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.

Inhibitors of sterol synthesis. Reverse phase high performance liquid chromatography for the separation of cholesterol, 5 alpha-cholest-8(14)-en-3 beta-ol-15-one, and their fatty acid esters

A relatively simple and rapid method was required for the separation of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one, a potent inhibitor of sterol synthesis, from its major metabolites. Conditions have been determined which permit the resolution of the 15-ketosterol and cholesterol and fatty acid esters of the two sterols by reverse phase high performance chromatography. This methodology also permits the resolution of the major esters of the 15-ketosterol and of cholesterol.

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. Spectral characterization of derivatives of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one

Described herein are the chemical syntheses of a number of deuterated derivatives of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one. These include the [2,2,3 alpha,4,4,7,7,9 alpha,16,16-2H10]-, [7 alpha,9 alpha,16,16-2H4]-, [7,7,9 alpha,16,16-2H5]-, and [2,2,3 alpha,4,4-2H5]-analogs of the delta 8(14)-15-ketosterol. Also included are the syntheses of the 3 beta-acetate derivatives of the latter three deuterated analogs and of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one, and 5 alpha-cholest-8(14)-en-3 alpha-ol-15-one. Low resolution mass spectral data on these compounds and on 5 alpha-cholest-8(14)-en-15-one, 5 alpha-cholest-8(14)-en-3 beta-ol-15-one, 5 alpha-cholest-8(14)-en-3 alpha-ol-15-one, 3 beta-benzoyloxy-5 alpha-cholest-8(14)-en-15-one, and the trimethylsilyl ethers of the free sterols have been presented. The results of these studies, supplemented with high resolution mass spectral data on five of these compounds, have been used to evaluate the electron impact mass spectral fragmentation of the delta 8(14)-15-ketosterols and their derivatives. Also presented herein are the results of 1H, 2H, and 13C nuclear magnetic resonance studies of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one and its derivatives.

Inhibitors of sterol synthesis. Synthesis and spectral characterization of fatty acids esters of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one

Reported herein are the chemical syntheses of 29 fatty acid esters of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one. These compounds were characterized by the results of ultraviolet, 1H nuclear magnetic resonance, and mass spectral studies.

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.

15 beta-Methyl-5 alpha,14 beta-cholest-7-ene-3 beta,15 alpha-diol. Synthesis, structure, and inhibition of sterol synthesis in animal cells

Treatment of 3 beta-benzoyloxy-14 alpha,15 alpha-epoxy-5 alpha-cholest-7-ene with methyl magnesium iodide gave, as the major product, 15 beta-methyl-5 alpha,14 beta-cholest-7-ene-3 beta,15 alpha-diol. The product was characterized as the free sterol and in the form of its 3 beta-acetoxy and 3 beta-p-bromobenzoate derivatives. Unambiguous assignment of structure was based upon X-ray analysis of the latter derivative. 15 beta-Methyl-5 alpha,14 beta-cholest-7-ene-3 beta,15 alpha-diol was found to be a potent inhibitor of sterol synthesis in cultured mammalian cells. The 15 beta-methyl-3 beta,15 alpha-dihydroxysterol caused a 50% reduction of the level of HMG-CoA reductase activity and a 50% reduction in the incorporation of labeled acetate into digitonin-precipitable sterols in L cells at a concentration of 3.0 x 10(-6) M.

In vitro metabolism of mevalonic acid in the bovine retina

Bovine retinas were incubated with 3RS-[5-3H]-mevalonic acid under conditions similar to those previously shown to support opsin biosynthesis in vitro. TLC of the total lipids indicated the formation of numerous radiolabeled components, including sterols, hydrocarbons, and "fatty acid-like material." The nonsaponifiable lipids were analyzed by TLC, GLC, and chromatography on columns of silicic acid-Super Cel, silica gel G-Super Cel-silver nitrate, and alumina-Super Cel-silver nitrate. The major nonsaponifiable components had the chromatographic properties of squalene and "methylated sterols" (i.e., C30, C29, and C28 monohydroxy sterols). Cholesterol represented no more than 1% of the total radioactivity in the nonsaponifiable lipid fraction. The "fatty acid-like material" was derivatized with diazomethane, and the resulting methyl esters were analyzed by GLC before and after catalytic hydrogenation. The radioactivity did not correspond to the normal fatty acids endogenous to the retina, but rather had the chromatographic properties of C15 and C20 isoprenoid acids. These results obtained with intact retinas are consistent with our previous observations concerning mevalonic acid metabolism in cell-free homogenates of bovine retinas.

