Cholesterol-Lowering Activity of Sesamin Is Associated with Down-Regulation on Genes of Sterol Transporters Involved in Cholesterol Absorption

Sesame seed is rich in sesamin. The present study was to (i) investigate the plasma cholesterol-lowering activity of dietary sesamin and (ii) examine the interaction of dietary sesamin with the gene expression of sterol transporters, enzymes, receptors, and proteins involved in cholesterol metabolism. Thirty hamsters were divided into three groups fed the control diet (CON) or one of two experimental diets containing 0.2% (SL) and 0.5% (SH) sesamin, respectively, for 6 weeks. Plasma total cholesterol (TC) levels in hamsters given the CON, SL, and SH diets were 6.62 +/- 0.40, 5.32 +/- 0.40, and 5.00 +/- 0.44 mmol/L, respectively, indicating dietary sesamin could reduce plasma TC in a dose-dependent manner. Similarly, the excretion of total fecal neutral sterols was dose-dependently increased with the amounts of sesamin in diets (CON, 2.65 +/- 0.57; SL, 4.30 +/- 0.65; and SH, 5.84 +/- 1.27 mu mol/day). Addition of sesamin into diets was associated with down-regulation of mRNA of intestinal Niemann Pick Cl like 1 protein (NPC1L1), acyl-CoA:cholesterol acyltransferase 2 (ACAT2), microsomal triacylglycerol transport protein (MTP), and ATP-binding cassette transporters subfamily G members 5 and 8 (ABCGS and ABCG8). Results also showed that dietary sesamin could up-regulate hepatic cholesterol-7 alpha-hydroxylase (CYP7A1), whereas it down-regulated hepatic 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase and liver X receptor alpha (LXR alpha). It was concluded that the cholesterol-lowering activity of sesamin was mediated by promoting the fecal excretion of sterols and modulating the genes involved in cholesterol absorption and metabolism.