Fluorometric determination of cholesterol and cholesteryl ester in tissue on the nanogram level

Skin cholesterol and DNA in young patients with myocardial infarction

Disturbances in cholesterol metabolism are connected with an increased risk of clinical complications to atherosclerosis. Serum cholesterol has been used as an index of such disturbances. However, recently the significance of local tissue, and cellular factors in cholesterol metabolism and atherogenesis have been better appreciated. As easily accessible sources of cells and tissues, skin biopsies have been suggested to increase the possibilities to assess the extent of atherosclerosis in an individual. In order to test this hypothesis, skin biopsies were taken from 24 male patients, who had sustained a myocardial infarction before the age of 40, and from 42 healthy, randomly selected male volunteers, matched for age and serum cholesterol. Cholesterol and DNA contents were measured in epidermis and dermis separately; no significant differences were found between the groups. A significant, positive correlation between serum and dermis cholesterol was found in both groups. Our data do not support the hypothesis that skin biopsies discriminate individuals with atherosclerosis better than serum cholesterol. It is possible that previous data, suggesting a correlation between skin cholesterol and atherosclerosis, might reflect the well known correlation between serum cholesterol and atherosclerosis.

The restoring effect of trifluralin and benznidazole on the abnormal fatty-acid pattern induced by Trypanosoma cruzi in the liver microsomes of infected mice

The fatty-acid composition of liver lipids from mice infected with Trypanosoma cruzi (clone H510C8C3) or uninfected mice was investigated. The infected animals were treated orally for 30 days, with trifluralin (TFL) or benznidazole (BNZ), each at 100mg/kg.day, or only with the peanut oil used as the drug vehicle. The uninfected mice were also given the peanut oil. The treatments were stopped 10 days before the animals were killed. The liver microsomal lipids of each mouse were isolated and then analysed by gas-liquid chromatography. In terms of the total lipids, untreated infection evoked a significant increase in saturated fatty acids and the members of the n-9 fatty-acid family, with a concomitant decrease in the polyenoates of the n-3 and n-6 fatty-acid series. Each lipid subclass was affected to a different extent, the phospholipids being affected most. All lipid fractions, apart from the cholesterol esters, showed a significant increase in the proportion of n-9 isomers. Infection also produced a marked increase in the absolute amounts of triacylglycerides, cholesterol and cholesterol esters in liver microsomal membranes. After BNZ or TFL treatment, the fatty-acid pattern of mice that had been infected was indistinguishable from that of the control mice. The possible role of desaturase activity in the alterations observed is discussed.

Porcine smooth muscle cell-conditioned medium stimulates LDL receptor activity in Hep G2 cells

Paracrine factors may modulate low density lipoprotein (LDL) receptor activity in hepatocytes. To study this the effect of conditioned medium prepared from a range of cell types on the binding and internalisation of 125I-LDL in Hep G2 cells was studied. Seven of the fourteen conditioned media tested, including those from P388D1, U937, porcine smooth muscle (Pc SMC) Swiss 3T3, STO, = 48 and MDCK cells, were found to increase the binding and internalisation of 125I-LDL at 37 degrees C by Hep G2 cells (P < 0.01). The largest increase in LDL receptor activity was produced by conditioned medium from Pc SMC cells and was, therefore, selected for further analysis. The Pc SMC-conditioned medium increased LDL receptor number in Hep G2 cells by three-fold but had no effect on LDL receptor activity in human skin fibroblasts. DNA synthesis and cholesterol synthesis by Hep G2 cells were inhibited by Pc SMC-conditioned medium. Preliminary characterisation of the Pc SMC-derived factor(s) suggests that it is a protein(s) of low relative molecular mass.

