Gastroenterology and Nutrition Laboratory, Biomedical Center B11, Institution of Clinical Sciences, University of Lund, Lund, Sweden.
Lipids Health Dis. 2010 Apr 19;9:40. doi: 10.1186/1476-511X-9-40.
Curcumin is a polyphenol and the one of the principle curcuminoids of the spice turmeric. Its antioxidant, anti-cancer and anti-inflammatory effects have been intensively studied. Previous in vivo studies showed that administration of curcumin also decreased cholesterol levels in the blood, and the effects were considered to be related to upregulation of LDL receptor. However, since plasma cholesterol levels are also influenced by the uptake of cholesterol in the gut, which is mediated by a specific transporter Niemann-Pick Cl-like 1 (NPC1L1) protein, the present study is to investigate whether curcumin affects cholesterol uptake in the intestinal Caco-2 cells.
Caco-2 cells were cultured to confluence. The micelles composed of bile salt, monoolein, and 14C-cholesterol were prepared. We first incubated the cells with the micelles in the presence and absence of ezetimibe, the specific inhibitor of NPC1L1, to see whether the uptake of the cholesterol in the cells was mediated by NPC1L1. We then pretreated the cells with curcumin at different concentrations for 24 h followed by examination of the changes of cholesterol uptake in these curcumin-treated cells. Finally we determined whether curcumin affects the expression of NPC1L1 by both Western blot analysis and qPCR quantification.
We found that the uptake of radioactive cholesterol in Caco-2 cells was inhibited by ezetimibe in a dose-dependent manner. The results indicate that the uptake of cholesterol in this study was mediated by NPC1L1. We then pretreated the cells with 25-100 muM curcumin for 24 h and found that such a treatment dose-dependently inhibited cholesterol uptake with 40% inhibition obtained by 100 muM curcumin. In addition, we found that the curcumin-induced inhibition of cholesterol uptake was associated with significant decrease in the levels of NPC1L1 protein and NPC1L1 mRNA, as analyzed by Western blot and qPCR, respectively.
Curcumin inhibits cholesterol uptake through suppression of NPC1L1 expression in the intestinal cells.
姜黄素是一种多酚，也是香料姜黄中的主要姜黄素之一。其抗氧化、抗癌和抗炎作用已得到深入研究。先前的体内研究表明，姜黄素的给药也降低了血液中的胆固醇水平，并且这些作用被认为与 LDL 受体的上调有关。然而，由于血浆胆固醇水平也受到肠道中胆固醇摄取的影响，这是由特定的转运蛋白 Niemann-Pick Cl-like 1（NPC1L1）蛋白介导的，因此本研究旨在研究姜黄素是否影响肠道 Caco-2 细胞中的胆固醇摄取。
将 Caco-2 细胞培养至汇合。制备由胆汁盐、单油酸甘油酯和 14C-胆固醇组成的胶束。我们首先在存在和不存在 NPC1L1 的特异性抑制剂依泽替米贝的情况下，用胶束孵育细胞，以确定细胞内胆固醇的摄取是否由 NPC1L1 介导。然后，我们用不同浓度的姜黄素预处理细胞 24 小时，然后检查这些姜黄素处理细胞中胆固醇摄取的变化。最后，我们通过 Western blot 分析和 qPCR 定量确定姜黄素是否影响 NPC1L1 的表达。
我们发现 Caco-2 细胞中放射性胆固醇的摄取被依泽替米贝剂量依赖性抑制。结果表明，本研究中的胆固醇摄取由 NPC1L1 介导。然后，我们用 25-100 μM 的姜黄素预处理细胞 24 小时，发现这种处理以 100 μM 姜黄素获得 40%的抑制作用，剂量依赖性地抑制胆固醇摄取。此外，我们发现姜黄素诱导的胆固醇摄取抑制与 NPC1L1 蛋白和 NPC1L1 mRNA 水平的显著降低有关，分别通过 Western blot 和 qPCR 分析。
姜黄素通过抑制肠道细胞中 NPC1L1 的表达来抑制胆固醇摄取。
