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1.
Effects of dietary vegetable oil on atlantic salmon hepatocyte fatty acid desaturation and liver fatty acid compositions 总被引:5,自引:0,他引:5
Fatty acyl desaturase activities, involved in the conversion of the C18 EFA 18∶2n−6 and 18∶3n−3 to the highly unsaturated fatty acids (HUFA) 20∶4n−6, 20∶5n−3, and 22∶6n−3, are known to be under
nutritional regulation. Specifically, the activity of the desaturation/elongation pathway is depressed when animals, including
fish, are fed fish oils rich in n−3 HUFA compared to animals fed, vegetable oils rich in C18 FFA. The primary aims of the present study were (i) to establish the relative importance of product inhibition (n−3 HUFA)
vs. increased substrate concentration (C18 EFA) and (ii) to determine whether 18∶2n−6 and 18∶3n−3 differ in their effects on the hepatic fatty acyl desaturation/elongation
pathway in Atlantic salmon (Salmo salar). Smolts were fed 10 experimental diets containing blends of two vegetable oils, linseed (IO), and rapeseed oil (RO), and
fish oil (FO) in a triangular mixture design for 50 wk. Fish were sampled after 32 and 50 wk, lipid and FA composition of
liver determined, fatty acyl desaturation/elongation activity estimated in hepatocytes using [1-14C]18∶3n−3 as substrate, and the data subjected to regression analyses. Dietary 18∶2n−6 was positively correlated, and n−3
HUFA negatively correlated, with lipid content of liver. Dietary 20∶5n−3 and 22∶6n−3 were positively correlated with liver
FA with a slope greater than unity suggesting relative retention and deposition of these HUFA. In contrast, dietary 18∶2n−6
and 18∶3n−3 were positively correlated with liver FA with a slope of less than unity suggesting metabolism via β-oxidation and/or desaturation/elongation. Consistent with this, fatty acyl desaturation/elongation in hepatocytes was significantly
increased by feeding diets containing vegetable oils. Dietary 20∶5n−3 and 22∶6n−3 levels were negatively correlated with hepatocyte
fatty acyl desaturation. At 32 wk, 18∶2n−6 but not 18∶3n−3 was positively correlated with hepatocyte fatty acyl desaturation,
wheres the reverse was true at 50 wk. The data indicate that both feedback inhibition through increased n−3 HUFA and decreased
C18 fatty acyl substrate concentration are probably important in determining the level of hepatocyte fatty acyl desaturation
and that 18∶2n−6 and 18∶3n−3 may differ in their effects on this pathway. 相似文献
2.
The effect of a protein diet on the biosynthesis of polyunsaturated fatty acids of the linoleic acid family was studied by
incubation of rat liver microsomes with labeled linoleic acid. The incubation was performed in desaturating, elongating and
desaturating-elongating conditions. In desaturating conditions, linoleic acid was converted to γ-linolenic acid, whereas in
elongating conditions it was converted to 20∶2, 22∶2 and 24∶2. In desaturating-elongating conditions, labeling was found in
γ 18∶3, 20∶2, 20∶3, 20∶4 and 22∶2. A protein diet increased the oxidative desaturation of linoleic acid to γ-linolenic and
arachidonic acid biosynthesis, whereas the elongating reaction was not enhanced in the experimental conditions tested. It
is suggested that the main controllable step in the linoleic acid family is the oxidative desaturation of linoleic acid to
γ-linolenic acid. 相似文献
3.
The desaturation of14C-1-linoleic acid to γ-linolenic acid and their incorporation into the microsomal lipids of rats fed on a balanced diet and
a protein diet were measured in vitro. It was shown that a protein diet does not change significantly the distribution of
the radioactivity among the different lipidic fractions compared to the animals fed on a balanced diet. However the microsomal
desaturation of linoleic acid to γ-linolenic acid increased in the rats maintained on a protein diet. Besides, the amount
and composition of the free fatty acids present in the microsomes of the animals fed on both diets were similar enough to
discard the hypothesis that they may modify the desaturation of linoleic acid produced by the diet. The enzymic activity of
the linoleyl desaturase of liver microsomes of animals fed on a protein diet, measured in substrate saturating conditions,
is greater than in animals with balanced diet. Consequently the results support the hypothesis that a protein diet increases
specifically the desaturating activity of the microsomes. 相似文献
4.
