Showing papers on "Pyruvate dehydrogenase kinase published in 2019"

Metabolic Flexibility in Cancer: Targeting the Pyruvate Dehydrogenase Kinase:Pyruvate Dehydrogenase Axis.

Abstract: Cancer cells use alterations of normal metabolic processes to sustain proliferation indefinitely. Transcriptional and posttranscriptional control of the pyruvate dehydrogenase kinase (PDK) family is one way in which cancer cells alter normal pyruvate metabolism to fuel proliferation. PDKs can phosphorylate and inactivate the pyruvate dehydrogenase complex (PDHC), which blocks oxidative metabolism of pyruvate by the mitochondria. This process is thought to enhance cancer cell growth by promoting anabolic pathways. Inhibition of PDKs induces cell death through increased PDH activity and subsequent increases in ROS production. The use of PDK inhibitors has seen widespread success as a potential therapeutic in laboratory models of multiple cancers; however, gaps still exist in our understanding of the biology of PDK regulation and function, especially in the context of individual PDKs. Efforts are currently underway to generate PDK-specific inhibitors and delineate the roles of individual PDK isozymes in specific cancers. The goal of this review is to understand the regulation of the PDK isozyme family, their role in cancer proliferation, and how to target this pathway therapeutically to specifically and effectively reduce cancer growth.

Inhibition of mitochondrial pyruvate dehydrogenase kinase: a proposed mechanism by which melatonin causes cancer cells to overcome cytosolic glycolysis, reduce tumor biomass and reverse insensitivity to chemotherapy

Abstract: This review presents a hypothesis to explain the role of melatonin in regulating glucose metabolism in cancer cells. Many cancer cells use cytosolic glycolysis (the Warburg effect) to produce energy (ATP). Under these conditions, glucose is primarily converted to lactate which is released into the blood in large quantities. The Warburg effect gives cancer cells advantages in terms of enhanced macromolecule synthesis required for accelerated cellular proliferation, reduced cellular apoptosis which enhances tumor biomass and a greater likelihood of metastasis. Based on available data, high circulating melatonin levels at night serve as a signal for breast cancer cells to switch from cytosolic glycolysis to mitochondrial glucose oxidation and oxidative phosphorylation for ATP production. In this situation, melatonin promotes the synthesis of acetyl-CoA from pyruvate; we speculate that melatonin does this by inhibiting the mitochondrial enzyme pyruvate dehydrogenase kinase (PDK) which normally inhibits pyruvate dehydrogenase complex (PDC), the enzyme that controls the pyruvate to acetyl-CoA conversion. Acetyl-CoA has several important functions in the mitochondria; it feeds into the citric acid cycle which improves oxidative phosphorylation and, additionally, it is a necessary co-factor for the rate limiting enzyme, arylalkylamine N-acetyltransferase, in mitochondrial melatonin synthesis. When breast cancer cells are using cytosolic glycolysis (during the day) they are of the cancer phenotype; at night when they are using mitochondria to produce ATP via oxidative phosphorylation, they have a normal cell phenotype. If this day:night difference in tumor cell metabolism is common in other cancers, it indicates that these tumor cells are only cancerous part of the time. We also speculate that high nighttime melatonin levels also reverse the insensitivity of tumors to chemotherapy.

Pyruvate Dehydrogenase Kinase Is a Metabolic Checkpoint for Polarization of Macrophages to the M1 Phenotype.

Abstract: Metabolic reprogramming during macrophage polarization supports the effector functions of these cells in health and disease. Here, we demonstrate that pyruvate dehydrogenase kinase (PDK), which inhibits the pyruvate dehydrogenase-mediated conversion of cytosolic pyruvate to mitochondrial acetyl-CoA, functions as a metabolic checkpoint in M1 macrophages. Polarization was not prevented by PDK2 or PDK4 deletion but was fully prevented by the combined deletion of PDK2 and PDK4; this lack of polarization was correlated with improved mitochondrial respiration and rewiring of metabolic breaks that are characterized by increased glycolytic intermediates and reduced metabolites in the TCA cycle. Genetic deletion or pharmacological inhibition of PDK2/4 prevents polarization of macrophages to the M1 phenotype in response to inflammatory stimuli (lipopolysaccharide plus IFN-γ). Transplantation of PDK2/4-deficient bone marrow into irradiated wild-type mice to produce mice with PDK2/4-deficient myeloid cells prevented M1 polarization, reduced obesity-associated insulin resistance, and ameliorated adipose tissue inflammation. A novel, pharmacological PDK inhibitor, KPLH1130, improved high-fat diet-induced insulin resistance; this was correlated with a reduction in the levels of pro-inflammatory markers and improved mitochondrial function. These studies identify PDK2/4 as a metabolic checkpoint for M1 phenotype polarization of macrophages, which could potentially be exploited as a novel therapeutic target for obesity-associated metabolic disorders and other inflammatory conditions.

