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1.
Montanaro MA Rimoldi OJ Igal RA Montenegro S Tarrés MC Martínez SM Brenner RR 《Lipids》2003,38(8):827-832
Both diabetes mellitus type 1 and diabetes mellitus type 2 are widespread diseases that alter carbohydrate and lipid metabolism.
e Stilmann-Salgado (eSS) rats are experimental animals that spontaneously evolve to a state similar to that of young people
affected by non-insulin-dependent diabetes mellitus (NIDDM; type 2). Using 6-mon-old eSS rats that, according to the literature
[Martinez, S.M., Tarrés, M.C., Montenegro, S, Milo, R., Picena, J.C., Figueroa, N., and Rabasa, S.R. (1988) Spontaneous Diabetes
in eSS Rats, Acta Diabetol. Lat. 25, 303–313], had already developed insulin resistance, we investigated the changes evoked on Δ9, Δ6, and Δ5 liver desaturases.
The abundance of mRNA and enzymatic activities were measured, as well as the FA composition of liver microsomal lipids. Compared
to control rats, the mRNA content and activity of SCD-1 (stearoyl CoA-desaturase, isoform of the Δ9 desaturase) were significantly
higher, urase, isoform of the Δ9 desaturase) were significantly higher, whereas the mRNA and activities of Δ6 and Δ5 desaturases
were not significantly modified. Correspondingly, the proportion of 18∶1n−9 and the ratios of 18∶1n−9/18∶0 and 16∶1/16∶0 in
lipids were significantly increased, whereas the proportion of 20∶4n−6 was unaltered. These effects were found while glycemia
was constant or increased. The results are completely opposite those described in insulin-dependent diabetes mellitus (type
1), in which a depression of all the desaturases is found. They suggest that in eSS rats, the activities of the desaturases
were not modified by an insulin-resistance effect. Moreover, we suggest that the enhancement of SCD-1 activity might be considered
as another typical sign of the NIDDM syndrome, because it has also been found in other animal models of NIDDM, for example,
the ones evoked by the sucrose-rich diet and in the Zucker rat. 相似文献
2.
The combined effects of age and of diet deficient in n−3 fatty acids on Δ6 desaturation of linoleic acid and on lipid fatty
acid composition were studied in the liver of the rat at 2, 6, 12, 18 and 24 mon of age. The profiles of Δ6 desaturase activity
and fatty acid composition were studied in the deficient rats refed, at these different ages either with 18∶3n−3 (mixture
of peanut and rapeseed oils) or with 20∶5n−3+22∶6n−3 (fish oil) diets for 2, 4, 8 or 12 wk. Results showed that the liver
Δ6 desaturation activity in the control rats remained high at 2 and 6 mon, decreased by 30% from 6 to 12 mon, and then remained
stable from 12 to 24 mon. In the deficient rats, this activity remained high during the entire period studied. Thus, the profile
of liver Δ6 desaturase activity after puberty was not related to age only; it also depended on the polyunsaturated fatty acid
(PUFA) n−6 and n−3 balance in the diet. In the controls, in parallel with the Δ6 desaturase activity, PUFA metabolism could
be divided into three periods: a “young” period, and “old age” period, separated by a period of transition between 6 and 12
mon. Recovery from PUFA n−3 deficiency occurred at all ages but in a different manner depending on whether the rats were “young”
or “old”. Recovery was faster if long-chain n−3 PUFA rather than α-linolenic acid were supplied in the diet. 相似文献
3.
