NAD+ biosynthesis from tryptophan in the presence of nicotinic acid or vice versa by rat hepatocytes--effect of clofibrate-feeding
Shin, M.; Nakakita, S.; Hashimoto, C.; Sano, K.; Umezawa, C.
International Journal for Vitamin and Nutrition Research. Internationale Zeitschrift für Vitamin- und Ernahrungsforschung. Journal International de Vitaminologie et de Nutrition 68(2): 104-108
1998
ISSN/ISBN: 0300-9831 PMID: 9565825 Document Number: 492545
NAD+ biosynthesis from tryptophan in the presence of nicotinic acid or vice versa by rat hepatocytes was investigated. In the control hepatocytes, NAD+ synthesis from tryptophan was not affected by nicotinic acid from 0.026 to 0.26 mM. NAD+ synthesis from nicotinic acid was slightly inhibited with varying concentrations of tryptophan from 0.1 to 1.0 mM. In the clofibrate-treated hepatocytes, NAD+ synthesis from tryptophan was greatly increased (234% of the control), while that from nicotinic acid was decreased (71.2% of the control). Both, NAD+ synthesis from tryptophan and that from nicotinic acid were decreased by the coexisting nicotinic acid or tryptophan. Total amount of NAD+ synthesized from tryptophan and nicotinic acid at their physiological concentrations was significantly higher than that in the control hepatocytes as a result of a large increase of NAD+ synthesized from tryptophan. When the metabolic flux of 0.1 or 0.5mM tryptophan was investigated, the glutarate pathway was suppressed in the clofibrate-treated hepatocytes, the quinolinic acid-NAD+ flux being elevated. Similarly to clofibrate, DEHP and CPP revealed an increase in NAD+ synthesis from tryptophan. Mutual relationship of NAD+ biosyntheses from tryptophan and nicotinic acid in rat hepatocytes is discussed and the relevance with peroxisomal proliferation is suggested.