A comparative analysis of metabolomics and transcriptomics from prepartal liver of cows developing ketosis postpartum and healthy cows supplemented with Smartamine M and MetaSmart during the transition period

Abstract Text: Cows overfed energy during the dry period are most-susceptible to developing ketosis postpartum. Supplementation with Smartamine M (SM) and MetaSmart (MS) during the transition period improves postpartal dry matter intake and resulted in fewer cases of clinical ketosis postpartum. 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 on 7 d postpartum or were diagnosed with clinical ketosis (K, n = 8). From -21 d to calving all cows consumed a higher-energy diet without (developed K) or with SM (n = 8) and MS (n = 8) (clinically healthy). From 313 identified biochemical compounds, metabolomics analysis (P ≤ 0.10) revealed 34 or 33 affected in the comparison of K vs. SM or K vs. MS. Comparing profiles in K vs. SM revealed 13 compounds up-regulated and 21 down-regulated. Among the up-regulated compounds most belong to bile acid, fatty acid, branched-chain amino acid, and arginine and proline metabolism. Among the down-regulated compounds, there were several lysolipids and di-carboxylic acids along with components of pentose, purine, and sphingolipid metabolism. Citrate was markedly lower in liver of K vs. SM. In the comparison of K vs. MS, 7 compounds were up-regulated and 26 were down-regulated. The up-regulated compounds are intermediates of glycolysis/gluconeogenesis/pyruvate, histidine, glycine/serine/threonine, and fatty acid metabolism. Among down-regulated compounds 7 were lysolipids but also citrate, squalene, several pentoses, and purines were affected. Analysis of transcriptomics data resulted in 834 or 1,261 differentially expressed genes (DEG, P ≤ 0.05) in K vs. SM or K vs. MS. Bioinformatics analysis using the Dynamic Impact Approach (DIA) revealed a strong activation in K vs. MS of Notch, Hedgehog, and TGF-beta signaling pathways along with ‘steroid biogenesis’. In contrast, ‘synthesis and degradation of ketone bodies’ was markedly inhibited. The pathway response in K vs. SM was less pronounced in part due to the fewer number of DEG. For example, the Hedgehog signaling pathway was highly-impacted but moderately activated; whereas, the ‘renin-angiotensin system’ was the most-impacted and markedly inhibited. Preliminary data analysis suggests that supplemental MS and SM elicit distinct metabolomics and transcriptomics responses in liver before calving. Cows developing K post-partum also had a distinct molecular phenotype compared with those supplemented with methionine. The functional relevance of these differences remains to be determined.

Keywords: Ketosis, Transition cows, Metabolomics