Effects of Two Highly Monounsaturated Oils on Lipid Composition and Enzyme Activities in Rat Jejunum

The effects of two monounsaturated fatty acid (MUFA) oils, olive oil (OO)and high-oleic sunflower oil (HOSO), with high content in oleic acid butdiffering in their non-fatty acid fraction, on brush-border membrane(BBM) lipid composition and fluidity and on mucosal enzyme activitiesof rat jejunum were studied. Animals were given semipurified diet withlinoleic acid to prevent essential fatty acid deficiency (control group)or semipurified diet containing 10% of either OO or HOSO for 12weeks. There was a significant decrease in the content of jejunalBBM phospholipids together with an increase in the level of freecholesterol in both oil-fed rats, when compared to controlgroup. Although the increase in the BBM free cholesterol levelwas not statistically significant in HOSO-fed rats, a significantdecrease in the phospholipid/free cholesterol ratio was found inboth OO and HOSO-fed animals compared to control group. Rat jejunalBBM had a high level of free fatty acids which was increased in BBMisolated from OO and HOSO-fed animals. There was no statisticalsignificant difference in the phospholipid distribution between thecontrol and the OO group. However, HOSO-fed animals showed the lowestlevel of phosphatidylethanolamine together with the highestphosphatidylcholine content and the phosphatidylcholine/sphingomyelinratio. The fatty acid pattern of jejunal BBM lipids was modifiedaccording to the major fatty acids in the oils. There was a decreasein both stearic acid (18:0) and linoleic acid (18:2 n-6), togetherwith an increase in oleic acid (18:1 n-9) in jenunal BBM isolatedfrom both oil experimental groups. All these results were accompaniedby a significant increase in the BBM fluidity (as assessed bysteady-state fluorescence polarization of diphenylhexatriene) isolatedfrom oil-fed rat, when compared to control group. OO and HOSO-fedanimals had the lowest activities of sucrase and maltase, whilealkaline phosphatase activity only was decreased in HOSO-fedanimals. The specific activity of maltase was not modified in anyexperimental rats. In summary, both MUFA oils induced similar effectson jejunal BBM lipid composition, fluidity, sucrase, maltase andlactase activities. Furthermore, HOSO intake resulted in a lowestalkaline phosphatase activity which was accompanied by changes inindividual phospholipid composition. All these results suggest thateffects of MUFA oils on jejunal BBM lipid composition and hydrolaseactivities are most likely due to the presence of high content ofoleic acid rather than other components contained in the non-fattyacid of olive oil.     

Role of dietary oleic acid from two different sources on fatty acid composition of erythrocyte membrane and blood pressure in healthy subjects

This study has been undertaken to determine the effect of a diet enriched with olive oil (OO) and high-oleic sunflower oil (HOSO) on fatty acid composition of erythrocyte membrane phospholipids and blood pressure in healthy women. OO and HOSO were used as natural sources of monounsaturated fatty acids (MUFAs) in a random-order sequence over two 4-week periods with a 4-week washout period between both MUFA diets. HOSO diet resulted in significant increases in oleic [(18:1n-9) 8.6%, P < 0.001], eicosenoic [(20:1n-9) 33.3%, P < 0.05], arachidonic [(20:4n-6) 6.2%, P < 0.05], and docosapentaenoic [(22:5n-6) 56.0%, P < 0.001] acids, whereas OO diet besides increased the content of stearic acid [(18:0) 13.6%, P < 0.01] and long-chain polyunsaturated fatty acids (PUFAs) of the n-3 family (22:5n-3 and 22:6n-3), when compared with the baseline [a diet high in saturated fatty acids (SFAs) and low in MUFAs]. In contrast, there was a significant decrease in linoleic acid [(18:2n-6) 21.8%, P < 0.001] for both MUFA diets. Consistent with these data, dietary intake of OO significantly raised total PUFAs (7.2%, P < 0.05), the n-3 fatty acids (22.2%, P < 0.01) and the PUFAs/SFAs ratio (9.3%, P < 0.01), as well as decreased the ratio of cholesterol to phospholipids (26,1%, P < 0.001) versus HOSO-based diet. Interestingly, dietary OO, but not HOSO, was able to significantly reduce the systolic (3%, P < 0.05) and diastolic (4%, P < 0.05) blood pressures. Although both vegetable oils provided a similar content of MUFAs (mainly oleic acid), our findings rather indicate that OO has important benefits to modulate the fatty acid composition of membranes and the mechanisms involved in the regulation of blood pressure in human.     

