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1.
Compartmental study of rat renal phospholipid metabolism 总被引:1,自引:1,他引:1
Norma Sterin-Speziale Veronica L. Kahane Clara Patricia Setton Maria del Carmen Fernandez Emir H. Speziale 《Lipids》1992,27(1):10-14
Phospholipid content and metabolism were studied in rat renal papillary, medullary and cortical slices. The highest concentration
of phospholipids was found in cortex and the lowest in papilla samples (ratio cortex/medulla, 1.3; cortex/papilla, 3.7). The
profile of the various phospholipids was different depending on the zone. The most important difference was the relative concentrations
of sphingomyelin (CerPCho) and phosphatidylinositol (PtdIns) with ratios for PtdIns/CerPCho of 5.0, 3.3 and 2.5 in papilla, medulla, and cortex, respectively. In the three zones, PtdIns showed the highest specific
activity for [2-14C]glycerol and [1-14C]arachidonic acid incorporation. By contrast, a higher amount of [1-14C]palmitic acid was incorporated into phosphatidylcholine than into any other phospholipid. The various radioactive precursors
were only poorly incorporated into phosphatidylethanolamine. No radioactivity was associated with phosphatidylserine. The
papilla possesses the most active phospholipid metabolism of all the pathways studied. 相似文献
2.
Studies are reported on the capacity of isolated rat renal papilla (inner medulla) to synthesize and release prostaglandin
(PG) E from endogenous and exogenous precursor(s) during development of an essential fatty acid (EFA) deficiency in the rat.
Weanling (21-day-old) male Sprague-Dawley rats were fed a fat-free diet supplemented with either 5% hydrogenated coconut oil
(HCO) or 5% safflower oil (SO). At approximately 3, 6 and 7 weeks (6, 9 and 10 weeks of age), groups of animals fed each diet
were killed for studies of PGE synthesis in the renal papillae. Differences in the fatty acid composition of the papillae
lipids of the animals of each group were also determined. The in vitro production of PGE from endogenous precursor(s) was
significantly reduced in the papillae from the 6-week-old rats fed the HCO diet compared to the control (SO) rats, and appeared
to be near maximally depressed in the 10-week-old animals compared to that of animals fed an EFA deficient diet for over a
year in an accessory experiment. Analyses of the fatty acids of the papillae lipids of the HCO groups showed that the levels
of 18∶2 and 20∶4 were markedly reduced, and those of 16∶1, 18∶1 and 20∶3 were elevated compared to the controls even in the
6-week-old animals, typical of an EFA deficiency. The papillae lipids of the animals fed the HCO diet were also depleted of
their stores of 22∶4ω6. A fatty acid believed to be derived by chain elongation of 20∶3ω9, 22∶3, was found in large concentrations
in the papillae triglycerides of the EFA deficient rats. Incubations of exogenous arachidonic acid (20∶4) in homogenates and
tissue slices of the papillae of the HCO dietary groups showed that the PG synthetase was not impaired by an EFA deficiency.
The rate of PGE synthesis in the papillae of the EFA deficient animals was generally enhanced when exogenous 20∶4 was added,
indicating that the concentration of available precursor(s) is a primary factor in the control of PGE synthesis in the papilla
of the rat. 相似文献
3.
Freshly isolated rat hepatocytes were used to examine the effects of dibutyryl cyclic AMP on the incorporation of14C-acetate and14C-cholesterol into bile acids. After an initial lag period, both precursors were incorporated into cholic and chenodeoxycholic
acids at a linear rate for the subsequent 60 min. An apparent stimulation of bile acid formation from14C-acetate by dibutyryl cyclic AMP was complicated by the concomitant inhibition of cholesterol synthesis. In experiments with14C-cholesterol, dibutyryl cyclic AMP (1 mM) increased the labeled cholic and chenodeoxycholic acids in the medium by 83 and
224%, respectively, but cellular levels of labeled bile acids were unchanged. As a result, the nucleotide stimulated the overall
incorporation of14C-cholesterol into cholic acid by 39% and into chenodeoxycholic acid by 123%. The mean ratio of labeled cholic to chenodeoxycholic
acid declined from 55∶45 in control cells to 41∶59 in cells incubated with dibutyryl cyclic AMP. The results demonstrate that
label incorporation can be used to study the regulation of bile acid synthesis in isolated hepatocytes. We propose that dibutyryl
cyclic AMP enhances bile acid production by phosphorylating, and thus stimulating the activity of, cholesterol 7α-hydroxylase,
the rate-limiting enzyme in bile acid synthesis. 相似文献
4.
