GR-mediated transcriptional regulation of m^(6)A metabolic genes contributes to dietinduced fatty liver in hens

Background:Glucocorticoid receptor(GR)mediated corticosterone-induced fatty liver syndrome(FLS)in the chicken by transactivation of Fat mass and obesity associated gene(FTO),leading to demethylation of N6-methyladenosine(m^(6)A)and post-transcriptional activation of lipogenic genes.Nutrition is considered the main cause of FLS in the modern poultry industry.Therefore,this study was aimed to investigate whether GR and m^(6)A modification are involved in high-energy and low protein(HELP)diet-induced FLS in laying hens,and if true,what specific m^(6)A sites of lipogenic genes are modified and how GR mediates m^(6)A-dependent lipogenic gene activation in HELP diet-induced FLS in the chicken.Results:Laying hens fed HELP diet exhibit excess(P<0.05)lipid accumulation and lipogenic genes activation in the liver,which is associated with significantly increased(P<0.05)GR expression that coincided with global m^(6)A demethylation.Concurrently,the m^(6)A demethylase FTO is upregulated(P<0.05),whereas the m^(6)A reader YTHDF2 is downregulated(P<0.05)in the liver of FLS chickens.Further analysis identifies site-specific demethylation(P<0.05)of m^(6)A in the mRNA of lipogenic genes,including FASN,SREBP1 and SCD.Moreover,GR binding to the promoter of FTO gene is highly enriched(P<0.05),while GR binding to the promoter of YTHDF2 gene is diminished(P<0.05).Conclusions:These results implicate a possible role of GR-mediated transcriptional regulation of m^(6)A metabolic genes on m^(6)A-depenent post-transcriptional activation of lipogenic genes and shed new light in the molecular mechanism of FLS etiology in the chicken.