Polysaccharide extracted from pomelo fruitlets attenuate hepatic lipid accumulation in hybrid groupers (Epinephelus lanceolatus♂ × Epinephelus fuscoguttatus♀)

Introduction Pomelo is one of the most consumed fruits due to its distinct flavor and sour taste, while large quantities of pomelo fruitlets discard during cultivation and most of them are disposed of as wastes. Such an issue has led to some research on how to make a high value-added reutilization of these fruitlets. Therefore, it was aimed to determine the structural characteristics of the polysaccharide of pomelo fruitlets and evaluate its attenuating effect on the hepatic lipid accumulation in hybrid groupers ( Epinephelus lanceolatus♂ × Epinephelus fuscoguttatus♀ ). Methods and results In this research, YZ-0.5A is a 15,332 Da NaCl-soluble polysaccharide extracted from pomelo fruitlet which was characterized to mainly contain galactose and galacturonic acid and its putative structure was proven to be →2,4)- α-L-Rhap-(1→4)-α-D-GalAp-(1→4)-α-D-GalAp-(1→ with 3 branches. In vivo study, five isolipidic diets (containing 15% lipid) were fed to the groupers with an initial weight of 13.46 ± 0.08 g for 8 weeks, of which the dietary level of YZ-0.5A was 0 mg/kg (control), 150 mg/kg, 300 mg/kg, 600 mg/kg and 1200 mg/kg respectively. We found that the treatment of YZ-0.5A, especially 600 mg/kg, exerted an improved effect on the excessive lipid accumulation in grouper fed with a high-fat diet. In vitro , three graded concentrations of YZ-0.5A (75, 150 or 300 μg/ml) were added to the grouper primary hepatocytes respectively after incubation with 20% lipid emulsion (2 ml/L). The signs of recovery on morphological features observed under examined by histological evaluation supported the lipid lowering effect of YZ0.5-A. Further investigation showed that YZ0.5-A mitigated lipid emulsion-induced irregular lipid deposition by regulating various lipometabolism-related indicators, thereby alleviating oxidative stress and apoptosis. Discussion Overall results exhibited the therapeutic potential of YZ0.5-A and elucidated its underlying mechanism in the fish with excessive lipid deposition, which first suggested the feasibility of reprocessing discarded pomelo fruitlet as medicine in aquaculture.