Quantitation of serum lipids by a simple TLC-charring method

Effect of Sublethal Copper Overload on Cholesterol De Novo Synthesis in Undifferentiated Neuronal Cells

Although copper (Cu) is an essential trace metal for cells, it can induce harmful effects as it participates in the Fenton reaction. Involuntary exposure to Cu overload is much more common than expected and has been linked with neurodegeneration, particularly with Alzheimer's disease (AD) evidenced by a positive correlation between free Cu in plasma and the severity of the disease. It has been suggested that Cu imbalance alters cholesterol (Chol) homeostasis and that high membrane Chol promotes the amyloidogenic processing of the amyloid precursor protein (APP) secreting the β-amyloid (Aβ) peptide. Despite the wide knowledge on the effects of Cu in mature brain metabolism, the consequence of its overload on immature neurons remains unknown. Therefore, we used an undifferentiated human neuroblastoma cell line (SH-SY5Y) to analyze the effect of sublethal concentrations of Cu on 1- de novo Chol synthesis and membrane distribution; 2-APP levels in cells and its distribution in membrane rafts; 3-the levels of Aβ in the culture medium. Our results demonstrated that Cu increases reactive oxygen species (ROS) and favors Chol de novo synthesis in both ROS-dependent and independent manners. Also, at least part of these effects was due to the activation of 3-hydroxy-3-methyl glutaryl CoA reductase (HMGCR). In addition, Cu increases the Chol/PL ratio in the cellular membranes, specifically Chol content in membrane rafts. We found no changes in total APP cell levels; however, its presence in membrane rafts increases with the consequent increase of Aβ in the culture medium. We conclude that Cu overload favors Chol de novo synthesis in both ROS-dependent and independent manners, being at least in part, responsible for the high Chol levels found in the cell membrane and membrane rafts. These may promote the redistribution of APP into the rafts, favoring the amyloidogenic processing of this protein and increasing the levels of Aβ.

Protein and lipid species in seminal plasma of fertile Holstein-Friesian bulls

Protein and lipid molecules in seminal plasma (SP) collected from fertile bulls were investigated. Semen was collected from 10 bulls (2 ejaculates each) and examined for standard semen analysis. Raw SP was recovered by centrifugation and total protein (TP) concentration was determined using a refractometer. Raw SP was desalted using a Sephadex G-25 desalting column then both raw and desalted SP was subjected to SDS-PAGE. Neutral lipids and phospholipids of raw and desalted SP were separated by thin-layer chromatography (TLC). The results revealed that, all bulls had normal semen characteristics and TP concentration in SP ranged from 7.0 to 10.4 g/dL except bull No. 6 had a relatively low concentration of 4.9 to 6.8 g/dL. Neither proteins nor lipids species were different between raw and desalted SP. Seventeen proteins were detected ranging from 8.5 to 185.8 kDa, and those of 12, 13.5, 15, 21, 23 and 38 kDa were predominant. Notably, proteins of 10, 17.5, 19, 21, 80 and 185.8 kDa might be new candidates of SP proteins (SPPs). The detected neutral lipid spots corresponded to cholesterol, 1,2-dimyristoyl glycerol, 1,2-dioleoyloglycerol, 1,3-dimyristoyl glycerol and 1,3-dioleoyloglycerol. The detected phospholipids spots corresponded to non-migrating phospholipids, sphingomyelin (SM), phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylinositol (PI), phosphatidylethanolamine (PE), cerebroside and polyglycerol phosphatide. Cholesterol represents the major molecule of neutral lipids, whereas SM, PC, PI and PE represent the major phospholipids. Noteworthy, there were 2 species of diacylglycerol (DAG) and 3 species of PI in bovine SP. In conclusion, this study gave a general picture of SP protein and lipid species in fertile bull semen, which might serve as fundamental knowledge for either semen analysis or prediction of male fertility.

Analytical Techniques in Lipidomics: State of the Art

Current studies related to lipid identification and determination, or lipidomics in biological samples, are one of the most important issues in modern bioanalytical chemistry. There are many articles dedicated to specific analytical strategies used in lipidomics in various kinds of biological samples. However, in such literature, there is a lack of articles dedicated to a comprehensive review of the actual analytical methodologies used in lipidomics. The aim of this article is to characterize the lipidomics methods used in modern bioanalysis according to the methodological point of view: (1) chromatography/separation methods, (2) spectroscopic methods and (3) mass spectrometry and also hyphenated methods. In the first part, we discussed thin layer chromatography (TLC), high-pressure liquid chromatography (HPLC), gas chromatography (GC) and capillary electrophoresis (CE). The second part includes spectroscopic techniques such as Raman spectroscopy (RS), Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR). The third part is a synthetic review of mass spectrometry, matrix-assisted laser desorption/ionization (MALDI), hyphenated methods, which include liquid chromatography-mass spectrometry (LC-MS), gas chromatography-mass spectrometry (GC-MS) and also multidimensional techniques. Other aspects are the possibilities of the application of the described methods in lipidomics studies. Due to the fact that the exploration of new methods of lipidomics analysis and their applications in clinical and medical studies are still challenging for researchers working in life science, we hope that this review article will be very useful for readers.

