Flaxseed Oil Group Research Articles

Effect of dietary lipid sources on odour‐active compounds in muscle of turbot (Psetta maxima)

AbstractOdour‐active compounds in muscle of turbot (Psetta maxima) fed experimental diets containing fish oil (FO), soybean oil (SO) or linseed oil (LO) were investigated by a gas chromatography/olfactometry technique. Thirty‐one areas associated with odours were detected in muscle extracts. Among the compounds responsible for these odours, 23 were formed by oxidation of unsaturated fatty acids. Independently of diet, (E)‐2‐penten‐1‐ol and (E)‐3‐hexen‐1‐ol contribute strongly to the odour of turbot. (E,Z)‐2,6‐Nonadienal, (E)‐2‐pentenal and (E,E)‐1,3‐(Z)‐5‐octatriene seem to contribute strongly to the odour of turbot fed diets containing high levels of n‐3 PUFA (FO and LO groups). Hexanal and decanal show a high detection frequency in turbot fed diets containing vegetable oils. Odorous compounds which are not formed by lipid oxidation (methional, 1‐acetyl pyrazine, 4‐ethyl benzaldehyde and 2‐acetyl‐2‐thiazoline) were not affected by dietary lipid sources.© 2001 Society of Chemical Industry

Nutritional Characteristics of Oil Containing Conjugated Octadecatrienoic Fatty Acid

The nutritive value of conjugated octadecatrienoic fatty acid (C18:3 Δ9,11,13α-elaeostearic acid) as occurs in karela seed (Momordica charantia) oil was studied. When rats were fed at the 20% level for 6 weeks, the growth pattern of rats and the food efficiency ratio showed a slightly significant difference compared to the group raised on linseed oil with non-conjugated octadecatrienoic acid (C18:3 Δ9,12,15α-linolenic acid) as control. The concentrations of total cholesterol, triglyceride, VLDL-cholesterol, LDL-cholesterol and LDL/HDL-cholesterol in serum were significantly higher in karela oil than in linseed oil. The liver lipid profile showed no difference. The total lipid as well as phospholipid concentrations of heart lipid were significantly higher in karela oil. The brain weight of the linseed oil group was significantly higher than the karela group. The brain phospholipid concentration of the karela oil group was significantly higher than that of the linseed oil group.

Dietary linolenic acid-mediated increase in vascular prostacyclin formation.

To define vascular effects of an enhanced dietary alpha-linolenic acid intake, 28 spontaneously hypertensive rats were fed a 3% sunflowerseed oil (44% linoleic acid) diet; in 3 groups (7 rats each), the diet was supplemented with 1, 2.5 or 5% linseed oil containing 62% alpha-linolenic acid. alpha-Linolenic acid was incorporated up to 12% in the aorta of the 5% linseed oil group. The eicosapentaenoic acid content was not significantly increased. The content of arachidonic acid and docosatetraenoic acid was moderately reduced in rats fed 5% linseed oil. The generation of 6-keto-PGF1 alpha (degradation product of prostacyclin) assessed by HPLC/electrochemical detection was, however, markedly increased (p < 0.05) in rats fed 2.5 and 5% linseed oil. The minor prostanoids TXB2, PGE2 and PGF2 alpha were not significantly altered. The high systolic and diastolic blood pressure of SHR monitored by radio telemetry was more effectively reduced (p < 0.05) in the light, i.e. sleep, cycle. An increased prostacyclin formation and lowered vascular arachidonic acid content associated with enhanced dietary alpha-linolenic acid intake would thus be expected to prove beneficial in the prevention of vascular disorders.

Effects of moderate fat intake with different n-3 fatty acid sources and n-6/n-3 ratios on serum and structural lipids in rats.