Effect of n-6 and n-3 polyunsaturated fatty acids ingestion on rat liver membrane-associated enzymes and fluidity

The influences of diets having different fatty acid compositions on the fatty-acid content, desaturase activities, and membrane fluidity of rat liver microsomes have been analyzed. Weanling male rats (35–45 g) were fed a fat-free semisynthetic diet supplemented with 10% (by weight) marine fish oil (FO, 12.7% docosahexaenoic acid and 13.8% eicosapentaenoic acid), evening primrose oil (EPO, 7.8% γ-linolenic acid and 70.8% linoleic acid) or a mixture of 5% FO-5% EPO. After 12 weeks on the respective diets, animals fed higher proportions of (n-3) polyunsaturated fatty acids (FO group) consistently contained higher levels of 20:3(n-6), 20:5(n-3), 22:5(n-3), and 22:6(n-3), and lower levels of 18:2(n-6) and 20:4(n-6), than those of the EPO (a rich source of (n-6) polyunsaturated fatty acids) or the FO + EPO groups. Membrane fluidity, as estimated by the reciprocal of the order parameter S_DPH, was higher in the FO than in the EPO or the FO + EPO groups, and the n-6 fatty-acid desaturation system was markedly affected.     

Effect of long-term feeding olive and sunflower oils on fatty acid composition and desaturation activities of liver microsomes

Changes in microsomal fatty acid composition, delta 9- and delta 6-desaturase activities and cholesterol and phosphorus liver content were studied in dogs fed olive and sunflower oil diets. No changes were observed in the saturated fatty acids between dietary groups. The level of monounsaturated fatty acids was more elevated in animals fed the OO diet, because of its high relative content in this diet although the in vitro delta 9-desaturase activity was similar in microsomes from the two groups. The proportion of arachidonic acid was similar in SO and OO fed animals. This similar level occurred despite a significant increase in the level of linoleic acid in membrane lipids as a result of feeding the SO supplement. The in vitro delta 6-desaturase activity in liver microsomes showed no differences between dogs fed the two diets. Thus, the higher desaturation presented in vivo by microsomes from OO group may be related to the inhibition by linoleic acid of delta 6-desaturase in dogs fed the SO diet. The polyunsaturated fatty acids (PUFA) from the n-3 series were higher in microsomal phosphatidylcholine and phosphatidylethanolamine from animals fed the OO supplemented diet. The cholesterol/phosphorus molar ratio was higher in the SO group in which the unsaturation index was only slightly affected in phospholipids.     

Effect of dietary fish oil on tumor-induced hyperlipidemia and tumor growth in rats implanted with a methylcholanthrene-induced sarcoma

Male Fischer 344 rats implanted with a methylcholanthrene-induced sarcoma (MCS), along with normal (or control) animals, were fed diets containing either 10% com oil (CO) or 2% CO + 8% fish oil (FO), designated as diets CO and FO, respectively, in a study designed to determine the effect of dietary FO on serum lipids (in the presence or absence of a tumor) and the growth and fatty acid composition of the MCS. For both diets, MCS-bearing rats had significantly (p < 0.05) higher serum levels of triglycerides, cholesterol, phospholipids, and total lipids than controls. For both controls and tumor-bearers, serum levels of all these lipids were, with the exception of cholesterol for the tumorbearers, significantly lower in rats receiving the FO diet than for the corresponding groups receiving the CO diet. Relative to rats fed the CO diet, those fed the FO diet had significantly higher serum levels of some fatty acids (e.g., 20:5n-3) but significantly lower levels of others (e.g., 18:2n-6), regardless of tumor status. For the tumor-bearers, differences in the levels of fatty acids in MCS tissue reflected differences in the fatty acid composition of total serum lipids. Sarcoma growth was unaffected by diet. Thus, feeding dietary FO resulted in changes in the lipid status of both control and tumor-bearing rats. Since sarcoma growth was unaffected by diet, the reduction in the severity of MCS-induced hyperlipidemia by FO appears to be due to an effect of the oil per se.     

