Gene expression profiling indicates a shift in ammonia assimilation capacity along the hepatic acinus induced by different forms of selenium in vitamin–mineral mixes fed to beef steers grazing on toxic endophyte-infected tall fescue

Recently, we demonstrated that supplementing (with 3 mg Se per day) the diets of growing beef steers grazing on Se-deficient toxic endophyte-infected tall fescue-based forage with either organic (OSe, SEL-PLEX) or a 1:1 blend (MIX) OSe and inorganic (ISe, sodium selenite) in vitamin–mineral mixes, rather than forms Se, ameliorated several classic serum symptoms fescue toxicosis. Importantly, higher levels hepatic glutamine synthetase activity were observed MIX steers. Accordingly, transcriptome level targeted mRNA expression analyses conducted same liver tissue to determine if treatments affected other metabolic pathways, especially those are responsible for supplying substrates synthetase. The effect ISe, OSe, ( n = 8/treatment) relative abundances [determined using microarray real-time reverse-transcription PCR (RT-PCR)] protein (determined Western blotting) was assessed by ANOVA. Fisher’s protected LSD procedure used separate treatment means, significance being declared at p ≤ 0.05. Microarray analysis identified < 0.01, false discovery rate of< 33%) 573 annotated differentially expressed gene (DEG) transcripts. Canonical pathway DEGs central glutamate biosynthesis/degradation proline biosynthesis. Targeted RT-PCR found had lower periportal ammonia-assimilation urea-synthesizing capacities (lower glutaminase 2, key ornithine cycle enzymes, mitochondrial ornithine/citrulline exchanger mRNA) ISe In addition, capacity pericentral ammonia assimilation (higher activity) production hepatocytes from α-ketoglutarate dehydrogenase, decreased arginase 2 aminotransferase mRNA). form supplemental also steers’ metabolism, having synthesis pyroline-5-carboxylate synthesis. conclusion, shifts urea production, thus potentially increasing whole-animal N efficiency supply hepatic-synthesized glutamine.