Changes in branched-chain amino acids in an infant with maple syrup urine disease during perioperative pediatric liver transplant: A case report.

An 11-month-old female infant diagnosed with classic subtype IB maple syrup urine disease underwent living donor liver transplantation. Blood samples for plasma amino acid analysis were collected during the three phases of the operation. Despite the perioperative prophylactic administration of 12.5% hypertonic dextrose solution with insulin and a 20% intralipid emulsion, the blood levels of the branched-chain amino acids increased dramatically during surgery, consistent with an acute intraoperative metabolic decompensation. However, these blood levels normalized soon after liver transplantation with an excellent outcome. We suggest that the occurrence of an intraoperative metabolic crisis during liver transplantation is not necessarily a sign of graft failure.

Metabolic crisis in maple syrup urine disease: an unusual complication of a rare disease: a case report.

A 19-year-old woman with known maple syrup urine disease presented to hospital with metabolic crisis in the setting of influenza type A infection and intractable vomiting, rapidly progressing to acute cerebral oedema manifesting as refractory seizures and decreased level of consciousness needing emergency intubation and mechanical ventilation, continuous veno-venous haemodiafiltration and thiopentone coma. A computed tomography scan and magnetic resonance imaging of the brain demonstrated classic signs of cerebral oedema secondary to a metabolic crisis from the metabolic disorder. Her management posed multiple challenges to all teams involved due to lack of familiarity and experience in managing this clinical scenario in the adult intensive care setting.

Memantine Improves Memory and Neurochemical Damage in a Model of Maple Syrup Urine Disease.

Maple Syrup Urine Disease (MSUD) is a metabolic disease characterized by the accumulation of branched-chain amino acids (BCAA) in different tissues due to a deficit in the branched-chain alpha-ketoacid dehydrogenase complex. The most common symptoms are poor feeding, psychomotor delay, and neurological damage. However, dietary therapy is not effective. Studies have demonstrated that memantine improves neurological damage in neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. Therefore, we hypothesize that memantine, an NMDA receptor antagonist can ameliorate the effects elicited by BCAA in an MSUD animal model. For this, we organized the rats into four groups: control group (1), MSUD group (2), memantine group (3), and MSUD + memantine group (4). Animals were exposed to the MSUD model by the administration of BCAA (15.8 µL/g) (groups 2 and 4) or saline solution (0.9%) (groups 1 and 3) and treated with water or memantine (5 mg/kg) (groups 3 and 4). Our results showed that BCAA administration induced memory alterations, and changes in the levels of acetylcholine in the cerebral cortex. Furthermore, induction of oxidative damage and alterations in antioxidant enzyme activities along with an increase in pro-inflammatory cytokines were verified in the cerebral cortex. Thus, memantine treatment prevented the alterations in memory, acetylcholinesterase activity, 2',7'-Dichlorofluorescein oxidation, thiobarbituric acid reactive substances levels, sulfhydryl content, and inflammation. These findings suggest that memantine can improve the pathomechanisms observed in the MSUD model, and may improve oxidative stress, inflammation, and behavior alterations.

Branched-Chain Amino Acid Assembly into Amyloid-like Fibrils Provides a New Paradigm for Maple Syrup Urine Disease Pathology.

Inborn error of metabolism disorders (IEMs) are a family of diseases resulting from single-gene mutations that lead to the accumulation of metabolites that are usually toxic or interfere with normal cell function. The etiological link between metabolic alteration and the symptoms of IEMs is still elusive. Several metabolites, which accumulate in IEMs, were shown to self-assemble to form ordered structures. These structures display the same biophysical, biochemical, and biological characteristics as proteinaceous amyloid fibrils. Here, we have demonstrated, for the first time, the ability of each of the branched-chain amino acids (BCAAs) that accumulate in maple syrup urine disease (MSUD) to self-assemble into amyloid-like fibrils depicted by characteristic morphology, binding to indicative amyloid-specific dyes and dose-dependent cytotoxicity by a late apoptosis mechanism. We could also detect the presence of the assemblies in living cells. In addition, by employing several in vitro techniques, we demonstrated the ability of known polyphenols to inhibit the formation of the BCAA fibrils. Our study implies that BCAAs possess a pathological role in MSUD, extends the paradigm-shifting concept regarding the toxicity of metabolite amyloid-like structures, and suggests new pathological targets that may lead to highly needed novel therapeutic opportunities for this orphan disease.

