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PubMed1995

Linoleic acid and its metabolites, hydroperoxyoctadecadienoic acids, stimulate c-Fos, c-Jun, and c-Myc mRNA expression, mitogen-activated protein kinase activation, and growth in rat aortic smooth muscle cells.

Previous studies from other laboratories suggest that linoleic acid and its metabolites, hydroperoxyoctadecadienoic acids, play an important role in modulating the growth of some cells. A correlation has been demonstrated between hydroperoxyoctadecadienoic acids and conditions characterized by abnormal cell growth such as atherosclerosis and psoriasis. To determine if linoleic acid and its metabolites modulate cell growth in atherosclerosis, we measured DNA synthesis, protooncogene mRNA expression, and mitogen-activated protein kinase (MAPK) activation in vascular smooth muscle cells (VSMC). Linoleic acid induces DNA synthesis, c-fos, c-jun, and c-myc mRNA expression and MAPK activation in VSMC. Furthermore, nordihydroguaiaretic acid, a potent inhibitor of the lipoxygenase system, significantly reduced the growth-response effects of linoleic acid in VSMC, suggesting that conversion of linoleic acid to hydroperoxyoctadecadienoic acids (HPODEs) is required for these effects. HPODEs also caused significant induction of DNA synthesis, protooncogene mRNA expression, and MAPK activation in growth-arrested VSMC, suggesting that linoleic acid and its metabolic products, HPODEs, are potential mitogens in VSMC, and that conditions such as oxidative stress and lipid peroxidation which provoke the production of these substances may alter VSMC growth.

Animals↗
PubMed1983

Dietary linoleic acid deprivation: effects on blood pressure and PGI2 synthesis.

The possible role of arachidonic acid metabolites in the regulation of arterial blood pressure was investigated in rats receiving 0, 5, or 9 energy (en) % linoleic acid in their diet (groups 1-3) over 6 wk. In group 1 animals, systolic arterial blood pressure significantly increased from 100.5 +/- 2.0 to 110.6 +/- 3.1 mmHg (P less than 0.01) after 6 wk of dietary linoleic acid deprivation, whereas no effect on blood pressure was observed in group 2 and 3 animals receiving dietary linoleic acid supplements. Generation of prostacyclin (PGI2)-like activity by isolated aorta from rats fed the different diets was determined using a platelet-aggregation bioassay following incubation of aortic tissue for 12, 15, and 30 min, respectively. In isolated aorta from rats fed the 5 en% linoleic acid, production of PGI2 was 55.9 +/- 1.2, 70.5 +/- 2.6, and 90.9 +/- 3.6 pmol/mg over the three incubation periods. In group 1 animals, a significant suppression of PGI2 generation to 35.4 +/- 1.5, 41.1 +/- 1.7, and 55.0 +/- 1.2 pmol/mg (P less than 0.005) was observed, whereas PGI2 production was unaltered in aortic tissue from group 3 animals. In contrast, plasma concentrations of circulating thromboxane B2 were highest in group 1 animals (2.15 +/- 0.38 pmol/ml) and measured 1.28 +/- 0.17 and 0.83 +/- 0.10 pmol/ml in group 2 and 3 animals, respectively. Our results demonstrate that dietary deprivation of the arachidonic acid precursor linoleic acid increases arterial blood pressure that is associated with a suppression of vascular PGI2 synthesis and, most likely, a secondary rise in circulating thromboxane concentrations.

Animals↗
PubMed2006

Linoleic acid, vitamin D and other nutrient intakes in the risk of non-Hodgkin lymphoma: an Italian case-control study.

BACKGROUND: Dietary habits have been suggested as a factor related to the increase of non-Hodgkin lymphoma (NHL) incidence in western populations, but the role of individual nutrients is still unclear. PATIENTS AND METHODS: A hospital-based case-control study was conducted in Italy, 1999-2002. CASES: 190 incident, histologically-confirmed NHL cases aged 18-84 years. CONTROLS: 484 subjects admitted to hospital for acute, non-neoplastic diseases unrelated to diet. Dietary habits were assessed by a validated food-frequency questionnaire; nutrient intakes were computed using the Italian food composition database. Odds ratios (ORs) and corresponding 95% confidence intervals (CI) for tertiles of intake of nutrient were computed using the energy-adjusted residual models. RESULTS: Inverse association emerged for polyunsaturated fatty acids (OR=0.6; 95% CI: 0.4-0.9), linoleic acid (OR=0.6; 95% CI: 0.4-0.9), and vitamin D (OR=0.6; 95% CI: 0.4-0.9). The protective effect for linoleic acid (OR=0.3; 95% CI: 0.2-0.7) and vitamin D (OR=0.4; 95% CI: 0.2-0.9) was stronger in women; no differences emerged according to age. Linoleic acid was inversely related to follicular and diffuse large B-cell lymphoma; the protective effect of vitamin D emerged most clearly for follicular subtypes. CONCLUSIONS: Our study suggests that a diet rich in polyunsaturated fatty acids and vitamin D is associated with a reduced risk of NHL.