Trinidad Prez‐Palacios Teresa Antequera Elena Muriel Jorge Ruiz 《European Journal of Lipid Science and Technology》2006,108(10):835-841
The fatty acid and dimethyl acetal (DMA) compositions of the sn‐1 and the sn‐2 positions from individual phospholipid (PL) classes [phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI)], obtained from the Longissimus dorsi muscle of rat were studied. The profile of fatty acids and DMA in the sn‐1 and sn‐2 positions of all the PL classes showed marked differences. Overall, saturated fatty acids and monounsaturated fatty acids were in a higher proportion in the sn‐1 position than in the sn‐2 one, while polyunsaturated fatty acids were mainly in the sn‐2 position. Significant differences in the DMA and fatty acid compositions between individual PL classes for each position were found. PC contained the highest proportion of palmitic acid (16:0) in the sn‐1 position and of linoleic acid (18:2 n‐6) in the sn‐2 one. The highest values for stearic acid (18:0) and DMA in the sn‐1 position and for docosahexaenoic acid (22:6 n‐3) in the sn‐2 position were found in PE. PS and PI showed the highest proportion of oleic acid (18:1 n‐9) in the sn‐1 position and of arachidonic acid (20:4 n‐6) in the sn‐2 position. 相似文献
5.
Synthesis of phospholipids and phospholipid fatty acids in isolated perfused rat lung was studied. The perfusion fluid was a Krebs-Ringer bicarbonate buffer containing a14C labeled substrate. It was found that 1-14C-acetate, 1-14C-laurate, 1-14C-palmitate, 1-14C-stearate, 1-14C-oleate, or U-14C-D-glucose was incorporated into tissue lipids in the isolated perfused lung at a rate geeater than that in incubated minced tissue. However, the patterns of the newly synthesized lipids from these two systems were similar. In 1 hr of perfusion, 6.8, 3, 14.5, 7.5, 7, and 2% of the initial14C-radioactivity of 1-14C-acetate, 1-14C-laurate, 1-14C-palmitate, 1-14C-stearate, 1-14C-oleate, and U-14C-D-glucose, respectively, were incorporated into phospholipids. Phospholipid fatty acids accounted for 95–96% total phospholipids-14C when14C-substrates, other than glucose, were used. For glucose, only 20% phospholipids-14C was in phospholipid fatty acids. More than 80% phospholipid fatty acids-14C was in palmitic acid when 1-14C-acetate and U-14C-D-glucose were used, while 37, 61, 80, and 94% phospholipid fatty acid-14C from 1-14C-laurate, 1-14C-sterate, 1-14C-oleate, and 1-14C-palmitate, respectively were recovered in the original form of the fatty acid used. The newly synthesized phospholipid fatty acid (13–24%) from 1-14C-laurate, 1-14C-stearate, and 1-14C-oleate was palmitic, and 10% of phospholipid fatty acid from 1-14C-stearate was in oleic acid. Hydrolysis by phospholipase A showed that14C from perfused substrates was esterified to both α and β positions of phospholipids. It was found that positional selectivity of phospholipid fatty acids was determined by chain length, degree of unsaturation, and source of fatty acid. 相似文献
6.
Streptozotocin diabetes in the rat alters liver microsomal membrane fatty acid composition. The present study was undertaken
to determine if such changes in fatty acid composition were due to changes in the amount of individual phosphoglycerides or
to disproportionate changes in fatty acid composition in any of the individual phosphoglycerides. The diabetic animals showed
a small increase in total microsomal phospholipid, which is due to a selective increase in the phosphatidylethanolamine fraction.
The changes in fatty acid composition in the total lipid extract (decreased palmitoleic, oleic and arachidonic acids and increased
linoleic and docosahexaenoic acids) from the diabetic animals were present in both the major phosphoglycerides, phosphatidylcholine
and phosphatidylethanolamine, with very little change in fatty acid composition in the phosphatidylserine and inositol fraction.
Further studies are necessary to delineate the cause of the abnormal membrane phospholipid composition in the diabetic animal.
Abbreviations: The abbreviated fatty acid nomenclature refers to the number of carbon atoms in the chain, the number of unsaturated
bonds, and the position of the first unsaturated bond counting from the terminal methyl group; thus arachidonic acid, 5,8,11,14-eicosatetraenoic
acid, is 20∶4ω6. 相似文献
7.
