Biomedical subjects

F A Kummerow

Publications and source records attributed to F A Kummerow.

At least 37 records · Page 2Linked to original sources

PubMed1996

The hemolytic activity of homocysteine is increased by the activated polymorphonuclear leukocytes.

Homocysteine is an accepted risk factor when its plasma level exceeds the physiological upper limit of 12 mumol/L. We found in vitro that homocysteine is able to lyse the erythrocytes (RBCs) at higher concentrations than 15 mumol/L only when activated polymorphonuclear leukocytes (PMNL) are present. The hemolytic effect of homocysteine was higher in RBCs obtained from cardiac catheterized patients with 100% stenosis of the coronary arteries. Homocysteine was also able to increase the activation in vitro of PMNLs triggered by opsonized zymosan. The hemolytic action of homocysteine was found to be dependent on the ratio of PMNLs to RBCs. This relationship may help to explain the great individual variations in the hemolytic activity noticed in blood obtained from cardiac catheterized patients, and also may explain the mild anemia in some patients suffering from cardiovascular disease.

Coronary Disease↗

PubMed1996

Cholestane-3 beta, 5 alpha, 6 beta-triol stimulates phospholipid synthesis and CTP-phosphocholine cytidyltransferase in cultured LLC-PK cells.

The present study was conducted to examine the effect, if any, of triol on the rate of total or individual phospholipid synthesis by LLC-PK cells in culture. LLC-PK cells were incubated in medium with or without 10 micrograms/ml of 5 alpha-cholestane-3 beta, 5 alpha,6 beta-triol (triol) for 24 h. Triol-treated and control cells were then incubated with medium containing either [14C]glycerol or [32P]phosphate for 1, 6 or 12 hr. In triol-treated cells, the amount of labeled glycerol and [32P]phosphate incorporated into glycerophospholipids and phospholipids (PL), respectively, were higher in triol-treated cells than in control cells, indicating a higher rate of PL synthesis in triol-treated cells. The results also showed that the increase in PL synthesis was higher in magnitude for some PL than others, thus disturbing the ratios among the PL fractions in the cell membrane. CTP-phosphocholine cytidyltransferase activity was greatly enhanced in the cytosolic as well as the particulate fractions of the triol-treated cells, which explains the increase of PC synthesis under triol effect. The rate of [3H]acetate incorporation into the total and free fatty acid fractions was significantly increased in triol-treated cells. The activation of the cytidyl transferase enzyme was related to the enhanced de novo synthesis and cellular uptake of fatty acids in triol-treated cells, which make fatty acids more available in these cells and can upregulate the enzyme. The increased synthesis of phospholipids in the triol cells and the increased level of phospholipid in these cells (as micrograms lipid phosphorus/mg cell protein) observed in our previous study indicate changes in the phospholipid head group composition of the triol cells. These changes can affect several membrane properties and membrane bound enzymes.

Acetates↗

PubMed1996

Effect of magnesium on secretion of platelet-derived growth factor by cultured human arterial smooth muscle cells.

Two conditioned media were prepared by culturing human umbilical artery smooth muscle cells (SMC) in 75 cm2 flasks with minimum essential medium (MEM) under magnesium (Mg) sufficient (900 microM) or deficient (100 microM) conditions for 72 h ([900]- and [100]-MEM), respectively. A third conditioned medium was obtained by adjusting the Mg concentration of half of the [100]-MEM to 900 microM ([100-900]-MEM). SMC in 12-well plates were incubated in one of the three conditioned media and the growth rates of SMC were determined by [3H]-thymidine incorporation and cell counting. The growth rate in [100-900]-MEM was significantly higher than in [900]- and [100]-MEM. When platelet derived growth factor (PDGF) was neutralized by the addition of a mixture of anti-PDGF-AA and -BB antibodies, [3H]-thymidine incorporation in [100-900]-MEM decreased by 23.3 per cent, but only by 7.0 per cent in [900]-MEM. The quantity of PDGF in the Mg-deficient media was greater than in the magnesium-sufficient media at all indicated times, as shown by radioimmunoassay for PDGF-BB or -AB. These results indicate that Mg deficiency increases the secretion of PDGF by SMC.

