Dietary protein and fatty acid composition of liver lipids in the rat

In order to compare the effects of different sources of dietary protein on the fatty acid composition of phosphatidylcholines (PC), phosphatidylethanolamines (PE), phosphatidylinositols (PI), cholesteryl esters and triacylglycerols, male rats were fed for a 4-week period on cholesterol-free, or cholesterol-containing, diets based on casein, or soybean protein and olive oil. The most conspicuous difference observed was the occurrence of significantly higher levels of 5,8,11-eicosatrienoic acid, 20:3 (n - 9), in the different lipid classes of casein-fed, compared with soybean protein-fed, animals. In the PI fraction of livers from the groups of rats fed casein diet, this fatty acid amounted to between 9.9 and 13.3% by weight of the total fatty acids. Phospholipids from livers of casein-fed rats contained increased levels of oleic acid, 18:1 (n - 9) (in PC and PE) and reduced levels of stearic acid (18:0). Moreover, in this group of rats PI contained a reduced level of arachidonic acid, 20:4 (n - 6). A casein-related decrease in the linoleic acid, 18:2 (n - 6), content of PC and PE was observed only in the rats fed on cholesterol-free diet. Effects on the fatty acid composition were also observed in the triacyglycerol and cholesteryl ester fractions, in which the rats fed casein diet showed higher levels of palmitoleic acid, 16:1 (n - 7) (cholesterol-supplemented diet) and lower values for linoleic acid, than the soybean protein-fed rats.     

Maternal dietary fat alters amniotic fluid and fetal intestinal membrane essential n-6 and n-3 fatty acids in the rat

We investigated whether maternal fat intake alters amniotic fluid and fetal intestine phospholipid n-6 and n-3 fatty acids. Female rats were fed a 20% by weight diet from fat with 20% linoleic acid (LA; 18:2n-6) and 8% alpha-linolenic acid (ALA; 18:3n-3) (control diet, n = 8) or 72% LA and 0.2% ALA (n-3 deficient diet, n = 7) from 2 wk before and then throughout gestation. Amniotic fluid and fetal intestine phospholipid fatty acids were analyzed at day 19 gestation using HPLC and gas-liquid chromotography. Amniotic fluid had significantly lower docosahexaenoic acid (DHA; 22:6n-3) and higher docosapentaenoic acid (DPA; 22:5n-6) levels in the n-3-deficient group than in the control group (DHA: 1.29 +/- 0.10 and 6.29 +/- 0.33 g/100 g fatty acid; DPA: 4.01 +/- 0.35 and 0.73 +/- 0.15 g/100 g fatty acid, respectively); these differences in DHA and DPA were present in amniotic fluid cholesterol esters and phosphatidylcholine (PC). Fetal intestines in the n-3-deficient group had significantly higher LA, arachidonic acid (20:4n-6), and DPA levels; lower eicosapentaenoic acid (EPA; 20:5n-3) and DHA levels in PC; and significantly higher DPA and lower EPA and DHA levels in phosphatidylethanolamine (PE) than in the control group; the n-6-to-n-3 fatty acid ratio was 4.9 +/- 0.2 and 32.2 +/- 2.1 in PC and 2.4 +/- 0.03 and 17.1 +/- 0.21 in PE in n-3-deficient and control group intestines, respectively. We demonstrate that maternal dietary fat influences amniotic fluid and fetal intestinal membrane structural lipid essential fatty acids. Maternal dietary fat can influence tissue composition by manipulation of amniotic fluid that is swallowed by the fetus or by transport across the placenta.     

Distribution of omega-3 and omega-6 fatty acids in the ether- and ester-linked phosphoglycerides from tissues of the rainbow trout, Salmo gairdneri

1. Data presented here demonstrate that polyunsaturated fatty acids in the phospholipids of rainbow trout tissues are compartmentalized differently than in mammalian tissues. 2. We have determined the distribution of omega-3 (n-3) and omega-6 (n-6) fatty acids in the alkyl-, alk-1-enyl-, and diacyl- subclasses of phosphatidylcholines (PC), phosphatidyl-ethanolamines (PE), phosphatidylinositols (PI), and phosphatidylserines (PS) from gill, kidney and spleen of rainbow trout. 3. Alkyl-linked PC and alk-1-enyl-linked PE were the most abundant ether-containing phospholipids, amounting to 10-15% of each class; no ether-linked PI or PS was detected. 4. C20:4 n-6 was found in high concentrations only in PI; the n-3 fatty acids were found in highest concentration in the ether-linked phospholipids as compared with the diacyl subclasses and C20:5 n-3 was especially prevalent in 1-O-alk-1'-enyl-2-acyl-sn-glycero-3-phosphoethanolamine and C22:6 n-3 was prevalent in PS.     

