Dietary fish oil dose-response effects on ileal phospholipid fatty acids and contractility

We have reported that dietary fish oil (FO) leads to the incorporation of long-chain n−3 PUFA into the gut tissue of small animal models, affecting contractility, particularly of rat ileum. This study examined the FO dose response for the incorporation of n−3 PUFA into ileal tissue and how this correlated with in vitro contractility. Groups of ten to twelve 13-wk-old Wistar-Kyoto rats were fed 0, 1, 2.5, and 5% FO-supplemented diets balanced with sunflower seed oil for 4 wk, after which ileal total phospholipid FA were determined and in vitro contractility assessed. For the total phospholipid fraction, increasing the dietary FO levels led to a significant increase first evident at 1% FO, with a stepwise, nonsaturating six-fold increase in n−3 PUFA as EPA (20∶5n−3), DPA (docosapentaenoic acid, 22∶5n−3), and DHA, but mainly as DHA (22∶6n−3), replacing the n−6 PUFA linoleic acid (18∶2n−6) and arachidonic acid (20∶4n−6) over the dosage range. There was no difference in KCl-induced depolarization-driven contractility. However, a significant increase in receptor-dependent maximal contractility occurred at 1% FO for carbachol and at 2.5% FO for prostaglandin E₂, with a concomitant increase in sensitivity for prostaglandin E₂ at 2.5 and 5% FO. These results demonstrate that significant increases in ileal membrane n−3 PUFA occurred at relatively low doses of dietary FO, with differential receptor-dependent increases in contractility observed for muscarinic and prostanoid agonists.     

Tropical Vegetable Oils Do Not Alter Growth Performance in African Catfish through a High n-6 Polyunsaturated Fatty Acids Biosynthesis Capacity

The main objective of this study was to determine the best vegetable oils (VO) for nutrition of African catfish by assessing the effects of a complete replacement of fish oil (FO) by different VO sources on its growth performance, fatty acid composition, and elongase-desaturase gene expression levels. Fish (16.2 g of initial body weight) were fed with five experimental isonitrogenous, isolipidic, and isoenergetic diets in which FO was totally replaced by cottonseed oil (CO), palm oil (PO), desert date oil (DO), or Shea butter (SB). Complete replacement of FO with VO did not affect growth performance except for low values in fish fed SB diet. Muscle n-3 LC-polyunsaturated fatty acids (PUFA) were significantly reduced in fish fed VO-based diets when compared with FO fed fish. However, the muscle arachidinic acid (ARA) levels in phospholipid class were 1.4 to 1.6 times higher in fish fed CO and DO diets than FO fed fish despite the lower ARA suppliers from these VO-based diets, suggesting endogenous LC-PUFA biosynthesis from PUFA precursors in fish fed these VO. The fads2 and elovl5 gene expression levels in liver of fish fed DO were also higher compared to FO controls. Therefore, all the results support the hypothesis that African catfish has higher biosynthesis capacity to convert vegetable n-6 PUFA precursors like linoleic acid (LNA, 18:2n-6) into n-6 LC-PUFA of the ARA type, compared to the conversion of vegetable α-linolenic acid (ALA, 18:3n-3) into n-3 LC-PUFA of the eicosapentanoic acid (EPA) or docosahexanoic acid (DHA) type. The results also indicate that DO can be recommended as the best alternative to FO replacement in African catfish nutrition.     

Dietary fish oil dose- and time-response effects on cardiac phospholipid fatty acid composition

Fish consumption is associated with reduced cardiovascular mortality, and elevated myocardial long-chain n−3 polyunsaturated FA (PUFA) content is implicated in this cardioprotection. This study examined the dose and time responses for incorporation of n−3 PUFA into cellular membranes in rats fed fish oil (FO)-containing diets. For the time course study, rats were fed a 10% FO diet for periods ranging from 0 to 42 d, after which myocardial and erythrocyte membrane fatty acid composition was determined. For the dose response study, rats (n=3) were fed 0, 1.25, 2.5, 5, or 10% FO for 4 wk, with myocardial, erythrocyte, and skeletal muscle membrane FA determined. Myocardial DHA (22∶6n−3) levels doubled in 2 d, stabilizing at levels ≈200% higher than control after 28 d feeding with 10% FO. By comparison, DHA levels doubled after 4 wk of 1.25% FO feeding. In myocardium and skeletal muscle, EPA (20∶5n−3) levels remained low, but in erythrocytes EPA levels reached 50% of DHA levels. The n−3 PUFA were incorporated at the expense of n−6 PUFA in myocardium and skeletal muscle, whereas erythrocytes maintained arachidonic acid levels, and total n−3 PUFA incorporation was lower. This study shows that low doses of FO produce marked changes in myocardial DHA levels; maximal incorporation takes up to 28 d to occur; and while erythrocytes are a good indicator of tissue n−3 incorporation in stable diets, they vary greatly in their time course and pattern of incorporation.     

