Abstract
We investigated the effects of mineral deficiency on the tryptophan-nicotinamide metabolism in rats. Male Wistar rats (3-weeks old) were fed with a 20% casein diet containing 5% mineral mixture (control diet) or a 20% casein diet containing 1% mineral mixture (deficient diet) for 47 days. The food intake was lower in the deficient group than in the control group and so, the gain in body weight was also lower in the deficient group. However, the food intake in terms of 100 g body weight was higher in the deficient group (5.25 g vs. 6.64 g). Under the conditions, the activity of aminocarboxymuconate-semialdehyde decarboxylase, which locates a branching point of tryptophan-nicotinamide and tryptophan-glutaric acid pathways, was higher in the tryptophan-nicotinamide and tryptophan-glutaric acid pathways, was higher in the deficient group. The result indicates that the flow from tryptophan to nicotinamide was reduced in the deficient group. In fact, the sum of the urinary excretion of nicotinamide, N^1-methylnicotinamide (MNA), N^1-methyl-2-pyridone-5-carboxamide (2-Py), and N^1-methyl-4-pyridone-3-carboxamide (4-Py) was lower in the deficient group. The activity of 2-Py- and 4-Py-forming MNA oxidases was lower in the deficient group and then the urinary excretion ratio of (2-Py + 4-Py)MNA was lower in the deficient group.
