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 arrythmia 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 ω-6 family of fatty acids, whereas feeding the relatively linoleic acid-poor sheep fat supplement decreased the level of ω-6 fatty acids but increased the levels of the ω-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, ω-6/22∶6, ω-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. As dosahexaenoic acid does not occur in the diet, the increase in this acid which occurs after feeding animal fat, presumably arises from increased conversion of the small amounts of linolenic acid in all diets when the amount of linoleic acid present is reduced.     

Diet-induced changes in the fatty acid composition of mouse hepatocyte plasma membranes

Hepatocyte plasma membranes were isolated from the livers of mice fed either a low fat diet or high fat diets containing polyunsaturated or saturated fat. The combined rate and isopycnic ultracentrifugation technique which was used produced highly purified hepatocyte plasma membrane fractions. The efficacy of the procedure was checked by electron microscopy and the assay of marker enzymes for the different subcellular organelles. Mice were maintained on a low fat diet until 60–70 days of age, when they were fed high fat diets containing polyunsaturated or saturated fat. The hepatocyte plasma membrane lipids of mice fed the polyunsaturated fat diet for 4 wk contained increased proportions of the major dietary unsaturated fatty acid, linoleic acid, and increased proportions of arachidonic acid. The proportion of linoleic and arachidonic acids decreased with continued feeding of the polyunsaturated fat diet. The hepatocyte plasma membrane lipids of mice fed the saturated fat diet contained increased proportions of oleic acid.     

Essential fatty acids alter the activity of manganese-superoxide dismutase in rat heart

The effects of oil-derived dietary essential fatty acids on the activities of mitchondrial Mn-SOD (manganese-superoxide dismutase) and cytosolic cupric zinc-superoxide dismutase (Cu/Zn-SOD) were investigated in rat heart. A control group of rats was fed a stock diet for 29 d, and a second group was fed on a fat-free diet. Three other groups were fed fat-free diets that were supplemented with (i) borage oil, which is rich in linoleic (18∶2n−6) and γ-linolenic (18∶3n−6) acids, (ii) fungal oil, which is rich in γ-linolenic, but low in linoleic acid, or (iii) evening primrose oil, which is rich in linoleic acid and low in γ-linolenic acid. An increase in the percentage composition of arachidonic acid (20∶4n−6) in both the choline and ethanolamine phospholipids, together with a decrease in linoleic acid in ethanolamine phospholipids, were found in heart membranes after feeding the rats with diets containing borage oil or fungal oil as compared to those fed the stock diet. The respective activities of Mn-SOD in rats fed the borage or fungal oil diets were also significantly higher than in rats fed the stock diet alone. No change in cytosolic Cn/Zn-SOD activity was observed. Dietary supply of linoleic acid-rich evening primrose oil resulted in an increased proportion of choline phospholipid linoleic acid without any changes in arachidonic acid content or in the activity of Mn-SOD. By contrast, a reduction in the activity of Mn-SOD was detected in rats fed a fat-free diet. These results show that the activity of heart mitochondrial Mn-SOD is influenced by dietary essential fatty acids, whereas the activity of cytosolic Cu/Zn-SOD remained unaffected.     

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 Sprague-Dawley male rat is more fragile, leading to greater cellular breakdown and focal necrosis. Contribution No. 914 from the Animal Research Institute.     

Homeostatic control of membrane fatty acid composition in the rat after dietary lipid treatment

Diets in which both the lipid content and composition (polyunsaturated to saturated fatty acid ratio) were varied were fed to rats for 20 weeks, and the effects on the tissue lipid profiles were determined. The fatty acid profile of the plasma lipids, and the phospholipid fatty acids of the mitochondrial and microsomal fractions of liver, heart, kidney and brain, as well as erythrocyte membranes were determined. Despite large differences in the level and type of lipid present in the experimental diets and in the proportion of saturated fatty acids in the plasma lipids in response to the various diets, there was little effect on the proportion of saturated to unsaturated fatty acids in the phospholipids of the various membranes examined. The major effect of altering the dietary level of polyunsaturated to saturated fatty acids was on the ratio of the ω6/ω3 series of unsaturated fatty acids in the membrane lipids. This change occurred in all tissues except the brain, in which only a small response to altered dietary lipid intake was observed. The ω6/ω3 ratio was elevated upon feeding a diet rich in ω6 polyunsaturated fatty acids, but decreased when a diet rich in saturated fatty acids was fed. The failure to significantly alter membrane lipid saturation/unsaturation in the tissues examined would suggest that a homeostatic mechanism is operative in biological membranes and may act to buffer membranes from the effects of changes in the nature of the dietary lipid intake.     

