title: Ceramide mediates TNF-alpha-induced insulin resistance on GLUT4 gene expression in brown adipocytes.
abstract: Tumour necrosis factor (TNF)-alpha impaired insulin induction on GLUT4 mRNA in foetal brown adipocytes, as demonstrated by quantitative RT-PCR and Northern blot. We have explored the hypothesis that some effects of TNF-alpha could be mediated by the generation of ceramide, since TNF-alpha treatment induced the production of ceramide in these primary cells. A short-chain ceramide analogue, C2-ceramide, precluded insulin-induced GLUT4 mRNA accumulation and GLUT4-chloramphenicol acetyltransferase (CAT) full promoter activation. Moreover, inhibition of the ceramide biosynthesis with fumonisin B, which inhibits ceramide synthase, completely restored insulin-induced GLUT4 mRNA and protein accumulation as well as GLUT4-CAT transactivation in the presence of TNF-alpha. In consequence, TNF-alpha-induced insulin resistance on glucose uptake was completely alleviated. In addition, TNF-alpha down-regulated insulin-induced CCAAT/enhancer binding protein (C/EBP)-alpha gene expression and DNA binding activity, but fumonisin B precludes these effects. Furthermore, co-transfection with a wild-type C/EBP-alpha construct transactivates GLUT4-CAT construct. Our results indicate that de novo ceramide produced by TNF-alpha-induced insulin resistance on GLUT4 gene expression in brown adipocytes by interfering C/EBP-alpha expression, a transcription factor essential for the expression of GLUT4.
authors.affiliation: Departamento de Bioquimica y Biologia Molecular, Facultad de Farmacia, Universidad Complutense, 28040, Madrid, Spain.
authors.forename: Sonia
authors.initials: S
authors.lastname: Fernández-Veledo
authors.forename: Rosario
authors.initials: R
authors.lastname: Hernandez
authors.forename: Teresa
authors.initials: T
authors.lastname: Teruel
authors.forename: Jose Antonio
authors.initials: JA
authors.lastname: Mas
authors.forename: Manuel
authors.initials: M
authors.lastname: Ros
authors.forename: Margarita
authors.initials: M
authors.lastname: Lorenzo
mesh_terms: D017667:Adipocytes / Q000502:physiology*; D002001:Adipose Tissue, Brown / Q000166:cytology / Q000502:physiology*; D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D002518:Ceramides / Q000378:metabolism*; D015536:Down-Regulation; D005333:Fetus; D005786:Gene Expression Regulation / Q000235:genetics; D051275:Glucose Transporter Type 4 / Q000235:genetics*; D007333:Insulin Resistance / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D002518:Ceramides; D051275:Glucose Transporter Type 4; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha