Fan et al. (2017, 2018) found that intraperitoneal (i.p.)injection of apelin-13 significantly mitigates mouse anxiety-like behavior induced by chronic normobaric hypoxia by inhibition of the nuclear factor kappa-B (NF-κB) pathway. In addition, apelin had anti-neuroinflammatory (Zhou et al., 2019), anti-apoptotic, and neuroprotective effects (Liu et al., 2019). Further, apelin played a role in Parkinson’s disease (Acar et al., 2019) and post-traumatic stress disorder (Chen et al., 2019). Here, APLN is linked to Parkinson disease.