Effects And Its Mechanism Of GPR109A On Mammary Gland Development And Lactation In Mice

With people's higher and higher requirements for dairy products,the problems of low milk fat,milk protein rate and per unit yield of dairy cows in China's animal husbandry have gradually become prominent.As people's requirements for dairy products are getting higher and higher,the problems of low milk fat and milk protein rates in my country's animal husbandry and low yields of dairy cows have gradually become prominent.How to improve the quality and output of dairy products has also become the focus of lactation research in my country.The realization of the lactation function of the mammary glands depends on the good development of the mammary glands at different stages.Genes are the effect factors of the functional phenotype of mammary glands.In-depth exploration of the regulation mechanism of related genes in the process of mammary gland development and lactation and the development of intervention methods for them are of great significance for accelerating the development of the dairy industry.The mammary gland is the only place for mammals to achieve lactation.Therefore,the development status of the early mammary gland directly determines the quality of late lactation,and each stage of mammary gland development is regulated by genes.Therefore,it is of great significance to deeply explore the regulation mechanism of related genes in the process of breast development.This research group focused on the related research of GPR109 A in the early stage,and found that GPR109 A is highly expressed at different stages of breast development.Therefore,in this study,mice were used as the research model to study the effect of GPR109 A on different stages of breast development and milk quality and its mechanism by knocking out GPR109 A in vivo.It is expected to provide a potential target for artificial regulation of lactation function.First,we constructed GPR109 A knockout mice.It was observed that the amount of milk in the stomach of young rats drinking GPR109 A knockout mothers increased significantly.According to the weight tracking monitoring of young rats,we found that the weight of GPR109 A knockout mothers,whether fed WT or GPR109 A knockout infants,was significantly higher than that of WT and GPR109 A knockout infants fed wt mothers.These results suggest that knockout of GPR109 A may affect the milk yield of female rats or change the milk quality of female rats.Subsequently,we performed transcriptomic studies on the mammary glands of lactating WT and GPR109 A knockout mice.The results showed that there were 352 differential genes,including 122 up-regulated genes and 230 down-regulated genes.Go analysis showed that these differential genes were mainly concentrated in the biological processes of stem cell differentiation and cell proliferation,protein absorption and transport,and lipid metabolism.KEGG enrichment analysis showed that the differential genes were mainly enriched in PI3K-Akt-mTOR signal pathway,JAK-STAT signal pathway and PPAR signal pathway.These signaling pathways are closely related to breast development and lactation.These results suggest that the deletion of GPR109 A may affect breast development and the synthesis of milk fat and milk protein.In order to further study the effect of GPR109 A knockout on lactation function.We detected the expression of milk protein in breast and milk of WT and GPR109 A knockout mice during lactation.The results showed that the expression of WAP,casein and LA in mammary gland and milk increased significantly.In addition,the milk yield of GPR109 A knockout mice was also significantly increased.Further study found that STAT5 signal pathway was significantly activated after knockout of GPR109 A.Then we detected the development of mammary gland in puberty,pregnancy and lactation.The results showed that after knockout of GPR109 A,the branch and distribution area of mammary duct in adolescent,pregnant and lactating mice increased significantly.In addition,the protein expressions of cyclin D1,cyclin D3,PCNA,cyclin E2 and cyclin A1 were significantly increased in the mammary glands of GPR109 A knockout mice during puberty,pregnancy and lactation.These results suggest that GPR109 A knockout mice can significantly promote mammary gland development and lactation,and the realization of this function is closely related to STAT5 signaling pathway.Finally,we detected the effect of GPR109 A on milk fat globules.The results showed that knocking out GPR109 A significantly increased the size of lipid droplets in the liver and mammary gland.The knockout of GPR109 A reduces the expression of the endoplasmic reticulum protein SRZR complex.The low expression of these endoplasmic reticulum protein SRZR complexes is the main factor regulating lipid droplet diameter.The expression of the SRZ complex is mainly regulated by its member RINT1.In addition,the low expression of RINT1 also significantly increased the diameter of lipid droplets in m MECs.Then we added niacin,an agonist of GPR109 A,and found that GPR109 A can regulate the expression of RINT1 through the PI3K-AKT-mTOR signaling pathway.The above results indicate that niacin can regulate the expression of RINT1 by activating the PI3K-AKT-mTOR signaling pathway mediated by GPR109 A,thereby affecting the formation of the endoplasmic reticulum complex SRZR,and ultimately regulating the size of lipid droplets.In summary,this study reported for the first time the regulation of GPR109 A on mouse mammary gland development,milk protein synthesis and lipid droplet size.And preliminarily clarified the regulation mechanism of GPR109 A on mammary gland development,milk fat and milk protein through PI3K-AKT-mTOR signal pathway and endoplasmic reticulum complex SRZR.At the same time,the above research also provides basic data for the research on the regulation mechanism of milk cow mammary gland development in different periods.