Studies On The Factors Of Signal Transduction Involved In Intramuscular Fat Metabolism Of Pigs

Dynamic changes of factors of signal transduction involved in intramuscular fat metabolism in Rongchang and Duroc×Landrace×Yorkshire(DLY)pigs fed at different dietary nutrient levels were studied in this thesis with muscle explants culture technologies and molbiology technologies.There were two parts in this study. Part1.Studies on the dynamic changes of factors of signal transduction involved in intramuscular fat metabolism in Rongchang and DLY pigs fed at two dietary nutrient levels.84 healthy Rongchang and DLY barrows(10kg BW) were respectively allocated to two groups(high and low nutrition level), each group having 6 replicates of 7 pigs.The low dietary nutrient levels for the two genetic types pigs were arranged according to recommendations of GB 7223-1987(feeding standard for Rongchang pigs),and the high dietary nutrient levels were arranged according to feeding standard for lean-type pigs(GB 8471-87,for Rongchang pigs) and feeding standard for pigs by NRC(1998)(for DLY) respectively.One pig from every replicate was slaughtered when their body weight (BW) arrived at 20,35,50,80 and 110 kg to determine hormones[insulin(INS),somatotropin(ST), epinephrine(Epi),glucagons (GCG),leptin (LP)and tumor necrosis factorα(TNFα)]in the serum, insulin receptor(IR),cyclic adenosinemonophos- phate (cAMP), gene expression of enzymes involved in intramuscular fat metabolism [hormone-sensitive lipase(HSL), lipoprotein lipase (LPL), acetyl-CoA carboxylase(ACC) and fatty acid synthase(FAS)] and intramuscular fat(IMF) in Longissimus Dorsi.The results showed that: (1) Genetic type significantly affected LP content in the serum, IR and cAMP concentration,LPL and ACC mRNA level,the homeostasis of intramuscular fat metabolism and IMF content in Longissimus Dorsi.And dietary nutrient level significantly affected LP content in the serum, ACC mRNA level,FAS mRNA level, LPL/ HSL mRNA, ACC/HSL mRNA,MIand IMF content in Longissimus Dorsi; (2)ACC and FAS mRNA level,ACC/HSL mRNA,MI and FAS/HSL mRNA in Longissimus Dorsi of Rongchang pigs and DLY had a peak when BW was at 35 kg;(3)When the dietary nutrient levels was lowed on the basis of feeding standard for pigs by NRC(1998),the IMF concentration in Longissimus Dorsi of DLY had the tendency of increase.But in the meantime, ST concentrations in the serum, IR,cAMP, and ACC/HSL mRNA levels in Longissimus Dorsi were all decreased; (4)IMF content in the Longissimus Dorsi of Rongchang pigs was higher than it of DLY after BW was at 35 kg when Rongchang pigs and DLY were respectively fed with the diets according to GB7223-1987(feeding standard for Rongchang pigs)and feeding standard for pigs by NRC(1998). LPL/HSL mRNA,ACC/HSL mRNA,FAS/HSL mRNA and MI levels in Longissimus Dorsi of Rongchang pigs were higher than of DLY in the growing period,and the IR,cAMP concentration and LPL mRNA levels in Longissimus Dorsi of Rongchang pigs were higher than of DLY in the finishing period; (5)In this experiment, IMF concentration in Longissimus Dorsi of DLY was lower than of Rongchang pigs even if the dietary nutrient level was the same as Rongchang pigs;(6) The LP concentration in the serum and LPL mRNA level in Longissimus Dorsi were significantly positive correlation with IMF content in Longissimus Dorsi.Part2.Studies on the effect of hormonomics on the intramuscular fat metabolism in muscle explants.Longissimus Dorsi muscle was collected and muscle tissue explants were prepared from 3 finishing Rongchang barrows (100.5±5.3kg BW) and cultured by sterile technique.The experiment was conducted with an orthogonal design with a L9(34) and each treatment had 3 replicates.INS,ST,Epi and GCG were used in the experiment, and each of them had 3 levels.Results showed that ST and INS significantly affected intramuscular fat metabolism.and it was suggested that the combination of hormones (INS:1×10-7,ST:5×10-10,Epi:1×10-7,GCG:1×10-8) could improve IMF content in finishing pigs.