从肠黏膜免疫与神经内分泌调节网络探讨黄连整体降糖调脂效应的局部机制

The therapeutic effect of Rhizoma coptidis and its principal component berberine in treatment of type 2 diabetes has been supported by the modern clinical and laboratory findings, but the pharmaceutical mechanisms are not fully understood. Recent studies demonstrated that berberine might alleviate glucose metabolic disorders through its regulation on intestinal microbiota, which suggests a new way to understand the mechanisms of Rhizoma coptidis in treatment of type 2 diabetes. The fact that the very low rate of absorbance from intestine and the exact therapeutic effect of berberine prompts that the major site of pharmaceutical action of berberine could be in the gut. Therefore, we hypothesize that "Gut might be the primary site of action of Rhizoma coptidis and its component berberine in treatment of type 2 diabetes. In addition to the regulation on intestinal flora, Rhizoma coptidis and berberine might realize their pharmaceutical effects also through their protection of intestinal mucosal barrier, and through their regulation on intestinal mucosal immune and neuroendocrine networks". In this proposal the model with type 2 diabetes will be eastabolished through inducing rats by feeding with high sugar and high fat diet. The modern techniques including pathophysiology, biochemistry and cell molecular biology will be performed in vivo or in vitro experiments. Focused on murine intestinal mucosa, the effets of Rhizoma coptidis and berberine on improving glucose and lipid metabolism and alleviating metabolic inflammation will be observed, and the relation bewteen the effect and plasma concentration of berberine will be analyzed. The influence of Rhizoma coptidis and berberine on intestinal mucosal barrier, mucosal immune and neuroendorine networks will be investigated. It is aimed to find out the intestinal local mechanism on the holistic hypoglycemic and lipid-regulating effects of Rhizoma coptidis and berberine.

黄连及其有效成分小檗碱治疗2型糖尿病的疗效已获现代临床与实验研究结果的支持，但其作用机理却不十分清楚。最近研究表明小檗碱通过对肠道菌群的调节而改善糖代谢紊乱，为我们认识黄连治疗2型糖尿病的机制提供了新思路。小檗碱从肠道的低吸收性与其疗效的确切性，提示小檗碱主要作用部位就在肠道。为此，我们提出"肠道是黄连及其有效成分小檗碱治疗2型糖尿病的主要作用部位；其除了对肠道菌群进行调节外，还可通过保护肠黏膜屏障、调节肠黏膜免疫与神经内分泌网络而起作用"的假说。本课题将以高糖高脂诱导大鼠建立2型糖尿病模型，采用现代病理生理、生物化学、细胞分子生物学等技术，整体观察与离体实验相结合，以肠黏膜为靶部位，观察黄连及小檗碱改善糖脂代谢紊乱和减轻代谢性炎症的效应，分析效应与血药浓度之间的关系，探讨其对肠黏膜屏障、黏膜免疫与神经内分泌网络的调节作用，从而阐明黄连及小檗碱治疗2型糖尿病整体降糖调脂效应的肠道局部机制。

黄连及其有效成分小檗碱治疗2型糖尿病和改善糖脂代谢疗效确切，近来研究显示小檗碱通过调节肠道菌群而改善糖脂代谢紊乱，而肠道黏膜屏障及内分泌-免疫网络是糖尿病发病的关键病理环节。本研究采用高糖高脂联合尾静脉注射STZ方法诱导2型糖尿病大鼠模型，以脂多糖诱导Caco-2细胞建立肠上皮单层细胞屏障模型。以脂多糖诱导Raw264.7细胞及原代腹腔巨噬细胞建立巨噬细胞极化模型，系统地探讨了黄连及小檗碱对肠黏膜屏障，肠黏膜免疫与神经内分泌的调节作用。动物实验表明，黄连有效成分小檗碱可有效降低糖尿病大鼠血糖和血浆甘油三酯水平，保护糖尿病大鼠肠黏膜屏障，调节肠黏膜免疫和胃肠激素分泌；离体实验表明，黄连有效成分小檗碱可降低Caco-2肠上皮细胞单层屏障通透性，上调紧密连接相关蛋白ZO-1、Occludin等的表达。黄连有效成分小檗碱可降低LPS诱导的腹腔巨噬细胞和Raw264.7细胞炎症反应，降低巨噬细胞极化比例，其机制可能与TLR4/MyD88/NFκB有关。因此，本研究提示黄连有效成分小檗碱的主要作用部位在肠道，主要通过作用于局部的肠黏膜屏障、黏膜免疫与神经内分泌网络而发挥整体性的降糖调脂效应。