| Abstract [eng] |
Creatine and phosphocreatine play an essential role in energy storage and transmission in several tissues. Two enzymes are involved in creatine biosynthesis: arginine:glycine amidinotransferase, which converts arginine and glicine to ornithine and guanidinoacetate, and S-adenosyl-lmethionine:N-guanidinoacetate methyltransferase, which converts guanidinoacetate to creatine. The latter is transported to tissues by the Cr transporter, and is non-enzymatically converted to creatinine. Creatine deficiency syndromes are a newly described group of inborn errors of creatine synthesis (arginine : glycine amidinotransferase (AGAT) deficiency and guanidinoacetate methyltransferase (GAMT) deficiency) and of creatine transport (creatine transporter (CrT) deficiency). The common clinical feature of creatine deficiency syndromes is mental retardation and epilepsy. Measurement of guanidinoacetate in body fluids may discriminate between the GAMT (high concentration), AGAT (low concentration) and CrT (normal concentration) deficiencies. Further biochemical characteristics include changes in creatine and creatinine concentrations in body fluids. GAMT and AGAT deficiency are treatable by oral creatine supplementation, while patients with CrT deficiency do not respond to this type of treatment. Creatine and guanidinoacetate analysis by GC-MS can be very informative and important method in diagnosing the inborn errors of creatine metabolism. In this work the urine samples of patients with suspected creatine metabolism disorders were analysed by GC-MS. The profiles of creatine and guanidinoacetate showed that creatine transporter defect for one patient and AGAT deficiency for another patient were detected. Nevertheless additional confirmative laboratory tests should be done before reaching the final diagnosis. |
