Figure 7.

Central Aβ_1–42 decreases hypothalamic leptin sensitivity of HFD mice. (a,b) ScrP or Aβ_1–42 (3.36 µg/kg) given to HFD mice (starting at week 6) for 35 days, then given saline or leptin (2 mg/kg) twice daily for 3 days (n = 8–9/group). Food intake (a) and percentage body weight change (b) at end of injection period. (c) RCD WT (n = 7/group) and Bace1 ^KO (n = 4/group) mice given saline or leptin (2 mg/kg) twice daily for 3 days and percentage body weight change determined. (d) 7 days later icv osmotic minipumps were inserted and Aβ_1–42 (10 µg/kg) given to all mice for 21 days, then leptin sensitivity tested as above over the last 3 days. (e) leptin responsiveness of WT and Bace1 ^KO mice before (PRE) and after (POST) Aβ_1–42 treatment. (f) Immunoblots for saline and leptin-stimulated pSTAT3^Tyr705, STAT3, PTP1B, and actin of HFD mice given ScrP or Aβ_1–42, then injected with saline or leptin. (g) Ratio of signal intensities for pSTAT3^Tyr705 to STAT3 (n = 5–7/group) and pSTAT3^Tyr705 (n = 6–10/group) by ELISA in ScrP and Aβ_1–42 treated mice after injection of saline or leptin. (h) Quantified signal intensity of PTP1B to actin for mice given ScrP or Aβ_1–42 after injection of saline or leptin (n = 5–7/group). (i) Immunoblots of SOCS3 and actin of HFD mice given ScrP or Aβ_1–42 after injection of saline or leptin, with quantified signal shown (n = 5–7/group). RT-qPCR for Socs3 for mice given ScrP and Aβ_1–42 after injection of saline or leptin (n = 5–6/group), (j) Hypothalamic relative protein levels of ER stress markers in HFD mice given ScrP or Aβ_1–42 (n = 5–7/group). (k) Hypothalamic cytokine levels by ELISA in HFD mice given ScrP or Aβ_1–42 compared to untreated controls (n = 5–13/group). Data are means ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001 by one-way ANOVA with Bonferroni’s multiple comparisons test (a,b,c,d,g,k), two-way ANOVA (e), Kruskal-Wallis test (h,i) or 2-tailed Student’s t-test with Welch correction (j). Uncropped images of immunoblots can be found in Supplementary Fig. 11.