Inhibition of in vitro CO2 production and lipid synthesis by 2-hydroxybutyric acid in rat brain

2-Hydroxybutyric acid appears at high concentrations in situations related to deficient energy metabolism (e.g., birth asphyxia) and also in inherited metabolic diseases affecting the central nervous system during neonatal development, such as "cerebral" lactic acidosis, glutaric aciduria type II, dihydrolipoyl dehydrogenase (E3) deficiency, and propionic acidemia. The present study was carried out to determine the effect of 2-hydroxybutyric acid at various concentrations (1-10 mM) on CO2 production and lipid synthesis from labeled substrates in cerebral cortex of 30-day-old Wistar rats in vitro. CO2 production was significantly inhibited (30-70 percent) by 2-hydroxybutyric acid in cerebral cortex prisms, in total homogenates and in the mitochondrial fraction. We also demonstrated a significant inhibition of lipid synthesis (20-45 percent) in cerebral cortex prisms and total homogenates in the presence of 2-hydroxybutyric acid. However, no inhibition of lipid synthesis occurred in homogenates free of nuclei and mitochondria. The results indicate an impairment of mitochondrial energy metabolism caused by 2-hydroxybutyric acid, a fact that may secondarily lead to reduction of lipid synthesis. It is possible that these findings may be associated with the neuropathophysiology of the situations where 2-hydroxybutyric acid is accumulated

Chronic postnatal administration of methylmalonic acid provokes a decrease of myelin content and ganglioside N-acetylneuraminic acid concentration in cerebrum of young rats

Levels of methylmalonic acid (MMA) comparable to those of human methylmalonic acidemia were achieved in blood (2-2.5 mmol/l) and brain (1.35 æmol/g) of rats by administering buffered MMA, pH 7.4, subcutaneously twice a day from the 5th to the 28th day of life. MMA doses ranged from 0.76 to 1.67 æmol/g as a function of animal age. Control rats were treated with saline in the same volumes. The animals were sacrificed by decapitation on the 28th day of age. Blood was taken and the brain was rapidly removed. Medulla, pons, the olfactory lobes and cerebellum were discarded and the rest of the brain ("cerebrum") was isolated. Body and "cerebrum" weight were measured, as well as the cholesterol and triglyceride concentrations in blood and the content of myelin, total lipids, and the concentrations of the lipid fractions (cholesterol, glycerolipids, phospholipids and ganglioside N-acetylneuraminic acid (ganglioside-NANA)) in the "cerebrum". Chronic MMA administration had no effect on body or "cerebrum" weight, suggesting that the metabolites per se neither affect the appetite of the rats nor cause malnutrition. In contrast, MMA caused a significant reduction of plasma triglycerides, but not of plasma cholesterol levels. A significant diminution of myelin content and of ganglioside-NANA concentration was also observed in the "cerebrum". We propose that the reduction of myelin content and ganglioside-NANA caused by MMA may be related to the delayed myelination/cerebral atrophy and neurological dysfunction found in methylmalonic acidemic children

ATP diphosphohydrolase activity in synaptosomes from cerebral cortex of rats subjected to chemically induced phenylketonuria

ATP diphosphohydrolase (apyrase)(EC3.6.1.5) activity was measured in synaptosomes from cerebral cortex of Wistar rats of both sexes subjected to experimental phenylketonuria, i.e., chemical hyperphenylaninemia induced by subcutaneous administration of 5.2 µmol phenylalanine/g body weight (twice a day) plus 0.9 µmol p-chlorophenylalanine/g body weight (once a day). ATP diphosphohydrolase specific activity (nmol Pi min-1 mg protein-1) of synaptosomes was significantly decreased compared to controls for both ATp (from 147.6 to 129.9) and ADP (from 70.2 to 63.1) hydrolysis one hour after single administration of the drugs to 35-day old rats. Chronic treatment was performed from the 6th to the 28th postpartum day. The enzyme specific activity of synaptosomes was measured one week after the last administration of the drugs and was significantly reduced compared to controls for both ATP (from 164.1 to 150.2) and ADP (from 76.3 to 62.1) hydrolysis. The in vitro effects of the drugs on the synaptosome enzyme specific activity were also investigated. Phenylalnine alone or associated with p-chlorophenylalanine significantly reduced enzyme specific activity for both ATP (from 150.2 to 136.0) and ADP (from 70.5 to 59.3) nucleotides as substrates. Since ATP diphosphohrolase seems to play an important role in neurotransmission, these findings may be related to the neurological dysfunction characteristic of human phenylketonuria

