Under severe ER stress (indicated by an upregulation of CHOP) induced by tunicamycin, IRE1α and ATF6a pathways are activated to slow down hepatic steatosis via the upregulation of CHOP to suppress different transcriptional regulators of lipid homeostasis including C/EBPα (lipogenesis), PPARα (fatty acid oxidation), Pgc1α (fatty acid oxidation regulator), Srebp1 (lipogenesis), and ChREBP (another coregulator of lipogenesis alongside Srebp1 [174]) in mice. This evidence concerns the gene ERN1 and fatty liver disease.