Fatty Acid Composition Of Cholesteryl Esters Research Articles

Associations between fatty acid composition in serum cholesteryl esters and liver fat, basal fat oxidation, and resting energy expenditure: a population-based study

ABSTRACTBackgroundWe have repeatedly shown in short-term feeding trials that a high intake of dietary n–6 PUFAs, i.e. linoleic acid, prevents liver fat accumulation compared with saturated fat. However, population-based data is lacking and the mechanisms behind such effects are unclear.ObjectiveTo investigate associations between serum cholesteryl ester (CE) fatty acids and liver fat, basal fat oxidation [respiratory quotient (RQ)], and resting energy expenditure (REE). We hypothesized that PUFA in particular is inversely associated with liver fat and that such a relation is partly explained by a PUFA-induced increase in basal fat oxidation or REE.MethodsCross-sectional analyses using linear regression models in a population-based cohort with data on serum CE fatty acid composition and liver fat (n = 308).ResultsLinoleic acid (18:2n–6) (β = −0.03, 95% CI: −0.06, −0.001) and Δ5 desaturase index were inversely associated, whereas, γ-linolenic acid (18:3n–6) (β = 0.59, 95% CI: 0.28, 0.90), dihomo-γ-linolenic acid (20:3n–6) (β = 1.20, 95% CI: 0.65, 1.75), arachidonic acid (20:4n–6) (β = 0.08, 95% CI: 0.002, 0.16), palmitoleic acid (16:1n–7) (β = 0.37, 95% CI: 0.04, 0.70), Δ6 desaturase, and stearoyl CoA desaturase-1 (SCD-1) index were directly associated with liver fat after adjustment for confounders. Several serum CE fatty acids were correlated with both liver fat and REE, but only the association between DHA (22:6n–3) and liver fat was clearly attenuated after adjustment for REE (from β = −0.63 95% CI: −1.24, −0.02 to β = −0.34, 95% CI: −0.95, 0.27). Palmitoleic acid and SCD-1 were weakly inversely correlated with RQ but could not explain a lower liver fat content.ConclusionsSeveral serum CE fatty acids are associated with liver fat, among them linoleic acid. Although we identified novel associations between individual fatty acids and RQ and REE, our findings imply that PUFAs might prevent liver fat accumulation through mechanisms other than enhanced whole-body energy metabolism.

LIPA gene mutations affect the composition of lipoproteins: Enrichment in ACAT-derived cholesteryl esters

Background and aimsCholesteryl ester storage disease (CESD) due to LIPA gene mutations is characterized by hepatic steatosis, hypercholesterolemia and hypoalphalipoproteinemia, exposing affected patients to an increased cardiovascular risk. Further insights into the impact of LIPA gene mutations on lipid/lipoprotein metabolism are limited. Aim of the study was to investigate the effect of carrying one or two mutant LIPA alleles on lipoprotein composition and function. MethodsLipoproteins were isolated from 6 adult CESD patients, 5 relatives carrying one mutant LIPA allele (carriers) and 12 sex/age matched controls. Lipid profile, lipoprotein mass composition and the fatty acid distribution of cholesteryl esters (CEs) were assessed. HDL function was evaluated as the ability to promote nitric oxide release by endothelial cells. ResultsDespite the lipid-lowering therapy, total cholesterol, LDL-cholesterol and triglycerides were increased in CESD patients compared to controls, while HDL-cholesterol was reduced. Carriers also displayed elevated total and LDL-cholesterol. Very low and intermediate density lipoproteins from CESD patients and carriers were enriched in CEs compared to the control ones, with a concomitant reduction of triglycerides. Fatty acid composition of CEs in serum and lipoproteins showed a depletion of linoleate content in CESD patients, due to the reduced LCAT activity. In CESD HDL, fatty acid distribution of CEs was shifted towards saturated ones, if compared to control HDL. The changes in HDL composition did not affect HDL ability to promote nitric oxide release by endothelial cells. ConclusionsLIPA gene mutations significantly affected plasma levels and lipid composition of lipoproteins, likely contributing to the increased cardiovascular risk of affected patients.

