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PubMed2002

Potent cytotoxic effect of the trans10, cis12 isomer of conjugated linoleic acid on rat hepatoma dRLh-84 cells.

We evaluated the cytotoxic effect of conjugated linoleic acid (CLA) on rat hepatoma dRLh-84 cells in vitro. When cells were cultured in the presence of CLA, strong cytotoxic effect on dRLh-84 cells was recognized at 1 microM level compared to the control vehicle group, and trans10, cis12-CLA but not cis9, trans11-CLA was shown to be an active isomer for inducing this effect. Increase of the sub-G1 population and activation of caspase-3 and 9 accompanied with a time-dependent cleavage of poly(ADP-ribose) polymerase were recognized in dRLh-84 cells treated with trans10, cis12-CLA. In addition, we could see nuclear fragmentation in dRLh-84 cells treated with trans10, cis12-CLA by laser scanning confocal microscopy observation. Cytotoxic effect of trans10, cis12-CLA on normal hepatocytes was weaker than on dRLh-84 cells. These data indicate trans10, cis12-CLA has a potent cytotoxic effect on dRLh-84 cells through at least in part by an apoptotic pathway.

Animals↗
PubMed2005

Trans10, cis12-conjugated linoleic acid induces mitochondria-related apoptosis and lysosomal destabilization in rat hepatoma cells.

Conjugated linoleic acid (CLA) is a powerful anti-carcinogenic fatty acid. Previously, we showed that 10trans 12cis (10t, 12c) CLA induced apoptotic cell death in rat hepatoma. Here, we demonstrated significant cytotoxic effects of 1 muM 10t, 12c-CLA, but not 9c, 11t-CLA, on dRLh-84 rat hepatoma cells. 9t, 11t and 9c, 11c-CLA also showed low levels of cytotoxic activity. 10t, 12c-CLA activated caspase-3, 9 followed by cytochrome c release from mitochondria into the cytosol. Inhibitors of caspase-3, 9 blocked the cytotoxicity of 10t, 12c-CLA. 10t, 12c-CLA also induced translocation of Bax protein into the mitochondrial membrane and cleavage of Bid protein. Lysosomal destabilization induced by 10t, 12c-CLA was observed by monitoring the re-localization of Acridine Orange and the leakage of beta-hexosaminidase from lysosomes. 10t, 12c-CLA directly degraded the isolated lysosomes from the rat liver. Our observations indicate that 10t, 12c-CLA induces mitochondria-related apoptosis accompanied by lysosomal destabilization in rat hepatoma cells.

Animals↗
PubMed2004

Suppressed permeation of linoleic acid in a liposomal formulation through reconstructed skin tissue.

Since the liposomal formulation of linoleic acid (LA) exhibited an enhanced skin-whitening effect, the influence of liposomalization on the cutaneous absorption of LA was examined using a three-dimensional (3D) reconstructed skin model. Liposome entrapped [(14)C]-LA was applied on the skin model, and the permeation of LA through the skin was monitored. The permeation rate of LA in the liposomal formulation was found to be lower than that in the conventional formulation without liposomes, suggesting the increased retention time of LA in the skin by the liposomal formulation. Next, to investigate the dependence of the LA permeation on melanocyte conditions and intactness of the reconstructed skin model, the effect of UV irradiation on LA permeation was examined. Low-dose UVB irradiation (0.03 J/cm(2) for 3 times), which activated melanocytes in the skin, did not influence the extent of LA permeation, while high-dose irradiation (0.30 J/cm(2) for 3 times) enhanced the permeation of LA in both the conventional and liposomal formulation. The present results suggest the importance of skin intactness for LA permeation and that the 3D reconstructed skin model would be useful for evaluating the characteristics of skin-oriented cosmetics and drugs.

Chemistry, Pharmaceutical↗
PubMed2005

Conjugated linoleic acid impairs endothelial function.

