MAPK8 and Hepatic fibrosis: Taken together, our results show that high-calorie diet-induced ER stress increases PCPE-1 production in BAT through the activation of the IRE-1/JNK/c-Fos/c-Jun pathway and enhances liver fibrosis (Fig. 4Q), suggesting that inhibition of the BATokine PCPE-1 may represent a therapeutic modality for MASH.