RESUMO
The study of polyphenols' effects on health has been gaining attention lately. In addition to reacting with important enzymes, altering the cell metabolism, these substances can present either positive or negative metabolic alterations depending on their consumption levels. Naringenin, a citrus flavonoid, already presents diverse metabolic effects. The objective of this work was to evaluate the effect of maternal naringenin supplementation during pregnancy on the tricarboxylic acid cycle activity in offspring's cerebellum. Adult female Wistar rats were divided into two groups: (1) vehicle (1 ml/kg by oral administration (p.o.)) or (2) naringenin (50 mg/kg p.o.). The offspring were euthanised at 7th day of life, and the cerebellum was dissected to analyse citrate synthase, isocitrate dehydrogenase (IDH), α-ketoglutarate dehydrogenase (α-KGDH) and malate dehydrogenase (MDH) activities. Molecular docking used SwissDock web server and FORECASTER Suite, and the proposed binding pose image was created on UCSF Chimera. Data were analysed by Student's t test. Naringenin supplementation during pregnancy significantly inhibited IDH, α-KGDH and MDH activities in offspring's cerebellum. A similar reduction was observed in vitro, using purified α-KGDH and MDH, subjected to pre-incubation with naringenin. Docking simulations demonstrated that naringenin possibly interacts with dehydrogenases in the substrate and cofactor binding sites, inhibiting their function. Naringenin administration during pregnancy may affect cerebellar development and must be evaluated with caution by pregnant women and their physicians.
Assuntos
Cerebelo/enzimologia , Ciclo do Ácido Cítrico/efeitos dos fármacos , Suplementos Nutricionais , Flavanonas/administração & dosagem , Fenômenos Fisiológicos da Nutrição Materna , Animais , Citrato (si)-Sintase/efeitos dos fármacos , Feminino , Isocitrato Desidrogenase/efeitos dos fármacos , Complexo Cetoglutarato Desidrogenase/efeitos dos fármacos , Malato Desidrogenase/efeitos dos fármacos , Simulação de Acoplamento Molecular , Gravidez , Ratos , Ratos WistarRESUMO
Tyrosinemia type II is an inborn error of metabolism caused by a deficiency in hepatic cytosolic aminotransferase. Affected patients usually present a variable degree of mental retardation, which may be related to the level of plasma tyrosine. In the present study we evaluated effect of chronic administration of L-tyrosine on the activities of citrate synthase, malate dehydrogenase, succinate dehydrogenase and complexes I, II, II-III and IV in cerebral cortex, hippocampus and striatum of rats in development. Chronic administration consisted of L-tyrosine (500 mg/kg) or saline injections 12 h apart for 24 days in Wistar rats (7 days old); rats were killed 12 h after last injection. Our results demonstrated that L-tyrosine inhibited the activity of citrate synthase in the hippocampus and striatum, malate dehydrogenase activity was increased in striatum and succinate dehydrogenase, complexes I and II-III activities were inhibited in striatum. However, complex IV activity was increased in hippocampus and inhibited in striatum. By these findings, we suggest that repeated administrations of L-tyrosine cause alterations in energy metabolism, which may be similar to the acute administration in brain of infant rats. Taking together the present findings and evidence from the literature, we hypothesize that energy metabolism impairment could be considered an important pathophysiological mechanism underlying the brain damage observed in patients with tyrosinemia type II.
