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PubMed2003

Structural analysis of conjugated linoleic acid produced by Lactobacillus plantarum, and factors affecting isomer production.

An isomer of the conjugated linoleic acid (CLA) produced from linoleic acid by Lactobacillus plantarum was identified as cis-9,trans-11-octadecadienoic acid by proton nuclear magnetic resonance spectroscopy. Together with earlier results, we concluded that the bacterium produces two CLA isomers, cis-9,trans-11- and trans-9,trans-11-octadecadienoic acid from linoleic acid. The addition of L-serine, glucose, AgNO3, or NaCl to the reaction mixture reduced production of the latter.

Culture Media↗
PubMed1994

[Effects of dietary linoleic acid on lipogenesis enzyme activity in adipose tissue in the pig].

The effect of dietary linoleic acid on lipogenesis was determined on 36 Large White castrated male pigs fed between 35 and 100 kg liveweight diets containing 4% of total lipids including 3 levels of linoleic acid 1.5, 2.0 and 2.5%. The elevation in dietary linoleic acid increases the carcass fatness (P < 0.01). At slaughter, linoleic acid content in the backfat increases with the level of dietary linoleic acid (P < 0.001). The lipogenesis measured by the activities of acetyl-coenzyme A carboxylase, malic enzyme and glucose-6-phosphate dehydrogenase increases significantly in adipose tissues (backfat and lean fat) with the dietary linoleic supply, whereas no effect was noticed in intramuscular fat. The increase in fat synthesis can explain the higher increase in carcass fatness of pigs fed diets containing high levels of linoleic acid.

Acetyl-CoA Carboxylase↗
PubMed2004

Total antioxidant capacity of arginine-conjugated linoleic acid (CLA) complex.

Conjugated linoleic acids (CLA) have shown diverse biological activities, including anti-carcinogenic, anti-atherosclerotic, anti-adipogenic, and anti-diabetogenic effects. Recent reports also showed that CLA has free radical scavenging capacity, which may give health benefits to human beings. However, the application of CLA as a bioactive ingredient has been limited due to its insolubility in water. To overcome this problem, we investigated antioxidant activities of arginine (Arg)-CLA, a water-soluble CLA salt, using both 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assays. CLA, Arg, and Arg-CLA all exerted radical scavenging activities in a dose-dependent manner in both assays. Arg-CLA at 20 mM scavenged 89 and 55% of ABTS and DPPH radicals in 3 h, respectively, whereas CLA alone quenched only 48 and 26% of them under the same conditions. The antioxidant activity of the Arg-CLA complex was found to be synergistic in ABTS assay and comparable to that of vitamin E in DPPH assay.

Antioxidants↗
PubMed2003

Dietary alpha-linolenic acid suppresses the formation of lysophosphatidic acid, a lipid mediator, in rat platelets compared with linoleic acid.

Rats fed a high linoleic acid (LA, 18:2n-6) diet or a high alpha-linolenic acid (ALA, 18:3n-3) diet for 4 months after weaning. Platelets from the high-LA group contained more arachidonic acid (AA, 20:4n-6) and less eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) compared with those from the high-ALA group. Incorporation of [32P]orthophosphate into platelet phospholipids was increased by thrombin-treatment, and was greater by ca. 30% in the high-LA group than in the high-ALA group both in the presence and absence of thrombin. The formation of [32P]lysophosphatidic acid (LPA), a lipid messenger, in [32P]orthophosphate-labeled platelets was increased 6.6-fold in the high-LA group and 4.1-fold in the high-ALA-group by thrombin-treatment. The formation of [32P] LPA in activated platelets was reduced by 35% in the high-ALA group.

Animals↗
PubMed2000

Gamma-linolenic acid provides additional protection against ventricular fibrillation in aged rats fed linoleic acid rich diets.

