Body Compositional Changes and Growth Alteration in Chicks from Hens Fed Conjugated Linoleic Acid

Effects of feeding conjugated linoleic acid (CLA) to hens on progeny chick development and composition at hatch (NHC) and three weeks of age (TWC) were assessed. CLA (0 or 0.5%, composed of mixed isomers of cis-9,trans-11 or trans-10,cis-12-CLA) was fed to hens with either safflower (SO) or olive oil (OO) (3 or 3.5%) to assure successful hatch for 2 weeks prior to collection for incubation. Maternal CLA feeding had no effect on hatchability, but improved egg fertility (p < 0.05). Maternal feeding of CLA with SO increased 21 day-old progeny growth, while CLA with OO decreased growth (oil*CLA, p < 0.05). In 25 day-old chicks (TWC), but not NHC, maternal CLA decreased the proportion of total body water (p < 0.05) and increased body ash (p < 0.05). While monounsaturated fatty acids were decreased and saturated fatty acids increased in eggs and NHC from hens fed CLA, no differences in fatty acid composition were observed in chicks at 25 days of age from hens fed CLA. Maternal CLA feeding resulted in the presence of c9,t11 and t10,c12-CLA in NHC, but only c9,t11 in the TWC. In conclusion, hens fed CLA led to improved fertility and altered body composition at 3 weeks of age.     

High Dose trans-10,cis-12 CLA Increases Lean Body Mass in Hamsters, but Elevates Levels of Plasma Lipids and Liver Enzyme Biomarkers

The current study examined the efficacy of graded doses of c9,t11 and t10,c12 CLA isomers on body composition, energy expenditure, hepatic and serum lipid liver biomarkers in hamsters. Animals (n = 105) were randomized to seven treatments (control, 1, 2, 3% of c9,t11; 1, 2, 3% of t10,c12) for 28 days. After 28 days treatment, 1–3% of t10,c12 lowered (p < 0.05) body fat mass compared to the control group. The 1–3% t10,c12 and 3% c9,t11 fed groups showed higher (p < 0.05) lean mass compared to other groups. We observed unfavorable changes in plasma total cholesterol and non-HDL cholesterol levels in animals fed with 3% t10,c12 CLA isomers. The 2%, 3% t10,c12 groups presented elevated (p < 0.05) ALT levels. The present data suggest that a diet enriched with more than 2% t10, c12 led to liver malfunction and poses unfavorable changes on plasma lipid profiles. The 1% t10,c12 CLA lowered (p < 0.05) body fat mass and increased (p < 0.05) lean body mass. The c9,t11 CLA has less potent actions than t10,c12 CLA. We conclude that the actions of CLA on energy and lipid metabolism are form and dose dependent in the hamster model.     

Modulation of arachidonic acid distribution by conjugated linoleic acid isomers and linoleic acid in MCF-7 and SW480 cancer cells

