Effect And Mechanism Of Sodium Butyrate On Milk Fat Synthesis Of Bovine Mammary Epithelial Cells

Milk fat is an important measure of milk cow production performance indicators,the dairy production efficiency and economic benefit is very important.Milk fat contains essential linolenic acid,phospholipids and a variety of fat-soluble vitamins,especially cephalin,lecithin and neurolipin,which play an important role in human brain and nerve cells.Mammary epithelial cells(MECs)are the key sites for milk synthesis.Therefore,it is of great significance to explore the key factors in the regulation of milk fat synthesis by taking bovine mammary epithelial cells(bMECs)as the research object for the artificial regulation of milk quality and the improvement of human physique.Butyric acid is a short chain fatty acid formed by carbohydrate fermentation in the rumen of ruminants and is one of the key precursors of de novo synthesis of milk fat.Studies have shown that butyric acid can also act as a signaling molecule and play a variety of biological functions by activating its receptor G protein-coupled receptor 41(GPR41),such as lipid metabolism,anti-cancer,anti-inflammatory,etc.However,is it possible for sodium butyrate(NaB)to regulate the process of milk fat synthesis in bMECs by activating GPR41 and downstream signaling pathways? It has not been reported at home or abroad.Therefore,this study took bMECs as the research object to explore whether NaB promotes milk fat synthesis through GPR41 and its downstream signaling pathway.First,bMECs were treated with different concentrations of NaB,and the effects of NaB on milk fat synthesis were detected by BODIPY staining and triglyceride kit.The results showed that 1 m M NaB significantly promoted the synthesis of milk fat in bMECs.1 m M NaB was selected as the experimental concentration.GPR41 is the receptor of NaB,and the expression of GPR41 gene was detected by RT-PCR,and the results showed that NaB promoted the expression of GPR41 gene.To further investigate the mechanism of NaB promoting milk fat synthesis of bMECs,si RNA was used to inhibit GPR41.The results showed that si RNA GPR41 inhibited milk fat synthesis of bMECs induced by NaB,indicating that NaB promoted milk fat synthesis of bMECs by activating GPR41.Further study found that the NaB in bMECs activated the promotion of mechanistic target of rapamycin(m TOR)and S6kinase(S6K)activity,inhibited AMPK activation of protein kinase(AMPK)and sirtuin1(SIRT1)activity,choose corresponding blocking agent and activating agent can inhibit the NaB to promote bMECs milk fat synthesis.These results indicated that NaB promoted the nuclear translocation of sterol regulatory element binding protein 1(SREBP1)via GPR41/AMPK/m TOR/S6 K signaling pathway,and promote the acetylation of mature SREBP1 via GPR41/AMPK/SIRT1,thus promoting the synthesis of milk fat.In summary,NaB promotes milk fat synthesis by increasing nuclear translocation and acetylation of SREBP1 via activation of GPR41 and its downstream signaling pathways.