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1.
Four sources of long-chain polyunsaturated fatty acids (LCP) differing in their chemical structure (triglycerides or phospholipids)
and in their origin (tuna triglycerides, fungal triglycerides, egg phospholipids, and pig brain phospholipids) were analyzed
to determine the distribution of the component fatty acids within the molecule. Lipase and phospholipase A2 hydrolysis was performed to obtain 2-monoacylglycerols and lysophospholipids, respectively, which allowed us to determine
the distribution of fatty acids between the sn-2 and sn-1,3 positions of triglycerides or between the sn-1 and sn-2 position of phospholipids. Fatty acids in the LCP sources analyzed were not randomly distributed. In tuna triglycerides,
half of the total amount of 22∶6n−3 was located at the sn-2 position (49.52%). In fungal triglycerides, 16∶0 and 18∶0 were esterified to the sn-1,3 (92.22% and 91.91%, respectively) 18∶1 and 18∶2 to the sn-2 position (59.77% and 62.62%, respectively), and 45% of 20∶3n−6 and only 21.64% of 20∶4n−6 were found at the sn-2 position. In the lipid sources containing phospholipids, LCP were mainly esterified to the phosphatidylethanolamine fraction.
In egg phospholipids, most of 20∶4n−6 (5.50%, sn-2 vs. 0.91%, sn-1) and 22∶6n−3 (2.89 vs. 0.28%) were located at the sn-2 position. In pig brain phospholipids, 22∶6n−3 was also esterified to the sn-2 (13.20 vs. 0.27%), whereas 20∶4n−6 was distributed between the two positions (12.35 vs. 5.86%). These results show a different
fatty acid composition and distribution of dietary LCP sources, which may affect the absorption, distribution, and tissue
uptake of LCP, and should be taken into account when supplementing infant formulas. 相似文献
2.
Molecular species of 1-O-alk-1′-enyl-2-acyl-, 1-O-alkyl-2-acyl-, and 1,2-diacyl-sn-glycero-3-phosphoethanolamine (EPL) andsn-glycero-3-phosphocholine (CPL) of Japanese oysterCrassostrea gigas were analyzed by selectedion monitoring gas chromatography/mass spectrometry using electron impact ionization. The characteristic
fragment ions, [RCH=CH+56]+ due to the alkenyl residue in thesn-1 position and [RCO+74]+ due to the acyl residue in thesn-2 position of alkenylacylglycerols, [R+130]+ due to the alkyl residue in thesn-1 position and [RCO+74]+ due to the acyl residue in thesn-2 position of alkylacylglycerols, [RCO+74]+ due to the acyl residues in thesn-1 and/orsn-2 positions of diacylglycerols, and [M−57]+ being indicative of the corresponding molecular weight, were used for structural assignments.
For alkenylacyl EPL and CPL, 19 and 16 molecular species were determined, respectively. Two molecular species, 18∶0alkenyl-22∶6n−3
and 18∶0-alkenyl-22∶2-non-methylene interrupted diene (NMID), amounted to 53.2% and 47.9%, respectively. The alkylacyl EPL
and CPL consisted of 16 and 20 molecular species, respectively, and the prominent components were 18∶0alkyl-22∶2NMID, 20∶1alkyl-20∶1n−11
(27.4%) and 20∶1alkyl-20∶2NMID (16.3%) in the former, and 16∶0alkyl-20∶5n−3 (23.0%) and 16∶0alkyl-22∶6n−3 (21.6%) in the latter.
For the diacyl EPL and CPL, 14 and 51 molecular species were determined, respectively. The major molecular species were 18∶0–20∶5n−3
(37.4%), 16∶0–20∶5n−3 (14.2%) and 18∶1n−7–22∶2NMID (13.2%) in the former, and 16∶0–20∶5n−3 (33.4%) and 16∶0–22∶6n−3 (22.3%)
in the latter. It was found that there were significant differences in the molecular species between the alkylacyl and diacyl
EPL and the alkylacyl and diacyl CPL; the number of molecular species was larger in CPL than in EPL, while the number of total
carbons and double bonds of the major molecular species were larger in the EPL than in the CPL. Alkenylacyl EPL were similar
to alkenylacyl CPL in molecular species composition. 相似文献
3.
