Abstract: Objective：To explore the effect of vitamin  B12 supplementation in early life on DNA methylation level and Aβ toxicity in hippocampal neuron cells(HNCs) and its mechanism.
Methods：HNCs in 12 h of birth of the newborn rats were taken for culture in vitro, which were randomly divided into 5 groups: blank group, model group, lowdosage vitamin  B12 group, medium-dosage group and high-dosage group. Different dosages of vitamin  B12 were given for intervention. HPLC method was used to determine the level of DNA methylation; meanwhile, observe the effect of early intervention by vitamin  B12 on proliferation rate(PR) and apoptosis rate(AR) of mature HNCs after Aβ1-42  toxification, MDA content, SOD activity and GSH-PX activity.
Results：The DNA methylation level of HNCs intervened by vitamin  B12 at early stage was significantly lower than the control group(P<0.05);Aβ toxification could significantly decrease the PR and increase the AR of HNCs, and increase MDA content and reduce the activity of SOD and GSH-PX(P<0.05). Compared with model group, vitamin  B12supplementation in early life could increase PR of mature HNCs after Aβ toxification, decrease the AR, reduce MDA content, and increase the activity of SOD and GSH-PX, the difference being statistical((P<0.05).
Conclusion:Supplementation of vitamin  B12  in early life is helpful to decrease the methylation level of neuron cells, which plays an anti-Aβ neurotoxicity role in mature neuron cells, participates in oxidative stress of neuron cells, promotes cell proliferation and slows down apoptosis of neuron cells.

Key words: Alzheimer disease, Vitamin , B12, DNA methylation, Prevention