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1.
Changes in fatty acid desaturation in hepatic and intestinal tissues induced by intestinal resection
We have studied the activities of Δ9, Δ6 and Δ5 desaturases in rat liver and jejunum when the entero-hepatic circulation was
interrupted by either 50 or 75% intestinal resection. Desaturase activities in caecal mucosa were also determined in control
and operated rats. Distal small bowel resection significantly altered the activities of desaturase enzymes in liver, jejunum
and caecum. Thus, the Δ9 desaturase activity was lower in hepatic microsomes from operated animals, and this decrease was
not related to the extent by which the intestine was removed. However, a significant increase in both Δ6 and Δ5 desaturases
was found in these animals compared to shamoperated rats, the increase in both desaturases being higher after 75% than after
50% intestinal resection. The activities of Δ9 and Δ5 desaturases were significantly increased in jejunal mucosa of resected
rats. The activity of Δ6 desaturase was increased only in 50% resected-animals. An increase in Δ6 desaturase activity was
observed in caecal mucosa after resection, together with a decrease in Δ9 desaturase and no change in Δ5 desaturase activities.
Enzyme activities were highest in the liver relative to the activity in jejunal and caecal homogenates. In sham rats, the
caecal mucosa showed higher Δ9 and Δ6 but lower Δ5 desaturase activities than in jejunal mucosa. 相似文献
2.
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
3.
We examined the in vivo contribution of insulin, T090137 (T09), agonist of liver X receptor (LXR), fenofibrate, agonist of
peroxisome proliferator activated receptor (PPAR-α) and sterol regulatory element binding protein-1c (SREBP-1c) on the unsaturated
fatty acid synthesis controlled by Δ6 and Δ5 desaturases, compared with the effects on stearoylcoenzyme A desaturase-1. When
possible they were checked at three levels: messenger RNA (mRNA), desaturase protein and enzymatic activity. In control rats,
only fenofibrate increased the insulinemia that was maintained by the simultaneous administration of T09, but this increase
has no specific effect on desaturase activity. T09 enhanced SREBP-1 in control animals and the mRNAs and activity of the three
desaturases in control and type-1 diabetic rats, demonstrating a LXR/SREBP-1-mediated activation independent of insulin. However,
simultaneous administration of insulin and T09 to diabetic rats led to a several-fold increase of the mRNAs of the desaturases,
suggesting a strong synergic effect between insulin and LXR/retinoic X receptor (RXR). Moreover, this demonstrates the existence
of an interaction between unsaturated fatty acids and cholesterol metabolism performed by the insulin/SREBP-1c system and
LXR/RXR. PPAR-α also increased the expression and activity of the three desaturases independently of the insulinemia since
it was equivalently evoked in streptozotocin diabetic rats. Besides, PPAR-α increased the palmitoylcoenzyme A elongase, evidencing
a dual regulation in the fatty acid biosynthesis at the level of desaturases and elongases. The simultaneous administration
of fenofibrate and T09 did not show additive effects on the mRNA expression and activity of the desaturases. Therefore, the
results indicate a necessary sophisticated interaction of all these factors to produce the physiological effects. 相似文献
4.
Age-related changes in Δ6 desaturation of [1-14C]α-linolenic acid and [1-14C]linoleic acid and in Δ5 desaturation of [2-14C]dihomo-γ-linolenic acid were studied in liver microsomes from Wistar male rats at various ages ranging from 1.5 to 24 mon.
Desaturase activities were expressed both as specific activity of liver microsomes and as the capacity of whole liver to desaturate
by taking into account the total amount of liver microsomal protein. Δ6 Desaturation of α-linolenic acid increased from 1.5
to 3 mon and then decreased linearly up to 24 mon to reach the same desaturation capacity of liver measured at 1.5 mon. The
capacity of liver to desaturate linoleic acid increased up to 6 mon and then remained constant, whereas microsomal specific
activity was equal at 1.5 and 24 mon of age. The capacity of liver to convert dihomo-γ-linolenic acid to arachidonic acid
by Δ5 desaturation decreased markedly from 1.5 to 3 mon. It then increased to reach, at 24 mon, the same level as that observed
at 1.5 mon. Age-related changes in the fatty acid composition of liver microsomal phospholipids at the seven time points studied
and of erythrocyte lipids at 1.5 and 24 mon were consistent with the variations in desaturation capacity of liver. In particular,
arachidonic acid content in old rats was slightly higher than in young rats whereas contents in linoleic and docosahexaenoic
acids varied little throughout the life span. The results suggest that, in liver, the activity of desaturases may be regulated
in the course of aging to maintain a constant level of polyunsaturated fatty acids in cellular membranes. 相似文献
5.