The aim of this study was to compare the effects of dietary polyunsaturated fatty acids (PUFA) on serum and membrane lipids in rats fed diets containing moderate levels of fats (6% by weight). Control rats received enough PUFA to prevent any deficiency. Experimental rats were fed linseed oil, salmon oil, or sunflower oil. After 8 weeks of feeding, fasting serum triacylglycerol and cholesterol levels were not altered in the linseed oil group. In contrast, in the salmon oil group, serum cholesterol was lowered by 58% (P < 0.05) and the specific binding of heterologous LDL to liver plasma membrane was reduced by 31% (P < 0.05). Unexpectedly, serum triacylglycerol levels were not significantly lowered (-14%) whereas they decreased (-32%; P < 0.05) in the sunflower oil group. Oleic acid, which has a stimulating effect on triacylglycerol synthesis and secretion, was less incorporated in serum and liver plasma membrane in rats fed sunflower oil than in rats fed other dietary lipids. This finding suggests that the effect of dietary sunflower oil was partly mediated by the reduction of oleic acid available for triacylglycerol synthesis.

Differential Effects of Various Oil Diets on the Risk of Cardiac Arrhythmias in Rats

Independently of the problem of atherogenesis, the amount and type of fat intake influences the risk of cardiac arrhythmias. However, the relative effectiveness of different fats and the underlying mechanisms are controversial. The aim of the present study was to compare the effects of various oil-enriched diets on the risk of ventricular arrhythmias in rat hearts under conditions of ischaemia and reperfusion and to help clarify the mechanisms underlying the differing effects of the oils on the occurrence of arrhythmias. Over a 10-week period, we studied five groups of young male Wistar rats given a low-fat chow diet or one enriched with 10% hydrogenated coconut oil, corn oil, linseed oil or sardine oil. Electrocardiograms were recorded from the isolated hearts (Langendorff preparation) perfused with a modified Krebs-Henseleit solution. Ischaemia was induced by a 20 min occlusion of the left anterior descending coronary artery. In another series of experiments, a 10 min occlusion was followed by a 20 min reperfusion period. The times between the first occurrence of extrasystole and the incidence of ventricular tachycardia and fibrillation were determined. The size of the ischaemic zone was assessed using malachite green. The fatty acid composition of the myocardial tissue was analysed using gas chromatography. An increase in the risk of ventricular arrhythmias under conditions of both ischaemia and reperfusion was obvious in the rats that consumed large quantities of saturated fatty acids (coconut oil) and in the group with a very low intake of fat. Polyunsaturated fatty acids (PUFAs), particularly fish oil, exerted a protective effect. The incidence of ventricular fibrillation was 75% in the low-fat group, 67% in the coconut-oil group, 44% in the corn-oil group, 40% in the linseed-oil group and 10% in the fish-oil group. The time until the first occurrence of extrasystole, the incidence of ventricular tachycardia and the incidence of reperfusion-induced ventricular fibrillation were influenced in a similar manner. The size of the ischaemic zone was significantly reduced in the groups given diets enriched with PUFAs. All protective effects were abolished, however, by cyclooxygenase inhibition with aspirin. The fatty acid composition of myocardial tissue, the ratio of n-3 to n-6 fatty acids and the double-bond index were significantly affected by the various diets. Whereas saturated fatty acids are obviously proarrhythmic, diets enriched with n-6 or n-3 PUFAs both exert antiarrhythmic effects. Although n-3 fatty acids seem to be more effective, cardioprotection cannot simply be related to the replacement of n-6 by n-3 fatty acids in cardiac membrane phospholipids, given the beneficial effects of corn oil. In any case, replacement of n-3 by n-6 fatty acids is not the underlying mechanism. The overall reduction of prostaglandin formation cannot be the primary mechanism because the beneficial effects of diets rich in PUFAs were abolished by cyclooxygenase inhibition. We conlcude that, besides prostacyclin (PGI2 or PGI3), membrane fluidity and accompanying alterations in functional membrane proteins (e.g. protection from calcium overload) are key factors apart from vascular effects that influence the size of the ischaemic zone.

Recycling of docosahexaenoic acid in rat retinas during n-3 fatty acid deficiency.

