大黄素通过激活PPARγ促进HepG2细胞葡萄糖摄取

Emodin stimulates glucose uptake by HepG2 hepatocyte through activation of PPARγ

目的 构建PPARγ和PPARγ应答元件（PPRE）荧光素酶系统，并确定大黄单体成分大黄素是否能够通过激活PPARγ促进HepG2肝细胞葡萄糖摄取。方法 （1）构建PPARγ和PPRE荧光素酶系统并对20余种中药成分进行筛选；（2）将能够激活PPARγ和PPRE系统的大黄素与HepG2肝细胞进行培养，分别用RT-PCR／Southern杂交测定PPARγmRNA的表达；（3）用Western印迹法测定大黄素处理后的HepG2细胞的PPARγ和葡萄糖转运蛋白2（Glut2）的表达水平；（4）测定大黄素作用后的HepG2细胞对2-脱氧-[^3H]-D-葡萄糖摄取率。结果 （1）在筛查的中药成分中，大黄素作用24h后，呈剂量（0．04～180μmol／L）依赖性地增强COS-7细胞PPRE荧光素酶活性，其中90μmol／L浓度时达到最高值，为对照组的4倍（P〈0．01），而10μmol／L浓度的吡格列酮作用强度为对照组的6倍（P〈0．01）；（2）大黄素在90μmol／L浓度时刺激HepG2细胞PPARγmRNA表达水平增加2．7倍（P〈0．01）；（3）大黄素的作用呈剂量和时间依赖性地刺激HepG2细胞PPARγ和Glut2蛋白的表达水平。其中，PPARγ蛋白水平在90μmol／L和作用16h刺激作用最强，约为对照组的3．1—3．8倍（P〈0．01）；Glut2蛋白水平在90μmol／L和作用16h刺激作用最强，约为对照组的2．5—4．3倍（P〈0．01）；（4）HepG2细胞的葡萄糖摄取率在90μmol／L浓度的大黄素作用24h后，约为对照组的5倍（P〈0．01）。结论 研究结果显示大黄素刺激HepG2肝细胞PPARγ和Glut2蛋白表达，并促进葡萄糖的摄取。

Objective To construct PPARγ and PPARγ response element （PPRE）-controlled luciferase expression vectors, and to determine whether the traditional Chinese medicine emodin activates PPARγ and improves the glucose uptake by HepG2 hepatocytes. Methods （ 1 ） PPARγ and PPRE luciferase expression vectors were constructed and were applied to screen more than 20 ingredients of the traditional Chinese medicine. （2） HepG2 cells were incubated with emodin which can activate PPARγ and PPRE luciferase activity, and the PPARγ mRNA expression level was evaluated by RT-PCR/Southern blot. （3） PPARγ and glucose transporter 2 （Glut2） proteins were determined by Western blot analysis in HepG2 cells treated with emodin. （4） The glucose uptake rate was measured using 2-deoxy-[ ^3H ]-D-glucose in HepG2 cells after treatment with emodin. Results （ 1 ） Emodin stimulated luciferase activity controlled by PPRE in dose-dependent manner at concentrations of 0.04 to 180 μmol/L in COS-7 cells. The highest value was about 4 folds of control in the cells treated with 90 μmol/L emodin （P〈0.01）, and the effect of 10 μmol/L pioglitazone was 6 folds （P 〈0.01）. （2） PPARγ mRNA expression level in the HepG2 cells treated with 90 μmol/L emodin was 2.7-fold of control cells （ P 〈 0.01 ）. （ 3 ） Both PPARγ and Glut2 proteins were dose- and time-dependently increased by emodin. The maximum expression of PPARγ protein were observed after treatment with 90 μmol/L emodin for 16 h, being 3.1 to 3.8 folds （P 〈0.01 ） of the control. And Glut2 protein reached the highest level in the treatment of 90 μmol/L emodin for 16 h, being 2.5 to 4.3 folds of the control （ P 〈 0.01 ）. （4） The glucose uptake rate in HepG2 cells treated with 90 μmol/L of emodin for 24 h was about 5 folds of control （P 〈 0. 01 ）. Conclusion The results show that emodin stimulates PPARγ and Glut2 protein expressions and improves the glucose uptake in HepG2 hepatocyte.