Upregulation Of Pyruvate Dehydrogenase Kinase Research Articles

Upregulation of the AMPK-FOXO1-PDK4 pathway is a primary mechanism of pyruvate dehydrogenase activity reduction in tafazzin-deficient cells

Barth syndrome (BTHS) is a rare disorder caused by mutations in the TAFAZZIN gene. Previous studies from both patients and model systems have established metabolic dysregulation as a core component of BTHS pathology. In particular, features such as lactic acidosis, pyruvate dehydrogenase (PDH) deficiency, and aberrant fatty acid and glucose oxidation have been identified. However, the lack of a mechanistic understanding of what causes these conditions in the context of BTHS remains a significant knowledge gap, and this has hindered the development of effective therapeutic strategies for treating the associated metabolic problems. In the current study, we utilized tafazzin-knockout C2C12 mouse myoblasts (TAZ-KO) and cardiac and skeletal muscle tissue from tafazzin-knockout mice to identify an upstream mechanism underlying impaired PDH activity in BTHS. This mechanism centers around robust upregulation of pyruvate dehydrogenase kinase 4 (PDK4), resulting from hyperactivation of AMP-activated protein kinase (AMPK) and subsequent transcriptional upregulation by forkhead box protein O1 (FOXO1). Upregulation of PDK4 in tafazzin-deficient cells causes direct phospho-inhibition of PDH activity accompanied by increased glucose uptake and elevated intracellular glucose concentration. Collectively, our findings provide a novel mechanistic framework whereby impaired tafazzin function ultimately results in robust PDK4 upregulation, leading to impaired PDH activity and likely linked to dysregulated metabolic substrate utilization. This mechanism may underlie previously reported findings of BTHS-associated metabolic dysregulation.

Abstract 13208: A Small Molecule Macrophage Migration Inhibitory Factor Agonist Ameliorates Age-Related Myocardial Intolerance to Ischemia-Reperfusion Insults via Metabolic Regulation

Introduction: The macrophage migration inhibitory factor (MIF) is emerged as a critical mediator during myocardia ischemia and reperfusion (I/R). An impaired MIF signaling is occurred in aging. MIF agonist, MIF20, can argument cardiac MIF signaling through increasing the binding affinity between MIF and its receptor, CD74/CD44. Hypothesis: Administration of MIF20 can increase the resistance of aged myocardium to ischemic insults caused by I/R via modulating the MIF signaling regulated energy metabolism. Methods: Young (3-5 months) and aged (24-26 months) wild-type C57BL/6J mice, cardiomyocyte specific MIF knock out C57BL/6J mice (cMIF-/-) and wild type littermates (MIF flox/flox ) were injected with MIF20 (0.15 μg/kg, I.V.) 5 minutes before reperfusion after 45 minutes of ischemia. The left ventricular myocardium was for immunoblotting, NAD/NADH assay, and metabolomics analysis. The working heart perfusion and the SeaHorse system were for metabolic measurements. Results: The small molecule MIF agonist, MIF20, which binds to MIF to increase signaling through its cognate receptor CD74/CD44 not only decreases infarct size but also preserves cardiac systolic function in the aged versus young hearts. MIF20 contributes to the maintenance of mitochondrial fitness and preserves the contractility of cardiomyocytes under hypoxia and reoxygenation stress. These beneficial effects of MIF20 are reduced in cardiomyocyte-specific MIF knock-out (cMIF -/- ) versus littermates (MIF flox/flox ) mice, supporting the autocrine role of MIF in mediating ischemic cardiac protection. The age-related disruption of metabolic homeostasis in aged versus young hearts was modulated by MIF20’s ability to upregulate glucose oxidation and downregulate the oxidation of fatty acid. These actions were associated with an upregulation of pyruvate dehydrogenase kinase 4 (PDK4) and downregulation of Long-chain acyl-CoA dehydrogenase (LCAD). MIF20 as MIF signaling agonism modulation of metabolic adaptation in aged hearts further led to reduced generation of reactive oxygen species (ROS) in the myocardium. Conclusions: MIF agonists such as MIF20 may have a therapeutic role by limiting cardiac damage and rescuing cardiac dysfunctions of senescent hearts to I/R stress.