Exposure of antigenic sites during immunization. Monoclonal antibodies to monomer of lactose repressor protein

Monoclonal antibodies specific for the lactose repressor protein have been purified from three mouse hybridoma cell lines, and ascitic fluids from five other cell lines producing repressor antibodies have been assayed for immunoglobulin subclass and antigenic specificity. The chymotryptic core region (amino acids 57-360) of the repressor reacted with all antibodies examined, while no reaction with the NH2-terminal domain (1-56) could be detected. All of the purified antibodies and ascitic fluids reacted with the carboxyl-terminal fragment (amino acids 281-360) produced by cyanylation and base-catalyzed cleavage at the cysteine residues. Although none of the purified antibodies associated with native, tetrameric lac repressor, reaction was observed with repressor which had been denatured or dissociated into monomers by treatment with low levels of sodium dodecyl sulfate. Additionally, a mutant repressor which exists as a monomer in solution reacted with the antibodies in the absence of any denaturing treatments. These data indicate the carboxyl-terminal region is inaccessible in the intact repressor tetramer and further suggest that denaturation/dissociation of a protein during the initial immunologic challenge may result in the production of monoclonal antibodies to antigenic areas of the protein which are not exposed in the native conformation.

5 alpha-Cholest-8(14)-en-3 beta-ol-15-one lowers serum cholesterol and induces profound changes in the levels of lipoprotein cholesterol and apoproteins in monkeys fed a diet of moderate cholesterol content

5 alpha-Cholest-8(14)-en-3 beta-ol-15-one has been found to have significant hypocholesterolemic activity upon oral administration at a daily dosage of 75 mg/kg of body weight to Rhesus monkeys fed a diet of moderate cholesterol (Chol) content [0.19 mg/kcal (1 cal = 4.184 J) of diet]. The reductions in total serum Chol levels (mean, -41%) were associated with even more striking reductions (mean, -61%) in the levels of low density lipoprotein (LDL) plus very low density lipoprotein (VLDL) Chol and also with increases in high density lipoprotein (HDL) Chol levels (mean, +61%). The mean increase in HDL Chol was 33 mg/dl. In one animal, that with the lowest pretreatment HDL Chol level, the extent of the rise was 49 mg/dl (+120%). These changes were associated with reductions in the % of total serum Chol associated with LDL/VLDL, in the ratios of total Chol to HDL Chol and of LDL/VLDL Chol to HDL Chol, and in the levels of LDL protein. The 15-ketosterol also increased the % of total Chol associated with HDL, increased the level of HDL protein, and induced a shift in the HDL profile to one in which the HDL2 species was the predominant species. All of these changes are those generally considered desirable for the treatment and/or prevention of atherosclerosis.

Metabolism of mevalonic acid in cell-free homogenates of bovine retinas. Formation of novel isoprenoid acids

The metabolism of 3RS-[2RS-3H]mevalonate in the 10,000 x g supernatant fractions of homogenates of bovine retinas has been studied. Very efficient incorporation of the labeled mevalonate, approaching quantitative utilization of its 3R-isomer, into lipid products was observed. The extent of incorporation into saponifiable lipids was very substantial. Analysis of the labeled saponifiable lipids indicated that these lipids were composed almost exclusively of C15 and C20 isoprenoid acids. The major C15 acids corresponded chromatographically to trans,trans-farnesoic acid and cis,cis-farnesoic acid. The major C20 isoprenoid acids corresponded chromatographically to trans,trans,-trans-geranylgeranoic acid and an unidentified C20 isoprenoid acid containing at least one cis-double bond. Analyses of the nonsaponifiable lipids indicated the presence of labeled squalene, a C30 fraction containing lanosterol and/or 24,25-dihydrolanosterol, and a C27 fraction containing cholesterol, 5 alpha-cholest-7-en-3 beta-ol, 5 alpha-cholesta-8,24-dien-3 beta-ol, 5 alpha-cholesta-7,24-dien-3 beta-ol, and cholesta-5,24-dien-3 beta-ol. Trace components corresponding chromatographically to 5 alpha-cholest-8(14)-en-3 beta-ol and cholesta-5,7-dien-3 beta-ol were also detected.

