bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of modified dairy fat on postprandial and fasting plasma lipids and lipoproteins in healthy young men
Authors: Tholstrup Tine , Sandström Brittmarie , Hermansen John E. , Hølmer Gunhild 
Published: November 2006

AbstractFatty acid profile of milk fat can be modified by cow feeding strategies. Our aim was postprandially and after 4 wk to compare the effect of a modified milk fat (M diet) [with 16% of the cholesterolemic saturated fatty acid (C12–16) replaced by mainly oleic and stearic acids] with the effect of D diet, including a conventional Danish milk fat on plasma lipids and lipoproteins. A side effect of the cow feeding regime was a 5% (w/w) increase in trans fatty acid in M diet. Eighteen subjects were fed for two periods of 4 wk strictly controlled isoenergetic test diets with 40% of energy from total fat and the same content of dietary cholesterol in a randomized study with cross‐over design. Contrary to expectations, fasting low density lipoprotein (LDL) cholesterol concentration did not differ after the experimental periods. However, M diet resulted in a higher fasting total triacylglycerol concentration compared to D diet (P=0.009). Postprandial samples were taken at two different occasions (i) at day 21, after breakfast and lunch and (ii) on the last day of the study 2, 4, 6, and 8 h after a fat load. Postprandial plasma triacylglycerol and chylomicron triacylglycerol showed higher peak values after D diet than M diet (interaction effect, diet × times P<0.05). In conclusion, M diet did not lower LDL cholesterol compared to D diet. Thus any cholesterol‐lowering effect of oleic and stearic acids may have been obscured by the high content of cholesterol‐raising saturated fatty acids in milk fat. A higher content of the trans fatty acids in M diet might have counteracted the cholesterol neutral/decreasing effect and increased plasma triacylglycerol.
Regulation of very low density lipoprotein apo B metabolism by dietary fat saturation and chain length in the guinea pig
Authors: Abdel‐Fattah Ghada , Fernandez Maria Luz , McNamara Donald J. 
Published: November 2006

AbstractStudies investigated the effects of dietary fatty acid composition and saturation on the regulation of very low density lipoprotein (VLDL) apo B flux, clearance, and conversion to low density lipoprotein (LDL) in guinea pigs fed semipurified diets containing 15% (w/w) corn oil (CO), lard (LA), or palm kernel oil (PK). Plasma cholesterol levels were highest with dietary PK (3.1±1.0 mmol/L) followed by LA (2.4±0.4 mmol/L) and CO (1.6±0.4 mmol/L) intake. VLDL particles were larger (P<0.05) in the LA (78±7 nm) and PK (69±10 nm) groups compared to animals fed CO (49±5 nm). VLDL‐apo B fractional catabolic rates (FCR) were highest in guinea pigs fed the LA diet (P<0.05) and VLDL apo B flux, estimated from VLDL 125I‐apo B turnover kinetics, were higher in LA compared to PK or CO fed guinea pigs. In the case of PK consumption, the kinetic estimates of VLDL apo B flux significantly underestimated rates compared to direct VLDL apo B secretion measurements and LDL turnover analyses. These data demonstrate that differences in the composition and amount of saturated fatty acids have differential effects on VLDL apo B flux, catabolism, and conversion to LDL which, together with changes in LDL receptor‐mediated catabolism, determine plasma LDL cholesterol levels in guinea pigs. The data also indicate that kinetic analysis of VLDL metabolism in PK fed animals is inaccurate possibly due to the presence of a small, nonequilibrating pool of newly synthesized VLDL which is rapidly converted to LDL.
Enhancement of low density lipoprotein binding to both low density lipoprotein receptor‐positive and‐ negative cells by tetracycline antibiotics
Authors: Miura Shinji , Hasumi Keiji , Takayasu Ritsuko , Sugimoto Maki , Endo Akira 
Published: November 2006

