Interaction between albumin originating from persons with uncontrolled diabetes mellitus type 2 and food antioxidants.

Background and Purpose: Dietary interventions are a cornerstone in the management of type 2 diabetes mellitus. The efficiency, however, depends on pharmacokinetic factors, including the interaction of food ingredients with plasma proteins. The concept of this study was to investigate the binding effects of three pronounced antioxidants present in the Mediterranean diet: resveratrol, (dihydro)lipoic acid and oleuropein, with albumin isolated from persons with diabetes (HbA1c 63±7 mmol/mol, or 7.9±0.6%) and healthy persons, carrying its intrinsic ligands. Experimental approach: Spectrofluorometric analysis, native electrophoresis and immunoblotting were performed with albumin before and after the interaction with antioxidants. Key results: Fluorescence spectra of the protein from two study groups were similar, whereas a spectrum of methylglyoxal-modified albumin (in vitro oxidised) was different. Calculated binding constants were also similar for the two study groups for all three ligands. Kinetic fluorescence measurements revealed significantly altered activity of albumin-bound (dihydro)lipoic acid in persons with diabetes compared to healthy individuals, and no significant difference in the activity of resveratrol in expressing antioxidant protection of albumin upon its exposure to oxidative stress. Conclusions: Although the findings should be further validated using other antioxidants and glycated albumin derived from persons stratified according to the severity of a disease, the results have documented that in vitro methylglyoxal-oxidised albumin, routinely employed for diabetes-simulated investigations, was shown not to reflect this pathophysiological condition properly and not to be adequate for the assessment of relevant nutritional/biochemical potential of food antioxidants.