Department of Biology, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
Food Funct. 2010 Oct;1(1):84-9. doi: 10.1039/c0fo00036a. Epub 2010 Sep 13.
Onion has been shown to favorably modify the lipoprotein profile. However, research on its underlying mechanism is lacking. The present study investigated the interaction of dietary onion powder with the protein expression of key receptors and enzymes involved in cholesterol metabolism. Thirty-six male hamsters were randomly divided into three groups and fed a high-cholesterol control diet or the two experimental diets supplemented with 1% onion powder (OP-1) or 5% onion powder (OP-5), for a period of 8 weeks. It was found that onion dose-dependently decreased plasma total cholesterol (TC) level. The change in plasma lipoprotein profile was accompanied by a greater excretion of both fecal neutral and acidic sterols. Western blot analysis revealed that onion up-regulated sterol regulatory element binding protein 2 (SREBP-2), liver X receptor alpha (LXRα) and cholesterol-7α-hydroxylase (CYP7A1) with no effect on 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) and LDL receptor (LDL-R). It was concluded that the hypocholesterolemic activity of onion powder was mediated by enhancement of fecal sterol excretion and up-regulation of LXRα and CYP7A1.
洋葱已被证明可有效地改善脂蛋白谱。然而，其潜在机制的研究还很缺乏。本研究调查了膳食洋葱粉与胆固醇代谢关键受体和酶的蛋白表达之间的相互作用。36 只雄性仓鼠被随机分为三组，分别喂食高胆固醇对照饮食或补充 1%洋葱粉（OP-1）或 5%洋葱粉（OP-5）的两种实验饮食，为期 8 周。结果发现，洋葱粉呈剂量依赖性地降低了血浆总胆固醇（TC）水平。血浆脂蛋白谱的变化伴随着粪便中性和酸性固醇排泄量的增加。Western blot 分析表明，洋葱粉上调了固醇调节元件结合蛋白 2（SREBP-2）、肝 X 受体α（LXRα）和胆固醇 7α-羟化酶（CYP7A1），而对 3-羟-3-甲基戊二酰辅酶 A 还原酶（HMGR）和低密度脂蛋白受体（LDL-R）没有影响。结论：洋葱粉的降胆固醇活性是通过增加粪便固醇排泄和上调 LXRα 和 CYP7A1 来介导的。
