Topic
Pyruvate dehydrogenase kinase
About: Pyruvate dehydrogenase kinase is a research topic. Over the lifetime, 4224 publications have been published within this topic receiving 161052 citations. The topic is also known as: [pyruvate dehydrogenase (lipoamide)] kinase & pyruvate dehydrogenase (lipoamide) kinase.
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TL;DR: Human spermatozoa seem to rely mainly, if not entirely, on glycolysis as the source of ATP fueling the energy-demanding processes of motility and capacitation, as seen in other mammals.
Abstract: background: There has been an ongoing debate in the reproductive field about whether mammalian spermatozoa rely on glycolysis, oxidative phosphorylation or both for their energy production. Recent studies have proposed that human spermatozoa depend mainly on glucose for motility and fertilization but the mechanism behind an efficient glycolysis in human spermatozoa is not well understood. Here, we demonstrate how human spermatozoa utilize exogenous pyruvate to enhance glycolytic ATP production, motility, hyperactivation and capacitation, events that are crucial for male fertility. methods: Purified human spermatozoa from healthy donors were incubated under capacitating conditions (including albumin, bicarbonate and glucose) and tested for changes in ATP levels, motility, hyperactivation and tyrosine phosphorylation after treatment with pyruvate. The experiments were repeated in the presence of sodium cyanide in order to assess the contribution from mitochondrial respiration. The metabolism of 13 C labeled glucose and pyruvate was traced by a combination of liquid chromatography and mass spectrometry. results: The treatment of human spermatozoa with exogenous pyruvate increased intracellular ATP levels, progressive motility and hyperactivation by 56, 21 and 130%, respectively. In addition, added pyruvate induced a significant increase in tyrosine phosphorylation levels. Blocking of the electron transport chain did not markedly affect the results, indicating that the mechanism is independent of oxidative phosphorylation. However, the observed effects could be counteracted by oxamate, an inhibitor of lactate dehydrogenase (LDH). Metabolic tracing experiments revealed that the observed rise in ATP concentration resulted from an enhanced glycolytic flux, which was increased by more than 50% in the presence of exogenous pyruvate. Moreover, all consumed 13 C labeled pyruvate added was converted to lactate rather than oxidized in the tricarboxylic acid cycle. conclusions: Human spermatozoa seem to rely mainly, if not entirely, on glycolysis as the source of ATP fueling the energydemanding processes of motility and capacitation. The efficient glycolysis is dependent on exogenous pyruvate, which indirectly feeds the accelerated glycolysis with NAD + through the LDH-mediated conversion of pyruvate to lactate. Pyruvate is present in the human female reproductive tract at concentrations in accordance with our results. As seen in other mammals, the motility and fertility of human spermatozoa seem to be dictated by the available energy substrates present in the conspecific female.
122 citations
TL;DR: Cancer, the main cause of human deaths in the modern world is a group of diseases and an extensive study on the regulation of each step of these pathways may help find a potential cancer target.
Abstract: Cancer, the main cause of human deaths in the modern world is a group of diseases. Anticancer drug discovery is a challenge for scientists because of involvement of multiple survival pathways of cancer cells. An extensive study on the regulation of each step of these pathways may help find a potential cancer target. Up-regulated HIF-1 expression and altered metabolic pathways are two classical characteristics of cancer. Oxygen-dependent (through pVHL, PHDs, calcium-mediated) and independent (through growth factor signaling pathway, mdm2 pathway, HSP90) regulation of HIF-1α leads to angiogenesis, metastasis, and cell survival. The two subunits of HIF-1 regulates in the same fashion through different mechanisms. HIF-1α translation upregulates via mammalian target of rapamycin and mitogen-activated protein kinase signaling pathways, whereas HIF-1β through calmodulin kinase. Further, the stabilized interactions of these two subunits are important for proper functioning. Also, metabolic pathways crucial for the formation of building blocks (pentose phosphate pathway) and energy generation (glycolysis, TCA cycle and catabolism of glutamine) are altered in cancer cells to protect them from oxidative stress and to meet the reduced oxygen and nutrient supply. Up-regulated anaerobic metabolism occurs through enhanced expression of hexokinase, phosphofructokinase, triosephosphate isomerase, glucose 6-phosphate dehydrogenase and down-regulation of aerobic metabolism via pyruvate dehydrogenase kinase and lactate dehydrogenase which compensate energy requirements along with high glucose intake. Controlled expression of these two pathways through their common intermediate may serve as potent cancer target in future.
122 citations
TL;DR: Quantitative data on the fate of pyruvate are in accord with the conclusion that the NADH(2) was primarily formed intramitochondrially by the dehydrogenases of cell respiration, with pyruVate as the major substrate.
