A leaky splicing mutation in NFU1 is associated with a particular biochemical phenotype. Consequences for the diagnosis.

Mutations in NFU1 were recently identified in patients with fatal encephalopathy. NFU1 is an iron-sulfur cluster protein necessary for the activity of the mitochondrial respiratory chain complexes I-II and the synthesis of lipoic acid. We report two NFU1 compound heterozygous individuals with normal complex I and lipoic acid-dependent enzymatic activities and low, but detectable, levels of lipoylated proteins. We demonstrated a leaky splicing regulation due to a splice site mutation (c.545+5G>A) that produces small amounts of wild type NFU1 mRNA that might result in enough protein to partially lipoylate and restore the activity of lipoic acid-dependent enzymes and the assembly and activity of complex I. These results allowed us to gain insights into the molecular basis underlying this disease and should be considered for the diagnosis of NFU1 patients.

Safety of ornithine phenylacetate in cirrhotic decompensated patients: an open-label, dose-escalating, single-cohort study.

AIMS: Confirm in patients with cirrhosis and gastrointestinal bleeding the safety of ornithine phenylacetate (OP) and assess the pharmacokinetic profile of OP and its effects on plasma ammonia. BACKGROUND: OP is a drug that has shown experimentally to decrease hyperammonemia and improve hepatic encephalopathy. OP is safe in healthy subjects and in stable patients with cirrhosis, but there are no data in decompensated cirrhosis. METHODS: We performed a study to assess safety and tolerance of OP in cirrhotic patients after an episode of upper gastrointestinal bleeding.Ten patients were included within 24 hours of an upper gastrointestinal bleeding. OP was administered as a continuous infusion up to a maximum of 10 g/24 h (0.42 g/h) for 5 days. The infusion was started at 33% of the target dose and increased at 12-hour intervals achieving target dose at 24 hours. Ammonia was also assessed in control group of 10 patients. RESULTS: No severe adverse events were observed. Mild adverse events were reported in 4 patients. Plasma ammonia (baseline: 80±43 µmol/L) showed a progressive drop between baseline and 36 hours (42±15 µmol/L), 72 hours (44±15 µmol/L), 96 hours (40±24 µmol/L), and 120 hours (33±14 µmol/L). Plasma ammonia at 24 hours was significantly higher in the control group. Plasma glutamine showed a significant decrease (-37% at day 5) and its excretion in urine as phenylacetylglutamine, a progressive rise (52±35 mmol at day 5). CONCLUSIONS: OP is a safe and well-tolerated drug in decompensated cirrhotics that may decrease plasma ammonia by inducing its appearance as phenylacetylglutamine in urine.

Protein expression profiles in patients carrying NFU1 mutations. Contribution to the pathophysiology of the disease.

Cofactor disorders of mitochondrial energy metabolism are a heterogeneous group of diseases with a wide variety of clinical symptoms, particular metabolic profiles and variable enzymatic defects. Mutations in NFU1 were recently identified in patients with fatal encephalopathy displaying a biochemical phenotype consistent with defects in lipoic acid-dependent enzymatic activities and respiratory chain complexes. This discovery highlighted the molecular function of NFU1 as an iron-sulfur(Fe-S) cluster protein necessary for lipoic acid biosynthesis and respiratory chain complexes activities. To understand the pathophysiological mechanisms underlying this disease we have characterized the protein expression profiles of patients carrying NFU1 mutations. Fibroblasts from patients with the p.Gly208Cys mutation showed complete absence of protein-bound lipoic acid and decreased SDHA and SDHB subunits of complex II. In contrast, subunits of other respiratory chain complexes were normal. Protein lipoylation was also decreased in muscle and liver but not in other tissues available (brain, kidney, lung) from NFU1 patients. Although levels of the respiratory chain subunits were unaltered in tissues, BN-PAGE showed an assembly defect for complex II in muscle, consistent with the low enzymatic activity of this complex. This study provides new insights into the molecular bases of NFU1 disease as well as into the regulation of NFU1 protein in human tissues. We demonstrate a ubiquitous expression of NFU1 protein and further suggest that defects in lipoic acid biosynthesis and complex II are the main molecular signature of this disease, particularly in patients carrying the p.Gly208Cys mutation.

Hyperlactatemia and in utero exposure to antiretrovirals: is the control group the clue?

