Mass spectrometry-based proteomic analysis of middle-aged\ud vs. aged vastus lateralis reveals increased levels of carbonic\ud anhydrase isoform 3 in senescent human skeletal muscle

摘要

The age-related loss of skeletal muscle mass and\udassociated progressive decline in contractile strength is a\udserious pathophysiological issue in the elderly. In order to\udinvestigate global changes in the skeletal muscle proteome\udafter the fifth decade of life, this study analysed total extracts\udfrom human vastus lateralis muscle by fluorescence difference\udin-gel electrophoresis. Tissue specimens were derived from\udmiddle-aged (47-62 years) vs. aged (76-82 years) individuals\udand potential changes in the protein expression profiles were\udcompared between these two age groups by a comprehensive gel\udelectrophoresis-based survey. Age-dependent alterations in the\udconcentration of 19 protein spots were revealed and mass spectrometry\udidentified these components as being involved in the\udexcitation-contraction-relaxation cycle, muscle metabolism, ion\udhandling and the cellular stress response. This indicates a generally\udperturbed protein expression pattern in senescent human\udmuscle. Increased levels of mitochondrial enzymes and isoform\udswitching of the key contractile protein, actin, support the idea\udof glycolytic-to-oxidative and fast-to-slow transition processes\udduring muscle aging. Importantly, the carbonic anhydrase\ud(CA)3 isoform displayed an increased abundance during muscle\udaging, which was independently verified by immunoblotting\udof differently aged human skeletal muscle samples. Since the\udCA3 isoform is relatively muscle-specific and exhibits a fibre\udtype-specific expression pattern, this enzyme may represent an\udinteresting new biomarker of sarcopenia. Increased levels of CA\udare indicative of an increased demand of CO2-removal in senescent muscle, and also suggest age-related fibre type shifting to\udslower-contracting muscles during human aging.