OBJECTIVE: To determine the effect of dietary supplementation with conjugated linoleic acid (CLA) on body mass index (BMI), body fat distribution, endothelial function, and markers of cardiovascular risk. METHODS AND RESULTS: Forty healthy volunteers with BMI >27 kg/m2 were randomized to receive a CLA isomeric mixture or olive oil in a 12-week double-blind study. Subcutaneous body fat and abdominal/hepatic fat content were assessed using skin-fold thicknesses and computed tomography scanning, respectively. Endothelial function was assessed by brachial artery flow-mediated dilatation (FMD). Plasma isoprostanes were measured as an index of oxidative stress. CLA supplementation did not result in a significant change in BMI index or total body fat. There was a significant decrease in limb (-7.8 mm, P<0.001), but not torso skin-fold thicknesses or abdominal or liver fat content. Brachial artery FMD declined (-1.3%, P=0.013), and plasma F2-isoprostanes increased (+91 pg/mL, P=0.042). CONCLUSIONS: A CLA isomeric mixture had at most modest effects on adiposity and worsened endothelial function. On the basis of these results, the use of the isomeric mixture of CLA as an aid to weight loss cannot be recommended.

Adult↗
PubMedDate not supplied

The 10trans, 12cis isomer of conjugated linoleic acid promotes energy metabolism in OLETF rats.

OBJECTIVE: We investigated the effect of conjugated linoleic acid (CLA) on energy metabolism in Otsuka Long-Evans Tokushima Fatty (OLETF) rats. METHODS: In experiment 1, male OLETF rats were fed either control diet, 10% safflower oil or CLA diet, 9% safflower oil plus 1% CLA for 4 wk. In experiment 2, male OLETF rats were fed either 9c,11t-CLA diet, 9% safflower oil plus 1% 9c,11t-CLA-rich oil or 10t,12c-CLA diet, 9% safflower oil plus 1% 10t,12c-CLA-rich oil for 10 d. RESULTS: In experiment 1, after 4 wk of feeding, serum and hepatic triacylglycerol concentrations in the CLA group were decreased significantly as compared with the control group. The CLA diet increased oxygen consumption and energy expenditure as compared with the control diet in OLETF rats. In experiment 2, a significant reduction of serum and hepatic triacylglycerol concentrations was seen in the 10t,12c-CLA group as opposed to the 9c,11t-CLA group. Oxygen consumption and energy expenditure were significantly higher in the 10t,12c-CLA group than in the 9c,11t-CLA group. CONCLUSIONS: These results demonstrated that the hypolipidemic effect and the enhancement of energy metabolism by CLA can be attributed to the effect of the 10t,12c-CLA isomer.

Animals↗
PubMed2005

Association between dietary conjugated linoleic acid and bone mineral density in postmenopausal women.

OBJECTIVE: To determine if dietary conjugated linoleic acid (CLA) is associated with bone mineral density (BMD) of different skeletal sites in postmenopausal women. METHODS: A cross-sectional analysis in 136 Caucasian, healthy, postmenopausal women, mean age 68.6 years. BMD and soft tissue were assessed by dual energy x-ray absorptiometry (DXA). Energy, calcium, protein, fat, CLA and other relevant nutrients were estimated using 3 day dietary records. Supplement use was recorded as well. Current and past physical activity were determined using the Allied Dunbar National Fitness Survey for older adults. RESULTS: CLA (63.1 +/- 46.8 mg, mean +/- SD) was a significant predictor of Ward's triangle BMD (p = 0.040) in a multiple regression model containing years since menopause (18.5 +/- 8.4 y), lean tissue, energy intake (1691 +/- 382 kcal/day) dietary calcium (873 +/- 365 mg), protein (70.6 +/- 18.6 g), fat (57.9 +/- 23.9 g), zinc (19.2 +/- 13.6 mg), and current and past physical activity, with R(2)(adj) = 0.286. Subjects were also divided into groups below (Group 1) and above (Group 2) the median intake for CLA. Group 2 had higher BMD in the forearm, p = 0.042, and higher BMD in the hip, lumbar spine and whole body, however statistical significance was not reached. CONCLUSION: These findings indicate dietary CLA may positively benefit BMD in postmenopausal women. More studies are warranted examining the relationship between dietary CLA and BMD.

