RESUMO
Strawberry is one of the most popular fruits in the world, because their high fruit quality, especially with respect to the combination of aroma, flavor, color, and nutritional compounds. Pyruvate decarboxylase (PDC) is the first of two enzymes specifically required for ethanolic fermentation and catalyzes the decarboxylation of pyruvate to yield acetaldehyde and CO2. The ethanol, an important alcohol which acts as a precursor for the ester and other alcohols formation in strawberry, is produced by the PDC. The objective was found all different PDCs genes present in the strawberry genome and investigate PDC gene expression and ligand-protein interactions in strawberry fruit. Volatile organic compounds were evaluated during the development of the fruit. After this, eight FaPDC were identified with four genes that increase the relative expression during fruit ripening process. Molecular dynamics simulations were performed to analyze the behavior of Pyr and TPP ligands within the catalytic and regulatory sites of the PDC proteins. Results indicated that energy-restrained simulations exhibited minor fluctuations in ligand-protein interactions, while unrestrained simulations revealed crucial insights into ligand affinity. TPP consistently displayed strong interactions with the catalytic site, emphasizing its pivotal role in enzymatic activity. However, FaPDC6 and FaPDC9 exhibited decreased pyruvate affinity initially, suggesting unique binding characteristics requiring further investigation. Finally, the present study contributes significantly to understanding PDC gene expression and the intricate molecular dynamics underlying strawberry fruit ripening, shedding light on potential targets for further research in this critical biological pathway.
Assuntos
Fragaria , Piruvato Descarboxilase , Piruvato Descarboxilase/genética , Piruvato Descarboxilase/metabolismo , Fragaria/genética , Fragaria/metabolismo , Frutas/metabolismo , Ligantes , Proteínas de Plantas/metabolismo , Etanol/metabolismo , Piruvatos/metabolismo , Regulação da Expressão Gênica de PlantasRESUMO
The epigenetic reprogramming that occurs during the earliest stages of embryonic development has been described as crucial for the initial events of cell specification and differentiation. Recently, the metabolic status of the embryo has gained attention as one of the main factors coordinating epigenetic events. In this work, we investigate the link between pyruvate metabolism and epigenetic regulation by culturing bovine embryos from day 5 in the presence of dichloroacetate (DCA), a pyruvate analog that increases the pyruvate to acetyl-CoA conversion, and iodoacetate (IA), which inhibits the glyceraldehyde-3-phosphate dehydrogenase (GAPDH), leading to glycolysis inhibition. After 8 h of incubation, both DCA and IA-derived embryos presented higher mitochondrial membrane potential. Nevertheless, in both cases, lower levels of acetyl-CoA, ATP-citrate lyase and mitochondrial membrane potential were found in blastocysts, suggesting an adaptative metabolic response, especially in the DCA group. The metabolic alteration found in blastocysts led to changes in the global pattern of H3K9 and H3K27 acetylation and H3K27 trimethylation. Transcriptome analysis revealed that such alterations resulted in molecular differences mainly associated to metabolic processes, establishment of epigenetic marks, control of gene expression and cell cycle. The latter was further confirmed by the alteration of total cell number and cell differentiation in both groups when compared to the control. These results corroborate previous evidence of the relationship between the energy metabolism and the epigenetic reprogramming in preimplantation bovine embryos, reinforcing that the culture system is decisive for precise epigenetic reprogramming, with consequences for the molecular control and differentiation of cells.
