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

BACKGROUND

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.

MATERIAL AND METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

[Kinurenin degradation pathway in eye: present state of knowledge]

In this review the kinurenin degradation pathway is presented. The role of indoleamine 2.3-dioxygenase (IDO)--the first enzyme of the tryptophan degradation--is also described. The implications of these findings for cataract as well as for other disturbances of vision process are discussed.

[Content of certain sugars and polyols in cataractous nucleus in non-diabetics and diabetic patients with type II diabetes]

PURPOSE

Sugars and polyols content assessment in cataractous nucleus in diabetics and non-diabetics.

MATERIAL AND METHODS

Cataractous nucleus was obtained during extracapsular cataract extraction derived from 52 diabetic and 58 non-diabetic patients. The content of glucose, fructose, sorbitol and mioinositol in examined material was determined using iquid gas chromatography.

RESULTS

Average contents of sorbitol, glucose and fructose in cataractous nucleus diabetic patients (ZSC) are significantly higher than in non-diabetics (ZS). No changes were observed in mioinositol content in both studied groups.

CONCLUSION

The role of the polyol pathway in the development of diabetic cataract is considerable.

[The role of polyol pathways in formation of diabetic cataracts]

The authors present current knowledge concerning the role of polyols in the formation of cataract in diabetic patients. Sugar alcohols are formed in lens as a consequence of glucose conversion in the sorbitol pathway. The pharmacological modulation of this process by the application of aldose reductase inhibitors are also discussed.

[Serotonin in diabetic retinopathy]

PURPOSE

The present study was designed to evaluate a possible participation of serotonin in the development of retinopathy in diabetes mellitus.

MATERIAL AND METHODS

Serotonin of whole blood and platelets was studied in 12 patients with Type I and II diabetes using high pressure liquid chromatography method.

RESULTS

The concentration of serotonin in the blood was markedly increased (210 +/- 50 ng/ml in diabetes and 150 +/- 35 ng/ml in control, p < 0.01) and not changed in platelets in diabetes. There was a relation between blood serotonin level and the presence of retinopathy.

CONCLUSION

These results suggest that serotonin may be involved in the pathogenesis of diabetic microangiopathy.

[Serotonin--its significance in physiology and pathology of the eye]

In this review the basic data concerning metabolism of serotonin, its receptors and effects are presented. The authors have underlined the significance of serotonin in the physiology and pathology of the eye with special regards to the effectiveness of serotonergic system affecting drugs in the disturbances of vision process.

[The role of some arachidonic metabolites in pathophysiology of the eye]

The author gives a brief review of the biochemistry and physiology of prostanoids and leucotriens. The development and contemporary knowledge regarding the participation if prostanoids and leucotriens in pathophysiological processes of the eye is also described.

[Value of leukotriene C4 in human subretinal fluid]

Concentration of leukotriene C4 (LT C4) in subretinal fluid and plasma of 12 patients with idiopathic retinal detachment has been studied. In 10 cases the subretinal fluid contained LT C4 (0.34 +/- 0.24 ng/ml) and concentration of this substance was about 10 times lower than that observed in plasma (4.05 +/- 0.83 ng/ml). The presence of LT C4 in subretinal fluid may result from retinal damage and it can be considered as an important prognostic factor.