RESUMEN
PURPOSE: This study examined the impact of a 5-wk sprint interval training (SIT) intervention on time to task failure (TTF) during severe-intensity constant work rate (CWR) exercise, as well as in glycolytic enzymatic content and activity, and glycogen content. METHODS: Fourteen active males were randomized into either a SIT group ( n = 8) composed of 15 SIT sessions over 5 wk, or a control group ( n = 6). At pretraining period, participants performed i) ramp incremental test to measure the cardiorespiratory function; ii) CWR cycling TTF at 150% of the power output (PO) at the respiratory compensation point (RCP-PO) with muscle biopsies at rest and immediately following task failure. After 5 wk, the same evaluations were repeated (i.e., exercise intensities matched to current training status), and an additional cycling CWR matched to pretraining 150% RCP-PO was performed only for TTF evaluation. The content and enzymatic activity of glycogen phosphorylase (GPhos), hexokinase (HK), phosphofructokinase (PFK), and lactate dehydrogenase (LDH), as well as the glycogen content, were analyzed. Content of monocarboxylate transporter isoform 4 (MCT4) and muscle buffering capacity were also measured. RESULTS: Despite improvements in total work performed at CWR posttraining, no differences were observed for TTF. The GPhos, HK, PFK, and LDH content and activity, and glycogen content also improved after training only in the SIT group. Furthermore, the MCT4 concentrations and muscle buffering capacity were also improved only for the SIT group. However, no difference in glycogen depletion was observed between groups and time. CONCLUSIONS: Five weeks of SIT improved the glycolytic pathway parameters and total work performed; however, glycogen depletion was not altered during CWR severe-intensity exercise, and TTF remained similar.
Asunto(s)
Glucógeno , Glucólisis , Hexoquinasa , Entrenamiento de Intervalos de Alta Intensidad , Músculo Esquelético , Fosfofructoquinasas , Humanos , Masculino , Glucógeno/metabolismo , Músculo Esquelético/metabolismo , Músculo Esquelético/fisiología , Entrenamiento de Intervalos de Alta Intensidad/métodos , Glucólisis/fisiología , Fosfofructoquinasas/metabolismo , Hexoquinasa/metabolismo , Adulto Joven , L-Lactato Deshidrogenasa/metabolismo , Glucógeno Fosforilasa/metabolismo , AdultoRESUMEN
McArdle disease results from a lack of muscle glycogen phosphorylase in skeletal muscle tissue. Regenerating skeletal muscle fibres can express the brain glycogen phosphorylase isoenzyme. Stimulating expression of this enzyme could be a therapeutic strategy. Animal model studies indicate that sodium valproate (VPA) can increase expression of phosphorylase in skeletal muscle affected with McArdle disease. This study was designed to assess whether VPA can modify expression of brain phosphorylase isoenzyme in people with McArdle disease. This phase II, open label, feasibility pilot study to assess efficacy of six months treatment with VPA (20â¯mg/kg/day) included 16 people with McArdle disease. Primary outcome assessed changes in VO2peak during an incremental cycle test. Secondary outcomes included: phosphorylase enzyme expression in post-treatment muscle biopsy, total distance walked in 12 min, plasma lactate change (forearm exercise test) and quality of life (SF36). Safety parameters. 14 participants completed the trial, VPA treatment was well tolerated; weight gain was the most frequently reported drug-related adverse event. There was no clinically meaningful change in any of the primary or secondary outcome measures including: VO2peak, 12 min walk test and muscle biopsy to look for a change in the number of phosphorylase positive fibres between baseline and 6 months of treatment. Although this was a small open label feasibility study, it suggests that a larger randomised controlled study of VPA, may not be worthwhile.
