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PubMed1979

Lipid protein interactions in mitochondria. VIII. Effect of general anesthetics on the mobility of spin labels in lipid vesicles and mitochondrial membranes.

We have studied the effect of general anesthetics on the mobility of two stearic acid spin labels (5-doxyl stearic acid and 16-doxyl stearic acid) in bovine heart mitochondria and in phospholipid vesicles made from either mitochondrial lipids or commercial soybean phospholipids. The general anesthetics used include nonpolar compounds (alcohols, halothane, pentane, diethyl ether, chloroform) and the amphiphatic compound, ketamine. All anesthetics tested increase the mobility of the spin labels in phospholipid vesicles to a limited extent up to a concentration where the ESR spectra become those of free spin labels. On the other hand, anesthetics have a pronounced effect on mitochondrial membranes at concentrations as low as those known to produce general anesthesia; the effect is lower near the bilayer surface (5-doxyl stearic acid) and very strong in the bilayer core (16-doxyl stearic acid). The effects of anesthetics are mimicked by the detergent, Triton X-100. We suggest that the discrepancy between the action of anesthetics in mobilizing the spin labels in lipid vesicles and in membranes results from labilization of lipid protein interactions.

Anesthetics↗
PubMed1985

Effects of Acipimox on plasma lipids and biliary lipids in healthy subjects.

The effects of Acipimox (5-methylpyracine-2-carboxylic acid-4-oxide, 3 X 250 mg/day) on plasma lipids, lipoproteins, and biliary lipids were studied in 14 healthy male volunteers using a double blind cross-over design. There was a significant (P less than 0.05) rise of HDL-cholesterol by 9.8%, while effects on other lipids and lipoproteins were small and insignificant (total cholesterol minus 6.5%, LDL-cholesterol minus 11.8%, free cholesterol minus 4.2%, total triglycerides plus 13.5% and phospholipids plus 3.9%). There was a significant rise of the HDL-cholesterol/LDL-cholesterol ratio by 23.6% (P less than 0.02) and of the HDL-cholesterol/total cholesterol ratio by 16% (P less than 0.05). Apolipoproteins AI, AII, and B were not significantly affected. The ratio of HDL-cholesterol/Apo AI increased significantly (P less than 0.05), and the ratio of HDL-cholesterol/Apo AII rose from 1.22 to 1.32 (P less than 0.05), while the ratio LDL-cholesterol/Apo B fell from 1.96 to 1.73. The composition of HDL and LDL, therefore, must have been altered by Acipimox. The relative cholesterol concentration in bile was significantly (P less than 0.05) increased by treatment with Acipimox, while bile acids and phospholipids were not significantly affected. The lithogenic index rose significantly by 15.1% (P less than 0.02) as calculated according to Admirand and Small, while calculations according to Hegard and Dam yielded a slight insignificant rise (P less than 0.1). The findings suggest that treatment with Acipimox might be associated with an increased risk of cholelithiasis. However, only long-term epidemiologic studies can ultimately demonstrate whether or not Acipimox increases the risk of gallstone formation.

Adult↗
PubMed1983

Role of membrane lipids in the immunological killing of tumor cells: II. Effector cell lipids.

Peritoneal macrophages (M phi) from mice become cytotoxic after incubation in lymphokine (LK)-rich supernatants of antigen-stimulated spleen cell cultures. Tumoricidal activity is evident with M phi treated with LK for 4 hr, becomes maximal after 8-12 hr incubation and decreases to control levels by 24-36 hr. To gain insight into LK-induced functional changes, the lipid composition of M phi cultured with LK for 0-36 hr was analyzed by high pressure liquid chromatography. LK induced marked changes in M phi lipid composition: cellular content of cholesterol (CHOL) and polyunsaturated fatty acids increased 2- to 3-fold after 8 hr when the cells showed maximal tumoricidal activity. Cellular lipid and fatty acid content returned to control levels by 24 hr when the M phi had lost tumoricidal activity. These changes were not observed with equal numbers of M phi cultured in control supernatants. To analyze further the role of CHOL and unsaturated fatty acids in M phi tumor cytotoxicity, M phi were enriched in CHOL or linolenic acid (18:3) and tested for their ability to kill 1023 tumor cells. Within 1 hr of culture, M phi showed a 3- to 4-fold increase in CHOL or 18:3 content. 18:3-enriched cells were markedly tumoricidal, whereas controls cultured in delipidized medium alone or enriched with saturated fatty acids were cytotoxic. CHOL-enriched M phi were not tumoricidal; indeed, these cells were inhibited in their killing after treatment with LK compared to M phi cultured in delipidized medium with LK alone. These results suggest that UFA aids, whereas CHOL negates, expression of M phi tumor cytotoxicity.