5 alpha-Cholest-8(14)-en-3 beta-ol-15-one, a potent inhibitor of sterol biosynthesis, lowers serum cholesterol and alters distributions of cholesterol in lipoproteins in baboons

5 alpha-Cholest-8(14)-en-3 beta-0l-15-one has been found to have significant hypocholesterolemic action on oral administration to baboons at dosages of 50 and 75 mg/kg of body weight. The 15-ketosterol decreased the levels of total serum cholesterol and low density lipoprotein plus very low density lipoprotein (LDL/VLDL) cholesterol and the percentage of total cholesterol associated with LDL/VLDL and increased the percentage of total cholesterol associated with high density lipoprotein (HDL). Moreover, administration of the steroid was associated with an absolute increase in the concentration of HDL cholesterol in those animals with low HDL levels (or with a low percentage of total serum cholesterol in the HDL fraction.

Sterol composition of bovine retinal rod outer segment membranes and whole retinas

The sterol composition of bovine retinal rod outer segment membranes and whole retinas was studied by detailed chromatographic analyses. Cholesterol represented at least 98% of the total 3 beta-monohydroxy sterols of rod outer segment membranes, accounting for 1.68 +/- 0.15% of the dry weight. Whole retinas contained 1.76 +/- 0.29% cholesterol by dry weight, representing at least 99% of the total 3 beta-monohydroxy sterols. Trace amounts of a component having the chromatographic properties of 5 alpha-cholestan-3 beta-ol were found in rod outer segment membranes and whole retinas. Very small amounts of a component having the chromatographic properties of 5 alpha-cholest-7-en-3 beta-ol were found in whole retinas, but not in rod outer segment membranes. The molar ratio of cholesterol to rhodopsin in bovine rod outer segment membranes was approximately 4.7. Cholesterol accounted for only 5-7 mol% of total rod outer segment membrane lipids.

Inhibitors of sterol biosynthesis. Carbon-13 nuclear magnetic resonance studies of 9 alpha-fluoro-5 alpha-cholest-8(14)-en-3 beta-ol-15-one and related compounds

The natural abundance 13C nuclear magnetic resonance spectra of a number of 9 alpha-fluoro and 9 alpha-hydroxy-delta 8(14)-15-ketosterols and their derivatives have been studied. Peak assignments for individual carbons of 9 alpha-fluoro-5 alpha-cholest-8(14)-en-3 beta-ol-15-one, 9 alpha-hydroxy-5 alpha-cholest-8(14)-en-3 beta-ol-15-one, 5 alpha-cholest-8(14)-ene-3,15-dione, 9 alpha-fluoro-5 alpha-cholest-8(14)-ene-3,15-dione, 9 alpha-hydroxy-5 alpha-cholest-8(14)-ene-3,15-dione, 3 beta-benzoyloxy-5 alpha-cholest-8(14)-en-3 beta-ol-15-one, 3 beta-benzoyloxy-9 alpha-fluoro-5 alpha-cholest-8(14)-en-15-one, 3 beta-benzoyloxy-5 alpha-cholest-8(14)-en-9 alpha-ol-15-one, 3 beta-acetoxy-9 alpha-fluoro-5 alpha-cholest-8(14)-en-15-one, and 3 beta-acetoxy-5 alpha-cholest-8(14)-en-9 alpha-ol-15-one have been made. Also presented herein are: 1) considerations of the substituent effects of the 9 alpha-hydroxy and 9 alpha-fluoro groups on carbon shieldings, 2) demonstration that the state of oxidation of C-3 in the various delta 8(14)-15-ketosteroids affects the olefinic carbon shieldings due to an apparent long range through space effect of the electric field on the olefinic carbon shieldings, 3) the results of analyses of 13C-19F spin-spin couplings, and 4) the results of considerations of 13C nuclear magnetic resonance studies of the concerned compounds with respect to the conformation of ring B in the various 9 alpha-substituted sterols.