Effects of Three Bacterial Infections on Serum Lipids of Rabbits

Alteration of the rabbit serum lipids as a result of three bacterial infections was studied by quantitative thin-layer and gas-liquid chromatography. Anthrax infection slightly changed the serum lipid. Cholesterol did not change, though free fatty acids, triglycerides, and cholesteryl esters doubled, and lecithin increased threefold. Tularemia infection produced drastic changes in the serum lipid content of rabbits, increasing levels of cholesterol over 4-fold, free fatty acids 17-fold, triglycerides 11-fold, cholesteryl esters 2.5-fold, and lecithin almost 3-fold. Pneumococcus infection increased cholesterol 2.5 times, free fatty acids were more than doubled, triglycerides were increased 9.5 times, and lecithin was increased almost 4 times. Gas-liquid chromatographic analysis of the methyl esters of free fatty acids showed only quantitative changes in these acids due to infection. Some possible mechanisms of alteration of serum lipid content are discussed.     

Changes in cellular composition during magnesium deficiency.

1. Concentrations and compositions of liver, serum and milk lipids of cows were measured during 6 days' starvation and serum lipids during 60 days' re-feeding. 2. The concentration of free fatty acid in serum increased fivefold during starvation. 3. The content of total lipid in liver (g/100g of liver dry matter) doubled owing to a 20-fold increase in triglyceride, an eightfold increase in cholesterol ester, a three fold increase in free fatty acid and a 20% increase in cholesterol. There were no changes in the content or composition of liver phospholipids. 4. Starvation lowered the concentrations of total lipid, phospholipid and cholesterol ester of dextran sulphate-precipitable serum lipoproteins. Total lipid and cholesterol ester concentrations in lipoproteins of d greater than 1.055 and in lipoproteins not precipitable by dextran sulphate decreased from day 4 of the starvation period and during the first 20 days' re-feeding. 5. During starvation there were decreases in percentages of stearic acid and increases in oleic acid in serum free fatty acids and triglycerides and in liver neutral lipid. 6. Throughout starvation total milk lipid yield decreased, yields and percentages of C4-14 fatty acids decreased and percentages of C18 fatty acids increased. 7. It is suggested that accumulation of triglyceride in liver may be caused by increased uptake of plasma free fatty acids without corresponding increase in lipoprotein secretion.     

Nutritional evaluation of structured lipid containing omega 6 fatty acid synthesized from coconut oil in rats

Coconut oil is rich in medium chain fatty acids, but deficient in polyunsaturated fatty acids (PUFA). Structured lipids (SL) enriched with omega 6 PUFA were synthesized from coconut oil triglycerides by employing enzymatic acidolysis with free fatty acids obtained from safflower oil. Rats were fed a diet containing coconut oil, coconut oil-safflower oil blend (1:0.7 w/w) or structured lipid at 10% levels for a period of 60 days. The SL lowered serum cholesterol levels by 10.3 and 10.5% respectively in comparison with those fed coconut oil and blended oil. Similarly the liver cholesterol levels were also decreased by 35.9 and 26.6% respectively in animals fed structured lipids when compared to those fed on coconut oil or the blended oil. Most of the decrease observed in serum cholesterol levels of animals fed structured lipids was found in LDL fraction. The triglyceride levels in serum showed a decrease by 17.5 and 17.4% while in the liver it was reduced by 45.8 and 23.5% in the structured lipids fed animals as compared to those fed coconut oil or blended oil respectively. Differential scanning calorimetric studies indicated that structured lipids had lower melting points and solid fat content when compared to coconut oil or blended oils. These studies indicated that enrichment of coconut oil triglycerides with omega 6 fatty acids lowers its solid fat content. The omega 6 PUFA enriched structured lipids also exhibited hypolipidemic activity.     

