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At least 19 recordsLinked to original sources
PubMed1992

Cholesterol modulation of lipid intermixing in phospholipid and glycosphingolipid mixtures. Evaluation using fluorescent lipid probes and brominated lipid quenchers.

Carbazole- and indole-labeled phospholipids have been used to monitor the homo- or heterogeneity of lipid mixing in several types of lipid bilayers combining a brominated and a nonbrominated lipid with varying amounts of cholesterol. Experimental quenching curves (relating the normalized probe fluorescence intensity to the mole fraction of brominated lipid) show a characteristic smooth, monophasic form for homogeneous liquid-crystalline lipid mixtures. However, for mixtures exhibiting lipid lateral segregation, such curves show marked perturbations in form over the region of composition where segregation occurs. Using this approach, it is found that high mole fractions of cholesterol (40-50 mol %) promote the formation of apparently homogeneous solutions in mixtures of disaturated and monounsaturated phosphatidylcholines (PCs) that exhibit extensive thermotropic phase separations in the absence of sterol. At only slightly lower levels of cholesterol, however, these systems exhibit inhomogeneous lipid mixing over a wide range of relative proportions of the two PC components. Mixtures of cerebroside and monounsaturated PCs, even at high bilayer cholesterol contents, exhibit significant inhomogeneity in lipid mixing over a wide range of cerebroside/PC ratios. Phase-separating PC/PC and PC/cerebroside mixtures can readily form long-lived metastable solutions when the level of the higher-melting component in the liquid-crystalline phase exceeds its equilibrium solubility by as much as 20-30 mol %; this tendency is significantly increased by cholesterol. Cholesterol shows no significant ability to enhance lipid intermixing in a third type of phase-separating lipid system, combining a monounsaturated PC with a monounsaturated phosphatidic acid--calcium complex. Experiments using cleavable phospholipid conjugates, linking a fluorescent lipid to a brominated lipid, suggest that each fluorescent molecule probes a local lipid domain comprising approximately less than 40-50 nearby acyl chains.

Animals↗
PubMed1991

In vivo and in vitro loading of lipid by artificially lipid-depleted lipophorins: evidence for the role of lipophorin as a reusable lipid shuttle.

Lipid transport in the hemolymph of Manduca sexta is facilitated by a high density lipophorin in the resting adult insect (HDLp-A, d approximately 1.109 g/ml) and by a low density lipophorin during flight (LDLp, d approximately 1.060 g/ml). Lipophorin presumably shuttles different lipids between sites of uptake or storage, and sites of utilization. In order to shuttle lipid, a lipid-depleted lipophorin should be able to reload with lipid. To test this hypothesis, we used HDLp-A particles that were artificially depleted of either phospholipid (d approximately 1.118 g/ml) or diacylglycerol (d approximately 1.187 g/ml) and subsequently radiolabeled in their protein moiety. Upon injection into adult moths, both particles shifted their density to that of native HDLp-A, indicating lipid loading. Also, upon subsequent injection of adipokinetic hormone, both particles shifted to a lower density (d approximately 1.060 g/ml) indicating diacylglycerol loading and conversion to LDLp. Both phospholipid and diacylglycerol loading were also studied using an in vitro system. The lipid-depleted particles were incubated with fat body that had been radiolabeled in either the phospholipid or the triacylglycerol fraction. Transfer of radiolabeled phospholipid and diacylglycerol from fat body to lipophorin was observed. During diacylglycerol loading, apoLp-III associated with lipophorin, whereas phospholipid loading occurred in the absence of apoLp-III. The results show the ability of lipid-depleted lipophorins to reload with lipid and therefore reaffirm the role of lipophorin as a reusable lipid shuttle.

Animals↗
PubMed1979

Plasma lipid distributions in selected North American populations: the Lipid Research Clinics Program Prevalence Study. The Lipid Research Clinics Program Epidemiology Committee.