About 50% of the fatty acids in retinal rod outer segments is docosahexaenoic acid [22:6(n-3)], a member of the linolenic acid [18:3(n-3)] family of essential fatty acids. Dietary deprivation of n-3 fatty acids leads to only modest changes in 22:6(n-3) levels in the retina. We investigated the mechanism(s) by which the retina conserves 22:6(n-3) during n-3 fatty acid deficiency. Weanling rats were fed diets containing 10% (wt/wt) hydrogenated coconut oil (no n-3 or n-6 fatty acids), linseed oil (high n-3, low n-6), or safflower oil (high n-6, less than 0.1% n-3) for 15 weeks. The turnover of phospholipid molecular species and the turnover and recycling of 22:6(n-3) in phospholipids of the rod outer segment membranes were examined after the intravitreal injection of [2-3H]glycerol and [4,5-3H]22:6(n-3), respectively. Animals were killed on selected days, and rod outer segment membranes, liver, and plasma were taken for lipid analyses. The half-lives (days) of individual phospholipid molecular species and total phospholipid 22:6(n-3) were calculated from the slopes of the regression lines of log specific activity versus time. There were no differences in the turnover rates of phospholipid molecular species among the three dietary groups, as determined by the disappearance of labeled glycerol. Thus, 22:6(n-3) is not conserved through a reduction in phospholipid turnover in rod outer segments. However, the half-life of [4,5-3H]22:6(n-3) in the linseed oil group (19 days) was significantly less than in the coconut oil (54 days) and safflower oil (not measurable) groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin-tumour interrelationships in EL4-lymphoma or thymoma-bearing mice. II. Effects of dietary omega-3 and omega-6 polyunsaturated fatty acids

Male C57BL/65 mice received a basal diet supplemented with 4% soya-bean oil, linseed oil or fish oil, in which the major polyunsaturated fatty acids were linoleic acid, alpha-linolenic acid and long chain omega-3 fatty acids, respectively. Groups of animals were injected into the right flank with EL4-lymphoma cells, others with thymoma cells. Tumour implantation caused a gradual decrease in food consumption with both types of tumour, while body weight increased, especially in the EL4-bearing animals receiving the soya-bean diet. The weight gain was due to body water accumulation and was accompanied by decreases in body fat and minor changes in carcass protein and ash contents. The dietary treatments did not produce significant differences in tumour incidence and mortality, but tumour size was decreased by diets supplying omega-3 fatty acids: in the EL4 mice tumour weight was markedly depressed by linseed oil, compared to soya-bean oil, whereas thymoma tumour weight was lowest in mice receiving fish oil and highest in the soya-bean oil group. Both types of tumour caused pronounced hypoglycaemia and hyperinsulinaemia in the hosts, and the effect was modulated by the diets in the EL4 but not in the thymoma animals: the plasma glucose level was especially low in the linseed oil group and relatively highest in the soya-bean oil treatment. The degree of hyperinsulinaemia depended on the diet only in the thymoma-bearing mice, with linseed and fish oils producing higher insulin levels than soya-bean oil. A slight hyperinsulinaemia was also observed in linseed and fish oil-fed control mice. Serum triglycerides were elevated in tumour-bearing animals, without consistent differences between dietary treatments. Although no clear pattern emerged concerning total cholesterol and LDL levels, HDL values were strongly affected by the type of oil: in the control animals linseed oil caused an increase in HDL-cholesterol compared to the other two oils. The thymoma-bearing mice responded to the linseed and fish oil diets with greatly elevated HDL-cholesterol levels. The results point to important differences in the responses of the two implanted tumours and hosts not only to the omega-6 and omega-3 fatty acids, but also to the type of dietary omega-3 fatty acids, namely alpha-linolenic acid and long chain fish oil polyunsaturated fatty acids.

Effects of moderate dietary supplementations with n — 3 fatty acids on macrophage and lymphocyte phospholipids and macrophage eicosanoid synthesis in the rat

