trans-10,cis-12-conjugated linoleic acid isomer exhibits stronger oxyradical scavenging capacity than cis-9,trans-11-conjugated linoleic acid isomer

Comparative analysis of the seasonal influence on polyphenolic content, antioxidant capacity, identification of bioactive constituents and hepatoprotective biomarkers by in silico docking analysis in Premna integrifolia L

The present study reports the effect of different seasons on polyphenol content and antioxidant potential of ethanolic, methanolic, ethyl acetate, and aqueous extracts of leaves, stems, and roots of Premna integrifolia. Ethyl acetate extract of leaves (EAEPI) collected in the rainy season showed potent antioxidant activity with highest total phenol (74.33 ± 2.26 µg/mg, gallic acid equivalent), and flavonoid (98.83 ± 0.26 µg/mg, rutin equivalent) content. Therefore, EAEPI extract was subjected to characterization by UHPLC-Q-TOF-MS/MS and GC-MS analysis for the identification of active constituents. UHPLC-Q-TOF-MS/MS analysis in + ve ion mode revealed the presence of eight polyphenolic compounds namely quercetin-3-D-xyloside, kaempferol-3,7-O-bis-alpha-L-rhamnoside, isorhamnetin-3-Oglucoside, luteolin-3',7-di-O-glucoside, eriodictyol-7-O-glucoside, syringetin-3-O-galactoside, petunidin-3-O-beta-glucopyranoside and vitexin-2″-O-rhamnoside. GC-MS analysis confirmed the presence of 26 compounds with six major compounds viz; citronellol, phytol acetate, campesterol, squalene, stigmasterol, and hexadecanoic acid. These compounds are reported for the first time from P. integrifolia except phytol and stigmasterol. Our previous study validates the hepatoprotective potential of P. integrifolia but there was no idea about the bioactive compound responsible for the activity. So, in present work, the major compounds identified in spectrometry analysis were subjected to in silico docking against an important liver enzyme alanine amino transaminase to confirm its hepatoprotective properties. Docking analysis validates the presence of two hepatoprotective lead compounds stigmasterol, and campesterol, which satisfy the drug-likeness criteria with good absorption, distribution, metabolism, and toxicity properties. Thus, present work gives a clear insight about the influence of season on the total polyphenolic constituent in different plant parts of P. integrifolia, their antioxidant potential and preclinical evaluation of hepatoprotective lead compounds.

Effect of CLA supplementation on factors related to vascular dysfunction in arteries of orchidectomized rats

The vascular endothelium is a monolayer of flat epithelial cells located between the circulating blood and the underlying connective tissue. It conveys key functions that when impaired, lead to endothelial dysfunction. This condition is responsible for the pathogenesis of vascular diseases. The cardioprotective effect of sex hormones is widely known; hence, a murine orchidectomized model has been employed to study the effects caused by their deficiency. In the search for approaches to maintain vascular health, the effect of dietary fatty acids as CLA on cardiovascular diseases has been studied. Some proven beneficial properties of CLA are antioxidant, antiatherogenic and anti-inflammatory. Our objective was to evaluate the effect of a diet supplemented with 1.8 % (w/w) of CLA, administered during eight weeks, on the amount of cholesterol oxidation products (COPs) produced by orchidectomy and on factors related to vascular dysfunction in the aorta and the mesenteric arteries. The diet with CLA prevented the increase in prostanoids formation and maintained the normal physiological conditions of NO and antioxidant activity. In addition, it prevented the increase in cholesterol and COPs at the vascular wall. CLA-supplemented diet prevented the orchidectomy-induced alterations on prostanoids, NO and COPs and also improved the antioxidant activity. These findings could contribute to understand the mechanisms of actions of CLA involved in the prevention of cardiovascular diseases.

Dietary conjugated linoleic acid supplementation alters skeletal muscle mitochondria and antioxidant status in young horses

Conjugated linoleic acid (CLA) improves oxidative stress and mitochondrial biogenesis in various species but has not been thoroughly investigated in horses. We collected blood and muscle samples from lightly exercising horses before and 6 and 12 wk after receiving either soybean oil (CON; n = 5) or CLA (CLA; n = 5) supplementation. Samples were analyzed for markers of mitochondrial characteristics, antioxidant status, oxidative stress, and muscle damage. Data were analyzed using a linear model with repeated measures. In the triceps brachii (TB), citrate synthase (CS) activity was higher in CON than CLA horses (P = 0.003) but was unaffected by diet in the gluteus medius (GM). Integrative (relative to mg protein) cytochrome c oxidase (CCO) activity was higher in TB than the GM (P < 0.0001), while intrinsic (relative to CS) CCO was lower in the TB than the GM (P = 0.02) and tended to be lower in CON than CLA horses (P = 0.06). Neither CS nor integrative CCO activities were affected by time. In the GM, superoxide dismutase activity tended to increase in CON through week 12 (P = 0.10). Over both muscle groups, glutathione peroxidase activity tended to be higher in CON compared with CLA at week 12 (P = 0.06). Malondialdehyde was higher in the TB than the GM (P = 0.0004) but was unaffected by diet, while serum creatine kinase activity tended to be lower in CLA than CON horses (P = 0.07). These results suggest that CLA supplementation may lead to mitochondrial adaptations and prevent myofiber perturbation in skeletal muscle of young, lightly exercised horses.

