bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural modifications of rat serum high density lipoprotein by pancreatic phospholipase A2
Authors: Swaney John B. , Orishimo Margaret W.
Published: November 2006

An important and unusual aspect of the high density lipoprotein (HDL) in the rat is its tendency to undergo marked alterations in structure in response to physiological perturbations. In this study, the role of the surface lipids for maintenance of HDL integrity were investigated. Hydrolysis by pancreatic phospholipase A2 of the phospholipids of rat HDL in the presence of the d>1.21 g/ml fraction of rat serum results in an increase in the particle diameter and an uptake of apo‐E and apo A‐IV from the lipoprotein‐free fraction; augmentation of the albumin concentration in the incubation mixture intensified the observed changes, probably due to enhancement of the compositional changes brought about by phospholipase treatment. Phospholipase A2 treatment of the d<1.21 g/ml fraction of rat serum produces only minor changes in the properties of the isolated HDL. These data suggest that changes in apoprotein content reflect an uptake of A‐IV and E by the rat HDL, rather than a net loss of apo A‐I. Likewise, titration of the action of pancreatic phospholipase A2 on HDL apoprotein composition showed that initially a modest increase in apo A‐IV content occurred, but with more extensive phospholipolysis there was a considerably greater increase in the apo‐E content of the particle. The data suggest that hydrolysis of phospholipids such as occurs physiologically through the action of lecithin: cholesterol acyl transferase and hepatic lipase may alter the HDL structure independently from changes effected in the neutral lipid core.
Normalization of high density lipoprotein in fish eye disease plasma by purified normal human lecithin: Cholesterol acyltransferase
Authors: Holmquist Lelf , Carlson Lars A.
Published: November 2006

Plasma from a patient with fish eye disease has been enriched with autologous high density lipoproteins (HDL) and supplemented with highly purified normal human plasma lecithin:cholesterol acyltransferase (LCAT). Incubation of such plasma at 37 C in vitro resulted in normalization of its low HDL cholesteryl ester percentage, from 23% to 79%, associated with a two‐fold increase in both the cholesteryl ester and triglyceride contents of the HDL fraction, as compared to incubation experiments with absent or heat‐inactivated purified normal LCAT.

The normalization of the HDL cholesteryl ester percentage induced by incubation with purified normal LCAT also was accompanied by an increase in the size of the original fish eye disease HDL particles, which had a mean mass of 115 kd, to HDL particle populations with mean particle masses ranging from 130–220 kd, depending on the concentration of purified LCAT in the incubate. Both HDL cholesterol esterification and particle enlargement were abolished completely by the LCAT inhibitor DTNB and by heat inactivation of the purified normal LCAT. The results give further evidence that fish eye disease is an α‐LCAT deficiency.
Cholesterol synthesis in the pathogenesis of lithocholic acid‐induced cholestasis
Authors: Yousef I. M. , Tuchweber B. , Morazain R. , Gauvin M. , Roy C. C. , Weber A. M.
Published: November 2006

Lithocholic acid (LCA)‐induced intrahepatic cholestasis is associated with increased de novo synthesis of hepatic cholesterol and augmented cholesterol content of the liver cell plasma membrane fraction enriched in bile canalicular complexes (BCM). To determine whether inhibition of cholesterol synthesis could prevent LCA‐induced cholestasis, adult male Wistar rats were treated daily with the hypocholesterolemic agents, clofibrate (250 mg/kg) or mevinolin (25 mg/kg), for one, two or four days. After bile duct cannulation and bile collection for one hr, the animals were injected intravenously with 120 μmoles/kg of LCA or its carrier (albumin). Cholesterol synthesis was measured in liver homogenates, and its contribution to the BCM was estimated. LCA reduced bile flow by 51%, 35% and 25% after clofibrate pretreatment for one, two and four days, respectively, and by 51%, 30% and 42% in mevinolin‐pretreated animals after one, two and four days. In control animals, cholesterol synthesis and the contribution of newly synthesized cholesterol in the BCM were increased after LCA injection. However, despite that cholesterol synthesis and the contribution of newly synthesized cholesterol in the BCM were reduced in drug‐pretreated rats, LCA injection caused a relative increase in these parameters of a magnitude similar to that observed in controls. Thus, the ability of LCA injection to augment de novo cholesterol synthesis and its transport to the BCM may be an important pathogenetic step in the development of cholestasis.
Lipogenic enzyme activities in primary cultures of adult mouse hepatocytes
Authors: Hillyard Lewis A. , Lin C. Y. , Abraham S.
Published: November 2006

The effects of various unsaturated fatty acids such as oleic (18∶1n−9), linoleic (18∶2n−6) and arachidonic (20∶4n−6) on the activities of fatty acid synthetase (FAS), malic enzyme (ME), glucose‐6‐phosphate dehydrogenase (G6PDH) and 6‐phosphogluconate dehydrogenase (6PGDH) all were determined in primary cultures of mouse hepatocytes. Activities of FAS and ME were found to decrease with time in culture regardless of whether hepatocyte donors were fed diets containing polyunsaturated fatty acid‐free hydrogenated cottonseed oil (HCTO) or corn oil (CO). On the other hand, while G6PDH activity also declined in cultured hepatocytes obtained from HCTO‐fed mice, the activity of this enzyme increased in cells cultured from CO‐fed mice. 6PGDH activity was found to increase in hepatocytes obtained from both diet groups. Neither 18∶2 nor 20∶4 when added to media could alter FAS or ME activities compared with those observed with either 18∶1‐containing or fatty acid‐free media. Since lactic dehydrogenase activity and the rate of incorporation of [3H] leucine into FAS protein were unaltered with time in hepatocyte cultures, the decreased activities of FAS and ME cannot be attributed to a loss in cell viability during culture but rather appear to be specific for those enzymes which respond to diet hormones in vivo. Examination of the fatty acid contents of the cells after the culture period showed that the values for the ratios of 16∶0/16∶1 and of 18∶0/18∶1 were elevated when either 18∶2 or 20∶4 was added to the medium even though there was no evidence for elongation of the added 18∶2 or for 20∶4 being converted to 22∶4. This result suggest that Δ9‐desaturase activity was inhibited by these polyunsaturated fatty acids and that conversion of 18∶2 to 20∶4 was not required for such action.