Animals↗
PubMed2000

Long-term feeding of dietary oils alters lipid metabolism, lipid peroxidation, and antioxidant enzyme activities in a teleost (Anabas testudineus Bloch).

Anabas testudineus (climbing perch), average body weight 21+/-1 g, were maintained in culture tanks and fed a 35% protein feed plus an additional supplementation of three dietary oils (20% each of coconut oil, palm oil, or cod liver oil). Body weight gain was similar among all groups. However, several hepatic lipogenic enzymes such as malic enzyme (ME), NADP-isocitrate dehydrogenase (ICDH), glucose 6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH) and beta-hydroxy-1-methyl glutaryl CoA reductase (HMG CoA reductase) were assayed, and they responded differently. Hepatic ME and G6PDH activities showed a significant decrease in the coconut oil and palm oil groups, but there was no significant change in ICDH activity. The 6PGDH activities were reduced, whereas HMG CoA reductase activity was increased in the palm oil-treated group. Cholesterol synthesis in the liver and muscle increased in the palm oil-treated group, but liver phospholipids did not show any significant change in fish supplemented with oils rich in saturated fatty acids. Triacylglycerol and free fatty acid concentrations were high in the coconut oil- and palm oil-supplemented groups. Lipid peroxidation products such as thiobarbituric acid-reactive substances and conjugated dienes decreased in the same two groups. Antioxidant potential was high in all groups as evidenced by increased activity of superoxide dismutase, glutathione peroxidase, and glutathione content. The results of this study indicate that in fish, dietary lipids depress hepatic lipogenic activity as well as lipid peroxidation products by maintaining high levels of antioxidant enzymes.

Animals↗
PubMed1989

Activity of rat liver microsomal glutathione transferase toward products of lipid peroxidation and studies of the effect of inhibitors on glutathione-dependent protection against lipid peroxidation.

Rat liver microsomal glutathione transferase displays glutathione peroxidase activity with linoleic acid hydroperoxide, linoleic acid ethyl ester hydroperoxide, and dilinoleoyl phosphatidylcholine hydroperoxide, with rates of 0.2, 0.3, and 0.3 mumol/min/mg, respectively. The activities are increased between three- and fourfold when the enzyme is activated with N-ethylmaleimide. Microsomal glutathione transferase can also conjugate 4-hydroxynon-2-enal with a specific activity of 0.5 mumol/min/mg. These findings show that the enzyme can remove harmful products of lipid peroxidation and thereby possibly protect intracellular membranes against oxidative stress. A set of glutathione transferase inhibitors (rose bengal, tributyltin acetate, S-hexylglutathione, indomethacin, cibacron blue, and bromosulfophtalein) which abolish the glutathione-dependent protection against lipid peroxidation in liver microsomes have been characterized. These inhibitors were found to be effective in the micromolar range and could prove valuable in studying the factor responsible for glutathione-dependent protection against lipid peroxidation.

Animals↗
PubMed1981

The role of nonbilayer lipid structures in the fusion of human erythrocytes induced by lipid fusogens.

