Leptin increases myoblast proliferation.

<p>A. Leptin-treatment (100 ng/ml) significantly increases cell proliferation and metabolic activity measured using MTS assay in primary myoblasts from mice 12 months of age. B. Leptin-treatment (100 ng/ml) also significantly increases cell proliferation and metabolic activity measured using MTS assay in primary myoblasts from mice 24 months of age. C. -treatment (100 ng/ml) significantly increases the expression of the myogenic factors MyoD and myogenin in primary myoblasts from mice 24 months of age. Leptin did not increase the expression of these factors in myoblasts from mice 12 months of age. D. Box-and-whisker plots showing ΔΔCt values (y-axis) for leptin (LEP) and leptin receptor (LEPR) expression in the soleus (SOL; top row) and extensor digitorum longus (EDL; bottom row) muscles of mice 12 and 24 months of age (x-axis). The whiskers mark the minimum and maximum values, the boxes the first and third quartiles, and the bar within the box indicates the median. Expression of the leptin receptor is not increased with age, and is significantly (P<.05) downregulated in aged soleus (SOLLEPR).