Changes in rat heart phospholipid composition after rapeseed oil feeding

High Levels of Erucic Acid Cause Lipid Deposition, Decreased Antioxidant and Immune Abilities via Inhibiting Lipid Catabolism and Increasing Lipogenesis in Black Carp (Mylopharyngodon piceus)

This study investigated the effects of dietary erucic acid (EA) on growth, lipid accumulation, antioxidant and immune abilities, and lipid metabolism in black carp fed six diets containing varying levels of EA (0.00%, 0.44%, 0.81%, 1.83%, 2.74%, and 3.49%), for 8 weeks. Results showed that fish fed the 3.49% EA diet exhibited lower weight gain, compared to those fed the 0.81% EA diet. In a dose-dependent manner, the serum triglycerides and total cholesterol were significantly elevated in the EA groups. The 1.83%, 2.74%, and 3.49% levels of EA increased alanine aminotransferase and aspartate aminotransferase activities, as well as decreased acid phosphatase and alkaline phosphatase values compared to the EA-deficient group. The hepatic catalase activity and transcriptional level were notably reduced, accompanied by increased hydrogen peroxide contents in the EA groups. Furthermore, dietary EA primarily increased the C22:1n-9 and C20:1n-9 levels, while decreasing the C18:0 and C18:1n-9 contents. In the EA groups, expressions of genes, including hsl, cpt1a, cpt1b, and ppara were downregulated, whereas the fas and gpat expressions were enhanced. Additionally, dietary EA elevated the mRNA level of il-1β and reduced the expression of il-10. Collectively, high levels of EA (2.74% and 3.49%) induced lipid accumulation, reduced antioxidative and immune abilities in black carp by inhibiting lipid catabolism and increasing lipogenesis. These findings provide valuable insights for optimizing the use of rapeseed oil rich in EA for black carp and other carnivorous fish species.

Dedicated Industrial Oilseed Crops as Metabolic Engineering Platforms for Sustainable Industrial Feedstock Production

Feedstocks for industrial applications ranging from polymers to lubricants are largely derived from petroleum, a non-renewable resource. Vegetable oils with fatty acid structures and storage forms tailored for specific industrial uses offer renewable and potentially sustainable sources of petrochemical-type functionalities. A wide array of industrial vegetable oils can be generated through biotechnology, but will likely require non-commodity oilseed platforms dedicated to specialty oil production for commercial acceptance. Here we show the feasibility of three Brassicaceae oilseeds crambe, camelina, and carinata, none of which are widely cultivated for food use, as hosts for complex metabolic engineering of wax esters for lubricant applications. Lines producing wax esters >20% of total seed oil were generated for each crop and further improved for high temperature oxidative stability by down-regulation of fatty acid polyunsaturation. Field cultivation of optimized wax ester-producing crambe demonstrated commercial utility of these engineered crops and a path for sustainable production of other industrial oils in dedicated specialty oilseeds.

Rapeseed oil-rich diet alters hepatic mitochondrial membrane lipid composition and disrupts bioenergetics

Diet is directly related with physiological alterations occurring at a cell and subcellular level. However, the role of diet manipulation on mitochondrial physiology is still largely unexplored. Aiming at correlating diet with alterations of mitochondrial membrane composition and bioenergetics, Wistar-Han male rats were fed for 11, 22 and 33 days with a rapeseed oil-based diet and mitochondrial bioenergetics, and membrane composition were compared at each time point with a standard diet group. Considerable differences were noticed in mitochondrial membrane lipid composition, namely in terms of fatty acyl chains and relative proportions of phospholipid classes, the modified diet inducing a decrease in the saturated to unsaturated molar ratio and an increase in the phosphatidylcholine to phosphatidylethanolamine molar ratio. Mass spectrometry lipid analysis showed significant differences in the major species of cardiolipin, with an apparent increased incorporation of oleic acid as a result of exposure to the modified diet. Rats fed the modified diet during 22 days showed decreased hepatic mitochondrial state 3 respiration and were more susceptible to Ca(2+)-induced transition pore opening. Rapeseed oil-enriched diet also appeared to promote a decrease in hydroperoxide production by the respiratory chain, although a simultaneous decrease in vitamin E content was detected. In conclusion, our data indicate that the rapeseed oil diet causes negative alterations on hepatic mitochondrial bioenergetics, which may result from membrane remodeling. Such alterations may have an impact not only on energy supply to the cell, but also on drug-induced hepatic mitochondrial liabilities.

