Regulation of somatic growth and gene expression of the GH–IGF system and PRP-PACAP by dietary lipid level in early juveniles of a teleost fish, the pejerrey (Odontesthes bonariensis)

Abstract

Growth and mRNA levels of the pituitary adenylate cyclase-activating polypeptide (PACAP) and its related peptide (PRP), and the system controlled by the growth hormone (GH) and insulin-like growth factors (IGFs) were analyzed in pejerrey fry fed with graded levels of dietary lipids: 10% (L10), 13% (L13) and 21% (L21). First, the full sequence of pejerrey PRP-PACAP was obtained by RT-PCR, using primers based on conserved fragments of teleosts PACAP sequences. The growth of the fish at 83 days after hatching (dah) and the GH mRNA levels were not significantly affected by the dietary treatment. Conversely, PRP-PACAP expression significantly decreased with increasing dietary lipids (L10 > L21). While GH receptor (GHR)-I and IGF-I transcripts did not differ among groups, GHR-II transcripts decreased in group L21. IGF-II expression apparently followed the same trend. These results in combination with the lower expression of the anorexigenic PRP-PACAP in fish fed diet L21 and the correlation analysis evidencing a particularly fine tuning of the GH-IGF system in group L13, suggest that this diet may cover the energy demands for growing pejerrey from 27 dah onwards. Our results show for first time in fish a differential response of PRP-PACAP transcripts to dietary manipulations, and confirm the sensitivity of the pejerrey GH-IGF system to changes in diet composition despite the lack of (or in advance to) a clear response of somatic growth.

New approaches for growth improvement in pejerrey Odontesthes bonariensis (Valenciennes, 1835) culture (Atherinomorpha: Atherinopsidae)

“…Similar results were also reported for extensive culture based on only zooplankton intake resulted in higher length and weight values Garcia de Souza et al, 2013). However, since nutritional requirements of the pejerrey are still unknown (Gómez-Requeni et al, 2012), growth rates attained under intensive culture conditions without a proper formulation of an artificial food cannot be as higher as the one achieved in cages in natural environments. This statement reinforces the idea that the current situation of pejerrey culture is still far from having reached a state of optimal development and that zooplankton supply represents an essential diet component for obtaining a good growth performance.…”

Neuroendocrine regulation of somatic growth in fishes

“…PACAP levels increase as a result of excessive feeding or refeeding after a period of food-deprivation [64,65]. Conversely, PRP-PACAP expression can be significantly down-regulated by increasing the level of dietary lipids [66]. These observations suggest that PACAP is involved in regulating food intake and somatic growth in fish.…”

Acclimation to different environmental salinities induces molecular endocrine changes in the GH/IGF-I axis of juvenile gilthead sea bream (Sparus aurata L.)

“…However, GH mRNA did not change under PACAP treatment in the olive flounder Paralichthys olivaceus (Nam et al 2013). Also, dietary lipid changes influenced more PACAP, GH receptors and IGF-I than GH itself (Gómez-Requeni et al 2012).…”