Evidence that the trans-10,cis-12 isomer of conjugated linoleic acid induces body composition changes in mice

You are what you ate: the Biosetpoint hypothesis

The current epidemic of obesity has developed at a rate that cannot be attributed to genetic drift. Attempts to treat obesity using diet and activity have been largely disappointing. Genes are fixed at conception, but genetic expression is known to be influenced by nutriture during the stages of growth and development, these occurring in humans from conception through arrival at adulthood. Based on an extrapolation from existing data and cultural models, it is hypothesized that there is a mechanism by which diet and lifestyle habits present during the individual stages of growth and development help to define and program genetic expression in a way that resists change. It is through this mechanism that current nutritional and lifestyle practices have impacted genetic expression and contributed to the rapid development of resistant obesity. The details of the interaction between nutrition, lifestyle and genetic expression during growth must be examined, and intervention strategies devised for early stages of growth to prevent the seeds of obesity from taking root.

Factors affecting conjugated linoleic acid content in milk and meat

Conjugated linoleic acid (CLA) has been recently studied mainly because of its potential in protecting against cancer, atherogenesis, and diabetes. Conjugated linoleic acid (CLA) is a collective term for a series of conjugated dienoic positional and geometrical isomers of linoleic acid, which are found in relative abundance in milk and tissue fat of ruminants compared with other foods. The cis-9, trans-11 isomer is the principle dietary form of CLA found in ruminant products and is produced by partial ruminal biohydrogenation of linoleic acid or by endogenous synthesis in the tissues themselves. The CLA content in milk and meat is affected by several factors, such as animal's breed, age, diet, and management factors related to feed supplements affecting the diet. Conjugated linoleic acid in milk or meat has been shown to be a stable compound under normal cooking and storage conditions. Total CLA content in milk or dairy products ranges from 0.34 to 1.07% of total fat. Total CLA content in raw or processed beef ranges from 0.12 to 0.68% of total fat. It is currently estimated that the average adult consumes only one third to one half of the amount of CLA that has been shown to reduce cancer in animal studies. For this reason, increasing the CLA contents of milk and meat has the potential to raise the nutritive and therapeutic values of dairy products and meat.

Metabolically active functional food ingredients for weight control

The scale of the obesity epidemic creates a pressing consumer need as well as an enormous business opportunity for successful development and marketing of food products with added benefits for weight control. A number of proposed functional food ingredients have been shown to act post-absorptively to influence substrate utilization or thermogenesis. Characteristics and supporting data on conjugated linoleic acid, diglycerides, medium-chain triglycerides, green tea, ephedrine, caffeine, capsaicin and calcium, are reviewed here, giving examples of how these could act to alter energy expenditure or appetite control. Consideration is also given to other factors, in addition to efficacy, which must be satisfied to get such ingredients into foods. We conclude that, for each of the safe, putatively metabolically active agents, there remain gaps in clinical evidence or knowledge of mechanisms, which need to be addressed in order to specify the dietary conditions and food product compositions where these ingredients could be of most benefit for weight control.

Insulin secretion after dietary supplementation with conjugated linoleic acids and n-3 polyunsaturated fatty acids in normal and insulin-resistant mice

Conjugated linoleic acids (CLAs) and n-3 polyunsaturated fatty acids (PUFAs) improve insulin sensitivity in insulin-resistant rodents. However, the effects of these fatty acids on insulin secretion are not known but are of importance to completely understand their influence on glucose homeostasis. We therefore examined islet function after dietary supplementation consisting of 1% CLAs in combination with 1% n-3 enriched PUFAs for 12 wk to mice on a normal diet and to insulin-resistant mice fed a high-fat diet (58% fat). In the mice fed a normal diet, CLA/PUFA supplementation resulted in insulin resistance associated with low plasma adiponectin levels and low body fat content. Intravenous and oral glucose tolerance tests revealed a marked increase in insulin secretion, which nevertheless was insufficient to counteract the insulin resistance, resulting in glucose intolerance. In freshly isolated islets from mice fed the normal diet, both basal and glucose-stimulated insulin secretion were adaptively augmented by CLA/PUFA, and at a high glucose concentration this was accompanied by elevated glucose oxidation. In contrast, in high-fat-fed mice, CLA/PUFA did not significantly affect insulin secretion, insulin resistance, or glucose tolerance. It is concluded that dietary supplementation of CLA/PUFA in mice fed the normal diet augments insulin secretion, partly because of increased islet glucose oxidation, but that this augmentation is insufficient to counterbalance the induction of insulin resistance, resulting in glucose intolerance. Furthermore, the high-fat diet partly prevents the deleterious effects of CLA/PUFA, but this dietary supplementation was not able to counteract high-fat-diet-induced insulin resistance.

Production of trans-10, cis-12 Conjugated Linoleic Acid in Rice

Conjugated linoleic acid (CLA) has anti-carcinogenic and anti-atherosclerosis activity, and modulatory effects on the immune system and lipid metabolism. To produce a transgenic rice plant that can accumulate CLA, a linoleate isomerase gene that can convert linoleic acid to trans-10, cis-12 CLA was introduced and expressed under the control of seed-specific promoters from the oleosin and globulin genes. The fatty acid composition of the transgenic rice grain was analyzed by gas chromatography. Although there was no clear difference in the fatty acid composition between seeds from transformed versus untransformed plants, a peak of trans-10, cis-12 CLA methyl ester, which was not present in seeds from untransformed plants, was found in transformed plants. The trans-10, cis-12 CLA comprised an average of 1.3% (w/w) of the total fatty acids in seeds carrying the oleosin promoter in comparison to 0.01% (w/w) in seeds carrying the globulin promoter. In addition, approximately 70 and 28% of the total amount of the CLA isomer were present in the triacylglycerol and free fatty acid fractions, respectively. These results demonstrate the ability to produce fatty acid components of vegetable oils with novel physiological activities in crops.

Conjugated Linoleic Acid Impairs Endothelial Function

OBJECTIVE

To determine the effect of dietary supplementation with conjugated linoleic acid (CLA) on body mass index (BMI), body fat distribution, endothelial function, and markers of cardiovascular risk.

METHODS AND RESULTS

Forty healthy volunteers with BMI >27 kg/m2 were randomized to receive a CLA isomeric mixture or olive oil in a 12-week double-blind study. Subcutaneous body fat and abdominal/hepatic fat content were assessed using skin-fold thicknesses and computed tomography scanning, respectively. Endothelial function was assessed by brachial artery flow-mediated dilatation (FMD). Plasma isoprostanes were measured as an index of oxidative stress. CLA supplementation did not result in a significant change in BMI index or total body fat. There was a significant decrease in limb (-7.8 mm, P<0.001), but not torso skin-fold thicknesses or abdominal or liver fat content. Brachial artery FMD declined (-1.3%, P=0.013), and plasma F2-isoprostanes increased (+91 pg/mL, P=0.042).

CONCLUSIONS

A CLA isomeric mixture had at most modest effects on adiposity and worsened endothelial function. On the basis of these results, the use of the isomeric mixture of CLA as an aid to weight loss cannot be recommended.

