AMPK

AMPK (AMP-activated protein kinase) is the master cellular energy sensor. It activates when the AMP:ATP ratio rises — i.e., when the cell is energy-stressed — and triggers catabolic pathways: fatty-acid oxidation, glucose uptake, mitochondrial biogenesis, and autophagy. It also suppresses anabolic pathways including mTOR.

AMPK activation is one of the canonical longevity targets. Caloric restriction, exercise, metformin, and several investigational longevity peptides exert at least part of their effect by raising AMPK activity. MOTS-c, the mitochondrial-derived peptide, is one example with documented AMPK-modulating activity.

AMPK and mTOR are functionally opposed: in broad strokes, AMPK is the ‘stress / repair / autophagy’ switch and mTOR is the ‘grow / build / protein synthesis’ switch. Many longevity protocols intentionally cycle between the two states.