Cross-sectional age- and sex-specific plasma lipid distributions (means, medians and selected percentiles) are given for 48,431 white participants in visit 1 of the Lipid Research Clinics (LRC) Prevalence Study. This study consisted of two visits in which 10 LRCs screened participants selected from well-defined North American target populations that included a broad range of sociodemographic subgroups. These data confirm findings from earlier studies in developed countries, showing age-related differences in plasma lipid levels. However, for overall distributions, the LRC data showed slightly lower cholesterol and markedly higher triglyceride values than those previously reported for North America. Some variation in plasma lipid values was evident among the clinic populations. The large number of participants within most subgroups permitted a variety of analytic and comparative studies. For example, data from the large pediatric population revealed a drop in plasma cholesterol levels in adolescent males and females. Males aged 20--50 years had higher cholesterol levels than females in the same age group, and higher triglyceride levels between ages 20--70 years. Numbers were also sufficient for meaningful comparisons between lipid distributions of females who were taking sex hormones and those who were not: In females taking sex hormones, cholesterol and triglyceride levels were higher for subjects younger than 45 years, but slightly lower after age 45, than lipid levels in females not taking hormones.

Adolescent↗
PubMed1990

Effects of dietary lipidic charge in the concentration of bovine plasmatic lipids and lipoproteins. Its influence on the saturation degree of fatty acids' storaged lipids.

To estimate physiological changes due to added fat in bovine diet, whole cottonseed (19% lipids) was furnished to half-breed zebu cattle during 7 months. Thirty animals had increased its dietary lipidic charge in 2.6% (lot S), thirty were used as controls (lot C) and other two bovines were hyper-dosed with 7.9% added fat (lot H). Weight, clinical signs and plasmatic values of total cholesterol (TC), triglycerides (TG), lipoproteins (LP) and other biochemical parameters were monthly controlled. At the end of the assay the steers were sacrificed and the quality of meat and fat was evaluated. The initial levels of TC were statistically homogeneous in all groups (mean = 1.0 g/l); they remained without modifications in C (1.53 g/l), but they had increased progressively in supplemented animals. At the end of the work TC was greater in H (3.95 g/l) than in S (2.44 g/l). Latest TG (initial mean = 0.30 g/l) also were greater in H (0.74 g/l) than in S (0.71 g/l). The lipoproteinogram stayed inalterable in C, meanwhile alpha LP were increased and beta LP were decreased in animals on which the dietary lipidic charge had been increased. The weight's gain/animal/day (X) was 130 g (C), 290 g (S) and 88 g (H). The general physiological condition was deteriorated in the last lot. After comparing lots C and S, results indicated that beefsteaks in the last group were heavier (2.45 vs. 2.33 kg), with more lipids (0.47 vs. 0.36 kg) and major fat veined proportion (1.40 vs. 1.25%). The stored lipids showed high saturation degree in S, with increment in the mean percentage of stearic acid (28.6%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1976

Lipid-lipid and lipid-protein interactions as studied with a novel type of fluorescent fatty acid and phospholipid probes.

A novel fluorescent-labelled group of fatty acids and phospholipids has been applied to determine phase transitions in liposomes by fluorescence intensity and polarisation measurements. The chromophore of these amphiphilic lipids proved to be very suitable to demonstrate temperature-dependent lipid-lipid interactions. Liposomes from 1,2-dipalmitoyl-3-sn-glycero-phosphoethanolamine and from lipids isolated from membranes of E. coli K 1062 mutant grown on elaidic acid were used in these studies. These probes also made it possible to observe conformational changes in membrane proteins in isolated plasma membranes from this mutant. The changes in protein conformation were dependent on structural changes in the lipid phase.

Binding Sites↗
PubMed1991

Dietary fiber and lipid peroxidation: effect of dietary fiber on levels of lipids and lipid peroxides in high fat diet.

Effect of feeding coconut and blackgram fiber isolated as neutral detergent fiber (NDF) on the levels of lipids and lipid peroxides was studied in rats given a high fat diet. Concentration of cholesterol, free falty acid and phospholipids showed significant decrease in the serum, liver aorta and intestine of coconut and blackgram fiber groups. Concentration of malondialdehyde (MDA) and conjugated dienes was significantly decreased in liver and intestine of both fiber groups, while hydroperoxides showed significant increase in liver and heart of both the fiber groups. SOD and catalase activity was found to be increased in liver, intestine, heart proximal colon and distal colon of both the fiber groups. Serum ceruloplasmin levels showed a slight increase in animals fed coconut and blackgram fiber groups. Glutathione levels in liver, intestine proximal colon, distal colon and heart also showed a significant decrease in the animals of both the fiber groups.

