scholarly journals Aging alters gene expression of growth and remodeling factors in human skeletal muscle both at rest and in response to acute resistance exercise

2008 ◽  
Vol 32 (3) ◽  
pp. 393-400 ◽  
Author(s):  
Richard A. Dennis ◽  
Beata Przybyla ◽  
Cathy Gurley ◽  
Patrick M. Kortebein ◽  
Pippa Simpson ◽  
...  
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Cell Structure ◽  
Muscle Growth ◽  
Cell Activity ◽  
Growth And Remodeling ◽  
Expression Of Genes ◽  
Before And After ◽  
Aging Muscle ◽  
Response To Exercise

The purpose of this investigation was to compare expression of genes that function in inflammation and stress, cell structure and signaling, or remodeling and growth in skeletal muscle of young (32 ± 7 yr, n = 15) and elderly (72 ± 5 yr, n = 16) healthy subjects before and after a bout of resistance leg exercises. A real-time RT-PCR method was used to screen 100 transcripts in v. lateralis biopsies obtained before and 72 h postexercise. The screen identified 15 candidates for differential expression due to aging and/or exercise that were measured quantitatively. The median levels of four mRNAs (insulin-like growth factor-1 and its binding protein IGFBP5, ciliary neurotrophic factor, and the metallopeptidase MMP2) were significantly affected by aging and were greater (1.6- to 2.3-fold, P ≤ 0.05) in the young than elderly muscle at both time points. The median levels of three mRNAs were significantly ( P ≤ 0.05) affected by exercise in the young. The metallopeptidase inhibitor TIMP1 and α-cardiac actin mRNAs increased 2-fold and 6.5-fold, respectively, and GDF8 (myostatin) mRNA decreased by 50%. However, elderly muscle did not display any significant changes in gene expression postexercise. Thus, aging muscle shows decreased levels at rest and an impaired response to exercise for a number of mRNAs for factors potentially involved in muscle growth and remodeling. Future studies must determine the functional importance of these gene expression changes to protein synthesis, satellite cell activity, and other processes that are directly involved in the mechanisms of muscle hypertrophy.

scholarly journals PPADS does not block contraction-induced prostaglandin E2 synthesis in cat skeletal muscle

2008 ◽  
Vol 295 (5) ◽  
pp. H2043-H2045 ◽  
Author(s):  
Jennifer L. McCord ◽  
Shawn G. Hayes ◽  
Marc P. Kaufman
Keyword(s):  
Skeletal Muscle ◽  
Pyridoxal Phosphate ◽  
Pressor Response ◽  
Triceps Surae ◽  
Prostaglandin E ◽  
Exercise Pressor Reflex ◽  
Before And After ◽  
Pressor Reflex ◽  
Response To Exercise

Pyridoxal-phosphate-6-azophenyl-2′-4-disulfonate (PPADS), a purinergic 2 (P2) receptor antagonist, has been shown to attenuate the exercise pressor reflex in cats. In vitro, however, PPADS has been shown to block the production of prostaglandins, some of which play a role in evoking the exercise pressor reflex. Thus the possibility exists that PPADS blocks the exercise pressor reflex through a reduction in prostaglandin synthesis rather than through the blockade of P2 receptors. Using microdialysis, we collected interstitial fluid from skeletal muscle to determine prostaglandin E2 (PGE2) concentrations during the intermittent contraction of the triceps surae muscle before and after a popliteal arterial injection of PPADS (10 mg/kg). We found that the PGE2 concentration increased in response to the intermittent contraction before and after the injection of PPADS (both, P < 0.05). PPADS reduced the pressor response to exercise ( P < 0.05) but had no effect on the magnitude of PGE2 production during contraction ( P = 0.48). These experiments demonstrate that PPADS does not block the exercise pressor reflex through a reduction in PGE2 synthesis. We suggest that PGE2 and P2 receptors play independent roles in stimulating the exercise pressor reflex.

Activation of insulin-like growth factor gene expression during work-induced skeletal muscle growth

1990 ◽  
Vol 259 (1) ◽  
pp. E89-E95 ◽  
Author(s):  
D. L. DeVol ◽  
P. Rotwein ◽  
J. L. Sadow ◽  
J. Novakofski ◽  
P. J. Bechtel
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Growth Factor ◽  
Muscle Growth ◽  
Experimental Period ◽  
Mrna Levels ◽  
Insulin Like Growth Factor ◽  
Muscle Weight ◽  
Skeletal Muscle Growth ◽  
Igf I

We have investigated the hypothesis that there is local regulation of insulin-like growth factor (IGF) gene expression during skeletal muscle growth. Compensatory hypertrophy was induced in the soleus, a predominantly slow-twitch muscle, and plantaris, a fast-twitch muscle, in 11- to 12-wk-old female Wistar rats by unilateral cutting of the distal gastrocnemius tendon. Animals were killed 2, 4, or 8 days later, and muscles of the nonoperated leg served as controls. Muscle weight increased throughout the experimental period, reaching 127% (soleus) or 122% (plantaris) of control values by day 8. In both growing muscles, IGF-I mRNA, quantitated by a solution-hybridization nuclease-protection assay, rose by nearly threefold on day 2 and remained elevated throughout the experimental period. IGF-II mRNA levels also increased over controls. A more dramatic response was seen in hypophysectomized rats, where IGF-I mRNA levels rose by 8- to 13-fold, IGF-II values by 3- to 7-fold, and muscle mass increased on day 8 to 149% (soleus) or 133% (plantaris) of the control contralateral limb. These results indicate that signals propagated during muscle hypertrophy enhance the expression of both IGF genes, that modulation of IGF-I mRNA levels can occur in the absence of growth hormone, and that locally produced IGF-I and IGF-II may play a role in skeletal muscle growth.

