linoleic-acid and trans-10-cis-12-conjugated-linoleic-acid

Evidence from animal studies suggests that conjugated linoleic acid (CLA) modulates plasma and tissue appearance of newly synthesized PUFA. The effects of a 1.2g (0.5 % energy) daily intake of the cis-9,trans-11 (c9,t11) isomer of CLA, trans-10,cis-12 (t10,c12) isomer of CLA or olive oil (placebo) on linoleic acid (LA) and linolenic acid (LNA) metabolism in healthy human volunteers was investigated. Fifteen subjects were fed an experimental diet and supplemented with c9,t11-CLA, t10,c12-CLA or placebo for 7 d before consuming a tracer dose of U-[(13)C]LA (50 mg) and U-[(13)C]LNA (50 mg). Blood samples were taken at 0, 2, 4, 6, 8, 24, 48, 72 and 168 h and analysed using high-precision MS. No differences between the groups in peak plasma [(13)C]LA (10.3-11.6 % of dose), [(13)C]LNA (2.5-2.9 % of dose), [(13)C]arachidonic acid (0.09-0.12 % of dose), [(13)C]EPA (0.04-0.06 % of dose) or [(13)C]DHA (0.06-0.10 % of dose) were detected. Concentration v. time curves (area under the curve) also showed no significant differences between groups. This suggests that, in healthy human subjects consuming a diet with adequate intake of essential fatty acids, CLA does not affect metabolism of LA or LNA.

Topics: Adolescent; Adult; alpha-Linolenic Acid; Carbon Isotopes; Cholesterol Esters; Diet; Dietary Supplements; Female; Humans; Linoleic Acid; Linoleic Acids, Conjugated; Male; Middle Aged; Olive Oil; Plant Oils; Triglycerides

The objective of this study consisting of 2 trials was to investigate the antioxidant role of conjugated linoleic acid (CLA) isomers (c9, t11-CLA and t10, c12-CLA) and the underlying mechanism by which they act in modulating redox status in a primary laying hen hepatocyte culture. In trial 1, the cytotoxicity of CLA isomers or linoleic acid (LA) (0, 25, 50, 100, 200, 400, 800 μmol/L) was evaluated by 3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide (MTT) assay. The concentration of CLA isomers or LA (25, 50, 100 μmol/L) for proper antioxidant activity was evaluated by measuring the antioxidant enzyme activity. In trial 2, there were 5 groups: control group, cells were untreated; H2O2 group, cells were exposed to 4 mmol/L H2O2 for 2 h; c9, t11 or t10, c12 or LA group, cells were treated with c9, t11-CLA or t10, c12-CLA or LA for 24 h and then exposed to 4 mmol/L H2O2 for 2 h. Trial 1 showed that the non-toxic dose range for CLA isomers was 0 to 200 μmol/L. The optimum concentration of c9, t11-CLA and t10, c12-CLA for trial 2 was 100 μmol/L. In trial 2, pretreatment with t10, c12-CLA but not c9, t11-CLA attenuated the increase in reactive oxygen species (ROS) compared to hydrogen peroxide (H2O2) group (P < 0.05). t10, c12-CLA elevated the superoxide dismutase (SOD) and catalase (CAT) activities compared with the H2O2 group (P < 0.05). In addition, t10, c12-CLA up-regulated the mRNA expression of nuclear factor E2-related factor-2 (Nrf2) as well as its target genes, Cu-Zn superoxide dismutase (SOD1) and CAT (P < 0.05). Pretreatment with t10, c12-CLA but not c9, t11-CLA decreased Nrf2 protein expression in the cytoplasm and increased Nrf2 protein expression in the nucleus compared with the H2O2 group (P < 0.05). The results indicate that t10, c12-CLA exhibits a stronger antioxidant capacity than c9, t11-CLA in primary cultured laying hen hepatocytes. t10, c12-CLA increases the activity and mRNA expression of antioxidant enzymes via facilitating nuclear translocation of Nrf2.