Modulation of antioxidant enzyme activities, platelet aggregation and serum prostaglandins in rats fed spray-dried milk containing n-3 fatty acid

Spray-dried milk enriched with n-3 fatty acids from linseed oil (LSO) or fish oil (FO) were fed to rats to study its influence on liver lipid peroxides, hepatic antioxidant enzyme activities, serum prostaglandins and platelet aggregation. Significant level of α linolenic acid, eicosapentaenoic acid and docosahexaenoic acid were accumulated at the expense of arachidonic acid in the liver of rats fed n-3 fatty acid enriched formulation. The linseed oil and fish oil enriched formulation fed group had 44 and 112% higher level of lipid peroxides in liver homogenate compared to control rats fed groundnut oil enriched formulation. Catalase activity in liver homogenate was increased by 37 and 183% respectively in linseed oil and fish oil formulation fed rats. The glutathione peroxidase activity decreased to an extent of 25–36% and glutathione transferase activity increased to an extent of 34–39% in rats fed n-3 fatty acids enriched formulation. Feeding n-3 fatty acid enriched formulation significantly elevated the n-3 fatty acids in platelets and increased the lipid peroxide level to an extent of 4.2 to 4.5-fold compared to control. The serum thromboxane B₂ level was decreased by 35 and 42% respectively in linseed oil and fish oil enriched formulation fed rats, whereas 6-keto-prostaglandin F1α level was decreased by 17 and 23% respectively in linseed oil and fish oil enriched formulation fed rats. The extent and rate of platelet aggregation was decreased significantly in n-3 fatty acids enriched formulation fed rats. This indicated that n-3 fatty acids enriched formulation beneficially reduces platelet aggregation and also enhances the activities of hepatic antioxidant enzymes such as catalase and glutathione transferase.     

Partial replacement of dietary fish oil with blends of vegetable oils (rapeseed, linseed and palm oils) in diets for European sea bass (Dicentrarchus labrax L.) over a long term growth study: effects on muscle and liver fatty acid composition and effectiveness of a fish oil finishing diet

Triplicate groups of European sea bass (Dicentrarchus labrax L.), of initial mass 5 g, were fed one of three practical type diets for 64 weeks. The three diets differed only in the added oil and were 100% fish oil (FO; diet A), 40% FO/60% vegetable oil blend (VO; diet B) where the VO blend was rapeseed oil, linseed oil and palm oil in the ratio 10/35/15 by weight and 40% FO/60% VO blend (diet C) where the ratio was 24/24/12 by weight. After final sample collection the remaining fish were switched to a 100% FO finishing diet for a further 20 weeks. After 64 weeks fish fed 60% VO diet B had significantly lower live mass and liver mass than fish fed diets A and C although SGR, FCR and length were not different between groups. There were no differences in any of the above parameters after either 14 or 20 weeks on the FO finishing diet. Fatty acid compositions of flesh were correlated to dietary fatty acids although there was selective retention of docosahexaenoic acid (22:6n-3; DHA) regardless of dietary input. Inclusion of dietary VO resulted in significantly reduced flesh levels of DHA and eicosapentaenoic acid (20:5n-3; EPA) while 18:1n-9, 18:2n-6 and 18:3n-3 were all significantly increased in fish fed the 60% VO diets. Fatty acid compositions of liver showed broadly similar changes, as a result of dietary fatty acid composition, as was seen in flesh. However, the response of flesh and liver to feeding a FO finishing diet was different. In flesh, DHA and EPA values were not restored after 14 or 20 weeks of feeding a FO finishing diet with the values in fish fed the two 60% VO diets being around 70% of the values seen in fish fed FO throughout. Conversely, and despite liver DHA and EPA levels being reduced to only 40% of the value seen in fish fed 100% FO after 64 weeks, the levels of liver DHA and EPA were not significantly different between treatments after feeding the FO finishing diet for 14 weeks. However, a 200 g portion of sea bass flesh, after feeding the experimental diets for 64 weeks followed by a FO diet for 14 weeks, contained 1.22 and 0.95 g of EPA + DHA for fish fed FO or 60% VO, respectively. Therefore, sea bass grown for most of the production cycle using diets containing 60% VO can still contribute a significant quantity of healthy n-3 HUFA to the human consumer.     

