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PubMed2001

Fatty acids and epithelial permeability: effect of conjugated linoleic acid in Caco-2 cells.

Conjugated linoleic acid (CLA) is a collective term referring to the positional and geometric isomers of linoleic acid. This novel fatty acid has been shown to have a number of beneficial actions, including immunomodulatory, anticarcinogenic, and antiatherogenic effects. Tight junctions of epithelial cells determine epithelial membrane integrity and selective paracellular permeability to ions and macromolecules. Occludin and ZO-1 are integral structural components of the tight junction, which are involved in the biogenesis and functional integrity of the epithelial monolayer. This study investigated the effects of two isomers of CLA (cis-9 and trans-10 isomers) on Caco-2 cell transepithelial resistance (TER) development, paracellular epithelial permeability, and occludin and ZO-1 expression. Caco-2 cells were grown in media supplemented with 0.05 mM linoleic acid, cis-9 CLA, or trans-10 CLA for 21 days. The trans-10 CLA isomer delayed Caco-2 cell TER development, which is an in vitro measure of epithelial cell integrity, and increased paracellular epithelial permeability. Immunofluorescent staining of Caco-2 cell epithelial monolayers grown in media supplemented trans-10 CLA showed that the trans-10 CLA isomer altered distribution of occludin and ZO-1. The trans-10 CLA isomer delayed the acquisition of transepithelial resistance and altered the cellular distribution of occludin, which have important implications in relation to epithelial permeability.

Analysis of Variance↗
PubMed1977

Biohydrogenation and availability of linoleic acid in lactating cows.

Linoleic acid biohydrogenation, absorption and availability for maintenance and milk production in dairy cows fed high grain (60--85% of dry matter) diets were quantitatively estimated by isotope dilution, using two methods of dosing. [1-14C]Linoleic acid-labeled chylomicra and very low density lipoproteins (VLDL) were obtained from lymph of a calf fed [1-14C]linoleic acid and fitted with a thoracic duct-venous shunt. Labeled chylomicra were injected intravenously into two cows: a Jersey (trial 1), and a Holstein (trial 2). Labeled VLDL was injected intravenously into a Holstein cow (trial 3). In trials 4 and 5 the [1-14C]linoleic acid was placed into the omasal canal of two rumen-fistulated Holstein cows. Linoleic acid biohydrogenation (%), absorption (g/day), and availability above requirements for milk production (mg/kg body wt 3/4) were: 68.1 +/- 2.28, 52.1 +/- 2.92, and 244 +/- 19.4 (mean +/- SE), respectively. The biohydrogenation data indicate that both methods of dosing the cows were equally dependable. The estimates of linoleic acid biohydrogenation are consistent with limited data previously reported, indicating that the isotope dilution technique used is a reliable method to estimate linoleic acid absorption in lactating cows. Linoleic acid available to the lactating cow above milk production requirements was more than double the requirement of weanling female rats, when compared on the basis of metabolis body size.

Animal Feed↗
PubMedDate not supplied

Incorporation of linoleic acid by cultured human keratinocytes.