PDK4-dependent hypercatabolism and lactate production of senescent cells promotes cancer malignancy

Senescent cells remain metabolically active, but their metabolic landscape and resulting implications remain underexplored. Here, we report upregulation of pyruvate dehydrogenase kinase 4 (PDK4) upon senescence, particularly in some stromal cell lines. Senescent cells display a PDK4-dependent increase in aerobic glycolysis and enhanced lactate production but maintain mitochondrial respiration and redox activity, thus adopting a special form of metabolic reprogramming. Medium from PDK4+ stromal cells promotes the malignancy of recipient cancer cells in vitro, whereas inhibition of PDK4 causes tumor regression in vivo. We find that lactate promotes reactive oxygen species production via NOX1 to drive the senescence-associated secretory phenotype, whereas PDK4 suppression reduces DNA damage severity and restrains the senescence-associated secretory phenotype. In preclinical trials, PDK4 inhibition alleviates physical dysfunction and prevents age-associated frailty. Together, our study confirms the hypercatabolic nature of senescent cells and reveals a metabolic link between cellular senescence, lactate production, and possibly, age-related pathologies, including but not limited to cancer.

Dual-specificity Tyrosine Phosphorylation-regulated Kinase Inhibitor ID-8 Promotes Human Somatic Cell Reprogramming by Activating PDK4 Expression.

Human induced pluripotent stem cells (hiPSCs) hold great potentials in disease modeling, drug screening and cell therapy. However, efficiency and costs of hiPSCs preparation still need to be improved. We screened the compounds that target signaling pathways, epigenetic modifications or metabolic-process regulation to replace the growth factors. After small molecule treatment, TRA-1-60, which is a cell surface antigen expressed by human embryonic stem cells (hESCs), staining was performed to quantify the efficiency of somatic cell reprogramming. Next, small molecule cocktail-induced ESCs or iPSCs were examined with pluripotent markers expression. Finally, Genome-wide gene expression profile was analyzed by RNA-seq to illustrate the mechanism of human somatic cell reprogramming. Here, we found that a dual-specificity tyrosine phosphorylation-regulated kinase (DYRK) inhibitor ID-8 robustly enhanced human somatic cell reprogramming by upregulation of pyruvate dehydrogenase kinase 4 (PDK4) and activation of glycolysis. Furthermore, we identified a novel growth-factor-free hiPSC generation system using small molecules ID-8 (I) and TGFβ signal pathway agonist Kartogenin (K). Importantly, we developed IK medium combined with low-dose bFGF to support the long-term expansion of human pluripotent stem cells. IK-iPSCs showed pluripotency and normal karyotype. Our studies may provide a novel growth-factor-free culture system to facilitate the generation of hiPSCs for multiple applications in regenerative medicine. In Brief Xu et at. found that a dual-specificity tyrosine phosphorylation-regulated kinase (DYRK) inhibitor ID-8 robustly enhanced human somatic cell reprogramming by upregulation of PDK4 and activation of glycolysis. Furthermore, we established a novel growth-factor-free hiPSC generation system using small molecules ID-8/Kartogenin (IK). IK medium combined with Low-dose bFGF (IKB medium) supported the long-term expansion of human pluripotent stem cells. Highlights ID-8 Enhanced Reprogramming of Human Fibroblasts and Astrocytes Establishment of the Growth-factor-free Reprogramming System Using Small Molecule Compounds IK IKB Medium Maintained the Long-term Expansion of Human Pluripotent Stem Cells ID-8 Promoted Human Somatic Cell Reprogramming by Activating PDK4 Expression.

Reduction of mitochondria and up regulation of pyruvate dehydrogenase kinase 4 of skeletal muscle in patients with chronic kidney disease.

