Dietary Exposure to 2,2′,4,4′-Tetrabromodiphenyl Ether (BDE-47) Causes Inflammation in the Liver of Common Carp (Cyprinus carpio) and Affects Lipid Metabolism by Interfering with Steroid Hormone Biosynthesis Pathways

2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) is a common environmental contaminant and widely detected in aquatic surroundings, while only a few reports exist on the hazard mechanism in economic aquatic animals. It has been shown that 40 and 4000 ng/g of BDE-47 dietary exposure over 42 days significantly increased the levels of blood triglycerides, glucose, and liver glycogen in carp (Cyprinus carpio). Tissue observations showed that BDE-47 resulted in vacuolation, atrophy, and fat deposition in hepatocytes. Combined metabolomic and transcriptomic analyses revealed that BDE-47 affected the inflammatory response and the biosynthesis of steroid hormones. This was further confirmed by gene expression related to inflammatory factors (il-10, tnf-α, il-1β, and tgf-β1), lipid metabolism (acc, fas, srebp, rxr, atgl, hsl, and lpl), and the steroid hormone biosynthetic pathway (11bhsd, hsd3b, and star). Thus, BDE-47 affects liver inflammatory response and lipid deposition through steroid hormone biosynthesis in carp. This helps us to understand how BDE-47 dietary exposure impacts inflammation and lipid metabolism in fish, which affects the health of aquaculture and has potential risks to human health.