A reassessment of the carnivorous status of salmonids : hepatic glucokinase is expressed in wild fish in Kerguelen Islands

• Published in: Science of The Total Environment
• Main Authors: Marandel, Lucie, Gaudin, Philippe, Gueraud, Francois, Glise, Stéphane, Herman, Alexandre, Plagnes- Juan, Elisabeth, Veron, Vincent, Panserat, Stéphane, Labonne, Jacques
• Other Authors: Nutrition, Métabolisme, Aquaculture (NuMéA), Institut National de la Recherche Agronomique (INRA)-Université de Pau et des Pays de l'Adour (UPPA), Ecologie Comportementale et Biologie des Populations de Poissons (ECOBIOP), This work benefited from the financial support of the Fédération de recherche MIRA (Milieu et ressources aquatiques) on behalf of University of Pau and Pays de l'Adour. This study is part of SALMEVOL 1041 program, funded by the French Polar Institute Paul Emile Victor (IPEV).
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: gluconeogenesis; environment; glucose metabolism; carbohydrate; polar; salmonids; kerguelen islands; glyconeogenesis; glucokinase; métabolisme du glucose; environnement; gluconeogénèse; iles kerguelen; salmonidae; poisson sauvage; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDV.BA]Life Sciences [q-bio]/Animal biology; Antarctic; Kerguelen; Kerguelen Islands; Antarc*
• Online Access: https://hal.science/hal-01607554; https://doi.org/10.1016/j.scitotenv.2017.08.247

International audience Salmonids belong to a high trophic level and are thus considered as strictly carnivorous species, metabolically adapted for high catabolism of proteins and low utilisation of dietary carbohydrates. However they conserved a “mammalian-type” nutritional regulation of glucokinase encoding gene and its enzymatic activity by dietary carbohydrates which remains puzzling regarding their dietary regime. The present study investigates the hypothesis that this conservation could be linked to a real consumption by trout of this nutrient in their natural habitat. To do so, brown trout were sampled in the sub-Antarctic Kerguelen Islands, a site presenting oligotrophic hydrosystems and no local freshwater fish fauna prior the introduction of salmonids fifty years ago. Qualitative and quantitative analysis of carbohydrate content within Kerguelen trout stomachs demonstrate that these animals are fed on food resources containing digestible carbohydrates. Additionally, glycaemia and more particularly gck mRNA level and gck enzymatic activity prove that Kerguelen trout digest and metabolise dietary carbohydrates. Physiological and molecular analyses performed in the present study thus strongly evidence for consumption of dietary carbohydrates by wild trout in natural environments. Investigating differences between Kerguelen individuals, we found that smaller individuals presented higher glycaemia, as well as higher carbohydrates contents in stomach. However no relationship between scaled mass index and any physiological indicator was found. Thus it appears that Kerguelen trout do not turn to carbohydrate diet because of a different condition index, or that the consumption of carbohydrates does not lead to a generally degraded physiological status. As a conclusion, our findings may explain the evolutionary conservation of a “mammalian-type” nutritional regulation of gck by dietary carbohydrates in these carnivorous fish