Influence of total polar compounds on lipid metabolism, oxidative stress and cytotoxicity in HepG2 cells

BACKGROUND: Recently, the harmful effects of frying oil on health have been gradually realized. However, as main components of frying oils, biochemical effects of total polar compounds (TPC) on a cellular level were underestimated. METHODS: The effects of total polar compounds (TPC) in the frying oil on the lipid metabolism, oxidative stress and cytotoxicity of HepG2 cells were investigated through a series of biochemical methods, such as oil red staining, real-time polymerase chain reaction (RT-PCR), cell apoptosis and cell arrest. RESULTS: Herein, we found that the survival rate of HepG2 cells treated with TPC decreased in a time and dose dependent manner, and thereby presented significant lipid deposition over the concentration of 0.5 mg/mL. TPC were also found to suppress the expression levels of PPARα, CPT1 and ACOX, elevate the expression level of MTP and cause the disorder of lipid metabolism. TPC ranged from 0 to 2 mg/mL could significantly elevate the amounts of reactive oxygen species (ROS) in HepG2 cells, and simultaneously increase the malondialdehyde (MDA) content from 21.21 ± 2.62 to 65.71 ± 4.20 μmol/mg of protein (p < 0.05) at 24 h. On the contrary, antioxidant enzymes superoxide dismutase (SOD), glutathione (GSH), and catalase (CAT) respectively decreased by 0.52-, 0.56- and 0.28-fold, when HepG2 cells were exposed to 2 mg/mL TPC for 24 h. In addition, TPC could at least partially induce the apoptosis of HepG2 cells, and the transition from G0/G1 to G2 phase in HepG2 cells was impeded. CONCLUSIONS: TPC could progressively cause lipid deposition, oxidative stress and cytotoxicity, providing the theoretical support for the detrimental health effects of TPC. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12944-019-0980-0) contains supplementary material, which is available to authorized users.