Ligation of the coronary artery in rats produces severe ventricular fibrillation (VF) and malignant cardiac arrhythmia. Mortality increases with the age of the animal. Diets rich in saturated fatty acids (SF) but low in linoleic acid (LA) increase, but diets high in LA and low in SF decrease the severity of VF and mortality in older animals. The effects of an LA enriched diet can be blocked by inhibition of cyclooxygenase suggesting that conversion of LA to eicosanoids is central to the development of VF. Conversion of LA to gamma-linolenic acid (GLA) via delta-6 desaturase is the first step in the process. The activity of delta-6 desaturase declines with age. Thus inclusion of GLA in the diet of older animals may provide an additional benefit over LA alone. Dietary supplements of evening primrose oil (EPO) to one year old rats reduced ischaemic VF more than a supplement of sunflower seed oil (SSO) without GLA. Substitution of borage oil (more GLA than EPO but less LA than either EPO or SSO) was without additional benefit.

Aging↗
PubMed2006

Maintenance of adiponectin attenuates insulin resistance induced by dietary conjugated linoleic acid in mice.

Conjugated linoleic acid (CLA) causes insulin resistance and hepatic steatosis in conjunction with depletion of adipokines in some rodent models. Our objective was to determine whether the maintenance of adipokines, mainly leptin and adiponectin, by either removing CLA from diets or using an adiponectin enhancer, rosiglitazone (ROSI), could attenuate CLA-induced insulin resistance. Male C57BL/6 mice were consecutively fed two experimental diets containing 1.5% CLA mixed isomer for 4 weeks followed by a diet without CLA for 4 weeks. CLA significantly depleted adiponectin but not leptin and was accompanied by hepatic steatosis and insulin resistance. These effects were attenuated after switching mice to the diet without CLA along with restoration of adiponectin. To further elucidate the role of adiponectin in CLA-mediated insulin resistance, ROSI was used in a subsequent study in male ob/ob mice fed either control (CON) or CLA diet. ROSI maintained significantly higher adiponectin levels in CON- and CLA-fed mice and prevented the depletion of epididymal adipose tissue and the development of insulin resistance. In conclusion, we show that insulin resistance induced by CLA may be related more to adiponectin depletion than to leptin and that maintaining adiponectin levels alone either by removing CLA or using ROSI can attenuate these effects.

Adiponectin↗
PubMed2002

Production of conjugated linoleic acids through KOH-catalyzed dehydration of ricinoleic acid.

Production of conjugated linoleic acids (CLA) using castor oil as starting material involves conversion of ricinoleic acid to methyl 12-mesyloxy-octadec-9-enoate (MMOE) followed by dehydration. This process usually uses 1,8-diazabicyclo-(5.4.0)-undec-7-ene (DBU) as an expensive dehydrating reagent. The present study reports that potassium hydroxide (KOH) can serve as a dehydrating reagent in replacement of DBU. The results showed that conversion of MMOE to CLA catalyzed by KOH was an efficient reaction, with a 77% conversion efficiency at 80 degrees C. The CLA isomeric profile produced in KOH-catalyzed dehydration reaction was similar to that catalyzed by DBU. The CLA mixture produced in KOH-catalyzed dehydration of MMOE at 80 degrees C contained 72% 9c,11t-18:2 and 26% 9c,11c-18:2 while in that catalyzed by DBU, 9c,11t-18:2 and 9c,11c-18:2 accounted for 78 and 16%, respectively. It was found that the temperature of dehydration was an important factor in the determination of CLA isomer composition and yield of conversion. Elevating the temperature from 78 to 180 degrees C decreased not only the conversion efficiency but also production of total c,t-18:2 and c,c-18:2 isomers regardless of dehydration catalyzed by either DBU or KOH. It is concluded that KOH may replace DBU as a dehydrating reagent in conversion of MMOE to CLA when the reaction conditions are optimized.

Castor Oil↗
PubMed1976

The effects of linoleic acid and prostaglandin E1 on arterial thrombosis.