Muscle weakness is commonly among chronic kidney disease (CKD) patients. Muscle mitochondrial dysfunction and decreased pyruvate dehydrogenase (PDH) activity occur in CKD animals but have not been confirmed in humans, and changes in pyruvate dehydrogenase kinase (PDK) and pyruvate dehydrogenase phosphatase (PDP) expression have not been evaluated in CKD muscle. We presume that the reduction of muscle mitochondria and post-translational modification of PDH may cause muscle weakness in CKD patients. Herein, we explored changes in mitochondrial morphology, PDH expression and activity, and PDK/PDP expression in CKD patient muscle. Twenty patients with stage 4-5 CKD (CKD group) and 24 volunteers (control group) were included. Clinical characteristics, biochemical information and handgrip strength (HGS) were determined. Skeletal muscle samples were collected from eight stage 5 CKD patients from CKD group. Other eight non-CKD surgical subjects' muscle samples were collected as control. PDH activity was determined using a PDH enzyme activity assay kit, and real-time PCR and western blotting analyses were performed to measure gene expression and protein levels, respectively. Transmission electron microscopy was used to study mitochondria morphology. CKD patients had lower HGS than non-CKD subjects, and HGS was correlated with gender, age, haemoglobin and albumin. Mitochondria were decreased in end-stage renal disease (ESRD) patients muscle. Mfn-1 expression and phospho-Drp1(S637)/Drp1 ratio were inhibited in the ESRD group, implicating dysfunctional mitochondrial dynamics. Muscle PDH activity and phospho-PDH(S293) were decreased in ESRD patient muscle, while PDK4 protein level was up regulated. Decreased mitochondria and PDH deficiency caused by up regulation of PDK 4 contribute to muscle dysfunction, and could be responsible for muscle weakness in CKD patients.

Retrodifferentiation of Human Tumor Hepatocytes to Stem Cells Leads to Metabolic Reprogramming and Chemoresistance.

Human hepatocellular carcinoma (HCC) heterogeneity promotes recurrence and therapeutic resistance. We recently demonstrated that inflammation favors hepatocyte retrodifferentiation into progenitor cells. Here, we identify the molecular effectors that induce metabolic reprogramming, chemoresistance, and invasiveness of retrodifferentiated HCC stem cells. Spheroid cultures of human HepaRG progenitors (HepaRG-Spheres), HBG-BC2, HepG2, and HuH7 cells and isolation of side population (SP) from HepaRG cells (HepaRG-SP) were analyzed by transcriptomics, signaling pathway analysis, and evaluation of chemotherapies. Gene expression profiling of HepaRG-SP and HepaRG-Spheres revealed enriched signatures related to cancer stem cells, metastasis, and recurrence and showed that HepaRG progenitors could retrodifferentiate into an immature state. The transcriptome from these stem cells matched that of proliferative bad outcome HCCs in a cohort of 457 patients. These HCC stem cells expressed high levels of cytokines triggering retrodifferentiation and displayed high migration and invasion potential. They also showed changes in mitochondrial activity with reduced membrane potential, low ATP production, and high lactate production. These changes were, in part, related to angiopoietin-like 4 (ANGPTL4)-induced upregulation of pyruvate dehydrogenase kinase 4 (PDK4), an inhibitor of mitochondrial pyruvate dehydrogenase. Upregulation of ANGPTL4 and PDK4 paralleled that of stem cells markers in human HCC specimens. Moreover, the PDK4 inhibitor dichloroacetate reversed chemoresistance to sorafenib or cisplatin in HCC stem cells derived from four HCC cell lines. In conclusion, retrodifferentiated cancer cells develop enhanced invasion and therapeutic resistance through ANGPTL4 and PDK4. Therefore, restoration of mitochondrial activity in combination with chemotherapy represents an attractive therapeutic approach in HCC. SIGNIFICANCE: Restoring mitochondrial function in human hepatocellular carcinomas overcomes cancer resistance.

Postnatal induction of muscle fatty acid oxidation in mice differing in propensity to obesity: a role of pyruvate dehydrogenase.

