Hepatic glucose utilization and lipogenesis of hybrid striped bass (Morone chrysops × Morone saxatilis) in response to dietary carbohydrate level and complexity

The influence of carbohydrate level and complexity on in vitro hepatic glucose utilization and lipogenesis were determined in hybrid striped bass, Morone chrysops ♀ × Morone saxatilis ♂. Six isocaloric, isonitrogenous diets containing glucose, maltose, or dextrin at two different levels (200 or 400 g kg−1 diet) were fed to adult fish for 15 weeks. Liver explants were obtained at near-maximum postprandial glycaemic response and incubated with radioactive labelled substrates. Glycogen synthesis from [14C]glucose was not different among treatments and was less than 14CO2 formation. 14CO2 production increased as a function of carbohydrate level but was unrelated to carbohydrate complexity. There was no detectable conversion of [14C]glucose to lactate for any treatment. Rates of de novo lipogenesis from [1-14C]acetate were high in comparison to [U-14C]glucose or [9,10-3H]palmitate incorporation into liver lipids and differed in response to carbohydrate level and complexity. [9,10-3H]palmitate esterification was an order of magnitude less than glycogen and CO2 production but 4–10 times greater than [14C]glucose incorporation into liver lipids. Palmitate incorporation did not differ among treatments. Incorporation of [14C]glucose into liver lipids was higher in fish fed diets containing 400 g kg−1 carbohydrate. These data support the idea that glucose is not a major oxidative substrate in hybrid striped bass and indicate that the level of soluble carbohydrate should be limited to 200 g kg−1 diet or less for hybrid striped bass.