High intake of folic acid or complex of B vitamins provides anti-Parkinsonism effect: No role for serum level of homocysteine

Several lines of evidence show that homocysteine (Hcy) levels are increased in blood and CSF of patients with Parkinson's disease. B vitamins are necessary for Hcy metabolism and their deficiencies cause hyperhomocysteinemia and neurodegeneration. In present study, effect of B vitamin supplementation on the severity of 6-hydroxydopamine (6-OHDA)-induced Parkinsonism was investigated. Rats were nourished with B vitamin supplements from 1 month before of stereotaxic injection of 6-OHDA to the end of experiments. Total serum Hcy was measured at the end of experiments to identify its association with Parkinsonism. Both rotational and rotarod tests revealed that supplementation of folic acid, in a dose dependent manner, attenuates severity of Parkinsonism. Supplement of B complex also had beneficial effect and improved motor performance in rotarod test and decreased biased swings in elevated body swing test but had no effect on the apomorphine-induced rotational behavior. Supplement of B6 attenuated rotational behavior but had no effect on the rotarod performance and swinging behavior. Supplement of B12 or combination of folic acid with B6 and B12 had no effect on the behavioral symptoms of Parkinsonism. Except one group, the levels of Hcy in other vitamin B treated groups were near to that in control group. Surprisingly, Hcy in group of rats that received high intake of folic acid was significantly higher than that in control group. Our results indicate that high intake of folic acid or B complex provides anti-Parkinsonism effect but it is not mediated by lowering plasma Hcy.

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► High intake of folic acid or B complex ameliorates 6-OHDA-induced Parkinsonism.
► Neuroprotective effect of folic acid supplement is dose dependent.
► Neuroprotective effect of B vitamins is not mediated by lowering of homocysteine.
► High intake of B12 or B6 or folate + B12 + B6 has no anti-Parkinsonism effect.
► High intake of folic acid increases plasma homocysteine in 6-OHDA treated rats.