Effects of dietary supplementation of saturated fatty acids and of n−6 or n−3 polyunsaturated fatty acids on plasma and red blood cell membrane phospholipids and deformability in weanling guinea pigs

The fatty acid composition of plasma cholesteryl esters, plasma phospholipids, red blood cell (RBC) membrane phosphatidylcholine (corresponding to the outer membrane leaflet), and phosphatidylethanolamine (corresponding to the inner membrane leaflet) was investigated in weanling guinea pigs fed with diets of cacao (saturated fatty acids), sunflower oil [n−6 polyunsaturated fatty acids (PUFA)] or fish oil (n−3 PUFA) for 20 wk. RBC deformation was measured by means of a cell-transit analyzer (filtration) and a cone-plate rheoscope. The contents of saturated fatty acids in plasma phospholipids and RBC membrane leaflets were similar in all three groups. Diets with sunflower oil resulted in a high content of linoleic acid in plasma cholesteryl esters and in the outer leaflet of RBC membranes. Fatty acids of fish oil were mainly incorporated in plasma phospholipids and in the inner leaflet of RBC membranes. The arachidonic acid content was high in all groups in the plasma phospholipids and in the inner leaflet. The n−6 and n−3 PUFA were mainly incorporated in the inner leaflet. In all groups the polyunsaturated/saturated fatty acid ratio and the total PUFA content were similar in the inner RBC membrane. The RBC filtration times and the RBC deformation indices were not affected by the dietary treatment.     

Dietary α-linolenic acid lowers postprandial lipid levels with increase of eicosapentaenoic and docosahexaenoic acid contents in rat hepatic membrane

This study was designed to examine the effects of dietary n−3 and n−6 polyunsaturated fatty acids (PUFA) on postprandial lipid levels and fatty acid composition of hepatic membranes. Male Sprague-Dawley rats were trained for a 3−h feeding protocol and fed one of five semipurified diets: one fat-free diet or one of four diets supplemented with 10% (by weight) each of corn oil, beef tallow, perilla oil, and fish oil. Two separate experiments were performed, 4-wk long-term and 4-d short-term feeding models, to compare the effects of feeding periods. Postprandial plasma lipid was affected by dietary fats. Triacylglycerol (TG) and total cholesterol levels were decreased in rats fed perilla oil and fish oil diets compared with corn oil and beef tallow diets. Hepatic TG and total cholesterol levels were also reduced by fish oil and perilla oil diets. Fatty acid composition of hepatic microsomal fraction reflected dietary fatty acids and their metabolic conversion. The major fatty acids of rats fed the beef tallow diet were palmitic, stearic, and oleic. Similarly, linoleic acid (LA) and arachidonic acid in the corn oil group, α-linolenic acid (ALA) and eicosapentaenoic acid (EPA) in the perilla oil group, and palmitic acid and docosahexaenoic acid (DHA) in the fish oil group were detected in high proportions. Both long- and short-term feeding experiments showed similar results. In addition, microsomal DHA content was negatively correlated with plasma lipid levels. Hepatic lipid levels were also negatively correlated with EPA and DHA contents. These results suggest that n−3 ALA has more of a hypolipidemic effect than n−6 LA and that the hypolipidemic effect of n−3 PUFA may be partly related to the increase of EPA and DHA in hepatic membrane.     

