The Regulation Of Estrogen On Lipid Metabolism Of Tilapia

Tilapia,native to Africa,belongs to the Cichlid family,tilapia.Because tilapia has the characteristics of FASt growth,strong reproduction ability and tolerance to hypoxia,the Food and Agriculture Organization of the United Nations has promoted tilapia farming to countries around the world.China has introduced tilapia and carried out aquaculture activities since the 1960 s.Nowadays,tilapia has become one of the main freshwater aquaculture fish in China.In this study,different concentrations of E2(0 mg/kg,10 mg/kg,25 mg/kg,and 50 mg/kg)and its receptor inhibitors ICI 182,780(ICI,35 mg/kg)were injected into the hybrid tilapia.In addition,an exposed aqueous phase experiment was performed on Nile tilapia with different concentrations of E2(0 ng/L,10 ng/L,25 ng/L,and 50 ng/L),ICI(1 ?M/L),and ICI(1 ?M/L)+ E2(25 ng/L).QPCR was used to detect 12 genes including very low-density lipoprotein(VLDL)synthesis,lipoprotein lipase and lipoprotein receptor,fatty acid uptake,and triacylglycerol metabolism which related with lipid metabolism in the liver.Oil red O staining was used to observe lipid deposition in tilapia liver.Total kits were used to analyze total cholesterol(TC),triglyceride(TG),and high-density lipoprotein(HDL),low-density lipoprotein(LDL),and free fatty acid(NEFA)in tilapia serum.The effects of estradiol on tilapia lipid metabolism were explored.In addition,the expression patterns of related to intestinal lipid metabolism genes of three species of tilapia,hybrid,blue and Nile were analyzed by q PCR.The main findings are as follows:1.The effect of estradiol on lipid metabolism in the liver of hybrid tilapiaIn order to explore the effect of E2 injection on lipid metabolism in tilapia,this chapter analyzed the effects of injection experiments on the expression of 12 genes which related to lipid metabolism in hybrid tilapia.The deposition of liver lipids in tilapia was observed,and the expression changes of TC,TG,HDL,LDL and NEFA in tilapia serum were detected.The results showed that the injection of 50 mg kg E2 could significantly increase the lipid droplets in the liver of hybrid tilapia.At the same time,E2 injection up-regulated the concentrations of TC,TG,LDL and HDL in tilapia serum without affecting the concentration of NEFA.After 50 mg/kg E2 injection,the expression of genes related to VLDL synthesis in the liver of hybrid tilapia was significant increased,but the expression of LDLR and LRP1 were down-regulated.In addition,50 mg/kg E2 injection up-regulated the levels of FABP3,FABP11 a and DGAT2 in the liver and decreased the expression of CD36 and ACO1.10 mg/kg E2 injection did not affect the expression of most genes which related lipid metabolism,but10 mg/kg E2 treatment significantly reduced the levels of LDLR and ACO1.ICI injection inhibited the expression of MTP,LPL,LRP1,CD36,FABP11 a,ACO1 and FAS m RNA in tilapia liver.2.The effect of estradiol on lipid metabolism of Nile tilapiaIn order to explore the effect of E2 exposure on tilapia lipid metabolism,this chapter analyzed the effect of water phase exposure on the expression of 12 genes which related to lipid metabolism in Nile tilapia.The changes of hepatopancreas ratio and survival rate were measured.The results showed that short-term E2 exposure did not affect the survival rate and hepatopancreas ratio of Nile tilapia.In addition,E2 exposure up-regulated the expression of lipid metabolism-related genes including MTP,LPL,CD36,and DGAT2.But it did not affect the expression of APOA4 B,LRP1,FABP3,ACO1,and FAS.E2 receptor inhibitor ICI alone inhibited the expression of LDLR,FABP3,FABP11 a and ACO1 in the liver of tilapia.Furthermore,ICI alone promoted the expression of APOA4 B,APOB and LPL genes.For DGAT2,significant differences were observed between the ICI alone and the ICI+E2 combined exposure groups.The level of this gene in the co-exposure group was significantly higher than that of the ICI alone treatment.3.The differential expression of lipid metabolism related genes in the intestine of female Nile tilapia,male Oreochromis and their hybridsIn order to analyze the differential expression of genes which related to lipid metabolism among the hybrid tilapia and their parents.This chapter analyzed the expression patterns of genes related to intestinal lipid metabolism in three species of tilapia: Nile,blue and hybrid.In the intestine of hybrid tilapia,APOA4 B was expressed at mod-erate levels,but APOB and MTP were ELD-B and ELD-N expression patterns,respectively.LPL and LRP1 showed a transgressive up-regulation pattern in the offspring,while LDLR was selected as the ELD-B pattern.As for fatty acid uptake-related genes,only FABP11 a was transgressive up-regulated expression,CD36 and FABP3 were additively expressed in hybrid.FAS and DGAT2 which related to TG metabolism were transgressive up-regulated in hybrid.Eight of the twelve genes that analyzed in this study were non-additive expression patterns,and five of them are transgressive up-regulated expression patterns.In addition,this study did not find that lipid-metabolism-related genes have transgressive down-regulated expression patterns in hybrid.The results in this study indicated that according to stimulated related genes with VLDL synthesis,inhibited lipoprotein lipase and lipoprotein receptor-related genes,and promoted the expression of rate-limiting enzyme-related genes in TG synthesis,E2 induces lipid deposition in the liver of tilapia.In addition,the expression of genes related to lipid metabolism in the hybrid is higher,which is beneficial to the lipid metabolism in fish.Overall,the results of this study indicate the role of E2 in lipid metabolism in fish and provide related clues to explore the role of sex steroids in liver energy metabolism.