Increase In Esterified Cholesterol Research Articles

Differential distribution of cholesterol pools across arteries under high-cholesterol diet

Excessive cholesterol constitutes a major risk factor for vascular disease. Within cells, cholesterol is distributed in detergent-sensitive and detergent-resistant fractions, with the largest amount of cholesterol residing in cellular membranes. We set out to determine whether various arteries differ in their ability to accumulate esterified and non-esterified cholesterol in detergent-sensitive versus detergent-resistant fractions throughout the course of a high-cholesterol diet. Male Sprague-Dawley rats were placed on 2 % cholesterol diet while a control group was receiving iso-caloric standard chow. Liver, aorta, and pulmonary, mesenteric, and cerebral arteries were collected at 2–6, 8–12, 14–18, and 20–24 weeks from the start of high-cholesterol diet. After fraction separation, esterified and free non-esterified cholesterol levels were measured. In all arteries, largest cholesterol amounts were present in detergent-sensitive fractions in the non-esterified form. Overall, cholesterol in aorta and cerebral arteries was elevated during 14–18 weeks of high-cholesterol diet. Cerebral arteries also exhibited increase in esterified cholesterol within detergent-sensitive domains, as well as increase in cholesterol level in the detergent-resistant fraction at earlier time-points of diet. Pulmonary artery and mesenteric artery were largely resistant to cholesterol accumulation. Quantitative polymerase chain reaction (qPCR) analysis revealed up-regulation of low-density lipoprotein receptor (Ldlr) and low-density lipoprotein receptor-related protein 1 (Lrp1) gene expression in cerebral arteries when compared to mesenteric and pulmonary arteries, respectively. In summary, we unveiled the differential ability of arteries to accumulate cholesterol over the course of a high-cholesterol diet. The differential accumulation of cholesterol seems to correlate with the up-regulated gene expression of proteins responsible for cholesterol uptake.

Alcohol-Induced Hepatic Steatosis: A Comparative Study to Identify Possible Indicator(s) of Alcoholic Fatty Liver Disease.

Fatty liver is an early sign of both nonalcoholic and alcoholic fatty liver diseases. Ethanol feeding using a Lieber-DeCarli liquid diet (LD) model which contains 35% fat to rats or mice is a well-established model for alcoholic fatty liver. However, LD diet alone can also induce fatty liver and its differential metabolic profile may be able to differentiate steatosis induced by LD versus LD plus ethanol. We investigated the lipidomic differences in the livers of Sprague-Dawley (SD) rats fed a pellet diet (PD), LD and liquid ethanol diet (LED) for six weeks. Male Sprague Dawley rats were fed with nonalcoholic diets PD, LD or LED (ethanol in LD) for six weeks. Lipids were extracted and analyzed by nuclear magnetic resonance (NMR)- based metabolomics. The NMR data obtained was analyzed by multivariate Principal Component Analysis (PCA) and Spotfire DecisionSite 9.0 software to compare PD versus LD and LD versus LED groups. PCA of the NMR spectral data of livers of both comparisons showed a clear separation of PD from LD group and LD from LED group indicating differences in lipid profiles which corresponded with changes in total lipid weights. LD showed increases for cholesterol, esterified cholesterol, cholesterol acetate and triglycerides with decreases for fatty acyl chain, diallylic and allylic protons, while the LED showed increases in esterified cholesterol, cholesterol acetate, fatty acid methyl esters, allylic protons and some triglyceride protons with decreases in free cholesterol and phosphatidylcholine (PC). Our data suggest that altered lipid signature or PC levels could be an indicator to differentiate between nonalcoholic versus alcoholic fatty liver.

Membrane plasmalogen composition and cellular cholesterol regulation: a structure activity study

