GCG and Parkinson disease: Similar to BDNF, a range of studies has confirmed that single GLP-1 or dual-activating GLP-1/GIP incretin analogues stimulate the phosphorylation of Akt and CREB (Jalewa et al., 2017) to rescue GDNF expression in the SNpc and striatum of MPTP-microinjected PD rodents (Jalewa et al., 2017; Yuan et al., 2017; Feng et al., 2018; Zhang et al., 2019; Lv et al., 2021).