[Show abstract][Hide abstract] ABSTRACT: The present study compared the effects of diets formulated with reduced fishmeal (FM) content and either 100% fish oil (FO) or 100% of a vegetable oil (VO) blend in post-smolts of three family groups of Atlantic salmon. Two groups were selected as being either “Lean” or “Fat” based on estimated breeding values (EBV) for flesh adiposity of their parents derived from a breeding programme, while the third group (CAL) was a mix of non-pedigreed commercial families unrelated to the two groups above. The VO blend comprised rapeseed, palm and a new product, Camelina oil in a ratio of 5/3/2, and diets were fed to duplicate pens of each salmon group. After an ongrowing period of 55 weeks, to reach a mean weight of 3kg, the fish from all treatments were switched to a decontaminated FO for a further 24 weeks to follow restoration of long-chain n-3 polyunsaturated fatty acids (LC-PUFA) in the fish previously fed VO. Final weights were significantly affected by family group and there was also an interaction between diet and group with Fat and Lean FO fish being larger than the same fish fed VO. Specific growth rate (SGR) was highest in CAL fish (1.01), feed conversion ratio (FCR) was highest in the Lean fish but there were no significant effects on thermal growth coefficient (TGC). Condition Factor (CF) was lowest in CAL fish while the hepato-somatic index (HSI) was highest in Lean fish and viscero-somatic index (VSI) highest in Fat fish. Flesh and viscera lipid content was affected by both family group and diet with a significant interaction between the two. Flesh lipid in fish fed FO was in the order Fat > CAL > Lean although this order was Fat = Lean > CAL when fed VO. Flesh fatty acid compositions were affected mainly by diet although some minor fatty acids were also influenced by group. Fish fed VO had n-3 LC-PUFA reduced by ~65% compared to fish fed FO but this could be restored by a 16 week FO finishing diet phase. The differences observed in lipid and fatty acid deposition suggested that genetics affected lipid deposition and metabolism and that breeding programmes could select for fish that retained more n-3 LC-PUFA in their flesh, particularly when fed diets low in these fatty acids.
[Show abstract][Hide abstract] ABSTRACT: Recent legislation in the European Union (EC/2065/2001) requires that seafood must provide the consumer with information that describes geographical origin and production method. The present studies aimed to establish methods, based on chemical and stable isotopic analysis, that could reliably differentiate between wild and farmed European sea bass (Dicentrarchus labrax). The study measured fatty acid and isotopic compositions (delta13C and delta18O) of total flesh oil, delta15N of the glycerol/choline fraction, and compound-specific analysis of fatty acids (delta13C) by isotope ratio mass spectrometry. The sample set comprised 10 wild and 10 farmed sea bass from England (wild) and Scotland or Greece (farmed). Discrimination was achieved using fatty acid composition with 18:0, 18:2n-6, 20:4n-6, and 22:6n-3 providing the highest contributions for discrimination. Principal component analysis of the data set provided good discrimination between farmed and wild sea bass where factor 1 and factor 2 accounted for 60% of the variation in the data.
