Response of rainbow trout’s (Oncorhynchus mykiss) hypothalamus to glucose and oleate assessed through transcription factors BSX, ChREBP, CREB, and FoxO1

Abstract

We aimed to obtain information regarding mechanisms that link glucose- and fatty acid-sensing systems to expression of neuropeptides that regulate food intake in the fish brain. We assessed the relative expression and protein levels of the transcription factors BSX, ChREBP, FoxO1, and CREB in the hypothalamus of rainbow trout (Oncorhynchus mykiss) treated for 6 h with either glucose or oleate in vivo (intra-cerebroventricular treatment with 1 µl 100 g body weight of 40 µg glucose or 1 µmol oleate) or in vitro (incubation with 4-8 mM glucose or 100-500 µM oleate). BSX levels decreased after oleate treatment for mRNA (10% in vitro and 47% in vivo) and protein (25%), while minor changes occurred after glucose treatment. CREB values generally decreased after glucose or oleate treatment for mRNA (50% in vivo) as well as the phosphorylation status of protein (80%). Foxo1 mRNA levels increased in vivo with glucose (129%) and decreased in vivo with oleate (60%), and protein phosphorylation status increased with glucose (in vivo) and oleate. mRNA values of chrebpα decreased in response to glucose and oleate, while protein levels decreased with oleate and increased with glucose. The results support the association of several transcription factors with metabolic control of food intake in fish.

Effects of CCK-8 and GLP-1 on fatty acid sensing and food intake regulation in trout

“…Accordingly, in rainbow trout the phosphorylation status and mRNA abundance of CREB decreased in the hypothalamus and hindbrain after treatment with CCK-8 and GLP-1. This situation is comparable to that observed in mammals under food deprivation (Ren et al 2013) and in fish under anorexigenic conditions such as those elicited by oleate ICV treatment (Conde-Sieira et al 2018). Nevertheless, the phosphorylation status (hypothalamus) and mRNA abundance of FoxO1 (hypothalamus and hindbrain) increased after treatment with CCK-8 and GLP-1.…”

“…Hypothalamus protein lysates (10 μg) were used for Western blot with antibodies from (1) Cell Signaling Technology: anti-phospho AMPKα (Thr172) reference #2531, anti-AMPKα reference #2532, anti-phospho CREB (Ser133) reference #9198, anti-CREB reference #9197, anti-phospho-FoxO1 (Thr24) reference #9464, anti-FoxO1 reference #9454, anti-phospho mTOR (Ser2448) reference #5536 and anti-β-tubulin reference #2146; (2) Sigma: anti-mTOR reference #T2949; (3) Abcam: anti-BSX reference #56092. All these antibodies cross-react successfully with rainbow trout proteins of interest (Skiba-Cassy et al 2009, Kamalam et al 2012, Velasco et al 2016a, Conde-Sieira et al 2018. After washing, membranes were incubated with an IgG-HRP secondary antibody reference #2015718 (Abcam) and bands were quantified by Image Lab software version 5.2.1 (BIO-RAD) in a Chemidoc Touch imaging system (BIO-RAD).…”

“…The knowledge regarding central integration of metabolic and endocrine information eliciting changes in neuropeptide expression ultimately regulating food intake is scarce in fish (Delgado et al 2017. Available studies in fish (Dai et al 2014, Conde-Sieira et al 2018 pointed to a network comparable to that known in mammals , Martínez de Morentin et al 2011, Gao et al 2013. In this network, mTOR and AMPK would operate as mediators between the activation of nutrient-sensing systems and the modulation of the expression of neuropeptides via modulation of the transcription factors FoxO1, CREB and BSX.…”

The characteristics of glucose homoeostasis in grass carp and Chinese longsnout catfish after oral starch administration: a comparative study between herbivorous and carnivorous species of fish

“…A previous study showed that the expression of chrebp was induced in blunt snout bream in response to high dietary levels of carbohydrate (19) . Another study reported that the increased expression of chrebp enhanced the expression of target genes involved in glycolysis, glycogen storage and lipogenesis (60) . In the present study, the up-regulated expression of srebp1 (3 and 6 h), chrebp (6 h), acc (6 h), fas (1, 3 and 6 h) in the livers of grass carp following the oral administration of starch indicated that the process of lipogenesis had been activated.…”

In vitro insulin treatment reverses changes elicited by nutrients in cellular metabolic processes that regulate food intake in fish

“…Activation of nutrient-sensing systems leads to the activation of mammalian target of rapamycin (mTOR) and the inhibition of AMP-activated protein kinase (AMPK), which in turn modulate the transcription factors forkhead box protein O1 (FOXO1), cAMP response element binding protein (CREB) and brain homeobox transcription factor (BSX). Such transcription factors produce changes in the abundance of neuropeptides, as demonstrated in mammals (Blanco Martínez de Morentin et al, 2011;Diéguez et al, 2011;Gao et al, 2013) and fish (Conde-Sieira et al, 2018;Dai et al, 2014;Librán-Pérez et al, 2015b;Otero-Rodiño et al, 2017).…”