Effect of conjugated linoleic acids and omega-3 fatty acids with or without resistance training on muscle mass in high-fat diet-fed middle-aged mice

NEW FINDINGS

What is the central question of this study? This study examined the effects of 20 weeks of administration of conjugated linoleic acids/omega-3 fatty acids with or without programed resistance exercise training on body composition, skeletal muscle properties and functional capacity in middle-aged mice fed a high-fat diet. What is the main finding and its importance? Chronic daily administration of conjugated linoleic acids/omega-3 fatty acids with resistance exercise training can help to blunt fat gain, alleviate loss of myogenic capacity and sensorimotor function and lower tissue inflammation in middle-aged mice during chronic high-fat diet-induced catabolism. This study investigated the effects of 20 weeks of combined conjugated linoleic acid (CLA)/omega-3 fatty acid (n-3) administration independently or combined with resistance exercise training (RET) on skeletal muscle in middle-aged mice consuming a high-fat diet (HFD). Nine-month-old C57BL/6 mice were randomly assigned into four experimental groups (H, high-fat diet; HE, H + RET; HCN, H + CLA/n-3; and HECN, H + CLA/n3 + RET). Body composition and functional capacity were assessed pre- and post-intervention. Muscle tissues were collected at 14 months of age. ANOVA was used, with significance set at P ≤ 0.05. Fat mass significantly increased in H (+74%), HE (+142%) and HECN (+43%) but not in HCN. Muscle wet weights were significantly lower in H and HCN than in HE and HECN. Grip strength substantially declined in H (-15%) and HCN (-17%), whereas sensorimotor function significantly declined only in H (-11%). HECN exhibited improvement in strength (+22%) and sensorimotor coordination (+17%). In comparison to H, muscle tumour necrosis factor-α mRNA expression was significantly lower in HE (-39%), HCN (-24%) and HECN (-21%), respectively. Mean myofibre cross-sectional areas were markedly lower in H and HCN than in HE and HECN. H showed significantly lower satellite cell abundance and numbers of myonuclei than all other groups. Our findings suggest that long-term daily CLA/n-3 intake with resistance training improved sensorimotor function, ameliorated fat gain and prevented loss of myogenic capacity while lowering tumour necrosis factor-α expression during chronic HFD.

The effect of conjugated linoleic acid supplements on oxidative and antioxidative status of dairy cows

Dairy cows develop frequently negative energy balance around parturition and in early lactation, resulting in excessive mobilization of body fat and subsequently in increased risk of ketosis and other diseases. Dietary conjugated linoleic acid (CLA) supplements are used in dairy cows mainly for their depressing effect on milk fat content, but are also proposed to have antioxidative properties. As negative energy balance is associated with oxidative stress, which is also assumed to contribute to disease development, the present study was conducted to examine effects of CLA on oxidative and antioxidative status of lactating dairy cows. German Holstein cows (primiparous n=13, multiparous n=32) were divided into 3 dietary treatment groups receiving 100g/d of control fat supplement, containing 87% stearic acid (CON; n=14), 50g/d of control fat supplement and 50g/d of CLA supplement (CLA 50; n=15), or 100g/d of CLA supplement (CLA 100; n=16). The CLA supplement was lipid-encapsulated and contained 12% of trans-10,cis-12 CLA and cis-9,trans-11 CLA each. Supplementation took place between d1 and 182 postpartum; d 182 until 252 postpartum served as a depletion period. Blood was sampled at d -21, 1, 21, 70, 105, 140, 182, 224, and 252 relative to calving. The antioxidative status was determined using the ferric-reducing ability of plasma, α-tocopherol, α-tocopherol-to-cholesterol mass ratio, and retinol. For determination of oxidative status concentrations of hydroperoxides, thiobarbituric acid-reactive substances (TBARS), N'-formylkynurenine, and bityrosine were measured. Mixed models of fixed and random effects with repeated measures were used to evaluate period 1 (d -21 to 140) and 2 (d182-252) separately. Cows showed increased oxidative stress and lipid peroxidation during the periparturient period in terms of increased serum concentrations of hydroperoxides and TBARS, which decreased throughout lactation. During period 1, the supplemented cows had lower TBARS concentrations, which was not detectable in period 2. The other determined parameters were not affected by CLA supplementation. The obtained results show that dietary CLA supplementation in the chosen dosage, formulation, and application period had a marginal antioxidative effect in terms of lipid peroxidation in lactating dairy cows.

Effect of conjugated linoleic acid enrichment on the quality characteristics of Turkish dry fermented sausage

The effects of conjugated linoleic acid (CLA) enrichment on lipid oxidation, the fatty acid profile, physico-chemical, sensory and microbiological features of sucuk were investigated. The control sucuk did not contain CLA, however, other groups contained 0.5 %, 1 %, 1.5 %, 2 %, 2.5 %, and 3 % CLA, respectively. The results indicated that CLA concentration was increased in sucuk with CLA addition (p < 0.05). CLA concentration decreased (p < 0.05) during the fermentation period, but did not alter during the storage. Lipid oxidation gradually increased with the increasing of storage in all treatments (p < 0.05). However, addition of CLA decreased lipid oxidation compared to control (p < 0.05). With regard to color, higher L* values were observed in 2 % CLA treatment group compared to other treatments during storage (p < 0.05). Moreover, CLA addition resulted in increased a* values in sucuk (p < 0.05). With the addition of CLA, saturated fatty acids in sucuk decreased and poly-unsaturated fatty acids and conjugated linoleic acids increased (p < 0.05).