Antibodies↗

PubMed1996

Cholesterol metabolism in human umbilical arterial endothelial cells cultured in low magnesium media.

To study the time- and dose-dependent effects of low magnesium on free [H3]cholesterol uptake, [H3]mevalonolactone incorporation into cholesterol, and both of which labelled precursors and [H3]oleic acid incorporations into cholesteryl esters, cultured human umbilical arterial endothelial cells were exposed to experimental media containing decreasing magnesium concentrations at 94, 188, 376 and 564 microM until 48 h. A level of magnesium at 949 microM was used as a control. The results showed that reduced magnesium in the cultured medium led to a decrease in [H3]cholesterol, uptake, an inhibition of the incorporation of [H3]mevalonolactone into cholesterol and a stimulation of the incorporation of [H3]cholesterol, [H3]mevalonolactone and [H3]oleic acid into cholesteryl esters, but the time- and dose-dependent effects of magnesium deficiency were not significant. We suggest that reduced cholesterol uptake and synthesis might contribute to hypercholesterolaemia under a condition of magnesium deficiency, and that enhanced cholesterol esterification might be explained by a stimulated activity of acyl-Coenzyme A: cholesterol O-acyltransferase (ACAT).

Cells, Cultured↗

PubMed1995

Inhibition of metal-catalyzed oxidation of low-density lipoprotein by free and albumin-bound bilirubin.

Both free and albumin-bound bilirubin are known to scavenge peroxyl radicals in vitro. In the present work we showed that free and albumin-bound bilirubin at the physiological concentration of the bile pigment in blood plasma could greatly inhibit the metal-catalyzed oxidation of low density lipoprotein (LDL) as shown by the reduced thiobarbituric acid reactivity, smaller or no shifts in electrophoretic mobility, less apo B fragmentation and a decreased amount of cholesterol oxidation products as detected by gas chromatography. Free bilirubin (BR) was more effective in inhibiting the production of thiobarbituric acid reactive substances in iron-catalyzed LDL peroxidation as compared to the copper-catalyzed reaction up to a BR to metal molar ratio of 4:1. Above this ratio the same degree of inhibition was observed for both metal ions. It was found that serum albumin provided full protection against Cu(2+)-dependent oxidative stress only at very high protein to metal molar ratio, i.e., 30:1, that is similar to that in human plasma. Complexation of BR to albumin brought about a marked increase in the capacity of the complex to bind metal ions, particularly iron, as opposed to albumin alone. At a molar ratio of metal ion to albumin-BR of 1:1 the inhibition of lipid peroxidation was about 96% and it was almost complete at a molar ratio of 1:2. The ability of albumin-BR complex to inhibit effectively the transition metals-dependent oxidative stress could be important in the extravascular space where local concentrations of metal ions may exceed the protein binding capacity. In addition, the strong binding of iron to the albumin-BR complex may be clinically important, especially in iron loaded sera of hemochromatosis patients, where the transferrin is fully saturated with this ion and the free iron could catalyze lipid peroxidation unless bound by a metal trapping device such as the albumin-BR complex.

Apolipoproteins B↗

PubMed1995

Esterification of oxysterols by human plasma lecithin-cholesterol acyltransferase.

