LEP and metabolic disease: Leptin, also known as the satiety hormone, has special importance in the context of immune system-neuronal control link in metabolic diseases, not only because hyperleptinemia is a hallmark of almost all metabolic diseases (Haynes et al. 1997) but also because both central and peripheral leptin levels and leptin receptor activity alterations are associated with sympathetic nervous system disarrangement and adipose tissue dysfunction (Ramseyer and Granneman 2016).