scholarly journals Metabolic effects of bacitracin in isolated rat hepatocytes

1983 ◽  
Vol 216 (2) ◽  
pp. 369-375 ◽  
Author(s):  
L Agius ◽  
C Wilding ◽  
K G M M Alberti
Keyword(s):  
Fatty Acid ◽  
Pyruvate Dehydrogenase ◽  
Acid Metabolism ◽  
Tricarboxylic Acid Cycle ◽  
Rat Hepatocytes ◽  
Pyruvate Dehydrogenase Kinase ◽  
Metabolic Effects ◽  
Acid Oxidation ◽  
Isolated Rat Hepatocytes ◽  
Intracellular Processing

Bacitracin is a proteolytic inhibitor which interacts with the intracellular processing of insulin. Its effects on pyruvate, fatty acid and amino acid metabolism were examined in rat hepatocyte suspensions. Bacitracin (0.25-1.0 mM) increased the oxidation of [1-14C]pyruvate by 50-70% and presumably therefore increased the flux through pyruvate dehydrogenase. This was found both in the presence of extracellular Ca2+ and in its absence, but not in the presence of 2 mM-2-chloropropionate, which inhibits pyruvate dehydrogenase kinase. Insulin did not further stimulate [1-14C]pyruvate oxidation in the presence of 1 mM-bacitracin. Bacitracin decreased 14CO2 formation from [2-14C]pyruvate (20-40%) and [U-14C]palmitate (30-70%), suggesting a decreased flux through the tricarboxylic acid cycle. Fatty acid oxidation before acetyl-CoA formation was also decreased. Bacitracin decreased the incorporation of label from [3H]leucine into protein in the absence of insulin, but not in its presence. Bacitracin is commonly used in studies on insulin action. Our results suggest that in such studies the effects noted may be related not only to an interaction of bacitracin with the intracellular processing of insulin but also to direct metabolic effects of bacitracin independent of insulin.

Abstract 331: Recovery of Mitochondrial Bioenergetics after Hypoxia via Regulating Pyruvate Dehydrogenase Kinase and Adenosine Monophosphate-activated Kinase

2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Jessica M Toli ◽  
Minzhen He ◽  
Carolyn Suzuki ◽  
Maha Abdellatif
Keyword(s):  
Fatty Acid ◽  
Oxidative Phosphorylation ◽  
Cardiac Myocytes ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Kinase ◽  
Neonatal Rat ◽  
Acid Oxidation ◽  
Peroxisome Proliferator ◽  
Mitochondrial Bioenergetics ◽  
Peroxisome Proliferator Activated Receptor

Mitochondrial quality control is critical for the survival of cardiac myocytes during stress. The purpose of this study was to examine the effect of metabolic substrates and regulators of metabolism on mitochondrial bioenergetics, as an indicator of mitochondrial quality, and how these factors might influence the recovery of the cell’s bioenergetics after hypoxia/ischemia. By monitoring oxygen consumption rates (OCR), in real-time, in live neonatal rat myocytes and human cardiac myocyte-differentiated induced pluripotent stem cells, we found that both cell types can maintain basal OCR efficiently with any metabolic substrate; however, the neonatal cells require both glucose and fatty acid, while the human adult cells require fatty acid only, for mounting maximum reserve respiratory capacity (RRC). Our data also show that subjecting cardiac myocytes to hypoxia results in a reduction of the cells’ basal OCR and oxidative phosphorylation, and exhausts the RRC, which is accompanied by an increase in pyruvate dehydrogenase kinase (Pdk) 1 and 4. Except for normalization of Pdk1 levels, there was little or no recovery of these parameters after reoxygenation. We, thus, hypothesized, that inhibition of Pdks may help recovery of the cell’s bioenergetics. Indeed, our results show that by inhibiting Pdks with dichloroacetate (DCA) before or after hypoxia, the cells’ bioenergetics, including OCR, oxidative phosphorylation, and RRC in neonatal myocytes, and RRC in the human myocytes fully recover within 24 h. On the other hand, activating AMP-activated kinase (AMPK) resulted in delayed (96 h) improvement of the cells’ RRC that was accompanied by an increase in peroxisome proliferator-activated receptor gamma, coactivator 1α (3.5x), peroxisome proliferator-activated receptor-α (2x), and mitochondrial number (2x). These results led us to conclude that compromised mitochondrial quality can be rescued through mechanisms that regulate glucose or fatty acid oxidation by either inhibiting Pdks or activating AMPK, respectively, in rodent and human myocytes.

