Studies on phospholipids with particular reference to cardiolipin of rat heart after feeding rapeseed oil

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.

Effects of various dietary fats on cardiolipin acyl composition during ontogeny of mice

Cardiolipin (CL) is a unique mitochondrial phospholipid, containing up to 85 wt% 18:2n-6 in mammals. The influence of maternal dietary fatty acids on the acyl composition of offspring CL has not been examined previously. Adult female mice were thus fed diets rich in 18:1n-9 (olive oil), 18:2n-6 (safflower oil), 18:3n-3 (linseed oil) or 20:5n-3 and 22:6n-3 (fish oil/safflower, 9:1, w/w), for a five month period, encompassing two breeding cycles. Offspring from the second breeding cycle were then fed these diets. The acyl composition of CL, phosphatidylcholine and phosphatidylethanolamine from liver and heart was evaluated from mice killed 3, 18 and 42 days after parturition. The primary nutrient sources at these three time points were transplacental nutrients, breast milk and the diet, respectively. Maternal diet was found to influence the acyl composition of CL via both placental transfer of fatty acids and breast milk. Fish oil feeding resulted in replacement of a substantial portion of 18:2n-6 with 22:6n-3; after 42 days, the area% of 18:2n-6 in heart CL was reduced from 62% in safflower oil fed mice to 12%. In comparison to fish oil feeding, linseed oil feeding resulted in a much lower accumulation of 22:6n-3. Olive oil feeding resulted in substantial replacement of 18:2n-6 with 18:1n-9 (18:2n-6 was reduced from 62% to 31%). Physiologically, these findings are relevant because changes in CL acyl composition may influence the activity of associated inner mitochondrial membrane enzymes.

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)

Age-related changes of lipid fractions and total fatty acids in liver lipids and heart lipids of female and male rats aged 37-1200 days (liver) and 331-1200 days (heart)

1. Total lipids and the lipid fractions cholesterol ester, triacylglycerol, free cholesterol, free fatty acids and phospholipids, as well as the fatty acid patterns of total lipids, were measured in liver homogenates of female and male rats (Wistar SPF, strain Hannover) aged 37-1213 days. 2. The same parameters were measured in the apex of the heart in female and male rats aged 331-1213 days. 3. All parameters were monitored every 49th day. Five female and five male animals were used in each experiment. 4. The lipid fractions in liver showed a positive linear regression vs age, whereas all lipids in rat heart showed a negative regression vs age in both sexes. 5. The significance of regression vs age of fatty acids was much less than that in the lipid fractions of liver and heart of these animals.

Changes in phospholipid composition of the mitochondrial membrane after orthotopic liver transplantation

Changes in phospholipids and their fatty acid composition in liver mitochondria obtained from allogenic rats with orthotopic liver transplants were measured with and without immunosuppressive treatment. In untreated allogenic rats, mitochondrial phosphorylation activity was severely deteriorated at 8 days after transplantation. A significant change was also found in the amount of cardiolipin compared with other classes of phospholipids. Namely, cardiolipin decreased, and lysodiphosphatidylglycerol and phosphatidylglycerol increased concomitantly. Furthermore, the percentage of linoleic acid in cardiolipin decreased dramatically. Decrease in cardiolipin and changes in its fatty acid composition may be attributed to the deterioration of mitochondrial function upon acute rejection.

Dietary modulation of retina phospholipids and photoreceptor function with particular reference to phosphatidylinositol

The effect of dietary partially hydrogenated herring oil (HHO) on the fatty acid composition of the phospholipids of rat retina and on the amplitude of the a-wave of the electroretinogram (ERG) was studied in rats raised for several generations on an essential fatty acid poor diet. The most significant effect of the dietary treatment was a decreased content of arachidonic acid (C20:4 omega 6) and an increased concentration of docosahexaenoic acid (C22:6 omega 2) and 18:1 isomers associated with the phosphatidylinositol (PI). The a-wave of the ERG showed a decreasing amplitude during the experiment and was reduced with about 30% (P less than 0.004) of the initial value in all rats at the end of the experiment. The pronounced change in the arachidonic content in PI and the decreased amplitude of the a-wave of the ERG suggest that arachidonic acid of the PI has an important function in the visual phototransduction process.