Replacement of Dietary Fish Oils by Alpha-Linolenic Acid-Rich Oils Lowers Omega 3 Content in Tilapia Flesh

A 20-week feeding trial was conducted to determine whether increasing linolenic acid (18:3n-3) in vegetable oil (VO) based diets would lead to increased tissue deposition of 22:6n-3 in Nile tilapia (Oreochromis niloticus). Five isonitrogenous and isoenergetic diets were supplemented with 3% of either linseed oil (LO), a mixture of linseed oil with refined palm olein oil (PO) (LO–PO 2:1) and a mixture of refined palm olein oil with linseed oil (PO–LO 3:2) or with fish oil (FO) or corn oil (CO) as controls. The PO–LO, LO–PO and LO diets supplied a similar amount of 18:2n-6 (0.5% of diet by dry weight) and 0.5, 0.7 and 1.1% of 18:3n-3, respectively. Increased dietary 18:3n-3 caused commensurate increases in longer-chain n-3 PUFA and decreases in longer-chain n-6 PUFA in the muscle lipids of tilapia. However, the biosynthetic activities of fish fed the LO-based diets were not sufficient to raise the tissue concentrations of 20:5n-3, 22:5n-3 and 22:6n-3 to those of fish fed FO. The study suggests that tilapia (O. niloticus) has a limited capacity to synthesise 20:5n-3 and 22:6n-3 from dietary 18:3n-3. The replacement of FO in the diet of farmed tilapia with vegetable oils could therefore lower tissue concentrations of 20:5n-3 and 22:6n-3, and consequently produce an aquaculture product of lower lipid nutritional value for the consumer.     

Changes in Tissue Lipid and Fatty Acid Composition of Farmed Rainbow Trout in Response to Dietary Camelina Oil as a Replacement of Fish Oil

Camelina oil (CO) replaced 50 and 100 % of fish oil (FO) in diets for farmed rainbow trout (initial weight 44 ± 3 g fish^?1). The oilseed is particularly unique due to its high lipid content (40 %) and high amount of 18:3n‐3 (α‐linolenic acid, ALA) (30 %). Replacing 100 % of fish oil with camelina oil did not negatively affect growth of rainbow trout after a 12‐week feeding trial (FO = 168 ± 32 g fish^?1; CO = 184 ± 35 g fish^?1). Lipid and fatty acid profiles of muscle, viscera and skin were significantly affected by the addition of CO after 12 weeks of feeding. However, final 22:6n‐3 [docosahexaenoic acid (DHA)] and 20:5n‐3 [eicosapentaenoic acid (EPA)] amounts (563 mg) in a 75 g fillet (1 serving) were enough to satisfy daily DHA and EPA requirements (250 mg) set by the World Health Organization. Other health benefits include lower SFA and higher MUFA in filets fed CO versus FO. Compound‐specific stable isotope analysis (CSIA) confirmed that the δ¹³C isotopic signature of DHA in CO fed trout shifted significantly compared to DHA in FO fed trout. The shift in DHA δ¹³C indicates mixing of a terrestrial isotopic signature compared to the isotopic signature of DHA in fish oil‐fed tissue. These results suggest that ~27 % of DHA was synthesized from the terrestrial and isotopically lighter ALA in the CO diet rather than incorporation of DHA from fish meal in the CO diet. This was the first study to use CSIA in a feeding experiment to demonstrate synthesis of DHA in fish.     