Abstract: 1. Kidney-cortex slices incubated with pyruvate formed glucose and lactate in relatively large and approximately equimolar quantities. The formation of these products involves two exclusively cytoplasmic NADH(2)-requiring reductions, catalysed by lactate dehydrogenase and triose phosphate dehydrogenase. From the rates of glucose and lactate formation it can be calculated that over 1000mu-moles of NADH(2) must have been produced in the cytoplasm/g. dry wt. of tissue/hr. 2. When lactate is a gluconeogenic precursor the required NADH(2) is generated in the cytoplasm, but, when a substrate more highly oxidized than glucose, such as pyruvate, is the precursor, there is no direct cytoplasmic source of NADH(2). Quantitative data on the fate of pyruvate are in accord with the conclusion that the NADH(2) was primarily formed intramitochondrially by the dehydrogenases of cell respiration, with pyruvate as the major substrate. 3. Similar observations and conclusions apply to experiments with mouse-liver slices incubated with pyruvate, serine or aspartate. 4. Addition of ethanol, which increases the formation of NADH(2) in the cytoplasm, increased the formation from pyruvate of lactate but not of glucose. 5. In view of the low permeability of mitochondria for NAD and NADH(2) it must be postulated that special carrier mechanisms transfer the reducing equivalents of intramitochondrially generated NADH(2) to the cytoplasm. Reasons are given in support of the assumption that the malate-oxaloacetate system acts as the carrier. 6. Various aspects of the generation of reducing power and its transfer from mitochondria to cytoplasm are discussed.
122 citations
TL;DR: It is hypothesized that FOXO1-mediated PDK4 upregulation causes bioenergetic impairment and RV dysfunction, which can be reversed by dichloroacetate, leading to improved bioenergetics and RV function in RVH.
Abstract: Pyruvate dehydrogenase kinase (PDK) is activated in right ventricular hypertrophy (RVH), causing an increase in glycolysis relative to glucose oxidation that impairs right ventricular function. The stimulus for PDK upregulation, its isoform specificity, and the long-term effects of PDK inhibition are unknown. We hypothesize that FOXO1-mediated PDK4 upregulation causes bioenergetic impairment and RV dysfunction, which can be reversed by dichloroacetate. Adult male Fawn-Hooded rats (FHR) with pulmonary arterial hypertension (PAH) and right ventricular hypertrophy (RVH; age 6–12 months) were compared to age-matched controls. Glucose oxidation (GO) and fatty acid oxidation (FAO) were measured at baseline and after acute dichloroacetate (1 mM × 40 min) in isolated working hearts and in freshly dispersed RV myocytes. The effects of chronic dichloroacetate (0.75 g/L drinking water for 6 months) on cardiac output (CO) and exercise capacity were measured in vivo. Expression of PDK4 and its regulatory transcription factor, FOXO1, were also measured in FHR and RV specimens from PAH patients (n = 10). Microarray analysis of 168 genes related to glucose or FA metabolism showed >4-fold upregulation of PDK4, aldolase B, and acyl-coenzyme A oxidase. FOXO1 was increased in FHR RV, whereas HIF-1α was unaltered. PDK4 expression was increased, and the inactivated form of FOXO1 decreased in human PAH RV (P < 0.01). Pyruvate dehydrogenase (PDH) inhibition in RVH increased proton production and reduced GO’s contribution to the tricarboxylic acid (TCA) cycle. Acutely, dichloroacetate reduced RV proton production and increased GO’s contribution (relative to FAO) to the TCA cycle and ATP production in FHR (P < 0.01). Chronically dichloroacetate decreased PDK4 and FOXO1, thereby activating PDH and increasing GO in FHR. These metabolic changes increased CO (84 ± 14 vs. 69 ± 14 ml/min, P < 0.05) and treadmill-walking distance (239 ± 20 vs. 171 ± 22 m, P < 0.05). Chronic dichloroacetate inhibits FOXO1-induced PDK4 upregulation and restores GO, leading to improved bioenergetics and RV function in RVH.
121 citations
TL;DR: The pyruvate dehydrogenase complex from pea (Pisum sativum L.) mitochondria was purified 23-fold by high speed centrifugation and glycerol gradient fractionation and activity was found to be coincident with the proplastid peak on all of the gradients.
Abstract: The pyruvate dehydrogenase complex from pea ( Pisum sativum L) mitochondria was purified 23-fold by high speed centrifugation and glycerol gradient fractionation The complex had a s 20, w of 475S but this is a minimal value since the complex is unstable The complex is specific for NAD + and pyruvate; NADP + and other keto acids give no reaction Mg 2+ , thiamine pyrophosphate, and cysteine are also required for maximal activity The pH optimum for the complex was between 65 and 75 Continuous sucrose density gradients were used to separate castor bean ( Ricinus communis L) endosperm proplastids from mitochondria Pyruvate dehydrogenase complex activity was found to be coincident with the proplastid peak on all of the gradients Some separation of proplastids and mitochondria could be achieved by differential centrifugation and the ratios of the activities of the pyruvate dehydrogenase complex to succinic dehydrogenase and acetyl-CoA carboxylase to succinic dehydrogenase were consistent with both the pyruvate dehydrogenase complex and acetyl-CoA carboxylase being present in the proplastid The proplastid fraction has to be treated with a detergent, Triton X-100, before maximal activity of the pyruvate dehydrogenase complex activity is expressed, indicating that it is bound in the organelle The complex had a sharp pH optimum of 75 The complex required added Mg 2+ , cysteine, and thiamine pyrophosphate for maximal activity but thiamine pyrophosphate was inhibitory at higher concentrations
121 citations