Identification of tryptophan metabolites in the healthy epidermis of diabetics.

The urinary excretion of metabolites of the tryptophan leads to niacin pathway after an L-tryptophan load in patients with potential and latent diabetes, and in a third of those with chemical diabetes, was normal. In the remaining subjects with chemical diabetes and in those with clinical diabetes it was altered and characterized by an increase of xanthurenic acid and by a reduction of kynurenines and 3-hydroxyanthranilic acid. The thin-layer chromatographic pattern of tryptophan metabolites in the epidermis of patients with potential, latent, chemical, clinical diabetes was characterized by the kynurenine pathway metabolites that were also present in the epidermis of healthy subjects. Morevoer, the above pattern was characterized by the appearance of 5-hydroxytrptamine, and in patients with chemical and clinical diabetes by the appearance of xanthurenic acid.