Appetite control and feed intake- Can AgRP serve as a biomarker for appetite in the teleost Atlantic salmon, Salmo salar?

In mammals, the main center for appetite control is the arcuate nucleus (ARC), which contains different neuronal populations. Anorexigenic neurons co-express cocaine- and amphetamine-regulated transcript ( cart) and proopiomelanocortin ( pomc) neuropeptides. The pomc peptide undergoes posttranslational modifications and one of its products, α-MSH, is released together with CART to inhibit appetite. The orexigenic neurons co-express and release neuropeptide Y (NPY) and agouti-related peptide (AgRP) to stimulate appetite. Together, these two ARC neuronal populations comprise the key neuropeptide expression of the melanocortin system (MCS).The MCS is relatively well-conserved among vertebrates, including teleost species. However, in Atlantic salmon ( Salmo salar), the salmonid-specific fourth round whole-genome duplication has resulted in the presence of several paralogous genes, some of which may have resulted in divergent functions. Our in-silico analyses have shown that in Atlantic salmon the key potential neuropeptides of the MCS repertoire comprises three npy, one agrp, ten cart and three pomc genes.Analyses of mRNA distribution of the genes for the MCS neuropeptides across brain regions in salmon reveal significant spatial and quantitative differences in their expression profile between paralogs. In situ hybridization analyses show that agrp1 is only expressed in the nucleus lateralis tuberis (NLT) region of the Atlantic salmon, the putative homolog to the mammalian ARC. In this NLT area, npya, agrp1, cart2b, and pomca are predominantly localized in distinct neurons, however, some neurons co-express cart2b/ pomca. This contrasts with what is known for higher vertebrates and show that co-expression is not required for homeostatic feeding control. Further, studies of fed and fasted fish support that agrp1 acts as an orexigenic signal in Atlantic salmon. In addition, the distinct and well-defined localization of agrp1 in the NLT region suggest that the hypothalamic agrp1 gene may serve as a biomarker for appetite and feed intake in the Atlantic salmon. Research Council of Norway (Projects# 221568; 254894, 267626, 268987, 315106, 317770) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.