scholarly journals Gene expression analysis in mitochondria from chagasic mice: alterations in specific metabolic pathways

2004 ◽  
Vol 381 (3) ◽  
pp. 743-752 ◽  
Author(s):  
Nisha GARG ◽  
Arpad GERSTNER ◽  
Vandanajay BHATIA ◽  
James DeFORD ◽  
John PAPACONSTANTINOU
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Metabolism ◽  
Mitochondrial Function ◽  
Pyruvate Dehydrogenase ◽  
Acid Metabolism ◽  
Tricarboxylic Acid Cycle ◽  
Pyruvate Dehydrogenase Complex ◽  
Tricarboxylic Acid ◽  
Acid Cycle ◽  
Dehydrogenase Complex

Cardiac hypertrophy and remodelling in chagasic disease might be associated with mitochondrial dysfunction. In the present study, we characterized the cardiac metabolic responses to Trypanosoma cruzi infection and progressive disease severity using a custom-designed mitoarray (mitochondrial function-related gene array). Mitoarrays consisting of known, well-characterized mitochondrial function-related cDNAs were hybridized with 32P-labelled cDNA probes generated from the myocardium of mice during immediate early, acute and chronic phases of infection and disease development. The mitoarray successfully identified novel aspects of the T. cruzi-induced alterations in the expression of the genes related to mitochondrial function and biogenesis that were further confirmed by real-time reverse transcriptase–PCRs. Of note is the up-regulation of transcripts essential for fatty acid metabolism associated with repression of the mRNAs for pyruvate dehydrogenase complex in infected hearts. We observed no statistically significant changes in mRNAs for the enzymes of tricarboxylic acid cycle. These results suggest that fatty acid metabolism compensates the pyruvate dehydrogenase complex deficiencies for the supply of acetyl-CoA for a tricarboxylic acid cycle, and chagasic hearts may not be limited in reduced energy (NADH and FADH2). The observation of a decrease in mRNA level for several subunits of the respiratory chain complexes by mitoarray as well as global genome analysis suggests a limitation in mitochondrial oxidative phosphorylation-mediated ATP-generation capacity as the probable basis for cardiac homoeostasis in chagasic disease.

scholarly journals Logical modelling reveals the PDC-PDK interaction as the regulatory switch driving metabolic flexibility at the cellular level

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Samar HK Tareen ◽  
Martina Kutmon ◽  
Ilja CW Arts ◽  
Theo M de Kok ◽  
Chris T Evelo ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Pyruvate Dehydrogenase ◽  
Tricarboxylic Acid Cycle ◽  
Pyruvate Dehydrogenase Complex ◽  
Tricarboxylic Acid ◽  
Cellular Level ◽  
Acid Oxidation ◽  
Metabolic Flexibility ◽  
Acid Cycle

Abstract Background Metabolic flexibility is the ability of an organism to switch between substrates for energy metabolism, in response to the changing nutritional state and needs of the organism. On the cellular level, metabolic flexibility revolves around the tricarboxylic acid cycle by switching acetyl coenzyme A production from glucose to fatty acids and vice versa. In this study, we modelled cellular metabolic flexibility by constructing a logical model connecting glycolysis, fatty acid oxidation, fatty acid synthesis and the tricarboxylic acid cycle, and then using network analysis to study the behaviours of the model. Results We observed that the substrate switching usually occurs through the inhibition of pyruvate dehydrogenase complex (PDC) by pyruvate dehydrogenase kinases (PDK), which moves the metabolism from glycolysis to fatty acid oxidation. Furthermore, we were able to verify four different regulatory models of PDK to contain known biological observations, leading to the biological plausibility of all four models across different cells and conditions. Conclusion These results suggest that the cellular metabolic flexibility depends upon the PDC-PDK regulatory interaction as a key regulatory switch for changing metabolic substrates.

