The Study Of Methylation Of POMC Gene Promoter In Neonatal Mice Induced By Conjugated Linoleic Acid

The objective of this study was to explore the methylation of POMC genepromoter in neonatal mice induced by conjugated linoleic acid and the mechanism inthis process. In our experiment kunming females with pups were divided into twogroups(n=10mums,12pups/mum) randomly.On the third day of life,one group wasfed with a diet supplemented with LA(1.5%w/w) and the other was fed with a dietwith CLA(1.5%w/w) for10days.After that,all animals were fed with a standardchow diet until the end of the experiment. To study the milk composition and fattyacid composition,mouse milk were collected at the tenth day of feeding CLA/LA.Compared to LA group, the content of total CLA in milk increased significantly(P<0.01) in CLA group,but long-chain fatty acids (C10,C12, C14,C9C12C18:2, C20:2,C20:3(8,11,14)C22:4) reduced significantly (P<0.05). Milk fat and milk lactosereduced significantly (P<0.01,P<0.05) in CLA group while milk protein have nosignificant changes between the two groups(P>0.05). These results indicate that CLAcould be transmitted to offspring through breast milk and can change milk fat,milklactose and fatty acid composition. Food intake and body weight of these pups weremeasured daily after weaning.The results show that body weight in CLA group wassignificantly lower (P<0.05), but the relative food intake was significantly higher thanthat of in LA group (P<0.05), These data demonstrated CLA enhanced the appetite ofoffsprings.The plasma and hypothalamus were collected to explore the mechanism ofthe change of appetite.We find that leptin in plasma have no significant changesbetween the two groups(P>0.05). The mRNA level of POMC in hypothalamus ofCLA mice significantly reduced compared to that in LA mice (P<0.05).BSP showsthat the methylation level of SP1-bing site of POMC gene promoter in CLA grouphigher and luciferase report system test indicate POMC gene SP1methylation inhibitsthe activity of POMC promoter in293Rb cells stimulated by leptin or not, gelmobility shift experiment result shows that POMC gene SP1methylation blocked itsbinding to SP1protein. These results suggest that the hypermethylation of SP1-binding site in POMC gene promoter blocked the POMC signal pathway which playsa key role in appetite.In order to study hypothalamic POMC promoterhypermethylation in newborns whether effect its metabolism in adult, the body weight and food intake were measured weekly after weaning.The data shows that the bodyweight of mice CLA group catch up and then higher than that in LA group. The bloodglucose level in CLA mice with insulin resistance significantly higher than that of inthe LA group in adulthood (P<0.05). Conclusion: the maternal lactation diets addingCLA reduced the content of milk lactose,milk fat and long chain fatty acids, butsignificantly increased total CLA content in milk and cause hypothalamicPOMC promoter hypermethylation in neonatal mice; The hypermethylation ofSP1-binding site in hypothalamic POMC gene promoter blocked the POMC pathwayand affects the glucose metabolism in adulthood of offspring.