The effects of increasing dietary levels of soy protein concentrate (SPC) on the immune responses and disease resistance (furunculosis) of vaccinated and non-vaccinated Atlantic salmon (Salmo salar L.) parr.

Juvenile salmon, with an initial weight of 9 g, were fed three experimental diets, formulated to replace 35 (SPC35), 58 (SPC58) and 80 (SPC80) of high quality fishmeal (FM) with soy protein concentrate (SPC) in quadruplicate tanks. Higher dietary SPC inclusion was combined with increased supplementation of methionine, lysine, threonine and phosphorus. The experiment was carried out for 177 days. On day 92 salmon in each tank were bulk weighed. Post weighing eighty salmon from each tank were redistributed in two sets of 12 tanks. Salmon from the first set of tanks were vaccinated, while the second group was injected with phosphate buffer saline (PBS). Salmon were sampled on day 92 (pre-vaccination), day 94 (2 days post vaccination [dpv]/PBS injection [dpPBSinj]) and day 154 (62 dpv/dpPBSinj) of the trial for the assessment of their immune responses, prior to the performance of salmon bulk weights for each tank. On day 154, fish from each tank were again bulk weighed and then seventeen salmon per tank were redistributed in two sets of twelve tanks and intra-peritoneally infected with Aeromonas salmonicida. At Day 154, SPC80 demonstrated lower performance (weight gain, specific growth rate and thermal growth coefficient and feed conversion ratio) compared to SPC35 salmon. Reduced classical and total complement activities for salmon fed diets with over 58% of protein from SPC, were demonstrated prior to vaccination. Reduced alternative complement activity was detected for both SPC58 and SPC80 salmon at 2 dpv and for the SPC80 group at 62 dpv. Total and classical complement activities demonstrated no differences among the dietary groups after vaccination. Numerical increases in classical complement activity were apparent upon increased dietary SPC levels. Increased phagocytic activity (% phagocytosis and phagocytic index) was exhibited for the SPC58 group compared to SPC35 salmon at 62 dpPBSinj. No differences in serum lysozyme activity, total IgM, specific antibodies, protein, glucose and HKM respiratory burst were detected among the dietary groups at any timepoint or state. Mortalities as a result of the experimental infection only occurred in PBS-injected fish. No differences in mortality levels were demonstrated among the dietary groups. SPC58 diet supported both good growth and health in juvenile Atlantic salmon while SPC80 diet did not compromise salmon' immunity or resistance to intraperitoneally inflicted furunculosis.

The effects of increasing dietary levels of amino acid-supplemented soy protein concentrate and constant dietary supplementation of phosphorus on growth, composition and immune responses of juvenile Atlantic salmon (Salmo salar L.).

Diets with 50 (SPC50), 65 (SPC65) and 80 % (SPC80) substitution of prime fish meal (FM) with soy protein concentrate (SPC) were evaluated against a commercial type control feed with 35 % FM replacement with SPC. Increases in dietary SPC were combined with appropriate increases in methionine, lysine and threonine supplementation, whereas added phosphorus was constant among treatments. Diets were administered to quadruplicate groups of 29 g juvenile Atlantic salmon were exposed to constant light, for 97 days. On Day 63 salmon were subjected to vaccination. Significant weight reductions in SPC65 and SPC80 compared with SPC35 salmon were observed by Day 97. Linear reductions in body cross-sectional ash, Ca/P ratios, and Ca, P, Mn and Zn were observed at Days 63 (prior vaccination) and 97 (34 days post-vaccination), while Mg presented a decrease at Day 63, in salmon fed increasing dietary SPC. Significant reductions in Zn, Ca, P and Ca/P ratios persisted in SPC65 and SPC80 compared with SPC35 salmon at Day 97. Significant haematocrit reductions in SPC50, SPC65 and SPC80 salmon were observed at Days 63, 70 and 97. Enhanced plasma haemolytic activity, increased total IgM, and a rise in thrombocytes were demonstrated in SPC50 and SPC65 salmon on Day 97, while increased lysozyme activity was demonstrated for these groups on Days 63, 70 and 97. Leucocyte and lymphocyte counts revealed enhanced immunostimulation in salmon fed with increasing dietary SPC at Day 97. High SPC inclusion diets did not compromise the immune responses of salmon, while SPC50 diet also supported good growth without compromising elemental concentrations.

Adrenocorticotrophic hormone-stimulated cortisol release by the head kidney inter-renal tissue from sea bream (Sparus aurata) fed with linseed oil and soyabean oil.

