Title: Glucose Oxidation and Lipogenesis in Hybrid Striped Bass Fed Diets with Different Starch Ratios Authors
|Lochmann, Rebecca - UAPB|
Submitted to: American Society of Animal Science Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: February 22, 2005
Publication Date: April 21, 2005
Citation: Rawles, S.D., Gaylord, T.G., Lochmann, R. 2005. Glucose oxidation and lipogenesis in hybrid striped bass fed diets with different starch ratios [abstractM72]. American Society of Animal Science Annual Meeting. Journal of Animal Science 83 (Supplement 1):24. Technical Abstract: Increasing the ratio of amylose (AMY) to amylopectin (PEC) in the diet improves carbohydrate (CHO) use in some mammals. Slower digestion of AMY results in lower glycemic index, lipogenesis, and leaner growth. Carnivorous fish may benefit from this strategy since fish do not use CHO well and any increase in dietary inclusion could reduce feed costs. A 7-wk feeding trial with hybrid striped bass (HSB) was conducted using isonitrogenous, isocaloric, semipurified diets containing 25% CHO of increasing AMY:PEC ratio. Liver slices were then incubated with radiotracers ([U-14C]glucose, glc and [3H]palmitate, pal) to determine glc utilization and de novo lipid and triacylglycerol biosynthesis. Hepatic glycogen production decreased with increasing AMY and was 10X lower than the rate of [14C]glc oxidation to CO2 in all treatments. CO2 production accounted for 88 to 96% of total glc utilization and was lowest in fish fed either the GLC diet or the highest amount of AMY (30PEC). Rates of both esterification (from pal) and glyceride formation (from glc) were of similar magnitude as glycogen production and also appeared lowest in fish fed the GLC or 30PEC diets. Trends in glc oxidation, therefore, mirrored trends in lipogenesis and are most likely due to differences in digestion, excretion, and glc sequestering at the cellular level. Concentrations and activities of glc metabolizing enzymes are lowest in fish. Although glc requires no enzymatic digestion, reduced glc phosphorylation results in significant loss via urinary excretion. On the other hand, in vitro glc metabolism and lipogenesis were inversely related to dietary AMY content and also suggests significant CHO loss. High-amylose starch may be resistant to HSB digestion. High rates of CO2 production among all treatments suggest significant oxidation of dietary CHO; however, the tracers used preclude distinction of Krebs vs. pentose cycle CO2. In conclusion, high-amylose diets had minimal positive effects on HSB carbohydrate use.