Comprehensive assessment of detoxification mechanisms of hydrolysis fish peptides in largemouth bass (Micropterus salmoides) under copper exposure: Tracing from bioaccumulation, oxidative stress, lipid deposition to metabolomics

As a heavy metal, copper is toxic to aquatic organisms in water, causing oxidative stress and lipid deposition. However, there is currently no effective dietary strategy to prevent damage caused by copper exposure. Here, copper bioaccumulation, antioxidant enzymes, lipogenic enzymes, lipid metabolism-related gene expression levels and metabolic pathways were synthesized and evaluated in copper-exposed largemouth bass (Micropterus salmoides) after hydrolysis fish peptides (HFP) pretreatment. The results showed that supplementation with 1% (P < 0.05), 3% (P < 0.01) and 5% (P < 0.05) HFP significantly reduced the copper bioaccumulation in largemouth bass. Hydrolysis fish peptides supplementation significantly reduced the activities of total antioxidant capacity (P < 0.01) and catalase (P < 0.01) and the contents of glutathione (P < 0.01) and malondialdehyde (P < 0.05). Fatty acid synthetase concentration was significantly reduced in fish supplemented with 3% (P < 0.05) and 5% HFP (P < 0.05). Similarly, fish fed 3% (P < 0.05) and 5% (P < 0.01) HFP significantly reduced the glucose-6-phosphate dehydrogenase concentration. Serum metabolomics revealed that 85, 144 and 207 differential metabolites were obtained in fish supplemented with 1%, 3% and 5% HFP, respectively. The differential metabolites were mainly lipids and lipid-like molecules, which were associated with the lipid metabolism pathways. The expression levels of fatty acid synthase (P < 0.01), sterol regulatory element binding protein-1c (P < 0.05), liver X receptor (P < 0.001), peroxisome proliferator activated γ (P < 0.01), apolipoprotein B (P < 0.001) and fatty acid-binding protein 1 (P < 0.01) were significantly down-regulated and the expression levels of carnitine palmitoyltransferase 1α (P < 0.01), hormone-sensitive lipase (P < 0.001), apolipoprotein A 1 (P < 0.05) were significantly up-regulated in fish fed with 3% HFP. Additionally, supplementation with 3% (P < 0.01) and 5% (P < 0.001) HFP significantly up-regulated the expression level of B-cell lymphoma-2 with a dose-dependent effect. In conclusion, our study confirmed that HFP supplementation was closely associated with oxidative stress, enzymatic activities and related pathways of lipid metabolism, and apoptosis, and in general alleviated lipid deposition caused by copper exposure in largemouth bass.