Adaptation to the extrauterine environment depends on a switch from glycolysis to catabolism of fatty acids (FA) provided as milk lipids. We sought to learn whether the postnatal induction of muscle FA oxidation in mice could reflect propensity to obesity and to characterize the mechanisms controlling this induction. Experiments were conducted using obesity-resistant A/J and obesity-prone C57BL/6J (B6) mice maintained at 30 °C, from 5 to 28 days after birth. At day 10, both A/J and B6 mice with genetic ablation (KO) of α2 subunit of AMP-activated protein kinase (AMPK) were also used. In skeletal muscle, expression of selected genes was determined using quantitative real-time PCR, and AMPK subunits content was evaluated using Western blotting. Activities of both AMPK and pyruvate dehydrogenase (PDH), as well as acylcarnitine levels in the muscle were measured. Acylcarnitine levels and gene expression indicated transient increase in FA oxidation during the first 2 weeks after birth, with a stronger increase in A/J mice. These data correlated with (i) the surge in plasma leptin levels, which peaked at day 10 and was higher in A/J mice, and (ii) relatively low activity of PDH linked with up-regulation of PDH kinase 4 gene (Pdk4) expression in the 10-day-old A/J mice. In contrast with the Pdk4 expression, transient up-regulation of uncoupling protein 3 gene was observed in B6 but not A/J mice. AMPK activity changed during the development, without major differences between A/J and B6 mice. Expression of neither Pdk4 nor other muscle genes was affected by AMPK-KO. Our results indicate a relatively strong postnatal induction of FA oxidation in skeletal muscle of the obesity-resistant A/J mice. This induction is transient and probably results from suppression of PDH activity, linked with a postnatal surge in plasma leptin levels, independent of AMPK.

Metabolic Changes Associated With Muscle Expression of SOD1G93A.

Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disorder, classified into sporadic or familial forms and characterized by motor neurons death, muscle atrophy, weakness, and paralysis. Among the familial cases of ALS, approximately 20% are caused by dominant mutations in the gene coding for superoxide dismutase (SOD1) protein. Of note, mutant SOD1 toxicity is not necessarily limited to the central nervous system. ALS is indeed a multi-systemic and multifactorial disease that affects whole body physiology and induces severe metabolic changes in several tissues, including skeletal muscle. Nevertheless, whether alterations in the plasticity, heterogeneity, and metabolism of muscle fibers are the result of motor neuron degeneration or alternatively occur independently of it remain to be elucidated. To address this issue, we made use of a mouse model (MLC/SOD1G93A) that overexpresses the SOD1 mutant gene selectively in skeletal muscle. We found an alteration in the metabolic properties of skeletal muscle characterized by alteration in fiber type composition and metabolism. Indeed, we observed an alteration of muscle glucose metabolism associated with the induction of Phosphofructokinases and Pyruvate dehydrogenase kinase 4 expression. The upregulation of Pyruvate dehydrogenase kinase 4 led to the inhibition of Pyruvate conversion into Acetyl-CoA. Moreover, we demonstrated that the MLC/SOD1G93A transgene was associated with an increase of lipid catabolism and with the inhibition of fat deposition inside muscle fibers. All together these data demonstrate that muscle expression of the SOD1G93A gene induces metabolic changes, along with a preferential use of lipid energy fuel by muscle fibers. We provided evidences that muscle metabolic alterations occurred before disease symptoms and independently of motor neuron degeneration, indicating that skeletal muscle is likely an important therapeutic target in ALS.

173 - To investigate the Physiological/ Pathophysio-logical Function of Glutaredoxin-1 on the Metabolic Cardiovascular Disease

