Brain-derived neurotrophic factor in human cerebrospinal fluid is elevated after exercise

Brain-derived neurotrophic factor (BDNF) is implicated in neuronal differentiation, maturation, survival, and synaptic plasticity. Circulating BDNF is often quantified to represent brain neuronal plasticity following acute exercise. However, BDNF in the fluid compartment surrounding the brain has not been quantified in healthy humans following exercise. We measured total and free BDNF in arterial and internal jugular venous (IJV) blood to assess cross-brain BDNF release, and in cerebrospinal fluid (CSF) via lumbar puncture, before and following ∼2 h of cycling exercise. We hypothesized that exercise would elevate both systemic circulating BDNF and CSF BDNF concentrations. Herein, in humans, we demonstrate that BDNF in the CSF is elevated following exercise. We also report a net release of BDNF from the brain into circulation despite being several orders of magnitude less concentrated in the CSF.NEW & NOTEWORTHY Across species, acute exercise increases brain-derived neurotrophic factor in circulation and so is considered a therapeutic strategy to improve brain health. We coupled arterial and jugular venous cannulation with concurrent cerebrospinal fluid measurement via lumbar puncture, to measure the cerebral exchange of brain-derived neurotrophic factor, before and after participants cycled for ∼2 h. The current data demonstrate that brain-derived neurotrophic factor in the cerebrospinal fluid is elevated following exercise.