Animals↗
PubMed1990

Organic pesticides modify lipid-lipid and lipid-protein domains in model membranes. A laser Raman study.

The effect of hexachlorocyclohexane (all isomers) on the thermal transition properties of phospholipid liposomes was determined by Raman spectroscopy. Raman spectra of liposomes with and without the presence of hexachlorocyclohexanes were recorded in the C-H stretching region which shows three major bands around 2850, 2880 and 2930 cm-1. Thermal transition properties were estimated from plots of I2880/I2850 and or I2930/I2850 vs. temperature, where I represents the intensity of the respective band. Our data on phospholipid liposomes reveal that delta- and gamma-hexachlorocyclohexanes drastically reduce and broaden the main thermal transitions of phospholipids at toxic level concentrations. These effects are more pronounced in liposomes containing 18 or more carbon atom long acyl chains. Alpha- and beta-isomers at similar concentrations show a minimum effect on the thermal transition properties of phospholipids. Raman analysis of phospholipid liposomes containing melittin, interestingly, reveal that the delta-isomer unlike the gamma-isomer strongly alters the transition properties of boundary lipids. These data suggest that the effect of hexachlorocyclohexanes on the thermal transition properties of membranes is stereo specific and that the delta-isomer preferably disrupts the lipid-protein domains. Results are explained on the basis of the dynamic flexibility owing to the equatorial and axial chlorine atoms of various hexachlorocyclohexane isomers.

Chemical Phenomena↗
PubMed1979

Lipid protein interactions in mitochondria. VII. A comparison of the effects of lipid removal and lipid perturbation of the kinetic properties of mitochondrial ATPase.

We investigated the kinetics of mitochondrial ATPase in bovine heart mitochondria and submitochondrial particles upon treatment with phospholipase A2, or upon addition of n-butanol to perturb the lipid protein interactions. The changes observed are the following: (1) Lipid removal or perturbation with butanol is accompanied by loss of ATPase activity with decrease of both V and of the KM for ATP. (2) There are changes of activation energy of ATPase activity at temperatures above the discontinuity normally observed for membrane-bound enzymes in mitochondria. In particular, butanol abolishes the discontinuity, and induces a constant activation energy of about 32 kcal/mol in the range 8--37 degrees C. (3) Butanol modifies the pH dependence of ATPase shifting the pH optimum from around 10 to less alkaline values. The optimum for Mg2+ concentrations is increased by the solvent. (4) Treatment with phospholipase A2 results in a removal of oligomycin-sensitive ATPase, whereas butanol addition prevents oligomycin inhibition of ATPase. (5) In beef heart mitochondria, a spin-labelled analog of the inhibitor, dicyclohexyl carbodiimide, did not show any change in environment upon butanol addition, unlike that found in mitochondria from Saccharomyces cerevisiae.

Adenosine Triphosphatases↗
PubMedDate not supplied

Interaction of lipid and carbohydrate metabolism after infusions of lipids or of lipid lowering agents: lack of a direct relationship between free fatty acid concentrations and glucose disposal.

The present work was planned to study the effects of changes in lipid metabolism irrespective of FFA concentrations (FFA) on the regulation of oxidative and nonoxidative disposal of a glucose infusion during hyperinsulinaemia. Fifteen normal volunteers participated in the 3 protocols, in which 1) Intralipid 2) beta-pyridylcarbinol or 3) isotonic saline were infused during 2 hours. Thereafter, these infusions were discontinued and a two-hour euglycaemic hyperinsulinaemic clamp was performed. All three studies were carried out in combination with indirect calorimetry to measure glucose uptake, and oxidative and nonoxidative glucose disposal (corresponding essentially to glucose storage). Plasma FFA concentrations were 508 +/- 34, 601 +/- 43 and 546 +/- 45 mumol/l in the basal state during the Intralipid, beta-pyridylcarbinol and control protocols. It increased to 960 +/- 71 mumol/l after the Intralipid infusion, fell to 246 +/- 17 mumol/l after the beta-pyridylcarbinol infusion, vs 600 +/- 48 mumol/l in the control. At the end of the glucose-insulin clamp the values were low in the 3 protocols: 263 +/- 17, 233 +/- 19 and 204 +/- 14 mumol/l. Intralipid infusion prior to the clamp protocol induced a suppression of both insulin-mediated glucose uptake (4.91 +/- 0.46 (Intralipid) vs 6.83 +/- 0.63 mg.kg-1.min-1 (saline)) and storage (1.61 +/- 0.34 vs 2.99 +/- 0.53 mg.kg-1.min-1) while beta-pyridylcarbinol infusion induced an increased insulin-mediated glucose uptake (8.58 +/- 0.37 mg.kg-1.min-1) and in glucose storage (4.29 +/- 0.31 mg.kg-1.min-1) (p less than 0.5 vs Intralipid). These changes occurred even though FFA plasma concentrations were similar in the 3 experimental conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Black lipid membranes of tetraether lipids from Thermoplasma acidophilum.

