Adequate or elevated dietary folate does not ameliorate the reduced antioxidant capacity induced by vitamin B deficiency in aged rats.

Folate could have an antioxidant role but also may be detrimental under vitamin B deficiency. The aim was to investigate the effect of different dietary folic acid (FA) levels, on oxidative stress in B induced deficient aged rats. Thirty-five male aged Sprague-Dawley rats, were fed either a vitamin B deficient (n = 27) or a control diet (n = 8) during eight weeks. Then, animals were divided into four groups: B and FA deficient diet (DBDF), B deficient diet and FA control diet (DBCF), B deficient diet and FA supplemented diet (DBSF), and control diet (CBCF) for a 30 days period. Methionine metabolism and antioxidant status were evaluated. Both vitamins deficiencies elevated serum homocysteine (Hcy) (7.7 . 4.3 μmol/L, p < 0.05) and reduced S-adenosylmethionine hepatic content (283.7 . 581.9 μg/g protein, p < 0.05), the total antioxidant capacity (155.7 . 189.3 μmol/L, p < 0.05), glutathione (GSH) (120.5 . 419.9 μg/mg protein, p < 0.05) and oxidized glutathione (0.9 2.6 μg/mg protein, p < 0.05) compared to control. Activities of glutathione peroxidase and glutathione reductase enzymes or damage to macromolecules were unaffected. Adequate or elevated dietary FA in B deficiency rats decreased Hcy (5.7 and 6.3 μmol/L, respectively) and increased total antioxidant capacity (189.8 and 192.6 μmol/L, respectively) to values similar to control group, whereas GSH concentration was significantly lower than control (209.1 and 208.0 μg/mg protein respectively, p < 0.05). In conclusion, in a vitamin B deficiency status, adequate or elevated FA prevented impairment in one-carbon metabolism, but does not fully reverse the decrease in antioxidant capacity.