RESULTS
Two model phospholipids were incubated with glucose at
physiological pH and temperature for increasing time intervals.
PE contains a free amino group that can react with
glucose-derived carbonyls to form Schiff base and Amadori
products. PC was used as a control. In contrast to PE, PC
contains a blocked, tertiary amine that cannot react with
glucose to form the initial Schiff base. Anaerobic, buffered
suspensions of PE or PC (14 mM) were prepared and incubated
at 37°C with glucose (500 mM) and EDTA (1 mM). PE
but not PC was observed to react with glucose to form
products with the absorbance and the fluorescence properties
of AGEs (Figs. 1 and 2). The lipid-derived fluorophores
showed an excitation maximum of 360 nm and an emission
maximum of 440 nm. Progress curves for the development of
lipid-derived AGEs are shown in Fig. 2. The time-dependent
formation of lipid-derived AGEs was confirmed by immunoassay
with a specific anti-AGE antibody (Fig. 2C) (23).
Immunoreactive AGEs formed in incubation mixtures that
contained PE and glucose, but not PE alone, PC and glucose,
or PC alone.