Amide form of vitamin B₃. Plasma membrane and blood-brain barrier permeable. Precursor for β-nicotinamide adenine dinucleotide (NAD⁺). Essential for the synthesis of NAD⁺ phosphate (NADP⁺). Essential for energy metabolism, normal physiology and disease progression. Associated with a number of signaling pathways including oxidative stress, cell survival and inflammation. These effects are orchestrated partly through forkhead, Akt, Bad, caspase, MAPK and PARP signaling. Non-selective sirtuin inhibitor. Commonly used as 3D growth matrix components and additive for long-term growth.