Figure 4

Liver-derived FGF21 regulates sympathetic nerve activity to BAT during cold exposure. (A) Plasma FGF21 levels and (B) hepatic Fgf21 mRNA levels in 12–14 week old male wild type (WT) C57Bl/6J mice administered norepinephrine (1 mg/kg) for the indicated time (n = 8/group). (C) Plasma FGF21 levels in WT and FGF21 LivKO mice 30 min post-norepinephrine injection (n = 5–9/group). (D) Basal SNA to brown adipose tissue (BAT) in 12–14 week old male WT and FGF21 LivKO mice at ambient temperature and (E) during incremental cooling (n = 6–7/group). (F) Final percent change in BAT SNA in wild type and FGF21 LivKO mice at the final cooling point of 29 °C. (G) Basal SNA to BAT in 13 week old male WT mice administered ICV vehicle or PD173074 (25 µg) or (H) during incremental cooling (n = 10–11/group). (I) Final percent change in BAT SNA at 29 °C in wild type mice administered vehicle or PD173074. Values are mean ± SEM; ^*P ≤ 0.05; ^**P ≤ 0.01; and ^***P ≤ 0.005 compared to time 0 for (A,B) and relative to wild type mice (C–I).