Low serum levels of leptin have been linked to severe malnutrition (Caro et al., 1996; Pinos et al., 2007; Amirkalali et al., 2010), acceleration of brain aging, and higher risk to develop AD (Power et al., 2001; Lieb et al., 2009; Fadel et al., 2013). Here, LEP is linked to nutritional deficiency disease.