Novel markers for tying-up in horses by proteomics analysis of equine muscle biopsies

The aim of the study was to identify new biomarkers for acute tying-up in horses. Skeletal muscle biopsies were taken from 3 horses suffering from acute tying-up and 3 healthy horses. We performed 2D gel electrophoresis and mass spectrometry for identification of proteins that are differentially expressed in tying-up. 2D gel electrophoresis of skeletal muscle sequential extracts yielded more than 350 protein spots on each gel, of which 14 were differentially expressed more than two-fold (p < 0.05). In-gel digestion followed by peptide mass fingerprinting enabled identification of three significantly increased proteins: alpha actin, tropomyosin alpha chain and creatine kinase M chain (CKM). CKM was represented by multiple spots probably due to posttranslational modification, one of which appeared to be unique for tying-up. Since changes in the rates of synthesis and degradation of proteins are likely to lead to pathological conditions, identification of differentially expressed proteins in acute tying-up might result in the finding of more specific diagnostic markers and in new hypotheses for the common mechanisms that result in this condition. Our findings point to a specific isoform of CKM as a novel biomarker for tying-up suggesting that altered energy distribution within muscle cells is part of the disease etiology.