L. Ulmann J. P. Blond C. Maniongui J. P. Poisson G. Durand J. Bézard G. Pascal 《Lipids》1991,26(2):127-133
The combined effects of age and dietary n−6 and n−3 fatty acids were studied in 3-, 6- and 9-month-old rats. At each age,
two groups were fed diets containing 5% (w/w) of vegetable oils rich in either 18∶3n−6 (borage group) or 18∶3n−6 plus 18∶4n−3
(black currant group), for a period increasing with age. A control group was fed the essential fatty acids 18∶2n−6 and 18∶3n−3
only. For each group, Δ6, Δ5 and δ9 desaturase activities were measured in liver microsomes, and fatty acid composition was
determined in microsomal phospholipids. Desaturase activity varied as a function of age and dietary lipids. Δ6 Desaturation
of 18∶3n−3 was more sensitive to these factors while Δ6 desaturation of 18∶2n−6 and Δ9 desaturation were more dependent on
season than the other two. Desaturase activity was influenced more by the black currant than by the borage diet, especially
at 6 and 9 months of age. A large proportion of arachidonic acid was maintained in the microsomes independent of the diet.
Changes in the fatty acid composition did not strictly reflect the differences in desaturase activities. The effects of the
two factors (age and diet) on the activities of the desaturases are complex, suggesting that the enzymes are susceptible to
other factors as well. 相似文献
4.
Eurasian perch, Perca fluviatilis, were fed a semipurified fat-free diet for 4 wk, followed by a 16% feeding supplementation of either olive oil (OO), safflower
oil (SO), linseed oil (LO), or cod liver oil (CLO) as the only lipid source in each diet for 10 wk. Significant reductions
in total lipid of tissues were observed (31.4% in viscera, 66.7% in muscle, and 74.1% in liver) after feeding the fat-free
diet. The SO-, LO-, and CLO-fed fish significantly increased lipid deposition in liver and viscera compared to fish fed the
OO diet; however, muscle lipid levels were not significantly affected. Large amounts of dietary 18∶1n−9 were incorporated
directly into tissue lipids when fish were fed the OO diet. The LO diet significantly elevated 18∶4n−3, 20∶5n−3, 22∶5n−3,
and 22∶6n−3 in the liver compared to fish fed OO or SO diets, and the n−3/n−6 ratio was 16 times that of the SO group, with
significantly high desaturation and elongation products of 18∶3n−3. These results suggest that Δ6 and Δ5 desaturases are highly
active in Eurasian perch, and that the enzymes at this dietary n−3/n−6 ratio favor 18∶3n−3 over 18∶2n−6 as substrate. The
SO diet significantly increased 18∶3n−6, 20∶3n−6, and 22∶5n−6 in the liver and significantly decreased EPA and DHA. This indicates
that desaturation enzymes were not specifically favoring n−3 over n−6 acids in perch lipid metabolism, and that these elongation
and desaturation enzymes were influenced by n−3 and n−6 FA content in the diet. The present study indicates that high tissue
content of DHA in the muscle of Eurasian perch was attributable to the greater ability for n−3 acid bioconversion. 相似文献
5.
Roberto J. de Antueno Richard C. Cantrill Yung-Sheng Huang Michele Elliot David F. Horrobin 《Lipids》1993,28(4):285-290
This study was undertaken to investigate the total plasma fatty acid composition and the relationship between plasma triacylglycerol
(TG) levels and liver Δ9 desaturase activity in mice fed n−3 and/or n−6 fatty acid or hydrogenated coconut oil (HCO) (maximum
25 mg/g) supplemented diets. Generally, plasma TG levels and Δ9 desaturase activity were inversely correlated with the ratio
of the sum of long chain n−3 fatty acids to 18∶2n−6 and to the ratio of the sum of long chain n−3 fatty acids to 18∶n−3, but
they were positively correlated with the ratio of products and substrates (18∶1/18∶0) of the enzyme in plasma total lipids.
The n−3 fatty acid (mainly 20∶5n−3) enriched diet, when compared to the HCO diet at 21 d, caused a significant reduction in
plasma TG levels but not in Δ9 desaturase activity. However, a marked reduction in plasma TG content (50–60%) and Δ9 desaturase
activity (55–70%) was observed when both 20∶5n−3 and 18∶3n−6 were supplemented in the diet. The plasma TG levels and Δ9 desaturase
activity rose again when the animals were fed the HCO diet or chow. The results suggest that low dose supplementation of a
mixture of n−3 (mainly 20∶5n−3) and n−6 (18∶3n−6) fatty acids modified both plasma TG content and liver Δ9 desaturase activity,
in parallel. 相似文献
6.
