Department of Animal Science, Iowa State University, Ames 50011, USA.
J Anim Sci. 2013 Aug;91(8):4007-16. doi: 10.2527/jas.2013-6413. Epub 2013 Jun 5.
The objective of this study was to evaluate the contribution of muscle protein turnover (synthesis and degradation) to the biological basis for genetic differences in finisher pigs selected for residual feed intake (RFI). Residual feed intake is defined as the difference between expected feed intake (based on the achieved rate of BW gain and backfat depth of individual pigs) and the observed feed intake of the individual pig. We hypothesized that protein turnover would be reduced in pigs selected for low RFI. Twelve gilts from a line selected for 7 generations for low RFI and 12 from a contemporary line selected for 2 generations for high RFI were paired by age and BW and fed a standard corn-soybean diet for 6 wk. Pigs were euthanized, muscle and liver samples were collected, and insulin signaling, protein synthesis, and protein degradation proteins were analyzed for expression and activities. Muscle from low RFI pigs tended to have less μ- and m-calpain activities (P = 0.10 and 0.09, respectively) and had significantly greater calpastatin activity and a decreased μ-calpain:calpastatin activity ratio (P < 0.05). Muscle from low RFI pigs had less 20S proteasome activity compared with their high RFI counterparts (P < 0.05). No differences in insulin signaling intermediates and translation initiation signaling proteins [mammalian target of rapamycin (mTOR) pathway] were observed (P > 0.05). Postmortem proteolysis was determined in the LM from the eighth generation of the low RFI pigs versus their high RFI counterparts (n = 9 per line). Autolysis of μ-calpain was decreased in the low RFI pigs and less troponin-T degradation product was observed at 3 d postmortem (P < 0.05), indicating slowed postmortem proteolysis during aging in the low RFI pigs. These data provide significant evidence that less protein degradation occurs in pigs selected for reduced RFI, and this may account for a significant portion of the increased efficiency observed in these animals.
本研究旨在评估肌肉蛋白质周转率（合成和降解）对选择用于剩余采食量（RFI）的育肥猪遗传差异的生物学基础的贡献。剩余采食量定义为预期采食量（基于个体猪的体重增加率和背膘厚度）与个体猪的实际采食量之间的差异。我们假设选择低 RFI 的猪的蛋白质周转率会降低。从选择 7 代低 RFI 的品系中选择了 12 头母猪，从选择 2 代高 RFI 的当代品系中选择了 12 头母猪，按年龄和体重进行配对，并饲喂标准玉米 - 豆粕日粮 6 周。对猪进行安乐死，采集肌肉和肝脏样本，并分析胰岛素信号、蛋白质合成和蛋白质降解蛋白的表达和活性。低 RFI 猪的肌肉 μ-和 m-钙蛋白酶活性较低（分别为 P=0.10 和 0.09），钙蛋白酶抑制剂活性较高，μ-钙蛋白酶：钙蛋白酶抑制剂活性比降低（P<0.05）。与高 RFI 猪相比，低 RFI 猪的 20S 蛋白酶体活性较低（P<0.05）。未观察到胰岛素信号中间产物和翻译起始信号蛋白[雷帕霉素靶蛋白（mTOR）途径]的差异（P>0.05）。在第八代低 RFI 猪与高 RFI 猪的 LM 中测定死后蛋白水解（n=9 头/系）。低 RFI 猪的 μ-钙蛋白酶自溶减少，死后 3 天观察到较少的肌钙蛋白-T 降解产物（P<0.05），表明低 RFI 猪在衰老过程中死后蛋白水解速度较慢。这些数据提供了重要证据，表明选择减少 RFI 的猪的蛋白质降解减少，这可能是这些动物观察到的效率提高的重要原因。