The mode of action of highly unsaturated fatty acids (HUFA) in regulating gilthead sea bream (Sparus aurata) head kidney (HK) cortisol production was studied through in vitro trials using a dynamic superfusion system. Fish were previously fed with different diets containing several inclusion levels of linseed oil (LO) or soyabean oil (SO) for 26 weeks. Five diets were tested; anchovy oil was the only lipid source for the control diet (fish oil, FO) and two different substitution levels (70 and 100 %) were tested using either LO or SO (70LO, 70SO, 100LO and 100SO). Fatty acid compositions of the HK reflected the dietary input, thus EPA, DHA, arachidonic acid and n-3 HUFA were significantly (P < 0·05) reduced in fish fed vegetable oils compared with fish fed the FO diet. Feeding 70 or 100 % LO increased significantly (P < 0·05) cortisol release in HK after stimulation with adrenocorticotrophic hormone (ACTH), while feeding SO had no effect on this response. Cortisol stimulation factor (SF) was increased in fish fed the 70LO and 100LO diets compared with fish fed the control diet. Moreover, eicosanoid inhibition by incubating the HK tissue with indomethacin (INDO) as a cyclo-oxygenase (COX) inhibitor, or nordihydroguaiaretic acid (NDGA) as a lipoxygenase (LOX) inhibitor, significantly reduced (P < 0·05) the cortisol release after ACTH stimulation in the 70LO and 100LO diets. Cortisol SF was reduced in the FO, 70LO and 100LO diets when incubating the HK with INDO or NDGA, while it was increased in the 70SO diet. The present results indicate that changing the fatty acid profile of gilthead sea bream HK by including LO and/or SO in the fish diet affected the in vitro cortisol release, and this effect is partly mediated by COX and/or LOX metabolites.

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.

Effect of dietary lipids on plasma fatty acid profiles and prostaglandin and leptin production in gilthead seabream (Sparus aurata).

The aim of this study was to investigate the effects of different levels of substitution of fish oil by vegetable oils rich in oleic, linoleic and linolenic acids on gilthead seabream plasma and leukocyte fatty acid compositions and prostaglandin (PG) and leptin production. Juvenile seabream of 24 g initial body mass were fed four iso-energetic and iso-proteic experimental diets for 281 days. Fatty acid composition of plasma lipids was markedly affected by the inclusion of vegetable oils (VO). ARA (arachidonate), EPA (eicosapentaenoate) and DHA (docosahexaenoate) were preferentially incorporated into polar lipids of plasma, and DHGLA (di-homogammalinoleate) accumulated with increased vegetable oil inclusion. Dietary treatments resulted in alterations of DHGLA/ARA ratios, but not ARA/EPA. ARA-derived PGE(2) production in plasma was not affected by vegetable oils, in agreement with similar eicosanoid precursor ratio (ARA/EPA) in leukocytes total lipids and plasma phospholipids among fish fed with the different dietary treatments. Feeding vegetable oils leads to a decrease in plasma EPA which in turn reduced plasma PGE(3) concentration. Moreover, PGE(3) was the major prostaglandin produced in plasma of fish fed fish oil based diet. Such findings point out the importance of EPA as a precursor of prostaglandins in marine fish, at least for the correct function of the blood cells, and correlates well with the predominant role of this fatty acid in immune regulation in this species. A negative correlation was found between plasma PGE(2) and leptin plasma concentration, suggesting that circulating levels of leptin may act as a metabolic signal modulating PGE(2) release. The present study has shown that increased inclusion of vegetable oils in diet for gilthead seabream may profoundly affect the fatty acid composition of plasma and leukocytes, specially HUFA (highly unsaturated fatty acids), and consequently the production of PGE(3), which can be a major PG in plasma. Alteration in the amount and type of PG produced can be at least partially responsible for the changes in the immune system and health parameters of fish fed diets with high inclusion of VO.

Essential fatty acids and phospholipase A2 in autistic spectrum disorders.

