Insulin-like growth factor (IGF) signalling and genome-wide transcriptional regulation in fast muscle of zebrafish following a single-satiating meal

Abstract

Male zebrafish (Danio rerio) were fasted for 7days and fed to satiation over 3h to investigate the transcriptional responses to a single meal. The intestinal content at satiety (6.3% body mass) decreased by 50% at 3h and 95% at 9h following food withdrawal. Phosphorylation of the insulin-like growth factor (IGF) signalling protein Akt peaked within 3h of feeding and was highly correlated with gut fullness. Retained paralogues of IGF hormones genes were regulated with feeding, with igf1a showing a pronounced peak in expression after 3h and igf2b after 6h. Igf-I receptor transcripts were markedly elevated with fasting, and decreased to their lowest levels 45min after feeding. igf1rb transcripts increased more quickly than igf1ra transcripts as the gut emptied. Paralogues of the insulin-like growth factor binding proteins (IGFBPs) were constitutively expressed, except for igfbp1a and igfbp1b transcripts, which were significantly elevated with fasting. Genome-wide transcriptional responses were analysed using the Agilent 44K oligonucleotide microarray and selected genes validated by qPCR. Fasting was associated with the upregulation of genes for the ubiquitin-proteasome degradation pathway, anti-proliferative and pro-apoptotic genes. Protein chaperones (unc45b, hspd1, hspa5, hsp90a.1, hsp90a.2) and chaperone interacting proteins (ahsa1 and stip1) were upregulated 3h after feeding along with genes for the initiation of protein synthesis and mRNA processing. Transcripts for the enzyme ornithine decarboxylase 1 showed the largest increase with feeding (11.5-fold) and were positively correlated with gut fullness. This study demonstrates the fast nature of the transcriptional responses to a meal and provides evidence for differential regulation of retained paralogues of IGF signalling pathway genes. © 2011. Published by The Company of Biologists Ltd.