Pyruvate Dehydrogenase Activity Research Articles

Dichloroacetate, a pyruvate dehydrogenase activator, alleviates high-fat-induced impairment of myogenic differentiation in skeletal muscles.

Obesity-induced impairment of myogenic differentiation leads to muscle loss and sarcopenia. Pyruvate dehydrogenase (PDH) plays a crucial role in glucose metabolism and is associated with muscle differentiation. However, the effect of dichloroacetate (DCA), a PDH activator, on obesity-induced impairment of myogenic differentiation remains unknown. Here, we evaluated the effects of DCA treatment on high-fat intake-induced impairment of myogenic differentiation in C2C12 cells and C57BL/6 mice. In C2C12 cells, DCA treatment improved PDH activity that was reduced by palmitate (PAL) and decreased the lactate concentrations in the media. Additionally, DCA reversed PAL- and high-fat diet (HFD)-induced decrease in the expression of myoblast determination protein 1 (MyoD), myogenin (MyoG) and myosin heavy chain (MyHC) in C2C12 cells and C57BL/6 mice. To explore the possible mechanism, DCA treatment restored the levels of p-Akt, p-FoxO1, p-FoxO3a and p-p38 MAPK levels in PAL-treated C2C12 cells. Moreover, the protective effects of DCA were reversed by treatment with the Akt inhibitor MK2206 in C2C12 cells. In summary, DCA treatment alleviated high-fat intake-induced impairment of myogenic differentiation via Akt signalling, suggesting its potential in treating obesity-associated muscle loss and sarcopenia.

Insights into the Binding of Metadoxine with Bovine Serum Albumin: A Multi-Spectroscopic Investigation Combined with Molecular Docking.

Metadoxine, also known as pyruvate dehydrogenase activator, is a small molecule drug that has been used in the treatment of various medical conditions. Bovine serum albumin is a commonly studied protein that serves as a plasmatic for understanding protein-drug interactions due to its abundance. This research suggests that metadoxine can bind to bovine serum albumin with moderate affinity, leading to an alteration in the secondary structure of the protein, which may also influence the protein's stability and function, which could provide a comprehensive understanding of the interaction at a molecular level. In this study, a variety of methodologies wereused to determine various thermodynamic parameters. The study uses UV-visible, Fluorescence, Fourier-transform infrared, Circular dichroism spectroscopy, and Molecular docking to analyze the interaction between bovine serum albumin and metadoxine, providing thermodynamic parameters for understanding the protein structure and its binding. The binding of metadoxine with bovine serum albumin, causes a hyperchromic shift. In fluorescence spectroscopy, the value of the Stern Volmer increases constantly with an increase in temperature, suggesting a stronger interaction between the Metadoxine and the Bovine serum albumin, leading to dynamic quenching. Additionally, Fourier-transform infrared and circular dichroism indicated a reduction in the secondary structure of Bovine serum albumin. The interactions between metadoxine and bovine serum albumin, cause hyperchromic shift revealed by UV-visible spectroscopy, whereas in Fluorescence spectroscopy, the value of the Stern Volmer constant increases with an increase in temperature, suggesting a stronger interaction between the MD and the BSA, leading to dynamic quenching. Additionally, Fourier-transform infrared and circular dichroism spectroscopy indicated a reduction in the secondary structure of the protein, as evidenced by the shifting of the amide II band and leading to a slight decrease in the αhelix content. The molecular docking shows that metadoxine was docked in the subdomain IIA binding pocket of BSA.

Lanthanide conjugate Pr-MPO elicits anti-cancer activity by targeting lysosomal machinery and inducing zinc-dependent cataplerosis.