The effects of a moderate dietary intake of n − 3 polyunsarurated fatty acids were determined on the eicosanoid synthesis by rat peritoneal macrophages: the availability of arachidonic acid (20:4 ( n − 6)) and eicosapentaenoic acid (20:5 ( n −3)) in the membrane phospholipids of peritoneal macrophages and splenic lymphocytes and the synthesis of the main eicosanoids were evaluated in parallel. The n− 6 n−3 ratio was decreased from 13.5 in the control diet rich in 18:2( n −6) to about 2 by an addition of either linseed oil providing 18:3( n −3) (linseed oil diet) or fish oil providing 20:5( n −3) and 22:6( n −3) (fish oil diet). The dietary linoleic acid content was at least 3.5% of energy in each diet. In peritoneal macrophage and splenic lymphocyte membrane phospholipids, arachidonic acid content was significantly decreased with the linseed oil and fish oil diets. 20:5( n −3) content was significantly raised up in the linseed oil group (3-fold in macrophage phospholipids) and more strikely in the fish oil group (7-fold). In response to a stimulation by the calcium ionophore A23187, peritoneal macrophages released 6-ketoPGFlα, TXB2, PGE2 and LTB4 and/or 5, but no or few peptidoleukotrienes. The linseed oil did not affect significantly the synthesis of these eicosanoids, except for LTB5, which was increased 2-fold. In contrast, the fish oil diet led to significant decreases in the productions of 6-ketoPGFlα and PGE2 (−50%) and LTB4 (−40%) and to a 10-fold increase in the release of LTB5. TXB2 was also decreased (−35%), but not significantly. These results and the parallel evolutions of the two ratios 20:4(n−6) 20:5(n−3) and LTB4/LTB5 showed that eicosanoid synthesis is greatly dependent on the relative availability of the two substrates in competition.

Effects of Dietary Oils and α‐Tocopherol Supplementation on Lipid Composition and Stability of Broiler Meat

ABSTRACTBroilers were fed diets containing oils of varying degrees of unsaturation, namely coconut oil, olive oil, linseed oil and partially hydrogenated soybean oil (HSBO), with and without α‐tocopherol supplementation. The different oils significantly (P&lt;0.01) affected the fatty acid composition of the neutral lipids and, to a lesser extent, the fatty acid composition of the phopholipids. Fatty acid composition, in turn, influenced the oxidative stability of the meat during refrigerated and frozen storage. Meat from broilers fed olive oil or coconut oil was consistently more stable than meat from the linseed oil group. Dietary supplementation with α‐tocopherol significantly (P&lt;0.01) improved the oxidative stability of the dark and white broiler meat during refrigerated and frozen storage compared to meat from the broilers fed HSBO.

Effect of menhaden oil and various seedoils on serum lipids and lipoproteins in rabbits

Four groups of New Zealand White rabbits (n=8) were fed semi-synthetic diets containing 7.6% fat (w/w) for 20 weeks. The fats were: 1. hydrogenated soybean oil (HSBO), 80% stearic acid, with 2% safflower oil (SO), 2. safflower oil, 78% linoleic acid, 3. linseed oil (LO), 54% linolenic acid, and 4. menhaden oil (MO), 21% palmitic acid, 13% eicosapentaenoic acid (EPA), and 8% docosahexaenoic acid (DHA). The diets contained 20% of calories from protein, 56% from carbohydrate, and 24% from fat. The MO diet also contained 0.06% cholesterol while the other diets were cholesterol free. Before assignment to experimental diets, the animals had serum cholesterol values of 62.1±20.3 mg/dl and triglyceride concentration of 40.3±14.3 mg/dl (mean±S.D.). After 4 weeks on the diets, the cholesterol values in the four groups were: HSBO, 70.9±21.2 mg/dl; SO, 59.1±15.9 mg/dl; LO, 65.1±50.7 mg/dl; and MO, 141.7±67.2 mg/dl. Only the MO value differed significantly from the pre-diet value (P<0.01). For the remainder of the study serum cholesterol value in the MO group did not change significantly while in the HSBO group the cholesterol and triglyceride concentrations rose significantly to 127.8±82.2 mg/dl, and 130.6±60.3 mg/dl, respectively, at the end of the study (P<0.05). The MO group's serum triglycerides trended higher but the change did not reach statistical significance. Low density lipoproteins (LDL) were significantly elevated (P<0.01) in the HSBO and MO groups but not in the SO and LO groups. It remains to be determined if the twenty and twenty-two carbon n-3 fatty acids (EPA and DHA) in menhaden oil will elevate serum cholesterol in rabbits in the absence of dietary cholesterol.

