The influence of marine oil intake upon levels of lipids, alpha-tocopherol and lipid peroxidation in serum and liver of rats

Effect of Docosahexaenoic Acid Ingestion on Temporal Change in Urinary Excretion of Mercapturic Acid in ODS Rats

We hypothesized a suppressive mechanism for docosahexaenoic acid (22:6n-3; DHA)-induced tissue lipid peroxidation in which the degradation products, especially aldehydic compounds, are conjugated with glutathione through catalysis by glutathione S-transferases, and then excreted into urine as mercapturic acids. In the present study, ascorbic acid-requiring ODS rats were fed a diet containing DHA (3.6% of total energy) for 31 days. Lipid peroxides including degradation products and their scavengers in the liver and kidney were determined, and the temporal change in the urinary excretion of mercapturic acids was also measured. The activity of aldehyde dehydrogenase, which catalyzes the oxidation and detoxification of aldehydes, tended to be higher in the liver of DHA-fed rats. The levels of lipid peroxides as measured by thiobarbituric acid-reactive substances and aldehydic compounds were higher and that of alpha-tocopherol was lower in the liver, and the pattern of temporal changes in the urinary excretion of mercapturic acids was also different between the n-6 linoleic acid and DHA-fed rats. Accordingly, we presume from these results that after dietary DHA-induced lipid peroxidation, a proportion of the lipid peroxidation-derived aldehydic degradation products is excreted into urine as mercapturic acids.

Dietary docosahexaenoic acid-induced generation of liver lipid peroxides is not suppressed further by elevated levels of glutathione in ODS rats

OBJECTIVES

We examined the effects of ascorbic acid (AsA) and glutathione (GSH; experiment 1) and of GSH in acetaminophen-fed rats (experiment 2) on dietary docosahexaenoic acid (DHA)-induced tissue lipid peroxidation.

METHODS

In experiment 1, AsA-requiring Osteogenic Disorder Shionogi/Shi-od/od (ODS) rats were fed soybean protein diets containing DHA (10.0% total energy) and AsA at 50 (low) or 300 (normal) mg/kg without (low) or with (normal) methionine at 2 g/kg for 32 d. In experiment 2, ODS rats were fed diets containing DHA (7.8% total energy) and acetaminophen (4 g/kg) with different levels of dietary methionine (low, moderate, high, and excessive at 0, 3, 6, and 9 g/kg, respectively) for 30 d. Tissue lipid peroxides and antioxidant levels were determined.

RESULTS

In experiment 1, liver lipid peroxide levels in the low-AsA group were lower than those in the normal-AsA group, but kidney and testis lipid peroxide levels in the low-AsA group were higher than those in the normal-AsA group. Dietary methionine tended to decrease tissue lipid peroxide levels but did not decrease vitamin E (VE) consumption. In experiment 2, a high level of methionine (6 g/kg) decreased liver lipid peroxide levels and VE consumption. However, generation of tissue lipid peroxides and VE consumption were not decreased further by a higher dose of methionine (9 g/kg).

CONCLUSIONS

Higher than normal levels of dietary methionine are not necessarily associated with decreased dietary DHA-induced generation of tissue lipid peroxides and VE consumption except that the GSH requirement is increased in a condition such as acetaminophen feeding.

Oxidant status and lipid profile in vegetarians and fish eaters

Habitual consumption of moderate amounts of fish is associated with reduced mortality from coronary heart disease. However the beneficial effects of fish enriched diet seem contradictory, due to the susceptibility of the PUFAs in them to oxidation. It is also acclaimed that vegetarians in general, have a lower serum total cholesterol and LDL-cholesterol and a better antioxidant status. This contradiction was the basis for the study, where the validity of the above finding was tested in a general population consuming a vegetarian or predominantly fish diet as a regular dietary habit. The oxidant status and the lipid profile of 23 vegetarians and 22 fish eaters was studied by estimating the plasma lipid peroxides measured as malondialdehyde (MDA) and the lipid parameters viz. Total Cholesterol (TC), HDL-Cholesterol (HDL-C) and triglycerides (TG). Statistical analysis was carried out to compare the MDA values and the lipemic status between the two groups. MDA was also correlated with the various lipid indices among the study groups. None of the compared and correlated values was statistically significant, although certain altered trends were seen. From this study, it may be concluded that oxidant status and lipid profile does not vary significantly in the two groups, suggesting that neither a vegetarian diet nor a fish diet has a definite benefit over the other.

Dietary supplementation with docosahexaenoic acid, but not with eicosapentaenoic acid, reduces host resistance to fungal infection in mice

The effect of dietary docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on host resistance to Paracoccidioides brasiliensis infection was investigated. Mice fed palm oil supplemented with DHA showed reduced antifungal activity in the spleen and liver, as compared with mice fed palm oil or soybean oil without supplementation with DHA. Mice fed DHA-supplemented soybean oil also showed reduced antifungal activity in the liver, but the extent of reduction was less profound. This reduction in antifungal activity was not observed with EPA-supplemented palm or EPA-supplemented soybean oil. These results suggest that two factors, DHA and palm oil in combination, are involved in reducing the host resistance. DHA-enriched palm oil was also responsible for an increase in DHA concentration and a marked decrease in arachidonic acid content in the spleen and liver. However, this group did not show elevated spleen and liver phospholipid hydroperoxide levels compared with the other groups, excluding the possibility that the reduction in antifungal activity observed with DHA-enriched palm oil is due to acceleration of in vivo lipid peroxidation. Greater infection-induced increases in spleen and serum interferon-gamma concentrations were observed in mice fed DHA-enriched palm oil compared with the other groups.

Effects of fish oil in parenteral nutrition

OBJECTIVE

Fish oil is a rich source of omega-3 fatty acids (FAs), especially eicosapentaenoic acid and docosahexaenoic acid. The existing data suggest that eicosapentaenoic acid and docosahexaenoic acid are the active agents in fish oil. A number of clinical trials have shown that dietary fish oil supplementation has antiatherogenic properties and immunomodulation effects. Fish oils are not used widely in parenteral nutrition because fish oil emulsions have not been commercially available until very recently. Studies concerning the use of fish oil in parenteral route are rare.

METHODS

We reviewed the effect of parenteral fish oil infusion on lipid metabolism and immune response in normal and disease conditions.

RESULTS

Studies showed that the main effects of parenteral infusion of fish oil are: 1) incorporation of omega-3 FAs into cellular membranes of many cell populations that consequently influence the disease process of some disease conditions, 2) an effect on eicosanoid metabolism leading to a decrease in platelet aggregation and thrombosis, 3) amelioration of the severity of diet-induced hepatic steatosis, 4) less accumulation of lipid peroxidation products in liver tissue, and 5) immunomodulation effects and therapeutic benefits in animal disease models or various disease conditions of humans. Most of these studies suggested that parenteral infusion of omega-3 FAs have clinical beneficial effects comparable to those of dietary administration. However, different effects of omega-3 and omega-6 FAs in some situations has been reported. For example, plasma triacylglycerol levels were not lowered after fish oil infusion in normal or diabetic rats when compared with those of safflower oil or soybean oil infusion. The reason for the difference remain unclear.

