SPX and major depressive disorder: In human, SPX is encoded by the gene c12orf39 located in chromosome 12 (21) and abnormalities in SPX expression/serum levels can be associated with childhood (22, 23) and adult obesity (24), type I/II diabetes (6, 25), gestational diabetes (26), metabolic syndrome (27), cardiovascular disease (28), and psychiatric disorders including anorexia nervosa (29) and anxiety/depression (30, 31).