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S. A. Shippy, M.-J. Lu, J. S. Pulido, R. M. Hatfield, R. F. Dundervill, III; Elevation of Vitreous Glutamate Levels With Diabetic Macular Edema. Invest. Ophthalmol. Vis. Sci. 2008;49(13):169.
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There is increasing animal model and clinical evidence that elevations in glutamate at the retina is involved in the pathology of diabetic retinopathy. While the elevations in glutamate have been determined from the vitreous of patients with more severe proliferative diabetic retinopathy, damage due to excess glutamate may occur at earlier stages or more mild manifestations of diabetic retinopathy. The purpose of this study is to determine the vitreous glutamate levels from patients with diabetic macular edema.
A volume of 100 µL of vitreous was collected at the time of vitrectomy. To minimize proteases activity vitreous samples were diluted 1:1 with a protease inhibitor cocktail in acetic acid prior to shipment to the analysis site. Amino acid analysis was performed by capillary electrophoresis following fluorescent derivatization of amines for detection.
The inclusion of protease inhibitors in the vitreous samples in this study has led to a decrease protease activity and more viscous samples that required new separation conditions for capillary electrophoresis. A total of 7 identified amino acids were resolved and studied from vitreous samples including Arg, Trp, Lys, Gln, Ala and Tau. Compared to control samples from patients with epiretinal membrane or macular holes (n=4), a significantly higher level of glutamate was found in the vitreous of patients with diabetic macular edema (n=6) that is similar to proliferative diabetic retinopathy (n=13).
The results confirm previous reports of elevated glutamate in the vitreous of patients with proliferative diabetic retinopathy and expand this finding to those with diabetic macular edema. This highlights the growing evidence that glutamate is involved in retinal damage due to diabetes and that glutamate may be a potential therapeutic target.
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