Biomarkers of prolonged exposure to microcystin-LR in mice

The effects of prolonged exposure to microcystins (MCs) on health are not yet sufficiently understood and this type of poisoning is often undiagnosed. Even though chronic exposure has been linked with liver cancer and alterations have been described in liver damage marker enzymes in exposed populations, there are not profile parameters that indicate prolonged exposure to microcystins. The aim of this work is to determine, based on an animal model of prolonged exposure to successive i.p. doses of 25 μg MC-LR/kg body weight, several plasma parameters which could be useful as exposure biomarkers. Hemoglobin (Hb) and methemoglobin (MetHb) levels were determined on blood samples. We also studied plasma levels of hydroperoxides (ROOHs), α-tocopherol, glutathione and lipid profile as well as superoxide dismutase (SOD) and catalase (CAT) erythrocyte activities. In addition, the determination of MC-LR levels in liver, kidney, plasma, urine and feces of treated mice was carried out. We found that alteration in MetHb, ROOHs, glutathione, α-tocopherol levels, SOD activity and plasma lipid profile, correlates with those expected if the alteration derived from hepatic damage. The alterated plasma paramenters together with MC-LR determination could be used as biomarkers, helpful tools in screening and epidemiological studies.

Lipid analysis by thin-layer chromatography--a review of the current state

High-performance thin-layer chromatography (HPTLC) is a widely used, fast and relatively inexpensive method of separating complex mixtures. It is particularly useful for smaller, apolar compounds and offers some advantages over HPLC. This review gives an overview about the special features as well as the problems that have to be considered upon the HPTLC analysis of lipids. The term "lipids" is used here in a broad sense and comprises fatty acids and their derivatives as well as substances related biosynthetically or functionally to these compounds. After a short introduction regarding the stationary phases and the methods how lipids can be visualized on an HPTLC plate, the individual lipid classes will be discussed and the most suitable solvent systems for their separation indicated. The focus will be on lipids that are most abundant in biological systems, i.e. cholesterol and its derivates, glycerides, sphingo- and glycolipids as well as phospholipids. Finally, a nowadays very important topic, the combination between HPTLC and mass spectrometric (MS) detection methods will be discussed. It will be shown that this is a very powerful method to investigate the identities of the HPTLC spots in more detail than by the use of common staining methods. Future aspects of HPTLC in the lipid field will be also discussed.

Effect of pesticides on cell survival in liver and brain rat tissues

Pesticides are the main environmental factor associated with the etiology of human neurodegenerative disorders such as Parkinson's disease. Our laboratory has previously demonstrated that the treatment of rats with low doses of dimethoate, zineb or glyphosate alone or in combination induces oxidative stress (OS) in liver and brain. The aim of the present work was to investigate if the pesticide-induced OS was able to affect brain and liver cell survival. The treatment of Wistar rats with the pesticides (i.p. 1/250 LD50, three times a week for 5 weeks) caused loss of mitochondrial transmembrane potential and cardiolipin content, especially in substantia nigra (SN), with a concomitant increase of fatty acid peroxidation. The activation of calpain apoptotic cascade (instead of the caspase-dependent pathway) would be responsible for the DNA fragmentation pattern observed. Thus, these results may contribute to understand the effect(s) of chronic and simultaneous exposure to pesticides on cell survival.

Ameliorating effect of capsaicin on alterations in lipid metabolism during mice lung carcinoma

Spices and vegetables possess antioxidant activity that can be applied for preservation of lipids and lower lipid peroxidation in biological systems. In the present study, we have investigated the effect of capsaicin on lipid metabolism during benzo(a)pyrene induced lung cancer in Swiss albino mice. Benzo(a)pyrene (50 mg/kg wt) induced lung cancer animals showed abnormal changes in the tissue and serum lipids, lipoproteins and lipid metabolizing enzymes. Treatment with capsaicin (10 mg/kg body wt) remarkably attenuated all the above alterations and restored normalcy. These findings reveal the chemomodulatory potential of capsaicin in attenuating the alterations in lipid metabolism during experimental lung carcinogenesis.

