PSEN1 and Alzheimer disease: Studies have shown that in human neuroblastoma cells and the specific brain regions of AD mouse model, such as the frontal cortex and hippocampus, showing about 3.5- and 1.3-fold increase, respectively, in PSEN1 expression in vitB deficient conditions, whereas SAM is able to restore PSEN1 normal expression (Fuso et al., 2007).