M. Naglak, K. Madsen, P. P. Dembure
1987
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Journal
Pediatric Research
Abstract
Isovaleric Acidemia is treated with L-leucine restriction and supplemental glycine. Added glycine augments conversion of isovaleric acid (IVA) to isovalerylglycine (IVG) through glycine-N-acylase. The optimum glycine dosage for management of isovaleric acidemia is not known. In this study we evaluate a 9 year old female whose cultured fibroblasts have 4% of control isovaleryl-CoA dehydrogenase activity. Glycine supplements between 0 and 600 mg/kg/d were compared at weekly intervals with restricted leucine intake (54 mg/kg/d) and after acute loading with leucine (120 mg/ kg). Under restricted leucine intake IVG excretion rose from 12.3 to 33.6 mmols/gm creatinine when glycine supplements were increased from 0 to 50 mg/kg/d. As glycine supplements of 100 and 150 mg/kg/d were added, maximum excretion of IVG continued; however, when increased to 300 (x plasma gly=978 μM) and 600 mg/kg/ d (x plasma gly=2547.5 μM) IVG excretion fell to 13.8 and 16.3 mmoles/gm creatinine, respectively (N1 plasma gly=219 μM). When acute leucine loads were compared at glycine supplements of 190 mg/kg/d (x plasma gly=424 μM) and 600 mg/kg/d (x plasma gly=1636 μM), urinary IVG excretion was 194 and 419 mmoles/gm creatinine, respectively. We conclude that when IVA accumulation is minimal, optimum glycine dosage is < 150 mg/kg/d; under these conditions glycine intakes of 300 and 600 mg/kg/d inhibit IVG production. However, when acute insults raise IVA production glycine supplements of 600 mg/kg/d increase IVG production two fold.