Treatment of maple syrup urine disease: Benefits, risks, and challenges of liver transplantation.

Maple syrup urine disease (MSUD) is caused by a deficiency in the activity of the branched-chain α-ketoacid dehydrogenase (BCKD) complex, promoting the accumulation of the branched-chain amino acids (BCAA) leucine, isoleucine, and valine, as well as their respective α-keto acids. MSUD is an autosomal recessive hereditary metabolic disorder characterized by ketoacidosis, ataxia, coma, and mental and psychomotor retardation. The mechanisms involved in the brain damage caused by MSUD are not fully understood. Early diagnosis and treatment, as well as proper control of metabolic decompensation crises, are crucial for patients' survival and for a better prognosis. The recommended treatment consists of a high-calorie diet with restricted protein intake and specific formulas containing essential amino acids, except those accumulated in MSUD. This treatment will be maintained throughout life, being adjusted according to the patients' nutritional needs and BCAA concentration. Because dietary treatment may not be sufficient to prevent neurological damage in MSUD patients, other therapeutic strategies have been studied, including liver transplantation. With transplantation, it is possible to obtain an increase of about 10% of the normal BCKD in the body, an amount sufficient to maintain amino acid homeostasis and reduce metabolic decompensation crises. However, the experience related to this practice is very limited when considering the shortage of liver for transplantation and the risks related to the surgical procedure and immunosuppression. Thus, the purpose of this review is to survey the benefits, risks, and challenges of liver transplantation in the treatment of MSUD.

Melatonin improves behavioral parameters and oxidative stress in zebrafish submitted to a leucine-induced MSUD protocol.

Maple syrup urine disease (MSUD) is an inherited metabolic disorder caused by a deficiency in branched-chain alpha-ketoacid dehydrogenase complex (BCKAC). The treatment is a standard therapy based on a protein-restricted diet with low branched-chain amino acids (BCAA) content to reduce plasma levels and, consequently, the effects of accumulating their metabolites, mainly in the central nervous system. Although the benefits of dietary therapy for MSUD are undeniable, natural protein restriction may increase the risk of nutritional deficiencies, resulting in a low total antioxidant status that can predispose and contribute to oxidative stress. As MSUD is related to redox and energy imbalance, melatonin can be an important adjuvant treatment. Melatonin directly scavenges the hydroxy radical, peroxyl radical, nitrite anion, and singlet oxygen and indirectly induces antioxidant enzyme production. Therefore, this study assesses the role of melatonin treatment on oxidative stress in brain tissue and behavior parameters of zebrafish (Danio rerio) exposed to two concentrations of leucine-induced MSUD: leucine 2 mM and 5mM; and treated with 100 nM of melatonin. Oxidative stress was assessed through oxidative damage (TBARS, DCF, and sulfhydryl content) and antioxidant enzyme activity (SOD and CAT). Melatonin treatment improved redox imbalance with reduced TBARS levels, increased SOD activity, and normalized CAT activity to baseline. Behavior was analyzed with novel object recognition test. Animals exposed to leucine improved object recognition due to melatonin treatment. With the above, we can suggest that melatonin supplementation can protect neurologic oxidative stress, protecting leucine-induced behavior alterations such as memory impairment.

Acute effects of intracerebroventricular administration of α-ketoisocaproic acid in young rats on inflammatory parameters.

Maple Syrup Urine Disease (MSUD) is an autosomal recessive inborn error of metabolism (IEM), responsible for the accumulation of the branched-chain amino acids (BCAA) leucine, isoleucine, and valine, in addition to their α-keto acids α-ketoisocaproic acid (KIC), α-keto-ß-methylvaleric acid (KMV), and α-ketoisovaleric acid (KIV) in the plasma and urine of patients. This process occurs due to a partial or total blockage of the dehydrogenase enzyme activity of branched-chain α-keto acids. Oxidative stress and inflammation are conditions commonly observed on IEM, and the inflammatory response may play an essential role in the pathophysiology of MSUD. We aimed to investigate the acute effect of intracerebroventricular (ICV) administration of KIC on inflammatory parameters in young Wistar rats. For this, sixteen 30-day-old male Wistar rats receive ICV microinjection with 8 µmol KIC. Sixty minutes later, the animals were euthanized, and the cerebral cortex, hippocampus, and striatum structures were collected to assess the levels of pro-inflammatory cytokines (INF-γ; TNF-α, IL-1ß). The acute ICV administration of KIC increased INF-γ levels in the cerebral cortex and reduced the levels of INF-γ and TNF-α in the hippocampus. There was no difference in IL-1ß levels. KIC was related to changes in the levels of pro-inflammatory cytokines in the brain of rats. However, the inflammatory mechanisms involved in MSUD are poorly understood. Thus, studies that aim to unravel the neuroinflammation in this pathology are essential to understand the pathophysiology of this IEM.

