Polyamine Metabolism in Brain Health and Disease.

Polyamines, primarily spermidine and spermine, are small polycationic molecules essential for cell growth, signaling, and survival. Through electrostatic interactions with nucleic acids, lipids, and proteins, they regulate gene expression, organelle function, and adaptive responses to environmental cues. Polyamine metabolism also intersects with a myriad of other cellular pathways, including methionine, acetyl-CoA, and oxidative stress pathways, and is therefore involved in epigenetic control, cellular metabolism, and stress-response regulation. In the brain, beyond these general cellular functions, polyamines act as dynamic modulators of neurodevelopment, neural maintenance, and synaptic plasticity by influencing local proteostasis, transmitter release, and ion channel activity in both neurons and glia. Emerging evidence indicates that disruption of polyamine homeostasis contributes to neurological disorders as diverse as rare inborn errors of metabolism and common neurodegenerative diseases. Mutations in polyamine metabolic or transport genes lead to syndromes characterized by intellectual disability, hypotonia, movement disorders, and neurodegeneration; therefore, polyamine balance is critical for brain development and maintenance. In conditions such as Alzheimer's and Parkinson's diseases, dysregulated polyamine synthesis, catabolism, or lysosomal transport perturbs autophagic flux and proteostasis, thereby promoting Tau and α-synuclein aggregation, oxidative stress, and neuronal loss. Multi-omics analyses have further revealed that polyamine metabolism shapes glial inflammatory responses. Therapeutically, modulation of polyamine metabolism offers multiple intervention points. Spermidine supplementation or administration of polyamine analogues has been found to enhance autophagy and improve cognitive performance in models of aging and Alzheimer's disease. Additional strategies to reestablish metabolic equilibrium and support neuronal resilience include targeted manipulation of key enzymes, such as ornithine decarboxylase 1 (ODC1), spermidine/spermine acetyltransferase 1 (SAT1), spermine oxidase (SMOX), and spermine synthase (SMS), or restoration of lysosomal polyamine export via ATP13A2. This review synthesizes current understanding of polyamine metabolism in brain health and disease, by integrating molecular, cellular, and systems-level perspectives, and further highlights emerging therapeutic directions aimed at harnessing this pathway to mitigate neurological pathology.