Fig. 1. (A) Leptin levels measured in homogenized mouse tissue normalized by total protein. Means with different superscripts differ significantly from one another (P<0.05). (B) Immunostaining for the long form of the leptin receptor (Ob-R) in cross-sections of mouse skeletal muscle, showing positive staining relative to control samples (no primary antibody). (C) Peripheral, direct (muscle) and central (hypothalamic) pathways through which leptin alters pathways regulating skeletal muscle hypertrophy. (D) Leptin levels measured in homogenized mouse tissue normalized by total protein in young adult (12 months) and aged (12 months) mouse samples. ns, not statistically significant (P<0.05) for age-related differences; GH, growth hormone; IGF, insulin-like growth factor; mTOR, mechanistic target of rapamycin.