Acquired drug resistance is a major challenge in the management of cancer, which underscores the need for discovery and development of novel therapeutic strategies. We report here the mechanism of the anti-cancer activity of a small coordinate complex composed of the rare earth metal praseodymium (Pr) and mercaptopyridine oxide (MPO; pyrithione). Exposure of cancer cells to relatively low concentrations of the conjugate Pr-MPO (5 µM) significantly impairs cell survival in a p53-independent manner and irrespective of the drug resistant phenotype. Mechanistically, Pr-MPO-induced cell death is caspase-independent, not inhibitable by necrostatin, but associated with the appearance of autophagy markers. However, further analysis revealed incomplete autophagic flux, thus suggesting altered integrity of lysosomal machinery. Supporting the lysosomal targeting activity are data demonstrating increased lysosomal Ca2+ accumulation and alkalinization, which coincides with cytosolic acidification (drop in pHc from 7.75 to 7.00). In parallel, an increase in lysosomal activity of glycosidase alpha acid (GAA), involved in passive glycogen breakdown, correlates with rapid depletion of glucose stores upon Pr-MPO treatment. This is associated with swift cataplerosis of TCA cycle intermediates, loss of NAD+/NADH and increase in pyruvate dehydrogenase (PDH) activity to compensate for pyruvate loss. Addition of exogenous pyruvate rescued cell survival. Notably, lysosomal impairment and metabolic catastrophe triggered by Pr-MPO are suggestive of Zn2+-mediated cytotoxicity, which is confirmed by the ability of Zn2+ chelator TPEN to block Pr-MPO-mediated anti-tumor activity. Together, these results highlight the ability of the small molecule lanthanide conjugate to target the cells' waste clearing machinery as well as mitochondrial metabolism for Zn2+-mediated execution of cancer cells, which could have therapeutic potential against cancers with high metabolic activity.

Role of Exogenous Pyruvate in Maintaining Adenosine Triphosphate Production under High-Glucose Conditions through PARP-Dependent Glycolysis and PARP-Independent Tricarboxylic Acid Cycle.

Pyruvate serves as a key metabolite in energy production and as an anti-oxidant. In our previous study, exogenous pyruvate starvation under high-glucose conditions induced IMS32 Schwann cell death because of the reduced glycolysis-tricarboxylic acid (TCA) cycle flux and adenosine triphosphate (ATP) production. Thus, this study focused on poly-(ADP-ribose) polymerase (PARP) to investigate the detailed molecular mechanism of cell death. Rucaparib, a PARP inhibitor, protected Schwann cells against cell death and decreased glycolysis but not against an impaired TCA cycle under high-glucose conditions in the absence of pyruvate. Under such conditions, reduced pyruvate dehydrogenase (PDH) activity and glycolytic and mitochondrial ATP production were observed but not oxidative phosphorylation or the electric transfer chain. In addition, rucaparib supplementation restored glycolytic ATP production but not PDH activity and mitochondrial ATP production. No differences in the increased activity of caspase 3/7 and the localization of apoptosis-inducing factor were found among the experimental conditions. These results indicate that Schwann cells undergo necrosis rather than apoptosis or parthanatos under the aforementioned conditions. Exogenous pyruvate plays a pivotal role in maintaining the flux in PARP-dependent glycolysis and the PARP-independent TCA cycle in Schwann cells under high-glucose conditions.

Pyruvate dehydrogenase kinase 1 controls triacylglycerol hydrolysis in cardiomyocytes.

Pyruvate dehydrogenase kinase (PDK) 1 is one of four isozymes that inhibit the oxidative decarboxylation of pyruvate to acetyl-CoA via pyruvate dehydrogenase. PDK activity is elevated in fasting or starvation conditions to conserve carbohydrate reserves. PDK has also been shown to increase mitochondrial fatty acid utilization. In cardiomyocytes, metabolic flexibility is crucial for the fulfillment of high energy requirements. The PDK1 isoform is abundant in cardiomyocytes, but its specific contribution to cardiomyocyte metabolism is unclear. Here we show that PDK1 regulates cardiomyocyte fuel preference by mediating triacylglycerol turnover in differentiated H9c2 myoblasts using lentiviral shRNA to knockdown Pdk1 . Somewhat surprisingly, PDK1 loss did not affect overall PDH activity, basal glycolysis, or glucose oxidation revealed by oxygen consumption rate experiments and 13 C 6 glucose labelling. On the other hand, we observed decreased triacylglycerol turnover in H9c2 cells with PDK1 knockdown, which was accompanied by decreased mitochondrial fatty acid utilization following nutrient deprivation. 13 C 16 palmitate tracing of uniformly labelled acyl chains revealed minimal acyl chain shuffling within triacylglycerol, indicating that the triacylglycerol hydrolysis, and not re-esterification, was dysfunctional in PDK1 suppressed cells. Importantly, PDK1 loss did not significantly impact the cellular lipidome or triacylglycerol accumulation following palmitic acid treatment, suggesting that effects of PDK1 on lipid metabolism were specific to the nutrient-deprived state. We validated that PDK1 loss decreased triacylglycerol turnover in Pdk1 knockout mice. Together, these findings implicate a novel role for PDK1 in lipid metabolism in cardiomyocytes, independent of its canonical roles in glucose metabolism.