The rate of synthesis determined by the relative rate of incorporation of [3H]leucine into FAS was two to five times higher in hepatocytes prepared from mice fed the HCTO diet than in hepatocytes from mice fed the CO diet. We have concluded that the mechanisms for long‐term regulation may not be contained entirely within the liver.
Quantitation of 1,2‐diacylglycerol in rat heart by latroscan TLC/FID
Authors: Okumura Kenji , Hashimoto Hidekazu , Ito Takayuki , Ogawa Kouichi , Satake Tatsuo
Published: November 2006

1,2‐Diacylglycerol, which has been recognized as one of the intracellular second messengers, was measured quantitatively in the lipid extract from rat hearts using the thin layer chromatography and flame ionization detection (TLC/FID) method. Cholesterol acetate was added to the tissue as an internal standard, and the crude lipids from the tissue were purified with silicic acid column to eliminate phospholipids. Development of Chromarods was carried out using two solvent systems and a three‐step development technique. The relationship of the peak area ratio detected by flame ionization detector to weight ratio was linear compared with cholesteryl acetate. The 1,2‐diacylglycerol content in the rat heart in the unstimulated condition was 72.5±15.3 ng/mg wet wt (mean±SD).
Molecular species of glycerolipids of ehrlich ascites cells and of their fat granules
Authors: Myher J. J. , Kuksis A. , Pind S. , Kay E. R. M.
Published: November 2006

Ehrlich ascites cells were grown in mice and were isolated by centrifugation of the ascites fluid. The cells were lysed with distilled water, and the floating fat particles were collected by centrifugation. The particles contained about 90% neutral and 10% polar lipid. The neutral lipid was made up of about 50% triacylglycerol, 30% alkyldiacylglycerol, 3% cholesteryl esters, 3% free cholesterol and 4% free diacylglycerols. The phospholipid fraction was comprised of about 50% phosphatidylcholine, 35% phosphatidylethanolamine, 10% sphingomyelin and small amounts (less than 5% total) of serine and/or inositol phosphatides. The triacylglycerol and alkyldiacylglycerol fractions possessed total carbon number and fatty acid compositions closely similar to these reported in the literature for whole ascites cells and for a cell membrane preparation. Likewise, the fatty acid composition of phospholipids from the granules in general was similar to that reported for Ehrlich ascites cells. On the basis of the polar and neutral lipid ratio, the lipid granules of the ascites cells were calculated to possess lipid core diameters of 30–50 nm, which were 40–70 times smaller than those (up to 2μ) measured for the lipid granules of the intact cells by electron microscopy. The characterization of the lipid composition of the Ehrlich ascites lipid granules was completed by determing the molecular species composition of the diacyl, alkylacyl and alkenylacyl phosphatidylethanolamines and of the diacyl and alkylacyl phosphatidylcholines of the ascites cells. It is concluded that the alkyldiacylglycerols of the Ehrlich ascites cells occur largely in the cytoplasmic lipid granules, which appear to consist of many particles of the size and structure of very low density lipoproteins enclosed in membranous sacs.
Effect of dietary vitamin E and selenium on susceptibility of brain regions to lipid peroxidation
Authors: Meydani Mohsen , Macauley John B. , Blumberg Jeffrey B.
Published: November 2006

The effect of dietary vitamin E and/or selenium (Se) supplementation (200 IU and/or 0.2 ppm, respectively) or deficiency for two months on lipid peroxidation in cerebrum, cerebellum, mid‐brain, and brain stem of one‐month‐old male F344 rats was investigated. Dietary treatment had a minimal effect on weight gain of rats for the period tested. Plasma α‐tocopherol (α‐T) concentration and glutathione peroxidase (GSH‐Px) activity were reflective of dietary treatments. Supplementation of diets with vitamin E and/or Se increased plasma α‐T and/or GSH‐Px activity, while diets devoid of these nutrients reduced them significantly. Increased GSH‐Px activity in Sesupplemented rats was further enhanced by vitamin E supplementation. Differential concentrations of α‐T among brain regions were affected by dietary vitamin E but not by Se. In vitro lipid peroxidation of brain homogenates was inhibited by dietary vitamin E supplementation and increased by deficiency. Addition of 0.25 mM ascorbic acid or 0.1 mM of Fe2+ to brain homogenates markedly increased in vitro lipid peroxidation. Ascorbic acid‐induced lipid peroxidation was inversely correlated with dietary vitamin E and Se in cerebrum. In vitro Fe2+‐addition induced the greatest stimulation of lipid peroxidation, with cerebellum and brain stem of vitamin E‐deficient rats showing the highest response to Fe2+ challenge. These findings indicate that concentrations of α‐T among the brain regions are different and can be altered by dietary vitamin E treatments, cerebellum and brain stem are more susceptible to in vitro challenge by peroxidative agents than other regions, and the degree of lipid peroxidation of brain regions is partially affected by dietary vitamin E but not by Se in the levels tested.
Isolation and characterization of proteolipids from rat liver (LSP) and kidney (KSP)
Authors: Jüngst Dieter , Blumenstingl Johann , Caselmann Wolfgang H.
Published: November 2006