AbstractSome tetracycline (TC) antibiotics, including TC and anhydrotetracycline, have been found to enhance specific binding of low density lipoprotein (LDL) to both LDL receptor‐positive and‐negative cells at relatively higher concentrations. When incubated at 37°C, the ability of LDL receptor‐negative human fibroblasts to bind 125I‐LDL was increased from<2 to 45 ng/mg by 170 μM TC. In normal human fibroblasts and Hep G2 cells, 125I‐LDL binding was elevated 1.4‐ to 2‐fold by 113 μM TC. The 125I‐LDL binding in the presence of TC was diminished by both heparin and EDTA. The enhancement by TC was not observed when 125I‐LDL binding was assayed at 4°C. TC enhanced LDL binding to paraformaldehyde‐fixed Hep G2 cells, excluding LDL receptor induction in the mechanism. These results demonstrated that TC enhanced cellular LDL binding through a process not involving functional LDL receptors.
Stereospecific metabolism of isomeric epoxyoctadecanoic acids in the lactone‐producing yeast Sporidiobolus salmonicolor
Authors: Haffner Thomas , Tressl Roland 
Published: November 2006

AbstractThe metabolic course of four isomeric epoxyfatty acids derived from oleic‐, elaidic‐, (Z)‐, and (E)‐vaccenic acids in the lactone‐producing yeast, Sporidiobolus salmonicolor, was studied by using the deuterium‐labeled precursors. Dihydroxy‐, hydroxyoxo‐, and hydroxy fatty acids as well as γ‐lactones were identified as metabolic intermediates. Quantitative analysis of the label content and estimation of the enantiomeric composition of the lactones established that, in the first step, the racemic epoxyfatty acids were enantiospecifically hydrolyzed by an epoxide hydrolase. During the subsequent metabolism, the stereochemical orientation of the hydroxy groups of the dihydroxyfatty acids were modified by an oxidation/reduction step.
Reaction of α‐tocopherol in heated bulk phase in the presence of methyl linoleate (13S)‐hydroperoxide or methyl linoleate
Authors: Yamauchi Ryo , Goto Kumiko , Kato Koji 
Published: November 2006

Abstractα‐Tocopherol and methyl (9Z, 11E)‐(S)‐13‐hydroperoxy‐9, 11‐octadecadienoate (13‐MeLOOH) were allowed to stand at 100°C in bulk phase. The products were isolated and identified as methyl 13‐hydroxyoctadecadienoate (1), stereoisomers of methyl 9,11,13‐octadecatrienoate (2), methyl 13‐oxo‐9, 11‐octadecadienoate (3), epoxy dimers of methyl linoleate with an ether bond (4), a mixture of methyl (E)‐12, 13‐epoxy‐9‐(α‐tocopheroxy)‐10‐octadecenoates and methyl (E)‐12, 13‐epoxy‐9‐(α‐tocopheroxy)‐11‐(α‐tocopheroxy)‐9‐octadecenoates (5), a mixture of methyl 9‐(α‐tocopheroxy)‐10,12‐octadecadienoates and methyl 13‐(α‐tocopheroxy)‐9, 11‐octadecadienoates (6), α‐tocopherol spirodiene dimer (7), and α‐tocopherol trimer (8). α‐Tocopherol and 13‐MeLOOH were dissolved in methyl myristate, and the thermal decomposition rate and the distributions of reaction products formed from α‐tocopherol and 13‐MeLOOH were analyzed. α‐Tocopherol disappeared during the first 20 min, and the main products of α‐tocopherol were 5 and 6 with the accumulation of 1–4 which were the products of 13‐MeLOOH. The results indicate that the alkyl and alkoxyl radicals from the thermal decomposition of 13‐MeLOOH could be trapped by α‐tocopherol to produce 5 and 6. The reaction products of α‐tocopherol during the thermal oxidation of methyl linoleate were compounds 6 and 7. Since the radical flux during the autoxidation might be low, the excess α‐tocopheroxyl radical reacted with each other to form 7.
Penetration and distribution of α‐tocopherol, α‐ or γ‐tocotrienols applied individually onto murine skin
Authors: Traber Maret G. , Rallis Michalis , Podda Maurizio , Weber Christine , Maibach Howard I. , Packer Lester 
Published: November 2006

