Showing papers on "Sterol published in 1993"
822 citations
TL;DR: Surprisingly, campestanol, the 5α saturated derivate of campesterol, was shown to have higher absorbability compared with its unsaturated compound, in contrast to previous assumptions that hydrogenisa‐tion of the nucleus double bond of a sterol causes a decrease of absorbability.
Abstract: . Intestinal absorption of cholesterol, campes-terol, campestanol, stigmasterol and sitosterol were measured in 10 healthy subjects by an intestinal perfusion technique over a 50 cm segment of the upper jejunum using sitostanol as non-absorbable marker. Cholesterol absorption was highest and averaged 33%, whereas the absorption rate of sitosterol averaged 4.2% and of stigmasterol 4.8%. Higher absorption rates were found for campesterol (9.6%). Canipestanol, the 5a saturated derivative of campesterol, showed the highest absorption rate (12.5%) of all plant sterols. A positive correlation between the absorption rate of cholesterol and campesterol was established. In addition, there was a negative correlation between the ratio of sitosterol to cholesterol and the mass of cholesterol absorption. These results are in agreement with previous observations in animal studies, namely, that increasing the length of the side-chain of cholesterol decreases the absorbability of the sterol. Surprisingly, campestanol, the 5α saturated derivate of campesterol, was shown to have higher absorbability compared with its unsaturated compound. This finding is in contrast to previous assumptions, that hydrogenisa-tion of the nucleus double bond of a sterol causes a decrease of absorbability, as has been demonstrated for cholesterol/cholestanol and sitosterol/sitostanol.
397 citations
TL;DR: Organelles of the yeast Saccharomyces cerevisiae were isolated and analyzed for sterol composition and the activity of three enzymes involved in sterol metabolism, leading to the view that ergosteryl esters of lipid particles might serve as intermediates for the supply of ergosterol from internal membranes to the plasma membrane.
Abstract: Organelles of the yeast Saccharomyces cerevisiae were isolated and analyzed for sterol composition and the activity of three enzymes involved in sterol metabolism. The plasma membrane and secretory vesicles, the fractions with the highest sterol contents, contain ergosterol as the major sterol. In other subcellular membranes, which exhibit lower sterol contents, intermediates of the sterol biosynthetic pathway were found at higher percentages. Lipid particles contain, in addition to ergosterol, large amounts of zymosterol, fecosterol, and episterol. These sterols are present esterified with long-chain fatty acids in this subcellular compartment, which also harbors practically all of the triacylglycerols present in the cell but very little phospholipids and proteins. Sterol delta 24-methyltransferase, an enzyme that catalyzes one of the late steps in sterol biosynthesis, was localized almost exclusively in lipid particles. Steryl ester formation is a microsomal process, whereas steryl ester hydrolysis occurs in the plasma membrane and in secretory vesicles. The fact that synthesis, storage, and hydrolysis of steryl esters occur in different subcellular compartments gives rise to the view that ergosteryl esters of lipid particles might serve as intermediates for the supply of ergosterol from internal membranes to the plasma membrane.
312 citations
TL;DR: Sitostanol, a nonabsorbable plant sterol, could be the drug of choice for treating familial hypercholesterolemia in childhood, and the reduction in serum lipid levels was of the same magnitude as that observed with systemic lipid-lowering drugs.
212 citations
TL;DR: The first identification of dinosterol (or its C-24 epimer since the two are not separable on conventional non-polar capillary columns) in a laboratory culture of a marine diatom Navicula sp.
210 citations
TL;DR: Comparative studies allowed differentiation of plasma membrane lipid changes associated with increased freezing tolerance following CA from lipid changes that can result from metabolic adjustment to reduced temperature during CA.
