IGF-1 induces SOCS-2 but not SOCS-1 and SOCS-3 transcription in juvenile Nile tilapia (Oreochromis niloticus)

Insulin-like growth factor-1 (IGF-1) plays a crucial role in regulating growth in vertebrates while suppressors of cytokine signaling (SOCS) act as feedback inhibitors of the GH/IGF-1 axis. Although SOCS-2 binds IGF-1 receptor and inhibits IGF-1-induced STAT3 activation, presently there is no clear evidence whether IGF-1 could induce SOCS genes expression. The current study aimed to determine whether IGF-1 could induce the transcription of SOCS in juvenile Nile tilapia (Oreochromis niloticus). We show that there is a common positive relationship between the mRNA expression of IGF-I and SOCS-2 under different nutritional statuses and stimulants, but not the expression of SOCS-1 and SOCS-3 mRNA. Furthermore, rhIGF-1 treatment and transcriptional activity assay confirmed the hypothesis that IGF-1 could induce SOCS-2 expression, while has no effect or even decreased the expression of SOCS-1 and SOCS-3. Overall, we obtained evidence that the transcription of SOCS-2, but not SOCS-1 or SOCS-3 could be induced by IGF signaling, suggesting the SOCS-2 serves as a feedback suppressor of IGF-1 axis in juvenile Nile tilapia.