RESUMO
BACKGROUND & AIMS: Methionine metabolic impairment and selenium deficit have been associated to neural tube defects. The relationship between thiol metabolism and selenium is not well known. We assessed the status of aminothiols and selenium, as well as thiolic status and the amino acids involved in arginine synthesis in the case of selenium depletion and repletion, studying their relationship to neural tube defects. METHODS: We studied 44 women of 37 +/- 8 years (mean +/- SD) who had conceived fetuses with neural tube defects as cases; and 181 women of 39 +/- 7 years (mean +/- SD) with healthy children as controls. We determined selenium, vitamin B12, serum folates, plasma thiol compounds and amino acids. Homocysteine transsulfuration was assessed using total cysteine/total homocysteine ratio (tCys/tHcy), and selenium repletion cut-off value was 1.06 micromol/l (84 microg/l). RESULTS: Cases showed significantly lower levels (median) than controls of total homocysteine (P = 0.001), total cysteinylglycine (P < 0.001), selenium (P < 0.001) and tryptophane (P = 0.002); and higher tCys/tHcy levels (P < 0.001), glutathione (P = 0.008) and L-arginine (P = 0.001). Cases with selenium depletion (selenium < or = 1.06 micromol/l) had significantly higher levels than controls of cysteine (P = 0.010), glutathione (P = 0.005), tCys/tHcy (P < 0.001), and arginine (P = 0.004), but significantly lower levels than controls of tryptophane (P = 0.027), cysteinylglycine (P < 0.001) and folates (P < 0.001). Only cysteinylglycine was lower than controls (P < 0.001) when selenium > 1.06 micromol/l. Methionine levels were higher in cases with selenium depletion than in repletion (P = 0.029). CONCLUSIONS: According to our data, a diet deficient in selenium and folates or their absorption impairment, and/or other mechanisms related to polyamines and nitric oxide can lead to oxidant/antioxidant imbalance and to a higher occurrence of these malformations.