Synthesis of very long chain (up to 36 carbon) tetra, penta and hexaenoic fatty acids in retina.

The synthesis of very long chain (C24 to C36) polyunsaturated (four, five and six double bonds) fatty acids (VLCPUFA) is investigated in bovine retina using [14C]acetate. Saturates on the one hand (mainly palmitate), and polyenes on the other (mainly VLCPUFA), incorporate most of the label found in lipids. Phosphatidylcholine (PC) is the most highly labelled lipid class, since both types of 14C-labelled fatty acids, but especially this novel series of VLCPUFA, are concentrated in this phospholipid. Radioactivity from [14C]acetate is found in very long chain tetra, penta and hexaenoic fatty acids of PC. The labelling of 20:4(n - 6), 20:5(n - 3), 22:5(n - 6) and 22:6(n - 3) is much lower than that of longer polyenes of each of these series, indicating that VLCPUFA are synthesized in situ by successive elongations of the above polyenes, pre-existing in retina lipids. In various subcellular fractions isolated from retinas after incubations with [14C]acetate (including cytosol, microsomes, mitochondria and photoreceptor membranes), the labelling of the VLCPUFA of PC is very high, even at relatively short intervals of incubation. The results suggest that not only the synthesis but also the intracellular traffic among membranes of VLCPUFA-containing species of PC are very active processes in the retina.     

Fatty acid composition and incorporation of arachidonic acid into phospholipids of hemocytes from the tobacco hornworm Manduca sexta

The fatty acid compositions were determined for total lipids, triacylglycerols, phospholipids and four phospholipid fractions, including phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine/phosphatidylinositol (PS/PI) and cardiolipin (CA) obtained from hemocytes and cell-free serum from second day, fifth instar larvae of the tobacco hornworm Manduca sexta and the standard Manduca rearing medium. The hemocyte fatty acid profiles were considerably different from the profiles of the medium the insects were reared on and from the profiles of the cell-free serum. Hemocyte neutral lipids had lower proportions of polyunsaturated fatty acids than phospholipids. The fatty acid profiles of PC, PE, PS/PI and CA differ from each other and from the total lipid profiles, indicating selective fatty acid incorporation into hemocyte phospholipid species. Studies with radioactive arachidonic acid similarly indicated selective incorporation of polyunsaturated fatty acids into hemocyte lipids. Under our in vitro conditions, >40% of the total radioactivity was incorporated into hemocyte lipids. About 93% of the incorporated radioactivity was found in phospholipids. Within phospholipids. most of the radioactivity was associated with PC (46%), and less with PE (28%) and PS/PI (21%). Very little radioactivity was recovered in CA (0.9%).     

Apparent relative retention of the phosphatidylethanolamine molecular species 18:0-20:5(n-3), 16:0-22:6(n-3) and the sum 16:0-20:4(n-6) plus 16:0-20:3(n-9) in the liver microsomes of pig on an essential fatty acid deficient diet.