Assuntos
Química Encefálica/efeitos dos fármacos , Metabolismo Energético/efeitos dos fármacos , Tirosina/toxicidade , Tirosinemias , Animais , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/enzimologia , Citrato (si)-Sintase/análise , Citrato (si)-Sintase/antagonistas & inibidores , Ciclo do Ácido Cítrico/efeitos dos fármacos , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/enzimologia , Modelos Animais de Doenças , Complexo de Proteínas da Cadeia de Transporte de Elétrons/análise , Complexo de Proteínas da Cadeia de Transporte de Elétrons/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Hipocampo/enzimologia , Malato Desidrogenase/análise , Malato Desidrogenase/efeitos dos fármacos , Masculino , Proteínas do Tecido Nervoso/análise , Ratos , Ratos WistarRESUMO
Objective: Several studies support the hypothesis that metabolism impairment is involved in the pathophysiology of depression and that some antidepressants act by modulating brain energy metabolism. Thus, we evaluated the activity of Krebs cycle enzymes, the mitochondrial respiratory chain, and creatine kinase in the brain of rats subjected to prolonged administration of fluvoxamine. Methods: Wistar rats received daily administration of fluvoxamine in saline (10, 30, and 60 mg/kg) for 14 days. Twelve hours after the last administration, rats were killed by decapitation and the prefrontal cortex, cerebral cortex, hippocampus, striatum, and cerebellum were rapidly isolated. Results: The activities of citrate synthase, malate dehydrogenase, and complexes I, II-III, and IV were decreased after prolonged administration of fluvoxamine in rats. However, the activities of complex II, succinate dehydrogenase, and creatine kinase were increased. Conclusions: Alterations in activity of energy metabolism enzymes were observed in most brain areas analyzed. Thus, we suggest that the decrease in citrate synthase, malate dehydrogenase, and complexes I, II-III, and IV can be related to adverse effects of pharmacotherapy, but long-term molecular adaptations cannot be ruled out. In addition, we demonstrated that these changes varied according to brain structure or biochemical analysis and were not dose-dependent. .
Assuntos
Animais , Masculino , Encéfalo/efeitos dos fármacos , Metabolismo Energético/efeitos dos fármacos , Fluvoxamina/administração & dosagem , Inibidores Seletivos de Recaptação de Serotonina/administração & dosagem , Antidepressivos/administração & dosagem , Encéfalo/enzimologia , Ciclo do Ácido Cítrico/efeitos dos fármacos , Creatina Quinase/efeitos dos fármacos , Transtorno Depressivo/tratamento farmacológico , Transporte de Elétrons/efeitos dos fármacos , Malato Desidrogenase/efeitos dos fármacos , Ratos WistarRESUMO
OBJECTIVE: Several studies support the hypothesis that metabolism impairment is involved in the pathophysiology of depression and that some antidepressants act by modulating brain energy metabolism. Thus, we evaluated the activity of Krebs cycle enzymes, the mitochondrial respiratory chain, and creatine kinase in the brain of rats subjected to prolonged administration of fluvoxamine. METHODS: Wistar rats received daily administration of fluvoxamine in saline (10, 30, and 60 mg/kg) for 14 days. Twelve hours after the last administration, rats were killed by decapitation and the prefrontal cortex, cerebral cortex, hippocampus, striatum, and cerebellum were rapidly isolated. RESULTS: The activities of citrate synthase, malate dehydrogenase, and complexes I, II-III, and IV were decreased after prolonged administration of fluvoxamine in rats. However, the activities of complex II, succinate dehydrogenase, and creatine kinase were increased. CONCLUSIONS: Alterations in activity of energy metabolism enzymes were observed in most brain areas analyzed. Thus, we suggest that the decrease in citrate synthase, malate dehydrogenase, and complexes I, II-III, and IV can be related to adverse effects of pharmacotherapy, but long-term molecular adaptations cannot be ruled out. In addition, we demonstrated that these changes varied according to brain structure or biochemical analysis and were not dose-dependent.
