Acute aerobic exercise and Irisin serum levels in young and middle-aged adults

Purpose: Irisin is a hormone-like myokine involved in several and relevant physiological processes. Recently, there is an increasing interest in studying irisin, and its response to acute aerobic exercise (1). Indeed, aerobic physical activity can increase the circulating level of this myokine, promoting pleiotropic beneficial effects on human health. However, the exact outcome of acute aerobic exercise on the amount and time release of irisin is unknown (1, 2). The aims of this study were to explore the impact of an incremental exercise on serum irisin level in healthy male adults and to compare the acute exerciseinduced irisin changes in young and middle- aged individuals. Methods: Sixteen participants, young adults (YA: n = 8; age: 24.5 ± 2 y; BMI: 22.8 ± 2 kg/m2; peak oxygen uptake (VO2peak): 47.5 ± 6 ml/kg/min) and middle-aged adults (MA: n = 8; age: 43.0 ± 9 y; BMI: 23.5 ± 2 kg/m2; VO2peak 47.0 ± 8 ml/kg/min) performed an incremental exercise until exhaustion on a cycle ergometer. Their VO2peak was determined via direct gas analysis and their blood samples were collected before the test, 15 min and 24 h post-exhaustion. The serum levels of irisin were determined using ELISA Assay (#EK-067–29). Results: There were no differences between groups in BMI and VO2peak (p[0.05). Baseline irisin levels were significantly higher in YA with respect to MA (9.4 ± 1.1 vs 7.5 ± 1.8 ng/ml; p\0.05). A significant increase of irisin level was detected 24 h after acute aerobic exercise both in young and middle-aged adults (4.2 ± 2.1 and 5.8 ± 2.5 ng/ml, respectively; p\0.001). Noteworthy, after acute aerobic exercise, the change in serum irisin concentrations from 15 min to 24 h was significantly greater in MA than YA (4.4 ± 1.7 vs 2.8 ± 1 ng/ml; p\0.05), resulting in a comparable irisin level 24 h post-exercise (13.3 ± 1.9 vs 13.6 ± 1.5 ng/ml; p = ns). Conclusions: This study has shown that an acute aerobic exercise determined an increase in serum irisin concentration (both in MA and YA) and the highest values of irisin concentration were obtained 24 h post-exhaustion. Surprisingly, 24 h after exercise MA have achieved the equivalent irisin level of YA, despite having lowerbasal irisin values