Asunto(s)
Encéfalo/patología , Glucógeno Fosforilasa/metabolismo , Músculo Esquelético/citología , Ácido Valproico/uso terapéutico , Animales , Estudios de Factibilidad , Glucógeno Fosforilasa/farmacología , Humanos , Fibras Musculares Esqueléticas/patología , Fosforilasas/metabolismo , Proyectos Piloto , Calidad de VidaRESUMEN
Acanthamoeba keratitis is an ophthalmic disease with no specific treatment that specially affects contact lens users. The silencing of serine phosphatase (SP) and glycogen phosphorylase (GP) proteins produced by Acanthamoeba has been shown to significantly reduce the cytopathic effect, although no vehicle was proposed yet to deliver the siRNA sequences to the trophozoites. In this study, PEGylated cationic liposomes were proposed and optimized using Box-Behnken design. The influence of DOTAP:DOPE ratio, DSPE-PEG concentration, and siRNA/DOTAP charge ratio were evaluated over both biological response and physicochemical properties of liposomes. The ratio of DOTAP:DOPE had an effect in the trophozoite activity whereas the charge ratio influenced both size and protease activity. The predicted values were very close to the observed values, yielding a formulation with good activity and toxicity profile, which was used in the following experiments. A murine model of ocular keratitis was treated with siGP + siSP-loaded liposomes, as well as their respective controls, and combined treatment of liposomes and chlorhexidine. After 15 days of eight daily administrations, the liposomal complex combined with chlorhexidine was the only treatment able to reverse the more severe lesions associated with keratitis. There was 60% complete regression in corneal damage, with histological sections demonstrating the presence of an integral epithelium, without lymphocytic infiltrate. The set of results demonstrate the efficacy of a combined therapy based on siRNA with classical drugs for a better prognosis of keratitis caused by Acanthamoeba.
Asunto(s)
Queratitis por Acanthamoeba/terapia , Acanthamoeba/efectos de los fármacos , Clorhexidina/farmacología , Sistemas de Liberación de Medicamentos/métodos , Liposomas/química , Proteínas Protozoarias/antagonistas & inhibidores , Trofozoítos/efectos de los fármacos , Acanthamoeba/enzimología , Acanthamoeba/patogenicidad , Queratitis por Acanthamoeba/parasitología , Queratitis por Acanthamoeba/patología , Animales , Córnea/efectos de los fármacos , Córnea/parasitología , Córnea/patología , Modelos Animales de Enfermedad , Esquema de Medicación , Composición de Medicamentos/métodos , Quimioterapia Combinada , Análisis Factorial , Ácidos Grasos Monoinsaturados/química , Regulación de la Expresión Génica , Glucógeno Fosforilasa/antagonistas & inhibidores , Glucógeno Fosforilasa/genética , Glucógeno Fosforilasa/metabolismo , Humanos , Liposomas/metabolismo , Fosfatidiletanolaminas/química , Monoéster Fosfórico Hidrolasas/antagonistas & inhibidores , Monoéster Fosfórico Hidrolasas/genética , Monoéster Fosfórico Hidrolasas/metabolismo , Polietilenglicoles/química , Proteínas Protozoarias/genética , Proteínas Protozoarias/metabolismo , Compuestos de Amonio Cuaternario/química , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/metabolismo , Ratas , Ratas Wistar , Trofozoítos/enzimología , Trofozoítos/patogenicidadRESUMEN
p-Synephrine is one of the main active components of the fruit of Citrus aurantium (bitter orange). Extracts of the bitter orange and other preparations containing p-synephrine have been used worldwide to promote weight loss and for sports performance. The purpose of the study was to measure the action of p-synephrine on hepatic enzyme activities linked to carbohydrate and energy metabolism and the levels of adenine mononucleotides. Enzymes and adenine mononucleotides were measured in the isolated perfused rat liver and in vivo after oral administration of the drug (50 and 300 mg/kg) by using standard techniques. p-Synephrine increased the activity of glycogen phosphorylase in vivo and in the perfused liver. It decreased, however, the activities of pyruvate kinase and pyruvate dehydrogenase also in vivo and in the perfused liver. p-Synephrine increased the hepatic pools of adenosine diphosphate and adenosine triphosphate. Stimulation of glycogen phosphorylase is consistent with the reported increased glycogenolysis in the perfused liver and increased glycemia in rats. The decrease in the pyruvate dehydrogenase activity indicates that p-synephrine is potentially capable of inhibiting the transformation of carbohydrates into lipids. The capability of increasing the adenosine triphosphate-adenosine diphosphate pool indicates a beneficial effect of p-synephrine on the cellular energetics.
