The Important Regulators And Related Metabolic Changes Occur In Non-alcoholic Fatty Liver Disease

Objective Perturbed endoplasmic reticulum(ER)homeostasis and increased levels of lipid regulators(GOS2 and FGF21)have been documented in hepatic steatosis models.TFEB as a transcription factor,translocate to nucleus when ER stress.We investigated the mechanisms underlying the important regulators(G0S2 or FGF21)of NALFD and ER stress-induced hepatic steatosis,especially the regulation of TFEB on these important regulators of NALFD.Meanwhile,LAMTOR1 deficiency in macrophage induce cytoplasm-to-nucleus shuttling of TFEB,then we tested the effects of LAMTOR1 on TFEB subcellular localization in liver and the lipid metabolism especially ketogenesis in mice with liver-specific ablation of Lamtor 1.Methods We first analyzed GOS2 and FGF21 expression and the activation of ER stress in several hepatic steatosis models to search for the regulation of ER stress on GOS2 and FGF21 expression.The transcription activation of TFEB on FGF21 was estimated by TFEB over-expression or luciferase reporter assay.LAMTOR1 may modulate TFEB subcellular localization,and therefore co-IP,Immunofluorescence staining or western blotting were used to determine TFEB subcellular localization and the interaction between LAMTOR 1 and TFEB.Lipid metabolism especially ketogenesis was determined in Lamtor 1LKO mice and their controls who have been applied ketogenic stimulus including fasting,ketogenetic diet or octanoate treatment.Finally,knockdown of TFEB via adenoviral infection was used to demonstrate the role of TFEB in ketogenesis regulated by LAMTOR1.Results ER stress was accompanied by elevation of FGF21 and G0S2 expression in the occurrence of fatty liver disease.In addition to under the regulation of ER stress,FGF21 is a direct transcriptional target of TFEB by direct binding and activating TFEB promoter.LAMTOR1 modulates TFEB subcellular localization by directly binding and anchoring TFEB to lysosome.Ketogenic conditions weakened the interaction between LAMTOR 1 and TFEB and rapidly induced TFEB nuclear translocation to transcriptional activate genes expression about fatty acids β-oxidation and ketogenesis.Indeed,relative to WT counterparts,Lamtor 1LKO mice had significant increases in the levels of circulating β-hydroxybutyrate and less hepatic lipid accumulation.Notably,shRNA-mediated TFEB knockdown resulted in serious hepatic steatosis and the reduction of circulating β-hydroxybutyrate in Lamtor 1LKO mice.These data indicate that TFEB acts downstream of LAMTOR1 to regulate β-oxidation and ketogenesis.Conclusions The simultaneous elevation of G0S2 and FGF21 expression were associated with ER stress in the occurrence of nonalcoholic fatty liver disease.G0S2 plays a crucial role in hepatic steatosis by inhibiting lipolysis.Furthermore,not just as a downstream target gene of PPARa and ER stress,FGF21 is also a direct transcriptional gene of TFEB.LAMTOR1 modulates TFEB subcellular localization by combining with TFEB.Ketogenic conditions may weaken their interaction and TFEB progressively translocated into the nucleus to transcriptional activate the genes expression about fatty acids β-oxidation and ketogenesis.In conclusion,TFEB acting as a downstream effector of LAMTOR1,regulates fatty acids β-oxidation and ketogenesis.