Effects of vitamin E on prostacyclin release and lipid composition of the ischemic rat heart

Free radical-mediated reperfusion injury has been established as an important mechanism leading to post-ischemic reperfusion myocardial damage. The present study was undertaken to determine the protective role of vitamin E, a membrane-bound free-radical scavenger, on ischemia-reperfusion myocardial injury. After 4 months of feeding a semipurified diet containing 0, 30, and 3000 ppm of R,R,R,-alpha-tocopherol acetate, rat hearts were subjected to Langendorff perfusion. Myocardial damage was judged by the release of creatine phosphokinase (CPK) after 45 min of global ischemia followed by 20 min of reperfusion. Effluent CPK was significantly lowered in the two tocopherol-supplemented groups, although increasing dietary vitamin E by 100-fold above requirement did not confer further protection. However, effluent prostacyclin, detected as the stable metabolite 6-keto-PGF1 alpha by radioimmunoassay, was potentiated by dietary vitamin E in a dose-dependent manner. Analysis of lipids in cardiac subcellular fractions showed considerable enrichment of tocopherol in these membranes by diets, but the levels of polyunsaturated fatty acids, phospholipids, and cholesterol were essentially unchanged by dietary treatment or ischemia-reperfusion. These data demonstrated that requirement level of tocopherol (30 ppm) in the diet is sufficient to protect against reperfusion injury of the myocardium and suggests that tocopherol is important in maintaining cardiac prostacyclin synthesis under conditions of oxygen stress.

Aortic intimal lipid content and serum lipoproteins in patients undergoing coronary by-pass surgery as related to clinical prognosis

Intimal lipid concentrations were determined in aortic biopsies obtained during coronary by-pass surgery. In addition serum lipoprotein and apolipoprotein levels were quantitated and their relationships to aortic intimal lipid concentrations were analysed. The possibility to use aortic intimal lipid and serum lipoprotein or apolipoprotein concentrations to predict clinical prognosis following the coronary by-pass operation was also evaluated. Intimal cholesterol, cholesterol ester, phosphatidylcholine and sphingomyelin were intercorrelated, whereas none of these lipid fractions correlated to aortic intimal triglyceride levels. Patients with hypertension had higher aortic intimal cholesterol ester levels than normotensive patients. There was a positive correlation between the number of stenosed coronary arteries and serum apo B or triglyceride levels. In addition there was a negative correlation between the number of stenosed arteries and HDL-cholesterol. Prognosis after the operation was inversely correlated to serum apo A-I levels. Our data do not, however, support the notion that aortic intimal lipid levels can be used to evaluate prognosis after coronary by-pass surgery.

Oxygen consumption in aortic tissue from rabbits with diet-induced atherosclerosis

The inner parts of the arterial wall depend upon diffusion for nutrition and oxygenation. During the atherosclerotic process, increased intimal thickness leads to impaired diffusion, and at the same time the oxygen requirements increase. On this basis it has been suggested that the balance between the supply and demand of oxygen in the arterial wall may be important for the fate of the initiated lesion. In the first part of the present study, the oxygen consumption was measured during perfusion in aortic intima-media segments from cholesterol-fed rabbits. The results indicated that the oxygen consumption per DNA increased with increasing degree of atherosclerotic involvement up to a certain level. For more diseased aortas, however, the oxygen consumption decreased again. In the second part of the study, the oxygen consumption was measured in foam cell and smooth muscle cell fractions isolated from rabbit aortic intima-media. These measurements indicated that the oxygen consumption of isolated foam cells was three times higher than that of isolated smooth muscle cells. It is proposed in the study that the increased oxygen consumption of the less diseased aortas reflected an increased proportion of foam cells in the arterial wall. As the lesions grow and the number of foam cells in the intima increases, the available diffusion capacity for oxygen and nutrients to deeper parts of the lesion may become insufficient, leading to the observed decrease in cellular oxygen consumption of the more diseased samples. Hypoxic cell damage and further tissue reactions may occur and the healing of the initiated lesion may be endangered.

Hyperalphalipoproteinaemic activity of BRL 26314—II

Optimization of a combination of balloon catheter-induced aortic de-endothelialization with provision of a palatable atherogenic diet to rabbits leads to hyperbetalipoproteinaemia and atherosclerosis rather than to the cholesterol-storage disease which characterized earlier models. Administration of BRL 26314 [N-(4-chlorobenzyl)-L-phenylalanine] during the induction of atherosclerosis specifically raised high-density lipoprotein (HDL) and decreased the arterial content of cholesterol and collagen in association with reduction in severity of thoracic sudanophilic lesions and intimal-thickening. This anti-atherosclerotic activity was superior to that observed for various standard compounds, and the present studies, using BRL 26314 as a pharmacological tool, provide evidence in vivo for an association between the elevation of HDL and reduction of arterial disease.