(1) A comparative study of the polymorphic phase behaviour of reconstituted erythrocyte phospholipase with 'fusogens' and chemically related 'non-fusogens' using 31P-NMR techniques has been made. We demonstrate that only fusogens can induce a conformational change in the membrane lipids from the bilayer of the hexagonal (HII) phase. (2) The tendency of erythrocyte (ghost) membranes to adopt nonbilayer structures is correlated with the extent of fusion in erythrocytes at various membrane concentrations of glycerol monooleate. Above a certain critical membrane concentration of glycerol monooleate, there is an increase in the tendency of ghost membranes to adopt the HII phase, which is paralleled by a marked increase in fusion processes in the intact erythrocytes. (3) These observations are consistent with a common mechanism of action for fusogenic lipids whereby inverted lipid structures such as long cylinders (HII configuration) or inverted micelles are induced, which serve as intermediates in the fusion event.

Cell Fusion↗
PubMed1989

Intrinsic molecules in lipid membranes change the lipid-domain interfacial area: cholesterol at domain interfaces.

A theoretical analysis of the effects of intrinsic molecules on the lateral density fluctuations in lipid bilayer membranes is carried out by means of computer simulations on a microscopic interaction model of the gel-to-fluid chain-melting phase transition. The inhomogeneous equilibrium structures of gel and fluid domains, which in previous work (Cruzeiro-Hansson, L. and Mouritsen, O.G. (1988) Biochim. Biophys. Acta 944, 63-72) were shown to characterize the transition region of pure lipid membranes, are here shown to be enhanced by intrinsic molecules such as cholesterol. Cholesterol is found to increase the interfacial area and to accumulate in the interfaces. The interfacial area, the average cluster size, the lateral compressibility, and the membrane area are calculated as functions of temperature and cholesterol concentration. It is shown that the enhancement by cholesterol of the lateral density fluctuations and the lipid-domain interfacial area is most pronounced away from the transition temperature. The implications of the results are discussed in relation to passive ion permeability and function of interfacially active enzymes such as phospholipase.

Cell Membrane Permeability↗
PubMed1992

Optimized determination of malondialdehyde in plasma lipid extracts using 1,3-diethyl-2-thiobarbituric acid: influence of detection method and relations with lipids and fatty acids in plasma from healthy adults.

We investigated the influence of different concentrations of Fe3+, phosphoric acid, butylated hydroxytoluene and glutathione on the production of the malondialdehyde-1,3-diethyl-2-thiobarbituric acid adduct in plasma lipid extracts. Following organic solvent extraction the stable product was analyzed by spectrophotometry (537 nm), fluorometry (547 nm) and high-performance liquid chromatography with fluorometric detection. Using optimized reaction conditions there was good agreement between the three methods, with slightly higher values for the spectrophotometric method. Plasma total lipid malondialdehyde reference values for 24 healthy adults amounted to 1.30 +/- 0.23 mumol/l (spectrophotometric method) and 1.11 +/- 0.31 mumol/l (fluorometric method). Plasma lipid malondialdehyde concentrations correlated significantly with plasma triglycerides (r = 0.527), total cholesterol (r = 0.612) and total fatty acids (r = 0.810) and with the total number of double bonds present in plasma fatty acids with three or more double bonds (r = 0.923).

Adult↗
PubMedDate not supplied

Actions of vitamins A and E and some nicotinic acid derivatives on plasma lipids and on lipid infiltration of aorta in cholesterol-fed rabbits.

Marked hypercholesterolemia and moderate lipid infiltration of the aorta were induced by feeding rabbits a diet containing 1% cholesterol + 3% corn oil for 70 days. In the liver the concentration and pool size of cholesterol increased and those of triglycerides (TG) decreased. On dietary addition of vitamin A and vitamin E (44 000 I.U. and 125 mg respectively, once daily for 5 days a week) the following changes were noted in comparison with the fat-fed rabbits not receiving extra addition of vitamins. There was a slight decrease of the levels of plasma cholesterol and an increase of those of plasma TG. The liver cholesterol concentration increased but, according to the concomitant reduction of the liver weight, there was no significant change in lever cholesterol or TG pools. In the aorta the vitamins markedly reduced the lipid infiltrated area as well as the cholesterol content. Both niceritrol** and S-2040 [pyridine-2,5-dicarboxylic acid di(beta-pyridylcarbinol ester)] in a dietary concentration of 0.5% decreased plasma cholesterol by about 20%. This reduction, as well as that induced by the vitamins, was confined to the VLDL-fractions only. S-2040 slightly reduced the cholesterol accumulation in the aorta. In rabbits given both the vitamins and niceritrol or S-2042 there was an additive reduction of plasma cholesterol. Here the nicotinic acid derivatives were partly able to counteract the increases of plasma TG induced by the vitamins. In the aorta the combination vitamins + S-2042 but not that of vitamins + niceritrol tended to give a better protection than the vitamins alone. On a normal diet vitamins A + E significantly increased the liver cholesterol concentration and pool and decreased the liver TG pool, but did not affect the other parameters. Possible mechanisms for the prophylactic action of the vitamins against lipid infiltration of the aorta of cholesterol-fed rabbits are discussed.

