Plasma proteomic profiling and pathway analysis of normal and overconditioned dairy cows during the transition from late pregnancy to early lactation

摘要

This study applied a quantitative proteomics approachalong with bioinformatics analyses to investigatechanges in the plasma proteome of normal and overconditioneddairy cows during the transition period.Fifteen weeks before their anticipated calving date, 38multiparous Holstein cows were selected based on theircurrent and previous body condition scores (BCS) andallocated to either a high or a normal BCS group (19cows each). They received different diets until dry-offto reach targeted differences in BCS and back fat thickness(BFT) until dry-off. At dry-off, normal BCS cowshad a BCS <3.5 (minimum, 2.75) and BFT <1.2 cm(minimum, 0.58), and the high BCS cows had a BCS>3.75 (maximum, 4.50) and BFT >1.4 cm (maximum,2.90). The proteomics study used a subset of 5 animalsfrom each group. These cows were selected based ontheir circulating concentrations of fatty acids (FA) ond 14 postpartum and β-hydroxybutyrate (BHB) on d21 postpartum, representing the greater or the lowerextreme values within their BCS group, respectively.The high BCS subset (HE-HBCS) had 4.50 < BCS >3.75, FA = 1.17 ± 0.46 mmol/L, and BHB = 2.15 ±0.42 mmol/L (means ± SD), and the low BCS subset(LE-NBCS) had 3.50 < BCS > 2.75, FA = 0.51 ± 0.28mmol/L, and BHB = 0.84 ± 0.17 mmol/L. Plasmasamples from d −49, +7, and +21 relative to parturitionwere used for proteome profiling by applying thequantitative tandem mass tags (TMT) approach. Nondepletedplasma samples were subjected to reductionand digestion and then labeled with TMT 10plex reagents.High-resolution liquid chromatography-tandemmass spectrometry analysis of TMT-labeled peptideswas carried out, and the acquired spectra were analyzedfor protein identification and quantification. Intotal, 254 quantifiable proteins (criteria: 2 unique peptidesand 5% false discovery rate) were identified in theplasma samples. From these, 24 differentially abundantproteins (14 more abundant, 10 less abundant) wereobserved in the LE-NBCS cows compared with theHE-HBCS cows during the transition period. Plasmaα-2-macroglobulins were more abundant in HE-HBCSversus LE-NBCS cows at d +7 and +21. Gene Ontologyenrichment analyses of differentially abundant proteinsrevealed that the acute inflammatory response,regulation of complement activation, protein activationcascade, and regulation of humoral immune responsewere the most enriched terms in the LE-NBCS groupcompared with the HE-HBCS group. In addition, weidentified 24 differentially abundant proteins (16 in theLE-NBCS group, and 8 in the HE-HBCS group) duringthe transition period. The complement componentsC1q and C5 were less abundant, while C3 and C3d weremore abundant in LE-NBCS compared with HE-HBCScows. Overall, overconditioning around calving was associatedwith alterations in protein pathways related toacute inflammatory response and regulation of complementand coagulation cascades in transition cows.