Exploring the effects of dietary cholesterol on growth, immunity, and lipid metabolism of juvenile Chinese mitten crabs (Eriocheir sinensis)

This study aims to investigate the nutritional needs and physiological functions of dietary cholesterol in juvenile Chinese mitten crabs (Eriocheir sinensis). In the 8-week feeding experiment, we evaluated the effects of various cholesterol levels (0 control, 0.6, 1.3, 2.6, 5.9, 12.0 g/kg diet) on growth, immune capacity, lipid metabolism, molting, and cholesterol and bile acid metabolism. Crabs (1.06 ± 0.04 g) were divided into six groups with four replicates of 40 crabs per tank. The highest weight gain was found in crabs fed 5.9 g/kg cholesterol (P < 0.05), while the highest molting frequency was observed in the 0.6 g/kg group (P < 0.05). Cholesterol significantly changed fatty acid composition in the hepatopancreas, and 5.9 g/kg cholesterol increased immune enzyme activities (acid phosphatase, alkaline phosphatase, and polyphenol oxidase) (P < 0.05). A 5.9 g/kg cholesterol significantly upregulated lipogenesis- and catabolism-related genes, while higher levels of cholesterol (12.0 g/kg) downregulated lipogenesis-related genes significantly (P < 0.05). Low cholesterol levels upregulated chitinase expression, while ecdysone receptor and molt-inhibiting hormone expressions were upregulated with cholesterol levels (P < 0.05). Cholesterol also upregulated the gene in bile acid metabolism. The total bile acids, the proportion of primary bile acids, and the content of primary bile acids increased significantly compared to the control. Based on quadratic regression model analysis, the optimal dietary cholesterol level for juvenile E. sinensis is 5.74–5.77 g/kg. The study suggests that cholesterol promotes growth and immunity in juvenile E. sinensis by regulating molting frequency, improving lipid and HUFA utilization, and increasing bile acids.