Pyruvate Dehydrogenase Kinase 4 Gene Expression Research Articles

Exploring diet-induced promoter hypomethylation and PDK4 overexpression: implications for type 2 diabetes mellitus.

Type 2 diabetes mellitus (T2DM) is a metabolic disorder characterized by limited metabolic flexibility in the body. Such limitation implicates the pyruvate dehydrogenase kinase 4 (PDK4) gene Poor nutrition, frequently observed among Southeast Asians usually involves excessive intakes of carbohydrates and monosodium glutamate (MSG), that have been frequently linked to an increased risk of T2DM. The 14-week study aimed to assess the effects of high-carbohydrate (HC), high-MSG (HMSG), and a combination of high-carbohydrate and high-MSG (HCHMSG) diets on the development of T2DM using male mice. To assess the effects, the male mice were divided into four groups: control (C), HC, HMSG, and HCHMSG for 14weeks. After 14weeks, both the HC and HCHMSG groups showed signs of T2DM (168.83 ± 32.33; 156.42 ± 32.46). The blood samples from the HMSG, HC, and HCHMSG groups (57.67 ± 2.882; 49.22 ± 7.36; 48.9 ± 6.43) as well as skeletal muscle samples from the HMSG, HC, and HCHMSG groups (57.78 ± 8.54; 42.13 ± 7.25; 37.57 ± 10.42) exhibited a gradual hypomethylation. The HC groups particularly displayed significant PDK4 gene expression in skeletal muscle. A progressive overexpression of the PDK4 gene was observed as well in the HMSG, HCHMSG, and HC groups (2.03 ± 3.097; 3.21 ± 2.94; 5.86 ± 2.54). These findings suggest that T2DM can be induced by high-carbohydrate and high-MSG diets. However, the sole consumption of high MSG did not lead to the development of T2DM. Further research should focus on conducting long-term studies to fully comprehend the impact of a high MSG diet on individuals with pre-existing T2DM.

Changes in Serum Levels and Gene Expression of PGC-1α in The Cardiac Muscle of Diabetic Rats: The Effect of Dichloroacetate and Endurance Training.

Objective Physical activity leads to changes in the level of gene expression in different kinds of cells, including changes in mitochondrial biogenesis in the myocardium in diabetic patients. Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) is a gene that plays an important role in regulating mitochondrial biogenesis. The purpose of this study was to investigate changes in serum levels and cardiac muscle expression of PGC-1α in diabetic rats in response to the administration of dichloroacetate (DCA) and endurance training. Materials and Methods In this experimental study, 64 male Wistar rats were selected and randomly divided into eight groups after induction of diabetes with streptozotocin (STZ). The endurance training protocol was performed on a treadmill for 6 weeks. Intraperitoneal injection of DCA of 50 mg/ kg body weight was used for the inhibition of Pyruvate Dehydrogenase Kinase 4 (PDK4) in the myocardium. Gene expression were measured using real-time polymerase chain reaction (PCR). One-way ANOVA and Tukey’s test were used to statistically analyze the data. Results The results of the study showed that PDK4 gene expression in the endurance training group, diabetes+endurance training group, diabetes+endurance training+DCA group and endurance training+DCA group was higher compared to the control group. Expression of PGC-1α was higher in the endurance training group compared to the control group but was lower compared to the control group in diabetes+endurance training+DCA group and diabetes+DCA group (P<0.05). ConclusionConsidering that PGC-1α plays an important role in mitochondrial biogenesis, it is likely that by inhibiting PDK4 and subsequently controlling oxidation of fatty acid (FA) in the heart tissue, oxidative stress in the heart tissue of diabetic patients will be reduced and cardiac efficiency will be increased.

