Cerebrospinal fluid synaptic proteins as useful biomarkers in tyrosine hydroxylase deficiency.

Tyrosine hydroxylase (TH) deficiency is an inborn error of dopamine biosynthesis and a cause of early parkinsonism. Two clinical phenotypes have been described. Type "B": early onset severe encephalopathy; type "A": later onset, less severe and better response to L-dopa. We aimed to study the expression of several key dopaminergic and gabaergic synaptic proteins in the cerebrospinal fluid (CSF) of a series of patients with TH deficiency and their possible relation with the clinical phenotype and response to L-DOPA. Dopamine transporter (DAT), D2-receptor and vesicular monoamine transporter (VMAT2) were measured in the CSF of 10 subjects with TH deficiency by Western blot analysis. In 3 patients, data of pre- and post-treatment with L-DOPA were available, and in one of them, GABA vesicular transporter was determined. Results were compared to an age-matched control population. The concentration of D2-receptors in CSF was significantly higher in patients with TH deficiency than in controls. Similarly, DAT and vesicular monoamine transporter type 2 were up-regulated. Studies performed before L-DOPA, and on L-DOPA therapy showed a paradoxical response with D2 receptor expression increase as L-Dopa doses and homovanillic concentration gradually raised in a B phenotype patient. The opposite results were found in two patients with A phenotype. However, this is a very small sample, and further studies are needed to conclude robust differences between phenotypes. Synaptic proteins are detectable in the CSF and their quantification can be useful for understanding the pathophysiology of neurotransmitter defects and potentially to adjust and personalize treatments in the future.

Infantile parkinsonism and GABAergic hypotransmission in a patient with pyruvate carboxylase deficiency.

Pyruvate carboxylase deficiency is a rare metabolic disorder, with three different phenotypes. We aim to report the case of a newborn presenting the severe neonatal form of this deficiency (the B or "French" phenotype, hypokinesia and rigidity being the main features) and the results of the study of classic neurotransmitters involved in movement control. Hyperdopaminergic transmission (both in the cerebrospinal fluid and in the substantia nigra) and hypoGABAergic transmission (in the substantia nigra) were found. Both gamma-aminobutyric acid and dopamine markers were found coexisting in individual neurons of the substantia nigra. This is the first time this phenomenon has been reported in the literature. We discuss the possible role of GABAergic deficiency, its interaction with other neurotransmitters and its implication in neurotransmitter homeostasis. A better comprehension of that field would increase understanding of the pathophysiology of neurological symptoms and neurotransmitter plasticity.

[Amino acids in cerebrospinal fluid and plasma: its usefulness in the study of neuropaediatric diseases]. / Aminoacidos en liquido cefalorraquideo y plasma: utilidad en el estudio de las enfermedades neuropediatricas.

INTRODUCTION: Studying the amino acids in cerebrospinal fluid (CSF) is essential in the diagnosis of some neurological diseases and is an important aid in the diagnosis of others. No research has been published in the literature to prove the physiological relationship between the values of amino acids in CSF and plasma in the paediatric population. AIM: To define a set of ratios for amino acids in plasma and CSF in the paediatric population that can be used in daily clinical practice. PATIENTS AND METHODS: The aminograms in plasma and CSF of 105 patients with ages between 0 and 12 months were collected and analysed retrospectively. Aminograms with amino acid values that are considered to be normal according to the reference values of our laboratory were included in the sample. The quantitative analysis of amino acids was performed using high-resolution liquid chromatography and statistical analysis with the software application SPSS 19.0. RESULTS: The mean values, range and standard deviation of the amino acid concentrations in plasma and CSF, together with the CSF/plasma ratios, are reported. Significant correlations were found from 0.6 onwards between different neutral amino acids, above all in those with smaller molecular weights (Thr, Ser, Gly and Ala). CONCLUSIONS: The existence of significant correlations between the different neutral amino acids supports the idea that they share the same transporters in the blood-brain barrier. Standardising the amino acid ratios will make it possible to increase sensitivity in the detection of pathological values in plasma and CSF, to further knowledge of the pathophysiology of neurological diseases and perhaps to describe new aminoacidopathies.

Assessment of plasma ammonia and glutamine concentrations in urea cycle disorders.

OBJECTIVES: To analyze the association between ammonia and glutamine used for metabolic control in inherited urea cycle disorders (UCD) in a large series of patients. DESIGN AND METHODS: Paired plasma amino acid-ammonia data from 26 UCD patients were analyzed (n=921). RESULTS: Increased plasma glutamine values were consistently observed in UCD patients, despite normal plasma ammonia concentrations, especially for mitochondrial UCD. CONCLUSIONS: Further therapeutic efforts are probably needed to control increased glutamine values, considering their potentially neurotoxic effect.

Mutations in the urocanase gene UROC1 are associated with urocanic aciduria.

