Determination of Early Biochemical Markers in the Progression of Diabetic Retinopathy Using an Akita Mouse Model

Student: Gretchen Weaver
Mentor: Ivy Samuels (Cleveland Clinic Cole Eye Institute – Louis Stokes VA Medical Center)

I studied the effects of diabetic retinopathy in a mouse model. The protein GLUT1 stimulates more oxidative stress in the retina and leads to more damage of the eye’s tissue. After examining a wildtype and mutant mouse type for a gene that accelerates the disease, we found there was no significant difference in the progression in the early stages of diabetic retinopathy.

Diabetic retinopathy is the progressive loss of retinal function due to an excess amount of blood glucose in the body.  This excess glucose in the blood can block the tiny vessels that nourish the retina; to compensate the eye undergoes angiogenesis, or the formation of new blood vessels.  These new blood vessels, however, are weak and leaky and break more easily, resulting in further progression of diabetic retinopathy.  Prior studies have shown that several proteins may play an early mechanistic role in diabetic retinopathy, including GLUT1 (glucose transporter 1 protein) and GFAP (glial fibrillary acidic protein).  Oxidative stress, or the increase of reactive oxidative species, has also been shown to be involved with the progression of diabetic retinopathy. 

A mouse model was utilized to simulate Type I diabetes.  Akita mice are a strain of mice with a spontaneous mutation in the insulin 2 gene.  This mutation leads to an improper folding of the insulin protein causing toxicity, and eventual destruction, of the beta cells in the pancreas.  The Akita strain of mice are therefore a good model for the progression of diabetic retinopathy due to Type 1 diabetes. 

In order to determine early changes between the Akita wildtype and Akita mutant mouse, mice were sacrificed at one month of age.  Eyes were then fresh frozen, cryosectioned onto slides, and then stained for dihydroethidium, or DHE, a biochemical marker for reactive oxidative species and oxidative stress.  Another set of eyes were then fresh frozen, paraformaldehyde fixed, cryosectioned onto slides, and then double-stained for the expression of GLUT1 and GFAP.  These slides were then imaged under a fluorescent microscope. Upon examination of the results, it was determined there was no significant between the wildtype and mutant Akita mice.