Coordinated regulation of the GH/IGF system genes during refeeding in rainbow trout (Oncorhynchus mykiss)

Abstract

The GH/IGF system is a complex regulation network strongly dependent on nutrient availability. While the effect of starvation on the GH/IGF system has been extensively studied, the time course of events leading to the restoration of GH/IGF system activity after starvation is largely unknown. We, therefore, measured the plasma levels of GH, IGF-I and IGF-II and the expression of the GH/IGF system in liver and muscle. Starvation increased the plasma GH level and 1 day of refeeding completely restored it (1$10G0$27 vs 1$12G0$28 ng/ml). Thereafter, plasma GH continued to decrease until day 7 and returned to control values from day 15. Starvation decreased plasma IGF-I and IGF-II and refeeding raised plasma IGF-I only from day 4. In contrast, the plasma IGF-II level doubled after 1 day's refeeding (26$5G1$9 vs 44$0G3$4 ng/ml; P!0$01). Starved fish exhibited higher GH receptor (GHR)1 mRNA abundance in liver and muscle than in controls, whereas GHR2 mRNA abundance was increased only in muscle. In liver, 1 day of refeeding, decreased GHR1 (twofold), but increased GHR2 mRNA abundance (twofold). Thereafter, a progressive return to normal values was observed. Liver IGFBP-4 mRNA abundance was lowered in starved fish followed by a progressive restoration during refeeding. Starvation had no effect on liver IGFBP-2 and IGFBP-6 mRNA abundance, whereas refeeding provoked a peak of IGFBP-2 and IGFBP-6 expression at day 7. In muscle, starvation led to a decrease of the IGFBP-2 mRNA level, which was restored only from day 7. IGFBP-4 mRNA abundance in starved fish was lower than in the controls and refeeding led to a transient upregulation (sevenfold) of IGFBP-4 gene at day 1. IGF-I, IGFBP-5, and IGFBP-related protein 1 (rP1) expression profiles were similar, showing a decrease of expression after starvation, a first peak of expression at day 2, a second peak at day 7, and a return to normal value from day 15. Moreover, IGF-I, IGFBP-5, and IGFBP-rP1 mRNA abundance were positively correlated (rZ0$6-0$8; P!0$0001). In conclusion, plasma IGF-I was restored later than plasma GH level, which suggests that plasma IGF-I levels cannot account for plasma GH changes. The coordinated regulation of IGF-I, IGFBP-5, and IGFBP-rP1 expression would be a signature for the resumption of myogenic activity.

Increased food intake in growth hormone-transgenic common carp (Cyprinus carpio L.) may be mediated by upregulating Agouti-related protein (AgRP)

“…These results are in concordance with the studies in goldfish, flounder, rainbow trout and salmons (Canosa et al, 2005;Fuentes et al, 2012;Gabillard et al, 2006;Pierce et al, 2005;Shimizu et al, 2009). Next, we observed high expression levels of serum GH in both fasted and fed TG common carp, while there is no significant difference between them ( Fig.…”

“…Furthermore, changes in GH levels are tightly coupled to nutritional status (Canosa et al, 2007). For example, reduced food intake or starvation causes GH to rise, while GH returns to baseline after resumed feeding (Gabillard et al, 2006;Pierce et al, 2005;Shimizu et al, 2009).…”

Tissue-specific molecular immune response to lipopolysaccharide challenge in emaciated anadromous Arctic charr

“…Additionally, it has also been shown that SOCS proteins interact with GH receptor signalling (Wang et al, 2011). Fish growth is a complex function mostly regulated by the growth hormone (GH)/insulin-like growth factor (IGF) system (Gabillard et al, 2006). Over-expression of SOCS-2 has been shown to interfere with the JAK2-STAT5b pathway and inhibit growth hormone signalling (Croker et al, 2008).…”

Advances in research on the prenatal development of skeletal muscle in animals in relation to the quality of muscle-based food. I. Regulation of myogenesis and environmental impact

“…For example, in both rainbow trout and gilthead sea bream, fasting increased plasma GH levels and decreased tissue expression and plasma levels of IGFs and upregulated IGF-I binding (Gabillard et al, 2006a;Montserrat et al, 2007a and. In trout, fasting followed by refeeding causes a switch to fast growth and involves the local upregulation of several components of the IGF system (Gabillard et al, 2006a).…”

“…For example, in both rainbow trout and gilthead sea bream, fasting increased plasma GH levels and decreased tissue expression and plasma levels of IGFs and upregulated IGF-I binding (Gabillard et al, 2006a;Montserrat et al, 2007a and. In trout, fasting followed by refeeding causes a switch to fast growth and involves the local upregulation of several components of the IGF system (Gabillard et al, 2006a). Moreover, IGF-I stimulates cell proliferation in both rainbow trout (Castillo et al, 2004 and2006) and gilthead sea bream (Montserrat et al, 2007c) muscle cells in vitro and IGF-II has both mitogenic and metabolic effects in trout muscle cell cultures (Codina et al, 2008).…”