Spermidine

Polyamine that induces autophagy — the cellular self-cleaning pathway that's the most mechanistically defensible aging lever we have. Rodent lifespan data is solid (Eisenberg 2009 onward), human epidemiology consistently points the right way (high dietary spermidine → lower mortality, Bratislava 2018), but the human RCT base is still a couple of small trials with mixed signals. Cheap, exceptionally safe, no acute felt effect. For a 20yo brain-priority MMA athlete: a low-cost longevity insurance bet, not a primary lever.

Spermidine is an endogenous polyamine — the body makes it, gut bacteria make it, and you eat it (aged cheese, wheat germ, mushrooms, soy, mature seeds). Endogenous and dietary spermidine levels both decline with age, and that decline tracks the age-related decline in autophagy. The mechanism story is unusually clean for a "longevity supplement" because autophagy is the most validated cellular aging pathway we have — knock it out in a model organism and lifespan crashes; boost it pharmacologically or via fasting, and lifespan extends.

1. EP300 acetyltransferase inhibition → autophagy induction (the Madeo-lab thesis): Spermidine binds and inhibits EP300, an acetyltransferase that suppresses autophagy by acetylating multiple ATG (autophagy-related) proteins. Inhibit EP300 → ATG proteins go un-acetylated → autophagy machinery activates. This is the canonical caloric-restriction-mimetic mechanism — caloric restriction also induces autophagy via overlapping pathways. Frank Madeo's lab in Graz has been the primary driver of this thesis since 2009.

2. Hypusination of eIF5A: Spermidine is the metabolic precursor to hypusine, a unique modified amino acid found only in eIF5A — a translation factor specifically required for translating proteins with polyproline stretches and for mitochondrial translation. Hypusinated eIF5A enables proper expression of TFEB (the master autophagy/lysosomal regulator), mitochondrial proteins, and immune-cell metabolism switches. Loss of hypusination tracks aging; spermidine restores it.

3. Mitophagy and chaperone-mediated autophagy: Beyond bulk autophagy, spermidine specifically promotes mitophagy (clearance of damaged mitochondria) and CMA (selective lysosomal degradation of misfolded proteins). Both decline with age and both are implicated in neurodegeneration.

4. GCN5 inhibition (caloric-restriction mimetic axis): Spermidine inhibits GCN5 histone acetyltransferase, contributing to the broader hypoacetylation pattern that overlaps with caloric restriction and rapamycin. This is part of why it's classed as a CR-mimetic.

5. Cardiac, immune, and neuro effects downstream:

• Cardiomyocyte autophagy improves diastolic function in aged mice (Eisenberg et al., Nature Medicine, 2016).
• T-cell autophagy declines with age and contributes to immunosenescence; spermidine partially restores it.
• Hippocampal autophagy and BDNF support memory in aged mice; the mechanism for the cognitive RCT signal.