Effect of low density lipoprotein on glycosaminoglycan secretion by cultured human smooth muscle cells and fibroblasts. Influence of serum concentration and cell proliferation rate

Glycosaminoglycan (GAG) secretion was studied in cultures of human fibroblasts and arterial smooth muscle cells. Supplementation of culture medium with whole human serum increased the secretion of GAG but this effect disappeared as cell density increased. Lipoprotein-free serum (LFS) supported cell growth but led to a decrease in GAG secretion and in cell cholesterol. Addition of human low density lipoprotein (LDL) to the medium containing 10% LFS produced increases in GAG secretion (200%) and cell cholesterol (300%) and a decrease (60%) in cell population. The effects of LDL were considerably smaller in medium containing 5% LFS; this was related to the lower rate of proliferation in this medium, since there was a close relationship between rate of proliferation and stimulation of GAG secretion by LDL independent of serum concentration. In addition, fetal smooth muscle cells showed a qualitatively different response to LDL in 5% LFS, with a biphasic dose-response of GAG secretion and cell number. It is concluded that: (1) whole human serum stimulates GAG secretion by sparse cell cultures, (2) LFS can support cell growth but not GAG secretion, (3) LDL stimulates GAG secretion but has a cytotoxic effect, (4) the degree of GAG stimulation by LDL is dependent on the proliferative state of cells, (5) at low serum concentrations fibroblasts and fetal smooth muscle cells show differences in response to LDL which are not evident at higher serum concentration.

Micromethods for quantitative lipid analysis of human liver needle biopsy specimens

Micromethods are described for rapid quantitative lipid analysis of human liver specimens obtained by percutaneous needle biopsy. Total phospholipid, free fatty acids, triacylglycerol and free and esterified cholesterol were separated by thin layer chromatography and, with the aid of an internal standard, quantitated by specific chemical assays. Individual phospholipids were also separated and quantitated. Fatty acid esters were transmethylated and assayed by gas-liquid chromatography. The results of recovery and reproducibility experiments and lipid values for normal human liver are reported. These methods provide a new approach for investigating the pathogenesis of liver disease and may well prove useful in analysing lipids from biopsies of other tissues.

The role of cholesterol 7 alpha-hydroxylase in the hypobetalipoproteinaemic activity of SKF-525A in rats

Administration of SKF-525A to rats fed on a stock diet specifically decreased the serum concentration of low-density lipoprotein. SKF-525A and cholestryamine also reversed the rise in circulating concentration of both very-low density and low-density lipoprotein that was observed in rats given a sucrose-based, cholesterol-supplemented diet. The enhancement of hepatic cholesterol 7 alpha-hydroxylase by SKF-525A or by cholestyramine is accompanied by homeostatic responses by the liver which include induction of low-density lipoprotein clearance and increased cholesterogenesis to attempt to replenish sterol pools. These compensatory mechanisms are separately controlled.

Arterial cholesterol and DNA contents in relation to serum lipids and apolipoproteins. Studies on cystic artery biopsies

Though various relationships between serum lipoprotein levels and risk for atherosclerotic disease have been shown there are only a few studies on the relationships between serum lipoprotein levels and the lipid contents of the arterial wall. This study presents cholesterol and DNA contents of arterial tissue from biopsies of the cystic artery in 23 patients with uncomplicated cholecystolithiasis. Serum levels of cholesterol, triglycerides, alphalipoprotein cholesterol, apoA-I, A-II and B were determined, and the relationships between artery and serum variables were calculated. There was a positive correlation between serum apoB and the arterial cholesterol, normalized to the DNA contents (r = 0.43, P less than 0.05). There was a tendency towards an inverse correlation between the alpha-lipoprotein cholesterol levels and the arterial cholesterol (r = 0.39, P less than 0.10). There were no significant correlations between serum apoA-I or A-II and the arterial cholesterol contents. These data indicate that deposition of cholesterol in the arterial wall is related to the serum level of apoB, with higher levels of arterial cholesterol at higher serum levels of apoB. Earlier observations of an inverse correlation between alphalipoprotein cholesterol and arterial cholesterol could, however, not be conclusively confirmed.U

Isolation and partial characterization of the lipoprotein families A and A-I from high-density lipoproteins of human serum

