Phytosterols and fatty acids, but not phytosterol esters, affect cholesterol micellarization in vitro

Abstract

The mechanisms by which consumption of phytosterols and their fatty acyl esters decreases LDL cholesterol, an atherosclerotic risk factor, are incompletely characterized. To test the hypothesis that phytosterols, phytosterol esters, and simulated hydrolysis products of the esters differentially affect micellarization of cholesterol (a necessary step in efficient cholesterol absorption), we measured the influence of these compounds on cholesterol incorporation in model mixed‐bile micellar systems. We found that sterols and fatty acids independently altered cholesterol incorporation: oleic acid increased cholesterol micellarization as compared with palmitic and stearic acids; phytosterols resulted in an almost 50% reduction in cholesterol micellarization in a dose‐dependent manner, with no differences among phytosterols. Phytosterol esters did not incorporate into the micelles, nor did they result in a change in cholesterol micellarization. We conclude that phytosterols decrease micellarization by competition, and that fatty acids can differentially affect cholesterol micellarization.Grant Funding Source: Research supported by USDA‐NRI competitive grant no. 2007‐35200‐18298