Attempts at a better understanding of the cell membrane organization and functioning need to assess the physical properties which partly depend (i) on the positional distribution of the fatty acids in the membrane phospholipids (PLs) and (ii) on the way by which the PL molecular species are affected by exogenous fatty acids. To do that, the effects of essential (polyunsaturated) fatty acid (EFA) deficiency and enrichment were studied in the liver microsomes of piglets feeding on either an EFA-deficient diet or an EFA-enriched diet containing hydrogenated coconut oil or a mixture of soya + corn oils, respectively. After derivatization, the diacylated forms of choline and ethanolamine PLs were analyzed using a combination of chromatographic techniques and fast-atom bombardment-mass spectrometry. The dinitrobenzoyl-diacylglycerol derivatives corresponding to the molecular species of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were identified. It appears that three factors brought about a marked apparent relative retention: the nature of (i) the base of the polar head, (ii) fatty acids at the sn-1 position and (iii) fatty acids at the sn-2 position. The highest apparent relative retentions were displayed by the 18:0-20:5(n-3)-PE and 16:0-22:6(n-3)-PE. It is noteworthy that the behavior of 20:3 n-9--which is synthesized during the EFA-deficient diet by the same bioconversion system as 20:4 n-6--was very similar to that of 20:4 n-6 during the formation of PC and PE molecular species and that the molecular species of PE containing 20:4(n-6) and 20:3(n-9), gathered together as metabolical homologues, were also apparently retained, particularly in association with 16:0. Present observations are consistent with some others showing retention or preferential distribution of EFA in PE and suggest that specific acyltransferase(s), ethanolamine phosphotransferase and methyltransferase would be mainly involved for PE and PC formation in liver endoplasmic reticulum. Fast-atom bombardment-mass spectrometry of intact phospholipids enables us to show that there is no very long chain dipolyunsaturated phospholipid in liver endoplasmic reticulum.     

Effects of corn oil- and fish oil-supplemented diets on phospholipid fatty acid composition of rat liver nuclei

The effects of dietary fat on fatty acid compositions of phospholipids in liver nuclei were investigated. By feeding a diet containing 5% corn oil or fish oil to rats, the proportions of n -6 or n -3 polyunsaturated fatty acids (PUFA), respectively, were increased in phospholipids of the liver nuclei. By feeding a fat-free diet, endogenous PUFA were increased. Even after feeding the fat-free diet for 40 weeks, the n - 6 still remained at about 10% in both phosphatidylcholine (PC) and phosphatidylethanolamine (PE), while the n -3 PUFA remained at about 5 and 16% in PC and PE, respectively. The fatty acid compositions of phospholipids in the liver nuclei were influenced by dietary fat and were roughly similar to those in the microsomes. The proportion of n - 3 PUFA was high in PE of both the nuclear membrane and matrix. The proportion of n - 6 was higher in both PC and PE of the nuclear matrix than in those of the membrane.     

Fatty acid profiles of brain phospholipid subclasses of rats fed n - 3 polyunsaturated fatty acids of marine or vegetable origin. A two generation study.

The effects of dietary n - 3 polyunsaturated fatty acids (PUFA) on fatty acid profiles of rat brain phospholipid subclasses as well as on heart phosphatidylethanolamine through two generations were examined: Three groups of rats were fed 20 weight% fat diets in which approx. 30% of the fatty acids were polyunsaturated, either 17% linoleic acid + 13% C20(-) + C22 polyunsaturates from fish oil or 17% linoleic + 13% alpha-linolenic acid from linseed oil or 30% linoleic acid. The rats of the two generations were killed as adults at 18 weeks of age. The results demonstrated that fish oil was a better source than alpha-linolenic acid for incorporation of n - 3 PUFA into the examined phospholipids. This was seen both in brain and heart tissue and in both generations of rats. In the brain phosphatidylethanolamine (PE) and phosphatidylserine (PS) similar fatty acid profiles were found in 1st and 2nd generation, but fish oil was more efficient than 18:3(n - 3) in increasing the levels of 22:6(n - 3), 20:5(n - 3), 22:5(n - 3) and reducing 20:4(n - 6) and 22:5(n - 6). Fatty acid profiles of phosphatidylinositol (PI), phosphatidylinositol-4-phosphate (PIP) and phosphatidylinositol-4,5-bisphosphate (PIP2) were affected by dietary fats. In PIP and PIP2 of 2nd generation rats 20:4(n - 6) was reduced from 36 to 29% following fish oil intake, whereas alpha-linolenic acid had no effects. The cholesterol/phospholipid ratio was not affected in the brain, neither was the degree of unsaturation of the phospholipids. In heart PE the highest levels of 20:5(n - 3)(2%) and 22:6(n - 3) (36%) were observed following fish oil intake. However, in rats fed alpha-linolenic acid a considerable increase in the level of 22:6(n - 3) was observed from the 1st (21%) to the 2nd generation (26%).     

