Occupational risk assessment of exposure to metals in chrome plating workers.

Inhalation of xenobiotics during manufacture process in chrome plating bath produce hazards to workers' health. Chromium (Cr) is a metal widely used by industry, and its hexavalent (VI) form has been classified as mutagenic and carcinogenic. This study aimed to evaluate the occupational risk of exposure to metals in chrome plating workers. Biological monitoring was performed through quantification of Cr, Pb, As, Ni, and V in blood by ICP-MS in 50 male chrome-plating workers from the exposed group and 50 male non-exposed workers. The inflammatory parameters assessed were ß-2 integrin, intercellular adhesion molecule-1 (ICAM-1), and L-selectin expression in lymphocytes. The genotoxicity was evaluated with comet and micronucleus (MN) assays and as a biomarker of oxidative damage the lipid peroxidation (MDA) and protein carbonyl (PCO). The results demonstrated that Cr levels in blood and urine were increased in the exposed group compared to the non-exposed group. Although the biomarkers of exposure proved to be within the levels considered safe in exposed individuals, chrome plating workers presented significantly increase in the percentage of lymphocytes expressing ß-2 integrin, ICAM-1, and L-selectin as well as DNA damage (comet assay) and plasmatic MDA and PCO levels. Therefore, it is possible also assign the injuries caused to lipids, proteins, and DNA assessed due to the increased presence of other metals such as Pb, As, Ni, and V in exposed subjects. These results suggest that exposure to xenobiotics present in the occupational environment in chrome plating industry could play a crucial role toward the inflammation, genetic, and oxidative damage.

Effects of bovine enterovirus and type 1 diabetes on liver and kidney pyruvate kinase activity in an animal model

Type 1 diabetes (T1D) is an autoimmune disease characterized by the selective destruction of pancreatic beta cells. In addition to genetic factors, enteroviruses have been considered the main environmental factor involved in this pathology. Therefore, the objective of this study was to evaluate the effects of streptozotocin-induced diabetes and bovine enterovirus (BEV) on liver and kidney pyruvate kinase activity in rats. Fourteen male Wistar rats were divided in three groups: control, diabetes and a third group, which was fed with water experimentally contaminated by BEV. Increased blood glucose levels were found in both diabetes and enterovirus groups, whereas there were no alterations in the lipid profile. A reduced pyruvate kinase activity was observed in the liver and kidney of animals from diabetes and enterovirus groups. Under our experimental conditions, the ingestion of water experimentally contaminated by BEV induced alterations in glycaemia, and also interfered in the pyruvate kinase activity in liver and kidney of the rats, which might be one of the possible mechanisms involved in the T1D development.

Effects of chronic exposure to hexavalent chromium in water on oxidative stress parameters in Wistar rats

Hexavalent chromium [Cr (VI)] is a metal utilized in different industries and consequently disposed in the environment. It is a toxic substance and its reduction to trivalent Cr [Cr (III)] generates intermediates, which are responsible for the oxidation of molecules, and cause the oxidative stress. Therefore, the aim of this study was to evaluate if Cr (VI) could induce oxidative stress in Wistar rats. In this study, Wistar rats were chronically exposed to 25 and 50 ppm of potassium dichromate in drinking water for 30 days. The levels of Cr were evaluated in the blood and tissues (liver, kidneys, and lungs). Oxidative stress was determined in the liver, kidneys, and lungs and was evaluated by DFCH, TBA-RS and carbonyl test. Antioxidant enzymes were evaluated through catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities. Regarding the results, Cr concentration was significantly elevated in all tissues, however, it was lower in the lungs. In relation to the oxidative stress parameters, there was a significant increase of DCFH levels in the kidneys and carbonyls in liver and kidneys. Regarding the antioxidant enzymes, SOD was decreased in all organs and GPx was diminished in the kidneys. These data indicated that Cr (VI) could induce oxidative stress in the kidneys and liver due to an imbalance between oxidative and antioxidant parameters. The lungs were little affected, possibly by the lowest chromium accumulation.