Enrichment of n-3 containing ether phospholipids in plasma after 30 days of krill oil compared with fish oil supplementation

There are conflicting findings over the bioavailability of long-chain n-3 polyunsaturated fatty acids (n-3 PUFA) from krill oil (KO) compared with fish oil (FO) in short- and long-term studies. The aim of this study was to compare the effects of KO versus FO on the enrichment of molecular species of plasma phospholipids in young women following a 30-day consumption of the n-3 oils. Eleven healthy women aged 18–45 years consumed seven capsules of KO per day (containing a total of 1.27 g n-3 PUFA) or five capsules of FO per day (total of 1.44 g n-3 PUFA) for 30 days in a randomized crossover study, separated by at least a 30-day washout period. Fasting blood samples were collected at day zero (baseline), day 15 and day 30 and analyzed by HPLC-MS/MS for molecular species of phospholipids. Supplementation increased n-3 PUFA in main phospholipids classes in both groups. After 30 days of supplementation, 35 out of 70 molecular species containing eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and docosapentaenoic acid (DPAn-3) had a significantly greater concentration in KO group compared with the FO treated group. The majority (89%) of the differentiated molecular species were choline and ethanolamine ether-phospholipids. These data reveal that analysis of plasma phospholipids following 30 days of consumption of KO (a marine oil rich in phospholipids, including ether phospholipids) resulted in an enrichment of n-3 PUFA in molecular species of ether-phospholipids compared with FO (a triacylglycerol-rich marine oil).     

Supplementation of DHA-Rich Microalgal Oil or Fish Oil During the Suckling Period in Mildly n-3 Fatty Acid-Deficient Rat Pups

Long-chain polyunsaturated fatty acids (LC-PUFA), particularly arachidonic acid (ARA) and docosahexaenoic acid (DHA), are considered critical for the development of infants and are commonly supplemented in infant formulae. In this study, two common sources of n-3 LC-PUFA, fish oil (FO) and DHA-rich microalgal oil (DMO), were fed to rat pups of mildly n-3 PUFA-deficient dams to compare changes in LC-PUFA of tissue phospholipids. The milk from dams fed a n-3 PUFA-deficient diet contained less n-3 LC-PUFA than that of dams fed a control diet (AIN-93G). The pups' were given orally 1 mg/g weight of either FO or DMO for 17 days between the ages of 5 and 21 days, the pups were weaned, and sacrificed 1 week later for analysis of fatty acid compositions of brain, heart, kidney, spleen, and thymus phospholipids. Although both FO and DMO brought about a recovery in the tissue DHA levels compared to those of the control group (pups from AIN-93G-fed dams), DMO was more effective at restoring tissue LC-PUFA status because it was richer in DHA than FO. FO had a slightly lower PUFA level than that required to bring the LC-PUFA status completely to normal levels in this experiment, and EPA did not accumulate in tissues under the conditions tested here. These results demonstrate the effectiveness of ingesting either FO or DMO in the pre-weaning period for improving mild n-3 PUFA deficiency.     

Effects of the flaxseed oil on the fatty acid composition of tilapia heads

The objective of this study was to evaluate the effects of adding flaxseed oil (FO) to feed on the incorporation of n‐3 PUFA in tilapia heads. Tilapia were given diets with increasing levels of FO (0.00, 1.25, 2.50, 3.75 and 5.00% for treatments A, B, C, D and E, respectively), as a source of LNA for 150 days. The proximate composition of the heads indicated high nutritional value and 40 FA (fatty acids) common to all treatments were identified in total lipids. Intake of LNA caused storage of LNA and sequential desaturation‐elongation to eicosapentaenoic acid (EPA) and DHA. With increasing levels of FO in the diet, the content of LNA in tilapia heads increased (1.7 and 14.0% for diets A and E, respectively), as well as the contents of EPA (0.1 and 0.9% for diets A and E, respectively) and DHA (0.5 and 1.8% for diets A and E, respectively). Adding FO to tilapia feed markedly increased the total content of n‐3 PUFA (3.0 and 21.1% for diets A and E, respectively), decreased the total content of n‐6 PUFA (41.3 and 24.9% for diets A and E, respectively), and consequently resulted in a decrease in the n‐6/n‐3 ratio (13.8 and 1.2 for diets A and E, respectively). Therefore, feeding tilapia with FO is a good way of valorizing this part of the fish by creating a valuable nutritional food source.     