Linoleic acid is required for the formation and maintenance of the epidermal barrier, but most of the current in vitro keratinocyte culture systems are linoleic acid-deficient. The aim of the present study was to examine the efficiency of linoleic acid uptake in human keratinocyte cultures grown under submerged and air-exposed conditions in serum-free medium. The water-insoluble linoleic acid was bound to carrier molecules (cyclodextrin or bovine serum albumin). Comparable results were obtained with home-made and commercially available linoleic acid complexes. In the submerged cultures, the increase of the linoleic acid medium concentration (ranging from 0 to 20 microg/ml) resulted in a gradual increase in the linoleic acid cellular content, which exceeded 1.4 times the value found in native epidermis when the highest concentration of linoleic acid was used. The addition of linoleic acid did not alter the profile of the other epidermal fatty acids, with the exception of oleic acid, which decreased in parallel with the increasing linoleic acid content. While the content of linoleic acid found in phospholipids was similar to that in native epidermis, a large excess of linoleic acid was detected in triglycerides, the synthesis of which was markedly increased in cultures grown submerged in medium containing higher concentrations of linoleic acid. Under air-exposed conditions, the dermal substrate used seemed to be the most limiting factor for efficient linoleic acid supplementation. A low linoleic acid cellular content was detected when an inert filter was used. De-epidermized dermis was found to be the most permeable substrate for linoleic acid complexes. The cellular linoleic acid content increased in a parallel with the increasing linoleic acid concentration (ranging from 4 to 30 microg/ml), but the overall amount incorporated was lower than that in submerged cultures. The content of linoleic acid in the phospholipid and ceramide fractions isolated from reconstructed epidermis grown under air-exposed conditions was close to that of native epidermis, but the triglycerides remained abnormally enriched in linoleic acid, indicating persistence of some anomalies in epidermal lipogenesis in vitro.

Air↗
PubMed2006

Suppressive effect of alkyl ferulate on the oxidation of linoleic acid.

The oxidation processes of linoleic acid in the presence of ferulic acid, and 1-pentyl, 1-hexyl and 1-heptyl ferulates were observed at various temperatures and different molar ratios of each additive to linoleic acid. The processes were analyzed based on a kinetic equation of the autocatalytic type to evaluate the oxidative rate constant, k, and the kinetic parameter, Y(0), by which the initiation period for the oxidation of linoleic acid was mainly governed. The k values for linoleic acid mixed with each of the alkyl ferulates were smaller than that for linoleic acid mixed with ferulic acid. The greater suppressive effect of the alkyl ferulates would be ascribable to their higher solubility in linoleic acid. Both the activation energy, E, and the frequency factor, k(0), for the oxidation of linoleic acid mixed with ferulic acid or pentyl ferulate decreased with increasing molar ratio of the additive to linoleic acid.

Alkylation↗
PubMed1995

Preferential formation of the hydroperoxide of linoleic acid in choline glycerophospholipids in human erythrocytes membrane during peroxidation with an azo initiator.

The formation of phospholipid hydroperoxides was monitored in human red blood cell (RBC) membranes that had been peroxidized with an azo initiator. Peroxidation of RBC membranes caused a profound decrease in the amount of polyunsaturated fatty acids and concomitantly hydroperoxides, as primary products of peroxidation, appeared in the phospholipids. Hydroperoxides were predominantly generated in choline glycerophospholipid (CGP), while the extent of formation of ethanolamine glycerophospholipid (EGP) hydroperoxides was low and their presence was transient. Hydroxy and hydroperoxy moieties in CGP were identified as 9-hydroxy and 13-hydroxy octadecanoic acid, derived from linoleic acid, by gas chromatography-mass spectrometric analysis. No consistent generation of hydroperoxide from arachidonic acid was evident in CGP. The CGP-hydroperoxide accounted for approximately 76% of linoleic acid consumed during peroxidation of RBC membranes. The prominent generation of phospholipid hydroperoxides was observed in the linoleic acid-rich membranes from rabbit RBC, indicating that the level of linoleic acid in phospholipids determines, in part, the extent of formation of phospholipid hydroperoxides. Aldehydic phospholipids, as secondary products of peroxidation, were detected in oxidized membranes. EGP was the most prominent aldehydic phospholipid, while negligible amounts of aldehydic CGP were formed. This study indicates that the process of oxidation of individual phospholipids clearly differs among phospholipids and depends on the structure of each.

Adult↗
PubMed2003

Two distinct pathways for the formation of hydroxy FA from linoleic acid by lactic acid bacteria.

