Abstract
During disease and infection it is probable that growth is attenuated, the molecular pathways involved are poorly characterised. We postulated that the insulin-like growth factor (IGF) axis a central endocrine governor of vertebrate growth is repressed during infection to promote resource reallocation towards immunity. This hypothesis was tested in rainbow trout (Oncorhynchus mykiss) challenged by Aeromonas salmonicida (AS), a Gram-negative bacterial pathogen, or viral hemorrhagic septicemia virus (VHSv) at hatch, first feeding and 3 weeks-post first-feeding. Quantitative transcriptional profiling was performed for genes encoding IGF hormones, all salmonid IGF-I receptor and IGF binding proteins, and a panel of marker genes for growth and immune status. Many IGF axis genes were developmentally upregulated in concert with genes controlling muscle protein synthesis, recapturing the onset of complex growth regulation. There were also differences in the developmental response of the IGF axis to AS and VHSv, with the VHSv challenge causing strong downregulation of many genes. Despite this, IGFBP-1A1 and IGFBP-6A2 subtypes each negative regulators of IGF signalling were massively induced by AS and VHSv in striking correlation with host defence genes regulated by cytokine pathways. Follow up experiments demonstrated a massive upregulation of IGFBP-1A1, IGFBP-6A2 and proinflammatory cytokine genes, associated with large downregulation of genes encoding IGF hormones and IGF-I receptor in spleen and head kidney of rainbow trout challenged by a different bacterium, Yersinia ruckeri. Based on our findings, we propose a model where certain IGFBP subtypes are directly regulated by cytokine signalling pathways, allowing immediate modulation of growth and/or immune system phenotypes according to the level of activation of immunity. Our findings provide new and comprehensive insights into cross-talk between conserved pathways regulating teleost growth, development and immunity.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