Dietary conjugated linoleic acid alters oxidative stability and alleviates plasma cholesterol content in meat of broiler chickens

This study was conducted to investigate the effects of dietary conjugated linoleic acid (CLA) on fatty acid composition, lipoprotein content, lipid peroxidation, and meat colour of broiler chickens. A total of 180 broiler chickens were allocated to 3 dietary treatments (0, 2.5, and 5% Lutrell) and given a standard broiler starter diet and finisher diet. Body weight of chickens and feed intake were recorded weekly. After slaughter, the breast meat was aged at 4 °C for 0, 3, and 6 days. The fatty acid composition was measured in the breast meat. Body weight (BW) and feed efficiency were decreased by dietary CLA level (P < 0.05). Chicken fed with 2.5% Lutrell had the highest feed intake compared to the control (CON) group. The total CLA increased significantly (P < 0.05) in breast meat from birds supplemented with CLA. Propensity for lipid peroxidation was significantly higher after 6 days of meat storage (P < 0.05) and the redness in chicken breast meat was lower in CLA-fed birds (P < 0.05). It is also notable that a 5% Lutrell supplementation decreased the plasma total cholesterol (TC), low density protein (LDL), and HDL (high-density lipoprotein)/LDL ratio in chickens (P < 0.05).

Free radical scavenging activity of conjugated linoleic acid as single or mixed isomers

CONTEXT

Conjugated linoleic acids (CLAs) are a mixture of positional and geometric isomers of linoleic acid (LA) and believed to have many positive biological activities.

OBJECTIVE

The present study was undertaken to assess the antioxidant activity of cis-9, trans-11 and trans-10, cis-12 as single or mixed CLA isomers at two ratios, 1:6 and 1:13 (trans-10, cis-12/cis-9, trans-11).

MATERIALS AND METHODS

A microplate reader was used to determine the free radical scavenging properties of CLAs against DPPH radical in ethanol.

RESULTS

The kinetic reactions of CLA-DPPH(•) showed that all tested CLAs have exerted radical scavenging activities in a dose-dependent manner and observed to immediately react and quench DPPH radicals at all tested levels and no lag phase was noticed in CLA-DPPH(•) reactions. The median inhibitory concentration (IC₅₀) value for cis-9, trans-11 CLA was observed to be more effective than other tested CLA. Total antioxidant capacity (TAC) of all tested CLAs were less effective radical scavengers as compared to vitamin E and butylated hydroxytoluene, although all tested CLAs were quenched a high amount (P < 0.05) of DPPH free radicals.

DISCUSSION AND CONCLUSION

All tested CLAs have the ability to directly react and quench DPPH free radicals in ethanol. Furthermore, trans-10, cis-12 CLA has greater maximal efficacy than other tested CLAs as free radical scavenger, while cis-9, trans-11 CLA is the most potent isomer to directly react and quench free radicals at low concentrations in the system, suggesting that the free radical scavenging activity of CLA isomers may contribute to their diverse biological activities.

Optimization of sunflower oil transesterification process using sodium methoxide

In this study, the methanolysis process of sunflower oil was investigated to get high methyl esters (biodiesel) content using sodium methoxide. To reach to the best process conditions, central composite design (CCD) through response surface methodology (RSM) was employed. The optimal conditions predicted were the reaction time of 60 min, an excess stoichiometric amount of alcohol to oil ratio of 25%w/w and the catalyst content of 0.5%w/w, which lead to the highest methyl ester content (100%w/w). The methyl ester content of the mixture from gas chromatography analysis (GC) was compared to that of optimum point. Results, confirmed that there was no significant difference between the fatty acid methyl ester content of sunflower oil produced under the optimized condition and the experimental value (P ≥ 0.05). Furthermore, some fuel specifications of the resultant biodiesel were tested according to American standards for testing of materials (ASTM) methods. The outcome showed that the methyl ester mixture produced from the optimized condition met nearly most of the important biodiesel specifications recommended in ASTM D 6751 requirements. Thus, the sunflower oil methyl esters resulted from this study could be a suitable alternative for petrol diesels.

Effect of antioxidants on soy oil conjugated linoleic acid production and its oxidative stability

Conjugated linoleic acid (CLA)-rich soy oil can be produced by photoisomerization of soy oil linoleic acid to produce a soy oil with up to 20% CLA. Recent studies indicate that mixed soy tocopherols added to refined bleached deodorized (RBD) oil produced significant increase in soy CLA yield during soy oil linoleic acid photoisomerization. However, the effect of common synthetic free radical scavenging antioxidants and specific tocopherols on CLA yield and its oxidative stability is not known. Therefore, this investigation evaluated the effects of various antioxidant systems on soy oil CLA yield and oxidative stability. Soy oil with added antioxidants consisting of combinations of mixed tocopherols (MT), ascorbyl palmitate (AP), butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ) was photoisomerized to produce CLA- rich soy oil. The CLA content was determined by GC-FID analysis and oxidative stability by peroxide value (PV). The soy oil in the presence of TBHQ, MT alone and MT with 500 ppm of AP produced significantly greater CLA yields and improved oxidative stability compared to a control without added antioxidants (p < 0.05). However, added mixed tocopherols produced the greatest CLA yield and also reduced PV relative to the control. Tocopherols in the form of α-, γ- and δ-tocopherols were then each examined as to their relative effect on CLA yields and PV. The largest increase in CLA yield was obtained with 1800 ppm of γ-tocopherols with reduced PV. Mixed tocopherols, TBHQ and γ-tocopherols can be used to increase CLA yield and reduce PV of soy oil during linoleic acid photoisomerization.