Assuntos
Epigênese Genética , Transcriptoma , Feminino , Gravidez , Animais , Bovinos , Acetilcoenzima A/metabolismo , Desenvolvimento Embrionário/genética , Blastocisto/metabolismo , Perfilação da Expressão Gênica , Piruvatos/metabolismoRESUMO
Interleukin 6 (IL6) is an multifunctional cytokine that modulates several biological responses, including glucose metabolism. However, its acute effects on hepatic glucose release are still uncertain. The main purpose of this study was to investigate the effects of IL6 on gluconeogenesis from several glucose precursors (alanine, pyruvate and glutamine) and on the suppressive action of insulin on cAMP-stimulated glycogen catabolism in rat liver. IL6 effect on insulin peripheral sensitivity was also evaluated. IL6 was injected intravenously into rats and, 1 h later, gluconeogenesis and glycogenolysis were assessed in liver perfusion and peripheral insulin sensitivity by insulin tolerance test (ITT). IL6 intravenous injection increased hepatic glucose production from alanine, without changing pyruvate, lactate and urea production. IL6 injection also increased hepatic glucose production from pyruvate and glutamine. In addition, IL6 decreased the suppressive effect of insulin on cAMP-stimulated glucose and lactate production and glycogenolysis, without affecting pyruvate production. Furthermore, IL6 reduced the plasma glucose disappearance constant (kITT), an indicator of insulin resistance. In conclusion, IL6 acutely increased hepatic glucose release (gluconeogenesis and glycogenolysis) by a mechanism that likely involved the induction of insulin resistance in the liver, as evidenced by the reduced suppressive effect of insulin on cAMP-stimulated glycogen catabolism. In consistency, IL6 acutely induced peripheral insulin resistance.
Assuntos
Glicogenólise , Resistência à Insulina , Ratos , Animais , Gluconeogênese , Insulina/farmacologia , Insulina/metabolismo , Interleucina-6/metabolismo , Glutamina/metabolismo , Glutamina/farmacologia , Glucose/farmacologia , Glucose/metabolismo , Glicogênio/metabolismo , Glicogênio/farmacologia , Fígado/metabolismo , Ácido Láctico/farmacologia , Ácido Láctico/metabolismo , Piruvatos/metabolismo , Piruvatos/farmacologia , Alanina/farmacologia , Alanina/metabolismo , GlicemiaRESUMO
Microcystins (MC) are hepatotoxic for organisms. Liver MC accumulation and structural change are intensely studied, but the functional hepatic enzymes and energy metabolism have received little attention. This study investigated the liver and hepatocyte structures and the activity of key hepatic functional enzymes with emphasis on energetic metabolism changes after subchronic fish exposure to cyanobacterial crude extract (CE) containing MC. The Neotropical erythrinid fish, Hoplias malabaricus, were exposed intraperitoneally to CE containing 100 µg MC-LR eq kg-1 for 30 days and, thereafter, the plasma, liver, and white muscle was sampled for analyses. Liver tissue lost cellular structure organization showing round hepatocytes, hyperemia, and biliary duct obstruction. At the ultrastructural level, the mitochondria and the endoplasmic reticulum exhibited disorganization. Direct and total bilirubin increased in plasma. In the liver, the activity of acid phosphatase (ACP) increased, and the aspartate aminotransferase (AST) decreased; AST increased in plasma. Alkaline phosphatase (ALP) and alanine aminotransferase (ALT) were unchanged in the liver, muscle, and plasma. Glycogen stores and the energetic metabolites as glucose, lactate, and pyruvate decrease in the liver; pyruvate decreased in plasma and lactate decreased in muscle. Ammonia levels increased and protein concentration decreased in plasma. CE alters liver morphology by causing hepatocyte intracellular disorder, obstructive cholestasis, and dysfunction in the activity of key liver enzymes. The increasing energy demand implies glucose mobilization and metabolic adjustments maintaining protein preservation and lipid recruitment to supply the needs for detoxification allowing fish survival.
Assuntos
Caraciformes , Cianobactérias , Hepatopatias , Fosfatase Ácida/metabolismo , Alanina Transaminase/metabolismo , Fosfatase Alcalina/metabolismo , Amônia , Animais , Aspartato Aminotransferases/metabolismo , Bilirrubina/metabolismo , Misturas Complexas/metabolismo , Misturas Complexas/toxicidade , Cianobactérias/metabolismo , Glucose/metabolismo , Glicogênio/metabolismo , Lactatos , Lipídeos , Fígado/metabolismo , Hepatopatias/metabolismo , Microcistinas/metabolismo , Microcistinas/toxicidade , Piruvatos/metabolismoRESUMO
Trypanosoma cruzi, the causative agent of Chagas' disease, belongs to the Trypanosomatidae family. The parasite undergoes multiple morphological and metabolic changes during its life cycle, in which it can use both glucose and amino acids as carbon and energy sources. The glycolytic pathway is peculiar in that its first six or seven steps are compartmentalized in glycosomes, and has a two-branched auxiliary glycosomal system functioning beyond the intermediate phosphoenolpyruvate (PEP) that is also used in the cytosol as substrate by pyruvate kinase. The pyruvate phosphate dikinase (PPDK) is the first enzyme of one branch, converting PEP, PPi, and AMP into pyruvate, Pi, and ATP. Here we present a kinetic study of PPDK from T. cruzi that reveals its hysteretic behavior. The length of the lag phase, and therefore the time for reaching higher specific activity values is affected by the concentration of the enzyme, the presence of hydrogen ions and the concentrations of the enzyme's substrates. Additionally, the formation of a more active PPDK with more complex structure is promoted by it substrates and the cation ammonium, indicating that this enzyme equilibrates between the monomeric (less active) and a more complex (more active) form depending on the medium. These results confirm the hysteretic behavior of PPDK and are suggestive for its functioning as a regulatory mechanism of this auxiliary pathway. Such a regulation could serve to distribute the glycolytic flux over the two auxiliary branches as a response to the different environments that the parasite encounters during its life cycle.