Tissue phospholipid fatty acid compositions in streptozotocin-induced diabetic rats were studied. The major changes in liver,
plasma, erythrocyte and heart were increased proportions of linoleic and dihomo-γ-linolenic acids and a decreased proportion
of aracchidonic acid. The latter was not significantly changed in phospholipids of kidney, adrenal gland and testis. Skin
fatty acids in diabetic rats showed an increase in the proportion of arachidonic acid and a reduction in the proportion of
linoleic acid. The fatty acid desaturating activity in diabetes may be regulated differently in different tissues. 相似文献
8.
Insulin-resistant muscle tissue contains low proportions of arachidonic acid (AA), and increased proportions of muscle AA
correlate with improved insulin sensitivity. Dehydroepiandrosterone (DHEA) and AA, like the thiazolidinedione drugs that decrease
insulin resistance (IR), are peroxisome proliferators. Long-chain fatty acids (FA) have been named the “one true” endogenous
ligand for activating the peroxisome proliferator-activator receptor (PPAR), and DHEA has been named a “good candidate” as
a naturally occurring indirect activator of PPAR. This study was conducted to determine DHEA’s effects on lipid profiles of
skeletal and cardiac muscle in lean and obese Zucker rats (ZR), a model of IR, type 2 diabetes mellitus, and obesity. We hypothesize
that DHEA may alter long-chain FA profiles in muscle tissue of obese rats such that they more closely resemble that of the
lean. In our experiments we employed a DHEA and a pair-fed (PF) group (n=6) for 12 lean and 12 obese ZR. For 30 d, the diet of the two DHEA groups was supplemented with 0.6% DHEA; PF groups were
given the average daily calories consumed by their corresponding treatment group. Hearts and gastrocnemius muscles were assayed
for phospholipid (PL), free FA, and triglyceride (TG) FA profiles. The proportion of PL AA was significantly greater in both
muscle types of lean compared to obese rats. Hearts from both DHEA groups had greater PL proportions of AA and less oleic
(18∶1) acid than their PF controls. Likewise, 18∶1 proportions were significantly lower in the gastrocnemius; however, AA
proportions were not significantly different. Similar phenotypic profile differences were observed in the TG fraction of both
muscle types. There were no DHEA-related TG FA profile alterations. 相似文献
9.
The influence of long duration rapeseed oil feeding with high or low levels of erucic acid has been investigated on rat heart
phospholipids. The rats treated for 20 wk with rapeseed oil containing 46.2% erucic acid showed a twofold increase in the
sphingomyelin content of the heart. Treatment with primor rapeseed oil (3.7% erucic acid) for 20 wk did not modify phospholipid
composition of rat heart. The fatty acid patterns of phosphatidylethanolamine and phosphatidylcholine were slightly influenced
by the high erucic rapeseed oil; eicosenoic acid was incorporated preferentially into position one, but erucic acid showed
a random distribution in both. After high erucic rapeseed oil feeding, 22∶1 was incorporated into cardiolipin (5.6%) and sphingomyelin
(10.5%). The incorporation of 22∶1 into sphingomyelin was associated with an increase of the percentage of 24∶1 (14.6%) and
a decrease of saturated long chain fatty acid (22∶0, 24∶0) percentages. Primor rapeseed oil caused a slight increase of 24∶1
and a decrease of 22∶0 and 24∶0 in rat heart sphingomyelin. As cardiolipin is localized in the inner membrane of mitochondria
and sphingomyelin in plasma and microsomal membranes, the acyl-moiety alterations of both phospholipids might be correlated
to the pathological lesions of rat heart after a long duration of rapeseed oil feeding. 相似文献
10.
Neuronal membranes are highly enriched with docosahexaenoic acid (22∶6n−3), and its content can be altered by ethanol consumption.
