Effects of lipoproteins and insulin on phospholipid transfer protein and gene transcription in Hep G2 cells

The purpose of this study was to investigate the effects of lipoproteins and insulin on phospholipid transfer protein (PLTP) content and gene transcription in human hepatoblastoma (Hep G2) cells. Upon 90% confluency, the cells were switched to serum-free medium for 24 hours followed by incubation with HDL (50 μg/mL), LDL (50 μg/mL), VLDL (50 μg/mL) or insulin (1 μg/mL) for 12-24 hours. The conditioned medium was collected at 12 and 24 hours for protein analysis. Cells were collected after 24 hours for the measurements of PLTP content and mRNA expression. The results showed that the total protein secretion into the conditioned medium in the LDL, VLDL and insulin treatment groups was significantly lower than the control group at both 12 and 24 hours (p<0.05). However, the cellular PLTP (MW 44 kDa) and mRNA were not significantly different among the five groups after Western blotting and slot blotting analyses, respectively. Therefore, PLTP content and gene transcription in Hep G2 cells were not regulated after 24-h incubation with 50 μg/mL lipoproteins or 1 μg/mL insulin.