Full-text · Article · Aug 2007 · Journal of Agricultural and Food Chemistry
[Show abstract][Hide abstract] ABSTRACT: Dietary conjugated linoleic acid (CLA) affects fat deposition and lipid metabolism in mammals, including livestock. To determine CLA effects in Atlantic salmon (Salmo salar), a major farmed fish species, fish were fed for 12 weeks on diets containing fish oil or fish oil with 2% and 4% CLA supplementation. Fatty acid composition of the tissues showed deposition of CLA with accumulation being 2 to 3 fold higher in muscle than in liver. CLA had no effect on feed conversion efficiency or growth of the fish but there was a decreased lipid content and increased protein content after 4% CLA feeding. Thus, the protein:lipid ratio in whole fish was increased in fish fed 4% CLA and triacylglycerol in liver was decreased. Liver beta-oxidation was increased whilst both red muscle beta-oxidation capacity and CPT1 activity was decreased by dietary CLA. Liver highly unsaturated fatty acid (HUFA) biosynthetic capacity was increased and the relative proportion of liver HUFA was marginally increased in salmon fed CLA. CLA had no effect on fatty acid Delta6 desaturase mRNA expression, but fatty acid elongase mRNA was increased in liver and intestine. In addition, the relative compositions of unsaturated and monounsaturated fatty acids changed after CLA feeding. CLA had no effect on PPARalpha or PPARgamma expression in liver or intestine, although PPARbeta2A expression was reduced in liver at 4% CLA feeding. CLA did not affect hepatic malic enzyme activity. Thus, overall, the effect of dietary CLA was to increase beta-oxidation in liver, to reduce levels of total body lipid and liver triacylglycerol, and to affect liver fatty acid composition, with increased elongase expression and HUFA biosynthetic capacity.
Full-text · Article · Nov 2006 · Comparative Biochemistry and Physiology - Part A Molecular & Integrative Physiology
[Show abstract][Hide abstract] ABSTRACT: Atlantic salmon (Salmo salar L.) juveniles were fed either 100% fish oil (FO), 75% vegetable oil (VO), or 100% VO throughout their life cycle to harvest weight followed by a finishing diet period when all groups were fed 100% FO. The two experimental VO diets were tested at two different locations (Scotland and Norway) against the same control diet (100% FO). The VO blend was composed of rapeseed oil, palm oil, and linseed oil using capelin oil as a control for fatty acid class compositions. Flesh fatty acid profiles were measured regularly throughout the experiment, with the times of sampling determined by changes in pellet size/lipid content and fish life stage. Growth and mortality rates were not significantly affected by dietary fatty acid compositions throughout the life cycle, except during the seawater winter period in Norway when both growth and protein utilization were increased in salmon fed 100% VO compared to 100% FO. Flesh fatty acid composition was highly influenced by that of the diet, and after the finishing diet period the weekly intake recommendations of very long chain n-3 polyunsaturated fatty acid (VLCn-3 PUFA) for human health were 80 and 56% satisfied by a 200 g meal of 75% VO and 100% VO flesh, respectively. No effect on flesh astaxanthin levels was observed in relation to changing dietary oil sources. Sensory evaluation showed only minor differences between salmon flesh from the dietary groups, although prior to the finishing diet period, flesh from 100% VO had less rancid and marine characteristics and was preferred over flesh from the other dietary groups by a trained taste panel. After the finishing diet period, the levels of typical vegetable oil fatty acids in flesh were reduced, whereas those of VLCn-3 PUFA increased to levels comparable with a 100% FO fed salmon. No differences in any of the sensory characteristics were observed between dietary groups. By blending VOs to provide balanced levels of dietary fatty acids, up to 100% of the fish oil can be replaced by the VO blend without compromising growth or flesh quality. At the same time, 75% of the dietary fish oil can be replaced without compromising flesh VLCn-3 PUFA content, thereby providing a beneficial nutritional profile for human consumption.
Full-text · Article · Jan 2006 · Journal of Agricultural and Food Chemistry
[Show abstract][Hide abstract] ABSTRACT: Highly unsaturated fatty acid (HUFA) synthesis in Atlantic salmon (Salmo salar) was known to be influenced by both nutritional and environmental factors. Here we aimed to test the hypothesis that both these effectors involved similar molecular mechanisms. Thus, HUFA biosynthetic activity and the expression of fatty acyl desaturase and elongase genes were determined at various points during an entire 2 year production cycle in salmon fed diets containing either 100% fish oil or diets in which a high proportion (75% and 100%) of fish oil was replaced by C18 polyunsaturated fatty acid-rich vegetable oil. The results showed that HUFA biosynthesis in Atlantic salmon varied during the growth cycle with peak activity around seawater transfer and subsequent low activities in seawater. Consistent with this, the gene expression of Delta6 desaturase, the rate-limiting step in the HUFA biosynthetic pathway, was highest around the point of seawater transfer and lowest during the seawater phase. In addition, the expression of both Delta6 and Delta5 desaturase genes was generally higher in fish fed the vegetable oil-substituted diets compared to fish fed fish oil, particularly in the seawater phase. Again, generally consistent with this, the activity of the HUFA biosynthetic pathway was invariably higher in fish fed diets in which fish oil was substituted by vegetable oil compared to fish fed only fish oil. In conclusion, these studies showed that both nutritional and environmental modulation of HUFA biosynthesis in Atlantic salmon involved the regulation of fatty acid desaturase gene expression.