Effect of dietary n−3 and n−6 polyunsaturated fatty acids on lipid-metabolizing enzymes in obese rat liver

This study was designed to examine whether n−3 and n−6 polyunsaturated fatty acids at a very low dietary level (about 0.2%) would alter liver activities in respect to fatty acid oxidation. Obese Zucker rats were used because of their low level of fatty acid oxidation, which would make increases easier to detect. Zucker rats were fed diets containing different oil mixtures (5%, w/w) with the same ratio of n−6/n−3 fatty acids supplied either as fish oil or arachidonic acid concentrate. Decreased hepatic triacylglycerol levels were observed only with the diet containing fish oil. In mitochondrial outer membranes, which support carnitine palmitoyltransferase I activity, cholesterol content was similar for all diets, while the percentage of 22∶6n−3 and 20∶4n−6 in phospholipids was enhanced about by 6 and 3% with the diets containing fish oil and arachidonic acid, respectively. With the fish oil diet, the only difference found in activities related to fatty acid oxidation was the lower sensitivity of carnitine palmitoyltransferase I to malonyl-CoA inhibition. With the diet containing arachidonic acid, peroxisomal fatty acid oxidation and carnitine palmitoyltransferase I activity were markedly depressed. Compared with the control diet, the diets enriched in fish oil and in arachidonic acid gave rise to a higher specific activity of aryl-ester hydrolase in microsomal fractions. We suggest that slight changes in composition of n−3 or n−6 polyunsaturated fatty acids in mitochondrial outer membranes may alter carnitine palmitoyltransferase I activity.     

Increments of dietary linoleate raise liver arachidonate,but markedly reduce heart n−6 and n−3 fatty acids in the rat

Four diets containing 20% of energy (en%) as fat and with linoleic acid contents of 1.9, 3.1, 7.7 and 10.1 en%, respectively, were fed to one-month-old male rats for three months. The fatty acid profiles and the levels of the major n−6 and n−3 fatty acids in the lipids of plasma, liver, heart and kidney were measured. We found that with increasing concentrations of 18∶2n−6 in the diet, linoleic acid rose in plasma and in all organs, but long-chain n−6 and n−3 fatty acids responded differently. In liver, arachidonic acid increased and n−3 fatty acids were not significantly affected; in heart, both arachidonic and docosahexaenoic acids were progressively reduced; and in kidney, there was no change of n−6 and n−3. The results indicate that incremental changes in dietary, linoleate affect the levels of polyunsaturated fatty acids in liver and extrahepatic organs differently.     

Effects of dietary fats on fatty acid composition and Δ5 desaturase in normal and diabetic rats

We have studied the effect of various diets on the phospholipid fatty acid composition andin vitro Δ5 desaturase activity of hepatic microsomes derived either from the normal or streptozotocin-induced diabetic rat. The diets studied were the standard rat chow diet and a basal fat-free diet supplemented either with 20 percent saturated fat, 20 percent unsaturated fat, or 20 percent menhaden oil. Phospholipid fatty acid composition analysis revealed that the normal rat fed the saturated fat or menhaden oil diet had significantly decreased arachidonate levels, consistent with decreased Δ5 desaturase activities and decreased 18∶2n−6 intake. On the contrary, the unsaturated fat diet decreased dihomo-γ-linolenate and increased arachidonate levels, without increased Δ5 desaturase activity. Streptozotocininduced diabetes resulted in decreased arachidonate and Δ5 desaturase activity. The unsaturated fat diet fed to the diabetic rat also failed to correct this decreased Δ5 desaturase activity. The unsaturated fatty acids in this diet also displaced a substantial amount of n−3 fatty acids in both normal and diabetic microsomes, due to the competition between these two fatty acid families for incorporation into the membrane phospholipids. Conversely, the menhaden oil diet fed to the normal and diabetic rats displaced n−6 fatty acids, reduced Δ5 desaturase activity, and enhanced 22∶6n−3 incorporation into diabetic microsomes.     

