Cholesterol Ester Fatty Acids Research Articles

Endogenous triglyceride and glycogen in perfused rat hearts.

SummaryMobilization of endogenous lipid and glycogen by the isolated rat heart in vitro has been studied under a variety of conditions. Recirculating perfusion of hearts with Krebs bicarbonate buffer (45 min) led to a marked depletion (66%) of cardiac glycogen, while cardiac triglyceride was decreased by 24%. There were no changes in the levels of phospholipid, diglyceride, cholesterol ester, or free fatty acid. After perfusion for 90 min, in the absence of added substrates, endogenous glycogen and triglyceride were depleted to 16% and 38%, respectively, of the levels in the unperfused controls. During this second 45-min period of perfusion, a small but significant depletion of phospholipid also occurred, indicating that this lipid class is only used for energy after marked depletion of the other endogenous energy sources.Perfusions with epinephrine (10–5M) or dibutyryl adenosine 3′,5′-monophosphate (dibutyryl-cAMP) for 45 min produced marked decreases in the levels of cardiac glycogen and triglyceride, b...

The microdissection of large atherosclerotic plaques to give morphologically and topographically defined fractions for analysis: Part 1. The lipids in the isolated fractions

Thick sections of plaques from human aortas were dissected to give fractions for lipid analysis which were defined with respect to their morphological characteristics and their position in the plaque. In fibrous plaques containing no, or very few, fat-filled cells there was a significant positive correlation between percentage of free cholesterol and percentage of oleic acid in the cholesterol ester fatty acids (CEFA) within each tissue fraction, except the cap with low sudanophilia (mainly the surface layers). Percentage of free cholesterol was highest in the deep layers of the amorphous atheroma lipid pool (52%), and there was an almost 1 : 1 relationship with percentage oleic acid in the CEFA ( b = −0.924; r = 0.901). In the cap with low sudanophilia the lipid pattern resembled young normal intima. In plaques containing numerous fat filled cells lipid composition was the same in intact and apparently disintegrating fat-filled cells, but significantly different between apparently disintegrating cells and adjacent layers of the amorphous atheroma lipid pool. The deep layer of the amorphous atheroma lipid was identical with that in fibrous plaques. There was no correlation between free cholesterol and CEFA pattern within any fraction. This suggests that the difference in cholesterol esters between the fat-filled cells and amorphous lipid is due to infiltration of plasma cholesterol ester. It is calculated that, on average, 80% of the amorphous lipid in these large plaques containing numerous fat-filled cells is derived directly from plasma and only 20% from disintegrating fat-filled cells.

Vitamin D 3 induced alteration of microvillar membrane lipid composition

The lipid composition of microvillar membranes prepared from vitamin D 3-treated and vitamin D 3-deficient chick intestine has been investigated. Vitamin treatment results in an increase in the proportion of phospholipid in this target membrane as well as an alteration in the fatty acid composition of both membrane phospholipids and cholesterol esters. An increase in the weight percentage of several classes of phospholipid long chain polyunsaturated fatty acids results from vitamin treatment. The primary effect of vitamin treatment on cholesterol ester fatty acids appears to be in shorter chain species.

Interchangeability of fatty acids between phospholipids and esterified cholesterol in the plasma.

Experiments were performed to investigate incorporation of linoleic acid in lecithins probably synthesized from dietary linoleic acid within the intestinal wall and fatty acids in cholesterolesters, with plasma and liver homogenates pre-pared from albino rats.As a result, evidence has been obtained to demonstrate that linoleic acid con-tained in the α, β-dilinoleylphosphoryl choline molecule is incorporated into chole-sterol palmitate, and the palmitic acid in this cholesterolester into α, β-dilinoleyl-phosphoryl choline, respectively. These findings seem to suggest mutual inter-changeability of these fatty acids between the two forms of fat.

Contribution of thrombus free and esterified cholesterol to atherosclerotic plaques

<h2>Summary</h2> Free and esterified cholesterol content and cholesterol ester fatty acid composition were determined in organizing pulmonary thrombo-emboli and spontaneous aortic lesions in pigs. The transformation of emboli into fibrofatty plaques was not associated with changes in cholesterol composition similar to those of spontaneous atherosclerosis. This study suggests that little of the free and esterified cholesterol found in atherosclerotic plaques is derived directly from organizing thrombi.

