Serum levels of glucose-derived advanced glycation end products are associated with the severity of diabetic retinopathy in type 2 diabetic patients without renal dysfunction.

Reducing sugars can react nonenzymatically with the amino groups of proteins to form Amadori products and subsequently cross-linked, heterogeneous fluorescent derivatives called advanced glycation end products (AGE). AGE can arise in vivo from various types of reducing sugars or dicarbonyl compounds and their formation and accumulation are known to progress during normal aging. In individuals with diabetes mellitus, this progression is greatly accelerated. The aim of the present study was to investigate which kinds of serum AGE components were associated with the severity of diabetic retinopathy in 72 type 2 diabetic patients without renal dysfunction. Serum levels of glucose-, glyceraldehyde- or methylglyoxal-derived AGE (methyl-AGE) were measured by an enzyme-linked immunosorbent assay. No significant correlations were found between serum levels of various AGE and HbA1c level, current age, systolic and diastolic pressure, diabetes duration, serum creatinine or blood urea nitrogen level in type 2 diabetic patients. A significant elevation of serum glucose-AGE was found to be associated with severity of diabetic retinopathy. While no differences in serum methyl-AGE levels were found between patients with diabetic retinopathy and those without, serum levels of glyceraldehyde-AGE showed a tendency to increase as normal retinal status advanced to simple and proliferative retinopathy (p = 0.06). The present results suggest that among various types of AGE, glucose-AGE serum levels may be a useful marker of diabetic retinopathy in type 2 diabetic patients without renal dysfunction.