Abstract
Neuropeptide Y (NPY) is known as a potent orexigenic signal in vertebrates, but its role in Atlantic salmon has not yet been fully established. In this study, we identified three npy paralogs, named npya1, npya2, and npyb, in the Atlantic salmon genome. In silico analysis revealed that these genes are well conserved across the vertebrate’s lineage and the mature peptide sequences shared at least 77% of identity with the human homolog. We analyzed mRNA expression of npy paralogs in eight brain regions of Atlantic salmon post-smolt, and the effect of 4 days of fasting on the npy expression level. Results show that npya1 was the most abundant paralog, and was predominantly expressed in the telencephalon, followed by the midbrain and olfactory bulb. npya2 mRNA was highly abundant in hypothalamus and midbrain, while npyb was found to be highest expressed in the telencephalon, with low mRNA expression levels detected in all the other brain regions. 4 days of fasting resulted in a significant (p < 0.05) decrease of npya1 mRNA expression in the olfactory bulb, increased npya2 mRNA expression in the midbrain and decreased npyb mRNA expression in the pituitary. In the hypothalamus, the vertebrate appetite center, expression of the npy paralogs was not significantly affected by feeding status. However, we observed a trend of increased npya2 mRNA expression (p = 0.099) following 4 days of fasting. Altogether, our findings provide a solid basis for further research on appetite and energy metabolism in Atlantic salmon.
Highlights
Control of food intake and energy metabolism in vertebrates are complex processes involving several neural pathways
We provide an in silico characterization of the three newly identified Npy paralogs in Atlantic salmon, and investigate the regional brain distribution of npy in both fed or 4 days fasted salmon
Characterization of Atlantic Salmon Npy and Phylogenetic Analysis In Atlantic salmon, three npy genes were found to be located on chromosomes ssa14, ssa27, and ssa5
Summary
Control of food intake and energy metabolism in vertebrates are complex processes involving several neural pathways. In Atlantic salmon (Salmo salar), npy mRNA expression in the brain did not significantly change after 6 days of fasting (Murashita et al, 2009), but increased during the first 9 h after feeding (Valen et al, 2011). These studies suggests that effects of fasting and feeding in Atlantic salmon central npy are time-sensitive and that both spatial and temporal response may be different to that found in mammals. Knowledge about the different paralogs, their regional distribution and their responses to different feeding conditions is key to understand the role of Npy in appetite regulation of Atlantic salmon. A 2–4 days fasting period prior to handling, transportation and harvest is common practice in Atlantic salmon aquaculture production (Waagbø et al, 2017), and uncovering impact of fasting on farmed fish is essential to safeguard fish welfare and optimize the aquaculture feeding protocols
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