CONCLUSION

The metabolic and immunologic effects of parenteral use of omega-3 FAs requires further evaluation, especially in some disease conditions.

Relationship between tissue lipid peroxidation and peroxidizability index after alpha-linolenic, eicosapentaenoic, or docosahexaenoic acid intake in rats

In a previous study, we found that the extent of dietary n-3 docosahexaenoic acid (DHA)-stimulated tissue lipid peroxidation was less than expected from the relative peroxidizability index of the total tissue lipids in rats with adequate vitamin E nutritional status. This suppression of lipid peroxidation was especially prominent in the liver. To elucidate whether this phenomenon was unique to DHA, we compared the peroxidation effects of n-3 alpha-linolenic acid (alpha-LN) and n-3 eicosapentaeonic acid (EPA) with those of DHA in rats. Either alpha-LN (8.6 % of total energy), EPA (8.2 %), or DHA (8.0 %) and one of two levels of dietary vitamin E (7.5 and 54 mg/kg diet) were fed to rats for 22 d. Levels of conjugated diene, chemiluminescence emission and thiobarbituric acid (TBA)-reactive substance in the liver, kidney, and testis were determined as indicators of lipid peroxidation. In rats fed the DHA diet deficient in vitamin E (7.5 mg/kg diet), TBA values in the liver, kidney, and testis correlated well with the tissues' relative peroxidizability indices. In rats fed the alpha-LN diet with an adequate level of vitamin E (54 mg/kg diet), a close association between relative peroxidizability indices and lipid peroxide levels was observed in all the tissues analysed. However, in rats fed either the EPA diet or the DHA diet with an adequate level of vitamin E, the extent of lipid peroxidation in each tissue was less than expected from the relative peroxidizability index. This suppression was particularly marked in the liver. We concluded that suppression of lipid peroxidation below the relative peroxidizability index was not unique to DHA, but was also seen with EPA, which has five double bonds, in rats with adequate vitamin E nutritional status, but not with alpha-LN, which has three double bonds.

High dietary iron concentrations enhance the formation of cholesterol oxidation products in the liver of adult rats fed salmon oil with minimal effects on antioxidant status

The aim of this study was to investigate the effect of high dietary iron concentrations on the antioxidant status of rats fed two different types of fat. Four groups of male adult Sprague-Dawley rats were fed diets with adequate (50 mg iron supplemented per kg diet) or high (500 mg iron supplemented per kg diet) iron concentrations with either lard or salmon oil as dietary fat at 100 g/kg for 12 wk. The antioxidant status of the rats was profoundly influenced by the type of fat. Rats fed salmon oil diets had higher concentrations of thiobarbituric acid-reactive substances (TBARS) (P < 0.001), various cholesterol oxidation products (COP) (P < 0.001), total and oxidized glutathione (P < 0.05) and a lower concentration of alpha-tocopherol (P < 0.05) in liver and plasma than rats fed lard diets. The iron concentration of the diet did not influence the concentrations of TBARS, the activities of superoxide dismutase and glutathione peroxidase or the concentration of alpha-tocopherol in plasma or liver. The activity of catalase (P < 0.01) and the concentrations of total, oxidized and reduced glutathione (P < 0.05) in liver were slightly but significantly higher in rats fed high iron diets than in rats fed adequate iron diets, irrespective of the dietary fat. Rats fed the high iron diets with salmon oil, moreover, had higher concentrations of various COP in the liver (P < 0.001) than rats fed adequate iron diets with salmon oil. These results suggest that feeding a high iron diet does not generally affect the antioxidant status of rats but enhances the formation of COP, particularly if the diet is rich in polyunsaturated fatty acids.

Docosahexaenoic acid supplementation-increased oxidative damage in bone marrow DNA in aged rats and its relation to antioxidant vitamins

We compared the influence of docosahexaenoic acid (DHA) supplementation on oxidative DNA damage in bone marrow between young and aged rats. As a marker of oxidative DNA damage, 8-hydroxydeoxyguanosine (8-OHdG) in DNA was analyzed. Young (5-week-old) and aged (100-week-old) female Wistar rats were given DHA (300mg/kg body weight/day) or vehicle (control) orally for 12 weeks. The 8-OHdG in the bone marrow in the aged DHA group was significantly higher than that in the other groups. Vitamin E concentrations, however, did not differ among the groups regardless of the DHA supplementation. Vitamin C (ascorbic acid) concentrations in the aged control group were approximately 1/2 those in the young control group. The concentrations of vitamin C tended to be higher in the young DHA group and lower in the aged DHA group when compared to their respective control groups. Changes in the concentrations of vitamin C and vitamin E in plasma were similar to those in the bone marrow. The activity of hepatic l-gulono- gamma -lactone oxidase, an enzyme responsible for vitamin C synthesis, corresponded well to the concentrations of vitamin C in the bone marrow and the plasma. These results suggest that in aged rats, but not young rats, excess supplementation of DHA induces oxidative DNA damage in bone marrow and that the decrease in vitamin C synthesis in aged rats is involved in the mechanisms of DNA damage.

Enhanced level of n-3 fatty acid in membrane phospholipids induces lipid peroxidation in rats fed dietary docosahexaenoic acid oil

The effect of dietary docosahexaenoic acid (DHA, 22:6n-3) oil with different lipid types on lipid peroxidation was studied in rats. Each group of male Sprague-Dawley rats was pair fed 15% (w/w) of either DHA-triglycerides (DHA-TG), DHA-ethyl esters (DHA-EE) or DHA-phospholipids (DHA-PL) for up to 3 weeks. The palm oil (supplemented with 20% soybean oil) diet without DHA was fed as the control. Dietary DHA oils lowered plasma triglyceride concentrations in rats fed DHA-TG (by 30%), DHA-EE (by 45%) and DHA-PL (by 27%), compared to control. The incorporation of dietary DHA into plasma and liver phospholipids was more pronounced in the DHA-TG and DHA-EE group than in the DHA-PL group. However, DHA oil intake negatively influenced lipid peroxidation in both plasma and liver. Phospholipid peroxidation in plasma and liver was significantly higher than control in rats fed DHA-TG or DHA-EE, but not DHA-PL. These results are consistent with increased thiobarbituric acid reactive substances (TBARS) and decreased alpha-tocopherol levels in plasma and liver. In addition, liver microsomes from rats of each group were exposed to a mixture of chelated iron (Fe(3+)/ADP) and NADPH to determine the rate of peroxidative damage. During NADPH-dependent peroxidation of microsomes, the accumulation of phospholipid hydroperoxides, as well as TBARS, were elevated and alpha-tocopherol levels were significantly exhausted in DHA-TG and DHA-EE groups. During microsomal lipid peroxidation, there was a greater loss of n-3 fatty acids (mainly DHA) than of n-6 fatty acids, including arachidonic acid (20:4n-6). These results indicate that polyunsaturation of n-3 fatty acids is the most important target for lipid peroxidation. This suggests that the ingestion of large amounts of DHA oil enhances lipid peroxidation in the target membranes where greater amounts of n-3 fatty acids are incorporated, thereby increasing the peroxidizability and possibly accelerating the atherosclerotic process.

