Levels of purine, kynurenine and lipid peroxidation products in patients with inflammatory bowel disease.

The factors affecting gut activity in inflammatory bowel disease are unclear, but purines and kynurenines may be involved in the regulation of neuronal activity and therefore gut motility and secretion. We have measured the serum levels of these compounds in patients and in sex- and age-matched controls. Purines and kynurenines were analysed using HPLC. The levels of tryptophan and its metabolites 3-hydroxykynurenine, 3-hydroxyanthranilic acid and xanthurenic acid were unchanged in all patients. However, the levels of kynurenine and kynurenic acid were significantly elevated in patients with inflammatory bowel disease when compared to control subjects. There were no significant differences between patients and controls for any of the purines analysed or for neopterin. In the inflammatory bowel disease patients serum lipid peroxidation products were significantly elevated when compared to control subjects, suggesting the presence of increased oxidative stress consistent with inflammatory activity. The elevated level of kynurenic acid may represent either a compensatory response to elevated activation of enteric neurones, or a primary abnormality, which induces a compensatory increase in gut activity, but may indicate a role for kynurenine modulation of glutamate receptors in the symptoms of inflammatory bowel disease.