Analysis of hepatic transcript profile and plasma lipid profile in early lactating dairy cows fed grape seed and grape marc meal extract

As polyphenols are exerting a broad spectrum of metabolic effects, we hypothesize that feeding of GSGME might influence other metabolic pathways in the liver which could account for the positive effects of GSGME observed in cows during early lactation. In order to investigate this hypothesis, we used using a genome-wide transcript profiling technique to explore changes in the hepatic transcriptome of cows supplemented with GSGME during the transition period. Transcriptomic analysis of the liver revealed 207 differentially expressed transcripts (fold change > 1.3 or < -1.3, P < 0.05), from which 156 (155 mRNAs, 1 miRNA) were up- and 51 (43 mRNAs, 8 miRNAs) were down-regulated, between cows fed GSGME and control cows. Gene set enrichment analysis of the 155 up-regulated mRNAs showed that the most enriched gene ontology (GO) biological process terms were dealing with cell cycle regulation, such as M phase, cell cycle phase, mitotic cell phase and microtubule cytoskeleton and the most enriched KEGG database pathways were p53 signaling and cell cycle. Functional analysis of the 43 down-regulated mRNAs revealed that 13 genes (XBP1, HSPA5, HERPUD1, DNAJC5G, CALR, PDIA4, DNAJB11, PHLDA1, PPP1R3C, GADD45B, BAG3, HYOU1, MANF) are involved in ER stress-induced UPR. Moreover, several of the down-regulated mRNAs, like CXCL14 and CCL3L1L and the acute phase protein SAA4, play an important role in inflammatory processes. Accordingly, protein folding, response to unfolded protein, response to protein stimulus, unfolded protein binding, chemokine activity, chemokine receptor binding and heat shock protein binding were identified as one of the most enriched GO biological process and molecular function terms assigned to the down-regulated genes. In line with the transcriptomics data the plasma concentrations of the acute phase proteins SAA and haptoglobin were reduced in cows fed GSGME compared to control cows. Collectively, our findings from transcriptome analysis of down-regulated mRNAs and functional analysis of mRNAs targeted by the up-regulated mir-376c clearly indicate that GSGME is able to inhibit inflammatory processes and ER stress in the liver of dairy cows during early lactation. Moreover, our findings indicate that at least some of the GSGME effects on the hepatic transcriptome of dairy cows are mediated by miRNA-mRNA interactions. For microarray analysis, six RNA samples each of the control group and the GSGME group were used for hybridization to the Affymetrix GeneChip Bovine Gene 1.0 ST array.