FIGURE 4.

Hypothalamic Ob-Rb Tyr¹¹³⁸-mediated STAT3 is required for leucine deprivation-increased energy expenditure. Wild-type (WT) and knock-in mouse line with abrogated leptin receptor Tyr¹¹³⁸-mediated STAT3 signaling (Y3F) were fed a control (con) or leucine-deficient ((−)leu) diet for 7 days. Energy expenditure was measured by indirect calorimetry. Data are mean ± S.E. (n = 5–6 for each group). Statistical significance was determined by ANOVA followed by the SNK test. *, p < 0.05 for the effect of any group versus WT mice with control diet. #, p < 0.05 for the effect of Y3F mice with (−)leu diet versus Y3F mice with control diet. &, p < 0.05 for the effect of Y3F mice with (−)leu diet versus WT mice with (−)leu diet. A, body weight change; B, adipose tissue mass in proportion to body weight; C, daily food intake; D, 24 h oxygen consumption (VO₂); E, respiratory exchange ratio (RER); F, rectal temperature; G, physical activity; H, Ucp1 mRNA expression in BAT; I, UCP1 protein in BAT (upper panel, Western blot; lower panel, quantitative measurements of UCP1 protein relative to actin); J, p-HSL and p-PKA substrate protein in white adipose tissue (upper panel, Western blot; lower panel, quantitative measurements of p-HSL and p-PKA substrate protein relative to total HSL and actin, respectively); K, working model.