[11] Endurance-trained athletes have twice the expression of iNAMPT in skeletal muscle compared with sedentary type 2 diabetic persons.

[13] Aging, obesity, and chronic inflammation all reduce iNAMPT (and consequently NAD+) in multiple tissues,[14] and NAMPT activity was shown to promote a proinflammatory transcriptional reprogramming of immune cells (e.g. macrophages[15]) and brain-resident astrocytes.

[20] Rongvaux et al.[21] demonstrated genetically that the mouse PBEF gene conferred Nampt enzymatic activity and NAD-independent growth to bacteria lacking nadV.

Revollo et al.[22] determined biochemically that the mouse PBEF gene product encodes an eNAMPT enzyme, capable of modulating intracellular NAD levels.

[23] More recently, several groups have reported the crystal structure of Nampt/PBEF/visfatin and they all show that this protein is a dimeric type II phosphoribosyltransferase enzyme involved in NAD biosynthesis.

[29] It is reported that visfatin is enriched in the visceral fat of both humans and mice and that its plasma levels increase during the development of obesity.

[29] Noteworthy is that visfatin is reported to exert insulin-mimetic effects in cultured cells and to lower plasma glucose levels in mice by binding to and activating the insulin receptor.

On 26 October 2007, A. Fukuhara (first author), I.Shimomura (senior author) and the other co-authors of the paper,[29] who first described Visfatin as a visceral-fat derived hormone that acts by binding and activating the insulin receptor, retracted the entire paper[29] at the suggestion of the editor of the journal 'Science' and recommendation of the Faculty Council of Osaka University Medical School after a report of the Committee for Research Integrity.

[35] It is being tested for treatment of advanced melanoma, cutaneous T-cell lymphoma (CTL), and refractory or relapsed B-chronic lymphocytic leukemia.