In this study, the biochemical characteristics of proteolipids of rat liver and kidney homogenates were compared. In all preparations, the proteo‐lipids were eluted at the void volume of the Biogel A‐15 m column after gel chromatography, and a molecular weight over 15×106 was estimated. Electron microscopy of the concentrated void volume fractions showed globular particles with diameters of 30–100 nm for liver (LSP) and 30–60 nm for kidney (KSP) preparations that might be formed from plasma membrane fragments. After ultracentrifugation in a CsCl gradient, rat LSP and KSP floated in a small density range from 1.16–1.17 g/ml. There was no significant difference between the relative percentages of phospholipids, triglycerides and cholesterol of both proteo‐lipids. However, the relative mean amount of total protein in rat KSP (60.4% vs 50.4%) was significantly higher and the content of free fatty acids (4.3% vs 12.6%) significantly lower compared to rat LSP. SDS‐PAGE revealed at least 12 protein subunits ranging from 15,000–130,000 in both preparations, but one protein of about Mr 49,000 might represent a liver specific component. The isolated proteo‐lipids from rat liver and kidney homogenates showed similar biochemical characteristics as those from human sources, which could explain the known cross‐reactivity of antibodies against these preparations.

The putative function of these proteo‐lipids is not known, although there is some evidence from human studies that they carry receptor proteins.
Lipids of dermatophytes. III. Sterol‐induced changes in the lipid composition and functional properties ofEpidermophyton floccosum
Authors: Sanadi S. , Pandey R. , Khuller G. K.
Published: November 2006

Sterol supplementation, alone or in the presence of cerulenin, resulted in an increase in the total sterol content ofEpidermophyton floccosum. While the total phospholipid levels ofE. floccosum exhibited only marginal changes with sterol supplementation, the fatty acid profiles of these phospholipids were highly varied. In the presence or absence of cerulenin, the oleic acid content of phospholipids were increased significantly by cholesterol supplementation, whereas linoleic acid levels were enhanced by ergosterol supplementation. These variations resulted in higher unsaturated/saturated phospholipid fatty acid ratios in sterol‐supplemented cells. The uptake of labeled amino acids (aspartic acid, lysine, glycine) was influenced by sterol supplementation. Alterations in the number of binding sites for the membrane probe, 1‐anilino‐naphthalene‐8‐sulfonate (ANS), were seen based on Scatchard plot calculations. The results indicate a correlation between sterol‐induced changes in membrane lipid composition and function.
Occurrence of cholesterol as a major sterol component in leaf surface lipids
Authors: Noda Manjiro , Tanaka Mitsunobu , Seto Yukari , Aiba Takaaki , Oku Chiyo
Published: November 2006

Cholesterol has been detected as one of the major sterols in the surface lipids of higher plant leaves. It was widely distributed among the plant leaves of various species as a common main sterol component with a few exceptions. The content of cholesterol amounted to 71.5% of the total sterols in the surface lipids of rape leaves. However, the proportion of cholesterol in the intracellular lipids of rape leaves was lower than that in the surface lipids, and the seed lipids contained only a trace amount of cholesterol, as reported in the literature. In the leaf surface lipids examined, a minor amount of cholestanol associated with cholesterol often was detected by capillary gas chromatography and gas chromatography‐mass spectrometry. The related analysis for the surface lipids of fruits showed that cholesterol was one of the major component sterols also in those lipids of several species.
Premalignant alterations in the glycosphingolipids of small intestinal mucosa of rats treated with 1,2‐dimethylhydrazine
Authors: Dahiya R. , Dudeja P. K. , Brasitus T. A.
Published: November 2006

1,2‐Dimethylhydrazine is a procarcinogen with selectivity for the colon and proximal small intestine. In weekly subcutaneous (s.c.) doses of 20 mg/kg body weight, this agent produces colonic and proximal small intestinal tumors in a high percentage of rodents with a latency period of approximately six months. To determine whether alterations in the glycosphingolipid content of rat proximal and/or distal small intestinal mucose existed before the development of dimethylhydrazine‐induced cancer, rat were given s.c. injections of this agent (20 mg/kg body weight per wk) or diluent for five wk. Animals were killed at this time, and mucosa was isolated from each small intestinal segment of both groups. Glycosphingolipids then were extracted from these tissues and analyzed by high performance thin layer chromatography and gas liquid chromatography.

The results of these studies demonstrated that (1) the content of neutral and acidic glycosphingolipids was significantly decreased (approximately 20%) in the proximal small intestine of treated rats compared with their control counterparts; (2) no significant difference in the glycosphingolipid content was seen, however, in the distal small intestinal mucosa of control and treated rats; and (3) while significant differences were noted in the majority of fatty acids of GM3, glucosyl‐ and globotriaosylceramide in the proximal small intestine of control and treated animals, differences in the fatty acids of these glycosphingolipids in the distal segment of these groups were confined to stearic (18∶0) acid and/or arachidic (20∶0) acid.
Analysis of cardiac membrane phospholipid peroxidation kinetics as malondialdehyde: Nonspecificity of thiobarbituric acid‐reactivity
Authors: Janero David R. , Burghardt Barbara
Published: November 2006