Dietary Fat–Induced Alterations in Atherosclerosis Are Abolished by ACAT2-Deficiency in ApoB100 Only, LDLr −/− Mice

The enzyme acyl-coenzymeA (CoA):cholesterol O-acyltransferase 2 (ACAT2) in the liver synthesizes cholesteryl esters (CE) from cholesterol and fatty acyl-CoA, which get incorporated into apoB-containing lipoproteins that are secreted into the bloodstream. Dietary fatty acid composition influences the amount and fatty acid composition of CE within apoB-containing lipoproteins. We hypothesized that when ACAT2 activity is removed by gene deletion, hepatic CE synthesis and secretion would be minimal and, as a result, dietary fat-related differences in atherosclerosis would be eliminated. Groups of female apoB100 only, LDLr-/- mice with and without ACAT2 were fed diets enriched in either omega-3 or omega-6 polyunsaturated fat, saturated fat, and cis or trans monounsaturated fat. After 20 weeks on diet, mice fed diets enriched in monounsaturated or saturated fat exhibited significantly higher amounts of plasma cholesterol, larger LDL particles enriched in monounsaturated CE, and more atherosclerosis than mice fed polyunsaturated fat. The dietary fat-induced shifts in plasma cholesterol, LDL size, LDL CE composition, and atherosclerosis were not observed in ACAT2-/- mice. Regardless of the diet fed, the ACAT2-/- mice were protected from atherosclerosis. The results indicate that in apoB100 only, LDLr-/- mice, ACAT2 plays an essential role in facilitating dietary fat type-specific atherosclerosis through its various effects on plasma lipoprotein concentration and composition.

Low serum cholesteryl ester-docosahexaenoic acid levels in Alzheimer's disease: a case-control study.

Low n-3 polyunsaturated fatty acid (PUFA) status may be associated with neuro-degenerative disorders, in particular Alzheimer's disease, which has been associated with poor dietary fish or n-3 PUFA intake, and low docosahexaenoic acid (DHA) status. The present case-control study used an established biomarker of n-3 PUFA intake (serum cholesteryl ester-fatty acid composition) to determine n-3 PUFA status in patients with Alzheimer's disease, who were free-living in the community. All cases fulfilled the National Institute of Neurological and Communicative Disorders and Stroke and Alzheimer's Disease and Related Disorders Association criteria for Alzheimer's disease. Detailed neuropsychological testing and neuroimaging established the diagnosis in all cases. The subjects (119 females and twenty-nine males) aged 76.5 (SD 6.6) years had a clinical dementia rating (CDR) of 1 (SD 0.62) and a mini mental state examination (MMSE) score of 19.5 (SD 4.8). The control subjects (thirty-six females and nine males) aged 70 (SD 6.0) years were not cognitively impaired (defined as MMSE score <24): they had a mean MMSE score of 28.9 (SD 1.1). Serum cholesteryl ester-eicosapentaenoic acid and DHA levels were significantly lower (P<0.05 and P<0.001 respectively) in all MMSE score quartiles of patients with Alzheimer's disease compared with control values. Serum cholesteryl ester-DHA levels were progressively reduced with severity of clinical dementia. DHA levels did not differ in patients with Alzheimer's disease across age quartiles: all were consistently lower than in control subjects. Step-wise multiple regression analysis showed that cholesteryl ester-DHA and total saturated fatty acid levels were the important determinants of MMSE score and CDR. It remains to be determined whether low DHA status in Alzheimer's disease is a casual factor in the pathogenesis and progression of Alzheimer's disease.

Dietary Associates of Serum Total, LDL, and HDL Cholesterol and Triglycerides in Patients with Coronary Heart Disease