Absorptiometry, Photon↗
PubMed2004

The effect of dietary supplementation with linoleic acid to late gestation ewes on the fatty acid composition of maternal and fetal plasma and tissues and the synthetic capacity of the placenta for 2-series prostaglandins.

Linoleic acid (18:2n-6) is metabolised to arachidonic acid (20:4n-6), the precursor for 2-series prostaglandins (PGs). Increased consumption of 18:2n-6 during pregnancy may thus modify PG synthesis during labour. We have investigated whether increased 18:2n-6 composition during gestation altered the fatty acid consumption and PG synthesis of maternal and fetal tissues in the sheep. Ewes were fed a control diet or a diet providing 40% more 18:2n-6 from 96 days gestation. Half of each group received dexamethasone on day 136 to up-regulate the PG synthetic pathways promoting parturition. Maternal and fetal tissues were collected at 138 days. The 18:2n-6 diet significantly increased the 20:4n-6 content of maternal plasma, fetal plasma and allantochorion (51-81%) phosphatidylcholine, and fetal liver (40%) and maternal caruncular endometrium (57%) phosphatidylethanolamine. Increased 18:2n-6 intake increased production of PGF(2alpha) and PGE(2) in all placental tissues (maternal caruncular and intercaruncular endometrium and fetal allantochorion) by 23-98%, whereas dexamethasone increased it by 32-142%. This suggests that consumption of an 18:2n-6-enriched diet in late pregnancy enhanced placental PG production by increasing the supply of 20:4n-6. Variations in the extent to which the diet altered the polyunsaturated fatty acid (PUFA) content of the different tissues indicated complex interactions between nutrient availability and metabolic adaptation.

Allantois↗
PubMed2002

Trans-10,cis-12-conjugated linoleic acid inhibits Caco-2 colon cancer cell growth.

A commercially available mixture of conjugated linoleic acid (CLA) isomers decreases colon cancer cell growth. We compared the individual potencies of the two main isomers in this mixture [cis-9,trans-11 (c9t11) and trans-10,cis-12 (t10c12)] and assessed whether decreased cell growth is related to changes in secretion of insulin-like growth factor II (IGF-II) and/or IGF-binding proteins (IGFBPs), which regulate Caco-2 cell proliferation. Cells were incubated in serum-free medium with different concentrations of the individual CLA isomers. t10c12 CLA dose dependently decreased viable cell number (55 +/- 3% reduction 96 h after adding 5 microM t10c12 CLA). t10c12 CLA induced apoptosis and decreased DNA synthesis, whereas c9t11 CLA had no effect. Immunoblot analysis of 24-h serum-free conditioned medium using a monoclonal anti-IGF-II antibody revealed that Caco-2 cells secreted both a mature 7,500 molecular weight (M(r)) IGF-II and higher M(r) forms of IGF-II. The levels of the higher M(r) and the mature form of IGF-II were decreased 50 +/- 3% and 22 +/- 2%, respectively, by 5 microM t10c12 CLA. c9t11 CLA had no effect. Ligand blot analysis of conditioned medium using 125I-labeled IGF-II revealed that t10c12 CLA slightly decreased IGFBP-2 production; c9t11 CLA had no effect. Exogenous IGF-II reversed t10c12 CLA-induced growth inhibition and apoptosis. These results indicate that CLA-inhibited Caco-2 cell growth is caused by t10c12 CLA and may be mediated by decreasing IGF-II secretion in Caco-2 cells.