Polyunsaturated (n-3) fatty acids susceptible to peroxidation are increased in plasma and tissue lipids of rats fed docosahexaenoic acid-containing oils

Docosahexaenoic acid [DHA, 22:6(n-3)], a major component of membrane phospholipids in brain and retina, is profoundly susceptible to oxidative stress in vitro. The extent of this peroxidation in organs when DHA is ingested in mammals, however, is not well elucidated. We investigated the effect of dietary DHA-containing oils (DHA 7.0-7.1 mol/100 mol total fatty acids), in the form of triacylglycerols (TG), ethyl esters (EE) and phospholipids (PL), on tissue lipid metabolism and lipid peroxidation in rats. Groups of Sprague-Dawley rats were fed semipurified diets containing 15 g/100 g test oils and were compared with those fed 80% palm oil and 20% soybean oil as the control (unsupplemented group) for 3 wk. The DHA oil diets markedly increased (P: < 0.05) the levels of DHA in the plasma, liver and kidney, 1.5-1.9, 2.5-3.8 and 2.2-2.5 times the control values, respectively, whereas there was a concomitant reduction (P: < 0.05) in arachidonic acid. All forms of DHA oil caused lower TG concentrations in plasma (P: < 0.05) and liver (P: < 0.05), but had no effect in kidney. The DHA oil-fed rats had greater phospholipid hydroperoxide accumulations in plasma (191-192% of control rats), liver (170-230%) and kidney (250-340%), whereas the alpha-tocopherol level was reduced concomitantly (21-73% of control rats). Consistent with these results, rats fed DHA-containing oils had more thiobarbituric reactive substances in these organs than the controls. Thus, high incorporation of (n-3) fatty acids (mainly DHA) into plasma and tissue lipids due to DHA-containing oil ingestion may undesirably affect tissues by enhancing susceptibility of membranes to lipid peroxidation and by disrupting the antioxidant system.

Oxidation of plasma proteins is not increased after supplementation with eicosapentaenoic and docosahexaenoic acids

BACKGROUND

It is generally thought that as the intake of dietary polyunsaturated fatty acids increases, so should that of alpha-tocopherol, to protect the polyunsaturated fatty acids from increased in vivo peroxidation. However, there are little quantitative data about the concentration of alpha-tocopherol that is necessary when eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are consumed.

OBJECTIVE

The purpose of this study was to measure changes produced in 2 indexes of lipid oxidation after supplementation with EPA and DHA from fish oil and 3 doses of RRR-alpha-tocopheryl acetate in postmenopausal women.

DESIGN

Daily supplements of fish oil providing 2.5 g EPA and 1.8 g DHA and 0, 100, 200, or 400 mg alpha-tocopheryl acetate were given to 46 postmenopausal women in a 4-treatment, 4-period crossover design.

RESULTS

The supplements increased plasma concentrations of EPA, DHA, and alpha-tocopherol. The fish-oil supplement increased the plasma concentration of thiobarbituric acid-reactive substances (TBARS) (P: = 0.0001) but not that of oxidatively modified protein, as indicated by the carbonyl content. The alpha-tocopheryl acetate and fish-oil supplements had no significant effect on plasma concentrations of TBARS or oxidized protein.

CONCLUSIONS

Although these data show a small but statistically significant increase in oxidative stress on the basis of plasma TBARS concentrations after the consumption of EPA and DHA, the clinical relevance of this change is questionable. In addition, as supplements of alpha-tocopheryl acetate were added to the diet, neither the plasma TBARS concentration nor the protein oxidation changed. Consequently, the results of this study indicate that there is no basis for vitamin E supplementation after consumption of EPA and DHA.

Fish oil diet affects on oxidative senescence of red blood cells linked to degeneration of spleen cells in mice

The effect of dietary polyunsaturated fatty acids and alpha-tocopherol supplementation on erythrocyte lipid peroxidation and immunocompetent cells in mice was studied comparatively using seven dietary oils (15% oil/diet, w/w) including fish oil rich in eicosapentaenoic acid (EPA, 20:5, n-3) and docosahexaenoic acid (DHA, 22:6, n-3). A 43% increase in spleen weight, about twice as many spleen cells and no change in the subpopulations of spleen cells, as well as a significant depression of mitogen-induced blastogenesis of both T and B cells in the spleen were observed in mice fed fish oil for 30 days in comparison with soybean oil diet-fed mice. In the fish oil diet-fed mice, membranous lipid hydroperoxide (hydroperoxides of phosphatidylcholine and phosphatidylethanolamine) accumulation as a marker of oxidative senescence in red blood cells (RBC) was 2.7-3.5 times higher than that in mice fed soybean oil, although there was no difference in the plasma phosphatidylcholine hydroperoxide concentration. In spite of the supplementation of alpha-tocopherol to up to 10 times the level in the basal diet, the degeneration of spleen cells and the stimulated oxidative senescence of RBC found by the fish oil feeding could not be prevented. The results suggest that oral intake of excess polyunsaturated fatty acids, i.e. EPA and DHA, in a fish oil diet can lead to acceleration of membrane lipid peroxidation resulting in RBC senescence linked to the lowering of immune response of spleen cells, and that supplementation of alpha-tocopherol as antioxidant does not always effectively prevent such oxidative degeneration as observed in spleen cells and RBC in vivo.

