title: Impact of glycation on structural and antioxidant function of human serum albumin: Relevance in diabetic complications.
abstract: OBJECTIVE
  Non-enzymatic glycation impairs the structural and functional characterstics of human serum albumin (HSA) native conformation. Prolonged hyperglycemia causes cross links formation in proteins that may contribute to progression of diabetic complications.
  
  
  METHODS
  HSA (20μM) was incubated with different concentration of d-glucose100, 200, 300 and 400mg/dl for a period of 40 days in phosphate buffer saline (20mM pH=7.4) under sterile conditions. Incubated samples were extensively dialyzed and structural changes were analyzed by far and near UV circular dichroism spectra measurement. Fructosamine assay with nitroblue tetrazolonium was performed to confer isomerisation between glucose and protein. Aggregations of the glycated product (AGEs) formed during reduction of nitrobluetetrazolium dye were evaluated by transmission electron microscopy. Crosslinks aggregates were investigated by in-situ Congo red binding assay. Red blood cells hemolysis test was performed to decipher the antioxidant activity of albumin samples.
  
  
  RESULTS
  Fructosamine content in glycated albumin demonstrates the non-enzymatic addition of glucose to HSA and confers the formation of monoformazone (marker of glycation). Significant changes were found in the glycated samples of HSA compared to native (unmodified) in far and near UV circular dichroism. Transmission electron microscopy, Congo red staining, showed the formation of crosslink's aggregated mass in glycated HSA. Glycation of albumin reduces the antioxidant capacity of native albumin confirmed by red blood cells hemolysis test.
  
  
  CONCLUSIONS
  The finding of present study brings new evidences on the detrimental alterations of on albumin vital functions after non-enzymatic glycation with glucose. These results may emphasize the albumin associated diabetic complications under glycemic range of diabetes mellitus.
authors.affiliation: Rajiv Gandhi Centre for Diabetes and Endocrinology, J.N Medical College, Aligarh Muslim University, Aligarh, Uttar Pradesh 202002, India.
authors.forename: Alok
authors.initials: A
authors.lastname: Raghav
authors.affiliation: Rajiv Gandhi Centre for Diabetes and Endocrinology, J.N Medical College, Aligarh Muslim University, Aligarh, Uttar Pradesh 202002, India. Electronic address: jamalahmad11@rediffmail.com.
authors.forename: Jamal
authors.initials: J
authors.lastname: Ahmad
authors.affiliation: Department of Biochemistry, J.N Medical College, Aligarh Muslim University.
authors.forename: Khursheed
authors.initials: K
authors.lastname: Alam
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D048909:Diabetes Complications / Q000378:metabolism*; D019270:Fructosamine / Q000378:metabolism; D006801:Humans; D046529:Microscopy, Electron, Transmission; D012709:Serum Albumin / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D012709:Serum Albumin; D019270:Fructosamine
keywords: Antioxidant; Diabetes mellitus; Hyperglycemia; Non-enzymatic glycation