NUTRITIONAL REGULATION OF IGF-BINDING PROTEIN IN TURBOT (SCOPHTHALMUS MAXIMUS L.)

To investigate the impact of IGF-like growth factor binding protein (IGFBP) on the physiological growth and nutritional metabolism of aquatic animals, turbot muscle fibroblasts were chosen as the research subject. The amino acid sequence of igfbp gene in zebrafish (Danio rerio), Homo sapiens (Homo sapiens) and turbot (Scophthalmus maximus L.) was collectively analyzed through bioinformatics to infer their evolutionary history. Furthermore, turbot muscle fibroblasts were treated with IGFBPs inhibitor (NBI 31772) and IGF1R inhibitor (BMS 554417), followed by analysis using fluorescence quantitative PCR, protein western blotting, Annexin V-FITC staining, and metabolite determination. In this study, we investigated the IGFBP family in turbot, identifying 12 genes with distinct tissue expression patterns. Our findings reveal significant tissue-specific expression of different igfbp genes. Specifically, igfbp2a exhibited the highest expression in brain, gill, and gallbladder tissues, while igfbp5a displayed peak expression in the eye, muscle, kidney, and skin. Moreover, igfbp3b showed the highest expression in spleen and heart tissue, igfbp2b in the liver, and igfbp4 in intestinal tissues. Additionally, our study sheds light on the dynamic response of IGFBP expression to nutritional induction in turbot muscle fibroblasts. The expression levels of igfbp1a, igfbp3b, igfbp4, igfbp5a, and igfbp5b in turbot muscle fibroblasts decreased first and then increased after nutritional induction. Moreover, our results indicate that igf2 displays greater sensitivity to nutritional stimuli compared to igf1. We also investigated the effects of short-term and long-term inhibition of IGFBPs on IGF signaling. Short-term inhibition promoted IGF signaling, while long-term inhibition resulted in reduced IGF activity and apoptosis. In addition, prolonged IGFBP inhibition led to decreased glycolysis and tricarboxylic acid cycle metabolite levels, alongside intracellular accumulation of free amino acids. In summary, these results provide valuable insights into the role of IGFBPs and the IGF signaling pathways in aquatic animals, offering a foundation for further exploration in this field.