Response to creatine analogs in fibroblasts and patients with creatine transporter deficiency.

Creatine transporter (CRTR) deficiency is one of the most frequent causes of X-linked mental retardation. The lack of an effective treatment for this disease, in contrast to creatine (Cr) biosynthesis disorders that respond to Cr monohydrate (CM), led us to analyze the efficacy of a lipophilic molecule derived from Cr, creatine ethyl ester (CEE), in fibroblasts and patients with CRTR deficiency. CM and CEE uptake studies were performed in six controls and four fibroblast cell lines from patients. We found a significant increase in Cr uptake after 72 h of incubation with CEE (500 micromol/L) in patients and control fibroblasts compared to incubation with CM. Subsequently, we assayed the clinical effect of CEE administration in four patients with CRTR deficiency. After 1 year of treatment, a lack of significant improvement in neuropsychological assessment or changes in Cr level in brain (1)H MRS was observed, and CEE was discontinued. In conclusion, this 12-month trial with CEE did not increase the brain concentration of Cr. Our in vitro data lend support to the idea of a certain passive transport of CEE in both pathological and control cells, although more lipophilic molecules or other cell systems that mimic the BBB should be used for a better approach to the in vivo system.

PDH E1ß deficiency with novel mutations in two patients with Leigh syndrome.

Most cases of pyruvate dehydrogenase complex (PDHc) deficiency are attributable to mutations in the PDHA1 gene which encodes the E(1)α subunit, with few cases of mutations in the genes for E(3), E3BP (E(3) binding protein), E(2) and E(1)-phosphatase being reported. Only seven patients with deficiency of the E(1)ß subunit have been described, with mutations in the PDHB gene in six of them. Clinically they presented with a non-specific encephalomyopathy. We report two patients with new mutations in PDHB and Leigh syndrome. Patient 1 was a boy with neonatal onset of hyperlactataemia, corpus callosum hypoplasia and a convulsive encephalopathy. After neurological deterioration, he died at age 5 months. Autopsy revealed the characteristic features of Leigh syndrome. Patient 2, also a boy, presented a milder clinical course. First symptoms were noticed at age 16 months with muscular hypotonia, lactic acidosis and recurrent episodes of somnolence and transient tetraparesis. MRI revealed bilateral signal hyperintensities in the globus pallidus, midbrain and crura cerebri. PDHc and E(1) activities were deficient in fibroblasts in patient 1; in patient 2 PDHc deficiency was found in skeletal muscle. Mutations in PDHA1 were excluded. Sequencing of PDHB revealed a homozygous point mutation (c.302T>C), causing a predicted amino acid change (p.M101T) in patient 1. Patient 2 is compound heterozygote for mutations c.301A>G (p.M101V) and c.313G>A (p.R105Q). All three mutations appear to destabilize the E(1) enzyme with a decrease of both E(1)α and E(1)ß subunits in immunoblot analysis. To our knowledge, these patients with novel PDHB mutations are the first reported with Leigh syndrome.