BackgroundDisrupted cholesterol regulation leading to increased circulating and membrane cholesterol levels is implicated in many age-related chronic diseases such as cardiovascular disease (CVD), Alzheimer's disease (AD), and cancer. In vitro and ex vivo cellular plasmalogen deficiency models have been shown to exhibit impaired intra- and extra-cellular processing of cholesterol. Furthermore, depleted brain plasmalogens have been implicated in AD and serum plasmalogen deficiencies have been linked to AD, CVD, and cancer.ResultsUsing plasmalogen deficient (NRel-4) and plasmalogen sufficient (HEK293) cells we investigated the effect of species-dependent plasmalogen restoration/augmentation on membrane cholesterol processing. The results of these studies indicate that the esterification of cholesterol is dependent upon the amount of polyunsaturated fatty acid (PUFA)-containing ethanolamine plasmalogen (PlsEtn) present in the membrane. We further elucidate that the concentration-dependent increase in esterified cholesterol observed with PUFA-PlsEtn was due to a concentration-dependent increase in sterol-O-acyltransferase-1 (SOAT1) levels, an observation not reproduced by 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibition.ConclusionThe present study describes a novel mechanism of cholesterol regulation that is consistent with clinical and epidemiological studies of cholesterol, aging and disease. Specifically, the present study describes how selective membrane PUFA-PlsEtn enhancement can be achieved using 1-alkyl-2-PUFA glycerols and through this action reduce levels of total and free cholesterol in cells.

Studies on the mechanism of accumulation of cholesterol in the gallbladder mucosa. Evidence that sterol 27-hydroxylase is not a pathogenetic factor

Background/Aims: Cholesterolosis is characterized by accumulation of esterified cholesterol in human gallbladder mucosa. The present study aimed at investigating possible pathogenetic factors for cholesterolosis. The hypothesis was tested that a reduced sterol 27-hydroxylase or an increased amount of ACAT-1 enzyme may be of importance. Methods: Gall bladder mucosa and bile were obtained from patients with cholesterol gallstones undergoing cholecystectomy (30 with and 43 without cholesterolosis). Results: In cholesterolosis, the gall bladder mucosa was characterized by a several-fold increase in esterified cholesterol and normal content of free cholesterol. The amount of ACAT-1 protein, measured by immunoblotting, was similar in patients with and without cholesterolosis. The level of 27-hydroxycholesterol in gallbladder mucosa was elevated sevenfold as compared with cholesterol in patients with cholesterolosis. Most (87%) of this oxysterol was esterified and the accumulation is most probably secondary to the higher total amount of cholesterol in the cells. Patients with cholesterolosis had normal levels of both sterol 27-hydroxylase mRNA (real time polymerase chain reaction) and protein (immunoblotting). The enzymatic activity of the sterol 27-hydroxylase in gallbladder mucosa was normal or increased in cholesterolosis. Conclusions: The pathogenesis of cholesterolosis may be multifactorial, but is not caused by reduced efflux of cholesterol due to a defect sterol 27-hydroxylase mechanism.

Experimental autoimmune encephalomyelitis: antigen-induced inhibition of biochemical and immunohistological alterations.

A comprehensive biochemical, immunological, and histological study was undertaken during suppression of experimental autoimmune encephalomyelitis (EAE) induced by antigen-specific inhibition of the immune response. Pretreatment of Wistar rats by intraperitoneal administration of low doses of saline-soluble bovine myelin or myelin basic protein (MBP) but not with ovalbumin suppresses the appearance of the clinical symptoms of EAE induced by sensitization with bovine myelin in complete Freund's adjuvant. Analysis of the central nervous system (CNS) of animals pretreated with MBP or whole myelin shows inhibition of the diminution of MBP and 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) activity observed in the EAE animals or in rats pretreated with ovalbumin. With respect to the CNS lipid content, these suppressive treatments abolish the increase in esterified cholesterol and partially revert the diminution in the content of cerebrosides and total cholesterol characteristic of the acute stage of the disease. Concomitantly, meningeal and parenchymal infiltration with mononuclear cells and deposits of immunoglobulins in the infiltrated regions as well as in spinal cord motor neurons were reduced. Analysis of the humoral response to myelin antigens shows that all EAE as well as treated animals developed antibodies to MBP and other myelin proteins. However, a higher incidence and level of these antibodies was observed in nontreated EAE animals and MBP- and ovalbumin-treated rats, while rats treated with total bovine myelin showed a highly reduced humoral response. The present results indicate that intraperitoneal treatment with soluble forms of myelin antigens, concomitant with the suppression of the clinical symptoms of the disease, markedly reduces the biochemical and histological alterations occurring in EAE animals and produces changes in the autoimmune humoral response.

