Cholesterol diet increases plasma and liver concentrations of cholesterol epoxides and cholestanetriol

Cholesterol alpha-epoxide (5, 6 alpha-epoxy-5-alpha-cholestan-3 beta-ol), cholesterol beta-epoxide (5, 6 beta-epoxy-5 beta-cholestan-3 beta-ol), and cholestanetriol (5 alpha-cholestane-3 beta, 5, 6 beta-triol) were isolated from plasma and liver of rabbits by high performance liquid chromatography and identified by gas-chromatography-mass spectrometry. The 5, 6-oxygenated cholestanols in the plasma and liver of rabbits fed for two months on a diet supplemented with cholesterol wee elevated to 2-5 times and 5-8 times for normal level, respectively. Among the 5, 6-oxy-generated steroids, the beta-epoxide existed at the highest level in tissues of both control and cholesterol-fed rabbits. The ratios of the beta-epoxide to the alpha-epoxide were 2-3 in all the examined biological specimens just as the previously demonstrated ones in the vitro lipid peroxidation-mediated reaction of cholesterol. These results strongly suggest that the epoxidation of the cholesterol double bond in the animal may be mediated by lipid peroxidation. The elevated 5, 6-oxygenated cholestanol levels on long term cholesterol feeding will be discussed in relation to a possible physiological role of cholestanetriol in regulation of tissue cholesterol levels.