The Effects Of CIDEC On Milk Lipid Synthesis In Mammary Glands Of Dairy Cows

Milk lipid is a main nutritional component of milk and it is an important source of nutriton for humans.But in our country,the milk lipid percentage is lower and not enough to people's demand.Therefore,the problem we need to solve is improvement of milk production and milk lipid percentage.Cell death-inducing DNA fragmentation-factor-likeeffector C(CIDEC)is a lipid droplet-associated protein and functions to promote lipid accumulation and inhibit lipolysis.The mammary gland of dairy cow is one of the major lipid-synthesizing organs in lactation period.However,little is known about the effect of CIDEC on milk lipid sytnehsis in mammary gland of dairy cow.In order to investigate the relationship between CIDEC and milk lipid synthesis,q RT-PCR,in-situ hybridization,western blot,and immunofluorescence were used to detect CIDEC expression in mammary tissues of lactating cow with high-and low-quality milk,as well as mammary tissues of dry cows.The reuslts showed that CIDEC expression was significant higher in mammary tisssues of lactating cows with high-quality milk than in cows with low-quality milk and dry cows.This finding suggested that CIDEC expression was corelated to milk lipid synthesis.Then we investigated the effects of CIDEC on TAG content and gene expression involved milk lipid synthesis in cultured mammary epithelial cells of dairy cows.The results showd that the overexpression of CIDEC in cultured mammary epithelial cells increased milk lipid content and increased expression of genes associated with mammary denovot fatty acid synthesis,short-and long-chain intracellular fatty acid activation,triacylglycerol synthesis,and transcription regulation.The knockdown of CIDEC had the opposite effects.There results showed that CIDEC play an important role in regulationg milk lipid synthesis in mammary gland of dairy cows.In order to further investigated the signaling pathway involved in CIDEC expression and milk lipid syntheis in mammary gland of dairy cows,mammary epithelial cells were treated with 8 mmol/L sodium acetate and 1 mmol/L ?-hydroxy butyric acid sodium to induced milk lipid synthesis.Western blot results showed that addition of 8 mmol/L sodium acetate and 1 mmol/L ?-hydroxy butyric acid sodium increased the expression of 4EBP1,p-4EBP1,P70S6 K,p-P70S6 K,and AMPK,but decreased the expression of p AMPK,suggesting that CIDEC and milk lipid synthesis were regulated by m TOR and AMPK signaling pathway in mammary gland of dairy cow.In the end,we investigated the effect of PPAR? on CIDEC expression and milk lipid synthesis in mammary gland of dairy cow.The results showed that knockdown and overexpression of PPAR? affected CIDEC expression and TAG synthesis in mamamry epithelial cells of dairy cows.In PPAR? overexpressed cells,CIDEC knockdown significantly decreased TAG synthesis,suggesting that PPAR? regulated milk lipid synthesis via regulating CIDEC expression.Dual-luciferase reporter assay showed that PPAR? increased the transcriptional activity of CIDEC promoter,and cis-elements within the CIDEC promoter region from-100—-40 bp mediated this regulation.Ch IP-PCR analysis revealed that PPAR? induced CIDEC expression by promoting the associating of RXR? onto the promoter of CIDEC gene.These results of the research provide the experimental theory to improve milk lipid synthsis,which is important to our milk industry.