Evidence for a Defect in Tryptophan Metabolism in Chronic Alcoholism

IN addition to being a substrate for protein synthesis in the body, dietary tryptophan is metabolized to at least two physiologically important compounds, nicotinic acid and serotonin, via the intermediates outlined in Figure 1. The major urinary metabolites of these two compounds are respectively N-methylnicotinamide (and its 6-pyridone)1 and 5-hydroxyindoleacetic acid (5-HIAA).2 In this paper we wish to report a reduced rate of 5-HIAA excretion in the urine of patients with chronic alcoholism. Since the rate of N-methylnicotinamide formation from tryptophan was unchanged, the reduced 5-HIAA excretion may signify a defective conversion of tryptophan to serotonin in these addicts.MethodsThe . . .