The lipid composition of serum lipoproteins in the harbour seal, Phoca vitulina

The density profile of serum lipoproteins and their lipid composition was studied in 12 adult, female harbour seals. The animals were sampled after an approximate 20 hr fast. The density profile of lipoproteins showed that the harbour seals displayed a distinct VLDL (density less than 1.006 g/ml) and HDL band (density about 1.125 g/ml), but no clear LDL band. There was a rather diffuse population of lipoproteins in the density range of 1.019-1.100 g/ml. Mean serum total cholesterol concentration was 5.7 mmol/l; about 60% of this cholesterol was located in the HDL fraction (density greater than 1.063 g/ml). The fasted seals were found to carry 4% of serum total lipids in chylomicrons. These lipoproteins consisted of 51% of triaclyglycerols (on the basis of total chylomicron lipids). The LDL (defined as heparin-manganese precipitable lipoproteins in VLDL and chylomicron-deficient serum) contained 49% of cholesterol and 43% of phospholipids (on the basis of total LDL lipids). The HDL (defined as heparin-manganese soluble lipoproteins in VLDL and chylomicron-deficient serum) contained 36% of cholesterol and 58% of phospholipids (on the basis of total HDL lipids).     

Spin labeled lipid probes in serum lipoproteins

Observations are made relating to the local environment and motional behavior of spin labeled lipids incorporated into human serum lipoproteins. Use has been made of ascorbic acid as a spin subtracting agent to determine the accessibility of the labeled site to the aqueous region.     

Lipid composition of human serum lipoproteins

1. The lipid compositions of the low-density lipoproteins, the high-density lipoproteins and the ultracentrifugal residue of human serum are presented, with emphasis on certain lipoprotein classes and lipid components not previously described. 2. Except for the lipoproteins with the lowest and highest densities, there is a trend for stepwise successive increase or, respectively, decrease in the relative amounts of the main constituents of lipoproteins. 3. High-density lipoprotein-2 and high-density lipoprotein-3 have different amounts of certain lipids; high-density lipoprotein-2 has relatively more free cholesterol and sphingomyelin; high-density lipoprotein-3 has more free fatty acids, diglycerides and ceramide monohexosides. 4. All the lipoproteins contain hydrocarbons of the alkane series. The greatest amount, which averages 4.4% of total lipid extracted, is in the ultracentrifugal residue; n-alkanes comprise 18-50% of the hydrocarbons. 5. All the lipoproteins contain ceramide monohexosides. The highest relative contents of these glycolipids are in high-density lipoprotein-3 and in the ultracentrifugal residue. 6. The ultracentrifugal residue contains 55% of the total quantity of free fatty acids present in serum. The remaining free fatty acids are distributed among the other lipoprotein classes. 7. The choline-containing phospholipids (phosphatidylcholine, lysophosphatidylcholine and sphingomyelin) comprise about 90% of the phospholipids in all the lipoprotein classes except the low-density lipoprotein-2, which contains about 80% of these phospholipids. 8. The presence of a large amount of lysophosphatidylcholine in the ultracentrifugal residue and the successive decrease of sphingomyelin from the low-density lipoprotein-1 to the ultracentrifugal residue was confirmed. 9. The low-density lipoprotein-2 and the ultracentrifugal residue are characterized by relatively high contents of the lower glycerides.     

Effect of lipopolysaccharide toxin on lipid and protein composition of human serum low density lipoproteins

Complexes of lipopolysaccharide (LPS) B of Salmonella typhimurium with human low density lipoproteins (LDL) formed during in vitro coincubation via spontaneous incorporation of LPS (complex LDL-LPS) or through the incorporation stimulated by the serum protein fraction (LPS/LDL complex) were studied. The LPS/LDL complex was shown to maximally bind 0.24 mg of LPS per 1 mg of LDL protein, whereas the LDL-LPS complex contained only 0.07 mg of LPS per 1 mg of LDL protein. The observed incorporation of LPS into LDL particles was not possibly associated with a transfer of lipids or proteins from high density lipoproteins to LDL. The insertion of LPS was probably accompanied by the expulsion of a small portion of phosphatidylcholine molecules from the outer monolayer of LDL into the aqueous medium and by an increase in the phosphatidylethanolamine concentration in LDL. Simultaneously, the level of esterified cholesterol in the LPS/LDL complex decreased, and the concentrations of free cholesterol and triacylglycerols showed a rise. The level of free fatty acids in the LPS/LDL complex increased more than twofold compared with intact LDL. The enhancement of LPS incorporation did not result in the insertion of any serum proteins into LDL, in which apoB-100 remained the major apolipoprotein (ca. 90%); apoB-100 fragments made up to 5-7%, whereas apoE and apoC contained altogether ca. 3-5%. It is suggested that the LPS/LDL complex obtained can bind to three types of cell receptors, i.e., apoB/E receptors, LPS receptors and scavenger receptors of macrophages (monocytes); the increased level of free fatty acids in the LPS/LDL complex may accelerate its subsequent catabolism.     

