MEASUREMENT OF ADVANCED GLYCOSYLATION END-PRODUCTS IN DIABETIC PATIENTS BY ISOELECTRIC FOCUSING AND FLUORESCENCE, TO MONITOR DISEASE PROGRESSION

The non-enzymatic glycosylation (NEG) of proteins in diabetes damages both the structure and function of these proteins. In vivo and in vitro studies have shown that NEG of proteins and advanced glycosylation end-products (AGE) contribute to the pathogenesis of both macrovascular, such as atherosclerosis, and microvascular complications, such as retinopathy and nephropathy, in diabetes. We studied the electrophoretic mobility, fluorescence at isoelectric pH, and time-dependent AGE formation of glycosylated albumin. For the first time, we have used isoelectric focusing to study serum glycosylated albumin in diabetic patients and healthy controls. After 10 weeks incubation with glucose, the electrophoretic mobility of glycosylated albumin increased 21.3% compared with normal albumin. The isoelectric pH of albumin decreased from 4.6 on day 1 to 4.1 on day 7. The increase in electrophoretic mobility was accompanied by the drop in pH during the first week of incubation. These changes correlated well with those observed by fluorescence. The glucose content of the albumin samples decreased during the first week of incubation, but gradually increased thereafter. Fluorescence readings agreed with these observations. Using isoelectric focusing, there was a significant difference between the serum albumin of diabetic and normal individuals (p<0.001). Increased electrophoretic mobility during the first week with a simultaneous decline in isoelectric pH shows that AGE formation begins after the first week. The reduction in glucose concentration during the first week and its subsequent increase during the second week may be attributed to the formation and hydrolysis of AGE. This method may be used to determine the stability or progress of diabetes.