Fasting Insulin and Alanine Amino Transferase, but not FGF21, Were Independent Parameters Related with Irisin Increment after Intensive Aerobic Exercising

espanolAntecedentes: Irisin es una proteina escindida de la proteina 5 que contiene el dominio de fibronectina tipo III y se ha implicado en los efectos beneficiosos del ejercicio. Sin embargo, se desconoce que factores contribuyen al incremento de irisina despues del ejercicio intensivo en humanos. Este estudio tuvo como objetivo evaluar factores independientes relacionados con la irisina serica despues de 2 semanas de actividad fisica supervisada en mujeres jovenes sedentarias sanas. Diseno y metodos: desarrollamos un estudio comparativo, intervencionista, longitudinal y prospectivo en un centro de salud especializado de tercer nivel. Entre marzo de 2010 y agosto de 2011, se reclutaron 82 mujeres adultas jovenes sedentarias, sin enfermedades cronicas o tratamientos medicos regulares. Un total de 38 mujeres cumplieron los criterios de seleccion, y las concentraciones de irisina se cuantificaron antes y despues de la intervencion. Se evaluaron factores independientes relacionados con el incremento de irisina de acuerdo con la intensidad de actividad fisica leve a moderada y vigorosa. Se realizo una prueba supervisada de ejercicio en la cinta de correr siguiendo el protocolo de Bruce de lunes a viernes durante 2 semanas. Ademas, se tomaron medidas antropometricas y se midieron el factor de crecimiento de fibroblastos 21 (FGF21), glucosa, insulina y transaminasas hepaticas. Resultados: la intensidad del ejercicio se relaciono directamente conlos niveles sericos deirisina ( p = 0.02) y FGF21 ( p = 0.01). Sin embargo, no se confirmo una relacion independiente y significativa entre FGF21 e irisina. Se encontro una nueva asociacion entre alanina aminotransferasa (ALT) e irisina, que muestra una correlacion positiva y significativa ( r = 0.37, p = 0.02). La asociacion fue particularmente fuerte con una mayor intensidad de ejercicio aerobico ( r = 0.64, p = 0.01). El modelo de regresion lineal ajustado por glucosa e indice de masa corporal confirmo una asociacion independiente entre ALT e irisina y tambien entre insulina e irisina (R² ajustado = 0,12, p= 0.04). Dicha asociacion aumento despues de agrupar en intensidad de actividad fisica moderada a vigorosa (R² ajustado = 0.46, F = 4.7, p = 0.03). Conclusiones: los niveles sericos de irisina y FGF21 aumentaron significativamente despues de 2 semanas de actividad fisica supervisada. Sin embargo, solo la insulina en ayunas y ALT, pero no FGF21, fueron parametros independientes que explican el incremento de irisina, principalmente despues de un ejercicio moderado a vigoroso. EnglishBackground: Irisin 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 Methods: We 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. Results: Intensity 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). Conclusions: Serum 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. (REV INVEST CLIN. 2019;71:133-40)