To meet the constant energy demand, the heart utilizes fatty acid oxidation as the primary source and glucose, lactate, ketone bodies, and pyruvate as secondary sources to generate ATP. The healthy heart quickly adapts to changes in the abundance of these metabolites. Type II diabetes (T2D), however, impairs this metabolic flexibility, in part to insulin resistance. The loss of metabolic flexibility in T2D can damage cardiomyocytes leading to cardiomyopathy, cardiac remodeling and heart failure. Glutaredoxin-1 (Glrx) is an enzyme that removes glutathione adducts from proteins and participates in redox signaling. Ablation of Glrx perturbs lipid metabolism and causes dyslipidemia and obesity in mice. Glrx knockout mice fed high fat high sucrose (HFHS) diet for six months developed systolic dysfunction which led to around 25% decrease ejection fraction and fractional area shortening. Global gene expression analysis revealed changes in important metabolic enzymes including upregulation of pyruvate dehydrogenase kinase (PDK) 4 in Glrx KO hearts. PDK4 inhibits pyruvate dehydrogenase, which links glucose metabolism with the Krebs cycle and mitochondrial respiration. Upregulation of PDK4 limits glucose catabolism and increases fatty acid oxidation. Furthermore, other biomarkers of fibrosis and cardiac remodeling including CTGF and matrix metalloproteinases inhibitor (Timp3) were changed in HFHS fed Glrx KO mice. Overall, our data suggests that Glrx may play an important role in regulating cardiac lipid metabolism and metabolic flexibility that can lead to metabolic cardiomyopathy.

Succinate accumulation impairs cardiac pyruvate dehydrogenase activity through GRP91-dependent and independent signaling pathways: Therapeutic effects of ginsenoside Rb1

Altered mitochondrial oxidation increases vulnerability to cardiac ischemia/reperfusion (I/R) injury in metabolic disorders. However, the metabolic signaling responsible for the dysfunction remains partly unknown. We sought to test whether or not hypoxic succinate accumulation could inhibit pyruvate dehydrogenase (PDH) activity and subsequently aggravate I/R injury. Results showed that saturated fatty acid palmitate stimulation increased fatty acid oxidation and induced hypoxia in cardiomyocytes, leading to succinate accumulation. Intracellular succinate induced hypoxia inducible factor-1α (HIF-1α) expression and impaired PDH activity via upregulation of pyruvate dehydrogenase kinase 4 (PDK4) expression. Luciferase reporter assay showed that succinate increased PDK4 expression through gene promoter induction in a HIF-1α-dependent manner. Palmitate also induced the release of succinate into extracellular space. By activating GRP91, extracellular succinate induced the translocation of PKCδ to mitochondria and further exacerbated PDH impairment. These results demonstrated that succinate impaired PDH activity via GPR91-dependent and independent pathways. Ginsenoside Rb1 (a major compound isolated from ginseng) and trimetazidine (fatty acid β-oxidation inhibitor) prevented hypoxic succinate accumulation in cardiomyocytes and improved PDH activity by blocking succinate-associated HIF-1α activation and GPR91 signaling. Through improving PDH activity, Rb1 and trimetazidine prevented cardiac acidification, ameliorated mitochondrial dysfunction and thereby reduced apoptosis during hypoxia/reoxygenation insult. In isolated working rat hearts perfused with palmitate and in high-fat diet-fed mice, early intervention of Rb1 and trimetazidine reduced succinate production and resultantly increased heart resistance to ischemia/reperfusion injury. Taken together, our findings demonstrated that early intervention by targeting inhibition of succinate accumulation-induced PDH impairment is an effective strategy to alleviate I/R injury.

Cell competition with normal epithelial cells promotes apical extrusion of transformed cells through metabolicchanges.

Recent studies have revealed that newly emerging transformed cells are often apically extruded from epithelial tissues. During this process, normal epithelial cells can recognize and actively eliminate transformed cells, a process called epithelial defence against cancer (EDAC). Here, we show that mitochondrial membrane potential is diminished in RasV12-transformed cells when they are surrounded by normal cells. In addition, glucose uptake is elevated, leading to higher lactate production. The mitochondrial dysfunction is driven by upregulation of pyruvate dehydrogenase kinase 4 (PDK4), which positively regulates elimination of RasV12-transformed cells. Furthermore, EDAC from the surrounding normal cells, involving filamin, drives the Warburg-effect-like metabolic alteration. Moreover, using a cell-competition mouse model, we demonstrate that PDK-mediated metabolic changes promote the elimination of RasV12-transformed cells from intestinal epithelia. These data indicate that non-cell-autonomous metabolic modulation is a crucial regulator for cell competition, shedding light on the unexplored events at the initial stage ofcarcinogenesis.