Calcineurin Inhibitors Cause Kidney Fibrosis by Inactivating Pyruvate Dehydrogenase and Disrupting Energy Metabolism in Proximal Tubule Cells

Calcineurin Inhibitors Cause Kidney Fibrosis by Inactivating Pyruvate Dehydrogenase and Disrupting Energy Metabolism in Proximal Tubule Cells

The mitochondrial physiology of torpor in ruby-throated hummingbirds, Archilochus colubris.

Hummingbirds save energy by facultatively entering torpor, but the physiological mechanisms underlying this metabolic suppression are largely unknown. We compared whole-animal and pectoralis mitochondrial metabolism between torpid and normothermic ruby-throated hummingbirds (Archilochus colubris). When fasting, hummingbirds were exposed to 10℃ ambient temperature at night, they entered torpor; average body temperature decreased by nearly 25℃ (From ∼37 to ∼13℃), and whole-animal metabolic rate (VO2) decreased by 95% compared to normothermia, a much greater metabolic suppression compared with mammalian daily heterotherms. We then measured pectoralis mitochondrial oxidative phosphorylation (OXPHOS) fueled by either carbohydrate or fatty acid substrates at both 39℃ and 10℃ in torpid and normothermic hummingbirds. Aside from a 20% decrease in electron transport system complex I-supported respiration with pyruvate, the capacity for OXPHOS at a common in vivo temperature did not differ in isolated mitochondria between torpor and normothermia. Similarly, the activities of pectoralis pyruvate dehydrogenase and 3-hydroxyacyl-CoA dehydrogenase did not differ between the states. Unlike heterothermic mammals, hummingbirds do not suppress muscle mitochondrial metabolism in torpor by active, temperature-independent mechanisms. Other mechanisms that may underly this impressive whole-animal metabolic suppression include decreasing ATP demand or relying on rapid passive cooling facilitated by the very small body size of A. colubris.

Integration of metabolomic and transcriptomic analyses reveals novel regulatory functions of the ChREBP transcription factor in energy metabolism.

Carbohydrate Response Element-Binding Protein (ChREBP) is a transcription factor that activates key genes involved in glucose, fructose, and lipid metabolism in response to carbohydrate feeding, but its other potential roles in metabolic homeostasis have not been as well studied. We used liver-selective GalNAc-siRNA technology to suppress expression of ChREBP in rats fed a high fat/high sucrose diet and characterized hepatic and systemic responses by integrating transcriptomic and metabolomic analyses. GalNAc-siChREBP-treated rats had lower levels of multiple short-chain acyl CoA metabolites compared to rats treated with GalNAc-siCtrl containing a non-targeting siRNA sequence. These changes were related to a sharp decrease in free CoA levels in GalNAc-siChREBP treated-rats, accompanied by lower expression of transcripts encoding enzymes and transporters involved in CoA biosynthesis. These activities of ChREBP likely contribute to its complex effects on hepatic lipid and energy metabolism. While core enzymes of fatty acid (FA) oxidation are induced by ChREBP knockdown, accumulation of liver acylcarnitines and circulating ketones indicate diversion of acetyl CoA to ketone production rather than complete oxidation in the TCA cycle. Despite strong suppression of pyruvate kinase and activation of pyruvate dehydrogenase, pyruvate levels were maintained, likely via increased expression of pyruvate transporters, and decreased expression of lactate dehydrogenase and alanine transaminase. GalNAc-siChREBP treatment increased hepatic citrate and isocitrate levels while decreasing levels of distal TCA cycle intermediates. The drop in free CoA levels, needed for the 2-ketoglutarate dehydrogenase reaction, as well as a decrease in transcripts encoding the anaplerotic enzymes pyruvate carboxylase, glutamate dehydrogenase, and aspartate transaminase likely contributed to these effects. GalNAc-siChREBP treatment caused striking increases in PRPP and ZMP/AICAR levels, and decreases in GMP, IMP, AMP, NaNM, NAD(P), and NAD(P)H levels, accompanied by reduced expression of enzymes that catalyze late steps in purine and NAD synthesis. ChREBP suppression also increased expression of a set of plasma membrane amino acid transporters, possibly as an attempt to replenish TCA cycle intermediates. In sum, combining transcriptomic and metabolomic analyses has revealed regulatory functions of ChREBP that go well beyond its canonical roles in control of carbohydrate and lipid metabolism to now include mitochondrial metabolism and cellular energy balance.

