• Journal of Nutrition and Health
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• v.36 no.7
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• pp.661-666
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• 2003

The study was designed to compare the anti-carcinogenic effect of conjugated linoleic acid (CLA) isomers on colon carcinogenesis in 1,2-dimethylhydrazine (DMH)-treated rats by determining the levels of apoptosis, cell proliferation, eicosanoids and 1,2-diacylglycerol (DAG) in colonic mucosa. Sixty male Sprague Dawley rats were randomly divided into 3 groups depending on the types of CLA isomers, i.e. BT group (no CLA contained), CLA-C group (cis-9, trans11 isomer contained), and CLA- T group (trans-10, cis-12 isomer contained). The experimental diet was composed of protein at 20%, carbohydrate at 56.2%, and fat at 14.5% including 0.8% CLA isomers by weight. The experimental diet was fed for 14 weeks with the initiation of intramuscular injection of DMH, which was injected twice a week for 6 weeks to give total dose of l80mg per kg body weight. Two CLA isomers (c9t11 and t10c12) significantly increased the relative percentage of apoptosis but reduced cell proliferation in mucosal cell and also the levels of PGE$_2$, TXB$_2$, and DAG in colonic mucosa. However, there was no significant differences in anti-carcinogenic effect between c9t11 isomer and t10c12 isomer. Overall, colon carcinogenesis could be significantly inhibited by CLA isomers by increasing apoptosis and reducing cell proliferation, the levels of eicosanoids and DAG in colonic mucosa.

• Food Science of Animal Resources
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• v.30 no.6
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• pp.879-885
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• 2010

Conjugated linoleic acid (CLA) isomers are found naturally in foods, such as milk, milk products, beef and others, from biohydrogenation of vegetable oils. They are heterogenous group of isomers of linoleic acid in the family of polyunsaturated fatty acids. Among the isomers of linoleic acid cis9, trans11- CLA (c9, t11-CLA) and trans10, cis12- CLA (t10, c12-CLA) are found to be biologically active isomers. These biologically active isomers either individual or combined found to be health beneficial in various diseases, such as cancer, diabetes, obesity, and atherosclerosis, conclusive participation in physiological processes are necessary. This review focused on the current study of CLA in prevention of disease, such as cancer, diabetes and atherosclerosis, and their effective function in body fat reduction, improvement of bone and muscle mass at a cellular, clinical and systematic level.

• Preventive Nutrition and Food Science
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• v.5 no.2
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• pp.86-92
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• 2000

Conjugated linoleic acid(CLA) refers to a collective term of positional and geometric isomers of linoleic acid, which are different in their biological activities. The predominant isomer of CLA in animal tissues is cis-9, trans-11; smaller amounts of trans-10, cis-12 CLA isomers, CLA methyl ester (CLA-ME) was chemically syn-thesized from linoleic acid by the alkaline isomerization method. The synthetic CLA-ME, mainly composed of cis-9, trans-11 CLA and trans-10, cis-12 CLA, was dissolved in acetone, stored at 68$^{\circ}C$ for 1 day, and the supernatant(cis-9, trans-11 CLA-Me) was separated from the precipitate (trans-10, cis-12 CLA-Me). After the processes were repeated three times at -68$^{\circ}C$, the whole processes were repeated three times at -71$^{\circ}C$ in order to increase the purity of these two isomers. The cis-9, trans-11 CLA-Me and trans-10, cis-12 CLA isomers were further purified by the urea adduct. Purities of the cis-9, trans-11 CLA-Me and trans-10, cis-12 CLA-Me were 90.3 and 99.9%, respec-tively. This method could be employed for the preparation of a large quantity of highly purified cis-9, trans-11 CLA-Me or trans-10, cis-12 CLA-Me from synthetic CLA-Me.

• Journal of Life Science
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• v.27 no.8
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• pp.965-973
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• 2017

Conjugated linoleic acid (CLA) is a group of positional and geometric isomers of linoleic acid with conjugated double bonds at C9,C11 and C10,C12 positions. Of possible CLA isomers, a naturally occurring CLA isomer is c9,t11-CLA which is produced from linoleic acid by linoleate isomerase from various rumen and lactic bacteria, and mushroom mycelia. Meanwhile, synthetically prepared CLA contained an equal amount of c9,t11-CLA and t10,c12-CLA isomers, and other isomers as minor constituents. CLA was firstly mentioned in 1939 during the elaidinization reaction of linoleic acid. Thereafter, CLA was not an attractant to scientists because it was not scientifically interested any more. However, since the anticarcinogenic action was driven from 7,12-dimethylbenz[a]anthracene (DMBA)-induced mouse skin carcinogenesis in 1987, CLA-related researches were drastically elevated, resulting in approximately 6,100 research papers in literature, so far. CLA exhibited the significant biological activities: anticarcinogenic, antidiabetic, antihypertensive, antiatherosclerotic, body-fat reducing, antioxidative, antiinflammatory, testosterone producing and other activities. Interestingly, two major CLA isomers, c9,t11-CLA and t10,c12-CLA, exhibited different biological activities. Meanwhile, t,t-CLA isomers which is minor constituent of chemically synthesized CLA from linoleic acid exhibited more potent anticarcinogenic activity in carcinogen-induced animal models and cancer cell lines than other CLA isomrs. In the present review, the significant biological activities of CLA were discussed along with historical studies of CLA since 1939.