PDK4 drives metabolic alterations and muscle atrophy in cancer cachexia.

Abstract: Cachexia is frequently accompanied by severe metabolic derangements, although the mechanisms responsible for this debilitating condition remain unclear. Pyruvate dehydrogenase kinase (PDK)4, a critical regulator of cellular energetic metabolism, was found elevated in experimental models of cancer, starvation, diabetes, and sepsis. Here we aimed to investigate the link between PDK4 and the changes in muscle size in cancer cachexia. High PDK4 and abnormal energetic metabolism were found in the skeletal muscle of colon-26 tumor hosts, as well as in mice fed a diet enriched in Pirinixic acid, previously shown to increase PDK4 levels. Viral-mediated PDK4 overexpression in myotube cultures was sufficient to promote myofiber shrinkage, consistent with enhanced protein catabolism and mitochondrial abnormalities. On the contrary, blockade of PDK4 was sufficient to restore myotube size in C2C12 cultures exposed to tumor media. Our data support, for the first time, a direct role for PDK4 in promoting cancer-associated muscle metabolic alterations and skeletal muscle atrophy.-Pin, F., Novinger, L. J., Huot, J. R., Harris, R. A., Couch, M. E., O'Connell, T. M., Bonetto, A. PDK4 drives metabolic alterations and muscle atrophy in cancer cachexia.

Microenvironmental control of glucose metabolism in tumors by regulation of pyruvate dehydrogenase

Abstract: During malignant progression cancer cells undergo a series of changes, which promote their survival, invasiveness and metastatic process. One of them is a change in glucose metabolism. Unlike normal cells, which mostly rely on the tricarboxylic acid cycle (TCA), many cancer types rely on glycolysis. Pyruvate dehydrogenase complex (PDC) is the gatekeeper enzyme between these two pathways and is responsible for converting pyruvate to acetyl-CoA, which can then be processed further in the TCA cycle. Its activity is regulated by PDP (pyruvate dehydrogenase phosphatases) and PDHK (pyruvate dehydrogenase kinases). Pyruvate dehydrogenase kinase exists in 4 tissue specific isoforms (PDHK1-4), the activities of which are regulated by different factors, including hormones, hypoxia and nutrients. PDHK1 and PDHK3 are active in the hypoxic tumor microenvironment and inhibit PDC, resulting in a decrease of mitochondrial function and activation of the glycolytic pathway. High PDHK1/3 expression is associated with worse prognosis in patients, which makes them a promising target for cancer therapy. However, a better understanding of PDC's enzymatic regulation in vivo and of the mechanisms of PDHK-mediated malignant progression is necessary for the design of better PDHK inhibitors and the selection of patients most likely to benefit from such inhibitors.

Adropin regulates cardiac energy metabolism and improves cardiac function and efficiency

Abstract: Background Impaired cardiac insulin signalling and high cardiac fatty acid oxidation rates are characteristics of conditions of insulin resistance and diabetic cardiomyopathies. The potential role of liver-derived peptides such as adropin in mediating these changes in cardiac energy metabolism is unclear, despite the fact that in skeletal muscle adropin can preferentially promote glucose metabolism and improve insulin sensitivity. Objectives To determine the influence of adropin on cardiac energy metabolism, insulin signalling and cardiac efficiency. Methods C57Bl/6 mice were injected with either vehicle or a secretable form of adropin (450 nmol/kg, i.p.) three times over a 24-h period. The mice were fasted to accentuate the differences between animals in adropin plasma levels before their hearts were isolated and perfused using a working heart system. In addition, direct addition of adropin to the perfusate of ex vivo hearts isolated from non-fasting mice was utilized to investigate the acute effects of the peptide on heart metabolism and ex vivo function. Results In contrast to the observed fasting-induced predominance of fatty acid oxidation as a source of ATP production in control hearts, insulin inhibition of fatty acid oxidation was preserved by adropin treatment. Adropin-treated mouse hearts also showed a higher cardiac work, which was accompanied by improved cardiac efficiency and enhanced insulin signalling compared to control hearts. Interestingly, acute adropin administration to isolated working hearts also resulted in an inhibition of fatty acid oxidation, accompanied by a robust stimulation of glucose oxidation compared to vehicle-treated hearts. Adropin also increased activation of downstream cardiac insulin signalling. Moreover, both in vivo and ex vivo treatment protocols induced a reduction in the inhibitory phosphorylation of pyruvate dehydrogenase (PDH), the major enzyme of glucose oxidation, and the protein levels of the responsible kinase PDH kinase 4 and the insulin-signalling inhibitory phosphorylation of JNK (p-T183/Y185) and IRS-1 (p-S307), suggesting acute receptor- and/or post-translational modification-mediated mechanisms. Conclusions These results demonstrate that adropin has important effects on energy metabolism in the heart and may be a putative candidate for the treatment of cardiac disease associated with impaired insulin sensitivity.