Perinatal antiretroviral (ARV) exposure has been related to hyperlactatemia and lactic acidosis in infants born to HIV-infected mothers. Our objective was to determine the incidence of these conditions during the first year of life in uninfected infants born to HIV-infected mothers and compare the data with infants born to mothers with hepatitis C virus (HCV) infection. We investigated the relationships between hyperlactatemia and neurological and neurodevelopmental disorders by conducting a prospective, comparative cohort study (October 2004 to October 2007) consecutively including children of HIV- and HCV-infected mothers. Liver enzymes, pH, lactic acid, and plasma amino acids were determined at 1.5, 3, 6, and 12 months of life. Pathological hyperlactatemia was defined as lactate >2.1 mmol/liter together with alanine >475 µmol/liter. Seventy-nine patients (39 HIV-exposed patients and 40 unexposed patients) were included. Baseline maternal characteristics in the two groups were similar. Almost 90% of HIV-infected mothers received HAART during gestation, while 10.3% were given AZT monotherapy. Eight newborns received combined therapy and 31 received AZT-based monotherapy. Twelve patients (five exposed and seven nonexposed) had some neurological disorder, and four other patients (one vs. three) showed signs of neurodevelopmental delay, with no significant differences between the groups (p=0.34). Pathological hyperlactatemia was detected in 56.4% (95% CI 39.6-72.2) and 57.5% (95% CI 40.9-73.0) of patients, respectively (p=0.92), and this condition was more frequent in preterm children (p<0.05). ARV use during pregnancy and the neonatal period was not associated with pathological hyperlactatemia. The presence of hyperlactatemia was not associated with neurological or neurodevelopmental disorders. No association was established between the use of ARV agents and the development of hyperlactatemia or neurological disorders in HIV-exposed children during their first year of life.

Ornithine phenylacetate prevents disturbances of motor-evoked potentials induced by intestinal blood in rats with portacaval anastomosis.

BACKGROUND & AIMS: Ornithine phenylacetate (OP) is a new drug that has been proposed for the treatment of hepatic encephalopathy (HE) because it decreases plasma ammonia. We performed a study to assess if OP would impact on neuronal function. METHODS: Motor-evoked potentials (MEP), a surrogate of hepatic encephalopathy, were assessed (without anesthesia) in rats with portacaval anastomosis (PCA) that received gastrointestinal blood (GIB). Rats were pre-treated with OP prior to GIB. Ammonia and related metabolites (plasma, urine, and brain microdialysis) were assessed by HPLC and mass spectroscopy. RESULTS: OP (one dose or 3 days) prevented disturbances in MEP induced by GIB in PCA rats. In rats treated with OP for 3 days, the amplitude and latency of MEP remained stable (-1% and +1%), while in the control group the amplitude decreased -21% and the latency increased +12% (p<0.01). OP attenuated the rise of ammonia in plasma by 45%, ammonia in brain microdialysate by 48%, induced a faster glutamine rise and the appearance of phenylacetylglutamine in plasma and urine. In addition, OP was associated with a lower concentration of ammonia and glutamate in brain microdialysate (approx. 50%). CONCLUSIONS: OP prevents abnormalities in MEP precipitated by GIB in a model of HE. This is probably due to the enhancement of glutamine synthesis and metabolism, which results in a lower rise of plasma ammonia and the prevention of changes in glutamate in microdialysate. Thus, OP may be a good drug to prevent HE precipitated by gastrointestinal bleeding.

A fatal mitochondrial disease is associated with defective NFU1 function in the maturation of a subset of mitochondrial Fe-S proteins.

We report on ten individuals with a fatal infantile encephalopathy and/or pulmonary hypertension, leading to death before the age of 15 months. Hyperglycinemia and lactic acidosis were common findings. Glycine cleavage system and pyruvate dehydrogenase complex (PDHC) activities were low. Homozygosity mapping revealed a perfectly overlapping homozygous region of 1.24 Mb corresponding to chromosome 2 and led to the identification of a homozygous missense mutation (c.622G > T) in NFU1, which encodes a conserved protein suggested to participate in Fe-S cluster biogenesis. Nine individuals were homozygous for this mutation, whereas one was compound heterozygous for this and a splice-site (c.545 + 5G > A) mutation. The biochemical phenotype suggested an impaired activity of the Fe-S enzyme lipoic acid synthase (LAS). Direct measurement of protein-bound lipoic acid in individual tissues indeed showed marked decreases. Upon depletion of NFU1 by RNA interference in human cell culture, LAS and, in turn, PDHC activities were largely diminished. In addition, the amount of succinate dehydrogenase, but no other Fe-S proteins, was decreased. In contrast, depletion of the general Fe-S scaffold protein ISCU severely affected assembly of all tested Fe-S proteins, suggesting that NFU1 performs a specific function in mitochondrial Fe-S cluster maturation. Similar biochemical effects were observed in Saccharomyces cerevisiae upon deletion of NFU1, resulting in lower lipoylation and SDH activity. Importantly, yeast Nfu1 protein carrying the individuals' missense mutation was functionally impaired. We conclude that NFU1 functions as a late-acting maturation factor for a subset of mitochondrial Fe-S proteins.

Glycogen storage disease type III with hypoketosis.

A rare case of glycogen storage disease type III with unusually absent ketone body production during hypoglycemia is presented. A 10-month-old boy presented with asymptomatic hepatomegaly. GOT/GPT 2555/1160 IU/L, CK 302 IU/L, triglycerides 1223 mg/dL, cholesterol 702 mg/dL and uric acid 7.9 mg/dL. After a 9-hour fast, glucose was 27 mg/dL and adequate lipolysis without ketogenesis was observed (total/free carnitine 34.5/20 micromol/L, free fatty acids 1620 micromol/L and beta-hydroxybutyrate 172 micromol/L). Result of MCT (medium-chain triglycerides) load test: basal hydroxybutyrate 29 micromol/L rose to 5748 micromol/L. Treatment with a fat-restricted diet supplemented with formula containing MCT was initiated and the patient presented a satisfactory initial evolution. Three months later, CK were 3000 IU/L. Muscle biopsy was diagnostic of glycogenosis. Enzymatic activity in skin fibroblasts was 0% for amylo-1,6-glucosidase. The diagnosis of glycogenosis type III was established. Echocardiography performed at that time showed non-obstructive ventricular hypertrophy. Until now hypoketosis during hypoglycemia has only been described in glycogenosis type I.