Diet and cholesterol metabolism in young and old baboons

Cholesterol metabolism and serum lipids have been studied in young and old baboons fed a basal, low fat, commercial chow and then again after adding saturated fat and cholesterol to the chow. Serum cholesterol and triglyceride levels increased in all animals but there was little difference in these serum lipids between the two age groups. The change in cholesterol ester fatty acids was more marked in the young than in the old. The fractional contribution of dietary cholesterol to body pool was greater in the young than in the old group. The increase in fractional and absolute rate of cholesterol turnover was similar for the two age groups. The percentage of dietary cholesterol absorbed was also similar for the two age groups, however, there was a greater suppression of endogenous synthesis in the young group on transition to the high cholesterol diet.

Cholesterol ester and phospholipid composition of normal aortas and of atherosclerotic lesions in children

Gas chromatographic techniques have been used to study the lipid composition of children's arteries over the first decade of life. Children's aortas were separated into intima and media and, where present, into intimal fatty streak lesions and media underlying such lesions, and the level of cholesterol ester and of phospholipid and the fatty acid composition of these fractions in these various portions of the aortas was determined. The ester cholesterol concentration of the normal intima, but not of the media, increased with age. The ester cholesterol concentration of the fatty streak lesions exceeded that of the normal intima and also increased with age. No changes with age in phospholipid content for normal intima or media or for the intimal lesion were observed. The cholesterol ester fatty acid composition of the normal intima and of the media was similar to that of the lesions studied, and all tissues manifested a change in composition with age; cholesterol linoleate increasing and cholesterol palmitate decreasing during the first decade. These age changes for the aortic fractions were shown to resemble changes with age in the serum cholesterol ester fatty acids. The phospholipid fatty acid pattern of normal intima and media resembled those of the lesion but no change with age in phospholipid fatty acid pattern was found. No correspondence of the aortic phospholipid pattern with the serum pattern was demonstrated. These data are consistent with the view that arterial cholesterol ester, but not phospholipid, in both the normal intima and in the early fatty streak lesion in children arises initially from serum.

A potentially unique type of lipid storage in the migrating pink salmon.

Analysis of the composition of the hump developed by the pink salmon (Oncorhynchus gorbuscha) during the spawning migration has revealed that it consists largely of lipid at the start of the migration and that lipid is largely replaced by water at the end. Quantitation of the individual lipids reveals that the high triglyceride present at the start decreases, resulting in a relative increase of cholesterol ester and free fatty acid during the migration.

Position of double bonds in the fatty acids of cholesterol esters from human aorta

Cholesterol ester fatty acids (CEFA) from human aortas with fatty streaks and plaques were analyzed to determine the double bond positions of the unsaturated acids. Aorta CEFA contained a number of polyene fatty acids that were not identified in plasma CEFA. Nearly all the polyene fatty acids found in the aorta were derived from either linoleic or linolenic acid. Since these acids must be derived from the diet, it is presumed that long-chain polyene fatty acids derived from them represent chain elongation and desaturation by cells in the aorta. Polyene fatty acids derived by chain elongation and desaturation of palmitoleic or oleic acids were found in small amounts. The small amount of the 5, 8, 11 isomer of eicosatrierioic acid found suggests that at some point in the evolution of the lesions there is limited availability of linoleic acid.

