Abstract 881: Abrogation of Glucose-mediated Senescence in Human Endothelial Cells by Nicotinamide Phosphoribosyltransferase
Hyperglycemia-induced endothelial dysfunction is a major factor in the development of hypertension and atherosclerosis in diabetics. The extent to which endothelial cells withstand glucose overload depends on their ability to stabilize and repair the genome, and increase glucose utilization. These distinct processes are linked by their requirement for a continuous supply of NAD+. Therefore, we tested the hypothesis that nicotinimade phosphoribosyltransferase (Nampt, also known as Visfatin), the rate-limiting enzyme for NAD+ regeneration, could impart resistance to glucose-mediated endothelial dysfunction. Human aortic endothelial cells were infected with retrovirus containing cDNA for eGFP or eGFP-Nampt, and FACS-selected to yield populations with similar, and modest (1.5–2.0-fold), transgene expression. Using a chronic glucose exposure model and tracking each population to the end of their lifespan, we established that Nampt significantly extended endothelial cell longevity (43 ± 3 vs. 37 ± 2 population doublings, p < 0.05). Furthermore, Nampt substantially delayed the onset of terminal G1 arrest (38 ± 2 vs. 31 ± 2 population doublings, p < 0.05) and postponed the development of senescence, assessed by staining for senescence-associated ß-galacotsidase. By FACS assessment of DNA content, we also discovered that aging endothelial cells subjected to glucose became tetraploid, but this perturbation of the genome was almost completely abrogated by Nampt (16 ± 1 vs. 99 ± 6% tetraploid cells, p < 0.05).
Conclusion: In human endothelial cells subjected to glucose overload, Nampt confers a survival advantage sufficient to extend lifespan. Moreover, this NAD+ regenerating enzyme maintains genomic stability during cellular stress. These findings could have important implications for the treatment of endothelial dysfunction during diabetes.