Modulation of mitochondrial ATPase sensitivity to inhibitors and stimulators by diet-induced changes in membrane lipid

Weanling rats were fed diets differing in fatty acid composition to determine if changes induced in cardiac mitochondrial membrane structural components alter the sensitivity of mitochondrial ATPase to inhibition by oligomycin and stimulation by 2,4-dinitrophenol. Mitochondrial ATPase assayed in situ within the mitochodrial membrane isolated from animals fed diets higher in fatty acids of longer chain length, exhibited greater oligomycin sensitivity and lower 2,4-dinitrophenol-induced stimulation. Concomitant diet-induced changes occur in the fatty acid composition of phosphatidylcholine, phosphatidylethanolamine and cardiolipin, increasing overall length of fatty-acyl tails in the membrane phospholipids. Diet fat mediated alterations in oligomycin sensitivity of mitochondrial ATPase and membrane fatty acid chain length suggest that in vivo changes in thickness of the lipid bilayer may alter mitochondrial ATPase functions. The present study extends the concept that dietary fat affects mitochondrial membrane structure and function by demonstrating that the membrane-dependent sensitivity of mitochondrial ATPase to inhibitors and stimulators may be modulated by dietary fat.

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.

Influence of dietary partially hydrogenated vegetable and marine oils on membrane composition and function of liver microsomes and platelets in the rat

The aim of the present study was to investigate the influence of partially hydrogenated vegetable and marine oils on membrane composition and function of liver microsomes and platelets with particular reference to the metabolism of linoleic acid and the production of arachidonic acid metabolites. Four groups of male weanling rats were fed linoleic acid supplemented diets containing 20% (w/w) of partially hydrogenated low erucic acid rapeseed oil (HLRSO), partially hydrogenated herring oil (HHO), olive oil (OO) and trierucin + triolein (TE) for 10 weeks. An additional two groups were fed partially hydrogenated low erucic acid rapeseed oil and partially hydrogenated herring oil without linoleic acid supplementation (HLRSO- and HHO-, respectively). Substantial amounts of trans fatty acids were incorporated into liver microsomes (12.6% in group HLRSO) and platelets (7.0% in group HLRSO-). This incorporation was not dependent on the dietary linoleic acid level. Hepatic microsomal delta5 -desaturase activity was significantly increased after HLRSO feeding compared to 00 feeding. Delta6 -Desaturase activity did not vary in the linoleic acid supplemented groups. Both delta5 -and delta6 -desaturase activities were significantly increased in groups without linoleic acid supplementation. Docosenoic acid was incorporated into platelet phospholipids in contrast to liver microsomes. In the platelet, docosenoic acid seemed to have a special preference for phosphatidylserine. Very small amounts were incorporated into platelet phosphatidylinositol. Feeding diets HLRSO, HHO and 00 did not influence rat platelet cyclooxygenase or 12-lipoxygenase activity. Platelets from rats fed TE, however, produced significantly less 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) than platelets from rats fed OO. Feeding of HLRSO- and HHO- resulted in a significantly diminished production of the arachidonic acid metabolites 12-HETE, 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT) and 6-keto-prostaglandin F1alpha in stimulated platelets and aorta. Thus, high dietary levels of trans isomers of monoenoic acids do not interfere with platelet cyclooxygenase or lipoxygenase activity provided sufficient amounts of linoleic acid are available.