The relationship between growth and alterations in arachidonic acid (AA) metabolism in human breast (MCF-7) and colon (SW480) cancer cells was studied. Four different fatty acid preparations were evaluated: a mixture of conjugated linoleic acid (CLA) isomers (c9,t11, t10,c12, c11,t13, and minor amounts of other isomers), the pure c9,t11-CLA isomer, the pure t10,c12-CLA isomer, and linoleic acid (LA) (all at a lipid concentration of 16 microg/mL). 14C-AA uptake into the monoglyceride fraction of MCF-7 cells was significantly increased following 24 h incubation with the CLA mixture (P < 0.05) and c9,t11-CLA (P < 0.02). In contrast to the MCF-7 cells, 14C-AA uptake into the triglyceride fraction of the SW480 cells was increased while uptake into the phospholipids was reduced following treatment with the CLA mixture (P < 0.02) and c9,t11-CLA (P < 0.05). Distribution of 14C-AA among phospholipid classes was altered by CLA treatments in both cell lines. The c9,t11-CLA isomer decreased (P < 0.05) uptake of 14C-AA into phosphatidylcholine while increasing (P < 0.05) uptake into phosphatidylethanolamine in both cell lines. Both the CLA mixture and the t10,c12-CLA isomer increased (P < 0.01) uptake of 14C-AA into phosphatidylserine in the SW480 cells but had no effect on this phospholipid in the MCF-7 cells. Release of 14C-AA derivatives was not altered by CLA treatments but was increased (P < 0.05) by LA in the SW480 cell line. The CLA mixture of isomers and c9,t11-CLA isomer inhibited 14C-AA conversion to 14C-prostaglandin E2 (PGE2) by 20-30% (P < 0.05) while increasing 14C-PGF2alpha by 17-44% relative to controls in both cell lines. LA significantly (P < 0.05) increased 14C-PGD2 by 13-19% in both cell lines and increased 14C-PGE2 by 20% in the SW480 cell line only. LA significantly (P < 0.05) increased 5-hydroperoxyeicosatetraenoate by 27% in the MCF-7 cell line. Lipid peroxidation, as determined by increased levels of 8-epi-prostaglandin F2alpha (8-epi-PGF2alpha), was observed following treatment with c9,t11-CLA isomer in both cell lines (P < 0.02) and with t10,c12-CLA isomer in the MCF-7 cell line only (P < 0.05). These data indicate that the growth-promoting effects of LA in the SW480 cell line may be associated with enhanced conversion of AA to PGE2 but that the growth-suppressing effects of CLA isomers in both cell lines may be due to changes in AA distribution among cellular lipids and an altered prostaglandin profile.     

Responses of MAC‐T Cells to Inhibited Stearoyl‐CoA Desaturase 1 during cis‐9, trans‐11 Conjugated Linoleic Acid Synthesis

Cis‐9‐conjugated, trans‐11‐conjugated linoleic acid (CLA) is known for its positive activities on human health. The synthesis of cis‐9, trans‐11 CLA in mammary glands is generally thought to be catalyzed by stearoyl‐CoA desaturase 1 (SCD1), but this has not been rigorously established. In this study, we hypothesized that the inhibition of SCD1 (by CAY10566) would block the synthesis of cis‐9, trans‐11 CLA in bovine mammary alveolar cells (MAC‐T) cells. Results showed that MAC‐T cells incubated with 10 nM CAY10566 for 12 h (CAY) produced less cis‐9, trans‐11 CLA (p < 0.01), lower 14:1/(14:1 + 14:0)% (p < 0.01), more trans‐11 18:1 (TVA) accumulation (p < 0.01), and reduced SCD1 mRNA levels (p < 0.01) compared with the control group (CON). Moreover, the mRNA abundances of sterol regulatory element‐binding protein 1 [SREBPF1], acyl‐CoA synthetase short‐chain family member 2 [ACSS2], and lipin 1 [LPIN1] were significantly elevated when SCD1 was inhibited in the CAY group (p < 0.05). Taken together, CAY10566 inhibition of SCD1 resulted in lower cis‐9, trans‐11 CLA synthesis ability, and SREBF1, ACSSS2, and LPIN1 were negatively associated with SCD1. These findings not only provide the direct evidence that cis‐9, trans‐11 CLA synthesis is catalyzed by SCD1, but also help us understand the responses of MAC‐T cells to SCD1 inhibition.     

trans-10,cis-12 Conjugated Linoleic Acid Improved Growth Performance, Reduced Lipid Deposition and Influenced CPT I Kinetic Constants of Juvenile Synechogobius hasta