Dietary very long chain fatty acids directly influence the ratio of tetracosenoic (24:1) to tetracosanoic (24:0) acids of sphingomyelin in rat liver

Twenty-one groups of weanling male Wistar rats were fed semipurified diets containing 5% (w/w) of different dietary fats. After 2 wk, liver sphingomyelin (SM) fatty acid composition was determined. The ratio of 24:1 to 24:0 in liver SM varied over a tenfold range in response to dietary fat type. Step-wise multiple regression analysis indicated that dietary 24:1, 24:0, and 22:1 were the most significant factors in predicting the 24:1/24:0 ratio of liver SM. The mathematical relation between the dietary fatty acid composition and liver SM 24:1/24:0 was y = 1.88 (24:1) -1.49 (24:0) +0.21 (22:1) +0.01 (18:1) +0.26, r2 = 0.95, P < 0.0001. These results were confirmed by a second experiment in which the rats were fed olive oil-based diets supplemented with various fatty acid ethyl esters.

Lipids and cardiac arrhythmia

In any discussion of lipids and heart disease it is beneficial from the outset to recognise that at least three different pathological processes may be involved. The first of these is atherosclerosis which involves the deposition of "fat" in the coronary vessels, another is thrombogenesis which describes the formation of blood clots in the coronary vessels, and the third is arrhythmia which refers to disorders in the beating of the heart which may become sufficiently serious to cause sudden cardiac death (SCD). Also it is this disturbance in the rhythmic beating of the heart which is responsible for much of the mortality from 'heart attacks' which occur 'outside-of-hospital' in societies like U.S.A., U.K. and Australia. It is this latter condition of cardiac arrhythmia which is the major concern of this review. Because it is often difficult to differentiate the role of lipids in 'heart disease' in man, it has frequently been assumed that all dietary fatty acids have similar effects on the different processes involved, and many unwarranted generalisations have been made which have led to conflicts of opinion amongst physicians and confusion in the lay public. From the animal studies discussed in this review, it is apparent that dietary fatty acids have an important role to play in determining the vulnerability of the myocardium to develop serious ventricular fibrillation (VF) and potentially lethal cardiac arrhythmia. In general, diets rich in saturated fatty acids promote a state of myocardial vulnerability, whilst diets rich in PUFA significantly diminish the probability of developing lethal disorders in cardiac rhythm when the heart is placed under pharmacological (or emotional) stress, or deprived of sufficient blood flow and supply of oxygen. Very recent experiments with the monounsaturated fatty acid (MUFA) oleic acid clearly demonstrate that, at least in rats subjected to ligation of their coronary artery, this acid is not 'neutral' as has been suggested by some for its role in atherosclerosis, but in fact is indistinguishable from saturated fatty acids in its effect in promoting arrhythmia during either regional ischaemia or reperfusion arrhythmia in this animal model of SCD.(ABSTRACT TRUNCATED AT 400 WORDS)

Cardiolipins and biomembrane function

Evidence is discussed for roles of cardiolipins in oxidative phosphorylation mechanisms that regulate State 4 respiration by returning ejected protons across and over bacterial and mitochondrial membrane phospholipids, and that regulate State 3 respiration through the relative contributions of proteins that transport protons, electrons and/or metabolites. The barrier properties of phospholipid bilayers support and regulate the slow proton leak that is the basis for State 4 respiration. Proton permeability is in the range 10(-3)-10(-4) cm s-1 in mitochondria and in protein-free membranes formed from extracted mitochondrial phospholipids or from stable synthetic phosphatidylcholines or phosphatidylethanolamines. The roles of cardiolipins in proton conductance in model phospholipid membrane systems need to be assessed in view of new findings by Hübner et al. [313]: saturated cardiolipins form bilayers whilst natural highly unsaturated cardiolipins form nonlamellar phases. Mitochondrial cardiolipins apparently participate in bilayers formed by phosphatidylcholines and phosphatidylethanolamines. It is not yet clear if cardiolipins themselves conduct protons back across the membrane according to their degree of fatty acyl saturation, and/or modulate proton conductance by phosphatidylcholines and phosphatidylethanolamines. Mitochondrial cardiolipins, especially those with high 18:2 acyl contents, strongly bind many carrier and enzyme proteins that are involved in oxidative phosphorylation, some of which contribute to regulation of State 3 respiration. The role of cardiolipins in biomembrane protein function has been examined by measuring retained phospholipids and phospholipid binding in purified proteins, and by reconstituting delipidated proteins. The reconstitution criterion for the significance of cardiolipin-protein interactions has been catalytical activity; proton-pumping and multiprotein interactions have yet to be correlated. Some proteins, e.g., cytochrome c oxidase are catalytically active when dimyristoylphosphatidylcholine replaces retained cardiolipins. Cardiolipin-protein interactions orient membrane proteins, matrix proteins, and on the outerface receptors, enzymes, and some leader peptides for import; activate enzymes or keep them inactive unless the inner membrane is disrupted; and modulate formation of nonbilayer HII-phases. The capacity of the proton-exchanging uncoupling protein to accelerate thermogenic respiration in brown adipose tissue mitochondria of cold-adapted animals is not apparently affected by the increased cardiolipin unsaturation; this protein seems to take over the protonophoric role of cardiolipins in other mitochondria. Many in vivo influences that affect proton leakage and carrier rates selectively alter cardiolipins in amount per mitochondrial phospholipids, in fatty acyl composition and perhaps in sidedness; other mitochondrial membrane phospholipids respond less or not at all.(ABSTRACT TRUNCATED AT 400 WORDS)