5.
The effect of dietary protein, casein (CAS) and soybean protein (SOY), on linoleic acid desaturation in liver microsomes was
studied in rats. The activity of Δ6 desaturase in total and rough endoplasmic reticula (ER and RER) was significantly higher
in the CAS group than in the SOY group. In ER and smooth endoplasmic reticulum, the steady-state fluorescence anisotropy of
1,6-diphenyl-1,3,5-hexatriene, when incorporated into the membrane, was decreased in the SOY group and accompanied by a reduction
in the cholesterol/phospholipid (CHOL/PL) ratio, consistent with an increase in membrane fluidity. In a separate study, the
effect of varying dietary proteins, CAS, milk whey protein, egg albumin, SOY, potato protein and wheat gluten, on the relationship
between the Δ6 desaturase activity and microsomal membrane fluidity was also examined. The results indicated that the dietary
protein-dependent change in the liver microsomal CHOL/PL ratio affected membrane fluidity, and subsequently the activity of
Δ6 desaturase in liver microsomes. However, since dietary protein influenced the Δ6 desaturase activity in RER without influencing
membrane fluidity, it is possible that some regulation might have taken place at the level of enzyme synthesis. 相似文献
6.
The effect of glucagon, dibutyryl cyclic adenosine 3′,5′-monophosphate, and epinephrine on the biosynthesis of polyunsaturated
fatty acids of the linoleic acid family was studied. The incubations were performed with rat liver microsomes and labeled
linoleic acid under desaturating and elongating conditions. Under desaturating conditions, linoleic acid was converted to
γ-linolenic acid, whereas under elongating conditions it was converted to 20∶2ω6. Glucagon, dibutyryl cyclic AMP, and epinephrine
decreased the oxidative desaturation of linoleic acid to γ-linolenic acid while the elongating reaction was not modified in
the experimental conditions tested. Consequently, the results support the hypothesis that the oxidative desaturation of linoleic
acid to γ-linolenic acid is the main controllable step in the biosynthesis of polyunsaturated fatty acids of the linoleic
acid family in the microsomes. 相似文献
7.
The effect of dietary docosahexaenoic acid (22∶6n−3, DHA) on the metabolism of oleic, linoleic, and linolenic acids was investigated
in male subjects (n=6) confined to a metabolic unit and fed diets containing 6.5 or <0.1 g/d of DHA for 90 d. At the end of the diet period,
the subjects were fed a mixture of deuterated triglycerides containing 18∶1n−9[d6], 18∶2n−6[d2], and 18∶3n−3[d4]. Blood samples
were drawn at 0, 2, 4, 6, 8, 12, 24, 48, and 72 h. Methyl esters of plasma total lipids, triglycerides, phospholipids, and
cholesterol esters were analyzed by gas chromatography-mass spectrometry. Chylomicron triglyceride results show that the deuterated
fatty acids were equally well absorbed and diet did not influence absorption. Compared to the low-DHA diet (LO-DHA), clearance
of the labeled fatty acids from chylomicron triglycerides was modestly higher for subjects fed the high DHA diet (HI-DHA).
DHA supplementation significantly reduced the concentrations of most n-6[d2] and n-3[d4] long-chain fatty acid (LCFA) metabolites
in plasma lipids. Accumulation of 20∶5n−3[d4] and 22∶6n−3[d4] was depressed by 76 and 88%, respectively. Accumulations of
20∶3n−6[d2] and 20∶4n−6[d2] were both decreased by 72%. No effect of diet was observed on acyltransferase selectivity or on
uptake and clearance of 18∶1n−9[d6], 18∶2n−6[d2], and 18∶3n−3[d4]. The results indicate that accumulation of n−3 LCFA metabolites
synthesized from 18∶3n−3 in typical U.S. diets would be reduced from about 120 to 30 mg/d by supplementation with 6.5 g/d
of DHA. Accumulation of n−6 LCFA metabolites synthesized from 18∶2n−6 in U.S. diets is estimated to be reduced from about
800 to 180 mg/d. This decrease is two to three times the amount of n−6 LCFA in a typical U.S. diet. These results support
the hypothesis that health benefits associated with DHA supplementation are the combined result of reduced accretion of n−6
LCFA metabolites and an increase in n−3 LCFA levels in tissue lipids. 相似文献
8.