Retinal sensitivity loss in third-generation n-3 PUFA-deficient rats

A previous study conducted in guinea pigs suggested that ingestion of diets high in EPA and DHA may result in suboptimal retinal function. The aim of the present study was to evaluate retinal function in pigmented (Long-Evans) rats, raised to a third generation on diets that were either deficient in n-3 PUFA or adequate (with the addition of DHA). Electroretinographic assessment employed full-field white flash stimulation. Photoreceptor responses were evaluated in terms of peak amplitudes and implicit times (a-wave, b-wave), intensity-response functions (Naka-Rushton), and the parameters of a model of transduction (P3). Retinal phospholipid FA composition was measured by capillary GLC. DHA levels were reduced by 55% in n-3-deficient animals compared with the n-3-adequate group, whereas the levels of docosapentaenoic acid n-6 were 44 times higher in n-3-deficient animals. The level of arachidonic acid was marginally higher (12.8%) in n-6-adequate animals. The n-3-deficient animals exhibited significantly reduced retinal sensitivity (σ and S values were both affected by 0.29 log units) and increased b-wave implicit times compared with those fed the n-3-adequate diet. These data suggest that n-3 PUFA are required for development of retinal sensitivity, more so than other indices of retinal function assessed by current methods, such as maximal response amplitude. However, the benefit for retinal function of adding preformed DHA to diets already replete in n-3 PUFA remains unclear. This study was conducted at the Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health.     

Dietary n-3 and n-6 PUFA Enhance DHA Incorporation in Retinal Phospholipids Without Affecting PGE<Subscript>1</Subscript> and PGE<Subscript>2</Subscript> Levels

The purpose of this study was to determine whether dietary n-3 and n-6 PUFA may affect retinal PUFA composition and PGE₁ and PGE₂ production. Male Wistar rats were fed for 3 months with diets containing: (1) 10% eicosapentaenoic acid (EPA) and 7% docosahexaenoic acid (DHA), or (2) 10% γ-linolenic acid (GLA), or (3) 10% EPA, 7% DHA and 10% GLA, or (4) a balanced diet deprived of EPA, DHA, and GLA. The fatty acid composition of retinal phospholipids was determined by gas chromatography. Prostaglandin production was measured by enzyme immunoassay. When compared to rats fed the control diet, the retinal levels of DHA were increased in rats fed both diets enriched with n-3 PUFA (EPA + DHA and EPA + DHA + GLA diets) and decreased in those supplemented with n-6 PUFA only (GLA diet). The diet enriched with both n-6 and n-3 PUFA resulted in the greatest increase in retinal DHA. The levels of PGE₁ and PGE₂ were significantly increased in retinal homogenates of rats fed with the GLA-rich diet when compared with those of animals fed the control diet. These higher PGE₁ and PGE₂ levels were not observed in animals fed with EPA + DHA + GLA. In summary, GLA added to EPA + DHA resulted in the highest retinal DHA content but without increasing retinal PGE₂ as seen in animals supplemented with GLA only.     

Dietary Fish Oil Supplements Increase Tissue n-3 Fatty Acid Composition and Expression of Delta-6 Desaturase and Elongase-2 in Jade Tiger Hybrid Abalone

This study was conducted to investigate the effects of fish oil (FO) supplements on fatty acid composition and the expression of ∆6 desaturase and elongase 2 genes in Jade Tiger abalone. Five test diets were formulated to contain 0.5, 1.0, 1.5, 2.0 and 2.5% of FO respectively, and the control diet was the normal commercial abalone diet with no additional FO supplement. The muscle, gonad and digestive glands (DG) of abalone fed with all of the five test diets showed significantly high levels of total n-3 polyunsaturated fatty acid (PUFA), eicosapentaenoic acid (EPA), docosapentaenoic acid n-3 (DPAn-3), and docosahexaenoic acid (DHA) than the control group. In all three types of tissue, abalone fed diet supplemented with 1.5% FO showed the highest level of these fatty acids (P < 0.05). For DPAn-3 the higher level was also found in muscle and gonad of abalone fed diet supplemented with 2% FO (P < 0.05). Elongase 2 expression was markedly higher in the muscle of abalone fed diet supplemented with 1.5% FO (P < 0.05), followed by the diet containing 2% FO supplement. For ∆6 desaturase, significantly higher expression was observed in muscle of abalone fed with diet containing 0.5% FO supplement (P < 0.05). Supplementation with FO in the normal commercial diet can significantly improve long chain n-3 PUFA level in cultured abalone, with 1.5% being the most effective supplementation level.     