Cholesterol metabolism in liver and gallbladder mucosa of patients with cholesterolosis

The objective of this study was to investigate possible pathogenetic factors for cholesterolosis. Liver tissue, gallbladder mucosa, and gallbladder bile were collected in patients with cholesterol gallstones (GS) (14 patients with and 14 patients without cholesterolosis) and gallstone-free (GSF) subjects (11 with and 21 without cholesterolosis) undergoing cholecystectomy. In cholesterolosis, the gallbladder mucosa was characterized by a fivefold increase in esterified cholesterol and normal content of free cholesterol. The hepatic levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, governing cholesterol synthesis, and acyl coenzyme A: acyltransferase activity, catalyzing the esterification of cholesterol, were similar in patients with and without cholesterolosis. Also in the gallbladder mucosa, the 3-hydroxy-3-methylglutaryl coenzyme A reductase activity was similar in patients with and without cholesterolosis. The acyl coenzyme A: acyltransferase activity of the gallbladder mucosa was increased in the GSF subjects with cholesterolosis. The nucleation time of gallbladder bile was shorter in the GSF subjects with cholesterolosis compared with the time of those without cholesterolosis. Occurrence of cholesterol crystals, lipid composition, and cholesterol saturation of gallbladder bile were not significantly influenced by the absence or presence of cholesterolosis. The study has confirmed that cholesterolosis is associated with a several-fold increased level of esterified cholesterol. The data suggest that patients with cholesterolosis have normal hepatic cholesterol formation and esterification. The local synthesis of cholesterol in the gallbladder mucosa seems to be normal. A positive correlation was obtained between the cholesterol saturation of bile and the content of esterified cholesterol in the gallbladder mucosa in the whole series of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholesterol metabolism in liver and gallbladder mucosa of patients with cholesterolosis

The objective of this study was to investigate possible pathogenetic factors for cholesterolosis. Liver tissue, gallbladder mucosa, and gallbladder bile were collected in patients with cholesterol gallstones (GS) (14 patients with and 14 patients without cholesterolosis) and gallstone-free (GSF) subjects (11 with and 21 without cholesterolosis) undergoing cholecystectomy. In cholesterolosis, the gallbladder mucosa was characterized by a fivefold increase in esterified cholesterol and normal content of free cholesterol. The hepatic levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, governing cholesterol synthesis, and acyl coenzyme A: acyltransferase activity, catalyzing the esterification of cholesterol, were similar in patients with and without cholesterolosis. Also in the gallbladder mucosa, the 3-hydroxy-3-methylglutaryl coenzyme A reductase activity was similar in patients with and without cholesterolosis. The acyl coenzyme A: acyltransferase activity of the gallbladder mucosa was increased in the GSF subjects with cholesterolosis. The nucleation time of gallbladder bile was shorter in the GSF subjects with cholesterolosis compared with the time of those without cholesterolosis. Occurrence of cholesterol crystals, lipid composition, and cholesterol saturation of gallbladder bile were not significantly influenced by the absence or presence of cholesterolosis. The study has confirmed that cholesterolosis is associated with a several-fold increased level of esterified cholesterol. The data suggest that patients with cholesterolosis have normal hepatic cholesterol formation and esterification. The local synthesis of cholesterol in the gallbladder mucosa seems to be normal. A positive correlation was obtained between the cholesterol saturation of bile and the content of esterified cholesterol in the gallbladder mucosa in the whole series of patients. However, because cholesterolosis may occur in both GSF subjects and patients with cholesterol GS with or without cholesterol-saturated bile, the uptake of cholesterol from the gallbladder bile may not be the only mechanism for the development of cholesterolosis.

Modulation of sphingomyelinase-induced cholesterol esterification in fibroblasts, CaCo 2 cells, macrophages and smooth muscle cells

The present study has focused on three questions concerning the effect of sphingomyelinase on release of free cholesterol from the plasma membrane and its intracellular translocation: (i) Can one change the direction of the flow of cholesterol? (ii) Can one modulate the flow? (iii) May such a mechanism be relevant in atherogenesis? (i) The results obtained show that even in the presence of potent nonlipoprotein cholesterol acceptors in the medium, the intracellular flow of cholesterol is not reduced as measured by cholesterol esterification. Moreover, in sphingomyelinase-treated cells, cholesterol efflux in presence of nonlipoprotein acceptors was not enhanced even when intracellular esterification was inhibited. (ii) Modulation of the sphingomyelinase induced cholesterol flow can be obtained by 100 μM verapamil which reduces it. In human skin fibroblast, interference with the delivery of free cholesterol to its site of esterification was found in the presence of brefeldin A. (iiI) Aortic smooth muscle cells in culture are sensitive to low concentrations of sphingomyclinase and the increase in esterified cholesterol is evident also after exposure to the enzyme for 24 h. The present results suggest that in the plasma membrane, free cholesterol bound to sphingomyelin may be in a compartment which renders it more available for transport to the cell interior than for efflux. In view of the sensitivity of aortic smooth muscle cells to sphingomyelinase, this mechanism for enhanced esterification of cholesterol could be relevant to the transformation of arterial smooth muscle cells into foam cells in the process of atherogenesis.

