RESUMO
HepG2 cells were pre-incubated with insulin (Ins 0,1,0. 1,0.01 μol/L) and dexamethasone ( Dex 0,3,0. 3,0.03 μol/L) alone or together for 24 h to induce insulin resistance (IR) in vitro, the resistant level was estimated by glucose consumption, the optimal model of insulin resitance was chosen, and at the same time its lasting time of resistance was determined. In order to investigate the effects and mechanisms of mifepristone on in sulin-resistant HepG2 cells induced by insulin and dexamethasone, mifepristone and pioglitazone were adminis tered 24 h after the optimal model of insulin-resistant HepG2 cells was established. The glucose consumption, in tracellular concentrations of glucose, glycogen, ATP, and free fatty acid (FFA) in each group were detected. The expression of InsR-mRNA and GR-mRNA was detected by semi-quantitative reverse transcription and polymerase chain reaction (SqRT-PCR). Results revealed that pretreatment with insulin (0. 1 μmol/L) and dexamethasone (0.3 (μol/L) for 24 h caused optimal insulin resistance of HepG2 cells which lasted for 36 h. Compared with control group, the glucose consumption, intracellular glucose, glycogen, ATP contents and the level of InsR-mRNA in model cells decreased while FFAs concentrations and GR-mRNA increased. However, the tendency of insulin resistant HepG2 cells was obviously attenuated by pioglitazone at the concentration of 0. 2 mmol/L and mifepris tone at 200μmol/L and 20 μol/L while mifepristone at 2 μol/L had no effect on insulin-resistant cells. The findings indicated that mifepristone at 200 μol/L and 20 μol/L improved the insulin resistance via modulating intracellular glucolipid metabolism and the expression of InsR-mRNA and GR-mRNA.