Asunto(s)
Adenosina Trifosfato/metabolismo , Metabolismo de los Hidratos de Carbono/efectos de los fármacos , Hígado/efectos de los fármacos , Hígado/enzimología , Sinefrina/farmacología , Administración Oral , Animales , Citrus/química , Glucógeno Fosforilasa/metabolismo , Hígado/irrigación sanguínea , Hígado/cirugía , Masculino , Complejo Piruvato Deshidrogenasa/antagonistas & inhibidores , Complejo Piruvato Deshidrogenasa/metabolismo , Piruvato Quinasa/antagonistas & inhibidores , Piruvato Quinasa/metabolismo , Ratas , Ratas Wistar , Sinefrina/administración & dosificación , Sinefrina/químicaRESUMEN
Current treatments for Acanthamoeba keratitis are unspecific. Because of the presence of the resilient cyst form of the parasite, the infection is persistent. Silencing the key protein of cyst formation, glycogen phosphorylase, has shown potential for reducing encystment processes of the Acanthamoeba trophozoite. However, a suitable carrier to protect and deliver siRNA sequences is still needed. DOTAP: DOPE:DSPE-PEG liposomes were prepared by three different techniques and used to associate a therapeutic siRNA sequence. Liposomes prepared by film hydration followed by membrane extrusion were considered the most adequate ones with average size of 250 nm and zeta potential of +45 mV, being able to associate siRNA for at least 24 hr in culture medium. siRNA-liposomes could inhibit up to 66% of the encystment process. Cell viability studies demonstrated MTT reduction capacity higher than 80% after 3 hr incubation with this formulation. After 24 hr of incubation, LDH activity ranged for both the formulations from around 4% to 40%. In vivo tolerance studies in mice showed no macroscopic alteration in the eye structures up to 24 hr after eight administrations during 1 day. Histological studies showed regular tissue architecture without any morphological alteration. Overall, these results suggest that the formulations developed are a promising new strategy for the treatment of ocular keratitis caused by Acanthamoeba spp.
Asunto(s)
Acanthamoeba/efectos de los fármacos , Córnea/efectos de los fármacos , Liposomas/química , ARN Interferente Pequeño/metabolismo , ARN Interferente Pequeño/farmacología , Acanthamoeba/enzimología , Acanthamoeba/metabolismo , Animales , Línea Celular , Supervivencia Celular/efectos de los fármacos , Córnea/metabolismo , Córnea/parasitología , Córnea/patología , Ojo/efectos de los fármacos , Ojo/metabolismo , Ojo/parasitología , Ojo/patología , Glucógeno Fosforilasa/antagonistas & inhibidores , Glucógeno Fosforilasa/genética , Glucógeno Fosforilasa/metabolismo , Humanos , Liposomas/toxicidad , Masculino , Ratones , Tamaño de la Partícula , Proteínas Protozoarias/antagonistas & inhibidores , Proteínas Protozoarias/genética , Proteínas Protozoarias/metabolismo , Interferencia de ARN , ARN Interferente Pequeño/químicaRESUMEN
Lithium is administered for the treatment of mood and bipolar disorder. The aim of this study was to verify whether treatment with different concentrations of lithium may affect the glycogen metabolism in the salivary glands of the rats when compared with the liver. Mobilization of glycogen in salivary glands is important for the process of secretion. Two sets of experiments were carried out, that is, in the first, the rats received drinking water supplemented with LiCl (38,25 and 12 mM of LiCl for 15 days) and the second experiment was carried out by intraperitoneal injection of LiCl solution (12 mg/kg and 45 mg LiCl/kg body weight) for 3 days. The active form of glycogen phosphorylase was not affected by treatment with LiCl considering the two experiments. The active form of glycogen synthase presented higher activity in the submandibular glands of rats treated with 25 and 38 mM LiCl and in the liver, with 25 mM LiCl. Glycogen level was higher than that of control in the submandibular glands of rats receiving 38 and 12 mM LiCl, in the parotid of rats receiving 25 and 38 mM, and in the liver of rats receiving 12 mM LiCl. The absolute value of glycogen for the submandibular treated with 25 mM LiCl, and the liver treated with 38 mM LiCl, was higher than the control value, although not statistically significant for these tissues. No statistically significant difference was found in the submandibular and parotid salivary glands for protein concentration when comparing experimental and control groups. We concluded that LiCl administered to rats influences the metabolism of glycogen in salivary glands.