When exposed to xanthine oxidase (superoxide)‐dependent, iron‐promoted Fenton chemistry, purified cardiac membranes evidenced, by the thiobarbituric acid (TBA) test, a virtually instantaneous peroxidative response with a maximal linear rate of 5.8 nmol malondialdehyde (MDA)‐equivalents/mEquivalents lipid ester reacted/min. Yet when the lipids purified from these same membranes and reconstituted into liposomes were peroxidized under identical reaction conditions, the TBA test indicated that a pronounced (∼20‐min) lag period preceded a maximal peroxidation rate of only 2.1 nmol MDA‐equivalents/ mEquivalents lipid ester reacted/min. After 120 min of peroxidation, the cardiac membranes yielded some 300 nmol TBA‐reactive MDA‐equivalents/mEquivalent ester, whereas the isolated membrane lipids evidenced ∼40% less TBA‐reactivity. To verify that these quantitative and kinetic differences in membrane (phospho)‐lipid peroxidation occurred with removal of the lipids from their membrane milieu, the MDA produced during both cardiac membrane peroxidation and the peroxidation of the lipids derived therefrom was isolated as its free anion by ion‐pair high‐pressure liquid chromatography. As quantified spectrophotometrically, true MDA production during myocardial membrane peroxidation was identical in kinetics and in amount to the production of TBA‐reactive substance from the peroxidized isolated membrane lipids. These results demonstrate that significant non‐MDA. TBA‐reactive species are generated during the peroxidation of cardiac membranes, especially before the maximal rates of bona fide MDA production. As a direct consequence, artifactual levels and kinetics of membrane lipid peroxidation do result.
Lack of protein‐mediated α‐tocopherol transfer between membranes in the cytoplasm of acites hepatomas
Authors: Mowri Hiro‐omi , Nojima Shoshichi , Inoue Keizo
Published: November 2006

Transfer‐stimulating activity for α‐tocopherol and the concentration of α‐tocopherol and peroxidized lipids in rat ascites hepatoma cells were compared with those from normal and regenerating liver.

The ability of supernatants from ascites hepatomas (AH‐13, AH‐60C, AH‐109A) to enhance the transfer of α‐tocopherol was much lower than that from normal livers. The α‐tocopherol per mg protein of supernatant from ascites hepatomas was lower than that from normal liver. Regenerating liver showed almost the same values as normal liver in activity to stimulate the transfer of α‐tocopherol and α‐tocopherol content of the supernatant. By gel filtration, about 60% of α‐tocopherol in the supernatant of normal liver was detected in the fractions containing the 30 K protein, which stimulates transfer of α‐tocopherol between membranes, whereas no significant amount of α‐tocopherol was detected in 30 K protein fractions of AH‐60C supernatant. Little stimulating activity for α‐tocopherol transfer was detected in AH‐60C, AH‐109A and AH‐13.

All ascites hepatomas tested contained less arachidonic acid and docosahexaenoic acid than normal and regenerating liver. An absorption peak with maximum intensity at 233 nm, which is due to conjugated dienes, was observed in UV‐absorption spectra of ascites hepatoma total lipids, indicating that peroxidized lipids accumulate in these cells. With normal and regenerating liver, no significant peak due to conjugated dienes was detected.
Effect of 7‐methylated bile acids and bile alcohols on cholesterol metabolism in hamsters
Authors: Matoba Naoyuki , Kuroki Syoji , Cohen Bertram I. , Mosbach Erwin H. , McSherry Charles K.
Published: November 2006

The effect of 7‐methyl substituted bile acid and bile alcohol analogues on cholesterol metabolism was studied in the hamster. Animals were fed chow plus 0.1% cholesterol supplemented with 0.1% of one of the following steroids: chenodeoxycholic acid, 7‐methyl‐chenodeoxy‐cholic acid, 7β‐methyl‐24‐nor‐5β‐cholestane‐3α,7α,25‐triol, cholic acid, 7‐methyl‐cholic acid, or 7β‐methyl‐24‐nor‐5β‐cholestane‐3α,7α,12α,25‐tetrol. Cholesterol absorption was determined from fecal analysis after feeding of radiolabeled cholesterol and β‐sitosterol.

Of the six compounds studied, chenodeoxycholic acid and 7‐methyl‐chenodeoxycholic acid decreased intestinal cholesterol absorption (17% and 31% decrease, respectively). Only 7‐methyl‐chenodeoxycholic acid decreased serum cholesterol concentration (29% decrease), but there were no analogous changes of liver and biliary cholesterol concentration and cholesterol saturation of bile. Total fecal neutral sterol excretion was increased in the groups fed chenodeoxycholic acid and 7‐methyl‐chenodeoxycholic acid. In addition, the production of coprostanol was increased in both groups. These data suggest that 7‐methyl‐chenodeoxycholic acid resembles chenodeoxycholic acid in its effect on cholesterol metabolism and may be a potential candidate for further studies of its gallstone‐dissolving properties.
Compensatory mechanisms in erythrocyte lipids in patients with atherosclerosis
Authors: Michalak Jerzy , Kadziolka Adam , Pruszkowska Romualda , Ledwozyw Andrzej , Madejczyk Andrej
Published: November 2006

The quantitative coposition of phospholipids and fatty acids of erythrocytes was investigated in patients with atherosclerosis. It was stated that the erythrocyte lipids of atherosclerotic patients contained smaller quantitities of phosphatidylcholine and phosphatidylinositol, a significantly larger quantity of sphingomyelin, and higher sphingomyelin/phosphatidylcholine and cholesterol/phospholipid ratios. The existence of compensatory changes was stated, which was evident in the reduction of palmitic and stearic acids and the increase of linoleic and eicosatrienoic acids in erythrocyte phospholipids. These changes in fatty acid composition probably cause minimal changes in the membrane fluidity indiced by an increased cholesterol/phospholipid and sphingomyelin/phosphatidylcholine ratios. This paper was the first evidence of occurrence of those changes in erythrocytes during spontaneous atherosclerosis in human
Determination of individual long‐chain fatty acyl‐CoA esters in heart and skeletal muscle
Authors: Molaparast‐Saless F. , Shrago E. , Spennetta T. L. , Donatello S. , Kneeland L. M. , Nellis S. H. , Liedtke A. J.
Published: November 2006