The Fatty Acids of Adrenal Lipids from Essential Fatty Acid-deficient Rats

Male rats were fed for 36 weeks diets containing 10% corn oil or 10% hydrogenated coconut oil. The adrenal lipids were extracted, fractionated by column chromatography and the fatty acid composition of the fractions determined by gasliquid chromatography. The major fatty acid in the cholesterol ester fraction from the deficient rats was identified as 7,10,13-docosatrienoic acid (22:3ω9) and this accounted for 25% of the total fatty acids in this fraction. The polyunsaturated acid usually found in tissues from EFA-deficient animals, 5,8,11-eicosatrienoic acid (20:3ω9), constituted 21% of the total adrenal cholesterol ester fatty acids. This pattern in the deficient rats refiected that found in the control animals where 22:4ω6 and 20:4ω6 were the major acids. The structure of the 22:3ω9 acid was confirmed by ozonolysis. Just as the 22:4ω6 acid was characteristic of the adrenal cholesterol esters and was not a major component of the triglycerides or phospholipids of normal animals, no 22:3ω9 acid was found in the triglyceride fraction and very little in the phospholipid fraction from the adrenals of EFA-deficient rats. Arachidonic and 20:3ω9 were the major polyunsaturated acids of the phospholipids from normal and deficient rat adrenals, respectively.

Helical twisting power of steroidal solutes in cholesteric mesophases.

Shifts in the nematic temperature of a compensated cholesteric liquid-crystal solvent, consisting of cholesteryl chloride and cholesteryl myristate, are caused by adding steroidal solutes. A helical twisting power P can be defined which is a molecular property; there is a linear dependence of the inverse of the solute concentration on the helical pitch. The method has the advantages of (1) allowing study of compounds which do not form mesophases themselves and (2) eliminating temperature effects. For a series of fatty acid esters of cholesterol, P decreases with decreasing number of carbon atoms in the ester chain, and shows a zigzag fine structure with P having higher values for odd-numbered carbon-atom chains. P, and therefore the helix, changes rotational senses if the ester chain is replaced by Cl, Br, or OH. Changes are also discussed associated with modification of the 17 side chain or the steroid ring system itself. A model is proposed attributing P to the molecular asymmetry at the 3β position of the steroid ring, which can cause macroscopic twist if two lever arms are present, one of which lacks rotational symmetry.

The Influence of Chronic Vitamin C Deficiency on Fatty Acid Composition of Blood Serum, Liver Triglycerides and Cholesterol Esters in Guinea Pigs

Chronic hypovitaminosis C (2-week scorbutogenic regime followed by administration of maintenance dose of 0.5 mg ascorbic acid for 24 hours) in guinea pigs produced hypercholesterolemia and an increased accumulation of cholesterol in liver. Deficiency of ascorbic acid increased significantly the content of saturated fatty acids (up to chain length C16) and decreased content of mono- and polyunsaturated fatty acids in cholesterol esters of liver. Similar changes were observed after administration of the same diet supplemented with 0.25% of cholesterol to guinea pigs saturated with vitamin C. In blood serum of vitamin C-deficient guinea pigs, the cholesterol esters contain an increased amount of linoleic acid and a decreased amount of palmitic and oleic acids. The spectrum of fatty acids in triglycerides of blood serum and liver was not significantly affected by hypovitaminosis C. It is surmised that the primary cause of the observed changes is the disturbance of cholesterol metabolism, produced by chronic vitamin C deficiency.

Synthesis of Serum and Sub-cellular Liver Cholesterol Esters in Fasted and Fed Rats

The formation of serum and liver sub-cellular liver cholesterol esters was investigated in fasting and fed rats. Rats were injected with cholesterol-4-14C-labeled serum and the liver and serum cholesterol esters examined at 45, 90, and 180 minutes. There was a marked heterogeneity in the labeling of the cholesterol esters in the liver cell fractions and serum. In both fasting and fed rats the soluble fraction 14C-esters had a higher proportion of 14C-arachidonate than the particulate liver fractions. Fasting rats had a higher percentage of 14C-arachidonate in the liver cell fractions and serum cholesterol esters than fed rats. There were also comparable differences in the cholesterol ester fatty acid composition. The differences in 14C-activity distribution and cholesterol ester fatty acid composition were principally at the expense of monounsaturated esters. The specific activity of the liver cell fraction esters exceeded the specific activity of the corresponding esters in the serum. Cholesterol arachidonate in serum and liver had the highest fractional turnover rate. The data suggest that there is a compartmentalization of cholesterol ester metabolism in the liver and that the liver is the major source of the serum esters. The types of cholesterol esters synthesized in the liver and released into the blood are dependent on the nutritional status of the animal.

