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1.  Effect of a High Intake of Conjugated Linoleic Acid on Lipoprotein Levels in Healthy Human Subjects 
PLoS ONE  2010;5(2):e9000.
Trans fatty acids are produced either by industrial hydrogenation or by biohydrogenation in the rumens of cows and sheep. Industrial trans fatty acids lower high-density lipoprotein (HDL) cholesterol, raise low-density lipoprotein (LDL) cholesterol, and increase the risk of coronary heart disease. The effects of trans fatty acids from ruminants are less clear. We investigated the effect on blood lipids of cis-9, trans-11 conjugated linoleic acid (CLA), a trans fatty acid largely restricted to ruminant fats.
Methodology/Principal Findings
Sixty-one healthy women and men were sequentially fed each of three diets for three weeks, in random order, for a total of nine weeks. Diets were identical except for 7% of energy (approximately 20 g/day), which was provided either by oleic acid, by industrial trans fatty acids, or by a mixture of 80% cis-9, trans-11 and 20% trans-10, cis-12 CLA. After the oleic acid diet, mean (± SD) serum LDL cholesterol was 2.68±0.62 mmol/L compared to 3.00±0.66 mmol/L after industrial trans fatty acids (p<0.001), and 2.92±0.70 mmol/L after CLA (p<0.001). Compared to oleic acid, HDL-cholesterol was 0.05±0.12 mmol/L lower after industrial trans fatty acids (p = 0.001) and 0.06±0.10 mmol/L lower after CLA (p<0.001). The total-to–HDL cholesterol ratio was 11.6% higher after industrial trans fatty acids (p<0.001) and 10.0% higher after CLA (p<0.001) relative to the oleic acid diet.
High intakes of an 80∶20 mixture of cis-9, trans-11 and trans-10, cis-12 CLA raise the total to HDL cholesterol ratio in healthy volunteers. The effect of CLA may be somewhat less than that of industrial trans fatty acids.
Trial Registration NCT00529828
PMCID: PMC2815780  PMID: 20140250
2.  High conjugated linoleic acid enriched ghee (clarified butter) increases the antioxidant and antiatherogenic potency in female Wistar rats 
Hypercholesterolemia and oxidative stress are the main stimulating factors responsible for coronary artery disease and progression of atherosclerosis. Dairy food products are rich in conjugated linoleic acid (CLA) which is considered as an important component due to its potential health benefits such as anticarcinogenic, antiatherogenic, antidiabetic and antiadipogenic properties. In the present study, the effect of CLA enriched ghee on the antioxidant enzyme system and antiatherogenic properties in Wistar rats has been studied.
Female Wistar rats of 21 days were taken for the study and fed with soybean diet (Control diet), low CLA diet and high CLA ghee diet (treatments) for thirty five days for studying antioxidative enzymes and sixteen weeks in case of antiatherogenic studies.
Feeding of high CLA enhanced ghee during pubescent period in rats lead to an increase in catalase (CAT) and superoxide dismutase (SOD) enzyme activities in blood and increased CAT, SOD and glutathione transferase (GST) enzymes activities in liver by 27, 130 and 168 percent, respectively. Plasma nitrate concentration and Haemoglobin levels remained the same in all the treatments. Feeding of high CLA ghee resulted in lower (P < 0.01) plasma cholesterol & triglyceride level (52.17 and 30.27%), and higher high density lipoproteins (33.26%) than feeding of soybean oil (control group) and thus manifested in decreased (P < 0.05) atherogenic index (from 0.472 to 0.244). Lesser cholesterol and triglyceride levels were observed in the liver and aorta of high CLA fed rats than in those of the other groups. Histopathological studies of liver showed normal hepatic cords with portal triad in the high CLA ghee fed rats whereas fatty degeneration of hepatocytes containing fat vacuoles was observed in the liver of the other groups.
This paper is the first report of the antioxidant and antiatherogenic properties of the high CLA enriched ghee suggesting that high CLA ghee can be used as a potential food for decreasing the risk of cardiovascular diseases, particularly in India, where, ghee is widely used for culinary and medicinal purposes.
PMCID: PMC3766171  PMID: 23923985
High conjugated linoleic acid enriched ghee; Antiatherogenic; Antioxidant; Catalase; Superoxide dismutase; Cholesterol
3.  Effect of dietary conjugated linoleic acid isomers on lipid metabolism in hamsters fed high-carbohydrate and high- fat diets 
The British journal of nutrition  2008;101(11):1630-1638.
Dietary conjugated linoleic acids (CLA), have been reported to have a number of isomer-dependent effects on lipid metabolism including reduction in adipose tissue deposition, changes in plasma lipoprotein concentrations and hepatic lipid accumulation. The aim of this study was to compare the effect of individual CLA isomers against lipogenic and high “Western” fat background diets. Golden Syrian hamsters were fed a high-carbohydrate rodent chow or chow supplemented with 17.25% fat formulated to represent the type and amount of fatty acids found in a typical “Western” diet (including 0.2% cholesterol). Diets were further supplemented with 0.25% (w/w) rapeseed oil, cis9, trans11 (c9,t11)-CLA or trans10, cis12 (t10,c12)-CLA. Neither isomer had a significant impact on plasma lipid or lipoprotein concentrations. The t10,c12-CLA isomer significantly reduced perirenal adipose tissue depot mass. While adipose tissue acetyl coenzyme A carboxylase and fatty acid synthase mRNA concentrations (as measured by quantitative PCR) were unaffected by CLA, lipoprotein lipase mRNA was specifically reduced by t10,c12-CLA, on both background diets (p<0.001). This was associated with a specific reduction of SREBP1c expression in perirenal adipose tissue (p=0.018). The isomers appear to have divergent effects on liver triacylglycerol content with c9,t11-CLA producing lower concentrations than t10,c12-CLA. We conclude that t10,c12-CLA modestly reduces adipose tissue deposition in the Golden Syrian hamster independently of background diet and this may possibly result from reduced uptake of lipoprotein fatty acids, as a consequence of reduced LPL gene expression.
