小檗碱类化合物降血糖作用的分子和化学机理研究

Berberine (BBR) was reported efficacious in type 2 diabetes mellitus (T2DM) patients. The mechanisms were not fully understood, as the first cellular target of BBR was not discovered. Recent reports show BBR indirectly activated AMPK (AMP-activated protein kinase) and regulated glucose homeostasis by inhibiting mitochondrial complex Ⅰ and reducing cellular ATP production. Whether AMPK is essential for the glucose-lowering effect of BBR, the existing reports are controversial for this important issue. In this research, specific siRNAs will be used to down-regulate AMPK expression and activity in muscle, liver and adipose cells for the first time in vitro. The key cellular metabolic data, such as glucose consumption, hepatocyte glucose production, and the related gene expressions, would be examined and analyzed after BBR treatment in these cells, in order to systematically study the role of AMPK in the glucose-lowering effect of BBR. Because the first cellular target of BBR was not discovered as metioned above, BBR analogs can not be assessed or screened with a model aimed on that target. To improve the glucose-lowering potency of BBR with a poor oral bioavailability of less than 5% by structure modification and optimization, in this research we will try to establish a cellular model specific to examine the glucose consumption of cells treated with BBR analogs. This study will enrich our knowledge of molecular mechanisms and chemical fundamentals of the glucose-lowering effect of BBR and its analogs.

小檗碱的代谢调控作用已在高血脂和糖尿病病人中得以证实。但小檗碱的作用机理还没有完全搞清，表现在小檗碱细胞内的第一作用靶点还没有找到。有报道称，小檗碱抑制线粒体复合物Ⅰ，引起细胞内ATP合成减少，并间接激活AMPK而发挥降血糖等代谢调控作用。AMPK是不是小檗碱降血糖所必需的蛋白，已有的研究尚存在争议。本研究拟首次采用特异性siRNA在体外下调AMPK在肌肉、肝脏和脂肪细胞中的表达与活性，检测并分析小檗碱处理这些细胞引起的相关代谢指标（糖消耗量等）的变化情况，系统探讨AMPK在小檗碱降糖中所起的作用。由于不能根据第一作用靶标建立筛选模型，本研究拟构建并完善针对细胞糖消耗的体外筛选模型，筛选小檗碱类似物，并挑选活性强的化合物进行体内药效评价，以期通过结构改造的方式，解决小檗碱生物利用度低的问题。本研究将通过揭示BBR降糖作用的分子和化学机理，为提高和改善小檗碱的体内药效提供理论及应用基础。

小檗碱的代谢调控作用已在高血脂和糖尿病病人中得以证实。但小檗碱的作用机理还没有完全搞清，表现为小檗碱在细胞内的第一作用靶点还没有找到。有报道称，小檗碱抑制线粒体复合物Ⅰ，引起细胞内ATP 合成减少，并间接激活AMPK 而发挥降血糖等代谢调控作用。AMPK 是不是小檗碱降血糖所必需的蛋白，已有的研究尚存在争议。本研究首次采用特异性siRNA 和CRISPR手段，在体外下调或敲除细胞内AMPK α的表达，检测并分析了小檗碱处理这些细胞后，调控相关代谢指标（糖消耗量等）的变化情况，系统探讨了AMPK 在小檗碱降糖中所起的作用。同时，本研究首次总结了小檗碱类化合物对增加细胞糖消耗活性的构效关系，并筛选得到一个体外降糖活性优于小檗碱的结构类似物，可作为进一步改造的母核。本研究充实了小檗碱降糖的分子机理，了解了更多小檗碱类化合物降糖的化学基础。