Fatty acid changes in liver choline and ethanolamine glycerophospholipids in aspirin-treated rats fed linoleate, gamma-linolenate and fish oil

The effects of dietary linoleic acid, gamma-linolenic acid and marine fatty acids on the development of aspirin-induced gastric hemorrhage and the distribution of liver glycerophospholipid fatty acids in fat-deficient growing rats were studied. Aspirin (100 mg/day)-treated and nontreated rats were fed for 7 days, a mixed diet of 2.5% safflower oil and 7.5% hydrogenated coconut oil (SFO/HCO) or 7.5% fish oil (SFO/FO), or 2.5% gamma-linolenate concentrate and 7.5% fish oil (GLA/FO). Gastric hemorrhage was induced in animals by aspirin treatment to various extents. It was not affected by FO feeding, but was significantly alleviated by GLA feeding. Aspirin treatment reduced the proportions of 20:4n-6 in liver phosphatidylcholine. FO feeding (in SFO/FO and GLA/FO rats) further reduced the 20:4n-6 level and replaced it by n-3 fatty acids. GLA feeding, on the other hand, elevated the proportion of 20:4n-6. As a result, the reduction of 20:4n-6 by fish oil feeding, was less significant in GLA/FO rats than in SFO/FO rats. The degree of gastric hemorrhage appeared to relate negatively to the levels of 20:4n-6 in liver phosphatidylcholine, and to the sum of 20:4n-6 and 20:5n-3 when FO was included in the diet. It is suggested that long-chain polyunsaturated fatty acids (20:4n-6 and 20:5n-3) per se in addition to being precursors of prostaglandins, may also affect the development of gastric hemorrhage, possibly by modulating the permeability of cell membranes in the gastric mucosa.     

Interactive effects of dietary (n-3) polyunsaturated fatty acids and chronic ethanol intoxication on synaptic membrane lipid composition and fluidity in rats.

The influence of dietary polyunsaturated fatty acids on fatty acid composition, cholesterol and phospholipid content as well as 'fluidity' (assessed by fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) probes) of brain synaptic plasma membranes (SPM) and their interactions with chronic ethanol effects were studied in rats fed for two generations with diets either devoid of (n-3) fatty acids (sunflower oil diet), rich in alpha-linolenic acid (soya oil diet) or in long chain (n-3) fatty acids (sunflower + cod liver oil diet). Results were compared with rats fed standard lab chow. Sunflower oil led to an increase in the (n-6)/(n-3) ratio in the membranes with an increase of the 'fluidity' at membrane apolar level; sunflower + cod liver oil decreased the (n-6)/(n-3) ratio without affecting membrane 'fluidity' while no difference was seen between the SPM of rats fed soya oil and standard diet. After 3 weeks alcohol intoxication in rat fed the standard diet: oleic alpha-linoleic acids and cholesterol levels were increased, arachidonic acid and the double bond index/saturated fatty acids were decreased and there was a decrease of 'fluidity' in the lipid core of the SPM. Soya oil almost totally abolished these usually observed changes in the SPM fatty acids composition but increased oleic acid and cholesterol without any change in fluidity. Sunflower oil led to the same general alterations of fatty acid as seen with standard diet but to a greater extent, with decrease of the 'fluidity" at the apolar level and in the region probed by TMA-DPH. When sunflower oil was supplemented with cod liver oil, oleic and alpha-linoleic acids were increased while the 'fluidity' of the apolar core of SPM was decreased. So, the small changes in fatty acid pattern seem able to modulate neural properties i.e. the responses to a neurotoxic like ethanol. A structurally specific role of PUFA is demonstrated by the pernicious effects of the alpha-linolenic acid deficient diet which are not totally prevented by the supply of long chain (n-3) PUFA.     

