More recently, Yadav and co-authors [74] documented significantly higher concentrations of Hg in the whole blood of 50 AD patients compared to a group of age-matched non-demented subjects (p < 0.0001); however, as for Al and Cd, they failed to find a correlation between the metal level and the expression of selected genes upregulated in AD, namely APP, presenilin 1 (PSEN1), and presenilin 2 (PSEN2), with PSEN1,2 being the major components of Υ-secretase that mediate the final cleavage that releases Aβ [206] and APOE4, which contribute to the generation of Aβ oligomers in the brain [207]. The gene discussed is APOE; the disease is Alzheimer disease.