Inhibition of sterol biosynthesis in L cells and mouse liver cells by 15-oxygenated sterols

Inhibitors of sterol synthesis. The effects of dietary 5 alpha-cholest-8(14)-en-3 beta-ol-15-one on the fate of [4-14C]cholesterol and [2,4-3H]5 alpha-cholest-8(14)-en-3 beta-ol-15-one after intragastric administration to rats

The effect of dietary administration (0.1% in a rat chow diet) of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one, a potent inhibitor of cholesterol biosynthesis with marked hypocholesterolemic activity, on the fate of [4-14C]cholesterol and [2,4-3H]5 alpha-cholest-8(14)-en-3 beta-ol-15-one has been studied after intragastric administration of the labeled sterols to rats. In general, the distribution of 3H in major tissues paralleled that of 14C with no unusual concentration of 3H in any of the organs. Only trace amounts of 3H and 14C were recovered in urine. Administration of the 15-ketosterol was associated with decreased absorption of the labeled cholesterol as indicated by decreased levels of 14C in the various tissues and organs of the 15-ketosterol-treated rats (relative to ad libitum and pair-fed control animals) and increased levels of 14C in feces and intestinal contents at 12 and 48 h after the administration of the labeled cholesterol. Studies of the distribution of 3H in liver indicated rapid conversion of the 15-ketosterol to cholesterol and cholesteryl esters. The amounts of 3H recovered in the various tissues and organs at both 12 and 48 h after the administration of the labeled sterols were considerably less than the corresponding values for 14C, a finding which suggests a lower absorption of the 15-ketosterol (relative to cholesterol) and/or a more rapid clearance and biliary excretion of the 15-ketosterol and its metabolites.

Inhibitors of sterol synthesis. Concerning the structure of 15 beta-methyl-5 alpha,14 beta-cholest-7-ene-3 beta,15 alpha-diol, an inhibitor of cholesterol biosynthesis

The chemical synthesis of 3 beta-p-bromobenzoyloxy-15 beta-methyl-5 alpha,14 beta-cholest-7-en-15 alpha-ol from 15 beta-methyl-5 alpha, 14 beta-cholest-7-ene-3 beta,15 alpha-diol is described. The structure of the former compound was unambiguously determined by X-ray crystallographic analysis. The space group of the crystal was P2 with unit cell parameters a = 12.611 A, b = 9.826 A, c = 13.221 A, b = 91.71 degrees and Z = 2. The structure was solved by the heavy atom method and refined to a final R of 0.041. Asymmetry parameters indicated that ring A is a symmetrical chair, that rings B and C are half chairs, and that ring D is a 15 alpha-envelope.

Enzymatic formation and chemical synthesis of an active metabolite of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one, a potent regulator of cholesterol metabolism

The enzymatic (rat liver mitochondria) conversion of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one to 5 alpha-cholest-8(14)-ene-3 beta,26-diol-15-one is described. The enzymatic product was judged, on the basis of IH and 13C NMR studies, to be a 4:1 mixture of its 25R and 25S isomers. (25R)-5 alpha-Cholest-8(14)-ene-3 beta,26-diol-15-one was prepared through a five-step synthesis from (25R)-26-hydroxycholesterol. The (25R) isomer of the new compound was found to be highly active in the suppression of the levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in cultured mammalian cells and to inhibit the esterification of cholesterol in jejunal microsomes.

Inhibitors of sterol biosynthesis. Synthesis and activities of ring C oxygenated sterols

The chemical syntheses of a number of C27 ring C oxygenated sterols have been pursued to permit evaluation of their activity in the inhibition of sterol biosynthesis in cultured mammalian cells. Thus, 5 alpha-cholest-7-ene-3 beta, 11 alpha-diol, 3 alpha-hydroxy-5 alpha-cholest-9(11)-en-12-one, and the previously unreported 11 alpha-hydroxy-5 alpha-cholest-7-en-3-one, 5 alpha-cholest-9(11)-ene-3,12-dione, and 3 beta-hydroxy-5 alpha-cholest-9 (11)-en-12-one have been synthesized. The effects of these compounds on the synthesis of digitonin-precipitable sterols from labeled acetate in mouse L cells and on the levels of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity in the same cells have been investigated and compared with previously published data on other ring C oxygenated sterols. 5 alpha-Cholest-7-ene-3 beta, 11 alpha-diol was shown to be the most potent inhibitor of sterol synthesis.

5 alpha-cholest-8(14)-en-3 beta-ol-15-one. A competitive substrate for acyl coenzyme A:cholesterol acyl transferase

5 alpha-Cholest-8(14)-en-3 beta-ol-15-one, a potent inhibitor of cholesterol biosynthesis with hypocholesterolemic activity, has been found to serve as an efficient substrate for acyl CoA:cholesterol acyl transferase of rat hepatic and jejunal microsomes and to inhibit the esterification of cholesterol. Concentrations required to give 50% inhibition of cholesterol ester formation in liver and jejunal microsomes were approximately 10 microM and approximately 3 microM, respectively.

