Glassford Alexander J, Yue Patrick, Sheikh Ahmad Y, Chun Hyung J, Zarafshar Shirin, Chan Denise A, Reaven Gerald M, Quertermous Thomas, Tsao Philip S
Department of Medicine, Stanford University Medical Center, Stanford, CA, USA.
Am J Physiol Endocrinol Metab. 2007 Dec;293(6):E1590-6. doi: 10.1152/ajpendo.00490.2007. Epub 2007 Sep 18.
Apelin, a novel peptide with significant cardioactive properties, is upregulated by insulin in adipocytes. However, the mechanism by which insulin promotes apelin production is unknown. Hypoxia-inducible factor-1 (HIF-1), a heterodimeric transcription factor involved in the angiogenic and metabolic responses to tissue hypoxia, has been shown to be activated by insulin in various settings. We therefore hypothesized that HIF-1 regulates insulin-mediated apelin expression in adipocytes. 3T3-L1 cells were differentiated into adipocytes in culture. For experiments, serum-starved 3T3-L1 cells were exposed to insulin and/or a 1% O(2) environment. Apelin expression was assessed using quantitative real-time PCR and ELISA. To directly assess the role of HIF-1 in apelin production, we differentiated mouse embryonic fibroblasts (MEFs) containing a targeted deletion of the HIF-1alpha gene into adipocytes and measured their response to insulin and hypoxia. Apelin expression in mature 3T3-L1 adipocytes was increased significantly by insulin and was attenuated by pharmacological inhibition of insulin signaling. Exposure of cells to either hypoxia or the chemical HIF activators cobalt chloride (CoCl(2)) and dimethyloxaloylglycine (DMOG) resulted in significant upregulation of apelin, consistent with a role for HIF in apelin induction. Moreover, hypoxia-, CoCl(2)-, DMOG-, and insulin-induced apelin expression were all attenuated in differentiated HIF-1alpha-deficient MEFs. In summary, in cultured 3T3-L1 adipocytes and differentiated MEFs, HIF-1 appears to be involved in hypoxia- and insulin-induced apelin expression.
Apelin是一种具有显著心脏活性特性的新型肽，在脂肪细胞中受胰岛素上调。然而，胰岛素促进Apelin产生的机制尚不清楚。缺氧诱导因子-1（HIF-1）是一种参与组织缺氧的血管生成和代谢反应的异二聚体转录因子，已证实在各种情况下可被胰岛素激活。因此，我们推测HIF-1调节脂肪细胞中胰岛素介导的Apelin表达。3T3-L1细胞在培养中分化为脂肪细胞。实验中，将血清饥饿的3T3-L1细胞暴露于胰岛素和/或1% O₂环境中。使用定量实时PCR和ELISA评估Apelin表达。为直接评估HIF-1在Apelin产生中的作用，我们将含有HIF-1α基因靶向缺失的小鼠胚胎成纤维细胞（MEFs）分化为脂肪细胞，并测量它们对胰岛素和缺氧的反应。成熟3T3-L1脂肪细胞中的Apelin表达因胰岛素而显著增加，并因胰岛素信号的药理学抑制而减弱。细胞暴露于缺氧或化学HIF激活剂氯化钴（CoCl₂）和二甲基草酰甘氨酸（DMOG）导致Apelin显著上调，这与HIF在Apelin诱导中的作用一致。此外，缺氧、CoCl₂、DMOG和胰岛素诱导的Apelin表达在分化的HIF-1α缺陷型MEFs中均减弱。总之，在培养的3T3-L1脂肪细胞和分化的MEFs中，HIF-1似乎参与缺氧和胰岛素诱导的Apelin表达。