Urocanase is an enzyme in the histidine pathway encoded by the UROC1 gene. This report describes the first putative mutations, p.L70P and p.R450C, in the coding region of the UROC1 gene in a girl with urocanic aciduria presenting with mental retardation and intermittent ataxia. Computed (in silico) predictions, protein expression studies and enzyme activity assays suggest that none of the mutations can produce a fully functional enzyme. The p.L70P substitution, which probably implies the disruption of an alpha-helix in the N-terminus, would alter its properties and therefore, its function. The p.R450C change would render impossible any interaction between urocanase and its substrate and would loss its enzyme activity. Consequently, these studies suggest that both mutations could alter the correct activity of urocanase, which would explain the clinical and biochemical findings described in this patient.

Evaluation of CSF neurotransmitters and folate in 25 patients with Rett disorder and effects of treatment.

BACKGROUND: Rett disorder (RD) is a progressive neurodevelopmental entity caused by mutations in the MECP2 gene. It has been postulated that there are alterations in the levels of certain neurotransmitters and folate in the pathogenesis of this disease. Here we re-evaluated this hypothesis. PATIENTS AND METHODS: We evaluated CSF folate, biogenic amines and pterines in 25 RD patients. Treatment with oral folinic acid was started in those cases with low folate. Patients were clinically evaluated and videotaped up to 6 months after therapy. RESULTS: CSF folate was below the reference values in 32% of the patients. Six months after treatment no clinical improvement was observed. Three of the four patients with the R294X mutation had increased levels of a dopamine metabolite associated to a particular phenotype. Three patients had low levels of a serotonin metabolite. Two of them were treated with fluoxetine and one showed clinical improvement. No association was observed between CSF folate and these metabolites, after adjusting for the patients age and neopterin levels. CONCLUSION: Our results support that folinic acid supplementation has no significant effects on the course of the disease. We report discrete and novel neurotransmitter abnormalities that may contribute to the pathogenesis of RD highlighting the need for further studies on CSF neurotransmitters in clinically and genetically well characterized patients.

[Laboratory diagnosis of rare diseases]. / El laboratorio en el diagnóstico de las enfermedades raras.

Inborn errors of metabolism (IEM) are a group of diseases whose diagnosis is usually performed by quantification of several metabolites in biological fluids. The aim of this review is to report the role of the laboratory in IEM diagnosis, highlighting the methods available at present and their advantages and limitations. In conclusion, the huge number of recognized IEMs strongly advises the implementation of new high- output technologies in the laboratories devoted to IEM diagnosis. Although these technologies offer a high diagnostic ability, routine analyses are still very important, as well as consideration of several variables involved in biological sample collection and disease expression that may lead to misdiagnosis of IEMs.

Folate receptor autoantibodies and spinal fluid 5-methyltetrahydrofolate deficiency in Rett syndrome.

Rett syndrome was associated with low cerebrospinal fluid (CSF) 5-methyltetrahydrofolate (5MTHF) in 42-50% of European patients whereas approximately 93% of the patients from North-America had a normal CSF 5MTHF status. We determined the CSF folate status in Rett patients living in North- and South-Western Europe and measured serum folate receptor (FR) autoantibodies of the blocking type to explain the reduced folate transport across the choroid plexus. Irrespective of their MECP2 genotype and despite normal plasma folate values, 14 of 33 Rett patients (42%) had low CSF folate levels. Blocking FR autoantibodies were found in 8 of the Rett patients (24%), 6 of whom had low CSF folate levels. FR autoimmunity was primarily found within the group of Rett patients with low CSF folate status with a higher incidence in North-Western Europe. In Rett patients from North-America 74 of 76 girls had higher folate values in both serum and CSF than European patients. The food folate fortification in North-America may account for the higher folate levels and may prevent CFD in these Rett patients. FR autoimmunity occurred predominantly in Rett patients from North-Western Europe and may contribute to cerebral folate deficiency (CFD).

Secondary abnormalities of neurotransmitters in infants with neurological disorders.

Neurotransmitters are essential in young children for differentiation and neuronal growth of the developing nervous system. We aimed to identify possible factors related to secondary neurotransmitter abnormalities in pediatric patients with neurological disorders. We analyzed cerebrospinal fluid (CSF) and biogenic amine metabolites in 56 infants (33 males, 23 females; mean age 5.8mo [SD 4.1mo] range 1d-1y) with neurological disorders whose aetiology was initially unknown. Patients were classified into three clinical phenotypes: epileptic encephalopathy, severe motor impairment, and non-specific manifestations. All patients showed normal results for screening of inborn errors of metabolism. We report clinical, neuroimaging, and follow-up data. Among the patients studied, 10 had low homovanillic acid (HVA) levels and in four patients, 5-hydroxyindoleacetic acid (5-HIAA) was also reduced. Patients with neonatal onset had significantly lower levels of HVA than a comparison group. HVA deficiency was also associated with severe motor impairment and the final diagnosis related to neurodegenerative disorders. 5-HIAA values tended to be decreased in patients with brain cortical atrophy. The possibility of treating patients with L-Dopa and 5-hydroxytryptophan, in order to improve their neurological function and maturation, may be considered.

[Inborn errors of neurotransmitters in neuropaediatrics]. / Errores congénitos de los neurotransmisores en Neuropediatría.

