bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of cholesterol synthesis by cyclopropylamine derivatives of squalene in human hepatoblastoma cells in culture
Authors: Van Sickle W. A. , Angelastro M. R. , Wilson P. , Cooper J. R. , Marquart A. , Flanagan M. A.
Published: November 2006

Two squalene derivatives, trisnorsqualene cyclopropylamine and trisnorsqualeneN‐methylcyclopropylamine, were synthesized and tested for inhibition of lanosterol and squalene epoxide formation from squalene in rat hepatic microsomes, and for the inhibition of cholesterol syntheses in human cultured hepatoblastoma (HepG2) cells. Trisnorsqualene cyclopropylamine inhibited [3H]‐squalene conversion to [3H]squalene epoxide in microsomes (IC50=5.0 μM), indicating that this derivative inhibited squalene mono‐oxygenase. Trisnorsqualenen‐methylcyclopropylamine inhibited [3H]squalene conversion to [3H]lanosterol (IC50=12.0 μM) and caused [3H]‐squalene epoxide to accumulate in microsomes, indicating that this derivative inhibited 2,3‐oxidosqualene cyclase. Cholesterol biosynthesis from [14C]acetate in HepG2 cells was inhibited by both derivatives (IC50=1.0 μM for trisnorsqualene cyclopropylamine; IC50=0.5 μM for trisnorsqualeneN‐methylcyclopropylamine). Cells incubated with trisnorsqualene cyclopropylamine accumulated [14C]squalene, while cells incubated with trisnorsqualeneN‐methylcyclopropylamine accumulated [14C]squalene epoxide and [14C]squalene diepoxide. The concentration range of inhibitor which caused these intermediates to accumulate coincided with that which inhibited cholesterol synthesis. The results indicate that cyclopropylamine derivatives of squalene are effective inhibitors of cholesterol synthesis, and that substitutions at the nitrogen affect enzyme selectivity and thus the mechanism of action of the compounds.
Effects of n−3 and n−6 fatty acids on tumor necrosis factor cytotoxicity in WEHI fibrosarcoma cells
Authors: Brekke Ole‐L. , Espevik Terje , Bardal Tora , Bjerve Kristian S.
Published: November 2006

Modulation by fatty acids of the cytotoxic effect of recombinant tumor necrosis factor alpha (TNF) toward WEHI 164 mouse fibrosarcoma cells has been examined. Preincubating the highly TNF‐sensitive WEHI clone 13 cells for 44 hr with 50 μmol/L of 20∶5n−3, 22∶6n−3, 18∶3n−6, 20∶3n−6 or 20∶4n−6 reduced cell survival 22 hr after challenge with TNF (40 ng/L) by 65%, 72%, 60%, 98% and 85%, respectively. In comparison, 18∶3n−3, 18∶2n−6 and 18∶1n−9 had only negligible effects on TNF‐induced toxicity. Different extent of fatty acid incorporation into cell total phospholipids or triglycerides could not explain the observed effects on TNF cytotoxicity, and the enhanced cytotoxicity could therefore not be explained merely by an increased unsaturation of the cell membranes. In addition to the fatty acid supplied, preincubation with 18∶2n−6, 18∶3n−6 or 18∶3n−3 also enriched the cells with 20∶2n−6, 20∶3n−6 and 20∶3n−3, respectively, most likely due to chain elongation. The results suggest that the WEHI cells have a low Δ6 desaturase activity, and that n−6 and n−3 acids must have at least 3 or 4 double bonds, respectively, to enhance TNF cytotoxicity in WEHI cells. Dexamethasone partly inhibited TNF‐induced cytotoxicity, while cyclooxygenase, thromboxane synthetase or lipoxygenase inhibitors had no or negligible effects. The antioxidant butylated hydroxyanisole (BHA) completely inhibited TNF‐induced cytotoxicity, while the structurally and functionally similar antioxidant butylated hydroxy‐toluene had no such effect, indicating that BHA does not block TNF cytotoxicity through its antioxidant effect. The results suggest that TNF cytotoxicity involves, directly or indirectly, metabolism of long‐chain polyun‐saturated fatty acids, and we speculate that fatty acid metabolites are involved.
The effect of dietary supplementation with eicosapentaenoic acid on the phospholipid and fatty acid composition of erythrocytes of marmoset
Authors: Gibson Robert A. , Neumann Mark A. , Burnard Sharon L. , Rinaldi Josephine A. , Patten Glen S. , McMurchie Edward J.
Published: November 2006

Adult male marmoset monkeys were fed eicosapentaenoic acid (20∶5n−3) as the ethyl ester in diets containing either 32% (reference diet, no added cholesterol) or 7% (atherogenic diet with 0.2% added cholesterol) linoleic acid (18∶2n−6) for 30 wk. No changes were seen in the level of phosphatidylcholine (PC) or phosphatidylethanolamine (PE) but minor changes were observed in both the sphingomyelin (SPM) and phosphatidylinositol plus phosphatidylserine (PI+PS) fractions of erythrocyte lipids. The extent of total n−3 fatty acid incorporation into membrane lipids was higher in atherogenic diets (polyunsaturated/monounsaturated/saturated (P/M/S) ratio 0.2∶0.6∶1.0) than reference diets (P/M/S ratio 1∶1∶1) and this was true for both PE (33.4±1.0%vs 24.3±1.1%) and PC (9.3±0.5%vs 4.9±0.3%). Although suitable controls for cholesterol effects were not included in the study, earlier results obtained with marmosets lead us to believe such effects were probably small. Regardless of basic diet (atherogenic, reference), 20∶5n−3 was preferentially incorporated into PE (10.8±0.2%, 6.0±0.02%) while smaller amounts were incorporated into PC (6.9±0.4%, 3.2±0.2%). The major n−3 polyunsaturated fatty acid found in PE in response to dietary 20∶5n−3 was the elongation metabolite 22∶5n−3 in both the atherogenic (17.7±0.7%) and reference (14.3±1.0%) dietary groups; 22∶6n−3 levels were less affected by diet (4.7±0.3% and 3.9±0.2%, respectively). The results can be interpreted to indicate an inverse relationship between the amount of dietary 18∶2n−6 and incorporation of 20∶5n−3 into erythrocyte membrane phospholipids regardless of whether the major dietary n−3 fatty acid was α‐linolenate (18∶3n−3) or 20∶5n−3. This interpretation is supported by theoretical calculations.
Monoenoic fatty acids in human brain lipids: Isomer identification and distribution
Authors: Johnson D. W. , Beckman K. , Fellenberg A. J. , Robinson B. S. , Poulos A.
Published: November 2006