P731High-density lipoproteins rescue diabetes-impaired angiogenesis by restoring cellular metabolic reprogramming responses to hypoxia

Abstract Background We have previously identified that high-density lipoproteins (HDL) rescue hypoxia-induced angiogenesis in diabetes, however the underlying mechanisms remain unknown. A central component of hypoxia-induced angiogenesis is the reprogramming of endothelial cell (EC) metabolism to improve tolerance of hypoxia at the site of injury/repair, including following myocardial infarction. Pyruvate dehydrogenase kinase 4 (PDK4) suppresses mitochondrial respiration in hypoxia to decrease oxygen consumption and preserve cell survival. Diabetes impairs this adaptation to hypoxia, causing cellular dysfunction and may underlie delayed angiogenic responses to ischaemia in hyperglycaemia. Purpose To determine the role of metabolic reprogramming in angiogenesis and diabetes and the effect of reconstituted HDL (rHDL). Methods and results Using an in vitro functional angiogenesis assay, siRNA-mediated knockdown of PDK4 impaired human coronary artery endothelial cell (HCAEC) tubulogenesis in hypoxia by 82% versus siScrambled controls (P&lt;0.0001). HCAECs were treated with rHDL (20μM, apolipoproteinA-I + phosphatidylcholine) or PBS (vehicle) and exposed to glucose (5 or 25 mM, 72 h), then normoxia or hypoxia (1.2% O2, 6 h). PDK4 expression was increased by 65% in hypoxia versus the normoxia control (P&lt;0.05). By contrast, in high glucose PDK4 expression failed to increase in response to hypoxia. Incubation with rHDL rescued this impairment and elevated PDK4 expression by 40% in hypoxia and in high glucose (P&lt;0.01), versus the PBS control. In parallel, rHDL rescued high glucose-impaired tubulogenesis in hypoxia by 64% versus the PBS/normoxia control (P&lt;0.001). We next used a murine model of diabetic wound healing that tracks angiogenesis in the wound bed. We found daily topical application of rHDL (50μg/wound/day) increased wound angiogenesis by 10% (as assessed by Laser Doppler perfusion imaging) and promoted CD31+ neovessel formation by 46% in diabetic wounds, supporting an increased rate of wound closure in diabetic animals of 30% (P&lt;0.05). rHDL treated wounds from diabetic mice had a striking increase in PDK4 gene (180%) and protein expression (350%) in the early-mid stages (24 h and 3-day time points, P&lt;0.05) post-wounding, when the angiogenic response to wound ischaemia is most important. Conclusions We have demonstrated that the key protein controlling the metabolic reprogramming response to hypoxia, PDK4, plays an important role in endothelial cell angiogenesis. We also show that the PDK4 and angiogenesis responses to hypoxia are impaired in high glucose and can be rescued by rHDL. In vivo we find that topical rHDL increases wound angiogenesis and PDK4 levels, explaining the enhanced rate of wound closure in diabetic mice and has implications for improving cardiovascular outcomes for diabetic patients following myocardial infarction.

Diurnal Variation in PDK4 Expression Is Associated With Plasma Free Fatty Acid Availability in People.

Many biological pathways involved in regulating substrate metabolism display rhythmic oscillation patterns. In rodents, clock genes regulate circadian rhythms of metabolic genes and substrate metabolism. However, the interrelationships among substrate metabolism, metabolic genes, and clock genes have not been fully explored in people. We tested the hypothesis that the diurnal expression pattern of pyruvate dehydrogenase kinase 4 (PDK4), a key metabolic enzyme involved in fuel switching between glucose and free fatty acids (FFAs), is associated with plasma FFA concentration and clock genes. We analyzed peripheral blood mononuclear cells (PBMCs), subcutaneous adipose tissue, and plasma samples obtained serially during 24 hours from metabolically healthy women (n = 10) and evaluated the interrelationships among PDK4, plasma FFA, and clock genes. We also determined the potential mechanisms responsible for PDK4 transcriptional regulation by using primary human PBMCs and adipocytes. We found that PDK4 diurnal expression patterns were similar in PBMCs and adipose tissue (ρ = 0.84, P < 0.001). The diurnal variation in PBMC PDK4 expression correlated more strongly with plasma FFA and insulin (ρ = 0.86 and 0.63, respectively, both P < 0.001) concentrations than clock genes. Data obtained from primary culture experiments demonstrated that FFAs directly induced PDK4 gene expression, at least in part through activation of peroxisome proliferator-activated receptor α. Our results suggest that plasma FFA availability is an important regulator of diurnal expression patterns of PDK4, and we identify a novel interaction between plasma FFA and cellular diurnal rhythms in regulating substrate metabolism.