PMCID: PMC2695940  PMID: 18983716
Conjugated linoleic acid; lipoprotein lipase; SREBP; hamster
4.  Effects of Conjugated Linoleic Acid, Fish Oil and Soybean Oil on PPARs (α & γ) mRNA Expression in Broiler Chickens and Their Relation to Body Fat Deposits 
An experiment was conducted on broiler chickens to study the effects of different dietary fats (Conjugated linoleic acid (CLA), fish oil, soybean oil, or their mixtures, as well as palm oil, as a more saturated fat), with a as fed dose of 7% for single fat and 3.5 + 3.5% for the mixtures, on Peroxisome Proliferator-Activated Receptors (PPARs) gene expression and its relation with body fat deposits. The CLA used in this experiment was CLA LUTA60 which contained 60% CLA, so 7% and 3.5% dietary inclusions of CLA LUTA60 were equal to 4.2% and 2.1% CLA, respectively. Higher abdominal fat pad was found in broiler chickens fed with a diet containing palm oil compared to chickens in the other experimental groups (P ≤ 0.05). The diets containing CLA resulted in an increased fat deposition in the liver of broiler chickens (P ≤ 0.05). The only exception was related to the birds fed with diets containing palm oil or fish oil + soybean oil, where contents of liver fat were compared to the CLA + fish oil treatment. PPARγ gene in adipose tissue of chickens fed with palm oil diet was up-regulated compared to other treatments (P ≤ 0.001), whereas no significant differences were found in adipose PPARγ gene expression between chickens fed with diets containing CLA, fish oil, soybean oil or the mixture of these fats. On the other hand, the PPARα gene expression in liver tissue was up-regulated in response to the dietary fish oil inclusion and the differences were also significant for both fish oil and CLA + fish oil diets compared to the diets with palm oil, soybean oil or CLA as the only oil source (P ≤ 0.001). In conclusion, the results of present study showed that there was a relationship between the adipose PPARγ gene up-regulation and abdominal fat pad deposition for birds fed with palm oil diet, while no deference was detected in n-3 and n-6 fatty acids, as well as CLA on PPARγ down regulation in comparison to a more saturated fat. When used on its own, fish oil was found to be a more effective fat in up-regulating hepatic PPARα gene expression and this effect was related to a less fat deposition in liver tissue. A negative correlation coefficient (−0.3) between PPARα relative gene expression and liver tissue fat content confirm the anti-lipogenic effect of PPARα, however, the change in these parameters was not completely parallel.
PMCID: PMC3257090  PMID: 22272093
CLA; PUFA; PPARs; broiler chickens
5.  Rumen-protected conjugated linoleic acid supplementation to dairy cows in late pregnancy and early lactation: effects on milk composition, milk yield, blood metabolites and gene expression in liver 
Conjugated linoleic acid (CLA) is a collective term for isomers of octadecadienoic acid with conjugated double-bond system. Thus, it was the objective to investigate whether milk composition and metabolic key parameters are affected by adding CLA to the diet of dairy cows in the first four weeks of lactation.
A study was carried out with five primiparous cows fed a CLA supplemented diet compared to five primiparous cows without CLA supplementation. CLA supplemented cows received 7.5 g CLA/day (i.e. 50% cis(c)9,trans(t)11- and 50% t10,c12-CLA) starting two weeks before expected calving and 20 g CLA/day (i.e. 50% c9,t11- and 50% t10,c12-CLA) throughout day 1 to 28 of lactation.
The CLA supplement was insufficiently accepted by the animals: only 61.5% of the intended amount was ingested. Fed CLA were detectable in milk fat, whereas contents of c9,t11-CLA and t10,c12-CLA in milk fat were higher for CLA supplemented cows compared to the control group. On average over the entire treatment period, there was a decrease of saturated fatty acids (FA) in milk fat of CLA supplemented cows, combined with a higher content of monounsaturated and trans FA.
Our study revealed no significant effects of c9,t11- and t10,c12-CLA supplementation either on milk yield and composition or on metabolic key parameters in blood. Furthermore the experiment did not indicate significant effects of c9,t11- and t10,c12-CLA-supplementation on gene expression of peroxisome proliferator-activated receptor-alpha (PPARα), PPARγ, sterol regulatory element-binding protein-1 and tumor necrosis factor-alpha in liver tissue.
Feeding c9,t11- and t10,c12-CLA during the first weeks after calving did not affect metabolic key parameters of blood serum or milk composition of fresh cows. Milk fatty acid composition was changed by feeding c9,t11- and t10,c12-CLA resulting in higher contents of these isomers in milk fat. High contents of long chain FA in milk fat indicate that CLA supplementation during the first four weeks of lactation did not affect massive peripheral lipomobilization.
PMCID: PMC2835710  PMID: 20167061
6.  Effects of butter naturally enriched with conjugated linoleic acid and vaccenic acid on blood lipids and LDL particle size in growing pigs 
Cow milk is a natural source of the cis 9, trans 11 isomer of conjugated linoleic acid (c9,t11-CLA) and trans vaccenic acid (VA). These fatty acids may be considered as functional foods, and the concentration in milk can be increased by e.g. sunflower oil supplementation to the dairy cow feed.
The objective of this study was to compare the effects of regular butter with a special butter naturally enriched in c9,t11-CLA and VA on plasma lipids in female growing pigs. The experimental period lasted for three weeks and the two diets provided daily either 5.0 g c9,t11-CLA plus 15.1 g VA or 1.3 g c9,t11-CLA plus 3.6 g VA.
The serum concentrations of c9,t11-CLA, VA and alpha-linolenic acid were increased and myristic (14:0) and palmitic acid (16:0) were reduced in the pigs fed the CLA+VA-rich butter-diet compared to regular butter, but no differences in plasma concentrations of triacylglycerol, cholesterol, HDL-cholesterol, LDL-cholesterol, LDL particle size distribution or total cholesterol/HDL cholesterol were observed among the two dietary treatment groups.
