Source

Renal Pathophysiology Laboratory, University of Campinas (Unicamp), Investigation on Diabetes Complications, Faculty of Medical Sciences (FCM), Campinas, Sao Paulo, Brazil.

Abstract

PURPOSE:

Green tea (GT), widely studied for its beneficial properties in protecting against brain ischemia, is a rich source of polyphenols, particularly (-)-epigallocatechin gallate (EGCG). The results presented here demonstrate the beneficial effects of GT in diabetic retinas and in retinal cells under diabetic conditions.

METHODS:

Diabetes was induced in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats. Treatment animals received GT orally for 12 weeks. A vehicle was administered orally to the control animals. The protective effects of GT were also evaluated in Muller and in ARPE-19 cells.

RESULTS:

In diabetic rats, there was an increase in the expression of glial fibrillary acidic protein (GFAP), oxidative retinal markers, and glutamine synthetase levels. In addition, there was a decrease in occludin and glutamate transporter and receptor. Diabetic SHR also demonstrated blood-retinal barrier breakdown and impaired electroretinography results. Muller cells exposed to high-glucose medium produced higher levels of reactive oxygen species (ROS) and glutamine synthetase but reduced levels of glutathione, glutamate transporter and glutamate receptor. Similarly, ARPE-19 cells exhibited increased ROS production accompanied by decreased expression of claudin-1 and glutamate transporter. Treatment with GT fully restored all the above-mentioned alterations in diabetic animals as well as in retinal cells.

CONCLUSIONS:

GT protected the retina against glutamate toxicity via an anti-oxidant mechanism. These findings reveal a novel mechanism by which GT protects the retina against neurodegeneration in disorders such as diabetic retinopathy.

PMID: 23299475 [PubMed – as supplied by publisher]