UCP1 and obesity due to melanocortin 4 receptor deficiency: The hypothesis that UCP-1 could serve as a molecular link between metabolic and emotional disorders, was originally motivated by the consideration that (1) UCP-1 is strongly expressed in BAT, and BAT is critical to energy control and consequently relevant to metabolic dysfunctions, including those associated with affective disorders (e.g., obesity and type II diabetes mellitus); and (2) A bidirectional communication between BAT and the brain exists, using both neural and endocrine pathways (Ryu et al., 2015; Villarroya et al., 2017).