Duplication of neuropeptide Y and peptide YY in Nile tilapia Oreochromis niloticus and their roles in food intake regulation

Abstract

In vertebrates, the neuropeptide Y (NPY) family peptides have been recognized as key players in food intake regulation. NPY centrally promotes feeding, while peptide YY (PYY) and pancreatic polypeptide (PP) mediate satiety. The teleost tetraploidization is well-known to generate duplicates of both NPY and PYY; however, the functional diversification between the duplicate genes, especially in the regulation of food intake, remains unknown. In this study, we identified the two duplicates of NPY and PYY in Nile tilapia (Oreochromis niloticus). Both NPYa and NPYb were primarily expressed in the central nervous system (CNS), but the mRNA levels of NPYb were markedly lower than those of NPYa. Hypothalamic mRNA expression of NPYa, but not NPYb, decreased after feeding and increased after 7-days of fasting. However, both NPYa and NPYb caused a significant increase in food intake after an intracranial injection of 50ng/g body weight dose. PYYb, one of the duplicates of PYY, had an extremely high expression in the foregut and midgut, whereas another form of duplicate PYYa showed only moderate expression in the CNS. Both hypothalamic PYYa and foregut PYYb mRNA expression increased after feeding and decreased after 7-days of fasting. Furthermore, the intracranial injection of PYYb decreased food intake, but PYYa had no significant effect. Our results suggested that although the mature peptides of NPYa and NPYb can both stimulate food intake, NPYa is the main endogenous functional NPY for feeding regulation. A functional division has been identified in the duplicates of PYY, which deems PYYb as a gut-derived anorexigenic peptide and PYYa as a CNS-specific PYY in Nile tilapia.

Distribution and female reproductive state differences in orexigenic and anorexigenic neurons in the brain of the mouth brooding African cichlid fish, Astatotilapia burtoni

“…Similar to our results for npy, a previous study in A. burtoni also found no differences in whole brain npy expression among gravid (fed), starved, and brooding (starved) females (Grone et al, 2012). Studies in other fishes show considerable variation in the response of npy mRNA levels to feeding conditions (Murashita, Kurokawa, Ebbesson, Stefansson, & Ronnestad, 2009;Yan et al, 2017;Yokobori et al, 2012 as potential candidates regulating energy balance and feeding behavior because of their previously described role in zebrafish. For example, starvation in zebrafish led to a reduction in the population of cart2 mRNA-expressing cells of the E and NRL, and in the cart4 mRNAexpressing cells of the NLT (Akash et al, 2014).…”

“…Similar to our results for npy , a previous study in A. burtoni also found no differences in whole brain npy expression among gravid (fed), starved, and brooding (starved) females (Grone et al, ). Studies in other fishes show considerable variation in the response of npy mRNA levels to feeding conditions (Murashita, Kurokawa, Ebbesson, Stefansson, & Ronnestad, ; Yan et al, ; Yokobori et al, ). Thus, the regulation of npy mRNA may vary between species that differ in diet, digestive physiology, and metabolic trade‐offs associated with life‐history characteristics such as parental care.…”

“…Duplicate npy genes ( npya , npyb ) are identified in A. burtoni (Hu et al, ), and our npy ISH results likely represent the distribution of npya . We chose to examine this form rather than the teleost‐specific duplicate, npyb , because in the related Nile tilapia O. niloticus , npya is expressed at much higher levels in the brain compared to npyb , responds to changes in feeding conditions that are not evident in npyb , and intracranial injections stimulate food intake (Yan et al, ). Thus it is possible that the neurons labeled in DT and gTN with IHC in A. burtoni represent npyb populations.…”

Microarray and metabolome analysis of hepatic response to fasting and subsequent refeeding in zebrafish (Danio rerio)

“…RNA extraction and complementary DNA generation were performed as described previously [66]. A total of 10 μL of the PCR reaction volume contained 5 μL of SYBR® Green Realtime PCR Master Mix (TOYOBO, Japan), 0.6 μL of forward and reverse primers (10 μM each), 1 μL of 10-fold diluted cDNA templates and 3.4 μL of water.…”

Effect of food deprivation on neuropeptide Y immunoreactivity and concurrent biochemical and gonadal responses in tilapia Oreochromis mossambicus (Peters, 1852)

“…The feeding behaviour of animals is complex and the acts of feeding and ingestion are the final results of a number of factors between the animal and its ecological interactions (Sundstrom et al, 2016). Neuropeptide Y (NPY), a 36 amino acid peptide, is one of the most conserved neuroendocrine peptides (Larhammar, 1996) and is known to be involved in the regulation of feeding behaviour in mammals (Schwartz et al, 1993;Stanley, 1993;Kaiyala et al, 1995), amphibians (Crespi et al, 2004) as well as in fish (Subhedar, 2006;Volkoff, 2016;Yan et al, 2017). However, more comparative studies in different animals with varying life histories are needed for the understanding of evolution of regulation of energy balance in vertebrates (Crespi et al, 2004).…”