Effects of blocking plasma lipid transfer protein activity in the rabbit

Plasma lipid transfer protein activity was completely blocked in rabbits for up to 48 h by infusion with goat antibody to rabbit lipid transfer protein. Lipid transfer protein activity in plasma of control animals, infused with antibody from a non-immune goat, decreased during the experiment but was never less than 50% of pre-infusion levels. During the period that lipid transfer protein activity was completely blocked, there were changes in high-density lipoprotein composition (expressed as % by weight) with a reduction in triacylglycerol from 8.4 ± 2.4% to 1.0 ± 0.2% ( P < 0.05) and an increase in esterified cholesterol from 10.7 ± 1.7% to 14.5 ± 0.3% ( P < 0.1). In conjunction with the observed changes in high-density lipoprotein composition, there was an increase in high-density lipoprotein particle size from a mean radius of 4.7 to 5.4 nm. The change in composition and particle size was not observed in high-density lipoproteins from control animals. There was a change in the distribution of plasma cholesterol in control animals, with a fall in the proportion of cholesterol in high-density lipoproteins ( P < 0.02) and consequently an increase in the proportion of cholesterol in low-density lipoproteins ( P < 0.02). However, the distribution of plasma cholesterol in animals in which lipid transfer protein activity was inhibited was maintained at original levels during the period of inhibition. Consequently, in these animals, there was a less atherogenic distribution of cholesterol during the period of lipid transfer protein inhibition when compared with control animals. The changes observed in lipoproteins, in the absence of lipid transfer protein activity, demonstrate that lipid transfer protein modifies lipoproteins in vivo and appears to contribute to a more atherogenic lipid profile.

Study of the components of reverse cholesterol transport in lecithin: Cholesterol acyltransferase deficiency

Enzymatic and lipid transfer reactions involved in reverse cholesterol transport were studied in healthy and lecithin:cholesterol acyltransferase (LCAT), deficient subjects. Fasting plasma samples obtained from each individual were labeled with [ 3H]cholesterol and subsequently fractionated by gel chromatography. The radioactivity patterns obtained corresponded to the elution volumes of the three major ultracentrifugally isolated lipoprotein classes (very low density lipoproteins (VLDL), low density lipoproteins (LDL), and high density lipoproteins (HDL)). In healthy subjects, the LCAT activity was consistently found in association with the higher molecular weight portion of HDL. Similar observations were made when exogenous purified LCAT was added to the LCAT-deficient plasma prior to chromatography. Incubation of the plasma samples at 37 °C resulted in significant reduction of unesterified cholesterol (FC) and an increase in esterified cholesterol (CE). Comparison of the data of FC and CE mass measurements of the lipoprotein fractions from normal and LCAT-deficient plasma indicates that: (i) In normal plasma, most of the FC for the LCAT reaction originates from LDL even when large amounts of FC are available from VLDL. (ii) The LCAT reaction takes place on the surface of HDL. (iii) The product of the LCAT reaction (CE) may be transferred to either VLDL or LDL although VLDL appears to be the preferred acceptor when present in sufficient amounts, (iv) CE transfer from HDL to lower density lipoproteins is at least partially impaired in LCAT-deficient patients. Additional studies using triglyceride-rich lipoproteins indicated that neither the capacity to accept CE from HDL nor the lower CE transfer activity were responsible for the decreased amount of CE transferred to VLDL and chylomicrons in LCAT-deficient plasma.

Biochemical composition of coronary arteries in Finnish children.