Effect of dietary conjugated linoleic acid supplementation on early inflammatory responses during cutaneous wound healing

Inflammatory response is considered the most important period that regulates the entire healing process. Conjugated linoleic acid (CLA), a class of linoleic acid positional and geometric isomers, is well known for its antioxidant and anti-inflammatory properties. We hypothesized that dietary CLA supplementation accelerates cutaneous wound healing by regulating antioxidant and anti-inflammatory functions. To investigate wound closure rates and inflammatory responses, we used a full-thickness excisional wound model after 2-week treatments with control, 0.5%, or 1% CLA-supplemented diet. Mice fed dietary CLA supplementation had reduced levels of oxidative stress and inflammatory markers. Moreover, the wound closure rate was improved significantly in mice fed a 1% CLA-supplemented diet during early stage of wound healing (inflammatory stage). We conclude that dietary CLA supplementation enhances the early stage of cutaneous wound healing as a result of modulating oxidative stress and inflammatory responses.

Differential effects of conjugated linoleic acid isomers on the biophysical and biochemical properties of model membranes

Conjugated linoleic acids (CLA) are known to exert several isomer-specific biological effects, but their mechanisms of action are unclear. In order to determine whether the physicochemical effects of CLA on membranes play a role in their isomer-specific effects, we synthesized phosphatidylcholines (PCs) with 16:0 at sn-1 position and one of four CLA isomers (trans 10 cis 12 (A), trans 9 trans 11 (B), cis 9 trans 11 (C), and cis 9 cis 11 (D)) at sn-2, and determined their biophysical properties in monolayers and bilayers. The surface areas of the PCs with the two natural CLA (A and C) were similar at all pressures, but they differed significantly in the presence of cholesterol, with PC-A condensing more than PC-C. Liposomes of PC-A similarly showed increased binding of cholesterol compared to PC-C liposomes. PC-A liposomes were less permeable to carboxyfluorescein compared to PC-C liposomes. The PC with two trans double bonds (B) showed the highest affinity to cholesterol and lowest permeability. The two natural CLA-PCs (A and C) stimulated lecithin-cholesterol acyltransferase activity by 2-fold, whereas the unnatural CLA-PCs (B and D) were inhibitory. These results suggest that the differences in the biophysical properties of CLA isomers A and C may partly contribute to the known differences in their biological effects.

Antioxidant activity of conjugated linoleic acid isomers, linoleic acid and its methyl ester determined by photoemission and DPPH techniques

The chemiluminescent response of conjugated linoleic acid isomers (CLAs), linoleic acid (LA) and methyl linoleate (LAME) against the prooxidant t-butyl hydroperoxide (tBHP) was analyzed. The c9, t11-CLA and t10, c12-CLA isomers showed significant photoemission at the highest concentration used, while photoemission was not detected at any concentration of LA and LAME analyzed. These results show that CLAs are more susceptible to peroxidation than LA and LAME. Likewise, the effect of CLA, LA and LAME on lipid peroxidation of triglycerides rich in C20:5 omega3 and C22:6 omega3 (Tg omega3-PUFAs) was investigated. For that, chemiluminescence produced by triglycerides in the presence of tBHP, previously incubated with different concentrations of CLAs, LA and LAME (from 1 to 200 mM) was registered for 60 min. Triglycerides in the presence of t-BHP produced a peak of light emission (3151+/-134 RLUs) 5 min after addition. CLAs produced significant inhibition on photoemission, t10, c12-CLA being more effective than the c9, t11-CLA isomer. LA and LAME did not have an effect on lipid peroxidation of Tg omega3-PUFAs. CLA isomers, LA and LAME were also investigated for free radical scavenging properties against the stable radical (DPPH). Both CLA isomers reacted and quenched DPPH at all tested levels (from 5 to 25 mM), while LA and LAME did not show radical quenching activity even at the highest concentration tested. These data indicate that CLAs would provide protection against free radicals, but LA and LAME cannot.

Effects of water-soluble natural antioxidants on photosensitized oxidation of conjugated linoleic acid in an oil-in-water emulsion system

The effect of photosensitized oxidation of conjugated linoleic acid in an oil-in-water (o/w) emulsion system was studied. Water-soluble natural antioxidants, including apple polyphenols from apple extract, green tea extract, 4-hydroxy-2(or 5)-ethyl-5(or2)-methyl-3(2H)-furanone(HEMF), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF), and ascorbic acid, were tested for antioxidant activity in this system. The green tea extract showed the highest antioxidant activity followed by ascorbic acid. Apple polyphenols did not give significant antioxidant activity. HEMF and HDMF exhibited a prooxidant effect. The antioxidant activity of tea catechins was also investigated. Of them, EGCG and ECG exhibited antioxidant activity at 50 ppm, but the antioxidant activity between them was not significantly different (P < 0.05). Comparatively, EC, EGC, and GCG showed no significant antioxidative effect at 50 ppm. When the concentration increased to 100 ppm, the antioxidant activity of ECG and EGCG significantly increased compared with that at 50 ppm, and EGCG had higher antioxidant activity than ECG. GCG also showed significant antioxidant activity at 100 ppm. EGCG exhibited the highest antioxidant activity among the tea catechins in the emulsion system at 100 ppm.

Concentration-dependent antioxidant activities of conjugated linoleic acid and α-tocopherol in corn oil

BACKGROUND

Antioxidants prevent rancidity (lipid peroxidation) and natural antioxidants, e.g., α-tocopherol, likely provide additional value to oil-based food products because of their health benefits. Conjugated linoleic acid (CLA) has potential health benefits and may exhibit antioxidant properties. The main aim of this study was to compare the antioxidant efficacy of α-tocopherol, trans-10, cis-12-CLA and cis-9, trans-11-CLA (in graded concentrations) added to antioxidant-stripped corn oil.