Preferential incorporation of docosahexaenoic acid into nonphosphorus lipids and phosphatidylethanolamine protects rats from dietary DHA-stimulated lipid peroxidation

In a previous study, we found that dietary docosahexaenoic acid (DHA)-stimulated tissue lipid peroxide formation was suppressed to a lesser extent than expected from the peroxidizability index of tissue total lipids. This suppression was presumed to be potentiated by mechanisms other than the lipid peroxide-scavenging system. In this study, we focused primarily on the incorporation of DHA into tissue nonphosphorus lipids and phospholipid species. DHA and different levels of dietary vitamin E (VE; 7.5, 54, 134 and 402 mg/kg of diet) were fed to rats for 32 d. In rats with poor VE status, liver chemiluminescence intensity and kidney and testis thiobarbituric acid (TBA) values correlated with the tissue's peroxidizability index. In rats with normal VE nutriture, liver lipid peroxide formation was suppressed to a level below that expected from the peroxidizability index, likely because DHA was present in nonphosphorus lipids and utilized preferentially for phosphatidylethanolamine synthesis. In the kidney, differences in the TBA values were associated with differences in the peroxidizability index of total lipids, even in the DHA groups fed VE at higher than normal levels. This may be because the levels of lipid peroxide scavengers were lower than those of liver and because DHA was utilized preferentially for phosphatidylcholine synthesis. In testis, the lipid peroxide levels were not as high as expected from the peroxidizability index, even in rats fed a high DHA diet containing the normal level of VE. This may be because the testis was composed of a high proportion of (n-6) polyunsaturated fatty acids (PUFA), which are low in unsaturation, and thus the proportion of DHA was low. In addition, in testis, VE and ascorbic acid, which act as antioxidants, were retained at higher levels in rats with particularly poor and normal VE nutriture than those of liver and kidney. These results suggest that antioxidant protection against dietary DHA-stimulated lipid peroxidation below the extent expected from the peroxidizability index of tissue total lipids differed from tissue to tissue. The suppression was likely due to not only the lipid peroxide scavenging system but also preferential incorporation of DHA into nonphosphorus lipids and phosphatidylethanolamine, particularly in liver.

Effect of n-3 polyunsaturated fatty acid supplementation on lipid peroxidation of rat organs

The present study was undertaken in order to reexamine the effect of n-3 polyunsaturated fatty acid (PUFA)-rich diet supplementation on lipid peroxidation and vitamin E status of rat organs. Male Wistar rats were fed a diet containing safflower or fish oil at 50 g/kg diet and an equal amount of vitamin E at 59 mg/kg diet (1.18 g/kg oil; and 1.5 g/kg PUFA in safflower oil diet, and 4.3 g/kg PUFA in fish oil diet) for 6 wk. Fatty acid composition of total lipids of brain, liver, heart, and lung of rats fed fish oil was rich in n-3 PUFA, whereas that of each organ of rats fed safflower oil was rich in n-6 PUFA. The vitamin E levels in liver, stomach, and testis of the fish oil diet group were slightly lower than those of the safflower oil diet group, but the levels in brain, heart, lung, kidney, and spleen were not different between the two diet groups. The levels of phospholipid hydroperoxides were determined by the high-performance liquid chromatography-chemiluminescence method and the levels of thiobarbituric acid-reactive substances (TBARS) were determined at pH 3.5 in the presence of butylated hydroxytoluene with or without EDTA. Levels of phospholipid hydroperoxides and TBARS in the brain, liver, heart, lung, kidney, spleen, stomach and testis of the fish oil diet group were similar to those of the safflower oil diet group. The results indicate that high fish oil intake does not induce increased levels of phospholipid hydroperoxides and TBARS in rat organs.

Dietary docosahexaenoic acid does not promote tissue lipid peroxide formation to the extent expected from the peroxidizability index of the lipids

Changes in susceptibility of tissues to lipid peroxidation were investigated in rats after ingestion of oxidation-prone docosahexaenoic acid (C22:6n-3). Lipid peroxide levels in the liver, kidney and testis increased concomitant with increases in the peroxidizability indices calculated from the fatty acid composition of tissue total lipids. However, even in these cases, the lipid peroxides were not increased to the levels expected from the peroxidizability indices of these tissues, and thus no tissue injury was recognized. When low level of vitamin E was given to rats, the lipid peroxide levels of liver, kidney and testis nearly coincided with the peroxidizability indices of these tissues, where the cell injuries were observed as well. The mechanisms of defense to suppress lipid peroxide levels below the peroxidizability indices in normal vitamin E administration were presumed to be due to enhanced antioxidative function in the tissues mediated primarily by vitamin E, ascorbic acid and glutathione, and also to increased incorporation of docosahexaenoic acid into neutral lipids and phosphatidylethanolamine in the tissues, probably leading to acquiring stability against oxidative attack. Owing to these suppressive mechanisms, physiological efficacy of n-3 fatty acids may be exerted effectively.

Low doses of eicosapentaenoic acid, docosahexaenoic acid, and hypolipidemic eicosapentaenoic acid derivatives have no effect on lipid peroxidation in plasma

It was of interest to investigate the influence of both high doses of eicosapentaenoic acid (EPA) and low doses of 2- or 3-methylated EPA on the antioxidant status, as they all cause hypolipidemia, but the dose required is quite different. We fed low doses (250 mg/d/kg body wt) of different EPA derivatives or high doses (1500 mg/d/kg body wt) of EPA and DHA to rats for 5 and 7 d, respectively. The most potent hypolipidemic EPA derivative, 2,2-dimethyl-EPA, did not change the malondialdehyde content in liver or plasma. Plasma vitamin E decreased only after supplementation of those EPA derivatives that caused the greatest increase in the fatty acyl-CoA oxidase activity. Fatty acyl-CoA oxidase activity increased after administration of both EPA and DHA at high doses. High doses of EPA and DHA decreased plasma vitamin E content, whereas only DHA elevated lipid peroxidation. In liver, however, both EPA and DHA increased lipid peroxidation, but the hepatic level of vitamin E was unchanged. The glutathione-requiring enzymes and the glutathione level were unaffected, and no significant changes in the activities of xanthine oxidase and superoxide dismutase were observed in either low- or high-dose experiments. In conclusion, increased peroxisomal beta-oxidation in combination with high amounts of polyunsaturated fatty acids caused elevated lipid peroxidation. At low doses of polyunsaturated fatty acids, lipid peroxidation was unchanged, in spite of increased peroxisomal beta-oxidation, indicating that polyunsaturation is the most important factor for lipid peroxidation.

The metabolism and n-6/n-3 ratio of essential fatty acids in rats: effect of dietary arachidonic acid and a mixture of sesame lignans (sesamin and episesamin)

