E-25 Free Communication/Poster - Energy Metabolism, Weight Control and Body Composition Friday, May 30, 2014, 7:30 AM - 12:30 PM Room:WB1
Irisin is a recently discovered myokine that has been proposed to be secreted into circulation by skeletal muscle in response to exercise. In rodents, irisin activates thermogenic programs in white adipose tissue and improves glucose homeostasis. It is unknown how acute and chronic aerobic exercise alters circulating irisin levels in obese humans.
PURPOSE: We sought to determine whether irisin levels are exercise-responsive in obese individuals.
METHODS: A) Eleven obese females (BMI: 37.3 ± 2.1 kg/m2) completed, in random order, a single bout of continuous moderate exercise (CME; 55 min, 55% VO2peak) and high-intensity interval exercise (HIIE; 4 min 85% VO2max/3 min 50% VO2max x 4 intervals) at least 7 days apart. Plasma irisin concentrations were measured at 3 time intervals (rest t= -10 min, during exercise t=20 min, and post-exercise t=90 min). B) Pre- and post-exercise training irisin concentrations were measured in obese adults completing either 15 d or 12 wk of endurance exercise training (15d: n=13 BMI=34.6 ± 3.02 kg/m2 ; 12 wk: n=6, BMI=34.55 ± 3.03kg/m2).
RESULTS: Body weight and resting blood chemistry did not differ between CME and HIIE training days (p >0 .05). There was no significant interaction or main effect of exercise intensity (p > 0.05) on circulating irisin levels. Irisin concentrations were not different across time within CME (t= 0, 30, 100 min; 2.14 ± 0.08, 2.02 ± 0.19, 2.21 ± 0.13 μg/ml, respectively, p >0.05) or HIIE (t= 0, 30, 100 min; 2.04 ± 0.16, 2.21 ± 0.11, 2.08 ± 0.14 μg/ml, respectively, p >0.05). Neither 15 d (pre, 1.91 ± 0.07; post, 1.86 ± 0.1 μg/ml, p > 0.05) nor 12 wk (pre, 2.44 ± 0.17; post, 2.19 ± 0.2 μg/ml, p > 0.05) of exercise training had an effect on plasma irisin concentrations.
CONCLUSIONS: We found that circulating irisin was not altered during or after acute aerobic exercise nor was it affected by exercise intensity. Our findings suggest that circulating irisin concentrations are not responsive to acute or chronic aerobic exercise in obese adults. These data further question the link between exercise and irisin release in humans.