Relationship between depression and diabetes Mellitus / Relação entre depressão e diabetes Mellitus

Objective: To review studies examining the possible relationship between depression and diabetes Mellitus.Methods: Articles were searched in the following databases: the Latin-American and Caribbean Center on Health Sciences, the Scientific Library Online, Base in Nursing and Pubmed. The search was limited to articles published between January 2000 and October 2010. Search terms included: ?diabetes?, ?depression?, ?chronic diseases? and ?psychiatric disorders? Results: A total of 21 articles which examined the relationship between diabetes and depression were included in the present paper. There is a bidirectional relationship between these two chronic diseases. Diabetes could lead to depression due its effects on the quality life of patients, its complications and the difficulty in treatment adhesion. Depression could lead to diabetes on account of alterations in glucose transport function and increased immunoninflamatory activation, which could contribute to insulin resistance and beta islet cell dysfunction. Conclusion: There is a bidirectional relation between diabetes and depression and the nature of this relation is still unclear. However, this research contributes to the comprehension of this relation and possible mechanisms involved, since both diseases should be monitored and deserve attention from health professionals.

Objetivo: Revisar estudos que avaliaram a possível existência da relação entre depressão e diabetes Mellitus.Métodos: Artigos foram pesquisados nas seguintes bases de dados: Literatura Latino-Americana e do Caribe em Ciências da Saúde, Scientific Electronic Library Online, Bases de Dados em Enfermagem e Pubmed. A busca foi limitada aos artigos publicados de janeiro de 2000 a outubro de 2010. Os termos de busca utilizados foram ?diabetes?, ?depressão?, ?doenças crônicas? e ?distúrbios psiquiátricos? Resultados: Um total de 21 artigos que avaliaram a relação entre diabetes e depressão foi incluído e analisado no presente trabalho. Há uma relação bidirecional entre essas duas doenças crônicas. O diabetes poderia levar à depressão por afetar a qualidade de vida dos pacientes, dadas suas complicações e a dificuldade de adesão ao tratamento. A depressão poderia ocasionar o diabetes devido às alterações na função do transporte de glicose e ao aumento da ativação da resposta imunoinflamatória, o que poderia contribuir para a resistência à insulina e para a disfunção da célula betapancreática. Conclusão: Existe uma relação bidiretional entre diabetes e depressão, e a natureza dessa relação permanece desconhecida. Esta revisão contribui para a compreensão dessa relação e dos possíveis mecanismos envolvidos, visto que ambas as doenças devem ser monitoradas e merecem atenção dos profissionais da saúde.

Frequency of the anti-glutamic acid decarboxylase immunological marker in patients with diabetes duration longer than three years in southern Brazil / Frequência do marcador imunológico de anti-decarboxilase do ácido glutâmico em pacientes com diabetes há mais de três anos no Sul do Brasil

CONTEXT AND OBJECTIVE: The anti-GAD (glutamic acid decarboxylase) antibody is considered to be an important marker for type 1 diabetes mellitus (DM1), with frequency that varies depending on the population studied and the duration of the disease. Therefore, the aim of this study was to determine the frequency of this autoantibody in a group of patients in southern Brazil with DM1 that had been diagnosed more than three years previously. DESIGN AND SETTING: Analytical cross-sectional study with a control group conducted at the Biomedicine Laboratory of Universidade Feevale. METHODS: This study was conducted between June 2007 and December 2008, and 109 individuals were enrolled during this period. Fifty-eight were DM1 patients and 51 were individuals free from DM1 and without any history of diabetes, who constituted the control group. RESULTS: In the DM1 group, the mean age was 27 ± 1.7 years and 50 percent were men. The mean fasting blood glucose in the DM1 group was 208 ± 15 mg/dl and mean HbA1c (glycosylated hemoglobin) was 8.7 ± 0.25 percent. In the control group, the mean fasting blood glucose and HbA1c were 82 mg/dl and 5.0 percent respectively. Thirty-seven individuals with DM1 (63.8 percent) were positive for anti-GAD, and this proportion was significantly larger than in the control group. CONCLUSIONS: These results show the high prevalence of anti-GAD in the population of diabetic patients in southern Brazil, thus indicating that the antibody was still present a long time after the disease had been diagnosed.