Aged↗
PubMed1975

[About the formation of volatile products during lipoxigenase-linoleic-acid reaction (author's transl)].

Soya-lipoxigenase (E.C. 1.13.1.13) is incubated by linoleic acid at room temperature; the arising volatile products are isolated by different methods, concentrated, and investigated by means of gas chromatography. If the non-volatile hydroperoxides, formed during the incubation are also injected, 15-20% are decomposed to volatile products superposing the primarily enzymatically formed volatile components as artefacts and consequently falsifying the result. Without separating the linoleic acid hydroperoxides (LHPO) the quantitative proportion Hexanal/Decadienal is approximately in accordance with the proportion 13-linoleic acid hydroperoxide/9-linoleic acid hydroperoxide (this means for soya-lipoxigenase and pH 7 about 1:1). After separating the linoleic acid hydroperoxides only these volatile products are found which are arising during the lipoxigenase reaction. These are 1-2% in relation to the LHPO. In this case, the quantitative ratio Hexanal/Decadienal is not corresponding to the 13-/9-linoleic acid hydroperoxide proportion. Nearly the only product formed by this process is Hexanal.

Chromatography, Gas↗
PubMed1990

Changes in uptake of linoleic acid and cholesterol by jejunal sacs of rats in vitro, after distal small-bowel resection.

Both linoleic acid and cholesterol uptake were studied in small-intestinal sacs of rats in vitro after distal small-bowel resection (DSBR). The relationship between linoleic acid concentration and its absorption was non-linear at low concentrations and became linear at high concentrations in the three groups of animals. These observations indicate that a concentration-dependent dual mechanism of transport is operative in linoleic acid intestinal uptake. Experiments with rotenone and ouabain suggest that a facilitated diffusion is the predominant mechanism of absorption at low concentrations, whereas at high concentrations simple diffusion is predominant. The apparent kinetic constants of linoleic acid uptake (Kd, Kt, and Vmax) increased after DSBR. The uptake of linoleic acid is, however, influenced by the simultaneous presence of linolenic acid, the inhibition constant being decreased after the surgical operation. After the surgical operation an increase of cholesterol uptake was observed, with a parallel enhancement in the apparent mass-transfer coefficient (Kd). Taken together, these results suggest that both organ growth and changes in transport function of the enterocytes appear to be involved in the adaptive response of the bowel to intestinal resection.

Animals↗
PubMed1992

Changes in linoleic acid during follicular development and inhibition of spontaneous breakdown of germinal vesicles in cumulus-free bovine oocytes.

The fatty-acid composition of follicular fluid from small and large developing follicles was analysed and the effects of saturated and unsaturated fatty acids on spontaneous breakdown of germinal vesicles were investigated. Fatty acids were bound to bovine serum albumin and cultured with oocytes at 100 mumol/l. Linoleic acid (18:2) was the only fatty acid tested that significantly inhibited breakdown of germinal vesicles (P less than 0.01). The effect was dose-dependent and was greatest at 50 mumol fatty acid/l (% breakdown of control, 81.1 +/- 6.8 vs. 50 mumol linoleic acid/l, 35.4 +/- 7.3; P less than 0.02). Linoleic acid was the major fatty acid, constituting about a third of the total fatty acid in the follicular fluid; followed by 18.9 +/- 1.0% and 16.9 +/- 1.3% oleic acid (18:1) in small and large follicles, respectively. Saturated fatty acids accounted for less than 30% of the total fatty acid composition. There was a marked absence of tetraenoic acids in small and large follicles. Proportions of linoleic acid were significantly lower in follicular fluid from large follicles (31.1 +/- 1.2% of total fatty acid) than from small follicles (34.8 +/- 0.7% of total fatty acid) (P less than 0.05) and there was a significant inverse correlation between follicle diameter and percentage of linoleic acid in the follicular fluid (r = -0.6966; P less than 0.05). There was no significant alteration in any other fatty acid during follicular development.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

[Influence of linoleic acid (18:2 n-6) and alpha-linolenic acid (18:3 n-3) on the composition, permeability and fluidity of cardiac phospholipids in the rat: study using membrane models (liposomes)].