Milk and cheese from cows fed calcium salts of palm and fish oil alone or in combination with soybean products

Twenty cows were used in a randomized block design experiment for 6 wk to determine the influence of feeding partial ruminally inert Ca salts of palm and fish oil (Ca-PFO), alone or in combination with extruded full-fat soybeans or soybean oil, on milk fatty acid (FA) methyl esters composition and consumer acceptability of milk and Cheddar cheese. Cows were fed either a diet containing 44% forage and 56% concentrate (control) or a diet supplemented with 2.7% Ca-PFO (FO), 5% extruded full-fat soybeans + 2.7% Ca-PFO (FOESM), or 0.75% soybean oil + 2.7% Ca-PFO (FOSO). Total dietary FA content in the control, FO, FOESM, and FOSO diets were 4.61, 6.28, 6.77, and 6.62 g/100 g, respectively. There was no difference in nutrient intake, milk yield, or milk composition among treatments. Conjugated linoleic acid (CLA) C(18:2) cis-9, trans-11 isomer, C(18:1) trans-11 (VA), and total n-3 FA in milk from cows on the control, FO, FOESM, and FOSO treatments were 0.56, 1.20, 1.36, and 1.74; 3.29, 4.66, 6.34, and 7.81; 0.62, 0.69, 0.69, and 0.67 g/100 g of FA, respectively. Concentrations of CLA, VA, and total n-3 FA in cheese were similar to milk. A trained sensory panel detected no difference in flavors of milk and cheese, except for acid flavor below a slightly perceptible level in cheese from all treatments. Results suggest that feeding Ca-PFO alone or in combination with extruded full-fat soybeans or soybean oil enhanced the CLA, VA, total unsaturated and n-3 FA in milk and cheese without negatively affecting cow performance and consumer acceptability characteristics of milk and cheese.

Conjugated linoleic acid can prevent tumor necrosis factor gene expression by inhibiting nuclear factor binding activity in peripheral blood mononuclear cells from weaned pigs challenged with lipopolysaccharide

Twenty-four weanling barrows were fed corn-soybean diets supplemented with 2% conjugated linolenic acid (CLA) or soybean oil. On day 14 and 21, pigs were injected intraperitoneally with lipopolysaccharide (LPS) or sterile saline. Plasma samples were collected 2h after injection. Peripheral blood mononuclear cells (PBMC) were also collected on day 21, 2 h after injection to determine tumor necrosis factor-alpha (TNF-alpha) production and its mRNA expression. The results indicate that dietary CLA inhibited the production of TNF-alpha by pig PBMC both at the protein and mRNA expression level. In a second experiment, PBMC, collected from a healthy pig, were incubated with either c9,t11-CLA or t10,c12-CLA, or without CLA and stimulated with LPS. Both CLA isomers inhibited LPS-stimulated TNF-alpha production and expression, which may be partially due to inhibition of the binding activity of nuclear factor-kappaB. The t10,c12 isomer was more effective than the c9,t11-CLA isomer in reducing TNF-alpha levels and nuclear factor-kappaB activation.

Conjugated linoleic acid promotes human adipocyte insulin resistance through NFkappaB-dependent cytokine production

We previously demonstrated that trans-10, cis-12 conjugated linoleic acid (CLA) reduced the triglyceride content of human adipocytes by activating mitogen-activated protein kinase kinase/extracellular signal-related kinase (MEK/ERK) signaling via interleukins (IL) 6 and 8. However, the upstream mechanism is unknown. Here we show that CLA increased (>or=6 h) the secretion of IL-6 and IL-8 in cultures containing both differentiated adipocytes and stromal vascular (SV) cells, non-differentiated SV cells, and adipose tissue explants. CLA isomer-specific induction of IL-6 and tumor necrosis factor-alpha was associated with the activation of nuclear factor kappaB (NFkappaB) as evidenced by 1) phosphorylation of IkappaBalpha, IkappaBalpha kinase, and NFkappaB p65, 2) IkappaBalpha degradation, and 3) nuclear translocation of NFkappaB. Pretreatment with selective NFkappaB inhibitors and the MEK/ERK inhibitor U0126 blocked CLA-mediated IL-6 gene expression. Trans-10, cis-12 CLA suppression of insulin-stimulated glucose uptake at 24 h was associated with decreased total and plasma membrane glucose transporter 4 proteins. Inhibition of NFkappaB activation or depletion of NFkappaB by RNA interference using small interfering NFkappaB p65 attenuated CLA suppression of glucose transporter 4 and peroxisome proliferator-activated receptor gamma proteins and glucose uptake. Collectively, these data demonstrate for the first time that trans-10, cis-12 CLA promotes NFkappaB activation and subsequent induction of IL-6, which are at least in part responsible for trans-10, cis-12 CLA-mediated suppression of peroxisome proliferator-activated receptor gamma target gene expression and insulin sensitivity in mature human adipocytes.

Separation of conjugated linoleic acid isomers by cyclodextrin-modified micellar electrokinetic chromatography

A cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) method was developed for separating conjugated linoleic acid (CLA) isomers. All the seven CLA isomers (9cis,11cis-CLA, 9cis,11trans-CLA, 9trans,11trans-CLA, 10trans,12cis-CLA, 11cis,13cis-CLA, 11cis,13trans-CLA and 11trans,13trans-CLA) were completely separated in the optimized conditions (4% (w/v) beta-cyclodextrin (beta-CD), 54 mM sodium dodecyl sulphate (SDS), 80 mM borate (pH 9.0), 8 M urea, 4% (v/v) ethanol, 30 kV and 15 degrees C). The CD-MEKC method was superior to the gas chromatographic (GC) and silver-ion high-performance liquid chromatographic (Ag(+)-HPLC) methods that were generally used in analyzing CLA isomers.

Dietary coconut oil increases conjugated linoleic acid-induced body fat loss in mice independent of essential fatty acid deficiency

Conjugated linoleic acid (CLA) induces a body fat loss that is enhanced in mice fed coconut oil (CO), which lacks essential fatty acids (EFA). Our objective was to determine if CO enhancement of CLA-induced body fat loss is due to the lack of EFA. The CLA-EFA interaction was tested by feeding CO and fat free (FF) diets for varying times with and without replenishment of individual EFA. Mice fed CO during only the 2-week CLA-feeding period did not differ from control mice in their adipose EFA content but still tended (P=0.06) to be leaner than mice fed soy oil (SO). Mice raised on CO or FF diets and fed CLA were leaner than the SO+CLA-fed mice (P<0.01). Mice raised on CO and then replenished with linoleic, linolenic, or arachidonic acid were leaner when fed CLA than mice raised on SO (P<0.001). Body fat of CO+CLA-fed mice was not affected by EFA addition. In summary, CO-fed mice not lacking in tissue EFA responded more to CLA than SO-fed mice. Also, EFA addition to CO diets did not alter the enhanced response to CLA. Therefore, the increased response to CLA in mice raised on CO or FF diets appears to be independent of a dietary EFA deficiency.