Comparative Metabolomics Reveals Changes in the Metabolic Pathways of Ampicillin- and Gentamicin-Resistant Staphylococcus aureus.

Antibiotic resistance is a major global challenge requiring new treatments and a better understanding of the bacterial resistance mechanisms. In this study, we compared ampicillin-resistant (R-AMP) and gentamicin-resistant (R-GEN) Staphylococcus aureus strains with a sensitive strain (ATCC6538) using metabolomics. We identified 109 metabolites; 28 or 31 metabolites in R-AMP or R-GEN differed from those in ATCC6538. Moreover, R-AMP and R-GEN were enriched in five and four pathways, respectively. R-AMP showed significantly up-regulated amino acid metabolism and down-regulated energy metabolism, whereas R-GEN exhibited an overall decrease in metabolism, including carbohydrate, energy, and amino acid metabolism. Furthermore, the activities of the metabolism-related enzymes pyruvate dehydrogenase and TCA cycle dehydrogenases were inhibited in antibiotic-resistant bacteria. Significant decreases in NADH and ATP levels were also observed. In addition, the arginine biosynthesis pathway, which is related to nitric oxide (NO) production, was enriched in both antibiotic-resistant strains. Enhanced NO synthase activity in S. aureus promoted NO production, which further reduced reactive oxygen species, mediating the development of bacterial resistance to ampicillin and gentamicin. This study reveals that bacterial resistance affects metabolic profile, and changes in energy metabolism and arginine biosynthesis are important factors leading to drug resistance in S. aureus.

ECR Spotlight – Soren Coulson

ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Soren Coulson is an author on ‘ Regulation of muscle pyruvate dehydrogenase activity and fuel use during exercise in high-altitude deer mice’, published in JEB. Soren conducted the research described in this article while an MSc student in Grant McClelland's lab at McMaster University. He is now a PhD student in the lab of James Staples and Christopher Guglielmo at Western University, London, Ontario, investigating comparative exercise energetics.

Hypoxia-induced downregulation of PGK1 crotonylation promotes tumorigenesis by coordinating glycolysis and the TCA cycle

Protein post-translational modifications (PTMs) are crucial for cancer cells to adapt to hypoxia; however, the functional significance of lysine crotonylation (Kcr) in hypoxia remains unclear. Herein we report a quantitative proteomics analysis of global crotonylome under normoxia and hypoxia, and demonstrate 128 Kcr site alterations across 101 proteins in MDA-MB231 cells. Specifically, we observe a significant decrease in K131cr, K156cr and K220cr of phosphoglycerate kinase 1 (PGK1) upon hypoxia. Enoyl-CoA hydratase 1 (ECHS1) is upregulated and interacts with PGK1, leading to the downregulation of PGK1 Kcr under hypoxia. Abolishment of PGK1 Kcr promotes glycolysis and suppresses mitochondrial pyruvate metabolism by activating pyruvate dehydrogenase kinase 1 (PDHK1). A low PGK1 K131cr level is correlated with malignancy and poor prognosis of breast cancer. Our findings show that PGK1 Kcr is a signal in coordinating glycolysis and the tricarboxylic acid (TCA) cycle and may serve as a diagnostic indicator for breast cancer.

Mitochondrial copper overload promotes renal fibrosis via inhibiting pyruvate dehydrogenase activity

Copper is a trace element essential for numerous biological activities, whereas the mitochondria serve as both major sites of intracellular copper utilization and copper reservoir. Here, we investigated the impact of mitochondrial copper overload on the tricarboxylic acid cycle, renal senescence and fibrosis. We found that copper ion levels are significantly elevated in the mitochondria in fibrotic kidney tissues, which are accompanied by reduced pyruvate dehydrogenase (PDH) activity, mitochondrial dysfunction, cellular senescence and renal fibrosis. Conversely, lowering mitochondrial copper levels effectively restore PDH enzyme activity, improve mitochondrial function, mitigate cellular senescence and renal fibrosis. Mechanically, we found that mitochondrial copper could bind directly to lipoylated dihydrolipoamide acetyltransferase (DLAT), the E2 component of the PDH complex, thereby changing the interaction between the subunits of lipoylated DLAT, inducing lipoylated DLAT protein dimerization, and ultimately inhibiting PDH enzyme activity. Collectively, our study indicates that mitochondrial copper overload could inhibit PDH activity, subsequently leading to mitochondrial dysfunction, cellular senescence and renal fibrosis. Reducing mitochondrial copper overload might therefore serve as a strategy to rescue renal fibrosis.

