Neuropoietin (NP), also known as Cardiotrophin-2 and CTF2, is a member of the IL-6 cytokine family. It is structurally and functionally related with CNTF, cardiotrophin-1 and cardiotrophin-like cytokine. NP is highly expressed in embryonic neuroepithelia but expression is also seen in the retina and, to a lesser extent, in skeletal muscle. It promotes the survival of embryonic motor neurons and could increase the proliferation of neural precursor cells in the presence of EGF and FGF-2 (1). NP acts through a receptor complex comprised of CNTF receptor-α component, gp130 and leukemia inhibitory factor (LIF) receptor (1). Signaling through this receptor complex also involves STAT3 (2). Interestingly, the human NP gene has evolved toward a pseudogene, suggesting that the alternative signaling via the CNTF complex is an effective compensatory pathway (1). NP has been shown to possess the potential to induce neuroepithelial cells to differentiate into astrocytes and to promote astrocyte differentiation in a synergistic manner with BMP2 (2). It has the ability to block adipogenesis. Cultured adipocytes, as well as murine adipose tissue, are highly responsive to acute neuropoietin treatment. NP substantially attenuates insulin-stimulated glucose uptake in 3T3-L1 adipocytes and blocks insulin action in adipose tissue in vivo (3). Mature mouse NP has high homology to chimpanzee, canine and rat NP.