Supplemental safflower oil affects the fatty acid profile, including conjugated linoleic acid, of lamb

The objective of this study was to determine whether increasing levels of dietary safflower oil would alter unsaturated fat (especially CLA) and tocopherol content of lamb, animal performance, carcass characteristics, or color stability of lamb muscle tissue. Targhee x Rambouillet wethers (n = 60) were assigned to one of three diets (four pens per treatment with five lambs per pen) in a completely random design. Diets were formulated with supplemental safflower oil at 0 (control), 3, or 6% (as-fed basis) of the diet. Diets containing approximately 80% concentrate and 20% roughage were formulated, on a DM basis, to be isocaloric and isonitrogenous and to meet or exceed NRC requirements for Ca, P, and other nutrients. A subsample of 12 wethers per treatment was selected based on average BW (54 kg) and slaughtered. Carcass data (LM area, fat thickness, and internal fat content) and wholesale cut weight (leg, loin, rack, shoulder, breast, and foreshank), along with fatty acid, tocopherol, and color analysis, were determined on each carcass. The LM and infraspinatus were sampled for fatty acid profile. Increasing safflower oil supplementation from 0 to 3 or 6% increased the proportion of linoleic acid in the diet from 49.93 to 55.32 to 62.38%, respectively, whereas the percentage of oleic acid decreased from 27.94 to 23.80 to 20.73%, respectively. The percentage of oil in the diet did not (P > or = 0.11) alter the growth and carcass characteristics of lambs, nor did it alter the tocopherol content or color stability of meat. Increasing levels of safflower oil in lamb diets decreased (P < 0.01) the weight percentage of oleic acid in the infraspinatus and LM, and increased linoleic acid (P < 0.01). Oil supplementation increased (P < 0.01) the weight percentage of various isomers of CLA in muscle, with the greatest change in the cis-9,trans-11 isomer. Supplementation of sheep diets with safflower oil, up to 6% of the diet, resulted in increasing levels of unsaturated fatty acids and CLA in the lean tissue, without adversely affecting growth performance, carcass characteristics, or color stability of lamb.

Sulfur-substituted and alpha-methylated fatty acids as peroxisome proliferator-activated receptor activators

FA with varying chain lengths and an alpha-methyl group and/or a sulfur in the beta-position were tested as peroxisome proliferator-activated receptor (PPAR)alpha, -delta(beta), and -gamma ligands by transient transfection in COS-1 cells using chimeric receptor expression plasmids, containing cDNAs encoding the ligand-binding domain of PPARalpha, -delta, and -gamma. For PPARalpha, an increasing activation was found with increasing chain length of the sulfur-substituted FA up to C14-S acetic acid (tetradecylthioacetic acid = TTA). The derivatives were poor, and nonsignificant, activators of PPARdelta. For PPARgamma, activation increased with increasing chain length up to C16-S acetic acid. A methyl group was introduced in the alpha-position of palmitic acid, TTA, EPA, DHA, cis9,trans11 CLA, and trans10,cis12 CLA. An increased activation of PPARalpha was obtained for the alpha-methyl derivatives compared with the unmethylated FA. This increase also resulted in increased expression of the two PPARalpha target genes acyl-CoA oxidase and liver FA-binding protein for alpha-methyl TTA, alpha-methyl EPA, and alpha-methyl DHA. Decreased or altered metabolism of these derivatives in the cells cannot be excluded. In conclusion, saturated FA with sulfur in the beta-position and increasing carbon chain length from C9-S acetic acid to C14-S acetic acid have increasing effects as activators of PPARalpha and -gamma in transfection assays. Furthermore, alpha-methyl FA derivatives of a saturated natural FA (palmitic acid), a sulfur-substituted FA (TTA), and PUFA (EPA, DHA, c9,t11 CLA, and t10,c12 CLA) are stronger PPARalpha activators than the unmethylated compounds.

Lack of effect of dietary conjugated linoleic acids naturally incorporated into butter on the lipid profile and body composition of overweight and obese men

BACKGROUND

Dietary conjugated linoleic acid (CLA) is known to reduce atherosclerosis, plasma total and LDL-cholesterol concentrations, and body fat accumulation in several animal species. Of the few studies that investigated the effects of CLA supplementation in humans, all used commercially formulated oral supplements made from a mixture of CLA isomers.

OBJECTIVE

We compared the effects on plasma lipoproteins and body composition of the consumption of a modified butter naturally enriched with CLA (CLA-B: 4.22 g CLA/100 g butter fat) by the addition of sunflower oil to the diet of dairy cows with the consumption of a control butter (CON-B) that was low in CLA (0.38 g CLA/100 g butter fat).

DESIGN

In a crossover design study including an 8-wk washout period, 16 men [x +/- SD age: 36.6 +/- 12.4 y; body mass index (in kg/m2): 31.2 +/- 4.4] were fed each of the 2 experimental isoenergetic diets, providing 15% of energy as protein, 45% as carbohydrates, and 40% as lipids, of which >60% was derived from experimental fats, for 4 wk.

RESULTS

Consumption of the CLA-B diet induced a significantly (P < 0.05) smaller reduction in plasma total cholesterol and in the ratio of total to HDL cholesterol (-0.02 mmol/L and -0.00, respectively) than did consumption of the CON-B diet (-0.26 mmol/L and-0.34, respectively). Abdominal adipose tissue area measured by computed tomography showed no difference in accumulation of either visceral or subcutaneous adipose tissue after the 2 experimental diets.

CONCLUSION

These results suggest that a 10-fold CLA enrichment of butter fat does not induce beneficial metabolic effects in overweight or obese men.

Effect of abomasal infusions of geometric isomers of 10,12 conjugated linoleic acid on milk fat synthesis in dairy cows

The trans-10,cis-12 isomer of conjugated linoleic acid (CLA) decreases TAG accumulation in 3T3-L1 adipocytes, reduces lipid accretion in growing animals, and inhibits milk fat synthesis in lactating mammals. However, there is evidence to suggest that other FA may also exert antilipogenic effects. In the current experiment, the effects of geometric isomers of 10,12 CLA on milk fat synthesis were examined using four Holstein-British Friesian cows in a 4 x 4 Latin Square experiment with 14-d periods. Treatments consisted of abomasal infusions of skim milk, or skim milk containing trans-10,cis-12 CLA (T1), trans-10,trans-12 CLA (T2), or a mixture of predominantly 10,12 isomers containing (g/l00 g) trans-10,cis-12 (35.0), cis-10,trans-12 (23.2), trans-10,trans-12 (14.9), and cis-10,cis-12 (5.1). CLA supplements were prepared from purified ethyl linoleate and infused as nonesterified FA. Infusions were conducted over a 4-d period with a 10-d interval between treatments and targeted to deliver 4.5 g/d of 10,12 CLA isomers. Compared with the control, trans-10, trans-12 CLA had no effect (P> 0.05) on milk fat yield, whereas treatments T1 and T3 depressed (P < 0.05) milk fat content (19.8 and 22.9%, respectively) and decreased milk fat output (20.8 and 21.3%, respectively). Comparable reductions in milk fat synthesis to 4.14 and 1.80 g trans-10,cis-12/d supplied by treatments T1 and T3 indicate that other 10,12 geometric isomers of CLA have the potential to exert antilipogenic effects. The relative abundance of cis-10,trans-12 CLA in treatment T3 and the low transfer efficiency of this isomer into milk suggest that cis-10,trans-12 CLA was the active component..

Effects of conjugated linoleic acid on long term feeding in Fischer 344 rats

Weanling male Fischer 344 rats were fed either control or diet containing 1% CLA for 18 months. Weight gain and survival rate were not different between treatments, but CLA-fed animals ate slightly less food. CLA feeding did not significantly reduce body fat compared to that of control. Clinical chemistry and hematology analyses were performed on blood samples at week 69-72. CLA had no effects except on blood glucose, which was reduced in CLA-fed animals compared to control. All animals had chronic renal failure at the end of the study; however, CLA decreased the amount of protein in urine at week 70 of feeding. Necropsy and histo-pathology results indicated that there was no difference between treatment groups. Although this study used a limited number of animals and a single dose of CLA, our results suggest that long term CLA feeding did not cause any adverse effects in rats.

