The dynamics of energy metabolism in the tick embryo / A dinâmica do metabolismo energético em embriões de carrapato

Abstract The cattle tick Rhipicephalus (Boophilus) microplus is an ectoparasite capable of transmitting a large number of pathogens, causing considerable losses in the cattle industry, with substantial damage to livestock. Over the years, important stages of its life cycle, such as the embryo, have been largely ignored by researchers. Tick embryogenesis has been typically described as an energy-consuming process, sustaining cell proliferation, differentiation, and growth. During the embryonic stage of arthropods, there is mobilization of metabolites of maternal origin for the development of organs and tissues of the embryo. Glycogen resynthesis in late embryogenesis is considered as an effective indicator of embryonic integrity. In the cattle tick R.(B. (B.) microplus, glycogen resynthesis is sustained by protein degradation through the gluconeogenesis pathway at the end of the embryonic period. Despite recent advancements in research on tick energy metabolism at the molecular level, the dynamics of nutrient utilization during R. (B.) microplus embryogenesis is still poorly understood. The present review aims to describe the regulatory mechanisms of carbohydrate metabolism during maternal-zygotic transition and identify possible new targets for the development of novel drugs and other control measures against R. (B.) microplus infestations.

Resumo O carrapato bovino Rhipicephalus (B.) microplus é um ectoparasita capaz de transmitir diversos patógenos, sendo responsável por grandes perdas na pecuária pelos danos causados ao gado. Atualmente, muitos estudos têm negligenciado fases importantes do ciclo de vida deste parasita, como a fase embrionária. A embriogênese é classicamente descrita como um processo que demanda um consumo de energia, possibilitando a proliferação celular, diferenciação e crescimento. Além disso, em artrópodes, o estágio da embriogênese é caracterizado pela mobilização de metabolitos de origem materna para o desenvolvimento de novos tecidos e órgãos. A ressíntese de glicogênio no final da embriogênese tem sido descrita em diversas espécies de artrópodes, sendo considerada um indicador de integridade do embrião. No caso do R. (B.) microplus a ressíntese de glicogênio é sustentada pela degradação de proteínas durante a gliconeogênese, no terço final da embriogênese. Apesar dos recentes avanços, no estudo molecular e do metabolismo energético, os mecanismos envolvidos na dinâmica da utilização de diferentes substratos energéticos durante a embriogênese do carrapato R. (B.) microplus ainda é pouco entendido. Diante deste panorama, estudos que descrevam a regulação destes mecanismos e da associação do metabolismo de carboidratos com a transição materno zigótica, pode auxiliar na busca de novos alvos para o desenvolvimento de novos acaricidas e outras intervenções para o controle infestações de R. (B.) microplus.

A possible relationship between gluconeogenesis and glycogen metabolism in rabbits during myocardial ischemia

ABSTRACT Ischemia is responsible for many metabolic abnormalities in the heart, causing changes in organ function. One of modifications occurring in the ischemic cell is changing from aerobic to anaerobic metabolism. This change causes the predominance of the use of carbohydrates as an energy substrate instead of lipids. In this case, the glycogen is essential to the maintenance of heart energy intake, being an important reserve to resist the stress caused by hypoxia, using glycolysis and lactic acid fermentation. In order to study the glucose anaerobic pathways utilization and understand the metabolic adaptations, New Zealand white rabbits were subjected to ischemia caused by Inflow occlusion technique. The animals were monitored during surgery by pH and lactate levels. Transcription analysis of the pyruvate kinase, lactate dehydrogenase and phosphoenolpyruvate carboxykinase enzymes were performed by qRT-PCR, and glycogen quantification was determined enzymatically. Pyruvate kinase transcription increased during ischemia, followed by glycogen consumption content. The gluconeogenesis increased in control and ischemia moments, suggesting a relationship between gluconeogenesis and glycogen metabolism. This result shows the significant contribution of these substrates in the organ energy supply and demonstrates the capacity of the heart to adapt the metabolism after this injury, sustaining the homeostasis during short-term myocardial ischemia.