Molecular interaction studies on ellagic acid for its anticancer potential targeting pyruvate dehydrogenase kinase 3

Abstract: Pyruvate dehydrogenase kinase 3 (PDK3) plays a central role in the cancer metabolic switch through the reversible phosphorylation of pyruvate dehydrogenase complex thereby blocking the entry of pyruvate for its catabolism into the TCA cycle, and thus it is considered as an important drug target for various types of cancers. We have successfully expressed full length human PDK3 and investigated its interaction mechanism with dietary polyphenols in the search for potential inhibitors. Molecular docking analysis revealed that the selected compounds preferentially bind to the ATP-binding pocket of PDK3 and interact with functionally important residues. In silico observations were further complemented by experimental measurements of the fluorescence quenching of PDK3 and confirmed with the isothermal titration calorimetry measurements. Ellagic acid (EA) significantly binds and inhibits the kinase activity of PDK3. In vitro cytotoxicity and the anti-proliferative properties of EA were evaluated by MTT assay. Conformational dynamics of the EA-PDK3 complex during molecular dynamics simulation revealed that a stable complex was maintained by a significant number of hydrogen bonds throughout the 100 ns trajectories. In conclusion, EA may be considered as a promising molecule for PDK3 inhibition and could be exploited as a lead molecule against PDK3 associated diseases.

miR-497-5p inhibits gastric cancer cell proliferation and growth through targeting PDK3.

Abstract: MicroRNA plays an important role in gastric cancer (GC) development, while the function of miR-497-5p in this disease remains unknown. In the present study, we demonstrated miR-497-5p as a tumor suppressive microRNA in GC. miR-497-5p was down-regulated in GC tissues and its expression was associated with the disease stage. Inhibition of miR-497-5p promoted GC cell proliferation and growth. By contrast, miR-497-5p ectopic expression suppressed the proliferation and growth of GC cells. In addition, miR-497-5p inhibited DNA synthesis and enhanced apoptosis in GC cells. The cell cycle progression was suppressed by miR-497-5p. Mechanistically, miR-497-5p directly targeted and suppressed the expression of pyruvate dehydrogenase kinase 3 (PDK3), which is highly expressed in GC tissues. Over-expression of PDK3 promoted the proliferation of GC cells. Our study revealed that miR-497-5p inhibited GC cell proliferation and growth via targeting PDK3.

SIRT3 elicited an anti-Warburg effect through HIF1α/PDK1/PDHA1 to inhibit cholangiocarcinoma tumorigenesis.

Abstract: Cholangiocarcinoma (CCA) is an extremely invasive malignancy with late diagnosis and unfavorable prognosis. Surgery and chemotherapy are still not effective in improving outcomes in CCA patients. It is crucial to explore a novel therapeutic target for treating CCA. An NAD-dependent deacetylase also known as Sirtuin-3 (SIRT3) has been shown to regulate cellular metabolism in various cancers dynamically. However, the biological function of SIRT3 in CCA remains unclear. In this study, bioinformatics analyses were performed to identify the differentially expressed genes and pathways enriched. CCA samples were collected for immunohistochemical analysis. Three human CCA cell lines (HuCCT1, RBE, and HCCC9810) were used to explore the molecular mechanism of SIRT3 regulation of metabolic reprogramming and malignant behavior in CCA. A CCA xenograft model was then established for further validation in vivo. The data showed that SIRT3 expression was decreased and glycolysis was enhanced in CCA. Similar metabolic reprogramming was also observed in SIRT3 knockout mice. Furthermore, we demonstrated that SIRT3 could play an anti-Warburg effect by inhibiting the hypoxia-inducible factor-1α (HIF1α)/pyruvate dehydrogenase kinase 1 (PDK1)/pyruvate dehydrogenase (PDHA1) pathway in CCA cells. CCA cell proliferation and apoptosis were regulated by SIRT3-mediated metabolic reprogramming. These findings were further confirmed in CCA clinical samples and the xenograft model. Collectively, this study suggests that in the inhibition of CCA progression, SIRT3 acts through an anti-Warburg effect on the downstream pathway HIF1α/PDK1/PDHA1.

Pyruvate dehydrogenase kinase 1 contributes to cisplatin resistance of ovarian cancer through EGFR activation.