Phospholipids of the fungiConidobolus nanodes, Entomophthora exitalis andSaprolegnia parasitica were extracted and analyzed. The phospholipid content was the same (2.4%) for the three species and was independent of the
total lipid content. Phospholipase A2 degradation of individual phospholipid classes showed an asymmetrical distribution of polyunsaturated fatty acids (PUFA)
between the two fatty acyl positions of glycerol. There was a predominance of n-6 PUFA at position 2 and a predominance of
n-3 PUFA at position 1. WithC. nanodes andE. exitalis, 20∶5n−3 is derived from 18∶3n−3 and is located predominantly at position 1. InS. parasitica 20∶5n−3 is synthesized from 18∶3n−6via 20∶4n−6 and is located predominantly at position 2. It is suggested that the asymmetrical distribution of PUFA between positions
1 and 2 of glycerol Points towards different sites of synthesis of the two classes of PUFA, and that cross-over between PUFA
of the different types is prevented by thesn-1 orsn-2 positional specificity of the desaturases. 相似文献
4.
The fatty chain compositions of 1-O-alk-1′-enyl-2-acyl, 1-0-alkyl-2-acyl, and 1,2-diacyl glycerophospholipids of the Japanese oysterCrassostrea gigas (Thunberg) were investigated. Major fatty chains in thesn-1 position of 1-alk-1′-enyl-2-acyl ethanolamine phospholipids (EPL) were 18∶0 (64.7%) and 20∶1 (11.1%). Majorsn-1 chains of alkenylacyl choline phospholipids (CPL) were 18∶0 (63.3%) and 16∶0 (22.2%). In the case of 1-alkyl-2-acyl EPL,
the predominant fatty chains in thesn-1 position were 18∶0 (51.5%), 16∶0 (16.0%) and 20∶1 (12.5%); in the case of 1-alkyl-2-acyl CPL, the majorsn-1 chains were 16∶0 (44.0%) and 14∶0 (23.4%). Saturated fatty chains were predominant in both EPL and CPL. Prominent fatty
acids in thesn-2 position of the alkenylacyl EPL were 22∶6n−3 (29.0%), 20∶5n−3 (19.0%) and 22∶2 NMID (non-methylene interrupted dienes,
16.6%) contributing to about 65% of the total fatty acids, while alkenylacyl CPL was rich in the saturated acids 16∶0 (32.0%)
and 18∶0 (9.2%). In the alkylacyl EPL, 16∶0, 18∶1n−9, 18∶0 and 16∶1n−7 were prominentsn-2 fatty acids and accounted for 30.6%, 10.0%, 9.8%, and 8.3%, respectively. Polyunsaturated fatty acids were detected, but
were present at extremely low percentages. Majorsn-2 fatty acids in alkylacyl CPL were 16∶0 (25.4%), 22∶6n−3 (16.0%) and 20∶5n−3 (8.4%). The major fatty acids of diacyl EPL
were 20∶5n−3 (22.3%), 16∶0 (17.9%), and 18∶0 (16.1%), and those of diacyl CPL were 16∶0 (30.4%), 20∶5n−3 (17.6%) and 18∶1n−7
(7.4%). 相似文献
5.
