Altered dietary carbohydrates significantly affect gene expression of the major glucosensing components in Brockmann bodies and hypothalamus of rainbow trout.
Carnivorous fish have a limited capacity to utilize dietary carbohydrates even though glucosensing components exist in the hypothalamus and Brockmann bodies. Therefore, we fed trout for 10 days with two experimental diets containing a high level of carbohydrates (20%) or a carbohydrate-free level (<0.3%) to test the capacity of dietary carbohydrates to regulate gene expression of glucosensing components. Fish were fed and killed 1, 6, and 24 h after the meal to analyze plasma glucose levels, glucosensing-related biochemical parameters, and gene expression of the major components of the glucosensing system in the hypothalamus and Brockmann bodies. Glucose facilitative transporter type 2 and glucokinase gene expression were confirmed by real-time PCR data and two new components of the glucosensing mechanism, Kir6.-like and sulfonylurea receptor-like, were detected for the first time in fish in both tissues. In addition, a clear adaptation to dietary carbohydrates was found in trout Brockmann bodies, based on increased gene expression of major components of the system as well as enhanced glucokinase activities and glycogen levels. In contrast, in the hypothalamus, only glucokinase gene expression and activity showed a response to dietary carbohydrates, supporting the key role of that enzyme in glucosensing mechanism. Finally, a differential postprandial profile was found between tissues regarding the glucosensing potential, since the hypothalamus seems to respond to hyperglycemia earlier than the Brockmann bodies, whose response took place later. Altogether, these data describe for the first time in fish a complete response of major glucosensing components to dietary carbohydrates in trout hypothalamus and Brockmann bodies, supporting an efficient adaptation of both tissues to those dietary components.
Polakof
Sergio
S
Laboratorio de Fisioloxía Animal, Facultade de Bioloxía, Edificio de Ciencias Experimentais, Universidade de Vigo, E-36310 Vigo, Spain. spolakof @uvigo.es
Panserat
Stéphane
S
Plagnes-Juan
Elisabeth
E
Soengas
José L
JL
D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D050528:Diet, Carbohydrate-Restricted; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology; D064429:Fatty Acid Synthases / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D005941:Glucokinase / Q000235:genetics / Q000378:metabolism; D051273:Glucose Transporter Type 2 / Q000235:genetics / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D054086:KATP Channels / Q000235:genetics; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000235:genetics / Q000502:physiology*; D019518:Postprandial Period / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics; D011955:Receptors, Drug / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D064233:Sulfonylurea Receptors; D019014:fas Receptor / Q000235:genetics
D018528:ATP-Binding Cassette Transporters; D001786:Blood Glucose; D004040:Dietary Carbohydrates; D051273:Glucose Transporter Type 2; D054086:KATP Channels; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors; D019014:fas Receptor; D006003:Glycogen; D064429:Fatty Acid Synthases; D005941:Glucokinase