Abstract: Simultaneous comparisons were made between a freezing-tolerant, cold-acclimating (CA) wild potato species (Solanum commersonii) and a freezing-sensitive, nonacclimating (NA) cultivated species (Solanum tuberosum). Comparative studies allowed differentiation of plasma membrane lipid changes associated with increased freezing tolerance following CA from lipid changes that can result from metabolic adjustment to reduced temperature during CA. Following CA treatment lipid changes found in both the NA and CA species included a decrease in palmitic acid, an increase in unsaturated to saturated fatty acid ratio, an increase in free sterols, an increase in sitosterol, and a slight decrease in cerebrosides. Lipid changes detected only in the acclimating species included an increase in phosphatidylethanolamine, a decrease in sterol to phospholipid ratio, an increase in linoleic acid, a decrease in linolenic acid, and an increase in acylated steryl glycoside to steryl glycoside ratio. These changes were either absent or opposite in the NA species, suggesting an association of these lipid changes with CA. Furthermore, the lipid changes associated with increased freezing tolerance during CA were distinct from lipid differences between the two species in the NA state.
208 citations
TL;DR: In contrast, nicotinic acid and particularly adenosine caused moderate inhibition of HMG-CoA reductase activity and of cholesterol biosynthesis suggesting that these compounds participate, at least in part, in the early inhibition of sterol synthesis by garlic extracts.
Abstract: Exposure of primary rat hepatocytes and human HepG2 cells to water-soluble garlic extracts resulted in the concentration-dependent inhibition of cholesterol biosynthesis at several different enzymatic steps. At low concentrations, sterol biosynthesis from [14C]acetate was decreased in rat hepatocytes by 23% with an IC50 (half-maximal inhibition) value of 90μg/mL and in HepG2 cells by 28% with an IC50 value of 35 μg/mL. This inhibition was exerted at the level of hydroxymethylglutaryl-COA reductase (MHG-CoA reductase) as indicated by direct enzymatic measurements and the absence of inhibition if [14C]mevalonate was used as a precursor. At high concentrations (above 0.5 mg/mL), inhibition of cholesterol biosynthesis was not only seen at an early step where it increased considerably with dose, but also at later steps resulting in the accumulation of the precursors lanosterol and 7-dehydrocholesterol. No desmosterol was formed which, however, was a major precursor accumulating in the presence of triparanol. Thus, the accumulation of sterol precursors seem to be of less therapeutic significance during consumption of garlic, because it requires concentrations one or two orders of magnitude above those affecting HMG-CoA reductase. Alliin, the main sulfur-containing compound of garlic, was without effect itself. If converted to allicin, it resulted in similar changes of the sterol pattern. This suggested that the latter compound might contribute to the inhibition at the late steps. In contrast, nicotinic acid and particularly adenosine caused moderate inhibition of HMG-CoA reductase activity and of cholesterol biosynthesis suggesting that these compounds participate, at least in part, in the early inhibition of sterol synthesis by garlic extracts.
136 citations
TL;DR: A review about some of the most important cholesterol oxidation products and the current knowledge of their adverse biological effects can be found in this paper, where products of cholesterol oxidation are discussed as a possible cause of arteriosclerotic lesions.
127 citations
TL;DR: In this article, the sperm were collected from five rhesus monkeys by electroejaculation and analyzed the sperm for sterols, fatty acid composition, and the molecular species of the ethanolamine glycerophospholipids.
115 citations
TL;DR: The results taken collectively indicate that the 7.5% chitosan formula maintained adequate cholesterol homeostasis in rats, despite a greatly increased intake of cholesterol.