A health questionnaire based on parental observations of clinical signs of fatty acid deficiency (FAD) showed that patients with autism and Asperger's syndrome (ASP) had significantly higher FAD scores (6.34+/-4.37 and 7.64+/-6.20, respectively) compared to controls (1.78+/-1.68). Patients with regressive autism had significantly higher percentages of 18:0,18:2n-6 and total saturates in their RBC membranes compared to controls, while 24:0, 22:5n-6, 24:1 and the 20:4n-6/20:5n-3 ratio were significantly higher in both regressive autism and ASP groups compared to controls. By comparison, the 18:1n-9 and 20:4n-6 values were significantly lower in patients with regressive autism compared to controls while 22:5n-3, total n-3 and total dimethyl acetals were significantly lower in both regressive autism and ASP groups compared to controls. Storage of RBC at -20 degrees C for 6 weeks resulted in significant reductions in highly unsaturated fatty acid levels in polar lipids of patients with regressive autism, compared to patients with classical autism or ASP, or controls. Patients diagnosed with both autism and ASP showed significantly increased levels of EPA ( approximately 200%) and DHA ( approximately 40%), and significantly reduced levels of ARA ( approximately 20%), 20:3n-6 and ARA/EPA ratio in their RBC polar lipids, when supplemented with EPA-rich fish oils, compared to controls and non-supplemented patients with autism. Patients with both regressive autism and classical autism/Asperger's syndrome had significantly higher concentrations of RBC type IV phospholipase A2 compared to controls. However, patients with autism/ASP, who had taken EPA supplements, had significantly reduced PLA2 concentrations compared to unsupplemented patients with classical autism or ASP.

Hepatocyte fatty acid desaturation and polyunsaturated fatty acid composition of liver in salmonids: effects of dietary vegetable oil.

The desaturation and elongation of [1-(14)C]18:3n-3 was investigated in hepatocytes from different populations and three different species of salmonids indigenous to Scotland, brown trout, Atlantic salmon and Arctic charr. Two groups of fish were sampled, before and after they were fed two experimental diets, a control diet containing fish oil and a diet containing vegetable oil (a 1:1 blend of linseed and rapeseed oils) for 12 weeks. At each sampling time, fatty acyl desaturation and elongation activity was determined in isolated hepatocytes, and samples of liver were also collected for lipid compositional analysis. At the initiation of the dietary trial, the liver polar-lipid fatty acid compositions of salmon and brown trout were very similar to each other, and the two charr populations were similar to each other, having lower total n-3 polyunsaturated fatty acids (PUFA) and 22:6n-3, but higher 20:5n-3 than the other salmonids. Initially, hepatocyte desaturation activity varied, with the highest activity in brown trout, followed by salmon and then charr. Production of 20:5n-3 was particularly high in brown trout. Desaturation of [1-(14)C]18:3n-3 was significantly greater in all fish fed the diet containing vegetable oil compared to fish fed the diet containing fish oil. The increase in activity was less in brown trout compared to the other groups of fish. Feeding the vegetable oil diet increased the levels of 18:2n-6, 20:3n-6, total n-6 PUFA, 18:3n-3, 18:4n-3, 20:3n-3 and 20:4n-3, and decreased 22:6n-3 and the n-3/n-6 ratio in salmon and brown trout. By contrast, in charr fed the vegetable oil diet, there was no increase in 18:3n-3, 18:4n-3, 20:3n-3 or 20:4n-3 in liver polar lipids and the level of 22:6n-3 was not decreased. In addition, there was only a modest increase in the levels of 18:2n-6 and total n-6 PUFA, and so the n-3/n-6 ratio was only slightly decreased. The percentage of 20:4n-6, which was not increased in salmon and brown trout fed vegetable oil, was increased in charr fed the vegetable oil diet. Overall, the results indicated that there were significant differences in liver PUFA metabolism between Arctic charr and the other salmonids, which could have important consequences, both physiologically and in their ability to be successfully cultured on diets containing vegetable oils.

Replacement of fish oil with rapeseed oil in diets of Atlantic salmon (Salmo salar) affects tissue lipid compositions and hepatocyte fatty acid metabolism.

Duplicate groups of Atlantic salmon post-smolts were fed five practical-type diets in which the added lipid was 100% fish oil [FO; 0% rapeseed oil (0% RO)], 90% FO + 10% RO (10% RO), 75% FO + 25% RO (25% RO), 50% FO + 50% RO (50% RO) or 100% RO, for a period of 17 wk. There were no effects of diet on growth rate or feed conversion nor were any histopathological lesions found in liver, heart, muscle or kidney. The greatest accumulation of muscle lipid was in fish fed 0% RO, which corresponded to significantly lower muscle protein in this group. The highest lipid levels in liver were found in fish fed 100% RO. Fatty acid compositions of muscle lipid correlated with RO inclusion in that the proportions of 18:1(n-9), 18:2(n-6) and 18:3(n-3) all increased with increasing dietary RO (r = 0.98-1.00, P < 0.013). The concentrations of eicosapentaenoic acid [20:5(n-3)] and docosahexaenoic acid [22:6(n-3)] in muscle lipid were significantly reduced (P < 0.05), along with total saturated fatty acids, with increasing dietary RO. Diet-induced changes in liver fatty acid compositions were broadly similar to those in muscle. Hepatic fatty acid desaturation and elongation activities, measured using [1-(14)C] 18:3(n-3), were increased with increasing dietary RO. Limited supplies of marine fish oils require that substitutes be found if growth in aquaculture is to be maintained such that fish health and product quality are not compromised. Thus, RO can be used successfully as a substitute for fish oil in the culture of Atlantic salmon in sea water although at levels of RO >50% of dietary lipid, substantial reductions occur in muscle 20:5(n-3), 22:6(n-3) and the (n-3)/(n-6) polyunsaturated fatty acid (PUFA) ratio, which will result in reduced availability of the (n-3) highly unsaturated fatty acids that are beneficial for human health.

