GHRL and Alzheimer disease: Interestingly, the amino acid residues of the N-terminus sequence of ghrelin are largely hydrophobic (UniProtKB—Q9UBU3 (GHRL_HUMAN)), a significant reduction of ghrelin mRNA has been reported in the temporal gyrus of AD patients [50] and it has been proved that a single polymorphism mutation leading to a Gln/Leu substitution is associated with the onset age of AD [51].