CONTEXTO E OBJETIVO: O anticorpo anti-decarboxilase do ácido glutâmico (anti-GAD) é considerado um importante marcador no diabetes mellitus tipo 1 (DM1), cuja frequência varia segundo a população estudada e o tempo de duração da doença. Assim, o objetivo deste estudo foi determinar a frequência deste auto-anticorpo em um grupo de pacientes localizados no Sul do Brasil com mais de três anos de diagnóstico de DM1. TIPO DE ESTUDO E LOCAL: Estudo transversal analítico com grupo controle, realizado no Laboratório de Biomedicina da Universidade Feevale. MÉTODOS: Este estudo foi realizado no período de Junho de 2007 a Dezembro de 2008, em que 109 indivíduos foram incluídos, sendo 58 destes com DM1 e 51 indivíduos sem DM1 e sem antecedentes de diabetes, que constituíram o grupo controle. RESULTADOS: No grupo DM1, a idade média foi 27 ± 1,7 anos e 50 por cento eram homens. A média da glicemia de jejum no grupo DM1 foi 208 ± 15 mg/dL e a HbA1c média foi 8,7 ± 0.25 por cento. No grupo controle a glicemia de jejum média e a HbA1c (hemoglobina glicosilada) foram 82 mg/dL e 5,0 por cento, respectivamente. O anti-GAD foi positivo em 37 (63,8 por cento) indivíduos com DM1, valores significativamente maiores quando comparados com os do grupo controle. CONCLUSÕES: Estes resultados mostram a alta prevalência do anti-GAD na população de pacientes diabéticos da região Sul do Brasil, indicando que o anticorpo está presente após um longo período de diagnóstico da doença.

Lead inhibits in vitro creatine kinase and pyruvate kinase activity in brain cortex of rats.

Lead intoxication is a serious occupational disease that constitutes a major public health problem. Lead, a heavy metal, has been used by humans for many technological purposes, which is the main reason for its widespread distribution. The toxic mechanisms of lead on the molecular machinery of living organisms include metal transport, energy metabolism, diverse enzymatic processes, genetic regulation, and membrane ionic channels and signaling molecules. Since lead is able to cross the blood-brain barrier it may cause neurotoxicity. Creatine kinase and pyruvate kinase are two thiol-containing enzymes that exert a key role for cellular energy homeostasis in brain. Our main objective was to investigate the in vitro effect of lead on pyruvate kinase and creatine kinase activities of extracts and subcellular fractions from the brain cortex of rats in the presence or not of thiol-protecting substances such as glutathione and cysteamine. The results showed that lead inhibited the two enzyme activities and the thiol-protecting substances prevented their inhibition. These results suggest that lead inhibits creatine kinase and pyruvate kinase activity by interaction with their thiol groups. Therefore, lead may disrupt energy homeostasis and this effect may contribute to the neurological dysfunction found in lead exposed individuals.

Cysteamine prevents inhibition of adenylate kinase caused by cystine in rat brain cortex.

Cystinosis is a systemic genetic disease caused by a lysosomal transport deficiency accumulating cystine in the lysosomes of almost all tissues. Although tissue damage might depend on cystine accumulation, the mechanisms of tissue damage are still obscures. Adenylate kinase, along with creatine kinase, is responsible for the enzymatic phosphotransfer network, crucial for energy homeostasis. Taking into account that cystine is known to inhibit creatine kinase activity, the two enzymes have thiol groups, and the strong interaction between the two activities, our main objective was to investigate the effect of cystine on adenylate kinase activity in the brain cortex of Wistar rats. For the in vivo studies, the animals were injected twice a day with 1.6 micromol/g body weight of cystine dimethylester and/or 0.46 micromol/g body weight of cysteamine from the 25th to the 29th postpartum day and sacrificed after 12 h. Cystine inhibited the enzyme activity in vitro in a concentration dependent way, whereas cysteamine prevented the inhibition. Adenylate kinase activity was found diminished in the brain cortex of rats loaded with cystine dimethylester and co-administration of cysteamine prevented the diminution of the enzyme activity. Considering that adenylate kinase together with creatine kinase is crucial for energy homeostasis, the release of cystine from lysosomes with consequent enzymes inhibition could impair energy homeostasis, contributing to tissue damage in patients with cystinosis.

Cysteamine prevents inhibition of adenylate kinase caused by cystine in rat brain cortex.

Cystinosis is a systemic genetic disease caused by a lysosomal transport deficiency accumulating cystine in the lysosomes of almost all tissues. Although tissue damage might depend on cystine accumulation, the mechanisms of tissue damage are still obscures. Adenylate kinase, along with creatine kinase, is responsible for the enzymatic phosphotransfer network, crucial for energy homeostasis. Taking into account that cystine is known to inhibit creatine kinase activity, the two enzymes have thiol groups, and the strong interaction between the two activities, our main objective was to investigate the effect of cystine on adenylate kinase activity in the brain cortex of Wistar rats. For the in vivo studies, the animals were injected twice a day with 1.6 micromol/g body weight of cystine dimethylester and/or 0.46 micromol/g body weight of cysteamine from the 25th to the 29th postpartum day and sacrificed after 12 h. Cystine inhibited the enzyme activity in vitro in a concentration dependent way, whereas cysteamine prevented the inhibition. Adenylate kinase activity was found diminished in the brain cortex of rats loaded with cystine dimethylester and co-administration of cysteamine prevented the diminution of the enzyme activity. Considering that adenylate kinase together with creatine kinase is crucial for energy homeostasis, the release of cystine from lysosomes with consequent enzymes inhibition could impair energy homeostasis, contributing to tissue damage in patients with cystinosis.