We have previously reported that the 22∶6n−3 status in membrane affects the biosynthesis of phosphatidylserine (PS), a phospholipid
class which contains an exceptionally high proportion of 22∶6n−3. The aim of the present study is to investigate the effect
of chronic ethanol exposure on PS accumulation in relation to the 22∶6n−3 status. C-6 glioma cells were enriched with 25 μM
22∶6n−3 for 48 h and the PS accumulation was first evaluated in comparison to nonenriched cells as well as cells enriched
with arachidonic acid (20∶4n−6). Electrospray liquid chromatography-mass spectrometry analysis revealed that cells treated
with 22∶6n−3 showed significantly higher accumulation of PS in comparison to nonenriched or 20∶4n−6-enriched cells, primarily
due to an increase of 1-stearoyl-2-docosahexaenoyl-glycerophosphoserine (18∶0,22∶6-PS). Chronic ethanol exposure selectively
affected the accumulation of PS in 22∶6n−3-enriched cells. After cells were exposed to 20 or 50 mM ethanol for 4 wk, accumulation
of 18∶0,22∶6-PS upon 22∶6n−3 supplementation was significantly lower, resulting in a drastic reduction of total PS. Concomitantly,
ethanol-treated cells showed lower incorporation of serine in comparison to control cells. From these data, it was concluded
that supplementation of cells with 22∶6n−3 promotes the accumulation of PS and chronic ethanol treatment diminishes this effect
at least in part through impaired serine incorporation processes. Attenuated accumulation of 22∶6n−3 in PS and the reduction
of PS thus may have significant implications in pathophysiological effects of ethanol, especially in tissues with abundant
22∶6n−3. 相似文献
11.
Katarzyna Jasieniecka-Gazarkiewicz Sylwia Klińska-Bąchor Antoni Banaś 《European Journal of Lipid Science and Technology》2023,125(9):2200217
This study investigated the impact of different acyl-CoAs on remodeling efficiency of PC and PE via the action of acyl-CoA:lysophospholipid acyltransferases (LPLAT). Microsomal fractions from yeast ΔALE1 mutant transformed with an empty plasmid pYES2 or plasmid carrying AtLPCAT or ALE1 encoding genes were used in the experiments. In the preliminary assays, presence of 18:1-CoA in the reaction mixture increased remodeling efficiency of [14C]PC integrated with microsomal fraction of yeast overexpressing AtLPCAT compared to assays without exogenous acyl-CoA. In further experiments, the effect of five different acyl-CoAs (16:0-CoA, 18:0-CoA, 18:1-CoA, 18:2-CoA, and 18:3-CoA) on remodeling efficiency of yeast microsomal PC and PE via the action of three LPLATs (yeast SLC1 and ALE1 and Arabidopsis LPCAT2) were tested. It has been shown that acyl-CoAs used in the experiments had different effect on the remodeling intensity of PC and PE via action of the tested acyltransferases. Moreover, each acyl-CoA used had a different effect on the tested acyltransferases. Additionally, the assays with DTNB (inhibitor of the LPLAT backward reaction) showed that remodeling of PC and PE by LPLATs can also occur through reactions other than the backward reaction carried out by these enzymes, and that acyl-CoA present in the reaction mixture affected these processes. 相似文献
12.
The effect of altered methionine metabolism during pyridoxine deficiency on the activity of phosphatidyl-ethanolamine methyltransferase
(EC 2.1.1.17) and the levels of phosphatidylethanolamine (PE) and phosphatidylcholine (PC) has been evaluated in rat liver
microsomes. Animals fed a pyridoxine-deficient diet for 7 wk displayed a fivefold increase in the hepatic tissue level of
S-adenosylhomocysteine when compared to either control or pair-fed animal counterparts. When PE methyltransferase was assayed
in vitro, a significant increase in specific activity was observed using enzyme preparations from either pair-fed or pyridoxine-deficient
rats. On the other hand, phospholipid levels did not conform to the measured enzyme activity. The level of PC in microsomes
from either pyridoxine-deficient or pair-fed animal groups was significantly lower than that determined for the control group
of rodents. However, the level of PC was noticeably lower in microsomes from pyridoxine-deficient animals than that from pair-fed
animals, which received 45% of the feed intake of the control animals. In addition, the level of PE in microsomes from pair-fed
and pyridoxine-deficient animals was significantly higher than that analyzed from the control animals, further confirming
decreased methylation of substrate to product. It is concluded that pyridoxine deficiency may alter the methylation of phospholipid
in the endoplasmic reticulum above and beyond that produced by feed restriction alone. 相似文献
13.
Data presented in this study demonstrate that under normal physiological conditions milk phospholipids in the rat and the
goat originate predominantly, if not totally, by de novo synthesis within the mammary gland. Evidence to support this has
been obtained for the goat by measurement of P32-phosphate incorporation into milk phospholipids, and in the rat by measurement of P32-phosphate incorporation and by feeding radioactive phospholipid to measure the incorporation of serum phospholipids into
milk. The latter experiment showed that the fatty acid portion of the dietary phospholipid can readily be utilized by the
mammary gland for triglyceride synthesis, but that the contribution of the serum phospholipid “backbone” to milk phospholipid
is minimal. 相似文献
14.