Maternal Intake of Fish Oil but not of Linseed Oil Reduces the Antibody Response in Neonatal Mice

Dietary levels of n-3 PUFA are believed to influence the immune system. The importance of the source of n-3 PUFA is debated. This study addressed how the content and source of n-3 PUFA in the maternal diet influenced tissue FA composition and the immune response to ovalbumin (OVA) in mice pups. From the day of conception and throughout lactation, dams were fed diets containing 4% fat from linseed oil (LSO), fish oil (FO) or a n-3 PUFA-deficient diet (DEF). Pups were injected with OVA within 24 h of birth and sacrificed at weaning (day 21). Overall, the content of n-3 PUFA in milk, liver and spleen reflected the source and only minor differences were observed in brain phospholipid 22:6n-3. The source had only limited influence on the n-3 PUFA accretion in peripheral tissue, with most pronounced differences in the spleen. The marine PUFA-group had reduced levels of total OVA-specific antibodies and OVA-IgG1 titers in the pup blood, while the response in the LSO-group did not differ from that in the DEF-group. There were no statistical differences in the cytokine responses to OVA-stimulated splenocytes, but the decrease in IgG1 was paralleled by an increase in IFNγ-production and a decrease in IL-6-production. Our results indicate that maternal intake of FO, but not of LSO, changes the offspring’s antigen-specific response and potentially increases Th1-polarization.     

Accretion of Dietary Docosahexaenoic Acid in Mouse Tissues Did Not Differ between Its Purified Phospholipid and Triacylglycerol Forms

Recent studies suggest that dietary krill oil leads to higher omega-3 polyunsaturated fatty acids (n-3 PUFA) tissue accretion compared to fish oil because the former is rich in n-3 PUFA esterified as phospholipids (PL), while n-3 PUFA in fish oil are primarily esterified as triacylglycerols (TAG). Tissue accretion of the same dietary concentrations of PL- and TAG-docosahexaenoic acid (22:6n-3) (DHA) has not been compared and was the focus of this study. Mice (n = 12/group) were fed either a control diet or one of six DHA (1%, 2%, or 4%) as PL-DHA or TAG-DHA diets for 4 weeks. Compared with the control, DHA concentration in liver, adipose tissue (AT), heart, and eye, but not brain, were significantly higher in mice consuming either PL- or TAG-DHA, but there was no difference in DHA concentration in all tissues between the PL- or TAG-DHA forms. Consumption of PL- and TAG-DHA at all concentrations significantly elevated eicosapentaenoic acid (20:5n-3) (EPA) in all tissues when compared with the control group, while docoshexapentaenoic acid (22:5n-6) (DPA) was significantly higher in all tissues except for the eye and heart. Both DHA forms lowered total omega-6 polyunsaturated fatty acids (n-6 PUFA) in all tissues and total monounsaturated fatty acids (MUFA) in the liver and AT; total saturated fatty acid (SFA) were lowered in the liver but elevated in the AT. An increase in the DHA dose, independent of DHA forms, significantly lowered n-6 PUFA and significantly elevated n-3 PUFA concentration in all tissues. Our results do not support the claim that the PL form of n-3 PUFA leads to higher n-3 PUFA tissue accretion than their TAG form.     

Partitioning of Rumen-Protected n-3 and n-6 Fatty Acids is Organ-Specific in Growing Angus Heifers

Dietary polyunsaturated fatty acids (PUFA), especially n-3 and n-6 fatty acids (FA), play an important role in the regulation of FA metabolism in all mammals. However, FA metabolism differs between different organs, suggesting a distinct partitioning of highly relevant FA. For the present study in cattle, a novel technology was applied to overcome rumen biohydrogenation of dietary unsaturated FA. Angus heifers were fed a straw-based diet supplemented for 8 weeks with 450 g/day of rumen-protected oil, either from fish (FO) or sunflower (SO). The FA composition in blood and five important organs, namely heart, kidney, liver, lung, and spleen, was examined. In blood, proportions of polyunsaturated FA were increased by supplementing FO compared to SO. The largest increase of eicosapentaenoic acid (EPA) proportion was found with FO instead of SO in the kidney, the lowest in the lung. Docosahexaenoic acid (DHA) was increased more in the liver than in kidney, lung, and spleen. The heart incorporated seven times more EPA than DHA, which is more than all other organs and described here for the first time in ruminants. In addition, the heart had the highest proportions of α-linolenic acid (18:3n-3) and linoleic acid (18:2n-6) of all organs. The proportions of polyunsaturated FA in the lung and spleen were exceptionally low compared to heart, liver, and kidney. In conclusion, it was shown that the response to FO in the distribution of dietary n-3 FA was organ-specific while proportions of n-6 FA were quite inert with respect to the type of oil supplemented.     