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

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

Characterization of plasma membrane lipids and luteinizing hormone receptors of ovine corpora lutea during luteolysis and early pregnancy

Lipid composition of plasma membranes from luteal cells was examined to determine whether changes in this organelle occur during regression and maintenance of the corpus luteum in nonpregnant (NP) and pregnant (P) ewes, respectively. Forty ewes were assigned to be killed on Day 13 or 15 of the estrous cycle (D13-NP and D15-NP) or pregnancy (D13-P and D15-P). Purification of luteal plasma membranes on discontinuous sucrose gradients yielded two fractions, designated F1 and F2, that exhibited the greatest enrichment of 5'-nucleotidase activity (five- and fourfold, respectively) over that of the homogenate. These fractions also yielded the lowest contamination by endoplasmic reticulum as represented by nicotinamide adenine dinucleotide phosphate (NADPH) cytochrome C reductase activity and mitochondrial membranes as indicated by succinate dehydrogenase activity. Predominant phospholipids identified in membranes obtained from all groups were phosphatidylcholine (PC, 48.9 +/- 0.6% of total phospholipid), phosphatidylethanolamine (PE, 33.3 +/- 0.4%), sphingomyelin (SPH, 9.7 +/- 0.3%), phosphatidylserine (PS, 3.5 +/- 0.2%), and phosphatidylinositol (PI, 4.0 +/- 0.5%). No changes in microgram phospholipid/mg membrane protein were observed for any luteal phospholipid on D13 and 15 of the estrous cycle or pregnancy. No significant changes in the relative percentages of major fatty acids present in PC (palmitic [16:0], oleic [18:1]), PE (stearic [18:0], 18:1 and arachidonic [20:4]), or PS (18:0, 18:1, docosatetraenoic [22:4]), nor in the ratios of unsaturated (U) to saturated (S) fatty acids in these phospholipids were observed. Significant differences in unsaturated fatty acids of chain length greater than 20 carbons present in minor quantities in PC, PE, and PS were detected between NP and P ewes as well as between days within reproductive stage. The profile of major fatty acids present in PI revealed decreases in 18:0 and 20:4 in D15-NP and increases in 22:4 and docosapentaenoic acid (22:5) in luteal membranes of both D13- and D15-NP ewes relative to the levels of these fatty acids in PI of corresponding groups of pregnant ewes. There was a general trend for 20:4 levels of PC and PI in membranes of D15-NP ewes to be inversely related to those of D15-P ewes. Collectively, these changes were reflected by an increased U:S fatty acid ratio in luteal membrane PI during the estrous cycle. Specific binding of [125I] iodo-human chorionic gonadotropin to luteal plasma membranes from NP and P ewes on D13 and 15 (6/group) revealed similar affinities and concentrations of unoccupied luteinizing hormone (LH) receptors.(ABSTRACT TRUNCATED AT 400 WORDS)     

Apparent relative retention of the phosphatidylethanolamine molecular species 18:0–20:5(n−3), 16:0–22:6(n−3) and the sum 16:0–20:4(n−6) plus 16:0–20:3(n−9) in the liver microsomes of pig on an essential fatty acid deficient diet

Attempts at a better understanding of the cell membrane organization and functioning need to assess the physical properties which partly depend (i) on the positional distribution of the fatty acids in the membrane phospholipids (PLs) and (ii) on the way by which the PL molecular species are affected by exogenous fatty acids. To do that, the effects of essential (polyunsaturated) fatty acid (EFA) deficiency and enrichment were studied in the liver microsomes of piglets feeding on either an EFA-deficient diet or an EFA-enriched diet containing hydrogenated coconut oil or a mixture of soya + corn oils, respectively. After derivatization, the diacylated forms of choline and ethanolamine PLs were analyzed using a combination of Chromatographic techniques and fast-atom bombardmentmass spectrometry. The dinitrobenzoyl-diacylglycerol derivatives corresponding to the molecular species of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were identified. It appears that three factors brought about a marked apparent relative retention: the nature of (i) the base of the polar head, (ii) fatty acids at the sn−1 position and (iii) fatty acids at the sn−2 position. The highest apparent relative retentions were displayed by the 18:0–20:5(n−3)-PE and 16:0–22:6(n−3)-PE. It is noteworthy that the behavior of 20:3 n−9 — which is synthesized during the EFA-deficient diet by the same bioconversion system as 20:4 n−6 — was very similar to that of 20:4 n−6 during the formation of PC and PE molecular species and that the molecular species of PE containing 20:4(n−6) and 20:3(n−9), gathered together as metabolical homologues, were also apparently retained, particularly in association with 16:0. Present observations are consistent with some others showing retention or preferential distribution of EFA in PE and suggest that specific acyltransferase(s), ethanolamine phosphotransferase and methyltransferase would be mainly involved for PE and PC formation in liver endoplasmic reticulum. Fast-atom bombardment-mass spectrometry of intact phospholipids enables us to show that there is no very long chain dipolyunsaturated phospholipid in liver endoplasmic reticulum.     

