| Conjugated linoleic acids (CLA) refer to a collection of positional and geometricisomers of octadecadienoic acid with conjugated double bonds. A number of thesenaturally occurring C18 fatty acids, which have the conjugated double bonds structurelocated in either the cis or trans configuration at positions△7,9;△8,10;△9,11;△10,12;△11,13 of the carbon chain(3-6), have been identified.Natural CLA mainly comes from the fat of ruminant milk and meat. The mostimportant CLA isomers are c9,t11-CLA and t10,c12-CLA, c9,t11-CLA is thebiohydrogenation byproduct of Butyrivibrio fibrisolvens in cattle rumen. CLA can alsobe bioconverted by other bacteria, such as lactobacillus spp., and synthesized bychemical method.CLA exhibits a number of physiological effects, such as anti-adipogenic,anti-carcinogenic, anti-atherogenic, and immune modulation effects. In the recent years,much attention has been paid to the antiobesity effect.Various concentration(25, 50, 100, 200μmol/L) of 10,c12-CLA (purity of 98%)and c9,t11-CLA(purity of 92%), as well as the mixture of c9,t11-CLA andt9,t11-CLA(1:1, V/V) were applied to this study to investigate the inhibitive effects ofCLA on 3T3-L1 cell line in different treating times(1d, 2d, 3d).The proliferation of preadipocytes was detected by methyl thiazolyl tetrazolium(MTT) assay method. MTT analysis results showed that both t10,c12-CLA and themixture of CLA could inhibit 3T3-L1 cell proliferation remarkably (P＜0.05).t10,c12-CLA isomer was better than the mixture in the proliferation inhibition. Thestronger inhibition was occurred at the. concenration of 100μmol/L and with thetreating time increased. CLA mixture showed higher inhibition at higher concentrationand increased treating time. c9, t11-CLA showed no remarkable inhibitive effects on3T3-L1 cell proliferation. The result showed that t10,c12-CLA have higher inhibitiveactivity, following is CLA mixture, c9, t11-CLA respectively.3T3-L1 cell differentiation was observed by Oil Red O staining method. Fourtreatments included 50μmol/L and 100μmol/L t10,c12-CLA, 100μmol/L mixture CLA, as well as control (no CLA added) was tested in this study. 3T3-L1 cell, welldifferentiated by "cocktail method" (DEX, IBMX, INSULIN was added to the culturemedium), was performed by Oil Red Ostaining and colorimetry. The results indicatedthat t10,c12-CLA, particularly, at the concentration of 100μmol/L, had higherinhibitive effects on 3T3-L1 cell differentiation (P＜0.05).RT-PCR was performed to assay the effect of t10, c12-CLA on the expression ofPPARγ2 mRNA.. The results revealed that the expression of PPARγ2 mRNA wassignificantly reduced in the treatment groups of 100μmol/L and 50μmol/Lt10,c12-CLA, as 52.1%, 83.0% respectively in comparison with control group. It wassuggested that the inhibitive effect of CLA on 3T3-L1 differentiation might relate tothe reduction of the expression PPARγ2 mRNA. |
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