Article: article from journal or magazin.
Glucose down-regulates the expression of the peroxisome proliferator-activated receptor-alpha gene in the pancreatic beta -cell.
The Journal of biological chemistry
Publication types: Journal Article ; Research Support, Non-U.S. Gov't
Publication Status: ppublish
Publication Status: ppublish
To better understand the action of glucose on fatty acid metabolism in the beta-cell and the link between chronically elevated glucose or fatty acids and beta-cell decompensation in adipogenic diabetes, we investigated whether glucose regulates peroxisomal proliferator-activated receptor (PPAR) gene expression in the beta-cell. Islets or INS(832/13) beta-cells exposed to high glucose show a 60-80% reduction in PPARalpha mRNA expression. Oleate, either in the absence or presence of glucose, has no effect. The action of glucose is dose-dependent in the 6-20 mm range and maximal after 6 h. Glucose also causes quantitatively similar reductions in PPARalpha protein and DNA binding activity of this transcription factor. The effect of glucose is blocked by the glucokinase inhibitor mannoheptulose, is partially mimicked by 2-deoxyglucose, and is not blocked by the 3-O-methyl or the 6-deoxy analogues of the sugar that are not phosphorylated. Chronic elevated glucose reduces the expression levels of the PPAR target genes, uncoupling protein 2 and acyl-CoA oxidase, which are involved in fat oxidation and lipid detoxification. A 3-day exposure of INS-1 cells to elevated glucose results in a permanent rise in malonyl-CoA, the inhibition of fat oxidation, and the promotion of fatty acid esterification processes and causes elevated insulin secretion at low glucose. The results suggest that a reduction in PPARalpha gene expression together with a rise in malonyl-CoA plays a role in the coordinated adaptation of beta-cell glucose and lipid metabolism to hyperglycemia and may be implicated in the mechanism of beta-cell "glucolipotoxicity."
Animals, Cells, Cultured, DNA-Binding Proteins/genetics, DNA-Binding Proteins/metabolism, Dose-Response Relationship, Drug, Down-Regulation/drug effects, Glucose/analogs & derivatives, Glucose/metabolism, Glucose/pharmacology, Insulin/metabolism, Insulin/secretion, Islets of Langerhans/drug effects, Islets of Langerhans/metabolism, Islets of Langerhans/secretion, Kinetics, Malonyl Coenzyme A/metabolism, Models, Biological, Oleic Acid/metabolism, Oleic Acid/pharmacology, Oxidation-Reduction/drug effects, Palmitic Acid/metabolism, Protein Binding/drug effects, RNA, Messenger/genetics, RNA, Messenger/metabolism, Rats, Rats, Wistar, Receptors, Cytoplasmic and Nuclear/genetics, Receptors, Cytoplasmic and Nuclear/metabolism, Response Elements/drug effects, Transcription Factors/genetics, Transcription Factors/metabolism, Triglycerides/metabolism
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