Red blood cell fatty acid compositions in a patient with autistic spectrum disorder: a characteristic abnormality in neurodevelopmental disorders?

The fatty acid compositions of red blood cell (RBC) phospholipids from a patient with autistic spectrum disorder (ASD) had reduced percentages of highly unsaturated fatty acids (HUFA) compared to control samples. The percentage of HUFA in the RBC from the autistic patient was dramatically reduced (up to 70%) when the sample was stored for 6 weeks at -20 degrees C. However, only minor HUFA reductions were recorded in control samples stored similarly, or when the autistic sample was stored at -80 degrees C. A similar instability in RBC HUFA compositions upon storage at -20 degrees C has been recorded in schizophrenic patients. In a number of other neurodevelopmental conditions, including attention deficit hyperactivity disorder (ADHD) and dyslexia, reduced concentrations of RBC HUFA have been recorded. The extent and nature of these aberrations require further assessment to determine a possible common biochemical origin of neurodevelopmental disorders in general. To facilitate this, a large scale assessment of RBC fatty acid compositions in patients with ASD, and related disorders, should be performed as a matter of urgency. Supplementing cells in culture with the tryptophan metabolite indole acrylic acid (IAA) affected the levels of cellular HUFA and prostaglandin production. Indole acroyl glycine (IAG), a metabolite of IAA excreted in urine, is found in high concentrations in patients with neurodevelopmental disorders including ASD, ADHD, dyslexia, Asperger's syndrome and obsessive compulsive disorder.

Dietary n-3 long-chain polyunsaturated fatty acid deprivation, tissue lipid composition, ex vivo prostaglandin production, and stress tolerance in juvenile Dover sole (Solea solea L.).

Larval Dover sole fed an Artemia diet supplemented with n-3 long-chain (C20 + C22) polyunsaturated fatty acids (PUFA) are known to be more resistant to low-temperature injury. Here we explore the relationship between tissue fatty acid composition and tolerance of stressful environmental conditions over the larval and early juvenile periods. Artemia nauplii supplemented with n-3 long-chain PUFA-deficient and PUFA-enriched oil emulsions were fed to two groups of larvae. Whole body tissue samples from the resulting PUFA-deficient and -enriched juveniles possessed 12.1 and 21.9% n-3 long-chain PUFA, respectively. These differences were at the expense of C18 PUFA, while proportions of saturated fatty acids, monounsaturated fatty acids, and total PUFA were unaffected. Brain and eye tissues from the PUFA-deficient fish contained lower levels of 22:6n-3, known to be important for optimal nervous system function, incorporating instead a range of fatty acids of lower unsaturation. PUFA-deprived juveniles showed substantially greater mortality when exposed to a combination of low temperature and low salinity, as well as to high temperature and to hypoxia. After adaptation to the different diets, both dietary groups were fed a common formulated feed high in n-3 long-chain PUFA. Tissue PUFA in both groups progressively increased to the same high value, with a consequent loss of the differences in cold-susceptibility. These correlated changes support a link between dietary manipulation of n-3 long-chain PUFA and development of a stress-sensitive phenotype. PUFA deprivation had no detectable effect upon static hydrocarbon order of purified brain membranes (as assessed by fluorescence polarization) but was associated with an increase in the whole-body content of prostaglandins. We conclude that susceptibility to environmental stress is responsive to dietary n-3 long-chain PUFA manipulation, possibly due to altered tissue development or the overproduction of eicosanoids.

Depletion of alpha-tocopherol and astaxanthin in Atlantic salmon (Salmo salar) affects autoxidative defense and fatty acid metabolism.