Female rats warm-adapted at 30–32 C for 20–25 days and then shifted to 13–15 C for 12, 24, 48, 72 and 120 hr showed that Δ9
desaturase and fatty acid synthetase activity decay after 24 hr of cold exposure, while Δ6 and Δ5 desaturases were increased
after this period of time. These results were confirmed by an increase of arachidonic acid of heart and liver microsomes phosphatidylcholine
and a decrease of oleic acid. Neither NADH-cyt b5 reductase nor NADH-cyt c reductase activity of liver microsomes were significantly affected. Male rats warm-adapted under
the same conditions and then shifted to 13–15 C for 120 hr did not show significant changes in fatty acid synthetase, Δ9 and
Δ6 desaturases and enzymes of the microsomal electron transport chain. Therefore, the desaturase response to environmental
temperature changes could be plausibly linked to female hormones. 相似文献
6.
Pharmacological modulation of fatty acid desaturation and of cholesterol biosynthesis in THP-1 cells
In THP-1 cells, simvastatin decreases, in a concentration-dependent manner, cholesterol synthesis and increases linoleic acid
(LA) conversion to its long-chain derivatives, in particular to arachidonic acid, activating Δ6 and Δ5 fatty acid (FA) desaturases.
The intermediates in cholesterol synthesis, mevalonate and geranylgeraniol, partially reverse the effects of simvastatin on
the LA conversion. The aims of this work were to evaluate: (i) the correlation between cholesterol synthesis and desaturase
activity and (ii) the possible involvement of protein isoprenylation in desaturase activity, assessed through pharmacological
treatments. THP-1 cells were incubated with [1-14C]LA or with [1-14C]di-homo-γ-linolenic acid (DHGLA) and treated with simvastatin or with curcumin and nicardipine, inhibitors of desaturases.
Curcumin was more active than nicardipine in inhibiting LA and DHGLA conversion: 20 μM curcumin, alone or with simvastatin,
totally inhibited Δ6 and Δ5 desaturation steps; 10 μM nicardipine only partially inhibited the enzymes, being more active
on Δ5 desaturase. Simvastatin treatment decreased the incorporation of acetate in cholesterol (−93.8%) and cholesterol esters
(−70.2%), as expected. Curcumin and nicardipine also decreased cholesterol synthesis and potentiated simvastatin. Finally,
the isoprenylation inhibitors (perillic acid and GGTI-286) neither affected the conversion of LA nor inhibited the Δ5 desaturase
activity. In conclusion, our results indicate that there is no direct relationship between cholesterol synthesis and desaturase
activity. In fact, simvastatin decreased cholesterol synthesis and enhanced LA conversion (mainly Δ5 desaturation), whereas
curcumin and nicardipin decreased Δ5 desaturation, with a limited effect on cholesterol synthesis. 相似文献
7.
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
8.
Male rats injected with a single saturating dose of L-triiodothyronine (T3) showed, after a lag time of approximately eight hr, a sharp rise in Δ9 desaturase activity. Desaturase activity reached
a plateau which was 1–1.2 times above the base line levels of rats which were not hormone-treated. The plateau was maintained
for five days in animals which were kept on daily hormone-treatment. The increase in Δ9 desaturase activity by T3 required ongoing protein synthesis, because the increase in enzymatic activity due to hormone treatment was completely abolished
in the presence of cycloheximide. These findings suggest that cycloheximide may block the induction of Δ9 desaturase by T3 and/or inhibit the synthesis of protein(s) essential to the desaturation-response to T3. Modifications observed in liver microsomal fatty acid composition in T3 treated rats were independent of the effect on desaturation. It is suggested that other factors, such as diet, membrane lipid
synthesis and degradation, as well as fatty acid turnover and oxidation, could be involved in affecting the fatty acid composition
of thyroid hormone-treated rats. 相似文献
9.