Apoptosis↗
PubMed1989

Inhibition by linoleic acid hydroperoxide of alveolar macrophage superoxide production: effects upon mitochondrial and plasma membrane potentials.

Linoleic acid hydroperoxide (LOOH) is a naturally occurring product of lipid peroxidation. Incubation of rat alveolar macrophages with LOOH produced alterations of membrane properties and function at concentrations of LOOH as low as 0.1 microM. These included phorbol myristate acetate (PMA)-stimulated superoxide production, mitochondrial membrane potential, and plasma membrane potentials. These effects were clearly separated from gross loss of structural integrity as measured by lactate dehydrogenase release, in terms of both time of incubation and concentration of LOOH. PMA-stimulated superoxide production measured 15 min after addition of 10 microM LOOH was inhibited approximately 50%; however, addition of this concentration of the hydroperoxide after PMA stimulation was without effect. Superoxide production was also measured in a cell-free system produced by incubation of alveolar macrophages with sodium dodecyl sulfate. Prior incubation of alveolar macrophages with LOOH, H2O2, or t-butyl hydroperoxide, under conditions that significantly inhibited superoxide production by the intact cells, did not produce inhibition of the NADPH-dependent superoxide generating system in the cell-free preparation. These results suggest that the effect of LOOH was upon signal transduction involved in the stimulation of superoxide production rather than on the NADPH oxidase itself. Measurements of membrane potential changes were made using the lipophilic ions, 3,3'-dipentyloxacarbocyanine (DiOC5(3] and bis(3-phenyl-5-oxoisoxazol-4-yl)pentamethineoxonol (oxonol V). On the basis of their charge, DiOC5(3) fluorescence primarily reports mitochondrial potential and oxonol V absorbance reports plasma membrane potential. With 10 microM LOOH, depolarization of the plasma and mitochondrial membranes appeared to occur within seconds. As prior depolarization depresses superoxide production, these hydroperoxide-induced changes in membrane potential may be responsible for decreased PMA-stimulated superoxide production.

Animals↗
PubMed2005

Effect of dietary supplementation with conjugated linoleic acid on markers of calcium and bone metabolism in healthy adult men.

INTRODUCTION: Conjugated linoleic acid (CLA) has been shown to positively influence calcium and bone metabolism in experimental animals and cells in culture, but there are limited human data available. OBJECTIVE: To investigate the effect of CLA supplementation on biomarkers of calcium and bone metabolism in healthy adult males. DESIGN: The study consisted of a double-blind, placebo-controlled trial in which 60 healthy adult males (aged 39-64 y) were randomly assigned to receive daily either 3.0 g CLA isomer blend (50:50% cis-9,trans-11:trans-10,cis-12 isomers) or a palm/bean oil blend (placebo) for 8 weeks. Urine and blood samples were collected at weeks 0 and 8 and were analysed for biomarkers of calcium and bone metabolism. RESULTS: Supplementation with CLA or placebo for 8 weeks had no significant effects on markers of bone formation (serum osteocalcin and bone-specific alkaline phosphatase) or bone resorption (serum C-telopeptide-related fraction of type 1 collagen degradation products, urinary N-telopeptide-related fraction of type 1 collagen degradation products, urinary pyridinoline and deoxypyridinoline), or on serum or urinary calcium levels. Baseline levels of these biochemical parameters were similar in both groups of subjects. While the placebo had no effect, CLA supplementation resulted in a three-fold increase (P<0.00001) in cis-9,trans-11 CLA isomer in total plasma lipids. CONCLUSION: Under the conditions tested in this double-blind, placebo-controlled trial in adult men, a CLA supplement of mixed isomers did not affect markers of calcium or bone metabolism. Further investigation of the effects of CLA on calcium and bone metabolism in other gender- and age-groups is warranted.

Adult↗
PubMed2001

Dietary conjugated linoleic acids and lipid source alter fatty acid composition of juvenile yellow perch, Perca flavescens.