Composition of plasma fatty acids and non-cholesterol sterols in anorexia nervosa

Anorexia nervosa is a model of simple starvation accompanied by secondary hyperlipoproteinemia. The pattern of plasma fatty acids influences the levels of plasma lipids and lipoproteins. The concentration of plasma lathosterol is a surrogate marker of cholesterol synthesis de novo, concentrations of campesterol and beta-sitosterol reflect resorption of exogenous cholesterol. The aim of the study was to evaluate fatty acids in plasma lipid classes and their relationship to plasma lipids, lipoproteins, cholesterol precursors and plant sterols. We examined 16 women with anorexia nervosa and 25 healthy ones. Patients with anorexia nervosa revealed increased concentrations of total cholesterol, triglycerides, HDL-cholesterol, campesterol and beta-sitosterol. Moreover, a decreased content of n-6 polyunsaturated fatty acids was found in all lipid classes. These changes were compensated by an increased content of monounsaturated fatty acids in cholesteryl esters, saturated fatty acids in triglycerides and both monounsaturated and saturated fatty acids in phosphatidylcholine. The most consistent finding in the fatty acid pattern concerned a decreased content of linoleic acid and a raised content of palmitoleic acid in all lipid classes. The changes of plasma lipids and lipoproteins in anorexia nervosa are the result of complex mechanisms including decreased catabolism of triglyceride-rich lipoproteins, normal rate of cholesterol synthesis and increased resorption of exogenous cholesterol.     

Hyperlipidemic effects of trans fatty acids are accentuated by dietary cholesterol in gerbils

Trans isomers of dietary fatty acids, generated during the commercial hydrogenation of unsaturated fats, may contribute to coronary heart disease (CHD) in humans by interfering with lipid metabolism. To examine this possibility in a fat-sensitive model, the Mongolian gerbil (Meriones unguiculatus) was used to compare the cholesterolemic and triglyceridemic potential of modest increments of trans fatty acids from partially hydrogenated soybean oil with other saturated fatty acids in the presence and absence of dietary cholesterol. Age-, dose-, and time-dependent effects were examined in weanling, 6-month-old, and 1-year-old gerbils. Although lipoprotein metabolism in weanling gerbils was initially refractory to trans fat, even as perturbations by saturated fatty acids were demonstrable, these gerbils eventually (after 16 weeks) developed a trans-induced hypercholesterolemia that was intermediate between the response to 16:0 and 12:0 + 14:0. The hepatic and plasma 18:1/18:2 cholesteryl ester (CE) ratio was depressed by trans in a manner similar to saturated fatty acids. The 6-month-old gerbils readily developed hypertriglyceridemia but not hypercholesterolemia, again revealing a decrease in the plasma 18:1/18:2 CE ratio. The 1-year-old gerbils revealed a dose-related (0, 5, 10%en as trans) elevation in total cholesterol (TC), and especially triglycerides (TG), that was accentuated by 0.04% dietary cholesterol. Increases in plasma lipids were again accompanied by a significant decrease in the mass of hepatic esterified cholesterol, particularly 18:1-cholesteryl esters. Thus, dietary trans-fatty acids induce age-, time-, and dose-dependent modulations in gerbil plasma lipids associated with decreased 18:1 cholesteryl esters. Further investigation with gerbils may reveal mechanisms by which trans fat consumption disturbs lipoprotein metabolism.     

The Neutral Lipids of Paramecium tetraurelia: Changes with Culture Age and the Detection of Steryl Esters in Ciliary Membranes1

Neutral lipids, particularly triglycerides, accounted for the major decrease in the total lipid content in Paramecium cells that occurs with culture age. Sterols, triglycerides, and steryl esters were the major classes of neutral lipids in cells and isolated cilia. Free as well as high concentrations of esterified sterols were detected in purified ciliary membrane preparations. Stigmasterol and 7-dehydrostigmasterol were the major components of both free and esterified sterols of cells and cilia; however, when cholesterol was present in the growth medium, it was desaturated to 7-dehydrocholesterol and incorporated into cellular and ciliary lipids. Free fatty acids from cells and triglycerides from cells and cilia were low in polyunsaturated fatty acids and reflected the composition of fatty acids in the culture medium. An exception was the reduced concentration of stearate in triglycerides from whole cells. Greater than 50% of triglyceride fatty acids from cilia were saturated. The fatty acid compositions of cellular triglycerides and ciliary steryl esters did not change with culture age, but those of cellular steryl esters and ciliary triglycerides did change. In comparison with phospholipids, these neutral lipid fatty acid compositional changes were smaller. The sensitivity of these stigmasterol-containing cells to polyene antibiotics indicated that they were killed by nystatin > filipin > amphotericin B. The unexpected finding of high concentrations of steryl esters in ciliary membrane preparations is discussed.     