Control of cardiac pyruvate dehydrogenase activity in peroxisome proliferator-activated receptor-α transgenic mice

2003 ◽  
Vol 285 (1) ◽  
pp. H270-H276 ◽  
Author(s):  
Teresa A. Hopkins ◽  
Mary C. Sugden ◽  
Mark J. Holness ◽  
Ray Kozak ◽  
Jason R. B. Dyck ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Pyruvate Dehydrogenase ◽  
Glucose Oxidation ◽  
Pyruvate Dehydrogenase Kinase ◽  
Acid Oxidation ◽  
Peroxisome Proliferator ◽  
Wild Type ◽  
Peroxisome Proliferator Activated Receptor ◽  
Oxidation Rates

The pyruvate dehydrogenase enzyme complex (PDC) is rate limiting for glucose oxidation in the heart. Inhibition of PDC by end-product feedback and phosphorylation by pyruvate dehydrogenase kinase (PDK) operate in concert to inhibit PDC activity. Because the transcriptional regulator peroxisome proliferator-activated receptor (PPAR)-α increases PDK expression in some tissues, we examined what role PPAR-α has in regulating glucose oxidation in hearts from mice overexpressing PPAR-α (MHC-PPAR-α mice). Glucose oxidation rates were decreased in isolated working hearts from MHC-PPAR-α mice compared with wild-type littermates (428 ± 113 vs. 771 ± 63 nmol · g dry weight-1 · min-1, respectively), which was accompanied by a parallel increase in fatty acid oxidation. However, there was no difference in PDC activity between MHC-PPAR-α and wild-type animals, even though the expression of the PDK isoform PDK1 was increased in MHC-PPAR-α mice. Glucose oxidation rates in both MHC-PPAR-α and wild-type mouse hearts were decreased after 48-h fasting (which increases PPAR-α expression) or by treatment of mice with the PPAR-α agonist WY-14,643 for 1 wk. Despite this, PDC activity in both animal groups was not altered. Taken together, these data suggest that glucose oxidation rates in the heart can be dramatically altered independent of PDK phosphorylation and inhibition of PDC by PDK. It also suggests that PPAR-α activation decreases glucose oxidation in hearts mainly by decreasing the flux of pyruvate through PDC due to negative feedback of PDC by fatty acid oxidation reaction products rather than by the phosphorylated state of the PDC complex.

scholarly journals Effects of vasopressin and corticosterone on fatty acid metabolism and on the activities of glycerol phosphate acyltransferase and phosphatidate phosphohydrolase in rat hepatocytes

1984 ◽  
Vol 217 (2) ◽  
pp. 461-469 ◽  
Author(s):  
A D Pollard ◽  
D N Brindley
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Metabolism ◽  
Acid Metabolism ◽  
Rat Hepatocytes ◽  
Ionophore A23187 ◽  
Brattleboro Rats ◽  
Glycerol Phosphate ◽  
Isolated Rat Hepatocytes ◽  
Triacylglycerol Synthesis ◽  
Phosphatidate Phosphohydrolase

The effects of vasopressin on the short-term control of fatty acid metabolism were studied in isolated rat hepatocytes. Vasopressin increased the oxidation of oleate to CO2 and decreased the formation of ketones in hepatocytes from Wistar rats, but not from Brattleboro rats. Incubation with vasopressin for 30 min increased the conversion of oleate into triacylglycerol by 17% and 32% in hepatocytes from Wistar and Brattleboro rats respectively. The corresponding increases for the phospholipid fraction were 19% and 42%. When Wistar-rat hepatocytes were incubated with corticosterone for 6 h there was a 19% increase in triacylglycerol synthesis, and a 52% increase if vasopressin was added 30 min before the end of the incubation. Glycerol phosphate acyltransferase activity was not significantly increased by vasopressin. Incubation for 5-60 min with vasopressin increased the Vmax. of phosphatidate phosphohydrolase by 48% and 32% respectively in hepatocytes from Wistar and Brattleboro rats. These increases were antagonized if EGTA was added to the medium used for incubating the hepatocytes. The replacement of vasopressin by 5 microM-ionophore A23187 produced a significant increase of 13% in the phosphohydrolase activity. It is therefore likely that the effects of vasopressin on the phosphohydrolase are mediated by Ca2+. These results are discussed in relation to the possible function of phosphatidate phosphohydrolase in controlling the turnover of phosphoinositides, the synthesis of phosphatidylethanolamine, phosphatidylcholine and triacylglycerol, and the secretion of very-low-density lipoproteins.

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