Repression of glucocorticoid-stimulated angiopoietin-like 4 gene transcription by insulin
Repression of glucocorticoid-stimulated angiopoietin-like 4 gene transcription by insulin
Angiopoietin-like 4 (Angptl4) is a glucocorticoid receptor (GR) primary target gene in hepatocytes and adipocytes. It encodes a secreted protein that inhibits extracellular LPL and promotes adipocyte lipolysis. In Angptl4 null mice, glucocorticoid-induced adipocyte lipolysis and hepatic steatosis are compromised. Markedly, insulin suppressed glucocorticoid-induced Angptl4 transcription. To unravel the mechanism, we utilized small molecules to inhibit insulin signaling components and found that phosphatidylinositol 3-kinase and Akt were vital for the suppression in H4IIE cells. A forkhead box transcription factor response element (FRE) was found near the 15 bp Angptl4 glucocorticoid response element (GRE). Mutating the Angptl4 FRE significantly reduced glucocorticoid-induced reporter gene expression in cells. Moreover, chromatin immunoprecipitation revealed that GR and FoxO1 were recruited to Angptl4 GRE and FRE in a glucocorticoid-dependent manner, and cotreatment with insulin abolished both recruitments. Furthermore, in 24 h fasted mice, significant occupancy of GR and FoxO1 at the Angptl4 GRE and FRE was found in the liver. In contrast, both occupancies were diminished after 24 h refeeding. Finally, overexpression of dominant negative FoxO1 mutant abolished glucocorticoid-induced Angptl4 expression, mimicking the insulin suppression. Overall, we demonstrate that both GR and FoxO1 are required for Angptl4 transcription activation, and that FoxO1 negatively mediates the suppressive effect of insulin.
- University of California, San Francisco United States
- University of California, Berkeley United States
Male, Medical Physiology, Medical Biochemistry and Metabolomics, Biochemistry, Mice, Glucocorticoid, Receptors, glucocorticoid receptor, 2.1 Biological and endogenous factors, Insulin, Aetiology, Angiopoietin-like 4 Protein, Tumor, Forkhead Transcription Factors, Biological Sciences, forkhead box protein O1, Protein Transport, Transcription, Signal Transduction, Biochemistry & Molecular Biology, glucocorticoid response element, 1.1 Normal biological development and functioning, 610, Nerve Tissue Proteins, chromatin immunoprecipitation, QD415-436, Response Elements, Cell Line, Receptors, Glucocorticoid, Genetic, Underpinning research, Cell Line, Tumor, 616, Genetics, Medical biochemistry and metabolomics, Angiopoietin-Like Protein 4, Animals, Humans, Glucocorticoids, Biomedical and Clinical Sciences, Base Sequence, Lipid Metabolism, Rats, Gene Expression Regulation, Biochemistry and cell biology, Mutation, Biochemistry and Cell Biology, Angiopoietins
Male, Medical Physiology, Medical Biochemistry and Metabolomics, Biochemistry, Mice, Glucocorticoid, Receptors, glucocorticoid receptor, 2.1 Biological and endogenous factors, Insulin, Aetiology, Angiopoietin-like 4 Protein, Tumor, Forkhead Transcription Factors, Biological Sciences, forkhead box protein O1, Protein Transport, Transcription, Signal Transduction, Biochemistry & Molecular Biology, glucocorticoid response element, 1.1 Normal biological development and functioning, 610, Nerve Tissue Proteins, chromatin immunoprecipitation, QD415-436, Response Elements, Cell Line, Receptors, Glucocorticoid, Genetic, Underpinning research, Cell Line, Tumor, 616, Genetics, Medical biochemistry and metabolomics, Angiopoietin-Like Protein 4, Animals, Humans, Glucocorticoids, Biomedical and Clinical Sciences, Base Sequence, Lipid Metabolism, Rats, Gene Expression Regulation, Biochemistry and cell biology, Mutation, Biochemistry and Cell Biology, Angiopoietins
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