A method has been developed for determination of individual long‐chain fatty acyl‐CoA esters from heart and skeletal muscle using high performance liquid chromatography (HPLC). The esters were extracted from freezeclamped tissue of pig and rat hearts and rat skeletal muscle for analysis on a radially compressed C18 5μ reversephase column. Nine peaks in the extract with carbon chain lengths from C12 to C20 that subsequently disappeared on alkaline hydrolysis were identified. The major acyl‐CoA peaks were 14∶1, 18∶2, 16∶0 and 18∶1 and additionally in rat heart 18∶0. Total long‐chain acyl‐CoA esters obtained by summation of the individual molecular species was 11.34±1.48 nmol/g wet wt. pig heart; 14.51±2.11 nmol/g wet wt. in rat heart, and 4.35±0.71 nmol/g wet wt. in rat skeletal muscle. These values were approximately 132% of those obtained using a separate procedure that measured total CoA by HPLC after alkaline hydrolysis of the esters. The described method demonstrates the quantitation of individual acyl‐CoA species in muscle tissue. Therefore, it has a number of advantages in that it permits information to be obtained on the individual molecular species under various nutritional and metabolic conditions.
Influence of diet on (n−3) and (n−6) fatty acids in monkey erythrocytes
Authors: Carman Martha A. , Beare‐Rogers Joyce L.
Published: November 2006

Cynomolgus monkeys were fed oils high in linoleic acid or with half of the linoleic acid replaced by either (n−3) linolenic acid or marine fatty acids. When the diet contained similar quantities of linoleic and (n−3) linolenic acid, erythrocyte fatty acids maintained a ratio of (n−6) to (n−3) fatty acids of approximately 2∶4. Fatty acids from menhaden oil enhanced the incorporation of eicosapentaenoic and docosahexaenoic acids into the monkey erythrocytes, the composition of which was not altered by additional α‐tocopherol.
Stimulation of liver growth and DNA synthesis by glucosylceramide
Authors: Datta Subhash C. , Radin Norman S.
Published: November 2006

The nature of the growth‐stimulating effect of glucosylceramide was studied. Mice were injected intraperitoneally with emulsified glucosylceramide and conduritol B epoxide, an inhibitor of cerebroside glucosidase. Within one or two days, the liver grew 18–24%, as reported. Two enzymes involved in DNA synthesis also increased more than the weight. The total liver activity of thymidine kinase increased 46–73%, and the total activity of ornithine decarboxylase increased as much as 101%. It is suggested that elevated liver levels of glucocerebroside stimulate cell proliferation through a relatively direct mechanism.
Adipose hormone‐sensitive lipase preferentially releases polyunsaturated fatty acids from triglycerides
Authors: Gavino Victor C. , Gavino Grace R.
Published: November 2006

Rat adipose hormone‐sensitive lipase‐mediated release of fatty acids from triglycerides was studied in three model systems: i) cultured preadipocytes containing polyunsaturated fatty acid‐enriched triglyceride; ii) perfused epididymal fat pads; and iii)in vitro incubations of crude preparations of hormone‐sensitive lipase with synthetic triglyceride‐analogues as substrates. We found that cultured preadipocytes challenged with 10μM norepinephrine tended to release more ω6 and ω3 polyunsaturated fatty acids than saturated fatty acids. Fat pads perfused with 10 μM norepinephrine preferentially released arachidonate and α‐linolenate but tended to retain oleate and linoleate. Finally, crude preparations of hormonesensitive lipase released from the triglyceride‐analogue substrates α‐linolenate twice as fast as oleate. We conclude that rat adipose hormone‐sensitive lipase preferentially releases polyunsaturated fatty acids from triglycerides. We suggest that this may be a mechanism by which these fatty acids are kept from being trapped in fat depots and maintained in the circulation.
Production of the criegee ozonide during the ozonation of 1‐Palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphocholine liposomes
Authors: Squadrito Giuseppe L. , Uppu Rao M. , Cueto Rafael , Pryor William A.
Published: November 2006

It is likely that Criegee ozonides are formed in small amounts in the lungs of animals breathing ozone‐containing air. This makes these compounds potential candidates to act as secondary toxins which relay the toxic effects of ozone deeper into lung tissue than ozone itself could penetrate. Therefore, we have determined the yields of Criegee ozonides from unsaturated lipids in liposomal systems as a model of the types of yields of Criegee ozonides that might be expected both in the lung lining fluid layer and in biological membranes. Ozonation of 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphocholine liposomes produced bothcis‐ andtrans‐Criegee ozonides. These ozonides have been isolated by solid phase extraction and high‐performance liquid chromatography of the ozonized lipid, and the products have been identified by two‐dimensional1H nuclear magnetic resonance. The combined yield of thecis‐ andtrans‐Criegee ozonides is 10.7±2.8% (avg. ±SD, n=7) with small unilamellar liposomes and 10.6±2.7% (n=3) with large multilamellar liposomes. We had previously reported (Chem. Res. Toxicol. 5 505–511, 1992) that ozonation of methyl oleate in sodium dodecylsulfate micelles also produces an 11% yield of the Criegee ozonides. Thus, ozonation in a variety of models gives about 11% of the Criegee ozonide, suggesting that these products also would be formed in small but significant amounts in the lungs of animals breathing polluted air. Further research on the pharmacokinetics and possible toxicity of the Criegee ozonides of fatty acids is suggested.
Eicosapentaenoic acid at hypotriglyceridemic dose enhances the hepatic antioxidant defense in mice
Authors: Demoz Abraham , Willumsen Nina , Berge Rolf Kristian
Published: November 2006