Twenty-three of 86 strains of lactic acid bacteria transformed linoleic acid into hydroxy FA. Two distinct conversion pathways were in operation. Two strains of Lactobacillus acidophilus and a strain of Pediococcus pentosaceus produced 13(S)-hydroxy-9-octadecenoic acid 113(S)-OH 18:11 and 10,13dihydroxyoctadecanoic acid (10,13-OH 18:0) as main and minor products, respectively, whereas 13 strains, including L. casei subsp. casei, L. paracasei subsp. paracasei, L. rhamnosus, L. lactis subsp. cremoris, and Streptococcus salivarius subsp. thermophilus produced 10-hydroxy-12-octadecenoic acid (10-OH 18:1). Seven strains of L. plantarum converted linoleic acid to 10-hydroxyoctadecanoic acid (10-OH 18:0) through 10-OH 18:1. Linoleic acid at 2 g/L was converted by L. acidophilus IFO13951T to 1.3 g of 13(S)-OH 18:1 and 0.09 g of 10,13-OH 18:0 in 7 d. Lactobacillus paracasei subsp. paracasei JCM 1111 produced 10-OH 18:1 in 91% yield, and L. plantarum JCM 8341, 10-OH 18:0 in 59% yield from linoleic acid (2 g/L) under optimal conditions. To our knowledge, this is the first report on the production of 13(S)-OH 18:1 by lactic acid bacteria other than ruminal bacteria, and of 10,13-OH 18:0 by any bacteria.

Fatty Acids↗
PubMed2006

Effect of fatty acids on growth of conjugated-linoleic-acids-producing bacteria in rumen.

Microorganisms with high activity of linoleic acid delta12-cis,delta11-trans-isomerase were isolated from the digestive tract of ruminants and characterized. The isolate with the highest isomerase activity was identified as Pseudobutyrivibrio ruminis. The susceptibility of this strain to 3 fatty acids added to the grow medium was determined. A significant inhibition of bacterial growth (during a 3-d period) by linoleic acid (0.1 %) and oleic acid (5 ppm) was observed; no inhibition was found in the presence of stearic acid.

Animals↗
PubMed1994

BW A4C and other hydroxamic acids are potent inhibitors of linoleic acid 8R-dioxygenase of the fungus Gaeumannomyces graminis.

Linoleic acid is converted to 8R-hydroperoxylinoleic acid by the soluble 8R-dioxygenase of the fungus Gaeumannomyces graminis. Effects of different lipoxygenase inhibitors on the 8R-dioxygenase were evaluated. Three hydroxamic acid derivatives were investigated. BW A4C (N-(3-phenoxycinnamyl)acetohydroxamic acid) was the most potent with an IC50 of 0.2 microM, followed by zileuton (3-10 microM) and linoleate-hydroxamic acid (0.02 mM). Two other lipoxygenase inhibitors, nordihydroguaiaretic acid and eicosatetraynoic acid, were less potent (IC50 0.09 and 0.15 mM, respectively). The 8R-dioxygenase was also strongly inhibited by commonly used buffer additives, dithiothreitol, beta-mercaptoethanol and phenylmethanesulfonyl fluoride. G. graminis also contains a hydroperoxide isomerase, which converts 8R-hydroperoxylinoleic acid to 7S,8S-dihydroxylinoleic acid. Ammonium sulphate precipitation and gel filtration indicated that the dioxygenase and the hydroperoxide isomerase activities could be separated.

Benzeneacetamides↗
PubMed2003

Fresh forage and solin supplementation on conjugated linoleic acid levels in plasma and milk.