Regulation of Pyruvate Dehydrogenase Kinase 4 in the Heart through Degradation by the Lon Protease in Response to Mitochondrial Substrate Availability

Cardiac metabolic inflexibility is driven by robust up-regulation of pyruvate dehydrogenase kinase 4 (PDK4) and phosphorylation-dependent inhibition of pyruvate dehydrogenase (PDH) within a single day of feeding mice a high fat diet. In the current study, we have discovered that PDK4 is a short lived protein (t½ ∼ 1 h) and is specifically degraded by the mitochondrial protease Lon. Lon does not rapidly degrade PDK1 and -2, indicating specificity toward the PDK isoform that is a potent modulator of metabolic flexibility. Moreover, PDK4 degradation appears regulated by dissociation from the PDH complex dependent on the respiratory state and energetic substrate availability of mouse heart mitochondria. Finally, we demonstrate that pharmacologic inhibition of PDK4 promotes PDK4 degradation in vitro and in vivo These findings reveal a novel strategy to manipulate PDH activity by selectively targeting PDK4 content through dissociation and proteolysis.

Down-regulation of succinate dehydrogenase subunit B and up-regulation of pyruvate dehydrogenase kinase 1 predicts poor prognosis in recurrent nasopharyngeal carcinoma.

Succinate dehydrogenase subunit B (SDHB) and pyruvate dehydrogenase kinase 1 (PDK1) play key roles in the regulation of growth and survival of various cancers. This study aimed to investigate expression of SDHB and PDK1 in recurrent nasopharyngeal carcinoma (rNPC) tissues and analyzed the association of SDHB and PDK1 expression with the clinical significance and potential prognostic implication of rNPC. Immunohistochemistry was performed to determine the expression of SDHB and PDK1 in tissues in primary NPC (pNPC) and rNPC patients. Our results revealed that expression of SDHB in rNPC was significantly lower than that in pNPC, while the expression of PDK1 was higher compared to pNPC. The expression levels of SDHB and PDK1 were associated with T stage, N stage, clinical stage, and metastasis of rNPC. Survival analysis showed that patients with low SDHB expression had a significantly shorter overall survival time than those with high SDHB expression. Patients with high PDK1 expression had a shorter survival time than patients with low PDK1 expression. Multivariate analysis showed that the expression of SDHB and PDK1 was an independent predictor for the survival of patients with rNPC. Our results demonstrated that down-regulation of SDHB and up-regulation of PDK1 may be novel biomarkers for predicting advanced tumor progression and unfavorable prognosis in rNPC patients.

Discovery and optimization of 4,5-diarylisoxazoles as potent dual inhibitors of pyruvate dehydrogenase kinase and heat shock protein 90.

Upregulation of pyruvate dehydrogenase kinase (PDHK) has been observed in a variety of cancers. Inhibition of PDHK offers an attractive opportunity for the development of novel cancer therapies. To obtain novel PDHK inhibitors, we took advantage of the homology of the ATP-binding pocket between Heat Shock Protein 90 (HSP90) and PDHK, and utilized 4,5-diarylisoxazole based HSP90 inhibitor for structural design. Our efforts led to the identification of 5k that inhibited PDHK1 with an IC50 value of 17 nM, which, however, showed marginal cellular activity. Further structural optimization resulted in compound 11a with improved cellular activity which could effectively modulate the metabolic profile of cancer cells and lead to the inhibition of cancer cell proliferation, evidenced by the increased oxidative phosphorylation and decreased glycolysis and associated oxidative stress. Our results suggested 11a as an excellent lead compound and a favorable biological tool to further evaluate the therapeutic potential of PDHK and HSP90 dual inhibitors in the treatment of cancer.

