Serum levels of irisin predict short-term outcomes in ischemic stroke

Objective: Irisin is a 112-amino acid peptide found in rat and human skeletal muscle after exercise. Previous studies had suggested that higher circulating irisin levels were associated with an increased risk of vascular atherosclerosis and cardiovascular diseases. In this study, we determined irisin levels in serum, and investigated their associations with functional outcomes in a 3-month follow-up study in Chinese patients with first-ever acute ischemic stroke (AIS). Methods: From September 2015 to December 2016, consecutive first-ever AIS patients admitted to the Department of Emergency of our hospital were identified. Serum irisin levels were measured at admission. Functional impairment was evaluated at discharge using the modified Rankin scale. The levels of irisin were expressed as median and interquartile ranges [IQR]. Results: The irisin level was obtained in 324 patients (97.6%) with a median value of 291.2 ng/ml (IQR: 214.1-404.2 ng/ml). There were significantly negative correlations between levels of irisin and NHISS (r = 0.272; P < 0.001) and BMI (r = 0.193; P = 0.003). A poor functional outcome was found in 99 patients (30.6%; 95%CI: 25.5-35.6%). The poor functional outcome distribution across the irisin quartiles ranged between 51.9% (first quartile: Q1) to 12.4% (fourth quartile: Q4). In a multivariate model using the Q1 of irisin vs. Q2-4 together with the clinical variables, the marker displayed prognostic information and increased risk of poor outcomes by 94% (OR for Q1, 1.94 [95% CI, 1.19-3.42]; P = 0.018) and mortality 66% (OR for Q1, 1.66 [95% CI, 1.11-3.07]; P = 0.009). In addition, a model containing known risk factors plus irisin compared with a model containing known risk factors without irisin showed a greater discriminatory ability to predict poor outcomes (P = 0.01) and mortality (P = 0.02). Conclusions: A low serum irisin level is a predictor of poor early functional outcome in ischemic stroke patients. The underlying mechanisms of these associations remain to be investigated.