Molecules and Cells

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Fig. 3. During puberty, androgens surge via the hypothalamic-pituitary-gonadal axis. These high levels of androgens promote muscle growth and increase the myonuclei number per myofiber leading to an increase in muscle mass during puberty. However, after puberty, muscle mass and myonuclei number per myofiber reach a steady state and remain stable during adulthood. The maintenance of the limb muscle mass during adulthood is generally achieved by the conversion of proliferative juvenile muscle stem cells into quiescent adult muscle stem cells during the pubertal period. Intriguingly, the physiological increase of androgens induces the Mib1-Notch signaling axis to initiate muscle stem cell conversion and consequently establishes the pool of quiescent adult muscle stem cells throughout their lifetime. In summary, physiological androgens have a critical role in muscle stem cell conversion and muscle maintenance rather than anabolic effects on limb muscles.
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