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Myostatin inhibits IGF-I-induced myotube hypertrophy through Akt

Michael R Morissette1, Stuart A Cook, Cattleya Buranasombati

  • 1Cardiovascular Institute, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA.

American Journal of Physiology. Cell Physiology
|September 18, 2009
PubMed

Insights

Myostatin inhibits muscle growth. Removing myostatin increases muscle mass by boosting Akt signaling, a key pathway for skeletal muscle hypertrophy. This study clarifies myostatin

Area of Science:

  • Muscle physiology
  • Molecular biology
  • Cell signaling

Background:

  • Myostatin is a negative regulator of skeletal muscle mass.
  • Loss of myostatin function leads to increased muscle growth across species.
  • The precise molecular mechanisms driving myostatin-deficient muscle hypertrophy are not fully elucidated.

Purpose of the Study:

  • To investigate the role of myostatin in regulating Akt signaling in skeletal muscle.
  • To determine if Akt activation mediates the increased muscle mass observed in myostatin knockout models.
  • To explore the functional interaction between myostatin and Akt in skeletal muscle hypertrophy.

Main Methods:

  • Analysis of Akt protein expression, mRNA levels, and phosphorylation in myostatin knockout mice.
  • In vitro studies using C2C12 myotubes to examine myostatin's effect on insulin-like growth factor-I (IGF-I)-stimulated Akt phosphorylation and myotube diameter.
  • Genetic manipulation of myostatin and Akt pathways (overexpression, inhibition, dominant-negative constructs) in C2C12 myotubes.

Main Results:

  • Skeletal muscle from myostatin knockout mice exhibited increased Akt protein expression, mRNA, and activity.
  • Overexpression of myostatin in C2C12 myotubes attenuated IGF-I-induced myotube growth and Akt phosphorylation.
  • Inhibition of myostatin increased myotube diameter and Akt phosphorylation, while manipulating Akt activity modulated the effects of myostatin.
  • Increased ribosomal protein S6 phosphorylation and atrogin-1/muscle atrophy F box mRNA were observed in myostatin knockout mice.

Conclusions:

  • Myostatin negatively regulates skeletal muscle growth, at least in part, through modulation of the Akt signaling pathway.
  • Akt activation appears to be a key downstream mediator of the hypertrophic effects of myostatin deficiency.
  • These findings provide critical insights into the molecular mechanisms underlying muscle growth regulation.

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