Growing pigs fed diets containing butter naturally enriched in about 20 g c9,t11-CLA plus VA daily for three weeks, had increased serum concentrations of alpha-linolenic acid and decreased myristic and palmitic acid compared to pigs fed regular butter, implying a potential benefit of the CLA+VA butter on serum fatty acid composition. Butter enriched in CLA+VA does not appear to have significant effect on the plasma lipoprotein profile in pigs.
PMCID: PMC2533663  PMID: 18759970
7.  Effect of conjugated linoleic acids from beef or industrial hydrogenation on growth and adipose tissue characteristics of rats 
The conjugated linoleic acid (CLA) content of beef can be increased by supplementing appropriate beef cattle diets with vegetable oil or oil seed. Yet the effect of consumption of such beef on adipose tissue characteristics is unclear, thus the study was conducted to compare adipose tissue responses of rats to diets containing beef from steers either not provided or provided the oil supplements to alter CLA composition of the fat in muscle.
Effects of feeding synthetic (industrial hydrogenation) CLA or CLA from beef on growth and adipose tissue responses of weanling, male, Wistar rats (n = 56; 14 per treatment diet) were investigated in a completely randomized design experiment. Diets were: control (CON) diet containing casein and soybean oil, synthetic CLA (SCLA) diet; where 1.69% synthetic CLA replaced soybean oil, two beef-diets; CONM and CLAM, containing freeze dried beef from steers either not fed or fed 14% sunflower seeds to increase CLA content of beef. Diets were isonitrogenous (20% protein) and isocaloric. Rat weights and ad libitum intakes were recorded every 2 wk. After 9 wk, rats were fasted for 24 h, blood sampled by heart puncture, sacrificed, tissue and organs were harvested and weights recorded. The adipose tissue responses with regard to cellularity and fatty acid compositions of retroperitoneal and inguinal adipose tissue were determined.
Body weights and gains were comparable, but organ weights as percent of body weight were greater for rats fed SCLA than CONM. Fasting blood glucose concentration was lower (p < 0.01) in rats fed SCLA than those fed CONM or CLAM. Retroperitoneal and inguinal fat weights, as percent of body weight were greater (p < 0.01) in rats fed CONM or CLAM than those fed CON or SCLA diets. Adipocyte numbers were least in retroperitoneal tissue of rats fed SCLA, while inguinal tissue cell density and total number were lower (p = 0.02) in rats fed CLAM (7.26 × 107 cells/g and 8.03 × 108 cells) than those fed CONM (28.88 × 107 cells/g and 32.05 × 108 cells, respectively).
Study suggests that dietary CLA either as synthetic or high CLA-beef may alter adipose tissue characteristics by decreasing the number of adipocytes and by decreasing the size of the tissue.
PMCID: PMC2676290  PMID: 19386120
8.  Effect of Conjugated Linoleic Acid Feeding on the Growth Performance and Meat Fatty Acid Profiles in Broiler: Meta-analysis 
The effect of conjugated linoleic acid (CLA) feeding on growth performance and fatty acid profiles in thigh meat of broiler chicken was investigated using meta-analysis with a total of 9 studies. Overall effects were calculated by standardized mean differences between treatment (CLA fed) and control using Hedges’s adjusted g from fixed and random effect models. Meta-regression was conducted to evaluate the effect of CLA levels. Subgroups in the same study were designated according to used levels of CLA, CP levels or substituted oils in diets. The effects on final body weight, weight gain, feed intake and feed conversion ratio were investigated as growth parameters. Total saturated and unsaturated fatty acid concentrations and C16:0, C18:0, C18:2 and C18:3 concentrations in thigh meat of broiler chicken were used as fatty acid profile parameters. The overall effect of CLA feeding on final weight was negative and it was only significant in fixed effect model (p<0.01). Significantly lower weight gain, feed intake and higher feed conversion ratio compared to control were found (p<0.05). CLA feeding on the overall increased total saturated fatty acid concentration in broilers compared to the control diet (p<0.01). Total unsaturated fatty acid concentration was significantly decreased by CLA feeding (p<0.01). As for individual fatty acid profiles, C16:0, C18:0 and C18:3 were increased and C18:2 was significantly decreased by CLA feeding (p<0.01). In conclusion, CLA was proved not to be beneficial for improving growth performance, whereas it might be supposed that CLA is effective modulating n-6/n-3 fatty acids ratio in thigh meat. However, the economical compensation of the loss from suppressed growth performance and increased saturated fatty acids with the benefit from enhanced n-6/n-3 ratio should be investigated in further studies in order to propose an appropriate use of dietary CLA in the broiler industry.
PMCID: PMC4093496  PMID: 25049878
Broiler Chicken; Conjugated Linoleic Acid; Growth Performance; Meat Fatty Acids; Meta-analysis
9.  Bioavailability of nanoemulsified conjugated linoleic acid for an antiobesity effect 
The aim of this study was to enhance the bioavailability of conjugated linoleic acid (CLA), which has low water solubility, using nanoemulsion technology and to evaluate the effects of its improved bioavailability as an antiobesity agent.
The antiobesity effect of nanoemulsified water-soluble conjugated linoleic acid (N-CLA) was evaluated using in vitro and in vivo studies. Differentiated 3T3-L1 adipocytes were treated with CLA and N-CLA to assess their lipolytic effect. Further, to confirm the antiobesity effect of N-CLA, male Sprague-Dawley rats were randomly separated into four groups, ie, a group fed a normal diet, a group fed a high-fat diet (obesity rat model), a CLA-treated group, and an N-CLA-treated group.
