Rapid screening for potential cholesterol-lowering peptides using naturally derived micelle preparation

Several food constituents have been shown to reduce blood cholesterol levels and promote cardiovascular health via different mechanisms, such as inhibition of cholesterol synthesis and suppression of cholesterol uptake. Inhibition of cholesterol solubilisation into micelles and cellular cholesterol absorption are target sites of interventions for cholesterol reduction. Artificial micelles have been used as a model system for in vitro cholesterol solubilisation and/or cholesterol absorption assays to evaluate hypocholesterolemic activity of potential bioactive compounds, including milk whey protein. This study aimed to compare the efficacy of artificially prepared micelles with naturally derived micelles from pig's bile on micellar solubility of cholesterol and cellular cholesterol absorption assays to identify potential cholesterol-lowering compounds. Green tea catechins and IIAEK with previously reported inhibitory effects on cholesterol uptake were used as reference compounds. Tea catechins, e.g. epigallocatechin gallate (EGCG), significantly reduced the solubility of cholesterol in pig's bile-derived micelle preparations (56%, p<0.001), which was comparable with those in artificially prepared micelles (65%, p<0.001). Suppression of cholesterol absorption in Caco-2 cells by IIAEK was also noted when using either artificially-prepared or pig's bile-derived micelle preparations (24%, p<0.01). We conclude that pig's bile is a rapid, reproducible, convenient and cost-effective source of micelles for cholesterol micelle solubility and cellular uptake assay systems and is suitable for screening purposes focused on identifying potential cholesterol-lowering agents.