Tissue changes in experimental chronic endogenous hyperlipemia

Tissue changes produced by Triton-induced hyperlipemia were studied in dogs receiving a stock diet for 6–28 months: (1) Atheromatous plaques or calcification were not observed in these animals. (2) Mobilization of endogenous lipids resulted in diffuse deposition in the reticuloendothelial system, gallbladder and kidney. (3) Serum lipid patterns differed from those following high-cholesterol feeding. Each doubling in normal cholesterol concentration was accompanied by a 3-fold increase in free cholesterol and a 9 to 10-fold elevation in triglyceride. The ratio of total cholesterol to phospholipid, however, did not change. (4) Serum and other tissue fatty acid patterns were markedly changed. Cholesterol ester fatty acids were more affected than those of triglyceride or phospholipid. In general, a shift toward increased saturation of fatty acids took place in all tissues, except adipose. As a result of this change, fatty acid patterns approached those found in normal adipose tissue.

Purification of the fatty acid present in carcinolipin

Methods were developed for the chromatography of fatty acid methyl esters on urea-impregnated papers, thin layers and columns of urea and Celite. Fatty acids of cholesterol esters from beef liver were separated by clathrate chromatography into factions of unsaturated, branched chain saturated and straight chain saturated fatty acids. Cholesterol esters were synthesized from these fractions and commercial cholesterol and their effect was tested on the incorporation of labelled amino acids into s-RNA of rat liver in vitro. Only esters of the fraction of branched chain fatty acids were active. This fraction was further separated into 6 components by preparative GLC. The cholesterol ester of only one of these components, a saturated fatty acid with carbon number 16.7, showed a stimulating effect on protein synthesis. This fatty acid was purified to 98–99% by repeated preparative GLC and obtained in crystalline form. It is concluded that the combination of clathrate chromatography and preparative GLC is very suitable for the isolation of pure branched chain fatty acids from biological materials.

The lipids in raised fatty and fibrous lesions in human aorta: A comparison of the changes at different stages of development

Summary Raised atherosclerotic lesions were divided into two main types on a histological basis: (1) fatty lesions in which the lipid was primarily within fat-filled cells; (2) fibrous lesions which contained collagen and no fat-filled cells. Both types of lesion were then sub-divided into early stages, in which all the sudanophilic lipid is within fat filled cells (type 1) or in the form of intact perifibrous lipid (type 2), and later stages in which there is a central area of extracellular lipid. Lipid analyses were made on whole small lesions of both types and stages, and on the dissected caps and amorphous centres of larger lesions. The cholesterol ester fatty acid composition was completely different in the two types of lesion: fatty lesions with no amorphous lipid contained 53% oleic acid and 13% linoleic acid, whereas fibrous lesions with no amorphous lipid contained 25 % oleic acid and 43 % linoleic acid. In lesions with amorphous lipid the percentage of free cholesterol increases, and this is highly correlated with changes in the proportions of oleic and linoleic acid. In each type of lesion the proportion of the most abundant acid falls with increasing percentage of cholesterol in the free form ( fatty plaques -oleic acid; r=−0.765, P fibrous plaques -linoleic acid; r=−0.674, P = 0.001). This suggests that enzymic hydrolysis of cholesterol ester is occurring. The ratio of cholesterol to phospholipid increases significantly in fibrous but not in fatty lesions.

Cholesterol ester formation in aortas of cholesterol-fed rabbits

Intravenous injection of [ 14 C]acetate into cholesterol-fed rabbits from which liver, intestine and kidneys had been removed resulted in a rapid incorporation of 14 C into aortic cholesterol ester fatty acids whereas little or no 14 C was incorporated into the non-saponifiable fraction. Most of the label was found in saturated fatty acids and in monoenes. Incubation of aortic strips in serum labeled with [ 14 C]palmitate and [ 3 H] cholesterol resulted in a much more rapid incorporation of [ 14 C]palmitate than of [ 3 H]cholesterol into the aortic cholesterol ester fraction. A similar result was obtained after injection of [ 14 C]palmitate and [ 14 C]cholesterol into a cholesterol-fed animal. The hypothesis that in cholesterol-fed rabbits serum fatty acids penetrate more rapidly than serum cholesterol to the sites of esterification in the arterial wall is discussed.