AIMS: The aim of this work is to describe the clinical, biochemical and genetic characteristics of neurotransmitter diseases at the paediatric age, together with possible forms of treatment. We also sought to determine the diagnostic methodology of these disorders (collection and analysis of samples). DEVELOPMENT: These diseases essentially consist of a deficit of biogenic amines and alterations in GABA metabolism (gamma-aminobutyric acid). Disorders affecting the neurotransmission of biogenic amines often present in the form of hypokinesia, trunk hypotonia with increased limb tone, oculogyric crises, ptosis, faulty temperature regulation or abnormal movements. Defects in GABA metabolism give rise to epileptic encephalopathies and unspecific mental retardation, sometimes associated to signs of cerebellar dysfunction, convulsions and alterations in neuroimaging studies. Overall incidence of these diseases is low but they are unquestionably under-diagnosed, since they cannot be detected by conventional studies in plasma and urine, and require extraction and directed analysis of cerebrospinal fluid (CSF) for their detection. Additionally, the CSF study must be carried out in specific standardised conditions. Segawa's disease, or dopa-responsive dystonia, responds extremely well to therapy, whereas the other entities respond in varying ways to the different therapeutic alternatives. CONCLUSIONS: It is important for the paediatrician to know about these entities as a group of treatable neurometabolic diseases. Moreover, their detection would allow prenatal diagnosis in the vast majority of cases.

Cerebrospinal fluid concentrations of folate, biogenic amines and pterins in Rett syndrome: treatment with folinic acid.

BACKGROUND: Previous studies in Rett syndrome (RS) patients suggested various abnormalities in biogenic amines, pterins, and folate values in cerebrospinal fluid (CSF). Our aim was to analyse these metabolites in CSF of 16 RS patients (age range: 2 - 23 years). Biogenic amines, pterins, and 5-methyltetrahydrofolate were measured by HPLC with electrochemical and fluorescence detection. RESULTS: CSF values of 5-methyltetrahydrofolate were decreased in 8 out of 16 RS patients (average: 53.6 nmol/L; range: 19 - 92) when compared with our reference values (average: 74.6 nmol/L; range: 45 - 127). These eight patients had epilepsy, while 4 out of 16 RS patients who did not have epilepsy showed normal CSF 5-methyltetrahydrofolate concentrations. Values of biogenic amines or pterins were decreased in four of the patients with low values of 5-methyltetrahydrofolate. No correlation was observed between CSF values of 5-methyltetrahydrofolate and pterins, biogenic amines, or age. Supplementation with folinic acid was applied in six out of the eight patients with CSF 5-methyltetrahydrofolate deficiency. An improvement was noticed in all cases. CONCLUSIONS: An important percentage of RS patients showed 5-methyltetrahydrofolate concentrations under the reference values. Therefore, analysis of CSF 5-methyltetrahydrofolate seems advisable in RS, especially in patients with epilepsy and those resistant to antiepileptic drugs.

Platelet serotonin concentrations in PKU patients under dietary control and tetrahydrobiopterin treatment.

Tetrahydrobiopterin (BH4) supplementation has been applied in PKU treatment, resulting in successful control of blood phenylalanine (Phe) concentrations. We evaluated serotonin status in PKU patients under classical dietary treatment (n = 40) and in a group of 11 PKU patients under BH4 treatment, both during a 6-month period. Platelet serotonin values were significantly lower in PKU patients under dietary treatment when compared with controls. A negative correlation was observed between plasma Phe and platelet serotonin concentrations (r = -0.367, p = 0.017) in PKU patients. Platelet serotonin concentration increased significantly after both 1 and 6 months of BH4 therapy when compared with baseline conditions (Wilcoxon test: p = 0.013 and p = 0.021, respectively), while no differences were observed when comparing plasma Phe concentrations at the different points. Our results indicate that PKU patients under classical treatment have decreased platelet serotonin concentrations, probably owing to continued high Phe values, while BH4 supplementation restored platelet serotonin values.

[Pathogenetic mechanisms in phenylketonuria: disorders affecting the metabolism of neurotransmitters and the antioxidant system]. / Mecanismos de patogenia en la fenilcetonuria: alteraciones del metabolismo de los neurotransmisores y del sistema antioxidante.

AIM: To review the clinical and biochemical changes in neurotransmission and antioxidant system in phenylketonuric patients under dietary treatment. DEVELOPMENT: Phenylketonuria (PKU) is an inborn error of metabolism caused by decreased activity of the enzyme L-phenylalanine-4-mono-oxigenase that synthesizes tyrosine from phenylalanine. According to analytical data from PKU patients and to experimental studies in animal models, high phenylalanine values in plasma and tissues seem to be related with defective biosynthesis of neurotransmitter (mainly serotonin and dopamine) and impairment of antioxidant system. Despite dietary treatment, PKU patients usually present moderate hyperphenylalaninemia over the evolution of the disease that might cause clinical and biochemical abnormalities. CONCLUSIONS: Increased plasma phenylalanine concentrations and dietary treatment might be related with neurotransmitter and antioxidant system abnormalities in human phenylketonuria. These biochemical alterations might be involved in the physiopathology of PKU.