Mass spectral analysis of urine proteomic profiles of dairy cows suffering from clinical ketosis

Background: Ketosis is an important metabolic disorder in dairy cows during the transition period. The urine proteomics of ketosis has not been investigated using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS). Objective: The aim is to determine differences between urine proteomic profiles of healthy cows and those with clinical ketosis, and facilitate studies of the underlying physiological and biochemical mechanisms that lead to liver pathology in ketosis. Animals and methods: We analyzed the urine samples of 20 cows with clinical ketosis (group 1) and 20 control cows (group 2) using SELDI-TOF-MS. Results: Thirty-nine peptide peaks differed between both groups. Polypeptides corresponding to 26 of these differential peptide peaks were identified using the SWISS-PROT protein database. We found that the peaks of 11 distinct polypeptides from the urine samples of the ketosis group were significantly reduced, compared with those of the control group as based on the Wilcoxon rank sum test. Among these were VGF (non-acronymic) protein, amyloid precursor protein, serum amyloid A (SAA), fibrinogen, C1INH, apolipoprotein C-III, cystatin C, transthyretin, hepcidin, human neutrophil peptides, and osteopontin. Conclusion: These proteins may represent novel biomarkers of the metabolic changes that occur in dairy cows with ketosis. Our results will help to better understand the physiological changes and pathogenesis observed in cows with ketosis. Clinical importance: The SELDI-TOF-MS can be used to understand the physiological and biochemical mechanisms of ketosis and identify biomarkers of the disease.