trans-10,cis-12 (t10c12) Conjugated linoleic acid (CLA) reduced body lipid deposition in various experimental animals, but the mechanisms involved were still emerging. Carnitine palmitoyltransferase I (CPT I) catalyzes an important regulatory step in lipid metabolism. At present, no studies, to our knowledge, have evaluated the kinetic constants influenced by dietary CLA in fish. In the present study, we tested the hypothesis that changes in body lipid content in fish as a response to dietary t10c12 CLA was related to the change of CPT I kinetic constants [Michaelis constant (K _m), maximal velocity and catalytic efficiency for carnitine and palmitoyl-CoA]. Juvenile Synechogobius hasta were fed three experimental diets with fish oil replaced with 0 (control), 1, or 2 % t10c12 CLA for 8 weeks. Weight gain, specific growth rate and protein efficiency rate increased with dietary t10c12 CLA level. Dietary t10c12 CLA addition significantly reduced lipid contents both in liver and muscle. Dietary CLA addition also improved CPT I activities in muscle but did not significantly influence hepatic CPT I activity. CPT I kinetic parameters (K _m, V _max and catalytic efficiency) were significantly influenced by t10c12 CLA. CPT I catalytic efficiencies with carnitine and palmitoyl-CoA as substrates were higher in muscle and liver of fish fed increasing t10c12 CLA. For the first time, the findings demonstrated effect of dietary CLA addition on CPT I kinetics in fish and supported our starting hypothesis that dietary t10c12 CLA addition induced alterations in CPT I kinetic constants of muscle and liver. Increased CPT I catalytic efficiency might be the main reason for reduced lipid deposition in these tissues by dietary t10c12 CLA supplementation.     

Quantitative determination of conjugated linoleic acid isomers in beef fat

The amounts of 14 conjugated linoleic acid (CLA) isomers (t12t14, t11t13, t10t12, t9t11, t8t10, t7t9, t6t8; 12,14 c/t, t11c13, c11t13, t10c12, 9,11 c/t, t8c10, t7c9‐18:2) in 20 beef samples were determined by triple‐column silver‐ion high‐performance liquid chromatography (Ag⁺‐HPLC). Quantitation was performed using an external CLA reference standard consisting of cis9,trans11‐18:2,trans9,trans11‐18:2 and cis9,cis11‐18: 2. Linearity was checked as being r > 0.9999 between 0.02 × 10^‐3 to 2 mg/ml. The determination limit (5‐fold signal/noise ratio) of the CLA reference was estimated to be 0.25, 0.50, 1.0 ng/injection for the cis/trans, trans,trans and cis,cis isomers, respectively. As expected, cis9,trans11‐18:2 was the predominant isomer (1.95 ± 0.54 mg/g fat) in beef, followed by trans7,cis9‐18:2 (0.19 ± 0.04 mg/g fat); cis,cis isomers were below the determination limit in most beef samples. Total CLA amounts determined by Ag⁺‐HPLC were compared to total CLAs determined by gas chromatography (GC, 100 m CPSil^TM 88 column). The amounts obtained by GC were generally higher than those determined by Ag⁺ ‐HPLC due to co‐eluting compounds.     

Effect of <Emphasis Type="Italic">trans</Emphasis>8, <Emphasis Type="Italic">cis</Emphasis>10+<Emphasis Type="Italic">cis</Emphasis>9, <Emphasis Type="Italic">trans</Emphasis>11 Conjugated Linoleic Acid Mixture on Lipid Metabolism in 3T3-L1 Cells

Evidence suggests that minor isomers of conjugated linoleic acid (CLA), such as trans8, cis10 CLA, can elicit unique biological effects of their own. In order to determine the effect of a mixture of t8, c10+c9, t11 CLA isomers on selected aspects of lipid metabolism, 3T3-L1 preadipocytes were differentiated for 8 days in the presence of 100 μM linoleic acid (LA); t8, c10+c9, t11 CLA; t10, c12+c9, t11 CLA or purified c9, t11 CLA. Whereas supplementation with c9, t11 and t10, c12+c9, t11 CLA resulted in cellular triglyceride (TG) concentrations of 3.4 ± 0.26 and 1.3 ± 0.11 μg TG/μg protein, respectively (P < 0.05), TG accumulation following treatment with CLA mixture t8, c10+c9, t11 was significantly intermediate (2.5 ± 0.22 μg TG/μg protein, P < 0.05) between the two other CLA treatments. However, these effects were not attributable to an alteration of the Δ⁹ desaturation index. Adiponectin content of adipocytes treated with t8, c10+c9, t11 mixture was similar to the individual isomer c9, t11 CLA, and both the t8, c10+c9, t11 and c9, t11 CLA groups were greater (P < 0.05) than in the t10, c12+c9, t11 CLA group. Overall, these results suggest that t8, c10+c9, t11 CLA mixture affects TG accumulation in 3T3-L1 cells differently from the c9, t11 and t10, c12 isomers. Furthermore, the reductions in TG accumulation occur without adversely affecting the adiponectin content of these cells.     

