Shibata Katsumi, Fukuwatari Tsutomu, Suzuki Chiyomi
Department of Nutrition, School of Human Cultures, The University of Shiga Prefecture.
J Nutr Sci Vitaminol (Tokyo). 2014;60(2):86-93. doi: 10.3177/jnsv.60.86.
Two compounds are known as the vitamin niacIn: nicotinic acid (NiA) and nicotinamide (Nam). The physiological functions and metabolic fates of NiA and Nam are identical, but differ when pharmacological doses are administered. Our study aimed to investigate the metabolic interactions between NiA and Nam when their pharmacological doses were administered together. We measured seven major niacin catabolites, including NiA, Nam, N(1)-methylnicotinamide (MNA), N(1)-methyl-2-pyridone-5-carboxamide (2-Py), N(1)-methyl-4-pyridone-3-carboxamide (4-Py), Nam N-oxide, and nicotinuric acid (NuA). Under physiological conditions, niacin is chiefly catabolized to 4-Py via MNA. However, this was not the primary pathway when rats were fed a diet containing excess niacin. When rats were fed a diet containing excess NiA, NuA was the major catabolite, and on being fed a diet containing excess Nam, MNA was the major catabolite. When rats were fed a diet containing an excess of both NiA and Nam, MNA and NuA were the major catabolites. The metabolic fates of excess NiA and Nam did not mutually interfere. Therefore, the administration of NiA and Nam together may be better than the administration of NiA or Nam alone because different pharmacological effects are expected.
烟酸（NiA）和烟酰胺（Nam）。NiA和Nam的生理功能及代谢归宿是相同的，但给予药理剂量时则有所不同。我们的研究旨在探究同时给予药理剂量的NiA和Nam时它们之间的代谢相互作用。我们测定了七种主要的烟酸分解代谢物，包括NiA、Nam、N(1)-甲基烟酰胺（MNA）、N(1)-甲基-2-吡啶酮-5-甲酰胺（2-Py）、N(1)-甲基-4-吡啶酮-3-甲酰胺（4-Py）、烟酰胺N-氧化物和烟尿酸（NuA）。在生理条件下，烟酸主要通过MNA分解代谢为4-Py。然而，当给大鼠喂食含过量烟酸的饮食时，这并非主要途径。当给大鼠喂食含过量NiA的饮食时，NuA是主要分解代谢物，而喂食含过量Nam的饮食时，MNA是主要分解代谢物。当给大鼠喂食含过量NiA和Nam的饮食时，MNA和NuA是主要分解代谢物。过量NiA和Nam的代谢归宿不会相互干扰。因此，同时给予NiA和Nam可能比单独给予NiA或Nam更好，因为预期会有不同的药理作用。
