Ghrelin counteracted rotenone-induced cell loss (Yu et al., 2016; Liu et al., 2018), improved the impaired performance of rota-rod in the mouse MPTP-induced model of PD (Moon et al., 2009), and mediated the neuroprotective effects of caloric restriction (Bayliss et al., 2016b). This evidence concerns the gene GHRL and Parkinson disease.