Because observed brain VDR protein levels appeared to us to be inversely upregulated in vitamin D deficient AD patients, we became interested in knowing whether this inverse relationship was a cellular response to the xenobiotic stimulus of Aβ, since VDR has been implicated in endobiotic/xenobiotic‐activated metabolism in a vitamin D‐independent manner (Krasowski et al., 2011). This evidence concerns the gene VDR and Alzheimer disease.