FGF21 deficiency results in depressed heart rate and increased heart rate variability during endotoxemia. Ambulatory blood pressure and heart rate measured by in vivo telemetry before and after 2 mg/kg i.p. LPS, related to Fig. 4 D. (A) Hourly averages of heart rate and mean arterial pressure after LPS injection in Fgf21^fl/fl vs Fgf21^ΔLiv. Floating bars represent minimum and maximum hourly averages per genotype group. (B and C) Telemetry measurements were recorded every minute. Heart rate differences between each recording are shown. (B) Minute-to-minute HRV before and after LPS injection. (C) Minute-to-minute HRV after LPS injection, with Fgf21^ΔLiv (red curve) graphed in front to show the difference. n = 4/group; pooled data are from three independent experiments. ****, P < 0.0001, two-way ANOVA. Data are expressed as mean ± SEM.