摘要
Variations in phenotypic expression of feed efficiency could be associated with differences or inefficiencies in mitochondria function due to its impact on energy expenditure. The aim of this study was to determine hepatic mitochondrial density and function in terms of respiration, gene and protein expression, and enzyme activity of mitochondrial respiratory complex proteins, in steers of divergent residual feed intake (RFI) phenotypes. Hereford steers (n = 111 and n = 122 for year 1 and 2, respectively) were evaluated in postweaning 70 d standard test for RFI. Forty-six steers exhibiting the greatest (n = 9 and 16 for year 1 and 2; high-RFI) and the lowest (n = 9 and 12 for year 1 and 2; low-RFI) RFI values were selected for this study. After the test, steers were managed together until slaughter under grazing conditions until they reached the slaughter body weight. At slaughter, hepatic samples (biopsies) were obtained. Tissue respiration was evaluated using high-resolution respirometry methods. Data were analyzed using a mixed model that included RFI group as fixed effect and slaughter date and year as a random effect using PROC MIXED of SAS. RFI and dry matter intake were different (P < 0.001) between low and high-RFI groups of year 1 and year 2. Basal respiration and maximum respiratory rate were greater (P ≤ 0.04) for low than high-RFI steers when complex II substrates (succinate) were supplied. However, when Complex I substrates (glutamate/malate) were used maximum respiratory capacity tended to be greater (P < 0.09) for low vs. high-RFI steers. Low-RFI steers presented greater mitochondria density markers (greater (P < 0.05) citrate synthase (CS) activity and tended (P ≤ 0.08) to have greater CS mRNA and mtDNA:nDNA ratio) than high-RFI steers. Hepatic expression SDHA, UQCRC1, and CYC1 mRNA was greater (P ≤ 0.02) and expression of NDUFA4, NDUFA13, SDHD, UQCRH, and ATP5E mRNA tended (P ≤ 0.10) to be greater in low than high-RFI steers. Hepatic SDHA protein expression tended (P < 0.08) to be greater while succinate dehydrogenase activity was greater (P = 0.04) and NADH dehydrogenase activity was greater (P = 0.03) for low than high-RFI steers. High-efficiency steers (low-RFI) probably had greater efficiency in hepatic nutrient metabolism, which was strongly associated with greater hepatic mitochondrial density and functioning, mainly of mitochondrial complex II.
摘要译文
饲料效率表型表达的变化可能与线粒体功能的差异或效率低下有关，这是由于其对能量消耗的影响。这项研究的目的是确定不同的剩余摄食量（RFI）表型的肝脏中的线粒体密度和功能，包括呼吸，基因和蛋白质表达以及线粒体呼吸复合蛋白的酶活性。在断奶后70 d RFI标准测试中评估了赫里福德ste牛（第1年和第2年分别为111和122）。四十六头ers牛在第一年和第二年的表现最大（n = 9和16； RFI高）和最低（第1年和第2年的n = 9和12）；选择低RFI）的RFI值进行这项研究。试验后，将ste牛一起管理，直到在放牧条件下宰杀，直到达到屠宰体重。屠宰时获得肝样本（活组织检查）。使用高分辨率呼吸测定法评估组织呼吸。使用混合模型分析数据，该模型使用SAS的PROC MIXED将RFI组作为固定效应，将屠宰日期和年份作为随机效应。低和高RFI组在第1年和第2年之间的RFI和干物质摄入量有所不同（P <0.001）。低呼吸和最大呼吸速率比高RFI转向低，与复杂II型底物相比提供了（琥珀酸酯）。但是，当使用复合I底物（谷氨酸/苹果酸）时，低RFI和高RFI ers牛的最大呼吸能力往往更大（P <0.09）。低-RFI ers牛比高-RFI presented牛表现出更大的线粒体密度标志物（更大（P <0.05）柠檬酸合酶（CS）活性，并倾向于（P≤0.08）具有更大的CS mRNA和mtDNA：nDNA比。肝表达SDHA，UQCRC1和CYC1 mRNA较高（P≤0.02），而NDUFA4，NDUFA13，SDHD，UQCRH和ATP5E mRNA的表达在低（高于高RFI转向）下倾向于（P≤0.10）更高。低-高RFI ers牛肝脏SDHA蛋白表达趋向于（P <0.08）较大，而琥珀酸脱氢酶活性较高（P = 0.04），而NADH脱氢酶活性较高（P = 0.03）。高效率ers牛（低RFI）可能具有更高的肝脏营养代谢效率，这与较高的肝线粒体密度和功能（主要是线粒体复合体II）有密切关系。
Alberto Casal;Mercedes Garcia-Roche;Elly Ana Navajas;Adriana Cassina;Mariana Carriquiry. Hepatic mitochondrial function in Hereford steers with divergent residual feed intake phenotypes[J]. Journal of Animal Science, 2018,96(10): 4431-4443