Topics: Animal Feed; Animals; Antioxidants; Cells, Cultured; Chickens; Diet; Dietary Supplements; Dose-Response Relationship, Drug; Female; Hepatocytes; Linoleic Acid; Linoleic Acids, Conjugated

To study the effects of trans-10,cis-12 conjugated linoleic acid (CLA) on liver size and composition, as well as on hepatic lipogenesis and fatty acid oxidation, in adult hamsters.. Sixteen male Syrian Golden hamsters (8-month-old; initial body weight 167 +/- 5 g) were divided into two groups and fed on atherogenic diets supplemented either with 0.5% linoleic acid or trans-10,cis-12 CLA, for 6 weeks. Liver lipids, fatty acid profile, protein, water and DNA contents were analysed. The activity and expression of several enzymes involved in liver fatty oxidation and lipogenesis were assessed, as was the expression of transcriptional factors controlling these enzymes.. The addition of CLA to the diet led to significantly greater liver weight due to hyperplasia. No changes were observed in liver composition. CLA did not modify the expression or the activity of analysed oxidative enzymes. With regard to lipogenic enzymes, an increase in the expression and the activity of acetyl-CoA carboxylase was found.. These results show that the expected body fat-lowering effect of trans-10,cis-12 CLA, observed in young rodents, is not found in adult hamsters. The lack of increase in liver fatty acid oxidation, help to explain why that effect was not found in these animals. Further, the CLA treatment-induced hepatomegaly is a consequence of hyperplasia.

Topics: Acetyl-CoA Carboxylase; Age Factors; Animals; Cricetinae; Diet, Atherogenic; Dietary Fats; Fatty Liver; Hepatomegaly; Hyperplasia; Linoleic Acid; Linoleic Acids, Conjugated; Lipid Metabolism; Liver; Male; Mesocricetus; Organ Size; Oxidoreductases

Atherosclerosis is characterized by extensive thickening of the arterial intima partially resulting from deposition of collagen by vascular smooth muscle cells (SMCs). Polyunsaturated fatty acids stimulate collagen formation through NF-kappaB activation.. The present study aimed to explore the effect of conjugated linoleic acids (CLAs) which are known to inhibit NF-kappaB activation on collagen formation by SMCs.. Vascular SMCs were cultured with 50 micromol/l of CLA isomers (c9t11-CLA, t10c12-CLA) or linoleic acid (LA) and analysed for collagen formation and NF-kappaB p50 transactivation.. Treatment with CLA isomers but not LA significantly reduced PDGF-stimulated [(3)H] proline incorporation into cell layer protein of SMCs without altering cell proliferation. Simultaneous treatment with the PPARgamma inhibitor T0070907 abrogated this effect. Treatment of SMCs with c9t11-CLA and t10c12-CLA significantly reduced PDGF-induced NF-kappaB p50 activation.. CLA isomers inhibit PDGF-stimulated collagen production by vascular SMCs, which is considered to be a hallmark of atherosclerosis, in a PPARgamma-dependent manner. Whether inhibition of the NF-kappaB-pathway is of significance for the reduction of collagen formation by CLA isomers needs further investigation.

Topics: Analysis of Variance; Atherosclerosis; Benzamides; Cell Division; Cell Survival; Cells, Cultured; Collagen; Humans; Isomerism; Linoleic Acid; Linoleic Acids, Conjugated; Muscle, Smooth, Vascular; NF-kappa B; Platelet-Derived Growth Factor; PPAR gamma; Pyridines

The linoleic acid isomerase enzyme from Propionibacterium acnes responsible for bioconversion of linoleic acid to trans-10, cis-12 conjugated linoleic acid (t10, c12 CLA) was cloned and overexpressed in Lactococcus lactis and Escherichia coli, resulting in between 30 and 50 % conversion rates of the substrate linoleic acid to t10, c12 CLA. The anti-proliferative activities of the fatty acids produced following isomerization of linoleic acid by L. lactis and E. coli were assessed using the human SW480 colon cancer cell line. Fatty acids generated from both L. lactis and E. coli contained a mixture of linoleic acid and t10, c12 CLA at a ratio of approximately 1.35 : 1. Following 5 days of incubation of SW480 cells with 5-20 microg ml(-1) (17.8-71.3 microM) of the t10, c12 CLA, there was a significant (P<0.001) reduction in growth of the SW480 cancer cells compared with the linoleic acid control. Cell viability after treatment with the highest concentration (20 microg ml(-1)) of the t10, c12 CLA was reduced to 7.9 % (L. lactis CLA) and 19.6 % (E. coli CLA), compared with 95.4 % (control linoleic acid) and 31.7 % (pure t10, c12 CLA). In conclusion, this is believed to represent the first report in which recombinant strains are capable of producing CLA with an anti-proliferative potential.