Duplicate groups of Atlantic salmon post-smolts were fed four purified diets supplemented with both vitamin E and the carotenoid astaxanthin (Ax) (+E, +Ax), or supplemented with either vitamin E or Ax (-E, +Ax and +E, -Ax) or deficient in both vitamin E and Ax (-E, -Ax) for 22 wk. There were no effects of diet on growth rate, but an extensive lipoid liver degenerative lesion was observed in 15% of fish fed diets deficient in vitamin E. Tissue vitamin E concentrations varied in accordance with dietary vitamin E in liver, muscle, heart, plasma, brain and eye; levels were reduced to approximately 3% in liver but only to 40% in eye of fish fed diets deficient in vitamin E compared with those fed diets supplemented with vitamin E. An interactive sparing of Ax supplementation on tissue vitamin E concentration was observed, but only in brain. Dietary deficiency of both vitamin E and Ax significantly increased the recovery of desaturated and elongated products of both [1-(14)C] 18:3(n-3) and [1-(14)C] 20:5(n-3) in isolated hepatocytes, suggesting that conversion of fatty acids to their long-chain highly unsaturated products can be stimulated by a deficiency of lipid-soluble antioxidants. The antioxidant synergism of vitamin E and Ax was supported by their ability to reduce malondialdehyde formation in an in vitro stimulation of microsomal lipid peroxidation and to reduce plasma levels of 8-isoprostane. The results of this study suggest that both vitamin E and the carotenoid Ax have antioxidant functions in Atlantic salmon.

Growth, mortality, tissue histopathology and fatty acid compositions, eicosanoid production and response to stress, in juvenile turbot fed diets rich in gamma-linolenic acid in combination with eicosapentaenoic acid or docosahexaenoic acid.

Three diets containing either borage oil (BO) and southern hemisphere fish oil Marinol (MO), or BO and tuna orbital oil (TO), or a northern hemisphere fish oil (FO) were fed to duplicate groups of turbot (Scophthalmus maximus) of initial mean weight 1.2 g for a period of 12 weeks. The BO/MO and BO/TO diets were enriched in gamma-linolenic (18:3n-6, GLA) and eicosapentaenoic (20:5n-3, EPA) acids, and GLA and docosahexaenoic acid (22:6n-3, DHA), respectively. No differences were observed in final weights or growth rates, either between duplicate tanks or between dietary treatments. Half of the FO-fed fish sampled showed a histopathological lesion indicative of lipoid liver degeneration while the other treatments only showed a slight incidence of the same pathology. The fatty acid compositions of carcass and tissues broadly reflected the dietary input. In general, fish fed the BO/MO diet had increased levels of 18:2n-6, 18:3n-6, 20:3n-6 and 20:5n-3, but a lower level of 22:6n-3, compared to fish fed FO. In fish fed the BO/TO diet, levels of 18:2n-6, 18:3n-6, 20:3n-6 and 20:4n-6 were increased while levels of 20:5n-3 and 22:5n-3 were reduced, compared to fish fed FO. Concentrations of thromboxanes B (TXB) and leukotrienes B (LTB), derived from 20:4n-6 and 20:5n-3, were measured in plasma and stimulated blood cells. Levels of TXB2 were greatest in fish fed the BO/TO diet compared to both other treatments, while LTB4 was decreased in fish fed the BO/MO diet compared to both other treatments. In a stress test which involved anaesthesia followed by measurement of recovery times, fish fed the BO/MO diet had significantly lower recovery times compared to fish fed the FO diet.

Effects of dietary gamma-linolenic acid-rich borage oil combined with marine fish oils on tissue phospholipid fatty acid composition and production of prostaglandins E and F of the 1-, 2- and 3-series in a marine fish deficient in delta5 fatty acyl desaturase.

The effects of gamma-linolenic acid-rich borage oil (BO), in combination with different marine oils, namely an eicosapentaenoic acid (EPA) rich oil (MO) or a DHA-rich oil (TO), on tissue fatty acid composition and prostaglandin production were investigated in turbot, a species which lacks appreciable delta5 fatty acyl desaturase activity. The juvenile turbot grew well on the experimental diets and there were no significant differences in final weights between dietary treatments. Irrespective of the marine oil component, both the BO-containing diets increased tissue phospholipid levels of 18:2n-6 and 18:3n-6, and their respective elongation products, 20:2n-6 and 20:3n-6, compared to fish fed a control diet containing a standard Northern hemisphere fish oil. Both the BO-containing diets increased the production of 1-series prostaglandins (PG), this being observed across all tissues investigated with PGF and especially PGE. The BO/MO diet also reduced 20:4n-6 in tissue phospholipids without affecting 20:5n-3, whereas the BO/TO combination decreased 20:5n-3 but increased 20:4n-6. The production of 2-series and 3-series PGs was also altered by the dietary treatments but the changes were less dependent upon the tissue levels of their respective precursor fatty acids, 20:4n-6 and 20:5n-3. The BO-containing diets had very significant effects on gross fatty acid compositions of the phospholipids including increased proportions of saturated fatty acids and n-6 polyunsaturated fatty acids (PUFA) and decreased proportions of monounsaturated fatty acids and n-3 PUFA. Overall, this study shows that eicosanoid production in turbot tissues can be influenced by dietary fatty acids, not only by changes in the absolute and relative levels of specific eicosanoid precursor PUFA in tissue phospholipids, but also by general effects on membrane composition, structure and function induced by gross fatty acid compositional changes.