The effects of a 1% addition of cholesterol to a diet low in EFA on FA desaturases were examined. The administration of cholesterol
markedly increased the esterified cholesterol content in microsomes and total liver lipids from the first day, whereas the
proportion of free cholesterol remained unaltered throughout the treatment. An excellent homeostasis in the free cholesterol
content was apparently evoked by the acyl-CoA cholesterol acyltransferase. The cholesterol esters were mainly oleate, palmitate,
and stearate, and the addition of cholesterol increased the relative proportions of cholesterol palmitoleate and oleate. The
addition of cholesterol to a low-EFA diet induced, as in animals fed a high-FFA diet, a marked increase in liver stearoyl-CoA
desaturase-1 mRNA and enzyme activity. This increased activity apparently evoked a similar enhancement of palmitoleic and
oleic acids in total and microsomal liver lipids. The cholesterol-rich diet depressed the liver Δ6 and Δ5 desaturase activity.
However, the abundance of Δ6 desaturase mRNA was not modified throughout the treatment. This indicates that the depressive
effect is evoked at a step beyond that controlled by the mRNA level. The depression of both enzymatic activities was consistent
with the decrease in the percentages of arachidonic acid and DHA in total and microsomal liver lipids. Taken together, these
results indicate that through its modulating effect on the desaturases, dietary cholesterol may lead an animal or humaan fed
low-EFA diet to a true deficiency by the decreased synthesis of the highly polyunsaturated acids derived from linoleic and
α-linolenic acids. 相似文献
10.
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
11.
Sakayu Shimizu Kengo Akimoto Yoshifumi Shinmen Hiroshi Kawashima Michihiro Sugano Hideaki Yamada 《Lipids》1991,26(7):512-516
Incubation with sesame oil increases the mycelial dihomo-γ-linolenic acid content of an arachidonic acid-producing fungus,Mortierella alpina, but decreases its arachidonic acid content [Shimizu, S., K. Akimoto, H. Kawashima, Y. Shinmen and H. Yamada (1989)J. Am. Oil Chem. Soc. 66, 237–241]. The factor causing these effects was isolated and identified to be (+)-sesamin. The results obtained in experiments
with both a cell-free extract of the fungus and with rat liver microsomes demonstrated that (+)-sesamin specifically inhibits
Δ5 desaturase at low concentrations, but does not inhibit Δ6, Δ9 and Δ12 desaturases. Kinetic analysis showed that (+)-sesamin
is a noncompetitive inhibitor (Ki for rat liver Δ5 desaturase, 155 μM). (+)-Sesamolin, (+)-sesaminol and (+)-episesamin, also inhibited only Δ5 desaturases
of the fungus and liver. These results demonstrate that (+)-sesamin and related lignan compounds present in sesame seeds or
its oil are specific inhibitors of Δ5 desaturase in polyunsaturated fatty acid biosynthesis in both microorganisms and animals.
On leave from Suntory Ltd. 相似文献
12.
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
13.
Male Sprague-Dawley rats made diabetic with alloxan (37.5 mg/kg) or streptozotocin (65 mg/kg) were killed after 3–6 weeks
of disease; renal tissues were studied for phospholipid content and for fatty acid composition of the phospholipids. No consistent
change was noted in total phospholipid content nor in the proportion of various phospholipids in diabetics. However, diabetic
animals showed a consistent reduction of arachidonic acid content in phosphatidylcholine (PC) and phosphatidylethanolamine
in whole renal cortex, plasma membranes purified from renal cortex, and in isolated glomeruli. Associated with the fall in
arachidonic acid was a rise in linoleic acid in the samples studied. Insulin therapy returned the fatty acid profiles to normal.
These results are similar to patterns observed in other diabetic tissues and suggest that diabetes is associated with generalized
changes in cell membranes. That these structural changes may have functional significance is suggested by demonstrated alterations
in the temperature-dependence of adenylate cyclase in renal plasma membranes of diabetic animals. Adenylate cyclase is thought
to be intimately associated with PC in plasma membranes, a phospholipid showing significant changes in fatty acid content
in diabetes (unsaturation index 165±2 for normals, 147±5 for diabetics). Na+,K au+-ATPase which is thought to be primarily associated in vivo with phosphatidylinositol (PI), shows no change in apparent
energy of activation in diabetes. The fatty acid content of PI is minimally altered in diabetes, and the unsaturation index
is unchanged. 相似文献
14.
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
15.