scholarly journals New Role for Serum Response Factor in Postnatal Skeletal Muscle Growth and Regeneration via the Interleukin 4 and Insulin-Like Growth Factor 1 Pathways

2006 ◽  
Vol 26 (17) ◽  
pp. 6664-6674 ◽  
Author(s):  
Claude Charvet ◽  
Christophe Houbron ◽  
Ara Parlakian ◽  
Julien Giordani ◽  
Charlotte Lahoute ◽  
...  
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Growth Factor ◽  
Serum Response Factor ◽  
Muscle Growth ◽  
Interleukin 4 ◽  
Specific Gene ◽  
Response Factor ◽  
Insulin Like Growth Factor ◽  
Serum Response

ABSTRACT Serum response factor (SRF) is a crucial transcriptional factor for muscle-specific gene expression. We investigated SRF function in adult skeletal muscles, using mice with a postmitotic myofiber-targeted disruption of the SRF gene. Mutant mice displayed severe skeletal muscle mass reductions due to a postnatal muscle growth defect resulting in highly hypotrophic adult myofibers. SRF-depleted myofibers also failed to regenerate following injury. Muscles lacking SRF had very low levels of muscle creatine kinase and skeletal alpha-actin (SKA) transcripts and displayed other alterations to the gene expression program, indicating an overall immaturity of mutant muscles. This loss of SKA expression, together with a decrease in beta-tropomyosin expression, contributed to myofiber growth defects, as suggested by the extensive sarcomere disorganization found in mutant muscles. However, we observed a downregulation of interleukin 4 (IL-4) and insulin-like growth factor 1 (IGF-1) expression in mutant myofibers which could also account for their defective growth and regeneration. Indeed, our demonstration of SRF binding to interleukin 4 and IGF-1 promoters in vivo suggests a new crucial role for SRF in pathways involved in muscle growth and regeneration.

Exercise training alters DNA methylation patterns in genes related to muscle growth and differentiation in mice

2015 ◽  
Vol 308 (10) ◽  
pp. E912-E920 ◽  
Author(s):  
Timo Kanzleiter ◽  
Markus Jähnert ◽  
Gunnar Schulze ◽  
Joachim Selbig ◽  
Nicole Hallahan ◽  
...  
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Dna Methylation ◽  
Exercise Training ◽  
Metabolic Regulation ◽  
Muscle Growth ◽  
Epigenetic Mechanism ◽  
Myogenic Regulatory Factors ◽  
Regulatory Factors ◽  
A Genome

The adaptive response of skeletal muscle to exercise training is tightly controlled and therefore requires transcriptional regulation. DNA methylation is an epigenetic mechanism known to modulate gene expression, but its contribution to exercise-induced adaptations in skeletal muscle is not well studied. Here, we describe a genome-wide analysis of DNA methylation in muscle of trained mice ( n = 3). Compared with sedentary controls, 2,762 genes exhibited differentially methylated CpGs ( P < 0.05, meth diff >5%, coverage >10) in their putative promoter regions. Alignment with gene expression data ( n = 6) revealed 200 genes with a negative correlation between methylation and expression changes in response to exercise training. The majority of these genes were related to muscle growth and differentiation, and a minor fraction involved in metabolic regulation. Among the candidates were genes that regulate the expression of myogenic regulatory factors ( Plexin A2) as well as genes that participate in muscle hypertrophy ( Igfbp4) and motor neuron innervation ( Dok7). Interestingly, a transcription factor binding site enrichment study discovered significantly enriched occurrence of CpG methylation in the binding sites of the myogenic regulatory factors MyoD and myogenin. These findings suggest that DNA methylation is involved in the regulation of muscle adaptation to regular exercise training.

The effect of caffeine on skeletal muscle anabolic signaling and hypertrophy

2017 ◽  
Vol 42 (6) ◽  
pp. 621-629 ◽  
Author(s):  
Timothy M. Moore ◽  
Xavier M. Mortensen ◽  
Conrad K. Ashby ◽  
Alexander M. Harris ◽  
Karson J. Kump ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Muscle Growth ◽  
Mtor Signaling ◽  
Signaling Proteins ◽  
Signaling Protein ◽  
Before And After ◽  
Amp Activated Protein Kinase

Caffeine is a widely consumed stimulant with the potential to enhance physical performance through multiple mechanisms. However, recent in vitro findings have suggested that caffeine may block skeletal muscle anabolic signaling through AMP-activated protein kinase (AMPK)-mediated inhibition of mechanistic target of rapamycin (mTOR) signaling pathway. This could negatively affect protein synthesis and the capacity for muscle growth. The primary purpose of this study was to assess the effect of caffeine on in vivo AMPK and mTOR pathway signaling, protein synthesis, and muscle growth. In cultured C2C12 muscle cells, physiological levels of caffeine failed to impact mTOR activation or myoblast proliferation or differentiation. We found that caffeine administration to mice did not significantly enhance the phosphorylation of AMPK or inhibit signaling proteins downstream of mTOR (p70S6k, S6, or 4EBP1) or protein synthesis after a bout of electrically stimulated contractions. Skeletal muscle-specific knockout of LKB1, the primary AMPK activator in skeletal muscle, on the other hand, eliminated AMPK activation by contractions and enhanced S6k, S6, and 4EBP1 activation before and after contractions. In rats, the addition of caffeine did not affect plantaris hypertrophy induced by the tenotomy of the gastrocnemius and soleus muscles. In conclusion, caffeine administration does not impair skeletal muscle load-induced mTOR signaling, protein synthesis, or muscle hypertrophy.

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