In this study, the 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine content of human platelets was determined. The distribution of arachidonate among the 1,2-diacyl,
1-O-alkyl-2-acyl, and 1-O-alk-l′-enyl-2-acyl classes of choline- and ethanolamine-containing phosphoglycerides was also assessed. The major platelet
phospholipids were choline-containing phosphoglycerides (38%), ethanolamine-containing phosphoglycerides (25%) and sphingomyelin
(18%), with smaller amounts of phosphatidylserine (11%) and phosphatidylinositol (4%). In addition to the diacyl class, the
choline-linked fraction was found to contain both 1-O-alkyl-2-acyl (10%) and 1-O-alk-l′-enyl-2-acyl (9%) species. The ethanolamine-linked fraction, on the other hand, had an elevated level of the 1-O-alk-l′-enyl-2-acyl (60%) species and a small amount of the 1-O-alkyl-2-acyl component (4%). The major fatty acyl residues found in all classes of the choline and ethanolamine phospholipids
were 16∶0, 18∶0, (Δ9), 18∶2(n−6) and 20∶4(n−6). The 1-O-alk-l and 1-O-alk-l′-enyl fraction of the ethanolamine-linked phospholipids also contained substantial amounts of 22∶4(n−6), 22∶5(n−3)
and 22∶6(n−3) acyl chains. Arachidonate comprised 44% of the acyl residues in thesn-2 position of 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine. Corresponding values for the diacyl and 1-O-alk-l′-enyl-2-acyl species were 23% and 25%, respectively, based on all 20∶4(n−6) being linked to thesn-2 position of all classes. In the ethanolamine-linked phosphoglycerides, arachidonate constituted 60%, 20% and 68% of the
acyl groups in thesn-2 position of the 1,2-diacyl, 1-O-alkyl-2-acyl and 1-O-alk-l′-enyl-2-acyl classes, respectively. The content of 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine appears sufficient to support the synthesis of platelet activating factor by a deacylation-reacylation
pathway in platelets. Our findings also demonstrate that human platelets contain a significant amount of 1-O-alkyl-2-arachidonyl-sn-glycero-3-phosphocholine that could possibly serve as a precursor of both platelet activating factor and bioactive arachidonate
metabolites. 相似文献
6.
Phospholipid molecular species from human placenta lipids 总被引:1,自引:0,他引:1
The phospholipid molecular species from a large-scale preparation of human placenta lipids were analyzed. The major placental
phospholipids were choline glycerophospholipids (CPL) (53.2 wt%), sphingomyelin (21.7 wt%) and ethanolamine glycerophospholipids
(EPL) (14.6 wt%). 1,2-Diacyl-glycerophosphocholine was the most abundant subclass of CPL (91.7 mol%), while EPL contained
1,2-diacyl (54.6 mol%) and 1-alk-1′-enyl-2-acyl (43.8 mol%) subclasses. The level of polyunsaturated fatty acids (PUFA) in
total phospholipids was remarkably constant (38.4–39.9 mol%) within all placental batches tested. The long-chain PUFA, mainly
20∶4n−6 and 22∶6n−3 of the n−6 and n−3 series, respectively, were found in high proportion in all phospholipid classes, especially
in EPL (46.7 mol%) and in inositol glycerophospholipids (IPL) (39.9 mol%). CPL and serine glycerophospholipids were much richer
in 18∶1n−9 and 18∶2n−6. High levels of molecular species with arachidonic acid in thesn-2 position were found particularly in 1-alk-1′-enyl-2-acyl-glycerophospho-ethanolamine (with 24.0 mol% 16∶0 and 22.0 mol%
18∶0 insn-1 position) and in 1,2-diacyl glycerophosphoinositol with 42.6 mol% 18∶0 insn-1 position. EPL subclasses were rich in 22∶6n−3, which occurs mainly as 16∶0/22∶6n−3 (11.7 mol%) in the polasmalogen form
and as 18∶0/22∶6n−3, 16∶0/22∶6n−3 and 18∶1/22∶6n−3 in the diacyl forms. Based on their availability and composition, placental
phospholipids could be of interest, for example, for supplementing artificial milk preparations with n−3 and n−6 long-chain
PUFA for newborn infants with insufficiently developed 18∶2n−6 and 18∶3n−3 desaturation/elongation. 相似文献
7.
