Expression and methylation of microsomal triglyceride transfer protein and acetyl-CoA carboxylase are associated with fatty liver syndrome in chicken

The typical characteristic of fatty liver syndrome (FLS) is an increased hepatic triacylglycerol content, and a sudden decline in egg production often occurs. FLS may develop into fatty liver hemorrhagic syndrome (FLHS), characterized by sudden death from hepatic rupture and hemorrhage. DNA methylation is associated with transcriptional silencing, leading to the etiology and pathogenesis of some animal diseases. The roles of DNA methylation in the genesis of FLS, however, are largely unknown. The lipogenic methyl-deficient diet (MDD) caused FLS similar to human nonalcoholic steatohepatitis (NASH). After 16 Jingxing-Huang (JXH) hens were fed MDD for 10 wk, eight exhibited FLS (designated as FLS-susceptible birds); the remainder, without FLS, served as controls (NFLS). Physiological and biochemical variables, gene expression levels, and DNA methylation were determined in the liver. The development of FLS in JXH hens was accompanied by abnormal lipid accumulation. Relative expression of acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), and microsomal triglyceride transfer protein (MTTP) were significantly up-regulated in the FLS group in comparison with the NFLS group. The transcript abundance of sterol regulatory element binding protein 1 (SREBP-1c), stearoyl-CoA desaturase (SCD), liver X receptor alpha (LXR alpha), peroxisome proliferator-activated receptor alpha (PPAR alpha), and peroxisome proliferator-activated receptor gamma (PPAR gamma) did not differ between the two groups. Interestingly, MTTP and ACC mRNA abundance were negatively correlated with the level of promoter methylation. The extent of DNA methylation of the cytosine-guanine (CpG) sites in the SREBP-1c, FAS, PPAR alpha, and LXR alpha promoter regions was also analyzed by direct sequencing but none differed between FLS and NFLS birds. Taken together, these results specify link DNA methylation to the pathogenesis of FLS in chickens.