共查询到20条相似文献,搜索用时 31 毫秒
1.
Effects of dietary triolein and sunflower oil on insulin release and lipid metabolism in zucker rats
Obese and lean male Zucker rats were fed ad libitum on diets containing either 50 (L) or 200 (H) g/kg diet of either triolein
(T) or sunflowerseed oil (S). The specific activity of the hepatic microsomal Δ9 desaturase enzyme was depressed in both lean
and obese rats fed the HS diet compared with the other three diets. The fatty acid composition of liver and subcutaneous white
adipose tissue lipids were consistent with a lower Δ9 desaturation activity in rats fed the H diets, particularly for the
HS diet. In both genotypes, microsomal Δ9 desaturase activity and the ratio of 16∶1/(16∶0+16∶1) fatty acids in liver lipids
were inversely related to the proportion of 18∶2 in liver lipid. Plasma insulin concentrations and rates of glucose-stimulated
insulin release in vivo were higher in obese rats compared with lean rats, and plasma insulin levels were higher in rats fed
S compared with T. There was no relationship between Δ9 desaturase activity and either plasma insulin concentration or rates
of insulin release in vitro. These findings suggest that hepatic Δ9 desaturase activity of Zucker rats is responsive to changes
in the proportion of 18∶2 in liver lipids but is not affected by changes in insulin secretion. 相似文献
2.
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
3.
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
4.
Ricardo J. Pollero 《Lipids》1983,18(1):12-17
Neutral lipid, phospholipids and fatty acids of the sea anemonePhymactis clematis from the south-west Atlantic were characterized and quantified in spring and autumn. Neutral lipids predominated over phospholipids
in both seasons. Triacylglycerol and diacylglycerol ethers were the major lipids. In spring, an increase of esterified sterols
was noted. The major fatty acids found were 22∶5ω3, 20∶5ω3 and 16∶0. The sea anemones were also incubated in vivo with either
[1-14C]linoleate or [1-14C] α-linolenate for 2 hr. Isotope incorporation into lipids and their transformations into higher fatty acids were examined.
Both precursors were incorporated into the lipids, mainly in triacylglycerols and mono-acylglycerols, while α-linolenate was
also incorporated into phospholipids. The radioactive linoleate was elongated to 20∶2, 22∶2 and 24∶2 fatty acids, but not
desaturated to 18∶3ω6. α-Linolenate was desaturated by Δ6 desaturase to 18∶4ω3. The specificity of Δ6-desaturase is discussed. 相似文献
5.
The effect of simvastatin, a hypocholesterolemic drug, on the biosynthesis of arachidonic acid was studied in obese and lean
Zucker rats. After administration of 2 mg/kg body weight/d for 13 d, Δ6 and Δ5 desaturase activities were measured in liver
microsomes at two substrate concentrations. In untreated rats, the Δ6 desaturation rate was similar in the obese and lean
rats when measured at saturating substrate levels, whereas Δ5 desaturation was lower in the obese animals. Treatment with
simvastatin did not change Δ6 desaturation in either phenotype but increased Δ5 desaturation in obese rats to reach the unchanged
rate observed in lean animals. The changes were not reflected in the fatty acid composition of liver microsomal phospholipids
when expressed as μg fatty acid/g of liver. 相似文献
6.