The effects of partially hydrogenated marine oils on the mitochondrial function and membrane phospholipid fatty acids in rat heart

The influence of dietary partially hydrogenated marine oils containing docosenoic acid on rat heart mitochondrial membrane phospholipid fatty acid composition was studied with particular reference to cardiolipin and oxidative phosphorylation. Five groups of male weanling rats were fed diets containing 20% (w/w) peanut oil (PO), partially hydrogenated peanut oil (HPO), partially hydrogenated Norwegian capelin oil (HCO), partially hydrogenated herring oil (HHO), and rapeseed oil (RSO) for 10 weeks. All the cardiac phospholipids investigated were influenced by the experimental diets. An increased amount of arachidonic acid observed in phosphatidylethanolamine (PE) after feeding partially hydrogenated oils suggests a changed regulation of the arachidonic acid metabolism in comparison with PO treatment. 22:1 originating from the dietary oils was incorporated only to a small extent into phosphatidylcholine (PC) and PE. A selective incorporation of 18:1 isomers into the 1- and 2-positions of PC and PE with respect to geometry and position of the double bond was observed. Large amounts of 18:1 trans were incorporated into the 1-position of PC and PE, irrespective of the amount of 18:2 supplemented to the diets, replacing a considerable proportion of stearic acid in this position. After feeding HHO and RSO, the content of 22:1 in mitochondrial cardiolipin of rat heart was found to be 3% (mainly cetoleic acid) and 10% (mainly erucic acid), respectively, indicating a high affinity for cis isomers of 22:1, but also a considerable resistance against incorporation of trans isomers was observed. The ability of rat cardiac mitochondria to oxidize palmitoylcarnitine and to synthesize ATP was depressed after feeding HHO and RSO. Dietary cis isomers of 22:1 seem to have a specific ability to interfere with cardiac ATP synthesis and also to alter the fatty acid composition of cardiolipin of rat heart.

The effect of dietary partially hydrogenated marine oils on desaturation of fatty acids in rat liver microsomes

The influence of dietary partially hydrogenated marine oils on distribution of phospholipid fatty acids in rat liver microsomes was studied with particular reference to the metabolism of linoleic acid. Five groups of weanling rats were fed diets containing 20% (w/w) peanut oil (PO), partially hydrogenated peanut oil (HPO), partially hydrogenated Norwegian capelin oil (HCO), partially hydrogenated herring oil (HHO), and rapeseed oil (RSO) for 10 weeks. The partially hydrogenated oils were supplemented with linoleic acid corresponding to 4.6 cal % in the diets. Accumulation of linoleic acid and reduced amount of total linoleic acid metabolites were observed in liver microsomal phospholipids from rats fed partially hydrogenated oils as compared to PO feeding. The most striking effects on the distribution of omega 6-polyunsaturated fatty acids was obtained after feeding HHO, a marine oil with a moderate content of trans fatty acids in comparison with HPO but rich in isomers of eicosenoic and docosenoic acids. Liver microsomal delta 6- as well as delta 5-desaturase activities as measured in vitro were reduced in rats kept on HHO as compared to PO dietary treatment. The results obtained suggest that the dietary influence of partially hydrogenated marine oils on the metabolism of linoleic acid might be better related to the intake of isomeric eicosenoic and docosenoic acids than to the total intake of trans fatty acids.

Influence of dietary fat on the lipid composition of rat brain synaptosomal and microsomal membranes

The modulation of rat brain microsomal and synaptosomal membrane lipid by diet fat was examined. Brain synaptosomal and microsomal membrane composition was compared for rats fed on diets containing either soya-bean oil (SBO), SBO plus choline, SBO lecithin, sunflower oil (SFO), chow or low-erucic acid rape-seed oil (LER) for 24 days. Cholesterol and phosphatidylcholine levels in both membranes were altered by diet. Diet fat also affected the microsomal content of sphingomyelin. Change in membrane phosphatidylcholine level was related to the relative balance of omega-6, omega-3 and monounsaturated fatty acids within the diets fed. The highest phosphatidylcholine levels appeared in membranes of animals fed on SBO lecithin and the lowest in those fed on LER. Microsomal membrane cholesterol and sphingomyelin content increased by feeding on SBO lecithin. In both synaptosomal and microsomal membranes a highly significant correlation was observed between membrane phosphatidylcholine and cholesterol content. The fatty acyl composition of phospholipids from both membranes also altered with diet and age. Alteration in fatty acid composition was observed in response to dietary levels of omega-6, omega-3 and monounsaturated fatty acids, but the unsaturation index of each phospholipid remained constant for all diet treatments. These changes in lipid composition suggest that dietary fat may be a significant modulator in vivo of the physicobiochemical properties of brain synaptosomal and microsomal membranes.