The effects of dietary linoleic acid on arterial thrombus formation in rats were compared with the inhibitory effect of intravenous or intraaortic administration of PGE1, a potent inhibitor of platelet adhesion and aggregation. The "rat aorta-loop" model proved to be a useful method to induce a stable thrombus, obstructing the aortae of standard-fed rats with an obstruction time (OT) of about 96 h. Increasing the amount of dietary linoleic acid from 2.5 cal% to 30 cal% doubled OT to about 200 h. A constant intravenous PGE1 infusion of 10 mug/h increased OT significantly from the control value of 126.6 h to 160.1 h. When the same amount of PGE1 was infused intraarteriallu, the increase in OT was higher and doubled to 255.7 h. Using the "Filtragometer method" - in which platelet aggregatibility is measured in flowing human venous blood - a significant decrease in platelet stickiness was found in a group of patients consuming 12 cal% linoleic acid as compared to a similar group of patients with only 4 cal% linoleic acid in the diet. As similar results were obtained in patients with diabetes mellitus and in survivors of a myocardial infarction, increasing the amount of dietary linoleic acid may be of great therapeutic value for patients at risk of arterial thrombotic processes. These data support the hypothesis that part of the excess of dietary linoleic acid can lead to increased PGE1 concentrations.

Animals↗
PubMed2003

Relative potencies of statins in reducing cholesterol synthesis and enhancing linoleic acid metabolism.

Simvastatin enhances the conversion of linoleic acid to their long chain polyunsaturated fatty acid derivatives, e.g. arachidonic acid, in addition to typically inhibiting the de novo cholesterol synthesis, in cultured cells. The dose-response relationships for the above effects show that simvastatin, atorvastatin and fluvastatin affect linoleic acid conversion and the delta5 desaturase step more potently than the synthesis of cholesterol, simvastatin being the most effective in inhibiting sterol synthesis, whereas atorvastatin in stimulating the conversion of linoleic acid.

Arachidonic Acid↗
PubMed1999

Interaction of chickpea (Cicer arietinum L.) legumin with oxidized linoleic acid.

Chickpea legumin has been purified and incubated under oxidizing conditions with linoleic acid to investigate the influence of this acid on the structure and nutritional quality of the protein. At the end of the incubation time, >30% of the linoleic acid was oxidized. The oxidized linoleic acid was highly detrimental to legumin, and the electrophoretic pattern of the protein was completely changed after the incubation period. Nevertheless, neither polymerization nor cleavage of the protein was observed as deduced from gel filtration chromatography, suggesting that the changes observed in native electrophoresis were probably due to oxidation of legumin. The incubation of legumin with linoleic acid also produced a diminution of the contents of methionine and histidine, by 81.3 and 24.3%, respectively. Finally, in vitro protein digestibility of chickpea legumin was also seriously affected by the incubation with linoleic acid, decreasing from 84.1 to 69.2%.

Amino Acids↗
PubMed1997

Simultaneous measurement of the rates of appearance of palmitic and linoleic acid in critically ill infants.

Lipolysis has been measured in humans by means of stable isotope techniques using labeled palmitic acid (PA) or glycerol as tracers. If other fatty acids (FA) such as linoleic acid (LLA) have the same rate of appearance (Ra) as PA and therefore contribute equally to oxidative and nonoxidative metabolism is unknown. We infused albumin-bound [U-13C]PA and [U-13C]LLA in seven critically ill infants (weight 3.6 +/- 1.3 kg, age 57 +/- 64 d) receiving 20.9 +/- 5.4 kcal. kg-1.d-1 of i.v. glucose only, and measured simultaneously the Ra of PA and LLA from the isotopic enrichment of plasma FFA by mass spectrometry. A needle biopsy of the s.c. adipose tissue was obtained for FA composition. PA in adipose tissue was higher than LLA (40 +/- 6.7 versus 5.4 +/- 3.2 mol %, p < 0.001). The Ra values of PA and LLA were 5.73 +/- 2.79 and 1.34 +/- 0.92 mumol.kg-1.min-1, respectively (p = 0.005). However, the ratio of the FA's Ra to their respective mol% values in adipose tissue was lower for PA than for LLA (0.15 +/- 0.06 versus 0.25 +/- 0.06, p = 0.02). The Ra of LLA acid was higher than could be expected from the FA composition of adipose tissue, thus indicating a preferential release of LLA during lipolysis. In critically ill infants receiving only i.v. glucose, the contribution of LLA to the oxidative and nonoxidative metabolism may be larger than what assumed from the FA composition of plasma and adipose tissue.

Biological Transport↗
PubMed2001

Isomerization increases the postprandial oxidation of linoleic acid but not alpha-linolenic acid in men.

