Associations Between Circulating Basal BDNF, IGF-1 and Physical Fitness

Abstract

Exercise-induced increase in circulating insulin-like growth factor 1 (IGF-1) levels might stimulate brain-derived neurotrophic factor (BDNF) expression. Thus, circulating IGF-1 can travel from the periphery to the brain and there stimulate the expression of BDNF and facilitate long-lasting changes in neural activity. It has been shown that chronic training leads to upregulation of basal levels of both BDNF and IGF-1. Several longitudinal studies have also shown that aerobic exercise acutely elevates circulating BDNF levels in humans. PURPOSE: To investigate associations of peripheral BDNF and IGF-1 with several physical fitness components at rest. METHODS: 792 adults (26±6 yr) men participated. BDNF and IGF-1 concentrations were analyzed from venous blood samples using an ELISA Assay (Human BDNF ELISA kit, ScienCell Research laboratories, San Diego, California) and Dynex DS 2 ELISA processing system (Dynex Technologies, Chantilly, Virginia). Cardiorespiratory fitness (VO2max) was determined using an indirect graded cycle ergometer test until exhaustion. Bilateral maximal isometric leg (MVCleg) and arm extension forces (MVCarm) were measured using dynamometers. Muscular endurance tests consisted of repeated 1-min push-ups and sit-ups, while standing long jump assessed muscular power. RESULTS: The mean±SD BDNF and IGF-1 concentrations were 15.20±3.96 ng/ml, 25.0±6.9nmol/l, respectively, while VO2max was 41.1±8.8ml/kg/min, MVCleg 3394±933N, MVCarm 871±216N, push-ups 28±14reps/min, sit-ups 35±12reps/min, standing long jump 227±26cm. BDNF and IGF-1 correlated weakly with each other (r=-0.146, p=0.003). Linear regression analysis (adjusted for age, smoking and education) revealed that associations between BDNF and physical fitness were weak for VO2max (β=-0.077, p=0.006) and muscle fitness (β=-0.077, p=0.895). This was also the case for IGF-1. CONCLUSIONS: The associations between peripheral BDNF, IGF-1 and physical fitness components were weak or non-existent at rest in the present cross-sectional design. Thus, it seems that only exercise-induced elevated values of BDNF and IGF-1 may associate with each other and physical fitness components. Therefore, their interactions should be investigated in future studies during acute and / or chronic exercises.