Comparison of the effects of dietary fish oils with different n−3 polyunsaturated fatty acid compositions on plasma and liver lipids in rats

The effects of dietary fish oils with different n−3 polyunsaturated fatty acid compositions on plasma lipid profiles in rats have been studied. Forty-eight male rats, previously maintained on a cholesterol-free diet for 15 days, were fed for 60 days with diets supplemented with 10% fat of either marine hilsa fish (Hilsa ilisa, family clupeidae) or fresh-water chital fish (Notopterus chitala, family notopteridae). The diets had similar levels of total saturated (35–41%), monounsaturated (43–47%) and n−3 polyunsaturated (9–10%) fatty acids. Cholesterol contents of the diets were adjusted to 0.85%; γ-linolenic acid (3.3%) in chital oil and eicosapentaenoic acid (4.9%) in hilsa oil diets were the major n−3 contributors. The percentage of eicosapentaenoic acid in the chital oil diet was 0.57 times that of the hilsa oil diet, but the eicosapentaenoic (EPA) to arachidonic acid (AA) ratio in the latter (4.08) was 3.2 times that of the former (1.27). Sixty days of hilsa oil diet feeding decreased the levels of cholesterol (53.3±2.9 to 50.0±1.1 mg/dL), triacylglycerol (75.7±3.8 to 64.3±2.6 mg/dL) and phospholipid (55.8±1.5 to 51.7±3.1 mg/dL) in rat plasma. Similar treatment with chital oil diet elevated the plasma cholesterol level (53.3±2.9 to 62.3±7.6 mg/dL) while triacylglycerol and phospholipid contents remained unaltered. Both the dietary treatments decreased the levels of linoleic and arachidonic acids in liver but only under the hilsa oil diet did the eicosapentaenoic acid percentage increase markedly (0.8±0.06% to 5.5±0.06%) at the expense of arachidonic acid. This study strongly suggests that the hypolipidemic effect depends on the composition of the n−3 polyunsaturated fatty acids rather than on the total n−3 polyunsaturated fatty acid content of the dietary fish oil.     

Influence of genotype on diet-induced changes in membrane phosphatidylcholine and phosphatidylethanolamine composition of splenocytes,liver nuclear envelope and liver mitochondria

Inbred congenic mice of strains MRL/Mp-lpr/lpr (lpr/lpr) and MRL/Mp-+/+ (+/+) were fed nutritionally adequate semipurified diets containing 20% (w/w) fat and differing in linoleic acid content. Levels of linoleic acid (18∶2n−6) and arachidonic acid (20∶4n−6) in phospholipids of splenocytes, liver mitochondria and liver nuclear envelopes were determined. Membranes of lpr/lpr mice exhibited significantly lower levels of 18∶2n−6 and 20∶4n−6 in phospholipids compared with the +/+ strain. The high linoleic acid diet increased incorporation of 18∶2n−6 and 20∶4n−6 in most phospholipid fractions of these membranes. These observations indicate that genotype as well as dietary 18∶2n−6 content significantly influenced incorporation of 18∶2n−6 and 20∶4n−6 into membrane phospholipids. The results also suggest that membrane compositional abnormalities found in the lpr/lpr mice, which develop lymphoma and age faster than +/+ mice, are not restricted to the immune system but also extend to other organs. Differences observed in phospholipid fatty acid composition in splenocytes and liver subcellular membranes for mice fed diets differing in linoleic acid content suggest that the early expression of the lpr gene resulting in progression of autoimmunity may be delayed through dietary manipulation.     

The n−3 polyunsaturated fatty acid levels in rat tissue lipids increase in response to dietary olive oil relative to sunflower oil

In the present study, changes in phospholipid compositions of liver microsomes, erythrocyte membranes, platelets, aorta, cardiac muscle and brain of rats fed olive oil were compared with those of rats fed sunflower oil. Four groups of rats starting at weaning were fed for four weeks a basal diet containing 5 or 25% olive oil or sunflower oil. We found that oleic acid was higher and linoleic acid was lower in membrane phospholipids of olive oil fed rats compared to sunflower oil fed rats. Polyunsaturated fatty acids of the n−3 series were markedly elevated in all tissues of rats on the olive oil diets relative to those on the sunflower oil diets. The results are consistent with a lower linoleic/linolenic acid ratio induced by the olive oil diets, suggesting a positive correlation between olive oil ingestion and n−3 polyunsaturated fatty acid levels in cell and tissue lipids. The study suggests that an adequate intake of olive oil may enhance the conversion of n−3 fatty acids.     