Abstract: Chitosan, a natural product derived from chitin, possesses hypocholesterolemic properties similar to those of cholestyramine, but there has been no report concerning its effects on the equilibrium between dietary cholesterol and de novo cholesterol synthesis in the liver. In this work, we studied the effects of chitosan on plasma and liver cholesterol levels, liver weight, and the key regulatory enzyme of cholesterogenesis 3-hydroxy-3-methylglutaryl coenzyme-A (HMG-CoA) reductase in rats fed a sterol diet containing 1% cholesterol and 0.2% cholic acid. The animals given the sterol diet showed increases in plasma and liver cholesterol, which were lowered by 54% in plasma and 64% in liver by 5% chitosan, while cholestyramine completely blocked such increases. HMG-CoA reductase activity was considerably increased in the sterol-cholestyramine group, but was greatly decreased in both sterol and sterol-chitosan groups. There was no change in liver weight or appearance after treatment with chitosan, but cholestyramine-treated animals manifested secondary effects from the treatment, including smaller yellowish livers. High mol wt chitosans [> 750 kilodaltons (kDa)] were found to be less effective as hypocholesterolemia than a 70-kDa preparation. Also, when the 70-kDa chitosan was used at 2.5%, 5%, and 7.5% of the total diet, its effectiveness was greatest at the higher concentrations; indeed, incorporation of 7.5% chitosan in the sterol diet for 3 weeks completely prevented any decrease in plasma high density lipoprotein cholesterol or increase in the plasma cholesterol level and liver weight. This formula greatly reduced the increase in liver cholesterol content due to the sterol diet, with values of 8.8 +/- 1.3 for the sterol-chitosan diet vs. 18.2 +/- 0.8 mg/g tissue for the sterol diet. The increased intake of sterols considerably lowered both HMG-CoA reductase activity (33-fold) and HMG-CoA reductase mRNA levels (3-fold) in rat liver, but in the sterol-chitosan group, HMG-CoA reductase activity was 7.7 times more elevated than in the sterol group, although it was still lower than the control value, whereas HMG-CoA reductase mRNA levels were normal. The results obtained did not differ significantly when rats were studied for 1, 3, or 6 weeks. These results taken collectively indicate that the 7.5% chitosan formula maintained adequate cholesterol homeostasis in rats, despite a greatly increased intake of cholesterol.
111 citations
TL;DR: Cultures of Saccharomyces cerevisiae strain GL7 auxotrophic for sterol were incubated with a series of sterols and sterol-like molecules (tetracyclic and pentacyClic triterpenoids) in order to determine the structural requirements of sterol for bulk membrane function.
TL;DR: The finding that Emulgen 913 selectively inactivates 7 alpha-hydroxylation of 27-hydroxycholesterol indicates that the metabolic pathway for bile acid synthesis from 27-Hydroxych cholesterol is not governed by cholesterol 7alpha-Hydroxylase.
TL;DR: The complete inhibition of ergosterol synthesis and the accumulation of the 4,4,14-trimethylsterol and of the 3-ketosteroid together with the absence of sterols, such as 14 alpha-methylfecosterol and lanosterol, are at the origin of the high activity of itraconazole against C. neoformans.
Abstract: As in other pathogenic fungi, the major sterol synthesized by Cryptococcus neoformans var. neoformans is ergosterol. This yeast also shares with most pathogenic fungi a susceptibility of its cytochrome P-450-dependent ergosterol synthesis to nanomolar concentrations of itraconazole. Fifty percent inhibition of ergosterol synthesis was reached after 16 h of growth in the presence of 6.0 +/- 4.7 nM itraconazole, and complete inhibition was reached at approximately 100 nM itraconazole. This inhibition coincided with the accumulation of mainly eburicol and the 3-ketosteroid obtusifolione. The radioactivity incorporated from [14C]acetate in both compounds represents 64.2% +/- 12.9% of the radioactivity incorporated into the sterols plus squalene extracted from cells incubated in the presence of 10 nM itraconazole. The accumulation of obtusifolione as well as eburicol indicates that itraconazole inhibits not only the 14 alpha-demethylase but also (directly or indirectly) the NADPH-dependent 3-ketosteroid reductase, i.e., the enzyme catalyzing the last step in the demethylation at C-4. This latter inhibition obviates the synthesis of 4,4-demethylated 14 alpha-methylsterols that may function at least partly as surrogates of ergosterol. Eburicol and obtusifolione are unable to support cell growth, and the 3-ketosteroid has been shown to disturb membranes. The complete inhibition of ergosterol synthesis and the accumulation of the 4,4,14-trimethylsterol and of the 3-ketosteroid together with the absence of sterols, such as 14 alpha-methylfecosterol and lanosterol, which can partly fulfill some functions of ergosterol, are at the origin of the high activity of itraconazole against C. neoformans. Fifty percent inhibition of growth achieved after 16 h of incubation in the presence of 3.2 +/- 2.6 nM itraconazole.
