PBEF

PBEF stands for pre-B cell enhancing factor, a protein originally described as a cytokine that promotes the growth and differentiation of pre-B cells in vitro. In humans, PBEF is the same molecule as NAMPT (nicotinamide phosphoribosyltransferase), which is also known as visfatin when discussed as an adipokine.

Biological roles of NAMPT/PBEF span both intracellular and extracellular functions. Intracellular NAMPT (iNAMPT) is an enzyme in the NAD+ salvage pathway, catalyzing the conversion of nicotinamide to nicotinamide mononucleotide, a key step in NAD+ biosynthesis. Extracellular NAMPT (eNAMPT), also called PBEF or visfatin, is proposed to act as a secreted factor that influences immune and metabolic processes. eNAMPT has been implicated in inflammation, obesity, insulin resistance, and cancer, but the extent and mechanisms of its extracellular signaling remain debated, with uncertainty about receptors and physiological relevance.

Genetics and regulation: The NAMPT gene encodes both iNAMPT and secreted NAMPT. Circulating NAMPT/PBEF levels are influenced by metabolic state and inflammatory signals, and studies have reported elevation in several conditions, though findings are not consistent across all investigations.

Clinical and research considerations: Because NAMPT is central to NAD+ metabolism and potentially to inflammatory signaling, it is of interest as a therapeutic target in metabolic and inflammatory diseases. The dual roles of NAMPT as an intracellular enzyme and as an extracellular cytokine complicate interpretation of its functions and therapeutic potential. See also NAMPT; visfatin; nicotinamide adenine dinucleotide salvage pathway.