NONENZYMATIC GLYCATION OF FIBROUS COLLAGEN - REACTION-PRODUCTS OF GLUCOSE AND RIBOSE

Non-enzymic glycation of collagen involves a series of complex reactio ns ultimately leading to the formation of intermolecular cross-links r esulting in changes in its physical properties. During analysis for th e fluorescent cross-link pentosidine we identified the presence of an additional component (Cmpd K) in both glucose and ribose incubations. Cmpd K was formed more quickly than pentosidine in glucose incubations and more slowly than pentosidine in ribose incubations. Cmpd K repres ented 45% of the total fluorescence compared with 15%, for pentosidine in glucose incubations and 25% of the total fluorescence compared wit h 30% for pentosidine in the ribose incubations. Cmpd K is not an arte fact of in vitro incubations, as it was shown to be present in dermal tissue from diabetic patients. Subsequent high-resolution h.p.l.c, ana lysis of glucose-incubated collagen revealed Cmpd K comprise two compo nents (K1 and K2). Further, a similar analysis of Cmpd K from the ribo se incubations revealed two different components (K3 and K4). These di fferences indicate alternative mechanisms for the reactions of glucose and ribose with collagen. The amounts of these fluorescent components and the pentosidine cross-link determined for both glucose and ribose glycation were found to be far too low (about one pentosidine molecul es per 200 collagen molecules after 6 months incubation with glucose) to account for the extensive cross-linking responsible for the changes in physical properties, suggesting that a further additional series o f cross-links are formed. We have analysed the non-fluorescent high-mo lecular-mass components and identified a new component that increases with time of in vitro incubation and is present in the skin of diabeti c patients. This component is present in sufficient quantities (estima ted at one cross-link per two collagen molecules) to account for the c hanges in physical properties occurring in vitro.