A study was conducted to examine the effects of dietary conjugated linoleic acids (CLA; 0, 0.5 or 1.0 g/100 g total CLA) and lipid source (menhaden oil, soybean oil or a 1:1 mixture of menhaden:soybean oil) on growth rates and fatty acid composition of yellow perch. Dietary treatments were fed to apparent satiation to triplicate groups of fish initially weighing 37.9 g/fish. At the end of the 9-wk feeding trial, no significant differences were detected in weight gain or feed intake among fish fed any of the dietary treatments. Dietary CLA, lipid source and/or their interaction significantly affected feed efficiency, total liver lipid concentration, and muscle and liver fatty acid concentrations. Feed efficiency (g gain/g feed) was significantly lower in fish fed diets containing soybean oil (0.51) compared with fish fed menhaden oil (0.58) or menhaden:soybean oil (0.60). Liver total lipid concentrations were significantly reduced in fish fed 0.5 and 1.0 g/100 g CLA compared with fish fed the diets containing no CLA and in fish fed menhaden oil compared with those fed soybean oil or a 1:1 mixture of menhaden:soybean oil. Total CLA levels increased in both liver and muscle as dietary CLA concentration increased, irrespective of lipid source. However, total CLA concentrations were significantly lower in liver and muscle of fish fed soybean oil. Total muscle CLA concentrations were 0, 1.26 and 2.92 g/100 g fatty acids in fish fed diets containing menhaden oil and 0, 0.5 and 1.0 g/100 g CLA, respectively. Mono- and polyunsaturated fatty acid (PUFA) concentrations were significantly lower in muscle and liver of fish fed CLA compared with fish fed the diets containing no CLA. In contrast, liver concentrations of saturated fatty acids, 14:0, 16:0 and 18:0, were significantly higher in fish fed 1.0 g/100 g CLA.

Animals↗
PubMed1975

Autoxidation in milk rich in linoleic acid. I. An objective method of measuring autoxidation and evaluating antioxidants.

Autoxidation was studied in milk obtained from cows fed on formaldehyde-treated casein-safflower oil supplement. The fat of this milk contained high levels of linoleic acid. A rapid disappearance of dissolved oxygen (DO), measured by using a oxygen electrode, from milk samples stored at 0 degrees C in tubes without head-space, coincided with the development of oxidized flavours detected organoleptically. A correlation coefficient of 0.9 with 69 degrees of freedom (P smaller than 0.001) was obtained between the amount of DO disappearing and the taste panel scores for oxidized flavours. Butylated hydroxyanisole, sesamol, nordihydroguaiaretic acid, ethoxyquin, or butylated hydroxyanisole with propylgallate or tocopherols, when added in emulsified form to the milk at the rate of 10-15 mg/l milk checked the development of oxidized flavours and the rapid disappearance of DO. Other antioxidants tested were either ineffective or imparted off-flavours to milk. Samples of mare's milk neither developed oxidized flavours nor showed rapid disappearance of DO over a test period of 8 d. The oxygen electrode provides a convenient and sensitive method for studying autoxidation and evaluating antioxidants in milk.

Animals↗
PubMed1986

Inhibition of rabbit platelet activation by lipoxygenase products of arachidonic and linoleic acid.

The hydroperoxy fatty acids, 15-hydroperoxyeicosatetraenoic acid (15-HPETE), 13-hydroperoxy and 9-hydroperoxyoctadecadienoic acid (13- and 9-HPODE) and the corresponding hydroxy compounds (15-HETE and 13-HODE) were synthesized and purified. Washed rabbit platelets were incubated with these fatty acid derivatives before aggregation was induced. Arachidonic acid-induced aggregation, as well as the secretion of ATP and the formation of thromboxane B2 (TXB2) were dose-dependently inhibited by these compounds. Low thrombin-, collagen- and ADP-induced aggregations were also suppressed by 15-HPETE. Platelet activation induced by the calcium ionophore A23187 and by high thrombin concentrations were not affected by 15-HPETE. In addition, doses of 15-HPETE which were inactive by themselves, potentiated the anti-aggregating activity of prostacyclin (PGI2). It is suggested that the hydroperoxy and hydroxy compounds suppress platelet activation by interference with the rise in cytoplasmic calcium in addition to the inhibition of cyclo-oxygenase.