Short-term activation of microsomal cholesterol ester hydrolase by glucagon, cAMP analogues, and vasopressin in isolated rat
hepatocytes is described. Glucagon led to a dose-and time-dependent activation of cholesteryl oleate hydrolysis, but values
returned to basal levels within 120 min. Exposure of isolated hepatocytes to 0.5 mM concentrations of dibutyryl-cAMP or 8-[4-chlorophenylthio]-cAMP,
or 25 μM forskolin caused persistent activation of cholesterol ester hydrolase activity after a lag period of 30 min. The
three agents resulted in early marked intracellular accumulation of cAMP that declined progressively, and moderate and sustained
reductions in the diacylglycerol content. The actions of glucagon on hepatocytes were inhibited by pretreatment of cells with
10 nM [8-arginine] vasopressin. Vasopressin elicited a consistent and sustained increase in cholesterol ester hydrolase activity
and diacylglycerol without affecting cAMP while reducing the effect of glucagon on cAMP. Furthermore, the effects of glucagon
and vasopressin on the activation of cholesterol ester hydrolase were not additive despite the similarity of their stimulation
of diacylglycerol formation. Blockade of vasopressin-mediated activation of cholesterol ester hydrolase and diacylglycerol
content were induced by excess prazosin. These data suggest that stimulation of microsomal cholesterol ester hydrolase in
isolated liver cells may involve at least two signal transduction systems. 相似文献
15.
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
16.
Early and late effects of alloxan-diabetes on lipid/phospholipid composition in rat kidney microsomes and mitochondria were
examined. In microsomes, early diabetic state resulted in an increase in contents of total phospholipids (TPL), cholesterol
(CHL), with an increase in the lysophospholipids (Lyso), phosphatidylcholine (PC), and phosphatidylinositol (PI) components.
The sphinogmyelin (SPM), phosphatidylethanolamine (PE), phosphatidylserine (PS), and phosphatidic acid (PA) content decreased.
Treatment with insulin had no effect on PC but PE increased and the other components decreased. In the 1-month diabetic group
PI, PS, PE, and PA components decreased, whereas Lyso and PC increased. Treatment with insulin had restorative effects on
PE, PI, and PS; Lyso was further elevated whereas PA decreased. In mitochondria, at an early stage of diabetes marginally
increased CHL content was restored by insulin treatment. Long-term diabetes lowered the TPL and elevated the CHL content.
Treatment with insulin partially restored the TPL and CHL content. A diabetic state decreased the proportion of PE and diphosphatidylglycerol
(DPG) components but increased the Lyso, SPM, PC, PI, and PS components in the mitochondria. Treatment with insulin had a
partial restorative effect. The membrane fluidity of both microsomes and mitochondria decreased in general in the diabetic
condition and was not corrected by insulin treatment at a late stage. However, at an early stage, treatment with insulin fluidized
both membranes. 相似文献
17.
For eight weeks young male rats were fed diets rich in 18∶2 (stock diet, or 10% corn oil, CO) or those devoid of 18∶2 (fat
free, FF, or 10% hydrogenated coconut oil, HCNO). The CO and HCNO diets were fed in the absence or presence of eicosa-5,8,11,14-tetraynoic
acid (TYA). When 18∶2 was excluded, an increase in the level of 16∶1, 18∶1 and 20∶3 and a decrease in 18∶2 was observed in
the fatty acids of red cells. On feeding TYA, an increase in 18∶2 and in the case of the HCNO+TYA diet, a decrease of 12∶0
and 14∶0 was also observed. In all cases the levels of 20∶4 in erythrocyte fatty acids were similar. Saturated fatty acids
were predominant in phosphatidyl choline (PC), lysophosphatidylcholine, (LPC) and sphingomyelin whereas unsaturated acids
were predominant in phosphatidyl ethanolamine (PE), (PS), and phosphatidyl inositol (PI). Acids containing three or more double
bonds comprised about 90% of the total acids in PI. In all the phospholipids, the characteristic changes in the composition
of fatty acids were observed due to the exclusion of 18∶2 from the diet. However, changes due to the feeding of TYA were found
only in PC and LPC. In rats fed the 18∶2-rich diet, about 60% of the red cells were discocytes. In those fed the 18∶2-free
diet, the level of discocytes decreased to about 23%, and the levels of echinocytes II and III increased. The exclusion of
18∶2 for even a few days decreased the proportion of discocytes. The loss of discoid shape was reversed in a few days by feeding
an 18∶2-rich diet. Fatty acid analysis of erythrocytes of rats of the various dietary manipulations showed that the change
in the proportion of discocytes followed the change in the level of 18∶2. 相似文献
18.