Branched-chain amino acids (BCAA) administration increases autophagy and the autophagic pathway in brain tissue of rats submitted to a Maple Syrup Urine Disease (MSUD) protocol.

Maple Syrup Urine Disease (MSUD) is an inborn error of metabolism (EIM) biochemically characterized by the tissue accumulation of branched-chain amino acids (BCAA) and their branched-chain alpha-keto acids. The mechanisms by which BCAA and their branched-chain alpha-keto acids lead to the neurological damage observed in MSUD are poorly understood. Mounting evidence has demonstrated that BCAA induce the overproduction of reactive oxygen species, which may modulate several important signaling pathways necessary for cellular homeostasis maintenance, such as autophagy. Taking this into account, we evaluated the effects of BCAA on the autophagic pathway in brain structures of rats submitted to the administration of these amino acids (animal model of MSUD). Our findings showed that BCAA significantly increased the levels of Beclin-1, ATG7, and ATG5 in the cerebral cortex of rats. In addition, BCAA augmented ATG12 levels in the striatum and ATG5 and LC3 I-II in the hippocampus. Therefore, our work demonstrates that the administration of BCAA increases autophagy and autophagic cell death, possibly mediated by the elevated levels of reactive species generated by BCAA.

Neonatal maple syrup urine disease case report and literature review.

RATIONALE: The main clinical symptoms of maple syrup urine disease (MSUD) are dehydration, acidosis, nervous system symptoms and intellectual disability. The brain imaging findings were mainly caused by cytotoxic edema. The lesions usually occur at the site consistent with the myelination process of normal neonates. The distribution is mostly symmetric, and the diffusion is obviously limited. PATIENT CONCERNS: Herein, we report a rare case of an 8-day-old female patient who presented with abnormal symptoms, such as difficulty eating, convulsions, slow reaction, difficulty in correcting hypoglycemia and severe metabolic disorders. Brain magnetic resonance imaging (MRI) revealed abnormal signal intensity mainly involving the brainstem, cervical spinal cord, bilateral cerebellar hemispheres, basal ganglia, thalamus, precentral gyrus, and postcentral gyrus with characteristic hyperintensity on diffusion-weighted imaging (DWI) sequence. MSUD is rarely reported, while cervical spinal cord involvement is extremely rare. DIAGNOSES: Blood tandem mass spectrometry, urine organic acid detection, and genetic disease overall genetic tests were performed to further confirm the diagnosis of MSUD. INTERVENTIONS: Under general anesthesia, she underwent open surgical procedures for liver transplantation. OUTCOMES: The child was in a stable condition after liver transplantation, and the diet was not restricted. LESSONS: MSUD in neonates is rare. Our case report and literature review was aim to describe the clinic and imaging characteristics of it, and highlight physicians must be aware of this entity in newborns so as to reduce misdiagnosis due to unfamiliarity.

Quantification of Branched-Chain Amino Acids in Plasma by High-Performance Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS).

Branched-chain amino acids (BCAA), including valine, alloisoleucine, isoleucine, and leucine, play significant roles in a number of metabolic pathways in the body. Deficiency in branched-chain ketoacid dehydrogenase complex, an enzyme required for metabolism of those amino acids, will lead to elevation and accumulation of BCAA and ketoacids in bodily fluids. This results in maple syrup urine disease (MSUD), a condition estimated to affect 1 in 100,000-300,000 births. If MSUD is not diagnosed in the first few days of life, progression of this disease can lead to intellectual disability, coma, irreversible brain damage, seizures, or even death. If diagnosed early, MSUD can be managed by monitoring the blood concentrations of BCAA and adjusting the patient's dietary intake accordingly. Therefore, it is critical to have a rapid, accurate, and reliable BCAA assay for confirmation of MSUD in newborns as well as routine monitoring of MSUD patients. Here, we describe a high-performance liquid chromatography tandem mass spectrometry (LC-MS/MS) method for BCAA measurement which requires only 20 µL of plasma. The sample preparation does not require derivatization and only involves protein precipitation with LC/MS-grade methanol, which contains leucine(13C6;15N), isoleucine(13C6;15N), and valine(13C5;15N) as the internal standards. The final sample extracts do not require dry-down and reconstitution and are readily compatible with the liquid chromatography (LC) method. BCAA are separated using the isocratic gradient method on a mixed-mode Intrada column. Multiple-reaction monitoring (MRM) mode is used for MS/MS detection to monitor the parent-to-daughter transitions m/z 132.2 to 86.4 for leucine, isoleucine, and alloisoleucine; m/z 118.2 to 72.4 for valine; m/z 139.2 to 92.4 for leucine(13C6;15N) and isoleucine(13C6;15N); and m/z 124.2 to 77.4 for valine(13C5;15N).