Comparison of the effects of dietary fish oils with different n-3 polyunsaturated fatty acid compositions on plasma and liver lipids in rats

The effects of dietary fish oils with different n-3 polyunsaturated fatty acid compositions on plasma lipid profiles in rats have been studied. Forty-eight male rats, previously maintained on a cholesterol-free diet for 15 days, were fed for 60 days with diets supplemented with 10% fat of either marine hilsa fish (Hilsa ilisa, family clupeidae) or fresh-water chital fish (Notopterus chitala, family notopteridae). The diets had similar levels of total saturated (35-41%), monounsaturated (43-47%) and n-3 polyunsaturated (9-10%) fatty acids. Cholesterol contents of the diets were adjusted to 0.85%; gamma-linolenic acid (3.3%) in chital oil and eicosapentaenoic acid (4.9%) in hilsa oil diets were the major n-3 contributors. The percentage of eicosapentaenoic acid in the chital oil diet was 0.57 times that of the hilsa oil diet, but the eicosapentaenoic (EPA) to arachidonic acid (AA) ratio in the latter (4.08) was 3.2 times that of the former (1.27). Sixty days of hilsa oil diet feeding decreased the levels of cholesterol (53.3 +/- 2.9 to 50.0 +/- 1.1 mg/dL), triacylglycerol (75.7 +/- 3.8 to 64.3 +/- 2.6 mg/dL) and phospholipid (55.8 +/- 1.5 to 51.7 +/- 3.1 mg/dL) in rat plasma. Similar treatment with chital oil diet elevated the plasma cholesterol level (53.3 +/- 2.9 to 62.3 +/- 7.6 mg/dL) while triacylglycerol and phospholipid contents remained unaltered. Both the dietary treatments decreased the levels of linoleic and arachidonic acids in liver but only under the hilsa oil diet did the eicosapentaenoic acid percentage increase markedly (0.8 +/- 0.06% to 5.5 +/- 0.06%) at the expense of arachidonic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

High-performance liquid chromatographic determination of cholesteryl esters in the blood of obese children

The serum of obese children and adolescents was analyzed for cholesteryl esters. The test substances were first separated from the sample matrix by solvent extraction and thin-layer chromatography and then resolved in a reversed-phase high-performance liquid chromatographic system involving a Separon SGX C18 column and a mobile phase of 2-propanol-acetonitrile (40:60, v/v), with ultraviolet detection at 206 nm. Cholesterol and 10-cholesteryl esters could be separated and determined within ca. 25 min at a flow-rate of 1 ml/min. The method was applied to a study of the effect of external conditions (physical stress, diet) on the content of cholesteryl esters in a test group of obese boys and girls aged from 13 to 16 years. The analyses have demonstrated that the above conditions do not affect the concentrations of the individual cholesteryl esters, although the total cholesterol concentration decreased significantly after spa treatment.

Determination of alpha-tocopherol, free cholesterol, esterified cholesterols and triacylglycerols in human lipoproteins by high-performance liquid chromatography

The determination of alpha-tocopherol, free cholesterol, esterified cholesterols and triacylglycerols in human plasma and in fractions containing individual lipoproteins was achieved by reversed-phase high-performance liquid chromatography (HPLC). The lipoprotein fractions, such as chylomicron, VLDL, LDL, HDL2 and HDL3, were collected by ultracentrifugation of human plasma. The chromatographic separation was accomplished with a column packed with Hitachi Gel 3057, which is a spherical octadecylsilica of particle size 3 microns. The mobile phase was acetonitrile-2-propanol (75:25, v/v), and the eluate was monitored with ultraviolet absorption and fluorescence detectors connected in series. Qualitative analysis of the main chromatographic peaks collected during the HPLC of a plasma sample was done with the use of field-desorption mass spectrometry. The determination analysis of alpha-tocopherol, free cholesterol and esterified cholesterols was effected with a single chromatographic run with n-hexane extracts of plasma or lipoprotein fraction. The separation and determination of these fat-soluble components required as little as 5 microliters of plasma or lipoprotein fraction.

