| With the progress of society and economic development,people's demand for dairy products is increasing.At the same time,dairy industry has become a pivotal industry in modern agriculture.Milk as an important source of protein in daily life,with its rich nutritional content and easy to accept the flavor and price,is loved by the broad masses of the people.At the same time,milk-based derivatives of different flavors of food,such as yogurt,cheese,etc.,is to maximize the nutritional value of milk.Milk fat and protein,as an important nutrient,is a sign of the core competitiveness of the dairy industry and one of the important indicators to evaluate the quality of milk.Nowadays,how to improve the content of milk fat and milk protein has become a research hotspot at home and abroad.Studies have shown that most of the milk proteins are synthesized by mammary epithelial cells,and most of the milk lipid synthesis is carried out by nutrient transfer from feed or fatty acid ab initio synthesis in mammary epithelial cells.At present,in dairy cattle feed,increasing milk fat content can be achieved by adding functional oils.Functional oils such as soybean oil have been widely used in dairy cattle daily feeding.But camellia seed oil is also a kind of functional oil containing a variety of nutrients and few reports about the effect of camellia seed oil on milk synthesis.Therefore,this study was based on bovine mammary epithelial cells(MAC-T)as a cell model to explore the effect of extra camellia seed oil on the expression of genes related to milk fat and milk protein synthesis in MAC-T cells.Bovine mammary epithelial cells(MAC-T)were resuscitated and inoculated in a culture dish at a density of 1×105 cells/ml.When the adherent cells grew to more than 90% of the culture dish,fat addition test was carried out.The dosage was 150 ug/ml of camellia seed oil working fluid in the experimental group and 150 ug/ml of soybean oil working fluid in the control group.The effect of camellia seed oil on fatty acid composition in MAC-T cells was studied that camellia seed oil changed the composition of fatty acids in MAC-T cells.Compared with the control group,oleic acid(C18:1),palmitic acid(C16:0),linoleic acid(C18:2c,?-6)and gamma-linolenic acid(C18:3c,?-6)in MAC-T cells increased by 29.26%,23.51%,13.69% and 14.71% respectively,but there was no significant difference.Decic acid(C10:0),undecanate(C11:0),lauric acid(C12:0),myristic acid(C14:0),pentadecanoic acid(C15:0),palmitoleic acid(C16:1),stearic acid(C18:0)and erucic acid(C22:1)were higher than those of the control group,but there was no significant difference.But caproic acid(C6:0)was down-regulated and there was no significant difference.In addition,compared with the control group,the proportion of long-chain fatty acids(LCFA)in MAC-T cells increased by 21.48%,while the proportion of mediumchain fatty acids(MCFA)decreased by 25.69%,with no significant difference.Although the proportion of monounsaturated fatty acids(MUFA)and polyunsaturated fatty acids(PUFA)was higher than that of the control group,there was no significant difference.The proportion of saturated fatty acids(SFAs)was lower than that of the control group and there was no significant difference.Although the MUFA/SFA ratio and PUFA/SFA ratio were higher than those of the control group,there was no significant difference.On the other hand,the proportion of?-6 unsaturated fatty acids increased by 13.92%,but there was no significant difference.Compared with the control group,the desaturation index C18:1/(C18:0 + C18:1)of MAC-T cells increased significantly(P < 0.05),but the ratio of C16:1/(C16:0 + C16:1)decreased by 20% and had no significant difference.The effect of camellia seed oil on milk fat and related gene expression in mammary epithelial cells of dairy cows was studied that the detection of genes related to milk fat signaling pathway included SREBP1(steroid regulatory element binding protein)and PPAR-?(peroxisome proliferator activated receptor ?),FASN(complex isodimer enzyme),ACC(highly regulated enzyme in fatty acid synthesis pathway),LPL(lipid).Fatty acid transport related genes,SCD(the key enzyme for the synthesis of monounsaturated fatty acids in the breast).The addition of camellia seed oil to MACT cells promoted the expression of SREBP1 and de novo synthesis of fatty acids related genes ACC,FASN,LPL and SCD(P < 0.05),but had no effect on PPAR-?.The effect of camellia seed oil on milk protein synthesis and related gene expression in MAC-T cells was studied that the addition of camellia seed oil could promote the expression of beta-casein in MAC-T cells and inhibit the expression of ?S1-casein(P < 0.05).Compared with the control group,the addition of camellia seed oil promoted the expression of PI3 K and AKT1 genes in the upstream of m TOR(P < 0.05)and S6K1 genes in the downstream of m TOR(P < 0.05),but inhibited the expression of e IF4 E genes in the downstream of m TOR.Compared with the control group,the addition of camellia seed oil also had a positive effect on JAK2/STAT5,another classical signal pathway of casein synthesis,promoting the expression of JAK2,STAT5-? and ELF5 genes(P < 0.05);on the other hand,in the protein level test,the addition of camellia seed oil could actively promote m TOR and S6K1 compared with the control group.And STAT5-? protein expression(P < 0.05).In the phosphorylation level test,compared with the control group,the results after adding camellia seed oil showed that the phosphorylation of m TOR,S6K1 and STAT5-? protein was enhanced(P < 0.05).The results showed that PI3K/AKT/m TOR and JAK2/STAT5 signaling pathways were activated when camellia seed oil was added.In conclusion,the addition of camellia seed oil can promote the expression of SREP1 and de novo synthesis of fatty acids related signaling pathways in MAC-T cells,and promote the synthesis of ?-casein by regulating PI3K/AKT/m TOR and JAK2/STAT5 signaling pathways. |
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