Metabolic states influence chicken retinal pigment epithelium cell fate decisions.

During tissue regeneration, proliferation, dedifferentiation and reprogramming are necessary to restore lost structures. However, it is not fully understood how metabolism intersects with these processes. Chicken embryos can regenerate their retina through retinal pigment epithelium (RPE) reprogramming when treated with fibroblast factor 2 (FGF2). Using transcriptome profiling, we uncovered extensive regulation of gene sets pertaining to proliferation, neurogenesis and glycolysis throughout RPE-to-neural retina reprogramming. By manipulating cell media composition, we determined that glucose, glutamine or pyruvate are individually sufficient to support RPE reprogramming, identifying glycolysis as a requisite. Conversely, the activation of pyruvate dehydrogenase by inhibition of pyruvate dehydrogenase kinases, induces epithelial-to-mesenchymal transition, while simultaneously blocking the activation of neural retina fate. We also identified that epithelial-to-mesenchymal transition fate is partially driven by an oxidative environment. Our findings provide evidence that metabolism controls RPE cell fate decisions and provide insights into the metabolic state of RPE cells, which are prone to fate changes in regeneration and pathologies, such as proliferative vitreoretinopathy.

Regulation of muscle pyruvate dehydrogenase activity and fuel use during exercise in high-altitude deer mice.

Adult, lab-reared, highland deer mice acclimate to hypoxia by increasing reliance on carbohydrates to fuel exercise. Yet neither the underlying mechanisms for this shift in fuel use nor the impact of lifetime hypoxia exposure experienced in high alpine conditions, are fully understood. Thus, we assessed the use of fuel during exercise in wild highland deer mice running in their native environment. We examined a key step in muscle carbohydrate oxidation - the regulation of pyruvate dehydrogenase (PDH) - during exercise at altitude in wild highlanders and in first generation (G1) lab-born and -raised highlanders acclimated to normoxia or hypoxia. PDH activity was also determined in the gastrocnemius of G1 highlanders using an in situ muscle preparation. We found that wild highlanders had a high reliance on carbohydrates while running in their native environment, consistent with data from hypoxia-acclimated G1 highlanders. PDH activity in the gastrocnemius was similar post exercise between G1 and wild highlanders. However, when the gastrocnemius was stimulated at a light work rate in situ, PDH activity was higher in hypoxia-acclimated G1 highlanders and was associated with lower intramuscular lactate levels. These findings were supported by lower PDH kinase 2 protein production in hypoxia-acclimated G1 mice. Our findings indicate that adult phenotypic plasticity in response to low oxygen is sufficient to increase carbohydrate reliance during exercise in highland deer mice. Additionally, variation in PDH regulation with hypoxia acclimation contributes to shifts in whole-animal patterns of fuel use and is likely to improve exercise performance via elevated energy yield per mole of O2. .

Pharmacological activation of pyruvate dehydrogenase by dichloroacetate protects against obesity-induced muscle atrophy in vitro and in vivo

Obesity-induced muscle atrophy leads to physical impairment and metabolic dysfunction, which are risky for older adults. The activity of pyruvate dehydrogenase (PDH), a critical regulator of glucose metabolism, is reduced in obesity. Additionally, PDH activator dichloroacetate (DCA) improves metabolic dysfunction. However, the effects of PDH activation on skeletal muscles in obesity remain unclear. Thus, this study aimed to evaluate the effects of PDH activation by DCA treatment on obesity-induced muscle atrophy in vitro and in vivo and elucidate the possible underlying mechanisms. Results showed that PDH activation by DCA treatment ameliorated muscle loss, decreased the cross-sectional area, and reduced grip strength in C57BL/6 mice fed a high-fat diet (HFD). Elevation of muscle atrophic factors atrogin-1 and muscle RING-finger protein-1 (MuRF-1) and autophagy factors LC3BII and p62 were abrogated by DCA treatment in palmitate-treated C2C12 myotubes and in the skeletal muscles of HFD-fed mice. Moreover, p-Akt, p-FoxO1, and p-FoxO3 protein levels were reduced and p-NF-κB p65 and p-p38 MAPK protein levels were elevated in palmitate-treated C2C12 myotubes, which were restored by DCA treatment. However, the protective effects of DCA treatment against myotube atrophy were reversed by treatment with Akt inhibitor MK2206. Taken together, our study demonstrated that PDH activation by DCA treatment can alleviate obesity-induced muscle atrophy. It may serve as a basis for developing novel strategies to prevent obesity-associated muscle loss.