To study the early features of atherosclerosis, we analyzed coronary artery intima medias from 63 boys and 30 girls who were newborn to 15 years old at the time of accidental death. Fatty streaks were found in five boys and one girl and, with one exception, were not present until the second decade of life. From birth there was a continuous increase in esterified cholesterol (EC) and a two- to threefold rise in free cholesterol and phospholipid. DNA, total protein, and collagen tended to rise after the first decade. The content of hyaluronic acid remained fairly constant, but sulphated glycosaminoglycans (GAGs) rose during the second decade; the highest increases were in dermatan and chondroitin sulphates. The content of arterial EC showed significant positive correlations with those of GAGs, but associations with the contents of DNA, total protein, and collagen were not significant. As judged by the observed gradual increase in arterial EC and a change in its fatty acid composition, there is a continuous increase with age in LDL-derived EC in the arterial wall. The mechanism of this accumulation is unknown, but the findings provide circumstantial evidence to support the concept that arterial GAGs may cause retention of plasma-derived lipids, which may subsequently be altered and internalized by the intimal cells.

カイロミクロン, VLDL-TG水解過程での, HDLにおけるコレステロールエステル化能の選択的抑制

Effects of Intralipid on the increase of esterified cholesterol (EC) in each lipoprotein fraction in the fresh fasting plasma (FP) or triglyceride lipaserich plasma (PHP) from normal, and type V hyperlipoproteinemic subjects were investigated. FP or PHP was mixed with 14C-FC-albumin solution and was preincubated at 4°C for two hours. The mixture was incubated with Intralipid or with 0.15M NaCl solution. Incubation mixtures were collected at 0, 120 and 240 minutes. Chylomicron, VLDL, IDL, LDL and HDL were fractioned ultra-centrifugally at 4°C. Lipids were extracted with chloroform-methanol (2:1) and EC and FC were separated by TLC. The radioactivities of them were measured with a liquid scintillation counter. In the normal FP, Intralipid significantly increased 14C-EC in chylomicron, and VLDL fractions. However, Intralipid reduced cholesterol esterification, and this was solely due to the complete suppression of 14C-EC increase in HDL in normal PHP. The specific activities of EC in HDL were significantly lower than those in LDL in normal PHP with Intralipid. In FP of type V hyperlipoproteinemia, the increase of 14C-EC was more in chylomicron and VLDL fractions and less in LDL and HDL fractions than that in normal FP. The effect of Intralipid addition was very small in FP of type V hyperlipoproteinemia. In PHP of type V hyperlipoproteinemia, the results were very similar to those in normal FP with Intralipid. No increase of 14C-EC was observed in HDL. The effect of Intralipid addision was also small as in FP. Therefore, we concluded as following. Intralipid worked like chylomicron. There were two pathways for cholesterol esterification in the plasma. One was active in HDL and was blocked almost completely by Intralipid or chylomicron during the lipolysis. The other was active in other lipoproteins and was not inhibited by Intralipid or chylomicron during lipolysis.

Cholesterol esters and the ester-metabolizing enzymes in Jimpy and Quaking mouse brains

The concentration of free and esterified cholesterol and the activities of the cholesterol esterifying enzyme and cholesterol ester hydrolases in brains from Jimpy and Quaking mice and their normal littermates were determined. In Quaking affected mice these brain components did not differ significantly from those in brains of normal littermates. In the Jimpy affected mouse brain, however, the concentration of free cholesterol was reduced and the esterified cholesterol was increased. The increase in esterified cholesterol was accompanied by higher activity of cholesterol esterifying enzyme and a significant reduction in activity of hydrolases. In the absence of exogenous fatty acids, cholesterol esterification by cell-free preparations of brain from Jimpy affected mice was also significantly higher than the normal littermates. These data indicate that an increase in cholesterol ester concentrations in Jimpy affected brain may result either from an increase in esterification due to an increase in the availability of free fatty acid as substrate, or from deficiency in the activity of the hydrolases. In addition, the data indicate that in Jimpy mutants there is a significant reduction in brain cholesterol content, whereas in Quaking mutants the sterol content of developing brain is not significantly affected. This suggests that during brain development sterol synthesis in brain is reduced in Jimpy but not in Quaking mutants.

Influence of hormones on testicular lipids of adult rats.