Full-text · Article · Jun 2005 · Biochimica et Biophysica Acta
[Show abstract][Hide abstract] ABSTRACT: Five groups of salmon, of initial mean weight 127±3 g, were fed increasing levels of dietary linseed oil (LO) in a regression design. The control diet contained capelin oil (FO) only, and the same oil was blended with LO to provide the experimental diets. After an initial period of 40 wk, all groups were switched to a finishing diet containing only FO for a further 24 wk. Growth and flesh lipid contents were not affected by dietary treatment. The FA compositions of flesh total lipids were linearly correlated with dietary FA compositions (r
2=0.88–1.00, P<0.0001). LO included at 50% of added dietary lipids reduced flesh DHA and EPA (20∶5n−3) concentrations to 65 and 58%, respectively, of the concentrations in fish fed FO. Feeding 100% LO reduced flesh DHA and EPA concentrations to 38 and 30%, respectively, of the values in fish fed FO. Differences between diet and flesh FA concentrations showed that 16∶0, 18∶1n−9, and especially DHA were preferentially retained in flesh, whereas 18∶2n−6, 18∶3n−3, and 22∶1n−11 were selected against and presumably utilized for energy. In fish previously fed 50 and 100% LO, feeding a finishing diet containing FO for 16 wk restored flesh DHA and EPA concentrations, to ≈80% of the values in fish fed FO throughout. Flesh DHA and EPA concentrations in fish fed up to 50% LO were above recommended intake values for humans for these EFA. This study suggests that LO can be used as a substitute for FO in seawater salmon feeds and that any reductions in DHA and EPA can be largely overcome with a finishing diethigh in FO before harvest.
[Show abstract][Hide abstract] ABSTRACT: Atlantic salmon postsmolts were fed a control diet or one of 9 experimental diets containing various blends of two vegetable oils, linseed (LO) and rapeseed oil (RO), and fish oil (FO) in a triangular trial design, for 50 wk. After sampling, fish previously fed 100% FO, LO and RO were switched to a diet containing 100% FO for a further 20 wk. Fatty acid compositions of flesh total lipid were linearly correlated with dietary fatty acid compositions (r = 0.99-1.00, P < 0.0001). Inclusion of vegetable oil at 33% of total oil significantly reduced the concentrations of the highly unsaturated fatty acids, eicosapentaenoate [20:5(n-3)] and docosahexaenoate [22:6(n-3)], to approximately 70 and 75%, respectively, of the values in fish fed 100% FO. When vegetable oil was included at 100% of total dietary lipid, the concentrations of 20:5(n-3) and 22:6(n-3) were significantly reduced to approximately 30 and 36%, respectively, of the values in fish fed FO. Transfer of fish previously fed 100% vegetable oil to a 100% FO diet for 20 wk restored the concentrations of 20:5(n-3) and 22:6(n-3) to approximately 80% of the value in fish fed 100% FO for 70 wk, although the values were still significantly lower. However, in fish previously fed either 100% LO or RO, concentrations of 18:2(n-6) remained approximately 50% higher than in fish fed 100% FO. This study suggests that RO and LO can be used successfully to culture salmon through the seawater phase of their growth cycle; this will result in reductions in flesh 20:5(n-3) and 22:6(n-3) concentrations that can be partially restored by feeding a diet containing only marine FO for a period before harvest.
