Relationship between tryptophan metabolism and vitamin B6 and nicotinamide in aged subjects.

The urinary excretion of tryptophan metabolites was studied in 20 aged subjects (over 70 years) after oral tryptophan loading (100 mg/kg body weight). All the subjects considered showed an abnormal excretion of metabolites with mean values of 24.67% in men and 25.83% in women in comparison to 6.77% in young controls. Among the metabolites the highest excretion was from kynurenine; moreover kynurenic acid and N-alpha-acetylkynurenine were also excreted in signficantly high amounts. The other metabolites too showed increased values. As the abnormal tryptophan metabolism in aging seemed to be in connection with vitamin B6 and nicotinamide, in a group of 7 aged sugjects the urinary excretion of tryptophan metabolites was studied after aminoacid loading with or without simultaneous administration of these two vitamins. The results show that the abnormal excretory pattern is normalized after vitamin administration (from 16.49% to 7.42% total mean metabolite values).