The influence of ionic detergents on the phospholipid fatty acid compositions of Porphyridium purpureum

The phospholipid fatty acid composition of Porphyridium purpureum on a solid medium was studied in the presence of sodium dodecyl sulphate (SDS) and cetyl trimethylammonium bromide (CTAB). The most common fatty acids in phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) were palmitic (16:0), stearic (18: 0), linoleic (18:2ω 6), arachidonic (20:4ω 6) and eicosapentaenoic (20:5ω 3) acids, 20:4ω 6 being very abundant. In phosphatidyl glycerol (PG) the most common acids were 16:0, trans-hexadecenoic acid (tr 16:1ω 13), oleic acid (18:1) and 20:4ω 6. Both detergents increased the saturation grade of PC and PE by decreasing the relative amount of the polyunsaturated acids, especially 20:4ω 6. A corresponding increase in the amounts of saturated acids was observed in PC and PE. The changes in PG fatty acid composition were not very significant: a slight increase was observed in the amounts of 16:0 and tr 16:1ω 13 , with a corresponding decrease in the amounts of 20:4ω 6 and 20:5ω 3. Both detergents decreased the PC/PE and the (PC + PE)/PG ratios very markedly, most probably as a result of increases in the amounts of PE and PG. In the presence of CTAB the cells seemed to contain much more phospholipids than in the presence of SDS, perhaps as a result of the mucilage-precipitating effect of CTAB. The significance of the findings is discussed.     

Effects of hypothyroidism on the distribution and fatty acyl composition of phospholipids in sarcoplasmic reticulum of fast skeletal muscle of the rat

The distribution of phospholipids and fatty acyl composition of individual phospholipids in sarcoplasmic reticulum from fast skeletal muscle of hypothyroid and euthyroid (control) rats have been determined. Hypothyroidism resulted in a 24% decrease in the phosphatidylethanolamine (PE) content and a concomitant increase in the phosphatidylcholine (PC) content of the sarcoplasmic reticulum. The amounts of other phospholipids and cholesterol remained unaffected. Fatty acyl compositions of PE and PC were quantitatively different, but hypothyroidism affected these compositions similarly. Changes included an increase in the proportions of docosahexaenoic (22:6(n - 3)), arachidonic (20:4(n - 6)), icosatrienoic (20:3(n - 6)) and stearic (18:0) acids and a decrease in those of linoleic (18:2(n - 6)), palmitic (16:0) and oleic (18:1(n - 9)) acids. The effects of hypothyroidism on the phospholipid distribution could be reversed by treatment of hypothyroid animals with thyroid hormone for a period of 14 days (10 micrograms T3/100 g body weight per 2 days). The fatty acyl composition of the phospholipids was also restored to the euthyroid values by this treatment. Exceptions were 18:2 and 22:6 in PE, in which case reversal was significant but not complete, and 18:2, 20:4 and 22:6 in PC. The levels of these acids in PC were not reversed to the euthyroid values after the 14-day treatment, but rather the opposite occurred.     

