Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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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. 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).

ORGANISM(S): Homo sapiens

SUBMITTER: Simon Melov

PROVIDER: E-GEOD-14901 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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

Abadi Arkan A Glover Elisa I EI Isfort Robert J RJ Raha Sandeep S Safdar Adeel A Safdar Adeel A Yasuda Nobuo N Kaczor Jan J JJ Melov Simon S Hubbard Alan A Qu Xiaoyan X Phillips Stuart M SM Tarnopolsky Mark M

PloS one 20090805 8

Advancements in animal models and cell culture techniques have been invaluable in the elucidation of the molecular mechanisms that regulate muscle atrophy. However, few studies have examined muscle atrophy in humans using modern experimental techniques. The purpose of this study was to examine changes in global gene transcription during immobilization-induced muscle atrophy in humans and then explore the effects of the most prominent transcriptional alterations on protein expression and function ...[more]

PMID: 19654872

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Project description:Although short-term disuse does not result in measurable muscle atrophy, studies suggest that molecular changes associated with protein degradation may be initiated within days of the onset of a disuse stimulus. We examined the global gene expression patterns in sedentary men (n = 7, mean age Â± S.D = 22.1 Â± 3.7 yr) following 48h unloading (UL) via unilateral lower limb suspension and 24h reloading (RL). Biopsy samples of the left vastus lateralis muscle were collected at baseline, 48h UL, and 24h RL. Expression changes were measured by microarray and gene clustering; identification of enriched functions and canonical pathways were performed using the Database for Annotation, Visualization and Integrated Discovery (DAVID) and Ingenuity Pathway Analysis (IPA). Four genes were validated with qRT-PCR, and protein levels were measured with Western blot. Of the upregulated genes after UL, the most enriched functional group and highest ranked canonical pathway were related to protein ubiquitination. The oxidative stress response pathway was the second highest ranked canonical pathway. Of the downregulated genes, functions related to mitochondrial metabolism were the mostly highly enriched. In general, gene expression patterns following UL persisted following RL. qRT-PCR confirmed increases in mRNA for UPP-related E3 ligase Atrogin1 (but not accompanying increases in protein products) and stress response gene heme oxygenase-1 (HMOX, which showed a trend towards increases in protein products at 48h UL) as well as extracellular matrix (ECM) component COL4. The gene expression patterns were not readily reversed upon RL suggesting that molecular responses to short-term periods of skeletal muscle inactivity may persist after activity resumes. Biopsies were taken of the left vastus lateralis of healthy, sedentary men (N = 7) at baseline, immediately following 48h UL and 24h RL. A 5mm Berstrom biopsy needle was used. Biopsy samples were immediately snap-frozen in liquid nitrogen upon excision. All samples were stored at -80Â° C until analysis.

Dataset Information

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

Publications

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

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