In this study, we examined the effect of dietary arachidonic acid (AA) and sesame lignans on the content and n-6/n-3 ratio of polyunsaturated fatty acid (PUFA) in rat liver and the concentrations of triglyceride (TG) and ketone bodies in serum. For 4 wk, rats were fed two types of dietary oils: (i) the control oil diet groups (CO and COS): soybean oil/perilla oil = 5:1, and (ii) the AA-rich oil group (AO and AOS): AA ethyl esters/palm oil/perilla oil = 2:2:1, with (COS and AOS) or without (CO and AO) 0.5% (w/w) of sesame lignans. Dietary AA and sesame lignans significantly affected hepatic PUFA metabolism. AA content and n-6/n-3 ratio in the liver were significantly increased in the AO group, despite the dietary total of n-6 PUFA being the same in all groups, while AOS diet reduced AA content and n-6/n-3 ratio to a level similar to the CO and COS groups. These results suggest that (i) dietary AA considerably affects the hepatic profile and n-6/n-3 ratio of PUFA, and (ii) dietary sesame lignans reduce AA content and n-6/n-3 ratio in the liver. In the AO group, the concentration of acetoacetate was significantly increased, but the ratio of beta-hydroxybutyrate/acetoacetate was decreased. On the other hand, the AO diet increased the concentration of TG in serum by almost twofold as compared to other groups. However, the AOS diet significantly reduced serum TG level as compared to the AO group. In addition, the AOS diet significantly increased the acetoacetate level, but reduced the beta-hydroxybutyrate/acetoacetate ratio. These results suggest that dietary sesame lignans promote ketogenesis and reduce PUFA esterification into TG. This study resulted in two findings: (i) sesame lignans inhibited extreme changes of the n-6/n-3 ratio by reducing hepatic PUFA content, and (ii) the reduction of hepatic PUFA content may have occurred because of the effects of sesame lignans on PUFA degradation (oxidation) and esterification.

Changes in susceptibility of tissues to lipid peroxidation after ingestion of various levels of docosahexaenoic acid and vitamin E

To examine the effects of dietary docosahexaenoic acid (DHA) on the potential changes in endogenous lipid peroxidation in the liver and kidney, diets containing a fixed amount of vitamin E (VE; RRR-alpha-tocopherol equivalent; 134 mg/kg diet) and a graded amount of DHA at the levels of 0, 1.0, 3.4 and 8.7% of total dietary energy were fed to rats for 14 d (Expt 1). In Expt 2, diets containing a fixed amount of DHA (8.7% of total dietary energy) and a graded amount of VE at the levels of 54, 134 and 402 mg/kg were fed to rats for 15 d. In Expt 1 it was found that endogenous lipid peroxide contents of the liver and kidney, as measured by thiobarbituric acid value and chemiluminescence intensity, were higher, and their alpha-tocopherol contents lower than those of the controls, with a gradual increase and decrease in values respectively as the dietary DHA level increased (Expt 1). However, the contents of water-soluble antioxidants, i.e. ascorbic acid and non-protein-SH (glutathione), increased with increases in the dietary DHA level, while the Se-dependent glutathione peroxidase (EC 1.11.1.9) activities did not change or tended to be lower. When the graded level of VE was given to rats in Expt 2, lipid peroxide contents in the liver and kidney did not change significantly in response to the increasing levels of dietary VE, although their alpha-tocopherol contents were higher than control values, increasing with increases in the dietary VE levels. The lipid peroxide scavengers other than alpha-tocopherol changed similarly to those in Expt 1. The results obtained in Expts 1 and 2 indicate that DHA enhances the susceptibility of the liver and kidney to lipid peroxidation concomitant with higher levels of DHA in these tissues, as shown by the fatty acid composition. In addition, VE is unable to protect membranes of the liver and kidney rich in DHA from lipid peroxidation, even after ingestion of the highest level of VE. However, the liver lipid peroxide content of the group given the highest level of DHA was not as high as expected, based on the peroxidizability index which was calculated from the fatty acid composition of the liver lipid.

Oxidative stress and antioxidant status in mouse liver: effects of dietary lipid, vitamin E and iron

The purpose of this study was to determine the effects of dietary fat, vitamin E and iron on oxidative damage and antioxidant status. Male Swiss-Webster mice (1 mo old) were fed a basal vitamin E-deficient diet that contained either 8% fish oil + 2% corn oil or 10% lard with or without 1 g dl-alpha-tocopheryl acetate. The diets without vitamin E contained either 0.21 or 0.95 g ferric citrate/kg. Diets were fed for 4 wk/kg diet. Compared with the vitamin E-supplemented groups, mice fed diets without vitamin E (with or without supplemental iron) had significantly (P < 0.05) higher hepatic levels of thiobarbituric acid-reactive substances (TBARS), conjugated dienes and protein carbonyls when they were fed fish oil, but not lard. The levels of TBARS were further increased by iron supplementation in the mice fed fish oil. Significantly lower concentrations of alpha-tocopherol and higher glutathione (GSH) were found in the liver of mice fed fish oil and vitamin E than in those fed lard and vitamin E (P < 0.05). The activities of superoxide dismutase and glucose-6-phosphate dehydrogenase were lower in the fish oil-fed mice than in those fed lard (P < 0.05). The activities of Se-GSH peroxidase, non-Se-GSH peroxidase, catalase, and glutathione reductase were not altered by dietary fat or vitamin E/iron. The results obtained provide experimental evidence of the prooxidative effects of high dietary fish oil and iron, and suggest that vitamin E protects not only lipid-soluble compounds, but also water-soluble constituents, against oxidative damage. Further, dietary lipid plays a key role in determining cellular susceptibility to oxidative stress.

Fish oil source differentially affects rat immune cell alpha-tocopherol concentration

We have previously reported that both the source of dietary fish oil and the chemical form of vitamin E supplied in the diet affect the vitamin E status of immune cells in rats. The purpose of this study was to investigate further the effect of fish oil source on immune cell vitamin E status using free alpha-tocopherol (alpha-T) at the AIN recommended level as the sole source of vitamin E. Sixty weanling female rats were fed semipurified, high fat (20 g/100 g) diets containing either tocopherol-stripped lard (LRD), menhaden fish oil (MFO), sardine fish oil (SRD) or cod liver oil (CLO) as the primary lipid source. Endogenous alpha-T concentration was measured and equalized to 150 mg/kg oil by addition of free RRR-alpha-T to each lipid source, allowing for a final concentration of alpha-T in the mixed diet of 30 mg/kg. An additional group of rats was fed LRD without supplemental vitamin E (LRD-) as a negative control. After feeding experimental diets for 5 or 10 wk, tissues were collected for alpha-T analysis by HPLC. After 5 wk, plasma and liver alpha-T (micromol alpha-T/g lipid) were significantly lower in SRD- and CLO-fed rats compared with LRD-fed rats. At 10 wk, only plasma alpha-T in CLO-fed rats remained significantly depressed. Plasma and liver alpha-T concentrations (micromol alpha-T/g lipid) were not significantly lower in MFO-fed rats than LRD-fed rats at either time point. Compared with LRD, feeding MFO to rats for 5 or 10 wk resulted in significantly greater alpha-T content of immune cells. In similar fashion, SRD-fed rats, compared with LRD-fed rats, also had significantly greater alpha-T content in splenocytes at both time points and greater thymocyte alpha-T at 10 wk. In all instances, the alpha-T status of rats fed CLO was indistinguishable from that of rats fed the vitamin E-free diet (LRD-). These data further demonstrate the complexity of the relationship between vitamin E status and dietary (n-3) polyunsaturated fatty acids (PUFA).