Low-salt diet alters the phospholipid composition of rat colonocytes

The effect of low-salt diet on phospholipid composition and remodeling was examined in rat colon which represents a mineralocorticoid target tissue. To elucidate this question, male Wistar rats were fed a low-salt diet and drank distilled water (LS, low-salt group) or saline instead of water (HS, high-salt group) for 12 days before the phospholipid concentration and fatty acid composition of isolated colonocytes were examined. The dietary regimens significantly influenced the plasma concentration of aldosterone which was high in LS group and almost zero in HS group. Plasma concentration of corticosterone was unchanged. When expressed in terms of cellular protein content, a significantly higher concentration of phospholipids was found in LS group, with the exception of sphingomyelin (SM) and phosphatidylserine (PS). Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) accounted for more than 70% of total phospholipids in both groups. A comparison of phospholipid distribution in LS and HS groups demonstrated a higher percentage of PE and a small, but significant, decrease of PC and SM in LS group. The percentage of phosphatidylinositol (PI), PS and cardiolipin (CL) were not affected by mineralocorticoid treatment. With respect to the major phospholipids (PE, PC), a higher level of n-6 polyunsaturated fatty acids (PUFA) and lower levels of monounsaturated fatty acids were detected in PC of LS group. The increase of PUFA predominantly reflected an increase in arachidonic acid by 53%. In comparison to the HS group, oleic acid content was decreased in PC and PE isolated from colonocytes of the LS group. Our data indicate that alterations in phospholipid concentration and metabolism can be detected in rats with secondary hyperaldosteronism. The changes in phospholipid concentration and their fatty acid composition during fully developed effect of low dietary Na+ intake may reflect a physiologically important phenomenon with long-term consequences for membrane structure and function.     

Essential fatty acid metabolism in cultured human airway epithelial cells.

To characterize essential fatty acid metabolism of human airway epithelium, we examined the capacity of epithelial cells to incorporate and desaturate/elongate 18:2(n - 6) and the turnover of phospholipid fatty acyl chains in these cells. Epithelial cells were cultured for 5-7 days and incubated with [1-14C]18:2(n - 6) (1 microCi, 100 nmol). The essential fatty acid profile of the cells was readily modified by 18:2(n - 6) supplementation to culture medium. After 4 h incubation, 32 +/- 5.6 nmol of [1-14C]18:2(n - 6) was incorporated into phospholipids (65 +/- 9.5%, of which 74% was incorporated into phosphatidylcholine (PC)) and neutral lipid (31 +/- 10%) per mg protein of cultured cells. 30 +/- 8% of [1-14C]18:2(n - 6) incorporated, was converted to homologous trienes, tetraenes and pentaenes, the major products being 20:3(n - 6) and 20:4(n - 6). The conversion of 18:2(n - 6) was time-dependent and donor age-related. A higher proportion of 20:3(n - 6) and 20:4(n - 6) was incorporated into phosphatidylinositol (PI) and phosphatidylethanolamine (PE). About 10-15% of total products formed from 18:2(n - 6) was released from membrane to culture medium. Both 20:4(n - 6) and 20:5(n - 3) inhibited 18:2(n - 6) incorporation and desaturation. Rate of incorporation of 18:2(n - 6) was more than either 18:1(n - 9) or 16:0. With pulse-chase studies, the half-life of 18:2(n - 6) in PC, PI and PE was estimated to be 5.5, 6.0 and 7.3 h, respectively. These data indicate active metabolism of essential fatty acids in human airway epithelial cells. This metabolism may play a key role in the regulation of membrane properties and function in these cells.     

Fatty acid utilisation and metabolism in caecal enterocytes of rainbow trout (Oncorhynchus mykiss) fed dietary fish or copepod oil