FATTY ACID ABNORMALITY IN ADRENOLEUKODYSTROPHY

—Recent clinical and morphological evidence established that adrenoleukodystrophy is a distinct X-linked genetic disorder. Fatty acid compositions of lipids in the brain, adrenal and serum from seven patients were examined. Cholesterol esters of both brain and adrenal contained substantial proportions of fatty acids longer than C₂₂ (11.8–41.9% of total in the brain and 13.4-34.8% of total in the adrenal), while cholesterol esters from normal and pathological control specimens contained very little. These very long chain fatty acids were generally saturated in brain cholesterol esters but significant amounts of unsaturated long chain fatty acids were also present in adrenal cholesterol esters. The long chain fatty acids showed bell-shaped distribution with C₂₅ or C₂₆ at the peak. Ganglio-sides from patients’white matter also showed increased proportions of very long-chain fatty acids, up to 50% of the total. Qualitatively similar but much milder fatty acid abnormalities were also found in galactosylceramide of the brain. On the other hand, fatty acids and fatty aldehydes of brain glycerophospholipids, adrenal free fatty acids, triglycerides and glycerophospholipids were not abnormal. Furthermore, serum cholesterol esters from two patients did not show the long-chain fatty acid abnormality found in brain and adrenal cholesterol esters. Sequential extractions with acetone and hexane established that the characteristic birefringent material in the brain and adrenal is indeed cholesterol esters with very long chain fatty acids. This type of fatty acid abnormality has not been described in other pathological conditions and may well represent the unique biochemical abnormality that is directly related to the fundamental genetic defect underlying adrenoleukodystrophy.     

Various aspects of lipid metabolism in the rat testicle after sulpiride treatment]

Testicular lipids were extracted from 20 rats which had received 40 mg sulpiride per kg per day for 20 days as well as from 20 controls. The extracts were weighed and chromatographed on thin layer in order to analyse them for the main fatty constituants : phospholipids and neutral fats. In addition total cholesterol, triglycerides and lipid phosphorus were determined. The total testicular lipid content and the phospholipids were unaltered. The distribution of phospholipids wasn't influenced either. Among the neutral fats the precursors of steroid hormones such as cholesterol and its esters didn't show any modification. The triglycerides on the other hand suffered a significant decrease which was partly compensated in situ by the increase of free fatty acids. Since plasma electrophoresis didn't reveal a parallel increase of the complex albumin--free fatty acids, the hypothesis of an in situ lipolysis is proposed. But it is not possible yet to attribute to sulpiride the role of a direct activation on a testicular triglyceride lipase nor that of an indirect activator by way of prolactine for example.     

Studies of hyperlipidemia in drug-induced diabetic rats by high-performance liquid chromatography

A hyperlipidemic condition is often associated with diabetes. The possibility that specific serum lipids (i.e., individual triglycerides or cholesterol esters) may be altered in the diabetic state was investigated. Serum lipids from both controls and streptozotocin- and alloxantreated rats were separated into approximately twenty chromatographic fractions by reversed-phase high-performance liquid chromatography; a number of individual triglycerides and cholesterol esters were identified. The methodology described allowed subtle changes in individual lipid components to be detected. Only minor variations in the cholesterol and cholesterol ester fractions were observed between the control and diabetic samples. While not uniform throughout, elevations in the triglyceride fractions occurred in the diabetics. Also, differences in triglyceride content were found to exist between the groups of streptozotocin- and alloxan-treated animals.     