Topics: Antineoplastic Agents; Biotransformation; Cell Line, Tumor; Cell Proliferation; Cloning, Molecular; Escherichia coli; Gene Expression; Growth Inhibitors; Humans; Isomerases; Lactococcus lactis; Linoleic Acid; Linoleic Acids, Conjugated; Propionibacterium acnes; Recombinant Proteins

While conjugated linoleic acid (CLA) has received a great deal of attention as a supplement that can favourably modify body composition, its potential impact on insulin sensitivity has not received equal attention. The aim of the present work was to analyse the effects of trans-10,cis-12 CLA isomer on insulin sensitivity in hamsters fed an atherogenic diet. Hamsters were divided into three groups: one group was fed a chow diet (control) and the other two a semipurified atherogenic diet supplemented with 0.5% linoleic acid (LA) or trans-10,cis-12 CLA, respectively. Serum glucose, FFAs, insulin, leptin and adiponectin were measured using commercial kits. HOMA-IR was calculated using the formula of Matthews et al. PPARgamma mRNA was assessed in epididymal adipose tissue by reverse transcription-polymerase chain reaction (RT-PCR). After 6 weeks, atherogenic feeding produced an increase in body fat accumulation as compared with control feeding. The addition of trans-10,cis-12 CLA to the atherogenic diet avoided this feature. Atherogenic feeding also led to significantly higher serum concentrations of glucose, insulin, FFAs, as well as greater HOMA-IR values. trans-10,cis-12 CLA did not prevent these effects. No significant differences were found among experimental groups in serum leptin and adiponectin concentrations, nor in PPARgamma expression. In summary, although the addition of trans-10,cis-12 CLA to an atherogenic diet reduces fat accumulation, it does not improve the impairment of insulin action associated with this feeding. The maintenance of insulin resistance in hamsters fed the atherogenic CLA-enriched diet is probably due to the high serum FFA concentration observed in these animals.

Topics: Adiponectin; Adipose Tissue; Adiposity; Animals; Blood Glucose; Cricetinae; Diet; Diet, Atherogenic; Dietary Fats, Unsaturated; Epididymis; Fatty Acids, Nonesterified; Insulin; Insulin Resistance; Leptin; Linoleic Acid; Linoleic Acids, Conjugated; Male; Mesocricetus; PPAR gamma; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger

Conjugated linoleic acids (CLA) have attracted scientific interest due to their potential beneficial effects on atherosclerosis. Recently, a mixture of CLA isomers was demonstrated to upregulate LDL receptor expression in the human hepatoma cell line HepG2. However, the underlying mechanisms remain to be resolved. Thus, the aim of this study was to elucidate how CLA mediates upregulation of LDL receptor in HepG2 cells and whether this upregulation is isomer-specific. The results revealed that LDL receptor promoter activity and mRNA expression were strongly induced upon treatment with t10c12-CLA (P<0.05), whereas c9t11-CLA and linoleic acid (LA) had no effect. In addition, only treatment with t10c12-CLA markedly induced mRNA expression of SREBP-2 and HMG-CoA reductase and slightly induced that of SREBP-1 (P<0.05). Using SREBP-2 knockdown cells, we could demonstrate that the effect of t10c12-CLA on LDL receptor gene transcription was significantly reduced when compared to control cells (P<0.05). When using SREBP-1 knockdown cells the effect of t10c12-CLA on LDL receptor mRNA only slightly decreased compared to control cells. In addition, using different deletion constructs of the LDL receptor gene promoter we showed that the induction of the LDL receptor by t10c12-CLA is independent of the AP-1 motif in the LDL receptor promoter. In conclusion, the present study revealed that transcriptional activation of the LDL receptor gene by t10c12-CLA is dependent on the upregulation of SREBP-2 and is probably due to the activation of the SRE-1 in the LDL receptor gene promoter in HepG2 cells. Thus, the decreased plasma cholesterol levels in response to CLA as observed in a limited number of animal and human studies might be explained by an enhanced uptake of VLDL and LDL cholesterol via hepatic LDL receptors. However, it provides no explanation for the outcome of most human studies reporting unaltered or even increased plasma and LDL cholesterol concentrations in response to supplementation with CLA.

