In the present study, we investigated the possibility that
glucose-mediated advanced glycosylation reactions initiate
oxidative modification in vivo. Advanced glycosylation is a
major pathway for the posttranslational modification oftissue
proteins and begins with the nonenzymatic addition of sugars
such as glucose to the primary amino groups of proteins (13,
14). These early glucose-denrved Schiff base and Amadori
products then undergo a series of inter- and intramolecular
rearrangement, dehydration, and oxidation-reduction reactions
to produce the "late" products termed advanced glycosylation
end products (AGEs). Excessive accumulation of
AGEs on tissue proteins has been implicated in the pathogenesis
of many of the sequelae of diabetes and normal aging
(13-15). Protein-linked AGEs act to crosslink connective
tissue collagen (16) and to chemically inactivate nitric oxide
activity (17); they also act as recognition signals for AGE
receptor systems that are present on diverse cell types
(18-20).