Evaluating dietary cholesterol and taurine interactions: Implications for growth performance, bile acid metabolism, and lipid regulation in Chinese mitten crab (Eriocheir sinensis)

Cholesterol serves as a precursor for bile acids and molting hormones, while taurine is involved in bile acid conjugation and lipid regulation in vertebrates. However, their synergetic roles in crustacean nutrition remain poorly understood. This study investigated the interactions between dietary cholesterol (0%, 0.64%, and 1.00%) and taurine (0% and 0.65%) in juvenile Chinese mitten crabs (Eriocheir sinensis). A total of 960 juvenile crabs (3.08 ± 0.02 g) were randomly assigned to six dietary treatments (four replicates per treatment, 40 crabs per replicate) in a 3 × 2 factorial design for 8 weeks. Growth performance, body proximate composition, serum and hepatopancreas biochemical indices, bile acid profiles, and expression of genes related to lipid metabolism and the nutrient-sensitive mammalian target of rapamycin (mTOR) signaling pathway were evaluated. Significant improvements in final body weight, weight gain, specific growth rate, and feed conversion ratio were observed in crabs fed the diet containing 0.64% cholesterol and 0.65% taurine (P < 0.05). Dietary cholesterol significantly increased hepatopancreas total cholesterol and bile acid contents (P < 0.05), particularly taurohyodeoxycholic acid and epi-allolithocholic acid, while taurine supplementation further elevated cholic acid content. Taurine effectively reduced serum total cholesterol and low-density lipoprotein cholesterol concentrations (P < 0.05), especially at higher dietary cholesterol levels. The combination of cholesterol and taurine significantly alleviated antioxidant impairment by increasing superoxide dismutase activity (P < 0.001), and upregulated key genes in lipid metabolism (fas and cpt1a), cholesterol transport (abcg8), and mTOR pathway components (mtorc1, s6k1, and 4ebp1) (P < 0.05). Dietary 0.64% cholesterol in combination with 0.65% taurine optimized growth performance and improved the health of E. sinensis. Taurine enhanced cholesterol utilization by facilitating its conversion into bile acids and activating key nutrient-sensing pathways such as the mTOR pathway, thereby improving lipid metabolism and antioxidant capacity. These findings reveal a synergistic metabolic interaction in which taurine enhances the nutritional value of cholesterol by facilitating its conversion into signaling-active bile acids and directly modulating lipid metabolism pathways.