Background. Diet–lipid associations established in clinical trials have in general been weak or nonexistent in cross-sectional studies within a population. Our objective was to analyze the dietary associates of serum lipids in patients with coronary heart disease (CHD) not using lipid-lowering medication.Methods. Patients with coronary bypass grafting (n = 49), balloon angioplasty (n = 46), acute myocardial infarction (n = 79), and acute myocardial ischemia (n = 79) participated in a survey (EUROASPIRE). Patients were selected from hospital records at least 6 months after hospitalization. Diet was assessed by a food record, a short questionnaire, and fatty acid composition of serum cholesteryl esters (CE).Results. Neither the intake of total fat nor that of saturated, monounsaturated, or polyunsaturated fatty acids was associated with serum lipids. Use of soft margarine on bread (though not in cooking or baking) and high intake of fiber and cereal products were associated with low total cholesterol. Linoleic acid in CE was inversely associated with total cholesterol and triglycerides, and eicosapentaenoic acid was inversely associated with triglycerides and positively associated with HDL cholesterol.Conclusions. In the present study use of soft margarine on bread (though not in cooking or baking) and high intake of fiber and cereal products were associates of lowered serum cholesterol concentrations in CHD patients. Fatty acid composition of CE reflected dietary fatty acid intake involved in cholesterol lowering better than food records.

Tracking of serum fatty acid composition: a 6-year follow-up study in Finnish youths.

The composition of fatty acids in serum cholesteryl esters was analyzed with gas chromatography in 759 Finnish boys and girls aged 3-18 years in 1980 and again in the same subjects in 1983 and in 1986. The mean percentage of linoleate (18:2 n-6) increased from 50.85% in 1980 to 52.60% in 1986, while there was a decrease in myristate (14:0), palmitate (16:0), and eicosapentaenoate (20:5 n-3). The percentage of oleate (18:1) did not change. The stability (tracking) of cholesteryl ester fatty acid composition was examined by calculating linear correlation coefficients among the percentages of each fatty acid at the three study points. For linoleate, 3- and 6-year tracking correlations were 0.59-0.61 and 0.50, respectively; they were of about the same magnitude for arachidonate (20:4 n-6) and lower for the other fatty acids. Results indicate that the serum cholesteryl ester fatty acid composition has somewhat lower tracking than the total cholesterol concentration. The changes in the mean fatty acid composition of the study population obviously reflect a shift from saturated to unsaturated dietary fats.

Analysis of the physical state of cholesteryl esters in arterial-smooth-muscle-derived foam cells by differential scanning calorimetry

The physical state of cholesteryl esters (CE) in the arterial-smooth-muscle-derived foam cells may contribute to the documented reduction in CE hydrolysis. The physical state of CE may also provide a potential enhancing mechanism for increased CE accumulation. To explore these concepts, we therefore examined the influence of alterations in CE and triacylglycerol (TG) content and their fatty acid composition on the thermotropic behaviour of these lipids by differential scanning calorimetry (d.s.c.). After exposure to cationized LDL (cLDL) or after infection with herpes simplex virus type I (HSV), smooth-muscle cells accumulated significant amounts of CE. The CE/TG ratio was significantly higher in cells treated with cLDL compared with HSV infection. TG content was unaffected by either treatment. However, the fatty acid profile of both CE and TG was significantly different between treatment groups, with the polyunsaturated fatty acid/saturated fatty acid (PUFA/SFA) ratio being significantly higher in cLDL-treated cells than in HSV-infected cells. The d.s.c.-generated thermograms of intact cells revealed that neutral lipids of both treatment groups were in the isotropic-liquid state, similar to the state of lipids derived from 'fatty streak' types of atherosclerotic lesions. Differences in the thermograms between HSV-infected and cLDL-treated cells can be ascribed to differences in the CE content and the fatty acid composition of CE and TG (PUFA/SFA ratio). Polarizing optical microscopy revealed the presence of isotropic lipids in both groups. Biochemical and physicochemical data confirm the lysosomal localization of engorged CE, and indicate that the cellular isotropic CE in these foam cells are in a physical state which favours enzymic hydrolysis.

Intestinal apolipoprotein synthesis and secretion in the suckling pig.

