The concentrations of serum, plasma and platelet BDNF are all increased by treadmill VO₂max performance in healthy college men

The most current human-based studies in which brain-derived neurotrophic factor (BDNF) levels in the peripheral blood system are analyzed use it as an indicator that represents BDNF levels in the CNS. However, whether circulating BDNF (serum and plasma) is positively or inversely associated with cardiorespiratory fitness levels (VO(2max)) is still controversial, and no study has done to investigate exercise effects on the concentration of BDNF stored in circulating platelets which, in fact, store a large amount of circulating BDNF. Thus, the purpose of this study was to determine the relation between VO(2max) and all circulating BDNF levels (serum, plasma and platelets) in college male students (N=18; age, 19 ± 1 years; height, 173.22 ± 7.65 cm; weight, 78.25 ± 14.25 kg; body fat percent, 13.82 ± 5.68%). Dual X-ray energy absorptiometry whole body scan was used to measure their body composition. After the overnight fast, all participants were performed VO(2max) test, and their blood was collected at rest and immediately after the exercise. Our data resulted in significant increases in platelet counts and serum, plasma and platelet BDNF levels immediately after the exercise (p<0.01). VO(2max) had a significant negative correlation with serum BDNF, plasma BDNF and platelet BDNF at rest (p<0.05) but a significant positive correlation with serum, plasma BDNF, and platelet BDNF immediately after the exercise (p<0.01). However, our data show no correlation between VO(2max) and platelet count both at rest and immediately after the exercise. In conclusion, this is the first study showing that basal BDNF levels are inversely correlated with cardiorespiratory fitness levels but that the inverse correlations turn into positive correlations with all circulating BDNF levels immediately after the exercise. Moreover, it is the first time to provide evidence that platelet BDNF levels are also positively affected by the exercise. However, future studies will be needed to investigate what tissues provide BDNF into the circulating system and to elucidate the role of circulating BDNF.