In the present study, lecithin-cholesterol acyltransferase (LCAT) catalyzed esterification of oxysterols was investigated by using discoidal bilayer particles (DBP) containing various oxysterols, phosphatidylcholines, and apolipoprotein A-I. The esterified oxysterols were analyzed by high pressure liquid chromatography, gas chromatography, and mass spectrometry. LCAT esterified all oxysterols tested that are known to be present in human plasma. The esterification yields in almost all cases were relatively high, often as high as the yield of cholesterol esterification. When DBP preparations containing 27-hydroxycholesterol and various phosphatidylcholines were used for the LCAT reaction, both monoesters and diesters were produced. The mass spectrometry analysis showed that the monoester was produced by the esterification of the 3 beta-hydroxyl group and not the 27-hydroxyl group. The diesters were apparently produced by the esterification of the 27-hydroxyl group only after the esterification of the 3 beta-hydroxyl group. Phosphatidylcholine containing a saturated acyl group at sn-1 position and an unsaturated acyl group at sn-2 position gave generally high esterification yield. The esterification of various oxysterols was compared by using DBP containing dioleoyl-phosphatidylcholine and individual oxysterols. All oxysterols produced 3 beta-oleoyl monoesters. Unlike 27-hydroxycholesterol, 25-hydroxycholesterol, 7 alpha-hydroxycholesterol, 7 beta-hydroxycholesterol, or cholestanetriol did not produce diesters. Various factors influencing the formation of the monoesters and diesters from 27-hydroxycholesterol were investigated. When dioleoyl-phosphatidylcholine was used as the acyl donor, prolonged dialysis of DBP preparations and increase in the ratio of the enzyme concentration to substrate particle concentration increased the diester formation. Significant amounts of diesters were also produced by using 1-palmitoyl-2-oleoyl-phosphatidylcholine and other phosphatidylcholines as the acyl donors. By analyzing the conditions of monoester and diester formation, a scheme for the LCAT reaction pathway was proposed.

Apolipoprotein A-I↗

PubMed1995

Randomized, controlled trial of antioxidant vitamins and cardioprotective diet on hyperlipidemia, oxidative stress, and development of experimental atherosclerosis: the diet and antioxidant trial on atherosclerosis (DATA).

The effects of administration of guava and papaya fruit (100 g/day), vegetables, and mustard oil (5 g/day) (group A); antioxidant vitamins C (50 mg/day) and E (30 mg/day), plus betacarotene (10 mg/day) (group B); a high-fat (5-10 g/day) (group C); or a low-fat (4-5 g/day) diet (group D) were compared over 24 diet weeks in a randomized fashion, while all groups of rabbits (five in each of four groups) received a hydrogenated fat diet (5-10 g/day) for a period of 36 weeks. After 12 weeks on the high-fat diet, each group of rabbits had an increase in blood lipoproteins. The fruit and vegetable-enriched prudent diet (group A) caused a significant decline in blood lipids at 24 and 36 weeks, whereas the lipid levels increased significantly in groups C and D. Group A also had a significant rise in vitamin E (2.1 Umol/l), C (10.5 Umol/l), A (0.66 Umol/l), and carotene (0.08 Umol/l) and a decrease in lipid peroxides (0.34 nmol/ml at 36 weeks, whereas the levels were unchanged in groups C and D. Group B rabbits had a significant and greater increase than group A in plasma vitamins E, C, A, and carotene; a rise in HDL cholesterol; and a greater decrease in lipid peroxides after 24 and 36 weeks of treatment. After stimulation of lipid peroxidation in all rabbits, 3 of 5 group C and 2 of 5 group D rabbits died due to coronary thrombosis, whereas in groups A and B there were no deaths, indicating that antioxidant therapy can provide protection against lipid peroxidation and free radical generation. Aortic lipids and sudanophilia, indicating atherosclerosis, were significantly higher in groups C and D than in groups A and B. Fatty streaks and atheromatous and fibrous plaques were noted in all the rabbits in groups C and D. Intimal fibrosis and medial degeneration were also present in the group C rabbits. While group A (36.4 +/- 4.4 microns) and group B (37.1 +/- 4.2 microns) rabbits had minimal coronary artery plaque sizes, group C (75.4 +/- 10.6 microns) and group D rabbits (69.5 +/- 6.2 microns) had significantly greater plaque sizes. Aortic plaque sizes were also greater in groups C and D than in groups A and B. It is possible that combined therapy with antioxidant vitamins C, E, and carotene, and a diet rich in antioxidants, could independently inhibit free radical generation and the development of atherosclerosis.

