Chronic Effects Of High Palmitate, High Insulin And High Glucose On PKB Threonine Phosphorylation And Insulin Gene Expression In HIT-T15 Cells: Lipotoxicity, Glucose Toxicity Cause Insulin Resistance In β-cells

Part one.Chronic Effects of High Palmitate on PKB Threonine Phosphorylation and Insulin Gene Expression in HIT-T15 Cells Objective To study the chronic effects of high palmitate on PKB threonine phosphorylation and insulin gene expression in HIT-T15 cells.Methods HIT-T15 cells were incubated with palmitate(0, 0.25, 0.5, 1.0mmol/L) (presence of 11.1mmol/L glucose) for 24 hours before the cells were stimulated with 100nmol/L insulin for 5 min,Western blotting was used to assess the levels of PKB threonine phosphorylation.insulin mRNA levels were determined by RT-PCR. Result After HIT-Tl 5 cells were incubated with palmitate(0.25, 0.5, 1.0mmol/L) for 24 hours,there were a marked reduction in the PKB threonine phosphorylation,reaching72.1% , 35.8%(P<0.01) , 22.2%(P<0.01) of control levels, respectively,and the insulin mRNA levels were decreased to 88.9%, 66.7%(P<0.05), 37.1%(P<0.01) of control levels, respectively.Chronic exposure of HIT-T15 cells to palmitate(0.25 ~ 1.0mmol/L) induced a concentration-dependent decrease in PKB threonine phosphorylation and insulin gene expression .Conclusion Chronic high palmitate results in down-regulation of PKB threonine phosphorylation and insulin gene expression in HIT-T15 Cells. High palmitate cause insulin resistance and impairment of function in β -cells. Palmitate; PKB; Insulin gene; β cellsInsulin; PKB; Insulin gene; β cellsPart three.Chronic Effects of High Glucose on PKB ThreoninePhosphorylation and Insulin Gene Expression in HIT-T15 CellsObjective To explore the chronic effects of high glucose on PKBthreonine phosphorylation and insulin gene expression in HIT-T15cells.Methods HIT-T15 cells were incubated with glucose(5.6, 11.1,16.7, 27.8mmol/L) for 24 hours before the cells were stimulated with100nmol/L insulin for 5 min,Western blotting was used to assess thelevels of PKB threonine phosphorylation.insulin mRNA levels weredetermined by RT-PCR.Result After HIT-T15 cells were incubated with glucose( 11.1, 16.7,27.8mmol/L) for 24 hours,there were a marked reduction in the PKBthreonine phosphorylation.reaching 84.25% , 56.7%(P<0.05) ,39.0%(P<0.01) of control levels, respectively,and the insulin mRNAlevels were decreased to 55.6%(P<0.05) , 30.9%(P<0.01) ,9.55%(P<0.01) of control levels, respectively. Chronic glucose(ll.l~27.8mmol/L) treatment induced a concentration-dependent decreasein PKB threonine phosphorylation and insulin gene expression inHIT-T15 Cells.Conclusion Chronic high glucose results in down-regulation of PKBthreonine phosphorylation and insulin gene expression in HIT-T15Cells. High glucose cause insulin resistance and impairment offunction in β -cells.