Estradiol (E2) is a sex steroid hormone that modulates multiple physiological processes in teleosts. The aim of this study was to explore the role of E2 in the hepatic lipid metabolism of hybrid tilapia. The hybrid tilapias were injected with different concentrations of E2 (0 mg/kg, 10 mg/kg, 25 mg/kg and 50 mg/kg) and ICI 182,780 (ICI) (35 mg/kg) (an E2 receptor antagonist). Subsequently, the liver lipid depositions were analyzed by tissue sections with oil red O staining. Serum total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL) and nonesterified fatty acids (NEFAs) were assayed from the fish in different groups. Genes related to very low-density lipoprotein (VLDL) assembly, lipoprotein lipase and lipoprotein receptors, fatty acid uptake and triacylglycerol metabolism were determined by quantitative RT-PCR. The results showed that 50 mg/kg E2 injections enlarged the lipid droplets significantly. Simultaneously, the E2 injections tended to upregulate TC, TG, LDL, and HDL in the serum. The 50 mg/kg E2 group showed a significantly higher expression of the VLDL assembly genes but depressed levels of LDLR and LRP1. In addition, FABP3, FABP11a and DGAT2 were significantly elevated, while CD36 and ACO1 decreased in the 50 mg/kg E2 injection. The ICI injection inhibited the expression of MTP, LPL, LRP1, CD36, FABP11a, ACO1 and FAS in tilapia livers. These results demonstrated that by stimulating the expression of genes associated with the VLDL assembly, inhibiting lipoprotein lipase and lipoprotein receptor-related genes and promoting the rate-limiting enzyme in the synthesis of the TG, E2 induced deposition of lipids in the livers of hybrid tilapia. Overall, the results suggest a role for E2 in fish lipid metabolisms that provide new clues to illustrate the sex steroid function in energy metabolism in livers.

雌二醇（E2）是一种性甾体激素，可调节硬骨鱼的多个生理过程。这项研究的目的是探讨E2在杂交罗非鱼肝脂质代谢中的作用。向杂交罗非鱼注射不同浓度的E2（0 mg / kg，10 mg / kg，25 mg / kg和50 mg / kg）和ICI 182,780（ICI）（35 mg / kg）（一种E2受体拮抗剂）。随后，通过油红O染色的组织切片分析肝脂质沉积。从不同组的鱼中检测出血清总胆固醇（TC），甘油三酸酯（TG），高密度脂蛋白（HDL），低密度脂蛋白（LDL）和非酯化脂肪酸（NEFA）。与极低密度脂蛋白（VLDL）组装，脂蛋白脂酶和脂蛋白受体有关的基因，通过定量RT-PCR测定脂肪酸摄取和三酰基甘油代谢。结果表明，注射50 mg / kg E2可以显着增大脂质滴。同时，E2注射倾向于上调血清中的TC，TG，LDL和HDL。50 mg / kg E2组显示VLDL装配基因的表达明显较高，但LDLR和LRP1的水平降低。此外，在注射50 mg / kg E2时，FABP3，FABP11a和DGAT2显着升高，而CD36和ACO1降低。ICI注射可抑制罗非鱼肝中MTP，LPL，LRP1，CD36，FABP11a，ACO1和FAS的表达。这些结果表明，通过刺激与VLDL装配相关的基因的表达，抑制脂蛋白脂肪酶和脂蛋白受体相关基因并促进限速酶的合成，TG，E2诱导杂种罗非鱼肝脏中脂质的沉积。总体而言，这些结果表明E2在鱼类脂质代谢中的作用，为说明性类固醇在肝脏能量代谢中的作用提供了新线索。