Effect of dietary betaine supplementation on mRNA level of lipogenesis genes and on promoter CpG methylation of fatty acid synthase (FAS) gene in laying hens
Our aims are to determine the effects of dietary betaine supplementation on growth performance, percentage of abdominal fat, ratio of liver to body weight, mRNA expression levels of acetyl-CoA carboxylase (ACC), fat acid synthase (FAS) and adipose differentiation-related protein (ADRP) genes in the abdominal fat of hens. In addition, promoter DNA methylation patterns of FAS gene were also analyzed by bisulfite sequencing. A total 120 of Hy-Line White laying hens were randomly divided into four diet groups with supplemented betaine of 0, 0.04, 0.06 and 0.08%, respectively. At 180 old days of age, the significant difference in egg production was observed between the control and 0.08% betaine diet group (P < 0.05). The FAS mRNA abundance was increased in the abdominal adipose of hens receiving 0.08% betaine compared to the hens receiving control diet with no betaine (P < 0.05). However, supplementation of betaine had no significant effect on FAS expression level in 165-day-old hens. The ACC and ADRP gene expression levels were not significantly affected by betaine at either 165 or 180-day-old hens (P>0.05). Furthermore, the overall GpG methylation patterns at the FAS gene promoter region ranging from −961 to −749 were not significantly different among all groups in 180-day-old hens (P > 0.05), CpG methylation mainly occur from 1st to 5th sites. This study suggests that betaine could regulate lipogenesis of laying chickens by affecting the transcription of FAS genes, and that DNA methylation at some CpG dinucleotides may play a role in regulating FAS gene expression.
Key words: Betaine, CpG methylation, gene expression, laying hen, lipogenesis genes.