Hepatic mitochondrial function in Hereford steers with divergent residual feed intake phenotypes1

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 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.

Identification of Key Genes Associated With Early Calf-Hood Nutrition in Subcutaneous and Visceral Adipose Tissues by Co-Expression Analysis

“…As a milk protein related to mitochondrial oxidative metabolism, SDHA was proposed as a putative biomarker of negative energy balance based on its implication in metabolic adaptative pathways ( 48 ). As an important component of the mitochondrial respiratory chain, the hepatic SDHA expression of low residual feed intake (RFI) steers was significantly higher than that of high RFI steers ( 49 ). This can be attributed to greater hepatic mitochondrial density and function that lead to the higher efficiency in hepatic nutrient metabolism, which has a positive correlation with feed efficiency (low-RFI).…”

Proteomic Analysis of Liver from Finishing Beef Cattle Supplemented with a Rumen-Protected B-Vitamin Blend and Hydroxy Trace Minerals

“…Copper deficiency reduces the expression and activity of complex IV, but not other complexes once it contains two molecules of heme bound with Cu centers, all of which are involved in the electron transfer process [30][31][32]. The higher mitochondrial protein content and complex protein abundance of the respiratory chain might indicate greater metabolic efficiency according to research findings in steers and broilers [33][34][35].…”

Differential hepatic mitochondrial function and gluconeogenic gene expression in 2 Holstein strains in a pasture-based system

“…Determination of the ratio of mitochondrial DNA (mtDNA) to nuclear DNA (nDNA; mtDNA: nDNA) was performed according to Casal et al (2018). Briefly, real-time PCR reactions prepared in separate tubes to detect mitochondrial encoded cytochrome c oxidase I (mt-CO1, mitochondrial gene) and NADH: ubiquinone oxidoreductase core subunit V1 (NDUFV1, nuclear gene), respectively, and real-time PCR reactions were conducted as aforementioned.…”

“…cm) in the presence of 50 µM DCPIP, 1 mM potassium cyanide, 5 µM rotenone, and 50 µM decylubiquinone in a 25 mM phosphate buffer, pH 7.2. To quantify enzyme activity, baseline was subtracted from absorbance after addition of 10 mM succinate (Casal et al, 2018). Assays were performed in duplicate at 37°C using a final volume of 500 µL in a UV-2401 PC spectrophotometer (Shimadzu Corp.).…”