Dietary linoleic acid at high and reduced dietary fat level decreases the faecal excretion of vitamin E in young rats

Vitamin E is the major lipid-soluble antioxidant in human subjects and is crucial in protecting polyunsaturated fatty acids (PUFA) against lipid peroxidation. Dietary PUFA have been suggested to inhibit the absorption of vitamin E. The present study in young male rats was designed to investigate the effect of increasing concentrations of dietary linoleic acid on the faecal excretion of vitamin E. The rats were fed on semi-synthetic diets containing two concentrations of fat (59 g/kg diet, 15 energy % (en%) or 131 g/kg, 30 en%) for 3 weeks. Triacylglycerol rich in linoleic acid was added at the expense of triacylglycerol rich in saturated fatty acids to obtain dietary concentrations of 13, 39 or 66 g linoleic acid/kg diet for the high-fat diet (131 g fat/kg) and 12, 24 or 36 g linoleic acid/kg diet for the reduced-fat diet (59 g fat/kg). The results from the present study demonstrate that the faecal excretion of vitamin E was significantly lower in rats fed on diets with high levels of linoleic acid compared with rats fed on lower levels of linoleic acid irrespective of the dietary fat content. The concentration of vitamin E in liver and plasma was significantly lower in animals fed on the highest concentration of linoleic acid compared with those fed on the lowest level. Results from the present study also demonstrate that at the same concentration of linoleic acid, the faecal excretion of vitamin E in rats fed on reduced-fat diets was significantly lower than in rats fed on high-fat diets. Our findings indicate that the apparent absorption of vitamin E is not inhibited by dietary PUFA. Results from the present study also demonstrate that a reduction of dietary fat content from 30 en% to 15 en% does not lower the apparent absorption of vitamin E.

An esterification protocol for cis-parinaric acid-determined lipid peroxidation in immune cells

Loss of fluorescence from cis-parinaric acid (cPnA) is a sensitive indicator of lipid peroxidation. The purpose of this study was to utilize cPnA to determine, at the level of the intact immune cell, whether enrichment of membranes with polyunsaturated fatty acids (PUFA) increased lipid peroxidation. P388D1 macrophages were labeled by addition of cPnA as an ethanolic solution. Within two minutes of addition, in the absence-of serum, cPnA rapidly intercalated into the plasma membrane. Lipid peroxidation was initiated by addition of Fe(2+)-EDTA resulting in a dose-dependent decrease in fluorescence with increased oxidant concentration. Cells previously enriched with PUFA and labeled by intercalation showed no differences in spontaneous or Fe(2+)-induced lipid peroxidation. In separate experiments, 20 microM cPnA in ethanolic solution was injected into cell culture media containing 0.1% essentially fatty acid free bovine serum albumin (BSA). Cells were resuspended and incubated for 90 min at 37 degrees C. After washing with BSA to remove cPnA which had not incorporated, 0.5% (0.1 microM) of the added cPnA was found esterified within cellular lipids. This level of cPnA provided a 100-fold increase over basal autofluorescence levels. Cells labeled in this manner also lost fluorescence in a dose-dependent manner as levels of oxidant stress increased. Cells enriched with PUFA and labeled by esterification had significantly increased rates and total amounts of lipid peroxidation. Co-incubation with alpha-tocopherol and PUFA resulted in a decrease in lipid peroxidation which was not significantly different from control cells. In conclusion, esterification of cPnA into membrane phospholipids can sensitively detect changes in lipid peroxidation induced by alteration of membrane PUFA and/or vitamin E content.

Effects of fat emulsions with different fatty acid composition on plasma and hepatic lipids in rats receiving total parenteral nutrition

Effects of different fatty acids on the development of hepatic steatosis were studied in rats receiving total parenteral nutrition (TPN). 65 rats, with internal jugular catheters, were divided into one control group (n = 8), and four experimental groups (n = 13-15 each). The control group was fed a chow diet and all experimental groups received TPN. TPN provided 300 kcal/kg/day with 40% of the non-protein energy provided as fat. All TPN solutions were isonitrogenous and identical in nutrient composition except for the fatty acid composition of the fat emulsion. Four kinds of fat emulsions rich in: 1) medium chain fatty acids (C8:0,C10:0), 2) oleic acid (C18:1 n-9), 3) linoleic acid (C18:2 n-6), 4) eicosapentaenoic acid (C20:5 n-3)/docosahexaenoic acid (C22:6 n-3), were used. These fat emulsions were prepared with: 1) a mixture of medium chain triglycerides (MCT) and soybean oil (9:1), 2) olive oil, 3) safflower oil, 4) fish oil, respectively. The results of the study demonstrated a higher hepatic lipid content in the olive oil and safflower oil groups than in the control group, whereas no significant difference was seen between the MCT and control groups. Also, no difference was observed between the fish oil and control groups. With regard to the plasma lipids, the MCT group and olive oil group produced hyperlipidaemia. The plasma of the safflower oil and fish oil groups, however, had a low lipid concentration comparable to the control group. These results suggest that TPN with a fat emulsion prepared with fish oil does not cause hyperlipidaemia nor induce hepatic steatosis in normal rats.

Effect of dietary hyperlipidemic components and fish oil on concentration of lipids in liver and liver fatty acid profile of rats

This investigation was attempted to clarify the effects of dietary hyperlipidemic components and fish oil on concentration of lipids in liver and liver fatty acid profile of rats. In a first experiment male Sprague-Dawley rats were maintained on a semipurified low-fat diet with 6.5% coconut oil and 1.5% safflower oil, but without added cholesterol, or a high-fat hyperlipidemic diet supplemented with 7.3% coconut oil, 7.3% beef tallow, 0.4% safflower oil, and 1.5% cholesterol for 28 days. Rats fed the hyperlipidemic diet were then switched to fish oil diets with 1.4%, 2.8%, and 5.6% fish oil in exchange for coconut oil and beef tallow for, respectively, 10 and 20 days. In a second experiment male Sprague-Dawley rats were fed low-fat or high-fat diets without or with 1.5% added cholesterol for 28 days. Half of each group was then changed to a fish oil diet (for 20 days) which contained 5.6% fish oil in exchange for coconut oil and beef tallow. In experiment 1, rats fed the hyperlipidemic diet had enlarged fatty livers within 28 days. Experiment 2 showed that cholesterol in the diet was responsible for the accumulating liver lipids. Feeding diets with added cholesterol, the proportions of saturated fatty acids (SFA), especially 18:0, were markedly reduced in liver, whereas levels of monounsaturated fatty acids (MUFA) were greatly increased compared to diets without added cholesterol. This increase was most pronounced with respect to 16:1 and 18:1. In contrast, fish oil diets lowered MUFA level in liver in spite of its high MUFA content. Rats fed the highly saturated hyperlipidemic diet low in 18:2 n-6 had reduced 18:2 n-6 levels in liver compared to rats fed the low-fat diet without added cholesterol. Also, 20:4 n-6 level in liver was markedly reduced after the administration of the hyperlipidemic diet or the fish oil diets. Results of experiment 2 elucidate that cholesterol as well as fish oil sharply lowered 20:4 n-6 level in liver, which might be due to a reduced desaturation. In both experiments feeding fish oil increased all long-chain n-3 polyunsaturated fatty acids (PUFA) in liver. This occurred in a dose-dependent fashion and reached a maximum level with 5.6% fish oil in the diet. When additional cholesterol was applied 22:6 n-3 level in liver fell. This indicates also an impaired desaturation of PUFA due to dietary cholesterol.