Full-text · Article · Sep 2003 · Journal of Nutrition
[Show abstract][Hide abstract] ABSTRACT: Induction of fatty acid desaturation is very important for the temperature adaptation of poikilotherms. However, in oxygen-limited late-exponential-phase Acanthamoeba castellanii cultures, oxygen alone was able to induce increased activity of a fatty acid desaturase that converts oleate into linoleate and which has been implicated in the temperature adaptation of this organism. Experiments with Delta(10)-nonadecenoate showed that the enzyme is an n -6 desaturase rather than a Delta(12)-desaturase. It also used preferentially 1-acyl-2-oleoyl-phosphatidylcholine as substrate and NAD(P)H as electron donor. The involvement of cytochrome b (5) as an intermediate electron carrier was shown by difference spectra measurements and anti-(cytochrome b (5)) antibody experiments. Of the three protein components of the desaturase complex, oxygen only increased the activity of the terminal (cyanide-sensitive) protein during n -6 desaturase induction. The induction of this terminal protein paralleled well the increase in overall oleate n -6 desaturation. The ability of oxygen to induce oleate desaturase independently of temperature in this lower eukaryotic animal model is of novel intrinsic interest, as well as being important for the design of future experiments to determine the molecular mechanism of temperature adaptation in poikilotherms.
Full-text · Article · Dec 2002 · Biochemical Journal
[Show abstract][Hide abstract] ABSTRACT: The present study was undertaken to establish whether the formation of 22:6n-3 from 18:3n-3 and/or 20:5n-3 can occur in turbot liver and if this conversion is consistent with the operation of a Delta4 desaturase-independent pathway. At the same, time the effects of feeding a diet devoid of long chain polyunsaturated fatty acids (PUFA) on the patterns of esterification and modification of 18:3n-3, 20:5n-3 and 18:2n-6 by turbot hepatocytes and liver microsomes were examined. For this purpose, two groups of fish (25-30 g) were employed: one was fed a commercial diet containing fish oil (FO) and thus rich in long chain n-3 PUFA and the other was fed an experimental diet based on olive oil (OO). After 5 months of feeding, hepatocytes and liver microsomes isolated from individuals in the two groups of fish were incubated with [1-(14)C]-PUFA [either 18:3n-3, 20:5n-3 or 18:2n-6]. After 3 h of incubation, most radioactivity from all three radiolabelled substrates incorporated into lipids by hepatocytes and microsomes was recovered in the original substrate. The formation of desaturation products of n-3 radiolabelled substrates was higher in hepatocytes isolated from OO-fed than FO-fed fish. Small amounts of radiolabelled 22:6n-3 were formed from [1-(14)C]18:3n-3 and [1-(14)C]20:5n-3, but only by hepatocytes from fish fed OO, which also synthesised a small amount of radiolabelled 24:6n-3 from 14C-20:5n-3. Elongation products predominated over desaturation products in hepatic microsomes from both groups of fish studied, particularly in microsomes from fish fed FO. The results confirm that regardless of the long chain PUFA content of the diet, the production of 22:6n-3 in turbot liver from 18:3n-3 and/or 20:5n-3, and of 20:4n-6 from 18:2n-6, is very limited. The presence of radiolabelled 24:6n-3 in microsomes coupled with the absence of radiolabelled 22:6n-3 suggests that the formation of 22:6n-3 that does occur in turbot liver cells, may involve C24 intermediates and peroxisomal beta-oxidation.