Human lipid intake contains various amounts of trans fatty acids. Refined vegetable and frying oils, rich in linoleic acid and/or alpha-linolenic acid, are the main dietary sources of trans-18:2 and trans-18:3 fatty acids. The aim of the present study was to compare the oxidation of linoleic acid, alpha-linolenic acid, and their major trans isomers in human volunteers. For that purpose, TG, each containing two molecules of [1-(13)C]linoleic acid, alpha-[1-(13)C]linolenic acid, [1-(13)C]-9cis,12trans-18:2, or [1-(13)C]-9cis,12cis,15trans-18:3, were synthesized. Eight healthy young men ingested labeled TG mixed with 30 g of olive oil. Total CO(2) production and (13)CO(2) excretion were determined over 48 h. The pattern of oxidation was similar for the four fatty acids, with a peak at 8 h and a return to baseline at 24 h. Cumulative oxidation over 8 h of linoleic acid, 9cis,12trans-18:2, alpha-linolenic acid, and 9cis,12cis,15trans-18:3 were, respectively, 14.0 +/- 4.1%, 24.7 +/- 6.7%, 23.6 +/- 3.3%, and 23.4 +/- 3.7% of the oral load, showing that isomerization increases the postprandial oxidation of linoleic acid but not alpha-linolenic acid in men.

Adult↗
PubMed1999

Similar effects of diets high in oleic or linoleic acids on coagulation and fibrinolytic factors in healthy humans.

BACKGROUND AND AIM: Monounsaturated fatty acids (MUFA) have been shown to be beneficial. Their haemostatic effects, however, are poorly known. We compared the effects of oleic acid (OA) and linoleic acid (LA) on variables related with coagulation and fibrinolysis in healthy subjects. METHODS AND RESULTS: Thirty-eight healthy volunteers (20 women, 18 men; mean age 27) consumed a saturated fat baseline diet for four weeks and were then switched to either a high LA diet (11.5 en%) or a high OA diet (18.0 en%) for another four weeks when nearly all food was provided for the whole day. A control group of 13 subjects consumed their habitual diet throughout the study. No differences between the OA and LA diets were found in the plasma levels of fibrinogen, plasminogen activator inhibitor, antithrombin III, von Willebrand factor antigen or D-dimers. Factor FVII coagulant activity was significantly lower after the OA diet. CONCLUSIONS: The results indicate largely similar effects for OA and LA on factors related with coagulation and fibrinolysis in humans. The effects of dietary fatty acid composition on FVII coagulant activity should be further studied.

Adult↗
PubMed2006

Effects of conjugated linoleic acid supplementation in layer diet on fatty acid compositions of egg yolk and layer performances.

Conjugated linoleic acid (CLA) is a mixture of positional and geometric isomers of linoleic acid with conjugated double bonds. Conjugated linoleic acids have been reported to have a wide range of health-beneficial effects, including anticarcinogenic, antiatherogenic, antidiabetic, and immune stimulatory effects. The objective of this study was to investigate the incorporation of CLA into eggs. Three hundred 27-wk-old layers were allocated to 5 dietary treatments (0, 1, 2, 3, and 4% CLA) with 5 replicates. The results of the study showed that average daily feed intakes were similar in all treatment groups, although hens fed with 4% CLA tended to consume less feed than other hens. Body weight gain and mortality rate were not significantly different (P > 0.05). Hens fed 4% dietary CLA had reduced egg, yolk, and albumen weights (P < 0.05). Yolk color significantly decreased as dietary CLA increased (P < 0.01). Shell thickness and Haugh units were not influenced by the dietary CLA. Concentrations of CLA and saturated fatty acids in egg yolk lipids increased as dietary CLA increased (P < 0.01), whereas concentrations of monounsaturated fatty acids and polyunsaturated fatty acids decreased as dietary CLA increased (P < 0.01). It can be concluded from the present experiments that increasing the amount of CLA fed to hens will increase the amount of CLA in egg yolk and that this increase is accompanied by a reduction in the amount of yolk polyunsaturated fatty acids but an increase in yolk saturated fatty acids. Egg size, yolk weight, and Roche-fan determined yolk color significantly decreased at the highest level of CLA supplementation.