This study was designed to examine the variations among rat strains in hepatic fatty acid desaturase activities and to determine
the correlations between the activities of these enzymes and the levels of each microsomal fatty acid. Wistar rats from two
different sources as well as Long-Evans and Sprague-Dawley rats were selected to assess, under standard and identical experimental
conditions, the liver Δ5 and Δ6 desaturase activities. Both desaturase activities were significantly reduced by 56% in Sprague-Dawley
rats when compared to BB-Wistar control rats, whereas intermediate reduced values were detected in Wistar (CR) and Long-Evans
strains. The activities of Δ5 and Δ6 desaturases were significantly and positively correlated with each other. However, no
significant correlations were detected between either Δ5 or Δ6 desaturase activities and levels of any of their fatty acid
substrates or any other of the major microsomal fatty acids. Fatty acid composition of microsomal total lipids showed strain
dependency. A positive correlation was detected between the microsomal levels of the two major final products of both desaturases,
namely 20∶4n−6 and 22∶6n−3. In general, the sum of n−3 or n−6 fatty acids but not the ratio of one to the other, varied among
rat strains. The study demonstrated that Δ6 and Δ5 desaturase activities are strain-related. The data also suggested that
(i) the desaturation activity should be measured and not predicted from the fatty acid composition and (ii) different rat
strains should be used for lipid metabolic studies before conclusions are drawn for rats in general. 相似文献
7.
We have studied the effect of various diets on the phospholipid fatty acid composition andin vitro Δ5 desaturase activity of hepatic microsomes derived either from the normal or streptozotocin-induced diabetic rat. The diets
studied were the standard rat chow diet and a basal fat-free diet supplemented either with 20 percent saturated fat, 20 percent
unsaturated fat, or 20 percent menhaden oil. Phospholipid fatty acid composition analysis revealed that the normal rat fed
the saturated fat or menhaden oil diet had significantly decreased arachidonate levels, consistent with decreased Δ5 desaturase
activities and decreased 18∶2n−6 intake. On the contrary, the unsaturated fat diet decreased dihomo-γ-linolenate and increased
arachidonate levels, without increased Δ5 desaturase activity. Streptozotocininduced diabetes resulted in decreased arachidonate
and Δ5 desaturase activity. The unsaturated fat diet fed to the diabetic rat also failed to correct this decreased Δ5 desaturase
activity. The unsaturated fatty acids in this diet also displaced a substantial amount of n−3 fatty acids in both normal and
diabetic microsomes, due to the competition between these two fatty acid families for incorporation into the membrane phospholipids.
Conversely, the menhaden oil diet fed to the normal and diabetic rats displaced n−6 fatty acids, reduced Δ5 desaturase activity,
and enhanced 22∶6n−3 incorporation into diabetic microsomes. 相似文献
8.