For 9 weeks, 80 male SPF Wistar rats were fed purified diets containing mixtures of vegetable oils (15% by weight) with different linoleic and linolenic contents. Diet (L+) contained large amounts of linoleic acid (53% of the total fatty acids), diet (L+Ln) contained the same amount of linoleic acid but also 10% of alpha-linolenic acid, diet (L-) supplied a low level of linoleic acid (12% of the total fatty acids) and so did diet (L-Ln) which also contained 10% of alpha-linolenic acid. The levels and fatty acid composition of heart phospholipids were determined. Liposomes, prepared from the total phospholipids extracted from rat hearts, were tested at different temperatures (15 to 50 degrees C) for their permeability to urea and fluidity; fluidity was monitored by fluorescence depolarization of 1,6-diphenyl-1,3,5-hexatriene (DPH). As already demonstrated, dietary alpha-linolenic acid substituted C22 polyunsaturated fatty acids of the linoleic family (n-6) for those of the linolenic acid family (n-3). This substitution remained high, even though linoleic acid represented more than 50% of the total dietary fatty acids. Diphosphatidylglycerol markedly increased in heart phospholipids of rats fed diets (L+) and (L+Ln). The changes in liposome permeability observed were rather well correlated with the unsaturation index of the phospholipid fatty acids, whereas fluidity changes were not. Fluidity decreased in liposomes of rats fed high levels of linoleic acid. Factors such as diphosphatidylglycerol or (n-3) fatty acid concentration in heart phospholipids could explain these results.

Animals↗
PubMed2006

Rates and efficiencies of reactions of ruminal biohydrogenation of linoleic acid according to pH and polyunsaturated fatty acids concentrations.

Data from a previous study about the effects of pH and of linolenic acid (C18:3n-3) and linoleic acid (C18:2n-6) concentrations on C18:2n-6 biohydrogenation in ruminal cultures were used to calculate the rates and efficiencies of the three reactions of C18:2n-6 biohydrogenation (isomerisation of C18:2n-6 to CLA; reduction of CLA to trans-octadecenoic acids; reduction of trans-octadecenoic acids to stearic acid). First, low pH was confirmed to inhibit isomerisation and was shown to inhibit the second reduction, leading to an accumulation of vaccenic acid. This later effect had only been observed in some in vivo studies using high concentrate diets, because in in vitro experiments, the very low pH frequently used depresses isomerisation which consequently generates very low amount of substrates for reductions whose variations become difficult to ascertain. Second, C18:2n-6 at high concentration was confirmed to saturate its own isomerisation and the increase of CLA production due to high initial C18:2n-6 was shown to inhibit the two subsequent reductions. Third, C18:3n-3 at high concentrations was confirmed to inhibit C18:2n-6 isomerisation. Moreover, the second reduction was shown to be saturated, probably by all trans-octadecenoic acids intermediates of C18:2n-6 and C18:3n-3 biohydrogenation, leading to an accumulation of trans-octadecenoic acids, especially vaccenic acid. This fatty acid is partly desaturated into CLA in the mammary gland, which explains the synergy between C18:2n-6 and C18:3n-3 for milk CLA noticed by others in vivo. This approach helped explain the actions of pH and of C18:2n-6 and C18:3n-3 concentrations on C18:2n-6 biohydrogenation and allows some explanations about differences noticed between studies.

Animals↗
PubMed1976

The steady-state kinetics of the oxygenation of linoleic acid catalysed by soybean lipoxygenase.

The steady-state kinetics of the oxygenation of linoleic acid catalysed by soybean lipoxygenase-1 were studied. The results showed that lipoxygenase-1 is strongly inhibited by its substrate, linoleic acid. In the presence of the product of the reaction, 13-LS-hydroperoxy-linoleic acid, the substrate inhibition only affects the apparent affinity for O2 and is of a hyperbolic type. A kinetic scheme of the oxygenation reaction is presented, which postulates two substrate-binding sites on the enzyme, one for linoleic acid and one for O2, and a regulatory binding site, which can either bind the product or the fatty acid substrate. Since previous studies indicated that the product of the reaction influences the oxidation state of the iron present in protein, the steady-state kinetics of the native enzyme and of the enzyme pre-incubated with the product were compared. Pre-incubation of the enzyme with the product did not lead to altered steady-state kinetics of the reaction compared to those of the native enzyme.