The freshwater microalga Parietochloris incisa accumulates, under nitrogen starvation, large amounts of triacylglycerols containing approximately 60% of the ω6 very long-chain
polyunsaturated fatty acid (VLC-PUFA), arachidonic acid. Based on sequence homology, we isolated three cDNA sequences from
P. incisa, designated PiDesD12, PiDesD6, PiDesD5. The deduced amino acid sequences of the three genes contained three conserved histidine motifs; the front-end desaturases,
PiDes6 and PiDes5, contained a fused N-terminal cytochrome b5 domain. By functional characterization in the yeast Saccharomyces cerevisiae, we confirmed that PiDesD6, PiDesD5 cDNA encode membrane bound desaturases with Δ6, and Δ5 activity, respectively. Both PiDes6 and PiDes5 can indiscriminately
desaturate both ω6 and ω3 substrates. A phylogenetic analysis showed that the three genes were homologous to the corresponding
desaturases from green microalgae and lower plants that were functionally characterized. Quantitative real-time PCR revealed
the concerted expression pattern of all three genes in P. incisa cells subjected to nitrogen starvation, featuring maximum expression level on day 3 of starvation, corresponding to the sharpest
increase in the share of arachidonic acid. 相似文献
16.
This report describes the daily changes in fatty acid composition and fatty acid desaturation in rats feeding on a complete
diet and a fat-free diet successively. Rats on a complete diet showed a good homeostasis in the percentage of fatty acid in
plasma, with a possible palmitic acid rhythm, but the fat-free diet initiated an essential fatty acid-deficient pattern in
a few hours. The light-dark period in animals feeding on a complete diet motivates a feeding rhythm that causes changes in
linoleic and arachidonic acids in the whole liver and microsomes that are related to Δ6 and Δ5 desaturase activities. The
patterns of Δ6 and Δ5 desaturase changes were different. Linoleic acid intake during the dark periods (complete diet feeding)
caused a decrease of Δ6 desaturase activity and the activation of Δ5 desaturation that led to an increase of arachidonic acid
biosynthesis. The feeding of a fat-free diet eliminated the rhythm observed in linoleic and arachidonic acid composition in
the liver and changed the desaturase rhythms. The Δ9 desaturase activity in the liver also showed a daily rhythm in the complete-diet
period that disappeared with the change to a fat-free diet, while the activity increased markedly. A negative correlation
existed between the percentage of linoleic acid in the liver and the Δ9 desaturase activity. However, no correlation was found
between Δ9 desaturase activity and the percentage of 16∶1 and 18∶1 in the complete-diet period. 相似文献
17.
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
18.
Sakayu Shimizu Saeree Jareonkitmongkol Hiroshi Kawashima Kengo Akimoto Hideaki Yamada 《Lipids》1992,27(7):509-512
An extract of rhizomes ofCurcuma longta L. (turmeric) inhibited the desaturation of dihomo-γ-linolenic acid (DGLA) in the arachidonic acid (AA) producing fungusMortierella alpina 1S-4. The factor responsible for this phenomenon was isolated and identified as curcumin (diferuloyl methane). Mycelial DGLA
levels increased about two-fold (22.3 mg/g dry weight) with a concomitant decrease in AA levels when the fungus was cultivated
with curcumin. The 50% inhibitory concentration against Δ5 desaturase was 27.2 μM. Curcumin also inhibited rat liver microsomal
Δ5 and Δ6 desaturases. 相似文献
19.
Graciela E. Hurtado de Catalfo Elisabet C. Mandon Irma N. T. de Gómez Dumm 《Lipids》1992,27(8):593-598
The biosynthesis of arachidonic acid in Sertoli and Leydig cells isolated from the testes of mature rats has been investigated.
Both types of cells incorporated [2-14C]eicosatrienoic acid from the incubation medium and transformed it into arachidonic acid. The administration of adrenocorticotropin
(ACTH) to the rats decreased the Δ5 desaturating activity in the isolated testicular cells, while ACTH produced no changes
in the uptake of the substrate. Similar results were obtained when ACTH was added to the incubation medium of cells isolated
from non-hormone treated rats. The total fatty acid composition of the Sertoli cells isolated from ACTH-treated rats showed
a significant increase in the relative percentage of 18∶2n−6 and a decrease in the C20 and C22 polyenes. This may indicate that ACTH exerts an inhibitory effect on Δ6, Δ5 and Δ4 desaturase activities. Addition of corticosterone
to the incubation medium also produced a significant decrease in arachidonic acid biosynthesis. Because ACTH is known to stimulate
the release of corticosteronein vivo, both hormones may act cumulatively in the regulation of arachidonic acid metabolism in Sertoli and Leydig cells. 相似文献
20.
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