The effect of dietary TAG structure and fatty acid acyl TAG position on palmitic and linoleic acid metabolism was investigated
in four middle-aged male subjects. The study design consisted of feeding diets containing 61 g/d of native lard (NL) or randomized
lard (RL) for 28 d. Subjects then received an oral dose of either 1,3-tetradeuteriopalmitoyl-2-dideuteriolinoleoyl-rac-glycerol or a mixture of 1,3-dideuteriolinoleoyl-2-tetradeuteriopalmitoyl-rac-glycerol and 1,3-hexadeuteriopalmitoyl-2-tetradeuteriolinoleoyl-rac-glycerol. Methyl esters of plasma lipids isolated from blood samples drawn over a 2-d period were analyzed by GC-MS. Results
showed that absorption of the 2H-fatty acids (2H-FA) was not influenced by TAG position. The 2H-FA at the 2-acyl TAG position were 85±4.6% retained after absorption. Substantial migration of 2H-16∶0 (31.2±8.6%) from the sn-2 TAG position to the sn-1,3 position and 2H-18∶2n−6 (52.8±6.4%) from the sn-1,3 position to the sn-2 position of chylomicron TAG occurred after initial absorption and indicates the presence of a previously unrecognized isomerization
mechanism. Incorporation and turnover of the 2H-FA in chylomicron TAG, plasma TAG, and plasma cholesterol esters were not influenced by TAG acyl position. Accretion of
2H-16∶0 from the sn-2 TAG position in 1-acylphosphatidylcholine was 1.7 times higher than 2H-16∶0 from the sn-1,3 TAG positions. Acyl TAG position did not influence 2H-18∶2n−6 incorporation in PC. The concentration of 2H-18∶2n−6-derived 2H-20∶4n−6 in plasma PC from subjects fed, the RL diet was 1.5 times higher than for subjects fed the NL diet, and this result
suggests that diets containing 16∶0 located at the sn-2 TAG position may inhibit 20∶4n−6 synthesis. The overall conclusion is that selective rearrangement of chylomicron TAG structures
diminishes but does not totally eliminate the metabolic and physiological effects of dietary TAG structure. 相似文献
8.
Toru Ota Yasunosuke Kawabata Yasuhiro Ando 《Journal of the American Oil Chemists' Society》1994,71(5):475-478
This paper presents the positional distribution of very long-chain fatty acids, 24∶6(n−3), in triacyl-sn-glycerols (TG) of flathead flounder (Hippoglossoides dubius). Each of the liver and flesh TGs was subjected to the stereospecific analysis. The liver TGs contained 24∶6(n−3) at concentrations
of 1.5, 1.2 and 1.7 mole % in thesn-1,sn-2 andsn-3 positions, respectively, and the flesh TGs had 9.0, 7.8 and 7.1 mole % in thesn-1,sn-2 andsn-3 positions, respectively. This fatty acid was distributed almost evenly among the three positions of the TGs. No preference
for thesn-2 position was observed in contrast to the general tendency for the distribution of longer-chain polyunsaturated fatty acids,
such as 22∶6(n−3), 22∶5(n−3) and 20∶5(n−3). There was essentially no difference in the positional distributions of the liver
and flesh TGs. The results obtained in this study give new fundamental information to the investigation of very long-chain
fatty acids. 相似文献
9.
Phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) were isolated from aVibrio species of bacterium, known to produce eicosapentaenoic acid (20∶5n−3) andtrans-hexadecenoic acid (16∶1n−7), and subjected to phospholipase A2 degradation to determine the positional distribution of component fatty acids. At the two growth temperatures studied (20
and 5°C), both 20∶5n−3 andtrans 16∶1 n−7 were located mainly at positionsn−2 in PE. Increases in the proportions of 20∶5n−3 andtrans 16∶1n−7 in positionsn−2 with decreasing growth temperature were balanced mainly by decreases in the level ofiso-15∶0. In PG,trans 16∶1n−7 was located predominantly in positionsn-1, although the difference between the two positions was not as great as in PE. Eicosapentaenoic acid was preferentially
located in positionsn-2 of PG, particularly at 5°C when it comprised 29.9% of the total fatty acids in this position. It is concluded thattrans 16∶1n−7/20∶5n−3 is not a major molecular species of phospholipid in this species ofVibrio and that changes in the levels of molecular species of PE containingiso-15∶0 may feature in thermal acclimation. 相似文献
10.
Jim-Wen Liu Stephen DeMichele Marti Bergana Emil Bobik Jr. Christine Hastilow Lu-Te Chuang Pradip Mukerji Yung-Sheng Huang 《Journal of the American Oil Chemists' Society》2001,78(5):489-493
The seed oil from a genetically transformed canola (Brassica napus) containing 43% (w/w) of γ-linolenic acid (G, 18∶3n−6), 22% linoleic acid (L, 18∶2n−6), and 16% oleic acid (O, 18∶1n−9) was
evaluated. In this high γ-linolenic acid canola oil (HGCO), the predominant 18∶3n−6-containing triacylglycerol (TG) molecular
species were GGL (23%), GLO (20%), and GGG (11%). In the total TG, approximately 75% of the 18∶3n−6 was located at the sn-1,3 positions, while only 34% of linoleic acid was at the sn-1,3 positions. The GGL molecular species of HGCO contained approximately equal amounts of GLG and GGL positional isomers,
while the GLO molecular species had 95% GOL and 5% GLO isomers. The general characteristics and the tocopherol and phytosterol
contents were mostly similar between HGCO and nontransformed canola oil. No detectable amounts of amino acids and nucleotides
were observed in the HGCO. 相似文献
11.
