Using an APP/PS1 (Amyloid Precursor Protein/Presenilin 1) transgenic mouse model of AD (mice with APPswe/PS1ΔE9 Mutations), Wen Li and coworkers [55] found that supplementation with folic acid and/or SAM increases methylation potential and DNMT activity, modifies DNA methylation, and decreases APP, PS1, and Aβ protein levels. The gene discussed is PSEN1; the disease is Alzheimer disease.