The present studies report characterization of intestinal apolipoprotein (apoLp) synthesis and secretion in the suckling pig. Lipoproteins (d less than 1.006 g/ml) from mesenteric lymph were found to contain both apoB-100 and B-48, in addition to apoA-IV, E, A-I, and Cs. Lymph low density lipoproteins (LDL) and high density lipoproteins (HDL) contained mainly apoB-100 and apoA-I, respectively. Analysis of core cholesteryl ester fatty acid composition suggested filtration from plasma as the major source of lymph LDL and HDL. Dual radioisotope labeling of intestinal and hepatic apoLps in lymph, as well as immunoprecipitation of radiolabeled intestinal mucosa, demonstrated intestinal synthesis of apoB-48, A-IV, and A-I. There was no evidence for apoB-100 synthesis by intestinal mucosa. By contrast, piglet liver synthesized apoB-100, E, A-I, and Cs, but not apoB-48. Newly synthesized intracellular intestinal apoA-I was mainly (basic) isoform 1 (pI 5.58), while lymph and plasma HDL apoA-I were predominantly isoform 3 (pI 5.33), mature apoA-I. Lymph apoB (P less than 0.001) and apoA-I (P less than 0.04) mass output increased significantly during lipid absorption. Studies were subsequently conducted in fasting, fat-fed, bile-diverted, and sham-operated animals to determine the role of both dietary and biliary lipid in regulating intestinal apoLp biosynthesis. Proximal and distal small intestinal loops were pulse-radiolabeled with [3H]leucine, and apoB-48 and A-I were immunoprecipitated from cytosolic supernatants. Although a proximal to distal gradient in intestinal synthesis rates for both apoB and A-I was noted in all groups, the acute absorption of dietary lipid did not significantly increase apoB or A-I synthesis in either location. Complete removal of biliary lipid for 48 hr did not alter synthesis rates in jejunum or ileum. These studies suggest that mesenteric lymph apoLps in the suckling pig are derived both by filtration from plasma and by direct secretion from the intestine. Physiologic regulation of intestinal apoA-I and B-48 synthesis rates appears to be independent of luminal lipid availability.

Effect of cholesterol supplementation on plasma and liver cholesteryl ester fatty acids in rats fed casein or soy protein

The effect of supplementation with cholesterol on plasma and liver cholesteryl ester fatty acids was examined in rats fed diets containing different protein sources. Weanling male rats were fed a semi-purified diet containing 20% casein or 20% soy protein for seven weeks and then 1% (by weight) of cholesterol was added for three more weeks. Rats fed soy protein grew consistently slower than those fed casein. The plasma and liver cholesterol contents were not significantly different between the two protein groups in the unsupplemented rats; however, they were significantly increased in cholesterol-fed animals, particularly in casein-fed rats. Analysis of the cholesteryl ester fatty acid composition in plasma and liver demonstrated that cholesterol-feeding significantly increased the levels of saturated fatty acids, monounsaturated fatty acids and linoleic acid in casein-fed rats as compared to those fed soy protein. The level of cholesteryl arachidonate in liver, which was low initially, increased slightly in the liver of casein-fed rats but did not significantly change in the plasma of either protein group.

Fatty acid composition of serum cholesteryl esters in relation to serum lipids and apolipoproteins in 3–18-year-old finnish children and adolescents

Serum cholesteryl ester (CE) fatty acids, serum lipids and apolipoproteins were analysed from 1 348 Finnish children aged from 3 to 18 years. The study was part of a comprehensive survey of coronary heart disease risk factors and their determinants in Finnish children and adolescents. The percentage of CE linoleate (18: 2) had significant negative correlations with the serum concentrations of total and LDL cholesterol, triglycerides as well as apo B. The associations of HDL to CE fatty acids were weak, although there was a significant positive correlation of CE-18: 2 to HDL cholesterol and apo A-I. The ratio of HDL to total cholesterol and the ratio of apo A-1 to apo B increased strongly in quintiles of increasing percentage of CE-18: 2. In conclusion, the present results show significant associations between serum CE fatty acid composition and the different components of serum lipoproteins among free-living Finnish children and imply a relation between the quality of dietary fats and serum lipoproteins within this population.