Black lipid membranes were formed of tetraether lipids from Thermoplasma acidophilum and compared to the bilayer forming lipids diphytanoylphosphatidylcholine and diphythanylglucosylglycerol. Bilayer-forming lipids varied in thickness of black lipid membranes due to the organic solvent used. Measurements of the specific membrane capacitance (Cm = 0.744 microF/cm2) showed that the membrane-spanning tetraether lipids from Thermoplasma acidophilum form a monolayer of a constant thickness of 2.5-3.0 nm no matter from which solvent. This finding corresponds to the results of Gliozzi et al. for the lipids of another archaebacterium, Sulfolobus solfataricus. Black lipid membranes were formed at room temperature with a torus from bilayer-forming lipids, however, the torus could also be formed by the tetraether-lipid itself at room temperature and at defined concentration. In these stable black lipid membranes, conductance was measured in the presence of valinomycin, nonactin, and gramicidin. At 10(-7) M concentration, valinomycin mediated higher conductance in membranes from tetraether lipids (200-1200 microS/cm2) than from bilayer-forming lipids (125-480 microS/cm2). Nonactin, at 10(-6) M concentration, mediated a 6-fold higher conductance in a tetraether lipid membrane than in a bilayer, whereas conductance, in the presence of 5 x 10(-11) M gramicidin could reach higher values in bilayers than in tetraether lipid monolayers of comparable thickness. Monensin did not increase the conductance of black lipid membranes from tetraether lipids under all conditions applied in our experiments. Poly(L-lysine) destroyed black lipid membranes. Lipopolysaccharides from Thermoplasma acidophilum were not able to form stable black lipid membranes by themselves. The lipopolysaccharide complexes from Thermoplasma acidophilum and from Escherichia coli decreased the valinomycin-mediated conductance of monolayer and bilayer membranes. This influence was stronger than that of the polysaccharide dextran.

Electric Conductivity↗
PubMed1991

Acquisition of membrane lipids by differentiating glyoxysomes: role of lipid bodies.