The carbon chain length distribution and the double bond positional isomer composition of the monoenoic fatty acids of the lipids of total human brain tissue have been determined using gas chromatography and gas chromatography/mass spectrometry of the fatty acid methyl and picolinyl esters. The even chain length monoenoic C16 to C28 fatty acids contain predominantly two positional isomer series, the n−7 and n−9cis homologues, whose relative proportion varies significantly with chain length. The odd chain length long‐chain fatty acids consist of n−8 and n−10 isomers, whereas the odd chain length very long‐chain (more than 22 carbon) fatty acids are n−7 and n−9 isomers.
Effects of polyphenolic natural products on the lipid profiles of rats fed high fat diets
Authors: Yugarani T. , Tan B. K. H. , Teh M. , Das N. P.
Published: November 2006

Male Wistar rats were fed a high fat diet (HFD) containing 2.5% cholesterol and 16% lard supplemented with polyphenolic natural products namely quercetin, morin or tannic acid (100 mg/rat/day) for 4, 7 and 10 wk. Rats fed HFD without the supplements served as control. The effects of these compounds on blood lipid profiles, enzymes, liver fat and aorta of the rat were studied. In rats fed HFD containing tannic acid, plasma total cholesterol (TC), low density lipoprotein cholesterol (LDLC) and triglyceride (TG) were reduced by 33.3%, 29.6% and 65.1%, respectively, at week 10. High density lipoprotein cholesterol (HDLC) concentration was not altered. Fat deposition was also decreased in the liver of these rats. Morin significantly reduced plasma TG (65.1%) and liver fat only at week 7 while at week 10 it reduced plasma TC and LDLC by 30.9% and 29.3% respectively. The plasma HDLC concentration was increased by 47.3% at week 4 but no effect was seen at weeks 7 and 10. In the rats fed HFD containing quercetin, plasma HDLC was increased by 28.6% at week 7 but at week 10, plasma LDLC was increased by 21.2%. Quercetin did not cause any significant changes on the plasma TC, TG and liver fat at weeks 4, 7 and 10. Plasma alanine aminotransferase, alkaline phosphatase and bilirubin in control and treated groups were not significantly different. However, hepatic lipase activity in rats fed tannic acid was significantly lower. Aortae of all groups of rats showed no abnormalities. The present report indicates that tannic acid and morin are effective in reducing plasma and liver lipids when supplemented with a high fat diet in rats.
Subterminal hydroxylation of lauric acid by microsomes from a marine fish
Authors: Lemaire Philippe , Lafaurie Marc , Weissbart Daniel , Durst Francis , Pflieger Philippe , Mioskowski Charles , Salaün Jean‐Pierre
Published: November 2006

Microsomes from the liver of sea bass (Dicentrarchus labrax) were shown to hydroxylate lauric acid at subterminal positions. The cytochrome P‐450 system converted lauric acid to several mono‐hydroxylated metabolites including ω‐1 hydroxylaurate, which was the major metabolite (44% of total products). In addition, ω‐2, ω‐3, ω‐4 and a small amount (2.3%) of ω hydroxylaurates were found. Reaction products were identified using thin‐layer chromatography (TLC) and gas chromatography/mass spectrometry (GC/MS). Oxidation reactions were dependent upon O2 and NADPH, and did not occur with boiled microsomes or in the presence of a mixture of CO/O2. Hydroxylation proceeded linearly up to 20 min at 28°C for protein concentrations below 380 μg. Treatment of fish with benzo(α)pyrene (BP) (20 mg/kg) drastically increased xenobiotic metabolism (ECOD, EROD and BPMO activities), but no difference in laurate hydroxylase activity was observed between untreated and treated fish. Starvation strongly enhanced laurate hydroxylase activity, and resumption of feeding reduced by half this increase of activity. In all of the experiments we did not observe any modification of the regioselectivity of lauric acid hydroxylation by this microsomal in‐chain hydroxylating system. We suggest that cytochrome P‐450 enzymes involved in lauric acid and xenobiotics metabolism are regulated independently.
A sensitive and specific radioimmunoassay for platelet‐activating factor
Authors: Wang Chang‐jin , Tai Hsin‐Hsiung
Published: November 2006

A platelet‐activating factor (PAF) analog with a reactive ω‐aldehyde group at thesn‐1 position was synthesized. The hapten‐thyroglobulin conjugate was used to immunize rabbits to produce specific antibodies to PAF. The purified immunoglobulin G (IgG) fraction was found to bind stereo‐specifically to tritiated PAF and to crossreact minimally with lysoPAF, plasmalogens, and other phospholipids. The radioimmunoassay detected as little as 20 pg of PAF per assay tube and was used to explore agonist‐induced synthesis of PAF in rabbit neutrophils. Calcium ionophore A23187 at 1 μM induced PAF synthesis peaking at 2 min and reaching basal levels after 5 min.N‐Formyl‐Met‐Leu‐Phe (FMLP) at 0.1 μM also stimulated rapid synthesis and degradation of PAF with a peak at 5 min. Both A23187 and FMLP stimulated PAF synthesis in a dose‐dependent manner. The radioimmunoassay should be applicable to the quantitation of PAF in biological samples.
Metals and lipid oxidation. Contemporary issues
Authors: Schaich K. M.
Published: November 2006