Exposure to leucine alters glutamate levels and leads to memory and social impairment in zebrafish.

Maple Syrup Urine Disease (MSUD) is a metabolic disorder characterized by high levels in blood and urine of branched-chain amino acids leucine, isoleucine, and valine and their alpha-ketoacids, by a partial or total blockade in the activity of branched-chain complex alpha-keto acids dehydrogenase. The main symptoms in MSUD occur in the central nervous system, including cognitive deficits, locomotor, poor feeding, seizures, psychomotor delay, and mental retardation, but the mechanisms of neurotoxicity and behavior alteration due to this disease are poorly understood, thus this study aimed at showing the effects of leucine exposure on glutamate levels and behavior in zebrafish. For this, we analyzed the behavior using the social preference test and novel object recognition test, moreover, we analyse the glutamate levels and uptake using scintillation and high-performance liquid chromatography methods. Our results demonstrated a decrease in glutamate levels and uptake, accompanied by memory and social impairment. In conclusion, these results suggest that alterations in glutamate levels can be associated with behavior impairment, however, more studies are necessary to understand the mechanisms for brain damage in MSUD.

Pathophysiology of maple syrup urine disease: Focus on the neurotoxic role of the accumulated branched-chain amino acids and branched-chain α-keto acids.

Maple syrup urine disease (MSUD) is an autosomal recessive neurometabolic disorder caused by severe deficiency of branched-chain α-keto acid dehydrogenase complex activity, which catalyzes the oxidative decarboxylation of the branched-chain α-keto acids (BCKA). The metabolic blockage results in tissue accumulation and high urinary excretion of the branched-chain amino acids (BCAA) leucine, isoleucine and valine, as well as alloisoleucine, and their respective BCKA α-ketoisocaproic (α-KIC), α-ketoisovaleric and α-keto-ß-methylvaleric acids. Affected patients usually manifest acute episodes of encephalopathy associated with seizures, coma and life-threatening cerebral edema in the first weeks of life, which is followed by progressive neurological deterioration with motor delay, ataxia, intellectual disability and psychiatric symptoms. The pathophysiology of the brain damage in MSUD has been mainly focused on brain amino acid imbalance leading to deficient cerebral protein and neurotransmitter synthesis. However, the acute episodes of severe neurological symptoms accompanied by large increases of BCKA/BCAA levels suggest neurotoxic actions of these compounds. In this particular, mounting evidence from humans and animal models support an important role of particularly leucine and α-KIC on the pathogenesis of the brain injury in MSUD. In this review we will present the current knowledge of the major mechanisms presumably involved in MSUD neuropathology and highlight the neurotoxic properties of the BCAA and BCKA, disturbing brain bioenergetics and redox homeostasis, besides inducing neuroinflammation. We suggest that these pathomechanisms may contribute to the neurological sequelae of MSUD patients and hopefully allow the design of novel therapeutic strategies, including antioxidant and bioenergetics stimulating drugs targeting the mitochondria.

Coadministration of tianeptine alters behavioral parameters and levels of neurotrophins in a chronic model of Maple Syrup Urine disease.