The relative specific activities of phospholipids of hearts and livers of newborn and older rats were measured 2 hr after
intraperitoneal32P-orthophosphate. There was a close linear correlation between the specific activity of cardiolipin and the net increase in
the amount of this phospholipid. In one-day-old animals, the relative specific activities in the heart and liver were highest
and exceeded by 7.3- and 3-fold, respectively, the corresponding activities in the adult. The apparent half-lives of cardiolipins
were calculated on the basis of the linear correlation that was found between the net increase in cardiolipin and the rate
of incorporation. These half-lives were 4.7 days in liver and 6.4 days in heart. Though the changes in the phospholipid composition
of the organelles during neonatal development were small, the relative specific activities of the individual phospholipids
varied considerably. In addition to cardiolipin, there was a good correlation between the specific activity and the net increase
in mitochondrial phosphatidylinositol. At birth, the specific activity of mitochondrial phosphatidylcholine in liver was 2.9
times that in microsomes. During the 12 neonatal hours, the specific activity of microsomal phosphatidylcholine increased
6.3-fold and exceeded the corresponding mitochondrial activity. The relation between the activation of microsomal phosphatidylcholine
synthesis and the induction of serum lecithin synthesis in newborn liver is discussed. The finding that at birth the specific
activity of mitochondrial phosphatidylcholine unexpectedly was higher than that of microsomal phosphatidylcholine points out
the difficulties in interpreting the in vivo evidence for precursor-product relationship. 相似文献
19.
Skeletal muscle phospholipid fatty acid (PLFA) composition is associated with insulin sensitivity in animal models and in
man. However, it is not clear whether changes in insulin sensitivity cause a change in PLFA composition or vice versa. The
present studies have examined the effects of agents known to increase or decrease insulin sensitivity on PLFA composition
of the major phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), in soleus and extensor digitorum longus
muscle. Four groups of Sprague-Dawley rats— control, 0.2% troglitazone (Tgz), 60% fructose fed, and fructose + Tgz—were treated
for 3 wk. Fructose feeding was associated with a decrease in muscle membrane polyunsaturated fatty acids (PUFA) and n-3 fatty
acids in both PC and PE. Administration of Igz alone resulted in an increase in liver (3.75±0.93 to 6.93±1.00 μmol/min/mg
tissue, P<0.05) and soleus muscle (0.34±0.03 to 0.67±0.09 μmol/min/mg, P<0.01) elongase activity, which would be expected to increase membrane PUFA. However, Tgz decreased PLFA associated with greater
insulin sensitivity (e.g., PUFA and n-3 fatty acids) and increased PLFA associated with decreased insulin sensitivity (16∶0
and n-6 fatty acids) in both PC and PE. Co-administration of fructose and Tgz did not reverse the decrease in PUFA observed
with fructose alone. We conclude that the improvement in insulin sensitivity reported with Tgz is associated with an apparently
paradoxical effect to decrease PUFA and n-3 PLFA composition in rat skeletal muscle. These studies suggest that Tgz-mediated
increases in insulin sensitivity do not result in improved PLFA composition. 相似文献
20.
The calcium-stimulated incorporation of ethanolamine, choline and L-serine into rat brain microsomal phospholipids has been
investigated. The membranes were prelabeled in vitro in their choline or serine phosphoglycerides by base-exchange and then
chasing experiments were done by displacing the lipid-bound base by ethanolamine, choline, or L-serine labeled with a different
isotope. The results indicate that membrane phosphatidylcholine is presumably a substrate for the exchange with all the three
bases, whereas phosphatidylserine exchanges only with ethanolamine and L-serine but not with choline. A small phospholipid
pool (3–7% of the total available pool) is active in the calcium-dependent exchange with choline, ethanolamine, and L-serine.
When the microsomal membranes are prelabeled in vitro in their phosphatidylcholine moiety through the cytidine-dependent pathway
and then chasing experiments are performed with the three nitrogenous bases, as above, the small phospholipid pool is hardly
detectable. In view of these and other results (Gaiti et al., FEBS Letters 49:361 1975), it is suggested that at least two
different pools of phosphatidylethanolamine, phosphatidylserine, and phosphatidylcholine might exist in rat brain microsomes. 相似文献