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Grant, R., Nguyen, S., & Guillemin, G. (2010). Kynurenine pathway metabolism is involved in the maintenance of the intracellular NAD+ concentration in human primary astrocytes. International Journal of Tryptophan Research, 3, 151–156. doi:10.4137/IJTR.S4779

ISSN: 1178-6469


Efficient synthesis of NAD+ is critical to maintaining cell viability in all organs of the body. However, little is known of the pathway(s) by which cells of the central nervous system produce NAD+. The aim of this study was to investigate the relationship, between tryptophan degradation via the kynurenine pathway (KP) and de novo NAD+ synthesis in human astrocytes, a major cell type within the brain. In this study we observed that inhibition of single enzymes of the KP resulted in significant decreases in NAD+ levels in astroglial cells after a 24 hr period. We also observed that astrocytes cultured in media deficient in tryptophan, nicotinic acid and nicotinamide resulted in a 50% decrease in NAD+ levels after 24 hrs. This decrease in NAD+ was partially restored by supplementation of the culture media with either tryptophan or kynurenine, or nicotinic acid or with supply of the salvage pathway precursor nicotinamide.


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International Journal of Tryptophan Research may be accessed here.