TL;DR: Fractional and absolute endogenous cholesterol synthesis can be measured using stable isotopes in vivo by the MIDA technique, and absolute cholesterogenesis was 568 +/- 55 mg/day in normal women (follicular menstrual phase), similar to prior estimates based on whole body sterol balances.
Abstract: We used the mass isotopomer distribution analysis (MIDA) technique to measure endogenous synthesis of plasma cholesterol in vivo in rats and normal human subjects. Sodium [1-13C]- or [2-13C]acetate was infused, and plasma free cholesterol was analyzed by gas chromatography-mass spectrometry. Frequencies of mass isotopomers M0-M4 (mass-to-charge ratio 368-372) were quantified. The enrichment of the true precursor for cholesterol synthesis (acetyl-coenzyme A in contributing tissues) was determined using the MIDA method. This technique remains mathematically valid even if more than one tissue contributes to circulating free cholesterol. The fractional contribution (f) from endogenous synthesis to free cholesterol in normal women (n = 5) was 2.48 +/- 0.39% after 7 h in the postabsorptive state and 1.27 +/- 0.41% after 8 h of refeeding. In ad libitum-fed rats (n = 12), f was 2.89 +/- 0.44% after 12 h, whereas administration of recombinant tumor necrosis factor increased this value fourfold. Next, the rate constant (k) for removal of labeled free cholesterol from plasma was calculated. Higher masses (M2-M4) were followed to avoid the problem of persistent label incorporation. During the 60 h after cessation of [13C]acetate infusions, k was 0.02490 +/- 0.00298/h in humans. Using these values of k and f, absolute cholesterogenesis was 568 +/- 55 mg/day in normal women (follicular menstrual phase), similar to prior estimates based on whole body sterol balances. Women also exhibited a diurnal variation for endogenous cholesterol synthesis (34.6 +/- 5.4 mg/h nighttime vs. 15.9 +/- 5.2 mg/h daytime) consistent with current knowledge about rhythms in cholesterogenesis. Checks on the model were internally consistent (e.g., comparisons among different isotopomers for calculating precursor enrichment). We conclude that fractional and absolute endogenous cholesterol synthesis can be measured using stable isotopes in vivo by the MIDA technique.
Journal Article•
TL;DR: The results suggest that the presence and hydrolysis of cholesterol esters of meibomian secretions may contribute to the proliferation of Staphylococcus spp, especially Staphyllococcus aureus, observed in some chronic blepharitis disease groups.
Abstract: PURPOSE Many types of chronic blepharitis have been believed to be primarily microbial in origin; however, it was proposed that differences and changes in lipid composition of meibomian secretion may be the initiating factor in some of these It was recently reported that there are two subgroups of normals, those whose meibomian secretions contain high levels of cholesterol esters and those whose secretions contain very low levels of these esters Thus, these subgroups of normals were defined on the basis of detailed lipid analyses of meibomian secretions from individuals showing no clinical signs of chronic blepharitis All secretions from patients in the various disease groups contain high levels of these esters Based on previous observations that in some chronic blepharitis disease groups certain Staphylococcus species were capable of hydrolyzing cholesterol esters, the authors tested the hypothesis that the resulting cholesterol might affect growth of Staphylococcus aureus METHODS Staphylococcus aureus growth stimulation in Mueller-Hinton broth by cholesterol was determined by colony forming units Growth stimulation by cholesterol and other additives was also determined by the optical density 650 nm method Statistical analyses included analysis of variance and the Student's t test RESULTS Cholesterol stimulated Staphylococcus aureus growth was significant during the first 24 hr period (20% increase at 25 microM cholesterol, P < 002), and for the total 48 hr period (40% increase at 400 microM cholesterol, P < 0005) when compared to the respective control Growth stimulation, determined by OD at 650 nm, in the presence of cholesterol was significantly greater (P < 002) than that in the presence of either sitosterol or cholestanol when the sterol concentration was 190 microM CONCLUSION These results suggest that the presence and hydrolysis of cholesterol esters of meibomian secretions may contribute to the proliferation of Staphylococcus spp, especially Staphylococcus aureus, observed in some chronic blepharitis disease groups
TL;DR: The intracellular movement of cholesterol is an important regulated step in the process of steroidogenesis, however, the molecular mechanisms by which cholesterol is translocated to key organelles, including the mitochondria, remains poorly understood.
