LEP and Alzheimer disease: Although there is as yet no direct clinical evidence to support leptin’s efficacy in human neurodegenerative disorders, there is mounting evidence from pre-clinical studies that leptin has therapeutic potential as it has pro-cognitive and neuroprotective effects in cellular and rodent models of AD, PD and ALS (Greco et al., 2010; Doherty et al., 2013; Malekizadeh et al., 2017; Weng et al., 2007; Lim et al., 2014; Figure 2).