A 9-y-old girl with
ethylmalonic/adipic aciduria was hospitalized to determine the possible therapeutic efficacy of oral
carnitine and
glycine supplementation. To provoke a mild metabolic stress, her diet was supplemented with 440 mg/kg/d of medium-chain
triglycerides. She was treated successively with
carnitine (100 mg/kg/d) for 5 d, neither
carnitine nor
glycine for 2 d, and then
glycine (250 mg/kg/d) for 6 d. Consecutive 12-h urine collections were obtained throughout the entire period. The urinary excretion of eight organic
acids, four acylglycines, and four acylcarnitines, which accumulate as a result of a metabolic block of five mitochondrial
acyl-CoA dehydrogenases, were quantitatively determined by capillary gas chromatography, stable
isotope dilution gas chromatography/mass spectrometry, and radioisotopic exchange HPLC, respectively. The excretion of each group of metabolites was calculated as the mean percentage of total output (mumol/24 h) during the four phases of the protocol (organic
acids/acylglycines/acylcarnitines = 100.0%): 1) regular diet (3 d); 88.1/10.8/1.1; 2) medium-chain
triglyceride supplementation (4); 82.5/15.6/1.9; 3) medium-chain
triglycerides plus
carnitine (5); 79.2/8.2/12.6; and 4) medium-chain
triglycerides plus
glycine (6); 81.0/18.7/0.3. Comparison between total and individual excretion of acylglycines and acylcarnitines indicates that oral
glycine supplementation enhanced the conjugation and excretion of
fatty acyl-CoA intermediates as efficiently as
carnitine. We propose that oral
glycine supplementation should be considered in the treatment of other
inborn errors of metabolism associated with abnormal urinary excretion of acylglycines.