Curcumin mediated down-regulation of αV β3 integrin and up-regulation of pyruvate dehydrogenase kinase 4 (PDK4) in Erlotinib resistant SW480 colon cancer cells.

Erlotinib is a potent, selective, and orally active inhibitor of the epidermal growth factor receptor, but the development of erlotinib resistance during chemotherapy can lead to treatment failure. To shed light on the erlotinib-resistant pathway, this study investigated the effect of combination therapy using curcumin- and erlotinib-loaded nanoparticles on the expression of αv β3 integrin and pyruvate dehydrogenase kinase 4 (PDK4) in an erlotinib-resistant SW480 colon cancer cell line. An erlotinib-resistant SW480 colon cancer cell line was produced by long-term exposure to erlotinib. Curcumin-loaded Methoxy poly ethylene glycol Poly caprolactone (cur/mPEG-PCL) and erlotinib-loaded mPEG-PCL (erl/mPEG-PCL) micelles were provided using a single step nanoprecipitation method and used as combination therapy of resistant SW480 cancer cells. After that, gene expression levels of PDK4, αv, and β3 mRNA were determined by the semiquantitative reverse transcription-polymerase chain reaction. Protein levels of whole αv β3 integrin were evaluated using the enzyme-linked immunosorbent assay method. In SW480 cell line, the IC50 of nonresistant and resistant cells was 87.6±1.2nM and 19.1±0.14μM, for erlotinib and it was about 21.8 and 30μM for curcumin, respectively. Although PDK4 expression was not significantly different in resistant and nonresistant cells, its expression was up regulated (1.4 fold) in resistant cells by a combination therapy of cur/mPEG-PCL at a dose of 3μM and erl/mPEG-PCL at a dose of 5μM. β3 mRNA and the protein level of whole αv β3 integrin was significantly higher in resistant SW480 cells as compared with those in nonresistant cells. In terms of treatment, a combination of 6-μM cur/mPEG-PCL and 5-μM erl/mPEG-PCL down regulated β3 gene expression 6.6-fold in resistant cells as compared with nonresistant cells. At the protein level, a combination of 3-μM-cur/mPEG-PCL and 10-μM erl/mPEG-PCL reduced αv β3 protein in resistant cells. The results indicated that combination therapy using cur/mPEG-PCL and erl/mPEG-PCL could decrease αv β3 integrin expression and increase PDK4 gene expression in resistant colon cancer cells, which may have effects on drug resistance signaling pathways.

Hypoxia Induces PDK4 Gene Expression through Induction of the Orphan Nuclear Receptor ERRγ

Multiple cellular signaling pathways that control metabolism and survival are activated when cell are incubated under hypoxic conditions. Activation of the hypoxia inducible factor (HIF)-1 promotes expression of genes that increase the capacity to cope with the stress imposed by a reduced oxygen environment. Here we show that the orphan nuclear receptor estrogen related receptor γ (ERRγ) plays a critical role in hypoxia–mediated activation of pyruvate dehydrogenase kinase 4 (PDK4) gene expression. ERRγ mRNA and protein levels were increased by hypoxia or desferrioxamine (DFO) treatment in hepatoma cell lines. Co-expression of HIF-1α and β increased ERRγ promoter activity as well as mRNA expression, while knockdown of endogenous HIF-1α reduced the hypoxia-mediated induction of ERRγ. In addition, hypoxia also increased the promoter activity and mRNA level of PDK4 in HepG2 cells. Adenovirus mediated-overexpression of ERRγ specifically increased PDK4 gene expression, while ablation of endogenous ERRγ significantly decreased hypoxia-mediated induction of PDK4 gene expression. Finally, GSK5182, an inverse agonist of ERRγ, strongly inhibited the hypoxia-mediated induction of PDK4 protein and promoter activity. Regulation of the transcriptional activity of ERRγ may provide a therapeutic approach for the regulation of PDK4 gene expression under hypoxia.