Synthesis and Structural Analysis of Structured Triacylglycerols with CLA Isomers in the <Emphasis Type="Italic">sn</Emphasis>-2- Position

The present research deals with the chemical esterification of the sn-2- position of sn-1,3-diacylglycerol (sn-1,3-DAG) with 9cis,11trans (c9,t11) and 10trans,12cis (t10,c12) conjugated linoleic acid (CLA) isomers to obtain structured triacylglycerols (TAG); the sn-1,3-DAG substrates were produced from extra virgin olive oil by means of enzymatic reactions while CLA isomers were obtained using a three-step procedure based on alkaline hydrolysis of sunflower oil, urea purification of linoleic acid (LA) and alkaline isomerization of LA. The results showed good levels of CLA incorporation in structured TAG at the tested temperatures: 37.5% at 4 °C and 39.1% at 14 °C. To evaluate the incorporation of CLA isomers in sn-2- position of sn-1,3-DAG structural analysis of the newly synthesized TAG was carried out using an enzymatic and a chemical method. The results of the structural analysis also showed up the occurrence of acyl migration. The pancreatic lipase method allowed the direct determination of the fatty acid composition of TAG sn-2- position but this enzymatic method showed different results (p < 0.05) in respect to the chemical one; this occurrence could be due to an acylic specificity of the lipase. High incorporation of CLA isomers in sn-2- position of TAG was observed, 77.0% at 4 °C and 81.5% at 14 °C, considering the results of the chemical procedure.     

Conjugated Linoleic Acids and CLA-Containing Phospholipids Inhibit NO Formation in Aortic Endothelial Cells

This study examined the effects of five CLA isomers and the non-conjugated LA on nitric oxide (NO) production, an important modulator of vasodilation, inflammation, and cytotoxicity. Bovine aortic endothelial cells (BAECs) were pretreated with pure CLAs (c9, c11-, c9, t11-, t9, t11-, t10, c12-, c11, c13-CLA) and the non-conjugated c9, c12-analog, then stimulated by the ionophore A23187 followed by fluorescence monitoring of NO production. CLAs (5 μM) decreased NO formation in the range of 20–40% relative to non-fatty acid-treated controls with the t9, t11- and t10, c12-CLAs being the most effective. The inhibitory effect of either of these CLAs was not time dependent over a 120 min time interval. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) play crucial roles in membrane structure and cell signaling. Since CLAs are usually esterified in these phospholipids (PLs), the effects of three CLA-containing PLs and 2-linoleoyl-PC on NO production by A23187-stimulated BAECs were also examined. c9, t11-CLA-PC and 2-linoleoyl-PC dose-dependently inhibited NO production over a 60–1,000 μM concentration range whereas c9, c11-CLA-PC and c9, t11-CLA-PE were ineffective. Both c9, t11-CLA-PC and linoleoyl-PC exhibited a time-dependent decrease in NO production from 5 to 120 min. The results of the present study suggest that the influence of several C18 polyunsaturated fatty acids incorporated into cellular phospholipids on the A23187-induced formation of NO by BAECs is strongly dependent on the positional and geometric nature of the double bonds.     