Asunto(s)
Antimaníacos/farmacología , Glucógeno/metabolismo , Cloruro de Litio/farmacología , Glándula Parótida/efectos de los fármacos , Glándula Submandibular/efectos de los fármacos , Administración Oral , Animales , Antimaníacos/administración & dosificación , Relación Dosis-Respuesta a Droga , Glucógeno Fosforilasa/metabolismo , Glucógeno Sintasa/metabolismo , Inyecciones Intraperitoneales , Cloruro de Litio/administración & dosificación , Hígado/efectos de los fármacos , Hígado/metabolismo , Masculino , Glándula Parótida/metabolismo , Ratas Wistar , Glándula Submandibular/metabolismoRESUMEN
Muscle glycogen concentration (MGC) and lactate (LA), activity of glycogen debranching enzyme (GDE), glycogen phosphorylase (GP) and adenosine monophosphate kinase (AMPK) were determined at 0.5h (T0) and 24h (T24) post-mortem in Longissimus dorsi samples from 38 steers that produced high pH (>5.9) and normal pH (<5.8) carcasses at 24h postmortem. MGC, LA and glycolytic potential were higher (P<0.05) in normal pH carcasses. GDE activity was similar (P>0.05) in both pH categories. GP activity increased between T0 and T24 only in normal pH carcasses. AMPK activity was four times higher in normal pH v/s high pH carcasses, without changing its activity over time. Results reinforce the idea that differences in postmortem glycogenolytic/glycolytic flow in L. dorsi of steers showing normal v/s high muscle pH at 24h, could be explained not only by the higher initial MGC in normal pH carcasses, but also by a high and sustained activity of AMPK and an increased GP activity at 24h postmortem.
Asunto(s)
Proteínas Quinasas Activadas por AMP/metabolismo , Sistema de la Enzima Desramificadora del Glucógeno/metabolismo , Glucógeno Fosforilasa/metabolismo , Glucógeno/metabolismo , Glucólisis/fisiología , Carne/análisis , Músculo Esquelético , Adenosina Monofosfato/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Bovinos , Humanos , Concentración de Iones de Hidrógeno , Masculino , Músculo Esquelético/química , Músculo Esquelético/enzimología , FosforilaciónRESUMEN
Retinal tissue is exceptional because it shows a high level of energy metabolism. Glycogen content represents the only energy reserve in retina, but its levels are limited. Therefore, elucidation of the mechanisms controlling glycogen content in retina will allow us to understand retina response under local energy demands that can occur under normal and pathological conditions. Thus, we studied retina glycogen levels under different experimental conditions and correlated them with glucose-6-phosphate (G-6-P) content and glycogen synthase (GS) activity. Glycogen and G-6-P content were studied in ex vivo retinas from normal, fasted, streptozotocin-treated, and insulin-induced hypoglycemic rats. Expression levels of GS and its phosphorylated form were also analyzed. Ex vivo retina from normal rats showed low G-6-P (14±2 pmol/mg protein) and glycogen levels (43±3 nmol glycosyl residues/mg protein), which were increased 6 and 3 times, respectively, in streptozotocin diabetic rats. While no changes in phosphorylated GS levels were observed in any condition tested, a positive correlation was found between G-6-P levels with GS activity and glycogen content. The results indicated that in vivo, retina glycogen may act as an immediately accessible energy reserve and that its content was controlled primarily by G-6-P allosteric activation of GS. Therefore, under hypoglycemic situations retina energy supply is strongly compromised and could lead to the alterations observed in type 1 diabetes.