Animals↗
PubMed1993

Estimation of the extent of lipid peroxidation in the ischemic and reperfused heart by monitoring lipid metabolic products with the aid of high-performance liquid chromatography.

Estimation of lipid peroxidation (LPO) through malonaldehyde (MDA) formation measured by assaying thiobarbituric acid reactive products remains the method of choice to study the development of oxidative stress to assess myocardial ischemic reperfusion injury. However, MDA estimation by this assay is non-specific and often gives erroneous results. In this report, we describe a method to estimate MDA, formaldehyde (FDA), acetaldehyde (ADA), and acetone, the degradation products of oxygen free radicals (OFR) and polyunsaturated fatty acids (PUFA), as presumptive markers for LPO. Isolated rat hearts were made ischemic for 30 min, followed by 60 min of reperfusion. The perfusates were collected, derivatized with 2,4-dinitrophenylhydrazine, and extracted with pentane. Aliquots of 25 microliters in acetonitrile were injected on a Beckman Ultrasphere C18 (3 microns) column. The products were eluted isocratically with a mobile phase containing acetonitrile-water-acetic acid (40:60:0.1, v/v/v). The peaks were identified by co-chromatography with the hydrazine derivatives of authentic standards. The retention times of MDA, FDA, ADA and acetone were 5.0, 6.3, 9.8 and 15.7 min, respectively. The results of our study indicated progressive increase in all four lipid metabolites with reperfusion time. Thus, our results demonstrate that the release of lipid metabolites from the isolated heart increased in response to oxidative stress. Since MDA, FDA, ADA, and acetone are the products of OFR-PUFA interactions, this method allows proper estimation of LPO to monitor the oxidative stress developed during the reperfusion of ischemic myocardium.

Animals↗
PubMed1992

Accumulation of lead and effects on total lipids and lipid derivatives in the freshwater fish Anabas testudineus (Bloch).

Exposure of a freshwater fish to several sublethal concentrations (1.25, 2.50, 5.00, 10.00, and 20.00 mg/liter) of lead for a period of 30 days showed significant accumulation of lead in the blood and tissues. Lead bioaccumulated in the study showed organ-specific distribution, with high levels in the blood followed by the kidney, gill, liver, and brain and comparatively lesser amounts in the ovary and muscle tissues. The lead accumulation in tissues was found to increase with lead in water up to a concentration of 5 mg/liter, and at concentrations of 10 and 20 mg/liter the lead accumulation in the tissues, although indicating an increase, was not proportional to the concentration in water. Exposure of the freshwater fish Anabas testudineus to a sublethal (5 ppm) concentration of lead nitrate for a period of 30 days during the preparatory phase of its annual reproductive cycle reduced the total lipids, phospholipids, and cholesterol levels in the liver and ovary tissues while the free fatty acid levels were increased and lipase activity was elevated. All the parameters in the blood were found to increase. These results suggest that lead nitrate affects the lipid metabolism of the fish and this may reduce the fecundity of the fish since lipids are known to play an important role in teleost reproduction as an energy source and a precursor of steroids.

Animals↗
PubMed1995

DNA adducts induced by lipids and lipid peroxidation products: possible relationships to I-compounds.

