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.