Mechanism Of RBP4 Regulating Mammary Epithelial Cell Development And Milk Fat Synthesis In Dairy Cows

Retinol Binding Proteins 4(RBP4)binds to retinol(vitamin A)in plasma to transport retinol from the liver to target tissues.In addition to being a transporter of vitamin A,RBP4 is also an adipokine,a member of the lipid carrier protein family that acts as a fatty acid transporter.This study aims to investigate the effect of RBP4 on the growth and synthesis of lipid droplets in dairy cow mammary epithelial cells,and to study its related mechanism of action.First,siRNA or lentiviral transfection was used to interfere with or overexpress RBP4 gene,CCK8 method was used to detect cell viability,flow cytometry was used to detect apoptosis,RT-q PCR was used to detect cell development and the expression of genes related to milk fat synthesis,and the kit was used to determine the content of lipid droplets in cow mammary epithelial cells.Secondly,on the basis of RBP4 overexpression,PI3K/AKT signaling pathway activity was inhibited,cell activity and apoptosis,cell development and expression of genes related to milk fat synthesis,cell lipid droplet content and other indicators were detected,and its possible mechanism of action was explored.The results showed that:(1)interference with RBP4 significantly reduced the expression of Caspase3,BAX,P21 and P27(P <0.05),significantly reduced the expression of BCL-2(P<0.01)and significantly reduced the apoptosis rate(P<0.05).In addition,interference with RBP4 significantly reduced the expression of milk fat synthesis genes DGAT1,FABP3,LPIN1(P<0.05)and VLDLR expression(P<0.01),but did not have a significant effect on cell lipid droplet deposition(P>0.05).(2)Overexpression of RBP4 significantly reduced the expression of Caspase3,BCL-2 and P27(P<0.01),increased apoptosis rate significantly(P<0.01),and did not have a significant effect on lipid droplet deposition(P>0.05).(3)Overexpression of RBP4,while inhibiting PI3K/AKT signaling pathway,the expression of Caspase3 was significantly reduced(P<0.05),the expression of P21 was significantly reduced(P<0.01),the expression of Caspase9 and P27 was significantly increased(P<0.05),the apoptosis rate was significantly reduced(P<0.01),and the content of cell lipid droplets was significantly reduced(P<0.01).These results suggest that RBP4 may promote apoptosis by increasing the expression of Caspase3,BAX,P21,P27 and other genes,and interfere with RBP4 to significantly reduce the apoptosis rate.Interfering with or overexpressing RBP4 did not have a significant effect on cell lipid droplet deposition,but overexpression of RBP4 inhibited the PI3K/AKT signaling pathway significantly reduced lipid droplet synthesis in cells.