A Bout of High-Intensity Interval Training Increases Seric Musclin in Adults with Metabolic Syndrome

Abstract

Musclin is a myokine which induces insulin resistance (IR) in vitro, also proposed to favor aerobic capacity in murine models, which seems contradictory. Because of that, and since exercise contributes to improve IR in metabolic syndrome (MS) probably by regulating myokines, it is necessary to understand exercise´s role in regulating musclin in humans. PURPOSE: to study the effect of a bout of high-intensity interval training (HIIT) on seric musclin in adults with MS and IR. METHODS: 11 men and 4 women with MS and IR were evaluated in an experimental, pilot study. Musclin was measured by ELISA, and both glycemia and insulin by standard methods, at: 1) fasting conditions, 2) 60 minutes after a breakfast of 408 Kcal (55.1 g carbohydrates, 17.4 g fat, 9.2 g proteins), and 3) immediately after a session of HIIT (100 min after breakfast). Homeostatic model assessment (HOMA-IR) was used as indicator of IR. The HIIT session lasted 19 minutes and consisted of 5 cycles, each of them with one minute of high intensity (85% of VO2max) and two minutes of moderate intensity (50% of VO2max). Three minutes of warming up and cooling down at 3 MET intensity was always done. Data are presented as median (interquartile range). Comparisons were done with Friedman test. RESULTS: patients had an age of 52 years (45-59), a body mass index (BMI) of 26.8 kg·m-2 (24.9- 30.1), oxygen consumption (VO2max) of 34.6 ml·kg-1·min-1 (30.2-38.2) and HOMA-IR of 3.3 (2.6-4.3). Musclin values post-HIIT (709.6 pg·ml-1 (585.2-833.9)) showed a trend to be higher than fasting (599.1 pg·ml-1 (506.2-724.5), P=0.088) and refeeding (593.0 pg·ml-1 (466.4-918.2), P=0.061) conditions. Fasting musclin correlated with diastolic blood pressure during the HIIT bout (r=0.62, P<0.05). Insulin of 13.9 μU mL-1 (10.4-16.6), 59.4 μU mL-1 (23.1-159.8) and 30.8 μU mL-1 (22.4-41.5) and glycemia of 102.4 mg dl-1 (89.9-108), 111 mg dl-1 (84.4-127.4) and 97.1 mg dl-1 (87.3-110.3), were measured at conditions 1 to 3, respectively. CONCLUSIONS: a bout of HIIT trend to increase circulating musclin in humans with MS and IR, which does not support the idea of a myokine that induces IR. Future experiments will test if the increase in musclin could be explained by an increase in insulin. Colciencias 111562638757. CODI 2605. Interinstitucional 2016-1341. Colciencias Doctoral scholarships 727-2015.