Effects of postnatal methylmalonate administration on neurobehavioral development of rats

Administration of methylmalonic acid in rats has been used as a model for methylmalonicacidemia in humans. Nestling Wistar rats of both sexes received 5 injections daily at 3-h intervals (starting at 7:30 a.m.) of saline or methylmalonic acid (MMA, 10 mg/ml) in a volume of 9 microliters/g body weight per injection subcutaneously in the lumbar region from the 5th to the 9th day of life and 11 microliters/g from day 10 to 14. Growth and neuromotor development were assessed by monitoring the following parameters daily in 54 rats: body weight, ear unfolding, incisor eruption, eye opening, righting, palmar grasp, negative geotaxis, cliff avoidance, free-fall righting and startle reflex. The only statistically significant effects of MMA administration were on the day of appearance of the free-fall righting reflex: MMA, 12.44 +/- 1.55 vs 11.0 +/- 0.39 days for saline control (P < 0.05, by two-way ANOVA) and a significant decrease in weight (P < 0.05, by ANOVA with repeated measures). The results suggest that chronic MMA administration to rats has a selective effect on neuromotor development

Effect of postnatal methylmalonate administration on adult rat behavior

Methylmalonate (MMA) levels (2.0-2.5 mM) comparable to those of human methylmalonic acidemia were achieved in blood of young rats from the 5th to the 25th day of life by of life by injecting the drug subcutaneously twice a day with an interval of 8h. MMA doses ranged from 0.76 to 1.69 *mol/g body weight as a function of animal age. MMA-treated rats had normal body and brain weights. Behavioral studies using aversive and nonaversive tasks were performaed at 60 days of life. Motor activity was similar in MMA-treated and saline-treated controls. No differences in performance between these groups were identified in the shuttle-avoidance responses and in the inhibitory avoidance tasks. However, MMA-injected rats escaped footshock faster than the controls (1.22 ñ 0.11 vs 1.76 ñ 0.14 (mean ñ SEM) for 24 rats in each group (P<0.01)) suggesting that they may be hyperreactive to this stimulus. In the open field, a nonaversive behavior task, MMA-injected rats, in contrast to control rats, presented no habituation. Our results suggest that MMA by itself may impair central nervous system function, causing minor disabilities which result in specific learning deficiencies

Tay-Sachs disease: screening and prevention program in Porto Alegre.

Foi estabelecido um modelo para a triagem e heterozigotos e prevencao da doenca de Tay-Sachs (TSD) em Porto Alegre (Brasil).A comunidade judaica, de aproximadamente 14.000 pessoas, foi sensibilizada previamente atraves de palestras, entrevistas para a imprensa escrita e falada, afixacao de posters e distribuicao de material informativo escrito atraves da Federacao Israelita. Apos um ano deste processo de educacao comunitaria, 298 jovens em idade reprodutiva apresentaram-se como voluntarios para triagem. Os possiveis portadores identificados atraves de lagrima foram submetidos a determinacao de Beta-hexosaminidase A em leucocitos para confirmacao.Foram detectados 7 heterozigotos, dando uma frequencia ajustada de 0.024 para o gene da TSD, de acordo com o esperado para uma comunidade judaica de origem Ashkenazi, como a de Porto Alegre. Todos os portadores detectados foram submetidos a aconselhamento genetico. Os autores acreditam que este modelo possa ser estendido a outras comunidades judaicas brasileiras

Excrecao urinaria de oxalato em individuos com litiase renal. / Urinary excretion of oxalate in subjects with renal lithiasis

Sabe-se que a incidencia dos calculos urinarios constituidos por oxalato de calcio e bastante elevada. Contudo, a relacao entre excrecao elevada de oxalato e litiase renal tem sido posta em duvida por muitos autores, havendo maior concordancia em relacao a excrecao urinaria de calcio. A importancia de definir a participacao do oxalato na genese dos calculos urinarios reside na possibilidade de tomar medidas dieteticas simples para evitar sua recorrencia, previnindo a destruicao renal progressiva. No presente estudo,foi determinada a excrecao urinaria de oxalato por uma modificacao do metodo de Archer e colaboradores em 37 individuos higidos,sem historia familiar de litiase, e em 20 individuos que apresentaram pelo menos um episodio comprovado de litiase renal. Os resultados indicam que a excrecao urinaria de oxalato e maior em individuos litiasicos que na populacao controle. Nao foi encontrada correlacao entre volume urinario e excrecao de oxalato urinario em qualquer dos grupos estudados. Os resultados obtidos sao compativeis com a participacao do oxalato na genese dos calculos urinarios