Abstract 5514: Metformin sensitizes anticancer effect of dasatinib through AMPK-dependent ER stress in head and neck squamous cell carcinoma cells

Abstract Purpose: Head and neck squamous cell carcinoma (HNSCC) is an important endemic disease in Taiwan with aggressive course and dismal outcome. Dasatinib is a Bcr-bl and Src kinase inhibitor that has potential against HNSCC. We recently disclosed that EGFR degradation is critical for dasatinib-induced apoptosis. Here, we further demonstrate that AMPK-dependent ER stress is responsible for this effect. Experimental design: Dasatinib-induced ER stress and AMPK activation was investigated in HNSCC cells including Ca9-22, HSC3, and SAS. The anti-cancer activity of dasatinib in combination with AMPK activator was examined in vitro and in vivo. EGFR expression and AMPK activation were correlated in human specimens. Results: Dasatinib-induced ER stress was involved in dasatinib-induced EGFR degradation and apoptosis, and ER stress mediated EGFR degradation in a c-cbl-dependent manner. In addition, dasatinib-induced AMPK activation led to dasatinib-induced ER stress and EGFR degradation, and activation of AMPK might be due to ATP decrease through the up-regulation of pyruvate dehydrogenase kinase 4 (PDK4) induced by dasatinib. Furthermore, activation of AMPK by metformin potentiated dasatinib-induced anti-cancer effect in vitro and in vivo. The correlation of AMPK activation and EGFR expression was seen in HNSCC cells and human tumor specimens. Conclusions: Our results disclose that AMPK-dependent ER stress plays a crucial role in anti-cancer effect of dasatinib on HNSCC and activation of AMPK might enhance dasatinib efficacy. Note: This abstract was not presented at the meeting. Citation Format: Yu-Chin Lin, Meng-Hsuan Wu, Tzu-Tang Wei, Yun-Chieh Lin, Ching-Chow Chen. Metformin sensitizes anticancer effect of dasatinib through AMPK-dependent ER stress in head and neck squamous cell carcinoma cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5514. doi:10.1158/1538-7445.AM2014-5514

The right ventricle in pulmonary arterial hypertension: disorders of metabolism, angiogenesis and adrenergic signaling in right ventricular failure.

The right ventricle (RV) is the major determinant of functional state and prognosis in pulmonary arterial hypertension. RV hypertrophy (RVH) triggered by pressure overload is initially compensatory but often leads to RV failure. Despite similar RV afterload and mass some patients develop adaptive RVH (concentric with retained RV function), while others develop maladaptive RVH, characterized by dilatation, fibrosis, and RV failure. The differentiation of adaptive versus maladaptive RVH is imprecise, but adaptive RVH is associated with better functional capacity and survival. At the molecular level, maladaptive RVH displays greater impairment of angiogenesis, adrenergic signaling, and metabolism than adaptive RVH, and these derangements often involve the left ventricle. Clinically, maladaptive RVH is characterized by increased N-terminal pro-brain natriuretic peptide levels, troponin release, elevated catecholamine levels, RV dilatation, and late gadolinium enhancement on MRI, increased (18)fluorodeoxyglucose uptake on positron emission tomography, and QTc prolongation on the ECG. In maladaptive RVH there is reduced inotrope responsiveness because of G-protein receptor kinase-mediated downregulation, desensitization, and uncoupling of β-adrenoreceptors. RV ischemia may result from capillary rarefaction or decreased right coronary artery perfusion pressure. Maladaptive RVH shares metabolic abnormalities with cancer including aerobic glycolysis (resulting from a forkhead box protein O1-mediated transcriptional upregulation of pyruvate dehydrogenase kinase), and glutaminolysis (reflecting ischemia-induced cMyc activation). Augmentation of glucose oxidation is beneficial in experimental RVH and can be achieved by inhibition of pyruvate dehydrogenase kinase, fatty acid oxidation, or glutaminolysis. Therapeutic targets in RV failure include chamber-specific abnormalities of metabolism, angiogenesis, adrenergic signaling, and phosphodiesterase-5 expression. The ability to restore RV function in experimental models challenges the dogma that RV failure is irreversible without regression of pulmonary vascular disease.

