Effects of short-term starvation on ghrelin, GH-IGF system, and IGF-binding proteins in Atlantic salmon

Abstract

The effects of short-time fasting on appetite, growth, and nutrient were studied in Atlantic salmon (Salmo salar) smolts. Feed deprivation did change the energy metabolism with reduced plasma protein and muscle indispensible amino acid levels. Plasma levels of ghrelin were significantly higher in starved salmon compared with fed fish after 2 days, but no differences in circulating ghrelin were found between treatments after 14 days. Two mRNA sequences for ghrelin-1 and ghrelin-2, 430 and 533 bp long, respectively, were detected. In addition, the growth hormone secretagogues-receptor like receptor (GHSR-LR) 1a and 1b were identified. Ghrelin-1 but not ghrelin-2 mRNA levels were affected by starvation in the stomach. Lower ghrelin-1 mRNA levels were detected at day 2 in starved fish compared with fed fish. The mRNA levels of GHSR-LR1a were not affected by starvation. Fasting reduced the phenotypic growth and the transcription of insulin-like growth factor (IGF)-II together with IGF-IIR, but IGF-I mRNA were not regulated in fasted salmon after 14 days. Three IGF-binding proteins (IGFBP) at 23, 32, and 43 kDa were found in salmon, and circulating 23 kDa was significantly increased after 14 days of starvation compared with fed fish, indicating increased catabolism. The levels of IGFBP-1 mRNA were significantly higher in fed and starved fish after 14 days compared to those at the start of the experiment, but no significant difference was observed between the treatments. In conclusion, we have shown that circulating ghrelin and ghrelin-1 mRNA is related to changes in energy metabolism in Atlantic salmon.

Comparison of gene expression patterns of key growth genes between different rate growths in zebrafish (Danio rerio) siblings

“…The igfbp-1 and gck gene expressions are regulated by nutritional status or the glucose levels. The igfbp-1 is regulated by insulin levels and in consequently with glucose levels (Lee et al, 1993) and fasting increase its mRNA levels in fish (Shimizu et al, 2006;Hevrøy et al, 2011;Kawaguchi et al, 2013;Breves et al, 2014), according to the our study results. On the other hand, gck is a liver enzyme that catalyzes the phosphorylation of glucose to glucose-6-phosphate (Enes et al, 2009), is associated with individual nutritional status and showing an upregulation by feed intake (Caseras et al, 2000;González-Alvarez et al, 2009;Panserat et al, 2014).…”

“…Conversely, was observed uniformity in igf-1 mRNA levels between the larvae groups, in contrast to the most fasting reports in different fish species (Wood et al, 2005;Norbeck et al, 2007;Peterson & Waldbieser, 2009;Reinecke, 2010;Kawaguchi et al, 2013;Tian et al, 2015;Taniyama et al, 2016). However, Wen-Ying et al (2012) in Carassius auratus gibelio, Breves et al (2014) and Fox et al (2010) in Mozambique tilapia (Oreochromis mossambicus), and Hevrøy et al (2011) in Atlantic salmon (Salmon salar) only observed significant differences at the protein le- Figure 4. PCA analysis a) PCA-Correlation loadings plot of the variables (gene expression) in the principal components PC1 and PC2, b) PCA-Score plot in the PC1 and PC2 principal components.…”

Role of the GH-IGF-1 system in Atlantic salmon and rainbow trout postsmolts at elevated water temperature

“…Our earlier examinations in fish held at elevated temperatures in sea water have shown that plasma IGF-1 is regulated by three major circulating IGFBPs at 23, 32 and 43 kDa in Atlantic salmon (Hevrøy et al, 2011, corresponding to salmonid IGFBP-1b, -1a and -2b, respectively (Shimizu et al, 2011a(Shimizu et al, , 2011b. IGFBP-1b has been suggested to have a major role in regulating the metabolic action of IGF-1, showing higher levels under catabolic conditions induced by starvation and stress in Chinook salmon (Shimizu et al, 2006(Shimizu et al, , 2011a(Shimizu et al, , 2011b, during starvation in Atlantic salmon (Hevrøy et al, 2011) and by cortisol treatment of rainbow trout (Shimizu et al, 2011b).…”

Sequence, genomic organization and expression of ghrelin receptor in grass carp, Ctenopharyngodon idellus

“…It was the first report on the identification of a GHSR-1b transcript from species other than mammals and the demonstration that receptor interaction might provide a possible explanation for the existence and biological significance of the sbGHSR-1b transcript. Since then GHS-R has also been identified in the zebrafish Danio rerio (Olsson et al, 2008), orange-spotted grouper Epinephelus coioides (Chen et al, 2008), channel catfish Ictalurus punctatus (Small et al, 2009), rainbow trout Oncorhynchus mykiss (Kaiya et al, 2009a), Mozambique tilapia Oreochromis mossambicus (Kaiya et al, 2009b), goldfish Carassius auratus (Kaiya et al, 2010) and Atlantic salmon Salmo salar (Hevrøy et al, 2011).…”