Animal Feed↗
PubMed1986

Regulation of linoleic acid delta 6-desaturation by a cytosolic lipoprotein-like fraction in isolated rat liver microsomes.

A peripheral component of the delta 6-fatty acid-desaturase system of rat liver microsomes has been isolated from the cytosol by ultracentrifugation at a saline density of 1.26 g/ml. It exhibited lipoprotein characteristics with an approximate protein/lipid ratio of 1.22 and free fatty acids and phosphatidylcholine as its main lipid components. Linoleic acid desaturation activity diminished in washed microsomes, since they lost the adsorbed cytosolic fraction. Addition of the factor reactivated the reaction and the recovery was dependent on the concentration of the factor in the medium. Linoleic acid and linoleyl-CoA were bound by the cytosolic fraction. However, the transport of substrate to the desaturase was not apparently a main function of the cytosolic fraction, since transport occurred equally in the absence of the factor. Moreover, the solubilization of linoleyl-CoA was not enhanced and the free monomeric concentration was not altered by the presence of the cytosolic fraction. In addition, the factor did not divert delta 6-desaturase substrate to or from other metabolic pathways such as esterification to phospholipids. gamma-Linolenic acid produced by delta 6-desaturation of linoleic acid in the microsomes inhibited the desaturase, but it was removed by the factor from the membrane towards the cytosol, preventing the inhibition. The anti-inhibitory effect of the cytosolic factor was blockaded by addition of columbinic acid or gamma-linolenic acid to the factor. Moreover, the inhibitory effect of arachidonic acid was not prevented by addition of the cytosolic fraction. These results suggest that the cytosolic fraction studied would optimize the delta 6-desaturation of linoleic acid in vitro in rat liver microsomes by removal of the product, gamma-linolenic acid, as it is formed.

Animals↗
PubMed2001

Conjugated linoleic acid: effects on plasma lipids and cardiovascular function.

Conjugated linoleic acid is a collective name for mixtures of several positional and geometric conjugated dienoic isomers of linoleic acid, which have been shown to impact favorably on several biological processes, particularly carcinogenesis. Recent studies have clearly established that the c9, t11 and t10, c12 isomers have distinct biological effects. The latter may be of particular importance in affecting blood lipids. Because conjugated linoleic acid has been suggested to be anti-atherogenic, this review is focused on its effects on cardiovascular function. Careful scrutiny of the literature suggests that at present it is premature to assign any beneficial role to conjugated linoleic acid in terms of its ability to impact either blood lipids or atherogenesis.

Animals↗
PubMed1998

Protective effect of linoleic acid on IFN gamma-induced cellular injury in primary culture hepatocytes.

We have previously demonstrated that treatment of hepatocytes with IFN gamma results a series of cellular injury processes, including DNA synthesis arrest, membrane breakage and apoptosis. In the present work, we show that IFN gamma suppresses cellular respiration and protein synthesis in hepatocytes, and that cellular respiration suppression is an early event in the IFN gamma-induced cellular injuries. Polyunsaturated fatty acids (PUFAs) increased cellular respiration of hepatocytes, but only linoleic acid showed some protective effect against IFN gamma-induced cellular respiration suppression. Linoleic acid also reduced other IFN gamma-mediated cellular injuries, including membrane breakage and protein synthesis inhibition. Like linoleic acid, fetal bovine serum also inhibited IFN gamma-induced cellular damage. Increased NAD levels were found in both IFN gamma-treated and non-treated hepatocytes following the addition of PUFAs, but clofibrate, a peroxisome proliferator, bromophenacyl bromide (BPB), an inhibitor of phospholipase, nordihydroguaiaretic acid (NDGA), an inhibitor of lipoxygenase, and arachidonic acid, a metabolite of linoleic acid, did not inhibit IFN gamma-induced cellular injury. In addition, the combination of linoleic acid and IFN gamma induced nitric oxide (NO) synthesis in hepatocytes. These results suggest that fatty acid may play an important role in liver homeostasis during chronic inflammatory states and sepsis.

Animals↗