Characteristics of chloroplast thylakoid lipid composition associated with resistance to triazine herbicides

A detailed comparison of the polar-lipid composition of chloroplast thylakoid membranes isolated from triazine-susceptible and triazine-resistant biotypes of Chenopodium album, Senecio vulgaris, Poa annua and Amaranthus retroflexus has been carried out. No major differences in the composition of the bulk lipid matrix were found except for a slightly higher monogalactosyldiacylglycerol to digalactosyldiacylglycerol ratio in resistant compared with susceptible biotypes. There was, however, in the case of resistant plants a higher level of phosphatidylglycerol-containing transhexadecenoic acid in membrane fractions enriched in photosystem two. It is concluded that although the minor differences could contribute to triazine resistance it is more likely that they reflect secondary alterations in membrane organisation associated with changes in relative levels of pigment-protein complexes.Abbreviations DGDG digalactosyldiacylglycerol - MGDG monogalactosyldiacylglycerol - PG phosphatidylglycerol - PSII photosystem two     

Lipid composition of cells and low-density lipoproteins in blood serum of humans and some vertebrates species

To investigate interaction of atherogenic low-density lipoproteins (LDL) with erythrocytic membrane, the content of lipid components in blood cells and serum LDL was studied in human in norm (donors) and in 12 species of vertebrates (the mammals non-predisposed to atherosclerosis - birds and fish). Lipid composition of blood cells and LDL was analyzed also in patients with pathologies: ischemic heart disease (IHD), bronchial asthma (BA), and chronic obstructive bronchitis (COB), and in 2 species of mammals predisposed to atherosclerosis, in whose blood LDL predominates. The content of lipids in cells and LDL of the studied vertebrates has been found to depend on their taxonomy and the clear trends both to an increase of the cholesterol content and to a decrease if the phosphatidylcholine level in patients, particu- larly with IHD, and on a rise of the ratio of the content of the more saturated sphingomyelin and cholesterol to the less saturated phosphatidylcholine from the lower to the higher organisms, including humans (donors). The highest levels of free cholesterol in blood cells, of total cholesterol in LDL, and of ration of the cholesterol/phosphatidylcholine content have been revealed in patients, especially with 1HB, and in the mammals predisposed to atherosclerosis, i. e., in representatives with predominance of blood LDL, unlike donors and the mammals resistant to atherosclerosis. The highest parameters of lipid components were determined in cells and LDL inhuman with IHD. The lipid LDL composition affects directly the composition and ratio of lipids in blood cells.     

Lipid composition of cells and low-density lipoproteins in blood serum of human and some vertebrate species

To establish interaction of atherogenic low-density lipoproteins (LDL) with the erythrocyte membrane, the content of lipid components in blood cells and serum LDL was studied in healthy people (donors) and in 12 species of vertebrates (the mammals non-predisposed to atherosclerosis — birds and fish). Lipid composition of blood cells and LDL was also analyzed in patients with pathologies: ischemic heart disease (IHD), bronchial asthma (BA), and chronic obstructive bronchitis (COB), as well as in 2 species of mammals predisposed to atherosclerosis, in whose blood LDL predominated. The content of lipids in the blood cells and LDL of the studied vertebrates has been found to depend on their taxonomy and on the clear trends either for an increase in the cholesterol content and a decrease in the phosphatidylcholine level in patients, particularly with IHD, or for a rise of the ratio of the content of the more saturated sphingomyelin and cholesterol to the less saturated phosphatidylcholine from the lower to the higher organisms, including humans (donors). The highest levels of free cholesterol in blood cells of total cholesterol in LDL, as well as of parameters of ratio of the cholesterol/phosphatidylcholine content have been revealed in patients, especially with IHD, and in the mammals predisposed to atherosclerosis, i.e. in representatives with predominance of blood LDL, in contrast to donors and the mammals resistant to atherosclerosis. The highest parameters of lipid components were determined in blood cells and LDL in patients with IHD. The lipid LDL composition affects directly the composition and ratio of lipids in blood cells.     

