Adipose Cell Size And Molecular Mechanism Of Lipid Metabolism Regulating Intramuscular Fat In Chaohu Ducks

It is an important and complex research topics that the influence of lipid deposition on meat quality and the regulation mechanism of fat deposition in the field of genetic breeding of domestic ducks.In particular,the intramuscular fat(IMF)content is an important indicator for evaluating the meat quality of poultry.Currently,there is a lack of candidate genes and molecular markers for intramuscular fat content in duck breeding.The purpose of this study was to explore the molecular mechanism of adipose cell morphology and lipid metabolism-related genes affecting IMF content in Chaohu ducks,and to provide important candidate genes for IMF in duck molecular breeding.Sixty male and sixty female healthy Chaohu ducks were selected at 84 days old.Blood samples were collected from the subwing vein for the analysis of serum lipid level.Subcutaneous,abdominal,interclavicular adipose tissue,liver and pectoral muscle were collected from carcass one by one,next to been slaughtered with broken neck.Adipose cell size,slaughter performance,meat quality,serum lipids and intramuscular fat were measured respectively.According to the normal distribution of intramuscular fat,the males and females were divided into high intramuscular fat group and low intramuscular fat group separately(CHM,CLM,CHF,CLF,each 10).Then,RNA was extracted from liver in high and low group of males and used for transcriptome expression profile analysis by RNA-seq technology.The total protein was extracted from the same liver too,and used for differential proteome expression analysis using 2-DE technique,with identification by mass spectrometer.The lightness value of CHM group was significantly greater than that of CLM group(P<0.01),but the shear force of CHM group was significantly less(P?0.001).Subcutaneous and abdominal fat in the high group were significantly greater than those in the low group(P?0.05).The total cholesterol,high density lipoprotein and low density lipoprotein in the high group were significantly greater than those in the low group(P?0.05).There was an extremely significant positive correlation between subcutaneous fat,abdominal fat and intramuscular fat(P<0.001),and it was significantly positive correlated with total cholesterol,high-density lipoprotein and low-density lipoprotein(P?0.01).Intramuscular fat was significantly negative correlated with shear force(P?0.05).There were 147 differentially expressed genes between high and low IMF groups(78 up-regulated and 69 down-regulated)in males.And 108 significantly terms(P?0.05)were obtained through GO enrichment.Among them,3 biological processes were related to lipid metabolism,including aromatic compound catabolic process,organic cyclic compound catabolic process and organonitrogen compound catabolic process.And 15 significantly pathways(P?0.05)were obtained by KEGG enrichment.Of which,4 pathways were involved in lipid metabolism,including ?-Linolenic acid metabolism,linoleic acid metabolism,galactose metabolism,starch and sucrose metabolism.Seven differentially expressed genes(PLA2G10,PLA2G4F,UGP2,LCT,GBE1,HAAO,PDE4D)were screened out,which played a key role in regulating lipid metabolism and intramuscular fat deposition in Chaohu ducks.Comparison of total liver proteins between high and low IMF groups in males by 2-DE,sixty-eight differentially expressed protein spots were isolated(fold-change of OD?1.5).And 43 differentially expressed proteins(all up-regulated)were identified by mass spectrometer.Four significantly biological processes(P?0.05)were found to correlating with fat metabolism by GO enrichment,which contained carboxylic acid metabolic process,ATP metabolic process,oxoacid metabolic process,and organic acid metabolic process.It showed that 3 significant pathways(P?0.05)were participated in fat metabolism from KEGG enrichment,which contained glycolysis/gluconeogenesis,pentose phosphate pathway,fructose and mannose metabolism.Eight differentially expressed proteins were screened out,which closely related to fat synthesis and transportation in Chaohu ducks.There was significantly positive correlation between the fat cell size and intramuscular fat in Chaohu ducks.With the increase of intramuscular fat,it had a great influence on the meat quality in the males,but a less effect on the females.It had revealed several crucial regulatory genes(or proteins)and pathways about fat deposition and metabolism through transcriptomics and proteomics in Chaohu ducks.Further research was needed on the detailed functions and interrelationships of candidate genes(or proteins)in regulating fat deposition.