Abstract
The B-group of vitamins, including vitamins B1, B2, and B6, are involved in the catabolic metabolism of tryptophan. We investigated the effects of dietary vitamin content (low, moderate and sufficient) on the catabolism of tryptophan in both diabetic and healthy rats. We found that tryptophan catabolism was not affected by differences in dietary vitamin content in both diabetic and healthy rats. However, the tryptophan-nicotinamide conversion ratio was one-third lower in diabetic rats than in healthy rats. In addition, nicotinamide catabolism differed between diabetic and healthy rats. N1-methylnicotinamide, a nicotinamide catabolite, accumulated in diabetic rats, but not in normal rats, possibly contributing to the increase in free nicotinamide. It seems likely that this increase in the level of nicotinamide inhibited the activities of poly (ADP-ribose) synthetase and histone deacetylase. These results suggest that administration of nicotinamide might offer some effects, and warrants further investigation.
