The determination of AGE-peptides by flow injection assay, a practical marker of diabetic nephropathy

Background: Increasing evidence has suggested that advanced glycation end products (AGES) might play a central role in the pathogenesis of diabetic complications. Serum AGES concentration may serve as a useful marker for monitoring pathological processes and progression of diabetic complications. Methods: A flow injection assay (FIA) system was developed using high performance liquid chromatography (HPLC) to detect low molecular mass AGES (AGE-peptides, AGE-P). Serum from diabetic patients (n = 126), normal controls (n = 54) and diabetic mice (n = 20) and matched controls (n = 20) were collected. Results: The coefficient of variance for intra-assay and inter-assay were 1.2% and 6.3%, respectively. The range of recoveries was 94.9-101.9%. The serum AGE-P concentration was significantly increased both in diabetic patients (2.976 +/- 0.247 vs. 1.385 +/- 0.131 U/ml, P < 0.0001) and mice (6.71 +/- 0.50 vs. 2.49 +/- 0.10 U/ml, P < 0.0001) than their respective controls. Concentration of AGE-P was positively correlated with serum creatinine (Scr) (r = 0.7133, P < 0.0001), 24-h urinary protein (24-h UPro) (r = 0.8704, P < 0.0001) and urinary albumin excretion (UAE) (r = 0.5989, P < 0.0001). Conclusions: The present study suggested that FIA might be a reliable method for measuring the serum AGE-P. Furthermore, our results supported the notion that AGE-P might be a valuable marker for predicting the severity of diabetic nephropathy (DN). (C) 2001 Elsevier Science B.V. All rights reserved.