不同低氧暴露时间对小鼠骨骼肌ERRα/PDK4调节的影响

Effects of Hypoxia with Different Time on Regulations of ERRαBinding to the PDK4 Promoter in Skeletal Muscle of Mice

目的:研究不同低氧暴露时间对小鼠骨骼肌雌激素受体相关受体(estrogen receptor related receptorsα,ERRα)与丙酮酸脱氢酶激酶4(PDK4)DNA结合活性及PDK4基因表达的影响,以探讨低氧条件下影响糖代谢及其信号分子之间的相互调节可能的机制。方法:野生小鼠随机分为常氧组、低氧组(氧浓度11.25%左右,模拟海拔高度4 500m),而后又进一步分为0天、7天、14天、28天组,每组10只。低氧暴露时间为每天8h。同天数的小鼠常氧组与低氧组脱颈处死。染色质免疫共沉淀法(Chip)测定ERRα/PDK4结合活性,Real-Time PCR测定骨骼肌PDK4mRNA含量。结果:1)随着天数增加,低氧组ERRα/PDK4的结合活性有增加的趋势,但没有显著性差异;2)随着天数增加,低氧28天组PDK4mRNA相对表达量与0天组相比显著性升高(P<0.05),且与28天常氧组相比也有显著性增加(P<0.05)。结论:低氧28天小鼠骨骼肌PDK4mRNA相对表达量显著增加,但其ERRα/PDK4的结合活性并没有显著性变化,推测低氧下ERRα并不是促进PDK4mRNA表达的主要转录因子。

Objective. Different time hypoxic exposure inducing ERRs binding to the PDK4 pro- moter and PDK4 mRNA expression was investigated, which is to discuss the possible mecha- nism of carbohydrate metabolism and regulations among signal molecules under hypoxic condi- tions. Methods.. Wild-type C57BL/6J mice were subjected to either norrnoxia or hypoxia. Mice in the hypoxia groups were exposed to a hypobaric chamber that replicated the hypobaric hy- poxia conditions found at 4 500m altitude for 8 hours a day. And then each group with 10 mice is also randomly based on the different days（0,7,14,28）. Mice of the normoxic and hypoxic groups in the same days were sacrificed. Performing CHIP assay to confirm the hypoxia treated regulation of ERRs on PDK4 promoter. PDK4 mRNA was measured by Real Time-PCR. Re- sults： 1） When hypoxia exposed for 14 days and 28 days, ERRs recruitment on PDK4 promot- er trends to elevate but has no significance; 2） Comparing with 0 day groups and normoxia 28 days group, hypoxia 28 days group＇s PDK4 mRNA was significantly increased （P〈0.05）. Conclu- sion： Under 28 days＇ exposure of hypoxia, PDK4 mRNA was significantly increased in mice skele- tal;muscles, but the ERRa recruitment on PDK4 promoter has no significant augment. So, we con- jecture ERRa as a compensatory transcription control mechanism to PDK4.