Asunto(s)
Glucógeno Sintasa/metabolismo , Glucógeno/metabolismo , Retina/enzimología , Regulación Alostérica/efectos de los fármacos , Animales , Glucemia/efectos de los fármacos , Glucemia/metabolismo , Glucosa-6-Fosfato/metabolismo , Glucógeno Fosforilasa/metabolismo , Humanos , Insulina/administración & dosificación , Insulina/farmacología , Fosforilación/efectos de los fármacos , Ratas , Ratas Long-Evans , Retina/efectos de los fármacosRESUMEN
Anoxia-tolerant animal models are crucial to understand protective mechanisms during low oxygen excursions. As glycogen is the main fermentable fuel supporting energy production during oxygen tension reduction, understanding glycogen metabolism can provide important insights about processes involved in anoxia survival. In this report we studied carbohydrate metabolism regulation in the central nervous system (CNS) of an anoxia-tolerant land snail during experimental anoxia exposure and subsequent reoxygenation. Glucose uptake, glycogen synthesis from glucose, and the key enzymes of glycogen metabolism, glycogen synthase (GS) and glycogen phosphorylase (GP), were analyzed. When exposed to anoxia, the nervous ganglia of the snail achieved a sustained glucose uptake and glycogen synthesis levels, which seems important to maintain neural homeostasis. However, the activities of GS and GP were reduced, indicating a possible metabolic depression in the CNS. During the aerobic recovery period, the enzyme activities returned to basal values. The possible strategies used by Megalobulimus abbreviatus CNS to survive anoxia are discussed.
Asunto(s)
Sistema Nervioso Central/metabolismo , Glucógeno Fosforilasa/metabolismo , Glucógeno Sintasa/metabolismo , Glucógeno/metabolismo , Hipoxia/metabolismo , Caracoles/metabolismo , Animales , Sistema Nervioso Central/enzimología , Glucosa/metabolismo , Fosforilación/fisiología , Caracoles/enzimologíaRESUMEN
Here we report the identification of a glycogen phosphorylase (glgP) gene in the plant growth-promoting rhizobacterium Azospirillum brasilense, Sp7, and the characterization of a glgP marker exchange mutant of this strain. The glgP mutant showed a twofold reduction of glycogen phosphorylase activity and an increased glycogen accumulation as compared with wild-type Sp7, indicating that the identified gene indeed encodes a protein with glycogen phosphorylase activity. Interestingly, the glgP mutant had higher survival rates than the wild type after exposure to starvation, desiccation and osmotic pressure. The mutant was shown to be compromised in its biofilm formation ability. Analysis of the exopolysaccharide sugar composition of the glgP mutant revealed a decrease in the amount of glucose, accompanied by increases in rhamnose, fucose and ribose, as compared with the Sp7 exopolysaccharide. To the best of our knowledge, this is the first study that demonstrates GlgP activity in A. brasilense, and shows that glycogen accumulation may play an important role in the stress endurance of this bacterium.
Asunto(s)
Azospirillum brasilense/enzimología , Azospirillum brasilense/fisiología , Proteínas Bacterianas/metabolismo , Biopelículas , Glucógeno Fosforilasa/metabolismo , Azospirillum brasilense/genética , Regulación Bacteriana de la Expresión Génica , Glucógeno Fosforilasa/genética , Estrés FisiológicoRESUMEN
The activities of glycogen phosphorylase and synthase during infusions of glucagon, isoproterenol, or cyanide in isolated liver of fed rats submitted to short-term insulin-induced hypoglycemia (IIH) was investigated. A condition of hyperinsulinemia/hypoglycemia was obtained with an intraperitoneal injection of regular insulin (1.0 U kg(-1)). The control group received ip saline. The experiments were carried out 60 min after insulin (IIH group) or saline (COG group) injection. The rats were anesthetized and after laparotomy, blood was collected from the vena cava for glucose and insulin measurements. The liver was then infused with glucagon (1 nM), isoproterenol (2 microM), or cyanide (0.5 mM) during 20 min and a sample of the organ was collected for determination of the activities of glycogen phosphorylase and synthase 5 min after starting and 10 min after stopping the infusions. The infusions of cyanide, glucagons, and isoproterenol did not change the activities of glycogen synthase and glycogen phosphorylase. However, glycogen catabolism was decreased during the infusions of glucagon and isoproterenol in IIH rats, being more intense with isoproterenol (p < 0.05), than glucagon. It was concluded that short-term IIH promoted changes in the liver responsiveness of glycogen degradation induced by glucagon and isoproterenol without a change in the activities of glycogen phosphorylase and synthase.