The effects of dietary fish oil on alveolar type II cell fatty acids and lung surfactant phospholipids

The purpose of this study was to determine the responsiveness of alveolar type II cells to dietary fish oil and the consequent effects on alveolar and lung surfactant. Rats were fed a corn oil or a fish oil diet for four weeks. Dietary n−3 fatty acids were readily incorporated into the type II cell phospholipids as indicated by higher levels of eicosapentaenoic acid (2.77±0.10%) and docosahexaenoic acid (1.63±0.10%) in the group receiving the fish oil diet. The elevated levels of n−3 fatty acids were accompanied by concomitant reduction in arachidonic acid and linoleic acid. Neither eicosapentaenoic acid nor docosahexaenoic acid was incorporated into type II cell triacylglycerols. Feeding a fish oil containing diet increased surfactant phospholipids, particularly 1,2-disaturated acyl phosphatidylcholines in whole lung compared to a corn oil diet. However, the amount of surfactant found in the alveolus was not different between the two diet treatment groups. The results suggest that dietary n−3 fatty acids stimulate synthesis and/or inhibit degradation of lung surfactant without altering surfactant secretion in alveoli.     

Lipid composition and peroxide levels of mucosal cells in the rat large intestine in relation to dietary fat

To examine whether dietary fat alters membrane lipid composition and peroxidation of polyunsaturated fatty acids in “non-proliferative” and “proliferative” cells in the large intestine, Sprague-Dawley rats were fed diets providing a polyunsaturated-to-saturated fatty acid ratio of 1.2 or 0.3 at a high or low level of fat intake for a 25-day period. Cell populations were isolated and the effect of dietary fat on membrane polyunsaturated fatty acid content and peroxide levels was determined. Neither fat level nor fatty acid composition of diet influenced total cholesterol, total phospholipids, and percentage of phospholipid classes in membrane phospholipids. Feeding the high fat and/or high polyunsaturated-to-saturated fatty acid ratio diet increased polyunsaturated fatty acid content of mucosal cell phospholipids. Increase in polyunsaturated fatty acid content was paralleled by a decrease in the monounsaturated fatty acid content of mucosal cell phospholipids. Membrane content of total saturated fatty acids was not significantly affected by diet. Variation in phospholipid fatty acid composition between “non-proliferative” and ”proliferative” cells was observed. Lipid peroxide levels in mucosal cell lipid fractions were altered by dietary fat treatment. Animals fed high fat diets, compared to groups fed low fat diets, exhibited higher membrane peroxide levels when results are expressed as nmol/mg protein. Higher peroxide levels were observed in mucosal cells for rats fed high polyunsaturated-to-saturated fatty acid ratio diets when results were expressed per nmol of phospholipid. It is concluded that changes in fat level and fatty acid composition of the diet alters the mucosal cell membrane lipid composition in the rat large intestine and influences susceptibility of mucosal cell lipid to peroxidation. Further research is required to delineate which dietary factors—fat level, polyunsaturated-to-saturated fatty acid ratio, or both—have a primary influence on the degree of lipid peroxidation.     

The effect of dietary fat level and quality on plasma lipoprotein lipids and plasma fatty acids in normocholesterolemic subjects

