Expression Of Glucose Transporter 2 In Cultured HepG2 Cell Induced By Oleic Acid

OBJECTIVE:Nonalcoholic fatty liver disease(NAFLD) is defined as fatty infiltration of the liver exceeding 5% to 10% by weight. It is a spectrum of disorders ranging from simple fatty liver (steatosis without liver injury), nonalcoholic steatohepatitis (steatosis with inflammation), and fibrosis or cirrhosis that resembles alcohol-induced liver disease but which develops in individuals who are not heavy drinkers.Although many risk factors such as hypertriglyceridemia, obesity, diabetes, insulin resistance can lead to NAFLD, the presence of NAFLD is also considered as an independent disease which is not secondary to these factors. We can usually see some nondiabetic NAFLD patients in normal weight and there exist fast and postabsorptive hyperinsulinemia and insulin resistance in them.The mechanism about how NAFLD causes insulin resistance is not clear now. To determine if there is hepatic insulin resistance in fatty liver, when hepatic glucose production increase, we investigated the expression changes of GluT2 messenger ribonucleic acid levels in an fatty liver modelinduced by oleic acid.METHODS:Cultured HepG2 cell were devided into 6 groups: OA-treated group along with different concentration, Bezafibrate group, Bezafibrate and OA-treated groups with different concentration and control. Every group was treated for 24h. The morphology of hepatic steatosis were observed by staining with SudanIII under light microscope. The ultrastructure of HepG2 cell accumulating lipid was observed when we used transmisson electron microscopy. The expression of GluT2mRNA were studied by RT-PCR method.RESULTS:(1) lipid accumulation which can be stained with Sudanlll in HepG2 cell was induced by the addition of OA. There were a few cytosolic fat droplets at 0.1 mM OA group. But there exist a great deal of cytosolic fat droplets at lmM OA group, which is same as hepatic macrovesicular steatosis.(2) Compared with the control group, there was no significant difference on cell number or ALT, AST, ALP, LDH and GGT Levels in cell culture medium of 0. lmM OA group and lmM OA group.(3) The content of TG in HepG2 cell treated without OA, with OA at O.lmM and lmM were 5.01, 12.11 and 32.65 (ug/ug protein), respectively. These differences are all significant. The used dose of bezafibrate reduced significantly the content of cytosolic TG..(4) Under electron microscope, We can see that a great number oflipid droplets accumulated in hepatocyte of OA-treated and rough endoplasmic reticulum were expanded.(5) Control group has the expression of GluT2mRNA. The expression of GluT2mRNA increased with the increased concentration of oleic acid. The expression of GluT2mRNA level in bezafibrate and OA-treated group was lower than that in OA-treated group. The expression of GluT2mRNA level in bezafibrate group also was lower than that in normal HepG2 cell. CONCLUSIONS:(1) We succeeded in setting up an in vitro hepatic steatosis model induced by oleic acid.(2) The expression of GluT2mRNA existed in normal HepG2 cell. GluT2mRNA expression was increased in the cells with stestosis. Bezafibrate inhibited GluT2mRNA expression in the cells with and without steatosis.