TL;DR: The rate of synthesis of phospholipid and sterol species from L-lactate in neurons and astrocytes in primary culture was studied, finding different membrane fluidity being higher in astroCytes than in neurons.
Abstract: The rate of synthesis of phospholipid and sterol species from L-lactate in neurons and astrocytes in primary culture was studied. Both types of cells actively utilized lactate as lipid precursor, although the rate of lipogenesis was about 2-fold greater in astrocytes than in neurons. The incorporation of lactate into phospholipids was significantly higher than that into sterols in both types of cells, but the ratio of phospholipid/sterol synthesis was much higher in astrocytes than in neurons. Phosphatidylcholine (PC) was the main phospholipid synthesized in both types of cells, followed by phosphatidylethanolamine (PE), phosphatidylserine and phosphatidylinositol. No detectable synthesis of sphingomyelins was observed. The ratio of PC/PE synthesis was about 2-fold higher in astrocytes than in neurons. The main sterol synthesized in neurons was lanosterol, followed by desmosterol. However, the main sterol synthesized in astrocytes was desmosterol, followed by lanosterol and cholesterol. The different ratios of phospholipid/sterol and PC/PE synthesis found in neurons and astrocytes may result in different membrane fluidity being higher in astrocytes than in neurons. This may be associated with differences in the functionality of both types of cells.
TL;DR: Ergosterol was produced in all isolates examined, which represented the major orders of ectomycorrhizal fungi, and Calculations of viable fungal biomass associated with field-collected roots were in agreement with those reported by others using the method on resynthesized ectomy Corrhizae.
Abstract: Recently, ergosterol analysis has been used to quantify viable fungal biomass in resynthesized ectomycorrhizae. An objective of our study was to quantify ergosterol in a range of ectomycorrhizal isolates under differing growth conditions. In addition, we tested the applicability of the method on field-collected roots of ectomycorrhizal and vesicular-arbuscular (VA) mycorrhizal plants. Quantification of sitosterol as a biomass indicator of plant roots was also undertaken. Ergosterol was not detected in roots of uninoculated Betula populifolia seedlings, and sitosterol was not detected in an ectomycorrhizal fungal isolate but was present in birch roots. Ergosterol was produced in all isolates examined, which represented the major orders of ectomycorrhizal fungi. The range of values obtained, from 3 to nearly 18 μg ergosterol mg-1 dry mass, agrees well with reported values for other mycorrhizal and decomposer fungi. Hyphal ergosterol was the same during growth on phytic acid and KH2PO4. Reduction of growth temperature from 25° C to 15° C had little effect on ergosterol content of cultures harvested at similar growth stages. Ergosterol and sitosterol were detected in field-collected ectomycorrhizae of B. populifolia and Pinus sylvestris and VA mycorrhizae of Acer rubrum and Plantago major. Both ergosterol content and ergosterol to sitosterol ratios were significantly lower in VA mycorrhizae than ectomycorrhizae. Calculations of viable fungal biomass associated with field-collected roots were in agreement with those reported by others using the method on resynthesized ectomycorrhizae. Estimates of total mass could be obtained for field-collected B. populifolia roots by a simultaneously using ergosterol to estimate fungal biomass and sitosterol to estimate root mass. Some potential applications and limitations of sterol quantification in studies of mycorrhizal physiology and ecology are discussed.
TL;DR: The lipid class compositions of adult Pacific oysters [Crassostrea gigas (Thunberg)] were examined using latroscan thin-layer chromatography/flame ionization detection (TLC/FID), and fatty acid compositions determined by capillary gas chromatography and GC/MS as discussed by the authors.