Content of the main lipid components in blood serum lipoproteins of human and of various animal species

Using precipitation method, low-density (LDL) and high-density (HDL2 and HDL3) lipoproteins were isolated from blood serum of human (donors, patients with ischemic heart) diseases--IHD, with bronchial asthma--BA, with chronic obstructive bronchitis--COB), of mammals predisposed (pig, rabbit) and resistant (rat, mink, Arctic fox) to atherosclerosis, of birds (hen, pigeon), of bony fish (trout, white-fish, pike-perch, pike, bream, burbot), and of cartilaginous fish (sturgeon, white sturgeon). From each lipoprotein group, lipids were extracted, separated by thin-layer chromatography, and analyzed quantitatively by the spectrophotometric method. In phosphatidylcholine and HDL2 cholesterol esters, bound fatty acids (FA) were determined by the method of gas-liquid chromatography. The main amount of total cholesterol has been established to be concentrated in human LDL, especially in the cases of IHD, and in LDL in mammals predisposed to atherosclerosis. In mammals resistant to atherosclerosis and in fish the almost entire cholesterol was revealed in HDL. The phospholipid content in HDL was lower in patients with pathologies and in mammals predisposed to atherosclerosis, while the highest content--in fish and mammals resistant to atherosclerosis. In homoiothermal animals and in human the main FA amount in HDL was represented by the omega6-series. Acids of the omega3-series amounted to a negligible percentage, especially in IHD. On the contrary, the HDL FA composition of poikilothermal animals (fish) had a very high content of polyunsaturated FA of the omega3-series. A conclusion is made that composition of lipid components in animal lipoproteins by the example of several studied species and of human has a non-stable character and is submitted to changes. Their most pronounced modifications with a negative trend took place in human LDL and HDL in IHD.     

Content of the main lipid components in blood serum lipoproteins of human and of some animal species

Using precipitation method, low-density (LDL) and high-density (HDL₂ and HDL₃) lipoproteins were isolated from blood serum of human (donors and patients with ischemic heart diseases—IHD, bronchial asthma—BA, chronic obstructive bronchitis—(COB) and mammals predisposed (pig, rabbit) and resistant (rat, mink, Arctic fox) to atherosclerosis, of birds (hen, pigeon), of bony fish (trout, white-fish, pike-perch, pike, bream, burbot), and of cartilaginous fish (sturgeon, white sturgeon). From each lipoprotein group, lipids were extracted, separated by thin-layer chromatography, and analyzed quantitatively by spectrophotometric method. In phosphatidylcholine and HDL₂ cholesterol esters, bound fatty acids (FA) were determined by gas-liquid chromatography. The main amount of total cholesterol has been established to be present in human LDL, especially in the cases of IHD, and in LDL in mammals predisposed to atherosclerosis. In mammals resistant to atherosclerosis and in fish the almost entire cholesterol was revealed in HDL. The phospholipid (phosphatidylcholine) was represented by the ω6-series. Acids of the ω3-series accounted for a negligible percentage, especially in IHD. On the contrary, the HDL FA composition in poikilothermal animals (fish) was characterized by a very high content of polyunsaturated FA of the ω3-series. It is concluded that by the example of several studied species and of human, composition of lipid components in animal lipoproteins has a non-stable character and is submitted to changes. Their most pronounced modifications with a negative trend were revealed in human LDL and HDL in IHD.     

Interaction of lipoproteins in blood serum with steroid hormones

Interaction of human and serum lipoproteins with steroid hormones (corticosterone and cortisol) was studied. Methods of fluorescence quenching titration and equilibrium dialysis were used for quantitative evaluation of VLDL, LDL and HDL glucocorticoid-binding ability. Association constants were found to be 0.6-2.0 x 10(6) M-1 for corticosterone and 4.0-8.0 x 10(6) M-1 for cortisol. The number of binding sites varied from 3 to 300 for different classes of lipoproteins.     