Effect of dietary fat saturation and cholesterol on LDL composition and metabolism. In vivo studies of receptor and nonreceptor-mediated catabolism of LDL in cebus monkeys

The mechanism(s) by which polyunsaturated fats reduce low density lipoprotein (LDL) cholesterol and apolipoprotein (apo) B were investigated in 20 cebus monkeys (Cebus albifrons) fed diets containing corn oil or coconut oil as fat (31% of calories) with or without dietary cholesterol (0.1% by weight) for 3 to 10 years. Coconut-oil feeding compared to corn-oil feeding resulted in significant increases in levels of plasma total cholesterol (176%), very low density lipoprotein (VLDL)-LDL cholesterol (236%), high density lipoprotein (HDL) cholesterol (148%), apo B (78%), and apo A-I (112%). The addition of dietary cholesterol to corn oil compared to corn oil alone resulted in smaller, but significant, increases in levels of total cholesterol (44%), HDL cholesterol (40%), and apo A-I (33%). Although the increases in VLDL-LDL cholesterol were of similar magnitude (52%), they barely failed to reach statistical significance (p less than 0.08), while the changes in apo B levels were negligible. The addition of dietary cholesterol to coconut oil, compared to coconut oil alone, resulted in no significant changes in lipoprotein cholesterol or apoproteins, although levels of VLDL-LDL cholesterol and apo B values increased 22% and 16%, respectively. Although hepatic free cholesterol content was not altered by diet, coconut-oil compared to corn-oil feeding resulted in significant increases in hepatic cholesteryl esters (236%) and triglycerides (325%), the latter increasing still further when dietary cholesterol was added to coconut oil (563%). To further assess the effects of these dietary changes on LDL metabolism, radioiodinated normal and glucosylated LDL kinetics were performed. The production rate of LDL apo B was not altered by diet. With corn-oil feeding, 63% of LDL catabolism was via the receptor-mediated pathway. Coconut-oil compared to corn-oil feeding resulted in a 50% decrease in receptor-mediated LDL apo B fractional catabolic rate (FCR) and a 27% reduction in nonreceptor-mediated LDL apo B FCR. The addition of dietary cholesterol to corn oil, compared to corn oil alone, resulted in no significant effect on LDL apo B catabolism. The addition of dietary cholesterol to coconut oil, compared to coconut oil alone, was associated with no significant change in nonreceptor catabolism of LDL apo B but with a 58% decrease in receptor-mediated catabolism of LDL (p less than 0.059). The diet-induced alterations of LDL catabolism were significantly correlated with hepatic lipids, which were enriched in saturated fatty acids.(ABSTRACT TRUNCATED AT 400 WORDS)

Binding of straight-chain saturated dicarboxylic acids to albumin

Dicarboxylic acids are prominent features of several diseases, including Reye's syndrome. Long-chain dicarboxylic acids have profound effects on the function and structure of isolated mitochondria, suggesting that they could contribute to the mitochondrial dysfunction in Reye's syndrome. Binding of fatty acids to albumin and the intracellular fatty acid-binding proteins is important in regulating the transport and metabolism of fatty acids and protects against the toxic effects of unbound fatty acids. We studied the binding of dicarboxylic acids to defatted albumin using equilibrium dialysis to assess to what extent dicarboxylic acids are likely to be bound in the plasma of patients. Dicarboxylic acids bind weakly to albumin in a molar ratio of 3.8, 4.2, 1.6, 0.8, and 0.7 to 1 for octadecanedioic, hexadecanedioic, tetradecanedioic, dodecanedioic, and decanedioic acid, respectively. The dissociation constants for long-chain dicarboxylic acids are 100-1,000-fold larger than those of comparable monocarboxylic acids. Oleate competes with dicarboxylic acid and reduces the moles of dicarboxylic acid bound per mol of albumin to less than 1. Octanoate inhibits dicarboxylic acid binding. Our observations indicate that in Reye's syndrome, substantial concentrations of dicarboxylic acids of patients may be free and potentially toxic to mitochondria and other cellular processes.

Comparison of fatty acid and triacylglycerol metabolism of macrophages and smooth muscle cells

The response of macrophages and smooth muscle cells to culture in free fatty acid has been compared. Because oleate and linoleate promoted triacylglycerol enrichment of smooth muscle cells, whereas palmitate had little effect, oleate was used for these studies. The kinetics of the accumulation of triacylglycerol produced by oleate was comparable between smooth muscle cells and macrophages. When grown in increasing concentrations of oleic acid at various fatty acid to albumin molar ratios, the extent of triacylglycerol accumulation in both cell types was dependent on the concentration of oleate, the concentration of albumin, and the oleate to albumin molar ratio. However, macrophages contained 2.6-fold more triacylglycerol than smooth muscle cells in the presence of oleate at 0.36 mM or greater and at levels of albumin higher than 0.15 mM. The cellular triacylglycerol content of macrophages was linearly related to the oleate to albumin molar ratio at both a constant albumin concentration and a constant oleate concentration, whereas the accumulation of triacylglycerol in smooth muscle cells showed a curvilinear relationship. When cells were preloaded with triacylglycerol, smooth muscle cells showed a greater loss of lipid when exposed to albumin than macrophages did. Over a two-hr time period, macrophages incorporated twice as much labeled fatty acid as smooth muscle cells. Thus, while smooth muscle cells and macrophages showed similar responses to exogenous fatty acid and albumin, there were also significant quantitative distinctions.

