MAPT and Alzheimer disease: Since 5LO is known to be up-regulated in brain tissues of AD patients13, where it plays an active role as an endogenous modulator of Aβ formation and tau phosphorylation14, 15, it remains to be investigated whether the 5LO up-regulation during HHcy is directly involved and essential in modulating the development of AD phenotype secondary to this condition, or it is simply an associated and secondary event to the condition.