Regulation of pyruvate dehydrogenase kinase 4 (PDK4) by CCAAT/enhancer‐binding protein beta (C/EBPb)

Thyroid hormone (T3) regulates various aspects of hepatic metabolism. C/EBPβ modulates the expression of multiple hepatic genes including those involved in hepatic gluconeogenesis. The conversion of pyruvate to acetyl‐CoA in mitochondria is catalyzed by the pyruvate dehydrogenase complex (PDC). Activity of PDC is decreased via phosphorylation by the pyruvate dehydrogenase kinases (PDK). Here we investigated the role of the CCAAT/enhancer‐binding protein β (C/EBPβ) in the T3 regulation of PDK4 gene expression. Our data indicate that C/EBPβ induces PDK4 gene expression and decreases PDC activity. This transcriptional induction is mediated through C/EBPβ binding sites in the PDK4 promoter. T3 increased C/EBPβ abundance in primary rat hepatocytes. Knockdown of C/EBPβ with siRNA diminished the T3 induction of the PDK4. Our data suggest that C/EBPβ is an important accessory factor for the T3 activation of PDK4 gene.

Peroxisome proliferator activated receptor α (PPARα) and PPAR gamma coactivator (PGC-1α) induce carnitine palmitoyltransferase IA (CPT-1A) via independent gene elements

Long chain fatty acids and pharmacologic ligands for the peroxisome proliferator activated receptor alpha (PPARα) activate expression of genes involved in fatty acid and glucose oxidation including carnitine palmitoyltransferase-1A (CPT-1A) and pyruvate dehydrogenase kinase 4 (PDK4). CPT-1A catalyzes the transfer of long chain fatty acids from acyl-CoA to carnitine for translocation across the mitochondrial membranes and is an initiating step in the mitochondrial oxidation of long chain fatty acids. PDK4 phosphorylates and inhibits the pyruvate dehydrogenase complex (PDC) which catalyzes the conversion of pyruvate to acetyl-CoA in the glucose oxidation pathway. The activity of CPT-1A is modulated both by transcriptional changes as well as by malonyl-CoA inhibition. In the liver, CPT-1A and PDK4 gene expression are induced by starvation, high fat diets and PPARα ligands. Here, we characterized a binding site for PPARα in the second intron of the rat CPT-1A gene. Our studies indicated that WY14643 and long chain fatty acids induce CPT-1A gene expression through this element. In addition, we found that mutation of the PPARα binding site reduced the expression of CPT-1A-luciferase vectors in the liver of fasted rats. We had demonstrated previously that CPT-1A was stimulated by the peroxisome proliferator activated receptor gamma coactivator (PGC-1α) via sequences in the first intron of the rat CPT-1A gene. Surprisingly, PGC-1α did not enhance CPT-1A transcription through the PPARα binding site in the second intron. Following knockdown of PGC-1α with short hairpin RNA, the CPT-1A and PDK4 genes remained responsive to WY14643. Overall, our studies indicated that PPARα and PGC-1α stimulate transcription of the CPT-1A gene through different regions of the CPT-1A gene.

Regulation of pyruvate dehydrogenase kinase 4 (PDK4) by thyroid hormone: role of peroxisome proliferator activated receptor gamma coactivator (PGC‐1α)

