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Investigating the role of reactive oxygen species and mitochondria protein profile differences in pigs divergently selected for residual feed intake
Understanding the molecular mechanisms and the important role mitochondria play in swine feed efficiency is paramount to improving the efficiency of pork production. The objective of these projects was to characterize mitochondria protein profile and reactive oxygen species (ROS) differences between pigs divergently selected for residual feed intake (RFI). Pigs (n = 16-18) divergently selected for RFI were used in these studies. Mitochondria were isolated from the liver, longissimus dorsi (LD), and the red and white portions of the semitendinosus (RST and WST respectively). Cellular ROS production was determined using the dichlorofluorescein assay and mitochondrial protein profile differences were determined using 2-dimensional difference in gel electrophoresis. Phosphorylations were determined via two dimensional SDS-PAGE and staining for phosphoproteins. Mitochondria from the WST pigs in the more efficient, low RFI line produced 15-23% less ROS (P < 0.05) using glutamate as an electron donor for complex I of electron transport. Compared to high RFI, a similar trend (P < 0.1) in liver mitochondria ROS production was also seen in low RFI pigs (30-34% reduction). Positive Pearson correlations (r2= 0..493-0.423, P ≤ 0.1), dependent on the complex and electron donor source, for RFI and ROS production were observed. These ROS differences may be explained by alterations in mitochondrial protein profile and differences in posttranslational modifications, such as phosphorylations. Mitochondria specific isoforms of heat shock proteins 60 and 70 were determined to be increased in the low RFI line (9-50%, P < 0.05). Protein spots identified as heat shock proteins were phosphorylated, indicating posttranslational modifications may play a role in mitochondria function between RFI lines. Heat shock proteins have been shown to play a role in mitigating cellular stress. In addition to changes in cellular stress pathways, a general increase in the abundance of glycolytic enzymes was observed in the more efficient low RFI line, indicating potential changes in ATP production between the high and low RFI lines. Evidence of this shift was seen with the increase in ATP synthase beta subunit in the low RFI line (23-37%, P < 0.05). This increase could indicate either an increase in ATP production or the ability to produce more ATP. Altogether, these data show that selection for low RFI and improved feed efficiency may partially be explained by differences in ROS production, ATP synthesis efficiencies and the mitochondria protein profile. Supported by USDA AFRI Grant no. 2010-65206-20670
Keywords: Residual Feed Intake, 2D-DIGE, Protein profile