AbstractTo evaluate skin penetration of various vitamin E homologs, a 5% solution of either α‐tocopherol, α‐tocotrienol, or γ‐tocotrienol in polyethylene glycol was topically applied to SKH‐1 hairless mice. After 0.5, 1, 2, or 4 h (n=four per time point and four per vitamin E homolog), the skin was washed, the animals killed, the skin rapidlly removed, frozen on dry ice, and a biopsy taken and sectioned: stratum corneum (two uppermost, 5‐μm sections—SC1 and SC2), epidermis (next two 10μm sections—E1 and E2), papillary dermis (next 100μ, PD), dermis (next 400 μm, D), and subcutaneous fat (next 100 μm, SF). SC1 contained the highest vitamin E concentrations per μ thickness. To compare the distribution of the various vitamin E forms into the skin layers, the percentage of each form was expressed per its respective total. Most surprising was that the largest fraction of skin vitamin E following topical application was found in the deeper subcutaneous layers—the lowest layers, PD (40±15%) and D (36±15%), contained the major portion of the applied vitamin E forms. Although PD only represents about 16% of the total skin thickness, it contains sebaceous glands—lipid secretory organs, and, thus, may account for the vitamin E affinity for this layer. Hence, applied vitamin E penetrates rapidly through the skin, but the highest concentrations are found in the uppermost 5 microns.
Structure‐retention correlation of isomeric bile acids in inclusion high‐performance liquid chromatography with methyl β‐cyclodextrin
Authors: Momose Toshiaki , Yamaguchi Yoshiya , Iida Takashi , Goto Junichi , Nambara Toshio 
Published: November 2006

AbstractThe structure‐retention correlation of various C24 bile acid isomers was studied by the addition of methyl β‐cyclodextrin (Me‐β‐CD) to mobile phases in reversed‐phase high‐performance liquid chromatography (HPLC). The compounds examined include a series of monosubstituted bile acids related to cholanoic acids differing from one another in the position and configuration of an oxygen‐containing function (hydroxyl or oxo group) at the position C‐3, C‐6, C‐7, or C‐12 and the stereochemistry of the A/B‐ring fusion (trans 5α‐H and cis 5β‐H) in the steroid nucleus. The inclusion HPLC with Me‐β‐CD was also applied to biologically important 4β‐ and 6‐hydroxylated bile acids substituted by three to four hydroxyl groups in the 5β‐steroid nucleus. These bile acid samples were converted into their fluorescence prelabeled 24‐pyrenacyl ester derivatives and chromatographed on a Capcell Pak C18 column eluted with methanol‐water mixtures in the presence or absence of 5 mM Me‐β‐CD. The effects of Me‐β‐CD on the retentions of each compound were correlated quantitatively to the decreasing rate of capacity factors and the relative strength of host‐guest inter‐actions. On the basis of the retention data, specific and nonspecific hydrogen‐bonding interactions between the bile acids and the Me‐β‐CD were discussed.
Seasonal changes in leaf lipid and fatty acid composition of nine plants consumed by two African herbivores
Authors: Davidson Bruce C. 
Published: November 2006

AbstractIn the wild, nutrients from plants provide for the requirements of all herbivores and ultimately all animals, yet little work has been published on how such nutrients change with environmental conditions. Plant lipids are nutritionally important for browsing mammals, initially with respect to taste and palability, but ultimately how they fulfill a variety of functions. This study reports on seasonal changes in fatty acid (FA) profiles of nine plants commonly consumed by two herbivore species (kudu and impala) in South Africa. The FA composition of the plants varied with both season and plant species but not with geographic location. The overall profile of FA provided a maximum of n−3‐essential FA during the transition and wet seasons, but there was no parallel increase in n−6‐essential FA.
Low‐fat, monounsaturate‐rich diets reduce susceptibility of low density lipoproteins to peroxidation ex vivo
Authors: O'Byrne Dawn J. , O'Keefe Sean F. , Shireman Rachel B. 
Published: November 2006