Testosterone, oestradiol-17 beta, progesterone and prolactin were administered for 1 and 7 days to adult rats to study the short- and long-term effects of these hormones on testicular lipids. Testosterone administration induced a marked increase in testicular phospholipids and a significant fall in glycerides. Oestrogen, on the other hand, provoked a significant increase in total lipids and glycerides with no marked changes in testicular phospholipids. Progesterone elicited significant changes in cholesterol fractions; a marked increase in esterified cholesterol with a concurrent fall in free cholesterol was observed. Prolactin treatment resulted in a significant fall in total lipids and phospholipids with no marked change in tissue weight. It also induced a marked fall in total and free cholesterol with a significant increase in esterified cholesterol.

Effects of Testosterone, Progesterone and Testosterone plus Progesterone on Rat Testicular Lipids

The effects of testosterone, progesterone or testosterone plus progesterone on testicular lipids of pubertal rats are presented. The hormones were administered for 1 day as well as 7 days continuously to study both short and long term effects. Testosterone induced marked depletion of glycerides in short and long term treatments. It elicited a significant increase in phospholipids only in long term treatment. Progesterone brought about marked increase in esterified cholesterol with a congenital fall in free cholesterol. It had no significant effect on testicular glycerides and phospholipids Testosterone plus progesterone administration caused marked increase in phospholipids with a fall in glyceride levels even in short term treatment. There was a marked increase in esterified cholesterol with a concurrent fall in free cholesterol level. Thus, testosterone plus progesterone treatment brought out marked changes in phospholipids, glycerides and cholesterol fractions.These hormonal treatments did not have any significant effect on testicular weight in short as well as long term studies.

Role of prolactin on the development of the prepubertal testes of the rat.

The effects of prolactin, progesterone and prolactin plus progesterone (P-P) on the testes of adult rats have been reported in a previous paper. In the present studies, the responses of prepubertal testes to the administration of prolactin, progesterone and P-P are reported. The hormones were administered for 1 day as well as 7 days continuously to study both short- and long-term effects. Prolactin increased the weights of seminal vesicles significantly in both short- and long-term treatments. Progesterone did not exert any significant effect on tissue weights. P-P treatment, on the other hand, markedly reduced the weights of testes and seminal vesicles. This effect was more pronounced in long-term treatment. Prolactin when given alone or in combination with progesterone, brought about a marked fall in total testicular lipids and phospholipids. The depletion of phospholipids was found to be due to the significant decrease observed in phosphatidylcholine and phosphatidylethanolamine classes. Progesterone had no significant effect on total testicular lipids and phospholipids. Prolactin brought about a marked increase in esterified cholesterol and total cholesterol. Progesterone and P-P treatments, on the other hand, induced a significant increase in esterified cholesterol followed by a fall in free cholesterol. Thus prolactin, irrespective of the maturity of the animal, brings about a marked fall in total testicular lipids and phospholipids. The esterified- and total-cholesterol-increasing action of prolactin appears to be antagonized by progesterone which brings about a concurrent fall in free cholesterol following the increase in esterified cholesterol.

Effect of hyperlipemic serum on cholesterol accumulation in monkey aortic medial cells

The effect of hyperlipemic monkey serum on cholesterol ester formation and accumulation in monkey aortic medial cells grown in tissue culture was studied. The cellular incorporation and esterification of free cholesterol was followed using the specific activity of serum labeled with free [ 14C]cholesterol while the cellular sterol content was analyzed by gas-liquid chromatographic techniques. The effects produced by hyperlipemic monkey serum (HMS) and normal monkey serum (NMS) were evaluated at both comparable percentage levels in the media and at equivalent exogenous cholesterol concentrations. When the two sera were adjusted to equal exogenous free cholesterol levels, the incorporation of free cholesterol by the aortic medial cells was related to the free cholesterol concentration of the culture media whether supplied by normal or hyperlipemic serum, while hyperlipemic serum slightly stimulated the esterification of this free cholesterol. Under these conditions the total cholesterol content of the HMS-grown cells was 35% greater than that of NMS-grown cells, due to an elevation in free cholesterol of approximately 3 μg/mg cell protein and a 2- to 4-fold increase in esterified cholesterol. At similar percentage levels, the hyperlipemic serum stimulated a greater incorporation of free cholesterol into the monkey medial cells, accompanied by a 2-fold increase in the cellular esterification of this free cholesterol.