Adenosine Triphosphate↗
PubMed2006

Trans-10, trans-12 conjugated linoleic acid does not affect milk fat yield but reduces delta9-desaturase index in dairy cows.

Trans-10, cis-12 conjugated linoleic acid (CLA) is a potent inhibitor of milk fat synthesis, and the magnitude of milk fat depression is often correlated with the fat content of this isomer. However, the trans-10, cis-12 CLA content does not always correspond to the extent of milk fat depression, and in some instances, an increase in the milk fat content of trans-10, trans-12 CLA has been observed. We synthesized trans-10, trans-12 CLA (>90% purity) and investigated its effect on milk fat synthesis and incorporation into plasma lipids. Three rumen-fistulated Holstein cows were randomly assigned in a 3 x 3 Latin square experiment. Treatments were a 4-d abomasal infusion of 1) ethanol (control), 2) a trans-10, cis-12 CLA supplement (positive control), and 3) a trans-10, trans-12 CLA supplement; 5 g/d of the CLA isomer of interest was provided. Milk yield, dry matter intake, and milk protein were unaffected by treatment. Treatment with trans-10, trans-12 CLA had no effect on milk fat yield, whereas treatment with trans-10, cis-12 CLA reduced milk fat yield by 28%. Incorporation of CLA was greatest for the plasma triglyceride fraction, and the milk fat content was subsequently elevated within the respective treatment groups. The milk fatty acid composition indicated that delta9-desaturase was reduced significantly for both CLA treatments, but the reduction was greater for the treatment with trans-10, trans-12 CLA. Overall, abomasal infusion of trans-10, trans-12 CLA and trans-10, cis-12 CLA altered the desaturase ratios, but only trans-10, cis-12 CLA reduced milk fat synthesis.

Abomasum↗
PubMed2004

Dietary conjugated linoleic acid positively affects immunologic variables in lactating sows and piglets.

We studied the effects of conjugated linoleic acid (CLA) on metabolic and immunologic variables in lactating sows and piglets. Gestating sows (n = 16) were assigned to 1 of 2 weight- and parity-matched groups supplemented with 0% (C) or 0.5% (T) of a CLA preparation containing 50% CLA isomers. Supplementation started in late pregnancy and continued throughout lactation. At weaning, 80 piglets, half from each group of sows, were assigned to 0% CLA (C) or 0.5% CLA (T). Thus, there were four groups of 20 piglets: C-C, C-T, T-T, and T-C. Body weight and the number of piglets per litter at birth and weaning, and the chemical composition of colostrum did not differ among the groups. CLA affected the fatty acid composition of colostrum fat; palmitoleic and gamma-linolenic acid were significantly lower compared with controls, whereas eicosenoic and eicosatrienoic acids were significantly higher. Feeding CLA increased (P < 0.05) colostrum IgG in sows. Sows fed CLA had higher (P < 0.05) serum leptin, IgG, and lysozyme. Nursing piglets from CLA-fed sows had significantly higher (P < 0.01) serum lysozyme and IgG. Consumption of CLA did not affect postweaning growth. Postweaning piglets fed CLA (T-T, C-T) had a higher IgG titer at 25 d (P < 0.05) and 35 d (P < 0.01) after weaning. Serum lysozyme was also higher at 25 d (P < 0.05) in CLA-fed piglets (T-T, C-T). At 35 d, serum alpha-1 acylglicoprotein was lower (P < 0.05) in piglets fed CLA. Dietary CLA had a positive effect on immunologic variables in lactating sows and piglets.

Animals↗