Lutein and Insulin Effect on Retina and Lens After Three Months of Experimental Diabetes

Abstract

Purpose:: The aim of this study was to confirm biochemical and functional changes in retina and lens after three months of diabetes in rats using oxidative stress markers and functional tests. The effects of lutein treatment were also tested.

Methods:: The investigation conformed with ARVO Statement for the Use of Animals in Ophthalmic and Vision Research and Declaration of Helsinki. Diabetes was induced in 64 wistar rats (male, 300 g bodyweight) by injection of streptozotocin (STZ) (75 mg/kg i.p.) dissolved in 10mM phosphate citrate ph 4,5. Vehicle-treated rats served as controls. In the diabetic groups, hyperglycemia was confirmed 72 h after STZ injection using a reflectance meter (Accutrend, Boehringer, Mannheim, Germany). Rats were divided into subgroups: control, control+lutein, diabetic, diabetic+lutein, diabetic+insulin, and diabetic+insulin+lutein. Treatments started on day 4 after STZ injection and animals were sacrificed after 12 weeks. Glutathione concentrations and glutathione peroxidase activity were measured in retina and lens as oxidative stress markers. The last day of the experiment serial electroretinograms (ERG) were recorded, and measurements of a and b-wave amplitude and latency and implicit times were done.

Results:: Diabetic rats had reduced retinal glutathione peroxidase activity and glutathione content. The treatment with insulin alone or with insulin plus lutein reversed these changes, but only the treatment with insulin plus lutein was able to restored both levels to control values. After 10 weeks of diabetes, some of the rats developed cataracts. The degree of the cataracts was classified according to Suryanarayana (Suryanarayana et al, 2003). The degree of the cataracts was significantly lower in the diabetic rats treated with lutein when compared with the diabetic rats. Increases in the latency time and a-wave amplitude/b-wave amplitude of the ERG were observed. Although the treatment with insulin diminished both values, only the treatment with insulin+lutein was able to restored them to control values.

Conclusions:: Lutein could be an appropriate coadjuvant treatment for the changes observed in this study.

Keywords: carotenoids/carotenoid binding proteins • cataract • diabetic retinopathy