Metformin sensitizes anticancer effect of dasatinib in head and neck squamous cell carcinoma cells through AMPK-dependent ER stress

Head and neck squamous cell carcinoma (HNSCC) is an important endemic disease in Taiwan with aggressive course and dismal outcome. Dasatinib is a Bcr-bl and Src kinase inhibitor that has potential against HNSCC. We recently disclosed that EGFR degradation is critical for dasatinib-induced apoptosis. Here, we further demonstrate that AMPK-dependent ER stress is responsible for this event. Dasatinib induced ER stress which mediated EGFR degradation in a c-cbl-dependent manner. AMPK activation induced by dasatinib might be due to ATP decrease through the up-regulation of pyruvate dehydrogenase kinase 4 (PDK4). Furthermore, activation of AMPK by metformin sensitized dasatinib-induced in vitro and in vivo anti-cancer effect. The correlation of AMPK activation and EGFR expression was seen in HNSCC cells and human tumor specimens. Our results disclose that AMPK-dependent ER stress plays a crucial role in the anti-cancer effect of dasatinib in HNSCC and further activation of AMPK by metformin might enhance dasatinib efficacy.

Alteration of energy metabolism in the pathogenesis of bile duct lesions in primary biliary cirrhosis

AimPrimary biliary cirrhosis (PBC) is characterised by antimitochondrial antibody against the pyruvate dehydrogenase complex (PDC) and chronic non-suppurative destructive cholangitis (CNSDC). Pyruvate oxidation to acetyl-CoA by PDC is a key...

Agonist-Induced Hypertrophy and Diastolic Dysfunction Are Associated With Selective Reduction in Glucose Oxidation

Background— Activation of the renin-angiotensin and sympathetic nervous systems may alter the cardiac energy substrate preference, thereby contributing to the progression of heart failure with normal ejection fraction. We assessed the qualitative and quantitative effects of angiotensin II (Ang II) and the α-adrenergic agonist, phenylephrine (PE), on cardiac energy metabolism in experimental models of hypertrophy and diastolic dysfunction and the role of the Ang II type 1 receptor. Methods and Results— Ang II (1.5 mg·kg −1 ·day −1 ) or PE (40 mg·kg −1 ·day −1 ) was administered to 9-week-old male C57/BL6 wild-type mice for 14 days via implanted microosmotic pumps. Echocardiography showed concentric hypertrophy and diastolic dysfunction, with preserved systolic function in Ang II- and PE-treated mice. Ang II induced marked reduction in cardiac glucose oxidation and lactate oxidation, with no change in glycolysis and fatty acid β-oxidation. Tricarboxylic acid acetyl coenzyme A production and ATP production were reduced in response to Ang II. Cardiac pyruvate dehydrogenase kinase 4 expression was upregulated by Ang II and PE, resulting in a reduction in the pyruvate dehydrogenase activity, the rate-limiting step for carbohydrate oxidation. Pyruvate dehydrogenase kinase 4 upregulation correlated with the activation of the cyclin/cyclin-dependent kinase-retinoblastoma protein-E2F pathway in response to Ang II. Ang II type 1 receptor blockade normalized the activation of the cyclin/cyclin-dependent kinase-retinoblastoma protein-E2F pathway and prevented the reduction in glucose oxidation but increased fatty acid oxidation. Conclusions— Ang II- and PE-induced hypertrophy and diastolic dysfunction is associated with reduced glucose oxidation because of the cyclin/cyclin-dependent kinase-retinoblastoma protein-E2F–induced upregulation of pyruvate dehydrogenase kinase 4, and targeting these pathways may provide novel therapy for heart failure with normal ejection fraction.

Activating cardiac E2F1 induces up-regulation of pyruvate dehydrogenase kinase 4 in mice on a short term of high fat feeding

A high fat diet (HFD) induces substantial cardiac metabolic alteration(s), but the initiating molecular events remain unclear. We assessed the early cardiac energy metabolic changes in C57/BJ mice fed a HFD for 10days. Carbohydrate oxidation was markedly decreased in mice on a HFD, in which up-regulation of pyruvate dehydrogenase kinase 4 (PDK4) was evident. Concurrently, E2F1, a transcription factor controlling PDK4 expression, was activated, as was cyclin D1, an upstream-molecule of E2F1, and eukaryotic initiation factor 4E (eIF4E), a modulator of cyclinD1 translation. Hence, HFD may initiate early cardiac metabolic alterations through the eIF4E/cyclin D1/E2F1/PDK4 axis.