This study examined the effect on the plasma lipids and plasma phospholipid and cholesteryl ester fatty acids of changing from a typical western diet to a very low fat (VLF) vegetarian diet containing one egg/day. The effect of the addition of saturated, monounsaturated or polyunsaturated fat (PUFA) to the VLF diet was also examined. Three groups of 10 subjects (6 women, 4 men) were fed the VLF diet (10% energy as fat) for two weeks, and then in the next two weeks the dietary fat in each group was increased by 10% energy/week using butter, olive oil or safflower oil. The fat replaced dietary carbohydrate. The VLF diet reduced both the low density lipoprotein (LDL)-and high density lipoprotein (HDL)-cholesterol levels; addition of the monounsaturated fats and PUFA increased the HDL-cholesterol levels, whereas butter increased the cholesterol levels in both the LDL- and HDL-fractions. The VLF diet led to significant reductions in the proportion of linoleic acid (18∶2ω6) and eicosapentaenoic acid (20∶5ω3) and to increases in palmitoleic (16∶1), eicosatrienoic (20∶3ω6) and arachidonic acids (20∶4ω6) in both phospholipids and cholesteryl esters. Addition of butter reversed the changes seen on the VLF diet, with the exception of 16∶1, which remained elevated. Addition of olive oil resulted in a significant rise in the proportion of 18∶1 and significant decreases in all ω3 PUFA except 22∶6 compared with the usual diet. The addition of safflower oil resulted in significant increases in 18∶2 and 20∶4ω6 and significant decreases in 18∶1, 20∶5ω3 and 22∶5ω3. These results indicate that the reduction of saturated fat content of the diet (<6% dietary energy), either by reducing the total fat content of the diet or by exchanging saturated fat with unsaturated fat, reduced the total plasma cholesterol levels by approximately 12% in normocholesterolemic subjects. Although the VLF vegetarian diet reduced both LDL- and HDL-cholesterol levels, the long-term effects of VLF diets are unlikely to be deteterious since populations which habitually consume these diets have low rates of coronary heart disease. The addition of safflower oil or olive oil to a VLF diet produced favorable changes in the lipoprotein lipid profile compared with the addition of butter. The VLF diets and diets rich in butter, olive oil or safflower oil had different effects on the 20 carbon eicosanoid precursor fatty acids in the plasma. This suggests that advice on plasma lipid lowering should also take into account the effect of the diet on the fatty acid profile of the plasma lipids.     

Effects on plasma lipids and fatty acid composition of very low fat diets enriched with fish or kangaroo meat

The effects of very low fat diets (<7% energy) enriched with different sources of long chain (C20 and C22) polyunsaturated fatty acids (PUFA) on plasma lipid levels and plasma fatty acids (PUFA) on plasma lipid levels and plasma fatty acid composition were studied in 13 healthy volunteers. Three diets provided 500 g/day of tropical Australian fish (rich in arachidonic acid and docosahexaenoic acid), southern Australian fish (rich in docosahexaenoic acid) or kangaroo meat (rich in linoleic and arachidonic acids). The fourth diet was vegetarian, similarly low in fat but containing no 20- and 22-carbon PUFA. Subjects ate their normal or usual diets on weeks 1 and 4 and the very low fat diets in weeks 2 and 3. Weighed food intake records were kept, and weeks 2, 3 and 4 were designed to be isoenergetic with week 1. Plasma cholesterol levels fell significantly on all diets within one week. There were reductions in both low density (LDL) and high density lipoprotein (HDL) cholesterol levels, with effects on HDL cholesterol being more consistent. There were no consistent or significant effects on total triglyceride levels despite the high carbohydrate content of the diets. On all diets the percentage of linoleic acid fell in the plasma phospholipid and cholesteryl ester fractions, while the percentage of palmitic acid in the phospholipids and cholesteryl esters and palmitoleic acid in the cholesteryl ester fraction rose on all diets. The percentage of arachidonic acid rose in the phospholipid and cholesteryl esters on the two diets that were good sources of this fatty acid (tropical fish and kangaroo meat). The percentage of docosahexaenoic acid also rose on the two diets that were the richest sources of this fatty acid (the fish diets), and the percentage of eicosapentaenoic acid rose in the phospholipid and cholesteryl esters in proportion to the dietary level of this fatty acid (southern fish > kangaroo > tropical fish). The changes in fatty acid composition were almost completely reversed within seven days of returning to the usual higher fat diets.     