Asunto(s)
Conducta Alimentaria/efectos de los fármacos , Hipoglucemia/metabolismo , Insulina/administración & dosificación , Insulina/farmacología , Glucógeno Hepático/metabolismo , Animales , Activación Enzimática/efectos de los fármacos , Glucagón/administración & dosificación , Glucagón/farmacología , Glucosa/metabolismo , Glucógeno Fosforilasa/metabolismo , Glucógeno Sintasa/metabolismo , Glucogenólisis/efectos de los fármacos , Glucólisis/efectos de los fármacos , Hipoglucemia/inducido químicamente , Técnicas In Vitro , Inyecciones Intraperitoneales , Isoproterenol/administración & dosificación , Isoproterenol/farmacología , Ácido Láctico/metabolismo , Hígado/efectos de los fármacos , Hígado/enzimología , Masculino , Ácido Pirúvico/metabolismo , Ratas , Ratas Wistar , Factores de TiempoRESUMEN
Glucose is the main fuel for energy metabolism in retina. The regulatory mechanisms that maintain glucose homeostasis in retina could include hormonal action. Retinopathy is one of the chemical manifestations of long-standing diabetes mellitus. In order to better understand the effect of hyperglycemia in retina, we studied glycogen content as well as glycogen synthase and phosphorylase activities in both normal and streptozotocin-induced diabetic rat retina and compared them with other tissues. Glycogen levels in normal rat retina are low (46 +/- 4.0 nmol glucosyl residues/mg protein). However, high specific activity of glycogen synthase was found in retina, indicating a substantial capacity for glycogen synthesis. In diabetic rats, glycogen synthase activity increased between 50% and 100% in retina, brain cortex and liver of diabetic rats, but only retina exhibited an increase in glycogen content. Although, total and phosphorylated glycogen synthase levels were similar in normal and diabetic retina, activation of glycogen synthase by glucose-6-P was remarkable increased. Glycogen phosphorylase activity decreased 50% in the liver of diabetic animals; it was not modified in the other tissues examined. We conclude that the increase in glycogen levels in diabetic retina was due to alterations in glycogen synthase regulation.
Asunto(s)
Diabetes Mellitus Experimental/metabolismo , Glucógeno/metabolismo , Retina/metabolismo , Animales , Glucemia/metabolismo , Corteza Cerebral/enzimología , Electroforesis en Gel de Poliacrilamida , Glucógeno Fosforilasa/metabolismo , Glucógeno Sintasa/metabolismo , Hígado/enzimología , Epitelio Pigmentado Ocular/enzimología , Ratas , Ratas Long-Evans , Retina/enzimologíaRESUMEN
A prominent phenotype of the yeast sit4 mutant, which lacks the Ser-Thr phosphatase Sit4, is hyper-accumulation of glycogen and the failure to grow on respiratory substrates. We investigated whether these two phenotypes are linked by studying the metabolic response to SIT4 deletion. Although the sit4 mutant failed to grow on respiratory substrates, in the exponential growth, phase respiration was de-repressed; active respiration was confirmed by measuring oxygen consumption and NADH generation. However, the fermentation rate and the internal glucose 6-phosphate and pyruvate levels were reduced, while glycogen content was high. Respiro-fermentative and respiratory substrates such as galactose, glycerol and ethanol were directed toward glycogen synthesis, which indicates that sit4 mutant deviates metabolism to glycogenesis by activating a glycogen futile cycle and depleting cells of Krebs cycle intermediates. An important feature of the sit4 mutant was the lack of growth under anaerobic conditions, suggesting that respiration is necessary to meet the energy requirements of the cell. Addition of aspartic acid, which can restore Krebs cycle intermediates, partially restored growth on ethanol. Our findings suggest that inhibition of Sit4 activity may be essential for redirecting carbohydrate flux to gluconeogenesis and glycogen storage.