Fatty acid composition, eicosanoid production and permeability in skin tissues of rainbow trout (Oncorhynchus mykiss) fed a control or an essential fatty acid deficient diet.

Rainbow trout (Oncorhynchus mykiss) were fed either a control diet containing fish oil or an essential fatty acid (EFA) deficient diet containing only hydrogenated coconut oil and palmitic acid as lipid source (93.4% saturated fatty acids) for 14 weeks and the fatty acid compositions of individual phospholipid classes from skin and opercular membrane (OM) determined. The permeability of skin and OM to water and the production of eicosanoids in skin and gills challenged with the Ca2+ ionophore A23187 were also measured. Phospholipid (PL) fatty acid compositions were substantially modified in EFA-deficient fish, with increased saturated fatty acids and decreased polyunsaturated fatty acids (PUFA), especially arachidonic acid (AA) and eicosapentaenoic acid (EPA), while docosahexaenoic acid (DHA) was largely retained. The onset of EFA deficiency was shown by the appearance of n-9 PUFA, particularly 20:3n-9. The main effects of EFA deficiency on phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were to increase saturated fatty acids and monoenes, especially 16:1 and 18:1, and to decrease EPA and DHA. The content of DHA in phosphatidylserine (PS) was high in control animals (40% in skin and 35% in opercular membrane) and was mostly retained in EFA deficient animals. Arachidonic acid (AA) was the most abundant PUFA esterified to phosphatidylinositol (PI) and was significantly reduced in EFA deficient animals (from 31% to 13% in skin), where a large amount of 20:3n-9 (9% in skin) was also present. Influxes and effluxes of water through skin and opercular membrane were measured in vitro. No differences were detected between rainbow trout fed the control or the EFA deficient diet. 12-Hydroxyeicosatetraenoic acid (12-HETE), 12-hydroxyeicosapentaenoic acid (12-HEPE) and 14-hydroxydocosahexaenoic acid (14-HDHE) could not be detected in skin from control or EFA deficient fish. There was no difference between control and EFA deficient trout in the levels of leukotriene C4 (LTC4) and leukotriene C5 (LTC5) in skin cells challenged with the calcium ionophore A23187, and of prostaglandin F2alpha (PGF2alpha), 12-HETE and 12-HEPE in gill cells challenged similarly. Prostaglandin F3alpha (PGF3alpha) production by ionophore stimulated gill cells was significantly reduced in fish fed the EFA-deficient diet. 14-HDHE produced by gill cells was 3.3 fold higher in EFA deficient fish compared to controls.

The effect of dietary lipid on polyunsaturated fatty acid metabolism in Atlantic salmon (Salmo salar) undergoing parr-smolt transformation.

The aim of this study was to measure the changes in lipid metabolism which occur during smoltification and seawater transfer in Atlantic salmon (Salmo salar). Duplicate groups of Atlantic salmon parr were fed diets containing either fish oil (FO) or a blend of linseed and rapeseed oils, vegetable oil (VO), from October (week 0) to seawater transfer in May (week 26). From May to August (weeks 26-43), all fish were fed a fish oil-containing diet. Fatty acyl desaturation and elongation activity were followed in isolated hepatocytes incubated with radioactive 18:3n-3 and 18:2n-6. Metabolism of 18:3n-3 was consistently around 5-fold greater than metabolism of 18:2n-6, and total metabolism of both substrate polyunsaturated fatty acids (PUFA) was increased in fish fed both VO and FO up to seawater transfer after which desaturation activities were reduced. Desaturation activities with both 18:3n-3 and 18:2n-6 were significantly greater in fish fed VO, compared to fish fed FO, at 22 and 26 wk. Arachidonic acid (20:4n-6; AA) in liver polar lipids (PL) of fish fed VO increased consistently from weeks 0-22 but varied after seawater transfer. In fish fed FO, AA in liver PL remained constant up to week 17 before increasing at seawater transfer and leveling off thereafter. Eicosapentaenoic acid (20:5n-3; EPA) in liver PL of fish fed VO decreased significantly from week 0-22 before rising at seawater transfer and increasing rapidly posttransfer. EPA in liver PL of fish fed FO showed a similar trend except EPA was always greater in the freshwater phase compared to fish fed VO. Docosahexaenoic acid (DHA) levels in liver PL of fish fed VO remained constant in the seawater phase before increasing following seawater transfer. In fish fed FO, DHA in liver PL increased from weeks 0-17 reducing and leveling off postseawater transfer. The levels of PGF(2 alpha) and PGF(3 alpha) were measured in isolated gill cells stimulated with calcium ionophore A23187. PGF(2 alpha) production in fish fed VO increased significantly between 0-7 wk before decreasing toward seawater transfer. After transfer, PGF(2 alpha), production increased to a peak at 35 wk. PGF(2 alpha) production in fish fed FO was not significantly altered during the trial period. The changes in PGF(3 alpha) production were broadly similar to those occurring with PGF(2 alpha), but the latter was always in excess of the former (2- to 4-fold). Plasma chloride concentrations in fish subjected to seawater challenge at 20 wk were significantly lower in fish fed VO compared to those fed FO. This study has provided new information on the changes in lipid metabolism which accompany parr-smolt transformation and suggests that diets which have a fatty acid composition more similar to that in aquatic invertebrates may be beneficial in effecting successful seawater adaptation.