Abstract: Patients with ovarian cancer frequently develop acquired drug resistance after the long-term chemotherapy, leading to disease progression. Enhanced epithelial-mesenchymal transition (EMT) has been implicated in chemoresistance of ovarian cancer cells; however, the molecular mechanisms involved are largely undefined. Pyruvate dehydrogenase kinase 1 (PDK1), a key regulatory enzyme in glucose metabolism, has been recognized as a gatekeeper of the Warburg effect, a hallmark of cancer. In this study, the function of PDK1 in cisplatin resistance of ovarian cancer in terms of growth and EMT was investigated. PDK1 was upregulated in cisplatin-resistant ovarian cancer cells. PDK1 knockdown in resistant cells led to increased sensitivity to cisplatin-induced cell death and apoptosis. PDK1 downregulation also reversed the EMT and cell motility in cisplatin-resistant cells. In a mouse xenograft model, tumors derived from PDK1-silenced ovarian cancer cells exhibited decreased tumor growth and EMT compared with control after the cisplatin treatment. Mechanistically, PDK1 overexpression led to increased phosphorylation of EGFR, and blocking EGFR kinase activity by erlotinib reversed cisplatin resistance induced by PDK1 overexpression. Furthermore, in patients with ovarian cancer, higher PDK1 and p-EGFR levels were associated with chemoresistance. These results supported that PDK1 contributes to chemoresistance of ovarian cancer by activating EGFR. Therefore, PDK1 may serve as a promising target to combat chemoresistance of ovarian cancer.

Metabolic enzyme PDK3 forms a positive feedback loop with transcription factor HSF1 to drive chemoresistance.

Abstract: Background & Aims: Dysregulation of metabolism plays an important role in the development and progression of cancers, while the underlying mechanisms remain largely unknown. This study aims to explore the regulation and relevance of glycolysis in chemoresistance of gastric cancer. Methods: Biochemical differences between chemoresistant and chemosensitive cancer cells were determined by metabolism profiling, microarray gene expression, PCR or western blotting. Cancer cell growth in vitro or in vivo were analyzed by viability, apoptosis and nude mice assay. Immunoprecipation was used to explore the interaction of proteins with other proteins or DNAs. Results: By metabolic and gene expression profiling, we found that pyruvate dehydrogenase kinase 3 (PDK3) was highly expressed to promote glycolysis in chemoresistant cancer cells. Its genetic or chemical inhibition reverted chemoresistance in vitro and in vivo. It was transcriptionally regulated by transcription factor HSF1 (Heat shock factor 1). Interestingly, PDK3 can localize in the nucleus and interact with HSF1 to disrupt its phosphorylation by GSK3β. Since HSF1 was subjected to FBXW7-catalyzed polyubiquitination in a phosphorylation-dependent manner, PDK3 prevented HSF1 from proteasomal degradation. Thus, metabolic enzyme PDK3 and transcription factor HSF1 forms a positive feedback loop to promote glycolysis. As a result, inhibition of HSF1 impaired enhanced glycolysis and reverted chemoresistance both in vitro and in vivo. Conclusions: PDK3 forms a positive feedback loop with HSF1 to drive glycolysis in chemoresistance. Targeting this mitonuclear communication may represent a novel approach to overcome chemoresistance.

Repurposing dichloroacetate for the treatment of women with endometriosis.

Abstract: Endometriosis is a chronic pain condition affecting ∼176 million women worldwide. It is defined by the presence of endometrium-like tissue (lesions) outside the uterus, most commonly on the pelvic peritoneum. There is no cure for endometriosis. All endometriosis drug approvals to date have been contraceptive, limiting their use in women of child-bearing age. We have shown that human peritoneal mesothelial cells (HPMCs) recovered from the pelvic peritoneum of women with endometriosis exhibit significantly higher glycolysis, lower mitochondrial respiration, decreased enzymatic activity of pyruvate dehydrogenase (PDH), and increased production of lactate compared to HPMCs from women without disease. Transforming growth factor-β1 (TGF-β1) is elevated in the peritoneal fluid from women with endometriosis, and exposure of HPMCs to TGF-β1 exacerbates this abnormal phenotype. Treatment of endometriosis HPMCs with the pyruvate dehydrogenase kinase (PDK) inhibitor/PDH activator dichloroacetate (DCA) normalizes HPMC metabolism, reduces lactate secretion, and abrogates endometrial stromal cell proliferation in a coculture model. Oral DCA reduced peritoneal fluid lactate concentrations and endometriosis lesion size in a mouse model. These findings provide the rationale for targeting metabolic processes as a noncontraceptive treatment for women with endometriosis either as a primary nonhormonal treatment or to prevent recurrence after surgery.