Pyruvate dehydrogenase kinase 4 (PDK4) 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 (T3), glucocorticoids and long chain fatty acids. Here, we have identified two binding sites for the thyroid hormone receptor (TRß) in the promoter of the PDK4 gene. In addition, we have investigated the role of transcriptional coactivators and found that the peroxisome proliferator activated receptor gamma coactivator (PGC‐1α) enhances the T3 induction of PDK4. Addition of T3 to rat hepatocytes increased the abundance of the PGC‐1α and its association with the PDK4 promoter. Administration of T3 to hypothyroid rats increased PGC‐1α protein levels in the liver. In addition, we observed enhanced association of PGC‐1α not only with the PDK4 gene but also with phosphoenolpyruvate carboxykinase (PEPCK) and carnitine palmitoyltransferase 1a (CPT‐1a) genes. Knock‐down of PGC‐1α in rat hepatocytes reduced the T3 induction of PDK4, PEPCK and CPT‐1a genes. Our results indicate that T3 regulates PGC‐1α abundance and association with hepatic genes and in turn PGC‐1α is an important participant in the T3 induction of selected genes.

Regulation of Pyruvate Dehydrogenase Kinase 4 (PDK4) by Thyroid Hormone: ROLE OF THE PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR γ COACTIVATOR (PGC-1α)

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.

Adiponectin decreases pyruvate dehydrogenase kinase 4 gene expression in obese‐ and diabetic‐derived myotubes

To investigate the effects of globular adiponectin (gAd) on gene expression and whether these effects are mediated through 3',5'-cyclic monophosphate-activated protein kinase in skeletal muscle myotubes obtained from lean, obese and obese diabetic individuals. Rectus abdominus muscle biopsies were obtained from surgical patients to establish primary skeletal muscle cell cultures. Three distinct primary cell culture groups were established (lean, obese and obese diabetic; n = 7 in each group). Once differentiated, these cultures were then exposed to gAd or 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR) for 6 h. Stimulation with gAd decreased pyruvate dehydrogenase kinase 4 (PDK4) gene expression in the obese and diabetic samples (p < or = 0.05) and increased cytochrome c oxidase (COX) subunit 4 (COXIV) gene expression in the myotubes derived from lean individuals only (p < 0.05). AICAR treatment also decreased PDK4 gene expression in the obese- and diabetic-derived myotubes (p < or = 0.05) and increased the gene expression of the mitochondrial gene, COXIII, in the lean-derived samples only (p < 0.05). This study demonstrated distinct disparity between myotubes derived from lean compared with obese and obese diabetic individuals following gAd and AICAR treatment. Further understanding of the regulation of PDK4 in obese and diabetic skeletal muscle and its interaction with adiponectin signalling is required as this appears to be an important early molecular event in these disease states that may improve blood glucose control and metabolic flux.

PDC deletion: the way to a man's heart disease

the heart has continuous high-energy demands required to sustain efficient contraction. This is met by the metabolism of major circulating substrates (e.g., glucose, lactate, or lipids), according to availability, since the heart has a limited capacity for nutrient storage (reviewed in Ref. [16][1

Regulation of gluconeogenic gene expression by glucocorticoids, cAMP and cytokines

Phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate dehydrogenase kinase 4 (PDK4) regulate steps in the pathway of gluconeogenesis and pyruvate oxidation respectively. In the liver, the expression of the genes encoding these proteins is induced during starvation and diabetes. Two primary mediators of this induction are glucocorticoids and glucagon (via cAMP). In type II diabetes, hepatic insulin resistance is associated with increased glucose output by the liver and elevated PEPCK and PDK4 gene expression. Several cytokines including tumor necrosis factor alpha (TNFa) and interleukin 6 (IL-6) have been suggested as factors that contribute to insulin resistance. We have examined the mechanisms by which cAMP and glucocorticoids induce the PEPCK and PDK4 genes. Insulin will block the stimulatory actions of these hormones on the gluconeogenic genes. Insulin will inhibit the PDK4 gene in part through the forkhead/FoxO1 transcription factors. In these studies, we report that TNFa and IL6 will alter the expression of PEPCK and PDK4 genes and impact the insulin regulation of these genes.

