• Viridiana A de la Torre-Saldaña, Miguel Ángel Gómez-Sámano, Francisco Javier Gómez-Pérez, Juan Rosas-Saucedo, Andrés León-Suárez, Mariana Grajales-Gómez, Jorge Oseguera-Moguel, Arturo Vega-Beyhart, and Daniel Cuevas-Ramos.
• Department of Endocrinology and Metabolism, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico.
• Rev Invest Clin. 2019 Jan 1; 71 (2): 133-140.

BackgroundIrisin is a protein cleaved from fibronectin type III domain-containing protein 5 and has been implicated in the beneficial effects of exercise. However, it is unknown which factors contribute to irisin increment after intensive exercising in humans. This study aimed to assess independent factors related with serum irisin after 2 weeks of supervised physical activity in young sedentary healthy women.Design And MethodsWe developed a comparative, interventional, longitudinal, and prospective study at a third-level specialty health center. Between March 2010 and August 2011, 82 sedentary young adult women, without chronic diseases or regular medical treatments, were recruited. A total of 38 women fulfilled selection criteria, and irisin concentrations were quantified before and after the intervention. Independent factors related with irisin increment were evaluated according to mild to moderate and vigorous intensity of physical activity. A supervised treadmill exercise test following the Bruce's protocol was conducted from Monday to Friday during 2 weeks. In addition, anthropometric measurements were taken, and fibroblast growth factor 21 (FGF21), glucose, insulin, and liver transaminases were measured.ResultsIntensity of exercising was directly related to irisin (p = 0.02) and FGF21 (p = 0.01) serum levels. However, an independent and significant relationship between FGF21 and irisin was not confirmed. A novel association was found between alanine aminotransferase (ALT) and irisin, showing a positive and significant correlation (r = 0.37, p = 0.02). The association was particularly strong with higher intensity of aerobic exercising (r = 0.64, p = 0.01). Linear regression model adjusted for glucose and body mass index confirmed an independent association between ALT and irisin and also between insulin and irisin (adjusted R² = 0.12, p = 0.04). Such association increased after grouping in moderate to vigorous physical activity intensity (adjusted R² = 0.46, F = 4.7, p = 0.03).ConclusionsSerum irisin and FGF21 levels significantly increased after 2 weeks of supervised physical activity. However, only fasting insulin and ALT, but not FGF21, were independent parameters explaining irisin increment, mainly after moderate to vigorous exercising.Copyright: © 2019 SecretarÍa de Salud.

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