Detection and Modulation of Olfactory Sensing Receptors in Carnivorous Rainbow Trout (Oncorhynchus mykiss) Fed from First Feeding with Plant-Based Diet

Abstract

Sense of smell is mediated by diverse families of olfactory sensing receptors, conveying important dietary information, fundamental for growth and survival. The aim of this study was to elucidate the role of the sensory olfactory pathways in the regulation of feeding behavior of carnivorous rainbow trout (RT, Oncorhynchus mykiss), from first feeding until 8 months. Compared to a commercial diet, RT fed with a total plant-based diet showed drastically altered growth performance associated with feed intake from an early stage. Exhaustive examination of an RT genome database identified three vomeronasal type 1 receptor-like (ORA), 10 vomeronasal type 2 receptor-like (OLFC) and 14 main olfactory receptor (MOR) genes, all highly expressed in sensory organs, indicating their potential functionality. Gene expression after feeding demonstrated the importance in olfactory sensing perception of some OLFC (olfcg6) and MOR (mor103, -107, -112, -113, -133) receptor family genes in RT. The gene ora1a showed evidence of involvement in olfactory sensing perception for fish fed with a commercial-like diet, while ora5b, mor118, mor124 and olfch1 showed evidence of involvement in fish fed with a plant-based diet. Results indicated an impact of a plant-based diet on the regulation of olfactory sensing pathways as well as influence on monoaminergic neurotransmission in brain areas related to olfactory-driven behaviors. The overall findings suggest that feeding behavior is mediated through olfactory sensing detection and olfactory-driven behavior pathways in RT.

Elevated Water CO2 Can Prevent Dietary-Induced Osteomalacia in Post-Smolt Atlantic Salmon (Salmo salar, L.)

“…In studies on European sea bass ( Dicentrarchus labrax ), gilthead seabream ( Sparus aurata ), and rainbow trout, high CO 2 resulted in olfactory system impairment and reduced SGR [ 104 , 105 , 106 , 107 ]. Comparable to other teleost fishes, Atlantic salmon rely on smell (olfactory system) to detect feed [ 87 , 88 ] which could provide an explanation for the reduced feed intake under high CO 2 in the current study and in other studies [ 104 , 105 ]. In addition, acid-base regulation and stress related to increased plasma CO 2 are metabolically costly [ 108 , 109 , 110 , 111 ].…”

Characterization of free fatty acid receptor family in rainbow trout (Oncorhynchus mykiss): towards a better understanding of their involvement in fatty acid signalisation

“…Diets were isoenergetic ( c. 24.41 kJg -1 of dry diet) and were formulated to cover the nutritional requirements of the rainbow trout [ 21 ]. Nutrient compositions of the diets, crude protein and lipids, gross energy, ash and starch content and fatty acid profils were analyzed as previously described [ 16 ].…”

“…The reaction mix was 6 µl per sample, including 2 µl of diluted cDNA template (1:10), 0.24 µl of each primer (10 µmol l -1 ), 3 µl of Light Cycler 480 SYBR® Green I Master mix and 0.52 µl of DNAse/RNAse-free water (5 Prime GmbH, Hamburg, Germany). The qPCR protocol was initiated at 95 °C for 10 min for the initial denaturation of the cDNA and hot-start Taq-polymerase activation, followed by 45 cycles of a two-step amplification program (15 s at 95 °C; 10 s at 60 °C) [ 16 ]. Cycle thresholds values superior than 35 cycles were not considered.…”

“…Some studies reported that this absence of ω-3 LC-PUFA in plant products, especially DHA, is known to affect feeding behavior during the whole fish life-cycle by reducing feed intake [ 12 ] and feeding rhythms [ 13 ], and by increasing abnormal feeding behavior [ 14 ]. Recently, we revealed that rainbow trout have the fundamental mechanisms (sensory receptors) for nutrient perception related to different diet composition enriched or not with ω-3 LC-PUFA [ 15 , 16 ] and that ω-3 LC-PUFA controlled its feeding behavior [ 17 ]. Furthermore, we observed that a diet rich in ω-3 LC-PUFA impacted in a relatively high proportion the brain function [ 18 ] and brain lipid content [ 19 ] in rainbow trout.…”

Physical Enrichment Triggers Brain Plasticity and Influences Blood Plasma Circulating miRNA in Rainbow Trout (Oncorhynchus mykiss)

“…Compared to 18 s and actin , the elongation factor 1α gene ( eef1α ) showed the most stable expression between brain areas and tissues and was chosen as the reference gene. Relative expression of the target genes was determined by the ΔΔCT method [ 35 , 36 , 37 ]. Mean ± standard error of mean values for each group are expressed in fold changes relative to the BE treatment for all genes.…”