Fatty acyl desaturation in isolated hepatocytes from Atlantic salmon (Salmo salar): stimulation by dietary borage oil containing gamma-linolenic acid.

The effects of different dietary oils on the fatty acid compositions of liver phospholipids and the desaturation and elongation or [1-14C]18:3n-3 and [1-14C]18:2n-6 were investigated in isolated hepatocytes from Atlantic salmon. Atlantic salmon smolts were fed diets containing either a standard fish oil (FO) as a control diet, a 1:1 blend of Southern Hemisphere marine oil and tuna orbital oil (MO/TO), sunflower oil (SO), borage oil (BO), or olive oil (OO) for 12 wk. The SO and BO diets significantly increased the percentages of 18:2n-6, 18:3n-6, 20:2n-6, 20:3n-6, and total n-6 polyunsaturated fatty acids (PUFA) in salmon liver lipids in comparison with the FO diet. The BO diet also increased the percentage of 20:4n-6. Both the SO and BO diets significantly reduced the percentages of all n-3 PUFA in comparison with the FO diet. The OO diet significantly increased the percentages of 18:1n-3, 18:2n-6, total monoenes, and total n-6 PUFA in liver lipids compared to the FO diet, and the percentages of all n-3 PUFA were significantly reduced. With [1-14C]18:3n-3, the recovery of radioactivity in the products of delta 6 desaturation was significantly greater in the hepatocytes from salmon fed SO, BO, and OO in comparison with the FO diet. The BO diet also increased the recovery of radioactivity in the products of delta 5 desaturation. Only the BO diet significantly affected the desaturation of [1-14C]18:2n-6, increasing recovery of radioactivity in both delta 6- and delta 5-desaturation products. In conclusion, dietary BO, enriched in gamma-linolenic acid (18:3n-6), significantly increased the proportions of both 20:3n-6 and 20:4n-6 in salmon liver phospholipids and also significantly increased the desaturation of both 18:2n-6 and 18:3n-3 in salmon hepatocytes. The possible relationships between dietary fatty acid composition, tissue phospholipid fatty acid composition, and desaturation/elongation activities are discussed.

Modification of membrane fatty acid composition, eicosanoid production, and phospholipase A activity in Atlantic salmon (Salmo salar) gill and kidney by dietary lipid.

Atlantic salmon post-smolts were fed diets containing either fish oils (Fosol, FO and Marinol, MO) rich in long-chain n-3 polyunsaturated fatty acids (PUFA), or plant oils rich in 18:2n-6 (sunflower oil, SO) or 18:3n-3 (linseed oil, LO) for 12 wk. The major PUFA in individual phospholipids from gill and kidney were related to the dietary lipid intake. Levels of n-6 PUFA were highest while levels of n-3 PUFA were lowest in fish fed SO. Fish fed LO generally had lower levels of 20:4n-6 compared to the other treatments while fish fed SO generally had the highest levels of 20:4n-6. In all phospholipid classes except phosphatidylinositol (PI) 20:5n-3 was greatest in fish fed MO followed by FO, LO, and SO. In PI, 20:5n-3 was also highest in fish fed MO but those fed LO contained more 20:5n-3 than those fed FO. This resulted in the ratio of the eicosanoid precursors, 20:4n-6/20:5n-3, being significantly greater in fish fed SO, for all phospholipid classes, compared to fish fed the other three dietary oils. The activity of gill phospholipase A was greatest in fish fed FO and was lowest in fish fed SO. The concentration of PGF3 alpha was significantly increased in gill homogenates from fish fed MO compared to the other three treatments while PGF2 alpha was significantly increased in fish fed SO compared to those fed LO. The concentration of PGE3 was significantly reduced in kidney homogenates from fish fed SO compared to the other three treatments while PGE2 was significantly increased in fish fed SO compared to those fed either FO or LO.

