Autophagy

Autophagy (from the Greek 'self-eating') is a highly conserved intracellular degradation pathway in which cytoplasmic components including damaged organelles, aggregated proteins, and intracellular pathogens are enclosed within double-membrane vesicles called autophagosomes and delivered to lysosomes for degradation and recycling. There are three main types: macroautophagy, microautophagy, and chaperone-mediated autophagy, each with distinct mechanisms but shared goals of cellular quality control. Autophagy is upregulated in response to nutrient deprivation, oxidative stress, and infection, serving as both a survival mechanism and a quality-control system. Declining autophagic efficiency with age is linked to the accumulation of cellular damage, neurodegeneration, and metabolic dysfunction. NAD+ has been shown to enhance autophagy via sirtuin activation (particularly SIRT1), making it a compound of significant interest in longevity research.