Cysteamine prevents inhibition of thiol-containing enzymes caused by cystine or cystine dimethylester loading in rat brain cortex.

Cystinosis is a systemic genetic disease caused by a lysosomal transport deficiency accumulating cystine in the lysosomes of all tissues. Although tissue damage might depend on cystine accumulation, the mechanisms of tissue damage are still obscures. Considering that thiol-containing enzymes are critical for several metabolic pathways, our main objective was to investigate the effects of cystine or cystine dimethylester load on the thiol-containing enzymes creatine kinase and pyruvate kinase, in the brain cortex of young Wistar rats. The animals were injected twice a day with 1.6 micromol/g body weight of cystine dimethylester or 1 micromol/g body weight of cystine and/or 0.46 micromol/g body weight of cysteamine from the 16th to the 20th postpartum day and sacrificed after 12 h. Cystine or cystine dimethylester administration inhibited the two enzyme activities. Co-administration of cysteamine, the drug used to treat cystinotic patients, normalized the two enzyme activities. Lactate dehydrogenase activity, a nonthiol-containing enzyme was not affected by cystine dimethylester administration. Cystine inhibits creatine kinase and pyruvate activities possibly by oxidation of the sulfhydryl groups of the enzymes. Considering that creatine kinase and pyruvate kinase, like other thiol-containing enzymes, are crucial for energy homeostasis and antioxidant defenses, the enzymes inhibition caused by cystine released from lysosomes could be one of the mechanisms of tissue damage in patients with cystinosis.

Tryptophan administration induces oxidative stress in brain cortex of rats.

Despite the significant brain abnormalities, the neurotoxic mechanisms of brain injury in hypertryptophanemia are virtually unknown. In this work, we determined the thiobarbituric acid-reactive substances, 2',7'-dihydrodichlorofluorescein oxidation, reduced glutathione and the activities of catalase, superoxide dismutase and glutathione peroxidase in cerebral cortex from rats loaded with L-tryptophan. High L-tryptophan concentrations, similar to those found in hypertryptophanemic patients were induced by three subcutaneous injections of saline-buffered tryptophan (2 micromol/g body weight) to 30-day-old Wistar rats. The parameters were assessed 1 h after the last injection. It was observed that tryptophan significantly increased thiobarbituric acid-reactive substances, 2',7'-dihydrodichlorofluorescein oxidation and reduced glutathione, whereas it reduced catalase activity. Pre-treatment with taurine (1.6 micromol/g of body weight), or alpha-tocopherol plus ascorbic acid (40 and 100 microg/g body weight, respectively) prevented those effects of tryptophan, reinforcing the hypothesis that tryptophan induces oxidative stress in brain cortex of the rats. Therefore, these findings also occur in human hypertryptophanemia or in other neurodegenerative diseases in which tryptophan accumulates, then oxidative stress may be involved in the mechanisms leading to the brain injury observed in patients affected by these disorders.

Effects of cysteamine on oxidative status in cerebral cortex of rats.

Cystinosis is a systemic genetic disease caused by a lysosomal transport deficiency accumulating cystine in most tissues. Tissue damage depends on cystine accumulation, but the mechanisms of this damage are still obscure. Cysteamine administration depletes cystine accumulated, increasing survive of affected patients. Studies performed in fibroblasts of cystinotic patients suggest that apoptosis is enhanced in this disease. Considering that oxidative stress is a known apoptosis inducer, our main objective was to investigate a possible antioxidant effect of cysteamine on several parameters of oxidative stress in the brain of young rats. Animals received three subcutaneous injections at 3-h intervals of a buffered solution (pH 7.4) of 10 mg/kg body weight cysteamine and were sacrificed 1 h after the last injection. Cysteamine decreased lipoperoxidation and glutathione peroxidase activity, and increased the carbonyl content of proteins and catalase activity. In vitro studies showed that cysteamine reduced lipoperoxidation, 2',7'-dihydrodichlorofluorescein oxidation, carbonyl content of proteins and catalase activity, and increased glutathione peroxidase activity. These results suggest that cysteamine may act as a scavenger of superoxide free radicals and hydrogen peroxide. Therefore, it is possible that cysteamine may extend life of cystinotic patients acting not only as a cystine depleting drug, but also as a free radical scavenger, reducing cell damage by apoptosis.