CD39 is induced by nutrient deprivation in colorectal cancer cells and contributes to the tolerance to hypoxia

Rapid tumor growth and insufficient blood supply leads to the development of a hypoxic and nutrient deprived microenvironment. To survive, tumor cells need to tolerate these adverse conditions. Here we found the expression of CD39 was enhanced in necrotic regions distant from blood vessels. We speculate that this is a strategy for tumor cells to actively adapt to the hostile environment. Further studies showed that CD39 was induced by nutrient deprivation through the AMPK signalling pathway. We next explored the significance of CD39 for tumor cells. Our results showed that CD39 reduced cellular oxygen consumption, which could be significant for tumor cells if the available oxygen is limited. Metabolomics analysis showed that overexpression of CD39 significantly altered cellular metabolism, and tricarboxylic acid (TCA) cycle was identified as the most impacted metabolic pathway. In order to explore the molecular mechanism, we performed RNA-seq analysis. The results showed that CD39 significantly up-regulated the expression of pyruvate dehydrogenase kinase isozyme 2 (PDK2), thus inhibiting the activity of pyruvate dehydrogenase (PDH) and TCA cycle. Finally, CD39 was shown to protect tumor cells from hypoxia-induced cell death and reduce intratumoral hypoxia levels. CD39 has attracted a great deal of attention as a newly discovered immune checkpoint molecule in recent years. Our results indicate that CD39 not only plays a role in immune regulation, but also enables tumor cells to tolerate hypoxia by inhibiting TCA cycle and reducing cellular oxygen consumption. This study provides evidence that targeting CD39 may be a novel strategy to prevent adaptation of tumor cells in stressed conditions.

Propane dehydrogenation performance of titanosilicate-1 supported CoOx catalysts by adjusting the acidity and reducibility

The development of low-cost and toxicity-free cobalt oxide-based catalysts for propane dehydrogenation to propylene (PDH) has gained momentum. In this paper, titanosilicate-1 (TS-1) supported CoOx catalysts doped with different alkali and alkaline earth metal ions (M = Na, K, Mg, Ca and Ba) were prepared by adjusting the acidity, reducibility and oxidation state to increase the activity and stability during the PDH reaction. It was found that the decrease in the number of Lewis acid sites and lack of Co2+Ox species with the addition of K ions led to an almost complete loss of the activity of the Co-K catalyst. However, Co-Ca catalyst exhibited moderate acidity, more Lewis acid sites, a larger amount of the in-situ formed highly-dispersed metallic Co0 nanoparticles (∼5 nm) and Co2+Ox species strongly interacting with the support, all of which were responsible for its highest space-time yield (STY) of propylene formation (0.88 kg h−1 kgcat.−1). Though Co3O4 particles were more active for the side reactions, they could be readily reduced to metallic Co0 nanoparticles during the PDH process, and increased the selectivity to propylene with time on stream. Specifically, it was demonstrated that the highly-dispersed metallic Co0 nanoparticles were also active for the PDH activity, but was lower than Co2+Ox species that were strongly interacted with TS-1 support. The deposited coke on the catalysts was related to the catalyst deactivation. The Co0 species could not completely return to the oxidation states after burning off the deposited coke, which seemed to be related to the incomplete recovery of catalytic activity after regeneration.

Liraglutide alleviates experimental diabetic cardiomyopathy in a PDH-dependent manner.

