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Limb immobilization induces a coordinate down-regulation of mitochondrial and other metabolic pathways in men and women

ABSTRACT: Advancements in animal models and cell culture techniques have been invaluable in the elucidation of molecular events and mechanisms regulating muscle atrophy. However, few studies have examined muscle atrophy in humans using modern experimental techniques. The purpose of this study was to examine and validate changes in global gene transcription during immobilization-induced muscle atrophy in humans. Healthy men and women (N=24) were subjected to two weeks of unilateral limb immobilization, with muscle biopsies obtained before, and after 48 hours (48H) and 14 days (14D) of immobilization. Both muscle cross sectional area (~ 5 %) and strength (10-20 %) were significantly reduced in men and women after 14D of immobilization. Micro-array analysis of total RNA extracted from biopsy samples uncovered 575 and 3,128 probes representing multiple genes, which were significantly altered at 48H and 14D, respectively. As a group, genes involved in mitochondrial bioenergetics and carbohydrate metabolism were predominant features at both 48H and 14D, with genes involved in protein synthesis and degradation significantly down-regulated and up-regulated, respectively, at 14D of muscle atrophy. There was also a significant decrease in the protein content of mitochondrial cytochrome c oxidase, and the enzyme activity of cytochrome c oxidase and citrate synthase after 14D of immobilization. Furthermore, protein ubiquitination and oxidative damage were significantly increased by 48H and 14D of immobilization, respectively. These results suggest that transcriptional and post-transcriptional suppression of mitochondrial processes is sustained throughout 14D of immobilization, while protein ubiquitination plays an early but transient role in the progression of immobilization-induced muscle atrophy in humans.

ORGANISM(S): Homo sapiens

PROVIDER: GSE14901 | GEO | 2009/02/21

SECONDARY ACCESSION(S): PRJNA112003

REPOSITORIES: GEO

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Project description:Advancements in animal models and cell culture techniques have been invaluable in the elucidation of molecular events and mechanisms regulating muscle atrophy. However, few studies have examined muscle atrophy in humans using modern experimental techniques. The purpose of this study was to examine and validate changes in global gene transcription during immobilization-induced muscle atrophy in humans. Healthy men and women (N=24) were subjected to two weeks of unilateral limb immobilization, with muscle biopsies obtained before, and after 48 hours (48H) and 14 days (14D) of immobilization. Both muscle cross sectional area (~ 5 %) and strength (10-20 %) were significantly reduced in men and women after 14D of immobilization. Micro-array analysis of total RNA extracted from biopsy samples uncovered 575 and 3,128 probes representing multiple genes, which were significantly altered at 48H and 14D, respectively. As a group, genes involved in mitochondrial bioenergetics and carbohydrate metabolism were predominant features at both 48H and 14D, with genes involved in protein synthesis and degradation significantly down-regulated and up-regulated, respectively, at 14D of muscle atrophy. There was also a significant decrease in the protein content of mitochondrial cytochrome c oxidase, and the enzyme activity of cytochrome c oxidase and citrate synthase after 14D of immobilization. Furthermore, protein ubiquitination and oxidative damage were significantly increased by 48H and 14D of immobilization, respectively. These results suggest that transcriptional and post-transcriptional suppression of mitochondrial processes is sustained throughout 14D of immobilization, while protein ubiquitination plays an early but transient role in the progression of immobilization-induced muscle atrophy in humans. 72 samples taken from quadriceps of healthy ambulatory young men and women. Samples were taken at 3 timepoints throughout a 14 day period, the initial sample was taken at time 0 (PRECAST), then the limb was immobilized via a brace, and the 2nd sample was taken at 48 hours (CAST02D). The third sample was taken following 14 days of immobilization (CAST14D).

Project description:Age-related skeletal muscle atrophy is a debilitating condition that has significant negative impacts on health and quality of life. Despite broad clinical impact, the molecular basis of age-related skeletal muscle atrophy is not well understood. Here, we determined protein turnover rates in skeletal muscle of 22-month-old control mice and 22-month-old muscle-specific ATF4 knockout (ATF4 mKO) mice, which are partially resistant to age-related muscle atrophy. All samples were analyzed by DDA TripleTOF 6600 mass spectrometer for downstream analysis of protein turnover. Quantitative MS1 peak areas were extracted from DDA raw files in the Skyline-Daily software platform. ProteinPilot search results were imported into the Skyline software to build a spectral library, followed by import of raw MS files for extraction of chromatographic peak areas. A custom skyline report containing all peptide and protein characteristics, annotations, and quantitative information including isotopologue peak areas was exported and used for downstream analysis and calculation of protein turnover rates in R using in-house R scripts (TurnoveR tool). Precursor-pool corrected protein turnover rates were calculated using the same approach employed in previous studies using the Topograph software platform. For calculation of protein abundance changes, DIA acquisitions from six samples (3 ATF4 KO and 3 WT samples) were quantitatively processed using Spectronaut v14. Analysis of protein turnover indicates that most proteins with altered turnover rates in ATF4 mKO muscles have decreased half-lives and are components of the mitochondrion. These proteins include subunits of the ATP Synthase (Atp5b, Atp5o), Ubiquinol-Cytochrome C Reductase (Uqcrc1, Uqcrh) and Cytochrome C Oxidase (Cox6b1) complexes, among others. These findings implicate increased rates of mitochondrial protein turnover as a mechanism that underlies, at least in part, the protection from age-induced muscle atrophy in ATF4 mKO mice.

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Limb immobilization induces a coordinate down-regulation of mitochondrial and other metabolic pathways in men and women

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