The Mechanism And Effect Of Melatonin Regulating Milk Fat Synthesis In Bovine Mammary Epithelial Cells

Milk is the main nutritional components of milk fat,can provide nutrients and energy for human,butterfat rate in milk quality of high and low relationship both milk and dairy products processing features,but it is also an important symbol of dairy industry core competitiveness.At present,the content of milk fat in our country is generally low,even partially below the national standard,which weakens the competitiveness of dairy products in domestic and foreign markets.Therefore,how to improve the milk yield and the milk fat content is still the important scientific question of the dairy industry in China.Through revealing cows milk fat synthesis regulatory mechanism and screening of candidate genes related to milk fat,for the development of related genes and their molecular markers,high quality cow breeding high butterfat rate provides theoretical basis and technical support.In this experiment,the genetic polymorphism of 3 SNPs sites in the two genes of melatonin receptor MT1 and MT2 were analyzed by direct sequencing method in the experimental materials of 344 dairy cattle center in shanxi province.The correlation between the three mutants of the two genes and the determination of milk yield,milk fat rate and total milk fat were analyzed,and the molecular markers could be used for the production of the two genes.Secondly by in vitro culture cow mammary gland epithelial cells,studies of melatonin on cow mammary gland epithelial cell function and its mechanism of milk fat synthesis,in order to offer new ideas to improve milk fat content and technical means.The main results are as follows:1.Detection of g.22354 G>A mutation site in the second exon region of the melatonin receptor MT1 gene,the genotypes of AA,AG and GG were obtained,the AG genotype is the dominant allele,the results showed that GG genotype,milk protein,total protein and total milk fat were significantly higher than the AA genotype(P<0.05).2.In the intron region of the melatonin receptor MT2 gene,g.13647 T>A and g.13810 T>A,two SNP sites were detected;The MT2 gene g.13810 T> A loci,TT was the dominant genotype,and T was the dominant allele of the site;g.13647 T >A loci,GG is the dominant genotype,G is the dominant allele of this site.The effects of g.13647 T >A and g.13810 T>A on the lactation characteristics of the MT2 gene were not significant(P>0.05).3.Different concentrations of melatonin treatment cow mammary gland epithelial cells,found that 10 ?M melatonin significantly inhibited the cow mammary gland epithelial cells in the formation of lipid droplets,10 ?M melatonin group triglyceride levels significantly lower than the control group;At the same time,10 ?M melatonin significantly reduced the mRNA expression of key genes C/EBP??C/EBP??FASN?FABP4?SCD1 and SREPBP1.After treatment with the receptor antagonist Luzindole,the inhibitory effect of melatonin on the synthesis of milk fat in milk cow breast epithelial cells was significantly inhibited.The inhibitory effect of melatonin on milk fat synthesis in milk cow mammary gland epithelial cells was still present after treatment with receptor antagonist 4P-PDOT.To sum up,melatonin receptor MT1 gene has a significant correlation effect with milk fat traits of dairy cows,and can be used as a candidate reference gene for selection and breeding of some production traits of dairy cows.Further cell experiments showed that melatonin inhibited the synthesis of milk fat in milk epithelial cells of dairy cows through its receptor MT1.The above results showed that the control of melatonin level in dairy cows may be an effective technique to improve the milk fat content and improve the quality of dairy products.