To investigate the effects of dietary fat quality on synthesis and esterification of cholesterol, Syrian hamsters were fed
diets containing corn, olive, coconut or menhaden oils (10% w/w) with added cholesterol (0.1% w/w). After 3 weeks, animals
were sacrificed 90 min following IP injection of3H2O. Synthesis of free cholesterol and movement of free cholesterol into ester pools were measured from3H-uptade rate in liver and duodenum. Plasma total cholesterol and triglycerides levels were highest in coconut oil-fed animals,
whereas hepatic total cholesterol and ester levels were elevated in olive oil-fed animals, as compared with all other groups.
No diet-related differences were seen in duodenal cholesterol or total fatty acid content. In duodenum, uptake of3H per g tissue into cholesterol was greater compared with liver; however, within each tissue,3H-uptake into cholesterol was similar across groups. Notably,3H-uptake into cholesterol ester in liver was highest in menhaden oil-fed animals. These data suggest that menhaden fish oil
consumption results in enhanced movement of newly synthesized cholesterol into ester as compared with other fat types. 相似文献
9.
The effects of different dietary oils on the fatty acid compositions of liver phospholipids and the desaturation and elongation
of [1-14C]18∶3n−3 and [1-14C]18∶2n−6 were investigated in isolated hepatocytes from Atlantic salmon. Atlantic salmon smolts were fed diets containing
either a standard fish oil (FO) as a control diet, a 1∶1 blend of Southern Hemisphere marine oil and tuna orbital oil (MO/TO),
sunflower oil (SO), borage oil (BO), or oliver oil (OO) for 12 wk. The SO and BO diets significantly increased the percentages
of 18:2n−6, 18:3n−6, 20:2n−6, 20:3n−6, and total n-6 polyunsaturated fatty acids (PUFA) in salmon liver lipids in comparison
with the FO diet. The BO diet also increased the percentage of 20:4n−6. Both the SO and BO diets significantly reduced the
percentages of all n−3 PUFA in comparison with the FO diet. The OO diet significantly increased the percentages of 18:1n−9,
18:2n−6, total monoenes, and total n−6 PUFA in liver lipids compared to the FO diet, and the percentages of all n−3 PUFA were
significantly reduced. With [1-14C]18:3n−3, the recovery of radioactivity in the products of Δ6 desaturation was significantly greater in the hepatocytes from
salmon fed SO, BO, and OO in comparison with the FO diet. The BO diet also increased the recovery of radioactivity in the
products of Δ5 desaturation. Only the BO diet significantly affected the desaturation of [1-14C]18:2n−6, increasing recovery of radioactivity in both Δ6- and Δ5-desaturation products. In conclusion, dietary BO, enriched
in γ-linolenic acid (18:3n−6), significantly increased the proportions of both 20:3n−6 and 20:4n−6 in salmon liver phospholipids
and also significantly increased the desaturation of both 18:2n−6 and 18:3n−3 in salmon hepatocytes. The possible relationships
between dietary fatty acid composition, tissue phospholipid fatty acid composition, and desaturation/elongation activities
are discussed. 相似文献
10.
The effect of catecholamines and adrenergic blocking agents on the oxidative desaturation of linoleic acid in rat liver microsomes
was studied. Epinephrine (1 mg/kg/body weight) produced a significant decrease on the conversion of [1-14C]linoleic acid to γ-linolenic acid. The effect of epinephrine was blocked by single injections of the β blockers propranolol
(10 mg/kg body weight) or dichloroisoproterenol 30 min before the hormone treatment. Isoproterenol (100 μg/kg body weight)
produced a significant decrease on the activity of the linoleyl-CoA desaturase. The effect of the catecholamines was postulated
to be mediated through β receptors by an enhancement of the intracellular levels of cyclic AMP. 相似文献
11.