Conjugated linoleic acid evokes de-lipidation through the regulation of genes controlling lipid metabolism in adipose and liver tissue

Conjugated linoleic acid (CLA) is a unique lipid that elicits dramatic reductions in adiposity in several animal models when included at < or = 1% of the diet. Despite a flurry of investigations, the precise mechanisms by which conjugated linoleic acid elicits its dramatic effects in adipose tissue and liver are still largely unknown. In vivo and in vitro analyses of physiological modifications imparted by conjugated linoleic acid on protein and gene expression suggest that conjugated linoleic acid exerts its de-lipidating effects by modulating energy expenditure, apoptosis, fatty acid oxidation, lipolysis, stromal vascular cell differentiation and lipogenesis. The purpose of this review shall be to examine the recent advances and insights into conjugated linoleic acid's effects on obesity and lipid metabolism, specifically focused on changes in gene expression and physiology of liver and adipose tissue.

Divergent mechanisms of cis 9, trans 11 ‐ and trans 10 , cis 12 ‐ conjugated linoleic acid affecting insulin resistance and inflammation in apolipoprotein E knockout mice: a proteomics approach

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.

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

INTRODUCTION

Conjugated linoleic acid (CLA) has been shown to positively influence calcium and bone metabolism in experimental animals and cells in culture, but there are limited human data available.

OBJECTIVE

To investigate the effect of CLA supplementation on biomarkers of calcium and bone metabolism in healthy adult males.

DESIGN

The study consisted of a double-blind, placebo-controlled trial in which 60 healthy adult males (aged 39-64 y) were randomly assigned to receive daily either 3.0 g CLA isomer blend (50:50% cis-9,trans-11:trans-10,cis-12 isomers) or a palm/bean oil blend (placebo) for 8 weeks. Urine and blood samples were collected at weeks 0 and 8 and were analysed for biomarkers of calcium and bone metabolism.

RESULTS

Supplementation with CLA or placebo for 8 weeks had no significant effects on markers of bone formation (serum osteocalcin and bone-specific alkaline phosphatase) or bone resorption (serum C-telopeptide-related fraction of type 1 collagen degradation products, urinary N-telopeptide-related fraction of type 1 collagen degradation products, urinary pyridinoline and deoxypyridinoline), or on serum or urinary calcium levels. Baseline levels of these biochemical parameters were similar in both groups of subjects. While the placebo had no effect, CLA supplementation resulted in a three-fold increase (P<0.00001) in cis-9,trans-11 CLA isomer in total plasma lipids.

CONCLUSION

Under the conditions tested in this double-blind, placebo-controlled trial in adult men, a CLA supplement of mixed isomers did not affect markers of calcium or bone metabolism. Further investigation of the effects of CLA on calcium and bone metabolism in other gender- and age-groups is warranted.

Ácido linoléico conjugado e perda de peso

O tratamento e a prevenção da obesidade têm sido considerados uma enorme batalha para os profissionais da área de saúde. As indústrias de alimentos e de fármacos, por sua vez, têm oferecido cada vez mais uma vasta gama de novos produtos que preconizam a perda de peso. O ácido linoléico conjugado, encontrado em maiores concentrações na gordura de animais ruminantes, parece apresentar efeitos favoráveis quanto à manutenção do peso corporal. Esta revisão apresenta uma análise crítica dos dados disponíveis na literatura, que relacionam o ácido linoléico conjugado com o metabolismo energético e a composição corporal. Os estudos realizados com humanos ainda não são conclusivos, embora alguns apontem um possível aumento da lipólise e/ou redução da lipogênese, que reflete em alterações apenas na composição corporal, especialmente no tecido adiposo abdominal, mas não na perda de peso. Entretanto, as altas doses usadas nesses estudos podem implicar efeitos colaterais indesejáveis. Portanto, mais estudos são necessários para uma indicação desse ácido graxo como um agente para a melhora da composição corporal e/ou como um agente anti-obesidade.

Changes in Conjugated Linoleic Acid and Palmitoleic Acid Are Correlated to Retinol Levels in Chronic Renal Failure in Both Hemodialysis and Conservative Treatment Patients

An increase in conjugated linoleic acid (CLA), a natural fatty acid present in our diet, which possesses anticarcinogenic and antiatherogenic activities in experimental models, has been found in both the plasma and adipose tissue of end-stage chronic renal failure (ESCRF) patients. Increased levels of retinol have also been found in those patients, due to a reduced excretion of the retinol-binding protein. Since retinol is known to influence lipid metabolism, we evaluated whether changes in retinol, CLA, and other fatty acids are correlated in the plasma of CRF patients. We measured CLA, retinol, and unsaturated fatty acids in the plasma of the following groups: (A) 35 ESCRF patients; (B) 20 hemodialysis (HD) patients; (C) 20 healthy controls. Subjects with total cholesterol and/or triglycerides higher than 250 mg/dL were excluded. We found a significant increase in CLA, retinol, palmitoleic (16:1), and oleic (18:1) acids in ESCRF patients. In HD patients we found a similar pattern, however, CLA increase was not significant. No changes were observed in the other fatty acids measured. In the groups of ESCRF and HD patients, a positive correlation between the levels of plasma retinol and CLA, and between retinol and 16:1 was found. These correlations were not detected in controls. The abnormal levels of plasma retinol in CRF patients might partly explain the changes in CLA and 16:1. The influence of retinol levels on these fatty acids might be due to an induction of delta 9 desaturase. In fact, 16:1 is known to be produced, partly, by delta 9 desaturation of palmitic acid. Moreover, the formation of CLA from delta 9 desaturation of vaccenic acid-a trans-monounsaturated fatty acid present in our diet-has recently been demonstrated in humans. Nevertheless, our data do not represent direct evidence supporting an increased delta 9 desaturase activity in CRF patients. Another possible explanation might be a variation in the exogenous intake.

The Combination of Dietary Conjugated Linoleic Acid and Treadmill Exercise Lowers Gain in Body Fat Mass and Enhances Lean Body Mass in High Fat–Fed Male Balb/C Mice

Nearly half of the U.S. adult population is overweight or obese, which may be related to increased energy intake combined with lack of physical activity. Obesity increases the risk of several chronic diseases including diabetes, coronary heart disease, hypertension, and stroke. Conjugated linoleic acids (CLA) were shown to decrease fat and increase lean mass in several animal studies. However, the effects of CLA in combination with exercise (Ex) on body composition have not been studied in an animal model. We examined the effect of a low concentration of either safflower oil as control (0.5%) or mixed isomers of CLA (0.4%) along with treadmill exercise on body composition in male Balb/C mice fed a high-fat diet (20% corn oil) in a 2 x 2 factorial design. CLA consumption lowered change in fat mass (P < 0.001) confirming the results of other studies, and change in fat mass decreased further (P < 0.001) with CLA and exercise. Change in lean mass did not increase with exercise alone; it increased, although not significantly, with CLA alone and increased significantly (P < 0.05) due to the combination of CLA and exercise. This effect was accompanied by decreased serum leptin levels and lower leptin mRNA expression in peritoneal fat (P < 0.001). Serum insulin, glucose, tumor necrosis factor (TNF)-alpha, and interleukin-6 were lower in CLA-fed mice than in controls (P < 0.05), whereas serum TNF-alpha was increased by exercise (P < 0.05). Exercise increased oxygen consumption and energy expenditure when measured under resting conditions (P < 0.05). In summary, the combination of dietary CLA and exercise decreased fat mass and increased lean mass in mice fed a high-fat diet, and these effects may be related in part to decreased serum leptin and exercise-induced increases in oxygen consumption and energy expenditure.