Effects of different medium-chain fatty acids on intestinal absorption of structured triacylglycerols 总被引:3,自引:0,他引:3
To study the effect of the chain length of medium-chain fatty acids on the intestinal absorption of long-chain fatty acids,
we examined the lymphatic transport of fat following administration of five purified structured triacylglycerols (STAG) containing
different medium-chain fatty acids in the sn-1, 3 positions and long-chain fatty acids in the sn-2 position in a rat model. Significant amounts of medium-chain fatty acids were found in lymph samples after intragastric
administration of 1,3-dioctanoyl-2-linoleyl-sn-glycerol (8∶0/18∶2/8∶0), 1,3-didecanoyl-2-linoleyl-sn-glycerol, and 1,3-didodecanoyl-2-linoleyl-sn-glycerol. The accumulated lymphatic transport of medium-chain fatty acids increased with increasing carbon chain length.
The recoveries of caprylic acid (8∶0), capric acid (10∶0), and lauric acid (12∶0) were 7.3±0.9, 26.3±2.4, and 81.7±6.9%, respectively.
No significant differences were observed for the maximal intestinal absorption of linoleic acid (18∶2n−6) when the chain length
of medium-chain fatty acids at the primary positions was varied, and the absorption of 18∶2 and oleic acid (18∶1) from 8∶0/18∶2/8∶0
and 1,3-dioctanoyl-2-oleyl-sn-glycerol was similar. We conclude that the chain length of the medium-chain fatty acids in the primary positions of STAG
does not affect the maximal intestinal absorption of long-chain fatty acids in the sn-2 position in the applied rat model, whereas the distribution of fatty acids between the lymphatics and the portal vein reflects
the chain length of the fatty acids.
Presented in part at the 3rd ISSFAL Conference, Lyon, France, June 1–5, 1998. 相似文献
12.
Robert L. Wolff 《Lipids》1995,30(10):893-898
When rats were fed elaidic (trans-9 18∶1) acid at a high load in diets that were otherwise marginally or almost completely deficient in linoleic (cis-9,cis-12 18∶2) acid, elaidic acid was desaturated tocis-5,trans-9 18∶2 acid. This polymethylene-interrupted acid was then incorporated into most phospholipids from rat mitochondria, cardiolipin
being an exception. Its level of esterification in phospholipids followed the increasing order: phosphatidylethanolamine <phosphatidylcholine
< phosphatidylinositol (PI). The content ofci-5,trans-9 18∶2 acid decreased in organs in the order liver > kidney > heart. The levels ofcis-5,trans-9 18∶2 acid increased in mitochondria phospholipids as the level of linoleic acid was lowered in the diet. In liver mitochondria
PI, it reached 16% of total fatty acids. After hydrolysis of liver mitochondria PI withNaja naja phospholipase A2, we observed that elaidic acid was essentially esterified to position 1 at the expense of saturated acids, whereascis-5,trans-9 18∶2 acid was exclusively esterified to position 2, along with 20∶3n−9 and 20∶4n−6 acids. As a consequence, the sums of
saturated andtrans-9 18∶1 acids on the one hand, and of 20∶3n−9, 20∶4n−6, andcis-5,trans-9 18⩺2 acids on the other hand, remained fairly constant in liver mitochondria PI (ca. 55 and 30%, respectively). Becausetrans-9 18∶1 andcis-5,trans-9 18∶2 acids differ only by thecis-5 ethylenic bond, which is also present in 20∶3n−9 and 20∶4n−6 acids, this distribution pattern indicates that thecis-5 double bond, rather than any other ethylenic bond, may be of major structural importance for channeling fatty acids to
position 2 of PI. 相似文献
13.