Effect of high fat corn oil,olive oil and fish oil on phospholipid fatty acid composition in male F344 rats

Epidemiological and laboratory animal model studies have provided evidence that the effect of dietary fat on colon tumorigenesis depends on the amount of fat and its composition. Because of the importance of the composition of dietary fat and of tissue membrane fatty acid composition in tumor promotion, experiments were designed to investigate the relative effects of high fat diets rich in ω3, ω6 and ω9 fatty acids and colon carcinogen on the phospholipid fatty acid composition of liver, colon, small intestine, erythrocytes and blood plasma. At 6 wk of age, groups of animals were fed diets containing 5% corn oil (LFCO), 23.5% corn oil (HFCO), 23.5% olive oil (HFOO), and 20.5% fish oil plus 3% corn oil (HFFO). Two weeks later all the animals except the vehicle-treated animals received azoxymethanes.c. once weekly for 2 wk at a dose rate of 15 mg/kg body weight. Animals were sacrificed 5 d later and liver, colon, small intestine and erythrocytes and blood plasma were analyzed for phospholipid fatty acids. The results indicate that the phospholipid fatty acid composition of liver, colon and small intestine of HFCO diet fed animals, were not significantly different from those fed the LFCO diet. The levels of palmitoleic acid and linoleic acid were increased in erythrocytes and blood plasma of the animals fed the HFCO diet compared to those fed the LFCO diet. Feeding the HFCO diet significantly increased the oleic acid content and decreased the linoleic acid and arachidonic acid levels in various organs when compared to the HFCO diet. Animals fed the HFFO diet showed a marked increase in eicosapentaenoic acid and docosahexaenoic acid and a decrease in linoleic acid and arachidonic acid levels as compared to those fed the HFCO diet. The results also indicate that carcinogen treatment had only a minimal effect on the phospholipid fatty acid composition.     

Influence of different fats in pig feed on fatty acid composition of phospholipids and physical meat quality characteristics

Two feeding experiments (i, ii) were conducted to investigate the influence of different dietary fats on the fatty acid (FA) composition of phospholipids as well as meat quality in pigs. In each experiment 12�4 siblings of Swiss Landrace or Large White breed were allocated to one of four feeding treatments according to sex, breed, and litter and fattened from about 25 to 105 kg liveweight. Pigs were fed a control diet (barley, wheat, soybean meal) or the control diet supplemented with 7% pork fat, 4.95% olive oil or 3.17% soybean oil (i) or 5% of olein or stearin fraction of pork fat or hydrogenated fat (ii). The dietary FA composition was reflected in the FA composition of phospholipids in M. long. dorsi and triceps brachii. However, the unsaturated to saturated ratio was not affected by the dietary intake of polyunsaturated FAs and was only slightly increased by the olive oil supplementation. Trans FAs including conjugated linoleic acid were incorporated into phospholipids only to a small extent. The dietary altered fatty acid composition of phospholipids did not cause any effect on pH, cooking loss, texture, or colour of pork, but meat quality as well as the proportion of saturated FA, arachidonic acid, and n‐3 fatty acids were significantly influenced by genetic effects.     

Linoleic acid requirement of rats fedtrans fatty acids

The amount of linoleic acid required to prevent undesirable effects of C18trans fatty acids was investigated. In a first experiment, six groups of rats were fed diets with a high content oftrans fatty acids (20% of energy [en%]), and increasing amounts of linoleic acid (0.4 to 7.1 en%). In a second experiment, four groups of rats were fed diets designed to comparetrans fatty acids with saturated andcis-monounsaturated fatty acids of the same chain length at the 2 en% linoleic acid level. After 9–14 weeks, the oxygen uptake, lipid composition and ATP synthesis of heart and liver mitochondria were determined. The phospholipid composition of the mitochondria did not change, but the fatty acid compositions of the two main mitochondrial phospholipids were influenced by the dietary fats.Trans fatty acids were incorporated in all phospholipids investigated. The linoleic acid level in the phospholipids, irrespective of the dietary content of linoleic acid, increased on incorporation oftrans fatty acids. The arachidonic acid level had decreased in most phospholipids in animals fed diets containing 2 en% linoleic acid. At higher linoleic acid intakes, the effect oftrans fatty acids on the phospholipid arachidonic acid level diminished. However, in heart mitochondrial phosphatidylethanolamine,trans fatty acids significantly increased the arachidonic acid level. Despite these changes in composition, neither the amount of dietary linoleic acid nor the addition oftrans fatty acids influenced the mitochondrial function. For rats, a level of 2 en% of linoleic acid is sufficient to prevent undesirable effects of high amounts of dietary C18trans fatty acids on the mitochondrial function.