The effect of exercise interventions on Irisin level: a systematic review and meta-analysis of randomized controlled trials

Abstract

Irisin is a hormone that is offered to be a hopeful remedial target in obesity and type 2 diabetes. It has received striking attention recently, whereas, the interactions between exercise training and irisin are still unclear. Therefore, this systematic review and meta-analysis investigated the impacts of exercise interventions on circulating irisin in adults. A systematic search was conducted in PubMed, CINAHL, MEDLINE, Cochrane, Google Scholar, and Scopus up to July 15, 2021. Twenty-four studies, which assessed a total of 921 participants were included and analyzed using a random-effects model to estimate weighted mean differences (MD) with 95 % confidence intervals (CI). Overall, data revealed that exercise training significantly increased circulating irisin (MD: 0.01, 95 % CI: 0.00, 0.01, p = 0.005), and declined insulin (MD: -2.09, 95 % CI: -2.81, -1.37, p < 0.00001), glucose (MD: -12.89, 95 % CI: -16.52, -9.26, p < 0.00001), and insulin resistance (MD: -0.89, 95 % CI: -1.15, -0.62, p < 0.00001). Subgroup analysis revealed that irisin raised significantly when resistance training (p = 0.04) and combined training (p = 0.002) were applied, and for the type 2 diabetes and prediabetes (p = 0.002 for both) groups. Moreover, subgroup analysis by the type of intervention demonstrated that insulin reduced when aerobic training (p < 0.00001) and combined training (p = 0.0003) were employed, but glucose and HOMA-IR reduced after all three types of exercise training. These findings demonstrate that exercise interventions may produce ameliorations in circulating irisin. Further long-term studies are required to confirm these findings.

Keywords: FNDC5; Irisin; PGC-1alpha; exercise intervention; meta-analysis.

Figure 1. PRISMA flow diagram

Figure 2. Forest plot of the effects of exercise training versus control on irisin. AE, aerobic; RT, resistance training; HCI, high-intensity concurrent interval; MCC, moderate-intensity concurrent continues; SIT, sprint interval training; HIIT. High intensity interval training; A-R, aerobic-resistance; R-A, resistance-aerobic; EE, endurance exercise; CETFAT, continuous endurance training with intensity equivalent to Fatmax (maximal fat oxidation); CETAT, continuous endurance training with intensity equivalent to anaerobic threshold

Figure 3. Forest plot of the effects of exercise training versus control on insulin. AE, aerobic; RT, resistance training; SIT, sprint interval training; HIIT. High intensity interval training; CETFAT, continuous endurance training with intensity equivalent to Fatmax (maximal fat oxidation); CETAT, continuous endurance training with intensity equivalent to anaerobic threshold

Figure 4. Forest plot of the effects of exercise training versus control on glucose. AE, aerobic; RT, resistance training; SIT, sprint interval training; HIIT. High intensity interval training; CETFAT, continuous endurance training with intensity equivalent to Fatmax (maximal fat oxidation); CETAT, continuous endurance training with intensity equivalent to anaerobic threshold

Figure 5. Forest plot of the effects of exercise training versus control on HOMA-IR. AE, aerobic; RT, resistance training; SIT, sprint interval training; HIIT. High intensity interval training; CETFAT, continuous endurance training with intensity equivalent to Fatmax (maximal fat oxidation); CETAT, continuous endurance training with intensity equivalent to anaerobic threshold