Clinical applications of creatine supplementation on paediatrics.
ABSTRACT Creatine plays a central role in energy metabolism and is synthesized in the liver, kidney and pancreas. In healthy patients, it is transported via the blood stream to the muscles, heart and brain with high and fluctuating energy demands by the molecule creatine transporter. Creatine, although naturally synthesized in the human body, can be ingested in the form of supplements and is commonly used by athletes. The purpose of this review was to assess the clinical applications of creatine supplementation on paediatrics. Creatine metabolism disorders have so far been described at the level of two synthetic steps, guanidinoacetate N-methyltransferase (GAMT) and arginine: glycine amidinotransferase (AGAT), and at the level of the creatine transporter 1(CrT1). GAMT and AGAT deficiency respond positively to substitutive treatment with creatine monohydrate whereas in CrT1 defect, it is not able to replenish creatine in the brain with oral creatine supplementation. There are also data concerning the short and long-term therapeutic benefit of creatine supplementation in children and adults with gyrate atrophy (a result of the inborn error of metabolism with ornithine delta- aminotransferase activity), muscular dystrophy (facioscapulohumeral dystrophy, Becker dystrophy, Duchenne dystrophy and sarcoglycan deficient limb girdle muscular dystrophy), McArdle's disease, Huntington's disease and mitochondria-related diseases. Hypoxia and energy related brain pathologies (brain trauma, cerebral ischemia, prematurity) might benefit from Cr supplementation. This review covers also the basics of creatine metabolism and proposed mechanisms of action.
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ABSTRACT: Creatine transporter deficiency was discovered in 2001 as an X-linked cause of intellectual disability characterized by cerebral creatine deficiency. This review describes the current knowledge regarding creatine metabolism, the creatine transporter and the clinical aspects of creatine transporter deficiency. The condition mainly affects the brain while other creatine requiring organs, such as the muscles, are relatively spared. Recent studies have provided strong evidence that creatine synthesis also occurs in the brain, leading to the intriguing question of why cerebral creatine is deficient in creatine transporter deficiency. The possible mechanisms explaining the cerebral creatine deficiency are discussed. The creatine transporter knockout mouse provides a good model to study the disease. Over the past years several treatment options have been explored but no treatment has been proven effective. Understanding the pathogenesis of creatine transporter deficiency is of paramount importance in the development of an effective treatment.Journal of Inherited Metabolic Disease 05/2014; · 4.07 Impact Factor
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ABSTRACT: A population of patients with unexplained neurological symptoms from six major French university hospitals was screened over a 28-month period for primary creatine disorder (PCD). Urine guanidinoacetate (GAA) and creatine:creatinine ratios were measured in a cohort of 6,353 subjects to identify PCD patients and compile their clinical, 1H-MRS, biochemical and molecular data. Six GAMT [N-guanidinoacetatemethyltransferase (EC 126.96.36.199)] and 10 X-linked creatine transporter (SLC6A8) but no AGAT (GATM) [L-arginine/glycine amidinotransferase (EC 188.8.131.52)] deficient patients were identified in this manner. Three additional affected sibs were further identified after familial inquiry (1 brother with GAMT deficiency and 2 brothers with SLC6A8 deficiency in two different families). The prevalence of PCD in this population was 0.25% (0.09% and 0.16% for GAMT and SLC6A8 deficiencies, respectively). Seven new PCD-causing mutations were discovered (2 nonsense [c.577C > T and c.289C > T] and 1 splicing [c.391 + 15G > T] mutations for the GAMT gene and, 2 missense [c.1208C > A and c.926C > A], 1 frameshift [c.930delG] and 1 splicing [c.1393-1G > A] mutations for the SLC6A8 gene). No hot spot mutations were observed in these genes, as all the mutations were distributed throughout the entire gene sequences and were essentially patient/family specific. Approximately one fifth of the mutations of SLC6A8, but not GAMT, were attributed to neo-mutation, germinal or somatic mosaicism events. The only SLC6A8-deficient female patient in our series presented with the severe phenotype usually characterizing affected male patients, an observation in agreement with recent evidence that is in support of the fact that this X-linked disorder might be more frequent than expected in the female population with intellectual disability.Orphanet Journal of Rare Diseases 12/2012; 7(1):96. · 4.32 Impact Factor
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ABSTRACT: Background Aberrations in about 10-15% of X-chromosome genes account for intellectual disability (ID); with a prevalence of 1–3% (Gécz et al., 2009 ). The SLC6A8 gene, mapped to Xq28, encodes the creatine transporter (CTR1). Mutations in SLC6A8, and the ensuing decrease in brain creatine, lead to co-occurrence of; speech/language delay, autism-like behaviours and epilepsy with ID. A splice variant of SLC6A8 – SLC6A8C, containing intron 4 and exons 5–13, was identified. Herein, we report the identification of a novel variant – SLC6A8D, and functional relevance of these isoforms. Methods Via (quantitative)RT-PCR, uptake assays, and confocal microscopy, we investigated their expression and function vis-à-vis creatine transport. Results SLC6A8D is homologous to SLC6A8C except for a deletion of exon 9 (without occurrence of a frame shift). Both contain an open reading frame encoding a truncated protein but otherwise identical to CTR1. Like SLC6A8, both variants are predominantly expressed in tissues with high energy requirement. Our experiments reveal that these truncated isoforms do not transport creatine. However, in SLC6A8 (CTR1)–overexpressing cells, a subsequent infection (transduction) with viral constructs encoding either the SLC6A8C (CTR4) or SLC6A8D (CTR5) isoform resulted in a significant increase in creatine accumulation compared to CTR1 cells re-infected with viral constructs containing the empty vector. Moreover, transient transfection of CTR4 or CTR5 into HEK293 cells resulted in significantly higher creatine uptake. Conclusions CTR4 and CTR5 are possible regulators of the creatine transporter since their overexpression results in upregulated CTR1 protein and creatine uptake. General Significance Provides added insight into the mechanism(s) of creatine transport regulation.Biochimica et Biophysica Acta (BBA) - General Subjects 01/2014; · 3.85 Impact Factor