系列衍生物。实验证明C6可显著抑制VEGFb与VEGFR1结合，可作为潜在的VEGFb-VEGFR1信号通路抑制剂。本文选择db/db小鼠糖尿病模型综合评价C6降糖活性，结果发现C6可显著降低db/db小鼠的餐后血糖水平、改善糖尿病小鼠的葡萄糖耐受程度，调节db/db小鼠血脂水平，抑制肝脏脂肪空泡形成，降低肝脏及肾脏损伤程度，保护胰腺形态，维护胰岛细胞功能稳态；改善胰岛素抵抗，提高糖耐量，阻断外周组织对游离脂质的摄取和运输，降低心肌内信号通路下游蛋白FATP3和FATP4的表达水平，验证了C6体内降血糖作用及VEGFb-VEGFR1通路的抑制作用。综上所述，金线莲苷衍生物C6具有显著的糖尿病治疗作用，有望成为首个抑制VEGFb-VEGFR1通路的降血糖先导化合物。