Promotion of oxidative stress in kidney of rats loaded with cystine dimethyl ester.

Cystinosis is a systemic genetic disease caused by a lysosomal transport deficiency accumulating cystine in most tissues. Although tissue damage might depend on cystine accumulation, the mechanisms of tissue damage are not fully understood. Studies performed in fibroblasts of cystinotic patients and in kidney cells loaded with cystine dimethyl ester (CDME) suggest that apoptosis is enhanced in this disease. Considering that oxidative stress is a known apoptosis inducer, our main objective was to investigate the effects of CDME loading on several parameters of oxidative stress in the kidney of young rats. Animals were injected twice a day with 1.6 micromol/g body weight CDME and/or 0.26 micromol/g body weight cysteamine (CSH) from the 16th to the 20th postpartum day and killed after 1 or 12 h. CDME induced lipoperoxidation and protein carbonylation and stimulated superoxide dismutase, glutathione peroxidase (GPx), and catalase activities, probably through the formation of superoxide anions, hydrogen peroxide, and hydroxyl free radicals. Coadministration of CSH, the drug used to treat cystinotic patients, prevented, at least in part, those effects, possibly acting as a scavenger of free radicals. These results suggest that the induction of oxidative stress might be one of the mechanisms leading to tissue damage in cystinotic patients.

Inhibition of creatine kinase activity by cystine in the kidney of young rats.

Nephropathic cystinosis is a lethal genetic disease caused by a lysosomal transport disorder leading to intralysosomal cystine accumulation in all tissues. Cystinosis is the most common inherited cause of Fanconi syndrome, but the mechanisms by which cystine causes tissue damage are not fully understood. Thiol-containing enzymes are critical for renal energy metabolism and may be altered by disulfides like cystine. Therefore, in the present study our main objective was to investigate the in vivo and in vitro effects of cystine on creatine kinase, which contains critical thiol groups in its structure, in the kidney of young Wistar rats. We observed that cystine inhibited in vivo and in vitro the enzyme activity and that this inhibition was prevented by cysteamine and glutathione. The results suggest oxidation of essential sulfhydryl groups necessary for creatine kinase function by cystine. Considering that creatine kinase and other thiol-containing enzymes are crucial for renal energy metabolism, and programmed cell death occurs in situations of energy deficiency, the enzyme inhibition caused by cystine released from lysosomes might be a mechanism of tissue damage in patients with cystinosis.

Promotion of oxidative stress by L-tryptophan in cerebral cortex of rats.

Despite the significant brain abnormalities, the neurotoxic mechanisms of brain injury in hypertryptophanemia are virtually unknown. In this work, it was investigated the in vitro effect of l-tryptophan on various parameters of oxidative stress, namely spontaneous chemiluminescence, thiobarbituric acid-reactive substances (TBA-RS), total radical-trapping antioxidant potential (TRAP), total antioxidant reactivity (TAR) and glutathione (GSH) levels in cerebral cortex from 30-day-old rats. Tryptophan significantly increased chemiluminescence and TBA-RS measurements indicating that this amino acid induced lipid peroxidation in vitro. We also observed that tryptophan significantly decreased the brain antioxidant defenses by reducing the values of TRAP, TAR and GSH, reflecting that the overall content of antioxidants was reduced by tryptophan. Furthermore, the tryptophan-induced increase of TBA-RS was fully prevented by GSH and by combination of catalase plus superoxide dismutase, but not by the inhibitor of nitric oxide synthase N(omega)-nitro-L-arginine methyl ester (L-NAME). In case these findings also occur in human hypertryptophanemia or in other neurodegenerative diseases in which tryptophan accumulates, it is feasible that oxidative stress may be involved in the mechanism leading to the brain injury observed in patients affected by these disorders.

The effects of the interactions between amino acids on pyruvate kinase activity from the brain cortex of young rats.