Effects of dietary n-3 fatty acids on the composition of cholesteryl esters and triglycerides in plasma and liver perfusate of the rat

The effects of polyunsaturated fatty acids of the omega-3 family (PUFA n-3), (addition of fish oil), on the molecular composition of cholesteryl esters and triglycerides in plasma and liver perfusate of rats were studied. Rats fed a diet rich in saturated fatty acids (addition of lard) served as controls. Supplemention with PUFA n-3 not only decreases the plasma concentrations of free cholesterol, cholesteryl esters, and triglycerides, it also significantly alters the plasma composition of cholesteryl esters and triglycerides. Analyses of liver perfusate indicate a decrease in triglycerides secretion by in vitro perfused liver and reciprocal changes in relative contents of cholesteryl esters fractions with C(16) and C(20) acyl chains. This finding may be a result of chain-shortening of long-chain fatty acids probably in peroxisomal beta-oxidative system. Alterations in plasma cholesteryl esters and triglycerides composition of the fish oil group could be affected further by additional factors such as increased plasma cholesterol esterification activity and presence of triglyceride species of intestinal origin.     

Comparative characteristics of the fatty acid composition of lipoproteins in human blood plasma and aortic wall]

A study was made of a fatty acid composition of individual lipid fractions in the lipoproteids of the blood serum of a very low, low and high density, and the wall of the aorta affected with atherosclerosis. There was a close similarity between a fatty acid composition of phospholipids, triglycerides, and cholesterol esters of all the lipoproteid classes of the vascular wall and blood plasma. The fatty acid compostion of individual fractions proved to be similar in all the lipoproteid fractions. The lipids of the vascular wall not included into the lipoproteid composition differed considerably by their fatty acid composition from the lipids isolated from lipoproteids; lipids of the wall of the aorta contained much less unsaturated fatty acids than lipoproteids.     

Separation and detection of neutral lipids and free fatty acids in a liver extract by high-performance liquid chromatography

A relatively simple method to determine hepatic neutral lipids and free fatty acids by highperformance liquid chromatography is described. This method involves the preparation of a chloroform extract of the total liver lipids, followed by removal of the phospholipids by adsorption onto silicic acid and elution of neutral lipids and free fatty acids with 50% diethyl ether in hexane. This fraction is then subjected to liquid-solid chromatography with a solvent system of 2,2,4-trimethylpentane (isooctane):tetrahydrofuran:formic acid (90:10:0.5) and is detected by refractive index. Cholesterol esters, fatty acids, cholesterol, and diglycerides each elute as single peaks, easily quantitated by comparison to appropriate standards. Baseline separation of triglycerides from cholesterol esters is also achieved.     

Lipid composition of spinal bone tissue in rabbits of different ages

Studies have been made on the lipid composition of total lipids, triglycerides and their fatty acids, cholesterol and phospholipids in the vertebral column of young and adult rabbits. It was shown that the content of total lipids and triglycerides increases, whereas that of cholesterol and phospholipids decreases with age. The content of total lipids in the vertebral column is 10 times higher as compared to that in the bones of the extremities. Mid-thoracic part of the vertebral column exhibits higher lipid content than other thoracic parts of the column. Lipid content of the vertebral processes is lower than that of the vertebral bodies. These data indicate lipid specificity and heterogeneity of bone tissue of the vertebral column. The main fatty acids of vertebral triglycerides are presented by those with 14-18 carbon atoms (90%), no acids with 22 atoms were found. Higher content of the linoleic acid (19%) and higher total unsaturation of triglycerides were found in the bone tissue of rabbits in comparison with those of man.     

