Spexin
Spexin (SPX) is a peptide identified in 2007 in mammalian adipose tissue. SPX expression is down-regulated in obese humans and rats, and subcutaneous injections of SPX reduce food intake and increase locomotion (Walewski et al., 2014).
In goldfish, SPX appear to act as an anorexigenic factor: brain injections of SPX inhibit both basal and NPY- or orexin-induced food consumption, decrease brain expressions of orexigenic factors (NPY, AgRP, and apelin) and increase that of anorexigenic factors (CCK, CART, POMC, MCH, and CRH), and brain SPX mRNA levels increase post-prandially (Wong et al., 2013). Similarly, in the orange-spotted grouper, IP administration of SPX increases hypothalamic mRNA levels of POMC and inhibits orexin expression, suggesting an anorexigenic role (Li S. et al., 2016). However, grouper SPX hypothalamic expression increases following long-term food deprivation (Li S. et al., 2016), suggesting that spexin might be a short-term satiety factor rather than a long-term hunger signal.