AQP5 and Alzheimer disease: We further validated, using RT-PCR, several IDD-DEGs and top MADAD DEGs with plausible biologic relevance to AD, including immune (CCL8, CD1E, IL-37, IL-36G), structural (AQP5, a water channel) and lipid (FAR2, ELOVL3, FA2H) genes, which encode enzymes involved in fatty acid and ceramide metabolism (Fig. 2a).