The fatty acid composition of subcellular membranes of rat liver, heart, and brain: diet-induced modifications

The influence of diets having different fatty acids composition on the fatty acid content of (the phospholipids) of rat liver mitochondria and microsomes, heart mitochondria, brain mitochondria and microsomes has been analyzed. It has been found that each organelle has its own peculiar composition in fatty acids. This composition may be profoundly influenced by the diet, but to different degrees in different organelles. Those of brain are most resistant. The changes observed are rather rapid, being generally already maximal after three weeks of treatment. The parallel between fatty acid composition of diets, and the changes observed in the organelles, is not strict, and is probably influenced by the metabolic competition among oleic acid, linoleic acid, linolenic acid. Unusual fatty acids like erucic acid, trans-oleic acid, and trans-linoleic acid can also become incorporated into the membranes of cell organelles.

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.

Friedreich's ataxia 1980. An overview of the physiopathology

Phase three of the Quebec Cooperative Study of Friedreich's Ataxia was devoted to an understanding of the physiopathology of individual symptoms on the basis of previously discovered biochemical leads. The present paper attempts to pull these results together by presenting, as a hypothesis, a unifying scheme of possible interactions and relationships. The central core of this hypothesis is the demonstration in Friedreich's ataxia of a state of mitochondrial energy deprivation. This is indirectly responsible for such associated and important symptoms as muscle weakness, dying-back neuropathy, scoliosis and hypertrophic cardiomyopathy. Secondarily, and possibly as an independent but linked-event, the entry of glucose into cells and pyruvate oxidation, are slowed down, favoring the development of diabetes. As a consequence, tissue concentrations of glutamic acid and aspartic acid are decreased, particularly in more vulnerable areas such as the cerebellum, brain stem and dorsal root ganglia. This tissue deficiency in putative excitatory neurotransmitters is directly responsible for the symptom of ataxia. This conclusion is reinforced by the correction of the ataxia in experimental animals, by the intraventricular injection of the same amino acids, and not by the injection of other stimulants of motricity. The observed mitochondrial energy deprivation could be the metabolic consequence of major changes in the linoleic acid (18.2) composition of inner mitochondrial membrane phospholipids, such as cardiolipin. Such decreases in membrane 18:2 could be the result of interference with the normal incorporation of this fatty acid to lipoproteins and/or cell membranes. It is at this level that the search for the specific enzyme defect in Friedreich's ataxia is continuing.

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.

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.

The role of dietary long chain fatty acids in mitochondrial structure and function. Effects on rat cardiac mitochondrial respiration

To evaluate the effect of dietary rapeseed oils on cardiac mitochondrial function and metabolic conservation of energy, male weanling rats derived from the Sprague-Dawley strain were fed three rations containing either 15% (w/w) soybean oil, low erucic acid rapeseed oil or a high erucic acid rapeseed oil. Cardiac mitochondria were isolated for measurement of mitochondrial respiratory functions. Pyruvate and malate plus malonate or succinate plus amytal, or alpha-ketoglutarate and malate plus malonate were utilized as substrates for oxidative phosphorylation. Net rates of state 3 oxygen uptake and therefore ATP synthesis were found to decline with chronic feeding of the 15% (w/w) oil containing diets. Significantly reduced ADP/O ratios were observed for groups fed high erucic acid rapeseed oil containing diets for 11 days. Decreased ADP/O ratios were also observed for groups fed high or low erucic acid rapeseed oils for 112 days. When pyruvate and malate plus malonate were utilized as substrates, reduced rates of ATP synthesis were observed after chronic feeding of high erucic acid rapeseed oil diets. Only prolonged feeding of low erucic acid rapeseed oils resulted in significant alterations in the efficiency of oxidative phosphorylation.

