BDNF/TrkB Signaling in the Brain–Kidney Axis Under Functional Stress

Brain-derived neurotrophic factor (BDNF) and its high-affinity receptor tropomyosin receptor kinase B (TrkB) are classically associated with neuroplasticity, but increasing evidence suggests a broader role for BDNF/TrkB signaling in systemic stress adaptation beyond the central nervous system. Strenuous exercise is a model of functional stress that may become a clinically relevant renal challenge under conditions such as dehydration, heat stress, vascular vulnerability, and repeated exposure. Neuroendocrine stress activation, hemodynamic perturbations, and cytoskeletal instability are key factors that may contribute to glomerular barrier dysfunction in this setting. BDNF biogenesis is complex, and circulating BDNF largely reflects platelet-associated pools and context-dependent release. At the tissue level, BDNF/TrkB signaling can activate actin-regulatory pathways involved in cellular resilience. The podocyte is of particular interest because its actin-dependent architecture functionally parallels that of neurons and is essential for maintenance of the glomerular filtration barrier. Within this framework, BDNF/TrkB signaling may stabilize podocyte actin dynamics, reduce foot process effacement, and attenuate proteinuria. The present review focuses on the brain–kidney axis and the potential renoprotective role of BDNF/TrkB signaling, while highlighting major knowledge gaps regarding BDNF availability to glomerular cells, isoform-specific TrkB actions, and causal inference in humans exposed to repeated exercise-related renal stress. However, current human evidence is insufficient to define the dominant source and delivery route of BDNF to glomerular cells during exercise-related renal stress. Therefore, BDNF/TrkB is discussed here as a candidate modulatory/resilience pathway rather than an established causal driver.