Atlantic salmon post-smolts were fed diets rich in linoleic acid (sunflower oil, SO), α-linolenic acid (linseed oil, LO) or
long-chain polyunsaturated fatty acids (fish oil, FO) for a period of 12 wk. In the liver phospholipids of fish fed SO, the
levels of 18∶2n−6, 20∶2n−6, 20∶3n−6 and 20∶4n−6 were significantly elevated compared to both other treatment. In choline phospholipids
(CPL), ethanolamine phospholipids (EPL) and phosphatidylserine (PS) the levels of 22∶4n−6 and 22∶5n−6 were significantly elevated
in fish fed SO. In liver phospholipids from fish fed LO, 18∶2n−6, 20∶2n−6 and 20∶3n−6 were significantly elevated but 20∶4n−6,
22∶4n−6 and 22∶5n−6 were similar or significantly decreased compared to fish fed FO. Liver phospholipids from fish fed LO
had increased 18∶3n−3 and 20∶4n−3 compared to both other treatments while EPL and phosphatidylinositol (PI) also had increased
20∶5n−3. In fish fed LO, 22∶6n−3 was significantly reduced in CPL, PS and PI compared to fish fed FO. Broadly similar changes
occurred in gill phospholipids. Production of 12-lipoxygenase metabolites in isolated gill cells stimulated with the Ca2+-ionophore A23187 were significantly reduced in fish fed either SO or LO compared to those fed FO. However, the ratio 12-hydroxy-5,8,10,14-eicosatetraenoic
acid (12-HETE)/12-hydroxy-5,8,10,14,17-eicosapentaenoic acid (12-HEPE) was significantly elevated in stimulated gill cells
from SO-fed fish. Although mean values of thromboxane B2 (TXB2) and prostaglandin E2 (PGE2) were increased in fish fed SO, they were not significantly different from those of the other two treatments. 相似文献
12.
Lu-Te Chuang Amanda E. Leonard Jim-Wen Liu Pradip Mukerji Tammy M. Bray Yung-Sheng Huang 《Lipids》2001,36(10):1099-1103
Conjugated linoleic acid (CLA; 18∶2) refers to a group of positional and geometric isomers derived from linoleic acid (LA; Δ9, 12–18∶2). Using a growing baker's yeast (Saccharomyces cerevisiae) transformed with human elongase gene, we examined the inhibitory effect of CLA at various concentrations (10, 25, 50, and 100 μM) on elongation of LA (25 μM) to eicosadienoic acid (EDA; Δ11,14–20∶2). Among four available individual CLA isomers, only c9,t11- and t10,c12-isomers inhibited elongation of LA to EDA. The extent of inhibition (ranging from 20 to 60%) was related to the concentration of CLA added to the medium. In the meantime, only these two isomers, when added at 50 μM to the media, were elongated to conjugated EDA (c11,t13- and t12,c14–20∶2) by the same recombinant elongase at the rate of 28 and 24%, respectively. The inhibitory effect of CLA on LA elongation is possibly due to competition between CLA isomers and LA for the recombinant elongase. Thus, results from this study and a previous study suggest that the biological effect of CLA is exerted through its inhibitory effect on Δ6-desaturation as well as elongation of LA which results in a decrease in long-chain n−6 fatty acids and consequently the eicosanoid synthesis. 相似文献
13.
Neurospora crassa incorporated exogenous deuterated palmitate (16∶0) and 14C-labeled oleate (18∶1Δ9) into cell lipids. Of the exogenous 18∶1Δ9 incorporated, 59% was desaturated to 18∶2Δ9,12 and 18∶3Δ9,12,15. Of the exogenous 16∶0 incorporated, 20% was elongated to 18∶0, while 37% was elongated and desaturated into 18∶1Δ9, 18∶2Δ9,12, and 18∶3Δ9,12,15. The mass of unsaturated fatty acids in phospholipid and triacylglycerol is 12 times greater than the mass of 18∶0. Deuterium
label incorporation in unsaturated fatty acids is only twofold greater than in 18∶0, indicating a sixfold preferential use
of 16∶0 for saturated fatty acid synthesis. These results indicate that the release of 16∶0 from fatty acid synthase is a
key control point that influences fatty acid composition in Neurospora. 相似文献
14.
Duplicate groups of Atlantic salmon (Salmo salar) post smolts were given diets in which the lipid component was either fish oil or a mixture of corn oil and lard. This difference
in the dietary lipid did not significantly affect growth over a period of sixteen weeks.
