Casal 2018 J Anim Sci
|Casal A, Garcia-Roche M, Navajas EA, Cassina A, Carriquiry M (2018) Hepatic mitochondrial function in Hereford steers with divergent residual feed intake phenotypes. J Anim Sci 96:4431-43.|
Abstract: 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 yr 1 and 2, respectively) were evaluated in post-weaning 70 d standard test for RFI. Forty-six steers exhibiting the greatest (n = 9 and 16 for yr 1 and 2; high-RFI) and the lowest (n = 9 and 12 for yr 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. Residual feed intake and dry matter intake were different (P < 0.001) between low and high-RFI groups of yr 1, yr 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.
Labels: MiParea: Respiration, mt-Biogenesis;mt-density, mtDNA;mt-genetics, nDNA;cell genetics, Exercise physiology;nutrition;life style
Organism: Bovines Tissue;cell: Liver Preparation: Intact cells Enzyme: Complex I, Complex II;succinate dehydrogenase, Complex III, Complex IV;cytochrome c oxidase, Complex V;ATP synthase
Coupling state: LEAK, OXPHOS, ET Pathway: N, S, ROX HRR: Oxygraph-2k