Impact Of Exercise Intensity On Acute Irisin Release And Insulin Sensitivity Across Obesity Status

Irisin is an adipo-myokine that has been shown to increase during acute exercise. Irisin may play a key role in exercise-related health benefits in individuals living with obesity and/or diabetes. However, it is unclear whether exercise intensity impacts irisin release and if these changes are associated with insulin sensitivity in individuals of different obesity status. PURPOSE: To determine the impact of exercise intensity on the acute release of irisin in non-obese (NOB) and overweight-obese individuals (OB), and whether irisin release was associated with greater insulin sensitivity. METHODS: A randomized controlled crossover design study was conducted on 26 NOB (body mass index (BMI): < 25 kg/m2) and 26 OB (BMI: > 28 kg/m2) adults (19-50 years). Participants performed, in a random order, 35 mins of: 1) a resting condition, 2) a moderate-intensity continuous training (MICT) session (50% of heart rate reserve (HRR)), and 3) a high-intensity interval training (HIIT) session (intervals increasing from 50% to 85-90% of HRR for 2 mins, every 5 mins). Blood samples were taken at 0, 14, 28, and 35 mins to quantify irisin via ELISA and western blotting. Each participant underwent a 2-hour oral glucose tolerance test from which insulin sensitivity (Si) was estimated using the Matsuda index. NOB and OB participants were categorized into low-Si (< 25 percentile Si) and high-Si (> 25 percentile Si). RESULTS: No significant differences in body composition, fitness, or metabolic profiles were observed between low- and high-Si groups in NOB nor OB individuals (p > .05). Insulin sensitivity was positively correlated with irisin release during MICT (all p < .05) and after 28 minutes of HIIT in NOB, but was not associated with irisin in neither MICT nor HIIT in OB. NOB individuals displayed significantly higher irisin release than OB in all conditions (p < .01). NOB individuals with low-Si had a 1.58-fold (p < .01) increase in irisin during HIIT exercise, while NOB with high-Si had a 3.17-fold (p < .05) increase. OB individuals with low-Si and high-Si had a 1.24 and 1.10-fold increase in irisin (all p < .05) during HIIT. CONCLUSION: Irisin may be released differently with varying intensities of exercise. The release of irisin may vary according to obesity status, with healthy individuals releasing more irisin compared to individuals with obesity. Canadian Institutes of Health Research, ResearchNB, Diabetes Action Canada