Assuntos
Encéfalo/efeitos dos fármacos , Metabolismo Energético/efeitos dos fármacos , Fluvoxamina/administração & dosagem , Inibidores Seletivos de Recaptação de Serotonina/administração & dosagem , Animais , Antidepressivos/administração & dosagem , Encéfalo/enzimologia , Ciclo do Ácido Cítrico/efeitos dos fármacos , Creatina Quinase/efeitos dos fármacos , Transtorno Depressivo/tratamento farmacológico , Transporte de Elétrons/efeitos dos fármacos , Malato Desidrogenase/efeitos dos fármacos , Masculino , Ratos WistarRESUMO
Arabidopsis thaliana is a plant species that accumulates high levels of organic acids and uses them as carbon, energy and reducing power sources. Among the enzymes that metabolize these compounds, one of the most important ones is malic enzyme (ME). A. thaliana contains four malic enzymes (NADP-ME 1-4) to catalyze the reversible oxidative decarboxylation of malate in the presence of NADP. NADP-ME2 is the only one located in the cell cytosol of all Arabidopsis organs providing most of the total NADP-ME activity. In the present work, the regulation of this key enzyme by fumarate was investigated by kinetic assays, structural analysis and a site-directed mutagenesis approach. The final effect of this metabolite on NADP-ME2 forward activity not only depends on fumarate and substrate concentrations but also on the pH of the reaction medium. Fumarate produced an increase in NADP-ME2 activity by binding to an allosteric site. However at higher concentrations, fumarate caused a competitive inhibition, excluding the substrate malate from binding to the active site. The characterization of ME2-R115A mutant, which is not activated by fumarate, confirms this hypothesis. In addition, the reverse reaction (reductive carboxylation of pyruvate) is also modulated by fumarate, but in a different way. The results indicate pH-dependence of the fumarate modulation with opposite behavior on the two activities analyzed. Thereby, the coordinated action of fumarate over the direct and reverse reactions would allow a precise and specific modulation of the metabolic flux through this enzyme, leading to the synthesis or degradation of C(4) compounds under certain conditions. Thus, the physiological context might be exerting an accurate control of ME activity in planta, through changes in metabolite and substrate concentrations and cytosolic pH.
Assuntos
Arabidopsis/enzimologia , Ácidos Carboxílicos/metabolismo , Fumaratos/farmacologia , Malato Desidrogenase/metabolismo , Regulação Alostérica/efeitos dos fármacos , Sítio Alostérico , Substituição de Aminoácidos , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Proteínas de Arabidopsis/efeitos dos fármacos , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Citosol/enzimologia , Ativação Enzimática/efeitos dos fármacos , Concentração de Íons de Hidrogênio , Cinética , Malato Desidrogenase/efeitos dos fármacos , Malato Desidrogenase/genética , Malatos/metabolismo , Mutagênese Sítio-Dirigida , NADP/metabolismo , Estrutura Terciária de Proteína , Proteínas Recombinantes de FusãoRESUMO
Arabidopsis mitochondria contain two NAD(+)-malic enzymes, NAD-ME1 and NAD-ME2. These proteins have similar affinity for their substrates but display opposite regulation by fumarate, which strongly stimulates NAD-ME1 but inhibits NAD-ME2 activity. Here, the interaction of NAD-ME1 and -2 with fumarate was investigated by kinetic approaches, urea denaturation assays and intrinsic fluorescence quenching, in the absence and presence of NAD(+). Fumarate inhibited NAD-ME2 at saturating, but not at low, levels of NAD(+), and it behaved as competitive inhibitor with respect to L-malate. In contrast, NAD-ME1 fumarate activation was higher at suboptimal NAD(+) concentrations. In the absence of cofactor, the fluorescence of both NAD-ME1 and -2 is quenched by fumarate. However, for NAD-ME2 the quenching arises from a collisional phenomenon, while in NAD-ME1 the fluorescence decay can be explained by a static process that involves fumarate binding to the protein. Furthermore, the residue Arg84 of NAD-ME1 is essential for fumarate binding, as the mutant protein R84A exhibits a collisional quenching by this metabolite. Together, the results indicate that the differential fumarate regulation of Arabidopsis NAD-MEs, which is further modulated by NAD(+) availability, is related to the gaining of an allosteric site for fumarate in NAD-ME1 and an active site-associated inhibition by this C(4)-organic acid in NAD-ME2.
