New research from the University of Bergen reveals that mitochondrial nicotinamide adenine dinucleotide (NAD+) pools are critical in cellular aging. Employing a model of constitutive NAD+ depletion within subcellular compartments, investigators found mitochondria are uniquely sensitive, showing metabolic defects when mitochondrial NAD+ is depleted. The study highlights that mitochondrial NAD+ is shuttled to other organelles to compensate for depletion elsewhere, underscoring mitochondria's central metabolic role. This work extends understanding about NAD+ compartmentalization and its implications for aging and metabolic regulation, with potential influence on therapies targeting age-related decline.