Considering the limited capacity of carnivorous fish to utilize dietary carbohydrates and the presence of glucosensor components in trout hypothalamus and Brockmann bodies, we fed trout for 10 days with two experimental diets containing a high level of carbohydrates (20%) or carbohydrate-free (<0.3%) to test the capacity of dietary carbohydrates to regulate gene expression of glucosensing components. Fish were fed and killed 1, 6 and 24h after the meal to analyze plasma glucose levels, glucosensing-related biochemical parameters and gene expression of major components of the glucosensing system in hypothalamus and Brockmann bodies. GLUT2 and glucokinase gene expression were confirmed by real time PCR data and two new components of the glucosensing mechanism, Kir6.-like and SUR-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 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 mechanism was activated 1h after feeding in hypothalamus, in contrast to Brockmann bodies where the response took place 6h after feeding. 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.