HIF-1 regulates hypoxia- and insulin-induced expression of apelin in adipocytes

• Published in: American journal of physiology: endocrinology and metabolism Vol. 293; no. 6; pp. E1590 - E1596
• Main Authors: Glassford, Alexander J, Yue, Patrick, Sheikh, Ahmad Y, Chun, Hyung J, Zarafshar, Shirin, Chan, Denise A, Reaven, Gerald M, Quertermous, Thomas, Tsao, Philip S
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.12.2007
• Subjects: 3T3-L1 Cells; Active Transport, Cell Nucleus - drug effects; Adipocytes - cytology; Adipocytes - drug effects; Adipocytes - metabolism; Adipokines; Amino Acids, Dicarboxylic - pharmacology; Androstadienes - pharmacology; Animals; Apelin; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell culture; Cell Hypoxia; Cell Line, Transformed; Cell Nucleus - drug effects; Cell Nucleus - metabolism; Cobalt - pharmacology; Enzyme Inhibitors - pharmacology; Gene Deletion; Gene Expression Regulation - drug effects; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit - genetics; Hypoxia-Inducible Factor 1, alpha Subunit - physiology; Insulin; Insulin - pharmacology; Intercellular Signaling Peptides and Proteins; Metabolism; Mice; Peptides; Proto-Oncogene Proteins c-akt - antagonists & inhibitors; Proto-Oncogene Proteins c-akt - metabolism; Rodents; Rotenone - pharmacology
• ISSN: 0193-1849; 1522-1555
• DOI: 10.1152/ajpendo.00490.2007

1 Division of Cardiovascular Medicine, Department of Medicine; 2 Department of Cardiothoracic Surgery; and 3 Department of Radiation Oncology, Stanford University Medical Center, Stanford, California Submitted 27 July 2007 ; accepted in final form 17 September 2007 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-1 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-1 -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. hypoxia-inducible factor; adipocyte; obesity Address for reprint requests and other correspondence: P. Yue, 300 Pasteur Dr., Falk CVRC, Stanford, CA 94305-5406 (e-mail: pyue{at}cvmed.stanford.edu )