The Medical Food Research and Development Center, Department of Transfusion Medicine, Faculty of Allied Health Sciences, Chulalongkorn University, Bangkok, Thailand.
Eur Rev Med Pharmacol Sci. 2012 Jan;16(1):49-56.
Gamma-oryzanol (gamma-OR) is a unique mixture of triterpene alcohol and sterol ferulates present in rice bran oil. Hypocholesterolemic activity of gamma-OR has been reported in various animal and human studies. However, the mechanisms for this hypocholesterolemic activity of gamma-OR remain unclear. Therefore, the aim of this in vitro study was to examine the effect of gamma-OR on the bioaccessibility and synthesis of cholesterol.
The effects of gamma-OR on the efficiency of incorporation of cholesterol into mixed micelles during digestion and apical uptake of cholesterol by Caco-2 human intestinal cells were determined using the coupled in vitro simulated digestion/Caco-2 human intestinal cell model. The impact of gamma-OR on the HMG-CoA reductase activity was also investigated.
Although incorporation of cholesterol into synthetic micelles was significantly inhibited by 15-fold molar excess of gamma-OR, efficiency of micellarization of cholesterol during simulated digestion of the rice meal was not significantly altered by the presence of as high as 20-fold molar excess of gamma-OR. Nevertheless, 20-fold molar excess of gamma-OR significantly decreased apical uptake of cholesterol into Caco-2 intestinal cells. In addition, gamma-OR inhibited 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase activity.
These findings suggest that the hypocholesterolemic activity of gamma-OR is due in part to impaired apical uptake of cholesterol into enterocytes and perhaps a decrease in HMG-CoA reductase activity.
γ-谷维素（γ-OR）是一种存在于米糠油中的独特的三萜醇和甾醇阿魏酸混合物。γ-OR 在各种动物和人体研究中均显示出降胆固醇活性。然而，γ-OR 降胆固醇活性的机制尚不清楚。因此，本体外研究旨在探讨 γ-OR 对胆固醇生物利用度和合成的影响。
采用体外模拟消化/Caco-2 人肠细胞模型，测定 γ-OR 对胆固醇在消化过程中掺入混合胶束的效率以及 Caco-2 人肠细胞摄取胆固醇的影响。还研究了 γ-OR 对 HMG-CoA 还原酶活性的影响。
尽管 15 倍摩尔过量的 γ-OR 显著抑制了胆固醇掺入合成胶束，但高达 20 倍摩尔过量的 γ-OR 存在并不显著改变米糠饭消化过程中胆固醇的胶束化效率。然而，20 倍摩尔过量的 γ-OR 显著降低了胆固醇向 Caco-2 肠细胞的顶端摄取。此外，γ-OR 抑制了 3-羟基-3-甲基戊二酰辅酶 A（HMG-CoA）还原酶的活性。
这些发现表明，γ-OR 的降胆固醇活性部分归因于肠细胞摄取胆固醇的能力受损，以及 HMG-CoA 还原酶活性的降低。