Animals↗

PubMed1995

Changes in linoleic acid metabolism and membrane fatty acids of LLC-PK cells in culture induced by 5 alpha-cholestane-3 beta,5,6 beta-triol.

The aim of this study was to investigate the effect of the oxysterol 5 alpha-cholestane-3 beta,5,6 beta-triol (triol) on the metabolism of linoleic acid (18:2n-6) to arachidonic acid (20:4n-6) and on the cell membrane fatty acid composition. Porcine kidney cells were incubated in medium with or without 10 microgram(s)/mL of triol for 24 h, then incubated for 1, 6, or 12 h in a medium which contained 50 muM of either [14C] linoleic acid or unlabeled linoleic acid. The cellular uptake of [14C] linoleic acid was significantly higher in the triol-treated cells than in control cells. After 1- and 6-h incubations despite the increase of [14C] linoleic acid pool size in the triol-treated cells, neither total n-6 polyunsaturated fatty acids (PUFA) metabolites nor arachidonic acid were increased in the triol-treated cells as compared to the control cells, but trienoic acids accumulated to a greater extent in the triol-treated cells. Therefore, the ratios of n-6 PUFA metabolites vs. pool size of linoleic acid and of tetraenoic acids vs. dienoic acids were significantly decreased in triol-treated cells as compared to the control cells. The cellular fatty acid composition also showed that linoleic acid percentage was significantly increased while arachidonic acid percentage was significantly decreased in the triol-treated cells, and that the accumulation of trienoic acids (18:3n-6 + 20:3n-6) observed from the [14C] linoleic acid experiment was due solely to increased 20:3n-6 content. This latter finding indicates that a decrease of elongase activity by triol is unlikely. Our results also showed that the triol-treated cells had a lower level of free cholesterol but higher levels of phospholipid and triol in their membranes, suggesting that triol displaced free cholesterol from the cell membrane.

Animals↗

PubMed1995

Failure of vitamin E to protect cultured human arterial smooth muscle cells against oxysterol-induced cytotoxicity.

OBJECTIVE: The cytotoxicity of oxysterols including 7 alpha-hydroxycholesterol (7 alpha OHC), 7 beta-hydroxycholesterol (7 beta OHC), cholesterol 5 alpha,6 alpha-epoxide (alpha epoxyC), cholesterol 5 beta,6 beta-epoxide (beta epoxyC), 7-ketocholesterol (7ketoC), 26-hydroxycholesterol (26OHC), cholesterol-3 beta,5 alpha,6 beta-triol (TriolC) and the possible protecting effect of vitamin E on 26OHC-induced cytotoxicity were investigated in smooth muscle cells isolated from the arteries of human umbilical cords. METHODS: To study the cytotoxicity of oxysterols, the cells were incubated with each oxysterol at a level of 10 micrograms/ml from 24 to 120 hours, then 45Ca++ uptake, cytosolic free Ca++ level, [3H]thymidine incorporation, total DNA content and viable cell number were measured. Cholesterol was used as a control. For tracing the possible origin of cytotoxicity of 26OHC, cholesterol, phospholipid and 26OHC content in the membrane were investigated from 24 to 72 hours. For determining whether antioxidants had a protective effect against the cytotoxicity of 26OHC, vitamin E and butylated hydroxytoluene (BHT) were used. RESULTS: The results indicated that the oxysterols elevated 45Ca++ uptake and cytosolic free Ca++ level, but diminished [3H]thymidine incorporation, total DNA content and viable cell number. 26OHC lowered the cholesterol content of the membrane and incorporated into the membrane after 24 hours of the incubation, but did not alter the total phospholipid content of the membrane until 72 hours. Neither vitamin E or BHT significantly protected the cells from the 26OHC-induced alterations. CONCLUSION: We suggest that the cytotoxicity of oxysterols, which might result in an alteration in Ca++ ion flow into the cell by decreasing cholesterol content and incorporating oxysterol itself into the membranes, could not be protected by vitamin E.

