[Immunochemical determination of advanced glycation end products in erythrocyte peripheral-membrane proteins from diabetic patients].

Nonenzymatic glycation of protein leads to changes in protein structure and function, including browning, crosslinking and polymerization. There are several functional abnormalities in erythrocytes of diabetic patients. However, nothing definite is known about the relationship between these abnormalities and nonenzymatic glycation products, especially advanced glycation end products (AGEs). In this view, the present study was aimed to determine the amount of AGEs in diabetic erythrocyte peripheral-membrane proteins (EPMPs) by an ELISA system using AGE-specific antibodies. Erythrocyte membrane proteins from 19 control and 48 diabetic subjects were treated with 0.1 N-NaOH solution and then, the supernatants of each sample, containing EPMPs, were used to measure the amount of AGEs. The amount of AGEs in EPMPs was approximately 3 times greater in diabetic patients than in controls (70.7 +/- 51.8 AU vs. 22.5 +/- 7.7 AU (mean +/- SD), p < 0.001). There was a significant correlation between levels of AGEs in EPMPs and HbA1C (r = 0.779, p < 0.001). In SDS-PAGE analysis of EPMPs, two major bands, 221 kDa and 242 kDa were observed. These two bands were defined to be spectrin by immunoblotting with mouse monoclonal anti-human spectrin antibody. Based on these findings, it was speculated that the formation of AGEs in erythrocyte peripheral-membrane proteins is related to the functional abnormalities of erythrocytes, including reduced deformability and lowered membrane fluidity, frequently observed in diabetic patients.