Lipid oxidation is now recognized to be a critically important reaction in physiological and toxicological processes as well as in food products. This provides compelling reasons to understand what causes lipid oxidation in order to be able to prevent or control the reactions. Redox‐active metals are major factors catalyzing lipid oxidation in biological systems. Classical mechanisms of direct electron transfer to double bonds by higher valence metals and of reduction of hydroperoxides by lower valence metals do not always account for patterns of metal catalysis of lipid oxidation in multiphasic or compartmentalized biological systems. To explain why oxidation kinetics, mechanisms, and products in molecular environments which are both chemically and physically complex often do not follow classical patterns predicted by model system studies, increased consideration must be given to five contemporary issues regarding metal catalysis of lipid oxidation: hypervalent non‐heme iron or iron‐oxygen complexes, heme catalysis mechanism(s), compartmentalization of reactions and lipid phase reactions of metals, effects of metals on product mixes, and factors affecting the mode of metal catalytic action.
Redox cycling of iron and lipid peroxidation
Authors: Minotti Giorgio , Aust Steven D.
Published: November 2006

Mechanisms of iron‐catalyzed lipid peroxidation depend on the presence or absence of preformed lipid hydroperoxides (LOOH). Preformed LOOH are decomposed by Fe(II) to highly reactive lipid alkoxyl radicals, which in turn promote the formation of new LOOH. However, in the absence of LOOH, both Fe2+ and Fe3+ must be available to initiate lipid peroxidation, with optimum activity occurring as the Fe2+/Fe3+ ratio approaches unity. The simultaneous availability of Fe2+ and Fe3+ can be achieved by oxidizing some Fe2+ with hydrogen peroxide or with chelators that favor autoxidation of Fe2+ by molecular oxygen. Alternatively, one can use Fe3+ and reductants like superoxide, ascorbate or thiols. In either case excess Fe2+ oxidation or Fe3+ reduction will inhibit lipid peroxidation by converting all the iron to the Fe3+ or Fe2+ form, respectively. Superoxide dismutase and catalase can affect lipid peroxidation by affecting iron reduction/oxidation and the formation of a (1∶1) Fe2+/Fe3+ ratio. Hydroxyl radical scavengers can also increase or decrease lipid peroxidation by affecting the redox cycling of iron.
Peroxide dependent and independent lipid peroxidation: Site‐specific mechanisms of initiation by chelated iron and inhibition by α‐tocopherol
Authors: Fukuzawa Kenji , Fujii Tomohito
Published: November 2006

Peroxidation of linoleic acid (LA) was catalyzed by Fenton reagent (H2O2, and Fe2+) in positively charged tetradecyltrimethylammonium bromide (TTAB) micelles, but not in negatively charged sodium dodecylsulfate (SDS) micelles. However, more hydroxyl radicals formedvia the Fenton reaction were trapped byN‐t‐butyl‐α‐phenylnitrone (PBN) in SDS micelles than in TTAB micelles. Generation of linoleic acid alkoxy (LO) radicals by Fe2+via reductive cleavage of linoleic acid hydroperoxide (LOOH) resulted in peroxidation of LA and formation of PBN‐LO· adducts in SDS micelles, but not in TTAB micelles. This LOOH dependent lipid peroxidation could be catalyzed in TTAB micelles in the presence of a negatively charged iron chelator, nitrilotriacetic acid (NTA). LO radicals formed by the LOOH dependent Fenton reaction were also trapped by PBN at the surface of TTAB micelles in the presence of NTA, but not in its absence. The consumption of a spin probe, 16‐(N‐oxyl‐4,4′‐dimethyloxazolidin‐2‐yl)stearic acid (16‐NS) during the LOOH dependent Fenton reaction in the presence of NTA was higher in TTAB micelles of LA than in those of lauric acid (LauA), although the rates and amounts of LO radicals formed in the two types of fatty acid micelles were similar. The rates of 5‐NS consumption in LA and LauA micelles were almost the same, and were lower than the rate of 16‐NS in LA micelles. NTA‐Fe2+ initiated peroxidation of LA in TTAB micelles without a lag time in the presence of LOOH, but after a lag period, peroxidation occurred without LOOH. α‐Tocopherol inhibited peroxidation of LA catalyzed by Fenton reagent by scavenging OH radicals in TTAB micelles. In contrast, α‐tocopherol enhanced free Fe2+ induced LOOH dependent lipid peroxidation through the regeneration of Fe2+ in SDS micelles. However, it inhibited NTA‐Fe2+ induced LOOH dependent lipid peroxidation in TTAB micelles. The rate and amount of α‐tocopherol oxidized by the Fe2+ induced, H2O2 dependent Fenton reaction were almost the same in TTAB micelles of LA and LauA. The oxidation of α‐tocopherol by the NTA‐Fe2+ induced, LOOH dependent Fenton reaction was greater and faster in LA micelles than in LauA micelles, although the rates of LO radical production in the two types of micelles were the same. During NTA‐Fe2+ induced, LOOH dependent lipid peroxidation, α‐tocopherol inhibited more effectively the consumption of 16‐NS than 5‐NS. The results are discussed in relation to the location of iron, the unsaturated bonding region of LA, the OOH group of LOOH, the radical trapping site of PBN, the spin sites of 5‐NS and 16‐NS, and the phenolic hydroxyl group of α‐tocopherol in micelles with different charges.
Dietary fat ratios and liver plasma membrane lipid composition
Authors: Hamm Michael W. , Sekowski Anna , Ephrat Roni
Published: November 2006