Glyoxysomes in cotyledons of cotton (Gossypium hirsutum, L.) seedlings enlarge dramatically within 48 h after seed imbibition (Kunce, C.M., R.N. Trelease, and D.C. Doman. 1984. Planta (Berl.). 161:156-164) to effect mobilization of stored cotton-seed oil. We discovered that the membranes of enlarging glyoxysomes at all stages examined contained a large percentage (36-62% by weight) of nonpolar lipid, nearly all of which were triacylglycerols (TAGs) and TAG metabolites. Free fatty acids comprised the largest percentage of these nonpolar lipids. Six uncommon (and as yet unidentified) fatty acids constituted the majority (51%) of both the free fatty acids and the fatty acids in TAGs of glyoxysome membranes; the same six uncommon fatty acids were less than 7% of the acyl constituents in TAGs extracted from cotton-seed storage lipid bodies. TAGs of lipid bodies primarily were composed of palmitic, oleic, and linoleic acids (together 70%). Together, these three major storage fatty acids were less than 10% of both the free fatty acids and fatty acids in TAGs of glyoxysome membranes. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) constituted a major portion of glyoxysome membrane phospholipids (together 61% by weight). Pulse-chase radiolabeling experiments in vivo clearly demonstrated that 14C-PC and 14C-PE were synthesized from 14C-choline and 14C-ethanolamine, respectively, in ER of cotyledons, and then transported to mitochondria; however, these lipids were not transported to enlarging glyoxysomes. The lack of ER involvement in glyoxysome membrane phospholipid synthesis, and the similarities in lipid compositions between lipid bodies and membranes of glyoxysomes, led us to formulate and test a new hypothesis whereby lipid bodies serve as the dynamic source of nonpolar lipids and phospholipids for membrane expansion of enlarging glyoxysomes. In a cell-free system, 3H-triolein (TO) and 3H-PC were indeed transferred from lipid bodies to glyoxysomes. 3H-PC, but not 3H-TO, also was transferred to mitochondria in vitro. The amount of lipid transferred increased linearly with respect to time and amount of acceptor organelle protein, and transfer occurred only when lipid body membrane proteins were associated with the donor lipid bodies. 3H-TO was transferred to and incorporated into glyoxysome membranes, and then hydrolyzed to free fatty acids. 3H-PC was transferred to and incorporated into glyoxysome and mitochondria membranes without subsequent hydrolysis. Our data are inconsistent with the hypothesis that ER contributes membrane lipids to glyoxysomes during postgerminative seedling growth.(ABSTRACT TRUNCATED AT 400 WORDS)

Biological Transport↗
PubMed1990

Interaction of endotoxic lipid A and lipid X with purified human platelet protein kinase C.

Lipid A, the toxic principle of endotoxic lipopolysaccharide, and its precursor, Lipid X, interact with human platelets and modulate protein kinase C therein (Grabarek, J., Timmons, S., and Hawiger, J. (1988) J. Clin. Invest. 82, 964-971). We have now purified protein kinase C from human platelets and studied its interaction with endotoxic Lipids A and X. Protein kinase C-dependent phosphorylation of histone III-S was increased 15 times in the presence of Lipid A and 300 microM Ca2+. The Ca2+ requirement for such activation was lower when 4 beta-phorbol 12-myristate 13-acetate (PMA) or 1,2-diolein were added. Lipid A also induced autophosphorylation of protein kinase C, and its activation was enhanced by phosphatidylserine without reducing the Ca2+ requirement. Kinetic analysis of protein kinase C activation induced by Lipid A, in regard to ATP as a substrate, demonstrated that Lipid A increased the rate of the reaction (Vmax) without modifying the affinity of the enzyme (Km) for the substrate. Lipid X inhibited the activation of the enzyme induced by Lipid A. Lipid X also inhibited protein kinase C activation by phosphatidylserine, 1,2-diolein, and PMA. However, 10 times more of Lipid X was required for 50% inhibition (IC50) when PMA was used as an activator of protein kinase C in the presence of phosphatidylserine than when Lipid A and 1,2-diolein were used. These results support the hypothesis that endotoxic Lipid A and Lipid X exert their biological effect in platelets through direct interactions with protein kinase C.

Blood Platelets↗
PubMed2026

Management of complex lipid disorders in a community lipid clinic setting: Implementing a multidisciplinary model.

BACKGROUND: Large treatment gaps exist in the management of lipid disorders, and many high-risk patients have factors that complicate management efforts. While lipid clinics exist within academic medical centers, most of these patients are cared for in community settings. OBJECTIVE: To report our experience and results managing challenging and complex lipid disorders in a community-based lipid clinic. METHODS: We established a specialized lipid clinic in a community medical setting, with a focus on patients with management challenges and/or suspicion of a genetic lipid disorder, employing a multidisciplinary approach to optimize patient outcomes, emphasizing appropriate medical therapies and lipid genetic testing in selected patients. Retrospective electronic health record data were collected to analyze patient characteristics, treatment patterns, and lipid results. RESULTS: Over the period 2022 through 2024, 183 patients were seen (mean 63 years, 62% female). The challenging nature of the patient population was highlighted by high rates of statin intolerance (50%), no lipid medical therapy at baseline (50%), and comorbidities (atherosclerotic cardiovascular disease [ASCVD], diabetes, and/or hypertension-61%). Despite this, over a mean follow-up of 9.4&#xa0;&#xb1;&#xa0;7.3 months, we observed a mean low-density lipoprotein cholesterol&#xa0;decrease of 49&#xa0;mg/dL (-24.5%, P&#xa0;<&#xa0;.001), along with significant decreases in total cholesterol and triglycerides. Pathogenic dyslipidemia genetic variants were discovered in 21 patients (of 105 tested). Significant lipid improvements in the whole cohort, as well as multiple subgroups, were associated with greater utilization of combination therapies. CONCLUSION: Patients with complex lipid disorders can be successfully managed within a specialized lipid clinic in community medical settings. Applying such a multidisciplinary model outside of traditional academic medical centers offers the potential to raise the level of lipid management and ASCVD prevention more broadly in larger populations.