N-CLA showed a greater lipolytic effect on differentiated 3T3-L1 adipocytes compared with normal CLA. N-CLA enhanced the release of glycerol from triglycerides, which accumulated in differentiated 3T3-L1 adipocytes. Further, N-CLA enhanced leptin secretion to an extent similar to that of orlistat, an antiobesity agent. In an animal obesity model fed a high-fat diet, N-CLA attenuated accumulation of triglycerides, total cholesterol, and low-density lipoprotein cholesterol in serum, and also significantly decreased the volume of triglycerides and cholesterol in liver tissue.
These results indicate that N-CLA has a greater antiobesity effect than CLA as a result of its improved bioavailability.
PMCID: PMC3575163  PMID: 23429301
conjugated linoleic acid; nanoemulsion; water-soluble; improved bioavailability; antiobesity
10.  The t10,c12 isomer of conjugated linoleic acid stimulates mammary tumorigenesis in transgenic mice overexpressing erbB2 in the mammary epithelium 
Carcinogenesis  2007;28(6):1269-1276.
Conjugated linoleic acid (CLA), a family of isomers of octadecadienoic acid, inhibits rat mammary carcinogenesis, angiogenesis, and lung metastasis from a transplantable mammary tumor. c9,t11-CLA, the predominant isomer in dairy products, and t10,c12-CLA, a component of CLA supplements, are equally effective. The objective of the current studies was to test the efficacy of these two CLA isomers in a clinically relevant breast cancer model. Transgenic mice overexpressing erbB2 in the mammary epithelium were fed control or 0.5% CLA-supplemented diets continuously from weaning. Unexpectedly, t10,c12-CLA stimulated lobular hyperplasia of the mammary epithelium and accelerated mammary tumor development, decreasing median tumor latency to 168 days of age compared to 256 and 270 days in the c9,t11-CLA and control groups, respectively. Metastasis was also increased by t10,c12-CLA, with percent of tumor-bearing mice with lung metastasis 73%, 14%, and 31%, in the t10,c12-CLA, c9,t11-CLA and control groups, respectively. A second study, in which CLA administration was initiated after puberty, confirmed the stimulatory effect of t10,c12-CLA on mammary tumor development and metastasis. Additionally, t10,c12-CLA, but not c9,t11-CLA, increased the size of the liver, heart, spleen and mammary lymph node. The effects of t10,c12-CLA were not specific to erbB2 transgenic mice, as t10,c12-CLA supplementation increased proliferation in the mammary epithelium of both wild type FVB and FVB/erbB2 mice. Moreover, the number of terminal end buds, the mammary epithelial structures most sensitive to a carcinogenic insult, was increased 30-fold in FVB/wild type mice fed t10,c12-CLA. These data suggest that it would be prudent to avoid CLA supplements containing the t10,c12-CLA isomer. However, even though c9,t11-CLA was not efficacious in the erbB2 model, its ability to inhibit mammary tumor development in rat models suggests that it may have activity for prevention of some types of breast cancer.
PMCID: PMC2776704  PMID: 17259656
CLA; erbB2; mammary; tumorigenesis; microenvironment; stroma
11.  Anti-obesity activity of diglyceride containing conjugated linoleic acid in C57BL/6J ob/ob mice 
Journal of Veterinary Science  2009;10(3):189-195.
This study was to investigate the anti-obesity effects of diglyceride (DG)-conjugated linoleic acid (CLA) containing 22% CLA as fatty acids in C57BL/6J ob/ob male mice. There were four experimental groups including vehicle control, DG, CLA, and DG-CLA. The test solutions of 750 mg/kg dose were orally administered to the mice everyday for 5 weeks. CLA treatments significantly decreased mean body weight in the obese mice throughout the experimental period compared to the control (p < 0.01). All test solutions significantly decreased the levels of triglyceride, glucose and free fatty acids in the serum compared with control (p < 0.05). The levels of total cholesterol were also significantly reduced in DG and DG-CLA groups compared with the control group (p < 0.05). CLA significantly decreased weights of renal and epididymal fats compared with the control (p < 0.05). DG and DG-CLA also significantly decreased the epididymal fat weights compared with the control (p < 0.05). A remarkable decrease in the number of lipid droplets and fat globules was observed in the livers of mice treated with DG, CLA, and DG-CLA compared to control. Treatments of DG and CLA actually increased the expression of peroxisome proliferator-activated receptor gamma. These results suggest that DG-CLA containing 22% CLA have a respectable anti-obesity effect by controlling serum lipids and fat metabolism.
PMCID: PMC2801123  PMID: 19687618
conjugated linoleic acid; C57BL/6J ob/ob mouse; diglyceride; obesity; PPAR-γ
12.  Dietary Conjugated Linoleic Acid Supplementation Leads to Downregulation of PPAR Transcription in Broiler Chickens and Reduction of Adipocyte Cellularity 
PPAR Research  2014;2014:137652.
Conjugated linoleic acids (CLA) act as an important ligand for nuclear receptors in adipogenesis and fat deposition in mammals and avian species. This study aimed to determine whether similar effects are plausible on avian abdominal fat adipocyte size, as well as abdominal adipogenic transcriptional level. CLA was supplemented at different levels, namely, (i) basal diet without CLA (5% palm oil) (CON), (ii) basal diet with 2.5% CLA and 2.5% palm oil (LCLA), and (iii) basal diet with 5% CLA (HCLA).The content of cis-9, trans-11 CLA was between 1.69- and 2.3-fold greater (P < 0.05) than that of trans-10, cis-12 CLA in the abdominal fat of the LCLA and HCLA group. The adipogenic capacity of the abdominal fat depot in LCLA and HCLA fed chicken is associated with a decreased proportion of adipose cells and monounsaturated fatty acids (MUFA). The transcriptional level of adipocyte protein (aP2) and peroxisome proliferator-activated receptor gamma (PPARγ) was downregulated by 1.08- to 2.5-fold in CLA supplemented diets, respectively. It was speculated that feeding CLA to broiler chickens reduced adipocyte size and downregulated PPARγ and aP2 that control adipocyte cellularity. Elevation of CLA isomers into their adipose tissue provides a potential CLA-rich source for human consumption.