Testing a short-term feeding trial to assess compositional and histopathological changes in hearts of rats fed vegetable oils

Male, female and castrated rats, three wk of age, were fed a low-fat diet for 14 wk followed by high-fat diets (20% by weight) for one wk containing graded levels of erucic acid from 1 to 50%, to evaluate the effect of short-term feeding and interaction of male sex hormones on formation of heart lesions. Some rats within each group were returned to the low-fat diet for one wk after the test period. For comparison, one group of three-wk-old male rats was fed the high fat 50% erucic acid diet for 15 wk. Erucic acid depressed growth rate and food consumption and increased cardiac lipidosis and triglycerides proportional to the erucic acid content of the diet. There were no sex differences, and the effects disappeared once rats were returned to the low-fat diet for one week. There was a significance (P less than 0.05) in the incidence of myocardial necrosis among male rats fed increased levels of erucic acid for one week, but the response was not linear to the increase in dietary erucic acid. Furthermore, the response was much less than in males fed the 50% erucic acid diet continually for 15 weeks. These results suggest that the short-term model is not a suitable substitute for the long-term feeding trial to test the cardiopathogenicity of a vegetable oil. The significantly lower incidence in myocardial lesions in female and castrated male rats compared with male rats suggests involvement of sex hormones.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac lipid changes in rats fed oils enriched in saturates and their apparent relationship to focal heart lesions

Weanling male Sprague-Dawley rats were fed diets containing 20% by weight corn, soybean or low erucic acid rapeseed oils or mixtures of the latter two with cocoa butter or triolein for 1, 2, 3 or 4 weeks. These diets previously had been fed to the same strain of rats for 16 weeks, and a reduction in the incidence of focal heart lesions had been observed with the addition of cocoa butter, but not triolein. The cardiac lipid classes and the fatty acid and alkenyl ethers of the cardiac phospholipids were analyzed to determine if changes could be attributed to the observed cardiopathological response, and at what time. Cardiac lipid classes changed during post-weaning development, but only triacylglycerol was diet-related. A number of fatty acid changes were observed in the cardiac phospholipids which reflected the relative concentration of saturates, monounsaturates, linoleic acid and linolenic acid in the diet, but only the changes in saturates and the C22 polyunsaturated fatty acids from the linolenic acid family appeared to be related to the incidence of focal heart lesions. Arachidonic acid and the total C22 polyunsaturated fatty acids remained fairly constant throughout the feeding trial. Cardiac diphosphatidylglycerol was least affected by dietary manipulation, while nervonic acid increased in cardiac sphingomyelin when small amounts of erucic acid were present in the diet. Fatty acid changes were essentially completed after one week on the experimental diets, whereas changes in the alkenyl ethers took two to three weeks.

The composition of cardiac phospholipids in rats fed different lipid supplements

Changes in dietary lipid intake are known to alter the fatty acid composition of cardiac muscle of various animals. Because changes in cardiac muscle membrane structure and function may be involved in the pathogenesis of arrhythmia and ischemia, we have examined the effects of dietary lipid supplements on the phospholipid distribution and fatty acid composition of rat atria and ventricle following 20 weeks feeding of diets supplemented with either 12% sunflower-seed oil or sheep fat. Neither lipid supplement produced significant changes in the proportions of cholesterol, total phospholipids or phosphatidylcholine, phosphatidylethanolamine or diphosphatidylglycerol,--the phospholipid classes that together account for more than 90% of the total phospholipids of rat cardiac muscle. Significant changes were found in the profiles of the unsaturated fatty acids of all 3 phospholipid components of both atria and ventricle. Although similar, the changes between these tissues were not identical. However, in general, feeding a linoleic acid-rich sunflower seed oil supplement resulted in an increase in the omega-6 family of fatty acids, whereas feeding the relatively linoleic acid-poor sheep fat supplement decreased the level of omega-6 fatty acids but increased the levels of the omega-3 family, resulting in major shifts in the proportions of these families of acids. In particular, the ratio of arachidonic acid: docosahexaenoic acid (20:4,omega-6/22:6,omega-3), which is higher in all phospholipids of atria than ventricle, is increased by feeding linoleic acid, primarily by increasing the level of arachidonic acid in the muscle membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Mitochondrial-membrane polar-head-group composition is influenced by diet fat

