Exercise‐induced irisin release as a determinant of the metabolic response to exercise training in obese youth: the EXIT trial

Abstract

The mechanisms underlying the metabolic improvements following aerobic exercise training remain poorly understood. The primary aim of this study was to determine if an adipomyokine, irisin, responded to acute exercise was associated with the metabolic adaptations to chronic aerobic exercise in obese youth. The acute response to exercise was assessed in 11 obese youth following 45‐min acute bouts of aerobic (AE) and resistance exercise (RE). The irisin area under the curve (pre‐exercise, 15, 30, and 45 min) during these AE sessions were the main exposure variables. The primary outcome measure was the change in insulin sensitivity using the Matsuda index, following 6 weeks of RE training, delivered for 45 min, three times per week at 60–65% 1RM. Participants were also categorized as either responders (above) or nonresponders (below) based on the percentage change in the Matsuda index following the 6‐week intervention. Irisin increased significantly during the acute bout of AE from 29.23 ± 6.96 to 39.30 ± 7.05 ng/mL; P = 0.028, but not significantly during the RE session (P = 0.182). Absolute and relative change in irisin during the acute bout of AE was associated with absolute and relative change in Matsuda index (r = 0.68; P = 0.022 and r = 0.63; P = 0.037) following the 6‐week RE intervention. No such association was observed with the irisin response to acute RE (all P > 0.05). Responders to the 6‐week RE intervention displayed a fourfold greater irisin response to acute AE (90.0 ± 28.0% vs. 22.8 ± 18.7%; P = 0.024) compared to nonresponders. Irisin increases significantly following an acute bout of AE, but not RE, and this response is associated with a greater improvement in insulin sensitivity in response to chronic resistance training.

Relationship of Circulating Irisin with Body Composition, Physical Activity, and Cardiovascular and Metabolic Disorders in the Pediatric Population

“…This was confirmed after observing a 2.23-fold increase in irisin levels after as little as 15 min of intense ergometer activity in normal-weight and obese German children [11]. A similar result was observed in the EXIT intervention trial in obese Canadian adolescents [26]. Circulating irisin was observed to increase by 60% after one 45-min session of aerobic exercise, but no change was observed after one 45-min session of weight-training exercise.…”

Circulating Irisin in Healthy Adults: Changes after Acute Exercise, Correlation with Body Composition, and Energy Expenditure Parameters in Cross-Sectional Study

“…The average pre-exercise irisin level was consistent with the baseline level found in healthy individuals in the KarMeN-study [32], in a study of adipose women of a similar age reported by Winn et al [33], a middle aged Chinese population [34], and even similar to the values measured in pregnant women between the second and third trimester of normal gestation [35]. However, the values that we report in the current study were almost 40 times lower than the baseline plasma irisin level determined in a small study sample of similar characteristics in Norway [20], and slightly lower than the baseline level detected in a group of adolescents [36]. In our study, there were no statistically significant differences between absolute male and female irisin serum concentrations, in neither the pre-exercise nor post-exercise blood sample.…”

Exercise-Induced Irisin, the Fat Browning Myokine, as a Potential Anticancer Agent

“…Another study conducted on humans indicated a significant increase in irisin levels among obese youth after exercise. However, this increase was observed directly after aerobic exercise while no change was observed after resistance exercise [23]. Other studies linked irisin levels with BMI, obesity, and leptin, where obese children who had undergone a physical activity program showed a significant increase in levels of irisin and leptin.…”

“…Thus, since irisin is linked to obesity, it follows to hypothesize that irisin could be associated with cancer as well (Figure 1). Tying together obesity, irisin, and cancer, exercise, which helps combat obesity, also increases irisin levels [23]. Exercise‐induced irisin could be used as a determinant of the metabolic response to exercise in obese individuals to track any decrease in cancer risk linked to obesity [35].…”