The effect of oral administration of purified (95%) eicosapentaenoic acid on serum lipids, hepatic peroxisomal enzymes, antioxidant enzymes and lipid peroxidation was compared with that of palmitic acid fed mice and corresponding controls. After 10 d, a dose of 1000 mg eicosapentaenoic acid per day/kg body weight lowered serum triglycerides by 45%, while no significant change in serum cholesterol level was noted in comparison to palmitic acid fed mice and controls. Hepatic acyl‐CoA oxidase and catalase activities increased by 50% and 30%, respectively, in the eicosapentaenoic acid fed group. In addition, the hepatic reduced glutathione content and the activities of glutathione transferase, glutathione peroxidase and glutathione reductase, increased significantly during eicosapentaenoic acid treatment. The levels of hepatic lipid peroxides were lower after eicosapentaenoic acid feeding, while no significant change was noted in the palmitic acid fed mice when compared to the controls. Taken together, the present data demonstrate for the first time that at hypolipidemic doses eicosapentaenoic acid feeding i) enhances the hepatic antioxidant defense, and ii) does not cause a significant differential induction of the two peroxisomal enzymes, acyl‐CoA oxidase and catalase, as was noted after administration of hypolipidemic peroxisome proliferating compounds, such as clofibrate in rodents.
Zinc deficiency in the rat alters the lipid composition of the erythrocyte membrane triton shell
Authors: Driscoll Eric R. , Bettger William J.
Published: November 2006

The effect of dietary zinc deficiency on the lipid composition of the erythrocyte membrane Triton shell was determined. Weanling male Wistar rats were fed an egg white‐based diet containing <1.0 mg Zn/kg dietad libitum. Control rats were either pair‐fed orad libitum‐fed the basal diet supplemented with 100 mg Zn/kg diet. A Zn refed group was fed the −Zn diet until day 18 and then pairfed the +Zn diet until day 21. Dietary, Zn deficiency caused an increased cholesterol/phospholipid ratio in Triton shells compared to those from pair‐fed controls. Zn deficiency caused a decreased double bond index of fatty acids in phosphatidylinositol (PI) and phosphatidylcholine (PC); there was a decreased proportion of 18∶2n−6 and 22∶4n−6 in PC and 20∶4n−6 in PI as compared to that found in pair‐fed controls. All glycerophospholipids that were retained in the shell had a lower double bond index and increased content of 16∶0 and/or 18∶0 relative to the phospholipid in the intact membrane.
Lipid composition of subcellular membranes from larvae and prepupae ofDrosophila melanogaster
Authors: Jones Helen E. , Harwood John L. , Bowen Ivor D. , Griffiths Gareth
Published: November 2006

Subcellular membranes were analyzed for their lipid composition and protein content at two developmental points representing the third instar wandering larvae and prepupal stages ofDrosophila. At both stages, phosphatidylethanolamine (PE) and phosphatidylcholine (PC) were the major constituents with phosphatidylinositol (PI), phosphatidylserine (PS), diphosphatidylglycerol (DPG) and phosphatidic acid (PA) being relatively minor components. In total homogenates and in the nuclear‐enriched fraction there was no significant difference in the phospholipid composition of the wandering larvae and prepupae. In mitochondria only a significant increase in the minor component PS was observed in the prepupae. In lysosomal membranes on the other hand, the relative abundance of the major components PE and PC increased in the prepupae although the molar ratios of the two lipids remained almost constant. The fatty acid composition of the phospholipids remained virtually unchanged in all of the fractions examined, including the lysosomes, and there was no evidence of lipid peroxidation. With regard to cellular degeneration and the involvement of lysosomes, we conclude that mechanisms other than gross modification of the lipid and/or lipid/protein ratio of their membranes are involved in the liberation of the acid phosphatase contents.
Free fatty acids inducing mouse lethal toxicity in lipid extracts ofEngraulis japonica, the Japanese anchovy
Authors: Sajiki Junko , Takahashi Katsuhiro
Published: November 2006

Mouse lethal toxicity was detected in the ether extract ofEngraulis japonica (anchovy). The mouse toxicity of extracts was more potent from viscera than from other organs. Okadaic acid (C44H68O13) and dinophysistoxin (C45H70O13), lipophilic toxins derived from phytoplankton, which are usually considered to be the diarrhetic shellfish toxins, were not detected in the ether extract of ancovy. There occurred, however, two prominent peaks in high‐performance liquid chromatography, which were identified as free eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The mouse toxicity observed correlated with the intensity of these two peaks. Toxicity was reduced considerably by pretreatment with Na2CO3. By quantitating EPA toxicity, it was concluded that the toxicity was not due to EPA only but also to DHA. The results indicate that substances in Japanese anchovy associated with mouse lethal toxicity include free polyunsaturated fatty acids, mainly EPA and DHA.
Palmitic acid enhances cholesterol gallstone incidence in sasco hamsters fed cholesterol enriched diets
Authors: Ayyad Nariman , Cohen Bertram I. , Mosbach Erwin H. , Miki Shigeo
Published: November 2006