Male Sprague‐Dawley weanling rats were fed isocaloric diets consisting of 10% (by wt) fat. The six groups differed in the ratio of corn oil and butter fat present in the diets such that: 10C, 10% corn oil (C); 8C2B, 8% C/2% butter fat (B); 6C4B, 6% C/4% B; 4C6B, 4% C/6% B; 2C8B, 2% C/8% B; and 10B, 10% B. Liver plasma membranes were analyzed for fatty acid composition and cholesterol/phospholipid molar ratio. The 18∶2n−6 content was constant in the 10C and 8C2B diets and then decreased linearly through the 2C8B diet. The 20∶4n−6 and 18∶1n−9 contents were constant except in the 10B diet, in which a significant decrease and increase, respectively, were observed. The cholesterol/phospholipid molar ratio increased between the 10C and 6C4B diets and subsequently (4C6B and 10B diets) remained constant. This data indicates that changes in n−6 fatty acid content in the liver plasma membrane are directly related to dietary intake only for 18∶2n−6. Arachidonic acid content in the membrane is maintained at a constant level until the linoleic acid content of the diet is reduced to 0.5% of calories. It also indicates that the cholesterol content of the membrane becomes saturated and does not increase with increasing concentrations of saturated fat in the diet.
Influence of dietary fats on pancreatic phospholipids of chronically ethanol‐treated rats
Authors: Cronholm Tomas , Neri Aldo , Karpe Fredrik , Curstedt Tore
Published: November 2006

Male rats were given liquid diets by pair‐feeding for 24–30 days, and phosphatidylinositols in pancreas were analyzed as derivatives of diacylglycerols and fatty acids. Addition of arachidonic acid or changing the fat component (35 energy%) in the liquid diet from olive oil/corn oil to oil fromBorago officinalis, which contains 22% γ‐linolenic acid, increased the fraction of arachidonoyl‐containing species. This fraction was decreased by more than 50% by substituting ethanol for 36 of the 47 energy% provided by carbohydrate. A smaller difference between ethanol‐fed and control rats was seen in the composition of phosphatidylcholines and phosphatidylethanolamines. There was no difference in the composition of phosphatidylinositols when fat, instead of ethanol, was used to substitute the 36 energy% in the diet containing olive oil/corn oil. Substituting ethanol for 28 of 35 energy% provided by fat as corn oil in a liquid diet had no effect on the fraction of arachidonoyl‐containing species. The results indicate that the effect of ethanol on phosphatidylinositols in pancreas is not due to a deficiency of arachidonic acid, and that the effect of the ethanol‐containing diet is not due to the lowered carbohydrate content. However, high contents of fat or of ethanol appear to be necessary for the effect.
Effects of estrogen‐induced hyperlipidemia on the erythrocyte membrane in chicks
Authors: Simon Cho B. H. , Smith Terrance L. , Park Jeong R. , Kummerow Fred A.
Published: November 2006

The effects of estrogen‐induced hyperlipidemia on plasma lipid peroxidation, fatty acid composition and osmotic fragility of erythrocytes in chickens were studied. Young male chickens implanted with estrogen for three wk developed a marked hyperlipidemia. Plasma levels of triglyceride, cholesterol and phospholipid were elevated 68‐, four‐ and 24‐fold, respectively, over controls. There was also a two‐fold increase in plasma lipid peroxidation measured by the thiobarbituric acid test. Vitamin E supplement (1,000 IU/kg diet) reduced the plasma lipid peroxidation to the control level, but had no effect on the plasma lipid content. Estrogen‐induced hyperlipidemia resulted in changes in the fatty acid composition of membrane lipids of erythrocytes. The major changes were an increase in oleic acid from 10.0% to 14.2% and a decrease in linoleic acid from 31.3% to 26.0%. The erytrocytes with an altered membrane fatty acid composition were found to have an increased osmotic fragility. It was apparent that there was a direct correlation between the oleic acid content and the osmotic fragility of erythrocytes.
Characterization of skin‐surface lipids from the monkey (Macaca fascicularis)
Authors: Nishimaki‐Mogami Tomoko , Minegishi Ken‐ichiro , Takahashi Atushi , Kawasaki Yasushi , Kurokawa Yuji , Uchiyama Mitsuru
Published: November 2006

Skin‐surface lipids from the monkeyMacaca fascicularis are composed of sterol esters (38%), cholesterol (4%) and two types of wax diesters, identified as Type II (IIa and IIb, 17% and 40%, respectively). Type IIa contained diesters of 1,2‐alkanediols esterified with two molecules of long‐chain (C14−C34) fatty acids having straight and branched chains. In the diesters IIa, fatty acids shorter than C19 predominated in position 1, and fatty acids longer than C20 predominated in position 2. Type IIb contained diesters of 1,2‐alkanediols esterified with C4 and C5 branched‐chain fatty acids (predominantly isovaleric acid) at position 1 and long‐chain (C14−C27) acids, having straight and branched chains, at position 2. The shortchain acids were converted to 2‐nitrophenylhydrazides and analyzed by high‐performance liquid chromatography (HPLC). Ammonia chemical ionization (CI)‐gas chromatography (GC)‐mass spectrometry (MS) resolved the intact diesters IIb into 12 peaks corresponding to molecular weights ranging from 597 to 748, and showed that the molecular species, such as C21−C16−C5 (diol, fatty acid in position 2, fatty acid in position 1), C22−C16−C5 and C23−C16−C5, were prevalent. The fatty acids from both diesters were mostly (>98%) saturated. The 1,2‐alkanediols from both diesters consisted of C16−C26 saturated straight‐ and branched‐chain components. The acyl groups of sterol esters contained 86% C14−C34 branched‐chain acids. The unsaturated fatty acids (5.4%) belonged to a straight‐chain monoenoic series having extremely long chains (C18−C34). The branched‐chain structures in the fatty acids and diols were iso and anteiso. These results show the species‐specific profile for the skin‐surface lipid synthesis.
Integral lipids of human hair
Authors: Wertz Philip W. , Downing Donald T.
Published: November 2006

It has long been recognized that hair is coated with nonpolar lipids originating in the sebaceous glands, and recently it has been shown that hair also contains cholesterol sulfate and small amounts of ceramides, similar to those found in the keratinized portion of the epidermis. In the present study, it is demonstrated that significant amounts of several additional lipids are tightly associated with hair in such a way as to be highly resistant to solvent extraction.