Cachexia Anorexia Syndrome and Associated Metabolic Dysfunction in Peritoneal Metastasis

Abstract: Patients with peritoneal metastasis (PM) of gastrointestinal and gynecological origin present with a nutritional deficit characterized by increased resting energy expenditure (REE), loss of muscle mass, and protein catabolism. Progression of peritoneal metastasis, as with other advanced malignancies, is associated with cancer cachexia anorexia syndrome (CAS), involving poor appetite (anorexia), involuntary weight loss, and chronic inflammation. Eventual causes of mortality include dysfunctional metabolism and energy store exhaustion. Etiology of CAS in PM patients is multifactorial including tumor growth, host response, cytokine release, systemic inflammation, proteolysis, lipolysis, malignant small bowel obstruction, ascites, and gastrointestinal side effects of drug therapy (chemotherapy, opioids). Metabolic changes of CAS in PM relate more to a systemic inflammatory response than an adaptation to starvation. Metabolic reprogramming is required for cancer cells shed into the peritoneal cavity to resist anoikis (i.e., programmed cell death). Profound changes in hexokinase metabolism are needed to compensate ineffective oxidative phosphorylation in mitochondria. During the development of PM, hypoxia inducible factor-1α (HIF-1α) plays a key role in activating both aerobic and anaerobic glycolysis, increasing the uptake of glucose, lipid, and glutamine into cancer cells. HIF-1α upregulates hexokinase II, phosphoglycerate kinase 1 (PGK1), pyruvate dehydrogenase kinase (PDK), pyruvate kinase muscle isoenzyme 2 (PKM2), lactate dehydrogenase (LDH) and glucose transporters (GLUT) and promotes cytoplasmic glycolysis. HIF-1α also stimulates the utilization of glutamine and fatty acids as alternative energy substrates. Cancer cells in the peritoneal cavity interact with cancer-associated fibroblasts and adipocytes to meet metabolic demands and incorporate autophagy products for growth. Therapy of CAS in PM is challenging. Optimal nutritional intake alone including total parenteral nutrition is unable to reverse CAS. Pressurized intraperitoneal aerosol chemotherapy (PIPAC) stabilized nutritional status in a significant proportion of PM patients. Agents targeting the mechanisms of CAS are under development.

Bortezomib-induced aerobic glycolysis contributes to chemotherapy-induced painful peripheral neuropathy.

Abstract: Chemotherapy-induced painful peripheral neuropathy (CIPN) is the most common toxicity associated with widely used chemotherapeutics. CIPN is the major cause of dose reduction or discontinuation of otherwise life-saving treatment. Unfortunately, CIPN can persist in cancer survivors, which adversely affects their quality of life. Moreover, available treatments are vastly inadequate, warranting a better understanding of the biochemical and metabolic mechanisms that occur in response to chemotherapeutics which would be critical for the development of novel therapies for CIPN. Using extracellular flux analysis, this study demonstrated that the proteasome inhibitor, bortezomib, enhanced glycolysis while suppressing oxidative phosphorylation in the sensory neurons of mice. This metabolic phenotype is known as aerobic glycolysis. Bortezomib upregulated lactate dehydrogenase A and pyruvate dehydrogenase kinase 1, which consequently enhanced the production of lactate and repressed pyruvate oxidation, respectively. Moreover, lactate dehydrogenase A- and pyruvate dehydrogenase kinase 1-driven aerobic glycolysis was associated with increased extracellular acidification, augmented calcium responses, and pain in bortezomib-induced CIPN. Remarkably, pharmacological blockade and in vivo knockdown of lactate dehydrogenase A or pyruvate dehydrogenase kinase 1 reversed the metabolic phenotype, attenuated calcium responses, and alleviated pain induced by bortezomib. Collectively, these results elucidate the mechanisms by which bortezomib induces aerobic glycolysis. Moreover, these findings establish aerobic glycolysis as a metabolic phenotype that underpins bortezomib-induced CIPN.

Melatonin Therapy Modulates Cerebral Metabolism and Enhances Remyelination by Increasing PDK4 in a Mouse Model of Multiple Sclerosis.

Abstract: Metabolic disturbances have been implicated in demyelinating diseases including multiple sclerosis (MS). Melatonin, a naturally occurring hormone, has emerged as a potent neuroprotective candidate to reduce myelin loss and improve MS outcomes. In this study, we evaluated the effect of melatonin, at both physiological and pharmacological doses, on oligodendrocytes metabolism in an experimental autoimmune encephalomyelitis (EAE) mouse model of MS. Results showed that melatonin decreased neurological disability scores and enhanced remyelination, significantly increasing myelin protein levels including MBP, MOG, and MOBP. In addition, melatonin attenuated inflammation by reducing pro-inflammatory cytokines (IL-1β and TNF-α) and increasing anti-inflammatory cytokines (IL-4 and IL-10). Moreover, melatonin significantly increased brain concentrations of lactate, N-acetylaspartate (NAA), and 3-hydroxy-3-methylglutaryl-coenzyme-A reductase (HMGCR). Pyruvate dehydrogenase kinase-4 (PDK-4) mRNA and protein expression levels were also increased in melatonin-treated, compared to untreated EAE mice. However, melatonin significantly inhibited active and total pyruvate dehydrogenase complex (PDC), an enzyme under the control of PDK4. In summary, although PDC activity was reduced by melatonin, it caused a reduction in inflammatory mediators while stimulating oligodendrogenesis, suggesting that oligodendrocytes are forced to use an alternative pathway to synthesize fatty acids for remyelination. We propose that combining melatonin and PDK inhibitors may provide greater benefits for MS patients than the use of melatonin therapy alone.