RESULTS

As compared to α-tocopherol, both CLA isomers displayed significant inhibition of corn oil lipid peroxidation induced by copper. Inhibition of thiobarbituric acid reactive substances (TBARS) were CLA concentration dependent for both isomers but with significant inhibition occurring at 0.1 and 1 ppm of CLA isomers or α-tocopherol, respectively (P < 0.05). Graded concentrations of α-tocopherol, and for both CLA isomers and time, had significant effects on TBARS formation (P < 0.0001). There were significant effects in interactions between graded concentrations and time for both CLA isomers (P < 0.0001) but not for α-tocopherol (P > 0.05).

CONCLUSION

CLA compounds could serve as useful food antioxidants and provide additional value because of their potential bioactivity in disease prevention. Copyright © 2007 Society of Chemical Industry.

Differences in oxidation kinetics between conjugated and non-conjugated methyl linoleate

The oxidation kinetics of conjugated methyl linoleate was compared with that of non-conjugated methyl linoleate under mild oxidation conditions (30 degrees C in the dark). Samples of methyl 9-cis,11-trans-linoleate, methyl 10-trans,12-cis linoleate and methyl 9-cis,12-cis linoleate were assayed separately and in mixtures. For comparative purposes, methyl alpha-linolenate and methyl oleate were also used. Two complementary analytical approaches were selected to monitor the progress of oxidation, (1) the traditional follow-up of residual substrate by gas liquid chromatography, and (2) an analytical procedure by high-performance size-exclusion chromatography (HPSEC) for direct measurement of the oxidation compounds formed. The HPSEC method enabled us to quantitate oxidized monomers, dimers and polymers concomitantly in a rapid and direct analysis. Results showed that conjugated methyl linoleate samples oxidized later than their non-conjugated counterparts, and showed a very different oxidation pattern. Thus, formation of oxidized monomers was negligible and the first and major compounds formed were polymerization products. Also, under the conditions used, non-conjugated and conjugated methyl linoleate samples in 1:1 mixtures led to decreased oxidation rate of non-conjugated methyl linoleate and increased oxidation rate of conjugated methyl linoleate. This study supports the view that oxidation kinetics of conjugated dienes differ substantially from that of methylene-interrupted dienes.

Potentiation of the anti-tumour effect of docetaxel by conjugated linoleic acids (CLAs) in breast cancer cells in vitro

Response rates of tumours to docetaxel (DOCT) are 45-60% in advanced breast cancer but problems associated with side effects, drug resistance and high costs occur. Conjugated linoleic acids (CLAs) also have anti-tumorigenic activity that elicits similar changes in oncogene expression to DOCT and could augment DOCT efficacy. CLA isomers appear to differ in cytotoxicity toward cancer cells. Effects of two CLA isomers on cytotoxicity of DOCT in breast cancer cells (MCF-7; MDA-MB-231) in vitro were assessed. Cells were incubated up to 72 h with 40 microM each of LA or CLA isomers (cis-9, trans-10 CLA, or trans-10, cis-12 CLA) or a 50:50 isomer mix, alone or with DOCT (0-64 microM); a pilot study determined IC(50) and IC(70) concentrations. Treatments were concurrent (CLA and DOCT together) or sequential (CLA then DOCT). MTT assay determined cell viability. Trans-10, cis-12 CLA was the most effective fatty acid (P<0.001) and increased with treatment time. IC(50) and IC(70) concentrations of DOCT were determined, concurrently or sequentially, with and without fatty acids, in the two cell types. Concurrent treatment with trans-10, cis-12 CLA and DOCT augmented inhibition of cell growth in one or both cell lines (decreased IC(50) and IC(70) in MCF-7; P<0.05 but only IC(50) in MDA-MB-231; P<0.05). CLA mix reduced IC(50) and IC(70) in MDA-MB-231 (P<0.001) but not in MCF-7. Cis-9, trans-11 CLA and LA had no effect. Sequential treatment with CLAs then DOCT reduced IC(50) and IC(70) in MCF-7 but not in MDA-MB-231. The latter had increased IC(50) and IC(70) with LA treatment (P<0.05) and increased IC(70) with cis-9, trans-11 CLA (P<0.05) with sequential but not concurrent treatment. Longer pre-incubation times with trans-10, cis-12 CLA (24-72 h) elicited greater reductions in IC(50) and IC(70) in MCF-7 cells. Results show that CLA isomers augment anti-tumour effects of docetaxel in breast cancer cells and suggest possible dual treatment regimens.

Preferential incorporation oftrans,trans-conjugated linoleic acid isomers into the liver of suckling rats

The present study was designed to compare the conjugated linoleic acid (CLA) isomeric distribution pattern in the liver of suckling rats in relation to those in the milk and maternal diet. Silver-ion HPLC was used to separate individual CLA isomers. It was found that the isomeric distribution pattern in the milk was very similar to that in the maternal dietary fat. However, the CLA isomeric distribution patterns in the liver phospholipids (PL) and triacylglycerols were different from those in the diet and milk. In the liver PL, totalcis/transisomers accounted for 63·6–63·9 % of total CLA, which was in contrast to the values of 88·1–89·1 % in the milk and diet. In the liver PL, totaltrans/transisomers were 20·6–20·8 % of the total CLA isomers whereas they were only 2·6–3·7 % in the milk and diet. It is concluded thattrans/trans-CLA were preferentially incorporated into the liver whereas for the incorporation ofcis/trans-CLA there was partial discrimination.