Male Sprague-Dawley rats were fed diets containing 20% (w/w) soya-bean oil, high-erucic acid rapeseed oil or low-erucic acid rapeseed oil for 0, 12 or 23 days. The type of fat present in the diet had no effect on the total phospholipid content of heart mitochondria (micrograms/mg of protein) but did influence the phospholipid class distribution. Rats fed high-erucic acid rapeseed oil for 12 or 23 days had significantly higher mitochondrial phosphatidylcholine content than rats fed soya-bean oil. Low-erucic acid rapeseed oil resulted in elevation of cardiac mitochondrial cardiolipin content after dietary treatment for 12 days. The results demonstrate in vivo that diet is a significant determinant of the phospholipid class content of subcellular membranes.

Dynamic modulation of mitochondrial inner-membrane lipids in rat heart by dietary fat

A novel longitudinal feeding design was used to investigate the controlling influence of dietary fatty acids on the dynamic incorporation of fatty-acyl chains into phosphatidylcholine, phosphatidylethanolamine and cardiolipin in inner membrane of cardiac mitochondria. Rats were fed a polyunsaturated-fatty-acid-rich oil (soya-bean oil) for 12 days, crossed-over to a monounsaturated-fatty-acid-rich oil (rapeseed oil) for the next 11 days, then returned to soya-bean oil for 11 more days. Additional rats were fed either soya-bean oil or rapeseed oil only throughout. Rats were killed serially. Regression analysis was used to represent longitudinal flux in membrane lipid fatty-acid composition occurring with change in dietary fat. The fatty-acid composition of phosphatidylcholine, phosphatidylethanolamine and cardiolipin was influenced by dietary oil in a reversible way. Maximal diet influence was achieved in the 11-day cross-over period. Soya-bean oil to rapeseed oil cross-over caused the fatty-acid composition of phosphatidylcholine, phosphatidylethanolamine and cardiolipin to resemble that of rats fed rapeseed oil only. These changes were reversed by crossing back to soya-bean oil, indicating the dynamic state and short half-life of membrane phospholipid fatty-acyl chains. This report demonstrates for the first time in the whole animal fed diets adequate in all nutrients that subcellular membrane lipids rapidly respond to change in dietary fatty-acid balance. The system may be used to assess in vivo the significance of dietary fat in determining membrane physicochemical properties and biochemical functions.

Comparative studies on composition of cardiac phospholipids in rats fed different vegetable oils

Male Sprague-Dawley rats were fed diets for 1 or 16 weeks, containing 20% by weight vegetable oils differing widely in their oleic, linoleic and linolenic acid content. No significant changes were observed in the level of the cardiac lipid classes. The fatty acid composition of the 2 major phospholipids, phosphatidylcholine and phosphatidylethanolamine, showed a remarkable similarity between diets in the concentration of total saturated, C22 polyunsaturated and arachidonic acids. Monounsaturated acids were incorporated depending on their dietary concentration, but the increases were moderate. Dietary linolenic acid rapidly substituted C22 polyunsaturated fatty acids of the linoleic acid family (n-6) with those from the linolenic acid family (n-3). The results suggest that dietary linolenic acid of less than 15% does not inhibit the conversion of linoleic to arachidonic acid but the subsequent conversion of arachidonic acid to the C22 polyunsaturates was greatly reduced. Significant amounts of dietary monounsaturated fatty acids were incorporated into cardiac cardiolipin accompanied by increases in polyunsaturated fatty acids, apparently to maintain an average of 2 double bonds/molecule. The cardiac sphingomyelins also accumulated monounsaturated fatty acids depending on the dietary concentration. It is quite evident from the results of this study that the incorporation of oleic acid and the substitution of linolenic for linoleic acid-derived C22 polyunsaturated fatty acids into cardiac phospholipids was related to the dietary concentration of these fatty acids and was not peculiar to any specific oil. Even though it is impossible to estimate the effect of such changes in cardiac phospholipids on membrane structure and function, results are discussed which suggest that the resultant membrane in the Spragu-Dawley male rat is more fragile, leading to greater cellular breakdown and focal necrosis.