Conjugated Linoleic Acid Isomers Trans‐10, Cis‐12 and Cis‐9, Trans‐11 Prevent Collagen‐Induced Arthritis in a Direct Comparison

Mixed‐isomer conjugated linoleic acid (CLA) and the individual isomers, trans‐10, cis‐12 (CLAt10c12) and cis‐9, trans‐11 (CLAc9t11), decrease severity of collagen‐induced arthritis (CA) when consumed after disease onset. Few studies have been conducted exploring the role of CLA in the prevention of autoimmune diseases. These studies suggest that isomer‐specific effects may be occurring; however, a direct comparison of CLAt10c12 and CLAc9t11 has yet to be conducted. A study to compare the ability of CLAt10c12 and CLAc9t11 to prevent CA and assess their effects on early inflammation was performed. DBA/1 mice were fed a semipurified diet containing 6% corn oil (CO), 5.5% CO and 0.5% CLAt10c12, or 5.5% CO and 0.5% CLAc9t11 (n = 27 per diet) starting three weeks before CA primary immunization. Effects on disease incidence and severity, anticollagen antibodies, plasma and paw cytokines, and hepatic fatty acids were measured. Arthritis incidence was reduced by a minimum of 34% in mice fed either CLA isomer compared to those fed CO diet (p = 0.06). In mice that did develop arthritis (n = 9–12 mice per treatment), CLAt10c12 reduced arthritic severity to a greater extent than CLAc9t11 and CO (p = 0.03). CLA isomer treatment attenuated the increased hepatic arachidonic acid (ARA; 20:4n‐6) observed with arthritis at one‐week postonset (p = 0.03), while no differences in anticollagen antibodies or cytokines were observed between dietary treatments. These results suggest that CLA isomers may be effective at preventing specific immune‐mediated inflammatory diseases, in part, through modulation of the ARA cascade.     

Physical Properties of Two Isomers of Conjugated Linoleic Acid

Thermal properties, powder X-ray diffraction patterns and FT-IR absorption spectra of crystals of two isomers of conjugated linoleic acid (CLA), 9-cis, 11-trans-CLA (c9t11), 10-trans, 12-cis-CLA (t10c12) were examined. To search for polymorphic modifications, we carefully performed crystallization from melt and solution phases, and isolated one type of crystalline form in c9t11 and t10c12. The melting temperature (T _m) was 14.9 °C, enthalpy of fusion (ΔH) was 38.7 kJ/mol, and entropy of fusion (ΔS) was 134 J/mol K for c9t11, and T _m = 19.8 °C, ΔH = 35.6 kJ/mol and ΔS = 122 J/mol K for t10c12. The X-ray diffraction and FT-IR measurements indicated O_⊥ subcell packing in the crystals of c9t11 and t10c12, and long spacing values of 4.22 nm for c9t11 and 3.88 nm for t10c12. The unique molecular structures of the two isomers of CLA are discussed in comparison to the polymorphism of oleic acid, petroselinic acid, elaidic acid and linoleic acid, all of which are unsaturated fatty acids having the same carbon number of 18 as that of the two CLA isomers.     

Proteomic Analysis Reveals PGAM1 Altering cis‐9, trans‐11 Conjugated Linoleic Acid Synthesis in Bovine Mammary Gland

cis‐9, trans‐11 Conjugated linoleic acid (CLA) is one of the most extensively studied CLA isomers due to its multiple isomer‐specific effects. However, the molecular mechanisms of cis‐9,trans‐11 CLA synthesis in ruminant mammary gland are still not clearly understood. This process may be mediated, to a certain extent, by trans‐11 C18:1 regulated by stearoyl‐CoA desaturase‐1 (SCD1) and/or its syntrophic proteins. This study aimed to investigate the effects of TVA on SCD1‐mediated cis‐9,trans‐11 CLA synthesis in MAC‐T cells and its potential molecular mechanism. Results showed that trans‐11 C18:1 was continually taken up and converted into cis‐9,trans‐11 CLA in MAC‐T cells during the 4‐h incubation of 50 μM trans‐11 C18:1. SCD1 protein expression increased more than twofold at 2 h (P < 0.01) and 2.5 h (P < 0.05) before decreasing to less than half of the normal level at 4 h (P < 0.05). One up‐regulated (RAS guanyl releasing protein 4 isoform 1 [RASGRP4]) and six down‐regulated proteins (glucosamine‐6‐phosphate deaminase 1 [GNPDA1], triosephosphate isomerase [TPI1], phosphoglycerate mutase 1 [PGAM1], heat shock protein beta‐1 [HSPB1], annexin A3 [ANXA3], thiopurine S‐methyltransferase [TPMT]) were found in MAC‐T cells treated with trans‐11 C18:1. Of these seven identified proteins, the presence of GNPDA1 and PGAM1 was verified in several models. More trans‐11 C18:1 was taken up after PGAM1 knockdown by small interfering RNA (siRNA). In conclusion, our data suggested that PGAM1 may have a negative relationship with SCD1 and seemed to be involved in cis‐9, trans‐11 CLA synthesis by facilitating the absorption of trans‐11 C18:1 in the bovine mammary gland.     

