Investigation of blood irisin, FNDC5 levels and metabolic profile before and after concentric and isometric skeletal muscle contraction

Exercise parameters that affect the release of the irisin are an important research subject. The aim of this study is to examine the irisin, FNDC5 and metabolic profile in blood before and after concentric and isometric skeletal muscle contraction. Concentric and isometric knee flexion / extension exercises, both of which lasted 5-6 minutes, were performed on an isokinetic dynamometer by 16 healthy men at 3-week intervals. Irisin level was determined by enzyme-linked immunosorbent assay (ELISA) method, FNDC5 level by western blot method and metabolic profile by liquid chromatography-time-of-flight mass spectrometry (Q-TOF LC/MS) from blood samples taken before and after the exercises. Maximum heart rates and physical activity status for the last 7 days were recorded. Participants' age, height, weight, body mass index (BMI), body composition information (measured by bioelectrical impedance analysis and bone densitometry), hand grip strength, isokinetic and isometric strength, and work values were recorded. While the change of irisin with concentric exercise was 1.23 ± 0.28 (p = 0.007), it was found to be 1.44 ± 1.04 (p = 0.134) with isometric exercise. The effects of the exercises at the metabolome and lipidome level differed significantly in the principal component analysis. The change in irisin level in response to concentric exercise and the change in androstenedione, N-acetyl aspartyl glutamic acid and some co-enzyme A (CoA) metabolites were found to be related (r>0.5 ve p<0.05, for all). The physical activity status of the participants in the last 7 days before exercise was inversely related with the response of the irisin (r = -0.481, p = 0.059). Leg muscle mass and resting metabolic rate were correlated with the change in the irisin seen with concentric exercise (r = -0.543, p = 0.03 and r = -0.511, p = 0.043, respectively). The effects of concentric and isometric exercises on irisin, FNDC5 and metabolome are distinct. Our findings related to metabolome should be confirmed by targeted metabolomics studies.