Biochemical, biophysical, and thermodynamic analysis of in vitro glycated human serum albumin.

Glycated human serum albumin (HSA) is known to be involved in the pathogenesis of several diseases, and we have therefore investigated possible alterations in HSA on glycation. HSA was incubated for 5 and 20 weeks independently with constant glucose concentration at 37 degrees C under aerobic conditions. Biochemical, spectral, electrophoretic, circular dichroism spectropolarimetric, and thermodynamic analyses confirmed that the structure and stability of HSA is significantly affected on glucose modification. Glycated HSA-AGE-20w showed appreciable elevation (15.8%) in beta-sheet structure and decrease in alpha-helix (10.4%) and random coil (5.7%) structures. Slight changes have also been observed in turns (3.2%) of HSA-AGE-20w. Quenching studies with antioxidants diethylene triaminepentaacetic acid and superoxide dismutase showed inhibition in glycation to the extent of 50-65 and 30-40%, respectively. The novelty of present study is that glycation of HSA can cause induction of secondary and tertiary structure changes that may generate thermodynamically more stable high molecular weight aggregates having remarkably increased beta-sheet structure than its non-glycated form. This may interfere with the normal function of HSA, thus contributing to diabetic complications.