Preliminary results of PBA-loaded nanoparticles development and the effect on oxidative stress and neuroinflammation in rats submitted to a chemically induced chronic model of MSUD.

Maple syrup urine disease (MSUD) is a genetic disorder that leads the accumulation of branched-chain amino acids (BCAA) leucine (Leu), isoleucine, valine and metabolites. The symptomatology includes psychomotor delay and mental retardation. MSUD therapy comprises a lifelong protein strict diet with low BCAA levels and is well established that high concentrations of Leu and/or its ketoacid are associated with neurological symptoms. Recently, it was demonstrated that the phenylbutyrate (PBA) have the ability to decrease BCAA concentrations. This work aimed the development of lipid-based nanoparticles loaded with PBA, capable of targeting to the central nervous system in order to verify its action mechanisms on oxidative stress and cell death in brain of rats subjected to a MSUD chronic model. PBA-loaded nanoparticles treatment was effective in significantly decreasing BCAA concentration in plasma and Leu in the cerebral cortex of MSUD animals. Furthermore, PBA modulate the activity of catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase enzymes, as well as preventing the oxidative damage to lipid membranes and proteins. PBA was also able to decrease the glial fibrillary acidic protein concentrations and partially decreased the reactive species production and caspase-3 activity in MSUD rats. Taken together, the data indicate that the PBA-loaded nanoparticles could be an efficient adjuvant in the MSUD therapy, protecting against oxidative brain damage and neuroinflammation.

Utilization of blood spot testing for metabolic-genetic disorders in Honduras: is it time for newborn screening?

Honduran infant mortality (20/1000) has fallen below the Latin American newborn screening target rate (<30/1000). The authors report 2 Honduran maple syrup urine disease cases and a newborn screening pilot study. The first infant, diagnosed by plasma/urine testing in the U.S., prompted this study. Although marked clinical/radiological improvement occurred after treatment, moderate neurodevelopmental delays persist at 5 years. This 1-month, prospective study used blood spot specimens from hospitalized term Honduran neonates shipped overnight to South Carolina for routine newborn screening with electronic result submission to Honduras for follow-up. Of 88 consecutive neonates (mean age: 4.2 days, standard deviation: 4.2 days) tested, 24 (0.6%) of 3837 completed tests were positive. Another infant with maple syrup urine disease, diagnosed after study completion by blood spot testing, later died. The study findings indicate that collaborative blood spot testing aids in the diagnosis of Honduran metabolic-genetic disease. Newborn screening is now needed to diagnose and treat these diseases before morbidity/mortality develops.

Amino acids levels and lipid peroxidation in maple syrup urine disease patients.

OBJECTIVE: In the present study we correlated the amino acids, branched-chain alpha-keto acids and alpha-hydroxy acids levels with the thiobarbituric acid-reactive species (TBARS) measurement, a lipid peroxidation parameter, in plasma from treated MSUD patients in order to examine whether these accumulated metabolites could be associated to the oxidative stress present in MSUD. DESIGN AND METHODS: TBARS, amino acids, branched-chain alpha-keto acids and alpha-hydroxy acids concentrations were measured in plasma samples from treated MSUD patients. RESULTS: We verified that plasma TBARS was increased, whereas tryptophan and methionine concentrations were significantly reduced. Furthermore TBARS measurement was inversely correlated to methionine and tryptophan levels. CONCLUSIONS: Considering that methionine and tryptophan have antioxidant activities, the data suggest that the imbalance of these amino acids may be involved with lipid peroxidation in MSUD.

Maple syrup urine disease in treated patients: biochemical and oxidative stress profiles.

OBJECTIVE: The objective of this study was to evaluate and correlate the biochemical and oxidative stress profiles in MSUD patients during the dietary treatment. DESIGN AND METHODS: Plasma samples from treated MSUD patients were used to evaluate the biochemical profile and oxidative stress parameters. RESULTS: It was observed that glucose, total cholesterol, albumin and creatinine are reduced and that aspartate aminotransferase and lactate dehydrogenase activities are increased in plasma from MSUD patients under treatment. Besides, it was verified an increase of thiobarbituric acid-reactive species (TBARS) and a decrease of total antioxidant reactivity (TAR). CONCLUSIONS: Our results suggest that oxidative stress occurs in treated MSUD patients and that dietary treatment and clinical conditions associated to the disease can lead to biochemical alterations in these patients.

Oxidative stress in plasma from maple syrup urine disease patients during treatment.

Maple Syrup Urine Disease (MSUD) is an autosomal recessive metabolic disorder caused by a deficiency of branched-chain alpha-keto acid dehydrogenase complex activity leading to accumulation of the branched-chain amino acids leucine, isoleucine and valine and their corresponding branched-chain alpha-keto acids. Affected patients usually present hypoglycemia, ketoacidosis, convulsions, poor feeding, coma, psychomotor delay and mental retardation. Considering that the pathophysiology of MSUD is still poorly understood, in this study we evaluated some parameters of oxidative stress, namely thiobarbituric acid-reactive substances (TBARS), total antioxidant reactivity (TAR) and total antioxidant status (TAS) in plasma from treated MSUD patients presenting high and low plasma leucine levels. We verified a significant increase of TBARS (lipid peroxidation) and a decrease of TAR (capacity to rapidly react with free radicals) in plasma from treated MSUD patients with low and with high plasma levels of leucine compared to the control group. It was also verified that TAS (quantity of tissue antioxidants) was not altered in plasma from treated MSUD patients with low and high blood leucine levels. Finally, we found no correlation between leucine, valine and isoleucine levels with the various parameters of oxidative stress. These results are indicative that increased lipid oxidative damage and decreased antioxidant defenses occur in plasma of MSUD patients and that the accumulating branched-chain amino acids are probably not directly associated to oxidative stress in this disorder.