Effect of dietary fish oil on serum lipids and lipoproteins of rats fed diets differing in cholesterol and fat

The investigation was attempted to clarify the effects of fish oil on the concentration of lipids in serum and lipoproteins in rats fed diets differing in cholesterol and fat. Male Sprague-Dawley rats were maintained on low-fat/high-fat diets without and with 1.5% cholesterol (base diets) for 28 days. Half of each group was then switched to a fish oil diet for 20 days with 5.6% fish oil for exchange of coconut oil and beef tallow. Total cholesterol in rat serum was increased following feeding high amounts of dietary cholesterol. This increase was due to raised VLDL and LDL cholesterol. Rats fed the high-cholesterol/high-fat diet had lower HDL cholesterol concentration than groups fed the other base diets. Dietary fish oil lowered serum and lipoprotein cholesterol, even in the presence of dietary cholesterol. In rats fed the high-fat/cholesterol-free diet triglyceride levels in total serum and VLDL were higher than in rats fed the other base diets. The hypertriglyceridemia in rats was diminished fed dietary cholesterol. Serum triglyceride concentration was markedly lowered by fish oil, whereas, this effect reached significance only using cholesterol-free diets. This was mainly associated with a reduction in VLDL triglycerides. Fish oil lowered HDL triglycerides only in rats fed the low-fat diet without cholesterol. Lipid components in the base diets did not influence serum and LDL phospholipids. Rats fed the high-fat/cholesterol-free diet had a higher VLDL phospholipid level than the other base groups. Irrespective of the base diet, phospholipid levels in serum and lipoproteins were markedly reduced by dietary fish oil. In conclusion, this study suggests that other dietary lipids should be considered when examining the hypolipemic effect of fish oil.

The vitamin E nutritional status of rats fed on diets high in fish oil, linseed oil or sunflower seed oil

Twelve groups of eight rats and two control groups of sixteen rats were given semisynthetic diets with 40% energy as fat for a period of 76 d. All diets contained a minimum of 3% energy as linoleic acid and comparable basal levels of D-alpha- and D-gamma-tocopherol. The diets varied in fat composition and in the content of DL-alpha-tocopheryl acetate. The diets high in polyunsaturated fatty acids (PUFA) were either rich in fish oil (FO; groups 1-4; 10% energy as fish oil PUFA), linseed oil (LN; groups 1-4; 10% energy as alpha-linolenic acid) or sunflower seed oil (SF; groups 1-4; 10 + 3% energy as linoleic acid). The control groups were given a diet high in monounsaturated fatty acids (MUFA; CO 1; 10 + 13% energy as oleic acid) or a diet with an 'average' linoleic acid content (CO 2; 8.5% energy as linoleic acid). Of each high PUFA diet three groups were supplemented with graded levels of DL-alpha-tocopheryl acetate. Steatitis, a sensitive histopathological indicator of vitamin E deficiency in animals fed on diets rich in fatty acids with three or more double bonds, was observed only in the adipose tissue of the FO groups, even in the group with the highest DL-alpha-tocopheryl acetate supplementation. Liver and serum alpha-tocopherol levels were found to be positively correlated and liver and serum gamma-tocopherol levels negatively correlated with dietary DL-alpha-tocopheryl acetate. The groups on the FO diets had significantly reduced liver and serum tocopherol levels in comparison with the groups on the other high-PUFA diets. With the supplementation scheme used for the FO groups the liver alpha-tocopherol levels of both control groups were reached but the serum control levels were not.

Effects of dietary oils and methyl ethyl ketone peroxide on in vivo lipid peroxidation and antioxidants in rat heart and liver

Weanling male Sprague-Dawley rats were fed diets for four weeks which differed in their content of n-6 (corn oil; CO) and n-3 fatty acids (fish oil; FO), but were similar in their content of saturated and monounsaturated fatty acids and vitamin E. At the end of the four-week feeding period, each dietary group was subdivided into two groups. One group received a single placebo injection of alpha-tocopherol-stripped corn oil (TSCO); the other group received a single injection of the free radical generator; methyl ethyl ketone peroxide (MEKP), in TSCO. Twenty-four hours after injection, the effect of dietary oil and MEKP treatment on endogenous lipid peroxide (LPO) production (measured as methylene blue formed by the "Determiner LPO" assay), glutathione (GSH) and vitamin E content, and fatty acid composition of phosphatidylcholine and phosphatidylethanolamine in heart and liver from unfasted animals were measured. FO-fed rats had significantly heavier hearts and livers, increased levels of n-3 fatty acids in membrane phospholipids, and higher liver LPO levels than CO-fed rats. MEKP treatment resulted in significantly lower body weights and liver GSH levels. The data indicate that dietary n-3 fatty acids increase lipid peroxidation in liver somewhat more than in heart. The study also demonstrates that the effect of induced oxidative stress due to a single dose of MEKP on lipid peroxide formation and antioxidant status in tissues from unfasted animals was independent of the dietary oils.

Effects of dietary linseed oil and marine oil on lipid peroxidation in monkey liver in vivo and in vitro

Diets rich in linoleic acid (CO) from corn oil, or in linoleic acid and either alpha-linolenic acid (LO) based on linseed oil or n-3 fatty acids (MO) from menhaden oil were fed to male and female Cynomolgus monkeys for 15 wk. In the liver a 40% reduction of alpha-tocopherol occurred in the MO group relative to the CO and LO groups followed by increased formation of lipofuscin in vivo. A four-fold increase of alpha-tocopherol in the MO diet (MO + E) brought the level in the liver to that found with CO and LO. The increased peroxidation in the MO group in the liver phospholipids was associated with the replacement of 60% of the n-6 fatty acids by n-3 fatty acids from menhaden oil. Similar fatty acid profiles were found in groups fed MO and MO + E, respectively. Compared to the CO fed group, feeding alpha-linolenic acid only resulted in a slight incorporation of n-3 fatty acids in the liver membranes mainly due to a direct incorporation of alpha-linolenic acid. However, in monkeys fed menhaden oil more than 30% of the total fatty acids in the liver phospholipids were n-3 fatty acids. The various diets did not influence the activity of liver catalase (EC 1.11.1.6) nor superoxide dismutase (EC 1.15.1.1), but glutathione-peroxidase activity (EC 1.11.1.9) was higher in monkeys fed the MO diet. The catalase activity in females was 20% higher than in males.(ABSTRACT TRUNCATED AT 250 WORDS)