Alterations in lipid composition of plasma lipoproteins during deposition of egg yolk

The profiles of total lipids and of the molecular species of individual lipid classes were compared among corresponding lipoproteins of plasma and yolk of the laying hen. A close qualitative correspondence was found in the makeup of the molecular species of glycerophospholipids and triglycerides of the very low density lipoproteins and the high density lipoproteins of plasma and yolk. There was a lower proportion of the trienoic triglycerides and of the dienoic glycerophospholipids in the egg yolk than in the plasma lipoproteins, and the greatest differences (20-30%) were noted between the high density lipoproteins. It was also observed that the plasma high density lipoproteins lost their cholesteryl esters upon entering the yolk. On the basis of these and comparable analyses of the plasma lipoproteins of the nonlaying hen, it is concluded that the laying hen synthesizes specific lipoproteins for deposition in the yolk, and these are carried in plasma and selectively transferred to the developing ovum without significant equilibration with the other plasma lipoproteins.     

Inhibition of lipid synthesis in isolated rat hepatocytes by serum lipoproteins

The incorporation of labeled acetate into lipids was studied in rat hepatocytes isolated after treatment of liver with collagenase and hyaluronidase. About 60% of the lipid radioactivity was in free cholesterol and 13% was in triglycerides. Acetate incorporation was markedly inhibited when human serum lipoproteins were present in the incubation medium. Very low, high, and low density lipoproteins, at concentrations of 1.0 mg/ml, inhibited acetate incorporation by 70, 55, and 35%, respectively. Chylomicrons, at similar concentrations, did not inhibit acetate incorporation. The distribution of radioactivity into lipid classes was unchanged by the addition of lipoproteins. Lipoproteins did not produce a nonspecific toxic effect on hepatocytes, since their addition did not alter the rate of leucine incorporation into protein. The addition of the delipidated protein from low density lipoprotein or of lecithin in amounts comparable to those present in inhibitory concentrations of lipoproteins failed to diminish acetate incorporation. Artificial cholesterol-lecithin emulsions containing small amounts of free cholesterol did not inhibit lipid synthesis. Although the mechanism for the inhibition of acetate incorporation by lipoproteins is unclear, such effects may play some physiological role in the control of lipid biosynthesis in the liver.     

Characteristics of binding and transport of benzo(a)pyrene by blood serum lipoproteins

Binding and distribution of 3H-benzo[a]pyrene in lipoprotein fraction of rat blood serum were studied. The binding was enhanced in the row: LDL, VLDL, HDL, Kd lipoprotein-benzo[a]pyrene complexes had been calculated by means of tryptophan fluorescence quenching. It was found, that Kd value benzo[a]pyrene complexes with VLD was 1.5 x 10(-6) M, with LDL -6.6 x 10(-7) M and with HDL -4.2 x 10(-6) M. Radiolabeled benzo[a]pyrene uptake by rat organs and tissues was investigated after i.v. injection of benzo[a]pyrene-complexes with LP of different classes. High uptake activity was revealed for liver, adrenals and kidneys, whereas heart, spleen, thymus were characterized by low 3H-benzo[a]pyrene accumulation. Radioactivity distribution pattern was depended on the class of LP used for complexation. Ours data permit to evaluate the participation of lipoproteins in transport and metabolic pathways of xenobiotics in organism.     

Concentration and composition of serum lipoproteins in the fetal rat]

1. Concentration and composition of the "very low density lipoproteins" (VLDL), "low density lipoproteins" (LDL) and "high density lipoproteins" (HDL) and of non-floatable lipids of fetal rat serum (day 22 of pregnancy) were determined by ultracentrifugation, thin-layer chromatographic separation of the floated lipids and quantitation of the lipid and protein moiety. 2. The concentration of VLDL is in the fetal rat by one order of magnitude lower, and that of LDL, 5fold higher than in the adult animal; the concentration of HDL in fetal serum amounts to 60% of the value of adult animals. 3. The composition of LDL and HDL of fetal serum does not differ from that in the serum of adult animals; in contrast, the fetal VLDL have a higher proportion of protein and cholesterol and a lower proportion of triglycerides than the VLDL of adult serum. The electrophoretic mobility of the fetal VLDL is lower than that of adult VLDL.     

