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This study aimed to analyze the acute impact of exercise on serum irisin levels in 22 young (YA, 24.6±3.5 yrs) and in 12 middle-aged male adults (MA, 54.6±5.7 yrs) 15 min and 24 h after an incremental cycling exercise test to exhaustion. ELISA assay was used for serum irisin detection. Circulating irisin increased significantly from baseline (9.0±2.0 ng/ml) to 15 min post-exercise (10.2±2.0 ng/ml, P <0.001), but the greatest increment was detected after 24 h (13.5±2.5 ng/ml, P <0.001) reaching more than 50% of the basal release. Levels were significantly higher in YA (9.7±1.7 to 11.1±1.8 to 14.5±2.2 ng/ml) than MA (7.6±1.6 to 8.7±1.5 to 11.8± 2.2 ng/ml) for all measured time-points (P <0.05). Nevertheless, MA showed a comparable increase in serum irisin levels when compared to YA. These findings highlight the importance of acute physical exercise as a countermeasure against age-related deterioration of skeletal muscle mass and function in both YA and MA. [ABSTRACT FROM AUTHOR]

Physical activity can increase the circulating level of irisin, fostering several beneficial effects on health. This exercise-induced myokine is generally analyzed in blood, but its collection is invasive and exposes to potential risks. Substitution of saliva sample for blood would represent a less invasive method for irisin detection. However, a limited number of studies evaluated the amount of irisin in saliva samples.3,4 Our purpose was to verify whether saliva could represent an alternative sample in which detecting irisin changes induced by an exogenous stimulus. Five active healthy adults (age: 29±14yrs; mean body mass index: 22,9±3,7kg/m²; mean peak oxygen uptake 54,0±16,5ml/kg/min) performed an incremental exercise until exhaustion on a cycle ergometer and their blood and saliva samples were collected before the exercise, 15min, 24h, 48h post-exhaustion. Irisin levels were determined using ELISA Assay Kit (#EK-067-29). Incremental exercise has determined consistent changes in irisin levels. Indeed, serum and salivary irisin levels increased from baseline to 24h post-exercise, and then returned to basal level after 48h of rest. A significant difference of serum irisin levels at 15min (p≤0,01) and 24h (p≤0,001) compared to baseline was found. Moreover, a significant correlation (r=0,92, P<0,05) was found between irisin percentage change in serum and saliva from baseline to 24h post-exercise. The findings, while preliminary, indicate that collecting saliva samples represents a valid and sensitive method of detecting irisin level changes in response to exercise. [ABSTRACT FROM AUTHOR]