Assuntos
Doença de Chagas/parasitologia , Piruvato Ortofosfato Diquinase/metabolismo , Trypanosoma cruzi/enzimologia , Monofosfato de Adenosina/metabolismo , Difosfatos/metabolismo , Glucose/metabolismo , Glicólise , Concentração de Íons de Hidrogênio , Cinética , Microcorpos/enzimologia , Fosfoenolpiruvato/metabolismo , Piruvato Ortofosfato Diquinase/química , Piruvatos/metabolismo , Proteínas Recombinantes/metabolismoRESUMO
The alkyl gallates are found in several natural and industrial products. In the latter products, these compounds are added mainly for preventing oxidation. In the present work, the potencies of methyl gallate, n-propyl gallate, n-pentyl gallate, and n-octyl gallate as inhibitors of pyruvate carboxylation and lactate gluconeogenesis were evaluated. Experiments were done with isolated mitochondria and the isolated perfused rat liver. The potency of the gallic acid esters as inhibitors of pyruvate carboxylation in isolated mitochondria obeyed the following decreasing sequence: n-octyl gallate > n-pentyl gallate > n-propyl gallate > methyl gallate. A similar sequence of decreasing potency for lactate gluconeogenesis inhibition in the perfused liver was found in terms of the portal venous concentration. Both actions correlate with the lipophilicity of the compounds. The effects are harmful at high concentrations. At appropriate concentrations, however, octyl gallate should act therapeutically because its inhibitory action on gluconeogenesis will contribute further to its proposed antihyperglycemic effects.
Assuntos
Ácido Gálico/análogos & derivados , Gluconeogênese/efeitos dos fármacos , Lactatos/metabolismo , Fígado/efeitos dos fármacos , Piruvatos/metabolismo , Animais , Ácido Gálico/farmacologia , Masculino , Mitocôndrias Hepáticas/efeitos dos fármacos , Piruvato Carboxilase/antagonistas & inibidores , RatosRESUMO
Fructose-1,6-bisphosphate activates ADP-glucose pyrophosphorylase and the synthesis of glycogen in Escherichia coli. Here, we show that although pyruvate is a weak activator by itself, it synergically enhances the fructose-1,6-bisphosphate activation. They increase the enzyme affinity for each other, and the combination increases Vmax, substrate apparent affinity, and decreases AMP inhibition. Our results indicate that there are two distinct interacting allosteric sites for activation. Hence, pyruvate modulates E. coli glycogen metabolism by orchestrating a functional network of allosteric regulators. We postulate that this novel dual activator mechanism increases the evolvability of ADP-glucose pyrophosphorylase and its related metabolic control.