Calcium↗

PubMed1995

Effect of magnesium on secretion of platelet-derived growth factor by cultured human umbilical arterial endothelial cells.

Conditioned media were prepared by incubating human cultured umbilical arterial endothelial cells for 48 h in magnesium (Mg) sufficient (900 microM) and deficient (100 microM) conditions. Minimum essential media (MEM) are designated as [900]- and [100]-MEM, respectively. After the incubation, a portion of the [100]-MEM media was adjusted from 100 to 900 microM magnesium ([100-900]-MEM). Smooth muscle cells were incubated with the three media and their growth rates were determined by [3H]-thymidine incorporation and cell counting. The growth rate in [100-900]-MEM was significantly higher than in [900]- or [100]-MEM. When platelet-derived growth factor (PDGF) was neutralized by the addition of a mixture of anti-PDGF-AA and -BB, [3H]-thymidine incorporation in [100-900]-MEM decreased by 12.5 per cent, but only by 4.9 per cent in [900]-MEM. These results indicate that magnesium deficiency increases the secretion of PDGF by endothelial cells. This is also supported by the results of the radioimmunoassay for PDGF-BB; the quantity of PDGF in the magnesium-deficient media was greater than in the magnesium-sufficient media.

Blood Proteins↗

PubMed1995

The effects of magnesium deficiency on DNA and lipid synthesis in cultured human umbilical arterial endothelial cells.

This study investigated the effects of magnesium deficiency on thymidine incorporation and lipid synthesis in human umbilical arterial endothelial cells. To study [3H]thymidine incorporation, the cells were exposed for 12 to 96 h to experimental media containing decreasing magnesium concentrations of 237, 118 and 5 microM. A magnesium concentration of 949 microM was used as control. At 48 h of exposure to the experimental media, magnesium was restored to 949 microM in half of the magnesium-deficient cultures. To determine [14C]acetic acid distributions among cholesterol, phospholipid and triglyceride, the cells were treated with decreased magnesium media at the levels mentioned above for 12 to 48 h. The results showed that [3H]thymidine incorporation into DNA was inhibited by magnesium deficiency. The inhibition was augmented correspondingly with decreased magnesium concentrations and increased exposure periods. When magnesium in the medium was enhanced to normal level, incorporation was no longer inhibited. Incorporation of [14C]acetic acid into phospholipid was inhibited, its incorporation into triglyceride was stimulated, but its incorporation into cholesterol was not affected by magnesium deficiency. We suggest (i) that with the restoration of adequate magnesium, the inhibiting effect of magnesium deficiency on thymidine incorporation is reversible; (ii) that magnesium deficiency can result in a redistribution of [14C]acetic acid between phospholipid and triglyceride.

Acetates↗

PubMed1995

Effects of adrenochrome and epinephrine on human arterial endothelial cells in vitro.

The effects of adrenochrome and epinephrine were investigated in cultured human umbilical arterial endothelial cells. The cells were exposed to either adrenochrome or epinephrine at levels of 50 and 200 microM, respectively, up to 24 hrs. At 3, 5, 7 and 24 hrs of the designed harvesting time, [3H]thymidine incorporation, protein content, [3H]cholesterol uptake, prostacyclin production and lipid peroxidation were measured. We found that adrenochrome at a level of 200 microM inhibited [3H]thymidine incorporation, decreased protein content, stimulated [3H]cholesterol uptake, and decreased prostacyclin production after 3, 5, 24 and 5 hrs of exposure, respectively, compared with control. It took 24 hrs however for epinephrine at a level of 200 microM to inhibit [3H]thymidine incorporation and prostacyclin production. When the concentration was reduced to 50 microM, only adrenochrome inhibited [3H]thymidine incorporation after 24 hrs of treatment. Both adrenochrome and epinephrine had no effect on lipid peroxidation. We suggest that atherogenic changes found in severe hypertension may be due to abnormal high concentration of epinephrine, especially oxidized epinephrine, on endothelial cell functions, such as DNA synthesis, cholesterol uptake and prostacyclin production.