Inhibitors of sterol synthesis. Effect of dietary 5 alpha-cholest-8(14)-en-3 beta-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.

Inhibitors of sterol synthesis. Dietary administration of 5 alpha-cholest-8(14)-en-3 beta-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.

5 alpha-Cholest-8(14)-en-3 beta-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 [2,4-3H]-I and [4-14C]-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 3H 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 [2,4-3H]-I, most of the 3H in plasma was associated with cholesterol and cholesteryl esters. The levels of total 3H and 14C in plasma at various times after the administration of the mixture of [2,4-3H]-I and [4-14C]-cholesterol differed markedly with 3H showing a maximum value at 4 hr and 14C showing a maximum value at 24 hr.

Chain length dependent modification of lipid organization by low levels of 25-hydroxycholesterol and 25-hydroxycholecalciferol. A laser Raman study

We have used Raman spectroscopy to investigate the thermal transitions of multibilayered liposomes composed of lecithins, i.e., dilauroyllecithin, dimyristoyllecithin, dipalmitoyllecithin, distearoyllecithin, or egg lecithin, plus 5-cholesten-3,25-diol (25-hydroxycholesterol), 25-hydroxycholecalciferol, and vitamin D3. We recorded the CH-stretching (2800-3000-cm-1) regions of the Raman spectra at various temperatures and employed plots of temperature vs. the intensity of the 2880- or 2930-cm-1 bands relative to that of the 2850-cm-1 feature, i.e., the ratios I2880/I2850 and I2930/I2850, to estimate thermal transitions. These plots show multiple discontinuities, each of which may be ascribed to a state change of a separate phase with distinctive proportions of lecithins and cholesterol derivatives. Low concentrations of 25-hydroxycholesterol and 25-OH-D3 (greater than or equal to 0.2 mol%) abolish the pretransition and split the main transitions of dilauroyllecithin (4 degrees C) and dimyristoyllecithin (23 degrees C) into two. The midpoint of the new small transition centers at about 3-4 degrees C lower than those of the respective main transitions of dilauroyllecithin and dimyristoyllecithin. A further increase in the molar ratio of 25-hydroxycholesterol and 25-hydroxycholecalciferol decreases the amplitudes of the new and the main transitions (dilauroyl- and dimyristoyllecithin). The transitions of dipalmitoyllecithin and distearoyllecithin at 2 mol % concentrations of either sterol remain unaffected. There was no splitting in the main transition of either dipalmitoyllecithin or distearoyllecithin in the presence of these sterols. The perturbing effect of the 25-hydroxysterols follows the order dilauroyllecithin greater than dimyristoyllecithin greater than dipalmitoyllecithin greater than distearoyllecithin.(ABSTRACT TRUNCATED AT 250 WORDS)

Lethal effect of cis- but not trans-22-dehydrocholesterol on mouse fibroblast cells

cis- and trans-22-dehydrocholesterol were incorporated into the culture medium for mouse fibroblasts cells. Although neither isomer had an effect on sterol biosynthesis, the cis isomer inhibited cell growth and viability and increased Rb+ efflux from the cells. The trans isomer had no effect on growth and could replace exogenous cholesterol for growth of cells for which sterol biosynthesis was blocked by 25-hydroxycholesterol.

Metabolism of hydroxy sterols by rat liver

5 alpha-[16-3H]lanost-8-ene-3 beta,15 alpha-diol and 5 alpha-[16-3H]lanost-8-ene-3 beta,15 beta-diol were both extensively metabolised by rat liver enzymes in vitro. Quantitatively, the most important product in both cases was a more polar compound, tentatively identified as a 5 alpha-lanost-8-enetriol. In addition, 5 alpha-[16-3H]lanost-8-ene-3 beta,15 beta-diol gave rise to the corresponding 3 beta,15beta-diol diester, whilst with 5 alpha-[16-3H]lanost-8-ene-3 beta,15 alpha-diol only the 3 beta-hydroxyl group was esterified. The enzymes involved may normally be responsible for metabolising spontaneously produced non-enzymic oxidation products of dietary or cellular cholesterol. High concentrations of 5 alpha-[16-3H]lanost-8-ene-3 beta,15 beta-diol stimulated ester formation. With both substrates, carbon monoxide inhibited formation of the polar sterol metabolite but stimulated ester formation. Under all conditions, cholesterol was a relatively minor metabolic product of either of the 5 alpha-lanost-8-ene-3 beta,15-diols.

Inhibition of sterol biosynthesis by 14 alpha-hydroxy-delta 7-sterols

5 alpha-Cholest-7-en-3 beta, 14 alpha-diol and 5 alpha-cholest-7-en-14 alpha-ol-3-one have been found to be potent inhibitors of the synthesis of digitonin-precipitable sterols in L cells in culture and to reduce the levels of HMG-CoA reductase activity in these cells.