Assuntos
Escherichia coli/enzimologia , Glucose-1-Fosfato Adenililtransferase/metabolismo , Piruvatos/metabolismo , Sítio Alostérico , Ativação Enzimática , Frutosedifosfatos/química , Frutosedifosfatos/metabolismo , Glicogênio/biossíntese , Cinética , Piruvatos/química , Especificidade por SubstratoRESUMO
Fisetin is a flavonoid dietary ingredient found in the smoke tree (Cotinus coggyria) and in several fruits and vegetables. The effects of fisetin on glucose metabolism in the isolated perfused rat liver and some glucose-regulating enzymatic activities were investigated. Fisetin inhibited glucose, lactate, and pyruvate release from endogenous glycogen. Maximal inhibitions of glycogenolysis (49%) and glycolysis (59%) were obtained with the concentration of 200 microM. The glycogenolytic effects of glucagon and dinitrophenol were suppressed by fisetin 300 microM. No significant changes in the cellular contents of AMP, ADP, and ATP were found. Fisetin increased the cellular content of glucose 6-phosphate and inhibited the glucose 6-phosphatase activity. Gluconeogenesis from lactate and pyruvate or fructose was inhibited by fisetin 300 microM. Pyruvate carboxylation in isolated intact mitochondria was inhibited (IC(50) = 163.10 +/- 12.28 microM); no such effect was observed in freeze-thawing disrupted mitochondria. It was concluded that fisetin inhibits glucose release from the livers in both fed and fasted conditions. The inhibition of pyruvate transport into the mitochondria and the reduction of the cytosolic NADH-NAD(+) potential redox could be the causes of the gluconeogenesis inhibition. Fisetin could also prevent hyperglycemia by decreasing glycogen breakdown or blocking the glycogenolytic action of hormones.
Assuntos
Flavonoides/farmacologia , Glucose/metabolismo , Fígado/metabolismo , Anacardiaceae/química , Animais , Flavonóis , Frutose/metabolismo , Glucagon/metabolismo , Gluconeogênese/efeitos dos fármacos , Glucose-6-Fosfatase/antagonistas & inibidores , Glucose-6-Fosfatase/metabolismo , Glicólise/efeitos dos fármacos , Lactatos/metabolismo , Masculino , Mitocôndrias Hepáticas/metabolismo , NAD/metabolismo , Piruvatos/metabolismo , Ratos , Ratos WistarRESUMO
NADP-malic enzyme (NADP-ME) catalyzes the oxidative decarboxylation of L-malate, producing pyruvate, CO2 and NADPH. The photosynthetic role of this enzyme in C(4) and Crassulacean acid metabolism (CAM) plants has been well established; however, the biological role of several non-photosynthetic isoforms described in C(3), C(4) and CAM plants is still speculative. In this study, the characterization of the NADP-ME isoforms from Nicotiana tabacum was performed. Three different nadp-me transcripts were identified in this C(3) plant, two of which encode for putative cytosolic isoforms (DQ923118 and EH663836), while the third encodes for a plastidic counterpart (DQ923119). Although the three transcripts are expressed in vegetative as well as in reproductive tissues, they display different levels of expression. With regards to enzyme activity, root is the tissue that displays the highest NADP-ME activity. Recombinant NADP-MEs encoded by DQ923118 and DQ923119 were expressed in Escherichia coli and their kinetic parameters and response to different metabolic effectors were analyzed. Studies carried out with crude extracts and with the recombinant proteins indicate that the cytosolic and plastidic isoforms aggregate as tetramers of subunits of 65 and 63 kDa, respectively. Real-time reverse transcription-PCR studies show that the three nadp-me tobacco transcripts respond differently to several biotic and abiotic stress stimuli. Finally, the physiological role of each isoform is discussed in terms of the occurrence, kinetic properties and response to stress. The structure of the NADP-ME family in tobacco is compared with those of other C(3) species.
Assuntos
Regulação da Expressão Gênica de Plantas/fisiologia , Malato Desidrogenase/metabolismo , Nicotiana/enzimologia , Clonagem Molecular , Dados de Sequência Molecular , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Piruvatos/metabolismoRESUMO
The action of orally administered dexamethasone (0.2 mg kg(-1) day(-1)) on metabolic parameters of adjuvant-induced arthritic rats was investigated. The body weight gain and the progression of the disease were also monitored. Dexamethasone was very effective in suppressing the Freund's adjuvant-induced paw edema and the appearance of secondary lesions. In contrast, the body weight loss of dexamethasone-treated arthritic rats was more accentuated than that of untreated arthritic or normal rats treated with dexamethasone, indicating additive harmful effects. The perfused livers from dexamethasone-treated arthritic rats presented high content of glycogen in both fed and fasted conditions, as indicated by the higher rates of glucose release in the absence of exogenous substrate. The metabolization of exogenous L: -alanine was increased in livers from dexamethasone-treated arthritic rats in comparison with untreated arthritic rats, but there was a diversion of carbon flux from glucose to L: -lactate and pyruvate. Plasmatic levels of insulin and glucose were significantly higher in arthritic rats following dexamethasone administration. Most of these changes were also found in livers from normal rats treated with dexamethasone. The observed changes in L: -alanine metabolism and glycogen synthesis indicate that insulin was the dominant hormone in the regulation of the liver glucose metabolism even in the fasting condition. The prevalence of the metabolic effects of dexamethasone over those ones induced by the arthritis disease suggests that dexamethasone administration was able to suppress the mechanisms implicated in the development of the arthritis-induced hepatic metabolic changes. It seems thus plausible to assume that those factors responsible for the inflammatory responses in the paws and for the secondary lesions may be also implicated in the liver metabolic changes, but not in the body weight loss of arthritic rats.