A combined fatty acid metabolism assay was employed to determine fatty acid uptake and relative utilisation in enterocytes isolated from the pyloric caeca of rainbow trout. In addition, the effect of a diet high in long-chain monoenoic fatty alcohols present as wax esters in oil derived from Calanus finmarchicus, compared to a standard fish oil diet, on caecal enterocyte fatty acid metabolism was investigated. The diets were fed for 8 weeks before caecal enterocytes from each dietary group were isolated and incubated with [1-14C]fatty acids: 16:0, 18:1n-9, 18:2n-6, 18:3n-3, 20:1n-9, 20:4n-6, 20:5n-3, and 22:6n-3. Uptake was measured over 2 h with relative utilisation of different [1-14C]fatty acids calculated as a percentage of uptake. Differences in uptake were observed, with 18:1n-9 and 18:2n-6 showing the highest rates. Esterification into cellular lipids was highest with 16:0 and C18 fatty acids, accounting for over one-third of total uptake, through predominant incorporation in triacylglycerol (TAG). The overall utilisation of fatty acids in phospholipid synthesis was low, but highest with 16:0, the most prevalent fatty acid recovered in intracellular phosphatidylcholine (PC) and phosphatidylinositol (PI), although exported PC exhibited higher proportions of C20/C22 polyunsaturated fatty acids (PUFA). Other than 16:0, incorporation into PC and PI was highest with C20/C22 PUFA and 20:4n-6 respectively. Recovery of labelled 18:1n-9 in exported TAG was 3-fold greater than any other fatty acid which could be due to multiple esterification on the glycerol 'backbone' and/or increased export. Approximately 20-40% of fatty acids taken up were beta-oxidised, and was highest with 20:4n-6. Oxidation of 20:5n-3 and 22:6n-3 was also surprisingly high, although 22:6n-3 oxidation was mainly attributed to retroconversion to 20:5n-3. Metabolic modification of fatty acids by elongation-desaturation was generally low at <10% of [1-14C]fatty acid uptake. Dietary copepod oil had generally little effect on fatty acid metabolism in enterocytes, although it stimulated the elongation and desaturation of 16:0 and elongation of 18:1n-9, with radioactivity recovered in longer n-9 monoenes. The monoenoic fatty acid, 20:1n-9, abundant in copepod oil as the homologous alcohol, was poorly utilised with 80% of uptake remaining unesterified in the enterocyte. However, the fatty acid composition of pyloric caeca was not influenced by dietary copepod oil.     

Studies on polyenoic acid incorporation into human platelet lipid stores: interactions with linoleic and arachidonic acids

Several polyunsaturated fatty acids (C18-C22 acids) have been compared in their uptake by human platelets and their acylation into glycerophospholipid subclasses. This was also studied in the presence of linoleic and/or arachidonic acids, the main fatty acids of plasma free fatty acid pool. Amongst C20 fatty acids, dihomogamma linolenic acid (20:3(n-6)), 5,8,11-icosatrienoic acid (20:3(n-9)) and arachidonic acid (20:4(n-6)) were better incorporated. The uptake of 5,8,11,14,17-icosapentaenoic acid (20:5(n-3)) was significantly lower and comparable to that of C22 fatty acids (7,10,13,16-docosatetraenoic acid (22:4(n-6)) and 4,7,10,13,16,19-docosahexaenoic acid (22:6(n-3)) and linoleic acid (18:2(n-6)). In this respect, linolenic acid (18:3(n-3)) appeared the poorest substrate. The bulk of each acid was acylated into glycerophospholipids although the presence of linoleic and/or arachidonic acids diverted a part towards neutral lipids. This was prominent for 18:3(n-3) and C22 fatty acids. The glycerophospholipid distribution of each acid differed substantially and was not affected by the presence of linoleic and or arachidonic acids, except for 18:3(n-3) and 22:6(n-3) that were strongly diverted towards phosphatidylethanolamine (PE) at the expense of phosphatidylcholine (PC). The main features were an efficient acylation of 20:3(n-9) into phosphatidylinositol (PI) followed by 20:3(n-6) and 20:4(n-6), then by 20:5(n-3) and 22:4(n-6), and finally 22:6(n-3) and C18 fatty acids. This was reciprocal to the acylation into PE and to a lesser extent into PC which remained the main storage species in all cases. We conclude that human platelets may exhibit a certain specificity for taking up polyunsaturated fatty acids both in terms of total uptake and glycerophospholipid subclass distribution. Also the presence of polyunsaturated fatty acids of normal plasma, like linoleic and arachidonic acids, may interact specifically with such an uptake and distribution.     