The sympathetic nervous system and atherosclerosis

Morphometric and chemical changes in the arterial wall were studied after 12 months of diet-induced atherosclerosis in rhesus monkeys treated with either bilateral surgical thoracic sympathectomy or propranolol. There was a marked reduction in the progression of atherosclerosis in the carotid arteries and a moderate reduction in the disease found in the thoracic aorta of monkeys treated initially with a sympathectomy, in comparison to control monkeys fed an atherogenic diet alone. Propranolol at a dose of 40 mg/12 hrs also seemed to reduce the progression of atherosclerosis in the carotid arteries and thoracic aorta, although the differences were less dramatic. There were minimal differences in the extent of atherosclerosis in the abdominal aorta or femoral arteries of animals in either treatment group as compared with the control group. Similarly, the chemical composition of these same major vessels showed no significant differences. Therefore, in the face of severe atherogenic stimuli, chemical or surgical sympathectomy may be useful in controlling atherosclerosis in specific arterial beds.

Egg size, postembryonic yolk, and survival ability

Neonates of many species are dependent upon a post-embryonic yolk (PEY), a residual of the energy reserve of the developing embryo. Offspring hatching from large eggs have relatively more PEY than offspring from small eggs. Among daphniid Cladocera, large species produce larger eggs than smaller species. We have found that the proportional amount of energy reserve in eggs of five species of Cladocera is similar, but neonates of the larger Cladocera are born with a greater relative amount of postembryonic yolk, as triacylglycerol, than small species. Apparently, more of the reserve is metabolized by embryos of small species. This is correlated with the higher unitweight metabolic rates of smaller animals. It has been argued that animals should produce relatively larger eggs when exposed to low or unpredictable food conditions to increase the survivorship of their offspring. The physiological constraint of greater relative energy requirements of small embryos may limit PEY and explain why offspring of larger eggs survive better in low or unpredictable food resource environments.

Serum dicarboxylic acids in patients with Reye syndrome

Reye syndrome resembles disorders of fatty acid metabolism. Analysis of serum free fatty acids from 18 patients with Reye syndrome revealed that dicarboxylic acids comprise as much as 55% (range 4% to 55%) of the patients' total free fatty acids; both medium- (6 to 12 carbon lengths) and long-chain (14 to 18 carbon lengths) dicarboxylic acids were identified. Long-chain dicarboxylic acids were not found in any control samples, whereas 86% +/- 4% of the serum dicarboxylic acids were long chain in 10 patients with Reye syndrome in state 3 to 4 coma and 31% +/- 8% in eight patients with a milder illness. The serum concentration of dicarboxylic acids correlated with the clinical state (P less than 0.001) and with the elevation in blood ammonia concentration (r2 = 0.8767). No long-chain dicarboxylic acids were found in the urine. The dicarboxylic acidemia in Reye syndrome may be secondary to the general mitochondrial dysfunction or could indicate that an insult to fatty acid metabolism or the stimulation of omega-oxidation is important in the pathogenesis of the illness. Measurement of serum dicarboxylic acids, especially long chain, may be important in assessing Reye syndrome and may prove useful in distinguishing this from other diseases.

Macrophage interaction with very-low-density lipoproteins results in triacylglycerol-enriched smooth muscle cells

Macrophage-conditioned medium containing very-low-density lipoproteins (VLDL) and its effects on smooth muscle cell triacylglycerol metabolism was investigated. Macrophages exposed to VLDL from normolipemic rats accumulated high levels of intracellular triacylglycerol, while similarly treated smooth muscle cells showed only slight changes. Medium, initially composed of VLDL and albumin, contained substantial levels of free fatty acids after exposure to macrophages. In the presence of albumin, the loss of VLDL triacylglycerol from the medium and the appearance of medium free fatty acids was consistent with a precursor-product relationship. The extent of medium fatty acid accumulation was dependent on the length of time of incubation with macrophages and was proportional to the concentration of VLDL and albumin added to the culture dish. This macrophage-conditioned medium, when given to smooth muscle cells, promoted a 6-12-fold increase in smooth muscle cell triacylglycerol levels over that produced by fresh VLDL and albumin. Similar increases in cell triacylglycerol levels could be produced using fresh medium approximating the oleate concentration and the fatty acid to albumin molar ratios found in macrophage-conditioned medium. In macrophage-conditioned medium with VLDL but without albumin, little free fatty acid was found. Other factors produced by macrophages did not seem to affect the metabolism of VLDL by smooth muscle cells since, in the absence of albumin, media with VLDL caused comparable responses in smooth muscle cell triacylglycerol accumulation whether or not the medium was previously exposed to macrophages. Thus, the minor changes in triacylglycerol content in smooth muscle cells promoted by medium containing VLDL and albumin were substantially enhanced by a prior exposure of the medium to macrophages, primarily due to the free fatty acids present in the macrophage-conditioned medium.

