HIF-1 regulates hypoxia- and insulin-induced expression of apelin in adipocytes.
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.
Glassford
Alexander J
AJ
Department of Medicine, Stanford University Medical Center, Stanford, CA, USA.
Yue
Patrick
P
Sheikh
Ahmad Y
AY
Chun
Hyung J
HJ
Zarafshar
Shirin
S
Chan
Denise A
DA
Reaven
Gerald M
GM
Quertermous
Thomas
T
Tsao
Philip S
PS
D041721:3T3-L1 Cells; D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D054392:Adipokines; D000600:Amino Acids, Dicarboxylic / Q000494:pharmacology; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D000073861:Apelin; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D015687:Cell Hypoxia; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003035:Cobalt / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017353:Gene Deletion; D005786:Gene Expression Regulation / Q000187:drug effects; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000502:physiology*; D007328:Insulin / Q000494:pharmacology*; D036341:Intercellular Signaling Peptides and Proteins; D051379:Mice; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D012402:Rotenone / Q000494:pharmacology; D000077191:Wortmannin
D054392:Adipokines; D000600:Amino Acids, Dicarboxylic; D000730:Androstadienes; D000073861:Apelin; C402826:Apln protein, mouse; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007328:Insulin; D036341:Intercellular Signaling Peptides and Proteins; D012402:Rotenone; D003035:Cobalt; D051057:Proto-Oncogene Proteins c-akt; C018021:cobaltous chloride; C040947:oxalylglycine; D000077191:Wortmannin