The Effects of Sodium Dichloroacetate on Mitochondrial Dysfunction and Neuronal Death Following Hypoglycemia-Induced Injury

Abstract: Our previous studies demonstrated that some degree of neuronal death is caused by hypoglycemia, but a subsequent and more severe wave of neuronal cell death occurs due to glucose reperfusion, which results from the rapid restoration of low blood glucose levels. Mitochondrial dysfunction caused by hypoglycemia leads to increased levels of pyruvate dehydrogenase kinase (PDK) and suppresses the formation of ATP by inhibiting pyruvate dehydrogenase (PDH) activation, which can convert pyruvate into acetyl-coenzyme A (acetyl-CoA). Sodium dichloroacetate (DCA) is a PDK inhibitor and activates PDH, the gatekeeper of glucose oxidation. However, no studies about the effect of DCA on hypoglycemia have been published. In the present study, we hypothesized that DCA treatment could reduce neuronal death through improvement of glycolysis and prevention of reactive oxygen species production after hypoglycemia. To test this, we used an animal model of insulin-induced hypoglycemia and injected DCA (100 mg/kg, i.v., two days) following hypoglycemic insult. Histological evaluation was performed one week after hypoglycemia. DCA treatment reduced hypoglycemia-induced oxidative stress, microglial activation, blood–brain barrier disruption, and neuronal death compared to the vehicle-treated hypoglycemia group. Therefore, our findings suggest that DCA may have the therapeutic potential to reduce hippocampal neuronal death after hypoglycemia.

Dichloroacetate-induced peripheral neuropathy.

Abstract: Dichloroacetate (DCA) has been the focus of research by both environmental toxicologists and biomedical scientists for over 50 years. As a product of water chlorination and a metabolite of certain industrial chemicals, DCA is ubiquitous in our biosphere at low μg/kg body weight daily exposure levels without obvious adverse effects in humans. As an investigational drug for numerous congenital and acquired diseases, DCA is administered orally or parenterally, usually at doses of 10-50mg/kg per day. As a therapeutic, its principal mechanism of action is to inhibit pyruvate dehydrogenase kinase (PDK). In turn, PDK inhibits the key mitochondrial energy homeostat, pyruvate dehydrogenase complex (PDC), by reversible phosphorylation. By blocking PDK, DCA activates PDC and, consequently, the mitochondrial respiratory chain and ATP synthesis. A reversible sensory/motor peripheral neuropathy is the clinically limiting adverse effect of chronic DCA exposure and experimental data implicate the Schwann cell as a toxicological target. It has been postulated that stimulation of PDC and respiratory chain activity by DCA in normally glycolytic Schwann cells causes uncompensated oxidative stress from increased reactive oxygen species production. Additionally, the metabolism of DCA interferes with the catabolism of the amino acids phenylalanine and tyrosine and with heme synthesis, resulting in accumulation of reactive molecules capable of forming adducts with DNA and proteins and also resulting in oxidative stress. Preliminary evidence in rodent models of peripheral neuropathy suggest that DCA-induced neurotoxicity may be mitigated by naturally occurring antioxidants and by a specific class of muscarinic receptor antagonists. These findings generate a number of testable hypotheses regarding the etiology and treatment of DCA peripheral neuropathy.

PDH-mediated metabolic flow is critical for skeletal muscle stem cell differentiation and myotube formation during regeneration in mice.