Assuntos
Artrite Experimental/metabolismo , Dexametasona/farmacologia , Alanina/metabolismo , Amônia/metabolismo , Animais , Artrite Experimental/induzido quimicamente , Glicemia/análise , Peso Corporal/efeitos dos fármacos , Jejum , Comportamento Alimentar/efeitos dos fármacos , Adjuvante de Freund , Glicogênio/metabolismo , Inflamação , Insulina/sangue , Lactatos/metabolismo , Masculino , Oxigênio/metabolismo , Perfusão , Piruvatos/metabolismo , Ratos , Ureia/metabolismo , Aumento de Peso/efeitos dos fármacosRESUMO
Dietary fibers, probably by generating short chain fatty acids (SCFA) through enterobacterial fermentation, have a beneficial effect on the control of glycemia in patients with peripheral insulin resistance. We studied the effect of propionate on glucose-induced insulin secretion in isolated rat pancreatic islets. Evidence is presented that propionate, one of the major SCFA produced in the gut, inhibits insulin secretion induced by high glucose concentrations (11.1 and 16.7 mM) in incubated and perfused pancreatic islets. This short chain fatty acid reduces [U-(14)C]-glucose decarboxylation and raises the conversion of glucose to lactate. Propionate causes a significant decrease of both [1-(14)C]- (84%) and [2-(14)C]-pyruvate (49%) decarboxylation. These findings indicate pyruvate dehydrogenase as the major site for the propionate effect. These observations led us to postulate that the reduction in glucose oxidation and the consequent decrease in the ATP/ADP ratio may be the major mechanism for the lower insulin secretion to glucose stimulus induced by propionate.
Assuntos
Trifosfato de Adenosina/biossíntese , Glicemia/metabolismo , Insulina/metabolismo , Ilhotas Pancreáticas/metabolismo , Propionatos/farmacologia , Difosfato de Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Insulina/sangue , Secreção de Insulina , Ilhotas Pancreáticas/efeitos dos fármacos , Ácido Láctico/metabolismo , Masculino , Piruvatos/metabolismo , Ratos , Ratos Endogâmicos , Taxa Secretória/efeitos dos fármacosRESUMO
In this work we investigated to what extent cellular metabolism and energetics regulate sporulation in Saccharomyces cerevisiae and which metabolic pathways are involved in such regulation. Sporulation, meiosis, and associated metabolic fluxes in S. cerevisiae strain CH1211 were studied in several experimental protocols involving changes of carbon source (acetate, lactate, or pyruvate) or cell density in sporulation medium, or changing the phase of batch growth at which cells were harvested before transfer to sporulation medium. In acetate-based sporulation medium, the rate at which cells utilized glyoxylate and gluconeogenic pathways correlated positively with the percentage of asci per cell at 72 h. In contrast, in lactate sporulation medium the frequency of sporulation correlated negatively with both the rate of lactate consumption and the fluxes through gluconeogenesis and the pyruvate-carboxylase catalyzed step. In the presence of lactate, the respiratory capacity did correlate positively with the percentage of asci per cell. The experimental data suggest that acetate limits fluxes to anabolic precursors during sporulation. In contrast, sporulation on lactate appears to be influenced by catabolic processes or, even more precisely, by the respiratory capacity of yeast cells. The results obtained are discussed in terms of the hypothesis that an imbalance between anabolic and catabolic fluxes may be required for an efficient sporulation.