Asunto(s)
Metabolismo de los Hidratos de Carbono , Fosfoproteínas Fosfatasas/metabolismo , Saccharomyces cerevisiae/enzimología , Secuencia de Bases , Cartilla de ADN , Fermentación , Glucógeno/metabolismo , Glucógeno Fosforilasa/metabolismo , Glucógeno Sintasa/metabolismo , Mutación , Fosfoproteínas Fosfatasas/genética , Reacción en Cadena de la Polimerasa , Proteína Fosfatasa 2 , Proteínas de Saccharomyces cerevisiaeRESUMEN
A glicogênio-fosforilase (GP) é uma enzima que participa do processo de glicogenólise, fundamental em casos de isquemia e hipoxia tissular. Possui três isoenzimas, sendo que a GPBB tem despertado muito interesse dos pesquisadores por estar presente de forma representativa no miocárdio, podendo tornar-se um futuro marcador de infarto. Seus níveis séricos elevam-se nas primeiras horas do início dos sintomas e retornam aos valores normais em 24 a 48 horas, demonstrando-se muito sensível. A especificidade da GPBB só não é confiável quando o paciente apresenta danos cerebrais concomitantes, isso porque a predominância da GPBB no organismo humano é no cérebro. Vários autores têm realizado extensa revisão do tema, abordando os principais aspectos desse possível novo marcador.
Asunto(s)
Humanos , Glucógeno Fosforilasa/metabolismo , Glucógeno Fosforilasa , Infarto del Miocardio/diagnóstico , Infarto del Miocardio/prevención & control , Biomarcadores , Isoenzimas , Transferasas , Troponina TRESUMEN
Inosine, an endogenous nucleoside, has recently been shown to exert potent effects on the immune, neural, and cardiovascular systems. This work addresses modulation of intermediary metabolism by inosine through adenosine receptors (ARs) in isolated rat hepatocytes. We conducted an in silico search in the GenBank and complete genomic sequence databases for additional adenosine/inosine receptors and for a feasible physiological role of inosine in homeostasis. Inosine stimulated glycogenolysis (approximately 40%, EC50 4.2 x 10(-9) M), gluconeogenesis (approximately 40%, EC50 7.8 x 10(-9) M), and ureagenesis (approximately 130%, EC50 7.0 x 10(-8) M) compared with basal values; these effects were blunted by the selective A3 AR antagonist 9-chloro-2-(2-furanyl)-5-[(phenylacetyl)amino][1,2,4]-triazolo[1,5-c]quinazoline (MRS 1220) but not by selective A1, A2A, and A2B AR antagonists. In addition, MRS 1220 antagonized inosine-induced transient increase (40%) in cytosolic Ca2+ and enhanced (90%) glycogen phosphorylase activity. Inosine-induced Ca2+ mobilization was desensitized by adenosine; in a reciprocal manner, inosine desensitized adenosine action. Inosine decreased the cAMP pool in hepatocytes when A1, A2A, and A2B AR were blocked by a mixture of selective antagonists. Inosine-promoted metabolic changes were unrelated to cAMP decrease but were Ca2+ dependent because they were absent in hepatocytes incubated in EGTA- or BAPTA-AM-supplemented Ca2+-free medium. After in silico analysis, no additional cognate adenosine/inosine receptors were found in human, mouse, and rat. In both perfused rat liver and isolated hepatocytes, hypoxia/reoxygenation produced an increase in inosine, adenosine, and glucose release; these actions were quantitatively greater in perfused rat liver than in isolated cells. Moreover, all of these effects were impaired by the antagonist MRS 1220. On the basis of results obtained, known higher extracellular inosine levels under ischemic conditions, and inosine's higher sensitivity for stimulating hepatic gluconeogenesis, it is suggested that, after tissular ischemia, inosine contributes to the maintenance of homeostasis by releasing glucose from the liver through stimulation of A3 ARs.