AbstractOxidative modification of low density lipoprotein (LDL) plays an important role in the process of atherosclerosis. The susceptibility of LDL to oxidation and the amount of peroxidation products formed are influenced by the lipoprotein content of 18∶1 n−9, 18∶2n−6, and the 18∶2n−6/18∶1n−9 ratio, which is dependent in part on dietary fatty acids. The purpose of this study was to determine if changing from a typical American diet to a low‐fat, monousaturate‐rich diet (LFMR) would result in favorable alterations in the fatty acid composition and oxidative profile of LDL in hypercholesterolemic individuals. Free‐living postmennopausal hypercholesterolemic women who routinely consumed a diet moderately high in total fat and total saturates (34 and 11%, respectively) followed an LFMR diet (26% fat, 6% saturated fat, and 14% monounsaturated fat) for 6 mon. Sixteen postmenopausal hypercholesterolemic women already following standard low‐fat (LF) diets acted as a control for seasonal variations in serum lipids. LDL from randomly selected subjects (LF n=6, LFMR n=5) was evaluated. LFMR diets resulted in LDL with increased concentrations and percentages of 18∶1n−9, reduced 18∶2n−6/18∶1n−9 ratio, and lower percentages of 18∶2n−6. No significant changes in LDL fatty acids occurred in the LF group. Conjugated diene lag time increased in both groups during copper‐induced in vitro oxidation. Only the LFMR group experienced an increase in lipid peroxide lag time and a decrease in lipid peroxide formation. The LFMR diet was well tolerated and may be of therapeutic value in the treatment of hypercholesterolemia.
A comparison of lycopene and canthaxanthin absorption: Using the rat to study the absorption of non‐provitamin a carotenoids
Authors: Clark Richard M. , Yao Lili , She Li , Furr Harold C. 
Published: November 2006

AbstractThe purpose of this study was to validate the use of the mesenteric lymph duct cannulated rat to study the absorption of carotenoids which do not have provitamin Activity. The absorption of two carotenoids, a hydrocarbon carotenoid (lycopene) and a xanthophyll carotenoid (canthaxanthin), were investigated. In the first experiment, lipid emulsions containing lycopene (LYC) or canthaxanthin (CTX) were continuously infused into the duodenum, and lymph was collected for analysis at 2‐h intervals. The time course for absorption of carotenoids and triacylglycerol (TAG) was similar. Carotenoids and TAG reached steady‐state concentrations in the lymph by 6 h. There was no evidence for a delayed release of either carotenoid from the intestine relative to TAG. During a second experiment, emulsions containing increasing concentrations of LYC or CTX (5, 10, 15, 20 μmol/L) were infused. The LYC and CTX in the lymph increased in a dose‐dependent manner. The average efficiency of CTX absorption was 16% while the efficiency of LYC absorption averaged only 6%. Efficiency of carotenoid absorption was not related to concentration infused. Finally, to test whether LYC and CTX interact during absorption both were added to a lipid emulsion at equal concentrations (20 μmol/L) and infused. The carotenoids did not significantly affect each other's absorption. These results demonstrate the usefulness of the rat as an animal model to study the absorption of non‐provitamin A carotenoids.
Hepatic cholesterol metabolism in experimental nephrotic syndrome
Authors: Al‐Shurbaji Ayman , Humble Elisabet , Rudling Mats , Lindenthal Bernhard , Berglund Lars 
Published: November 2006