The effect of phytic acid on the levels of blood glucose and some enzymes of carbohydrate and lipid metabolism / El Efecto del ácido fítico sobre los niveles de la glucosa en sangre y sobre algunas enzimas del metabolismo de carbohidratos y lípidos

In this study, six groups of rats were fed as follows: Groups 1 and 2 were fed formulated diets supplemented with zinc or without zinc respectively. Groups 3 and 4 were fed formulated diets supplemented with zinc plus phytic acid extracted from sweet potato (Ipomea batatas) or commercial phytic acid respectively. Groups 5 and 6 were fed formulated diets supplemented with phytic acid extract from sweet potato or commercial phytic acid respectively. The animals were fed for three weeks and then sacrificed The activities of key enzymes of carbohydrate and lipid metabolism as well as transaminases in the liver were determined. Blood glucose level was also assessed. Phytic acid extract consumption from sweet potato and commercial phytic acid plus zinc supplement lowered blood glucose levels. There was no significant change in the activity of 6-phosphogluconate dehydrogenase among the groups. Similarly, phytic acid supplementation showed no significant decrease in the activity of pyruvate kinase compared to the group fed formulated diets. There was a significant increase in the activity of glucose-6-phosphate dehydrogenase in the groups fed phytic extract from sweet potato compared to the other groups. The activities of malic enzyme and ATP-citrate lyase in this study were not significantly altered among the groups. There is a lowering of blood glucose levels which is desirable for diabetics who consume sweet potato diets. The changes in some of the hepatic metabolic enzymes are geared towards compensating for the decreased glycolytic responses

En este estudio, se alimentaron seis grupos de ratas de la forma que a continuación se describe. Los grupos 1 y 2 fueron alimentados con dietas formuladas con o sin suplemento de zinc respectivamente. Los grupos 3 y 4 fueron alimentados con dietas formuladas con suplemento de zinc más ácido fítico extraído del boniato (Ipomea batatas) o el ácido fítico comercial respectivamente. Los grupos 5 y 6 fueron alimentados con dietas formuladas con suplemento de extracto de ácido fítico del boniato o ácido fítico comercial respectivamente. Los animales fueron alimentados durante tres semanas y luego sacrificados. Se determinó la actividad de las enzimas claves del metabolismo de carbohidratos y lípidos, así como las transaminasas en el hígado. Asimismo se evaluó el nivel de glucosa en sangre. El consumo de extracto de ácido fítico del boniato y el ácido fítico comercial más el suplemento de zinc, diminuyeron los niveles de glucosa en sangre. No hubo cambios significativos en la actividad de la 6-fosfogluconato deshidrogenasa entre los grupos. De modo similar, la suplementación con ácido fítico no mostró una disminución significativa de la actividad de la piruvato kinasa en comparación con el grupo alimentado con dietas formuladas. Sin embargo, hubo un aumento significativo en la actividad de la glucosa-6-fosfato deshidrogenasa en los grupos alimentados con extracto fítico de boniato en comparación con los otros grupos. No hubo alteración significativa de las actividades de la enzima málica y la ATP-citrato liasa en este estudio. Hay una disminución de los niveles de glucosa en sangre, deseable para los diabéticos que consumen dietas de boniato. Los cambios en algunas de las enzimas metabólicas hepáticas están encaminados a compensar la disminución de las respuestas glicolíticas.

