| In order to explore the effect of the dietary lipid,diludin and injection of three triiodothyronine(T3)in vitro on growth performance,fat deposition and key gene of lipid metabolism for Nile tilapia(Oreochromis niloticus).The methods of nutrition,biochemical and molecular biological,were studied by the examination hypolipidemic effect and its mechanism.The main results of this study are presented as follows:(1)HSL and MGL clone and tissue specific expression in Nile tilapia(Oreochromis niloticus)In order to investigate the regulation of HSL and MGL genes in Nile tilapia metabolism of lipolysis,In the present study of Nile tilapia,HSL and MGL were firstly cloned,identified,and examined its expression pattern at different tissues.The results showed that cDNA sequences of HSL gene in Nile tilapia were 3147 bp,and the open reading frame was 2142 bp,encoding 714 amino acid,the molecular weight of the protein was 69.70 kDa,and the isoelectric point(pI)was 7.64.The cDNA sequences of MGL gene in Nile tilapia were 7448 bp,and the open reading frame was 918 bp,encoding 306 amino acid,and the molecular weight of MGL was 34 kDa,isoelectric point(pI)showed that 5.88.Quantitative real-time PCR revealed that HSL and MGL were ubiquitously expressed in all the tested tissues from normal nile tilapia,included brain,gill,heart,skin,white muscle,red muscle,liver,abdominal adipose,spleen,kideny,and intestinal tissues,with higher HSL gene expression in abdominal adipose,red muscle,white muscle and brain tissue,and with higher MGL gene expression in brain and skin tissue.This results show that HSL and MGL play an improtant role in body fat hydrolysis process,but the specific regulatory mechanisms still need further experimental verification.(2)Effects of dietary lipid levels and starvation on the expression of lipase gene in Nile tilapiaAn 6-weeks trial was conducted to evaluate the expression of lipolysis genes affected by dietary lipid levels and starvation.In the present study,the diet made from two lipid level,5%and 15%.100 Nile tilapia(initial weight,6.13 ± 0.20g)were randomly divided into two groups with 50 fish in each group,and each fish was embedded with a tracking tag.At the end of trial,fish were fasted for 1,5,12,24 and 168 hours,then the liver and white muscle were collected.Furthermore,using realtime PCR analysis the ATGL,HSL and MGL gene expression level at different fasting time in liver and white muscle.The results showed that the body lipid content of high fat group(15%)was higher than that of normal group,with the prolonging of starvation time the body lipid content was no significant differences.In adipose tissue,with the prolonging of starvation time,the high fat group ATGL gene expression decreased first and then increased,normal fat group gene expression increased in adipose tissue;HSL gene expression was first increased and then decreased,after 24h fasted,the gene expression was significantly increased(P<0.05).In high fat group,gene expression was higher than other groups in 5h and 24h group;each time point in adipose tissue of high fat group MGL gene expression had no significantly change(P>0.05),normal fat group gene expression decreased first and then increased,gene expression was up-regulated in 168h group(P<0.05).The results of present trial indicated that high fat and fasting could promote the expression of lipolytic genes,so as to promote the hydrolysis of fat.But under normal culture conditions,although it can promote fat hydrolysis of fasting,but it not conducive to the growth of the fish.(3)Effects of high fat diets supplemented diludine on growth performance,body composition,fat deposition and lipolysis gene expression of Nile tilapia(Oreochromis niloticus)235 juvenile nile tilapia with initial average weight of(5.91 ± 0.43g)g were randomly divided into five groups with 47 fish in each group.Five diets with two lipid levels(5%and 15%)and four diludine supplementation levels(0 mg/kg,50mg/kg,100 mg/kg and 150mg/kg)in high fat dites were formulated to feed five groups of juvenile nile tilapia respectively.The trial lasted for six weeks.The results showed that high fat diets supplemented diludine could promote the growth of tilapia.However,compared with the high fat diet group,high fat diet supplemented with 50mg/kg and 100mg/kg diludin can significantly reduce the crude fat content of the fish,but no significantly change in the 150mg/kg group.The results of paraffin section showed that compared with the high fat group,the 50mg/kg group had significantly decreased hepatic adipose vacuoles compared with that of the high lipid group,but there was no difference between the two groups of 150mg/kg two and the high lipid group.The change of T3 level in vivo increased with the addition of diludin.Supplementation of 50mg/kg two hydrogen pyridine can significantly increase the expression of genes and gene lipolytic beta oxidation,and significantly reduced the expression of fat synthesis genes.High fat diet can increase the inflammatory gene(IL-1?,TNF-?)expression,but the expression of 50mg/kg diludin can significantly inhibit the inflammatory gene(P<0.05),there was no significant difference between normal group and gene expression of inflammation(P>0.05),with the increasing of the amount of diludin,inflammatory gene expression increased.The results showed that the addition of 50mg/kg to the high fat diet could significantly reduce the fat deposition in fish,liver and muscle tissue,but the excessive addition(150mg/kg)had no obvious effect.At the same time,the addition of 50mg/kg in high fat diet can inhibit the expression of inflammation related genes,relieve inflammation,and promote the healthy growth of fish,and diludin will promote the secretion of T3 in vivoTherefore,guess diludin may play a role in promoting the growth and lipolysis by T3.(4)Effect of high-fat diet plus injecting triiodothyronine(T3)on lipolysis gene expression in Nile tilapiaIn order to explore the effect of T3 on body fat deposition in nile tilapia,this study uses diet with 15%fat to feed the Nile tilapia,after eight weeks,nile tilapia were injected 0.5,1 and 1.5nM/g body weight T3,and control group were injected with saline.Then after injection of 1,3 and 6 hours the tissue were collected.The results showed that the injection of T3 group decreased body fat ratio,and with the increasing of the concentration of T3 and the extension of the time of action,the ratio of limb ratio decreased.Compared with the control group,the expression of ATGL gene in the adipose tissue of fish was significantly decreased after injection 1h and 3h with 0.5nM/g body weight T3(P<0.05);After injection of 1h,the expression of HSL in adipose tissue of the InM/g and 1.5nM/g body weight T3 groups was significantly up-regulated(P<0.05),and there was no significantly change in the other groups(P>0.05);The expression of MGL in adipose tissue was significantly increased(P<0.05)after InM/g body weight T3 injection of 3h,but no significant change in other treatment groups(P>0.05).The experimental results show that the injection of T3 can effectively reduce the fat deposition in Nile tilapia,but on lipolytic related gene expression had no significant effect,so the T3 was not effect on the lipolysis by promoting the expression of genes,but through other ways to promote lipolysis. |
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