Dietary fats affect macrophage-mediated cytotoxicity towards tumour cells

In the present study, the effects of feeding mice diets of different fatty acid compositions on the production of TNF-alpha and nitric oxide by lipopolysaccharide-stimulated peritoneal macrophages and on macrophage-mediated cytotoxicity towards L929 and P815 cells were investigated. C57Bl6 mice were fed on a low-fat (LF) diet or on high-fat diets (21% fat by weight), which included coconut oil (CO), olive oil (OO), safflower oil (SO) or fish oil (FO) as the principal fat source. The fatty acid composition of the macrophages was markedly influenced by that of the diet fed. Lipopolysaccharide (LPS)-stimulated macrophages from FO-fed mice showed significantly lower production (up to 80%) of PGE2 than those from mice fed on each of the other diets. There was a significant positive linear correlation between the proportion of arachidonic acid in macrophage lipids and the ability of macrophages, to produce PGE2. Lipopolysaccharide-stimulated TNF-alpha production by macrophages decreased with increasing unsaturated fatty acid content of the diet (i.e. FO < SO < OO < CO < LF). Macrophages from FO-fed mice showed significantly lower production of TNF-alpha than those from mice fed on each of the other diets. Nitrite production was highest for LPS-stimulated macrophages from mice fed on the LF diet. Macrophages from FO-fed mice showed significantly higher production of nitrite than those from mice fed on the OO and SO diets. Compared with feeding the LF diet, feeding the CO, OO or SO diets significantly decreased macrophage- mediated killing of P815 cells (killed by nitric oxide). Fish oil feeding did not alter killing of P815 cells by macrophages, compared with feeding the LF diet; killing of P815 cells was greater after FO feeding than after feeding the other high fat diets. Compared with feeding the LF diet, feeding the OO or SO diets significantly decreased macrophage-mediated killing of L929 cells (killed by TNF). Coconut oil or FO feeding did not alter killing of L929 cells by macrophages, compared with feeding the LF diet. It is concluded that the type of fat in the diet affects macrophage composition and alters the ability of macrophages to produce cytotoxic and immunoregulatory mediators and to kill target tumour cells.     

Fatty acid composition and properties of the liver microsomal membrane of rats fed diets enriched with cholesterol.

Male rats were fed diets containing olive (OO) or evening primrose (EPO) oil (10% w/w), with or without added cholesterol (1% w/w). After 6-week feeding, the lipid and fatty acid compositions, fluidity, and fatty acid desaturating and cholesterol biosynthesis/esterification related enzymes of liver microsomes were determined. Both the OO and EPO diets, without added cholesterol, increased the contents of oleic and arachidonic acids, respectively, of rat liver microsomes. The results were consistent with the increases in delta 9 and delta 6 desaturation of n-6 essential fatty acids and the lower microviscosity in the EPO group. Dietary cholesterol led to an increase in the cholesterol content of liver microsomes as well as that of phosphatidylcholine (PC). The cholesterol/phospholipid and PC/PE (phosphatidylethanolamine) ratios were also elevated. Fatty acid composition changes were expressed as the accumulation of monounsaturated fatty acids, with accompanying milder depletion of saturated fatty acids in rat liver microsomes. In addition, the arachidonic acid content was lowered, with a concomitant increase in linoleic acid, which led to a significant decrease in the 20:4/18:2 ratio in comparison to in animals fed the cholesterol-free diets. Cholesterol feeding also increased delta 9 desaturase activity as well as membrane microviscosity, whereas it decreased delta 6 and delta 5 desaturase activities. There was a very strong correlation between fluidity and the unsaturation index reduction in the membrane. Furthermore, the activity of hydroxymethylglutaryl-CoA reductase increased and the activity of acyl-CoA:cholesterol acyltransferase decreased in liver microsomes from both cholesterol-fed groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Spray-dried milk supplemented with alpha-linolenic acid or eicosapentaenoic acid and docosahexaenoic acid decreases HMG Co A reductase activity and increases biliary secretion of lipids in rats