Procedures for the isolation of two lipoprotein fractions from plasma high-density lipoproteins (HDL), characterized by apolipoprotein A-I and apolipoprotein A-I together with apolipoprotein A-II, have been elaborated. Apolipoprotein A-I was identified as the protein moiety of one of these fractions (lipoprotein A-I) with polyacrylamide gel electrophoresis (at basic and acidic pH, as well as in the presence of sodium dodecyl sulphate), immuno-double-diffusion, and amino acid analysis. Apolipoproteins A-I and A-II were identified as the protein moiety of the other fraction (lipoprotein A) with polyacrylamide gel electrophoresis (basic and acidic pH) and immuno-double-diffusion. Lipoprotein A-I consisted of spherical particles with a diameter similar to that of HDL as judged from negative strains in the transmission electron microscope. The diameter was estimated to be 8.7 nm from gel chromatography. Lipoprotein A-I migrated in the HDL position on crossed immunoelectrophoresis. On iso-electric focusing lipoprotein A-I appeared as multiple bands in the pH range 5.05-5.55. Lipoprotein A-I had the density of an HDL-2 fraction (rho: 1.063-1.105). Lipoprotein A consisted of spherical particles with a diameter similar to that of HDL, as judged from negative strains in the transmission electron microscope. The diameter was estimated to be 7.9 nm from gel chromatography. The molar ratio between the A-I and A-II polypeptides was estimated to 1.3:1 with electroimmunoassay and calculations from the amino acid compositions. Lipoprotein A migrated in the position of HDL on crossed immuno-electrophoresis. On iso-electric focusing lipoprotein A appeared as one major and two minor bands in the pH range 5.10-5.30. Lipoprotein A had the hydrated density of an HDL-2 fraction.

Effect of concentration of perfusing free fatty acid on arterial lipid synthesis in perfused normal and atherosclerotic rabbit aortas

Normal and atherosclerotic rabbit aortas were perfused at physiological pressure for 1 hour with media containing various concentrations of [3H]oleic acid, between 0.5 and 2.0 mmoles/l, complexed to a fixed concentration 40 g/l of bovine serum albumin (BSA). The mass of free fatty acid (FFA), which entered the arterial wall and was subsequently utilised for lipid synthesis, was calculated from the measured specific activities of FFA in the perfusates. In normal tissue, at all concentrations of FFA in the perfusate, the highest rates of utilisation of perfusate FFA for arterial lipid synthesis were for phospholipids (PL) and triglycerides (TG), with only about 2% in cholesteryl esters (CE). In atherosclerotic tissue, at both low and high concentrations of perfusate FFA, about 25% of fatty acid entering arterial lipids was in CE. When the concentration of FFA in the perfusion medium was raised, the mass of FFA from the medium that was incorporated in the total arterial lipids, increased in both normal and atherosclerotic tissue. The increase was due in normal tissue, to significant increases in incorporation into FFA, lecithin (PC), phosphatidyl inositol (PI), phosphatidyl ethanolamine (PE), TG and CE, whilst in atherosclerotic tissue it was due to increased incorporation into PC, PI, TG and CE. The results suggest that raised concentrations of FFA in blood may increase the rate of synthesis of lipids in normal and atherosclerotic tissue and thus exacerbate the accumulation of certain lipids such as cholesteryl esters, in fatty streak lesions of atherosclerosis.

Increased arterial-tissue cholesterol after intestinal bypass in severe obesity

Cholesterol content was measured in biopsy specimens of mesenteric artery taken at the time of jejuno-ileal bypass from 4 very obese patients aged 19, 22, 27, and 42. When their body-weight had become stable (mean 22 months) after operation, biopsy specimens of the temporal artery were obtained from 3 patients and of a mesenteric artery from 1. Cholesterol content had increased significantly. The increase in arterial-tissue cholesterol was concomitant with decreases in serum high-density (H.D.L.) and low-density (L.D.L.) lipoprotien cholesterol.

Cholesterol and DNA content in arterial tissue in severe obesity: their relation to some risk factors for ischaemic heart disease

Arterial tissue was obtained from twelve severely obese patients during jejuno-ileal by-pass surgery. The arterial DNA content was inversely correlated with the sum of venous glucose values during an oral glucose tolerance test (rs = -0.72). This observation may have implications on the known relationship between decreased glucose tolerance and early manifestations of atherosclerosis.