Combination medical therapy↗
PubMed1991

Effect of dietary lipid and vitamin E on mitochondrial lipid peroxidation and hepatic injury in the bile duct-ligated rat.

To assess whether lipid peroxidation of hepatic mitochondria is associated with cholestatic hepatic injury we examined the effect of bile duct ligation (BDL) versus sham surgery on mitochondrial lipids of rats maintained on one of seven diets. Diets included vitamin E-deficient (E-) and vitamin E-sufficient (E+) combined with normal lipid (11.9% calories as stripped corn oil), high lipid (35% calories as stripped corn oil), or n-3 fatty acid (fish oil) supplementation. Rats were killed 17 days after surgery, mitochondria were isolated by differential centrifugation, and lipid-conjugated dienes and thiobarbituric acid-reacting substances (TBARS) were measured in mitochondrial lipids as indices of lipid peroxidation. BDL resulted in significant increases in lipid peroxidation in all dietary groups. The E- high lipid diets (with either corn oil or fish oil) were associated with higher lipid peroxide and serum bilirubin values in BDL rats compared to the normal lipid diets. Fish oil supplementation did not ameliorate cholestatic or oxidative injury. Serum alanine aminotransferase, bilirubin, alkaline phosphatase, and cholylglycine levels correlated significantly with levels of mitochondrial conjugated dienes and TBARS. These data suggest that free radical stress occurs during BDL in the rat and may result in mitochondrial lipid peroxidation, and that diets high in lipid may increase free radical damage to hepatic mitochondria. The role of free radicals in cholestatic hepatic injury requires further investigation.

Administration, Oral↗
PubMed1977

Lipid A antiserum-mediated protection against lipopolysaccharide- and lipid A-induced fever and skin necrosis.

The antiendotoxic activity of lipid A antiserum was studied in rabbits, using lipid A (lipopolysaccharide)-induced fever and skin necrosis as test systems. It was found that lipid A antiserum had no significant antipyretic effect when it was incubated with lipid A or injected intravenously before lipid A challenge. However, in animals that were pretreated (day 0) with a single dose of lipid A (lipopolysaccharide), a significant protective effect of passively transferred antiserum (day 1) to lipid A (lipopolysaccharide fever) (day 2) was observed. Also, the lipid A (lipopolysaccharide)-induced local shwartzman reaction could be prevented by lipid A antiserum. In the fever system, the degree of protection depended on the preparative and the challenge doses as well as on the amount of antiserum transferred. The fever protection mediated by lipid A antiserum seemed to be lipid A (lipopolysaccharide) specific with regard to both the preparative and the challenge injections. Lipid A specificity of the protective factor present in the antiserum was indicated by the fauggest that the factor might be identical with lipid A-specific immunoglobulin. The significance of the preparative injection is not understood at the present time. Iti is concluded, however, that in the fever protection system described, besides specific humoral factors, other factors, perhaps cellular, are involved.

Animals↗
PubMed1977

Lipids of cultured hepatoma cells: VIII. Utilization of D-[1-14C] glucose for lipid biosynthesis.