Consumer acceptability of conjugated linoleic acid-enriched milk and cheddar cheese from cows grazing on pasture

Two experiments were conducted to study the consumer acceptability attributes of conjugated linoleic acid (CLA)-enriched milk and cheese from cows grazing on pasture. In experiment 1, 15 cows were fed either a diet containing 51% alfalfa hay plus corn silage and 49% concentrate [total mixed ration (TMR)], were grazed on pasture, or were grazed on pasture and received 3.2 kg/d of a grain mix. The grain mix contained 75% full-fat extruded soybeans (FFES), 10% corn, 10% beet pulp, and 5% molasses. During the final 3 wk of the 6-wk experiment, milk was evaluated for sensory attributes. In experiment 2, 18 cows were fed similar diets as in experiment 1, except replacing the group of cows grazed on pasture and receiving the grain mix was a group of cows grazed on pasture and receiving 2.5 kg/d per cow of the FFES; Cheddar cheese was manufactured from milk. Average CLA contents (g/100 g of fatty acid methyl esters) were 0.52, 1.63, and 1.69 in milk and 0.47, 1.47, and 1.46 in cheese from cows fed a TMR, grazed on pasture, and grazed on pasture and fed the grain mix, respectively. An open and trained panel evaluated CLA-enriched milk for mouth-feel, color, flavor, and quality and evaluated cheese for color, flavor, texture, and quality. Open and trained panel evaluations of milk and cheese showed no differences among treatments for any of the attributes, except that the trained panel detected a more barny flavor in milk from cows grazing pasture compared with milk from cows fed the TMR only. Results suggest that consumer acceptability attributes of CLA-enriched milk and cheese from cows grazing pasture is similar to those of milk and cheese with low levels of CLA.

Effects of structural changes of fatty acids on lipid accumulation in adipocytes and primary hepatocytes

Conjugated linoleic acids (CLAs), tetradecylthioacetic acid (TTA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are all shown to differently affect lipid homeostasis. Additionally, previous studies have shown that introducing a methyl group in the molecule potentiates the hypolipidemic effect of EPA. The objective of this study was to determine how cis9,trans11 CLA, trans10,cis12 CLA, TTA, EPA and DHA affect lipid accumulation in 3T3-L1 adipocytes and in cultured primary rat hepatocytes, and to what extent changes in cis/trans configuration or introducing a methyl group in the molecules influence their way of affecting lipid accumulation in these cells. Our results show that trans10,cis12 CLA is highly specific in preventing lipid accumulation in adipocytes, and that small structural changes in the molecule (changing to trans/trans or introducing an alpha-methyl group) totally abolish this effect and up-regulate the expression levels of adipogenic marker genes towards control levels. Furthermore, all the fatty acids increased hepatic lipid accumulation, whereas the lipid content was normalized after adding an alpha-methyl group into the molecules. Taken together, our data demonstrate that the various fatty acids are highly specialized molecules, and that small structural changes markedly alter their way of affecting lipid accumulation in adipocytes and hepatocytes.

Impaired lipid accumulation by trans10, cis12 CLA during adipocyte differentiation is dependent on timing and length of treatment

Conjugated linoleic acids (CLAs) are a group of polyunsaturated fatty acids found in ruminant products, where the predominant isomers are cis9, trans11 (c9,t11) and trans10, cis12 (t10,c12) CLA. We have previously shown that t10,c12 CLA prevents lipid accumulation in mature adipocytes in part by acting as a peroxisome proliferator-activated receptor gamma (PPAR gamma) modulator. The objective of this study was to further establish the molecular mechanisms underlying the attenuating effect on lipid accumulation by t10,c12 CLA, with focus on time point and duration of treatment during adipogenesis. We have shown that t10,c12 CLA treatment has its most attenuating effect early (day (D) 0-6) during differentiation. Treatment during this period is sufficient to prevent lipid accumulation in mature adipocytes. The adipogenic marker genes PPAR gamma and CCAAT/enhancer binding protein alpha (C/EBP alpha) are both down-regulated after treatment within the period from D0-6, while additional treatment also down-regulates the expression of sterol regulatory element binding protein-1c (SREBP-1c), liver X receptor alpha (LXR alpha), fatty acid binding protein (aP2), fatty acid translocase (CD36) and insulin-sensitive glucose transporter 4 (GLUT4). These effects of t10,c12 CLA reflect the subsequent attenuation of lipid accumulation observed in mature adipocytes. Interestingly, the early B-cell factor (O/E-1), which is known to promote adipogenesis and to be involved in control of genes important for terminal adipocyte differentiation, is unaffected by treatment of t10,c12 CLA. Taken together, our data indicate that inhibition of lipid accumulation induced by t10,c12 CLA treatment during adipocyte differentiation is associated with a tight regulatory cross-talk between early (PPAR gamma and C/EBP alpha) and late (LXR alpha, aP2 and CD36) adipogenic marker genes.

Reaction of mono-epoxidized conjugated linoleic acid ester with boron trifluoride etherate complex

The reaction of methyl 11,12-E-epoxy-9Z-octadecenoate (1) with boron trifluoride etherate furnished a mixture of methyl 12-oxo-10E-octadecenoate (3a) and methyl 11-oxo-9E-octadecenoate (3b) in 66% yield. Methyl 9,10-Z-epoxy-11E-octadecenoate (2) with boron trifluoride etherate furnished a mixture of methyl 9-oxo-10E-octadecenoate (4a, 45%) and methyl 10-oxo-11E-octadecenoate (4b, 19%). A plausible mechanism is proposed for these reactions, which involves the attack on the epoxy ring system by BF3, followed by deprotonation, oxo formation, and double bond migration to give a mixture of two positional alpha,beta-unsaturated C18 enone ester derivatives (3a/3b, 4a/4b). The structures of these C18 enone ester derivatives (3a/3b, 4a/4b) were identified by a combination of NMR spectroscopic and mass spectrometric analyses.