Abstract: Skeletal muscle satellite cells (SMSCs), the major stem cells responsible for the regeneration of skeletal muscle, are normally cell cycle arrested but differentiate to generate myocytes upon muscle damage, forming new myofibers along with self-renewing stem cells in preparation for subsequent injury. In this study, we investigated which factors stimulate the proliferation and differentiation of SMSCs and found that pyruvate, the end product of glycolysis, stimulates their differentiation. Pyruvate antagonizes the effects of hypoxia on preferential self-renewal of SMSCs through dephosphorylation or activation of pyruvate dehydrogenase (PDH), which mediates opening of the gateway from glycolysis to the tricarboxylic acid (TCA) cycle by producing acetyl coenzyme A from pyruvate. PDH kinase 1, highly expressed under hypoxia, is down-regulated under normoxic conditions, leading to an increase in dephosphorylated PDH. Conditional deletion of PDH in SMSCs affects cell divisions generating myocytes and subsequent myotube formation, inefficient skeletal muscle regeneration upon injury, and aggravated pathogenesis of a dystrophin-deficient mouse model of Duchenne muscular dystrophy. Thus, the flow from glycolysis to the TCA cycle mediated by PDH plays a pivotal role in the differentiation of SMSCs, which is critical for the progression of skeletal muscle regeneration.-Hori, S., Hiramuki, Y., Nishimura, D., Sato, F., Sehara-Fujisawa, A. PDH-mediated metabolic flow is critical for skeletal muscle stem cell differentiation and myotube formation during regeneration in mice.

Resistance to anoikis in transcoelomic shedding: the role of glycolytic enzymes.

Abstract: Detachment of cells from the extracellular matrix into the peritoneal cavity initiates a cascade of metabolic alterations, leading usually to cell death by apoptosis, so-called anoikis. Glycolytic enzymes enable the switch from oxidative phosphorylation to aerobic glycolysis and allow resistance to anoikis of shed tumour cells. These enzymes also have moonlighting activities as protein kinases and transcription factors. Phosphoglycerate kinase (PGK) and pyruvate kinase are the only glycolytic enzymes generating ATP in the hexokinase pathway. Hypoxia, EGFR activation, expression of K-Ras G12V and B-Raf V600E induce mitochondrial translocation of phosphoglycerate kinase 1 (PGK1). Mitochondrial PGK1 acts as a protein kinase to phosphorylate pyruvate dehydrogenase kinase 1 (PDHK1), reducing mitochondrial pyruvate utilization, suppressing reactive oxygen species production, increasing lactate production and promoting tumourigenesis. PGK1 also plays a role as a transcription factor once transported into the nucleus. Resistance to anoikis is also facilitated by metabolic support provided by cancer-associated fibroblasts (CAFs). Our series of experiments in-vitro and in the animal model showed that PGK1 knock-out or inhibition is effective in controlling development and growth of peritoneal metastasis (PM) of gastric origin, establishing a causal role of PGK1 in this development. PGK1 also increases CXCR4 and CXCL12 expression, which is associated with a metastatic phenotype and plays a role in the metastatic homing of malignant cells. Thus, PGK1, its modulators and target genes may be exploited as therapeutic targets for preventing development of PM and for enhancing cytotoxic effects of conventional systemic chemotherapy.

Natural Product Albiziabioside A Conjugated with Pyruvate Dehydrogenase Kinase Inhibitor Dichloroacetate To Induce Apoptosis-Ferroptosis-M2-TAMs Polarization for Combined Cancer Therapy.

Abstract: The reprogramming of energy metabolism is considered to be one of the main characteristics of cancer. The development of therapeutic agents targeting glycolysis to alter aberrant glucose metabolism and restore oxidative phosphorylation has emerged as an effective approach for cancer therapy. In this way, we have developed a conjugate AlbA-DCA, which can induce a marked increase in intracellular ROS and alleviate the accumulation of lactic acid in TME. Meanwhile, AlbA-DCA selectively kills cancer cells and exhibits an excellent synergistic effect. Mechanism studies confirm that AlbA-DCA can induce apoptosis and ferroptosis. We also confirm that AlbA-DCA can remold the tumor immunosuppression microenvironment via eliminating M2-TAMs to inhibit both primary and distal tumor progression in a dual-4T1 tumor model in female BALB/c mice. As a result, rational design of natural saponin and PDK inhibitor to induce apoptosis-ferroptosis-M2-TAMs polarization for enhanced cancer therapy is a promising strategy, thus providing a new idea for cancer therapy.

Induction of Pyruvate Dehydrogenase Kinase 1 by Hypoxia Alters Cellular Metabolism and Inhibits Apoptosis in Endometriotic Stromal Cells.

Abstract: Endometriosis is a common gynecological disease, which is defined as the growth of endometrial tissues outside the uterine cavity. It often causes dysmenorrhea, dyspareunia, chronic pelvic pain, and infertility in reproductive-age women. However, the pathogenesis of endometriosis remains largely unclear. Since our previous study revealed that ectopic endometriotic stromal cells experience greater hypoxic stress than their eutopic counterparts, we aim to investigate whether the metabolic properties are changed in the ectopic endometriotic stromal cell when compared to its eutopic counterpart. Here, we found the expression of pyruvate dehydrogenase kinase 1 (PDK1), a critical enzyme in regulating glucose metabolism, was increased in ectopic stromal cells. Molecular characterization reveals that overexpression of PDK1 is induced by hypoxia through transcriptional regulation. Upregulation of PDK1 in ectopic endometriotic stromal cells was accompanied by increases in lactate production and oxygen consumption rate when compared to eutopic endometrial stromal cells. Furthermore, our data showed that inhibition of PDK1 activity by treatment with dichloroacetate inhibits the lactate production and oxygen consumption rate of ectopic stromal cells. In addition, hypoxia-induced PDK1 expression prevented cells from H2O2- and low nutrient-induced cell death. These data indicate that ectopic endometriotic cells may adapt to hypoxic microenvironment via upregulating PDK1 and reprogramming metabolism, which provides a survival advantage in the hostile peritoneal microenvironment.