The Influence of n-3 PUFA Supplements and n-3 PUFA Enriched Foods on the n-3 LC PUFA Intake of Flemish Women

Food consumption data of Flemish women of reproductive age collected in 2002 showed a large deficit for ALA and n-3 LC PUFA compared to the recommendations (mean ALA and EPA + DHA intake 1.4 g/day and 209 mg/day, respectively) and indicated a need to tackle the problem of low n-3 PUFA intake. Another recent Belgian study demonstrated that enrichment of commonly eaten food items with n-3 PUFA provides the opportunity to increase the n-3 PUFA intake up to 6.5 g/day and decrease the n-6/n-3 ratio. Since a large supply of n-3 PUFA supplements and n-3 PUFA enriched foods exists on the Belgian market, this study aimed at assessing the influence of these products on the n-3 LC PUFA intake for Flemish women of reproductive age. It was found that n-3 supplements are consumed by 5% of the Flemish women. Of all the n-3 PUFA enriched foods on the Flemish market, margarines and cooking fat are most frequently consumed by young women. The results indicated that a big gap remains between the EPA&DHA intake (mean = 276 mg/day) and the recommendation. Seafood remains the most important source of EPA&DHA. Only 11.6% of the population sample reached an intake level of 500 mg EPA&DHA per day. The study showed that other strategies will be needed to increase the EPA&DHA intake in the long term.     

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 PGF_3α was significantly increased in gill homogenates from fish fed MO compared to the other three treatments while PGF_2α 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.     

Comparative study between two different sources of n-3 poliunsaturated fatty acids and it effect on thymus and lipid profile in rats

In the present paper we analyzed the effect caused by different recovery diets enriched with n-3 polyunsaturated fatty acids (PUFA n-3) on thymus and serum lipid pattern. Severe depleted weanling Wistar rats (D) were divided in three groups that received during 10 days a 20% casein diet supplemented with EPA+DHA (group Cas), a 20% protein milk diet prepared using a commercial reduced-fat product enriched with linolenic and linoleic acids (group L) and a 20% casein diet as control group C. Cas and L gave each other 24 mg/day of PUFA n-3 being the ratio n-6/n-3 8.1/1 and 7.6/1, respectively. Thymus was removed and weighted and cell number were determined; blood was recollected and Total cholesterol, triacylglycerol, HDL and LDL-cholesterol fractions and myristic, palmitic, stearic, oleic, linoleic, linolenic, araquidonic, EPA and DHA fatty acid concentrations were measured in serum. Statistical analysis was performed using Anova test. Cell number were higher (p<0.01) in Cas (44.48+/-8.20) and in L (56.45+/-14.72) when compared to group D (1.80+/-0.70) and group C (23.70+/-4.04). L presented lower values of cholesterol, HDL and LDL-cholesterol (p<0.01) and higher values of triacylglycerol (p<0.05) when compared to Cas, being EPA (p<0.05) and DHA (p<0.01) higher in Cas. Being PUFA n-3 contribution the same in Cas and L, both diets were able to reverse the thymic athropy presenting a different hipolipemic behavior due to the different sources of PUFA n-3 used in the diets.     

Dietary Linseed Oil Reduces Growth While Differentially Impacting LC-PUFA Synthesis and Accretion into Tissues in Eurasian Perch (Perca fluviatilis)