Adrenochrome↗

PubMed1995

Cigarette smoking causes biochemical changes in blood that are suggestive of oxidative stress: a case-control study.

Cigarette smoking has been shown to be a major risk factor for cardiovascular disease, lung cancer, and respiratory diseases. Due to its high content of oxidants, the cigarette smoke is bound to cause a prooxidant/antioxidant imbalance in the blood plasma and tissues of smokers. The study groups were selected from an apparently healthy population living in urban areas, comprising 200 subjects aged 18 to 80 years, half of whom were smokers. In smokers aged 18 to 45 years, the changes of the plasma prooxidant parameters (i.e., lipid peroxides, leukocyte activation, and the antioxidant ones [thiol concentration, total antioxidant capacity]) were not significantly different from those of the age-matched controls, whereas in the 46 to 80 age group they were. In smokers, both antioxidant erythrocyte enzymes, glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD), exhibited increased activity in the 18 to 45 age group and decreased activity in the 46 to 80 age group. The differences in enzyme activity between the smoking and nonsmoking groups were highly significant for SOD in all ages, whereas for GSH-Px the difference in activity was significant only in the case of older smokers. These findings would suggest that a process of adaptation takes place in younger smokers, in whom the antioxidant systems are able to counteract the oxidant factors, while in older smokers this process is no longer occurring and the plasma and tissues are under permanent oxidative stress. Our results clearly demonstrated that a prooxidant/antioxidant imbalance exists in the blood of smokers, and the determination of leukocytes stimulation index may be a useful and simple way of assessing the oxidative stress status of these individuals. A hypothesis regarding a possible mechanism linking cigarette smoking to the development of coronary heart disease is presented.

Adolescent↗

PubMed1995

Cigarette smoke increases cholesterol oxidation and lipid peroxidation of human low-density lipoprotein and decreases its binding to the hepatic receptor in vitro.

Low-density lipoprotein (LDL) was exposed to six puffs of cigarette smoke (CS) filtered through a glass wool filter and then incubated for 6 or 20 h at 37 degrees C. Control LDL was similarly treated but exposed to air. In cigarette smoke-treated LDL (CS-LDL), compositional changes of the lipid fraction were most detectable after 20 h incubation. These changes included a decrease of polyunsaturated fatty acids (PUFA), slight degradation of phosphatidylethanolamine (PE) and phosphatidylcholine (PC) to their lysophospholipid lysoPE and lyso-PC, elevation of oxidized cholesterol content as well as thiobarbituric acid reacting substance (TBARS), indicating an oxidative effect of CS on LDL. CS-LDL also showed higher anodic electrophoretic mobility and crosslinking of its apoprotein by nondisulfide bonds. The binding affinity of CS-LDL to liver membrane receptor was much lower than control LDL as measured by the calcium-dependent binding of LDL-gold conjugate to the solubilized membrane protein dot blotted onto nitrocellulose strips. Our results indicate that CS induces changes in LDL, making it more atherogenic and cytotoxic.

Apolipoproteins B↗

PubMed1994

The influence of 25-hydroxycholesterol on phosphatidylinositol content in cultured smooth muscle cells.

The effect of 25-hydroxycholesterol on phosphatidylinositol content was studied in subconfluent human arterial smooth muscle cells exposed to myo-[2-3H]inositol for 90 min and then to 25-hydroxycholesterol at different concentrations or for different incubating periods. Ethanol at a concentration of 0.05% in culture medium was used as control. The results demonstrate that an increased incubation time or an increase in the concentration of 25-hydroxycholesterol produced an increase in phosphatidylinositol and its degraded products. The ratio of precursor to product at each stage of phosphatidylinositol turnover in 25-hydroxycholesterol-treated cells, however, was not different from that in control cells. The data indicate that the presence of 25-hydroxycholesterol in the media induced general activation of phosphatidylinositol synthesis and turnover.

Cells, Cultured↗

PubMed1994

Changes in arterial membrane lipid composition may precede growth factor influence in the pathogenesis of atherosclerosis.