Apparent inhibition of hepatic triacylglycerol secretion, independent of synthesis, in high-fat fish oil-fed rats: role for insulin

Rats were fed Chow (C; low-fat control) or a purified high-fat (30% of calories) low cholesterol diet containing menhaden oil (MO), corn oil (CO) or lard (L) for 2, 4 or 6 weeks. Rats were killed after an overnight fast. MO-fed rats had a larger weight/body weight that was accompanied by a lower mg liver DNA/g liver but unchanged liver DNA/body weight, indicating that hepatomegaly in the MO-fed rats was due to cellular hypertrophy. MO-feeding prevented the rise in plasma triacylglycerol and cholesterol observed with the other high-fat diets. There was a marked progressive accumulation of total liver triacylglycerol in the MO- and CO-fed rats. Plasma insulin was reduced in the MO-fed rats relative to all other groups. There were strong positive relationships between plasma insulin and triacylglycerol and between insulin and cholesterol in the high-fat-fed rats. Total liver glucose-6-phosphate dehydrogenase and malic enzyme activities were reduced by MO-feeding and were directly correlated with plasma cholesterol and insulin. These data are consistent with an apparent inhibition of hepatic triacylglycerol secretion by high-fat fish oil-feeding that is independent of the inhibitory effects on triacylglycerol synthesis. These data suggest a role for insulin in regulating the plasma triacylglycerol and cholesterol concentrations in MO-fed rats.

N-6 and N-3 PUFA in liver lipids, thromboxane formation and blood pressure from SHR during diets supplemented with evening primrose, sunflowerseed or fish oil

Spontaneously hypertensive rats (SHR) after weaning (at 4 weeks of age) were fed diets supplemented with either sunflowerseed oil (SO), evening primrose oil (EPO), fish oil (FO) or EPO + FO (50%: 50%, v/v) for 22 weeks. A diet with commercially available pellets served as control. Systolic blood pressure was significantly lower in the dietary groups receiving FO, EPO and FO + EPO, the former being most effective. In liver triglycerides (TG) EPO resulted in a markedly increased percentage of linoleic acid (LA; C 18:2, n-6), alpha-linolenic acid (alpha-LNA; C 18:3, n-6) and especially of arachidonic acid (AA; C 20:4, n-6), whereas the long-chain n-3 polyunsaturated fatty acids (PUFA), eicosapentaenoic acid (EPA; C 20:5, n-3) and docosahexaenoic acid (DHA; C 22:6 n-3), were depressed to undetectable and significantly lower levels, respectively. In liver phosphatidylcholine (PC) and phosphatidylethanolamine (PE) only slight changes of LA and AA were observed. Feeding of FO led to a significant rise of EPA and DHA in liver TG, PC and PE at the expense of n-6 PUFA (except LA in PC and PE). With a combination of both EPO and FO a significant increase of EPA and DHA, but on lower levels as compared to FO alone, was associated with a significant rise of LA, but with a slight decline of AA as compared to the control animals. Nevertheless, the levels of AA in the group fed EPO + FO were still higher than in the FO-group. In the SO-group the increase of LA was even higher when compared with the EPO-group.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on membrane lipid peroxidation in omega-3 fatty acid-fed autoimmune mice: effect of vitamin E supplementation

Enzyme-dependent and non-enzymatic in vitro lipid peroxidation was studied in autoimmune prone B/W mice fed diets containing high levels of dietary corn oil (CO) or menhaden fish oil (FO) as lipid source since weaning. Lipid analysis revealed that FO-fed mouse liver mitochondrial and microsomal membrane fractions incorporated 20:5 omega 3 and 22:6 omega 3 in replacement of 18:2 omega 6 and 20:4 omega 6 found in corn oil (CO) fed control animals reflecting the composition of the dietary oils. Lower concentrations of vitamin E were found in the FO-fed mouse membranes and serum than those of CO-fed mice when diets were supplemented with a standard 75 I.U. alpha-tocopheryl acetate/kg diet. The rate and extent of membrane lipid peroxidation was greatly increased in FO-fed, vitamin-E-depleted membranes. Full repletion of membrane vitamin E levels by supplementation with 500 I.U./kg of FO diet for 30 days significantly decreased lipid peroxidation and showed that in FO-fed mice, membrane peroxidation is inversely proportional to vitamin E content. However, due to a lower ratio of vitamin E and highly unsaturated fatty acids, FO-fed mouse membranes were more sensitive to pro-oxidant stimulus than were those from CO-fed mice. These findings illustrate the action of vitamin E against membrane lipid peroxidation and stress the importance of adequate supplementation of antioxidant with high omega-3 fatty acids intake.

Fish consumption and breast cancer risk: an ecological study

There is experimental evidence that fish oils protect against mammary carcinogens in animals. However, there has been little investigation of the possible relevance of this finding to breast cancer in humans. We compared breast cancer incidence and mortality rates with estimates of the consumption of fish and other foods and nutrients in the countries for which reliable data are available. The results showed an inverse association between percent calories from fish and breast cancer rates that was consistent with a protective effect. This analysis confirmed the finding of others that dietary fat is strongly associated with international variation in breast cancer rates. It also showed that of the dietary components considered, percent calories from fish was the factor most strongly correlated with breast cancer rates after statistical adjustment for dietary fat intake. This result is therefore in accord with animal experimental data and suggests that the omega-3 fatty acids contained in certain fish may protect against breast cancer.

Effect of age and dietary fat (fish, corn and coconut oils) on tocopherol status of C57BL/6Nia mice

The effect of age and dietary fat type on tocopherol status was investigated using young and old C57BL/6Nia mice fed semipurified diets containing 5% (by weight) fish, corn or coconut oils and supplemented with 30, 100 or 500 ppm dl-alpha-tocopheryl acetate for 6 wk. Tocopherol levels in the diets, plasma, liver, kidney and lung were measured by high performance liquid chromatography following appropriate extractions. The results indicate that mice fed fish oil maintain lower plasma and tissue tocopherol concentrations than those fed corn and coconut oils (fish less than corn oil less than coconut oil). The difference was not due to a loss of tocopherol prior to consumption, but rather appeared to occur during the absorption process. Old mice had lower plasma and liver tocopherol concentrations than young mice. Old mice fed fish oil, however, maintained plasma tocopherol levels better than young mice fed fish oil, presumably due to their larger tocopherol pool. No age effect was detected on kidney and lung tocopherol levels. It is concluded that tocopherol status is affected by age and dietary fat type, especially fish oil.