Jean Paul Blond Georges Durand Jean Bézard 《Journal of the American Oil Chemists' Society》1998,75(2):269-274
The effect of low levels of dietary arachidonic acid (20:4n-6) 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) were studied in liver microsomes of obese Zucker
rats, in comparison with their lean littermates. Fatty acid composition of serum total lipids and of phospholipids from liver
microsomes and from total heart and kidney was determined to see whether modifications of desaturation rate, if any, were
reflected in the tissue fatty acid profiles. Animals fed for 12 wk on a balanced diet, containing 20:4n-6 and 18:2n-6, were
compared to those fed 18:2n-6 only. The low amount of dietary 20:4n-6 greatly inhibited Δ6 desaturation of 18:2n-6 and Δ5
desaturation of 20:3n-6, whereas Δ6 desaturation of 18:3n-3 was slightly increased in obese rats. Inhibition of the biosynthesis
of long-chain n-6 fatty acids by dietary arachidonic acid was only slightly reflected in the 20:4n-6 content of liver microsome
phospholipids. On the contrary, the enrichment of serum total lipids and heart and kidney phospholipids in this fatty acid
was pronounced, more in obese than in lean animals. Our results show that, although the desaturation rate of the n-6 fatty
acids in liver microsomes was greatly decreased by the presence of arachidonic acid in the diet, the tissue phospholipid content
in arachidonic acid was not depressed. The potentiality of synthesis of eicosanoids of the 2 family from this fatty acid is
consequently not lower, especially in obese rats, in which certain tissues are deficient in arachidonic acid, in comparison
with their lean littermates. 相似文献
7.
Cats fed a diet containing linoleate as the only polyunsaturated fatty acid showed extremely low levels of arachidonate in
the plasma lipids, as well as an increase in linoleate, eicosadienoate and an unknown fatty acid. Administration of [1-14C] linoleic acid and [2-14C] eicosa-8,11,14-trienoic acid to cats showed that in the liver there was no conversion of the [1-14C] 18∶2 to arachidonate, whereas there was significant metabolism of [2-14C] 20∶3 to arachidonate. It was found when methyl-γ-linolenate was fed to cats that the level of 20∶3ω6 and 20∶4ω6 in the
erythrocytes increased significantly. These results show that there is no significant Δ6 desaturase activity in the cat, whereas
chain elongation and Δ5 desaturase enzymes are operative. The unknown fatty acid was isolated from the liver lipids and shown
to be a 20-carbon fatty acid with 3 double bonds and which by gas liquid chromatography could be separated from 20∶3ω9 and
20∶3ω6. The presence of the Δ5-desaturase activity and the results of the ozonolysis studies indicated that this unknown fatty
acid was eicosa-5,11,14-trienoic acid. 相似文献
8.
Young male rats were fed ad libitum for 8 weeks a low iron fat-free (FF-Fe) diet or a fat-free diet supplemented with iron
(FF+Fe). The relative levels of 16∶1 to 16∶0 and 18∶1 to 18∶0 in the total fatty acids of liver and other tissues (plasma,
erythrocytes and intestinal mucosa) were considerably decreased because of a lack of dietary iron. In rats fed the FF-Fe diet,
the levels of essential fatty acids (18∶2ω6+20∶4ω6) in tissues were 2-to 3-fold greater than in the corresponding tissues
of rats fed the FF+Fe diet. Eicosatrienoic acid (20∶3ω9) levels in tissue lipids from rats fed the FF+Fe diet were high (8–16%),
whereas they were low (2–5%) in the case of animals fed the FF-Fe diet. The proportion of 20∶4 in total fatty acids of tissues
was 2-to 3-fold greater in rats fed the FF-Fe diet than when they were fed the FF+Fe diet. Therefore, the relative levels
of 20∶3ω9/20∶4ω6 varied from 1-2.9 in tissue lipids of rats fed the FF+Fe diet, while it varied only from 0.2–0.3 in animals
fed the FF-Fe diet. These results suggest that a lack of dietary iron may reduce the synthesis of 16∶1, 18∶1, 20∶3 and 20∶4
and the metabolism of 20∶4. 相似文献
9.