Considering that pyruvate kinase activity, a crucial enzyme for glucose metabolism and energy liberation in brain, may be regulated by some amino acids, it is possible that diminution of this enzyme activity may contribute to the brain damage caused by amino acids accumulated in metabolic diseases, such as phenylalanine, tryptophan and cystine. Therefore, the present study was undertaken to investigate the effect of these amino acids on pyruvate kinase activity in the brain cortex of rats. We also investigated the effect of serine and alanine on pyruvate kinase activity in the same tissue. The results suggested that phenylalanine, tryptophan, cystine, alanine, and serine act at the same site on the enzyme, phenylalanine, tryptophan, and cystine causing inhibition, and alanine and serine preventing this effect. Cystine also inhibited the enzyme activity through a different mechanism, possibly acting on the enzyme thiol groups. Considering that this enzyme is a target for amino acids accumulated in some metabolic diseases of amino acid metabolism, it is possible that its inhibition may contribute to the brain damage found in these diseases.

Inhibition of pyruvate kinase activity by cystine in brain cortex of rats.

Cystinosis is a metabolic disturb associated with excessive lysosomal cystine accumulation secondary to defective cystine efflux. Patients affected by this disease develop a variable degree of symptoms depending of the involved tissues. Accumulation of cystine in the brain may lead to severe neurological symptoms. However, the mechanisms by which cystine is neurotoxic are not fully understood. Considering that pyruvate kinase (PK) is a thiolic enzyme crucial for the glycolytic pathway, and disulfides like cystine may alter thiolic enzymes by thiol/disulfide exchange, the main objective of the present study was to investigate the effect of cystine on PK activity in the brain cortex of developing Wistar rats. We also performed kinetic studies and investigated the effects of GSH, a biologically occurring thiol groups protector, and cysteamine (CysN), the drug used for cystinosis treatment, on the enzyme activity. We observed that cystine inhibited the enzyme activity by two different mechanisms, one through the competition with ADP and phosphoenolpyruvate (PEP), and the other non-competitively, probably through oxidation of the thiol groups of PK. We also observed that GSH and cysteamine fully prevented and reversed the inhibition caused by cystine. Considering that cysteamine is used in patients with cystinosis because it causes parenkimal organ cystine depletion, the present data provides a possible new beneficial effect for the use of this drug.

Characterization of the inhibition of pyruvate kinase caused by phenylalanine and phenylpyruvate in rat brain cortex.

Pyruvate kinase plays a crucial role on the glycolytic pathway, the main route that provides energy for brain functioning. In the present study, we investigated the kinetics of the inhibition of pyruvate kinase provoked by phenylalanine and its main metabolite, phenylpyruvate, in mitochondria-free cerebral cortex homogenate from 22-day-old Wistar rats. We found that phenylalanine and phenylpyruvate inhibit PK activity by competition with the enzyme substrates ADP and phosphoenolpyruvate. We also investigated the interaction between phenylalanine and phenylpyruvate, and the kinetics of alanine prevention of the inhibitory action of phenylalanine and phenylpyruvate on pyruvate kinase activity. We observed that alanine per se had no effect on PK activity but prevented the inhibitory action of phenylalanine and phenylpyruvate by competition. The data suggest that phenylalanine, phenylpyruvate, and alanine act on a common site in the enzyme, probably an allosteric one. It is possible that inhibition of brain PK activity may be related to the reduction of glucose metabolism observed in the brain of phenylketonuric patients and may be one of the mechanisms responsible for the neurological dysfunction found in these patients. Further studies, however, are necessary to evaluate the benefit of carbohydrate and alanine supplementation to the diet of phenylketonuric patients.

Alanine prevents the in vitro inhibition of glycolysis caused by phenylalanine in brain cortex of rats.

Glycolysis is the main route that provides energy to brain functioning. In this study we investigated the in vitro effects of phenylalanine, the main metabolite known to accumulate in phenylketonuria, and/or alanine, on pyruvate kinase activity, glucose utilization, lactate release, and ADP concentration in brain cortex homogenates from 30-day-old Wistar rats. We found that phenylalanine decreased PK activity, glucose utilization, and lactate release, and increased ADP brain levels. We also verified that alanine per se did not modify these parameters, but prevented the effects of phenylalanine. Our data suggest that the inhibition of pyruvate kinase by phenylalanine decreases glycolysis and energy production, and that alanine, a known competitor of phenylalanine on the enzyme activity, prevents the reduction of glycolysis and energy production caused by phenylalanine, probably by preventing the enzyme inhibition provoked by the amino acid. These results suggest that inhibition of brain PK activity by phenylalanine may be related to the diminution of glucose metabolism observed in the brain of phenylketonuric patients and may be one of the mechanisms responsible for the neurological dysfunction found in these patients.