FNDC5 and Sepsis: Circulating irisin levels were significantly lower in patients who presented with septic shock at enrollment (N = 42) compared to those presented with sepsis (N = 60), both upon enrollment (19.6 ± 5.1 μg/L vs. 24.2 ± 7.3 μg/L, p < 0.001) and one week after (23.6 ± 7 μg/L vs. 28.7 ± 10.5 μg/L, p = 0.004) (Table 2, Figure 2).