RESUMEN
Lipoate serves as a cofactor for the glycine cleavage system (GCS) and four 2-oxoacid dehydrogenases functioning in energy metabolism (α-oxoglutarate dehydrogenase [α-KGDHc] and pyruvate dehydrogenase [PDHc]), or amino acid metabolism (branched-chain oxoacid dehydrogenase, 2-oxoadipate dehydrogenase). Mitochondrial lipoate synthesis involves three enzymatic steps catalyzed sequentially by lipoyl(octanoyl) transferase 2 (LIPT2), lipoic acid synthetase (LIAS), and lipoyltransferase 1 (LIPT1). Mutations in LIAS have been associated with nonketotic hyperglycinemia-like early-onset convulsions and encephalopathy combined with a defect in mitochondrial energy metabolism. LIPT1 deficiency spares GCS deficiency and has been associated with a biochemical signature of combined 2-oxoacid dehydrogenase deficiency leading to early death or Leigh-like encephalopathy. We report on the identification of biallelic LIPT2 mutations in three affected individuals from two families with severe neonatal encephalopathy. Brain MRI showed major cortical atrophy with white matter abnormalities and cysts. Plasma glycine was mildly increased. Affected individuals' fibroblasts showed reduced oxygen consumption rates, PDHc, α-KGDHc activities, leucine catabolic flux, and decreased protein lipoylation. A normalization of lipoylation was observed after expression of wild-type LIPT2, arguing for LIPT2 requirement in intramitochondrial lipoate synthesis. Lipoic acid supplementation did not improve clinical condition nor activities of PDHc, α-KGDHc, or leucine metabolism in fibroblasts and was ineffective in yeast deleted for the orthologous LIP2.
Asunto(s)
Aciltransferasas/genética , Atrofia/patología , Encefalopatías/genética , Encéfalo/patología , Lipoilación/genética , Mitocondrias/metabolismo , Aminoácidos/metabolismo , Encéfalo/diagnóstico por imagen , Encefalopatías/patología , Mapeo Encefálico/métodos , Células Cultivadas , Metabolismo Energético/genética , Metabolismo Energético/fisiología , Glicina/sangre , Humanos , Recién Nacido , Imagen por Resonancia Magnética , Mitocondrias/genética , Consumo de Oxígeno/genética , Unión Proteica/genética , Ácido Tióctico/metabolismoRESUMEN
PURPOSE: To describe resistant epileptic encephalopathies that significantly improved after an acute febrile episode (FE). METHODS: We reviewed the clinical history of patients with daily pharmacoresistant seizures referred to the Saint-Vincent de Paul Hospital in the last 5 years. Four patients experienced seizure arrest in relation with a febrile episode. RESULTS: The four patients suffered from epileptic encephalopathy. Three were symptomatic, one cryptogenic. They presented spasms and atypical absences, beginning after the age of 1 year. All seizures stopped at the onset of fever, and significant EEG improvement was observed. The seizure-free period ranged from 2 to 24 months. DISCUSSION AND CONCLUSION: The close link between the occurrence of FE and the disappearance of seizures and EEG improvement, contrasting with the previous pharmacoresistance of this epileptic encephalopathy, supports a non fortuitous association. Several mechanisms could explain this phenomenon, including viral etiology, hyperthermia, inflammatory-immune reaction and ACTH release. Better understanding this phenomenon could open new therapeutic perspectives.