Kinetics↗
PubMedDate not supplied

[Metabolism of linoleic acid given with the feed in the calf liver].

Calves were fed with the whole milk substitute containing different amounts of linoleic acid--0.70, 1.44 and 3.65 per cent from the total energy content of the ratio--for the 1st, 2nd and 3rd groups, respectively, beginning from the 2nd to the 60th day of life. The feeding of different amounts of linoleic acid has no significant effect on the lipid content and the ratio of different type of lipids as well as on prostaglandins E2 and F 2 alpha contents. The increase of linoleic acid quantity in the liver lipids of calves occurs parallel to that of its uptake. During the liver homogenates incubation in the medium containing [1-14C] linoleic acid 0.15-0.22 per cent of the label are found in the composition of 14CO2, 85.7-85.9 per cent--in lipids, 13,9-14,6 per cent--in prostaglandins.

Animal Feed↗
PubMed1978

Reduction by linoleic acid of the severity of experimental allergic encephalomyelitis in the guinea pig.

This paper reports the effects of supplementation of the diet with linoleic acid on the severity of experimental allergic encephalomyelitis (EAE) in guinea pigs. Clinical signs of disease (e.g. paresis, paraplegia, urinary incontinence), weight loss, frequency of perivascular lesions in the central nervous system and ability of isolated lymph node cells to respond to myelin basic protein in vitro were all reduced by linoleic acid supplementation. Linoleic acid was effective when fed at a dose of 0.5 ml/day from 7 to 21 days after sensitization of the animals with basic protein, i.e., before and during the time in which clinical signs normally appeared. The same daily dose fed from 7 days before to 7 days after sensitization, i.e., ceasing about 7 days before the normal time of appearance of clinical signs, produced no significant effect. Feeding linoleic acid to normal guinea pigs significantly altered the fatty acid composition of their serum and lymph nodes, but not of their brain. Of several possible explantations for the protective effect of lineolic acid in EAE, we considered action by this essential fatty acid on the immune system most likely.

Animals↗
PubMed1994

Sequential oxygenation of linoleic acid in the fungus Gaeumannomyces graminis: stereochemistry of dioxygenase and hydroperoxide isomerase reactions.

Linoleic acid is sequentially oxygenated to (7S,8S)-dihydroxylinoleic acid by dioxygenase and hydroperoxide isomerase activities present in the fungus Gaeumannomyces graminis (Brodowsky, I. D., Hamberg, M., and Oliw, E. H., J. Biol. Chem. 267, 14738-14745 (1992)). Linoleic acids stereospecifically deuterated at C-7 and C-8 were prepared by biological desaturation of the corresponding stearates and used to determine the stereochemistry of the hydrogen abstractions occurring in the dioxygenase- and hydroperoxide isomerase-catalyzed reactions. The dioxygenase reaction was found to involve stereospecific abstraction of the pro-S hydrogen from C-8 followed by antarafacial insertion of dioxygen to produce (8R)-hydroperoxylinoleic acid. The hydroperoxide isomerase reaction consisted of conversion of (8R)-hydroperoxylinoleic acid into (7S,8S)-dihydroxylinoleic acid by stereospecific elimination of the pro-S hydrogen from C-7 and intramolecular suprafacial insertion of oxygen at C-7. Accordingly, during the conversion of linoleic acid into (8R)-hydroperoxylinoleic acid, the absolute configuration of C-8 was inverted, while the conversion of (8R)-hydroperoxylinoleic acid into (7S,8S)-dihydroxylinoleic acid occurred with retention of absolute configuration at C-7.

Deuterium↗
PubMed2006

Application of a continuous bioreactor cascade to study the effect of linoleic acid on hybridoma cell physiology.

The aim of the present study is to demonstrate the use of controlled bioreactors for toxicological studies. As a model system the effect of linoleic acid on hybridoma cells is studied in two well-controlled continuously operated bioreactors placed in series. In the first reactor the effect on rapid proliferating cells can be studied, while in the second reactor a special steady state is created, which allows studying the effect on apoptotic cells. Experiments are done at 0, 25, and 50 microM linoleic acid. At the end of the experiment with 50 microM linoleic acid, the concentration of linoleic acid is increased stepwise to determine the cytotoxic level. For rapid proliferating cells exposed to 25 and 50 microM stimulation of growth was observed. At 50 microM there was at the same time an increase in cell death through apoptosis. For stressed apoptotic cells linoleic acid caused partial growth inhibition at 25 and 50 microM and arrest of cell proliferation in the G(2)/M phase at 50 microM. For both, rapid proliferating cells and stressed apoptotic cells, complete growth inhibition occurred at 85 microM, with cells being arrested in the G(2)/M phase and dying mainly through necrosis. Cells in the bioreactor system appeared to be more sensitive towards linoleic acid than cells grown in multi-well plates. (IC(50) = 300 microM; IC(100) = 400 microM). Altogether the results of the present study reveal that the biostat experiments allow detailed analysis of the effect of a bioactive ingredient on cell physiology and behavior.