Production of eicosanoids derived from 20:4n-6 and 20:5n-3 in primary cultures of turbot (Scophthalmus maximus) brain astrocytes in response to platelet activating factor, substance P and interleukin-1 beta.

Primary cultures of turbot (Scophthalmus maximus) brain astroglial cells established in medium containing fetal bovine serum contain increased proportions of 18:1(n-9), total (n-9) and (n-6) polyunsaturated fatty acids (PUFA) and greatly reduced (n-3) PUFA in comparison with turbot brain. Supplementation with a mixture of 5 microM eicosapentaenoic [20:5(n-3)] and 25 microM docosahexaenoic [22:6(n-3)] acids for 4 days significantly increased the percentages of these acids in total cellular lipid of turbot astrocytes and restored the (n-3) PUFA composition of the cells to that found in turbot brain. The production of prostaglandins (PG) E and F of the 2- and 3-series and leukotrienes (LT) C4 and C5 in response to various agonists was determined in PUFA-supplemented astrocytes. Calcium ionophore A23187, platelet activating factor and substance P stimulated the production of both PGF and PGE. Interleukin-1 beta significantly stimulated the production of PGF only. There were differences between the agonists in their effects on the relative levels of 2- and 3-series PGs produced. Only very low amounts of LTC were produced by the turbot astrocytes, with only substance P showing a minor stimulatory effect.

Dietary lipid affects phospholipid fatty acid compositions, eicosanoid production and immune function in Atlantic salmon (Salmo salar).

Atlantic salmon (Salmo salar) post-smolts were fed diets containing either Fosol (FO), a North Sea fish oil, sunflower oil (SO), linseed oil (LO) or Marinol K (MO), a southern hemisphere fish oil rich in 20:5(n-3) for 12 weeks. A macrophage-enriched leucocyte preparation was obtained from head kidney and the fatty acid compositions of the individual membrane phospholipids measured. In general phospholipids from SO- and LO-fed fish had increased 18:2(n-6), 20:2(n-6) and 20:3(n-6) compared to the fish oil treatments while LO-fed fish had lower 20:4(n-6) than any other dietary treatment. Fish fed LO also had increased 18:3(n-3), 18:4(n-3), 20:3(n-3) and 20:4(n-3). The 20:5(n-3) content of kidney macrophage-enriched leucocyte phospholipids was highest in MO-fed fish followed by FO- and LO-fed fish with the lowest level in fish fed SO. The overall effect on the ratio of eicosanoid precursors, 20:4/20:5, showed the highest value in SO-fed fish and the lowest in fish fed LO. Production of LTB5 by kidney macrophage-enriched leucocytes stimulated with A23187 was highest in MO-fed fish and lowest in those fed SO. Production of LTB4 was greatest in SO-fed fish and lowest in fish fed LO. Serum Ig levels were significantly affected by dietary treatment with highest values in fish fed FO and SO and lowest in fish fed MO and LO.

Polyunsaturated fatty acid composition of the salmon (Salmo salar L.) pineal organ: modification by diet and effect on prostaglandin production.

To examine the influence of dietary polyunsaturated fatty acids (PUFA) on the lipid composition of the pineal organ and its production of prostaglandins, Atlantic salmon were fed diets containing either fish oils rich in long-chain n-3 polyunsaturated fatty acids, or plant oils with high levels of 18:2(n-6) (sunflower oil) or 18:3(n-3) (linseed oil) for 12 weeks. Lipid content and lipid class composition of the pineal organ were not greatly influenced by the type of oil fed to the fish: choline phosphoglycerides were always the predominant lipid class and the proportion of polar lipids exceeded that of neutral lipids. The pattern of PUFA present in total lipid and individual lipid classes was, however, related to that of the dietary oil. The major PUFA in pineal total lipid from all four dietary groups was 22:6(n-3) and the proportion of n-6 PUFA present was highest in lipid from salmon fed sunflower oil. Both PGE and PGF analogues of the 2- and 3-series were detected in pineal homogenates from all dietary groups with the former prostaglandin being the most abundant. The ratio of PGE2/PGE3 was greatest in fish fed sunflower oil and lowest in those fed linseed oil. The results provide further evidence that despite its anatomical location the pineal organ resembles non-neural tissues more than brain in terms of lipid composition and prostaglandin production.