Assuntos
Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/fisiologia , Esporos Fúngicos/fisiologia , Acetatos/metabolismo , Gluconeogênese , Glioxilatos/metabolismo , Cinética , Lactatos/metabolismo , Ácido Láctico , Meiose , Consumo de Oxigênio , Piruvatos/metabolismo , Ácido PirúvicoRESUMO
1. The actions of piroxicam, a nonsteroidal and noncarboxylic anti-inflammatory drug, on the metabolism of the isolated perfused rat liver were investigated. The main purpose was to verify if piroxicam is also active on glycogenolysis and energy metabolism, as demonstrated for several carboxylic nonsteroidal anti-inflammatories. 2. Piroxicam increased oxygen consumption in livers from both fed and fasted rats. 3. Piroxicam increased glucose release and glycolysis from endogenous glycogen (glycogenolysis). 4. Gluconeogenesis from lactate plus pyruvate was inhibited. 5. The action of piroxicam on oxygen consumption was blocked by antimycin A, but not by atractyloside. 6. The action of piroxicam in the perfused rat liver metabolism seems to be a consequence of its action on mitochondria. 7. It can be concluded that inhibition of energy metabolism and stimulation of glycogenolysis are not specific properties of carboxylic nonsteroidal anti-inflammatory drugs.
Assuntos
Anti-Inflamatórios não Esteroides/toxicidade , Metabolismo Energético/efeitos dos fármacos , Fígado/efeitos dos fármacos , Piroxicam/toxicidade , Trifosfato de Adenosina/metabolismo , Animais , Antibacterianos/toxicidade , Antimicina A/toxicidade , Atractilosídeo/toxicidade , Interações Medicamentosas , Jejum , Gluconeogênese/efeitos dos fármacos , Glucose/metabolismo , Glicogênio/metabolismo , Lactatos/metabolismo , Ácido Láctico , Fígado/metabolismo , Masculino , Mitocôndrias Hepáticas/efeitos dos fármacos , Mitocôndrias Hepáticas/metabolismo , NAD/metabolismo , NADP/metabolismo , Consumo de Oxigênio/efeitos dos fármacos , Perfusão , Piruvatos/metabolismo , Ácido Pirúvico , Ratos , Ratos WistarRESUMO
The amebicidal action of metronidazol is activated when the enzyme pyruvate: ferredoxin oxido reductase transfers reducing equivalents to the nitro group of the drug. The enzyme is present in Entanoeba histolytica and other anaerobic parasites like Giardia and Trichomonas that lack mitochondria. The selectivity of the drug can be ascribed to the absence of the reductasa in the human host. E. histolytica possesses other enzymes involved in glucose catabolism that are interesting for the rational desing of new drugs. It has glycolytic enzymes that are important for the production of energy like phosphofructokinase, pyruvate phosphate dikinase, phosphoenolpyruvate carboxytransphosphorylase and thiokinase, which use pyrophosphate as a phosphate donor and have no human counterparts. The first part of this article describes the reactions by which E. histolytica obtains energy from glucose degradation, and includes recent advances in thecloning of genes for the various participating enzymes. The second part shows an alternative view for the study of target enzymes that are unique to the parasite, and indicates their importance in therapautic research
Assuntos
Amebíase/enzimologia , Amebicidas/farmacologia , Carboidratos/metabolismo , Desenho de Fármacos , Entamoeba histolytica/citologia , Enzimas/análise , Nitroimidazóis , Doenças Parasitárias/terapia , Piruvatos/metabolismo , Transporte de Elétrons/fisiologiaRESUMO
The action of cyanide (500 microM), 2,4-dinitrophenol (50 microM) and atractyloside (100 microM) on glycogen catabolism and oxygen uptake was investigated in the bivascularly perfused liver of fed rats. Cyanide, 2,4-dinitrophenol and attractyloside were infused at identical rates into the hepatic artery in either the anterograde or retrograde perfusion. The accessible aqueous cell spaces were determined by means of the multiple-indicator dilution technique. Glucose release, oxygen uptake and glycolysis were measured as metabolic parameters. Oxygen uptake changes per unit cell space caused by atractyloside (inhibition) and 2,4-dinitrophenol (stimulation) were equal in the retrograde perfusion (periportal cells) and the anterograde perfusion (space enriched in perivenous cells); the decreases caused by cyanide were higher in the retrograde perfusion. Glucose release from periportal cells was not increased upon inhibition of oxidative phosphorylation, a phenomenon which was independent of the mechanism of action of the inhibitor. There were nearly identical changes in glycolysis in the periportal and perivenous cells. It was concluded that: (1) oxygen concentration in the perfused rat liver, if maintained above 100 microM, had little influence on the zonation of the respiratory activity; (2) in spite of the lower activities of the key enzymes of glycolysis in the periportal hepatocytes, as assayed under standard conditions, these cells were as effective as the perivenous ones in generating ATP in the cytosol when oxidative phosphorylation was impaired; (3) the key enzymes of glycogenolysis and glycolysis in periportal and perivenous cells responded differently to changes in the energy charge.
