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.
Highlights
Exercise is a cornerstone in the prevention and management of obesity-related cardiometabolic risk (Ross and Bradshaw 2009; Wasfy and Baggish 2016)
A prospective study of 24 weeks of aerobic exercise training showed that percent change in cardiorespiratory fitness varies between 0 and 100%, changes in insulin sensitivity vary from a decrease of 83.7% to an increase of 67.9% (Bouchard 1995; Bouchard and Rankinen 2001; Bouchard et al 2012), and reductions in systolic blood pressure vary between -3 mmHg and À13.4 mmHg (Bouchard et al 2012)
We observed a significant variability in our primary outcome going from a decrease of À19.8% to an increase of 85.7% in insulin sensitivity. These results align with previous results from our group where we found that cardiometabolic risk factors changes following a 6-month endurance training intervention ranged from a decrease of 68.9% to an increase of +54.6% in overweight and obese youth at risk of Type 2 diabetes (Senechal et al 2015) and from the HERITAGE family study that found substantially varied metabolic adaptations to endurance training where by over 10% of the population studied observed worsening of cardiometabolic risk, whereas >50% observed modest to profound improvements in ΔTotal cholesterol ΔTriglycerides ΔHDL-cholesterol ΔSystolic BP ΔDiastolic BP ΔOGTT glucose ΔOGTT glucose ΔOGTT insulin ΔOGTT insulin ΔMatsuda index ΔVO2peak
Summary
Exercise is a cornerstone in the prevention and management of obesity-related cardiometabolic risk (Ross and Bradshaw 2009; Wasfy and Baggish 2016). A prospective study of 24 weeks of aerobic exercise training showed that percent change in cardiorespiratory fitness varies between 0 and 100%, changes in insulin sensitivity vary from a decrease of 83.7% to an increase of 67.9% (Bouchard 1995; Bouchard and Rankinen 2001; Bouchard et al 2012), and reductions in systolic blood pressure vary between -3 mmHg and À13.4 mmHg (Bouchard et al 2012) In youth, this concept of heterogeneity was supported by our group (Senechal et al 2015) who showed that the metabolic response to exercise training ranged between a decrease of -68.9% to an increase as high as +54.6%. It is possible that the heterogeneity of the cardiometabolic adaptations that accompany either prolonged resistance or aerobic exercise training might be explained by a greater acute secretion of irisin in response to acute exercise
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