Proportions of docosahexaenoic acid [22∶6(n−3)] and total (n−3) fatty acids in the polar lipids of liver and white muscle
were unaffected by this difference in dietary lipid component over the time period used. Fish given the diet containing corn
oil and lard had significantly higher levels of 20∶2(n−6), 20∶3(n−6) and 20∶4(n−6) in the polar lipids of these tissues than
were present in the tissues of the fish given diets containing fish oil. There results suggest that linoleic acid [18∶2(n−6)]
undergoes elongation and desaturation to arachidonic acid [20∶4(n−6)] in post-smolt Atlantic salmon. 相似文献
15.
Cardiolipins (CL) have unique fatty acid profiles with generally high levels of polyunsaturated fatty acids, primarily 18∶2n−6,
and low levels of saturated fatty acids. In order to study the effect of dietary fatty acid isomers on the fatty acid composition
of cardiolipins, rats were fed partially hydrogenated marine oils (HMO), rich in 16∶1, 18∶1, 20∶1, and 22∶1 isomeric fatty
acids, supplemented with linoleic acid at levels ranging from 1.9% to 14.5% of total fat. Although the dietary fats contained
33%trans fatty acids, the levels oftrans fatty acids in CL were below 2.5% in all organs. The fatty acid profiles of cardiolipins of liver, heart, kidney and testes
showed different responses to dietary linoleic acid level. In liver, the contents of 18∶2 reflected the dietary levels. In
heart and kidney, the levels of 18∶2 also parallelled increasing dietary levels, but in all groups fed HMO, levels of 18∶2
were considerably higher than in the reference group fed palm oil. In testes, the 18∶2 levels were unaffected by the dietary
level of 18∶2 and HMO. 相似文献
16.
J. P. Kass W. O. Lundberg G. O. Burr 《Journal of the American Oil Chemists' Society》1940,17(3):50-53
The linoleic acid content of a series of seed fats was determined by the thiocyanometric and the tetrabromide-precipitation
methods in a search for isomeric linoleic acids. The results indicated the presence of only one form of linoleic acid. The
tetrabromide number was shown to be affected by the pronounced solubility of alpha tetrabromostearic acid in the other bromides
and in the solid acids, its determination therefore being of only limited value. The thiocyanogen numbers of pure linoleic
and linolenic acids were found to be empirical values differing markedly from the theoretical constants, requiring a revision
of the accepted equations for the calculation of the per cent concentration of the unsaturated acids in oils and mixed fatty
acids.
Aided by grants from the National Livestock and Meat Board and the Graduate School of the University. Presented before the
13th convention of the American Oil Chemists’ Society in Chicago, October 6, 1939. Assistance in the preparation of these
materials was furnished by the personnel of Work Projects Administration, Official Project No. 65-1-71-140, Sub-project No.
325. 相似文献
17.
Yung-Sheng Huang X. Lin R. S. Smith P. R. Redden D. K. Jenkins D. F. Horrobin 《Lipids》1992,27(9):711-715
The present study examined the effect of varying dietary linoleate intake (0.01, 0.24, 2.4, 24, 80 or 160 g/kg diet) for 24
weeks on the distribution of triacylglycerol (TG) molecular species in rat epididymal adipose tissue. Adipose TG fractions
were purified by thin-layer chromatography and separated into different molecular species by reversephase high-performance
liquid chromatography. The identification of TG species was based on fatty acid composition, retention time and the theoretical
carbon number. When the dietary 18∶2n−6 content was equal to or less than 24 g/kg, no significant amounts of n−6 fatty acids
(mainly 18∶2n−6) were observed in adipose tissue TG despite the fact that the levels of 20∶4n−6 in liver phospholipids increased
significantly. There were 12 major molecular species in adipose tissue when the dietary 18∶2n−6 content was less than 2.4
g/kg. When the diteary 18∶2n−6 content reached 24 g/kg, an additional six TG species containing one, two or three molecules
of 18∶2n−6 were observed. The levels of TG molecules containign two or three 18∶2n−6 residues were further increased when
the diet contained very large amounts of linoleic acid (160 g/kg). Conversely, those TG species containing only one 18∶2n−6
residue became less abundant. It is suggested that the accumulation of these linoleate-rich TG molecular species in adipose
tissue, particularly di- and trilinoleoyl containing TG, is the result of an adequate or an excessive intake of linoleic acid. 相似文献
18.