Erucic acid and phospholipids of newborn rat heart cells in culture

Erucic acid (delta 13-docosenoic acid), labeled with 14C in the 1- or 14-position, was incorporated into fetal calf serum and fed to beating, neonatal rat myocardial cell in culture. Uptake of the docosenoic acid during the first 6 hr of incubation was 41 nM/hr/mg protein in 7-day old cells and 29 nM/hr/mg protein in 14-day old cells. Fifty-seven percent of the 14C-activity was taken up from the medium in 24 hr, of which 77% was in the cells and 23% was unaccounted for. Of the 14C-activity taken up, 26% was in extractable lipid, with two-thirds in neutral lipid and one-third in phospholipid. Within the neutral lipid fraction, 88% of the 14C-activity was present in triglycerides; while in phospholipids, 66% of the 14C-activity was in phosphatidylcholine (PC); 14% in phosphatidylethanolamine (PE); 6% in sphinogomyelin (SPH) and 1% or less in cardiolipin (DPG). PC had the highest specific activity, followed by SPH and PE. The specific activity of PE was one-half that of SPH when the 14C-erucic acid substrate was labeled at the carboxyl position, but increased to equal that of SPH when the substrate was labeled at the double bond. The fatty acids of PC, PE, and SPH were influenced by erucic acid in the growth medium, but the amounts of each phospholipid were not affected. It is proposed that the altered fatty acid composition associated with incorporation of erucic acid or its metabolites into PC, PE, and SPH may affect integrity and function of heart cell membranes.

Changes in rat heart phospholipid composition after rapeseed oil feeding

The influence of long duration rapeseed oil feeding with high or low levels of erucic acid has been investigated on rat heart phospholipids. The rats treated for 20 wk with rapeseed oil containing 46.2% erucic acid showed a twofold increase in the sphingomyelin content of the heart. Treatment with primor rapeseed oil (3.7% erucic acid) for 20 wk did not modify phospholipid composition of rat heart. The fatty acid patterns of phosphatidylethanolamine and phosphatidylcholine were slightly influenced by the high erucic rapeseed oil; eicosenoic acid was incorporated preferentially into position one, but erucic acid showed a random distribution in both. After high erucic rapeseed oil feeding, 22:1 was incorporated into cardiolipin (5.6%) and sphingomyelin (10.5%). The incorporation of 22:1 into sphingomyelin was associated with an increase of the percentage of 24:1 (14.6%) and a decrease of saturated long chain fatty acid (22:0, 24:0) percentages. Primor rapeseed oil caused a slight increase of 24:1 and a decrease of 22:0 and 24:0 in rat heart sphingomyelin. As cardiolipin is localized in the inner membrane of mitochondria and sphingomyelin in plasma and microsomal membranes, the acyl-moiety alterations of both phospholipids might be correlated to the pathological lesions of rat heart after a long duration of rapeseed oil feeding.

Changes in the acyl and alkenyl group composition of cardiac phospholipids in boars fed corn oil or rapeseed oil

Boars fed diets containing rapeseed oil for 8 weeks showed significantly higher levels of neutral lipids and similar levels of phospholipids, compared to those fed corn oil. Erucic and eicosenoic acids were found to be high in ethanolamine phosphoglycerides, and in particular alkenyl acyl-ethanolamine phosphoglyceride. Furthermore, both long chain monoenes were incorporated preferentially in position 2 of the choline and ethanolamine phosphoglycerides. The alkenyl group composition of the cardiac lipids of pigs was influenced by dietary fatty acids. When rapeseed oil was fed, small amounts of 20:1 and 22:1 alkenyl constituents were detected.

