Physical exercise is one of the most robust interventions for promoting brain health and protecting against neurodegenerative diseases. Extensive research has demonstrated that regular physical activity reduces the risk of developing Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS), while also slowing disease progression in already-affected individuals [1].
This pathway explores the molecular and cellular mechanisms by which exercise exerts its neuroprotective effects, including neurotrophic factor release, anti-inflammatory actions, and metabolic benefits.
Exercise induces a cascade of molecular events that promote neuronal survival, plasticity, and function. The key mediators include brain-derived neurotrophic factor (BDNF), insulin-like growth factor-1 (IGF-1), vascular endothelial growth factor (VEGF), and myokines released from skeletal muscle [2]. These factors work through overlapping and distinct signaling pathways to exert neuroprotective effects across multiple neurodegenerative disease models.
Brain-Derived Neurotrophic Factor (BDNF): BDNF is the primary mediator of exercise-induced neurogenesis and synaptic plasticity. Exercise increases BDNF expression in the hippocampus and cortex through multiple mechanisms, including neuronal activity, muscle contraction, and metabolic stress [3]. BDNF binds to TrkB receptors on neurons, activating downstream signaling cascades that promote neuronal survival, dendritic branching, and synaptic plasticity.
Insulin-Like Growth Factor-1 (IGF-1): IGF-1 is a peptide hormone that crosses the blood-brain barrier from the periphery during exercise [4]. It promotes neuronal growth, differentiation, and survival through the PI3K/Akt and MAPK/ERK pathways. IGF-1 also synergizes with BDNF to enhance neuroprotective effects.
Vascular Endothelial Growth Factor (VEGF): VEGF promotes angiogenesis and neurogenesis in the brain. Exercise-induced VEGF expression improves cerebral blood flow and supports the vascular niche for neural stem cells [5].
Myokines are cytokines and peptides secreted by skeletal muscle during contraction. They mediate many of the systemic effects of exercise on brain health.
Irisin (FNDC5): Irisin is cleaved from the membrane protein FNDC5 during exercise and enters the brain via circulation. Once in the brain, irisin activates PGC-1α and promotes mitochondrial biogenesis, synaptic plasticity, and cognitive function [6].
Cathepsin B: This muscle-derived protease crosses the blood-brain barrier and promotes BDNF expression in the hippocampus. Cathepsin B has been shown to improve memory and learning in animal models [7].
Myostatin: Unlike other myokines, myostatin negatively regulates muscle growth. Exercise reduces myostatin levels, and myostatin inhibition has been shown to enhance neurogenesis and cognitive function [8].
AMPK: AMP-activated protein kinase serves as an energy sensor activated during exercise when cellular energy levels decline. AMPK activation promotes mitochondrial biogenesis, autophagy, and metabolic adaptation [9].
mTOR: The mechanistic target of rapamycin pathway regulates protein synthesis and synaptic plasticity. Exercise modulates mTOR activity to promote synaptic remodeling and memory formation.
CREB: cAMP response element-binding protein is a transcription factor that regulates BDNF and other neurotrophic gene expression. CREB activation is essential for exercise-induced neurogenesis.
FoxO: Forkhead box O transcription factors regulate autophagy and stress response. Exercise modulates FoxO activity to enhance protein clearance and cellular survival.
Aerobic exercise reduces amyloid-beta (Aβ) burden through multiple mechanisms [10]:
Exercise reduces tau phosphorylation and accumulation:
Exercise-induced hippocampal neurogenesis is critical for memory improvement:
Exercise provides significant vascular protection:
Exercise protects dopaminergic neurons and preserves motor function:
Exercise reduces α-synuclein aggregation through:
Exercise benefits non-motor symptoms in PD:
Exercise in ALS requires careful consideration due to fatigue susceptibility:
Aerobic Exercise:
Resistance Training:
Balance and Flexibility:
Research is ongoing on exercise mimetics:
Multiple clinical trials support exercise benefits in AD:
Clinical evidence supports exercise for PD:
Exercise may reduce neurodegenerative disease risk:
Mahalakshmi B et al. Possible Neuroprotective Mechanisms of Physical Exercise in Neurodegeneration. J Neurol Sci. 2020. ↩︎
Wang J et al. Exercise, BDNF and Cognitive Function. Neurochem Res. 2020. ↩︎
Liu Y et al. BDNF and Exercise in Alzheimer's Disease. J Mol Neurosci. 2015. ↩︎
Pintelon C et al. IGF-1 and Neuroprotection in Neurodegeneration. Front Cell Neurosci. 2015. ↩︎
Shen X et al. Exercise and Parkinson's Disease: Mechanisms and Outcomes. J Parkinsons Dis. 2016. ↩︎
Zhang L et al. Exercise, Depression and Neurotransmission. Front Behav Neurosci. 2024. ↩︎
Kim K et al. Exercise, Diabetes and Metabolic Mechanisms. Front Physiol. 2024. ↩︎
Liu X et al. BDNF and Physical Activity in Depression. Psychiatr Danub. 2024. ↩︎
Lee J et al. Myokines and Metabolic Regulation. Int J Mol Sci. 2024. ↩︎
Yang H et al. Exercise Neuroprotection in Parkinson's Disease. Neuropsychiatry. 2024. ↩︎