糖皮质激素和胰岛素对人肝癌细胞株丙酮酸脱氢酶激酶4在转录水平上的调节

Effect of dexamethason and insulin on the regulation of transcriptional activity of pyruvate dehydrogenase kinase-4 gene in HepG2

目的利用人肝癌细胞株(HepG2)探讨糖皮质激素和胰岛素对丙酮酸脱氢酶激酶4(PDK-4)在转录水平的相应作用。方法首先通过标准的分子生物学技术制备PDK-4的5‘启动子基因,而后利用荧光酶素方法在HePG2细胞株中,通过时间依赖探讨糖皮质激素和胰岛素对PDK-4在转录水平上表达的影响。结果人工合成的糖皮质激素地塞米松能有效的增加PDK-4基因在转录水平表达。相反,胰岛素单独使用作用很小,但可明显降低糖皮质激素的正面促进作用。结论糖皮质激素抑制丙酮酸脱氢酶复合物(PDC)的作用至少部分上是通过诱导PDK-4的表达而使丙酮酸向草酰乙酸转化(糖异生途径)。通过对抗糖皮质激素诱导的PDK-4的表达,胰岛素能够起到相反的作用。研究开发PDK-4的拮抗剂可对难治性血糖异常问题及脂代谢异常疾病的治疗开辟一条新的途径。

Objective To examine the effects of dexamethason and insulin on the regulation of transcriptional activites of pyruvate dehydrogenase kinase-4 （PDK-4） in HepG2 （Human hepatocellular liver carcinoma cell line）. Methods By using HepG2 cell line, a human hepatoma-derived cell line,into which the 5＇-promotor-luciferase fusion genes is stably incorporated, were treated with dexamethasone and insulin in a time-and dose gradient. The expression of PDK-4 in HepG2 cell line was detected by RT-PCR. Results Dexamethasone at 100nmol/L potently induced the transcriptional activity of PDK-4. In contrast, insulin at 10nmol/L alone had minimal effect but dampened the positive effects of dexamethasone. Conclusions In liver, dexamethasone facilitates gluconeogensis by increasing PDK-4 expression, whereas insulin exerts opposite effect. We assume that PDK-4 might be a molecular target for new drug of diabetes treatment.