Skeletal-muscle sarcolemma from normal and dystrophic mice. Isolation, characterization and lipid composition

1. Mouse skeletal-muscle sarcolemma was isolated, and the preparations obtained from normal mouse muscle and from muscle of mice with hereditary muscular dystrophy were characterized with respect to appearance under the optical and electron microscopes, distribution of marker enzymes, histochemical properties and biochemical composition. 2. The sarcolemmal membranes from normal and dystrophic muscle were subjected to detailed lipied analysis. Total lipid content was shown to increase in sarcolemma from dystrophic mice as a result of a large increase in neutral lipid and a smaller increase in total phospholipids. Further analysis of the neutral-lipid fraction showed that total acylglycerols increased 6-fold, non-esterified fatty acid 4-fold and cholesterol esters 2-fold, whereas the amount of free cholesterol remained unchanged in sarcolemma from dystrophic muscle. Significant increases were found in lysophosphatidylcholine, phosphatidylcholine and phosphatidylethanolamine in dystrophic-muscle sarcolemma; however, the relative composition of the phospholipid fraction remained essentially the same as in the normal case. 3. The overall result of alterations in lipid composition of the sarcolemma in mouse muscular dystrophy was an increase in neutral lipid compared with total phospholipid, and a 4-fold decrease in the relative amount of free cholesterol in the membrane. The possible impact of these changes on membrane function is discussed.

Methods for the rapid separation and estimation of the major lipids of arteries and other tissues by thin-layer chromatography on small plates followed by microchemical assays

Methods are described for the rapid separation of the major individual phospholipids and neutral lipids of tissues by thin-layer chromatography on small glass plates (75 X 75 mm), and for the specific microchemical estimation of separated lipids and for determination of fatty acid composition and radioactivity. The overall method, involving tissues extraction, thin-layer chromatographic separation and assay has been evaluated using pure standards and biological samples and gives good reproducibility and almost complete recovery of lipids.

Lipid metabolism in cultured aortic smooth muscle cells and comparison with other cell types. Part 2. Reversibility of lipid accumulation caused by hyperlipemic serum

The lipid compositions of cultured rabbit aortic smooth muscle cells and skin fibroblasts were determined for cells grown in media containing either normolipemic or hyperlipemic sera. Both cell types accumulated cholesteryl esters and triglycerides after treatment with hyperlipemic serum. Within 4 days of returning cells that had accumulated these neutral lipids to medium containing a low percentage of normolipemic serum, their concentrations in both cell types had returned to levels similar to those found in cells cultured in standard growth medium. Thus the accumulation of cholesteryl esters and triglycerides in smooth muscle cells, as in fibroblasts, may be completely reversed in vitro.

Summary of available data for cholesterol in foods and methods for its determination

A search of the literature has been conducted on the cholesterol content of foods and on the methods for its determination. The amount of cholesterol in food is important because of its possible relationship to the onset of atherosclerosis in humans. Cholesterol is present primarily in foods of animal origin. The main sources in the American diet are eggs, poultry, dairy products, fish and seafood, and meat products. Only a few samples of these products have been analyzed. In many cases there is a wide range in cholesterol values for samples analyzed. Much of the research was conducted many years ago. The most commonly used methods were gravimetric or colorimetric. In many cases the samples investigated were not adequately described. Cholesterol was often determined without isolating it from interfering materials. Although some of the cholesterol values reported in the literature appear to be reasonably accurate, there is an urgent need for reinvestigation of the cholesterol content of foods using more recently developed methods of analysis.

Studies on human serum high-density lipoproteins. VI. Studies on a cholesterol ester-releasing reaction in vitro

High-density lipoproteins (HDL) turn turbid during in vitro incubation, concomitant with the formation of a cholesterol ester-rich lipoprotein, designated HDL-sup. The increase in turbidity (A) formed in relation to incubation time (t) is an asymptotic function: A=Uo(1 - e-k1t), where Uo is the amount of HDL with the property of releasing HDL-sup and k1 the velocity constant of the reaction. The increase in turbidity and formation of HDL-sup was not related to cholesterol ester content of the incubated fraction nor to exogenous factors like bacterial growth. The in vitro incubation was accompanied by a cholesterol esterification with a mean production of 8 nmol cholesterol ester/mg HDL protein, but also by a more pronounced degradation of phosphatidyl choline, 148 nmol/mg HDL protein. These data indicate that the lipid changes are induced by a two-step lecithin:cholesterol acyltransfer (LCAT) reaction. This reaction caused in HDL lipids a consumption of surface material and an increase in 'lipid core', presumably leading to a weakening and disruption of the lipoprotein surface with a recombination of 'lipid core' material in the form of HDL-sup.

