Abstract
Abstract: :
Purpose: To define and compare the saccharides in normal and diabetic eye tissues. Methods: Donor eyes were obtained from the Cleveland Eye Bank. The optic nerve, sclera, RPE-choroid, retina, vitreous, ciliary body-iris, lens and cornea were isolated from normal and diabetic eyes. Each tissue was digested with proteinase K and ethanol precipitated. Equal aliquots of supernatant and precipitate fractions were either 2-aminoacridone (AMAC) derivatized directly or digested with hyaluronidase SD and chondroitinase ABC or glucoamylase. The saccharides were fluorotagged with AMAC and separated by electrophoresis. The bands were digitized and their intensities quantified. Results: Glucose levels were elevated in all the diabetic tissues relative to control levels. The two forms of glycogen, the expected macromolecular glycogen (measured as glucose after glucoamylase digestion in the precipitate fraction), and the unexpected low molecular weight maltooligosaccharide (present without enzyme treatment in the supernatant fractions), are decreased in the diabetic tissues. The other major difference was the significant decrease or lack of the rare monosulfated (Di2S) and di-sulfated (Di4,6S, and Di2,6S) chondroitin sulfate disaccharides in the diabetic tissues, while hyaluronan (DiHA) remained relatively the same in both groups. In addition, the ratio of Di4S/Di0S was higher in diabetic compared to control RPE-choroid. Other important features include the detection of mannose, mannose-6-P and glucose-6-P, as well as galactose and glyceraldehyde-3-P. Conclusion: This is the first study to define and compare saccharide distribution in normal and diabetic ocular tissues. The undersulfation of chondroitin saccharides in the diabetic tissues may be due to 1)the decreased levels of sulfate resulting from preferential sulfation of therapeutic agents destined for elimination, or 2) decreased levels of sulfotransferase, or 3) mutations in the gene coding for N-acetylglucosamine-6-sulfotransferase.
Keywords: 387 diabetes • 529 proteoglycans/glycosaminoglycans