Structural and glycation site changes of albumin in diabetic patient with very high glycated albumin

Background: Glycated albumin (GA) has been utilized to monitor mid-term glycemic control, and reflects the status of blood glucose more rapidly and effectively than hemoglobin A(1c) (HbA(1c)). To examine the relationship between GA level and structural changes or glycation sites of albumin, we analyzed pre- and post-treatment samples from a diabetic patient with extraordinary increase of GA. Method: A female diabetic patient with poor glycemic control had a GA >94% and was treated with intensive insulin therapy to decrease blood glucose. We analyzed changes in fluorescence derived from tryptophan (Trp) and advanced glycation end product (AGE) of albumin isolated/purified from pre- and post-treatment samples. To determine the sites of glycation of albumin, samples were carboxymethylated and digested by Glu-C endoprotease, and peptides were analyzed using liquid chromatography/mass spectrometry. Results: GA level decreased almost linearly and reflected the improved glycemic state well. Trp-related fluorescence of pre- and post-treated samples did not change while AGE-related fluorescence increased depending on GA level. Ten major glycation sites were detected in the pretreatment sample, while 3 major glycation sites were detected in post-treated samples. Conclusions: GA level reflects the status of blood glucose more rapidly than HbAlc. Since GA level was related to AGE-related fluorescence and number of glycation sites, it might be a good marker for not only glycemic control of diabetic patients but also structural and functional changes of albumin. (c) 2007 Elsevier B.V. All rights reserved.