In an established hamster model of cholesterol cholelithiasis, a semipurified lithogenic diet containing 4% butterfat and 0.3% cholesterol leads to the production of cholesterol gallstones in only 50–60% of animals after a 6‐wk feeding period. The purpose of this study was to investigate whether gallstone incidence could be increased while feeding a nutritionally adequate diet of moderate cholesterol content. The semipurified lithogenic diet was modified as follows: (i) substitution of 1.2% palmitic acid for 4% butterfat, and (ii) varying the amount of dietary cholesterol from 0.0 to 0.3% with either butterfat or palmitic acid as the lipid component of the diet. Substitution of palmitic acid for butterfat produced a significantly higher incidence of cholesterol gallstones (94%vs. 53%). Palmitic acid also raised the incidence of gallstones when added to the 0.1% and 0.2% cholesterol diets as compared to butterfat: 0%vs. 44% and 50%vs. 81%, respectively. Gallstone incidence increased from 0% to nearly 100% when the cholesterol content of the palmitic acid diets was raised from 0.0% to 0.3%, indicating a dose response effect with respect to dietary cholesterol. Hamsters fed cholesterol‐free diets did not form gallstones. Increased dietary cholesterol led to increased liver weight associated with a significant increase in liver cholesterol concentration. However, the palmitic acid groups had significantly lower liver cholesterol values than the corresponding butterfat groups. Serum and biliary cholesterol concentrations increased with increasing dietary cholesterol intake, but there were no differences between the butterfat and palmitic acid groups. The cholesterol saturation index increased from 0.56 to 1.32 in the butterfat groups and from 0.56 to 1.30 in the palmitic acid groups upon raising the dietary cholesterol from 0.0 to 0.3%. Biliary total bile acid concentration did not vary significantly within all groups; however, the addition of cholesterol produced an increase in the ratio of chenodeoxycholic acid to cholic acid. It is concluded that in Sasco hamsters the saturated fatty acid, palmitic acid, when substituted for butterfat in a nutritionally adequate lithogenic diet, is capable of increasing gallstone incidence to almost 100% during a 6‐wk feeding period.
Fecal bile acid excretion and composition in response to changes in dietary wheat bran, fat and calcium in the rat
Authors: Borum Marie L. , Shehan Kathleen L. , Fromm Hans , Jahangeer Saleem , Floor Marianne K. , Alabaster Oliver
Published: November 2006

The effect and possible interactive influence of different dietary amounts of wheat bran, fat and calcium on the fecal excretion, concentration and composition of bile acids was studied in Fischer‐344 rats. The fecal bile acids were analyzed using gas‐liquid chromatography. Dietary wheat bran increased both total bile acid excretion and fecal weight without changes in fecal bile acid concentration. The proportion of fecal hyodeoxycholic acid decreased with increasing dietary fiber, whereas that of lithocholic and deoxycholic acids increased significantly with fiber intake. The percent content of fecal chenodeoxycholic acid did not change. Increasing dietary fat led to an increase in bile acid excretion without changes in either fecal weight or bile acid concentration. In contrast, the level of dietary calcium did not affect the total excretion of bile acids. However, since calcium increased the fecal weight, it consequently diluted bile acids and decreased their fecal concentration. Dietary fat and calcium had no influence on fecal bile acid composition. There were no interactive effects of wheat bran, fat and calcium on fecal bile acids. The finding in this study that dietary fiber, fat and calcium induce significant changes in fecal bile acids may be of relevance to the potential of bile acids to promote carcinogenesis.
Reduction in triacylglycerol levels by fish oil correlates with free fatty acid levels inad libitum fed rats
Authors: Otto David A. , Baltzell Janet K. , Wooten Joseph T.
Published: November 2006

Rats were fed (for 2 or 6 wk) purified diets containing lard (LD) or menhaden oil (MO) at two levels of dietary fat,i.e., at 11.5 and 20.8% of energy in the low fat (LF) and the medium fat (MF) diets, respectively. Following the diet period, rats were sacrificed after either an overnight fast or after uninterruptedad libitum feeding. The studies were designed to investigate the dependence of our previously reported effects of MO,i.e. the reduction of plasma free fatty acid (FFA) levels and accumulation of hepatic triacylglycerols, on the dietary fat concentration and the nutritional state of the animal at the time of sacrifice. Reductions in plasma triacylglycerol and cholesterol levels in MO‐fed relative to LD‐fed rats were observed under all conditions. FFA levels were consistently reduced by MO‐feeding at both dietary fat concentrations, but only when blood was sampled fromad libitum fed rats. Under these conditions there was a significant positive relationship between plasma FFA and triacylglycerol concentrations. Reduction in plasma FFA levels may be an additional mechanism associated with the triacylglycerol‐lowering effect of fish oil (FO). The LF and MF MO diets caused a rise in plasma glucose levels with no significant change in insulin concentration, indicating that the reduction of FFA by MO was not related to changes in insulin concentration or insulin sensitivity. The MO diets had no effect on skeletal muscle or epididymal adipose tissue lipoprotein lipase activity, demonstrating that catabolism of triacylglycerol‐rich lipoproteins contributes little, if any, to the MO‐dependent reductions of plasma triacylglycerol and FFA. The previously reported accumulation of hepatic triacylglycerols after high fat (HF; 30% of energy) MO‐feeding was not observed with the LF or MF MO diets, suggesting that the apparent direct inhibition of triacylglycerol secretion by FO imposes a rate‐limitation only when feeding HF diets.
Borage or primrose oil added to standardized diets are equivalent sources for γ‐linolenic acid in rats
Authors: Raederstorff D. , Moser U.
Published: November 2006

The aim of this study was to evaluate the effect of different doses and sources of dietary γ‐linolenic acid (GLA) on the tissue phospholipid fatty acid composition. Rats fed four different levels of GLA (2.3, 4.6, 6.4 and 16.2 g of GLA/kg diet) in the form of either borage oil or evening primrose oil during 6 wk were compared with animals fed corn oil. The levels of dihomo‐γ‐linolenic acid (DHLA) and GLA showed a significant dose‐related increase in liver, erythrocyte and aorta phospholipids. Moreover, the arachidonic acid/DHLA ratios in tissues decreased with increasing intake of dietary GLA. There was no significant difference in tissue GLA and DHLA levels within groups given equal amounts of dietary GLA either as borage oil or evening primrose oil. The amount of dietary GLA administered did not significantly influence prostaglandin E2 production in stimulated aortic rings and thromboxane B2 levels in serum; however, an increase in prostaglandin E1 derived from DHLA was observed in the supernatants of stimulated aorta.
Effects of 17β‐estradiol and starvation on trout plasma lipoproteins
Authors: Wallaert Charlotte , Babin Patrick J.
Published: November 2006