PMCID: PMC4189438  PMID: 25309587
13.  A commonly used rumen-protected conjugated linoleic acid supplement marginally affects fatty acid distribution of body tissues and gene expression of mammary gland in heifers during early lactation 
Conjugated linoleic acids (CLA) in general, and in particular the trans-10,cis-12 (t10,c12-CLA) isomer are potent modulators of milk fat synthesis in dairy cows. Studies in rodents, such as mice, have revealed that t10,c12-CLA is responsible for hepatic lipodystrophy and decreased adipose tissue with subsequent changes in the fatty acid distribution. The present study aimed to investigate the fatty acid distribution of lipids in several body tissues compared to their distribution in milk fat in early lactating cows in response to CLA treatment. Effects in mammary gland are further analyzed at gene expression level.
Twenty-five Holstein heifers were fed a diet supplemented with (CLA groups) or without (CON groups) a rumen-protected CLA supplement that provided 6 g/d of c9,t11- and t10,c12-CLA. Five groups of randomly assigned cows were analyzed according to experimental design based on feeding and time of slaughter. Cows in the first group received no CLA supplement and were slaughtered one day postpartum (CON0). Milk samples were taken from the remaining cows in CON and CLA groups until slaughter at 42 (period 1) and 105 (period 2) days in milk (DIM). Immediately after slaughter, tissue samples from liver, retroperitoneal fat, mammary gland and M. longissimus (13th rib) were obtained and analyzed for fatty acid distribution. Relevant genes involved in lipid metabolism of the mammary gland were analyzed using a custom-made microarray platform.
Both supplemented CLA isomers increased significantly in milk fat. Furthermore, preformed fatty acids increased at the expense of de novo-synthesized fatty acids. Total and single trans-octadecenoic acids (e.g., t10-18:1 and t11-18:1) also significantly increased. Fatty acid distribution of the mammary gland showed similar changes to those in milk fat, due mainly to residual milk but without affecting gene expression. Liver fatty acids were not altered except for trans-octadecenoic acids, which were increased. Adipose tissue and M. longissimus were only marginally affected by CLA supplementation.
Daily supplementation with CLA led to typical alterations usually observed in milk fat depression (reduction of de novo-synthesized fatty acids) but only marginally affected tissue lipids. Gene expression of the mammary gland was not influenced by CLA supplementation.
PMCID: PMC3706325  PMID: 23827056
Conjugated linoleic acids; Milk fat depression; Fatty acid distribution; Liver; Mammary gland; Retroperitoneal fat; Gene expression
14.  Prolonged treatment of genetically obese mice with conjugated linoleic acid improves glucose tolerance and lowers plasma insulin concentration: possible involvement of PPAR activation 
Studies in rodents and some studies in humans have shown that conjugated linoleic acid (CLA), especially its trans-10, cis-12 isomer, reduces body fat content. However, some but not all studies in mice and humans (though none in rats) have found that CLA promotes insulin resistance. The molecular mechanisms responsible for these effects are unclear, and there are conflicting reports on the effects of CLA on peroxisomal proliferator-activated receptor-γ (PPARγ) activation and expression. We have conducted three experiments with CLA in obese mice over three weeks, and one over eleven weeks. We have also investigated the effects of CLA isomers in PPARγ and PPARα reporter gene assays.
Inclusion of CLA or CLA enriched with its trans-10, cis-12 isomer in the diet of female genetically obese (lepob/lepob) mice for up to eleven weeks reduced body weight gain and white fat pad weight. After two weeks, in contrast to beneficial effects obtained with the PPARγ agonist rosiglitazone, CLA or CLA enriched with its trans-10, cis-12 isomer raised fasting blood glucose and plasma insulin concentrations, and exacerbated glucose tolerance. After 10 weeks, however, CLA had beneficial effects on glucose and insulin concentrations. At this time, CLA had no effect on the plasma TNFα concentration, but it markedly reduced the plasma adiponectin concentration. CLA and CLA enriched with either isomer raised the plasma triglyceride concentration during the first three weeks, but not subsequently. CLA enriched with its trans-10, cis-12 isomer, but not with its cis-9, trans-11 isomer, stimulated PPARγ-mediated reporter gene activity; both isomers stimulated PPARα-mediated reporter gene activity.
CLA initially decreased but subsequently increased insulin sensitivity in lepob/lepob mice. Activation of both PPARγ and PPARα may contribute to the improvement in insulin sensitivity. In the short term, however, another mechanism, activated primarily by trans-10, cis-12-CLA, which probably leads to reduced adipocyte number and consequently reduced plasma adiponectin concentration, may decrease insulin sensitivity.
PMCID: PMC546236  PMID: 15642120
15.  t-10, c-12 CLA Dietary Supplementation Inhibits Atherosclerotic Lesion Development Despite Adverse Cardiovascular and Hepatic Metabolic Marker Profiles 
PLoS ONE  2012;7(12):e52634.
