LRP2 and Alzheimer disease: Vitamin D's active form (1,25-dihydroxyvitamin D3) maintains and stabilizes intracellular signaling pathways involved in memory and cognition (Eyles et al., 2013) by increasing VDR (Guo et al., 2016) and LRP2 expression in the choroid plexus and helping clear neurotoxic β-amyloids (Deane et al., 2004; Carro et al., 2005) involved in Alzheimer's disease (AD) pathogenesis (Roher et al., 1993).