Abstract
Ketosis is a common metabolic disease in dairy cows during early lactation. However, information about the metabolomic and proteomic profiles associated with the incidence and progression of ketosis is still limited. In this study, an integrated metabolomics and proteomics approach was performed on blood serum sampled from cows diagnosed with clinical ketosis (case, ≥ 2.60 mmol/L plasma β-hydroxybutyrate; BHBA) and healthy controls (control, < 1.0 mmol/L BHBA). Samples were taken 2 weeks before parturition and 2 weeks after parturition from 19 animals (nine cases, 10 controls). All serum samples (n = 38) were subjected to Liquid Chromatography-Mass Spectrometry (LC-MS) based metabolomic analysis, and 20 samples underwent Data-Independent Acquisition (DIA) LC-MS based proteomic analysis. A total of 97 metabolites and 540 proteins were successfully identified, and multivariate analysis revealed significant differences in both metabolomic and proteomic profiles between cases and controls. We investigated clinical ketosis-associated metabolomic and proteomic changes using statistical analyses. Correlation analysis of statistically significant metabolites and proteins showed 78 strong correlations (correlation coefficient, R ≥ 0.7) between 38 metabolites and 25 proteins, which were then mapped to pathways using IMPaLA. Results showed that ketosis altered a wide range of metabolic pathways, such as metabolism, metabolism of proteins, gene expression and post-translational protein modification, vitamin metabolism, signaling, and disease related pathways. Findings presented here are relevant for identifying molecular targets for ketosis and biomarkers for ketosis detection during the transition period.
Highlights
Dairy cows undergo both dramatic physiological and metabolic changes during the transition period, during which a metabolic disorder known as negative energy balance commonly occurs because the actual feed intake cannot meet the largely increased nutrient requirement for milk production (Esposito et al, 2014)
The pooled quality control (QC) sample was applied to ensure the reproducibility of the Liquid Chromatography-Mass Spectrometry (LC-MS) system
We evaluated the interactions of the 76 differentially accumulated metabolites (DAMs) identified between CK vs. PCK, which would help to unravel potential metabolic changes contributed to ketosis from prepartum to postpartum
Summary
Dairy cows undergo both dramatic physiological and metabolic changes during the transition period, during which a metabolic disorder known as negative energy balance commonly occurs because the actual feed intake cannot meet the largely increased nutrient requirement for milk production (Esposito et al, 2014). NEFA can be either uptaken by the mammary gland for milk fat synthesis or utilized by the liver for energy production (Sun et al, 2016). Because the ruminant liver has a limited capacity to completely oxidize NEFAs and synthesize very-low-density lipoprotein, excessive fatty acids will be metabolized into ketones or esterification to form triglycerides (Bezerra et al, 2014; White, 2015) and excess ketone accumulation that can lead to ketosis (Duffield et al, 2009). The mechanism of the incidence and progression of ketosis is not completely understood
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