Changes in the lipid composition of blood serum in girls with different somatotypes after a meal

Changes in the neutral lipid and phospholipid composition of blood serum in response to meals were analyzed in girls with different somatotypes. After meals, a statistically significant decrease in the content of free fatty acids was observed in all subjects, irrespective of the somatotype. Statistically significant increases in the contents of readily oxidized phospholipid fractions were observed in girls of subathletic and athletic somatotypes. These data show the changes in the relationship between variable components of the lipid spectrum of lipoproteins. The main structural constituents of membrane lipoproteins, such as stable phospholipid fractions and free cholesterol, did not change in response to meals in girls of any somatotype. These data demonstrate a stability of membrane lipoprotein complexes in response to this physiological stimulus.     

Blood serum concentration of lipids and lipoproteins and body composition

The purpose of this study is the analysis of the relationship of blood serum apolipoprotein E (apoE), total cholesterol (TC), triglycerides (TG) and high-density and low-density lipoproteins (HDL, LDL), with body mass index (BMI), relative body surface area (RBSA) and body muscle (BM) and body fat (BF). The subjects are males and females aged 14-16 (adolescent age group 1: n1M = 141, n1F = 151) and 18-25 (young adult group 2, n2M = 16, n2F = 46). Significant correlations of serum TG and HDL with somatometric indicators were not observed. In the female samples, TC content directly correlates (p < 0.05) with BF (r1 = 0.164; r2 = 0.418) and negatively correlates with BM (r1 = -0.165; r2 = -0.352). The blood serum concentration of apoE is significantly correlated with body composition in adolescent females (for BF r1 = -0.168; for BM r1 = 0.266; p < 0.05); in males 14-16 years old, the both correlations have a significance level p < 0.06. In young adult females TC and LDL content negatively correlates with RBSA (r2 = -0.386 and -0.377 respectively; p < 0.05) and positively correlates with BMI (r2 = 0.413 and 0.415 respectively; p < 0.05). Adolescent females and young adult females have opposite relationships between FC and apoE concentration. In females 14-15 years old apoE concentration decreases as FC increases. In females 16-17 the correlation disappears, and in older females apoE concentration and FC increase together.     

Modification of blood plasma lipoproteins by a lipid peroxidation product--hexanal

HDL treated with hexanal is shown to lose the ability for the cholesterol absorption. In the case of LDL at low concentration of the modifying agent the rate of their elimination from the blood stream of the rabbit decrease, but their uptake by the rat macrophages do not differ from the uptake of native lipoproteins. At high concentration of hexanal the rate of the elimination of LDL from the blood stream increases considerably and is close to that of acetylated LDL. Thus, the modification of plasma lipoproteins with monoaldehydes occurring in the aorta wall leads to the loss of the functional properties of the lipoprotein particles.     

Comparative analysis of lipid composition of normal and acute-phase high density lipoproteins

In the acute-phase response and in diseases with prolonged acute phases, normal HDL (NHDL) is converted into acute-phase HDL (APHDL) and becomes proinflammatory and unable to protect LDL against oxidative modification. Earlier work had demonstrated that these changes are associated with alterations in apolipoprotein composition and enzymatic activity of APHDL, but the effect of the acute-phase condition on the lipid composition of APHDL had remained obscure. The present study shows marked quantitative differences in lipid composition between NHDL and APHDL. Specifically, APHDL contained 25% less total lipid per milligram of protein. Up to 50% of cholesteryl ester in the lipid core of APHDL was replaced by triacylglycerol; however, the total phospholipid/total neutral lipid ratios were the same as in NHDL, both lipoproteins giving similar calculated lipid core radii. Furthermore, the phosphatidylcholine/sphingomyelin ratio in APHDL was nearly double that in NHDL, indicating a relative loss of sphingomyelin. A decrease was also seen in diacyl and alkenylacyl glycerophosphatidylethanolamine as well as in phosphatidylinositol of APHDL when compared with NHDL. APHDL contained proportionally more saturated and less polyunsaturated and isoprostane-containing species of phosphatidylcholine, as well as more saturated than unsaturated cholesteryl esters. APHDL also contained significantly more free fatty acids, lysophosphatidylcholine, and free cholesterol. These changes in the lipid composition of HDL are consistent with the alterations in the apoprotein composition and enzymatic activity of APHDL and indicate proinflammatory and proatherogenic roles for APHDL.