These integral hair lipids included cholesterol sulfate (3.3 mg/g of extracted hair), cholesterol (0.6 mg/g), fatty alcohols (0.2 mg/g) and free fatty acids (4.3 mg/g). The principal fatty acid, comprising 40% of the total fatty acids, was identified as 18‐methyl‐eicosanoic acid by cochromatography with authentic standard on gas‐liquid chromatography (GLC) and by mass spectrometry (MS).
Linoleic acid‐induced fatty acid changes in platelet and aorta of the rat: Effect of age and cholesterol
Authors: Takahashi R. , Horrobin D. F.
Published: November 2006

The influence of age and cholesterol on polyunsaturated fatty acids (PUFa) levels was studied in young and old male Sprague‐Dawley rats. Animals were fed a fat‐free diet supplemented with 10% (by wt) safflower oil with or without 1% cholesterol for 8 wk. As a result of cholesterol feeding, proportions of linoleic acid (18∶2n−6) and dihomo‐γ‐linolenic acid (30∶3n−6) were increased and and that of arachidonic acid (20∶4n−6) was decreased in the liver and platelet phospholipids in 64‐wk‐old rats, suggesting inhibitory effects of cholesterol on 20∶4n−6 synthesis from 18∶2n−6. The prominent age‐dependent effect on the levels of PUFA was a retention of C−22 n−3 PUFA, accompanied by decreased C−22 n−6 PUFA and increased 20∶3n−6 in the liver and platelet phospholipids. Ratio of 20∶3n−6/20∶4n−6 increased in 64‐wk‐old rats regardless of dietary cholesterol, suggesting depressed Δ5‐desaturase with age. In aorta phospholipids, 20∶3n−6 content and 20∶3n−6/20∶4n−6 ratio increased with cholesterol supplementation, but not with age. These results suggest that changes of PUFA composition of platelet phospholipids with age are closely linked with changes in liver phospholipids. The 20∶4n−6 content in both platelet and aorta phospholipids is kept constant, despite other n−6 and n−3 PUFA being affected by age.
Effects of aurothioglucose on iron‐induced rat liver microsomal lipid peroxidation
Authors: Beckman Jeffrey K. , Greene Harry L.
Published: November 2006

Aurothioglucose (ATG), an inhibitor of selenium‐dependent glutathione peroxidase activity, at a concentration of 100 μM, strongly increases lipid peroxidation of rat liver microsomes exposed to either ferrous ion (10 μM) or the combination of ferric ion (10 μM) and ascorbic acid (500 μM), in the presence of reduced glutathione (GSH, 800 μM). This effect was not achieved using heat‐inactivated microsomes and was dependent on the presence of GSH. ATG did not affect the lag period associated with ascorbic acid/ferric ion‐induced microsomal lipid peroxidation (previously attributed to an undefined GSH‐dependent microsomal agent), but did increase the rate of peroxidation subsequent to the lag period. The potent GSH‐dependent inhibition of microsomal lipid peroxidation by cytosol (10% of total volume) was completely reversed by ATG (100 μM). ATG similarly reversed an inhibition of phosphatidyl‐choline hydroperoxide‐dependent liposomal peroxidation that has been attributed to phospholipid hydroperoxide glutathione peroxidase (PHGPX), an enzyme distinct from the classical glutathione that cannot utilize intact phospholipids.

ATG inhibited, in addition to the classifical selenium‐dependent glutathione peroxidase, both cytosolic and microsomal (basal and N‐ethyl maleimide‐stimulated) glutathione S‐transferase activities with greater than 80% inhibition achieved at 100 μM ATG. ATG, at concentrations up to 250 μM, did not inhibit PHGPX activity measured by the coupled‐enzyme method in the presence of Triton X‐100 (0.1%). These data demonstrate the potential of ATG to increase toxicity of lipid peroxidative stimuli by inhibition of microsomal and cytosolic defense mechanisms. Although ATG did not inhibit Triton‐enhanced PHGPX activity, overall evidence points toward inhibition of this enzyme as the mechanism for ATG‐augmented lipid peroxidation and supports the conclusion that PHGPX plays a major role in the cellular defense mechanism.
Cell membrane localization of long chain C24−C30 fatty acids in two marine demosponges
Authors: Lawson Mishelle P. , Thompson Janice E. , Djerassi Carl
Published: November 2006

Subcellular fractionation by differential centrifugation was performed on two previously unstudied marine sponges (Reniera sp. andPseudaxinyssa sp.) that represent both major subclasses of the Demospongiae. Long chain fatty acids (LCFA) with 24–30 carbon units were found as major constituents of cell membrane isolates of both sponges. Most LCFA were polyunsaturated and were constituents of the phospholipids, which are typical membrane lipids, and in particular the amino‐phospholipids. The LCFA composition of phospholipids from whole sponge tissue was shown to provide a reliable indication of the LCFA composition of cell membrane phospholipids in the sponges studied. An unusual triply branched C16 isoprenoid fatty acid, 4,8,12‐trimethyltridecanoic acid, also was identified as a cell membrane acid in the spongePseudaxinyssa sp.
Cell membrane localization of sterols with conventional and unusual side chains in two marine demonsponges
Authors: Lawson Mishelle P. , Stoilov Ivan L. , Thompson Janice E. , Djerassi Carl
Published: November 2006

