Figure 4.

Female HSD2^OB/OCY-tg mice maintained normal leptin sensitivity with aging. (a) Daytime and nighttime energy expenditure in mice aged 3, 6, 12 and 18 months. Data are shown as scatterplots, with mean values shown as columns. (b) Food intake in wild-type and HSD2^OB/OCY-tg mice (n = 3–12/group, 1n = 1 cage, mean ± SEM is shown). (c) Fasting serum leptin (logarithmic scale) and (d) IGF-1 concentrations. (e) Twenty-four-hour food intake after i.p. injection of leptin (5 μg/g body weight) at 3 and 6 months of age. (f, g) Representative images of the arcuate nucleus (ARC) stained for phospho-STAT3 (P-STAT3), and quantification in 3-month-old mice. 3V – 3rd ventricle, scale bar = 100 μm. (h, i) Representative images of the ARC stained for P-STAT3 and quantification in 6-month-old mice, scale bar = 100 μm. (j, k) Representative images of the paraventricular nucleus (PVN) stained for tyrosine hydroxylase, and quantification in 6-month-old mice. Scale bar = 200 μm. Comparisons in figures (a)–(e) were made by two-way ANOVA, with Tukey's post hoc tests. Comparisons in (g), (i) and (k) were made using Student's t-tests. ∗, ∗∗, ∗∗∗ and ∗∗∗∗ indicate p < 0.05, p < 0.01, p < 0.001 and p < 0.0001, respectively.