Maple Syrup Urine Disease (MSUD) is caused by the deficiency in the activity of the branched-chain α-ketoacid dehydrogenase complex (BCKDC), resulting in the accumulation of the branched-chain amino acids (BCAA) leucine, isoleucine, and valine, and their respective branched-chain α-keto acids. Patients with MSUD are at high risk of developing chronic neuropsychiatric disorders; however, the pathophysiology of brain damage in these patients remains unclear. We hypothesize that MSUD can cause depressive symptoms in patients. To test our hypothesis, Wistar rats were submitted to the BCAA and tianeptine (antidepressant) administration for 21 days, starting seven days postnatal. Depression-like symptoms were assessed by testing for anhedonia and forced swimming after treatments. After the last test, the brain structures were dissected for the evaluation of neutrophins. We demonstrate that chronic BCAA administration induced depressive-like behavior, increased BDNF levels, and decreased NGF levels, suggesting a relationship between BCAA toxicity and brain damage, as observed in patients with MSUD. However, the administration of tianeptine was effective in preventing behavioral changes and restoring neurotrophins levels.

Exposure to leucine induces oxidative stress in the brain of zebrafish.

Maple Syrup Urine Disease (MSUD) is an autosomal recessive inherited disorder caused by a deficiency in the activity of the branched-chain alpha-ketoacid dehydrogenase complex leading to the accumulation of branched-chain amino acids (BCAA) leucine, isoleucine, and valine and their respective branched-chain α-ketoacids and corresponding hydroxy acids. Considering that Danio rerio, known as zebrafish, has been widely used as an experimental model in several research areas because it has favorable characteristics that complement other experimental models, this study aimed to evaluate oxidative stress parameters in zebrafish exposed to high levels of leucine (2 mM and 5 mM), in a model similar of MSUD. Twenty-four hours after exposure, the animals were euthanized, and the brain content dissected for analysis of oxidative stress parameters: thiobarbituric acid reactive substances (TBARS), 2',7'-dichlorofluorescein oxidation assay (DCF); content of sulfhydryl, and superoxide dismutase (SOD) and catalase (CAT) activities. Animals exposed to 2 mM and 5 mM leucine showed an increase in the measurement of TBARS and decreased sulfhydryl content. There were no significant changes in DCF oxidation. In addition, animals exposed to 2 mM and 5 mM leucine were found to have decreased SOD activity and increased CAT activity. Based on these results, exposure of zebrafish to high doses of leucine can act as a promising animal model for MSUD, providing a better understanding of the toxicity profile of leucine exposure and its use in future investigations and strategies related to the pathophysiology of MSUD.

A Gain-of-Function Mutation on BCKDK Gene and Its Possible Pathogenic Role in Branched-Chain Amino Acid Metabolism.

BCKDK is an important key regulator of branched-chain ketoacid dehydrogenase complex activity by phosphorylating and so inactivating branched-chain ketoacid dehydrogenases, the rate-limiting enzyme of the branched-chain amino acid metabolism. We identified, by whole exome-sequencing analysis, the p.His162Gln variant of the BCKDK gene in a neonate, picked up by newborn screening, with a biochemical phenotype of a mild form of maple syrup urine disease (MSUD). The same biochemical and genetic picture was present in the father. Computational analysis of the mutation was performed to better understand its role. Extensive atomistic molecular dynamics simulations showed that the described mutation leads to a conformational change of the BCKDK protein, which reduces the effect of inhibitory binding bound to the protein itself, resulting in its increased activity with subsequent inactivation of BCKDC and increased plasmatic branched-chain amino acid levels. Our study describes the first evidence of the involvement of the BCKDK gene in a mild form of MSUD. Although further data are needed to elucidate the clinical relevance of the phenotype caused by this variant, awareness of this regulatory activation of BCKDK is very important, especially in newborn screening data interpretation.

Metabolic Control and "Ideal" Outcomes in Liver Transplantation for Maple Syrup Urine Disease.

OBJECTIVES: To assess outcomes following liver transplantation for maple syrup urine disease by determining attainment and sustainability of metabolic control and apply an "ideal" outcome composite in long-term survivors. STUDY DESIGN: A single center, retrospective review collected clinical data including branched-chain amino acid (leucine, isoleucine, and valine) levels following liver transplant and determined achievement of an ideal long-term outcome profile of a first allograft stable on immunosuppression monotherapy, normal growth, and absence of common transplant-related sequelae. RESULTS: Of 77 patients meeting inclusion criteria identified, 23 were long-term (≥10-year) survivors and were additionally assessed for ideal outcome attainment. Patient and graft survival were 100% and 99%, respectively, and all patients were on an unrestricted protein intake diet. Although significant variation was noted in mean isoleucine (P < .01) and leucine (P < .05) levels postliver transplantation, no difference was seen in valine (P = .29) and overall clinical impact was likely negligible as metabolic stability was achieved and sustained beyond 3 years postliver transplantation and no metabolic crises were identified. Of 23 long-term survivors with available data, 9 (39%) achieved all composite metrics determined to define "ideal" outcomes in pediatric postliver transplantation populations. CONCLUSIONS: Liver transplant enables long-term metabolic stability for patients with maple syrup urine disease. A combination of experience and improvement in both pre- and postliver transplantation care has enabled excellent survival and minimal comorbidities following transplant.