No preview · Article · Aug 2002 · Comparative Biochemistry and Physiology Part B Biochemistry and Molecular Biology
[Show abstract][Hide abstract] ABSTRACT: Supplies of marine fish oils (FO) are limited and continued growth in aquaculture production dictates that substitutes must be found that do not compromise fish health and product quality. In this study the suitability of crude palm oil (PO) as a replacement for FO in diets of Atlantic salmon was investigated. Duplicate groups of Atlantic salmon post-smolts were fed four practical-type diets in which the added lipid was either 100% FO and 0% crude PO (0% PO); 75% FO and 25% PO (25% PO); 50% FO and 50% PO (50% PO); and 100% PO, for 30 wk. There were no effects of diet on growth rate or feed conversion ratio nor were any histopathological lesions found in liver, heart or muscle. Lipid deposition was greatest in fish fed 0% PO and was significantly greater than in fish fed 50% and 100% PO. Fatty acid compositions of muscle total lipid were correlated with dietary PO inclusion such that the concentrations of 16:0, 18:1(n-9), 18:2(n-6), total saturated fatty acids and total monoenoic fatty acids increased linearly with increasing dietary PO. The concentration of eicosapentaenoic acid [20:5(n-3)] was reduced significantly with increasing levels of dietary PO but the concentration of docosahexaenoic acid [22:6(n-3)] was significantly reduced only in fish fed 100% PO, compared with the other three treatments. Similar diet-induced changes were seen in liver total lipid fatty acid compositions. Hepatic fatty acid desaturation and elongation activities were approximately 10-fold greater in fish fed 100% PO than in those fed 0% PO. This study suggests that PO can be used successfully as a substitute for FO in the culture of Atlantic salmon in sea water. However, at levels of PO inclusion above 50% of dietary lipid, significant reductions in muscle 20:5(n-3), 22:6(n-3) and the (n-3):(n-6) PUFA ratio occur, resulting in reduced availability of these essential (n-3) highly unsaturated fatty acids to the consumer.
Full-text · Article · Mar 2002 · Journal of Nutrition
[Show abstract][Hide abstract] ABSTRACT: We hypothesized that replacing fish oil with 18:3n-3-rich linseed oil may enable salmon to maintain the levels of tissue n-3HUFA
levels through a combination of increased desaturation activity and increased substrate fatty acid provision. To this end
we investigated desaturation/elongation of [1-14C18:3n-3 in hepatocytes and intestinal enterocytes, and determined the extent to which 18:3n-3 was oxidized and desaturated
by measuring both simultaneously in a combined assay. Salmon smolts were stocked randomly into five seawater pens and fed
for 40 weeks on diets in which the fish oil was replaced in a graded manner by linseed oil. At the end of the trial, fatty
acyl desaturation/elongation and oxidation activities were determined in isolated hepatocytes and intestinal enterocytes using
[1-14C]18:3n-3 as substrate, and samples of liver and intestinal tissue were collected for analysis of lipid and fatty acid composition.
The results showed that, despite increased desaturation of [1-14C]18:3n-3 in hepatocytes, provision of dietary 18:3n-3 did not prevent the decrease in tissue n-3HUFA in fish fed linseed
oil. Intestinal enterocytes were a site of significant fatty acid desaturation but, in contrast to hepatocytes, the activity
was not increased by feeding linseed oil and was generally lower in fish fed linseed oil compared to fish fed only fish oil.
In contrast, oxidation of [1-14C]18:3n-3 in enterocytes was generally increased in fish fed linseed oil compared to fish fed the diet containing only fish
oil. However, oxidation of [1-14C]18:3n-3 in hepatocytes was 4- to 8-fold lower than in enterocytes and was not affected by diet. Furthermore, oxidation of
[1-14C]18:3n-3 in enterocytes exceeded desaturation irrespective of dietary treatment, whereas similar amounts of [1-14C]18:3n-3 were desaturated and oxidized in hepatocytes from fish fed only fish oil and desaturation exceeded oxidation by
3-fold in fish fed the diet containing 100% linseed oil. The molecular mechanisms underpinning these results were discussed.