Effects of zinc deficiency and castration on fatty acid composition and desaturation in rats 总被引:3,自引:0,他引:3
Sanda Clejan Mariano Castro-Magana Platon J. Collipp Ernesto Jonas Vaddanahally T. Maddaiah 《Lipids》1982,17(3):129-135
The effects of zinc deficiency and testosterone on fatty acid composition of plasma lipids and microsomes of liver, intestine
and testes were studied. The activities of fatty acid desaturase (Δ6 and Δ5) in rat liver and testes were also measured. A
significant decrease in the level of arachidonic acid was observed in plasma of normal rats fed the zinc-deficient diet. Castration
significantly decreased arachidonic acid but increased 20∶3 fatty acid, which is negligible in normal rats. Testosterone and
zinc administration restored arachidonic acid to normal values. Zinc deficiency does not significantly change the fatty acid
profile in liver, but castration decreased both arachidonic and 22∶6 fatty acid. Intestinal mucosal microsomes showed that
the predominant fatty acid in this tissue, palmitic acid, is independent of zinc status, whereas polyunsaturated fatty acids
18∶2 and 20∶4 were decreased by zinc-deficient diet or castration. Zinc deficiency sharply decreased 22∶5 fatty acid and to
some extent, other polyunsaturated fatty acids in testis microsomes. These changes in fatty acids are in agreement with increased
Δ9 desaturation and decreased Δ5 desaturase activity. In testes, both Δ6 and Δ5 desaturase activities are decreased in zinc
deficiency. It appears that zinc influences the conversion of linoleic to arachidonic acid, whereas testosterone influences
Δ6 desaturase activity. The data suggest that zinc deficiency may be one of the important factors in the causation of polyunsaturated
fatty acid deficiency, which in turn, may induce serum hypertriglyceridemia. 相似文献
10.
Diabetes-induced and age-related proportional changes in plasma fatty acids of triglycerides (TG), phospholipids (PL), and
cholesteryl esters (CE) were investigated using streptozotocin-induced diabetic and control rats. Among n-6 fatty acids from
diabetic rat plasma, increased proportions of 18∶2n-6 and 20∶3n-6 in all three lipid classes and of 18∶3n-6 in PL at 1–3 months
old and in TG at 3–5 months old were observed. The proportions of 20∶4n-6 decreased in both PL and CE, but were unchanged
in diabetic TG. Among the n-3 fatty acids, in the early stage, diabetes caused increases in the proportions of 18∶3n-3 in
PL and CE and of 20∶5n-3 and 22∶6n-3 in TG, while 22∶5n-3 was decreased later in the disease course. These results suggest
reduced Δ5-desaturase activities on 20∶3n-6 but not on 20∶4n-3, while Δ6-desaturase activity on 18∶2n-6 was essentially unaffected.
Furthermore, the reduction in Δ9-desaturase activity in diabetic rats may well explain the decreases in the proportions of
16∶1n-7 and 18∶1n-7. However, the proportion of 18∶1n-9, another product of Δ9-desaturase, was significantly increased in
CE and PL as compared to the controls. Thus, there was a discrepancy between our results and those of earlier studies with
respect to the n-9, n-6, and n-3 fatty acid proportions of plasma lipids in diabetic rats. We also investigated age-related
changes in the proportions of plasma fatty acids. Although rather small, age-related changes were evident in both diabetic
and control rats. 相似文献
11.
The effect of oral administration, for 24 or 48 hr, of different octadeca fatty acids containing a 9,12-dienoic structure
on the fatty acid composition and Δ9 desaturation activity of liver microsomes of rat fed a fat-free diet was studied. The
ethyl esters of linoelaidic and γ-linolenic acids, the methyl ester of linoleic acid and free columbinic acid were administered
to rats maintained on a fat-free diet. The supplementation of the fat-free diet with linoelaidate produced no relevant changes
in the fatty acid composition pattern of liver microsomes and did not modify the percentage of conversion of palmitic to palmitoleic
acid. The addition of linoleate or γ-linolenate to the fat-free diet returned liver microsome Δ9 desaturation activity toward
the control and partially restored the liver microsome fatty acid spectrum found in the fat-free diet. Columbinic acid (5-trans-9-cis,12-cis-18∶3), which cannot be transformed into arachidonic acid, also decreased the Δ9 desaturation activity enhanced by the fat-free
diet and evoked changes in the microsomal fatty acid composition similar to those produced by the ω6 fatty acids. These results
suggest that the modulation of Δ9 desaturase activity evoked by dietary administration of unsaturated acids of ω6 series would
depend on thecis double bond configuration of these acids. 相似文献
12.