Two experiments were run concurrently to determine the effect of fresh forage consumption on the production and proportions of plasma and milk fat vaccenic acid (VA), conjugated linoleic acid (CLA), and linolenic acid in diary cattle. In experiment 1, the cows consumed 50, 65, and 80% of their feed intake as pasture with the remainder of intake as a barley-based concentrate. The proportion of VA in milk fatty acids increased 12% when pasture intake increased from 50 to 65% of total dry matter intake and VA, CLA, and linolenic acid proportions increased 26, 18, and 27%, respectively, as pasture increased from 65 to 80% of dietary intake. In experiment 2, fresh forage was compared to conserved hay (cut from the same pasture the previous summer) to determine the effect on plasma and milk fat VA, CLA, and linolenic acid. Also, the effect of crushed solin seed (a flax cultivar that is high in linoleic acid) supplementation to the fresh forage diet was determined. Fresh forage compared to conserved hay in the diet, increased the proportion of CLA in the plasma very low density lipoproteins (VLDL) fraction by 71% but had no effect on linolenic acid. Supplementation of the fresh forage diet with a linoleic acid source increased VA and CLA in the plasma VLDL fraction 25 and 58% and slightly decreased the proportion of linolenic acid. Fresh forage, compared to conserved hay, increased milk fat VA and CLA proportions by 22 and 15%. Supplementing the fresh forage diet with linoleic acid from crushed solin seed further increased milk fat VA and CLA proportions 41 and 25%. Solin supplementation in a lactation diet is a superior method to increase CLA levels in milk fat than feeding fresh forage alone.

Animals↗
PubMedDate not supplied

Modulation of lipid metabolism and vitamin A by conjugated linoleic acid.

The term conjugated linoleic acid (CLA) refers to a collection of positional and geometrical isomers of octadeca- dienoic acid with conjugated double bonds. CLA has been shown to possess several beneficial activities in different experimental models, however, out of 28 isomers only two, c9, t11 and t10, c12 have been thus far demonstrated to be biologically active. The discovery that it can be elongated and desaturated as a regular fatty acid in human and animal tissues brought a new possibility that its activity may be related to its properties as a peculiar unsaturated fatty acid. In fact, CLA is able to be incorporated in lipid classes as oleic acid, accumulating in those tissues rich in neutral lipids; to be metabolized as linoleic acid and so influencing linoleic acid desaturation and elongation; and to be beta oxidized in peroxisomes which may account for, through activation of PPARs, its ability to increase free retinol levels and influence gene expression. These activities are amplified where CLA accumulates more such as mammary and adipose tissues and may explain its peculiar beneficial properties, at relative low dietary concentrations, in these tissues. Furthermore, it has been demonstrated that CLA can be endogenously formed by delta 9 desaturation of vaccenic acid (t11 18:1) thus forming the isomer c9, t11. Either endogenously formed or through dietary intake, CLA showed to be metabolized in the same way and to exert the same biological properties. We may conclude that a regular intake of CLA, or/and vaccenic acid as its precursor, should work as an excellent preventive agent by modulating lipid metabolism in target tissues thus conferring protection against the attack of insults of different type.

Adipose Tissue↗
PubMed1988

Changes in human plasma essential fatty acid levels as a result of administration of linoleic acid and gamma-linolenic acid.

Administration of doses of linoleic acid (LA) up to 36 g/d in humans raised blood levels of linoleic acid but not of its metabolites. This is probably because the conversion of LA to gamma-linolenic acid (GLA) is slow and rate-limiting. We have found that administration of relatively small amounts of GLA, up to 360 mg/d, raises human blood levels of dihomogammalinolenic acid (DGLA) and arachidonic acid (AA).

Adult↗
PubMed2004

Optimization of production of conjugated linoleic acid from soybean oil.

Linoleic acid from soybean oil was used to synthesize conjugated linoleic acid (CLA), and the response surface methodology (RSM) was applied to optimize the process. A temperature of -35 degrees C and a solvent to oil sample ratio of 8 were suggested for removal of saturated fatty acids by low-temperature crystallization. The ratio of oil sample/urea/methanol suggested was 1:2:5.5 (w/w/v) for removal of oleic acid by urea crystallization. A temperature of 150 degrees C and a time of 140 min were found to be the optimal conditions in the isomerization for the production of c-9,t-11 and t-10,c-12 CLA isomers.