Effect of Reye's syndrome serum on isolated chinchilla liver mitochondria

A general impairment of liver mitochondrial enzymes is central to Reye's syndrome (RS). The respiration of isolated liver mitochondria was measured after the addition of concentrated normal serum or RS serum derived from 12 patients. RS serum stimulates oxygen consumption in isolated rat liver mitochondria. This effect is due to the oxidation of uric acid by peroxisomes contaminating the preparation and a stimulation of mitochondrial respiration (1.05 +/- 0.14 nmol of O2/min X mg of protein; control 0.30 +/- 0.08 nmol O2/min X mg). The stimulation of respiration occurs in the presence of all respiratory substrates, is dependent on the amount of serum added, and represents an uncoupling of oxidative phosphorylation. RS serum reduces ATP formation by 15-76%. The uncoupling effect correlates with the amount of free fatty acid in the serum sample and resembles the effect induced by the addition of a dicarboxylic fatty acid. Dicarboxylic fatty acids, especially long-chain dicarboxylic acids, impair ATP formation. Dicarboxylic acids were found in the serum of all RS patients and comprised as much as 54% of the total serum free fatty acids. 90% of the serum dicarboxylic acids were of 16-18 carbon lengths. The amount of dicarboxylic acids in the RS serum corresponded directly with the reduction in ATP formation by the RS serum. This demonstrates that dicarboxylic acids occur in RS and may be important in the general impairment of mitochondrial function in RS and other disorders where they are present.

Very low density lipoproteins promote triglyceride accumulation in macrophages

Incubation of mouse peritoneal macrophages with very low density lipoproteins (VLDL) from normal rats or rhesus monkeys markedly increased the levels of intracellular triglycerides by 10- to 56-fold and was accompanied by the production of oil red O positive vacuoles. The stimulation of triglyceride accumulation in macrophages was time- and concentration-dependent and was specific for VLDL. Three possible mechanisms for the VLDL-stimulated triglyceride accumulation in macrophages were explored: receptor-mediated uptake, action of lipoprotein lipase, and phagocytosis. Macrophage uptake and degradation of 125I-monkey and rat VLDL demonstrated saturable and nonsaturable components. Uptake of 125I-VLDL could be inhibited by unlabeled normal VLDL, although hyperlipemic VLDL was more effective. HDL did not compete to a significant extent. Heparin released lipoprotein lipase-like activity from peritoneal macrophages. Addition of heparin with VLDL resulted in a greater, more rapid elevation in intracellular triglycerides, which was partially inhibited by albumin. Free fatty acid and Intralipid also produced triglyceride accumulation in macrophages. The data showed that all three of the mechanisms examined could contribute to the metabolism of VLDL by macrophages and cause the production of triglyceride-rich cells with a "foamy" appearance, although the evidence suggested that the action of lipoprotein lipase was probably the most important in this process.

Characteristics of the aortic intima in young and old cebus and squirrel monkeys

To document naturally occurring aortic intimal changes with age in squirrel and Cebus monkeys, the aortic lipid class composition, histology, and fine structure were quantitatively compared in the two species at birth and in old age. The aortic intima plus inner media in the young squirrel monkey contained more lipid, particularly in the phospholipid and cholesterol ester fractions than in young Cebus. The lipid class composition of the old Cebus monkey aorta resembled that of the young Cebus. In the old squirrel monkey aorta, cholesteryl ester, and to a lesser extent, free cholesterol were increased over young levels, while the phospholipid concentration tended to be lower. The aortic cholesteryl ester:phospholipid ratio increased with age in both species, but the old Cebus monkey aorta maintained the ratio below unity at 0.3, whereas the old squirrel monkey aorta ratio was 2.5. The abdominal aorta of the old squirrel monkey tended to have more lipid in each class than the thoracic segment. Morphologically, the old Cebus monkey aortic intima was similar to the young Cebus in terms of the intima:media ratio, intimal cellularity, and the distribution of intimal components determined by points in electron micrographs. In both age groups the Cebus monkey aorta was characterized by diffuse intimal thickening without lipid deposits. In contrast, that old squirrel monkey aorta had a much greater intima:media ratio, especially in the abdominal aorta, and a greater intimal cellularity than the young squirrel monkey. The distribution of intimal components in electron micrographs of the old squirrel monkey aorta shifted to a predominance of extracellular lipid, smooth muscle cells, and collagen. Deposits of small dense granules, presumably the products of cellular breakdown, were observed in aortic intimas and medias of both species in old age. Thus, differences between Cebus and squirrel monkey aortic intimas were evident at birth. By old age, the Cebus monkey aortic intima remodeled without accumulating lipid, whereas the squirrel monkey developed aortic intimal lesions resembling human atherosclerosis.