Comparison of phospholipid and fatty acid composition of wild and cultured striped bass eggs

The dominant fatty acids in all neutral lipid fractions of non-water hardened eggs from two wild and one cultured stock of striped bass Morone saxatilis were the monoenes, 18 : 1n9/n7>16 : 1n7>17 : 1. The dominant fatty acids in the phospholipid fraction of all eggs, regardless of origin, were 22 : 6n3>18 : 1n9/n7>20 : 5n3>16 : 1n7>16 : 0>18 : 0. Arachadonic acid (AA, 20 : 4n6) was significantly lower (2·0%) in cultured fish eggs compared to either wild stock (5·8–6·1%). Fatty acids from the liver and eggs of wild Shubenacadie fish were similar to one another with respect to both neutral and phospholipid fractions. However, the AA and eicosapentaenoic acid (EPA, 20 : 5n3) content of the phospholipid fraction varied according to the hypothesized migration behaviour of Shubenacadie fish. The total lipid content of wild fish eggs was significantly greater than that of cultured fish. The total phospholipid content of Shubenacadie eggs was significantly higher than either Roanoke or cultured fish eggs. Phosphotidylinositol (PI) was the dominant phospholipid found ins all egg samples from all origins as opposed to phosphotidylcholine, which is usually the dominant phospholipid. These data indicate that PI and AA may have important and as yet unidentified roles in fertilization and embryonic development in these fish.     

Effect of hypo- and hyperthyroid states on phospholipid composition in developing rat heart

The aim of this study was to examine the effect of hypo- and hyperthyroidism on the phospholipid composition in developing rat heart. The hypothyroid state (PTU) was induced by 0.05% 6-n-propyl-2-thiouracil in drinking water given to nursing mothers from the postnatal day 2–21. The hyperthyroidism (T₃) was made by daily injection of 3,3,5-triiodo-L-thyronine (10 g/100 g body wt) to newborns in the same time period. Age matched intact littermates were taken as euthyroid controls. PTU decreased the concentration of total phospholipids (PL), choline phosphoglycerides (PC), ethanolamine phosphoglycerides (PE) and diphosphatidylglycerol (DPG) and increased the proportion of plasmalogen component of PE (PLPE). T₃ increased the concentration of PL, PC, PE, DPG and decreased PLPE in comparison with euthyroid controls. The ratio of saturated/unsaturated fatty acids (FA) in PE was decreased in PTU and increased in T₃ group. The ratio of n-6/n-3 polyunsaturated FA in PC, PE and phosphatidylinositol (PI) was increased in PTU due to increase of 18:2n-6 and decrease of 22:6n-3 proportion. T₃ decreased this ratio because of decline in 20:4n-6 and rise in 22:6n-3 proportion. Both hypo- and hyperthyroidism decreased the ratio of 20:4n-6/18:2n-6 in the majority of phospholipids. PTU decreased the unsaturation index in PC, PI and phosphatidylserine. It is concluded that thyroid state plays an essential role in the development of membrane phospholipid components in cardiac membranes during the early postnatal period.     

Growth, fat content and fatty acid profile of South American catfish, surubim (Pseudoplatystoma fasciatum) juveniles fed live, commercial and formulated diets

South American catfish, barred surubim ( Pseudoplatystoma fasciatum ) juveniles (117.6 ± 11.8 mg individual weight; 28.3 ± 2.5 mm total length) were fed various diets: one live ( Tubifex worms), two commercial (Aglo Norse and Bio Kyowa), and one semi-purified formulated diet (75% peptide based protein) over a 2-week period. Fish fed the Aglo Norse diet showed the highest growth performance, but cannibalism also was very high (42%). Fish fed peptide based formulated diet demonstrated the lowest growth rate, with no cannibalism. The highest survival was achieved with fish fed Tubifex worms (100%). Lipid level in the whole body of the fish fed four different experimental diets did not differ significantly, averaging 3.6 ± 0.7%. Fatty acid composition of neutral and phospholipid fractions of whole body lipids of fish reflected the fatty acid composition of the diets. The high level of 20:4 n -6 in Tubifex worms resulted in a high level of this fatty acid in the tissue of fish fed this diet. It remains uncertain how high survival and no cannibalism is related to dietary lipids/fatty acids. In all cases, the increasing ratio of n -3 HUFA (highly unsaturated fatty acids)/ n -6 HUFA in phospholipid fractions suggested the elongation and desaturation of 18:3 n -3 to 22:6 n -3 via 20:5 n -3. Moreover, in respect to the 20:4 n -6 levels in the diets, an increase in the concentration of this fatty acid in phospholipid fraction suggests that South American catfish can transform linoleate into arachidonate.