Ca2+ dependence of gluconeogenesis stimulation by glucagon at different cytosolic NAD+-NADH redox potentials

The influence of Ca2+ on hepatic gluconeogenesis was measured in the isolated perfused rat liver at different cytosolic NAD+-NADH potentials. Lactate and pyruvate were the gluconeogenic substrates and the cytosolic NAD+-NADH potentials were changed by varying the lactate to pyruvate rations from 0.01 to 100. The following results were obtained: a) gluconeogenesis from lactate plus pyruvate was not affected by Ca2+-free perfusion (no Ca2+ in the perfusion fluid combined with previous depletion of the intracellular pools); gluconeogenesis was also poorly dependent on the lactate to pyruvate rations in the range of 0.1 to 100; only for a ratio equal to 0.01 was a significantly smaller gluconeogenic activity observed in comparison to the other rations. b) In the presence of Ca2+, the increase in oxygen uptake caused by the infusion of lactate plus pyruvate at a ratio equal to 10 was the most pronounced one; in Ca2+-free perfusion the increase in oxygen uptake caused by lactate plus pyruvate infusion tended to be higher for all lactate to pyruvate ratios; the most pronounced difference was observed for a lactate/pyruvate ratio equal to 1.c) In the presence of Ca2+ the effects of glucagon on gluconeogenesis showed a positive correlation with the lactate to pyruvate rations; for a ratio equal to 0.01 no stimulation ocurred, but in the 0.1 to 100 range stimulation increased progressively, producing a clear parabolic dependence between the effects of glucagon and the lactate to pyruvate ratio. d) In the absence of Ca2+ the relationship between the changes caused by glucagon in gluconeogenesis and the lactate to pyruvate ratio was substantially changed; the dependence curve was no longer parabolic but sigmoidal in shape with a plateau beginning at a lactate/pyruvate ratio equal to 1; there was inhibition at the lactate to pyruvate ratios of 0.01 and 0.1 and a constant stimulation starting with a ratio equal to 1; for the lactate to pyruvate ratios of 10 and 100, stimulation caused by glucagon was much smaller than that found when Ca2+ was present. e) The effects of glucagon on oxygen uptake in the presence of Ca2+ showed a parabolic relationship with the lactate to pyruvate ratios which was closely similar to that found in the case of gluconeogenesis.

Effect of intraperitoneal sublethal doses of dimethoate on rat hepatic gluconeogenesis

Male Wistar rats were injected with dimethoate [10 mg/0.5ml saline i.e. 5% LD[50]] intraperitonitally for 7 successive days. Treated animals suffered from a significant loss in body weight and liver weight as compared to control group. The gluconeogenic enzymes; phosphoenolpyruvate carboxykinase [PEPCK] and fructose 1, 6- bishosphatase [FBPase] were examined in liver. The activity of both enzymes decreased significantly in the treated group. PEPCK and FBPase activities were measured in vitro in the presence and absence of different concentrations of dimethoate. Addition of dimethoate to the reaction mixture resulted in a decrease in the activity of both enzymes. PEPCK activity was inhibited by 1mM dimethoate [28% inhibition] while FBPase activity showed a 30% inhibition by 0.5 mM dimethoate. Addition of 5 mM dimethoate caused 45% and 50% inhibition to PEPCK and FBPase, respectively. Lineweaver- Burk plot of PEPCK and FBPase activity at different substrate concentrations in the presence and absence of 2 mM dimethoate gave an uncompetitive type of inhibition

Gasto basal energético en cirugía / Basal metabolic energy expenditure during surgery

La estimación de las demandas metabólicas está sujeta a una gran variabilidad derivada de la talla,el peso,la edad,la actividad física,la ADE y el aumento de demandas metabólicas del proceso patológico.La calorimetría indirecta,efectuada con los modernos monitores metabólicos(en este estudio se utilizó el MGMTWO, Medicor Inc.) dan una buena estimación del GBE.En el presenteestudio se muestra la utilidad del GBE medido y expresado en índice de superficie.En el enfermo quirúrgico se utilizó el indice catabólico de Bristrian para estimar la magnitud del estrés. Se efectuaron 171 observaciones en 85 sujetos,que muestran datos significativos en los siguientes aspectos:confiabilidad del GBE medido y expresado por índice de superficie; relación de la edad con el GBE; influencia del postoperatorio y la sepsis sobre el GBE y el IC; relación del aporte calórico nitrogenado sobre el balance nitrogenado en función del IC; utilización proteica y grado de estrés, y acción dinámica específica del aporte calórico administrado.