Cholesterol and highly unsaturated fatty acids: Exploring their synergistic roles in growth and lipid metabolism of juvenile Chinese mitten crab (Eriocheir sinensis)

This study investigated the interactive effects of dietary cholesterol and highly unsaturated fatty acids (HUFAs) on the growth performance, molting dynamics, lipid metabolism, and nutrient signaling pathways in juvenile Chinese mitten crab (Eriocheir sinensis). A 3 × 2 factorial experiment was conducted over 8 weeks, manipulating three cholesterol levels (0 %, 0.06 %, 0.6 %) and two HUFAs levels (0 %, 0.4 %, EPA:DHA 1:3). Results demonstrated a significant synergistic interaction between dietary cholesterol and HUFAs. The combination of 0.06 % cholesterol and 0.4 % HUFAs yielded superior growth outcomes, including the highest final body weight, weight gain, specific growth rate, and lowest feed conversion ratio, surpassing the effects of individual supplementation. This optimal dietary combination also significantly increased whole-body crude protein and lipid content. Analysis of serum biochemical parameters revealed that cholesterol increased triacylglycerides, high-density lipoprotein cholesterol, and total cholesterol, while HUFAs decreased low-density lipoprotein cholesterol. Tissue lipid content and fatty acid profiles varied across molting stages. The combined diet enhanced lipid deposition in the hepatopancreas during the premolt stage. It also promoted the efficient utilization of lipids postmolt, particularly for EPA and DHA. Molecular analyses revealed a synergistic effect of the combined cholesterol and HUFAs supplementation, especially during the postmolt stage. This combination significantly upregulated key genes involved in lipid synthesis (srebp1, fas) in the hepatopancreas and muscle. Furthermore, it enhanced the expression of genes related to lipid transport (mttp, fatp, ldlr). Furthermore, the combined treatment significantly upregulated the expression of growth factor signaling pathway genes (mtorc1, s6k1, egfr, erk) in both the hepatopancreas and muscle. This upregulation likely facilitated rapid cell growth and tissue repair. These findings highlight that optimal dietary cholesterol and HUFAs interact synergistically to enhance growth performance and modulate lipid metabolism and growth signaling throughout the molting cycle in E. sinensis.