Curcumin is a polyphenol compound with many pharmacological activities including antioxidant, lipid-loweing and liver protective. Dihydrocurcumin (DHC) is one of the major metabolites of curcumin. So far, the pharmacological activity of DHC has not been reported. Here, we evaluate the effects of DHC on oleic acid (OA)-induced lipid accumulation, oxidative stress and insulin resistance and the underlying mechanism in L02 and HepG2 cells.

OA-induced L02 and HepG2 cells were used as the in vitro model of nonalcoholic fatty liver disease (NAFLD). Lipid accumulation, oxidative stress, glucose uptake and cell inflammation were evaluated by cellular biochemical assay, respectively. Signaling pathways involved in lipid metabolism including peroxisome proliferator activated receptor-α (PPARα), the sterol regulatory element binding protein-1C (SREBP-1C) and patatin-like phospholipase domain containing 3 (PNPLA3), glucose uptake including phosphatidylinositol 3-kinase (PI3K) and phosphorylated serine-threonine protein kinase (pAKT), and oxidative stress including nuclear factor E2-related factor 2 (Nrf2), cytochrome P450 4A (CYP4A) and 2E1 (CYP2E1) were investigated by western blotting and RT-qPCR, respectively.

DHC decreased the levels of cellular triglycerides (TG) by regulating the mRNA and protein expression levels of SREBP-1C, PNPLA3 and PPARα. At the same time, DHC improved the hepatocellular glucose uptake by increasing the protein expression levels of pAKT and PI3K. Furthermore, DHC reduced the levels of cellular NO and ROS via Nrf2 signaling pathways.

The present study firstly revealed that DHC ameliorated OA-induced steatosis through regulating the lipid metabolism, oxidative stress and insulin resistance in HepG2 and L02 cells.