Deep muscle proteomic analysis of freeze-dried human biopsies reveals fiber type specific adaptations to exercise training

Skeletal muscle conveys several of the health-promoting effects of exercise; yet the underlying mechanisms are not fully elucidated. Studying skeletal muscle is challenging due to its different fiber types and non-muscle cells, which can confound results. This can be circumvented by isolation of fibers from fresh tissues. We developed a workflow enabling proteomics analysis of isolated muscle fibers from freeze-dried human muscle biopsies. This allowed identification of more than 4000 proteins in pools of slow and fast muscle fibers. Exercise training altered expression of 237 and 172 proteins in slow and fast muscle fibers, respectively. Interestingly, expression levels of secreted proteins, and proteins involved in transcription, mitochondrial metabolism, Ca2+ signaling and fat and glucose metabolism were adapting to training in a fiber type-specific manner. Our data provide a resource to elucidate molecular mechanisms underlying muscle function and health, and our workflow now allows fiber type specific proteomic analyses of already stored muscle biopsies.