AbstractHypercholesterolemia is a consistent feature of the nephrotic syndrome. However, the mechanisms underlying this perturbation are unclear. In the present work, we have investigated different factors that influence hepatic cholesterol metabolism using the nephrotic rat as a model. The induction of nephrosis resulted in a severe and sustained hypercholesterolemia. However, no effect on the rate‐limiting enzyme in cholesterol synthesis, 3‐hydroxy‐3‐methylglutaryl CoA reductase, could be detected. Further, plasma lathosterol/cholesterol ratio, a measure of cholesterol synthesis, was not altered. Also, plasma levels of mevalonate, both a substrate for cholesterogenesis beyond the rate‐limiting step and a marker for cholesterol synthesis, did not differ between control rats and those with established hypercholesterolemia. There was no detectable change in the expression of low density lipoprotein (LDL) receptor between the two experimental groups. We conclude that the early increase in cholesterol synthesis reported after the induction of nephrosis is not necessary for the maintenance of hypercholeserolemia. Established hypercholesterolemia of the nephrotic syndrome seems to represent a steady state in which neither enhanced hepatic cholesterol synthesis nor retarded LDL cholesterol clearance is of major importance.
Eicosapentaenoic and docosahexaenoic acids alter rat spleen leukocyte fatty acid composition and prostaglandin E2production but have different effects on lymphocyte functions and cell‐mediated immunity
Authors: Peterson L. D. , Jeffery N. M. , Thies F. , Sanderson P. , Newsholme E. A. , Calder P. C. 
Published: November 2006

AbstractWeanling rats were fed on high‐fat (178 g/kg) diets which contained 4.4 g α‐linolenic (ALA), γ‐linolenic, arachidonic (ARA), eicosapentaenoic (EPA), or docosahexaenoic acid (DHA)/100 g total fatty acids. The proportions of all other fatty acids, apart from linoleic acid, and the proportion of total polyunsaturated fatty acids (PUFA) (approximately 35 g/100 g total fatty acids) were constant, and the n−6 to n−3 PUFA ratio was maintained as close to 7 as possible. The fatty acid compositions of the serum and of spleen leukocytes were markedly influenced by that of the diet. Prostaglandin E2production was enhanced from leukocytes from rats fed the ARA‐rich diet and was decreased from leukocytes from the EPA‐ or DHA‐fed rats. Replacing dietary ALA with EPA resulted in diminishedex vivolymphocyte proliferation and natural killer (NK) cell activity and a reduced cell‐mediated immune responsein vivo. In contrast, replacing ALA with DHA reducedex vivolymphocyte proliferation but did not affectex vivoNK cell activity or the cell‐mediated immune responsein vivo. Replacement of a proportion of linoleic acid with either γ‐linolenic acid or ARA did not affect lymphocyte proliferation, NK cell activity, or the cell‐mediated immune response. Thus, this study shows that different n−3 PUFA exert different immunomodulatory actions, that EPA exerts more widespread and/or stronger immunomodulatory effects than DHA, that a low level of EPA is sufficient to influence the immune response, and that the immunomodulatory effects of fish oil may be mainly due to EPA.
Catalytic properties of allene oxide synthase from flaxseed (Linum usitatissimum L.)
Authors: Schneider Claus , Schreier Peter 
Published: November 2006

AbstractWe investigated the catalytic and kinetic properties of allene oxide synthase (AOS; E.C. 3.2.1.92) from flaxseed (Linum usitatissimum L.). Both Michaelis constant and maximal initial velocity for the conversion of 9(S)‐and 13(S)‐hydroper‐oxides of linoleic and linolenic acid were determined by a photometric assay, 13(S)‐Hydroperoxy‐9(Z), 11(E)‐octadecadienoic acid [13(S)‐HPOD] as the most effective substrate was converted at 116.9±5.8 nkat/mg protein by the flax enzyme extract. The enzyme was also incubated with a series of variable conjugated hydroperoxy dienyladipates. Substrates with a shape similar to the natural hydroperoxides showed the best reactivity. Monoenoic substrates as oleic acid hydroperoxides were not converted by the enzyme. In contrast, 12‐hydroperoxy‐9(Z), 13(E)‐octadecadienoic acid was a strong competitive inhibitor for AOS catalyzed degradation of 13(S)‐HPOD. The inhibitor constant was determined to be 0.09 μM. Based on these results, we concluded that allene oxide synthase requires conjugated diene hydroperoxides for successful catalysis. Studying the enantiomeric preference of the enzyme, we found that AOS was also able to metabolize (R)‐configurated fatty acid hydroperoxides. Conversion of these substrates into labile allene oxides was confirmed by steric analysis of the stable α‐ketol hydrolysis products.
Stereospecific analysis of soybean triacylglycerols
Authors: Harp Teresa K. , Hammond Earl G. 
Published: November 2006

