[Abnormal antioxidant system in inborn errors of intermediary metabolism]

Oxidative stress may be implied in the pathogenic mechanisms of inborn errors of intermediary metabolism (IEIM).

The evaluation of the antioxidant status in IEIM by the measurement of erythrocyte antioxidant enzyme activities, superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase and catalase.

34 patients with IEIM: 1) eleven with organic acidurias on protein restricted diet; 2) nine without special diet; 3) five patients with aminoacidopathies on protein restriction; 4) three patients with galactosemia and six with aminoacidopathies on protein free diet. Erythrocyte antioxidant enzymes were measured by spectrometric procedures adapted to the Cobas Fara II analyser.

SOD activity was significantly higher in groups 2 and 4 (p= 0.009, p= 0.001, respectively), and significantly lower in group 3 (p= 0.001) compared with age matched controls. SOD activity was significantly higher in the patients with IEIM on protein free diet (groups 2 and 4) compared with those on protein restricted diet (groups 1 and 3; p= 0.002) or with controls (p= 0.003). GPx activity was found significantly lower in group 1 patients (p= 0.004), and higher in group 2 (p= 0.029) compared with controls.

35% of the patients with IEIM had SOD activity above the control range, most of them with organic acidurias or homocystinuria, suggesting an induction of enzyme protein synthesis owing to an excess of free radical generation. The lower activities observed in patients on natural protein restriction may likely be due to a deficient bioavailability of antioxidant cofactors.