A single element in the phosphoenolpyruvate carboxykinase gene mediates thiazolidinedione action specifically in adipocytes.
Phosphoenolpyruvate carboxykinase (PEPCK) is the key enzyme in glyceroneogenesis, an important metabolic pathway that functions to restrain the release of non-esterified fatty acids (NEFAs) from adipocytes. The antidiabetic drugs known as thiazolidinediones (TZDs) are thought to achieve some of their benefits by lowering elevated plasma NEFAs. Moreover, peroxisome proliferator activated receptor gamma (PPARgamma) mediates the antidiabetic effects of TZDs, though many TZD responses appear to occur via PPARgamma-independent pathways. PPARgamma is required for adipocyte PEPCK expression, hence PEPCK could be a major target gene for the antidiabetic actions of TZDs. Here we used tissue culture and transfection assays to confirm that the TZD, rosiglitazone, stimulates PEPCK gene transcription specifically in adipocytes. We made the novel observation that this effect was by far the most rapid and robust among several other genes expressed in adipocytes. Adipocytes were transfected with a PEPCK/chloramphenicol acetyltransferase chimeric gene, in which either of the two previously discovered PPARgamma/retinoid X receptor alpha response elements, PCK2 and gAF1/PCK1, had been inactivated by mutagenesis. We demonstrate that PCK2 alone is a bona fide thiazolidinedione response element. We show also that the regulation of PEPCK by PPARs is cell-specific and isotype-specific since rosiglitazone induces PEPCK gene expression selectively in adipocytes, and PPARalpha- and PPARbeta-specific activators are inefficient. Hence, TZDs could lower plasma NEFAs via PPARgamma and PEPCK by enhancing adipocyte glyceroneogenesis.
Glorian
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M
Inserm Unit 530, Centre Universitaire des Saints-Pères, 45, rue des Saints-Pères, 75006 Paris, France.
Duplus
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Beale
E G
EG
Scott
D K
DK
Granner
D K
DK
Forest
C
C
D016475:3T3 Cells; D017667:Adipocytes / Q000187:drug effects* / Q000201:enzymology; D000273:Adipose Tissue / Q000166:cytology; D000818:Animals; D006528:Carcinoma, Hepatocellular; D015870:Gene Expression / Q000187:drug effects*; D007004:Hypoglycemic Agents / Q000493:pharmacokinetics / Q000494:pharmacology; D008297:Male; D051379:Mice; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D012091:Repetitive Sequences, Nucleic Acid; D000077154:Rosiglitazone; D013844:Thiazoles / Q000493:pharmacokinetics / Q000494:pharmacology*; D045162:Thiazolidinediones; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured
D007004:Hypoglycemic Agents; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D013844:Thiazoles; D045162:Thiazolidinediones; D014157:Transcription Factors; D000077154:Rosiglitazone; C089946:2,4-thiazolidinedione; D010729:Phosphoenolpyruvate Carboxykinase (GTP)