SLC30A3 and Alzheimer disease: Furthermore, the decreased extracellular levels of MT3 observed in AD may facilitate hypermetallation of amyloid-β by zinc.559 A study utilizing microarray data from the human frontal cortex has shown that the expression of ZNT3 and ZNT4 significantly decreases with age, while the expression of ZIP1, ZIP9, and ZIP13 significantly increases.67