Introduction: Irisin, a novel adipo-myokine implicated in metabolic regulation, exerts anti-inflammatory actions.

Aims and objectives: To investigate serum irisin kinetics in sepsis and septic shock.

Methods: We prospectively enrolled 102 critically ill patients with new onset sepsis or septic shock (57 males, age 64.7±15.6 years, APACHE II 23±7.2, SOFA 10±3.3) and 102 age- and gender-matched healthy controls. Irisin was determined in serum by ELISA upon enrollment and one week after.

Results: Upon enrollment, irisin was significantly lower in patients than controls (22.3±6.8 vs 28.1±6.7?g/L, p<0.001), while it increased significantly one week later in patients (22.3±6.8 vs 26.6±9.5?g/L, p<0.001). Irisin was significantly lower in patients who presented with septic shock (N=42) than those with sepsis (N=60) both at enrollment (19.6±5.1 vs 24.2±7.3 ?g/L, p<0.001) and one week after (23.6±7 vs. 28.7±10.5 ?g/L, p=0.004). Irisin increased significantly during the first week of sepsis in both groups. However, kinetics of irisin did not differ between the groups (?irisin%: 25±47 vs 24±56, p=0.87). ROC curve analysis showed that irisin, CRP and procalcitonin at enrollment performed similarly in discriminating sepsis severity (AUC 0.72, 0.78, and 0.71 respectively) and outperformed interleukins 6 and 10, and suPAR (AUC 0.69, 0.68, and 0.64 respectively). Finally, irisin at enrollment exhibited significant negative correlations with the severity scores (APACHE II, SOFA), CRP, procalcitonin, white blood cells and lactate (p<0.05).

Conclusions: Serum irisin is decreased at sepsis onset and increases significantly one week later. Lower serum irisin during the first week of sepsis is associated with the severity of sepsis.