Subcellular fractionation by differential centrifugation was performed on two previously unstudied marine sponges that predominantly contain either conventional (Reniera sp.) or unconventional (Pseudaxinyssa sp.) sterols. Direct evidence for the presence of unconventional sterols with C24 alkylated side chains in the cellular membranes ofPseudaxinyssa sp. is provided, but the presence of unconventional sterols in sponge membranes is shown not to be a universal feature of the Porifera. Possible structural and functional roles of unconventional lipid molecules in sponge cell membranes are discussed.
Effects of 2‐(2,4‐dimethylphenyl)indan‐1,3‐dione on serum lipoprotein and lipid metabolism of rodents
Authors: Hall Iris H. , Murthy Akula R. K. , Day Patricia A. , Clavin John
Published: November 2006

2‐(2,4‐Dimethylphenyl)indan‐1,3‐dione was shown to be a potent hypolipidemic agent in rodents, lowering significantly both serum cholesterol and triglyceride levels at 20 mg/kg/day. The agent in vivo inhibited the enzymatic activities of ATP‐dependent citrate lyase, acetyl‐CoA synthetase, cholesterol‐7α‐hydroxylase, acyl‐CoA cholesterol acyl transferase,sn‐glycerol‐3‐phosphate acyl transferase and phosphatidylate phosphohydrolase. Tissue lipid levels of liver and small intestine also were reduced by the agent. The rat serum lipoprotein lipid content was modulated by the drug, which should be favorable for the removable of cholesterol from peripheral tissue for conduction to the liver for clearance from the body. Low density lipoprotein (LDL) cholesterol levels were reduced after treatment, which suggests that the agent potentially reduces deposition of cholesterol in plaques. If chemotherapy for atherosclerosis is to be successful, then the high density lipoprotein (HDL) cholesterol level needs to be elevated more than 16% to 25%, the level produced by current hypolipidemic agents. 2‐(2,4‐Dimethylphenyl)‐indan‐1,3‐dione offers a 75% increase in HDL cholesterol levels and a 30% reduction of LDL cholesterol levels with a suppression of de novo synthesis of lipids and a reduction of tissue cholesterol deposition.
Reaction of cholesterol 5,6‐epoxides with simulated gastric juice
Authors: Maerker Gerhard , Nungesser Edwin H. , Bunick Frank J.
Published: November 2006

Cholesterol 5α,6α‐epoxide (α‐epoxide) and cholesterol 5β,6β‐epoxide (β‐epoxide) were individually suspended in simulated gastric juice (pH 1.2) at 37 C, and their reaction was followed by gradient high performance liquid chromatography (HPLC) with flame ionization (FID) detection. Both epoxides reacted rapidly in the aqueous acid medium. The α‐epoxide formed 6β‐chlorocholestane‐3β,5α‐diol (α‐chlorohydrin) and 5α‐cholestane‐3β,5,6β‐triol (triol), while the β‐epoxide formed 5α‐chlorocholestane‐3β,6β‐diol (β‐chlorohydrin) and triol. The isomeric chlorohydrins reacted further to form the triol. In mildly alkaline aqueous medium, each chlorohydrin reverted to the epoxide from which it was formed. The data suggest that both epoxides, which have been reported to have adverse health effects in animals, would be largely hydrolyzed in the stomach and to the triol, which also has been reported to have biological activity. The data furher suggest that residual chlorohydrins surviving stomach residence can be expected to revert to epoxide in the more alkaline intestinal environment.
Essential fatty acid pattern of glycerolipids in rat hepatocytes in primary culture and in coculture with rat liver epithelial cells
Authors: Pepin D. , Chambaz J. , Rissel M. Y. , Guillouzo A. , Bereziat G.
Published: November 2006

The linoleic acid content of phosphatidylethanolamine (PE), phosphatidylcholine (PC) and triglyceride (TG) rapidly fell in rat hepatocytes in primary culture up to four days and in coculture with liver epithelial cells up to eight days. At the same time, the level of polyunsaturated fatty acids (PUFA), especially arachidonic acid, remained constant in PE, slightly decreased in PC and dropped in TG. There was no variation of the nonessential PUFA, 20∶3n−9.

Linoleic acid supplementation of cultures 24 hr before the harvest induced a rise in the linoleic acid level of the three lipid classes. Arachidonic acid remained constant in TG and only slightly decreased in PE and PC at day 4 of primary culture and day 8 of coculture. The level of 20∶3n−9 increased in PE and PC and much more in TG. This net increase in the arachidonic acid and 20∶3n−9 levels in TG could not be explained only by a transfer from the phospholipid pools of PUFA because the phospholipid content of hepatocytes and PUFA levels of phospholipids did not vary under linoleic supplementation. The low percentage of arachidonic acid in epithelial cells rules out any participation of these cells in the increase of arachidonic acid in supplemented cocultures.

Triglycerides may act as a storage pool for plasma PUFA up to four days of primary culture and eight days of coculture. Besides, coculture seems more potent than primary culture to maintain the phospholipid level, to spare the essential PUFA in PE and to increase the TG synthesis in response to linoleic acid supplementation.
Absorption and transport of deuterium‐substituted 2R,4′R,8′R‐α‐tocopherol in human lipoproteins
Authors: Traber Maret G. , Ingold Keith U. , Burton Graham W. , Kayden Herbert J.
Published: November 2006