AbstractThirty soybean germplasm lines representing a wide distribution of fatty acid compositions were analyzed stereospecifically by using a chiral column to resolve the sn‐1 and sn‐3 positions of glycerol. The amounts of each acyl group on each of the sn positions were plotted vs. the amount of that acyl group in the triacylglycerols (TAG), and the plots were fitted by linear regression. The deviation of individual data points from the linear regressions was much greater than observed in previous studies. This could be attributed to the inclusion of a number of germplasm lines with elevated or reduced percentages of saturates. The stereospecific distributions could not be fit with previously suggested mathematical models because the plots had intercepts that were not allowed by the models. Statistical tests of the analytical procedure indicated that slight oxidation of or bias against the polyunsaturates had occurred and that the Grignard deacylation method gave slightly less representative analyses of the sn‐2 position than pancreatic lipase deacylation on these TAG.
Phospholipase D hydrolyzes short‐chain analogs of phosphatidylcholine in the absence of detergent
Authors: Davis Leslee L. , Maglio Jeffrey J. , Horwitz Joel 
Published: November 2006

AbstractPhospholipase D is an important enzyme in signal transduction in neuronal tissue. A variety of assays have been used to measure phospholipase D activity in vitro. The most typical measure of phospholipase D activity is the production of phosphatidylethanol in the presence of ethanol. Phosphatidylethanol is a product of transphosphatidylation activity that is considered a unique property of phospholipase D. To support transphosphatidylation activity, high concentrations of ethanol may be required. Furthermore, most assays in the literature utilize a detergent. These extreme conditions, detergent and ethanol, may alter phospholipase D and hinder the study of its regulation. In this manuscript we describe an assay that eliminates these potentially confounding conditions. It utilizes high specific activity [3H]butanol as a nucleophilic receptor. This eliminates the need for high concentrations of alcohol. The substrate is an analog of phosphatidylcholine that contains short‐chain fatty acids, 1,2‐dioctanoyl‐sn‐glycero‐3‐phosphocholine. Phospholipase D readily hydrolyzes this substrate in the absence of detergent. This novel assay should be useful in the further characterization of phospholipase D.
Dietary methionine level affects linoleic acid metabolism through phosphatidylethanolamine N‐methylation in rats
Authors: Sugiyama Kimio , Kumazawa Akemi , Zhou Hong , Saeki Shigeru 
Published: November 2006

AbstractThe effects of dietary methionine level on the profiles of fatty acids and phospholipids and on the plasma cholesterol concentration were investigated to confirm whether the methionine content of dietary proteins is one of the major factors that cause differential effects on lipid metabolism. The effect of dietary supplementation with eritadenine, which is shown to be a potent inhibitor of phosphatidylethanolamine (PE) N‐methylation, was also investigated. Rats were fed six diets containing casein (100 g/kg) and amino acid mixture (86.4 g/kg) differing in methionine content (2.5, 4.5, and 7.5 g/kg) and without or with eritadenine supplementation (30 mg/kg) for 14 d. The ratio of arachidonic to linoleic acid of liver microsomal and plasma phosphatidylcholine (PC) was significantly increased as the methionine level of diet was elevated, indicating that dietary methionine stimulates the metabolism of linoleic acid. The PC/PE ratio of liver microsomes and the plasma cholesterol concentration were also increased by dietary methionine. These effects of methionine were completely abolished by eritadenine supplementation The S‐adenosylmethionine concentration in the liver reflected the methionine level of diet. These results support the idea that the differential effects of dietary proteins on lipid metabolism might be ascribed, at least in part, to their different methionine contents, and that methionine might exert its effects through alteration of PE N‐methylation.