Discovery proteomics in aging human skeletal muscle finds change in spliceosome, immunity, proteostasis and mitochondria

Abstract

A decline of skeletal muscle strength with aging is a primary cause of mobility loss and frailty in older persons, but the molecular mechanisms of such decline are not understood. Here, we performed quantitative proteomic analysis from skeletal muscle collected from 58 healthy persons aged 20 to 87 years. In muscle from older persons, ribosomal proteins and proteins related to energetic metabolism, including those related to the TCA cycle, mitochondria respiration, and glycolysis, were underrepresented, while proteins implicated in innate and adaptive immunity, proteostasis, and alternative splicing were overrepresented. Consistent with reports in animal models, older human muscle was characterized by deranged energetic metabolism, a pro-inflammatory environment and increased proteolysis. Changes in alternative splicing with aging were confirmed by RNA-seq analysis. We propose that changes in the splicing machinery enables muscle cells to respond to a rise in damage with aging.

Proteomic signatures of in vivo muscle oxidative capacity in healthy adults

“…Interestingly, we found that ATP‐binding cassette sub‐family B proteins were significantly associated with better oxidative capacity (smaller τ PCr ), while a recent study reported no association between of the expression of these proteins and chronological age or the level of habitual physical activity (Ubaida‐Mohien, Lyashkov, et al, ). This finding is particularly important because ABC transporters play major roles both in ATP hydrolysis and in active transport of a large number of substrates (Zutz, Gompf, Schagger, & Tampe, ).…”

“…Because of the fundamental dependence of mammalian life on adequate mitochondrial function, we searched for proteins patterns that could provide clues about resilience mechanisms aimed at maintaining mitochondrial function in spite of damage accumulation. We elected to focus on healthy adults spanning a wide age range, selected with strict inclusion criteria as being healthy (Adelnia et al, ; Ubaida‐Mohien, Lyashkov, et al, ), to allow for a robust assessment of underlying biological mechanisms associated with oxidative capacity independent of the confounding effect of diseases. After adjusting for age, habitual physical activity, sex, race, BMI, and muscle fiber type ratio, a subset of 253 out of 4,300 muscle proteins were significantly associated with better oxidative capacity of skeletal muscle.…”

“…Alternative splicing was first described 40 years ago (Alt et al, ), revealing that multiple splicing variants can be generated from a single gene, thereby multiplying the protein repertoire that can be generated from a limited number of genes (Nilsen & Graveley, ). Previous work showed that the modulation of alternative splicing correlates with ATP depletion in neuronal cells (Maracchioni et al, ) and that higher physical activity is linked to decreased expression of proteins that regulate alternative splicing (Ubaida‐Mohien, Lyashkov, et al, ). The mechanistic links between the mRNA splicing machinery with OXPHOS as well as the specific proteins and splicing variants involved in this putative mechanism of metabolic adaptation in skeletal muscle remain unknown.…”

“…We used data from 49 subjects from the Genetic and Epigenetic Study of Aging and Laboratory Testing (GESTALT) study and another 8 subjects from the Baltimore Longitudinal Study of Aging. Inclusion criteria for all participants were those of the GESTALT study (Adelnia et al, ; Ubaida‐Mohien, Lyashkov, et al, ). Briefly, participants were required to be free of major diseases or cognitive or physical impairment, with the exception of controlled hypertension.…”

“…A region above the vastus lateralis muscle, identified as the mid‐point of a line drawn between the great trochanter and the mid‐patella upper margin, was identified as the site of muscle biopsy. A trained physician performed the muscle biopsy following a standardized protocol as described previously (Gonzalez‐Freire, Scalzo, et al, ; Ubaida‐Mohien, Gonzalez‐Freire, et al, ; Ubaida‐Mohien, Lyashkov, et al, ;). Briefly, using conventional sterile technique and after provision of local anesthetic, a 6‐mm Bergstrom biopsy needle was inserted transcutaneously into the muscle following the introduction of a gauge needle.…”