Abstract
With its annually increasing prevalence, non-alcoholic fatty liver disease (NAFLD) has become a serious threat to people's life and health. After a preliminary research, we found that Lactucopicrin has pharmacological effects, such as lowering blood lipids and protecting the liver. Further research showed its significant activation for fatty acid β-oxidase hydroxyacyl-coenzyme A (CoA) dehydrogenase trifunctional multienzyme complex subunit alpha (HADHA), so we hypothesized that Lactucopicrin could ameliorate lipid accumulation in hepatocytes by promoting fatty acid β-oxidation. In this study, free fatty acid (FFA)-induced human hepatoblastoma cancer cells (HepG2) were used to establish an in vitro NAFLD model to investigate the molecular basis of Lactucopicrin in regulating lipid metabolism. Staining with Oil red O and measurements of triglyceride (TG) content, fatty acid β-oxidase (FaβO) activity, reactive oxygen species (ROS) content, mitochondrial membrane potential, and adenosine triphosphate (ATP) content were used to assess the extent to which Lactucopicrin ameliorates lipid accumulation and promotes fatty acid β-oxidation. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot methods were used to explore the regulatory effects of Lactucopicrin on factors related to fatty acid β-oxidation. Results showed that Lactucopicrin downregulated phosphorylated mammalian target of rapamycin (P-mTOR) by activating the adenosine monophosphate-activated protein kinase (AMPK) pathway and upregulated the messenger RNA (mRNA) and protein expression levels of coactivators (peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α)), transcription factors (peroxisome proliferator-activated receptor α (PPARα) and peroxisome proliferator-activated receptor γ (PPARγ)), and oxidative factors (carnitine palmitoyltransferase 1A (CPT1A) and HADHA). This phenomenon resulted in a significant increase in FaβO activity, ATP content, and JC-1 and a significant decrease in ROS level, TG content, and intracellular lipid droplets. With the addition of Dorsomorphin, all the effects of Lactucopicrin intervention were suppressed. In summary, Lactucopicrin promotes fatty acid β-oxidation by activating the AMPK pathway, thereby ameliorating FFA-induced intracellular lipid accumulation in HepG2 cells.