Full-text · Article · Feb 2002 · Fish Physiology and Biochemistry
[Show abstract][Hide abstract] ABSTRACT: The in vitro incorporation of 3H-radio-labeled arachidonic (20:4n-6) and docosahexaenoic (22:6n-3) acids by the photosensitive trout pineal gland was visualized using photon and electron microscopy. After 6 hr of incubation, 3H-20:4n-6 appeared distributed in photoreceptors, as well as in glial cells, whereas 3H-22:6n-3 was preferentially taken up by photoreceptors, mainly in the apical part (including the photoreceptive outer segment). Radioactivity was mainly seen over membranes of glia when the incorporation of 3H-20:4n-6 was followed by 12-18 hr of chase. We also report differences in the incorporation of 14C-radio-labeled linoleic (18:2n-6), linolenic (18:3n-3), eicosapentenoic (20:5n-3), 20:4n-6, and 22:6n-3 acids into the lipids in glands cultured under different lighting regimes. Phosphatidylcholine and triacylglycerols contained most of the radio-labeled polyunsaturated fatty acids (PUFA) incorporated. The proportion of incorporated 20:4n-6 recovered in phosphatidylinositol was always significantly higher than that found with the other PUFA. At least 10% of radioactivity from each incorporated substrate, except 22:6n-3, was recovered in elongation products. It is concluded that the pineal gland of the trout can assimilate exogenous PUFA into cellular lipids in vitro, in a manner consistent with our previous in vivo findings. In terms of lipid composition, the trout pineal gland resembles more the vertebrate retina than the rat pineal gland. This might be related to the loss of direct photosensitivity of the mammalian pineal. Together, the differences reported herein between 22:6n-3 and 20:4n-6 suggest the former plays an important role in the phototransduction process, whereas the latter might be more specifically involved in the production of phosphoinositide-derived second messengers.
No preview · Article · Oct 2001 · Journal of Pineal Research
[Show abstract][Hide abstract] ABSTRACT: The bed-forming brittlestars Ophiothrixfragilis, Ophiocominanigra and Amphiurachiajei from Oban Bay, Scotland were studied using methods previously employed to study chemoautotrophic symbioses. Ophiothrixfragilis and A.chiajei both contain symbiotic bacteria (SCB) while Ophiocominanigra is non-symbiotic. Samples were taken of Ophiothrixfragilis at approximately two-week intervals for one year. Symbiotic bacteria numbers were determined by direct counting of homogenates of the arms of 50 individual brittlestars. Water samples were analysed for chlorophyll content. Stable isotope ratios for carbon and nitrogen were determined for each homogenate sample. Regular SCB counts were made on the infaunal brittlestar A.chiajei. Homogenate samples of Ophiothrixfragilis, A.chiajei and the non-symbiotic Ophiocominanigra were analysed to produce fatty acid profiles for each species. Symbiotic bacteria count varied by up to one order of magnitude in both Ophiothrixfragilis and A.chiajei with no evidence of seasonality in this variation. Symbiotic bacteria number was inversely correlated with 13C. 16:17 fatty acids were used as putative bacterial markers. Both symbiotic species had higher percentages of 16:17 from its SCB. The SCB are heterotrophic and may contribute to the nitrogen budget of the host. The two symbiotic species studied here derive the bulk of their nutrition from conventional feeding but SCB make significant, additional contributions.
No preview · Article · Apr 2000 · Journal of the Marine Biological Association of the UK
[Show abstract][Hide abstract] ABSTRACT: Artemia nauplii were enriched for 24 h with radiolabelled fatty acid ethyl esters and then starved for a subsequent period of 24 h. Analyses of the distribution of radioactivity in lipids from samples taken at the end of the enrichment period and after the subsequent starvation showed that the ethyl esters were readily converted into other lipid classes, mainly triacylglycerols, during assimilation by the nauplii. The proportions of radioactivity recovered in free fatty acids and phospholipids increased during the starvation period indicating the mobilisation of fatty acids from triacylglycerols for use in catabolism and in the formation of biomembrane lipids. The distribution pattern of radioactivity from [U–]22:6n−3 in the fatty acids of the nauplii demonstrates that Artemia are capable of retroconverting 22:6n−3 to 20:5n−3.