Assuntos
Atractilosídeo/farmacologia , Cianetos/farmacologia , Dinitrofenóis/farmacologia , Glicogênio/metabolismo , Fígado/metabolismo , Oxigênio/metabolismo , 2,4-Dinitrofenol , Animais , Glucose/metabolismo , Glicólise , Lactatos/metabolismo , Ácido Láctico , Fígado/efeitos dos fármacos , Masculino , Oxirredução , Perfusão , Fosforilação , Piruvatos/metabolismo , Ácido Pirúvico , Ratos , Ratos Wistar , Sacarose/metabolismo , Água/metabolismoRESUMO
Glyceroneogenesis was assessed in epididymal adipose tissue from rats adapted to a high protein, carbohydrate-free (HP) diet. All experiments were performed in the fed state. Adaptation to the HP diet induced a two-fold increase in the activity of adipose tissue phosphoenolpyruvate carboxykinase (PEPCK). In the absence of glucose, the conversion of 14C-pyruvate (0.2, 1.0 or 5.0 mM) to glyceride-glycerol was significantly higher in adipose tissue from HP-fed rats than in controls. In the presence of glucose, rates of glycerol synthesis in tissues from HP-fed rats did not differ significantly from those in controls. Incorporation of 14C-pyruvate into fatty acids, both in the presence and absence of glucose, was not affected by the diet. The conversion of 14C-glucose (5 mM) into either glyceride-glycerol or fatty acids did not differ in HP-fed and control rats at any of the concentrations of pyruvate utilized. The data provide further evidence for the adaptative nature of adipose tissue PEPCK and suggest that in situations of reduced availability of glucose in the diet, glyceroneogenesis may be important to maintain an adequate supply of alpha-glycerophosphate for esterification of diet-derived fatty acids.
Assuntos
Adaptação Fisiológica/fisiologia , Tecido Adiposo/metabolismo , Dieta , Glicerol/metabolismo , Animais , Carboidratos da Dieta/farmacologia , Proteínas Alimentares/farmacologia , Ácidos Graxos/metabolismo , Glucose/metabolismo , Masculino , Fosfoenolpiruvato Carboxiquinase (GTP)/metabolismo , Piruvatos/metabolismo , Ratos , Ratos WistarRESUMO
1. This study examines the effect of propionate, normally produced in the gut, on lipid metabolism of resident macrophage. This cell is very abundant in the epithelial lining of the gut. 2. The activity of propionyl-CoA synthetase in macrophages was shown to be 0.39 nmol/min per mg protein, so this cell presents the ability to use propionate. Propionate at concentrations varying from 0.5 to 5 mM did not affect the activities of carnitine acetyltransferase, ATP-citrate lyase, acetoacetyl-CoA thiolase and 3-oxoacid-CoA transferase. 3. Thus this short chain fatty acid did not alter the capacity for transferring acetyl-CoA from mitochondria to cytosol and for ketone bodies formation and oxidation. However, propionate (40 mM) inhibited the incorporation of [1-14C]-palmitate into phospholipids, cholesterol, cholesterol ester and triacylglycerol and the incorporation of [3-14C]-pyruvate into phospholipids. 4. These findings suggest that fibre-rich diet by generating propionate may regulate macrophage lipid metabolism.