Abstract: The lipid class compositions of adult Pacific oysters [Crassostrea gigas (Thunberg)] were examined using latroscan thin-layer chromatography/flame-ionization detection (TLC/FID), and fatty acid compositions determined by capillary gas chromatography and gas chromatography/mass spectrometry (GC/MS). The fatty acid methyl esters were separated using argentation TLC and also analyzed as their 4,4-dimethyloxazoline derivatives using GC/MS. Major esterified fatty acids inC. gigas were 16∶0, 20∶5n−3, and 22∶6n−3. C20 and C22 nonmethylene interrupted (NMI) fatty acids comprised 4.5 to 5.9% of the total fatty acids. The NMI trienoic fatty acid 22∶3(7,13,16) was also identified. Very little difference was found in the proportions of the various lipid classes, fatty acids or sterols between samples of adult oysters of two different sizes. However, significant differences in some of the lipid components were evident according to the method of sample preparation used prior to lipid extraction with solvents. Lyophilization (freeze drying) of samples led to a significant reduction in the amounts of triacylglycerols (TG) extracted by solvents in two separate experiments (7.0 and 52.5% extracted). Extracts from lyophilized samples had less 16∶0, C18 unsaturated fatty acids, and 24-ethylcholest-5-en-3β-ol, while C20 and C22 unsaturated fatty acids comprised a higher proportion of the total fatty acids. There was no significant change in the amounts of polar lipids, total sterols, free fatty acids or hydrocarbons observed in extracts from lyophilized samples relative to extracts from nonlyophilized samples. Addition of water to the freezedried samples prior to lipid extraction greatly improved lipid yields and resulted in most of the TG being extracted.
TL;DR: Proton nuclear magnetic resonance studies of enzymatically produced 3 beta-hydroxy-4 beta,14 alpha-dimethyl-5 alpha-ergosta-9 beta,19-cyclo-24(1) alpha-carboxylic acid indicate that the 4 alpha-methyl group of 24-methylenecycloartanol is oxidized and subsequently removed during its enzymatic conversion to cycloeucalenol.
TL;DR: The apo-specific HDL particles Lp A-I and LpA-I/A-II are both effective promoters of cholesterol efflux from fibroblasts and aortic endothelial cells.
TL;DR: The results confirm the utility of combined gas chromatography-mass spectrometry in the analysis and characterization of sterols and cholesterol oxidation products.
Abstract: A GC-MS method has been studied for characterization and quantification of phytosterols, cholesterol and cholesterol oxidation products. Baseline separations have been achieved between cholesterol, cholesterol 5α-6α-epoxide, 5-cholestene-3β-ol-7one (7-keto-cholesterol), cholestene-3β-5α-6β-triol, 5-cholestene-3β-25-diol (25-hydroxycholesterol), 5-cholestene-3β-20α-diol (20α-hydroxycholesterol), 5-cholestene-3β-7β-diol (7β-hydroxycholesterol) and 5-cholestene-3β-19-diol (19-hydroxycholesterol) as well as between α-cholestane, cholesterol, stigmasterol, campesterol and β-sitosterol. Excellent linearity of response has been obtained permitting reliable quantification. The characterization of each derivatized sterol has been performed by mass-spectrometry. The results confirm the utility of combined gas chromatography-mass spectrometry in the analysis and characterization of sterols and cholesterol oxidation products.
TL;DR: Using a high performance liquid chromatography (HPLC) assay to simultaneously determine the activities of cholesterol 7 alpha-hydroxylase and cholesterol 27-Hydroxycholesterol in rat liver homogenates, it is demonstrated that the two enzymes are separately regulated.
TL;DR: At least two distinct protein kinase signalling pathways modulate transport of intracellular sterols in cholesterol-loaded cells, and N6-cAMP stimulated efflux of several subspecies of newly synthesized sterols, including cholesterol.
TL;DR: Analysis of isolates of Chaetoceros andkeletonema found that these algae could be an important source of the oyster's cholesterol, and cholesterol has rarely been reported as the major sterol from phytoplankton.