Retinoic acids and trichostatin A (TSA), a histone deacetylase inhibitor, induce human pyruvate dehydrogenase kinase 4 (PDK4) gene expression

Induction of pyruvate dehydrogenase kinase 4 (PDK4) conserves glucose and substrates for gluconeogenesis and thereby helps regulate blood glucose levels during starvation. We report here that retinoic acids (RA) as well as Trichostatin A (TSA), an inhibitor of histone deacetylase (HDAC), regulate PDK4 gene expression. Two retinoic acid response elements (RAREs) to which retinoid X receptor α (RXRα) and retinoic acid receptor α (RARα) bind and activate transcription are present in the human PDK4 (hPDK4) proximal promoter. Sp1 and CCAAT box binding factor (CBF) bind to the region between two RAREs. Mutation of either the Sp1 or the CBF site significantly decreases basal expression, transactivation by RXRα/RARα/RA, and the ability of TSA to stimulate hPDK4 gene transcription. By the chromatin immunoprecipitation assay, RA and TSA increase acetylation of histones bound to the proximal promoter as well as occupancy of CBP and Sp1. Interaction of p300/CBP with E1A completely prevented hPDK4 gene activation by RXRα/RARα/RA and TSA. The p300/CBP may enhance acetylation of histones bound to the hPDK4 promoter and cooperate with Sp1 and CBF to stimulate transcription of the hPDK4 gene in response to RA and TSA.

Protein Kinase B-α Inhibits Human Pyruvate Dehydrogenase Kinase-4 Gene Induction by Dexamethasone Through Inactivation of FOXO Transcription Factors

Starvation and diabetes increase pyruvate dehydrogenase kinase-4 (PDK4) expression, which conserves gluconeogenic substrates by inactivating the pyruvate dehydrogenase complex. Mechanisms that regulate PDK4 gene expression, previously established to be increased by glucocorticoids and decreased by insulin, were studied. Treatment of HepG2 cells with dexamethasone increases the relative abundance of PDK4 mRNA, and insulin blocks this effect. Dexamethasone also increases human PDK4 (hPDK4) promoter activity in HepG2 cells, and insulin partially inhibits this effect. Expression of constitutively active PKB alpha abrogates dexamethasone stimulation of hPDK4 promoter activity, while coexpression of constitutively active FOXO1a or FOXO3a, which are mutated to alanine at the three phosphorylation sites for protein kinase B (PKB), disrupts the ability of PKB alpha to inhibit promoter activity. A glucocorticoid response element for glucocorticoid receptor (GR) binding and three insulin response sequences (IRSs) that bind FOXO1a and FOXO3a are identified in the hPDK4 promoter. Mutation of the IRSs reduces the ability of glucocorticoids to stimulate PDK4 transcription. Transfection studies with E1A, which binds to and inactivates p300/CBP, suggest that interactions between p300/CBP and GR as well as FOXO factors are important for glucocorticoid-stimulated hPDK4 expression. Insulin suppresses the hPDK4 induction by glucocorticoids through inactivation of the FOXO factors.

Forkhead transcription factor FOXO1 (FKHR)-dependent induction of PDK4 gene expression in skeletal muscle during energy deprivation.

A forkhead-type transcription factor, DAF-16, is located in the most downstream part of the insulin signalling pathway via PI3K (phosphoinositide 3-kinase). It is essential for the extension of life-span and is also involved in dauer formation induced by food deprivation in Caenorhabditis elegans. In the present study, we addressed whether or not FOXO members AFX, FKHR (forkhead homologue in rhabdomyosarcoma) and FKHRL1 (FKHR-like protein 1), mammalian counterparts of DAF-16, are involved in starvation stress. We found a remarkable selective induction of FKHR and FKHRL1 transcripts in skeletal muscle of mice during starvation. The induction of FKHR gene expression was observed at 6 h after food deprivation, peaked at 12 h, and returned to the basal level by 24 h of refeeding. The induction was also found in skeletal muscle of mice with glucocorticoid treatment. Moreover, we found that the levels of PDK4 (pyruvate dehydrogenase kinase 4) gene expression were up-regulated through the direct binding of FKHR to the promoter region of the gene in C2C12 cells. These results suggest that FKHR has an important role in the regulation of energy metabolism, at least in part, through the up-regulation of PDK4 gene expression in skeletal muscle during starvation.