Marine fish have an absolute dietary requirement for C20 and C22 highly unsaturated fatty acids. Previous studies using cultured cell lines indicated that underlying this requirement in
marine fish was either a deficiency in fatty acyl Δ5 desaturase or C18–20 elongase activity. Recent research in turbot cells found low C18–20 elongase but high Δ5 desaturase activity. In the present study, the fatty acid desaturase/elongase pathway was investigated
in a cell line (SAF-1) from another carnivorous marine fish, sea bream. The metabolic conversions of a range of radiolabeled
polyunsaturated fatty acids that comprised the direct substrates for Δ6 desaturase ([1-14C]18∶2n−6 and [1-14C]18∶3n−3), C18–20 elongase ([U-14C]18∶4n−3), Δ5 desaturase ([1-14C]20∶3n−6 and [1-14C]20∶5n−3), and C20–22 elongase ([1-14C]20∶4n−6 and [1-14C]20∶5n−3) were utilized. The results showed that fatty acyl Δ6 desaturase in SAF-1 cells was highly active and that C18–20 elongase and C20–22 elongase activities were substantial. A deficiency in the desaturation/elongation pathway was clearly identified at the level
of the fatty acyl Δ5 desaturase, which was very low, particularly with 20∶4n−3 as substrate. In comparison, the apparent activities
of Δ6 desaturase, C18–20 elongase, and C20–22 elongase were approximately 94-, 27-, and 16-fold greater than that for Δ5 desaturase toward their respective n−3 polyunsaturated
fatty acid substrates. The evidence obtained in the SAF-1 cell line is consistent with the dietary requirement for C20 and C22 highly unsaturated fatty acids in the marine fish the sea bream, being primarily due to a deficiency in fatty acid Δ5 desaturase
activity. 相似文献
9.
The effects of hypothyroidism and of daily treatment for up to 21 days with thyroxin (T4, 0.5 μg/100 g body weight) on the
fatty acid composition of total lipid, phosphatidylethanolamine, and phosphatidylcholine of rat liver mitochondria were studied.
The fatty acid compositions of hypothyroid and euthyroid (control) rats of similar age were compared. The n−6 and n−3 polyunsaturated
fatty acids (PUFA) were affected differently by the hypothyroid state. The levels of linoleic (18∶2n−6), γ-linolenic (18∶3n−6)
and dihomo-γ-linolenic acids (20∶3n−6) were higher in hypothyroid rats than in controls, while the level of arachidonic acid
(20∶4n−6) was lower, which suggests an impairment of the elongase and desaturase activities. The n−3 polyunsaturated fatty
acids, eicosapentaenoic (EPA, 20∶5n−3) and docosapentaenoic (22∶5n−3) acids, were higher in hypothyroid rats, whereas the
linolenic acid (18∶3n−3) content remained constant. The level of docosahexaenoic acid (DHA, 22∶6n−3) was dramatically decreased
in hypothyroid rats, while the levels of C22 n−6 fatty acids were unchanged. The differences were probably due to the competition between n−3 and n−6 PUFA for desaturases,
elongases and acyltransferases. When hypothyroid rats were treated with thyroxin, the changes induced by hypothyroidism in
the proportions of n−6 fatty acids were rapidly reversed, while the changes in the n−3 fatty acids were only partially reversed.
After 21 days of thyroxin treatments, the DHA content was only half as high in hypothyroid rats than in euthyroid rats. These
results suggest that the conversion of 18∶2n−6 to 20∶4n−6 is suppressed in the hypothyroid state which favors the transformation
of 18∶3n−3 to 20∶5n−3. The marked decrease in DHA content indicates an impairment of the enzymes involved in the DHA metabolism,
possibly the n−3 Δ4 desaturase or the acyltransferases. The increased levels of EPA and 22∶5n−3 is consistent with the inhibition
of the n−3 pathway at the Δ4 desaturase step. Observed modifications in the fatty acid composition may significantly alter
eicosanoid synthesis and membrane functions in hypothyroidism. 相似文献
10.
Isolated hepatocytes from rainbow trout and rat were incubated with14C-labeled linoleic acid, linolenic acid, dihomogammalinolenic acid or eicosapentaenoic acid. The most striking difference
in the desaturase activity was the lower level of Δ5 desaturase in trout than in rat. No Δ4 desaturation of 22∶4(n−6) to 22∶5(n−6)
was observed in either of the two species, while the conversion of 22∶5(n−3) to 22∶6(n−3) was significant in both groups and
highest in rainbow trout. The chain-elongating activity was remarkably similar in the two species, except for the “dead-end”
elongation which was distinctly more important in fish. 相似文献
11.