Oral administration of a single dose of tri‐ or hexadeuterium substituted 2R,4′R,8′R‐α‐tocopheryl acetate (d3‐ or d6‐α‐T‐Ac) to humans was used to follow the absorption and transport of vitamin E in plasma lipoproteins. Three hr after oral administration of d3‐α‐T‐Ac (15 mg) to 2 subjects, plasma levels of d3‐α‐T were detectable; these increased up to 10 hr, reached a plateau at 24 hr, then decreased. Following administration of d6‐α‐T‐Ac (15–16 mg) to 2 subjects, the percentage of deuterated tocopherol relative to the total tocopherol in chylomicrons increased more rapidly than the corresponding percentage in whole plasma. Chylomicrons and plasma lipoproteins were isolated from 2 additional subjects following administration of d3‐α‐T‐Ac (140 or 60 mg). The percentage of deuterated tocopherol relative to the total tocopherol increased most rapidly in chylomicrons, then in very low density lipoproteins (VLDL), followed by essentially identical increases in low and high density lipoproteins (LDL and HDL, respectively) and lastly, in the red blood cells. This pattern of appearance of deuterated tocopherol is consistent with the concept that newly absorbed vitamin E is secreted by the intestine into chylomicrons; subsequently, chylomicron remnants are taken up by the liver from which the vitamin E is secreted in VLDL. The metabolism of VLDL in the circulation results in the simultaneous delivery of vitamin E into LDL and HDL.
Effect of previous nutritional status on the formation of cholesterol gallstones in the prairie dog
Authors: Cohen Bertram I. , Mosbach Erwin H. , McSherry Charles K.
Published: November 2006

In the prairie dog model of cholesterol cholelithiasis, a high incidence of gallstones is achieved by feeding a semipurified lithogenic diet containing 0.4% cholesterol for 2 mo. On occasion, we noted a decrease in the percentage of animals with gallstones from 90–100% to 50–55%. To explain this phenomenon, we studied the effect of dietary history on gallstone formation. After weaning, animals were fed either rodent chow or alfalfa plus corn (mo 0–3) followed by a cross‐over experiment at mo 4–6. Gallstone formation then was studied by feeding the lithogenic diet from mo 7 to 8. At sacrifice, the incidences of gallstones, biliary lipids and tissue cholesterol levels were correlated with dietary history. The incidence of gallstones was 100% only in animals fed the alfalfa‐corn diet from weaning to 3 mo. In addition, the feeding of the alfalfa‐corn diet at mo 4–6 increased gallstone incidence from 65% to 86%. The lithogenic index of all groups was highest when the animals received only alfalfa‐corn prior to the lithogenic stimulus. The activity of hepatic HMG‐CoA reductase was elevated in animals fed alfalfa‐corn from weaning to 8 mo, suggesting that this diet stimulates hepatic cholesterol synthesis, leading to increased biliary cholesterol secretion. It is concluded that previous nutritional conditioning affects the incidence of gallstones. The prairie dog is a useful model of cholesterol cholelithiasis, but the dietary history of the animals plays an important role in lithogenesis.
Location of methyl branchings in fatty acids: Fatty acids in uropygial secretion of Shanghai Duck by GC‐MS of 4,4‐dimethyloxazoline derivatives
Authors: Yu Q. T. , Liu B. N. , Zhang J. Y. , Huang Z. H.
Published: November 2006

2‐Substituted 4,4‐dimethyloxazolines (DMOX) have been found to be a useful alternative to the commonly used methyl esters for the localization of unsaturated bounds and other substituents in the fatty chain by mass spectrometry. The powerful directed fragmentation coupled with good gas chromatographic ability enables the structure elucidation of modified fatty acids in complex mixtures. Continuing our previous study, 76 out of a total of 86 fatty acids obtained from the preen gland wax of shanghai duck now have been identified by gas chromatography‐mass spectrometry (GC‐MS) of their oxazoline derivatives. The identification was based on the interpretation of the mass spectra and comparison with the spectra and equivalent chain lengths (ECL) of the corresponding methyl esters. Main components of this lipid mixture are straight chain fatty acids (8.22%), and 2‐, 4‐or 6‐monomethyl branched acids (53.69%), amounting to 61.91% of the total acid fraction. In addition, a large number of dimethyl‐substituted fatty acids (31.4%) also have been found. Typical mass spectra, which are easily recognizable and highly specific for fatty acids substituted at various positions, are presented and classified according to the structural feature of the chain.
Analysis of free malondialdehyde in photoirradiated corn oil and beef fat via a pyrazole derivative
Authors: Umano K. , Dennis K. J. , Shibamoto T.
Published: November 2006

Malondialdehyde (MA) formed in linolenic acid, linoleic acid, corn oil and beef fat upon photoirradiation was determined by gas chromatography (GC). The MA produced was reacted with methylhydrazine to give 1‐methyl‐pyrazole and was subsequently analyzed on a GC equipped with a nitrogen‐phosphorus specific detector and a fused silica capillary column. MA values determined by this method correspond to free or unbound MA levels. Linolenic and linoleic acids produced 867 μg MA/g and 106 μg MA/g, respectively. Oleic and stearic acids did not produce detectable levels of MA upon photoirradiation. Amounts of MA produced after eight hour irradiations of corn oil and beef fat were 56.24 μg/g and 25.01 μg/g, respectively. Some photoreaction products in irradiated corn oil also were identified as methylhydrazine derivatives.
Formation of octadecadienoate dimers by soybean lipoxygenases
Authors: van der Heijdt Lambertus M. , van der Lecq Fridolin , Lachmansingh Anand , Versluis Kees , van der Kerk‐van Hoof Anca , Veldink Gerrit A. , Vliegenthart Johannes F. G.
Published: November 2006

The aim of this investigation was to determine whether the regioselectivity found for lipoxygenases in the formation of fatty acid hydroperoxides from linoleic acid is reflected in the formation of dimeric products in secondary reactions involving linoleic acid, product hydroperoxide and lipoxygenase. A method was therefore developed for the separation and identification of dimers formed by fusion of two linoleic acid radicals or a linoleic acid radical and linoleate. The method includes solid‐phase extraction, preparative separation of products by thin‐layer chromatography, derivatization to the corresponding fully hydrogenated methyl esters and capillary gas chromatography (GC) coupled with electron impact mass spectrometry. We present evidence that the formation of octadecadienoate dimers, during the secondary reaction of soybean lipoxygenase‐1 or lipoxygenase‐3, is a nonenzymic process that can be envisaged by nonspecific association of intermediate fatty acid radicals (L*) that have dissociated from the enzyme. We could show that the relative amounts of different octadecadienoate dimers formed remain unaltered, regard‐less of pH and type of soybean isoenzyme used. Quantitative analysis by GC showed that under the reaction conditions used, the formation of dimers branching at the 13‐position is preferred.
Age‐dependent accumulation of phosphatidylcholine hydroperoxide in the brain and liver of the rat
Authors: Miyazawa Teruo , Suzuki Toshihide , Fujimoto Kenshiro
Published: November 2006