Effects of conjugated linoleic acid (CLA) isomers on oxygen diffusion-concentration products in liposomes and phospholipid solutions

Conjugated linoleic acids (CLAs) are a group of octadecadienoic acids (18:2) that are naturally present in food products and may have beneficial health effects. Liposomes and ethanol solutions were prepared by mixing synthetic phosphatidylcholines (PCs) with c9,t11-CLA, t10,c12-CLA, and linoleic acid (LA) in the sn-2 position into natural PCs from soybean, egg yolk, rat brain, and rat heart at 5 mol %. The oxygen diffusion-concentration products were measured using electron spin resonance spin-label oximetry methods. Individual synthetic PCs, the phospholipid matrix, and the tested lipid systems all exhibited influence on oxygen diffusion-concentration products during lipid peroxidation. Incorporating 5 mol % PC(c9,t11-CLA) into soy and egg yolk PC increased oxygen consumption in liposome suspensions while it was decreased in rat heart and brain PCs. On the other hand, PC(t10,c12-CLA) increased oxygen consumption in mixtures with egg yolk and rat heart PC but decreased it in soybean and rat brain PC. By comparison, PC(LA) decreased oxygen consumption in every case. In ethanol solutions, all of the synthetic PCs suppressed the capacity to generate peroxide radicals in the order of LA > c9,t11-CLA > t10,c12-CLA. In addition, PCs containing individual CLA isomers and LA differed in their capacities to react with and quench DPPH radicals in both ethanol solution and liposome, suggesting differences between CLA isomers and LA in DPPH radical-fatty acid interactions. Incorporation of CLA isomers and LA into dimyristyl-PC reduced the phase transition temperature from 23.6 to 23.1 and 23.3 degrees C, respectively. The results of this study provide evidence that the behavior of CLA isomers differs in the microenvironment of membranes possibly due to structural differences that affect the permeability of membranes to oxygen and lipid peroxidation.

Effects of fatty acids on skeletal muscle cell differentiation in vitro

Previous studies have shown stimulatory effects of linoleic acid (LA, C18:2) on differentiation of rat muscle cells in culture (Allen et al. 1985), but there appears to be little investigation of the effects of other fatty acids. The present study therefore compared the effects of different fatty acids on muscle cell differentiation in vitro. L6 myoblasts were cultured (Dulbecco's Modified Eagles Medium + 10 % fetal calf serum) in six-well plates until 80 % confluent (day 0). Cells were then either harvested or the medium switched to differentiation medium (Dulbecco's Modified Eagles Medium+2 % horse serum), supplemented with fatty acid or drug treatments. Cells were harvested on days 0-5 and assayed for creatine kinase (CK), protein and DNA contents, to give a measure of differentiation (CK/DNA). Initial studies indicated a stimulatory effect of the cis9,trans11 (c9,t11) isomer of conjugated linoleic acid (CLA) relative to control. By contrast, the trans10,cis12 (t10,c12) isomer of CLA inhibited differentiation. Further experiments indicated that inhibition of differentiation by the t10,c12 CLA isomer was dose-dependent (up to 200 microm) and may be via increased cell proliferation. LA and c9,t11 CLA stimulated differentiation at low concentrations (up to 50 microm), but inhibited differentiation at high concentrations (200 microm). In contrast, oleic acid stimulated differentiation at all concentrations, whereas the saturated fatty acid, palmitic acid, had no effect. The mechanism appeared not to involve either peroxisome proliferator-activated receptors alpha or gamma. The data suggest that only unsaturated fatty acids have an effect and the presence or absence of a cis-9 double bond may be important.

Exercise training and the antioxidant alpha-lipoic acid in the treatment of insulin resistance and type 2 diabetes

One hallmark of the insulin-resistant state of prediabetes and overt type 2 diabetes is an impaired ability of insulin to activate glucose transport in skeletal muscle, due to defects in IRS-1-dependent signaling. An emerging body of evidence indicates that one potential factor in the multifactorial etiology of skeletal muscle insulin resistance is oxidative stress, an imbalance between the cellular exposure to an oxidant stress and the cellular antioxidant defenses. Exposure of skeletal muscle to an oxidant stress leads to impaired insulin signaling and subsequently to reduced glucose transport activity. Numerous studies have demonstrated that treatment of insulin-resistant animals and type 2 diabetic humans with antioxidants, including alpha-lipoic acid (ALA), is associated with improvements in skeletal muscle glucose transport activity and whole-body glucose tolerance. An additional intervention that is effective in ameliorating the skeletal muscle insulin resistance of prediabetes and type 2 diabetes is endurance exercise training. Recent investigations have demonstrated that the combination of exercise training and antioxidant treatment using ALA in an animal model of obesity-associated insulin resistance provides a unique interactive effect resulting in a greater improvement in insulin action on skeletal muscle glucose transport than either intervention individually. Moreover, this interactive effect of exercise training and ALA is due in part to improvements in IRS-1-dependent insulin signaling. These studies highlight the effectiveness of combining endurance exercise training and antioxidants in beneficially modulating the molecular defects in insulin action observed in insulin-resistant skeletal muscle.

Effect of heating and processing methods of milk and dairy products on conjugated linoleic acid and trans fatty Acid isomer content

The conventional heating methods of milk did not cause any significant increase in the trans isomer content, with the exception of milk heated at 63 +/- 1.0 degrees C for 30 min and milk microwaved for 5 min, which were significantly increased by 19 and 31%, respectively. The chemical changes of lipids were generally accelerated with the severity of the heat treatment and duration of storage. The conjugated linoleic acid content of cheese heated in a microwave oven for 5 min decreased by 21%, and microwave heating for 10 min caused a decrease of 53% compared with that of freshly boiled cheese.

