Preventive effect and underlying mechanism of dihydrocumin on NAFLD in oleic acid-treated HepG2 cells / 中草药

ABSTRACT

Objective: To evaluate the preventive effect of dihydrocumin (DHC) on an in vitro model of nonalcoholic fatty liver disease (NAFLD) and investigate the signal transduction pathways underlying DHC treatment. Methods: Oleic acid (OA, 0.5 mmol/L) induced hepatic steatosis was established in HepG2 cells as in vitro model of NAFLD. After cells were co-treated by OA and DHC (0, 5, 10, and 20 μmol/L) for 24 h, the cellular contents of triglyceride (TG), reactive oxygen species (ROS) and NO were determined by cellular biochemical assays. Signaling pathways involved in glucolipid metabolism and oxidative stress including SREBP-1C, PNPLA3, PPARα, PI3K, the phosphorylation of AKT (pAKT), AKT, and Nrf2 on the mRNA and protein levels were determined by RT-qPCR and Western blotting. The glucose uptake was determined by fluorospectrophotometry using 2-NBDG as a fluorescence probe. Results: Compared with the control group, the content of TG, ROS and NO was significantly increased, the uptake of 2-NBDG was decreased. and the expression of SREBP-1C and PNPLA3on the mRNA and protein levels were up-regulated and the protein expression levels for PPARα, PI3K and Nrf2, as well as the ratio of pAKT to AKT were down-regulated in OA-induced cells. Compared with OA treated group, DHC decreased the levels of cellular TG and NO, as well as the mRNA and protein expression levels of SREBP-1C and PNPLA3, and increased the uptake of 2-NBDG, while at the same time increasing the cellular glucose uptake and the protein expression levels of PPARα, PI3K, pAKT/AKT, and Nrf2 in OA-induced HepG2 cells. Conclusion: DHC protected OA-induced hepatic steatosis by inhibiting lipid accumulation and oxidative/nitrative stress and increasing hepatic insulin sensitivity. Furthermore, the effect of DHC is likely associated with its role in the regulation of SREBP-1C, PNPLA3, PPARα, Nrf2, PI3K and AKT signaling pathways. DHC may have the effects on relieving the resistance of insulin and promoting the uptake of glucose in the hepatocytes by upregulating PI3K expression and pAKT/AKT level. Through increasing the expression of Nrf2 and reducing the content of NO in the cells, DHC could alleviate the inflammatory reaction and oxidative damage of liver cells.