Interaction of Zinc, Ascorbic Acid, and Folic Acid in Glycation with Albumin as Protein Model

Using albumin as model, we conducted series of in vitro glycation experiments to examine role of zinc in glycation using glucose at 4-100 mg/ml, incubations at 37 degrees C or 60 degrees C, duration of 2 or 4 weeks and in presence of zinc or ascorbic acid (AA) or folic acid (FA). Modifications of bovine serum albumin (BSA) were examined by using fluorescence of advanced glycation end products (AG Es) and dityrosine, UV, and Fourier transformed infrared spectroscopy. Adding zinc (0 to 768.5 mu mol/l) resulted in significant inhibition of albumin glycation by glucose with a linear fit, y = 0.0895x + 230.99(R-2 = 0.7676,p = 0.013). The glycation by fructose was greater than that of glucose with stronger inhibitory effect by zinc in fructose glycation (t=-5.8, p=0.002). Addition of zinc significantly decreased fluorescence as seen in Zn+FA or Zn+AA sets as compared to sets of FA alone (p=0.00056) or AA alone (p=0.037). The fluorescence for dityrosine and AGE had a correlation of 0.897 (p<0.01). The data from fluorescence, UV, and FTIR spectra collectively suggested inhibitory effect of zinc in BSA glycation alone or in presence of FA and AA, showing new dimension for the protective action of zinc in hyperglycemic conditions.