A recent review article on the pathogenesis of atherosclerosis stated that the lesions result from an excessive inflammatory-fibroproliferative response to various forms of insult of the endothelium and smooth muscle cells of the arterial wall, that a large number of growth factors participate in this process and that the injury is most apparent at branching points of the arterial tree. We found a significant increase in sphingomyelin and a decrease in other phospholipid components in the arterial wall at the branching points as compared to the non branching points of human and swine arteries. Because of the higher transition temperature of sphingomyelin, its replacement of other phospholipid components may increase the rigidity of the cell membrane and may alter negatively charged bilayers in such a way that they interact more strongly with cholesterol and calcium. Duplication of such conditions with arterial cells in tissue culture caused calcium infiltration into the cell. Furthermore, platelet derived growth factor (PDGF) synthesis was increased in smooth muscle cells grown in magnesium deficient media. It is possible that a change in phospholipid and cholesterol composition of arterial cells at the branching points of arteries and that factors other than PDGF may precede inflammatory-fibroproliferative response to various forms of insult.

Adult↗

PubMed1994

Cholesterol oxides in plasma and lipoproteins of magnesium-deficient rabbits and effects of their lipoproteins on endothelial barrier function.

The cholesterol oxide (ChO) levels in the plasma and low density lipoproteins (LDL and VLDL) in four groups of rabbits fed for seven weeks either normal (NC) or high cholesterol (HC) with low or normal magnesium (Mg) diets were determined and compared with the NC group fed a standard rabbit diet. The plasma from the NC group contained low levels of different cholesterol oxides. These cholesterol oxides were significantly elevated in the plasma of rabbits fed a HC-normal magnesium or a HC-low magnesium diet. In the NC-low Mg group, 7 alpha-hydroxycholesterol, 7 beta-hydroxycholesterol and 7-ketocholesterol were elevated while the other cholesterol oxides remained within the normal range of the NC group. When the cholesterol oxides were assayed in the LDL and VLDL fractions as micrograms/mg protein, the fractions obtained from the groups fed NC-low Mg, HC-normal Mg or HC-low Mg diets showed higher levels of cholesterol oxides than the fractions obtained from the NC group. When LDL and VLDL fractions from the different groups were incubated at equal protein concentration with confluent endothelial cell monolayers, transendothelial albumin transfer was significantly increased by the lipoproteins from the experimental groups as compared to the control group. These results suggest that elevation of cholesterol oxides in magnesium deficiency or hypercholesterolaemia may be related to their atherogenic effects through decreasing the endothelial barrier function which could enhance the deposition of cholesterol rich lipoproteins into the arterial wall.

Animal Feed↗

PubMed1994

Combined effects of magnesium deficiency and an atherogenic level of low density lipoprotein on uptake and metabolism of low density lipoprotein by cultured human endothelial cells. I. Biochemical data.

The effects of magnesium deficiency on uptake and metabolism of low density lipoprotein (LDL) were investigated using human arterial endothelial cells cultured in media containing various concentrations of magnesium (100-1000 microM) and a high concentration of LDL (2 mg LDL cholesterol/ml) labelled with [3H]cholesteryl linoleate. The LDL uptake was time-dependent and increased for up to 8 h in both the magnesium-deficient and magnesium-sufficient treatments. The extent of LDL uptake progressively increased with the decrease in magnesium concentration of the medium. Surface-bound LDL also increased in a similar manner during the incubation but less extensively than the LDL uptake. The majority of radioactivity from internalized LDL was detected in unesterified cholesterol at all time points in both the magnesium deficiency and sufficiency groups. Only small amounts of radioactivity were found in cholesteryl esters. These findings indicate that most LDL taken up by the cells was rapidly hydrolysed but not readily re-esterified. The lack of re-esterification may be due to a relative deficiency of acyl-CoA:cholesterol acyltransferase (ACAT) and the presence of large amounts of unesterified cholesterol.

Analysis of Variance↗