• Journal of Nutrition and Health
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• v.37 no.7
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• pp.533-539
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• 2004

It has been reported that CLA decreases fat deposition in vivo and in vitro experiments. Among CLA isomers, c9t11 and t10c12 have been shown to exert active biological activities. For example, t10c12 reduces body weight and increases lean body mass, whereas, c9t11 has little effect on body fattness. However, the underlying molecular mechanism for the anti-obesity action of CLA isomers are not well understood. The purpose of this study was to examine the effects of t10c12 and c9t11 on lipid accumulation, cell proliferation, cell death and the expression levels of Ucp genes which are proposed as targets for anti-obesity in 3T3-L1 preadipocytes. Isomers of CLA at 50$\mu$M were added into preadipocyte differentiation medium for 3, 6 and 9days. Control cells received only the vehicle in the differentiation medium. Cytochemical analyses for lipid accumulation, cell proliferation and apotosis were carried out to compare lipidogenesis and cellular activity. RT-PCR analysis of GAPDH, Ucp 2,3 and 4 were also performed to find any modulatory effects of CLA isomers on the metabolic genes. Lipid accumulation indicated by Oil Red-O staining was inhibited in CLA isomers as compared to the control. T10c12 isomer showed less lipidogenesis than c9t11 did. A decrease occurred in CLA isomers as shown by BrdU incorporation. Apotosis has occured at higher level in t10c12 when compared to that of t9c11. Ucp 2, 3 and 4 genes were also upregulated in CLA isomers. T10c12 showed higher level of Ucp gene expressions than the c9t11 did. The biological activities of CLA isomers were also found to be different during differentiation of 3T3-L1 preadipocytes, suggesting that different isomers may be active in certain stage of lipidogenesis. The results indicate that both c9t11 and t10c12 CLA isomers decrease lipidogenesis, inhibit cell proliferation, increase cell death and upregulate in Ucp gene expressions during 3T3-L1 preadipocyte differentiation. T10c12 isomer was more effective than c9t11 in overall anti-obesity activity.

• Nutrition Research and Practice
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• v.2 no.4
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• pp.326-330
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• 2008

Conjugated linoleic acids (CLA) were identified in 1980's, since then it has been intensively studied due to its various beneficial health effects such as anti-inflammatory, anti-atherogenic, anti-carcinogenic and anti-diabetic/obesity effects. Isomer specificity of a number of CLA isomers, especially predominant isomer 9Z,11E- and 10E,12Z-CLA, is now recognized. However, the less prevalent CLA isomers have not been well characterized. Recently, studies have reported the distinctively different effects of 9E, 11E-CLA in colon cancer cells, endothelial cells, and macrophage cells compared to the rest of CLA isomers. In this review, various effects of CLAs, especially anti-inflammatory and anti-atherogenic effects, will be discussed with focusing on the isomer-specific effects and potential mechanism of action of CLA. At last, recent studies about 9E,11E-CLA in in vitro and animal models will be discussed.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.3
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• pp.448-458
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• 2009

It has been well documented from animal and human studies that conjugated linoleic acid (CLA) has numerous beneficial effects on health. In chickens, CLA exerts many effects on performance ranging from egg quality and yolk lipids to meat quality. Although there are several CLA isomers available, not all CLA isomers have the same incorporation rates into egg yolk: cis-9,trans-11 and trans-10,cis-12 CLA isomers are more favorably deposited into egg yolk than other isomers investigated, but of the two isomers, the former has a higher incorporation rate than the latter. CLA alters the amounts and profiles of lipids in plasma, muscles and liver. Furthermore, increased liver weight was reported in chickens fed dietary CLA. As observed in egg yolk, marked reduction in intramuscular lipids as well as increased protein content was observed in different studies, leading to elevation in protein-to-fat ratio. Inconsistency exists for parameters such as body weight gain, feed intake, feed conversion ratio, egg production rate and mortality, depending upon experimental conditions. One setback is that hard-cooked yolks from CLA-consuming hens have higher firmness as refrigeration time and CLA are increased, perhaps owing to alterations in physico-chemistry of yolk. Another is that CLA can be detrimental to hatchability when provided to breeders: eggs from these breeders have impaired development in embryonic and neonatal stages, and have increased and decreased amounts of saturated fatty acids and monounsaturated fatty acids (MUFAs), respectively. Thus, both problems can be fully resolved if dietary sources rich in MUFAs are provided together with CLA. Emerging evidence suggests that CLA exerts a critical impact on stress and immune functions as it can completely nullify some of the adverse effects produced by immune challenges and reduce mortality in a dose-dependent manner. Finally, CLA is a key regulator of genes that may be responsible for lipid metabolism in chickens. CLA down-regulates both expression of the gene encoding stearoyl-CoA desaturase-1 and its protein activity in the chicken liver while up-regulating mRNA of sterol regulatory element-binding protein-l.

