NAD+ (Nicotinamide Adenine Dinucleotide) is an oxidized coenzyme widely present in living organisms. It participates in hundreds of key cellular metabolic reactions, mediating redox signaling, DNA repair, sirtuin activity, and energy metabolism pathways. As a biochemical reagent for scientific research, it is commonly used in laboratory studies focusing on energy metabolism, mitochondrial function, dehydrogenase activity, the Sirtuins pathway, PARP activity, CD38-related enzymatic reactions, cellular senescence, and neurodegenerative disease models.