Human milk triacylgycerols (TAG) were analyzed by tandem mass spectrometry. The SIMPLEX method and a simple linear model were
used to interpret the distribution of fatty acids between thesn-2 andsn-1,3 positions in 24 major molecular weight groups of TAG. The number of regio-isomeric pairs of TAG varied between 3 and
18 in each of these groups. Hexadecanoic (16∶0), tetradecanoic (14∶0) and dodecanoic acids (12∶0) typically occupied thesn-2 position in TAG containing less than 54 acyl carbons, whereas long-chain C18 and C20 acids were predominantly located at
the primary positions. The positions of the three fatty acids within a TAG molecule were shown to depend on the fatty acid
combination. The maximum of 12∶0 in thesn-2 position appeared at acyl carbon number (ACN) 48, the maxima of 14∶0 were at ACN 44 and ACN 50, and for 16∶0 at ACN 46
and 52. 相似文献
14.
The present study was designed to investigate the metabolism of the n−3 olyunsaturated fatty acids (PUFA) in adipose tissue
and its dependence upon dietary factors. Changes in the positional distribution of the fatty acids in triacylglycerols from
retroperitoneal adipose tissue were studied as a function of time on rats fed for 4 wk a diet enriched with fish oil. The
stereospecific analysis of triacylglycerols was based on random formation ofrac-1,2-diacylglycerols by Grignard degradation. This was followed by synthesis ofrac-phosphatidic acids and treatment with phospholipase A2. In the triacylglycerols of the fish oil diet, 57% of the total n−3 fatty acids were in position 3,i.e., two-thirds of 22∶5n−3 and 22∶5n−3 were esterified insn-3 position, whereas 22∶6n−3 was equally distributed in positions 2 and 3. After 4 wk of feeding fish oil, the fatty acid
composition of adipose tissue triacylglycerols reached a steady state. Half of the n−3 fatty acids were found in position
3, namely 75% of 22∶5n−3, 50% of 20∶5n−3 and 18∶4n−3 and 45% of 22∶6n−3, the latter being equally distributed in positions
2 and 3. This pattern of distribution resembled that found in triacylglycerols of the fish oil diet, except for a higher proportion
of 20∶5n−3 in adipose tissue in position 1 at the expense of position 3. Throughout the 4-wk period of fish oil feeding, the
distribution pattern of minor n−3 fatty acids (18∶4n−3 and 22∶5n−3) in adipose tissue triacylglycerols remained unchanged.
On the other hand, at the onset of fish oil feeding, 20∶5n−3 and 22∶6n−3 became concentrated in position 3, but thereafter
20∶5n−3 was progressively incorporated into position 1 and 22∶6n−3 into position 2. We thus conclude that n−3 fatty acids
are differentially esterified in triacylglycerols of white adipose tissue. Despite the complex sequence of hydrolysis and
acylation steps involved, the positional distribution of n−3 fatty acids was found to be similar in both the fish oil diet
and the stored fat, in contrast to what was observed for nonessential fatty acids. 相似文献
15.
Fat absorption may be compromised by pancreatic or bile insufficiency, resulting in low uptake of essential fatty acid and
energy. Using a rat model of malabsorption, we examined the absorption of defined triglycerides with medium-chain fatty acids
(MCFA) in thesn-1,3 positions and essential fatty acids in thesn-2 position (MLM) compared to other fats. The thoracic duct was cannulated for collection of lymph, and the common bile and
pancreatic duct was cannulated to divert both the pancreatic juice and bile. The rats were given a single bolus of triglyceride
as a taurocholate emulsion. Fat absorption was measured from collected lymph samples. The triglycerides administered were
a defined triglyceride, MLM [mainly (8∶0/10∶0)-(18∶2n−6)-(8∶0/10∶0)], a similar triglyceride subjected to chemical randomization,
a mixture of medium-chain triglycerides and soybean oil, and soybean oil, respectively. The first three triglycerides had
approximately 36 wt% linoleic acid (18∶2n−6) content. Administration of defined triglyceride was followed by significantly
higher lymphatic level (wt%) of 18∶2n−6 (P<0.01) as well as a relative enhancement in mol% of 18∶2n−6 (P<0.05) compared to the other triglycerides. Lymphatic absorption of MCFA was similar in the three first groups but not as
efficient as for long-chain fatty acids. Our results indicate that defined triglycerides thus may provide a means to increase
absorption of essential fatty acids in fat malabsorption, such as that seen in cystic fibrosis, or for pre-term infants.