Asunto(s)
Glucosa/metabolismo , Hepatocitos/metabolismo , Inosina/metabolismo , Receptor de Adenosina A3/fisiología , Adenosina/metabolismo , Adenosina/farmacología , Antagonistas del Receptor de Adenosina A3 , Animales , Calcio/metabolismo , Hipoxia de la Célula , AMP Cíclico/metabolismo , Gluconeogénesis/efectos de los fármacos , Glucógeno Fosforilasa/metabolismo , Glucogenólisis/efectos de los fármacos , Hepatocitos/efectos de los fármacos , Inosina/farmacología , Hígado/metabolismo , Masculino , Filogenia , Agonistas del Receptor Purinérgico P1 , Antagonistas de Receptores Purinérgicos P1 , Quinazolinas/farmacología , Ratas , Ratas Wistar , Receptor de Adenosina A3/genética , Receptores Acoplados a Proteínas G/genética , Receptores Purinérgicos/genética , Receptores Purinérgicos P1/genética , Triazoles/farmacología , Urea/metabolismoRESUMEN
The widely accepted idea that bees fuel flight through the oxidation of carbohydrate is based on studies of only a few species. We tested this hypothesis as part of our research program to investigate the size-dependence of flight energetics in Panamanian orchid bees. We succeeded in measuring rates of O(2) consumption and CO(2) production in vivo during hovering flight, as well as maximal activities (V(max) values) in vitro of key enzymes in flight muscle energy metabolism in nine species belonging to four genera. Respiratory quotients (ratios of rates of CO(2) production to O(2) consumption) in all nine species are close to 1.0. This indicates that carbohydrate is the main fuel used for flight. Trehalase, glycogen phosphorylase and hexokinase activities are sufficient to account for the glycolytic flux rates estimated from rates of CO(2) production. High activities of other glycolytic enzymes, as well as high activities of mitochondrial oxidative enzymes, are consistent with the estimated rates of carbohydrate-fueled oxidative metabolism. In contrast, hydroxyacylCoA dehydrogenase, an enzyme involved in fatty acid oxidation, was not detectable in any species. Thoracic homogenates displayed ADP-stimulated oxidition of pyruvate + proline, but did not oxidize palmitoyl l-carnitine + proline as substrates. A metabolic map, based on data reported herein and information from the literature, is presented. The evidence available supports the hypothesis that carbohydrate serves as the main fuel for flight in bees.
Asunto(s)
Abejas/fisiología , Metabolismo de los Hidratos de Carbono/fisiología , Metabolismo Energético/fisiología , Vuelo Animal/fisiología , Músculos/fisiología , 3-Hidroxiacil-CoA Deshidrogenasas/metabolismo , Animales , Abejas/enzimología , Dióxido de Carbono/metabolismo , Glucógeno Fosforilasa/metabolismo , Hexoquinasa/metabolismo , Mitocondrias/metabolismo , Músculos/enzimología , Consumo de Oxígeno/fisiología , Panamá , Especificidad de la Especie , Espectrofotometría Ultravioleta , Trehalasa/metabolismoRESUMEN
Experimental animal models of diabetes induced either by alloxan or streptozotocin have been used to study aspects of the pathophysiology of this disease. The purpose of this study was to examine the metabolism of glycogen in the submandibular and parotid salivary glands of diabetic rats. Diabetes was induced by an intraperitoneal injection of streptozotocin. Eight weeks after the induction of diabetes, the animals were sacrificed and the submandibular and parotid salivary glands were removed. The glands were analyzed for glycogen concentration, and activities of glycogen synthase and phosphorylase. Although the diabetic rats consumed more food than controls, they had a lower body weight eight weeks after diabetes induction. Glycogen concentration in the submandibular and parotid glands increased by about 27% and 130%, respectively. Glycogen phosphorylase a in the submandibular gland of diabetic rats showed a reduction of between 75% and 68% compared with controls. In parotid glands, phosphorylase a was reduced by between 84% and 79% compared with controls. The increase in the activity of glycogen synthase a (active) varied from 64% to 130% for the submandibular glands and from 75% to 110% for the parotid compared with controls. These results suggest that the diabetic state influences glycogen metabolism in the submandibular and parotid salivary glands of rats.