Supplementation with conjugated linoleic acid for 24 months is well tolerated by and reduces body fat mass in healthy, overweight humans

After 12 mo in a randomized, double-blind, placebo-controlled trial of conjugated linoleic acid (CLA) supplementation (2 groups received CLA as part of a triglyceride or as the free fatty acid, and 1 group received olive oil as placebo), 134 of the 157 participants who concluded the study were included in an open study for another 12 mo. The goals of the extension study were to evaluate the safety [with clinical chemistry analyses and reported adverse events (AEs)] and assess the effects of CLA on body composition [body fat mass (BFM), lean body mass (LBM), bone mineral mass (BMM)], body weight, and BMI. All subjects were supplemented with 3.4g CLA/d in the triglyceride form. Circulating lipoprotein(a) and thrombocytes increased in all groups. There was no change in fasting blood glucose. Aspartate amino transferase, but not alanine amino transferase, increased significantly. Plasma total cholesterol and LDL cholesterol were reduced, whereas HDL cholesterol and triglycerides were unchanged. The AE rate decreased compared with the first 12 mo of the study. Body weight and BFM were reduced in the subjects administered the placebo during the initial 12 mo study (-1.6 +/- 3.2 and -1.7 +/- 2.8 kg, respectively). No fat or body weight changes occurred in the 2 groups given CLA during the initial 12 mo. LBM and BMM were not affected in any of the groups. Changes in body composition were not related to diet and/or training. In conclusion, this study shows that CLA supplementation for 24 mo in healthy, overweight adults was well tolerated. It confirms also that CLA decreases BFM in overweight humans, and may help maintain initial reductions in BFM and weight in the long term.

Fat intake and energy-balance effects

This paper focuses on the effects of dietary fats or fatty acids on key targets of metabolic intermediates for body-weight control, i.e. satiety, thermogenesis, fat oxidation and body composition. With respect to sensory satiety, it appeared, e.g. that linoleic acid tasters showed a different mechanism for meal termination than non-tasters did. They stopped eating linoleic acid containing food based upon satiety, whereas the non-tasters stopped eating based upon the change in pleasantness of taste. Moreover, in the normal range of body mass index, an inverse relationship was shown between % 'tasters' and BMI. In a high fat diet vs. a low fat high protein high carbohydrate diet, metabolic satiety appeared to be continuously lower and correlated positively to diet-induced energy expenditure. However, with respect to the intermeal interval, satiety appeared to be more sustained following a high fat vs. a high CHO preload, resulting in a lower meal frequency. Covert fat replacement during breakfast by sucrose polyester was successful in combination with dietary restraint, yet overt fat replacement in snacks was successful in the dietary-unrestrained subjects, i.e. those who habitually ate snacks. With respect to fat oxidation, from a respiration-chamber experiment on the effects of diacylglycerol compared (DG) to triacylglycerol (TG) intake, it was concluded that consumption of DG increased fat oxidation and beta-hydroxy-butyrate levels, but did not affect energy metabolism or triacylglycerol level. Parameters of appetite were all lowered by DG compared to TG. With respect to body composition, the effects of 13 weeks CLA supplementation in overweight subjects during weight regain were assessed. Although CLA did not affect %body-weight regain, the regain of fat-free mass was increased by CLA, independently of %body-weight regain and physical activity, and as a consequence resting metabolic rate was increased. At the same time, appetite was reduced and satiety and fullness were increased. In conclusion, we also determined bright sports with respect to fat intake.

Conjugated linoleic acid preserves gastrocnemius muscle mass in mice bearing the colon-26 adenocarcinoma

Cancer cachexia is a syndrome of weight loss, muscle wasting, fatigue, and anorexia that occurs in patients with advanced or recurrent solid tumor disease. Tumor necrosis factor-alpha (TNFalpha) and prostaglandin E2 (PGE2) have been implicated in the biology of cachexia and serve as possible targets for treatment of this condition. Conjugated linoleic acid (CLA) is a polyunsaturated fatty acid that alters the synthesis of PGE2 and reduces the negative effects of TNF on body weight of healthy mice. We hypothesized that a diet supplemented with .5% CLA might reduce muscle wasting in mice bearing the colon-26 adenocarcinoma, an animal model of cancer cachexia. CLA preserved gastrocnemius muscle mass and reduced TNF receptors in muscle of tumor-bearing mice. These data suggest that CLA may preserve muscle mass by reducing the catabolic effects of TNF on skeletal muscle.

Dietary conjugated linoleic acid increases endurance capacity and fat oxidation in mice during exercise

Ingestion of CLA activates beta-oxidation and causes loss of body fat in rodents. We investigated the effects of dietary CLA on endurance capacity and energy metabolism during exercise in mice. Five-week-old male BALB/c mice were fed a control diet containing 1.0% linoleic acid or a diet containing 0.5% CLA that replaced an equivalent amount of linoleic acid for 1 wk. The maximum swimming time until fatigue was significantly higher in the CLA-fed group than in the control group. During treadmill running, the respiratory exchange ratio was significantly lower in the CLA-fed group, but oxygen consumption did not differ significantly between groups, suggesting that FA contributed more as an energy substrate in the CLA-fed mice. The muscle lipoprotein lipase activity was significantly higher in the CLA-fed group than in the control group. These results suggest that CLA ingestion increases endurance exercise capacity by promoting fat oxidation during exercise.

Consumption of conjugated linoleic acid (CLA) from CLA-enriched cheese does not alter milk fat or immunity in lactating women

Isomers of conjugated linoleic acid (CLA) decreased milk fat, altered immunity, and reduced the risk for cardiovascular disease (CVD) in some animals. The major form of CLA in the human diet is c9,t11-18:2 (rumenic acid; RA). We studied the effects of high RA consumption on plasma and milk RA concentration, milk composition, immunity, and CVD risk factors in lactating women (n = 36) assigned to 1 of 3 treatments: control, low CLA cheese (LCLA; 160 mg RA/d), or high CLA cheese (HCLA; 346 mg RA/d). The increase in plasma RA concentration between baseline and 8 wk in women consuming HCLA cheese was significantly greater than that of controls. At study completion (8 wk), milk RA concentration among women consuming HCLA cheese was greater (P < 0.05) than that of controls (0.37 vs. 0.26% of fatty acids). Treatment did not affect milk fat, protein, or lactose concentrations, immune indices (e.g., plasma T-helper cells and interleukin-2), or measured risk factors for CVD (e.g., plasma triacylglyceride and cholesterol). In summary, consumption of a RA-enriched cheese modestly increased plasma and milk RA concentrations without affecting total milk fat, plasma and milk indices of immunity, or selected risk factors for CVD.

The effect of conjugated linoleic acid on transepithelial calcium transport and mediators of paracellular permeability in human intestinal-like Caco-2 cells

Conjugated linoleic acid (CLA) increases paracellular permeability across human intestinal-like Caco-2 cell monolayers, which transport Ca predominantly by the transcellular route. In vivo, however, paracellular Ca transport is the predominant route of Ca transport. Therefore, the objective of this study was to investigate the effect of CLA on transepithelial Ca transport in Caco-2 cells transporting Ca predominantly by the paracellular route. Cells were seeded onto permeable transport membranes and allowed to differentiate, over 14 d, into intestinal-like cell monolayers. Monolayers (n=9/treatment) were exposed to 0 (control) or 80 microM- 18:2, -cis-9, trans-11 CLA or -trans-10, cis-12 CLA for 14 d prior to Ca transport studies. Overall transepithelial Ca transport as well as transcellular and parcellular Ca transport was significantly increased (P<0.001) by exposure of Caco-2 cells to both isomers of CLA, an effect which appeared to be related to altered localization of zona occludens 1 (a tight junction protein).