Liraglutide, a glucagon-like peptide-1 receptor (GLP-1R) agonist used for the treatment of T2D, has been shown to alleviate diabetic cardiomyopathy (DbCM) in experimental T2D, which was associated with increased myocardial glucose oxidation. To determine whether this increase in glucose oxidation is necessary for cardioprotection, we hypothesized that liraglutide's ability to alleviate DbCM would be abolished in mice with cardiomyocyte-specific deletion of pyruvate dehydrogenase (PDH; Pdha1CM-/- mice), the rate-limiting enzyme of glucose oxidation. Male Pdha1CM-/- mice and their α-myosin heavy chain Cre expressing littermates (αMHCCre mice) were subjected to experimental T2D via 10 weeks of high-fat diet supplementation, with a single low-dose injection of streptozotocin (75 mg/kg) provided at week 4. All mice were randomized to treatment with either vehicle control or liraglutide (30 µg/kg) twice daily during the final 2.5 weeks, with cardiac function assessed via ultrasound echocardiography. As expected, liraglutide treatment improved glucose homeostasis in both αMHCCre and Pdha1CM-/- mice with T2D, in the presence of mild weight loss. Parameters of systolic function were unaffected by liraglutide treatment in both αMHCCre and Pdha1CM-/- mice with T2D. However, liraglutide treatment alleviated diastolic dysfunction in αMHCCre mice, as indicated by an increase and decrease in the e'/a' and E/e' ratios, respectively. Conversely, liraglutide failed to rescue these indices of diastolic dysfunction in Pdha1CM-/- mice. Our findings suggest that increases in glucose oxidation are necessary for GLP-1R agonist mediated alleviation of DbCM. As such, strategies aimed at increasing PDH activity may represent a novel approach for the treatment of DbCM.

Targeting glucose metabolism with dichloroacetate (DCA) reduces zika virus replication in brain cortical progenitors at different stages of maturation

The underlying threat of new Zika virus (ZIKV) outbreaks remains, as no vaccines or therapies have yet been developed. In vitro research has shown that glycolysis is a key factor to enable sustained ZIKV replication in neuroprogenitors. However, neither in vivo nor clinical investigation of glycolytic modulators as potential therapeutics for ZIKV-related fetal abnormalities has been conducted. Accordingly, we tested the therapeutic potential of metabolic modulators in relevant in vitro systems comprising two pools of neuroprogenitors (NPCs), which resemble early and late stages of pregnancy. Effective doses of metabolic modulators [3.0 μM] dimethyl fumarate (DMF), [3.2 mM] dichloroacetate (DCA), and [6.3 μM] VER-246608 were determined for these cells by their effect on lactate release, pyruvate dehydrogenase (PDH) activity and cell survival. The drugs were used in a 24h pre-treatment and kept throughout ZIKV infection of NPCs. Drug effects and ZIKV replication were assessed at 24- and 56-h post-infection. In early NPCs treated with DMF, DCA and VER-246608, there was a significant reduction in the extracellular release of ZIKV potentially by PDH-mediated increased mitochondrial oxidation of glucose. Out of the three drugs, only DCA was observed to reduce viral replication in late NPCs treated with DCA. Altogether, our findings suggest that reduction of anaerobic glycolysis could be of therapeutic potential against ZIKV-related fetal abnormalities and that clinical translation should consider the use of specific glycolytic modulators over different trimesters.

Inactivation of Pseudomonas putida KT2440 pyruvate dehydrogenase relieves catabolite repression and improves the usefulness of this strain for degrading aromatic compounds.

Pyruvate dehydrogenase (PDH) catalyses the irreversible decarboxylation of pyruvate to acetyl-CoA, which feeds the tricarboxylic acid cycle. We investigated how the loss of PDH affects metabolism in Pseudomonas putida. PDH inactivation resulted in a strain unable to utilize compounds whose assimilation converges at pyruvate, including sugars and several amino acids, whereas compounds that generate acetyl-CoA supported growth. PDH inactivation also resulted in the loss of carbon catabolite repression (CCR), which inhibits the assimilation of non-preferred compounds in the presence of other preferred compounds. Pseudomonas putida can degrade many aromatic compounds, most of which produce acetyl-CoA, making it useful for biotransformation and bioremediation. However, the genes involved in these metabolic pathways are often inhibited by CCR when glucose or amino acids are also present. Our results demonstrate that the PDH-null strain can efficiently degrade aromatic compounds even in the presence of other preferred substrates, which the wild-type strain does inefficiently, or not at all. As the loss of PDH limits the assimilation of many sugars and amino acids and relieves the CCR, the PDH-null strain could be useful in biotransformation or bioremediation processes that require growth with mixtures of preferred substrates and aromatic compounds.