Impairment of energy metabolism in hippocampus of rats subjected to chemically-induced hyperhomocysteinemia

AbstractHomocystinuria is an inherited metabolic disease biochemically characterized by tissue accumulation of homocysteine (Hcy). Mental retardation, ischemia and other neurological features, whose mechanisms are still obscure are common symptoms in homocystinuric patients. In this work, we investigated the effect of Hcy administration in Wistar rats on some parameters of energy metabolism in the hippocampus, a cerebral structure directly involved with cognition. The parameters utilized were 14CO2 production, glucose uptake, lactate release and the activities of succinate dehydrogenase and cytochrome c oxidase (COX). Chronic hyperhomocysteinemia was induced by subcutaneous administration of Hcy twice a day from the 6th to the 28th day of life in doses previously determined in our laboratory. Control rats received saline in the same volumes. Rats were killed 12 h after the last injection. Results showed that Hcy administration significantly diminished 14CO2 production and glucose uptake, as well as succinate dehydrogenase and COX activities. It is suggested that impairment of brain energy metabolism may be related to the neurological symptoms present in homocystinuric patients

Inhibition of brain energy metabolism by the α-keto acids accumulating in maple syrup urine disease

AbstractNeurological dysfunction is a common finding in patients with maple syrup urine disease (MSUD). However, the mechanisms underlying the neuropathology of brain damage in this disorder are poorly known. In the present study, we investigated the effect of the in vitro effect of the branched chain α-keto acids (BCKA) accumulating in MSUD on some parameters of energy metabolism in cerebral cortex of rats. [14CO2] production from [14C] acetate, glucose uptake and lactate release from glucose were evaluated by incubating cortical prisms from 30-day-old rats in Krebs–Ringer bicarbonate buffer, pH 7.4, in the absence (controls) or presence of 1–5 mM of α-ketoisocaproic acid (KIC), α-keto-β-methylvaleric acid (KMV) or α-ketoisovaleric acid (KIV). All keto acids significantly reduced 14CO2 production by around 40%, in contrast to lactate release and glucose utilization, which were significantly increased by the metabolites by around 42% in cortical prisms. Furthermore, the activity of the respiratory chain complex I–III was significantly inhibited by 60%, whereas the other activities of the electron transport chain, namely complexes II, II–III, III and IV, as well as succinate dehydrogenase were not affected by the keto acids. The results indicate that the major metabolites accumulating in MSUD compromise brain energy metabolism by blocking the respiratory chain. We presume that these findings may be of relevance to the understanding of the pathophysiology of the neurological dysfunction of MSUD patients

Inhibition of cytochrome c oxidase activity in rat cerebral cortex and human skeletal muscle by d-2-hydroxyglutaric acid in vitro

Abstractl-2-Hydroxyglutaric (LGA) and d-2-hydroxyglutaric (DGA) acids are the characteristic metabolites accumulating in the neurometabolic disorders known as l-2-hydroxyglutaric aciduria and d-2-hydroxyglutaric aciduria, respectively. Although these disorders are predominantly characterized by severe neurological symptoms, the neurotoxic mechanisms of brain damage are virtually unknown. In this study we have evaluated the role of LGA and DGA at concentrations ranging from 0.01 to 5.0 mM on various parameters of energy metabolism in cerebral cortex slices and homogenates of 30-day-old Wistar rats, namely glucose uptake, CO2 production and the respiratory chain enzyme activities of complexes I to IV. DGA significantly decreased glucose utilization (2.5 and 5.0 mM) by brain homogenates and CO2 production (5 mM) by brain homogenates and slices, whereas LGA had no effect on either measurement. Furthermore, DGA significantly inhibited cytochrome c oxidase activity (complex IV) (EC 1.9.3.1) in a dose-dependent manner (35–95%) at doses as low as 0.5 mM, without compromising the other respiratory chain enzyme activities. In contrast, LGA did not interfere with these activities. Our results suggest that the strong inhibition of cytochrome c oxidase activity by increased levels of DGA could be related to the neurodegeneration of patients affected by d-2-hydroxyglutaric aciduria

Inhibition of cytochrome c oxidase activity in rat cerebral cortex and human skeletal muscle by d-2-hydroxyglutaric acid in vitro

Abstractl-2-Hydroxyglutaric (LGA) and d-2-hydroxyglutaric (DGA) acids are the characteristic metabolites accumulating in the neurometabolic disorders known as l-2-hydroxyglutaric aciduria and d-2-hydroxyglutaric aciduria, respectively. Although these disorders are predominantly characterized by severe neurological symptoms, the neurotoxic mechanisms of brain damage are virtually unknown. In this study we have evaluated the role of LGA and DGA at concentrations ranging from 0.01 to 5.0 mM on various parameters of energy metabolism in cerebral cortex slices and homogenates of 30-day-old Wistar rats, namely glucose uptake, CO2 production and the respiratory chain enzyme activities of complexes I to IV. DGA significantly decreased glucose utilization (2.5 and 5.0 mM) by brain homogenates and CO2 production (5 mM) by brain homogenates and slices, whereas LGA had no effect on either measurement. Furthermore, DGA significantly inhibited cytochrome c oxidase activity (complex IV) (EC 1.9.3.1) in a dose-dependent manner (35–95%) at doses as low as 0.5 mM, without compromising the other respiratory chain enzyme activities. In contrast, LGA did not interfere with these activities. Our results suggest that the strong inhibition of cytochrome c oxidase activity by increased levels of DGA could be related to the neurodegeneration of patients affected by d-2-hydroxyglutaric aciduria

Symposium 19: Federal University of Rio Grande do Sul: its Role in the Biochemistry Teaching in the Southernmost Brazilian States

K-Education(Portuguese) Chair: V. Trindade Bayardo Torres; Clovis Wannmacher; Denise Macedo  Federal University of Rio Grande do Sul: its Role in the Biochemistry Teaching in the Southernmost Brazilian States. Wannmacher, C.M.D. Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.   At present, most Biochemistry teaching in Rio Grande do Sul and Santa Catarina has its origin in the Department of Biochemistry of the Federal University of Rio Grande do Sul. In the 70’s, all the teachers of the Department wrote a book together: “Fundamental Biochemistry”. This book was always used in the classes by groups of students of different careers supervised by the respective teacher. At the same time, this methodology was not used by pharmaceutical teachers, but they recommended the Department’s book to their students. Along the next years, Biochemistry teaching was adapted according to the professional course and to the teacher’s personal characteristics. Today, there are two extremes strategies again: one traditional for the most basic biochemistry student’s formation (including theoretical, laboratorial, seminars and informatics classes) and the other, experimental-clinical, for physician’s formation (including seminars of molecular approach to the most prevalent diseases, mainly, those leading to failure of organs/systems and the interaction with patients from HCPA by the interpretation of their biochemical data). On the other hand, the Post Graduation Program, at first, emphasized biochemistry teaching in a traditional form, but gradually changed the emphasis to investigation, and most classes changed to scientific paper reports. To stimulate the teaching formation, two activities were offered to post-graduation students: Biochemistry Teaching Methodology and Teaching Practice in Biochemistry. These activities promote opportunity for the students to think about different teaching strategies and to plan, execute and evaluate a new project of Biochemistry teaching for graduate students. Most of these post graduates are now teaching Biochemistry in several institutions in Rio Grande do Sul and Santa Catarina. However, for many reasons, most of them teach in the traditional manner. Keywords: Teaching strategy, Biochemistry teaching