Cold Temperature↗
PubMed2000

Analysis of the cytotoxic properties of linoleic acid metabolites produced by renal and hepatic P450s.

Cytochrome P450 epoxidation of linoleic acid produces biologically active metabolites which have been associated with many pathological conditions that often lead to acute renal failure. In the present study, we evaluated the ability of specific cytochrome P450s to produce linoleic acid monoepoxides. We then tested the cytotoxic properties of linoleic acid, linoleic acid monoepoxides, and corresponding diols in a rabbit renal proximal tubule model. CYP1A2, CYP2E1, CYP2J2, CYP2J3, CYP2J5, and CYP2J9 metabolized linoleic acid at rates comparable to arachidonic acid and produced linoleic acid monoepoxides as major products. Cytotoxicity studies showed that linoleic acid, linoleic acid monoepoxides, and corresponding diols are toxic at pathologically relevant concentrations (100-500 microM). Concentration-dependent studies showed that linoleic acid and linoleic acid monoepoxides are the most toxic and induce mitochondrial dysfunction prior to cell death. Cytoprotectants known to block cell death associated with mitochondrial dysfunction and oxidative stress did not prevent cell death induced by linoleic acid and linoleic acid monoepoxides. This study shows that P450s in the CYP1 and CYP2 gene families metabolize linoleic acid to linoleic acid monoepoxides and that the monoepoxides, as well as linoleic acid, disrupt mitochondrial function without causing oxidative stress.

Animals↗
PubMed1998

Effect of dietary arachidonic acid on metabolism of deuterated linoleic acid by adult male subjects.

The influence of dietary supplementation with 20:4n-6 on uptake and turnover of deuterium-labeled linoleic acid (18:2n-6[d2]) in human plasma lipids and the synthesis of desaturated and elongated n-6 fatty acids from 18:2n-6[d21 were investigated in six adult male subjects. The subjects were fed either a high-arachidonic acid (HIAA) diet containing 1.7 g/d or a low-AA (LOAA) diet containing 0.21 g/d of AA for 50 d. Each subject was then dosed with about 3.5 g of 18:2n-6[d2] as the triglyceride (TG) at 8:00 A.M., 12:00, and 5:00 P.M. The total 18:2n-6[d21] fed to each subject was about 10.4 g and is approximately equal to one-half of the daily intake of 18:2n-6 in a typical U.S. male diet. Nine blood samples were drawn over a 96-h period. Methyl esters of plasma total lipid (TL), TG, phospholipid, and cholesterol ester were analyzed by gas chromatography-mass spectroscopy. Dietary 20:4n-6 supplementation did not affect uptake of 18:2n-6[d2] in plasma lipid classes over the 4-d study period nor the estimated half-life of 24-36 h for 18:2n-6[d2]. The percentages of major deuterium-labeled desaturation and elongation products in plasma TL, as a percentage of total deuterated fatty acids, were 1.35 and 1.34% 18:3n-6[d2]; 0.53 and 0.50% 20:2n-6[d2]; 1.80 and 0.92% 20:3n-6[d2] and 3.13 and 1.51% 20:4n-6[d2] for the LOAA and HIAA diet groups, respectively. Trace amounts (<0.1%) of the 22:4n-6[d2] and 22:5n-6[d2] metabolites were present. Plasma TL concentration data for both 20:3n-6[d2] and 20:4n-6[d2] were 48% lower (P < 0.05) in samples from the HIAA diet group than in samples from the LOAA diet group. For a normal adult male consuming a typical U.S. diet, the estimated accumulation in plasma TL of 20:4n-6 synthesized from 20 g/d (68 mmole) of 18:2n-6 is 677 mg/d (2.13 mmole). Dietary supplementation with 1.5 g/d of 20:4n-6 reduced accumulation of 20:4n-6 synthesized from 20 g/d of 18:2n-6 to about 326 mg/d (1.03 mmole).

Administration, Oral↗