Concerning the structure of 7 alpha,15 beta-dichloro-5 alpha-cholest-8(14)-en-3 beta-ol, a novel inhibitor of cholesterol biosynthesis

Treatment of 3 beta-p-bromobenzoyloxy-14 alpha,15 alpha-epoxy-5 alpha-cholest-7-ene with gaseous HCl in chloroform at -25 degrees C gave 3 beta-p-bromobenzoyloxy-7 alpha,15 beta-dichloro-5 alpha-cholest-8(14)-ene in 93% yield. The structure of the latter compound was unequivocally established by the results of X-ray crystallographic analysis.

Effects of various oxygenated sterols on cellular sterol biosynthesis in Chinese hamster lung cells resistant to 25-hydroxycholesterol

The effects of a wide variety of oxygenated sterols upon sterol biosynthesis and hydroxymethylglutaryl-CoA reductase (mevalonate: NADP+ oxidoreductase (CoA-acylating), EC 1.1.1.34) activity in a wild-type clone and in a 25-hydroxycholesterol-resistant clone of Chinese hamster lung (Dede) cells are described. Derivatives of cholesterol which were oxygenated in the 6, 7 or 15 positions of the sterol nucleus or in the 20, 22, 24 or 25 positions of the sterol side chain were shown to be potent inhibitors of sterol synthesis and reductase activity in the wild-type cells but none of these substitutions had any effect on the 25-hydroxycholesterol-resistant A2 clone. A 32-hydroxylated derivative of lanosterol also suppressed sterol synthesis and reductase activity in wild-type cells but had no significant effect upon the A2 line. It was also appraent that a complete sterol side chain was necessary for inhibitory activity. Studies of a wide range of inhibitory sterols indicated that there was a close correlation between their effects upon sterol synthesis and reductase activity and that their inhibitory action was specific for sterol biosynthesis since little effect was observed upon fatty acid or CO2 synthesis. Previous studies had shown that the uptake of 25-hydroxycholesterol by the resistant A2 line was unimpaired and the present results indicate that metabolism of this oxygenated sterol is also unaltered. These results, in conjunction with previous studies, suggest that the resistant A2 line is defective in feedback regulation of cholesterol synthesis and that all of the oxygenated sterols tested suppress the biosynthetic pathway through at least one common step.

Further studies on the inhibition of sterol biosynthesis in animal cells by 15-oxygenated sterols

The chemical syntheses of a number of C27 15-oxygenated sterols and their derivatives have been pursued to permit evaluation of their activity in the inhibition of sterol biosynthesis in animal cells in culture. Described herein are chemical syntheses of 3 alpha-benzoyloxy-5 alpha-cholest-8(14)-en-15-one, 5 alpha-cholest-8(14)-en-3 alpha-ol-15-one, 5 alpha-cholest-8(14)-en-15-one-3 beta-yl pyridinium sulfate, 5 alpha-cholest-8(14)-en-15-one-3 beta-yl potassium sulfate (monohydrate), 5 alpha-cholest-8(14)-en-15-one-3 alpha-yl pyridinium sulfate, 5 alpha-cholest-8(14)-en-3 alpha-yl potassium sulfate (monohydrate), 5 alpha-cholest-8(14)-en3,7,15-trione, 5 alpha-cholest-8(14)-en-15 alpha-ol-3-one, 5 alpha, 14 alpha-cholestan-3 beta, 15 beta-diol diacetate, 5 alpha, 14 beta-cholestan-3 beta, 15 beta-diol diacetate, 5 alpha, 14 alpha-cholestan-3 beta, 15 alpha-diol, 5 alpha, 14 alpha-cholestan-15 alpha-ol-3-one, 5 alpha, 14 beta-cholestan-3 beta, 15 beta-diol, 5 alpha, 14 alpha-cholestan-3,15-dione, and 5 alpha, 14 beta-cholestan-3,5-dione. The effects of 8 of the above compounds and of 5 alpha-cholesta-6,8(14)-dien-3 beta-ol-15-one, 3 beta-he misuccinoyloxy-5 alpha-cholest-8(14)-en-15 one, 3 beta-hexadecanoyloxy-5 alpha-cholest-8(14)-en-15-one, 5 alpha-cholest-8(14)-en-3,15-dione, 5 alpha-cholesta-6,8(14)-dien-3,15-dione, 5 alpha-cholest-8-en-3 beta, 15 alpha-diol, 5 alpha-cholest-7-en-3 beta, 15 alpha-diol, 5 alpha-cholest-8(14)-en-15 alpha-ol-3-one, 5 alpha-cholest-8-en-15 alpha-ol-3-one, and 5 alpha-cholest-7-en-15 alpha-ol-3-one on the synthesis of digitonin-precipitable sterols and on levels of HMG-CoA reductase activity have been investigated and compared with previously published data on 7 other C27 15-oxygenated sterols.