Animal and human studies have indicated that fatty acids such as the conjugated linoleic acids (CLA) found in milk could potentially alter the risk of developing metabolic disorders including diabetes and cardiovascular disease (CVD). Using susceptible rodent models (apoE−/− and LDLr−/− mice) we investigated the interrelationship between mouse strain, dietary conjugated linoleic acids and metabolic markers of CVD. Despite an adverse metabolic risk profile, atherosclerosis (measured directly by lesion area), was significantly reduced with t-10, c-12 CLA and mixed isomer CLA (Mix) supplementation in both apoE−/− (p<0.05, n = 11) and LDLr−/− mice (p<0.01, n = 10). Principal component analysis was utilized to delineate the influence of multiple plasma and tissue metabolites on the development of atherosclerosis. Group clustering by dietary supplementation was evident, with the t-10, c-12 CLA supplemented animals having distinct patterns, suggestive of hepatic insulin resistance, regardless of mouse strain. The effect of CLA supplementation on hepatic lipid and fatty acid composition was explored in the LDLr−/− strain. Dietary supplementation with t-10, c-12 CLA significantly increased liver weight (p<0.05, n = 10), triglyceride (p<0.01, n = 10) and cholesterol ester content (p<0.01, n = 10). Furthermore, t-10, c-12 CLA also increased the ratio of 18∶1 to 18∶0 fatty acid in the liver suggesting an increase in the activity of stearoyl-CoA desaturase. Changes in plasma adiponectin and liver weight with t-10, c-12 CLA supplementation were evident within 3 weeks of initiation of the diet. These observations provide evidence that the individual CLA isomers have divergent mechanisms of action and that t-10, c-12 CLA rapidly changes plasma and liver markers of metabolic syndrome, despite evidence of reduction in atherosclerosis.
PMCID: PMC3527580  PMID: 23285120
16.  Trans-10, cis-12 Conjugated Linoleic Acid Decreases de novo Lipid Synthesis in Human Adipocytes 
Conjugated linoleic acid (CLA) reduces adiposity in vivo. However, mechanisms mediating these changes are unclear. Therefore, we treated cultures of human adipocytes with trans-10, cis-12 (10,12) CLA, cis-9, trans-11 (9,11) CLA, or other trans fatty acids (FA) and measured indices of lipid metabolism. The lipid-lowering effects of 10,12 CLA were unique, as other trans FA did not reduce TG content to the same extent. Using low levels of [14C]-CLA isomers, it was shown that both isomers were readily incorporated into acylglycerols and phospholipids, albeit at lower levels than [14C]-oleic or [14C]-linoleic acids. When using [14C]-acetic acid and [14C]-pyruvic acid as substrates, 30 μM 10,12 CLA, but not 9,11 CLA, decreased de novo synthesis of triglyceride (TG), free FA, diacylglycerol, cholesterol esters, cardiolipin, phospholipids, and ceramides within 3–24 h. Treatment with 30 μM 10,12 CLA, but not 9,11 CLA, decreased total cellular lipids within 3 d and the ratio of monounsaturated FA (MUFA) to saturated FA, and increased C18:0 acyl-CoA levels within 24 h. Consistent with these data, stearoyl-CoA desaturase (SCD)-1 mRNA and protein levels were down-regulated by 10,12 CLA within 7–12 h, respectively. The mRNA levels of liver X receptor (LXR)α and sterol regulatory element binding protein (SREBP)-1c, transcription factors that regulate SCD-1, were decreased by 10,12 CLA within 5 h. These data suggest that the isomer-specific decrease in de novo lipid synthesis by 10,12 CLA is due, in part, to the rapid repression of lipogenic transcription factors that regulate MUFA synthesis, suggesting an anti-obesity mechanism unique to this trans FA.
PMCID: PMC3203310  PMID: 21775116
conjugated linoleic acid; adipocytes; lipid synthesis; stearoyl-CoA desaturase
17.  Moderate doses of conjugated linoleic acid reduce fat gain, maintain insulin sensitivity without impairing inflammatory adipose tissue status in mice fed a high-fat diet 
The enrichment of diet with nutrients with potential benefits on body composition is a strategy to combat obesity. Conjugated linoleic acid (CLA) due its beneficial effects on body composition and inflammatory processes becomes an interesting candidate, since the promotion and impairment of obesity is closely linked to a low-grade inflammation state of adipose tissue. Previously we reported the favourable effects of moderate doses of CLA mixture on body composition and inflammatory status of adipose tissue in mice fed a standard-fat diet. In the present study we assessed the potential beneficial effects of CLA mixture (cis-9, trans-11 and trans-10, cis-12, 50:50) in mice fed a high-fat diet.
Two doses were assayed: 0.15 g (CLA1) and 0.5 g CLA/kg body weight (CLA2) for the first 30 days of the study and then animals received a double amount for another 35 days.
The lowest dose (CLA1) had minor effects on body composition, plasma parameters and gene expression. However, a clear reduction in fat accumulation was achieved by CLA2, accompanied by a reduction in leptin, adiponectin and non-esterified fatty acids (NEFA) plasma concentrations. Insulin sensitivity was maintained despite a slight increase in fasting glucose and insulin plasma concentrations. The study of gene expression both in adipocytes and in the stromal vascular fraction (SVF) suggested that CLA may reduce either the infiltration of macrophages in adipose tissue or the induction of expression of pro-inflammatory cytokines.
In conclusion, the use of moderate doses of an equimolar mix of the two main CLA isomers reduces body fat content, improves plasma lipid profile, maintains insulin sensitivity (despite a moderate degree of hyperinsulinaemia) without the promotion of inflammatory markers in adipose tissue of mice fed a high-fat diet.
PMCID: PMC2831902  PMID: 20180981
18.  Dietary Conjugated Linoleic Acid Alters Oxidative Stability and Alleviates Plasma Cholesterol Content in Meat of Broiler Chickens 
The Scientific World Journal  2014;2014:949324.
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).
PMCID: PMC4216700  PMID: 25386625
19.  Hepatic Metabolic, Inflammatory, and Stress-Related Gene Expression in Growing Mice Consuming a Low Dose of Trans-10, cis-12-Conjugated Linoleic Acid 
Journal of Lipids  2012;2012:571281.