In our earlier study, we have shown that rats fed spray-dried milk containing alpha-linolenic acid (LNA 18:3 n-3) or eicosapentaenoic acid (EPA 20:5 n-3) and docosahexaenoic acid (DHA 22:6 n-3) had significantly lower amounts of serum and liver cholesterol. To evaluate the mechanism for hypocholesterolemic effect of n-3 fatty acids containing milk formulation, we fed male Wistar rats with spray-dried milk containing linseed oil (LSO) (source of LNA) or fish oil (FO) (source of EPA+DHA) for 8 weeks. Feeding n-3 fatty acid containing milk formulation lowered the hepatic 3-hydroxy-methylglutaryl coenzyme A (HMG Co A) activity by 17-22% compared to rats given control diet devoid of n-3 fatty acids. The cholesterol level in liver microsomes was found to be decreased by 16% and 20%, respectively, in LSO and FO containing formulation fed rats. The bile flow was enhanced to an extent of 19-23% in experimental groups compared to control animals. The biliary cholesterol and phospholipid secretion was increased to an extent of 49-55% and 140-146%, respectively, in rats fed n-3 fatty acid containing formulation. The increase in the total bile acids secretion in bile was mainly reflected on an increase in the levels of taurine conjugated bile acids. These results indicated that n-3 fatty acid containing spray-dried milk formulation would bring about the hypocholesterolemic effect by lowering HMG Co A reductase activity in liver and by increasing the secretion of bile constituents.     

Effect of Fish Oil and Coconut Oil on Antioxidant Defence System and Lipid Peroxidation in Rat Liver

Diets high in fish oil containing polyunsaturated fatty acids of the n-3 family. have been suggested to decrease the risk of cardiovascular disease. However these lipids are highly susceptible to oxidative deterioration. In order to investigate the influence of n-3 fatty acids on oxidative status, the effect of feeding rats with fish oil or cocunut oil diets was studied by measuring different parameters related to an oxidative free radical challenge. Synthetic diets containing 15% (w/v) fish oil or coconut oil were used to feed growing rats for 4 weeks. As compared to control diet, the fish oil containing diet produced a significant decrease of cholesterol and triglyceride concentration in serum. however there was a significant increase in lipid peroxidation products. In addition, in fish oil fed animals, there was also a decrease in vitamin E and A concentration. Furthermore, the rate of lipid peroxidation in isolated microsomes was three fold higher in rats fed fish oil as compared to rats with coconut oil diet. No significant differences between the two experimental groups were observed in superoxide dismutase (SOD) and phospholipid hydroperoxide glutathione peroxidase (PHGPX) activities. However, there was a decrease in glutathione peroxidase (GPX) activity. These results suggest that fish oil feeding at an amount compatible with human diet, although decreasing plasma lipids, actually challenge the antioxidant defence system, thus increasing the susceptibility of tissues to free radical oxidative damage.     

Dietary fatty acid composition affects the repeat swimming performance of Atlantic salmon in seawater

Repeated critical swimming performance trials (Ucrit) were performed on Atlantic salmon (Salmo salar) to test the null hypothesis that the source of dietary lipids (fish-based, poultry-based, and plant-based) does not influence exercise and recovery performance. Four diets were prepared by extensively replacing supplemental lipid from anchovy oil (AO; 100% AO at 150 g/kg) with cold pressed flaxseed oil (FO; 25% AO, 75% FO), sunflower oil (SO; 25% AO, 75% SO), or poultry fat (PF; 25% AO, 75% PF). These diets had equivalent protein and energy concentrations, but due to the different supplemental lipid sources, varied widely in their fatty acid composition. Fish fed AO had a significantly higher (P<0.05) first Ucrit (2.62+/-0.07 body lenght s(-1)) than those fed PF (2.22+/-0.12 body lenght s(-1)) that had low muscle ratios of n-3 highly unsaturated fatty acids (n-3 HUFA) to saturated fatty acids (SFA) and arachidonic acid (AA), and high levels of oleic acid. Fish in the FO and SO diet groups swam as well as AO-fed fish in both swimming trials. The performance of fish fed AO decreased significantly (P<0.05) during the second swimming trial (i.e. Ucrit2/Ucrit1=0.92+/-0.02). No significant differences occurred between diet groups for the second swim trial. There was a positive correlation between both n-3 HUFA/SFA and n-3 HUFA/AA ratios, and Ucrit1. A negative correlation was found between dietary AA and oleic acids, and Ucrit1. The present study suggests that low dietary n-3 HUFA/ SFA and n-3 HUFA/AA ratios may negatively affect swimming performance. The former possibly can be offset by increasing linoleic acid in the presence of nutritionally adequate n-3 HUFA (e.g. SO diet). Lipid supplements consisting largely of vegetable oils did not compromise fish cardiorespiratory physiology under the conditions of this study.     

