In support of this, a downregulation of the insulin receptor in the substantia nigra pars compacta and increased insulin resistance has been described in patients affected by PD (Moroo et al., 1994; Takahashi et al., 1996; Duarte et al., 2012), a phenomenon which may occur before the death of dopaminergic neurons (Moroo et al., 1994). The gene discussed is INS; the disease is Parkinson disease.