Alterations in biosynthesis and homeostatis of cholesterol and in lipoprotein patterns in mice bearing a transplanted lymphoid tumor

The membrane fluidity of murine lymphoid GRSL tumor cells has been shown to depend on their site of growth in the host. Tumor cells located in ascites, in contrast to those in the enlarged spleen, show a very high plasma membrane fluidity, mainly due to a decreased level of cellular (membrane) cholesterol. Yet, the rate of cholesterol biosynthesis in the tumor cells as estimated by the activity of HMG-CoA reductase and the incorporation of [ 14C]acetate into cholesterol was extremely high when compared to various lymphoid cells in normal control mice. Also the rate of biosynthesis and the cholesterol content in liver and spleen of tumor-bearing mice were substantially higher than in the organs of control mice. Blood plasma cholesterol, however, was decreased in tumor-bearing mice as a result of altered lipoprotein patterns. Outgrowth of the tumor was accompanied by a strong reduction in plasma high-density lipoproteins. Low-density lipoproteins became transiently increased, but eventually all lipoproteins, and consequently the plasma cholesterol content decreased to very low levels, especially so in the ascites plasma. The low transfer of [ 14C]cholesteryl ester-labeled lipoproteins between blood and ascites plasma after either intravenous or intraperitoneal injection suggested a hampered flow between the two compartments. Also apparent differences in cholesteryl ester fatty acid composition between lipoproteins of the blood and ascites plasma indicated the lack of a rapid equilibration between the two compartments. The results suggest that the limited availability of lipoproteins as an additional source of cholesterol to the rapidly growing ascites cells promotes their high membrane fluidity.

Lipids of human atherosclerotic plaques and xanthomas: clues to the mechanism of plaque progression.

While the content of fatty streaks and fibrous plaques has been extensively studied in autopsied specimens, little is known about the lipid composition of advanced human atherosclerotic plaques requiring surgical removal. We have analyzed free cholesterol, cholesteryl ester, and the cholesteryl ester fatty acid content in 19 carotid and 7 femoral obliterative plaques obtained at endarterectomy. These were compared with values from each subject's plasma and from xanthomas removed from eight patients. The total cholesterol content was 75.1 mg/g dry weight for carotid plaques, 56.0 mg/g for femoral plaques, and 106.8 mg/g for xanthomas. The free cholesterol content was 56.6% and 50.4% of the total cholesterol for carotid and femoral plaques, respectively, while the free cholesterol of xanthomas was only 25.5%. The fatty acids of cholesteryl esters were analyzed in an attempt to identify the site of their esterification, i.e., within plasma or within plaque. This can be determined using the ratio of linoleic acid (18:2) to oleic acid (18:1) in the cholesteryl ester. The ratios were 0.36 for xanthoma, 1.62 for carotid plaque, 1.73 for femoral plaque, and 2.51 in plasma. These data emphasize two chemical changes occurring with evolution of the atherosclerotic process: 1) The cholesteryl ester fatty acid composition of the plaque becomes increasingly similar to that of plasma, and 2) there is a continuing increase in the percentage of free cholesterol. These alterations reflect a decreased metabolic efficiency within atherosclerotic lesions and may initiate events that enhance plaque progression.

Plasma cholesteryl ester fatty acids in 3- and 12-year-old finnish children

Risk factors associated with coronary heart disease were surveyed in a multicentre study carried out in 1979 among children living in different parts of Finland. The survey included analyses of plasma lipids and cholesteryl ester (CE) fatty acids as well as a dietary interview by a 48-hour recall method. The present report gives the plasma fatty acid compositions obtained from 181 3-year-old and 226 12-year-old children and their relations to dietary factors and other plasma lipids. The mean percentages (±SD) of CE linoleate in the 3- and 12-year-old children were 49.2 ± 5.2 and 51.0 ± 5.0%, respectively. Differences in CE fatty acid composition between the various regions of Finland were relatively small, but there was a trend to higher proportions of polyunsaturated fatty acids in western and urban compared with eastern and rural communities. Among different dietary constituents the daily intake of margarine + oils or butter had the greatest effect on plasma CE fatty acid composition. There was a highly significant positive correlation between the dietary P/S ratio and the percentage of CE linoleate in plasma.