Abstract: Dietary sterol is required by the oyster for growth, and sterol is believed to be obtained primarily from dietary phytoplankton Seven isolates ofChaetoceros and one ofSkeletonema, which are of potential use as oyster food, were analyzed for sterol composition using gas chromatography, high-performance liquid chromatography and gas chromatography/mass spectrometrySkeletonema and five isolates ofChaetoceros contained cholesterol as their major sterol Two other isolates ofChaetoceros also contained cholesterol, but 24-methylenecholesterol was the principal sterol Cholesterol has rarely been reported as the major sterol from phytoplankton In view of the widespread occurrence ofSkeletonema andChaetoceros in the marine environment, these algae could be an important source of the oyster's cholesterol
TL;DR: Measurements of cellular cholesterol indicate that the hepatic cholesterol content of the cholesterol-fed resistant rabbit remains markedly lower than it does in normal animals fed the same diet, and it is believed that the increased excretion of bile acids by resistant animals is due, at least in part, to increased levels of cholesterol 7 alpha-hydroxylase expression.
TL;DR: The core aldehydes produced by peroxidation of cholesteryl linoleate were identified as mainly 9-oxononanoates of cholesterol and oxycholesterols, with smaller amounts of the 8-oxooctenoates, 10-oxodecenoate, 11-oxoundecenoates and 12-Oxodododicenoates.
Abstract: Synthetic cholesteryl 5-oxovalerate and 9-oxononanoate were used as reference standards for the isolation and identification of cholesteryl ester core aldehydes fromtert-butyl hydroperoxide/Fe++ oxidation of synthetic and natural cholesteryl esters. The core aldehydes were recovered from the peroxidation products by thin-layer chromatography as the free aldehydes or the 2,4-dinitrophenylhydrazones and were identified, respectively, by gas-liquid chromatography (GLC) and by GLC combined with mass spectrometry (GC/MS) or by reverse-phase high-performance liquid chromatography (HPLC) and by HPLC with MS (LC/MS). The core aldehydes produced by peroxidation of cholesteryl linoleate were identified as mainly 9-oxononanoates of cholesterol and oxycholesterols, with smaller amounts of the 8-oxooctenoates, 10-oxodecenoates, 11-oxoundecenoates and 12-oxododecenoates. Peroxidation of cholesteryl arachidonate yielded 5-oxovalerates of cholesterol and the oxycholesterols as the main products with smaller amounts of the 4-oxobutyrates, 6-oxohexenoates, 7-oxoheptenoates, 8-oxooctenoates, 9-oxononenoates, 9-oxononadienoates and 10-oxodecadienotes. The oxycholesterols resulting from the peroxidation of the steroid ring were identified as mainly 7-keto-, 7α-hydroxy- and 7β-hydroxy-cholesterols and 5α, 6α-and 5β,6β-epoxy-cholestanols. Cholesteryl palmitate and oleate did not yield core aldehydes in the present peroxidation system. In these esters, the sterol and linoleic acid moieties appeared to be oxygenated at about the same rate, while the arachidonic acid moiety reacted more rapidly than did the sterol moiety.
TL;DR: The results showed that the typical even anatomical distribution of sterols of bivalves can be disrupted by a drastic change in diet and is therefore not subject to strict internal regulation.
Abstract: The anatomical distributions of sterols and the incorporation of dietary phytosterols into different organs were studied in two populations of sea scallops, Placopecten magellanicus Gmelin, collected in 1989 from Georges Bank (Nova Scotia) and St. Pierre Bank (Newfoundland), respectively. In contrast to the well-established organ-specific lipid classes and fatty-acid compositions usually found in marine animals, the major organs of wild sea scallops (adductor muscle, digestive gland, gonads, gills and mantle) had the same sterol compositions. In order to know if anisomyarian bivalves require a uniform anatomical distribution of sterols, wild scallops were subjected to a microalgal diet containing high concentrations of brassicasterol, β-sitosterol and cholesterol. The sterol composition of the scallop adductor muscle was not changed by 6 wk of feeding on the experimental diet. In contrast, the proportions of brassicasterol, β-sitosterol and cholesterol in the digestive gland, and of brassicasterol and cholesterol in the male gonad, increased significantly (p<0.05). These results showed that the typical even anatomical distribution of sterols of bivalves can be disrupted by a drastic change in diet and is therefore not subject to strict internal regulation. Furthermore, the P. magellanicus results indicate that, although sea scallops may be capable of sterol biosynthesis, the incorporation of unmodified dietary phytosterols plays an influential role in establishing their sterol composition.