[Show abstract][Hide abstract] ABSTRACT: The lipid composition of sediments underlying salmon cages in a Scottish sealoch was determined along with that of the diet supplied to the fish to examine the influence of lipids originating from fish farm wastes. Sediments were taken at regular intervals along a transect line perpendicular to the line of cages and extending 50 m on either side. Lipids were extracted from regions of the sediment cores corresponding to different depth layers of sediment and analyzed for lipid class and fatty acid composition. The lipid content of the surface layer of sediment (0–5 mm) directly under the cages (2 mg/g sediment) was substantially higher than that of the deeper layers of sediment. The amount of lipid in the surface sediment decreased markedly with the distance from the cages, with the decrease being more rapid on one side of the fish farm than the other. At the 50-m sampling sites, the lipid content of the surface sediment layer (0.4 mg/g sediment) was closer to that of the underlying layers. Triacylglycerols, the main lipid class present in the diet fed to the salmon, were present in sediments in highest concentration (0.44 mg/g sediment) in surface sediments directly beneath the cages. Free fatty acids, sterols, polar lipids and a combined hydrocarbons/wax esters/cholesterol esters fraction were all present at similar levels to those of triacylglycerols in sediments beneath the cages. The distribution pattern of the amounts of individual lipid classes in sediments followed that of total lipid and showed a decrease with the distance from the cages. The lipid component of the fish feed contained a higher level of polyunsaturated fatty acids, particularly 20:5(n − 3) and 22:6(n − 3), than lipid extracted from the sediments, while branched chain and odd-chain length fatty acids were more abundant in the latter. The principal fatty acid of the fish diet, 22:1(n − 11) (14.7% total fatty acids) comprised around 9% of the fatty acids of surface sediment layer directly under the cages, but less than 5% of those at 50 m. The proportions of the other characteristic fatty acids of the diet, 20:1(n − 9), 20:5(n − 3) and 22:6(n − 3), showed a similar decrease with distance. The results show that the lipid composition of sediments underlying marine fish cages is influenced by that of waste material from the cages.
[Show abstract][Hide abstract] ABSTRACT: The betaine lipids diacylglycerylhydroxymethyltrimethyl-β-alanine (DGTA) and diacylglyceryltrimethylhomoserine (DGTS) can be identified by derivatization of their polar groups. Demethylation, deacylation and silylation of DGTS yields demethyl-deacyl-DGTS-TMSi; dihydro-deamino-deacyl-DGTA-TMSi is produced by deamination, hydrogenation, deacylation and silylation of DGTA. The characterization of the derivatives by GC-MS was used as a diagnostic method for the identification of DGTA in Chroomonas salina, where this lipid accounts for 20% of the total polar lipids. Major fatty acids of DGTA (%) are 22:6n−3 (22), 20:5n−3 (14), 18:1n−7 (12), 18:4n−3 (11), 16:0 (8), and 14:0 (8), indicating that this lipid contains a broad variety of different molecular species in this alga.
[Show abstract][Hide abstract] ABSTRACT: 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.