Comparison of reactive sites of different conjugated linoleic acid molecules by quantum chemical calculations

In this paper, quantum chemical calculations and Gaussian 09 software were used to investigate the similarities and differences in the reactive sites of different fatty acids. The molecule structures of linoleic acid (LA) and four conjugated linoleic acid (CLA) were analyzed at the level of density functional theory. Molecular geometries and energies, frontline molecular orbitals, and surface electrostatic potentials were also analyzed. The results showed that the reactive of LA and CLA among the five fatty acids were all near the –C = C– structure and the carboxyl hydrogen atom, 9c, 11t CLA and 10t, 12c CLA were more reactive compared with 9t, 11t CLA, 10t, 12t CLA. This study can provide a theoretical basis for revealing the relationship between different structures and properties of fatty acids and also provide a guidance for the selection of fatty acids in the oil and fat industry. Practical Applications: This experiment compares the differences between the reactive sites of CLA and the four CLAs at the molecular structure level, which can be used to deepen the understanding of the structure-property relationship of different fatty acids and also provides a theoretical basis for the selection of fatty acids in the food and oil industry.     

Conjugated Linoleic Acid Isomers, t10c12 and c9t11, are Differentially Incorporated into Adipose Tissue and Skeletal Muscle in Humans

Conjugated linoleic acid (CLA) is a popular supplement believed to enhance immune function, body composition and insulin sensitivity, but results of scientific studies investigating its effects are conflicting. The isomer- and tissue-specific effects of CLA may explain these conflicting results. Therefore, this study quantified the incorporation of the c9t11 and t10c12 CLA isomers into adipose tissue and skeletal muscle in response to supplementation in healthy, regularly-exercising, non-obese persons. The CLA group (n = 14) ingested 3.9 g per day CLA (50:50 t9c11:c10t12) and the placebo group (n = 11) 3.9 g per day high-oleic-acid sunflower oil for 12 weeks. Following supplementation, the t10c12 isomer was incorporated into adipose tissue triacylglycerol (P < 0.001), and the c9t11 isomer tended to increase in skeletal muscle phospholipids (P = 0.056). Therefore, human adipose tissue and skeletal muscle are enriched with CLA in an isomer-specific manner.     

Conjugated linoleic acids (CLA) as precursors of a distinct family of PUFA

One of the possibilities for distinct actions of c9,t11- and the t10,c12-conjugated linoleic acid (CLA) isomers may be at the level of metabolism since the conjugated diene structure gives to CLA isomers and their metabolites a distinct pattern of incorporation into the lipid fraction and metabolism. In fact, CLA appears to undergo similar transformations as linoleic acid but with subtle isomer differences, which may account for their activity in lowering linoleic acid metabolites in those tissues rich in neutral lipids where CLA is preferentially incorporated. Furthermore, c9,t11 and t10,c12 isomers are metabolized at a different rate in the peroxisomes, where the shortened metabolite from t10,c12 is formed at a much higher proportion than the metabolite from c9,t11. This may account for the lower accumulation of t10,c12 isomer into cell lipids. CLA isomers may therefore be viewed as a “new” family of polyunsaturated fatty acids (PUFA) producing a distinct range of metabolites using the same enzymatic system as the other (i.e., n−3, n−6 and n−9) PUFA families. It is likely that perturbation of PUFA metabolism by CLA will have an impact on eicosanoid formation and metabolism, closely linked to the biological activities attributed to CLA.     

