Alemka Kisic

Inhibitors of sterol synthesis. Hypocholesterolemic action of dietary 5α-cholest-8(14)-en-3β-ol-15-one in rats and mice☆

Abstract 5α-Cholest-8(14)-en-3β-ol-15-one, at a level of 0.1% in a low cholesterol diet has been shown to have a profound hypocholesterolemic effect in rats. In one experiment the mean serum cholesterol level (mg per 100 ml ± S.E.M.) decreased from 71.2 ± 0.9 to 36.9 ± 3.3 after 7 days on the diet. In a second experiment the mean serum cholesterol value decreased from 86.4 ± 1.2 to 33.4 ± 3.9 after 8 days on the ketone-containing diet. The effects of the 15-ketosterol on serum cholesterol levels were significantly (p

Inhibitors of sterol synthesis. Dietary administration of 5α-cholest-8(14)-en-3β-ol-15-one inhibits the intestinal absorption of cholesterol in lymph-cannulated rats☆

The effect of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one, a potent inhibitor of cholesterol synthesis with marked hypocholesterolemic activity, on the intestinal absorption of exogenous cholesterol has been studied in lymph-cannulated rats. Administration of the 15-ketosterol at a level of 0.05% in a rat chow diet for 10 days was associated with a marked decrease (-64%) in the absorption of cholesterol.

Concerning the chemical synthesis of 3β-hydroxy-5α-cholest-8(14)-en-15-one, a novel regulator of cholesterol metabolism

Abstract A four-step synthesis of 3β-hydroxy-5α-cholest-8(14)-en-15-one ( I ) from 7-dehydrocholesterol is described. This synthesis, which is efficient and suitable for kilogram scale work, was carried out in a 33% overall, average yield (39% overall best yield). A major byproduct of the hydrolysis of 3β-benzoyloxy-14α,15α-epoxy-5α-cholest-7-ene to I was found to be the ring C aromatic sterol 12-methyl-18-nor-5α-cholesta-8,11,13-trien-3β-ol. Several other intermediates and byproducts of these reactions were also identified. All new sterols were characterized by 1 H- and 13 C-NMR.

Inhibitors of sterol synthesis. Effect of dietary 5α-cholest-8(14)-EN-3β-OL-15-one on acat activity of jejunal microsomes of the rat

Dietary administration (0.1% in a chow diet for 8 days) of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one, a potent inhibitor of sterol biosynthesis with marked hypocholesterolemic action, to rats caused a 77% reduction in the levels of acyl co-enzyme A:cholesterol acyl transferase activity of jejunal microsomes relative to those observed in pair-fed control animals. No differences were observed in mean levels of cholesterol concentration in jejunal microsomes of experimental and pair-fed control animals.

5α-Cholest-8(14)-en-3β-ol-15-one. In vivo conversion to cholesterol upon oral administration to a nonhuman primate

The metabolism of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one (I), a potent inhibitor of cholesterol synthesis with marked hypocholesteremic activity, has been studied in a nonhuman primate. A mixture of (2,4-/sup 3/H)-I and (4-/sup 14/C)-cholesterol was administered to a male baboon in the form of a feedball. Blood was samples at 4, 8, 12, 16, and 24 hr. Detailed analyses of the plasma lipids indicated very rapid absorption of I (relative to cholesterol) and metabolism to cholesterol, cholesteryl esters, and esters of I. The labeled cholesterol was characterized by chromatographic techniques and by purification by way of its dibromide derivative. The levels of /sup 3/H in plasma associated with I, esters of I, cholesterol, and cholesteryl esters each showed a different time course. By 24 hr after the administration of (2,4-/sup 3/H)-I, most of the /sup 3/H in plasma was associated with cholesterol and cholesteryl esters. The levels of total /sup 3/H and /sup 14/C in plasma at various times after the administration of the mixture of (2,4-/sup 3/H)-I and (4-/sup 14/C)-cholesterol differed markedly with /sup 3/H showing a maximum value at 4 hr and /sup 14/C showing a maximum value at 24 hr.

Inhibitors of sterol synthesis. A major role of chylomicrons in the metabolism of 5α-cholest-8(14)-en-3β-ol-15-one in the rat

Abstract The metabolism of 5α-cholest-8(14)-en-3β-ol-15-one ( I ), a potent regulator of cholesterol (Chol) metabolism which has significant hypocholesterolemic activity upon oral administration to animals, has been investigated in male rats. After intragastric administration of [2,4- 3 H] I and [4- 14 C]Chol in triolein to intestinal lymph duct-cannulated rats, most of the 3 H of the lymph was associated with chylomicrons. Most of the 3 H in the chylomicrons was associated with fatty acid esters of I and the oleate ester represented the major species of the esters of I . After intravenous injection of the isolated doubly-labeled chylomicrons to intact rats, rapid clearance of 3 H and 14 C from blood was observed which was associated with a rapid and selective uptake of 3 H and 14 C by liver. The rate of disappearance of 3 H from blood and the rate of uptake of 3 H by liver were similar, if not identical, to those for 14 C. In contrast, the disappearance of 3 H from the liver was much more rapid than that of 14 C. Studies of the distribution of 3 H in liver demonstrated rapid formation of free I and the formation of [ 3 H]Chol. In addition, significant amounts of the 3 H in liver were associated with polar materials, a finding which was not observed in the case of 14 C. After intravenous administration of the doubly-labeled chylomicrons to bile duct-cannulated rats, very rapid and substantial metabolism of the administered 3 H to polar biliary metabolites was observed. The bulk of the 3 H not recovered in bile at 49 h after the injection of the labeled chylomicrons was recovered in blood and tissues and almost all (∼94%) of this material was associated with Chol and Chol esters. The combined results indicate an important role for chylomicrons in the overall metabolism of I . The selective delivery of I to liver as its oleate ester in chylomicrons (or, more probably, as chylomicron remnants) and the subsequent metabolism of the oleate ester of I in liver has important consequences with respect to the actions of I which are discussed herein.

