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Integrating metabolomics and transcriptomics of liver to study susceptibility to ketosis in response to prepartal nutritional management
Postpartal ketosis is associated with body fat mobilization postpartum. Sub-clinical and clinical ketosis arise more frequently in cows that are overfed energy during the entire dry period or during the close-up (i.e. last 21 d prior to parturition). Metabolomics (GC-MS, LC-MS; Metabolon Inc.) and transcriptomics (45K-whole-transcriptome microarray; Agilent) analyses were performed in liver tissue harvested at -10 d relative to parturition from cows that were healthy (H) on 7 d postpartum or were diagnosed with clinical ketosis (K). Cows in K consumed a higher-energy diet (OVE) from -21 d to calving. Cows in H consumed OVE (n = 8) or a high-straw lower-energy diet (CON; n = 8) from -21 d to calving. Out of 313 biochemical compounds identified, statistical analysis (P ≤ 0.10) of metabolomics data for K vs. CON, OVE vs. CON, and K vs. OVE revealed 34, 33 and 25 affected compounds, respectively. The top-five affected and up-regulated biochemical compounds in K vs. CON were taurocholate, adenine, hypotaurine, gamma-glutamylcysteine, and taurochenodeoxycholate. In OVE vs. CON cysteine, methylphosphate, cysteinylglycine, and taurocholate were up-regulated and gamma-glutamylthreonine was down-regulated. In K vs. OVE the top-five affected compounds were all down-regulated: xylitol, 1-palmitoylglycerophosphoglycerol, leucylaspartate, sphinganine, and glycylvaline. Bioinformatics analysis revealed that primary bile acid production through cysteine and taurine precursors, and oxidative stress-like activities were affected in both K and OVE vs. CON groups. In contrast, in K vs. OVE ketone body production was up-regulated and cell signaling pathways were inhibited. Bioinformatics analysis of 2,908 differentially expressed genes (DEG, P ≤ 0.05) using the Dynamic Impact Approach (DIA) revealed that the top-five impacted pathways in K vs. OVE were ‘hedgehog signaling’, ‘glycosphingolipid biosynthesis - globo series’, ‘renin-angiotensin system’, and ‘other glycan degradation’ all of which were inhibited. The ‘circadian rhythm’ pathway was among the most-induced pathways. Furthermore, there was marked inhibition in K vs. OVE of pathways associated with cellular growth, communication, signal transduction, fatty acid biosynthesis, and immune related responses. These results suggest that prepartal diet alters the hepatic metabolome and transcriptome. Liver from cows developing ketosis postpartum appears to exhibit unique alterations in the transcriptome and metabolome.
Keywords:
Ketosis, Transition Cows, Metabolomics, Systems Biology