title: Urinary excretion ratio of xanthurenic acid/kynurenic acid as a functional biomarker of niacin nutritional status.
abstract: The present study was conducted to survey functional biomarkers for evaluation of niacin nutritional status. Over 500 enzymes require niacin as a coenzyme. Of these, we chose the tryptophan degradation pathway. To create niacin-deficient animals, quinolinic acid phosphoribosyltransferase-knock out mice were used in the present study because wild type mice can synthesize nicotinamide from tryptophan. When the mice were made niacin-deficient, the urinary excretion of xanthurenic acid (XA) was extremely low compared with control mice; however, it increased according to the recovery of niacin nutritional status. The urinary excretion of kynurenic acid (KA) was the reverse of XA. Kynurenine 3-monooxygenase, which needs NADPH, was thought to be suppressed by niacin deficiency. Thus, we calculated the urinary excretion ratio of XA:KA as a functional biomarker of niacin nutrition. The ratio increased according to recovering niacin nutritional status. Low values equate with low niacin nutritional status.
authors.affiliation: a Department of Nutrition, School of Human Cultures , The University of Shiga Prefecture , Hikone , Japan.
authors.forename: Katsumi
authors.initials: K
authors.lastname: Shibata
authors.affiliation: a Department of Nutrition, School of Human Cultures , The University of Shiga Prefecture , Hikone , Japan.
authors.forename: Marika
authors.initials: M
authors.lastname: Yamazaki
authors.affiliation: a Department of Nutrition, School of Human Cultures , The University of Shiga Prefecture , Hikone , Japan.
authors.forename: Yukiyo
authors.initials: Y
authors.lastname: Matsuyama
keywords: QPRT; mice; niacin-deficiency; tryptophan catabolism; vitamin