Aquaculture Reports (Jun 2024)
Xylose and arabinose as potential feed additives to mitigate growth retardation and excess lipid deposition in rabbitfish (Siganus canaliculatus) fed a high-starch diet
Abstract
Starch is the main carbohydrate used in fish feed, but excess dietary starch may lead to excess fat deposition in tissues, especially liver, which can lead to health problems in farmed fish. Aaldopentose monosaccharides, such as xylose and arabinose, appear to have the potential to inhibit the glucose-based lipid synthesis pathway, although the mechanism is unclear. In the present study, rabbitfish (Siganus canaliculatus) were fed two diets with basal (BSD, 15%) and high (HSD, 25%) starch levels, and six other diets in which 1.25% 2.5% and 5% D-xylose (Diets X1, X2 and X3) or L-arabinose (Diets A1, A2 and A3) were added to the HSD by replacing corresponding starch component, respectively. After 8-week feeding experiment, the results showed the HSD reduced growth performance and increased tissue lipid deposition in rabbitfish and these negative effects were generally reversed by the addition of xylose and arabinose to HSD. Specifically, the inclusion of xylose and arabinose reduced the HSD-induced activities of enzymes related to carbohydrate metabolism, including digestion (maltase and sucrase), glycolysis (HK, PFK, PK) and the production of acetyl-CoA from pyruvate (PDH). Addition of xylose or arabinose also decreased the liver expression of genes related to lipid biosynthesis (srebp1, fas and acc), and increased liver gene expression (cpt-1, hsl and lpl) and protein levels of enzymes related to lipid catabolism. Therefore, both xylose and arabinose mitigated the negative effects of HSD on growth performance, and liver and muscle lipid contents by reducing the rate of carbohydrate digestion and metabolism, and inhibiting lipid accumulation by reducing lipid biosynthesis and increasing lipid catabolism in liver. The metabolic impacts of xylose and arabinose revealed in the present study provide further insights into the molecular mechanisms underpinning the actions of the dietary aldopentose monosaccharides in reducing excess fat deposition in tissues of fish fed HSD.