Trans-10,cis-12 CLA increases adipocyte lipolysis and alters lipid droplet-associated proteins: role of mTOR and ERK signaling

Lipid droplet-associated proteins play an important role in adipocyte triglyceride (TG) metabolism. Here, we show that trans-10,cis-12 conjugated linoleic acid (CLA), but not cis-9,trans-11 CLA, increased lipolysis and altered human adipocyte lipid droplet morphology. Before this change in morphology, there was a rapid trans-10,cis-12 CLA-induced increase in the accumulation of perilipin A in the cytosol, followed by the disappearance of perilipin A protein. In contrast, protein levels of adipose differentiation-related protein (ADRP) were increased in cultures treated with trans-10,cis-12 CLA. Immunostaining revealed that ADRP localized to the surface of small lipid droplets, displacing perilipin. Intriguingly, trans-10,cis-12 CLA increased ADRP protein expression to a much greater extent than ADRP mRNA without affecting stability, suggesting translational control of ADRP. To this end, we found that trans-10,cis-12 CLA increased activation of the mammalian target of rapamycin/p70 S6 ribosomal protein kinase/S6 ribosomal protein (mTOR/p70S6K/S6) pathway. Collectively, these data demonstrate that the trans-10,cis-12 CLA-mediated reduction of human adipocyte TG content is associated with the differential localization and expression of lipid droplet-associated proteins. This process involves both the translational control of ADRP through the activation of mTOR/p70S6K/S6 signaling and transcriptional control of perilipin A.

Biological activities of conjugated fatty acids: conjugated eicosadienoic (conj. 20:2Δc11,t13/t12,c14), eicosatrienoic (conj. 20:3Δc8,t12,c14), and heneicosadienoic (conj. 21:2Δc12,t14/c13,t15) acids and other metabolites of conjugated linoleic acid

The elongated form of conjugated linoleic acid (CLA), conjugated eicosadienoic acid (CEA, conj. 20:2delta(c11,t13/t12,c14)), was generated from CLA by liver microsomal fractions. Subsequent testing showed that dietary CEA significantly reduced body fat, and increased lean mass similar to CLA when compared to controls. CEA also decreased lipoprotein lipase activity and triacylglyceride, and increased glycerol release in 3T3-L1 adipocytes, correlated with the trans-12,cis-14 isomer, but CEA required a longer incubation period than cells treated with CLA. Based on the fact that CEA fed animals had CLA in tissue, we suggest that the effect of CEA is due to the CLA converted from CEA in the system. The delta-6 desaturated and elongated form of trans-10,cis-12 CLA (conjugated eicosatrienoic acid, CETA, conj. 20:3delta(c8,t12,c14)) inhibited LPL activity and increased glycerol release but was less active than trans-10,cis-12 CLA or CEA. The 21-carbon conjugated fatty acid, conjugated heneicosadienoic acid (CHDA, conj. 21:2delta(c12,t14/c13,t15)), was not active on LPL inhibition, triacylglyceride, or glycerol release in 3T3-L1 adipocytes. We also provide evidence that CLA was metabolized to conjugated dodecadienoic acid (conj. 12:2delta(c3,t5/t4,c6)). In addition, there were indications of the presence of conjugated tetradecadienoic acid (conj. 14:2delta(c5,t7/t6,c8)), suggesting that CLA can be metabolized through fatty acid beta-oxidation. This is the first work to report the presence of conjugated 12 and 14 carbon fatty acids, originated from CLA, and the biological activities of CEA, CETA and CHDA.

Milk fat synthesis is unaffected by abomasal infusion of the conjugated diene 18∶3 isomers cis-6, trans-10, cis-12 and cis-6, trans-8, cis-12

It has been previously established that trans-10,cis-12 CLA is a potent inhibitor of milk fat synthesis. Although the mechanism of this action is not completely understood, it has been speculated that eicosanoid-like metabolites of this isomer formed by the activity of tissue desaturases may be responsible for its activity. The objective of this study was to investigate the effects of an enrichment containing an 18:3 conjugated diene, produced in the metabolism of trans-10,cis-12 CLA, on milk fat synthesis. Three rumen-fistulated Holstein cows (210+/-8 d in milk) were randomly assigned in a 3 x 3 Latin square experiment. Treatments were (i) control, (ii) trans-10,cis-12 CLA supplement (2.1 g/d; positive control), (iii) enrichment providing two conjugated diene 18:3 isomers (2.6 g/d of cis-6,trans-10,cis-12 and 4.0 g/d of cis-6,trans-8,cis-12) and trans-10,cis-12 CLA (2.1 g/d). Treatments were abomasally infused for 5 d at 4-h intervals, and there was a 7-d interval between periods. Milk yield, dry matter intake, and milk protein yield were unaffected by treatments. In contrast, the trans-10,cis-12 CLA supplement reduced milk fat yield by 27%, whereas the supplement enriched with conjugated diene 18:3 isomers (treatment iii) had no effect on milk fat yield beyond that attributable to its trans-10,cis-12 CLA content. The transfer efficiency of trans-10,cis-12 CLA into milk fat was 25 and 24% for treatments ii and iii, respectively. At the same time, the abomasally infused conjugated diene 18:3 isomers were transferred to milk fat with an efficiency of 33 and 41% for cis-6,trans-10,cis-12 and cis-6,trans-8,cis-12 18:3, respectively. Overall, short-term abomasal infusion of the conjugated diene 18:3 isomers had no effect on milk fat synthesis, thereby offering no support for an involvement of metabolites of trans-10,cis-12 CLA in the regulation of milk fat synthesis.

Hydrogenation for Low Trans and High Conjugated Fatty Acids

Hydrogenated vegetable oils contain of trans fatty acids. Because of the increased health concern about trans fatty acids, new hydrogenations have been studied to seek ways for substantial reduction of the trans fatty acids in the hydrogenated vegetable oils. This paper reviews new hydrogenation processes such as electrocatalytic hydrogenation, precious catalyst hydrogenation, and supercritical fluid state hydrogen, which have shown promising results for the reduction of trans fatty acids below the level of 8%. This paper also reviews the recently introduced hydeogenation technique for high accumulation of conjugated linoleic acids, beneficiary functional components. The hydrogenated vegetable oils with high quantity conjugated linoleic acid might provide the possibility for the utilization of hydrogenated oils as health-prompting food ingredients.

Isomers of conjugated linoleic acid decrease plasma lipids and stimulate adipose tissue lipogenesis without changing adipose weight in post-prandial adult sedentary or trained Wistar rat

The respective effects and interactions of supplementation with two conjugated linoleic acid (CLA) isomers and exercise on plasma metabolic profile, activity of lipogenic enzymes and cellularity in two adipose tissue sites, those of the liver and heart, were examined in adult Wistar rats. Rats that were either sedentary or exercise-trained by treadmill running were fed one of four diets: a diet without CLA; a diet with either 1% cis 9, trans 11 CLA or 1% trans 10, cis 12 CLA; or a mixture of both isomers (1% of each) for 6 weeks. We observed that the exercise decreased lipogenic enzyme activities in epididymal and perirenal adipose tissue. Plasma cholesterol, insulin, and leptin concentrations were lower in exercise-trained rats than in sedentary rats. The ingestion of either CLA mixture or the trans 10, cis 12 CLA increased lipogenic enzyme activities in epididymal tissue and more markedly in perirenal adipose tissue, especially in sedentary rats, and without affecting adipose tissue weight or cellularity. A similar effect of trans 10, cis 12 CLA was observed in regard to malic enzyme activity in the liver. In addition, this isomer decreased plasma lipid and urea concentrations and increased plasma 3-hydroxybutyrate levels. The ingestion of cis 9, trans 11 CLA increased fatty acid synthase activity in perirenal adipose tissue in sedentary rats and decreased plasma cholesterol and leptin concentrations. These results show that isomers of CLA decrease plasma lipids and stimulate adipose tissue lipogenesis without changing adipose weight in adult sedentary or exercise-trained rat, thus suggesting a stimulation of adipose tissue turnover.