The effect of very low levels of dietary long-chain n−3 fatty acids on Δ6 desaturation of linoleic acid (18∶2n−6) and α-linolenic
acid (18∶3n−3), and on Δ5 desaturation of dihomo-γ-linolenic acid (20∶3n−6), in liver microsomes and its influence on tissue
fatty acids were examined in obese and lean Zucker rats and in Wistar rats. Animals fed for 12 wk a balanced diet containing
ca. 200 mg of long-chain polyunsaturated n−3 fatty acids per 100 g of diet were compared to those fed the same amount of α-linoleic
acid. Low amounts of long-chain n−3 fatty acids greatly inhibited Δ6 desaturation of 18∶2n−6 and Δ5 desaturation of 20∶3n−6,
while Δ6 desaturation of 18∶3n−3 was not inhibited in Zucker rats and was even stimulated in Wistar rats. Inhibition of the
biosynthesis of long-chain n−6 fatty acids was reflected in a decrease in arachidonic acid (20∶4n−6) content of serum lipids
when fasting, and also in the phospholipid fatty acids of liver microsomes. On the contrary, heart and kidney phospholipids
did not develop any decrease in 20∶4n−6 during fish oil ingestion. Docosahexaenoic acid (22∶6n−3), present in the dietary
fish oil, was increased in serum lipids and in liver microsome, heart, and kidney phospholipids. 相似文献
12.
The growth rate of a human mammary carcinoma, MX-1, was significantly reduced in athymic “nude” mice fed fish oil. Tumors
from the fish oil-fed animals also showed a greater sensitivity to two anti-neoplastic agents, mitomycin C and doxorubicin.
Mitochondria were isolated from control livers, host livers and tumors from fish oil-and corn oil-fed animals, and increased
levels of 20∶5n−3 and 22∶6n−3 were found in mitochondrial lipids in all three tissues from the fish oil-fed animals. To investigate
the effect of dietary n−3 fatty acids on lipid metabolism, the activity of the acyl-CoA:carnitine acyltransferase and three
acyl-CoA desaturases were measured. Carnitine acyltransferase activity toward all four acyl-CoA substrates tested was markedly
increased in mitochondria from liver by feeding fish oil. In mitochondria from tumors, feeding fish oil resulted in an increased
activity toward only 18∶3n−3. These data suggest that fish oil may induce an increase in the oxidation of fatty acids. The
Δ9-desaturase activity was decreased in microsomes from liver and tumor from fish oil-fed animals. However, both the Δ6 and Δ5 desaturases were increased in tumor and in control liver as a result of feeding fish oil. The Δ5 desaturase was not altered in microsomes from the host animals. The effect of fish oil on the Δ5 and Δ6 desaturases may involve alterations to metabolism of specific polyunsaturated fatty acids especially in the tumor tissue. 相似文献
13.
Δ6 Desaturation of linoleic acid (18∶2 n−6) and Δ5 desaturation of dihomo-γ-linolenic acid (20∶3 n−6) were measured in liver
microsomes from genetically obese Zucker rats (fa/fa) and from their lean littermates (Fa/−). Both groups were fed a balanced
commercial diet. The rats were 6, 9 and 12 weeks old, which corresponded to stages in their active growth period. The content
of total fatty acids and n−6 polyunsaturated fatty acids in whole liver and liver microsomes was also determined in order
to ascertain how the desaturase activities measuredin vitro reflected regulation of essential fatty acid metabolismin vivo. Contrary to values obtained for Δ6 desaturation, Δ5 desaturation at nonsaturating substrate levels were lower in obese rats
than in lean controls. In contrast, at saturating substrate level, the maximal Δ5 desaturase activities were the same in both
phenotypes and they increased with age. Study of Δ5 desaturation kinetics (1/V vs 1/S) showed that Vm did not differ between 12-week-old obese and lean rats, whereas KM in obese rats was much lower than in controls, expressing the very low affinity of the enzyme for the substrate in obese
animals. The fatty acid composition of liver lipids reflected the results of desaturase activitiesin vitro. In particular, the ratios 20∶4 n−6/20∶3 n−6 were lower in obese rats than in lean rats, which can be explained by the lower
conversion of 20∶3 n−6 into 20∶4 n−6 by Δ5 desaturation. However, the total amount of 20∶4 n−6 in the whole liver did not
differ between phenotypes, whatever their age. This work presents evidence for a relationship between the changes in fatty
acid compositional data in hepatic total lipids, total lipids of liver microsomes and modifications of fatty acid desaturase
activities in the genetically obese Zucker rat. 相似文献
14.