Administering 17β‐estradiol (E2) to juvenile trout results in plasma hyperlipidemia and hyperlipoproteinemia associated with significant increases in the concentrations of triglycerides (TG), free cholesterol, phospholipids, free fatty acids and proteins, both postprandial and during starvation. TG undergo the greatest increase (9 times control level 96 h after feeding). The concentration differences between E2‐treated and control trout increase during starvation, primarily by progressive decreases in the concentrations of various lipids in controls. E2‐induced hypertriglyceridemia is mainly caused by an increase in the concentration of very low density lipoproteins (VLDL) during both the postprandial period (6 times control level at 24 h) and during starvation (15 times control level at 96 h); hyperlipoproteinemia lasts up to at least 7 d after the last feeding. E2 treatment does not change the concentration of high density lipoproteins, but does increase plasma concentrations of a very high density lipoprotein, vitellogenin (VTG). In E2‐treated VLDL, cholesteryl esters are depleted while proteins are enriched. During the postprandial phase, the apolipoprotein (apo) profile of VLDL (d< 1.015 g/mL) is comparable in E2‐treated and control trout. Starvation of E2‐treated trout is accompanied by an enrichment in apo B240, A‐I and A‐II. The secretion levels of TG and VLDL‐TG, as determinedin vivo, by injecting Triton WR‐1339 to starving animals, are significantly higher in E2‐treated trout than in controls. In trout, as in chicks, E2 administration significantly increases the concentration and hepatic secretion of plasma VLDL independent of the nutritional status and the appearance of VTG in the plasma. This suggests the existence of similar mechanisms for the regulation of lipoprotein metabolism by estrogens in oviparous vertebrates.
A method for determination of the absolute stereochemistry of α,β‐epoxy alcohols derived from fatty acid hydroperoxides
Authors: Hamberg Mats
Published: November 2006

A method for the determination of the absolute configuration of the alcohol group of fatty acid α,β‐epoxy alcohols was developed. The method consists of:(i) deoxygenation of the saturated epoxy alcohol to an allylic alcohol by treatment with triphenylphosphine selenide and trifluoroacetic acid; (ii) oxidative ozonolysis of the (−)‐menthoxycarbonyl derivative of the allylic alcohol; and (iii) steric analysis of the resulting 2‐hydroxy acid (methyl ester, (−)‐menthoxycarbonyl derivative) by gas‐liquid chromatography using appropriate reference compounds. The result obtained, coupled with knowledge of the relative configuration of the epoxy alcohol (erythro/threo) and of the geometrical configuration of the epoxide group (cis/trans), permitted assignment of the absolute configuration of all three asymmetric carbons of the α,β‐epoxy alcohol. The method was applied to the determination of the absolute stereochemistry of two hepoxilins recently isolated from the red algaMurrayella perilados.
Headspace gas chromatography to determine human low density lipoprotein oxidation
Authors: Frankel E. N. , German J. Bruce , Davis Paul A.
Published: November 2006

We previously described a rapid headspace gas chromatographic method for the determination of hexanal, an important decomposition product of n−6 polyunsaturated fatty acid (PUFA) peroxidation in rat liver samples and human red blood cell membranes. This method was applied to the measurement of Cu2+ catalyzed‐oxidation of freshly prepared human low density lipoproteins (LDL) from 10 healthy adult volunteers. A twofold variation in oxidative susceptibility was found by this assay for hexanal and other volatiles. Hexanal values correlated significantly (P<0.05) with total polyunsaturated fatty acid (PUFA), 18∶2 and n−6 PUFA contents of LDL; but poorly with 20∶4 and with vitamin E. Therefore, in addition to α‐tocopherol, other endogenous antioxidants and factors may contribute, to LDL's resistance to oxidation. This simple, rapid and sensitive method for oxidative susceptibility provides a useful component in the analysis of the prooxidant/antioxidant status of biological samples. The method is used routinely in our laboratories to determine specific peroxidation products of n−6 and n−3 PUFA.
Fluorescence assay of glucosylceramide glucosidase using NBD‐Cerebroside
Authors: Abe Akira , Shayman James A. , Radin Norman S.
Published: November 2006

A sensitive fluorometric assay for glucocerebroside β‐glucosidase [Dinur, T., Grabowski, G.A., Desnick, R.J., and Gatt, S. (1984)Anal. Biochem. 136, 223–234] has been reexamined. It was found that the lipids containing the NBD moiety (12‐[N‐methyl‐N‐(7‐nitrobenz‐2‐oxa‐1,3‐diazol‐4‐yl)] used for standardization of the assay are light‐sensitive and that the yield of fluorescent light is very sensitive to the composition of the solvent used in the fluorometric measurement. Some protection against fading could be obtained by adding a free‐radical trapping agent, Slow Fade. The fading of the free NBD‐acid, when used for standardization, could be prevented by adding ethanol to the solvent, but this reduced the fluorescence yield. It is recommended that some of the fluorescent substrate be enzymatically hydrolyzed completely to NBD‐ceramide, which can be utilized as the standard without the need to add ethanol. A warning about enzyme reaction rate stability with time is given, with a suggestion for ensuring constancy of activity.