Influence of Trans-9-, Trans-12-, and CIS-12-octadecenoic acid isomers on fatty acid composition of human plasma lipids

Deuterium-labeled trans-9-, trans-12-, and cis-12-octadecenoic acid isomers were fed to young adult male subjects. Incorporation of these deuterated isomeric fats into plasma lipids was followed by GC-MS, and the influence of the isomers on plasma lipid fatty acid composition was determined. The 18:2 and 20:4 levels in the phospholipid fractions initially decreased and 16:0, 18:0 and 18:1 levels increased as the deuterated 12-octadecenoic acids were incorporated. A smaller reverse effect was found for 16:0 and 18:2 acids when trans-9-octadecenoic acid was fed. Fatty acid composition of phosphatidylcholine returned to near baseline values as the monoenoic acid isomers levels began to decrease. Initially after feeding 12–18:1, plasma triglyceride 16:0 levels increased and 18:2 levels decreased. The percentage of 18:2 continued to decrease after the 12-octadecenoic acid level began to decrease. Presumably this occurred because plasma tryglycerides continued to supply phospholipids with 18:2. Fluctuation of both the 16:0 and 18:2 fatty acid percentages in plasma tryglyceride samples were correlated with trans-9-octadecenoic acid content. Only low levels of all three octadecenoic acid isomers were incorporated into the plasma cholesteryl ester fraction, and none of the isomers had an effect on cholesteryl ester fatty acid composition.

The prevention of alcoholic fatty liver using dietary supplements: Dihydroxyacetone, pyruvate and riboflavin compared to arachidonic acid in pair‐fed rats

AbstractMale Sprague‐Dawley rats were fed for 30 days a high‐fat liquid ethanol diet with dihydroxyacetone, pyruvate and riboflavin added as supplements (AMA‐). Plasma triglyceride (TG) levels were 6‐fold greater in these rats than in those fed and alcohol with without the supplements (AA‐). The liver TG content in rats fed the AMA‐diet was similar to that of rats fed a control diet (CA‐) in which alcohol was replaced with isocaloric amounts of dextrose. Livers of rats fed the AA‐ diet had 3 times more TG than controls. Alcohol ingestion also enhanced the hepatic content of cholesteryl esters (CE) and phospholipids (PL). These lipids were reduced to levels found in livers of rats fed the control diet (CA‐) when dihydroxyacetone, pyruvate and riboflavin were included in the alcohol diet. The fatty acid compositions of TG, CE and PL from livers of rats fed the AMA‐diet were similar to those of corresponding lipids from rats fed the control diet (CA‐) but differed from compositions when fed the alcohol diet (AA‐). Regardless of the diet fed, TG had the same fatty acid composition in plasma and liver. The same was true of PL fatty acid composition. However, the fatty acid composition of CE differed between liver and plasma. The major fatty acid in liver CE was 18∶1 whereas in plasma it was arachidonic acid (20∶4). Reduced fatty liver was observed in an earlier study when rats were fed ad libitum an ethanol diet containing 20∶4. In the present study, we pair‐fed the same diet and fatty liver was not reduced. Dihydroxyacetone, pyruvate and riboflavin did not prevent alcohol‐induced fatty liver when 20∶4 was included in the AMA‐diet. Our results confirm that dietary dihydroxyacetone, pyruvate and riboflavin prevent alcohol‐induced fatty liver, and show that this effect may result from increased mobilization of fat from liver.

Adiposity, lipids, alcohol consumption, smoking, and gender

Indices of obesity, plasma lipids, and lipoprotein levels, plasma cholesteryl ester fatty acid composition, reported alcohol consumption and smoking habits were measured in 88 men and 87 women, ages over 15 years, randomly selected from the total respondents (1192) to a health survey. Most indices of obesity were related to plasma triglycerides and high-density lipoprotein levels in both sexes; to very low-density lipoprotein levels in men only; and to plasma cholesteryl ester fatty acid linoleic acid proportions in women only. The correlations with high-density lipoprotein cholesterol levels were dependent on very low-density lipoprotein triglyceride levels in men but not in women. Indices of obesity were significantly higher in nonsmoking women and reported alcohol consumption correlated with Quetelet's index (body mass index) in men. Smoking habits, but not alcohol consumption, influenced correlations between indices of obesity and plasma triglycerides and very low-density lipoprotein triglyceride levels in men. The present results showed several sex-related differences in relationships with indices of obesity. Lower very low-density lipoprotein levels, higher skinfold measurements, higher cholesteryl ester fatty acid linoleic acid proportions and lower alcohol intake in women than in men may be responsible. The data suggested that in women, altered diet composition may be linked with obesity.