Assuntos
Proteínas de Arabidopsis/metabolismo , Fumaratos/farmacologia , Malato Desidrogenase/metabolismo , Regulação Alostérica , Sítio Alostérico , Sequência de Aminoácidos , Substituição de Aminoácidos , Arabidopsis/enzimologia , Proteínas de Arabidopsis/efeitos dos fármacos , Fumaratos/metabolismo , Malato Desidrogenase/efeitos dos fármacos , Mitocôndrias/enzimologia , Dados de Sequência Molecular , NAD/metabolismoRESUMO
The primary Al-tolerance mechanism in plants involves exudation and/or accumulation of specific organic acid species, which form non-phytotoxic complexes with Al(3+) under physiological conditions. An evaluation was done of the role of organic acids in the tolerance mechanism of a cell suspension line of coffee Coffea arabica that exhibits Al-tolerance (LAMt) but for which the metabolic tolerance mechanism remains unknown. Significant differences existed in malate dehydrogenase and citrate synthase activities (key enzymes in organic acids metabolism) between protein extracts (day 7 of culture cycle) of the L2 (Al-sensitive) and LAMt (Al-tolerant) cells when cell suspensions were treated with 100 microM AlCl(3). HPLC analysis showed that the suspension cells of both lines exudate malate when incubated in a minimal solution but that exudation was not enhanced by treatment with AlCl(3) (100 microM). This is the first study demonstrating that plant Al-tolerance may be associated with down-regulation of malate dehydrogenase and citrate synthase activities.
Assuntos
Alumínio/farmacologia , Ácidos Carboxílicos/metabolismo , Coffea/metabolismo , Tolerância a Medicamentos , Citrato (si)-Sintase/efeitos dos fármacos , Coffea/citologia , Coffea/efeitos dos fármacos , Coffea/enzimologia , Regulação para Baixo/efeitos dos fármacos , Malato Desidrogenase/efeitos dos fármacos , MalatosRESUMO
OBJECTIVE: We investigated the effect of diets rich in omega-6 and omega-3 fatty acids on hepatic metabolism. METHODS: Male Wistar rats, just weaned, were fed ad libitum for 8 wk with one of the following diets: rat chow (C), rat chow containing 15% (w/w) soybean oil (S), rat chow containing 15% (w/w) fish oil (F), and rat chow containing 15% soy bean and fish oil (SF; 5:1, w/w). Casein was added to the fatty diets to achieve the same content of protein (20%) as the control chow. The rats were killed by decapitation, and the hepatic tissue was removed and weighed. Tissue lipid, glycogen, and protein content, in vivo lipogenesis rate, and adenosine triphosphate citrate lyase and malic enzyme activities were evaluated. Plasma total lipids, triacylglycerol, and cholesterol concentrations were assessed. RESULTS: Body weight gain was higher in F and SF than in C and S rats. Liver weight, lipid content, and lipogenesis rate increased in F and SF rats, although adenosine triphosphate citrate lyase activity decreased. Glycogen concentration decreased in S, F, and SF rats compared with C rats. Plasma total lipids and triacylglycerol concentrations were lower in F and SF than in C rats. Total and high-density lipoprotein cholesterol (HDL-C) plasma levels decreased in F rats, with maintenance of the total:HDL-C ratio. In SF rats, an increase in HDL-C led to a lower total:HDL-C ratio. CONCLUSIONS: These results indicated that an enrichment of the diet with omega-3 polyunsaturated fatty acids produces hypolipidemia but may cause changes in liver metabolism that favor lipid deposition. They also suggested that the addition of a small amount of eicosapentaenoic and docosahexaenoic polyunsaturated fatty acids to an omega-6-rich diet further improve the circulating lipid profile, in comparison with an omega-3-rich diet, but it does not prevent excess liver lipid accumulation.