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.

Whole-body metabolic fate of branched-chain amino acids.

Oxidation of branched-chain amino acids (BCAAs) is tightly regulated in mammals. We review here the distribution and regulation of whole-body BCAA oxidation. Phosphorylation and dephosphorylation of the rate-limiting enzyme, branched-chain α-ketoacid dehydrogenase complex directly regulates BCAA oxidation, and various other indirect mechanisms of regulation also exist. Most tissues throughout the body are capable of BCAA oxidation, and the flux of oxidative BCAA disposal in each tissue is influenced by three key factors: 1. tissue-specific preference for BCAA oxidation relative to other fuels, 2. the overall oxidative activity of mitochondria within a tissue, and 3. total tissue mass. Perturbations in BCAA oxidation have been implicated in many disease contexts, underscoring the importance of BCAA homeostasis in overall health.

The metabolic effect of α-ketoisocaproic acid: in vivo and in vitro studies.

Maple syrup urine disease (MSUD) is characterized by a deficiency in the mitochondrial branched-chain α-keto acid dehydrogenase complex activity and, consequently, accumulation of the branched-chain amino acids and their respective branched-chain α-keto acids in fluids and the tissue. MSUD clinical symptoms include neurological alterations. KIC is considered one of the significant neurotoxic metabolites since its increased plasma concentrations are associated with neurological symptoms. We evaluated the effect of KIC intracerebroventricular (ICV) injection in hippocampal mitochondria function in rats. We also investigated the impact of KIC in cells' metabolic activity (using MTT assay) and reactive species (RS) production in HT-22 cells. For this, thirty-day-old male rats were bilaterally ICV injected with KIC or aCSF. Thus, 1 hour after the administration, animals were euthanized, and the hippocampus was harvested for measured the activities of mitochondrial respiratory chain enzymes and RS production. Furthermore, HT-22 cells were incubated with KIC (1-10 mM) in 6, 12, and 24 h. Mitochondrial complexes activities were reduced, and the formation of RS was increased in the hippocampus of rats after KIC administration. Moreover, KIC reduced the cells' metabolic ability to reduce MTT and increased RS production in hippocampal neurons. Impairment in hippocampal mitochondrial function seems to be involved in the neurotoxicity induced by KIC.

Administration of branched-chain amino acids alters epigenetic regulatory enzymes in an animal model of Maple Syrup Urine Disease.

Maple Syrup Urine Disease (MSUD) is an autosomal recessive inherited disorder that affects the activity of the branched-chainα-keto acid dehydrogenase complex (BCDK). This deficiency on BCDK complex results in the accumulation of branched-chain amino acids (BCAA) leucine, isoleucine, valine, and their corresponding α-keto acids. Epigenetic changes can negatively affect the metabolism of BCAA. These changes are catalyzed by the epigenetic regulatory enzymes, e.g., DNA methyltransferase (DNMT), histone deacetylases (HDAC), and histone acetyltransferases (HAT). However, the impacts of BCAA administration on the activity of epigenetic regulatory enzymes in the brain of MSUD patients are still unknown. In this study, we aimed to demonstrate the impact of BCAA administration on the activity of DNMT, HDAC, and HAT in the brain structures of infant rats, an animal model of MSUD. For that, we administered a BCAA pool to infant rats for 21 days. We demonstrated that BCAA administration significantly increased the DNMT and HDAC activities in the hippocampus and striatum, but not in the cerebral cortex of MSUD infant rats. A positive correlation was observed between HDAC and DNMT activities in the hippocampus and striatum of animals exposed to BCAA injections. Our results showed that the BCAA administration could modulate epigenetic regulatory enzymes, mainly DNMT and HDAC, in the brains of infant rats. Therefore, we suggest that the increase in the activity of DNMT and HDAC in the hippocampus and striatum could partially explain the neurological impairments presented in animal models of MSUD.