Maternal protein restriction and fetal growth: lack of evidence of a role for homocysteine in fetal programming

The disease-programming effects of a maternal low-protein (MLP) diet in rat pregnancy have been suggested to be attributable of hyperhomocysteinaemia. The aim of the present study was to determine whether MLP feeding impacted upon maternal and day 20 fetal homocysteine concentrations, with ensuing effects upon oxidant/antioxidant status. Sixty-four pregnant rats were fed either MLP diet or control diet before termination of pregnancy at days 4, 10, 18 or 20 gestation (full-term gestation 22 d). Maternal plasma homocysteine concentrations were similar in control and MLP-fed dams at all points in gestation. Fetal plasma homocysteine was similarly unaffected by MLP feeding at day 20 gestation. Activities of superoxide dismutase and glutathione peroxidase were similar in livers of mothers and fetuses in the two groups. Whilst catalase activity was not influenced by diet in maternal liver, MLP exposure increased catalase activity in fetal liver at day 20. Oxidative injury (protein carbonyl concentration) was lower in the livers of MLP-fed animals at day 18 gestation (P < 0.05), but significantly greater at day 20. Hepatic expression of methionine synthase was similar in control and MLP-fed dams at all stages of gestation. Expression of DNA methyltransferase 1 in fetal liver was altered by maternal diet in a sex- and gestational age-specific manner. In conclusion, MLP feeding does not impact upon maternal or fetal homocysteine concentrations prior to day 20 gestation in the rat. There was no evidence of increased oxidative injury in fetal tissue that might explain the long-term programming effects of the diet.