Four groups of rats were fed diets containing 15% (w/w) high-oleic safflower oil (SFO, rich incis-18∶1 acids), a mixture of 80% partially hydrogenated soybean oil plus 20% corn oil (H+CO, rich intrans-18∶1 acids), lard (L, rich in saturated fatty acids) and corn oil (Co, rich in 18∶2ω6). Fatty acid composition of liver microsomes
and activities of the Δ5, Δ6 and Δ9 desaturases were determined. Microsomal Δ6 desaturase activity and arachidonic acid were lower in the H+CO group compared with SFO of L. No difference was found in
the Δ5 or Δ6 desaturase activity of CO and SFO groups. Thus, the oleic-acid level of the SFO diet had no effect on the metabolism of 18∶2ω6.
Fluorescent polarization studies, usingtrans-parinaric acid as a probe, showed no differences between the physical states of phospholipid vesicles made from lipids isolated
from each group. We concluded that thetrans-18∶1 acids in partially hydrogenated soybean oil have a more inhibitory effect than saturated acids on EFA metabolism, even
in the presence of adequate amounts of essential fatty acid. 相似文献
13.
Dietary manipulation produces marked alterations in desaturase activities of rat liver microsomes with no concomitant changes
in acyltransferase activities. Desaturation of stearoyl-CoA (Δ9-desaturase), linoleoyl-CoA (Δ6-desaturase), eicosatrienoyl-CoA
(Δ5-desaturase) and eicosatrienoyl-phosphatidylcholine (Δ5-desaturase) was elevated in animals fed a corn oil diet and lowered
in those fed a coconut oil diet compared to control animals. The Δ5-desaturase activities were also lowered in starved animals
and elevated in starved animals refed a fat-free diet. However, no changes in acyl-CoA:1-acylsn-glycero-3-phosphocholine acyltransferase activity were observed in the membranes of animals maintained on any of the dietary
regimens studied. These observations suggest that the desaturases of rat liver microsomes are regulated independently of the
acyltransferases and that desaturation of eicosatrienoyl-phosphatidylcholine is regulated at the level of the desaturase itself
and not by availability of the phospholipid substrate. 相似文献
14.
Δ5 Desaturation of eicosa-8,11,14-trienoic acid to arachidonic acid was studied in rat liver microsomes. It was shown that
Δ5 desaturation of fatty acids in vitro requires the participation of a peripheral component of cytosolic origin. Desaturation
of 20∶3n−6 to 20∶4n−6 decreases in washed microsomes as they lose an adsorbed cytosolic fraction (CF), but the enzymatic activity
can be recovered as a function of CF concentration in the incubation medium. Albumin does not substitute for CF. Δ5 Desaturation
of 20∶3n−6 is inhibited by arachidonic acid by a product inhibition effect, but CF prevents retroinhibition of Δ5-desaturase
by 20∶4n−6. This ability of CF is eliminated by preincubation of CF with 20∶4n−6, but not with γ−18∶3n−6, the product of Δ6
desaturation of 18∶2n−6, thus indicating that CF impairs the retroinhibitory effect of arachidonic acid on Δ5-desaturase in
a specific manner. Δ6 Desaturation of linoleic acid to γ−18∶3n−6 is also activated by CF and retroinhibited by γ−18∶3n−6.
CF activity on Δ6 desaturation is retained after preincubation with 20∶4n−6, but it is lost after preincubation with γ−18∶3n−6.