The aim of this study was to evaluate the impact of replacing dietary fish oil (FO) with linseed oil (LO) on growth, fatty acid composition and regulation of lipid metabolism in Eurasian perch (Perca fluviatilis) juveniles. Fish (17.5 g initial body weight) were fed isoproteic and isoenergetic diets containing 116 g/kg of lipid for 10 weeks. Fish fed the LO diet displayed lower growth rates and lower levels of DHA in the liver and muscle than fish fed the FO diet, while mortality was not affected by dietary treatment. However, DHA content recorded in the liver and muscle of fish fed the LO diet remained relatively high, despite a weight gain of 134 % and a reduced dietary level of long‐chain polyunsaturated fatty acids (LC‐PUFA), suggesting endogenous LC‐PUFA biosynthesis. This was supported by the higher amounts of pathway intermediates, including 18:4n‐3, 20:3n‐3, 20:4n‐3, 18:3n‐6 and 20:3n‐6, recorded in the liver of fish fed the LO diet in comparison with those fed the FO diet. However, fads2 and elovl5 gene expression and FADS2 enzyme activity were comparable between the two groups. Similarly, the expression of genes involved in eicosanoid synthesis was not modulated by dietary LO. Thus, the present study demonstrated that in fish fed LO for 10 weeks, growth was reduced but DHA levels in tissues were largely maintained compared to fish fed FO, suggesting a physiologically relevant rate of endogenous LC‐PUFA biosynthesis capacity.     

Replacement of Marine Fish Oil with de novo Omega-3 Oils from Transgenic Camelina sativa in Feeds for Gilthead Sea Bream (Sparus aurata L.)

Omega‐3 (n‐3) long‐chain polyunsaturated fatty acids (LC‐PUFA) are essential components of the diet of all vertebrates. The major dietary source of n‐3 LC‐PUFA for humans has been fish and seafood but, paradoxically, farmed fish are also reliant on marine fisheries for fish meal and fish oil (FO), traditionally major ingredients of aquafeeds. Currently, the only sustainable alternatives to FO are vegetable oils, which are rich in C₁₈ PUFA, but devoid of the eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) abundant in FO. Two new n‐3 LC‐PUFA sources obtained from genetically modified (GM) Camelina sativa containing either EPA alone (ECO) or EPA and DHA (DCO) were compared to FO and wild‐type camelina oil (WCO) in juvenile sea bream. Neither ECO nor DCO had any detrimental effects on fish performance, although final weight of ECO‐fed fish (117 g) was slightly lower than that of FO‐ and DCO‐fed fish (130 and 127 g, respectively). Inclusion of the GM‐derived oils enhanced the n‐3 LC‐PUFA content in fish tissues compared to WCO, although limited biosynthesis was observed indicating accumulation of dietary fatty acids. The expression of genes involved in several lipid metabolic processes, as well as fish health and immune response, in both liver and anterior intestine were altered in fish fed the GM‐derived oils. This showed a similar pattern to that observed in WCO‐fed fish reflecting the hybrid fatty acid profile of the new oils. Overall the data indicated that the GM‐derived oils could be suitable alternatives to dietary FO in sea bream.     

Artificial rearing of infant rats on milk formula deficient in n-3 essential fatty acids: A rapid method for the production of experimental n-3 deficiency

Research into the function of docosahexaenoic acid (DHA; 22:6n-3), the predominant polyunsaturated fatty acid (PUFA) in the central nervous system (CNS), is often hindered by the difficulty in obtaining dramatic experimental decreases in DHA in the brain and retina of laboratory rats. In this study, the artificial rearing procedure, whereby infant rats are removed from their mothers, gastrostomized, and fed synthetic formula, was used in an attempt to produce rapid changes in CNS levels of DHA. Female rats were raised, from day 4–5 of life, on one of two formulas—one containing the essential fatty acids of both the n-6 and n-3 series in proportions approximately equal to those of rat milk, and the other containing high levels of 18:2n-6 but very little n-3 fatty acid. At weaning, both groups were given AIN-76A diets modified so that the PUFA content resembled that of the preweaning formula. At eight weeks of age, the n-3-deficient group exhibited decreases of more than 50% in total DHA content in the brain, accompanied by increases in arachidonic acid (AA) (20:4n-6) and, especially, docosapentaenoic acid (22:5n-6). Other artificially-reared rats were mated and their offspring were also maintained on the respective diets. In spite of the fact that they had been reared artificially, the rats mated successfully and reared litters with no obvious abnormalities. At both ten days of age and again at eight weeks, offspring of the n-3-deficient mothers exhibited decreases of more than 90% in total DHA content. Again, the long-chain n-6 PUFA increased proportionately so that total PUFA levels in the brain were not lower. As these differences are greater than those commonly reported, even after 2–3 generations of normal dietary deprivation in prodents, this procedure may be an important tool in the study of the effects of n-3 deficiency on neural development and, subsequently, of the function of DHA in nervous tissue. Based on a presentation at the AOCS Annual Meeting & Expo in San Antonio, Texas, May 7–11, 1995.