Lipid metabolism in cultured aortic smooth muscle cells and comparison with other cell types. Part I. Composition of cells grown in hyperlipemic serum

The lipid compositions of cultured rabbit aortic smooth muscle cells, adventitial fibroblasts and skin fibroblasts were determined for cells grown in media containing either normolipemic or hyperlipemic serum. No significant changes were found in cell phospholipid composition. Each of the threee cell types responded similarly to hyperlipemic serum, accumulating esterified cholesterol and triglyerides.

Studies on human serum high-density lipoproteins. V. Isolation and characterization of a cholesterol ester-rich lipoprotein after in vitro incubation

Purified high-density lipoprotein (HDL), obtained by preparative ultracentrifugation at density 1.063-1.19 g/ml in the cold, were subfractionated by hydroxyl apatite column chromatography. Two of the obtained subfractions (subfractions II and III) turned turbid after incubation at 37 degrees C for 12 h. The turbid material was recovered in the supernatant of D 1.006 g/ml after centriguation at 30,000 g for 2 h. The lipoprotein fraction causing the turbidity was composed of 94% cholesterol ester and 2% apolipoprotein (by weight). On polyacrylamide gel electrophoresis the apolipoprotein moiety appeared as one polypeptide with the electrophoretic mobility of polypeptide A-I, revealed a blocked NH2-terminal amino acid, and had a total amino acid composition that differed from that of A-I and of the arginine-rich polypeptide.

Transfer of cholesterol in vitro between normal arterial smooth muscle tissue and serum lipoproteins of normo-lipidemic rabbits

During incubation of normal arterial tissue with serum lipoproteins, net transfer of cholesterol was observed in the direction from the lipoproteins into the arterial tissue. Such transfer was only observed during incubations with single, isolated lipoprotein fractions. It was independent of the type of lipoprotein, VLDL, LDL or HDL, which was incubated with the arterial tissue. On the other hand, no net transfer of cholesterol was observed during incubations of arterial tissue with a combination of serum lipoproteins equivalent to that in native serum. Studies on the transfer of radioactive cholesterol suggested that cholesterol elimination from arterial tissue in vitro was not affected by the composition of the incubation medium. Therefore, it is suggested that cholesterol accumulation more easily is influenced by the serum lipoprotein composition, and that serum lipoprotein dysbalance may promote cholesterol accumulation in the tissue. This effect may be present even when the dysbalance involves a decrease of specific serum lipoprotein fractions.

Role of phospholipids in the multiple forms of mammalian elongation factor 1

Evidence is presented that high-molecular-weight aggregates of elongation factor 1 from calf brain and liver contain phospholipids. Sucrose gradient analysis has shown that these high-molecular-weight species can be converted to a low-molecular-weight form after incubation with different phospholipase preparations. In addition, a partially purified elongation factor 1 from rabbit reticulocytes is also converted to a low-molecular-weight species by phospholipase treatment. These data indicate that phospholipids are involved in maintaining the integrity of the high-molecular-weight species and support the view that this species is an aggregate of the low-molecular-weight elongation factor 1.

Multiple forms of elongation factor 1 from calf brain

Heavy and light forms of elongation factor 1 (EF-1) from calf brain have been partially purified. The heterogeneous heavy species (EF-1(H)) with molecular weights of 2.5 x 10(5) to over 1 x 10(6) appears to be a complex or aggregate of the light form of the enzyme (EF-1(L)); the latter has a molecular weight of between 50,000 and 60,000. EF-1(H) but not EF-1(L), contains significant amounts of free and esterified cholesterol. Although EF-1(H) and EF-1(L) are both active in aminoacyl-tRNA binding to ribosomes, EF-1(L) reacts with GTP and aminoacyl-tRNA more efficiently than EF-1(H).