Activation of Δ6-desaturase by CF is associated with the removal of the reaction product in a specific manner. Chromatography
of CF by Sephacryl S-200 separates two major subfractions which show different efficiency in reactivating Δ5- and Δ6-desaturase
activities in washed microsomes. Therefore, CF may contain subfractions that can prevent Δ5- and δ6-desaturase retroinhibition
by apparently binding their respective reaction products specifically. 相似文献
15.
Pregnant rats were kept throughout gestation on a control diet (i.e., 25% protein), on a low protein diet (i.e., 5% protein)
or on a fat-free diet. At 20–21 days of gestation, the rate of 9-, 6-, and 5-desaturation was measured, using microsomes from
maternal and fetal livers and placenta microsomes. The effect of protein malnutrition was more evident upon Δ6-desaturase
activity from maternal liver, while a less severe reduction in the activities of Δ9- and Δ5-desaturases was observed. No measurable
activities of Δ5- and Δ6-desaturases were observed in fetal liver and placenta, while a low activity of Δ9-desaturase was
detected in both tissues from the three groups under study. We concluded that Δ6-desaturation is greatly affected by maternal
protein deprivation, and this fact could affect the normal supply of polyunsaturated fatty acids for the normal fetus growth
and tissue development. 相似文献
16.
The fatty acid composition of serum total lipids, of phospholipids of various organs (liver, heart, kidney), and of nervous
structures (brain, retina, sciatic nerve, myelin, synaptosomes) have been compared in lean (Fa/−) and genetically obese (fa/fa)
Zucker female rats. Both received a standard commercial diet including 37% of 18∶2n−6 and 5% of n−3 polyunsaturated fatty
acids (PUFA), 1.7% of which were in the form of 20∶5n−3 and 22∶6n−3. In comparison with lean rats, the results for the obese
rats pointed out (i) no difference in the fatty acid composition of nervous structures: (ii) a decrease of 18∶2n−6 (from −8%
to −35%) and of 20∶4n−6 (from −9% to −49%) in serum, liver and in kidney; this was compensated for by an increase in 20∶3n−6
(from +30% to +320%) and in total n−3 PUFA (from +68% to +76%); (iii) a decrease of 20∶4n−6 (−18%) and of 22∶6n−3 (−24%) in
heart compensated for by an increase in 18∶2n−6 (+39%) and in 20∶3n−6 (+233%); and (iv) constant levels of total PUFA (n−6
and n−3) in the various fractions studied, except in serum where this level decreased (−23%). Finally, except for the nervous
structures, tissue phospholipids of obese rats included a lower proportion of 20∶4n−6 and a higher proportion of 20∶3n−6.
This resulted in a significant reduction in the 20∶4n−6/20∶3n−6 ratio; by contrast, the 20∶3n−6/18∶2n−6 ratio increased. The
results suggest that in Zucker rats, the obese character (fa/fa) affects the desaturation-elongation process of 18∶2n−6 to
20∶4n−6 by specifically decreasing Δ5-desaturase activity. 相似文献
17.
Because copper and iron have been reported to be essential cofactors in Δ9 desaturation of fatty acids, the effects of different
dietary intakes of copper and iron on tissue fatty acids were studied. Male Long-Evans rats (ten per group) were fed diets
containing adequate, deficient or excess copper or iron. On day 42 of the dietary regimen, the animals were killed and tissues
and blood were removed for analysis of metals and fatty acids of phospholipids. Compared with the copper-adequate rats, the
copper-deficient rats showed increased 18∶0 in liver and decreased 16∶1ω7 in liver, heart and serum. There were no differences
for 16∶0 or 18∶1ω9. Intake of excess copper did not cause an increase in products of Δ9 desaturation. Comparisons between
iron-deficient and iron-adequate rats showed that iron deficiency increased 18∶2ω6 in liver and serum and decreased 20∶4ω6
in serum only. Relative percentages of 16∶0, 18∶0, 16∶1ω7 and 18∶1ω9 in liver and serum phospholipids were similar for both
groups. Intake of excess iron caused a decrease in 18∶2ω6; and 16∶0 and 18∶1ω9 were higher in the liver of the iron-excess
group than the iron-deficient group. This study did not support the requirement for copper or iron in the Δ9 desaturation
of fatty acids as expressed in phospholipids of liver, heart and serum. 相似文献
18.