Inhibition of Pyruvate Dehydrogenase Kinase Enhances the Antitumor Efficacy of Oncolytic Reovirus.

Abstract: Oncolytic viruses (OV) such as reovirus preferentially infect and kill cancer cells. Thus, the mechanisms that dictate the susceptibility of cancer cells to OV-induced cytotoxicity hold the key to their success in clinics. Here, we investigated whether cancer cell metabolism defines its susceptibility to OV and if OV-induced metabolic perturbations can be therapeutically targeted. Using mass spectrometry-based metabolomics and extracellular flux analysis on a panel of cancer cell lines with varying degrees of susceptibility to reovirus, we found that OV-induced changes in central energy metabolism, pyruvate metabolism, and oxidative stress correlate with their susceptibility to reovirus. In particular, reovirus infection accentuated Warburg-like metabolic perturbations in cell lines relatively resistant to oncolysis. These metabolic changes were facilitated by oxidative stress-induced inhibitory phosphorylation of pyruvate dehydrogenase (PDH) that impaired the routing of pyruvate into the tricarboxylic acid cycle and established a metabolic state unsupportive of OV replication. From the therapeutic perspective, reactivation of PDH in cancer cells that were weakly sensitive for reovirus, either through PDH kinase (PDK) inhibitors dichloroacetate and AZD7545 or short hairpin RNA-specific depletion of PDK1, enhanced the efficacy of reovirus-induced oncolysis in vitro and in vivo. These findings identify targeted metabolic reprogramming as a possible combination strategy to enhance the antitumor effects of OV in clinics. SIGNIFICANCE: This study proposes targeted metabolic reprogramming as a valid combinatorial strategy to enhance the translational efficacy of oncolytic virus-based cancer therapies.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/15/3824/F1.large.jpg.

Signal transducer and activator of transcription 3 promotes the Warburg effect possibly by inducing pyruvate kinase M2 phosphorylation in liver precancerous lesions.

Abstract: Background Study shows that signal transducer and activator of transcription 3 (STAT3) can increase the Warburg effect by stimulating hexokinase 2 in breast cancer and upregulate lactate dehydrogenase A and pyruvate dehydrogenase kinase 1 in myeloma. STAT3 and pyruvate kinase M2 (PKM2) can also be activated and enhance the Warburg effect in hepatocellular carcinoma. Precancerous lesions are critical to human and rodent hepatocarcinogenesis. However, the underlying molecular mechanism for the development of liver precancerous lesions remains unknown. We hypothesized that STAT3 promotes the Warburg effect possibly by upregulating p-PKM2 in liver precancerous lesions in rats. Aim To investigate the mechanism of the Warburg effect in liver precancerous lesions in rats. Methods A model of liver precancerous lesions was established by a modified Solt-Farber method. The liver pathological changes were observed by HE staining and immunohistochemistry. The transformation of WB-F344 cells induced with N-methyl-N'-nitro-N-nitrosoguanidine and hydrogen peroxide was evaluated by the soft agar assay and aneuploidy. The levels of glucose and lactate in the tissue and culture medium were detected with a spectrophotometer. The protein levels of glutathione S-transferase-π, proliferating cell nuclear antigen (PCNA), STAT3, and PKM2 were examined by Western blot and immunofluorescence. Results We found that the Warburg effect was increased in liver precancerous lesions in rats. PKM2 and p-STAT3 were upregulated in activated oval cells in liver precancerous lesions in rats. The Warburg effect, p-PKM2, and p-STAT3 expression were also increased in transformed WB-F344 cells. STAT3 activation promoted the clonal formation rate, aneuploidy, alpha-fetoprotein expression, PCNA expression, G1/S phase transition, the Warburg effect, PKM2 phosphorylation, and nuclear translocation in transformed WB-F344 cells. Moreover, the Warburg effect was inhibited by stattic, a specific inhibitor of STAT3, and further reduced in transformed WB-F344 cells after the intervention for PKM2. Conclusion The Warburg effect is initiated in liver precancerous lesions in rats. STAT3 activation promotes the Warburg effect by enhancing the phosphorylation of PKM2 in transformed WB-F344 cells.