Role of Vanin-1 Gene Methylation in Fat Synthesis in Goose Liver: Effects of Betaine and 5-Azacytidine Treatments

This study aimed to investigate the mediating effect of vanin-1 (VNN1) and its DNA methylation on the reduction in liver fat synthesis due to the role of betaine and 5-Azacytidine (5-AZA) in geese. Twenty-eight 35-day-old male Jiangnan white geese with similar body weight (BW) and good health conditions were randomized into four groups (seven birds per group). All the birds were housed with the same type of basal diet. The control group was treated with normal saline intraperitoneally (I.P.); the AZA group was treated I.P. with AZA (2 mg/kg); the betaine group was fed with betaine through the diet and treated I.P. with normal saline (1.2 g/kg); the AZA+betaine group was fed with betaine through the diet and treated I.P. with AZA. The results showed that the administration of AZA significantly increased serum levels of total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL), and VNN1 enzyme activity ( < 0.05); additionally, the expression levels of the molecules in various tissues were up-regulated to different extents, such as VNN1, fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), stearoyl-CoA dehydrogenase (SCD), and sterol regulatory element binding protein (SREBP); in contrast, the treatment of betaine reduced serum TC levels and the S-adenosylmethionine/S-adenosylhomocysteine (SAM/SAH) ratio; furthermore, hepatic DNA methylation in the AZA group was decreased in terms of the VNN1 promoter region. The results demonstrated that the expression of the gene was negatively correlated with DNA methylation. This finding verified the key role of and its methylation in the inhibition of liver lipid synthesis by betaine and provided a novel molecular mechanism for the regulation of liver lipid metabolism.