Effects Of CLA On Triacylglycerol Accumulation And Transcription Of MRNAs Of Genes Related To Fatty Acid Synthesis In Bovine Mammary Gland Epithelial Cells

Conjugated linoleic acids（CLAs）refer to a group of position and geometric isomers ofoctadecadienoic acid with conjugated double bonds. They exist widely in nature, ruminant meatand milk products are the main sources. Animal and human studies have confirmed that CLA had avariety of physioligical functions, mainly inculding anti-cancer, anti-atherosclerosis, loweringcholesterol level, reduction in body fat, decreasing fat deposition, modulation of bone tissuemetabolism, strengthening the body’s immunity and antidiabete.Based on the physiological functions of CLA, nutritionists strived to improve the CLAcontent of milk. But the studies found that with the increased CLA content in milk, it can led tomilk fat depression (MFD). The present studies confirmed that t10, c12-CLA was the major causethat can led to MFD in dairy cows, so bovine mammary gland epithelial cells were cultured in vitroby tissue blocks in this experiments and explore the pure c9, t11-CLA and t10, c12-CLA affect thetranscription of mRNAs of genes related to milk fat synthesis in mammary gland epithelial cells.At the molecular level, probe the effect of CLA on triacylglycerol (TAG) contents andtranscription of mRNAs of genes related to fatty acid synthesis in bovine mammary glandepithelial cells. The results showed that:(1) This experiment was used the tissue blocks to culture dairy cow mammary gland epithelialcells in vitro, and cell survival rate was higher, more than85%. After several passages andidentification of cytokeratin18, we can obtain the purified bovine mammary gland epithelial cells.Determination of biological characters of bovine mammary gland epithelial cells, the resultsshowed that the cell growth curve was “S” type, in line with the general cell growth pattern, cellpopulation doubling time was32.18h, cell planting survival efficiency was up to87%.(2) The results showed that c9, t11-CLA and t10, c12-CLA both significantly reduced TAGcontents in mammary gland epithelial cells (P<0.05), and the TAG inhibition ratio of t10, c12-CLAwas higher than c9, t11-CLA.(3) Study the effect of CLA on fatty acid composition in bovine mammary gland epithelial cellsby gas chromatograph, the results showed that150μmol/L c9, t11-CLA can significantly increasethe proportions of monounsaturated fatty acid (MUFA)(P<0.05),50μmol/L c9, t11-CLAsignificantly increased saturated fatty acid (SFA) proportions (P<0.05). With the increased concentrations of t10, c12-CLA, the proportions of MUFA had a downward trend (P<0.05). Thetwo CLA isomers didn’t affect the proportions of polyunsaturated fatty acid（PUFA）in bovinemammary gland epithelial cells (P＞0.05).(4) The bovine mammary gland epithelial cells were directly treated with differentconcentrations of exogenous c9, t11-CLA and t10, c12-CLA for48h, and then the transcription ofmRNAs of genes related to the uptake and transport of fatty acid and TAG synthesis in themammary gland epithelial cells was determined using the real-time fluorescence-basedquantitative PCR technology. The results showed that50-150μmol/L c9, t11-CLA and t10,c12-CLA both significantly downregulated LPL mRNA transcription level, compared with thecontrol group (P<0.05).50μmol/L c9, t11-CLA significantly downregulated the transcription levelof CD36(P＜0.05), but150μmol/L c9, t11-CLA significantly upregulated (P<0.05), and CD36mRNA transcription level was significantly increased with the increased concentrations of t10,c12-CLA (P<0.05).150μmol/L c9, t11-CLA and different concentrations of t10, c12-CLA bothsignificantly upregulated the transcription of ACBP gene (P<0.05). c9, t11-CLA and t10, c12-CLAboth significantly downregulated the transcription of FABP3, compared with the control group(P<0.05).150μmol/L c9, t11-CLA and t10, c12-CLA both significantly upregulated AGPAT mRNAtranscription level (P<0.05).This experiment was achieved the tissue blocks to culture bovine mammary gland epithelialcells in vitro, and cell planting survival efficiency was higher. The results indicated that CLAinbibited TAG accumulation and affected fatty acid synthesis in bovine mammary gland epithelialcells. The two CLA isomers both significantly downregulated the mRNA transcription levels ofLPL and FABP3, but the effect of t10, c12-CLA was apparent than that of c9, t11-CLA.