Contribution of conjugated linoleic acid to the suppression of inflammatory responses through the regulation of the NF-kappaB pathway

Data from a number of researchers have shown that conjugated linoleic acid (CLA) has some beneficial health activities in animal models. Because inflammatory responses are associated with pathophysiology of many diseases, the aim of this study is to explore the effect and mechanism of CLA in the regulation of lipopolysaccharide (LPS)-induced inflammatory responses in RAW 264.7 macrophages. The addition of increasing levels of CLA proportionally augmented the incorporation of CLA in cultures. CLA diminished LPS-induced mRNA and protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX2) as well as subsequent production of nitric oxide and prostaglandin E(2), respectively. We further examined the effect of CLA on LPS-induced NF-kappaB activation by Western blot and the electrophoretic mobility shift assay. The addition of CLA at 200 microM significantly diminished LPS-induced protein expression of the cytoplasmic phosphorylated inhibitor kappaBalpha and nuclear p65 as well as NF-kappaB nuclear protein-DNA binding affinity. In conclusion, our data suggest that CLA may inhibit LPS-induced inflammatory events in RAW 264.7 macrophages and this inhibitory activity of CLA, at least in part, occurs through CLA modulating the NF-kappaB activation and therefore negatively regulating expression of inflammatory mediators.

Effects of lipid-esterified conjugated linoleic acid isomers on platelet function: evidence for stimulation of platelet phospholipase activity

The effects of four conjugated linoleic acid (CLA) isomers on in vitro collagen-induced human platelet aggregation and thromboxane (TXB(2), the inactive metabolite of the proaggregatory TXA(2)) production were examined. As the free fatty acid (FFA), 9t, 11t-CLA was the most effective inhibitor of these two processes (I(50)s of 2.2 and 4 microM, respectively) and the 9c, 11c-CLA was the least effective (I(50)s of 8.3 and 37 microM) of the isomers tested. When platelets were preesterified with either 25 microM 9t, 11t-CLA or 9c, 11c-CLA, CLA incorporation in total platelet lipids increased from 0.24% to 0.31% and 0.38%, and most of this increase was found to be in the phosphatidyl choline and phosphatidyl ethanolamine subclasses. The decrease in arachidonic acid (AA) content in total fatty acids or phospholipids was an order of magnitude greater. Furthermore, no significant differences between platelets prelabeled with either 9t, 11t- or 9c, 11c-CLA in the inhibition of collagen-induced aggregation and TXB(2) formation were observed. However, platelets prelabeled with 9c, 11c-CLA stimulated basal TXB(2) production (4-fold) which was not observed with platelets pretreated with either 9t, 11t-CLA, linoleic acid or stearic acid. This enhancement was associated with a 2.4-5-fold increase in the release of endogenous AA. Our results suggest that the presence of a conjugated cis, cis double bond appears to change the lipid environment sufficiently to stimulate the basal platelet phospholipase activity, which in turn increases the formation of TXB(2).

Isomeric distribution of conjugated linoleic acids (CLA) in the tissues of layer hens fed a CLA diet

The isomeric distribution of conjugated linoleic acids (CLA) in the tissue lipids of hens in relation to that in the diet was examined. Silver-ion high-performance liquid chromatography was used to quantify individual CLA isomers in total tissue lipids, phospholipids, and triacylglycerols. It was found that the deposition of CLA isomers in hen tissues was selective. All tissues including serum, liver, heart, kidney, abdominal fat, and leg and breast muscles had lesser amounts of total cis/trans isomers ranging from 75.87 to 89.13% of total CLA, which was in contrast to the value of 92% of total CLA in the dietary lipids. Total trans/trans isomers in all tissue lipids ranging from 6.11 to 18.02% of total CLA were greater than that in the diet (4.19%). Among the individual trans/trans isomers, all tissues except for adipose tissue and brain incorporated greater amounts of t-12,t-14-18:2, t-11,t-13-18:2,t-10,t-12-18:2, t-9,t-11-18:2, and t-18,t-10-18:2 compared with the values of the diet. Within the cis/trans group, lesser amounts of c-10,t-12/t-10,c-12-18:2 were found to incorporate into all tissues compared with the value of the diet. Serum and liver had higher percentages of c-9,t-11/t-9,c-11, whereas the other tissues had similar levels of this isomer compared with that of the diet. It was also observed that supplementation of CLA in the diet of layer hens decreased the concentration of docosahexaenoic acid (22:6n-3) in all of the tissue lipids. It is concluded that dietary CLA can transfer to the tissue but that incorporation of CLA isomers into the tissue is selective in hens.

