Knocking down ZnT3 in mice leads to cognitive difficulties occurring earlier than expected.149 An interesting discovery revealed a decline in ZnT3 levels in the brains of mice and humans with aging; however, an even more significant reduction was observed in AD patients.544 Despite the downregulation of ZnT3, compensatory upregulations of ZnT4, ZnT6, and ZnT1 were observed in the hippocampus of AD.545,546. This evidence concerns the gene SLC30A4 and Alzheimer disease.