Flaxseed, echium, and canola oils contain α-linolenic acid (18∶3n−3, ALA) in a range of concentrations. To examine their effect
on elevating cardiac levels of long-chain n−3 FA, diets based on these n−3-containing vegetable oils were fed to rats for
4 wk. Sunflower oil, which contains little ALA, was a comparator. Despite canola oil having the lowest ALA content of the
three n−3-containing vegetable oils, it was the most potent for elevating DHA (22∶6n−3) levels in rat hearts and plasma. However,
the relative potencies of the dietary oils for elevation of EPA (20∶5n−3) in heart and plasma followed the same rank order
as their ALA content, i.e., flaxseed>echium>canola>sunflower oil. This paradox may be explained by lower ALA intake leading
to decreased competition for Δ6 desaturase activity between ALA and the 24∶5n−3 FA precursor to DHA formation. 相似文献
15.
P. E. Wainwright Y. S. Huang D. E. Mills G. R. Ward R. P. Ward D. McCutcheon 《Lipids》1989,24(12):989-997
This study assesses the combined effects on brain and behavioral development of ethanol administration and supplementation
of the maternal diet with long chain n−3 polyunsaturated fatty acids. From day 7 to 17 of gestation, pregnant mice were fed
equivalent daily amounts of isocaloric liquid diets; 20% of the energy was provided by either ethanol or maltose-dextrin,
and a further 20% by either safflower oil (rich in linoleic acid, 18∶2n−6), or a combination of safflower oil with a fish
oil concentrate (rich in eicosapentaenoic acid, 20∶5n−3, and docosahexaenoic acid, 22∶6n−3). On day 18 the liquid diets were
replaced by lab chow; a fifth group was maintained on lab chow throughout the experiment. Measures on the pups included brain
weight and the fatty acid composition of the brain phospholipids on days 22 and 32 post-conception (birth=day 19), as well
as behavioral development. Maternal weight gain during gestation was decreased by ethanol relative to maltose-dextrin, and
increased by fish relative to safflower oil. On day 32, the brain weight of ethanoltreated animals fed fish oil was greater
than their safflower oil controls, whereas the reverse was true in the two maltose-dextrin groups; a similar trend was apparent
on day 22. The brain phospholipid content of the longer chain fatty acids (20∶4n−6, 22∶4n−6, 22∶5n−6, 20∶5n−3, 22∶5n−3, 22∶6n−3)
on day 22 reflected that of the prenatal diet, with the proportion of n−3 compounds being higher and that of n−6 floer in
the fish oil than safflower oil groups. Prenatal dietary effects were absent by day 32, with the exception of lower 22∶5n−6
in fish oil groups. Dietary supplementation with n−3 fatty acids increased the ratio of 20∶3n−6 to 20∶4n−6, which is consistent
with a blockade of the activity of Δ-5 desaturase. On day 22 the incorporation of dietary long chain n−3 fatty acids into
the brain phosphatidylcholine fraction was enhanced in the ethanol-treated animals; by day 32 the animals treated prenatally
with ethanol also showed increased levels of long chain n−6 compounds. Behavioral development was retarded by ethanol, but
there was no effect of the dietary oils. These results support the hypothesis that effects of ethanol on the developing brain
may be modified by the availability of an exogenous supply of long chain fatty acids. 相似文献
16.