Interactions of conjugated linoleic acid and lipoic acid on insulin action in the obese Zucker rat

The fatty acid conjugated linoleic acid (CLA) and the antioxidant R-(+)-alpha-lipoic acid (R-ALA) individually enhance glucose tolerance and insulin action on skeletal muscle glucose transport in the insulin-resistant obese Zucker rat. To date, no study has assessed the potential interactions between these 2 interventions in treating insulin resistance. The present study was designed to determine whether chronic treatment with CLA and R-ALA in combination would enhance skeletal muscle glucose transport to a greater extent than either intervention individually. CLA, R-ALA, or a combination treatment of R-ALA and CLA were administered to female obese Zucker rats for 20 days at low or high doses. Whereas low-dose R-ALA (10 mg/kg body weight) alone did not alter muscle glucose transport, low-dose CLA (0.3 g/kg) induced a significant increase (38%, P <.05) in insulin-mediated glucose transport in epitrochlearis, but not in soleus. Low-dose combination therapy brought about the greatest enhancement of insulin-mediated glucose transport in epitrochlearis (77%) and soleus (54%), with the latter effect being associated with a 50% reduction in protein carbonyls (an index of tissue oxidative stress) and a 33% diminution in muscle triglycerides. High-dose treatments with CLA (1.5 g/kg), R-ALA (50 mg/kg), and the combination of CLA and R-ALA elicited increases in insulin-mediated glucose transport in epitrochlearis (57%, 58%, and 77%) and soleus (32%, 35%, and 54%). However, whereas the individual high-dose treatments with CLA and R-ALA reduced protein carbonyls (63% and 49%) and triglycerides (29% and 28%) in soleus, no further reductions were observed with the high-dose combination treatment groups. These findings support a significant interaction between low doses of CLA and R-ALA for enhancement of insulin action on skeletal muscle glucose transport, possibly via reductions in muscle oxidative stress and in lipid storage.

Antioxidant effect of conjugated linoleic acid and vitamin A during non enzymatic lipid peroxidation of rat liver microsomes and mitochondria

In the study reported here the effect of conjugated linoleic acid (CLA) and vitamin A on the polyunsaturated fatty acid composition, chemiluminescence and peroxidizability index of microsomes and mitochondria isolated from rat liver was analyzed. The effect of CLA on the polyunsaturated fatty acid composition of native microsomes was evidenced by an statistically significant p < 0.007 decrease of linoleic acid C18:2 n6, whereas in mitochondria it was observed a decrease p < 0.0001 of arachidonic acid C20:4 n6 when compared with vitamin A and control groups. Docosahexaenoic acid C22:6 n3 in mitochondria was reduced p < 0.04 in CLA and vitamin A groups when compared with control. After incubation of microsomes or mitochondria in an ascorbate (0.4 mM)-Fe++ (2.15 microM) system (120 min at 37 degrees C) it was observed that the total cpm/mg protein originated from light emission: chemiluminescence was lower in liver microsomes or mitochondria obtained from CLA group (received orally: 12.5 mg/daily during 10 days) than in the vitamin A group (received intraperitoneal injection: daily 0.195 g/ kg during 10 days). CLA reduced significantly maximal induced chemiluminescence in microsomes relative to vitamin A and control groups, whereas in mitochondria the effect was observed relative to control group. The polyunsaturated fatty acid composition of liver microsomes or mitochondria changed by CLA and vitamin A treatment. The polyunsaturated fatty acids mainly affected when microsomes native and peroxidized from control group were compared were linoleic, linolenic and arachidonic acids, while in vitamin A group linoleic and arachidonic acid were mainly peroxidized, whereas in CLA group only arachidonic acid was altered. In mitochondria obtained from the three groups arachidonic acid and docosahexaenoic acid showed a significant decrease when native and peroxidized groups were compared. As a consequence the peroxidizability index, a parameter based on the maximal rate of oxidation of fatty acids, show significant changes in the CLA group compare vitamin A and control groups. The simultaneous analysis of peroxidizability index, chemiluminescence and fatty acid composition demonstrated that CLA is more effective than vitamin A protecting microsomes or mitochondria from peroxidative damage.

Isomer-specific actions of conjugated linoleic acid on muscle glucose transport in the obese Zucker rat

The fatty acid-conjugated linoleic acid (CLA) enhances glucose tolerance and insulin action on skeletal muscle glucose transport in rodent models of insulin resistance. However, no study has directly compared the metabolic effects of the two primary CLA isomers, cis-9,trans-11-CLA (c9,t11-CLA) and trans-10,cis-12-CLA (t10,c12-CLA). Therefore, we assessed the effects of a 50:50 mixture of these two CLA isomers (M-CLA) and of preparations enriched in either c9,t11-CLA (76% enriched) or t10,c12-CLA (90% enriched) on glucose tolerance and insulin-stimulated glucose transport in skeletal muscle of the insulin-resistant obese Zucker (fa/fa) rat. Animals were treated daily by gavage with either vehicle (corn oil), M-CLA, c9,t11-CLA, or t10,c12-CLA (all CLA treatments at 1.5 g total CLA/kg body wt) for 21 consecutive days. During an oral glucose tolerance test, glucose responses were reduced (P < 0.05) by 10 and 16%, respectively, in the M-CLA and t10,c12-CLA animals, respectively, whereas insulin responses were diminished by 21 and 19% in these same groups. There were no significant alterations in these responses in the c9,t11-CLA group. Insulin-mediated glucose transport activity was enhanced by M-CLA treatment in both type I soleus (32%) and type IIb epitrochlearis (58%) muscles and by 36 and 48%, respectively, with t10,c12-CLA. In the soleus, these increases were associated with decreases in protein carbonyls (index of oxidative stress, r = -0.616, P = 0.0038) and intramuscular triglycerides (r = -0.631, P = 0.0028). Treatment with c9,t11-CLA was without effect on these variables. These results suggest that the ability of CLA treatment to improve glucose tolerance and insulin-stimulated glucose transport activity in insulin-resistant skeletal muscle of the obese Zucker rat are associated with a reduction in oxidative stress and muscle lipid levels and can be specifically ascribed to the actions of the t10,c12 isomer. In the obese Zucker rat, the c9,t11 isomer of CLA is metabolically neutral.