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Insulin resistance induced by physical inactivity is associated with multiple transcriptional changes in skeletal muscle in young men

ABSTRACT: Rationale: Physical inactivity is a risk factor for insulin resistance. We examined the effect of nine days of bed rest on basal and insulin stimulated expression of genes potentially involved in insulin action by applying hypothesis-generating microarray in parallel with candidate gene real-time PCR approaches in 20 healthy, young men. Furthermore, we investigated whether bed rest affected DNA methylation in the promoter region of the peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PPARGC1A) gene. Subjects were re-examined after four weeks of retraining. Findings: Bed rest induced insulin resistance and altered the expression of more than 4,500 genes. These changes were only partly normalized after four weeks of retraining. Pathway analyses revealed significant down-regulation of 34 pathways, predominantly those of genes associated with mitochondrial function including PPARGC1A. Despite induction of insulin resistance, bed rest resulted in a paradoxically increased response to acute insulin in the general expression of genes, particularly those involved in inflammation and endoplasmatic reticulum (ER) stress. Furthermore, bed rest changed gene expressions of several insulin resistance and diabetes candidate genes. We also observed a trend toward increased PPARGC1A DNA methylation after bed rest. Conclusions: Impaired expression of PPARGC1A and other genes involved in mitochondrial function as well as a paradoxically increased response to insulin of genes involved in inflammation and ER stress may contribute to the development of insulin resistance induced by bed rest. Lack of complete normalization of changes after four weeks of exercise retraining underscores the importance of maintaining a minimum of daily physical activity.

ORGANISM(S): Homo sapiens

PROVIDER: GSE24215 | GEO | 2010/09/21

SECONDARY ACCESSION(S): PRJNA132951

REPOSITORIES: GEO

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Project description:Microgravity has a dramatic impact on human physiology, illustrated in particular with skeletal muscle impairment. A thorough understanding of the mechanisms leading to loss of muscle mass and structural disorders is necessary for the definition of efficient clinical and spaceflight countermeasures. We investigated the effects of long-term bed rest on transcriptome of soleus (SOL) and vastus lateralis (VL) muscles in healthy women (BRC group, n=8), and the potential beneficial impact of protein supplementation (BRN group, n=8) and of a combined resistance and aerobic training (BRE group, n=8). Gene expression profiles were obtained using an in-house made microarray containing 6681 muscles-relevant genes. A two-class statistical analysis was applied on the 2103 genes with consolidated expression. We identified 472 and 207 modified genes, respectively for SOL and VL in BRC group. Further clustering approaches, identifying relevant biological mechanisms or pathways, underlined five main subclusters. Three are composed almost of upregulated genes involved mainly in nucleic acid and protein metabolism, and two composed almost of downregulated genes involved in energy metabolism. Exercise countermeasure demonstrated a drastic compensatory effect, decreasing the number of differentially-expressed genes by 89 and 96% in SOL and VL. In contrast, nutrition countermeasure had a moderate effect and decreased the number of differentially-expressed genes by 40 and 25% in SOL and VL. Our results allowed reporting a systematic, global and comprehensive view of long-term woman muscle atrophy and brought new lights and insights for space environment and for women who undergo a long-term clinical bed rest. Biological samples were collected from Pre- and Post- bed rest (BR) soleus and vastus lateralis biopsies of each subject from the three groups (bed rest only: BRC; Exercise: BRE; Nutrition: BRN). six technical replicate values (2 duplicate hybridizations âa et bâ to chips with triplicate spots âxxxâ) were obtained for each skeletal muscle sample. Thus for each subject, 12 expression measurements (6 before BR and 6 after BR) were obtained for each muscle.

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Insulin resistance induced by physical inactivity is associated with multiple transcriptional changes in skeletal muscle in young men

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