Studies on the urinary excretion of xanthurenic acid in diabetics

Xanthurenic acid (XA), kynurenic acid (KA) and creatinine in fasting urine were determined by reversed phase high pressure liquid chromatography in order to investigate the distortion of tryptophan metabolites in diabetes mellitus. The results of ten patients with non-insulin dependent diabetes mellitus and ten normal healthy subjects were compared. No tryptophan load test was performed in this study, because tryptophan loading produces further latent shortage of active vitamin B6 which results in exacerbation of the disease. The ratios of XA to KA and to creatinine were 0.35 +/- 0.099 (mean +/- S.D.) and 0.99 +/- 0.321 in the diabetic patients. The corresponding figures in the normal subjects were 0.17 +/- 0.064 and 0.55 +/- 0.22. Both ratios were significantly higher in the diabetic patients than in normal subjects (p less than 0.001 and p less than 0.01, respectively). This means that XA was excessively excreted in diabetic patients resulting in distortion of tryptophan metabolism. Our findings indicated that the ratios are useful to monitor excess XA excretion and also for detection of diabetes.