Possible involvement of kynurenamines in the pathogenesis of cataract in diabetic patients

It has been demonstrated that the products of tryptophan degradation, kynurenamines, play an important role in senile cataract formation. However, the involvement of these compounds in the development of diabetic cataract has not been studied. The aim of the present study was to compare the concentration of tryptophan and kynurenamines in the aqueous humor and lenses obtained from non-diabetic and diabetic patients with cataract.

The concentration of tryptophan, kynurenine, 3-hydroxykynurenine, kynurenic acid and anthranilic acid was measured using high-performance liquid chromatography (HPLC) with appropriate detection in aqueous humor and lenses obtained from 38 non-diabetic subjects and 20 patients with type II diabetes in course of surgical cataract extraction.

In diabetic patients the concentration of kynurenine, 3-hydroxykynurenine and anthranilic acid in the aqueous humor was increased in comparison with non - diabetic subjects, while the concentration of tryptophan and kynurenic acid was similar in both groups. In the lenses obtained from patients with diabetes accumulation of tryptophan and all of its assayed metabolites was observed.

Concentrations of the products of kynurenine pathway of tryptophan degradation in the aqueous humor and the lenses of diabetic patients are increased. We suggest that these compounds could play an important role in the development of diabetic cataract.