Effects of conjugated linoleic acid isomers on the hepatic microsomal desaturation activities in vitro 总被引:4,自引:0,他引:4
The influence of individual conjugated linoleic acid (CLA) isomers on the Δ6 desaturation of linoleic and α-linolenic acids
and on the Δ9 desaturation of stearic acid was investigated in vitro, using rat liver microsomes. The Δ6 desaturation of 18∶2n−6 was decreased from 23 to 38% when the ratio of 9cis,11trans-18∶2 to 18∶2n−6 increased from 0.5 to 2. The compound 10trans,12cis-18∶2 exhibited a similar effect only at the highest concentration. The Δ6 desaturation of α-linolenic acid was slightly affected
by the presence of CLA isomers. The sole isomer to induce an inhibitory effect on the Δ9 desaturation of stearic acid was
10trans,12cis-18∶2. 相似文献
19.
Michel Linder Excellent Matouba Jacques Fanni Michel Parmentier 《European Journal of Lipid Science and Technology》2002,104(8):455-462
Selective enzymatic hydrolysis of salmon oil extracted without solvent from by‐products was carried out under mild conditions, using a stereospecific sn‐1, sn‐3 lipase Novozyme®. A modification of the lipid class composition was obtained by controlling the degree of hydrolysis (40%, 24 h). The mixture of acylglycerols and free fatty acids was submitted to a filtration step to retain in the retentate most of the saturated fatty acids, with melting peaks ranging from ‐31.9 °C to +14.7 °C obtained by differential scanning calorimetry. This step allowed a significant increase of polyunsaturated fatty acids (PUFA) from 39.2 mol‐% in the crude oil to 43.3% in the permeate. The remaining free fatty acids in the permeate (20.2 wt‐%) was re‐esterified with an immobilized 1, 3‐specific lipase IM60. Acylglycerols synthesis reached 90% in optimized conditions. After 48 h of reaction, the distribution of monoacylglycerols, diacylglycerols and triacylglycerols was 22.1, 28.7, 43.4 (w/w), respectively. The re‐esterification step did not modify the PUFA content obtained after membrane filtration. 相似文献
20.
Various nutritional studies on CLA, a mixture of isomers of linoleic acid, have reported the occurrence of conjugated long-chain
PUFA after feeding experimental animals with rumenic acid, 9c,11t–18∶2, the major CLA isomer, probably as a result of successive desaturation and chain elongation. In the present work, in vitro studies were carried out to obtain information on the conversion of rumenic acid. Experiments were first focused on the in vitro Δ6-desaturation of rumenic acid, the regulatory step in the biosynthesis of long-chain n−6 PUFA. The conversion of rumenic
acid was compared to that of linoleic acid (9c,12c–18∶2). Isolated rat liver microsomes were incubated with radiolabeled 9c,12c–18∶2 and 9c,11t–18∶2 under desaturation conditions. The data indicated that [1-14C]9c,11t–18∶2 was a poorer substrate for Δ6-desaturase than [1-14C]-9c,12c–18∶2. Next, in vitro elongation of 6c,9c,11t–18∶3 and 6c,9c,12c–18∶3 (γ-linolenic acid) was investigated in rat liver microsomes. Under elongation conditions, [1-14C]6c,9c,11t–18∶3 was 1.5-fold better converted into [3-14C]8c,11c,13t–20∶3 than [1-14C]6c,9c,12c–18∶3 into [3-14C]8c,11c,14c–20∶3. Finally, in vitro Δ5-desaturation of 8c,11c,13t–20∶3 compared to 8c,11c,14c–20∶3 was investigated. The conversion level of [1-14C]8c,11c,13t–20∶3 into [1-14C]5c,8c,11c,13t–20∶4 was 10 times lower than that of [1-14C]8c,11c,14c–20∶3 into [1-14C]5c,8c,11c,14c–20∶4 at low substrate concentrations and 4 times lower at the saturating substrate level, suggesting that conjugated 20∶3
is a poor substrate for the Δ5-desaturase. 相似文献