Comparative study of lipids and fatty acids in blood plasma of river lamprey Lampetra fluviatilis and brown frog Rana temporaria at the periods of elimination of exogenous feeding

Lipids of blood plasma of lampreys and frogs are composed of phospholipids, triglycerides, free fatty acids (FA), cholesterol, cholesterol esters, and waxes. The lipids content in plasma of frogs is markedly lower as compared with that of lampreys. However, the percentage of lipid components is represented by close values. Fluidity of triglycerides and phospholipids in lampreys is determined predominantly by monoenic acids and polyenoic acids of the ω-3-type, whereas that in frogs—by monoenic acids and polyenic acids of the ω-6-type. Free FA are represented mainly by saturated and monoenic acids.     

Increased glucose disappearance rate after short-term clofibrate administration in normal subjects and in patients with chemical diabetes

Following seven days clofibrate administration, the glucose disappearance rate during an intravenous glucose tolerance test was significantly increased in 6 normal subjects and in 11 patients with chemical diabetes. Both the acute and the total insulin secretory response were unchanged. Though fasting serum levels of free fatty acids, triglycerides, and cholesterol were significantly lowered by treatment, no correlation was found between the decrease in serum lipids and the increase in glucose disappearance rate. It is suggested and clofibrate improves glucose utilization by reducing insulin resistance irrespective of its effects on serum lipids concentration.     

Bromine-Sudan Black: a general stain for lipids including free cholesterol

Synopsis Preliminary bromination (with bromine water) increases the intensity of staining of tissue lipids with Sudan Black and certain other dyes. The mechanism appears to be due to the formation of sudanophilic bromo-derivatives of cholesterol and to the retention of certain other lipids, notably phosphatidyl choline and free fatty acids, during staining. The advantage of the bromine-Sudan Black method is that all tissue lipids are stained, except saturated fatty acids, saturated triglycerides and perhaps saturated cholesterol esters. In practice, such lipids rarely, if ever, occur alone, and normally are admixed with their stainable unsaturated counterparts.     

Liquid chromatographic analysis of sebum lipids and other lipids of medical interest

A technique is described for the high-pressure liquid chromatographic (HPLC) analysis of sebum lipid classes. The lipid classes present in sebum are separated by gradient elution HPLC from a microparticulate silica column and detected using a moving-wire detector. The system described can be linked to a computer. Quantitation can be carried out by comparing peak areas obtained with those of an internal standard. Peak trapping for further investigations of the separated components, for example by gas chromatography—mass spectrometry, is very easy.Sebum lipids are separated into the following lipid classes: hydrocarbons and squalene, cholesterol esters and wax esters, fatty acids as their methyl esters, triglycerides, 1,3-diglycerides, 1,2-diglycerides, free cholesterol, monoglycerides and other polar materials. Besides to sebum, the method has been successfully applied to other lipid mixtures, such as serum lipids. Examples of other applications are shown.     

Circadian Rhythm of Liver Parameters (Cellular Structures, Mitotic Activity, Glycogen and Lipids in Liver and Serum) During Three Consecutive Cycles in Phenobarbital-Treated Rats

The circadian rhythm of gastric content, serum alkaline phosphatase (alk.P.), serum lipids, body weight (wt), relative (rel.) liver wt, cellular structures (by light- and electron-microscopy), mitotic activity of hepatocytes, glycogen content, protein and lipids in liver was studied in 180 male Sprague-Dawley rats orally treated at 0830-1030 with 50 mg/kg phenobarbital (PB) for 7 days. Thereafter, five PB-treated males and five controls each were studied at 4-hr intervals at 0600, 1000, 1400, 1800, 2200 and 0200 on 3 consecutive days. The lighting schedule in the colony was 12:12 = light/dark (light from 0600 to 1800). Following the rhythm of gastric emptying, the rel. liver wt showed a clear circadian rhythm with a peak at 0800. The rel. liver wt was raised in PB-treated rats at all times of the day. The circadian rhythm of cellular structures was closely related to the hepatic glycogen content which exhibited a clear rhythm with the peak also at 0800, but lowered values were found in PB-treated rats. The mitotic activity of hepatocytes was significantly increased in PB-treated rats but displayed the same circadian rhythm as controls with peaks at noon and troughs at midnight. The well-known hypertrophy of the smooth endoplasmic reticulum in PB-treated rats was not found at 0600, but was fully developed at 1400 and 2200. PB-treatment increased significantly the liver content of cholesterol, triglycerides and phospholipids. Liver cholesterol showed a clear circadian rhythm with peaks at 1800. No rhythm of liver protein, triglycerides and phospholipids was observed. In serum, levels of cholesterol were significantly elevated, those of triglycerides and alk.P. significantly lowered, while those of phospholipids were not affected by the treatment. The three serum lipids, alk.P. and beta-lipoprotein exhibited a clear circadian rhythm, while serum glucose and non-esterified fatty acids did not.     