Minimal deviation hepatoma 7288C cells (HTC) were incubated in serum-supplemented and serum-free Swim's 77 medium in the presence of D-[1-14C] glucose for 1, 2, 4, 8, 12 and 24 hr. Glucose oxidation to CO2, incorporation into total cell mass, and incorporation into cell and medium lipids were determined. The percentage distribution of total cell lipid radioactivity in individual neutral and polar lipid classes was followed as a function of time. Degradation studies of individual lipid classes were performed to ascertain the percentage of radioactivity in acyl and glycerol moieties. The percentage of D-[1-14C] glucose oxidized to 14CO2, incorporated into cell matter and cell lipids was elevated in cells incubated in serum-free medium as opposed to serum-supplemented medium. The percentage distribution of total cell lipid radioactivity into individual neutral lipid classes from both serum-free and serum-supplemented cultures was as follows: sterols greater than triglycerides greater than free fatty acids greater than sterol esters. The percentage distribution of total cell lipid radioactivity into individual polar lipid classes of serum-supplemented cultures was as follows: phosphatidylcholine greater than phosphatidylinositol greater than sphingomyelin greater than phosphatidylethanolamine greater than phosphatidylserine. The distribution of glucose radiolabel into individual polar lipid classes of serum-free HTC cells was different from their serum-supplemented counterparts: sphingomyelin greater than phosphatidylcholine greater than phosphatidylinositol greater than phosphatidylethanolamine greater than phosphatidylserine. Glycerol from glyceride classes contained a higher percentage of radioactivity than the acyl moieties, with this percentage significantly elevated in serum-free cultures. The data indicate that, although glucose is a substrate for HTC cell lipids, other precursors present in the culture system also contribute to the lipid constituency of this hepatoma cell line.

Blood↗
PubMed1978

The role of lipid components of the diet in the regulation of the fatty acid composition of the rat liver endoplasmic reticulum and lipid peroxidation.

The fatty acid compositions of the lipids and the lipid peroxide concentrations and rates of lipid peroxidation were determined in suspensions of liver endoplasmic reticulum isolated from rats fed on synthetic diets in which the fatty acid composition had been varied but the remaining constituents (protein, carbohydrate, vitamins and minerals) kept constant. Stock diet and synthetic diets containing no fat, 10% corn oil, herring oil, coconut oil or lard were used. The fatty acid composition of the liver endoplasmic reticulum lipid was markedly dependent on the fatty acid composition of the dietary lipid. Feeding a herring-oil diet caused incorporation of 8.7% eicosapentaenoic acid (C(20:5)) and 17% docosahexaenoic acid (C(22:6)), but only 5.1% linoleic acid (C(18:2)) and 6.4% arachidonic acid (C(20:4)), feeding a corn-oil diet caused incorporation of 25.1% C(18:2), 17.8% C(20:4) and 2.5% C(22:6) fatty acids, and feeding a lard diet caused incorporation of 10.3% C(18:2), 13.5% C(20:4) and 4.3% C(22:6) fatty acids into the liver endoplasmic-reticulum lipids. Phenobarbitone injection (100mg/kg) decreased the incorporation of C(20:4) and C(22:6) fatty acids into the liver endoplasmic reticulum of rats fed on a lard, corn-oil or herring-oil diet. Microsomal lipid peroxide concentrations and rates of peroxidation in the presence of ascorbate depended on the nature and quantity of the polyunsaturated fatty acids in the diet. The lipid peroxide content was 1.82+/-0.30nmol of malonaldehyde/mg of protein and the rate of peroxidation was 0.60+/-0.08nmol of malonaldehyde/min per mg of protein after feeding a fat-free diet, and the values were increased to 20.80nmol of malonaldehyde/mg of protein and 3.73nmol of malonaldehyde/min per mg of protein after feeding a 10% herring-oil diet in which polyunsaturated fatty acids formed 24% of the total fatty acids. Addition of alpha-tocopherol to the diets (120mg/kg of diet) caused a very large decrease in the lipid peroxide concentration and rate of lipid peroxidation in the endoplasmic reticulum, but addition of the synthetic anti-oxidant 2,6-di-t-butyl-4-methylphenol to the diet (100mg/kg of diet) was ineffective. Treatment of the animals with phenobarbitone (1mg/ml of drinking water) caused a sharp fall in the rate of lipid peroxidation. It is concluded that the polyunsaturated fatty acid composition of the diet regulates the fatty acid composition of the liver endoplasmic reticulum, and this in turn is an important factor controlling the rate and extent of lipid peroxidation in vitro and possibly in vivo.

Animals↗