Inhibitors of sterol synthesis. Metabolism of [2,4-3H]5α-cholest-8(14)-en-3β-ol-15-one after oral administration to a nonhuman primate

Abstract 5α-Cholest-8(14)-en-3β-ol-15-one is a potent inhibitor of cholesterol biosynthesis which has significant hypocholesterolemic activity upon oral administration to rodents and nonhuman primates. In the present study the metabolism of the 15-ketosterol has been investigated after the oral administration of a mixture of [2,4- 3 H]5α-cholest-8(14)-en-3β-ol-15-one and [4- 14 C]cholesterol to 8 baboons. Blood samples were obtained at 4, 8, 12, 16, and 24 h after administration of the labeled sterols. Clear differences in the time courses of the levels of 3 H and 14 C in plasma were observed, 3 H in plasma showed maximum values at 4 to 8 h, whereas maximum values for the levels of 14 C were observed much later. 3 H in plasma was shown to be primarily in the form of its metabolites, i.e. esters of the 15-ketosterol, cholesterol, and cholesteryl esters. The levels of the 15-ketosterol and of each of these metabolites showed different changes with time. The labeled cholesterol (and the cholesterol moiety of the cholesteryl esters), formed from the [2,4- 3 H]-15-ketosterol, was characterized by chromatography and by purification by way of its dibromide derivative. At 24 h after the administration of the labeled sterols, the distribution of 3 H in plasma lipoproteins fractions paralleled that of 14 C, with most of the 3 H and 14 C in high density lipoproteins (HDL) and low density lipoproteins (LDL). Almost all of the 3 H in HDL and in LDL was found as cholesterol, cholesteryl esters and esters of the 15-ketosterol. The distribution of 3 H in HDL in LDL of the free 15-ketosterol, esters of the 15-ketosterol, cholesterol, and cholesteryl esters was similar to that of plasma, thereby indicating no unusual concentration of any of the 3 H labeled components in HDL or LDL.

Inhibitors of sterol synthesis. Morphological studies in rats after dietary administration of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one, a potent hypocholesterolemic compound.

The morphological effects of short-term (9 days) dietary administration (0.1% in a laboratory chow diet) of 5α-cholest-8(14)-cn-3β-ol-15-onc, a novel regulator of cholesterol metabolism with significant hypocholesterolemic activity, has been studied in young male rats. Control animals included rats fed the basal diet ad libitum and a series of rats pair-fed to the individual experimental animals. At the time of necropsy, the morphological changes in rats which have been observed in rats following treatment with other absorbable hypolipidemic agents (myeloid bodies with triparanol, increased peroxisomes with clofibrate, and proliferation of smooth endoplasmic reticulum with compactin and mevinolin) were not apparent on ultrastructural examination of livers of rats treated with the 15-ketosterol. Two changes were observed in the rats fed the 15-ketosterol: a decrease in adipose tissue and enlargement of the small intestine. Diminished fat was also noted in the pair-fed controls and was presumably due to decreased food consumption. The intestines of rats fed the 15-ketosterol were morphometrically most enlarged in the jejunal region. Morphologically, this increase was distinguished by increased depth of crypts of Lieberkuhn and pseudostratification of epithelium at the base of the villi. These changes were qualitatively and quantitatively similar to the adaptive changes reported in the rat after resection of small bowel or following intestinal bypass (segment of bowel remaining in continuity). The morphological changes induced in the rat by administration of the 15-ketosterol were not observed in 4 baboons which received the compound orally at doses of 50, 75, or 100 mg per kilogram of body weight for up to 3 months.

Inhibitors of sterol synthesis. Chemical syntheses and activities of new derivatives of 15-oxygenated sterols

Abstract The chemical syntheses of 5α-cholestane-3β,14α,15β-triol, 5α-cholestane-14α-ol-3,15-dione, 5α-cholestane-3β,14α-diol-15-one, 14α,15α-epoxy-5α-cholestan-3β-ol, and 5α-cholest-8(14)-en-3β-ol-15-one oxime are described. All of these compounds were found to be potent inhibitors of sterol synthesis in cultured mouse L cells. However, the former three compounds had little or no effect on the levels of 3-hydroxy-3-methylgutaryl (HMG)-CoA reductase in the same cells. In contrast, in the case of the latter two compounds, the concentrations required to cause a 50% inhibition of the synthesis of digitonin-precipitable sterols were comparable to those required to cause a 50% reduction in the levels of HMG-CoA reductase in the same cells. 5α-Cholest-8(14)-en-3β-ol-15-one oxime had no effect on serum cholesterol levels when administered to male rats at a level of 0.15% in a cholesterol-free diet.

Inhibitors of sterol synthesis. Hypocholesterolemic action of dietary 9α-Fluoro-5α-cholest-8(14)-en-3β-ol-15-one☆

Abstract 9α-Fluoro-5α-cholest-8(14)-en-3β-ol-15-one, at a level of 0.15% in a laboratory chow diet, has been shown to have a significant hypocholesterolemic effect in normal rats. The mean serum cholesterol level (mg per 100 ml ± S.E.M.) decreased from 84.5 ± 1.5 to 53.3 ± 3.0, 54.1 ± 3.2, and 60.5 ± 2.6 after 5, 9, and 12 days, respectively, on the steroid-containing diet. The effects of the 9α-fluoro-15-ketosterol on serum cholesterol levels were significantly different from those of either ad libitum or pair-fed controls. The diet containing the steroid caused a significant decrease in food consumption which was associated with a decrease in the rate of gain in body weight.