Effect of strain, sex and duration of feeding on plasma fatty acids of rats fed various dietary oils

Experiments were conducted to determine if regression of cardiac lipidosis and strain or sex differences in susceptibility to cardiopathological change induced by rapeseed oils are coincident with physiological differences in fatty acid substrates supplied to the heart. Plasma fatty acid composition was determined in male Sprague-Dawley rats after 7 or 28 days and in female Sprague-Dawley and male Chester-Beatty rats after 28 days of feeding high or low erucic acid rapeseed oils, soybean oil or peanut oil. After 28 days, C14:0 and C18:1 fell and C20:4 increased as a percent of total fatty acid in all animals irrespective of oil fed, suggesting that changes in plasma fatty acids normally occur with development. Saturated and essential fatty acid profiles of male and female rats were different. Differences in plasma fatty acids stemming from sex-related physiological differences in whole body fat metabolism may form the basis of lower cardiopathological involvement for females. Results suggest physiological differences unrelated to plasma fatty acids determine strain differences in timing and severity of rapeseed oil-induced cardiac pathology.

Evidence of accumulation of ceramides containing [14C]nervonic acid in the rat lung following injection of [14C]erucic acid

A mixture of albumin-bound [14C]erucate and [3H]oleate was injected into rats fed a stock pellet diet containing 4% by weight of lipid. Chylomicrons containing the same labelled fatty acids were also injected into rats fed diets containing 15% by weight of rapeseed oil (48% of erucic acid), canbra oil (less than 5% of erucic acid) or ground nut oil (no erucic acid). Lung lipids were analyzed at various times after injection. In all cases, except in the rapeseed oil diet group, 14C radioactivity of lung 'monoacylglycerol' was ten times higher than 3H radioactivity. More than 85% of this 14C radioactivity was found in nervonic acid (24 : 1). It was shown by TLC and GLC analysis that 85-90% of the 14C radioactivity of this fraction was in ceramides (N-acyl-4-sphingenine). Ceramides containing [14C]nervonic acid disappeared from the lung with time and their incorporation with time into sphingomyelin was also observed. The absence of accumulation of 3H and 14C (18 : 1) in ceramides showed that oleic acid was not incorporated into sphingomyelin in the same way as nervonic acid. In the rapeseed oil diet group, there was no accumulation of 14C radioactivity in ceramides and conversion of erucic acid into nervonic acid was less, and into oleic acid more, than in other diet groups indicating a possible enzyme adaptation.

Cardiopathogenicity of soybean oil and tower rapeseed oil triglycerides when fed to male rats

The triglycerides of soybean oil were purified by molecular distillation and those of Tower rapeseed oil by molecular distillation and adsorption chromatography. The original oils and the purified triglycerides were incorporated in semisynthetic diets at 20% by weight and fed for 16 weeks to weanling male Sprague-Dawley rats to compare the nutritional and pathological effects of the oils and their triglyceride fractions on rats. The study was carried out at two independent laboratories. No significant differences were observed between the results of the two establishments. The incidence of myocardial lesions was significantly higher in rats fed Tower rapeseed oil than in those fed soybean oil. Purification of the triglycerides by molecular distillation and adsorption chromatography appeared to have no major effect on the incidence of myocardial lesions. This supports our previous findings that the cardiopathogenicity appeared to have no major effect on the incidence of myocardial lesions. This supports our previous findings that the cardiopathogenicity of the test oils to rats resides in the triglycerides of these oils.

Changes in fatty acid composition of cardiac mitochondrial phospholipids in rats fed rapeseed oil

Male Wistar rats were fed rapeseed oil containing high or low levels or erucic acid for 20 weeks, and changes in the fatty acid composition of cardiac mitochondrial phospholipids were studied. Treatment with rapeseed oil containing 46.2% erucic acid showed incorporation of 22:1 (5.6%) into isolated cardiolipin from heart mitochondria. After high or low (3.7%) erucic rapeseed oil feeding, linolenic acid was slightly incorporated into cardiolipin. Moreover, both of these rapeseed oils induced a significant increase of linoleate-arachidonate ratio in phosphatidylethanolamine and phosphatidylcholine. This ratio was also significantly increased in fatty acids esterified to the beta-position of these phospholipids. On the basis of such results, we have to consider the role of linolenic acid which is present at a high level in the different rapeseed oils used, as a possible inhibitor of heart microsomal enzymes involved in linoleate arachidonate conversion. Such alterations might account for mitochondrial fragility and myocardial lesions obtained in long term rapeseed oil feeding experiments.