A methanol-extractable lipid fraction of oats has been found previously to induce three specific I-compounds (age-dependent covalent DNA modifications) in female rat liver DNA, as detected by the 32P-postlabeling assay. The current report used an in vitro system to explore the possible mechanisms involved in the formation of these DNA derivatives. Ground oats or commercial oatmeal were extracted with methanol, and the extracts were incubated with rat lung DNA in vitro. DNA was recovered and analyzed by the nuclease P1-enhanced version of the 32P-postlabeling assay. A number of adducts were induced by the in vitro reaction but none of them was identical by chromatographic analysis to oats-specific I-compounds detected in vivo. Addition of rat liver microsomes and cofactors (NADPH or cumene hydroperoxide) to the in vitro reaction also failed to induce any of the oats-specific I-compounds. Pretreatment of oat lipids with soybean lipoxidase and oxygen enhanced formation of most adducts formed in vitro in a dose- and time-dependent manner. Several of these adducts were related to peroxide derivatives of linoleic acid. Chromatographic evidence suggests that one of the major adducts is derived from 4-hydroxynonenal, a reactive intermediate lipid peroxidation product. This adduct was detectable in liver and kidney DNA of untreated rats and its level increased with age. These results were in line with previous in vivo results, suggesting that the oats-specific I-compounds are presumably formed via an indirect mechanism rather than by direct binding of oats components to DNA.

Aging↗
PubMed2005

Enzymatic lipid removal from surfaces--lipid desorption by a pH-induced "electrostatic explosion".

Removal of lipidic molecules from surfaces can be accomplished using detergents containing lipases. Surface cleaning is usually performed under alkaline conditions due to increased solubility of the hydrolysis products, especially free fatty acids. This paper shows that removal of a triacylglycerol film from a surface can be dramatically enhanced in a sequential system where pH is shifted to alkaline conditions after an initial lipolytic reaction period at or below neutral pH. Data from three different biophysical techniques, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), quartz crystal microbalance with dissipation monitoring (QCM-D), and total internal reflection fluorescence spectroscopy (TIRF) clearly show the effects of such cleaning procedure. Initially the reaction is carried out at pH below the pKa value of the fatty acids formed upon triacylglycerol hydrolysis, and the protonated fatty acids accumulate in the film. The mechanism of lipid removal, induced by increasing pH to a value above the fatty acid pKa, is explained by a burst caused by electrostatic repulsion between rapidly ionised fatty acids, i.e. by an "electrostatic explosion". Performing the initial hydrolysis at pH 6 and the subsequent rinse at pH 10, using triolein as model substrate, lipid removal from surfaces by both commercial detergent lipases and non-commercial lipases was significantly improved compared to a reaction at constant pH 10.

Adsorption↗
PubMed2006

Effects of olive oil and tomato lycopene combination on serum lycopene, lipid profile, and lipid oxidation.

OBJECTIVE: We compared the effect of two diets (a diet high in olive oil and a diet high in carbohydrate and low in olive oil) with high lycopene content and other controlled carotenoids on serum lycopene, lipids, and in vitro oxidation. METHODS: This was a randomized crossover dietary intervention study carried out in Launceston, Tasmania, Australia in healthy free-living individuals. Twenty-one healthy subjects who were 22 to 70 y old were recruited by advertisements in newspapers and a university newsletter. A randomized dietary intervention was done with two diets of 10 d each. One diet was high in olive oil and the other was high in carbohydrate and low in olive oil; the two diets contained the same basic foods and a controlled carotenoid content high in lycopene. RESULTS: Significant increases (P<0.001) in serum lycopene concentration on both diets were to similar final concentrations. Higher serum high-density lipoprotein cholesterol (P<0.01), lower ratio of total cholesterol to high-density lipoprotein (P<0.01), and lower triacylglycerols (P<0.05) occurred after the olive oil diet compared with the high-carbohydrate, low-fat diet. There was no difference in total antioxidant status and susceptibility of serum lipids to oxidation. CONCLUSIONS: Serum lycopene level changes with dietary lycopene intake irrespective of the amount of fat intake. However, a diet high in olive oil and rich in lycopene may decrease the risk of coronary heart disease by improving the serum lipid profile compared with a high-carbohydrate, low-fat, lycopene-rich diet.

