HERSHEY, PA--Researchers from Penn State's College of Medicine have found that during diabetes subtle changes occur in the retina much earlier than previously thought. Further study of these changes may lead to novel and early therapeutic intervention to slow down or stop the progression of vision loss in people with diabetes.
Diabetic retinopathy refers to a change in the retina, which occurs in about 90 percent of the 8 million people in the United States diagnosed with diabetes. It is one of the major complications of diabetes.
"There are several stages of diabetic retinopathy. Many people may not notice a change in their vision for years. Usually it takes years for even an ophthalmologist to notice any difference," explains Erich Lieth, assistant professor of neuroscience and anatomy and member of the Penn State Retina Research Group (PSRRG).
"Most investigations so far have focused on the blood vessels of the eye, because these can be observed readily in humans. However, our tests in animal models indicate that cells away from blood vessels begin to change in less than three months."
Lieth and his colleagues' paper detailing this research titled, "Glial reactivity and impaired glutamate metabolism in short-term experimental diabetic retinopathy," was published in the May issue of the journal Diabetes.
Normal vision requires all the cells in the retina to work together properly. Lieth and the PSRRG's approach tries to understand how the retina malfunctions in diabetes, and is based on their observation that the normal interactions between the three main cellular components-neurons, glial cells and capillaries (tiny blood vessels) -- are disturbed. Lieth's group found that diabetes injures the glial cells so that they do not properly metabolize glutamate. Glutamate is a neurotransmitter used in the communication between neurons of the retina, and too much glutamate can cause neurons to die. Lieth and his colleagues found that glutamate accumulates in the retinas of experimental animals within three months after the onset of diabetes. In related findings, the Penn State Retina Research Group will soon publish findings that retinal neurons in diabetic animals die within the first months of diabetes.
"The electrical activity in the retina changes within a few years after people become diabetic. This is much earlier than the onset of vision impairment," Lieth adds. "Changes in electrical activity indicate that the neurons and glial cells of the retina function differently in diabetic eyes than they do in normal eyes. We are investigating how changes in the function of glia and neurons affect their health and ability to process visual information. The goal here is to find a means to make diabetic neurons function properly once again."
Lieth and his team studied the eyes of rats with experimentally induced diabetes to conduct this research. He says a good deal of further research will be needed before all of this information will be transferable for use in humans. Dr. Lieth's research is supported by a grant from the Juvenile Diabetes Foundation International.
Reporters and the public can learn more about this research, and Dr. Lieth as well as other members of the Penn State Retina Research Group, by visiting their web site at http://www.hmc.psu.edu/psrrg/.
Journal
Diabetes