Proteomic analysis in cerebrospinal fluid of patients with atypical nonketotic hyperglycinemia and pulmonary hypertension - A pilot study.

A variant phenotype of nonketotic hyperglycinemia has been described by our group associated with pulmonary hypertension. The aim of this study is to investigate the cerebrospinal fluid proteomes to get an insight into this neurodegenerative process producing leukoencephalopathy with white matter spongiform degeneration. DIGE and MALDI-TOF-TOF analyses were performed to carry out the proteomic study of four patients against three normal controls and one additional control of a classical nonketotic hyperglycinemia. The differential proteomic analysis showed a displacement of some series of spots toward the acidic side. The shifted proteins showed a high degree of carbonylation and increased methionine sulfoxidation was found in cystatin C and in vitamin-D-binding protein. These findings in addition to the increase of serum malondialdehyde concentration provide evidence of an oxidative stress in the patients under study, which is probably systemic rather than mainly confined to the CNS. The similarities of our findings with those found in other neurodegenerative diseases suggest that oxidative damage is commonly involved in these pathologies. DIGE technology improves the 2-D PAGE differential analysis and it is suitable in proteomic studies with a small number of cases.

Progressive vacuolating glycine leukoencephalopathy with pulmonary hypertension.

To report two unrelated patients with a new phenotype of nonketotic hyperglycinemia associated with idiopathic pulmonary hypertension. Clinical findings included rapidly progressive neurological deterioration with onset in the first year of life characterized by developmental regression without seizures or electroencephalogram abnormalities during follow-up. Both patients died before the age of 18 months. Glycine cleavage system deficiency was confirmed by enzymatic studies in frozen liver. Molecular analysis in the related genes showed no pathogenic mutation. Radiological and pathological findings were consistent with progressive vacuolating encephalopathy. Our patients with biochemical and enzymatic parameters consistent with atypical nonketotic hyperglycinemia. The clinical and radiological evolution, as progressive vacuolating leukoencephalopathy and the association with pulmonary hypertension constitute a previously unrecognized variant.

Reflexiones preliminares sobre una aplicación científico-médica de actualidad: la clonación / Prelminar reflecctions about a present techno medical application: clonatoon / Reflexõe prelimiinares sobre uma aplicaço científico-médica de atualidaade: da clonagem

Este artículo afronta el nuevo reto que la tecnociencia médica ha abierto: la posibilidad de clonación terapéutica o reproductiva. En el presente trabajo se aborda, clara y esquemáticamente, la terminología científico médica, desde los conceptos de reproducción sexual o asexual hasta la endonucleación, pasando por los conceptos de embrión gamético, somático, de cultivo y células madres, para ir realizando un análisis de los conflictos éticos que se abren en cada caso. La última parte del ensayo se centra en el problema ético del embrión y los problemas generados por los embriones sobrantes de los procesos de fertilización in vitro, origen de una importante controversia entre la comunidad científica, que pide que sean utilizados para fines de investigación, diferentes grupos sociales que se oponen a su utilización y la ley que los declara como no utilizables para fines reproductivos cuando su viabilidad no pueda ser garantizada.

This paper reflects about the new medical technoscience challenge opened: the possibility of therapeutic or reproductive clonation. The present paper approximates the medicalscientific terminology clearly and schematically, from the concepts of sexual or asexual reproduction to endonucleation, to the concepts of germinal, somatic or in vitro embryos and stem cells, to carry out an analysis of the ethical conflicts opened in each case. The last part of the essay centers in ethical issues related to the embryo, particularly the problems generated by the surplus embryos of fertilization in vitro, origin of an important controversy between the scientific community, that would like that they be utilized for research, different social groups, that opposed to their use, and the law, that declares them unusabel for reproductive purposes when their viability cannot be guaranteed.

Este artigo confronta o novo desafio que a tecnociência médica abriu: a possibilidade de clonagem terapêutica ou reprodutiva. O presente trabalho aborda de uma forma clara e esquemática, a terminologia científicomédica, a partir dos conceitos de reprodução sexual ou assexual até a endonucleação, passando pelos conceitos de embrião gamético, somático, de cultivos e células tronco, para analisar os conflitos éticos que surgem em cada caso. A última parte do ensaio centrase no problema ético do embrião e nos problemas criados pelos embriões excedentes dos processos de fertilização in vitro, origem de uma importante controvérsia entre a comunidade científica, que pede que sejam utilizados para fines de pesquisa, diferentes grupos sociais que se opõe à sua utilização e a lei que os declara como não utilizáveis para fins reprodutivos, quando sua viabilidade não pode ser garantida.