Dietary trans-10, cis-12-conjugated linoleic acid (trans-10, cis-12-CLA) fed to obese and nonobese rodents reduces body fat but leads to greater liver mass due to steatosis. The molecular mechanisms accompanying such responses remain largely unknown. Our study investigated the effects of chronic low trans-10, cis-12-CLA supplementation on hepatic expression of 39 genes related to metabolism, inflammation, and stress in growing mice. Feeding a diet supplemented with 0.3% trans-10, cis-12-CLA (wt/wt basis) for 6 weeks increased liver mass and concentration of long-chain fatty acids (LCFAs) in liver, while adipose tissue mass decreased markedly. These changes were accompanied by greater expression of genes involved in LCFA uptake (Cd36), lipogenesis, and triacylglycerol synthesis (Acaca, Gpam, Scd, Pck1, Plin2). Expression of these genes was in line with upregulation of the lipogenic transcription factor Srebf1. Unlike previous studies where higher >0.50% of the diet) doses of trans-10, cis-12-CLA were fed, we found greater expression of genes associated with VLDL assembly/secretion (Mttp, Cideb), ketogenesis (Hmgcs2, Bdh1), and LCFA oxidation (Acox1, Pdk4) in response to trans-10, cis-12-CLA. Dietary CLA, however, did not affect inflammation- and stress-related genes. Results suggested that a chronic low dose of dietary CLA increases liver mass and lipid accumulation due to activation of lipogenesis and insufficient induction of LCFA oxidation and VLDL assembly/secretion.
PMCID: PMC3438780  PMID: 22988513
20.  Influence of dietary conjugated linoleic acid on growth, fatty acid composition and hepatic lipogenesis in large yellow croaker (Pseudosciaena crocea R.)* §  
We examined the effects of conjugated linoleic acid (CLA) on growth, fatty acid composition and enzyme activity of fatty acid oxidation in the liver of large yellow croaker. We divided 1600 fish (average initial weight 150 g) into 4 groups and reared them in 8 cages. Four dietary treatments were formulated to contain 0%, 1%, 2% and 4% (w/w) CLA, respectively. The fish were fed for 10 weeks ad libitum twice daily. We found that the dietary CLA had no effect on growth, biometric parameters and whole body proximate (P>0.05), but showed some significant effects on the fatty acid composition in both muscle and the liver. The activities of lipogenic enzymes were slightly depressed in fish fed with increasing levels of CLA when compared with control (P>0.05). Dietary CLA supplementation had no effects on liver lipid content, but significantly increased the contents of saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA) (P<0.05) and decreased monounsaturated fatty acid (MUFA) content in both muscle and the liver. Dietary CLA inclusion resulted in significant increases of the biologically active cis-9, trans-11 and trans-10, cis-12 isomers in both tissues (P<0.05). The total accumulation of CLA was higher in the liver (3.83%, w/w) than in muscle (3.77%, w/w) when fed with 4% (w/w) CLA. This study demonstrates that large yellow croakers are capable of absorbing and depositing CLA and long-chain n-3 PUFA in the liver and muscle, showing that this species fed with CLA could be an important human food source for these healthful fatty acids.
PMCID: PMC2528883  PMID: 18763301
Conjugated linoleic acid (CLA); Fatty acids; Lipid; Lipogenic enzymes; Large yellow croaker
21.  Effect of conjugated linoleic acid, vitamin E and their combination on lipid profiles and blood pressure of Iranian adults with active rheumatoid arthritis 
Vascular Health and Risk Management  2008;4(6):1423-1432.
The aim of this study was to assess the impact of conjugated linoleic acids (CLAs), vitamin E, and combination of these nutrients on serum lipid profiles and blood pressure (BP) in patients with active rheumatoid arthritis (RA). In a randomized, double-blind, placebo-controlled trial, 87 patients with active RA were divided into four groups receiving one of the following daily supplements for three months: Group C: CLAs 2.5 g equivalent to 2 g mixture of cis 9-trans 11 and trans 10-cis12 CLAs in a rate of 50/50; Group E: vitamin E: 400 mg; Group CE: CLAs and vitamin E at above doses: Group P: placebo. After supplementation, SBP levels decreased significantly in the group C in comparison with groups E and P and mean arterial pressure reduced significantly in groups C and CE. There weren’t significant differences in the levels of prostaglandin E2 (PGE2), triglycerides, cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), LDL/HDL, cholesterol/HDL, fasting blood sugar, C-reactive protein (CRP), arylestrase activity, platelet count and body mass index between groups. CRP dropped nonsignificantly in groups P, C, E and CE (19%, 24%, 55%, and 39%, respectively). Erythrocytes sedimentation rate levels decreased in groups C, E and CE (P ≤ 0.05, P ≤ 0.05, P ≤ 0.001, respectively). It is concluded that supplementation of CLAs decreased BP and vitamin E decreased CRP. Therefore cosupplementation of CLAs and vitamin E might be profitable for heart disease prevention in RA patients.
PMCID: PMC2663461  PMID: 19337555
rheumatoid arthritis; lipid profiles; blood pressure; conjugated linoleic acids; vitamin E
22.  Non-fat milk solids attenuate hypercholesterolemic effect of conjugated linoleic acid 
The present study instigates the notion that non-fat milk has a beneficial effect on hypercholesterolemia caused by dietary conjugated linoleic acid (CLA). Two groups of mice (6 per group) were fed synthetic CLA (predominantly a mixture of t10, c12 and c9, t11 isomers) at 1 % level in the diet with or without skim milk powder (SMP). Another group (control) was fed a similar diet without CLA and SMP. The study was conducted for 60 days (d). Daily feed intake and weekly body weight were recorded. Plasma lipid profile was determined monthly. At the conclusion of experiment, animals were sacrificed and liver tissue was removed to assay cholesterol and triacylglycerols (TAG). Following 60 day feeding, the plasma total cholesterol content increased significantly in CLA group (218 mg/dl) than in control group (167 mg/dl), while in CLA + SMP group (fed non-fat milk solids along with CLA), it was similar to that in control group. The fractions of high density lipoproteins (HDL) and low density lipoprotein + very low density lipoprotein (LDL + VLDL) cholesterol as well as triacylglycerols (TAG) in plasma increased in CLA group, but in CLA + SMP group it remained similar to the control levels. Thus, it is concluded that dietary CLA increases plasma cholesterol and TAG contents in mice on normocholesterolemic diet and the inclusion of non-fat milk solids reverses this effect.
