Transcriptome Analysis Under Oxidative Stress Induced By Oxidized Lipid Diet And The Effect Of Oxidized Lipid On Fabp2 Gene Expression In Loach(Misgurnus Anguillicaudatus)

Lipid can be used as biological energy sources,and the high unsaturated fatty acids in some lipid like fish oil is indispensable material during fish growing.But lipid especially fish oil is easy to be oxidized.Lipid once be oxidized,decomposition aggregation of roll cis double bond of unsaturated fatty acids in lipid result in generating low molecular aldehydes and ketones complex mixture or under the action of microorganisms,resulting in aldehydes and ketones,cause oxidative rancidity of oil and grease.Oxidation of fish oil can cause the fish production performance degradation,increased mortality,lean back,liver disease,anemia,and so on.At present,the effects of oxidized fish oil for fish researches were more focus on growth performance and histological.Study on oxidized fish oil on fish transcriptome level and analysis report is also rare.RNA sequencing and short-read assembly was utilized to produce a transcriptome of livers from loaches(Misgurnus anguillicaudatus)fed with three different diets respectively containing fresh fish oil(FO group),medium oxidized fish oil(MO group)and high oxidized fish oil(HO group).A total of 60,663 Unigenes were obtained in this study,with mean length 848.74 bp.50,814,49,584 and 49,814 Unigenes were respectively obtained from FO,MO and HO group.There were 2,343 differentially expressed genes between FO and MO,with 855 down-and 1,488up-regulated genes in the MO group.2,813 genes were differentially expressed between FO and HO,including 1,256 down-and 1,552 up-regulated genes in the HO group.2,075 differentially expressed genes were found in the comparison of MO and HO,including 1,074 up-and 1,001 down-regulated genes in the MO group.Some differentially expressed genes,such as fatty acid transport protein(fatp),fatty acid binding protein(fabp),apolipoprotein(apo),peroxisome proliferator activated receptor-gamma(ppar-γ),acetyl-CoA synthetase(acs)and arachidonate5-lipoxygenase(alox5),were involved in lipid metabolism,suggesting these genes in the loach were responsive to dietary oxidized fish oil.Results of transcriptomeprofilings here were validated using quantitative real time PCR in fourteen randomly selected Unigenes.The present study provides insights into hepatic transcriptome profile of the loach,which is a valuable resource for studies of loach genomics.More importantly,this study identified some important genes responsible for dietary oxidized fish oil,which would benefit researches of lipid metabolism in fish.Screening obviously changed with oxidation degree in genetic pathways,we get the the most obvious changed genes--fatty acid binding protein 2(fabp2).This study cloned full length of loach fabp2 cDNA,resulting in full-length cDNA sequence is956 bp,including 5’ noncoding region 257 bp,3’ noncoding region 297 and open reading frame of 402 bp from 258 bp-659 bp encoding 134 amino acids.Loach fabp2 has higher homology with that of zebrafish and grass carp.The expression of fabp2 genes in loach tissues are different in different tissue.fabp2 expressed more in intestines,brain and muscle than other tissues.In the process of embryonic development,the fertilized eggs began to express after hatch,which laid a foundation for subsequent function research of loach fabp2.After feeding oxidized fish oil,loach fabp2 expression in intestine significantly lowered with the feeding time increased.It indicated that the oxidized fish oil can inhibit the expression of fabp2 gene.