The aim of the present study was to measure Δ9-, Δ6-, and Δ5-desaturase activities in liver microsomes, as well as phospholipid
FA composition of liver and erythrocytes in monkeys fed a control or low-protein diet during the postweaning period. Ten Saimiri sciureus boliviensis (Cebidae) of both sexes were employed; at 12 mon of age they were separated into two groups fed ad libitum on a control or a low-protein diet for 24 mon. Saimiri sciureus had active Δ9, Δ6, and Δ5 liver desaturase enzymes, and these activities were influenced by the diet. A low-protein diet
produced a significant reduction in Δ5-desaturation capacity, an increase in Δ9-desaturase activity, and no change in Δ6-desaturase
activity (P<0.05). These changes, evoked by protein deprivation, were reflected in the liver phospholipid FA composition. Increases in
the proportion of saturated FA and in monounsaturated oleic acid (18∶1n−9) and a decrease in the proportion of PUFA of the
n−6 and n−3 series were produced in the animals fed a low-protein diet (P<0.0001). Differences between the two dietary groups were less pronounced in the FA composition of erythrocyte phospholipids.
The authors are members of the Carrera del Investigador del Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET),
Argentina. 相似文献
17.
Differences in the FA composition of subcellular fractions from healthy and cancerous kidney tissues from the same patients
were examined. Only minor differences in CLA content were found between the healthy and the cancerous tissue portions. Regarding
the distribution pattern, CLA incorporation into nuclei and cytosol was significantly higher than incorporation into plasma
membranes and mitochondria, which could be correlated to the neutral lipid content of these fractions. The subcellular distribution
pattern of CLA was similar to that observed with monounsaturated FA but unlike that found with 18∶2n−6, which underlines the
different physiological properties of CLA and 18∶2n−6. Because PUFA have been suggested to have an effect on cancer risk,
the contents of n−3 and n−6 PUFA were determined in kidney and renal cell carcinoma (RCC). The 18∶2n−6 content and Δ5 desaturase activity were significantly lower, and the 18∶3n−6, 20∶3n−6, and 20∶5n−3 contents and Δ6 desaturase activity were significantly higher in RCC than in healthy renal tissue, indicating a changed PUFA metabolism in
RCC. Previous research has suggested that CLA inhibits the elongation and desaturation of 18∶2n−6 into 20∶4n−6. In that case,
one might speculate that a diet enriched in CLA would be a useful tool in preventing RCC. However, the involvement of CLA
in preventing renal cancer could not be demonstrated definitively from the design of this experiment. Further understanding
of the cause and/or consequence of the difference in FA metabolism may lead to a better understanding of RCC. 相似文献
18.
Male Fischer rats were fed the AIN76A diet containing varying n−6/n−3 FA ratios using sunflower oil (SFO), soybean oil (SOY),
and SFO supplemented with EPA-50 and GLA-80 (GLA) as fat sources. Hepatocyte nodules, induced using diethylnitrosamine followed
by 2-acetylaminofluorene/partial hepatoctomy promotion, were harvested, with surrounding and respective dietary control tissues,
3 mon after partial hepatectomy. The altered growth pattern of hepatocyte nodules in rats fed SFO is associated with a distinct
lipid pattern entailing an increased concentration of PE, resulting in increased levels of 20∶4n−6. In addition, there is
an accumulation of 18∶1n−9 and 18∶2n−6 and a decrease in the end products of the n−3 metabolic pathway in PC, suggesting a
dysfunctional Δ-6-desaturase enzyme. The hepatocyte nodules of the SFO-fed rats exhibited a significantly reduced lipid peroxidation
level that was associated with an increaser in the glutathione (GSH) concentration. The low n−6/n−3 FA ratio diets significantly
decreased 20∶4n−6 in PC and PE phospholipid fractions with a concomitant increase in 20∶5n−3, 22∶5n−3, and 22∶6n−3. The resultant
changes in the 20∶4/20∶5 FA ratio and the 20∶3n−6 FA level in the case of the GLA diet suggest a reduction of prostaglandin
synthesis of the 2-series. The GLA diet also counteracted the increased level of 20∶4n−6 in PE by equalizing the nodule/surrounding
ratio. The low n−6/n−3 ratio diets significantly increased lipid peroxidation levels in hepatocyte nodules, mimicking the
level in the surrounding and control tissue while GSH was decreased. An increase in n−3 FA levels and oxidative status resulted
in a reduction in the number of glutathione-S-transferase positive foci in the liver of the GLA-fed rats. Modulation of cancer
development with low n−6/n−3 ratio diets containing specific dietary FA could be a promising tool in cancer intervention in
the liver. 相似文献
19.
