5~Cholest-8(14)-en-3~-ol-15-one, a potent regulator of cholesterol metabolism: occurrence in rat skin

a-Cholest-8(14)-en-3~-ol-15-one is a potent inhibitor of cholesterol biosynthesis which has significant hypocholesterol- emic activity upon oral administration to animals. Described herein are the results of experiments that indicate the presence of the 15-ketosterol in rat skin. The 15-ketosterol was, after purifica- tion by medium pressure liquid chromatography on Lichroprep RP-8 columns, thin-layer chromatography on silica gel G, and reverse phase high performance liquid chromatography, charac- terized by gas-liquid chromatography-mass spectrometry in the form of its trimethylsilyl ether derivative. The use of an internal standard containing both tritium and deuterium permitted the determination of the levels of the 15-ketosterol by mass fragmen- tography. The results of five separate analyses of portions of the skin of a male Sprague Dawley rat showed a mean value of 84.5 * 4.1 (SEM) ng per g. Analyses of hair samples of ten male Sprague Dawley rats indicated a mean level of 143 * 19 (SEM) ng per g of hair. Most (- 72%) of the 15-ketosterol in hair was esterified. I This report constitutes the first isolation of the 15-ketmterol from animal tissues.-Emmons, G. T., J. St. Pyrek, B. Dam, M. Martin, K. Kudo, and G. J. Schroepfer, J. 5a-Cholest-8(14)-en-3~-01-15-0ne, a potent regulator of cholesterol metabolism: occurrence in rat skin. J Lipid Res, 1988. 29 1039-1054. Supplancntnry key wmda rat hair mass hgmentography gas-liquid chromatography-mass spectrometry medium pressure liquid chromatog- raphy 5a-Cholest-8(14)-en-3~-01-15-0ne (I) is a potent inhibitor of sterol synthesis in mammalian cells in culture and lowers the levels of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity in these cells (1-3). The levels of activity of two other key enzymes involved in the enzymatic formation of mevalonic acid, Le., cytosolic acetoacetyl-CoA thiolase and HMG-CoA synthase, have also been shown to be suppressed by the 15-ketosterol I in CHO-K1 cells (2). In addition to its effects on sterol synthe- sis, dietary administration of I has been shown to cause a marked inhibition of the intestinal absorption of exogenous cholesterol in rats (4). I has been shown to serve as a sub- strate for the enzyme acyl coenzyme Axholesterol acyl transferase (ACAT) of microsomes of rat liver and jejunum and to inhibit the oleoyl coenzyme A-dependent esterifica- tion