Lipid mediators of insulin resistance: ceramide signalling down-regulates GLUT4 gene transcription in 3T3-L1 adipocytes.

Abstract

We have previously demonstrated that chronic exposure of 3T3-L1 adipocytes to tumour necrosis factor-alpha (TNF) resulted in a marked decrease (approximately 90%) in cellular GLUT4 (insulin-responsive glucose transporter) mRNA content as a result of a decreased transcription rate of the GLUT4 gene (approximately 75%) and a reduced half-life of its mRNA (9 to 4.5 h). Investigation of the signalling mechanism responsible for this regulation demonstrated that in the 3T3-L1 adipocytes, sphingomyelin levels decreased to 50% of control levels within 40 min of exposure to TNF, consistent with activation of a sphingomyelinase. In the same manner as with TNF, treatment of the adipocytes with 1-3 microM C6-ceramide, a membrane-permeable analogue of ceramide, decreased GLUT4 mRNA content by approximately 60%. Subsequent investigations revealed that transcription of the GLUT4 gene was reduced by approximately 65% in response to C6-ceramide, demonstrating that the decrease in mRNA content is mediated by a reduction in the transcription of the genc. No effect on GLUT4 mRNA stability was observed after exposure of the adipocytes to C6-ceramide. These observations are interesting in light of our previous data demonstrating that TNF affects both GLUT4 transcription and mRNA stability in the 3T3-L1 adipocytes. In conclusion, the effect of ceramide on GLUT4 gene expression is at the level of transcription, suggesting that another pathway controls mRNA stability. These data establish that ceramide-initiated signal transduction pathways exist within the adipocyte, and provide a potential mechanism for control of GLUT4 gene expression.

• Authors: S D Long, P H Pekala
• Journal: The Biochemical journal (Biochem J) Vol. 319 ( Pt 1) Pg. 179-84 (Oct 01 1996) ISSN: 0264-6021 [Print] England
• PMID: 8870666 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Ceramides
• Glucose Transporter Type 4
• Isoenzymes
• Monosaccharide Transport Proteins
• Muscle Proteins
• NF-kappa B
• RNA, Messenger
• Slc2a4 protein, mouse
• Sphingomyelins
• Tumor Necrosis Factor-alpha
• N-caproylsphingosine
• 5,8,11,14-Eicosatetraynoic Acid
• Arachidonic Acid
• Prkcd protein, mouse
• Protein Kinase C
• Protein Kinase C-delta
• Sphingomyelin Phosphodiesterase
• Choline

Topics

• 3T3 Cells
• 5,8,11,14-Eicosatetraynoic Acid (metabolism)
• Adipose Tissue (drug effects, metabolism)
• Animals
• Arachidonic Acid (metabolism)
• Ceramides (pharmacology)
• Choline (metabolism)
• Down-Regulation
• Electrophoresis, Polyacrylamide Gel
• Enzyme Activation
• Gene Expression Regulation
• Glucose Transporter Type 4
• Insulin Resistance
• Isoenzymes (metabolism)
• Mice
• Monosaccharide Transport Proteins (genetics)
• Muscle Proteins
• NF-kappa B (metabolism)
• Phosphorylation
• Protein Kinase C (metabolism)
• Protein Kinase C-delta
• RNA, Messenger (metabolism)
• Sphingomyelin Phosphodiesterase (metabolism)
• Sphingomyelins (metabolism)
• Transcription, Genetic (drug effects)
• Tumor Necrosis Factor-alpha (pharmacology)