Amino Acid Metabolism in Friedreich's Ataxia

Abstract

SUMMARY:A study of amino acids determined by sequential Multi-sample Amino Acid Automatic Analyzer in plasma, urine and cerebrospinal fluid (CSF) in patients with Friedreich's ataxia and control subjects has revealed a number of mathematically significant variations from normal. Of practical physiological importance are the following: a high urinary excretion of alanine with slightly elevated plasma levels; a low plasma and CSF concentration of aspartic acid in the resence of normal urinary values and finally a low CSF concentration of taurine accompanied by normal plasma levels, but elevated urinary output and renal clearance rates. We postulate that the modifications in alanine and aspartic acid are less specific and probably secondary, but there could be a genetic defect in the membrane transport of taurine and the other β-amino acids in Friedreich's ataxia.

Complicated Optic Atrophy (Behr’s Disease) Associated with Epilepsy and Amino Acid Imbalance

“…The amino acid imbalance (decrease of most of them in plasma and CSF) is quite similar to the picture found in our cases of hereditary ataxias and in those of Lemieux et al (2), thus sup porting the view that also at biochemical levels there is a close link between Behr's disease and hereditary ataxias.…”

“…He underwent extensive neuroradiological examination and determination of the amino acid levels in plasma and cerebrospinal fluid (CSF) in order to ascertain similarities with Friedreich's disease (2).…”

The Beta-Amino Acid Transport System in Friedreich's Ataxia

“…These results support our previous data on the kinetics of /?-amino acid uptake (Melancon et al, 1979a) and confirm that Tau and Bala are normally transported in cultured skin fibroblasts of patients with F.A. The apparent discrepancy between urinary findings (Lemieux et al, 1976;Filla et al, 1979) and our fibroblast studies can be explained in many ways. First, the /3-amino acid uptake system in fibroblasts may be different from the tubular transport system in kidney.…”

“…Our interest in /3-amino acid transport in Friedreich's ataxia (F.A.) started with the observation of an apparent renal defect in the reabsorption of Tau (Filla et al, 1979) and Bala (Lemieux et al, 1976) in addition to uniformly elevated levels of Tau in various areas of the brain in two patients with F.A. (Huxtable et al, 1979).…”

Biochemical and clinical studies of Friedreich's ataxia

“…Most of the standard biochemical parameters including those suggested as possibly abnormal as a result of the extensive work of the Quebec co-operative study of Friedreich's ataxia2 :1 (bilirubin, amino acid, lipid and calcium metabolism) were normal in our patients. The amino acid data do not confirm the raised excretion of taurine and 8-amino acids reported by Lemieux et al 23 The Technicon TSM analyser was the instrument used in our own work and that of Lemieux et al Difficulties with the measurement of taurine may be encountered due to the low pKa of this compound because quantitative ion exchange with the cartridge resin used to load samples onto the column may not be achieved. This problem was overcome in the present work by direct injection, bypassing the cartridge.…”