Physiological predictors of exercise-induced increases in circulating BDNF isoforms and net cerebral lactate exchange...

We previously showed an acute intensity-dependent increase in circulating brain-derived neurotrophic factor (BDNF) after aerobic exercise, without a concurrent increase in its release from the brain. Several exercise-related factors have been suggested to influence BDNF signalling and lactate dynamics, implicated in neuroplastic processes. We investigated whether pre-exercise levels and exercise-induced changes in platelet count, lactate, cortisol and noradrenaline predict changes in forearm venous serum mature BDNF (mBDNF-S) and its precursor proBDNF. As lactate may stimulate neuronal BDNF expression, net cerebral lactate exchange (LAC-AV-B) and its correlates, including mBDNF-S and proBDNF, were investigated. An association with the proportion of fast-twitch muscle fibre cross-sectional area (fCSA%-II) and the moderating effect of BDNF genotype were also examined. Healthy, physically fit adults (n=16, 31 ± 6 yrs) cycled for 20 min at 40, 60 and 80% of VO₂max, separated by 30-min rest. All biomarkers were analysed in blood samples taken before and after cycling at each intensity. Increases in noradrenaline and lactate were related to increases in mBDNF-S, while increases in cortisol were related to increases in proBDNF. LAC-AV-B was related only to increases in circulating lactate. Changes in mBDNF-S were predicted by fCSA%-II, while increases in proBDNF were not. Exploratory analyses also revealed hypothesis-generating observations of a possible pattern of higher proBDNF levels in Val66Val carriers, whereas a trend toward greater increases in LAC-AV-B in Val66Met carriers. Finally, findings raise the possibility that catecholamine-related increases in mBDNF-S and cortisol-related increases in proBDNF may be linked to mechanisms previously associated with synaptic strengthening and pruning, respectively.