Effects of trans‐10,cis‐12 and cis‐9,trans‐11 CLA on atherosclerosis in apoE/LDLR−/− mice

The objective of our studies was to verify the potential health‐related, anti‐atherogenic potency of CLA isomers, fed to apolipoprotein E and LDL receptor double knockout mice (apoE/LDLR^?/?), representing a reliable model of atherogenesis. Additionally, the effect of CLA isomers on liver steatosis was observed. In a “long experiment” (LONG), 2‐month‐old mice with no atherosclerosis were randomly assigned to three experimental groups and fed for the next 4 months. In a “short experiment” (SHORT), 4‐month‐old mice, with pre‐established atherosclerosis, were randomly assigned to three experimental groups and fed for the next 2 months. The experimental diets were: AIN‐93G (control), AIN‐93G + 0.5% trans‐10,cis‐12 CLA (t10,c12), and AIN‐93G + 0.5% cis9,trans‐11 CLA (c9,t11). In both experiments, c9,t11 CLA increased mice body weight. In mice fed t10,c12 CLA weight of liver was threefold (p<0.05) increased what was linked with hepatic steatosis observed in LONG and SHORT experiment. In LONG experiment, t10,c12 CLA significantly (p<0.05) increased plasma TAGs, whereas no such effect was observed in SHORT one. In mice receiving the CLA isomers the level of PPARα and SREBP‐1 mRNA in liver were significantly decreased. The expression of their target genes like ACO (PPARα) or FAS (SREBP‐1) were not changed. Only c9,t11 increased ACO level in LONG experiment. There were no isomer‐specific effects of CLA isomers on the area of atherosclerotic plaque. In conclusion, our results do not support the notion that CLA isomers supplementation to the diet has anti‐atherosclerotic effects. CLA isomers have no effect on atherosclerosis in apoE/LDLR^?/? mice. Practical applications: CLAs have been shown to occur naturally in food. In the last 10 years, attempts have been made to enrich animal‐derived foods in CLA isomers through animal nutrition strategies. Indeed, these attempts resulted in production of functional food such as CLA‐enriched milk (butter and cheese), ruminant and non‐ruminant meat, as well as eggs. In addition to natural foodstuff, dietary CLA supplements can also contribute to CLA intake in humans. Commercial CLA preparations, fed to laboratory animals, showed several health‐related properties, including anti‐adipogenic, anti‐carcinogenic, anti‐atherogenic, and anti‐inflammatory effects. The underlying mechanisms of action, however, are only poorly understood. The major objective of our studies was to verify the potential health‐related, namely anti‐atherogenic potency of CLA isomers, fed to apoE/LDLR^?/? mice, representing unique and reliable model of atherogenesis. Additionally, effect of CLA isomers on steatosis was observed.     

Oxidation kinetics for <Emphasis Type="Italic">cis</Emphasis>-9,<Emphasis Type="Italic">trans</Emphasis>-11 and <Emphasis Type="Italic">trans</Emphasis>-10,<Emphasis Type="Italic">cis</Emphasis>-12 isomers of CLA

The autoxidation processes of the cis-9,trans-11 (c9,t11) and trans-10,cis-12 (t10,c12) isomers of CLA were separately observed at ca. 0% RH and different temperatures. The t10,c12 CLA oxidized faster than the c9,t11 isomer at all tested temperatures. The first half of the oxidation process of t10,c12 CLA obeyed an autocatalytic-type rate expression, but the latter half followed first-order kinetics. On the other hand, the entire oxidation process of c9,t11 CLA could be expressed by the autocatalytic-type rate expression. The apparent activation energies and frequency factors for the autoxidation of the isomers were estimated from the rate constants obtained at various temperatures based on the Arrhenius equation. The apparent activation energies for the CLA isomers were greater than those for the nonconjugated n−6 and n−3 PUFA or their esters. However, the enthalpyentropy compensation held during the autoxidation of both the CLA and PUFA. This suggested that the autoxidation mechanisms for the CLA and PUFA were essentially the same.