Ethyl 2-[2,3,4-Trimethoxy-6-(1-Octanoyl)Phenyl] Acetate (TMPA) Ameliorates Lipid Accumulation by Disturbing the Combination of LKB1 with Nur77 and Activating the AMPK Pathway in HepG2 Cells and Mice Primary Hepatocytes

Background The AMP-activated protein kinase alpha (AMPKα) pathway has widely been considered a key factor in energy metabolism. Ethyl 2-[2,3,4-trimethoxy-6-(1-octanoyl)phenyl] acetate (TMPA) is a novel AMPK agonist, which influences the stability of Nuclear Receptor Subfamily 4, Group A, Member 1 (Nur77)-serine-threonine kinase 11 (LKB1) in the nucleus. A recent study has determined that TMPA can ameliorate the reduction of insulin resistance in type II db/db mice. However, the role of TMPA in hepatocyte lipid metabolism has not been elucidated. Objective To investigate whether TMPA could ameliorate liver lipid accumulation under the stimulation of free fatty acids (FFAs) in vitro. Methods We evaluated differences of Nur77 and AMPK pathway in mice fed a high-fat diet and those fed a normal diet. In vitro, TMPA was added to HepG2 cells and primary hepatocytes before FFAs stimulation. Oil red O staining, Nile red staining were used to evaluate lipid deposition. Western blot and immunofluorescence were used to quantify related proteins. Results Nur77, AMPKα, LKB1, 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), acetyl-CoA carboxylase phosphorylation (p-ACC), and carnitine palmitoyltransferase 1 (CPT1A) showed significant differences in vivo. Under the intervention of TMPA, HepG2 cells and primary hepatocytes showed considerable amelioration of lipid deposition and improved the expression of phosphorylated (p)-AMPKα (p-AMPKα), p-LKB1, p-ACC, and CPT1A. Furthermore, Western blotting and immunofluorescence studies indicated that LKB1 dramatically increased expression in the cytoplasm but decreased in the nucleus. Further, AMPKα phosphorylation (p-AMPKα) also showed a higher expression in cytoplasm instead of the nucleus. Conclusion TMPA ameliorated lipid accumulation by influencing the stability of Nur77-LKB1 in vitro.