Effects of dietary oxidized soybean meal and oxidized soybean oil on hepatic lipid deposition, antioxidant capacity, inflammation, and apoptosis in blunt snout bream (Megalobrama amblycephala).

Soybean meal (SBM) and soybean oil (SO) are important aquafeed ingredients, but both are prone to oxidation. However, few studies have compared the effects of oxidized SBM (OSM) and oxidized SO (OSO) in fish. In this study, OSM and OSO were generated by SBM and SO under the same conditions and then used to evaluate their effects on liver antioxidant capacity, inflammation, and apoptosis in Megalobrama amblycephala. A total of 144 fish (initial body weight: 14.37 ± 0.13 g) were randomly divided into three groups and reared for 8 weeks. Both OSM and OSO increased plasma low-density lipoprotein cholesterol (LDL-C) and decreased high-density lipoprotein cholesterol (HDL-C). Oil Red O staining confirmed hepatic lipid accumulation in both groups. The OSO significantly increased plasma MDA levels, while hepatic protein carbonyl (PC) levels were significantly elevated only in the OSM group. Meanwhile, both treatments significantly increased interleukin-1β (IL-1β) levels and decreased transforming growth factor-β (TGF-β) levels. TUNEL assays confirmed increased hepatocyte apoptosis, associated with the downregulation of pi3k, akt, and nf-κb and changes in caspase family gene expression. Notably, OSO upregulated caspase-8 expression, whereas OSM significantly upregulated caspase-9 and caspase-3 expression, suggesting that OSM may be associated with the regulation of mitochondrial apoptosis-related genes. In conclusion, OSM and OSO induce hepatic lipid accumulation, oxidative stress, and inflammation, and the downregulation of pi3k, akt, and nf-κb expression may be associated with hepatocyte apoptosis. Overall, OSM and OSO exhibited different hepatic response patterns.