Adult↗
PubMed1998

Lipid polymorphism and protein-lipid interactions.

Non-lamellar-forming lipids play an important role in determining the physical properties of membranes. They affect the activity of membrane proteins and peptides. In addition, peptides which lyse membranes as well as those which promote membrane fusion facilitate the formation of non-lamellar phases, either micelles, cubic or hexagonal phases. The relationship of these diverse effects on membrane curvature is discussed in relation to the function of certain peptides and proteins. Specific examples of ionophoric peptides, cytotoxic peptides and viral fusion peptides are given. In addition, we compare the modulation of the rate of photoisomerisation of an integral membrane protein, rhodopsin, by non-lamellar-forming lipids with the effects of these lipids on an amphitropic protein, protein kinase C. Among these diverse systems it is frequently observed that the modulation of biological activity can be described in terms of the effect of the peptide or protein on the relative stability of lamellar and non-lamellar structures.

Animals↗
PubMed1985

Lipid-rich versus lipid-secreting carcinoma of the mammary gland.

An unusual case of a malignant breast tumor in a 70 year-old woman is reported. The histological picture displayed a mixed pattern of vacuolated and apocrine-like cells. At electron microscopical level the tumoral cells presented, in a very regular manner, lipidic intracytoplasmic vacuoles. These lipid droplets were secreted by the tumoral cells, and appeared surrounded by SER profiles. A differential diagnosis is discussed with other mammary gland neoplasms, such as histiocytoid carcinoma, apocrine cell carcinoma and other clear cell carcinomas. Based upon our findings we propose that this case should be considered as a lipid secreting carcinoma of the breast.

Aged↗
PubMed1987

Radiation-induced lipid peroxidation and the fluidity of erythrocyte membrane lipids.

The effect of radiation-induced peroxidation on the fluidity of the phospholipids of the erythrocyte membrane was studied using both erythrocyte ghosts and liposomes formed from the polar lipids of erythrocytes. In liposomes, the oxidation of the phospholipids increased with radiation dose, but there was no change in the fluidity of the lipids as measured by spin-label motion. Under the same conditions of irradiation, no oxidation of phospholipid was detected in erythrocyte ghosts, although changes occurred in the motion of spin labels intercalated with the membrane. These changes were attributed to radiation-induced alterations in the membrane proteins. It is concluded that alterations in motion of spin labels, observed with intact membranes after irradiation, are most likely the result of changes in the structure of membrane proteins rather than the lipids.

Dose-Response Relationship, Radiation↗
PubMed1996

Regulatory effects of dietary n-3 and n-6 lipids on plasma and hepatic lipid levels, liver cell number and microsomal protein content in spontaneously hypertensive rats.

Weanling male spontaneously hypertensive rats were fed semipurified diets containing either corn or fish oil for 8 weeks. Rats fed on fish oil diet had significantly lower plasma triglyceride, total cholesterol and HDL-cholesterol levels than rats fed on corn oil diet (P < 0.05). Moreover, rats fed on fish oil diet had significantly lower liver total lipid and triglyceride concentrations than rats fed on corn oil diet (P < 0.05). Dietary lipids were reflected in plasma fatty acid composition. Rats fed on fish oil diet had significantly greater plasma eicosapentaenoate (EPA) and docosahexaenoate (DHA) (n-3 PUFAs) with an accompanying decrease in plasma linoleate (LA) and arachidonate (AA) (n-6 PUFAs), in comparison with the rats fed corn oil (P < 0.05). Those results would suggest that the n-3 PUFAs were incorporated into plasma lipids at the expense of the n-6 PUFAs. Rats fed on corn oil diet had significantly greater liver DNA content than rats fed on fish oil diet (P < 0.05), thereby implying that the n-3 PUFAs in fish oil had an inhibitory effect on liver cell proliferation. Furthermore, rats fed on fish oil diet had significantly greater hepatic microsomal protein content than rats fed on corn oil diet (P < 0.05), indicating that fish oil exerted a stimulatory effect on hepatic microsomal enzymes.

Animals↗