• Journal of Nutrition and Health
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• v.37 no.9
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• pp.763-770
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• 2004

This study was designed to compare the anti-carcinogenic effect of conjugated linoleic acid isomers on tumor incidence, cell proliferation and the levels of thromboxane (TX) B$_2$, prostaglandin (PG) E$_2$ and 1,2-diacylglycerol (DAG), and the related enzyme expression of cyclooxygenase (COX)-2 and protein kinase C (PKC) in colonic mucosa of 1,2-dimethy- lhydrazine (DMH) -treated rats. One hundred eight male Sprague Dawley rats were randomly divided into 3 groups depending on the types of CLA isomers, i.e. control group (no CLA contained), c9t11 group (cis-9, trans-11 CLA contained), and t10c12 group (trans-10, cis-12 CLA contained). The experimental diet was composed of protein at 20%, carbohydrate at 56.2%, and fat at 14.5% including 1.0% CLA isomers by weight. The experimental diet was fed for 30 weeks with the initiation of intramuscular injection of DMH, which was injected twice a week for 6 weeks to give total dose of 180 mg per kg body weight. Two CLA isomers (c9, t11, t10, c12) significantly reduced tumor incidence and cell proliferation by reducing the protein expression of COX-2 and PKC, and the level of TXB$_2$, PGE$_2$, and DAG in colonic mucosa. However, there was no significant difference in anti-carcinogenic effect between c9t11-CLA and t10c12-CLA.

• Journal of Veterinary Clinics
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• v.21 no.4
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• pp.336-342
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• 2004

The immunoenhancing effect of CLA isomers (CLA mixture, 10t-12c CLA, 9c-11c CLA, 9c-11c CLA, and 9t-11t CLA) on phagocytic activity of porcine peripheral blood leukocytes was examined. The phagocytic activities of peripheral blood mononuclear cells (PBMC) and polymorphonuclear cells (PMN) were analyzed by a flow cytometry system. The direct treatments of CLA isomers have no effect on phagocytosis of PMN as well as PBMC composed of approximately 10% monocytes and 90% lymphocytes. However, the phagocytic activities of PMN and monocyterich fraction from PBMC were remarkably enhanced by culture supernatant from PBMC treated with CLA mixture, 10t-12c CLA and 9c-11t CLA but not 9c-11c CLA and 9t-11t CLA. The phagocytic activity of PBMC was not enhanced by culture supernatant from PBMC treated with all CLA isomers. These results indicated that CLA isomers such as CLA mixture, l0t -12c CLA and 9c-11t CLA have an enhancing effect on phagocytosis of PMN and monocytes, which may be mediated through active humoral substances produced by CLA-stimulated PBMC. This study suggested that CLA stimulates PBMC to elaborate soluble factor(s), which may be an important mechanism for the enhancement of phagocytosis in non-specific immunity.

• Journal of Animal Science and Technology
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• v.46 no.6
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• pp.967-974
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• 2004

The current study was undertaken to determine the effect of various conjugated linoleic acid (CLA) isomers on differentiation of pig preadipocyte during culture. Preadipocyte(stroma-vascular cell) was isolated from the backfat of newborn pigs and cultured to differentiate into mature fat cell. Different doses of CLA isomers were treated to the culture media at different times. Cell differentiation was determined by measuring the glycerol3-phosphate dehydrogenase activity of the cultured preadipocytes. Twenty and fifty $\mu$M of trans110_cis 12 isomer of CLA inhibited differentiation of pig preadipocyte whereas cis9-cis II isomer stimulated the differentiation. Both cis9-transII and trans9-trans11 isomers showed no effect. Effect of CLA isomer was more evident at the early stage of culture(day 0-8), than the late stage(day 8-14). These results suggest that each CLA isomer has different effect on pig preadipocyte differentiation.