Assuntos
Lipídeos/biossíntese , Macrófagos Peritoneais/efeitos dos fármacos , Macrófagos Peritoneais/metabolismo , Propionatos/farmacologia , ATP Citrato (pro-S)-Liase/metabolismo , Animais , Radioisótopos de Carbono , Carnitina O-Acetiltransferase/metabolismo , Células Cultivadas , Coenzima A/metabolismo , Coenzima A Ligases/metabolismo , Hidrolases/metabolismo , Macrófagos Peritoneais/enzimologia , Masculino , Ácido Palmítico , Ácidos Palmíticos/metabolismo , Piruvatos/metabolismo , Ácido Pirúvico , Ratos , Fatores de TempoRESUMO
This study examined the effect of Walker 256 tumor growth in vivo on the metabolism of glucose, glutamine and pyruvate in lymphocytes. A comparison between the metabolism of Walker 256 tumor cells obtained in vivo with that of lymphocytes was also carried out. Lymphocytes and tumor cells were isolated and incubated for 1 h for the following measurements: lactate production from glucose (5.6 mM) and pyruvate (3 mM), glutamate and aspartate formation from glutamine (3 mM) and decarboxylation of [U-14C]-glucose, [U-14C]-glutamine, [1-14C]-pyruvate and [3-14C]-pyruvate. The presence of the tumor increased lactate production (2.7-fold from glucose and 2-fold from pyruvate), decarboxylation of [U-14C]-glucose (3.7-fold) and [1-14C]-pyruvate (4.4-fold) and the formation of aspartate (6.3-fold) and glutamate (4.6-fold) from glutamine. The conversion of glucose to lactate and CO2 was higher in tumor cells as compared to lymphocytes. Tumor cells also showed a higher production of glutamate and an 8-fold increased decarboxylation rate of [U-14C]-glutamine in tumor cells, which was more active than that of lymphocytes even from tumor-bearing rats. Tumor growth stimulated glucose and glutamine metabolism in lymphocytes; however, the importance of this fact for the function of these cells remains to be elucidated.
Assuntos
Carcinoma 256 de Walker/metabolismo , Glucose/metabolismo , Glutamina/metabolismo , Linfócitos/metabolismo , Piruvatos/metabolismo , Animais , Carcinoma 256 de Walker/patologia , Linfócitos/patologia , Masculino , Ratos , Ratos WistarRESUMO
This study examined the effect of Walker 256 tumor growth in vivo on the metabolism of glucose, glutamine and pyruvate in lymphocytes. A comparison between the metabolism of Walker 256 tumor cells obtained in vivo with that of lymphocytes was also carried out. Lymphocytes and tumor cells were isolated and incubated for 1 h for the following measurements: lactate production from glucose (5.6 mM) and pyruvate (3 mM), glutamate and aspartate formation from glutamine (3 mM) and decarboxylation of [U-14C]-glucose, [U-14C]-glutamine, [1-14C]-pyruvate and [3-14C]-pyruvate. The presence of the tumor increased lactate production (2.7-fold from glucose and 2-fold from pyruvate), decarboxylation of [U-14C]-glucose (3.7-fold) and [1-14C]-pyruvate (4.4-fold) and the formation of aspartate (6.3-fold) and glutamate (4.6-fold) from glutamine. The conversion of glucose to lactate and CO2 was higher in tumor cells as compared to lymphocytes. Tumor cells also showed a higher production of glutamate and an 8-fold increased decarboxylation rate of [U-14C]-glutamine in tumor cells, which was more active than that of lymphocytes even from tumor-bearing rats. Tumor growth stimulated glucose and glutamine metabolism in lymphocytes; however, the importance of this fact for the function of these cells remains to be elucidated
Assuntos
Animais , Masculino , Ratos , Carcinoma 256 de Walker/patologia , Glucose/metabolismo , Glutamina/metabolismo , Linfócitos/metabolismo , Piruvatos/metabolismo , Carcinoma 256 de Walker/metabolismo , Linfócitos/patologia , Ratos WistarRESUMO
We have measured the action of glucagon, infused into the hepatic artery, on gluconeogenesis from lactate in the rat liver, bivascularly perfused in both the anterograde and retrograde modes. Concerning glucose production and oxygen uptake per unit cell space, the response of the periportal cells reached via the hepatic artery in retrograde perfusion to glucagon is superior to the response of the cells reached via the same vessel in anterograde perfusion. This phenomenon, however, most probably reflects zonation of gluconeogenesis rather than zonation of the hormonal action. The latter conclusion is based on the observation that the fractional change caused by the hormone is the same for all liver cells.