The activity of Δ6-desaturase of linoleic acid, a rate-limiting step in the formation of arachidonic acid, is decreased in
animal models of severe, uncontrolled diabetes. The aim of the study was to measure the activity of liver microsomal Δ6-desaturase
of spontaneously diabetic BioBreeding/Edinburgh rats receiving subcutaneous insulin daily and of genetically related nondiabetic
animals. The activity of Δ6-desaturase was then compared with indices of activity (plasma lipid fatty acid product/precursor
ratios) frequently used in human studies. Diabetic rats treated with insulin had 75±8% of the activity of microsomal Δ6-desaturase
of nondiabetic controls (P<0.05). Insulin withdrawal tended to reduce the activity further (61% of control), although the activity did not differ from
insulin-treated diabetic rats. The ratio of plasma phospholipid or cholesteryl ester γ-linolenic over linoleic acid was not
decreased in insulin-treated diabetic rats. By contrast, the ratio of γ-linolenic over linoleic acid of microsomes was almost
three-fold higher in insulin-treated diabetic rats (P<0.05). The γ-linolenic over linoleic acid ratio as an index of activity gave inconsistent results in insulin-deprived rats.
The ratio of γ-linolenic over linoleic acid of cholesteryl esters did not differ between control and diabetic rats, nor did
it correlate with microsomal Δ6-desaturase activity. Furthermore, the index of Δ6-desaturase activity, derived from the fatty
acid composition of microsomal phospholipids, did not correlate with microsomal Δ6-desaturase activity. Diabetes, even when
controlled by regular insulin injections, reduces the metabolism of linoleic acid, but the effect is less than previously
published. The fatty acid compositions of plasma and liver microsomal lipids are not reliable indices of Δ6-desaturase activity
in diabetes. 相似文献
19.
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
20.
A study was made of the influence of semisynthetic diets of low and high unsaturation on the fatty acid composition and desaturation-chain
elongation enzymatic activity of the liver microsomal fractions of male Sprague-Dawley rats of different ages. Groups of rats
were fed 5 or 20% coconut oil (CO), or a 5 or 20% mixture of corn and menhaden oils (3∶7) (CME) from weaning to 100 wk of
age. Growth rate and food consumption were measured during this period in which animals were sacrificed at 36, 57, 77 and
100 wk of age. Both the level and composition of the dietary fat supplements produced marked effects on the fatty acid composition
of the liver microsomal lipids. In general, the fatty acid composition of the microsomal fractions reflected that of the dietary
fat and was more unsaturated with the higher level of fat fed. The rate of conversion of linoleic to arachidonic acid in assays
performed in vitro with liver microsomal preparations from animals of the different groups also showed marked differences.
The 6-desaturase-chain elongation activity was higher in the 5% than 20% group and corresponded to the essential fatty acid
(EFA) status of the animals in these groups as represented by the triene-tetraene ratio of the microsomal lipid. The relationship
of the 6-desaturase activity to fatty acid composition of the microsomal lipid indicated that if varied directly with the
level of 20∶3ω9, 18∶1 and 16∶1 and was inhibited by arachidonic acid. The activity of the 6-desaturase enzyme system was lowest
in the liver microsomal fraction obtained from the animals fed the CME diets and appeared to be suppressed by the high levels
of 20∶5 and 22∶6 that accumulated in the microsomal lipid. Accordingly, the levels of arachidonic acid were lower in the microsomal
lipid of these groups than those of the corresponding CO groups in spite of a greater abundance of linoleic acid in the diet.
The data suggest that the activity of the 6-desaturase-chain elongation system is regulated by the fatty acid composition
of the microsomal lipid as influenced by the composition of the dietary fat. 相似文献