Incorporation of 14-C-labeled acetate into lipid by isolated foam cells and by atherosclerotic arterial intima.

The synthesis of lipid by rabbit atherosclerotic intima incubated in vitro has been investigated and compared with that of foam cells isolated from intimal lesions. In the atherosclerotic arterial intima, 14 C-labeled acetate is readily incorporated into the lipid fraction, most of the label being found in the phos-pholipid and cholesterol ester fatty acid fractions. Minimal incorporation into triglyceride, fatty acid, and cholesterol occurred. The major phospholipid synthesized was lecithin but significant incorporation into phosphatidyl inositol, phosphatidyl ethanolamine, and sphingomyelin also took place. The fatty acids synthesized were predominantly saturated in the phospholipid fraction. More monounsaturated fatty acids were present in the cholesterol ester fatty acids, but in both moieties little polyunsaturated fatty acids were labeled by the acetate. Isolated foam cells were also shown to incorporate 14 C-labeled acetate into both phospholipid and cholesterol ester fatty acids. The foam cells, however, incorporated a significantly higher proportion of acetate into cholesterol ester than did the whole intima. The fatty acids synthesized by the foam cells were more polyunsaturated in both the phospholipid and the cholesterol ester fraction than was the case with the whole intima. The relevance of these findings to the origin of lipid in the atherosclerotic lesion is discussed.

Lipid composition of the vascular system during infancy, childhood, and young adulthood

The object of this study was to determine the changes in lipid composition that occur in blood vessels from infancy to young adulthood. Analyses included levels of total cholesterol, total triglyceride, phospholipid, and cholesteryl ester fatty acids, and the distribution of saturated and unsaturated fatty acids. Triglyceride, total and monoenoic fatty acids, and linoleic acid were lower in the ascending, thoracic, and abdominal aorta than in the pulmonary artery and inferior vena cava. Phospholipids and arachidonic acid were higher in aortic segments than in the other two vessels. Aortic lipids showed significant changes with increasing age: total cholesterol and total fatty acids decreased from <1 wk to 5 yr, then increased to 22 yr of age. Triglycerides decreased whereas cholesteryl esters increased from 10 to 22 yr of age. Saturated fatty acids decreased from 1 wk to 10 yr, then remained relatively constant. Linoleic acid (3.7-9.8% of total fatty acids) and arachidonic acid (15.8-21.7%) both increased with age; the increase in cholesteryl linoleate was highly significant. After 10 yr of age, total cholesterol and total fatty acids were significantly higher in abdominal than in ascending and thoracic segments of aorta.

Quantitative and qualitative lipid correlation in experimental endogenous hyperlipemia

The reversible endogenous hyperlipemia in dogs, elicited by the detergent Triton which was given intravenously, was used to study the interrelations of serum lipids. In the cholesterol ester fraction an increase occurs in both monounsaturated and in saturated fatty acids, excepting myristic; while a decrease occurs in polyunsaturated fatty acids. The fatty acids of cholesterol esters of normal dogs contain 22% oleic acid, and only 24% when serum lipids are increased to almost double their normal value (TC=400-500 mg/100 ml). However there is a critical level above which a rapid rise in oleic acid occurs and, in severe hyperlipemia (TC=1500 +/-430 mg/100 ml), this acid constitutes almost half of the esterified fatty acid component.Since there is no evidence that Triton directly regulates fatty acid synthesis, the lipid fraction-fatty acid interrelationship may be secondary to lipid mobilization from endogenous sources. This concept is supported by the fact that the increased serum fatty acids are only those which can be synthesized by animals. It is suggested, on the basis of a marked increased of endogenously produced fatty acids, that, at critical lipid levels, shortage of polyunsaturated fatty acids from exogenous sources occurs. This might be of sufficient degree to accelerate fatty acid synthesis to meet the need for fatty acids for energy requirements. There may also be need of fatty acid for esterification of chiefly the accumulated free cholesterol split from lipoprotein by Triton.Triton-induced changes in cholesterol ester fatty acids result in patterns which closely resemble those in the adipose tissue of dog and man and in the serum of human endogenous hyperlipemia.