Cortistatin - a new neuroendocrine hormone?

Cortistatin (CST) is a recently described neuropeptide. Although the expression of CST was initially reported to be restricted to the rat cerebral cortex and hippocampus, it is currently known to have wide distribution in many human organs. CST shares high homology with somatostatin and binds with high affinity to all somatostatin receptor (SSTR) subtypes. Indeed, many of its endocrine and biological activities overlap with somatostatin. However, CST and somatostatin are expressed in only partially overlapping cortical neuron populations. They are regulated by different stimuli, their cortical actions are diverse and CST, at variance with somatostatin, was shown to have a possible role in the human immune system. The activities specific to cortistatin may be attributable to its unique binding to the GH secretagogue (GHS) receptor (GHS-R) and the orphan G-protein-coupled receptor, MrgX2, which is not shared by somatostatin. The potential biological roles and therapeutic use of CST and the receptors involved in its action require further investigation.