Dietary conjugated linoleic acids lower the triacylglycerol concentration in the milk of lactating rats and impair the growth and increase the mortality of their suckling pups

Recent studies showed that conjugated linoleic acids (CLA) lower triacylglycerol concentrations in the milk of lactating animals. This study was performed to determine the reasons for this phenomenon; we also investigated whether there is a relation between altered lipid metabolism in the liver and the reduction in milk triacylglycerols in rats fed CLA. Two groups of female rats were fed diets containing 0 [sunflower oil (SFO) group] or 14.7 g/kg diet of a CLA mixture (CLA group) at the expense of sunflower oil during growth, pregnancy, and lactation. CLA-fed rats had 49 and 80% lower mRNA concentration and activity of fatty acid synthase, respectively, a 51% lower mRNA concentration of lipoprotein lipase (LPL) in their mammary glands at d 17 of lactation, and a 46% lower milk fat content than SFO rats (P < 0.05). Although CLA rats had lower concentrations of triacylglycerols in the liver than SFO rats (20.8 +/- 2.6 vs. 62.6 +/- 27.7 micromol/g, P < 0.05), concentrations of triglycerides in plasma, which are the substrates of LPL, did not differ between the groups. Moreover, the number of pups per litter, litter weights, and pup weights at d 17 of lactation were 41, 35, and 22% lower, respectively, in the CLA group than in the SFO group. In conclusion, the present study suggests that dietary CLA reduces triacylglycerol concentrations in the milk via reduced de novo fatty acid synthesis in the mammary gland and an impaired uptake of fatty acids from lipoproteins into the mammary gland. This might be the reason for reduced growth rates and an increased mortality of suckling pups.

Influence of supplemental cracked high-linoleate or high-oleate safflower seeds on site and extent of digestion in beef cattle1

Our objectives were to evaluate ruminal fermentation patterns, apparent ruminal biohydrogenation, and site and extent of nutrient disappearance in cattle fed supplemental cracked safflower seeds differing in 18 C fatty acid profile. Nine Angus x Gelbvieh heifers (641 +/- 9.6 kg) fitted with ruminal and duodenal cannulas were used in a triplicated 3 x 3 Latin square. Cattle were fed (OM basis) 9.1 kg of bromegrass hay and either 1) 1.8 kg of corn and 0.20 kg of soybean meal (Control); 2) 0.13 kg of soybean meal and 1.5 kg of cracked high-linoleate (67.2% 18:2) safflower seeds (Linoleate); or 3) 1.5 kg of cracked high-oleate (72.7% 18:1) safflower seeds (Oleate). Safflower seed supplements were formulated to provide similar quantities of N and TDN and 5% dietary fat. Single degree of freedom orthogonal contrasts (Control vs. Linoleate and Oleate; Linoleate vs. Oleate) were used to evaluate treatment effects. True ruminal OM and ruminal NDF disappearances (percentage of intake) were greater (P < or =0.02) for Control than Linoleate and Oleate. True ruminal N degradability (% of intake) was not different (P = 0.38) among treatments. Apparent ruminal biohydrogenation of dietary 18:2 was greatest (Linoleate vs. Oleate, P < 0.001) for Linoleate, whereas biohydrogenation of dietary 18:1 was greatest (Linoleate vs. Oleate, P = 0.02) for Oleate. Duodenal flow of 18:0 was least (P < 0.001) for Control but did not differ (P = 0.92) between Oleate and Linoleate. Total flow of unsaturated fatty acid to the duodenum was greatest (P < 0.001) in cattle fed safflower seeds, and was greater with Linoleate (P < 0.001) than with Oleate. Duodenal flow of 18:1 and 18:2 increased (P < 0.001) in Oleate and Linoleate, respectively. Duodenal flow of 18:1trans-11 was greater (P < 0.001) in cattle fed safflower seeds and in Linoleate than in Oleate. Postruminal disappearance of saturated fatty acids was greatest (P < 0.001) for Control; however, postruminal disappearance of total unsaturated fatty acids was greater (P = 0.002) for Linoleate vs. Oleate. Supplemental high-linoleate or high-oleate safflower seeds to cattle fed forage-based diets may negatively affect ruminal OM and fiber disappearance but not N disappearance. Provision of supplemental fat in the form of safflower seeds that are high in linoleic acid increased intestinal supply and postruminal disappearance of unsaturated fatty acids, indicating that the fatty acids apparently available for metabolism are affected by dietary fat source.

Effects of supplemental fat on growth performance and quality of beef from steers fed barley-potato product finishing diets: II. Fatty acid composition of muscle and subcutaneous fat1

One hundred sixty-eight crossbred steers (317.1 +/- 1.0 kg) were used to evaluate the effects of supplemental fat in finishing diets on the fatty acid composition, including the 9,11 isomer of conjugated linoleic acid, of beef. Steers were allotted within three weight blocks to a randomized complete block design with a 3 x 2 + 1 factorial arrangement of dietary treatments. Main effects were level of yellow restaurant grease (RG; 0, 3, and 6%), and level of alfalfa hay (AH; 3.5 and 7%) with an added treatment containing 6% tallow (T) and 7% AH in barley-based diets containing 15% potato by-product and 7% supplement (all dietary levels are on a DM basis) fed for an average of 165 d. Fatty acids of the LM and s.c. fat from four randomly selected steers per pen were quantified using GC after methylation with sodium methoxide. Dietary treatment did not (P > 0.10) affect total fatty acid (FA) content of the LM (143 +/- 5.2 mg/g) or fat (958 +/- 7.9 mg/g). Myristic acid increased linearly (P < 0.01) with increasing RG from 3.1 to 3.7 +/- 0.1 g/100 g of FA in muscle. Stearic acid increased linearly (P < 0.05) as RG increased in the diet, from 11.4 to 12.9 +/- 0.4 g/100 g of FA in LM and from 9.9 to 12.2 +/- 0.3 g/100 g of FA in fat. Compared with T, steers fed 6% RG had more (P < 0.05) oleic acid in LM (42.7 vs. 40.3 +/- 0.5 g/100g FA) and in fat (43.0 vs. 40.9 +/- 0.5 g/100g FA). The cis-9, trans-11 conjugated linoleic acid (CLA) increased quadratically (P < 0.01) with increasing dietary RG in LM from 0.45 to 0.64 to 0.62 +/- 0.03 g/100 g of FA and increased in fat from 0.61 to 0.84 to 0.83 +/- 0.04 g/100 g of FA. Moreover, cis-9, trans-11 CLA was higher (P < 0.05) in fat from steers fed RG compared with T (0.81 vs. 0.69 +/- 0.04 g/100 g of FA), and tended to be higher (P = 0.07) in muscle (0.62 vs. 0.54 +/- 0.03 g/100 g of FA. Feeding yellow restaurant grease increased content of cis-9, trans-11 CLA in beef without an increase total FA content.