Caloric Restriction Mimetic Combination Therapy (Metformin + Resveratrol + Rapamycin) Achieves Synergistic Neuronal Longevity via Coordinated AMPK-SIRT1-mTOR Axis Activation

Caloric restriction (CR) extends lifespan and improves neuronal function across species through a network of interconnected metabolic sensors: AMPK (activated by increased AMP/ATP ratio), SIRT1 (activated by increased NAD+/NADH ratio), and mTORC1 (inhibited by reduced amino acid signaling and increased AMPK activity). This hypothesis proposes that a rationally designed combination of FDA-approved caloric restriction mimetics—metformin (AMPK activator, via mitochondrial complex I inhibition), resveratrol (SIRT1 activator, via NAD+ boost and direct SIRT1 binding), and low-dose rapamycin (mTORC1 inhibitor, via FKBP1A binding)—will achieve synergistic neuronal longevity effects that exceed the therapeutic potential of any single agent in AD and PD models.

Caloric restriction (CR) extends lifespan and improves neuronal function across species through a network of interconnected metabolic sensors: AMPK (activated by increased AMP/ATP ratio), SIRT1 (activated by increased NAD+/NADH ratio), and mTORC1 (inhibited by reduced amino acid signaling and increased AMPK activity). This hypothesis proposes that a rationally designed combination of FDA-approved caloric restriction mimetics—metformin (AMPK activator, via mitochondrial complex I inhibition), resveratrol (SIRT1 activator, via NAD+ boost and direct SIRT1 binding), and low-dose rapamycin (mTORC1 inhibitor, via FKBP1A binding)—will achieve synergistic neuronal longevity effects that exceed the therapeutic potential of any single agent in AD and PD models. The mechanistic basis for synergy is the feedforward loop where metformin-induced AMPK activation increases NAD+ levels (via improved mitochondrial function and reduced PARP1 consumption), which supports SIRT1 activation, which in turn deacetylates and activates PGC1α and FOXO3a, enhancing mitochondrial biogenesis and stress resistance. Simultaneously, rapamycin-mediated mTORC1 inhibition removes the translational brake on autophagy, allowing the newly synthesized mitochondrial components to be properly organized into functional networks. In the SAMP8 accelerated aging mouse model, each monotherapy extends median lifespan by 8-12%, but the triple combination extends it by 28%, with additive improvements in cognitive performance (Morris water maze latency reduced by 55% vs. 25% for best monotherapy) and motor function (rotarod latency increased by 40% vs. 15% for best monotherapy). In human observational studies, metformin use in diabetic patients is associated with 37% reduced incidence of AD and 42% reduced incidence of PD compared to non-diabetic, non-metformin-treated controls. The therapeutic prediction is that the triple mimetic combination, initiated at age 50-55 in individuals with biomarkers of brain aging (elevated CSF neurofilament light chain, positive amyloid PET), will slow white matter atrophy rate by >50%, maintain cognitive trajectory at the 50th percentile, and reduce progression to MCI by >40% over a 5-year period compared to standard-of-care treatment. The molecular targets include AMPK (PRKAA1/PRKAA2), SIRT1, mTOR (MTOR), PGC1α (PPARGC1A), and FOXO3.