The effects of original and randomized rapseed oils containing high or very low levels of erucic acid on cardiac lipids and myocardial lesions in rats

The nutritional status of the very lowerucate, rapseed oil, Brassica napus var. 'Tower,' was compared with that of the high-erucate oil, Brassica napus var. 'Target,' as well as with corn oil. The effect of randomization on the nutritional qualities of rapeseed oil was investigated as well. The feeding of diets containing the original and randomized 'Tower' oil or the original 'Target' oil, at the 20% level by weight, gave growth rates which were not significantly different from that for corn oil. However, the randomized 'Target' oil gave growth rates which were significantly less than all other groups. The growth results could not be explained simply on the basis of food consumption. The level of triglycerides in the hearts of rats fed the very low-erucate oils was not significantly different from the corn oil group. Triglyceride concentrations in the hearts of animals given the high-erucate oils were 7-12 times greater than all other groups. The level of total fatty acids in tissue phospholipids was the same regardless of dietary treatment. Fatty acid compositions of the tissue lipid were the same in animals fed either the original or randomized rapeseed oils. A much higher incidence of focal myocardial necrosis was found in animals receiving high-erucate rapeseed oil relative to animals given the corn oil. The incidence in rats fed diets containing very low-erucate rapeseed oil was intermediate between these latter two extremes.

Myocardial lipids and nucleotides of rats fed olive oil or rapeseed oil

After 1 week, the level of myocardial fatty acids was 4 times greater in young rats fed high erucic rapeseed oil than in those fed oliver oil. The proportion of erucic acid was 5.6% in the mitochondrial fraction, 15.1% in the microsomal fraction, and 34.8% in the floating fat fraction. This incorporation of erucic acid into triglycerides of the floating fat was evidence of esterification. The changes in the mitochondrial lipids did not alter the content of adenine nucleotides of the myocardium nor its apparent capacity to oxidize substrates.

Turnover of fatty acids in rat liver cardiolipin: comparison with other mitochondrial phospholipids

Following intraperitoneal administration of 1-14C-linoleic acid or 2-3H-acetate to rats, the specific radioactivities of both liver cardiolipin and other mitochondrial phospholipids after different time intervals were measured. Comparison of the data obtained with those from another stock of rats treated with 32P-phosphate or 2-3H-glycerol showed that the fatty acids of cardiolipin, like those of other phospholipids, exhibit an independent turnover with respect to the remaining parts of the molecule. The half-life of acyl moieties of cardiolipin is ca. 20% higher than that of the same components of other mitochondrial phospholipids. Moreover, it appears that, in both cardiolipin and other phospholipids, linoleyl residues turn over faster than nonessential fatty acids. Discussion is made as to whether this characteristic can be related to the role of phospholipids in the functioning of some enzymes bound to the inner mitochondrial membrane.

Failure of dietary erucic acid to impair oxidative capacity or APT production of rat heart mitochondria isolated under controlled conditions

1. Male, 8-week old rats were fed Purina Rat Chow for semisynthetic diets containing 20% by weight of rapeseed oil or corn oil for 3 days. 2. The hearts from the animals fed the three diets were analyzed for total lipid, phospholipid, free fatty acids, cholesterol esters, tri-, di- and monoacylglyerols. There was a seven-fold increase in the levels of triacylglycerols in the hearts of rats fed rapeseed oil diet compared to the levels in the hearts of animals fed the other two diets. Smaller increases in the content of other neutral lipid fractions were also observed. 3. Heart mitochondria from the three groups of animals were isolated under controlled conditions in the presence or absence of heparin. The rats of oxidation of different substrates and of ATP synthesis by these mitochondria were compared. 4. Mitochondria isolated in the absence of heparin from rapeseed oil-fed rats had much lower rates of oxidation and ATP synthesis than mitochondria isolated similarly from rats fed the other two diets. 5. With mitochondria freshly isolated in the presence of heparin, no significant differences in rates of oxidation or ATP synthesis were found among the three groups of animals. 6. It is concluded that, when properly isolated, mitochondria from rapeseed oil-fed rats are functionally intact with respect to oxidation and energy-coupling capacity.