Honored Student presentation, 84th AOCS Annual Meeting & Expo, Anaheim, California. 相似文献
16.
Adequate accumulation of polyunsaturated essential fatty acids, in particular docosahexaenoic acid (22∶6n−3), into membrane
phospholipids is critical for optimal fetal brain development. This process is maximal during the period of rapid neurite
outgrowth, neuritogenesis, which precedes the major growth phase, myelination. There is no information about differential
changes during gestation to individual brain phospholipid molecular species which contain 22∶6n−3. Such details of brain development
would be concealed by total fatty acid analysis of isolated phospholipid classes. We have detailed phosphatidylcholine (PC)
and phosphatidylethanolamine (PE) molecular species compositions in developing fetal guinea pig brain. Total brain PC concentration
increased substantially between 40 and 68 (term) d of gestation, corresponding to myelination, while PE increased in a biphasic
manner between 25–35 d, which was coincident with onset of neuritogenesis, and 40–68 d. Fetal brain development was accompanied
by complex changes in the concentration of individual phospholipid molecular species. During early gestation (25–40 d) 22∶6n−3
was enriched in both PC and PEsn−1 16∶0 molecular species. However, between 40 d and term there was no further increase in brain PC 22∶6n−3 content, while
brain PE was significantly enriched in both PE 18∶1/22∶6 and PE18∶0/22∶6. We hypothesize that accumulation of 22∶6n−3 intosn−1 18∶1 and 18∶0 species represents establishment of a 22∶6n−3-containing membrane PE pool which may be turned over more slowly
thansn−1 16∶0 species. Identification of specific changes in membrane phospholipids which are associated with defined events in
brain development may provide a basis for assigning functional roles to individual molecular species. 相似文献
17.
The positional distribution of fatty acids has been determined for the milk triacylglycerols of the Antarctic fur seal,Arctocephalus gazella. Of particular interest was the positional distribution of the polyunsaturated n−3 fatty acids in milk triacylglycerols (TG).
In adipocytes of pinnipeds, TG are synthesized with the n−3 fatty acids primarily in thesn-1,3 positions. To determine the positional distribution, extracts of enzymatically digested lipids were separated by thin-layer
chromatography, and the constituent fatty acids were separated and quantified by gas-liquid chromatography. Monoenoic and
saturated fatty acids comprised over 75% of the total, the ratio of monoenoic to saturated fatty acids being 2∶1. The percent
content of the long-chain n−3 fatty acids, 20∶5, 22∶5 and 22∶6, ranged between 15–20%. The positional analyses revealed that
at thesn-2 position of milk TG, saturated fatty acids were in excess (57%), and the content of n−3 fatty acids was less than 5%. More
than 80% of the n−3 fatty acids in milk were located in thesn-1,3 positions. The data indicate that in pinnipeds TG are synthesized in the mammary gland and adipose tissue with fatty
acids having similar positional distributions. 相似文献
18.
Acyl-CoA:lysophosphatidylcholine acyltransferase (LPCAT; EC 2.3.1.23) catalyzes the acyl-CoA-dependent acylation of lysophosphatidylcholine
(LPC) to produce PC and CoA. LPCAT activity may affect the incorporation of fatty acyl moieties at the sn-2 position of PC where PUFA are formed and may indirectly influence seed TAG composition. LPCAT activity in microsomes prepared
from microspore-derived cell suspension cultures of oilseed rape (Brassica napus L. cv Jet Neuf) was assayed using [1-14C]acyl-CoA as the fatty acyl donor. LPCAT activity was optimal at neutral pH and 35°C, and was inhibited by 50% at a BSA concentration
of 3 mg mL−1. At acyl-CoA concentrations above 20 μM, LPCAT activity was more specific for oleoyl (18∶1)-CoA than stearoyl (18∶0)- and
palmitoyl (16∶0)-CoA. Lauroyl (12∶0)-CoA, however, was not an effective acyl donor. LPC species containing 12∶0, 16∶0, 18∶0,
or 18∶1 as the fatty acyl moiety all served as effective acyl acceptors for LPCAT, although 12∶0-LPC was somewhat less effective
as a substrate at lower concentrations. The failure of LPCAT to catalyze the incorporation of a 12∶0 moiety from acyl-CoA
into PC is consistent with the tendency of acyltransferases to discriminate against incorporation of this fatty acyl moiety
at the sn-2 position of TAG from the seed oil of transgenic B. napus expressing a medium-chain thioesterase. 相似文献
19.