Age‐related changes in phosphatidylcholine hydroperoxide (PCOOH) content as an index for oxidative membrane lipid damage were determined by high‐performance liquid chromatography using chemiluminescence detection. Brain and liver PCOOH content increased significantly in male and female rats with age. The brain PCOOH content of male 18‐month‐old rats was 4.4 times that of 1‐month‐old rats, and that of female 18‐month‐old rats was 3.5 times that of 1‐month‐old females. The liver PCOOH content of the male 18‐month‐old rats was 9.3 times that of the 1‐month‐old; and of the famale 18‐month‐old rats was 4.7 times that of the 1‐month‐old. PCOOH levels in heart and lung did not show age dependency. In both brain and liver (but not in heart and lung), the phosphatidylcholine content significantly decreased upon aging. The results indicate that oxidative deterioration, such as phospholipid hydroperoxidation, is prevalent in the membrane lipids of brain and liver of the rat due to aging.
Modulation of phosphatidylcholine biosynthesis by peroxisome proliferating fatty acid analogues
Authors: Skorve Jon , Svardal Asbjørn M. , Mansoor Mohammed A. , Berge Rolf K.
Published: November 2006

The modulation of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) biosynthesis by sulfur‐substituted fatty acid analogues has been investigated in rats. We have compared the effects of two non‐β‐oxidizable fatty acid analogues, 3‐thiadicarboxylic acid and tetradecylthioacetic acid, which induce proliferation of peroxisomes, with those of the analogue tetradecylthiopropionic acid, which is a weak peroxisome proliferator. Repeated administration of 3‐thiadicarboxylic acid for seven days resulted in increased hepatic concentrations of both PC and PE, but the PC/PE ratio was decreased. PC synthesis was increased, as evidenced by increased incorporation of [3H]choline into PC and an increased activity of cytidinetriphosphate (CTP): phosphocholine cytidylyltransferase. This was accompanied by a reduction in the pool sizes of choline and phosphocholine. TheS‐adenosylmethione/S‐adenosylhomocysteine ratio (AdoMet/AdoHcy) was marginally affected, indicating no increase in the rate of methylation of PE to PC. Administration of tetradecylthioacetic acid also resulted in increased hepatic phospholipid levels, increased AdoMet/AdoHcy ratios and in slightly elevated activity of CTP:phosphocholine cytidylyltransferase. The most striking effect observed after tetradecylthiopropionic acid treatment was the development of fatty liver. The activity of CTP:phosphocholine cytidylyltransferase and the incorporation of [3H]choline into PC was reduced compared to 3‐thiadicarboxylic acid treatment. Although the rate of methylation of PE seemed to be increased at an elevated AdoMet/AdoHcy ratio, this resulted in only minor changes in the hepatic PC and PE levels, and the PC/PE ratio remained unchanged. Furthermore, the hepatic levels of choline and phosphocholine were reduced in these rats. The activities of the two enzymes competing for choline in the liver, choline kinase and choline dehydrogenase were changed in opposite directions, with the activity of choline kinase increasing approximately 1.5‐fold. In addition, it was found that the level of homocysteine was elevated in the liver of tetradecylthiopropionic acid‐treated rats. The possibility is discussed that this reflects a reduced flux of choline through the oxidative pathway in the liver. In tetradecylthiopropionic acid‐treated rats, there seemed to be a coordinated regulation of the two pathways for PC biosynthesis, with an increase in the methylation of PE to PC and a reduced synthesisvia the CDPcholine pathway. The increase in PC observed in rats treated with 3‐thiadicarboxylic acid and tetradecylthioacetic acid suggests that increased PC synthesis is linked to peroxisome proliferation.
Distribution of ubiquinone and ubiquinol homologues in rat tissues and subcellular fractions
Authors: Takahashi Takayuki , Okamoto Tadashi , Mori Koichi , Sayo Hiroteru , Kishi Takeo
Published: November 2006

The oxidized (UQox) and reduced (UQred) forms of ubiquinone (UQ) homologues in rat tissues and subcellular fractions were analyzed to elucidate their distribution and physiological role. UQ‐9 and UQ‐10 were detected in all tissues studied, and UQ‐9 was the predominant homologue. The total amount of UQox‐10 and UQred‐10 was 20–50% that of UQox‐9 and UQred‐9. The levels of these homologues were highest in heart with lesser amounts occurring in kidney, liver and other organs. In liver and blood plasma, the UQred homologue amounted to 70–80% of the total UQ (UQox+UQred=t‐UQ). UQred was less than 30% of t‐UQ in other tissues and blood cells. t‐UQ was much higher in leukocytes and platelets in blood than in erythrocytes. In erythrocytes, t‐UQ was exclusively located in the cell membranes. UQox and UQred were also found in all subcellular fractions isolated from liver and kidney in about the same ratio as UQred/t‐UQ was present in the whole organ. The levels of UQox and UQred per mg protein in subcellular fractions from liver were highest in mitochondria, with lesser amounts present in plasma membranes, lysosomes, Golgi complex, nuclei, microsomes and cytosol. In the mitochondria, the outer membranes were richer in t‐UQ than the inner membranes. In the Golgi complex, the light and intermediate fractions were rich in t‐UQ when compared to the heavy fraction. The possible physiological role of UQox and UQred in tissues and subcellular fractions is discussed.