Influence of dietary unsaturated and saturated fat on the plasma lipoproteins of Mongolian gerbils

Lipid and apoprotein moieties of the plasma lipoproteins of Mongolian gerbils (Meriones unguiculatus) were compared in animals fed semipurified diets containing either coconut oil (COC) or safflower oil (SAF). COC-induced hypercholesterolemia was associated with elevations in very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL). Saturated fat feeding also resulted in th saturation of fatty acids of triglycerides and cholesteryl esters of VLDL and LDL, but had little effect on HDL fatty acids. Lipoprotein composition and size were not influenced by the type of dietary fat, suggesting that the hypercholesterolemia with saturated fat feeding was due to the circulation of a greater number of lipoprotein particles. The apoproteins of gerbil lipoproteins had molecular weights comparable to other animals. The relative amounts of apoproteins, particularly the apoC peptides, increased with dietary fat saturation.

Relation between dietary fat composition and lipid metabolism in the rat

Three fats were used in a synthetic dietary formula containing 20% of its composition as fat from either lard, peanut oil or maize oil. Twelve groups of rats were included in this study, six groups served as controls; 3 from each sex. Control groups received the same dietary formula except fat content was 10%. Saturated dietary fats in male rats seems to be atherogenic while in females, increasing dietary fat to 20% gave atherogenic picture.

Comparison of the intracellular lipids of cultured vascular endothelial cells and fibroblasts

The lipids of human umbilical vein endothelial cells, calf aortic endothelial cells and foreskin fibroblasts have been compared. Cell cultures were established, and, upon confluency, the lipids were extracted and analyzed with respect to total lipid content, classes of lipids and total lipid fatty acid composition. The total quantity of lipid per milligram protein found in both human umbilical vein endothelium and calf aorta endothelium was similar to that found in fibroblasts grown in similar medium. Both types of endothelium contained the same major neutral lipid classes as fibroblasts, although they contained more phospholipid than did fibroblasts. The fatty acid composition of the three cells examined was influenced by cell type as well as the type of serum in the culture medium.

Effect of dietary fats and triiodothyronine administration on the lipid components of serum and tissues in the rat

Twelve groups of rats were included in this study. Six groups (3 males and 3 females) received high fat diets containing 20% of either peanut oil, maize oil or lard. The other six groups received the same diets plus triiodothyronine. Triiodothyronine T3 added to diets containing peanut oil caused slight increase in total serum lipids in female rats, while in male rats serum total lipids were increased about 20-fold. T3 administration caused almost no change in aortic total and all lipid fractions in male rats kept on diets containing any of the fats used. Female rats kept on lard plus T3 showed a rise in cholesterol free and esterified and phospholipid contents of aorta lipids.

Atherogenic diets and neutral-lipid organization in plasma low density lipoproteins

The plasma low density lipoproteins (LDL) of rhesus monkeys fed 3 atherogenic diets exhibited thermal transitions at temperatures much higher (37--43 degrees C) than those observed in control animals or in normal humans (20--33 degrees C). The same differences were noted in the neutral lipids (cholesteryl esters and triglycerides) which were isolated from the respective lipoproteins. In particular, the difference in thermal properties between the normal and abnormal LDLs was attributable to subtle differences in their cholesteryl ester compositions (mainly an increase in the saturated and monounsaturated fatty acid moieties), with altered triglyceride contents playing only a minor role. Thus, at body temperature, the hyperlipidemia that follows the administration of atherogenic diets is associated with a high degree of order of the neutral lipids in the core of the LDL particle. This, in turn, may be related to the atherogenicity of the abnormal lipoprotein species.

Determination of free, total, and esterified cholesterol by high-performance liquid chromatography

A method is described for measuring free, total, and esterified cholesterol in blood serum in which reversed-phase liquid chromatography is used and the eluate is monitored at 200 nm. The sample for total cholesterol is prepared according to the Abell-Kendall procedure, and for free cholesterol an extract of serum--isopropanol (1:5, v/v) is used. The column is a muBondapak C18, 10 micrometers, and the mobile phase for total cholesterol is isopropanol--acetonitrile (50:50, v/v); for free cholesterol, it is isopropanol--acetonitrile--water (60:30:10). An approximation of the free cholesterol, triglycerides, and individual cholesteryl esters is obtained from single chromatograms of isopropanol extracts of serum if the first mobile phase is used. In a comparison study with the Abell-Kendall method for total cholesterol, the correlation is excellent and the precision is acceptable.

