软脂酸诱导HepG2细胞胰岛素抵抗及花生四烯酸防治作用的机制研究

Study on the mechanism of insulin resistance for HepG2 cells induced by palmitate and the prevention effect of Arachidonic acid (AA)

目的探讨高浓度软脂酸(PA)诱导HepG2细胞胰岛素抵抗(IR)的机制及花生四烯酸(AA)对IR的防治作用。方法(1)用高浓度软脂酸(PA)或10-7mol/L高胰岛素(HI)培养HepG2细胞建立具有IR的细胞模型,测定培养液中葡萄糖含量及细胞内糖原含量作为鉴定指标;(2)用Westernblot检测胞内糖原合酶(GS)和蛋白激酶B(PKB)蛋白水平;(3)用磷脂酰肌醇3激酶(PI3K)抑制剂Wortmannin(WT)探讨其对胰岛素信号通路的影响;(4)观察AA是否对PA引起的IR有防治作用。结果(1)020mmol/LPA或HI培养HepG2细胞36h后,培养液中葡萄糖含量极显著增高,细胞内糖原含量极显著减少;(2)高浓度PA使磷酸化的PKB(PSer473)蛋白水平显著减少,磷酸化的糖原合酶(PSer641GS)蛋白水平极显著增加;(3)WT使对照组GS活性及胞内糖原含量极显著减少,HI组和PA组胞内糖原含量均无统计学差异,但各实验组PKB活性都极显著减少;(4)PA+AA组培养液中葡萄糖含量显著低于PA组,GS和PKB活性及胞内糖原含量显著增加。结论高浓度PA或HI培养HepG2细胞能够诱导IR,其机制可能是其引起胰岛素信号传递途径中自PKB下游到GS之间的信号通路受阻所致。AA能改善PA引起的IR。

Objective To study on the mechanism of insulin resistance (IR) for HepG2 cells induced by high concentrations of palmitate (PA) and the prevention effect of Arachidonic acid (AA). Methods (1)The model of IR was established with HepG2 cells cultured at high concentrations of PA or 10^-7 mol/L insulin, the glucose contents and hepatic glycogen contents were measured; (2) Protein levels of phosphate-glycogen synthase (P-Ser641 GS), and phosphate-PKB (P-Ser473 PKB) were determined in total cell lysates by Western blot; (3)Influence of the inhibitor of PI3K Wortmannin (WT) on the insulin signaling pathways was discussed; (4)The prevention effect of AA on PA-induced IR was observed. Results (1)The glucose contents were significantly higher than those in control and hepatic glycogen contents significantly lower as HepG2 cells cultured at high concentrations PA or insulin for 36 h; (2)P-Ser473 PKB in PA group was markedly lower than that in control, P-Ser641 GS significantly increased; (3)The GS activity and glucose contents in control group significantly reduced and protein levels of P-Ser641 GS elevated as cultured at WT,but the changes were not obvious in HI group and PA group, PKB activity in four groups significantly reduced; (4) The glucose contents in culture medium significantly decreased in PA with AA group; GS, PKB activity and glucose contents significantly increased comparing to PA group. Conclusions HepG2 cells cultured at high concentrations of PA or HI, could successfully induce hepatic insulin resistance. The possible mechanism for IR may be resulted from insulin signaling pathways being blocked from PKB to GS. AA can significantly improve IR induced by PA.