PMCID: PMC3722398  PMID: 24426013
CLA; Skim milk powder; Normocholesterolemic diet; Plasma lipid profile; Hypercholesterolemia
23.  Effect of the feeding system on the fatty acid composition, expression of the Δ9-desaturase, Peroxisome Proliferator-Activated Receptor Alpha, Gamma, and Sterol Regulatory Element Binding Protein 1 genes in the semitendinous muscle of light lambs of the Rasa Aragonesa breed 
Conjugated linoleic acids (CLAs) are receiving increasing attention because of their beneficial effects on human health, with milk and meat products derived from ruminants as important sources of CLA in the human diet. SCD gene is responsible for some of the variation in CLA concentration in adipose tissues, and PPARγ, PPARα and SREBP1 genes are regulator of SCD gene. The aim of this work was to evaluate the effect of the feeding system on fatty acid composition, CLA content and relative gene expression of Δ9-desaturase (SCD), Peroxisome Proliferator-Activated Receptor Gamma (PPARγ), Peroxisome Proliferator-Activated Receptor Alpha, (PPARα) and Sterol Regulatory Element Binding Protein (SREBP1) in Rasa Aragonesa light lambs in semitendinous muscle. Forty-four single-born male lambs were used to evaluate the effect of the feeding system, varying on an intensity gradient according to the use of concentrates: 1. grazing alfalfa, 2. grazing alfalfa with a supplement for lambs, 3. indoor lambs with grazing ewes and 4. drylot.
Both grazing systems resulted in a higher concentration of vaccenic acid (VA), CLA, CLA/VA acid ratio, and a lower oleic content, oleic acid (C18:1)/stearic acid (C18:0) ratio, PUFA n-6/n-3 ratio and SCD expression compared to other diets. In addition feeding system affected the fatty acid composition and SCD expression, possibly due to CLA concentration or the PUFA n-6/n-3 ratio. Both expression of the SCD gene and the feeding system were important factors affecting CLA concentration in the animal's semitendinous muscle. PPARγ, PPARα and SREBP1 expression seemed to be unaffected by the feeding system. Although no significant results were found, PPARγ, PPARα and SREBP1 showed similar expression pattern as SCD. Moreover, the correlation results between SCD expression and PPARγ (p < 0.01), as well as SREBP1 (p < 0.01) expression, may suggest that these genes were affecting SCD expression in a different way.
The data indicated that the feeding system is the main factor affecting the fatty acid composition and SCD gene expression, which is also affected by CLA and possibly by n-6/n-3 PUFAs.
PMCID: PMC2917425  PMID: 20649987
24.  Heterologous expression of linoleic acid isomerase from Propionibacterium acnes and anti-proliferative activity of recombinant trans-10, cis-12 conjugated linoleic acid 
Microbiology  2007;153(Pt 8):2483-2490.
The linoleic acid isomerase enzyme from Propionibacterium acnes responsible for bioconversion of linoleic acid to trans-10, cis-12 conjugated linoleic acid (t10, c12 CLA) was cloned and overexpressed in Lactococcus lactis and Escherichia coli, resulting in between 30 and 50 % conversion rates of the substrate linoleic acid to t10, c12 CLA. The anti-proliferative activities of the fatty acids produced following isomerization of linoleic acid by L. lactis and E. coli were assessed using the human SW480 colon cancer cell line. Fatty acids generated from both L. lactis and E. coli contained a mixture of linoleic acid and t10, c12 CLA at a ratio of ∼1.35 : 1. Following 5 days of incubation of SW480 cells with 5–20 μg ml−1 (17.8–71.3 μM) of the t10, c12 CLA, there was a significant (P<0.001) reduction in growth of the SW480 cancer cells compared with the linoleic acid control. Cell viability after treatment with the highest concentration (20 μg ml−1) of the t10, c12 CLA was reduced to 7.9 % (L. lactis CLA) and 19.6 % (E. coli CLA), compared with 95.4 % (control linoleic acid) and 31.7 % (pure t10, c12 CLA). In conclusion, this is believed to represent the first report in which recombinant strains are capable of producing CLA with an anti-proliferative potential.
PMCID: PMC2885616  PMID: 17660413
25.  Supplementation with conjugated linoeic acid decreases pig back fat deposition by inducing adipocyte apoptosis 
BMC Veterinary Research  2014;10:141.
Conjugated linoleic acid (CLA), a C18 fatty acid with conjugated double bonds, has been shown to serve as a powerful anti-obesity agent by several research groups, although the precise mechanism remains elusive. Previous studies showed that CLA induced apoptosis in 3T3-L1 cells and in mice. The aim of this research was to clarify the role of CLA in adipocyte apoptosis in pigs, a relevant model for obesity research.
Our results clearly show that back fat deposition of CLA-fed pigs was significantly lower than that of pigs in the control group. Moreover, some typical apoptotic cells were observed among the adipocytes of CLA-fed pigs. Furthermore, the CLA-fed pigs had reduced expression of the anti-apoptosis factor Bcl-2 and increased expression of the pro-apoptosis factors Bax and P53. Subsequently, increased cytochrome C was released from the mitochondria to the endochylema, and the caspase cascade was activated, resulting in cellular apoptosis. These results are consistent with the effects of Bcl-2 and Bax in regulating CLA-induced adipocyte apoptosis via the mitochondrial signaling pathway. However, the increased expression of tumor necrosis factor (TNF)-α and its receptor TNFR indicate that the effect of CLA might partly be through the death receptor signaling pathway in adipose cells.
Our study has demonstrated that CLA reduces pig body fat deposition, an outcome that is partly meditated by apoptosis of adipose cells, and that both the mitochondrial pathway and the death receptor pathway are involved in this effect.
PMCID: PMC4074849  PMID: 24969229
Conjugated linoleic acid; Fat deposition; Adipocyte; Apoptosis; Pig

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