Full-text · Article · Mar 1996 · Biochimica et Biophysica Acta
[Show abstract][Hide abstract] ABSTRACT: To examine the ability of pike (Esox lucius L.) to modify exogenous PUFA by desaturation and elongation, (14)C-labelled 18:2(n-6), 18:3(n-3), 20:4(n-6) and 20:5(n-3) were injected intraperitoneally and the distribution of radioactivity in tissue lipid classes and liver PUFA measured. In all tissues examined, radioactivity from all (14)C-PUFA was recovered in many classes of acyl lipids and the level of recovery generally reflected the relative abundance of the lipid classes. Triacylglycerols, CGP and EGP usually contained high levels of all incorporated (14)C-PUFA. PI contained higher levels of radioactivity from (14)C-20:4(n-6) than from other injected substrates. In liver lipid, the Δ6 desaturation products of (14)C-18:2(n-6) and (14)C-18:3(n-3) contained no measurable radioactivity although the elongation products of the Δ6 desaturation products were labelled, as were the direct elongation products of these injected substrates. No radioactivity from (14)C-18:2(n-6) or (14)C-18:3(n-3) was detected in C20 or C22 products of Δ5 and Δ4 desaturation. Almost all radioactivity from injected (14)C-20:4(n-6) was recovered in this PUFA. Of the total radioactivity from (14)C-20:5(n-3) incorporated into liver lipid, 7% was present as 24:5 and 16.4% was recovered in hexaenoic fatty acids. In liver, 24:5(n-3) and 24:6(n-3) each accounted for 1% of the mass of total fatty acids and were located almost exclusively in triacylglycerols. The presence of radioactivity in these C24 PUFA suggests that in pike the synthesis of 22:6(n-3) from 20:5(n-3) may proceed without Δ4 desaturase via the pathway which involves chain shortening of 24:6(n-3). It is concluded that under the circumstances employed in this study pike, do not exhibit Δ5 desaturase activity and are unable to synthesize 20:4(n-6) and 20:5(n-3) from 18:2(n-6) and 18:3(n-3), respectively. This suggests that pike may require 20:4(n-6) and 20:5(n-3) preformed in the diet.
No preview · Article · Jun 1995 · Fish Physiology and Biochemistry
[Show abstract][Hide abstract] ABSTRACT: The lipid composition of blubber, brain, muscle and heart from a Mediterranean monk sealMonachus monachus (an endangered species) were examined to allow comparisons with more common species of seals. Only neutral lipids (mainly
triacylglycerols) were detectable in the blubber lipids, whereas polar lipids predominated in the heart and in the brain.
Neutral and polar lipids comprised almost equal proportions in both liver and muscle. Choline glycerophospholipids (CGP) were
the major polar lipids, followed by ethanolamine glycerophospholipids (EGP) in the liver, heart and muscle. Cerebrosides accounted
for 28.8% of the brain lipids. All lipid classes of the liver contained high levels (31–47%) of polyunsaturated fatty acids
(PUFA), with the exception of phosphatidylserine. The total proportion of n−6 PUFA exceeded that of n−3 PUFA in all lipid
classes of the liver, due mainly to the high levels of 20∶4n−6. The highest level of 20∶4n−6 occurred in phosphatidylinositol,
where it comprised 32.4% of the total fatty acids. The CGP and EGP of the brain contained lower levels of PUFA than those
of the liver, muscle and heart. Alkenyl ethers accounted for 35.8% of the total long-chain moieties in brain EGP. The fatty
acid composition of blubber triacylglycerols differed from those of the lipid classes from other tissues in that it had a
very low ratio of n−6 to n−3 PUFA (0.3) as a result of a lower content of 20∶4n−6.
[Show abstract][Hide abstract] ABSTRACT: Fish oils containing different levels of polymers of triacylglycerols formed during autoxidation were incubated with pancreatic lipase to establish whether these polymers are substrates for lipase hydrolysis. With oils containing low amounts (less than 4%) of triacylglycerol polymers as substrates, both triacylglycerols and polymers of triacylglycerols were almost completely hydrolyzed, and fatty acid monomers and monoacylglycerols were the major lipid products. Under the same incubation conditions, some triacylglycerols remained intact when highly oxidized oils containing 20 or 30% triacylglycerol polymers were the substrate. The fatty acid composition of these residual triacylglycerols was almost identical to that of triacylglycerols present at the start of the assay. When fish oil containing 30% triacylglycerol polymers was incubated with the lipase, the component triacylglycerols and polymers of triacylglycerols were hydrolyzed at similar rates, and fatty acid dimers were detected as a product. It is concluded that the high molecular weight polymers of triacylglycerols present in oxidized fish oils can be hydrolyzed by pancreatic lipase in vitro.