黑米通过上调小鼠肝脏CYP7A1的表达调控胆固醇代谢

Black rice regulated cholesterol by up-regulation CYP7A1 expression

目的:研究黑米对小鼠血脂以及肝脏中胆固醇代谢相关基因及蛋白表达的影响。方法:雄性C57BL/6J小鼠随机分为4组,以玉米淀粉为碳水化合物来源的高脂高胆固醇膳食组为对照,实验组分别在高脂饲料中添加白米(精)和黑米(低剂量C+BL和高剂量C+BH)代替玉米淀粉。测定血清总胆固醇(TC)、甘油三酯(TG)和高密度脂蛋白胆固醇(HDL-C)水平,Real-time PCR(RT-PCR)法检测肝脏中胆固醇代谢调控相关基因HMG-Co A-R、LXR-α、SREBP-2、LDL-R、CYP7A1等的m RNA表达水平,Western blot法检测LDL-R和CYP7A1的蛋白表达水平。结果:白米组血清中TC、TG、HDL-C含量较对照组无统计学差异,但黑米组血清中TC和TG含量较对照组降低,且HDL-C显著升高(P<0.05)。RT-PCR结果显示,与高脂组相比,黑米添加组LXR-α、SREBP-2、CYP7A1 m RNA表达水平均上调(P<0.05)。与高脂组相比,C+BH组小鼠CYP7A1蛋白表达显著上调(p<0.05)。结论:黑米调节机体胆固醇代谢平衡可能是通过升高血清中HDL-C含量,上调肝脏中胆固醇向胆汁酸转化酶CYP7A1的表达。

Objective ：This study was designed to evaluate the effect of black rice on serum lipid（TC,TG,HDL-C）levels and hepatic cholesterol metabolism-related genes（LDL-R,LXR-α,CYP7A1,SREBP-2,HMG-Co A-R）expression and protein（LDL-R,CYP7A1）expression to regulate the metabolism of cholesterol in mice fed high fat and high cholesterol diet. Method ：Male C57BL/6J mice（n=12/group）were divided into four groups,and fed a HFHC diet（C group）,composed with 52.6g/100 g corn starch or with white rice（C＋W group）,26.3g/100 g black rice（C＋BL group）or 52.6g/100 g black rice（C＋BH group）for 8 weeks. Serum total cholesterol（TC）,triglyceride（TG）and high-density lipoprotein cholesterol（HDL-C）were detected by kits. The m RNA expression levels of hepatic HMG-Co A-R,LXR-α,SREBP-2,LDL-R,CYP7A1 were assayed with realtime PCR. Western blot was used to measure the content of LDL-R and CYP7A1 protein. Results ：The content of serum TC,TG,HDL-C in experimental group were similar with that of control. However,HDL-C in black rice groups were significantly elevated compared with that of control group（P 0.05）. The m RNA expression level of hepatic LXR-α,SREBP-2,CYP7A1 were up-regulated with back rice added（P 0.05）compared with that in control group. Meanwhile,western blot results demonstrated that CYP7A1 protein expression in C＋BH group was significantly increased compared the that in control group（p 0.05）. Conclusion ：black rice induced cholesterol lowing mostly likely via increasing serum HDL-C and up-regulation of CYP7A1 in liver.