Effect of Fish Oil and Coconut Oil on Antioxidant Defence System and Lipid Peroxidation in Rat Liver

Diets high in fish oil containing polyunsaturated fatty acids of the n-3 family. have been suggested to decrease the risk of cardiovascular disease. However these lipids are highly susceptible to oxidative deterioration. In order to investigate the influence of n-3 fatty acids on oxidative status, the effect of feeding rats with fish oil or cocunut oil diets was studied by measuring different parameters related to an oxidative free radical challenge. Synthetic diets containing 15% (w/v) fish oil or coconut oil were used to feed growing rats for 4 weeks. As compared to control diet, the fish oil containing diet produced a significant decrease of cholesterol and triglyceride concentration in serum. however there was a significant increase in lipid peroxidation products. In addition, in fish oil fed animals, there was also a decrease in vitamin E and A concentration. Furthermore, the rate of lipid peroxidation in isolated microsomes was three fold higher in rats fed fish oil as compared to rats with coconut oil diet. No significant differences between the two experimental groups were observed in superoxide dismutase (SOD) and phospholipid hydroperoxide glutathione peroxidase (PHGPX) activities. However, there was a decrease in glutathione peroxidase (GPX) activity. These results suggest that fish oil feeding at an amount compatible with human diet, although decreasing plasma lipids, actually challenge the antioxidant defence system, thus increasing the susceptibility of tissues to free radical oxidative damage.     

The influence of dietary essential fatty acids on uterine C20 and C22 fatty acid composition.

The effect of dietary fatty acids on uterine fatty acid composition was studied in rats fed control diet or semi-synthetic diet supplemented with 1.5 microliter/g/day evening primrose oil (EPO) or fish oil (FO). Diet-related changes in uterine lipid were detected within 21 days. Changes of 2- to 20-fold were detected in the uterine n-6 and n-3 essential fatty acids (EFA) and in certain saturated and monounsaturated fatty acids. The FO diet was associated with higher uterine C20 and C22 n-3, and the EPO diet, with higher uterine n-6 fatty acid. High uterine C18:2 n-6 was detected in neutral lipid (NL) of rats fed high concentrations of this fatty acid, but there was little evidence of selective incorporation or retention of C18:2 n-6 by uterine NL. The incorporation of EFA into uterine phospholipids (PL) was greater than NL EFA incorporation, and uterine PL n-3/n-6 ratios showed greater diet dependence. Tissue/diet fatty acid ratios in NL and PL also indicated preferential incorporation/synthesis of C16:1 n-9, and C16:0, and there was greater incorporation of C12:0 and C14:0 into uteri of rats fed EPO and FO. Replacement of 50-60% of arachidonate with n-3 EFA in uterine PL may inhibit n-6 EFA metabolism necessary for uterine function at parturition.     

Effects of water temperature and diets containing palm oil on fatty acid desaturation and oxidation in hepatocytes and intestinal enterocytes of rainbow trout (Oncorhynchus mykiss)

Food grade fisheries have reached their sustainable limits while aquaculture production has increased to meet consumer demands. However, for growth in aquaculture to continue and utilise sustainable, feeding ingredients, alternatives to fish oil (FO), the predominant lipid component of fish diets, must be developed. Therefore, there is currently considerable interest in the regulation of fatty acid metabolism in fish in order to determine strategies for the best use of plant oils in diets for commercially important cultured fish species. Plant oils are characteristically rich in C18 polyunsaturated fatty acids (PUFA) but devoid of C20 and C22 highly unsaturated fatty acids (HUFA) found in FO. The fatty acyl desaturase enzyme activities involved in the biosynthesis of HUFA from PUFA are known to be under nutritional regulation and can be increased in fish fed diets rich in plant oils. However, fatty acid desaturase activity is also known to be modulated by water temperature in fish. The present study aimed to investigate the interaction between water temperature and diet in the regulation of fatty acid metabolism in rainbow trout. Trout, acclimatized to 7, 11 or 15 degrees C, were fed for 4 weeks on diets in which the FO was replaced in a graded manner by palm oil. At the end of the trial, fatty acyl desaturation/elongation and beta-oxidation activities were determined in isolated hepatocytes and intestinal enterocytes using [1-14C]18:3n-3 as substrate, and samples of liver were collected for analysis of lipid and fatty acid composition. The most obvious effect of temperature was that fatty acid desaturation/elongation and beta-oxidation were reduced in both hepatocytes and intestinal enterocytes from fish maintained at the highest water temperature (15 degrees C). There were differences between the two tissues with the highest desaturation/elongation and beta-oxidation activities tending to be in fish held at 11 degrees C in the case of hepatocytes, but 7 degrees C in enterocytes. Correlations between fatty acid metabolism and dietary palm oil were most clearly observed in desaturation/elongation activities in both hepatocytes and enterocytes at 11 degrees C. The highest beta-oxidation activities were generally observed in fish fed FO alone in both hepatocytes and enterocytes with palm oil having differential effects in the two cell types.     