Erythrocyte glutathione peroxidase activity and plasma selenium concentration are reduced in maple syrup urine disease patients during treatment.

Maple syrup urine disease (MSUD) is an inherited disorder caused by a deficiency of the branched-chain alpha-keto acid dehydrogenase complex activity. In the present study we evaluated selenium levels in plasma from MSUD patients at diagnosis and under treatment and the activities of glutathione peroxidase, catalase and superoxide dismutase in erythrocytes from treated patients. We verified that MSUD patients present a significant selenium deficiency at diagnosis, which becomes more pronounced during treatment, as well as a decrease of erythrocyte glutathione peroxidase activity during treatment. In contrast, erythrocyte catalase and superoxide dismutase activities were not altered in these patients. Our present results suggest that the reduction of an important antioxidant enzyme activity may be partially involved in the pathomechanisms of this disorder and that plasma selenium levels must be corrected through dietary supplementation in MSUD patients.

Enfermedad de orina con olor a jarabe de arce: enfrentamiento de un caso / Maple syrup urine disease: case management

Maple syrup urine disease (MSUD) is an amino acidopathy secondary to a catabolic defect of branched amino acids (aa) valine, isoleucine and leucine (VIL). The accumulation of these elements and their keto acids in body fluids leads to encephalopathy and progressive neurological degeneration in untreated children (2-4-5-6)). The case of a newborn is analysed presenting with a classic form of this disease, its clinical evolution with metabolic and neurological involvement, diagnosis and intrahospital care till discharge.

Reduction of large neutral amino acid levels in plasma and brain of hyperleucinemic rats.

Neurological dysfunction is common in patients with maple syrup urine disease (MSUD). However, the mechanisms underlying the neuropathology of this disorder are poorly known. In the present study we investigated the effect of acute hyperleucinemia on plasma and brain concentrations of amino acids. Fifteen-day-old rats were injected subcutaneously with 6 micromol L-leucine per gram body weight. Controls received saline in the same volumes. The animals were sacrificed 30--120 min after injection, blood was collected and their brain rapidly removed and homogenized. The amino acid concentrations were determined by HPLC using orthophtaldialdehyde for derivatization and fluorescence for detection. The results showed significant reductions of the large neutral amino acids (LNAA) L-phenylalanine, L-tyrosine, L-isoleucine, L-valine and L-methionine, as well as L-alanine, L-serine and L-histidine in plasma and of L-phenylalanine, L-isoleucine, L-valine and L-methionine in brain, as compared to controls. In vitro experiments using brain slices to study the influence of leucine on amino acid transport and protein synthesis were also carried out. L-Leucine strongly inhibited [14C]-L-phenylalanine transport into brain, as well as the incorporation of the [14C]-amino acid mixture, [14C]-L-phenylalanine and [14C]-L-lysine into the brain proteins. Although additional studies are necessary to evaluate the importance of these effects for MSUD, considering previous findings of reduced levels of LNAA in plasma and CSF of MSUD patients during crises, it may be speculated that a decrease of essential amino acids in brain may lead to reduction of protein and neurotransmiter synthesis in this disorder.

Reduction of large neutral amino acid concentrations in plasma and CSF of patients with maple syrup urine disease during crises.

Neurological dysfunction is common in patients with maple syrup urine disease (MSUD). However, the mechanisms underlying the neuropathology of this disorder are poorly understood. We determined the concentrations of all amino acids in plasma of patients with MSUD during crises (with severe CNS symptoms) and after recovery in the hope of detecting possible alterations of these levels during metabolic decompensation. Blood samples obtained from 11 children with MSUD aged 1 month to 7 years and from 10 age-matched controls (5 months to 6 years) with no evidence of metabolic disease were examined for their amino acid content by high-performance liquid chromatography. We observed that leucine, isoleucine and valine concentrations were respectively 30, 9 and 3 times higher than normal values, whereas the concentrations of the large neutral amino acids (LNAA) phenylalanine, tyrosine, tryptophan and methionine were significantly lower during metabolic decompensation as compared to the controls. In addition, concentrations of leucine, but not of valine or isoleucine, were inversely related to the LNAA concentrations in plasma. The concentrations of these amino acids in plasma returned to normal values when patients were clinically well. CSF amino acid concentrations also showed decreased amounts of LNAA and increased concentrations of branched-chain amino acids. It is possible that the decrease in plasma concentrations of LNAA may lead to a deficit of these essential amino acids in the brain as well as of their products such as proteins and neurotransmitters, a fact that might be related to the neurological dysfunction of MSUD.

Chronic early leucine administration induces behavioral deficits in rats.

Sustained levels of leucine comparable to those of human Maple Syrup Urine Disease (MSUD) were achieved in blood and brain of rats by subcutaneous leucine administration twice a day from the 6th to the 28th day of life. Control rats were treated with saline in the same volumes. Behavioral studies using aversive and nonaversive tasks were performed during adult age. Chronic early leucine treatment impaired acquisition of a two-way shuttle avoidance task and altered habituation to an open field. Our results suggest that early postnatal leucine administration induces long-lasting behavioral deficits.

Continuous venovenous hemofiltration in the management of acute decompensation in inborn errors of metabolism.

Continuous venovenous hemofiltration was used to treat two neonates, one with maple syrup urine disease and the other with an inborn error of long-chain fatty acid oxidation. The latter infant had hypoglycemia, hyperammonemia and lactic acidosis. In both cases, acceptable biochemical control was achieved within 8 hours. This therapy offers the potential to overcome acute crises rapidly in a wide range of inborn errors of intermediary metabolism.