Cholesteryl esters of pigeon ( Columba livia) aortas as a function of age

1. 1. The amounts of free and esterified cholesterol and the cholesteryl ester fatty acid composition of upper thoracic aortas and muscular foci at the celiac bifurcation in 1-day-old, 6-week-old and 6-month-old pigeons ( Columba livia) were determined. 2. 2. There were no significant age differences in the amounts of free and esterified cholesterol or in the cholesteryl ester fatty acid composition of upper thoracic aortas. 3. 3. In celiac foci the amount of cholesteryl esters increased with age. Accumulation of saturated cholesteryl esters accounted for 70% of the increase. 4. 4. The pattern of cholesteryl ester accumulation in celiac foci of young pigeons resembles that seen in the aortas of other young animals including humans.

Compositional mapping of cholesteryl ester droplets in the fatty streaks of human aorta.

Frozen sections prepared from human aortic tissue containing fatty streak lesions were examined on a thermally controlled stage with a polarizing light microscope. Distinct birefringent droplets, 0.5-5 mum in diameter, were observed, many apparently aggregated into clusters. The clusters were about 20 X 20 mum in diameter (the approximate size of foam cells). Upon being heated, each smectic droplet exhibited a sudden change of birefringence, indicating a change of state. The transition temperatures were compared to assess compositional distributions in the tissue. We found that for 52% of the clusters the standard deviation of the cluster's droplet melting point distribution was less than half that observed in the surrounding microscopic field. If clusters were intracellular lipid inclusions, this observation indicates that the lipid composition within a foam cell is more homogeneous than that of the overall field. However, using statistical methods, we compared droplet melting populations from cluster to cluster and found significant heterogeneity. The observations can be interpreted to suggest that many foam cells modify the cholesteryl ester fatty acid composition of their accumulations be selective uptake, temporal sampling, or chemical reaction. Furthermore, the intercellular heterogeneity suggests that different cells in the lesion may have different metabolic and transport enzyme affinities or be in different states.

Hepatoma, host liver, and normal rat liver neutral lipids as affected by diet

Groups of normal and hepatoma (7288CTC) bearing rats were maintained on normal chow and fat-free diets for 4 weeks. Normal liver, host liver, and hepatoma neutral lipids were examined in detail and compared. Water content, unaffected by diet was: hepatoma, 82 percent; host liver, 71 percent; and normal liver, 67 percent. The fat-free diet had no effect upon the hepatoma neutral lipids but elevated the triglyceride level in normal and host liver, shifted the triglyceride carbon number distribution to lower mol wt, and elevated the percentage of monoenoic acids in triglycerides and cholesteryl esters. Host triglyceride concentrations were ca. half, and cholesterol levels were reduced moderately relative to normal liver values. Hepatoma cholesterol levels were higher and triglyceride concentrations lower than normal and host liver values. Hepatoma triglycerides differed dramatically from liver and were characterized by increased concentrations of high mol wt species and a fivefold increase in the percentage of C-20 and C-22 fatty acids. The percentage of C-20 and C-22 fatty acids in hepatoma cholesteryl esters also increased ca. fivefold relative to liver. The data indicate that the systems that regulate triglyceride and cholesteryl ester fatty acid composition in liver do not control the compositions of these lipid classes in this hepatoma. The unchanged high level of essential fatty acids in the hepatoma lipids from the fat-free fed animals demonstrates the hepatoma's ability to absorb and conserve specific fatty acids.

Fatty acid composition of tissue lipids from miniature swine: Influence of dietary sucrose and starch

AbstractThe fatty acid composition of serum, liver and adipose tissue from Pitman‐Moore miniature swine was determined following their consumption of starch‐ or sucrose‐containing diets for a period of one year. Among the tissues studied there were no significant differences in the fatty acid composition due to the type of dietary carbohydrate (starch or sucrose). The cholesteryl ester fatty acid composition of all samples studied remained quite constant. There were minor fluctuations in fatty acid composition of phospholipids and triglycerides from serum collected at diferent intervals following initiation of the diets.