不同脂肪源对泥鳅稚鱼生长性能及脂肪酸组成的影响

为研究饲料不同脂肪源对泥鳅稚鱼生长性能及鱼体脂肪酸组成的影响, 实验选择初始体重为(10.002.00) mg的健康泥鳅稚鱼1500尾, 随机分为5组, 每组3个重复, 每个水箱100尾鱼, 分别投喂5种含有鱼油(FO)、大豆油(SO)、玉米油(CO)、花生油(PeO)和棕榈油(PaO)的配合饲料, 每种饲料3个重复, 饲养期为40d。结果显示, 摄食不同脂肪源饲料的泥鳅稚鱼在增重率、成活率、饲料系数等生长性能指标和体成分上没有显著差异(P0.05), 但是, 摄食FO组鱼体极性脂肪含量显著高于其他植物油组(P0.05)。鱼油组鱼体中性和极性脂肪中总n-3系脂肪酸含量和EPA+DHA含量显著高于其他植物油组(P0.05)。植物油组鱼体极性脂肪中20:4n-6含量显著高于鱼油组(P0.05), 表明泥鳅稚鱼具有将C18转换为C20的能力。研究表明, 在饲料中添加足量磷脂, 鱼油、大豆油、玉米油、花生油、棕榈油都可以用作泥鳅稚鱼期专用饲料脂肪源。     

Effect of olive oil- and corn oil-enriched diets on the tissue mineral content in mice

The mineral content (zinc, iron, magnesium, and calcium) in the liver, spleen, and thymus of male Balb/C mice was analyzed. Animals were fed, over 21 d, diets enriched with corn oil (FCO diet) or olive oil (FOO diet) (5% addition to standard pellet, w/w). Olive oil with predominant oleic acid (C18:1, n-9) had a quite different composition than corn oil, in which linoleic acid (C18:2, n-6) prevails. The zinc and magnesium tissue concentrations were not changed in either group. The calcium concentration in liver as well as the calcium concentration in spleen increased in mice fed both the FCO and FOO diets. Furthermore, mice fed both the FOO and FCO diets had increased spleen iron concentration. Mice fed the FCO diet had increased thymus calcium concentration compared to controls. The results show the effect of diets with unsaturated, particularly polyunsaturated fatty acids, on the calcium and iron concentration in some organs.     

Effect of dietary fish oil (active EPA-30) on liver phospholipids in young and aged rats.

We explored the uses of fish oil (active EPA-30) as a source of eicosapentaenate (EPA; 20:5 n-3), to young and old rats. We treated three subgroups of rats each comprising 20 young or old rats, respectively. The first group was kept on the basal ration (lab-pellet) as control diet, the second group was fed semi-purified diets contained 5% pig-fat (n-3 fatty acids deficient diet). The third group was fed a modified diet in which 50% of pig-fat was replaced by active EPA-30. Livers of young rats fed pig-fat had a drastic decrease in the amount of phosphatidylethanolamine (PE) and omega-3 polyunsaturated fatty acids (EPA, 20:5 n-3 and docosahexaenoic, DHA, 22:6 n-3) and compensatory increase of phosphatidylcholine, saturated fatty acids and n-6 polyunsaturated fatty acids in the liver phospholipids. In contrast, the liver of young rats fed active EPA-30 had large amounts of PE and concomitant enrichment in polyunsaturated fatty acids. The liver of old rats, fed on active EPA-30 supplemented diet had lower amounts of PE and there were no significant changes in the phospholipid fatty acid composition.