NPY and early-onset autosomal dominant Alzheimer disease: We cannot fully explain this result, but offer a few tentative hypotheses: first, in humans, reduced NPY metabolism has been strongly correlated with Alzheimer's disease (Minthon et al., 1996; Borbély et al., 2013), suggesting that if NPY up-regulation is a consequence of normal aging, then its failure could lead to pathological results.