Topics: Cell Line, Tumor; Cholesterol; Humans; Hydroxymethylglutaryl CoA Reductases; Linoleic Acid; Linoleic Acids, Conjugated; Promoter Regions, Genetic; Receptors, LDL; RNA, Messenger; Signal Transduction; Sterol Regulatory Element Binding Protein 1; Sterol Regulatory Element Binding Protein 2; Transcription Factor AP-1; Up-Regulation

Conjugated linoleic acids (CLA) affect atherogenesis, but mechanisms are not well understood. We explored how two isomers of CLA, cis9, trans11-CLA and trans10, cis12-CLA, affected lipid and glucose metabolism, as well as hepatic protein expression, in apolipoprotein E knockout mice. After 12 wk of intervention, plasma triglyceride, NEFA, and glucose concentrations were significantly higher in the trans10, cis12-CLA group, whereas plasma triglyceride, NEFA, glucose, and insulin concentrations were significantly lower in the cis9, trans11-CLA group, compared with control mice consuming linoleic acid. Proteomics identified significant up- or down-regulation of 113 liver cytosolic proteins by either CLA isomer. Principal component analysis revealed that the treatment effect of cis9, trans11-CLA was mainly explained by the up-regulation of different posttranslational forms of heat shock protein 70 kD. In contrast, the treatment effect of trans10, cis12-CLA was mainly explained by up-regulation of key enzymes in the gluconeogenic, beta-oxidation, and ketogenesic pathways. Correlation analysis again emphasized the divergent effects of both CLA isomers on different pathways, but also revealed a linkage between insulin resistance and increased levels of hepatic serotransferrin. Thus, our systems biology approach provided novel insights into the mechanisms by which individual CLA isomers differentially affect pathways related to atherogenesis, such as insulin resistance and inflammation.

Topics: Animal Feed; Animals; Apolipoproteins E; Atherosclerosis; Blood Glucose; Blotting, Western; Body Composition; Body Weight; Cytosol; Diet; Fatty Acids; Genetic Linkage; Glucose; HSP70 Heat-Shock Proteins; Inflammation; Insulin; Insulin Resistance; Linoleic Acid; Linoleic Acids, Conjugated; Liver; Male; Mice; Mice, Knockout; Oxygen; Perfusion; Principal Component Analysis; Proteomics; Systems Biology; Triglycerides

Interaction of eosinophils and bronchial epithelial cells plays a pivotal role in maintaining inflammatory airway disease. Since conjugated linoleic acids (CLA) are suggested to exert anti-inflammatory effects, one purpose of this study was to compare cis-9,trans-11-CLA and trans-10,cis-12-CLA with regard to their influence on the stimulus-induced activation of eosinophils. ECP (eosinophil cationic protein) released in co-culture of stimulated and CLA-treated eosinophils with stimulated bronchial epithelial cells (BEAS-2B) was measured and cis-9,trans-11-CLA was found to be most potent in inhibiting ECP formation. Further, expression of the activation markers CD69 and CD13 induced by various stimuli (TNF-alpha, IL-5, IL-3) was significantly reduced in the presence of cis-9,trans-11-CLA. Subsequently, various concentrations of cis-9,trans-11-CLA vs. linoleic acid (LA, cis-9,cis-12-octadecadienoic acid) were tested for the effect on proliferative response and release of the pro-inflammatory cytokine IL-8 in stimulated BEAS-2B. Addition of cis-9,trans-11-CLA attenuated cell growth and significantly reduced IL-8 production at mRNA and protein levels. In contrast, LA had a slight stimulating effect on proliferation and was less effective in reducing the cytokine release. It was demonstrated that the inhibitory effect of cis-9,trans-11-CLA on IL-8 production is mediated through activation of the nuclear receptor PPARgamma, since blocking the receptor with a selective antagonist (GW9662) restored the stimulus-induced enhancement in IL-8 mRNA expression and protein secretion. PPARgamma has previously been shown to be closely involved in the downregulation of inflammation during hyperresponsiveness related to pulmonary immune responses. Thus, targeting PPARgamma, cis-9,trans-11-CLA might be of therapeutic value in the focus of airway disease while ameliorating inflammatory processes by affecting epithelial and eosinophil functions.

Topics: Anti-Inflammatory Agents, Non-Steroidal; Antigens, CD; Antigens, Differentiation, T-Lymphocyte; Base Sequence; Bronchi; CD13 Antigens; Cell Line; Cell Proliferation; Eosinophil Cationic Protein; Eosinophils; Epithelial Cells; Humans; Interleukin-8; Lectins, C-Type; Linoleic Acid; Linoleic Acids, Conjugated; RNA, Messenger; Stereoisomerism