ABSTRACT
AIM:To investigate the effects of extracellular cysteine/cystine redox potential (EhCys/CySS) on the mitochondrial function of nonalcoholic fatty liver disease ( NAFLD) hepatocytes.METHODS:LO2 cells were incuba-ted with EhCys/CySS of the oxidized (0 mV), the normal (-80 mV), or the reduced (-150 mV) status medium, then treated with oleic acid to establish NAFLD model in vitro.DCFH-DA and MitoSOX were used as the fluorescent probes for determining reactive oxygen species (ROS).Apocynin (NADPH oxidase inhibitor), MitoQ10 (mitochondria-targeted an-tioxidant), rotenone (mitochondrial respiratory chain complex I inhibitor) and antimycin A (mitochondrial respiratory chain complex III inhibitor) were used to investigate the sources of ROS.RESULTS:An increase in ROS in LO2 cells by oleic acid was aggravated by the oxidized extracellular EhCys/CySS (0 mV), which was removed by the reduced EhCys/CySS (-150 mV) .ROS generation by 0 mV was significantly eliminated by MitoQ10 .ROS levels were dependent on ex-tracellular Eh Cys/CySS in rotenone treated LO2 cells.A decline of mitochondrial membrane potential in the cells with NAFLD was aggravated by 0 mV and reversed by -150 mV.CONCLUSION:The oxidized extracellular Eh Cys/CySS via inhibitiing of complex I intensifies ROS generation and reducing the mitochondrial membrane potential in the NAFLD hepa-tocytes, which were reversed by reduced Eh Cys/CySS.
ABSTRACT
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.
ABSTRACT
Glucocorticoids are among those most important hormones that maintain the energy metabolic homeostasis within body.The actions of glucocorticoids on target tissues,such as liver and adipose tissue,are not only dependent on circulating glucocorticoid levels but also on glucocorticoid receptor expression.The elevated level of circulating glucocorticoid caused by exogenous or endogenous reasons may contribute to insulin resistance and the other metabolic syndrome such as dyslipidemia,visceral obesity and hypertension.This review summarizes recent advances in the study of glucocorticoid receptor-mediated insulin resistance and its antagonists.