Apoptosis↗
PubMed1988

Investigations on the mechanism of a diminished inotropic isoprenaline effect in isolated rat hearts after high linoleic acid diet.

Male Wistar rats were fed on a diet rich (13.3 J%) or poor (0.5 J%) in linoleic acid for 10 weeks. The inotropic and chronotropic effects of isoprenaline (100 ng) in isolated perfused hearts were reduced after a linoleic acid rich diet by 36% and 51%, respectively, with an accompanying reduction in isoprenaline-induced increase in the ventricular cAMP content. Moreover, the stimulation of adenylate cyclase in homogenates of ventricular tissue was diminished after linoleic acid rich diet. We postulate that the diminished adrenergic cardiac response after high vs. low linoleic acid diets could be due to alterations in the adenylate cyclase activity and cAMP formation.

Animals↗
PubMed1998

Production of conjugated linoleic acid by dairy starter cultures.

Nineteen different strains of lactobacilli, lactococci, streptococci and propionibacteria commonly used as dairy starter cultures were tested for their ability to produce conjugated linoleic acid (CLA) from free linoleic acid in vitro. Two strains of Propionibacterium freudenreichii ssp. freudenreichii and one strain of P. freudenreichii ssp. sheramnii were found to be capable of converting free linoleic acid to extracellular CLA. The highest level of CLA formed in the media was 265 micrograms ml-1. Of the different isomers, cis- and trans-9,11-octadecadienoic acid represented more than 70% of the total CLA formed. The inhibitory effect of linoleic acid on the growth of the bacteria and its conversion to CLA in different media by propionibacteria are discussed.

Food Microbiology↗
PubMed2000

[Effect of linoleic acid on the production of secondary metabolites].

The paper examines the effect of linoleic acid in various concentrations on the production of flavonoids in an Ononis arvensis culture in vitro and the production of anthracene derivatives in a Rheum palmatum culture in vitro. The content of the metabolites under study after elicitation with linoleic acid, which is the precursor of jasminic acid intervening into the course of elicitation, was examined after 12; 24; 48 and 168 hours. The maximal increase in the content of flavonoids (118%) was found after the application of linoleic acid in a concentration of 2 mg/ml after 48 hrs. In concentrations of 0.01; 0.20, and 1 mg/ml after 48 hours of application of the elicitor, the highest increase in the content of flavonoids was observed after 24 hrs in a concentration of 2.0 mg/ml. In the elicitation of the Rheum palmatum culture, the highest response (100%) in the production of anthracene derivatives was observed in linoleic acid in a concentration of 1 mg/ml.

Anthracenes↗
PubMed2000

Conjugated linoleic acid induces lipid peroxidation in humans.

Conjugated linoleic acid (CLA) is shown to have chemoprotective properties in various experimental cancer models. CLA is easily oxidised and it has been suggested that an increased lipid oxidation may contribute to the antitumorigenic effects. This report investigates the urinary levels of 8-iso-PGF(2alpha), a major isoprostane and 15-keto-dihydro-PGF(2alpha), a major metabolite of PGF(2alpha), as indicators of non-enzymatic and enzymatic lipid peroxidation after dietary supplementation of CLA in healthy human subjects for 3 months. A significant increase of both 8-iso-PGF(2alpha) and 15-keto-dihydro-PGF(2alpha) in urine was observed after 3 months of daily CLA intake (4.2 g/day) as compared to the control group (P<0.0001). Conjugated linoleic acid had no effect on the serum alpha-tocopherol levels. However, gamma-tocopherol levels in the serum increased significantly (P=0. 015) in the CLA-treated group. Thus, CLA may induce both non-enzymatic and enzymatic lipid peroxidation in vivo. Further studies of the mechanism behind, and the possible consequences of, the increased lipid peroxidation after CLA supplementation are urgently needed.

Adult↗