The molecular species composition of the major glycerophospholipids from white matter of human brain were determined by high-performance
liquid chromatography of the 3,5-dinitrobenzoyl derivatives of the corresponding diradylglycerols. In phosphatidylcholine
(PC) and phosphatidylserine (PS), molecular species containing only saturated fatty acids (SFA) and monounsaturated fatty
acids (MUFA) comprised 85.7 and 82.4% of the respective totals, with 18∶0/18∶1 predominant in PS and 16∶0/18∶1 in PC. These
molecular species were also abundant in phosphatidylethanolamine (PE), but in this phospholipid species containing polyunsaturated
fatty acids (PUFA), largely 18∶0/22∶6n−3 and 18∶0/20∶4n−6, accounted for over half the total; 18∶1/18∶1 was also abundant
in PE. In contrast, 1-O-alk-1′-enyl-2-acylsn-glycero-3-phosphoethanolamine (GPE) had much more SFA- and MUFA-containing species, predominantly 16∶0a/18∶1, 18∶0a/18∶1
and 18∶1a/18∶1, with low amounts of species containing 20∶4n−6 and 22∶6n−3. In alkenylacyl GPE, 22∶4n−6 was the major PUFA
and 16∶0a/22∶4n−6 and 18∶1a/22∶4n−6 the main PUFA-containing species. There was six times more 22∶6n−3, twice as much 20∶4n−6
and half the amount of 22∶4n−6 in PE as compared to alkenylacyl GPE.
Molecular species are abbreviated as follows:e.g., 16∶0/18∶1 PE is 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine; the corresponding alkenylacyl species, 1-O-hexadec-1′-enyl-2-oleoyl-sn-glycero-3-phosphoethanolamine is 16∶0a/18∶1. 相似文献
20.
Liver nuclear incorporation of stearic (18∶0), linoleic (18∶2n−6), and arachidonic (20∶4n−6) acids was studied by incubation
in vitro of the [1-14C] fatty acids with nuclei, with or without the cytosol fraction at different times. The [1-14C] fatty acids were incorporated into the nuclei as free fatty acids in the following order: 18∶0>20∶4n−6≫18∶2n−6, and esterified
into nuclear lipids by an acyl-CoA pathway. All [1-14C] fatty acids were esterified mainly to phospholipids and triacylglycerols and in a minor proportion to diacylglycerols.
Only [1-14C] 18∶2n−6-CoA was incorporated into cholesterol esters. The incorporation was not modified by cytosol addition. The incorporation
of 20∶4n−6 into nuclear phosphatidylcholine (PC) pools was also studied by incubation of liver nuclei in vitro with [1-14C]20∶4n−6-CoA, and nuclear labeled PC molecular species were determined. From the 15 PC nuclear molecular species determined,
five were labeled with [1-14C]20∶4n−6-CoA: 18∶0–20∶4, 16∶0–20∶4, 18∶1–20∶4, 18∶2–20∶4, and 20∶4–20∶4. The highest specific radioactivity was found in
20∶4–20∶4 PC, which is a minor species. In conclusion, liver cell nuclei possess the necessary enzymes to incorporate exogenous
saturated and unsaturated fatty acids into lipids by an acyl-CoA pathway, showing specificity for each fatty acid. Liver cell
nuclei also utilize exogenous 20∶4n−6-CoA to synthesize the major molecular species of PC with 20∶4n−6 at the sn-2 position. However, the most actively synthesized is 20∶4–20∶4 PC, which is a quantitatively minor component. The labeling
pattern of 20∶4–20∶4 PC would indicate that this molecular species is synthesized mainly by the de novo pathway. 相似文献