Effects of Type of Dietary Fat on Indices of Immune Status of Rabbits

We have compared the effects of dietary saturated and unsaturated fats of the n-6 and n-3 types on the immune status of male New Zealand white rabbits. Four groups of rabbits (n = 8) were fed purified diets containing one of the following fats (7.6% w/w, 23 kcal%) for 5 mo, hydrogenated soybean oil (HSO); safflower oil (SFO); linseed oil (LSO); or menhaden oil (MHO). In vitro proliferation of peripheral blood lymphocytes (PBL) cultured with T-cell mitogens was significantly higher in the LSO group than in the other three groups, and that in the HSO group was higher than in the MHO and SFO groups which were not different from each other. Proliferation of PBL in response to B-cell mitogens was significantly higher in the LSO group than in the SFO and MHO groups. In vitro proliferation of splenocytes (SPC) from the LSO group was higher than that from the other three groups only when SPC were cultured with T-cell mitogens. Serum antibody levels against bovine serum albumin were significantly higher in the LSO group than in the SFO group after second and third immunizations. Spleen weights, number of SPC or PBL, and delayed-type hypersensitivity were not different among the four dietary groups. Our data show that linseed oil diet enhanced several indices of immune status in rabbits.

Effects of various combinations of omega 3 and omega 6 polyunsaturated fats with saturated fat on serum lipid levels and eicosanoid production in rats.

The effects of varying the ratio of polyunsaturated/saturated fatty acids (P/S) and omega 3/omega 6 polyunsaturated fatty acids (PUFA) of dietary fats on lipid metabolism were studied in rats using safflower oil (SFO), linseed oil (LSO), palm oil (PLO), and a 1:1 combination of these oils. The hypocholesterolemic and hypotriglyceridemic effects depended on the P/S ratio of dietary fats, LSO (omega 3 PUFA) being more effective than SFO (omega 6 PUFA). A similar pattern of the response was observed on liver cholesterol and triglyceride. The liver cholesterol-lowering effect of LSO, but not SFO, remained even when they were combined with PLO. The activity of liver delta 6-desaturase tended to be higher while that of liver phospholipase A2 was significantly lower in the LSO group than in the SFO or PLO groups. The aortic PGI2 production and the production by platelets of thromboxane A2 were significantly low in rats fed LSO accompanying a distinct reduction of arachidonate in tissue phospholipids. The depressing effect of LSO disappeared when it was combined with SFO but not with PLO. There were no significant differences in enzyme activities and eicosanoid production between SFO and PLO in spite of a large difference in their P/S ratio. Thus, lipid parameters examined were complicatedly regulated by the ratios of omega 3/omega 6 as well as P/S, suggesting an existence of an appropriate ratio for these variables.

Influence of dietary fat mixtures on platelet adhesiveness, atherosclerosis and plasma cholesterol content in rabbits

Summary Platelet adhesiveness, degree of atherosclerosis and plasma cholesterol content were examined in rabbits fed for 62 weeks a diet deficient in essential fatty acids (EFA) containing 40 cal % hardened coconut oil, or diets in which 10 cal % of the hardened coconut oil had been replaced by linseed oil (rich in linolenic acid) or by safflower oil (rich in linoleic acid). Additionally, histopathological and clinical investigations, were carried out to gain some information about the consequences of feeding rabbits a diet deficient in EFA for a prolonged period. The results are: (1) The three dietary groups showed no significant differences as to platelet adhesiveness to glass. (2) Atherosclerosis of the aorta was more severe in the hardened coconut oil group (Mean Atheroma Index = 2.33) than in the linseed oil group (m.a.i. = 1.00) or the safflower oil group (m.a.i. = 0.25). The frequency of coronary artery changes was also significantly higher in the hardened coconut oil group than in the two other groups. One animal of the hardened coconut oil group showed a myocardial infarction. (3) The plasma cholesterol content was significantly higher in the hardened coconut oil group than in the two other groups. (4) All but one animal of the hardened coconut oil group showed a cirrhotic liver, whereas the animals of the other two groups displayed hardly any liver changes. (5) Haemolysis time in isotonic thiourea solutions showed significant differences between all dietary groups of rabbits. The hardened coconut oil group showed the shortest time; the safflower oil group the longest. A positive correlation was found between haemolysis time and the polyunsaturated fatty acids content of the erythrocytes. Since their saturated fatty acid content was fairly constant, a negative correlation also existed between the haemolysis time and the monounsaturated fatty acid content. However, this correlation was not found within every dietary group since either the number of individual values is insufficient or the correlation is spurious. The conclusion is drawn that linseed oil has no specially favourable effect on platelet adhesiveness or atherosclerosis. With regard to the latter aspect, safflower oil is preferable.