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Regulation of pyruvate dehydrogenase kinase 4 (PDK4) by thyroid hormone: role of the peroxisome proliferator-activated receptor gamma coactivator (PGC-1 alpha).

ABSTRACT: PDK4 (pyruvate dehydrogenase kinase 4) regulates pyruvate oxidation through the phosphorylation and inhibition of the pyruvate dehydrogenase complex (PDC). PDC catalyzes the conversion of pyruvate to acetyl-CoA and is an important control point in glucose and pyruvate metabolism. PDK4 gene expression is stimulated by thyroid hormone (T(3)), glucocorticoids, and long chain fatty acids. The effects of T(3) on gene expression in the liver are mediated via the thyroid hormone receptor. Here, we have identified two binding sites for thyroid hormone receptor beta in the promoter of the rat PDK4 (rPDK4) gene. In addition, we have investigated the role of transcriptional coactivators and found that the PGC-1 alpha (peroxisome proliferator-activated receptor gamma coactivator) enhances the T(3) induction of rPDK4. Following T(3) administration, there is an increase in the association of PGC-1 alpha with the rPDK4 promoter. Interestingly, this increased association is with the proximal rPDK4 promoter rather than the distal region of the gene that contains the T(3) response elements. Administration of T(3) to hypothyroid rats elevated the abundance of PGC-1 alpha mRNA and protein in the liver. In addition, we observed greater association of PGC-1 alpha not only with the rPDK4 gene but also with phosphoenolpyruvate carboxykinase and CPT-1a (carnitine palmitoyltransferase 1a) genes. Knockdown of PGC-1 alpha in rat hepatocytes reduced the T(3) induction of PDK4, PEPCK, and CPT-1a genes. Our results indicate that T(3) regulates PGC-1 alpha abundance and association with hepatic genes, and in turn PGC-1 alpha is an important participant in the T(3) induction of selected genes.

SUBMITTER: Attia RR

PROVIDER: S-EPMC2807296 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature

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Regulation of pyruvate dehydrogenase kinase 4 (PDK4) by thyroid hormone: role of the peroxisome proliferator-activated receptor gamma coactivator (PGC-1 alpha).

Attia Ramy R RR Connnaughton Sara S Boone Lindsey R LR Wang Fang F Elam Marshall B MB Ness Gene C GC Cook George A GA Park Edwards A EA

The Journal of biological chemistry 20091130 4

PDK4 (pyruvate dehydrogenase kinase 4) regulates pyruvate oxidation through the phosphorylation and inhibition of the pyruvate dehydrogenase complex (PDC). PDC catalyzes the conversion of pyruvate to acetyl-CoA and is an important control point in glucose and pyruvate metabolism. PDK4 gene expression is stimulated by thyroid hormone (T(3)), glucocorticoids, and long chain fatty acids. The effects of T(3) on gene expression in the liver are mediated via the thyroid hormone receptor. Here, we have ...[more]

PMID: 19948729

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Project description:PGC-1a is a transcriptional coactivator known to regulate a broad gene program of nutrient and mitochondrial metabolism. Many splice variants of this protein have been identified, but their functions were unknown. This experiment was designed to delineate the downstream targets of two different PGC-1alpha isoforms (PGC-1a1 and PGC-1a4) in hepatocytes, and to determine whether inflammatory signaling (via TNFR activation) modulated these targets Liver is exposed to constantly changing metabolic and inflammatory environments. It must quickly sense and adapt to metabolic need while balancing resources required to protect itself from harmful inflammatory molecules. PGC-1α is a transcriptional coactivator that mediates cellular adaptation to diverse stimuli including inflammation. PGC-1α has a protective role against inflammation in several organs, including brain, heart, kidney, muscle, and liver. However, it is not known how hepatic PGC-1α integrates extracellular signals to mitigate inflammatory outcomes. PGC-1α exists as multiple, alternatively spliced variants whose expression is differentially regulated by different gene promoters. In human liver, we found that inflammatory conditions preferentially activated the alternative versus proximal PPARGC1A promoter. Gene expression analysis performed in primary mouse hepatocytes identified many shared and isoform-specific roles for PGC-1α variants during acute inflammation. PGC-1α1 primarily impacted gene programs of nutrient and mitochondrial metabolism, while TNFα treatment revealed that PGC-1α4 uniquely influenced several pathways related to innate immunity and cell death. Gain- and loss-of-function models showed that PGC-1α4 specifically attenuated apoptosis in response to TNFα or LPS, in contrast to PGC-1α1, which reduced expression of a wide inflammatory gene network. We conclude that PGC-1α variants have distinct, yet complimentary roles in hepatic responses to inflammation, with PGC-1α4 being an important mitigator of apoptosis.

Dataset Information

Regulation of pyruvate dehydrogenase kinase 4 (PDK4) by thyroid hormone: role of the peroxisome proliferator-activated receptor gamma coactivator (PGC-1 alpha).

Publications

Regulation of pyruvate dehydrogenase kinase 4 (PDK4) by thyroid hormone: role of the peroxisome proliferator-activated receptor gamma coactivator (PGC-1 alpha).

Similar Datasets

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