Plasma lipid analysis by thin-layer chromatography with flame ionisation detection and quantitation

A method is presented whereby cholesterol, cholesterol ester, triacylglycerol, non-esterified fatty acid and polar lipid in plasma may be simultaneously quantitated. Following the addition of umbelliferyl palmitate as internal standard, plasma (0.1 ml) is extracted with chloroform/methanol (2 : 1, v/v). A portion of the extract is chromatographed on silica gel fused to a narrow cylindrical quartz rod. After chromatography the rod is traversed through a flame ionisation detector and the responses recorded and integrated. The procedure is shown to be sensitive, linear, reproducible and to compare well with conventional methods for the determination of plasma lipid classes.

Isolation and characterization of a larval lipoprotein from the hemolymph of Manduca sexta

1. The larval high density lipoprotein (HDL) from the hemolymph of Manduca sexta, isolated by density gradient centrifugation, contains 61% protein, 37% lipid and 2% carbohydrate. 2. The molecular weight of HDL is 6 x 10(5), with two apoproteins of 2.85 x 10(5) and 8.1 x 10(4) daltons. 3. The large apoprotein is destroyed by trypsin treatment of the particle, while the small one is not. 4. Calculations based upon size and composition show that this particle is very different in structure from mammalian lipoproteins. It is proposed that a portion of the apoprotein occupies the central core region.

The distribution and lipid composition of ultracentrifugally separated lipoproteins of young and old rat plasma

The lipoproteins of young and old Wistar rats differ markedly in distribution and chemical composition. The major differences are: (1) the presence of high levels of free and esterified cholesterol, triglycerides and free fatty acids in the lipoproteins of old rat plasma when lipids are analyzed/100 ml of plasma. However, the ratio of total cholesterol to protein mass indicates the presence of comparable cholesterol pools in all lipoprotein fractions of young and old rats excepting the d 1.063--1.21 fraction where a higher cholesterol pool in old rats is indicated. (2) The amount of sphingomyelin increases in lipoprotein fractions of old rat plasma thereby actually decreasing the lecithin/sphingomyelin ratio in these plasma fractions. (2) Unsaturated fatty acids predominate in young rat plasma lipoproteins, and saturated fatty acids predominate in old rat lipoprotein fractions. The ratio of polyunsaturated (linoleic, linolenic, arachidonic) to saturated (palmitic, stearic) fatty acids in young rat sera was 0.89 and in old rat sera, 0.55.

The effects of serum albumin and phospholipid on sterol excretion in tissue culture cells

Serum albumin was as effective as whole serum or alpha-globulins in facilitating sterol release from strain L mouse fibroblasts. Commercial bovine serum albumin preparations, however, had markedly different absolute effects in this regard. These differences were attributable to the variation in phospholipid content of these products. All but one of these albumins enhanced sterol release when supplemented with phospholipid. The exception was fatty acid-poor albumin which contained an adequate amount of phospholipid. Among the phospholipids examined, lecithin proved to be most effective, while phosphatidylethanolamine had little potentiating influence. As the unsaturation of the test lecithins increased, enhancement of sterol release decreased. The potentiating effect of the phospholipid was in turn dependent on the protein used, since the phenomenon was not observed with non-serum proteins like ovalbumin or with non-transport serum proteins such as gamma-globulins. The results of these studies raise the possibility that serum albumin together with phospholipid can play an important role in sterol release in tissue culture cells.

Lipoprotein composition in diabetes mellitus

Lipoprotein cholesterol and triglyceride levels have been determined in normal and diabetic Pima Indian women aged 20-35, HDL cholesterol levels were lower, LDL cholesterol levels were higher, and the ratio of HDL cholesterol/LDL cholesterol, a reflection of lipoprotein cholesterol distribution, was lower in the diabetics compared to the normals. VLDL triglyceride levels were also elevated in the diabetics. An analysis of lipoprotein composition suggested that these changes primarily reflect changes in numbers of particles, since lipid composition and lipid/protein ratios were similar in lipoproteins isolated from normals and diabetics. The ratio of ester/free cholesterol in LDL and HDL was lower in normal Pima Indians than in a comparable group of Caucasians, although plasma LCAT activity was not significantly different. The data indicate that diabetes may be associated with shifts in distribution of LDL and HDL, as well as with increases in VLDL.