ACTH-induced hydrolysis of cholesteryl esters in rat adrenal cells.

Rat adrenal cortical cells have been prepared by collagenase dissociation of trypsin-treated adrenal tissue. The content and compositions of cholesteryl ester, phospholipid, and triglyceride fatty acids compare favorably with those of undissociated rat adrenal tissue. During 2-hour control incubations of adrenal cortical cells, steroidogenesis was not detected, and the levels of sterol ester, phospholipid, and triglyceride fatty acids were not significantly altered. Incubations with adrenocorticotropic hormone (ACTH) resulted in coricosterone production and significant depletions of sterol ester and triglyceride fatty acids, but not of phospholipid fatty acids. Although all fatty acid esters of cholesterol were hydrolyzed under these conditions, the greatest contributions to the net decrease in sterol esters were by oleate, arachidonate, and adrenate. Incubations with dibutyryl cyclic adenosine monophosphate (0.5 mM) resulted in significantly greater levels of corticosterone production than did ACTH (250 muunits), but the effects on cellular lipids were comparable to those seen with the tropic hormone. This study represents the first demonstration of hormone-induced hydrolysis of sterol esters in an in vitro cell suspension system. The results are discussed with respect to hormone-sensitive sterol ester hydrolase of adrenal cortex, and to the role of endogenous cholesteryl esters in the steroidogenic pathway.     

Circadian Rhythm of Liver Parameters (Cellular Structures,Mitotic Activity,Glycogen and Lipids in Liver and Serum) During Three Consecutive Cycles in Phenobarbital-Treated Rats

The circadian rhythm of gastric content, serum alkaline phosphatase (alk.P.), serum lipids, body weight (wt), relative (rel.) liver wt, cellular structures (by light- and electron-microscopy), mitotic activity of hepatocytes, glycogen content, protein and lipids in liver was studied in 180 male Sprague-Dawley rats orally treated at 0830-1030 with 50 mg/kg phenobarbital (PB) for 7 days. Thereafter, five PB-treated males and five controls each were studied at 4-hr intervals at 0600, 1000, 1400, 1800, 2200 and 0200 on 3 consecutive days. The lighting schedule in the colony was 12:12 = light/dark (light from 0600 to 1800). Following the rhythm of gastric emptying, the rel. liver wt showed a clear circadian rhythm with a peak at 0800. The rel. liver wt was raised in PB-treated rats at all times of the day. The circadian rhythm of cellular structures was closely related to the hepatic glycogen content which exhibited a clear rhythm with the peak also at 0800, but lowered values were found in PB-treated rats. The mitotic activity of hepatocytes was significantly increased in PB-treated rats but displayed the same circadian rhythm as controls with peaks at noon and troughs at midnight. The well-known hypertrophy of the smooth endoplasmic reticulum in PB-treated rats was not found at 0600, but was fully developed at 1400 and 2200. PB-treatment increased significantly the liver content of cholesterol, triglycerides and phospholipids. Liver cholesterol showed a clear circadian rhythm with peaks at 1800. No rhythm of liver protein, triglycerides and phospholipids was observed. In serum, levels of cholesterol were significantly elevated, those of triglycerides and alk.P. significantly lowered, while those of phospholipids were not affected by the treatment. The three serum lipids, alk.P. and beta-lipoprotein exhibited a clear circadian rhythm, while serum glucose and non-esterified fatty acids did not.