Docosahexaenoic acid (DHA, 22∶6n−3) is an n−3 polyunsaturated fatty acid which attenuates the development of hypertension
in spontaneously hypertensive rats (SHR). The effects of DHA on delta-9-desaturase activity in hepatic microsomes and fatty
acid composition were examined in young SHR. Two groups of SHR were fed either a DHA-enriched diet or a control diet for 6
wk. Desaturase activity and fatty acid composition were determined in hepatic microsomes following the dietary treatments.
Delta-9-desaturase activity was decreased by 53% in DHA-fed SHR and was accompanied by an increase in 16∶0 and a reduction
in 16∶1n−7 content in hepatic microsomes. The DHA diet also increased the levels of eicosapentaenoic acid (20∶5n−3) and DHA.
The n−6 fatty acid content was also affected in DHA-fed SHR as reflected by a decrease in gamma-linolenic acid (18∶3n−6),
arachidonic acid (20∶5n−6), adrenic acid (22∶4n−6), and docosapentaenoic acid (22∶5n−6). A higher proportion of dihomo-gamma-linolenic
acid (20∶3n−6) and a lower proportion of 20∶4n−6 is indicative of impaired delta-5-desaturase activity. The alterations in
fatty acid composition and metabolism may contribute to the antihypertensive effect of DHA previously reported. 相似文献
20.
Michael V. Bell Robert S. Batty James R. Dick Karen Fretwell Juan Carlos Navarro John R. Sargent 《Lipids》1995,30(5):443-449
In the retina of herring (Clupea harengus L.), rods are recruited from about 8 wk after hatching, and from this time there is a linear relationship between the number
of rods in the photoreceptor cell population and the content of di22∶6n−3 molecular species of phospholipids. Juvenile herring
were reared from four weeks' post-hatching for 15 wk on eitherArtemia nauplii deficient in 22∶6n−3 or on enrichedArtemia nauplii containing 4.3% 22∶6n−3. The visual performance of the fish was then determined at three light intensities (0.01,
0.1, and 1.0 lux) by observing their frequency of striking at liveArtemia nauplii using infrared video recording. Herring reared on the diet containing no 22∶6n−3 were less active predators, especially
at the lowest light intensity where very few strikes were observed. The eyes of these fish contained greatly reduced levels
of di22∶6n−3 molecular species of total phospholipid, 2.1% vs. 12.0% in fish supplemented with 22∶6n−3. The contribution of
saturated and monounsaturated fatty acids in the molecular species of phosphatidylethanolamine (PE), phosphatidylserine (PS),
and phosphatidylcholine (PC) was virtually unchanged, while 20∶5n−3 and 22∶5n−3 largely replaced 22∶6n−3. There was an almost
complete disappearance of di22∶6n−3 PC, while the amounts of di22∶6n−3 PE and PS fell by 18.1 and 20.6% to 2.7 and 7.6%, respectively.
The dipolyunsaturated molecular species di20∶5n−3, 20∶5n−3/22∶5n−3, and di22∶5n−3 made up a substantial part of the deficit.
We conclude that a dietary deficiency of 22∶6n−3 during the period early in rod development impairs visual performance such
that the fish can no longer feed at low light intensities.
Deceased. 相似文献