Origin of esterified cholesterol transported in the very low density lipoproteins of human plasma

In two subjects the specific activity of esterified cholesterol in plasma lipoprotein subfractions was measured for up to 9 hr after an intravenous injection of [(3)H]mevalonic acid. It was found to be consistently higher in larger (S(f) > 100) than in smaller (S(f) 20-100) very low density lipoproteins (VLDL). Four subjects were given an intravenous injection of heparin so that the VLDL could be studied as its concentration fell and subsequently rose again. During the first hour the relative reduction was greatest for triglyceride, intermediate for free cholesterol, and least for esterified cholesterol. Between 1 and 7 hr postheparin, the VLDL pool was restored, but the pattern of increase of individual lipids was not parallel. The triglyceride increment was much greater during the 1-4-hr period than during the 4-7-hr period; in three of the subjects the free cholesterol increment was also greater during the earlier period. The increase in esterified cholesterol, however, was consistently greater during the 4-7-hr period. In six other subjects the specific activity of VLDL esterified cholesterol was related to that of its possible plasma precursors in samples collected at 1-hr intervals for 8 hr after the injection of [(3)H]mevalonic acid. Free cholesterol emerged as the most likely immediate precursor with the possibility of a hepatic as well as an intraplasma origin. The results did not support a major in vivo transfer of esterified cholesterol from high density lipoproteins to VLDL.

Movement of cholesterol in vitro in rat blood and quantitation of the exchange of free cholesterol between plasma and erythrocytes

After administration of [4-(14)C]cholesterol to rats, blood was obtained and incubated for 6 hr or less. Incubation resulted in a net loss of erythrocyte cholesterol and, simultaneously, in an increase of esterified cholesterol in plasma and alpha-lipoproteins. Erythrocyte labile cholesterol was shown to be the sole precursor of esterified cholesterol. However, the relation between loss and esterification was not absolute. Loss of erythrocyte cholesterol could be inhibited without affecting esterification and vice versa. A catenary turnover model is proposed, which links in vivo erythrocyte labile cholesterol and plasma esterified cholesterol. Free cholesterol also exchanged between erythrocytes and lipoproteins. The topological model, as tested by analog computer, appears to be a bicompartmental system governed by nonconstant exchange fluxes. They are exponential functions of time and vary from 0.065 to 0.020 mg/hr/g of blood. The fitting of the curves obtained by analog computer analysis to the experimental curves requires esterification as described above. Variation of the exchange fluxes would be the consequence of lipoprotein structural alterations. If this is true, the initial value of the measured flux in vitro is identical with the in vivo value, and the turnover time of erythrocyte cholesterol is 9.2 hr. Initial exchange flux is not dependent on plasma cholesterol level or on the age of the rats, but it is temperature dependent. Addition of amphotericin B to the plasma does not modify exchange fluxes, but erythrocyte cholesterol loss is increased.

Lipid Composition of rat brain myelin in triethyl tin-induced edema

Chronic triethyl tin intoxication was induced in young adult rats by oral feeding of triethyl tin sulfate. Progressively severe brain edema developed during the 3-month experimental period. The yield of myelin from the brains of the experimental animals decreased to almost half normal per brain, but the isolated myelin appeared morphologically normal. The analysis of whole brain showed corresponding decreases in proteolipid protein and total lipid, particularly galactolipids. The proportions of the major constituents of isolated myelin (chloroform-methanol-insoluble residue, proteolipid protein, and total lipid) were unchanged despite the low yield. However, the proportion of cholesterol increased from 16 to 21% dry weight, and that of total galactolipid decreased from 21 to 15%, as the yield of myelin decreased. This decrease of total galactolipid was mainly due to the decrease in cerebroside. Total phospholipid remained constant initially but showed a slight decrease toward the end of the experiment, due mostly to decreased ethanolamine phospholipid. There was no preferential loss or preservation of phosphatidalethanolamine. The fatty acid composition of sulfatide showed statistically significant shifts to less long-chain fatty acids and less monoenoic acids, but cerebroside and sphingomyelin did not show significant changes in the fatty acid composition. There was no increase in esterified cholesterol. These findings generally support our hypothesis of nonspecific chemical abnormalities of the myelin sheath undergoing secondary degeneration. In an acute experiment, a single intraperitoneal injection of triethyl tin sulfate produced acute and transient brain edema. There were slight decreases in the yield of myelin, but no detectable changes in the chemical composition.