Reprod. Nutr. Dev. 44 (2004) 233-242
DOI: 10.1051/rnd:2004027

Response of hexokinase enzymes and the insulin system to dietary carbohydrates in the common carp, Cyprinus carpio

Encarnación Capilla^a, Françoise Médale^b, Stephane Panserat^b, Christiane Vachot^b, Paulo Rema^c, Emidio Gomes^d, Sadasivam Kaushik^b, Isabel Navarro^a and Joaquim Gutiérrez<sup>a

a</sup>  Departament de Fisiologia, Facultat de Biologia, Universitat de Barcelona, 08028 Barcelona, Spain
^b  Fish Nutrition lab., Unité Mixte Inra-Ifremer, Station d'hydrobiologie INRA, 64310 Saint-Pée-sur-Nivelle, France
^c  Universidade de Tras-os-Montes e Alto Douro (UTAD), Apartado 202, 501 Vila Real Codex, Portugal
^d  Instituto de Ciencias Biomedicas Abel Salazar (ICBAS), Largo Abel Salazar 2, 4050 Porto, Portugal

(Received 2 July 2003; accepted 4 March 2004)

Abstract - The response of the common carp to diets with varying amounts of digestible starch, provided either as pea meal (LP, HP, 30 and 46% peas, respectively) or as cereal (LW, HW, 30 and 46% wheat, respectively), was studied and compared with the response to a carbohydrate-free protein-rich diet (CF). Here we focused on the utilisation of dietary carbohydrates by examining the relationship between dietary starch intake, hepatic hexokinase activities, circulating insulin and muscle insulin receptor system. Plasma glucose concentration and hepatic high Km hexokinase (glucokinase, GK) activity were not affected by the content of digestible starch, but 6 h after feeding enzyme activity was higher in the fish fed carbohydrate diets. Similarly, low Km hexokinase (HK) activity was also higher in the fish 24 h after feeding. Fat gain and protein retention were significantly improved by increased digestible starch intake, especially in the HP group, which in turn, presented the highest plasma insulin levels. Glycogen stores were moderately increased by the ingestion of digestible starch. The number of insulin receptors was greater in the CF group than in fish on carbohydrates, except the HP group. Our results confirmed that the common carp uses dietary carbohydrates efficiently, especially when there are provided by peas. This efficiency might be related to the enhanced response of postprandial insulin observed in the HP group.

Key words: glycaemia / insulinemia / hexokinases / fish / insulin muscle receptors

Corresponding author: Joaquim Gutiérrez joaquim@porphos.bio.ub.es

© INRA, EDP Sciences 2004