Levels of fructosyllysine in collagen are low compared with the loss of lysine in diabetic rats: involvement of oxidation in increased cross-linking.

Abstract

1. It is thought that early glycation products on lysine residues of collagen are re-arranged to form collagen cross-links (advanced glycation end-products), which are increased in hyperglycaemia. We have previously reported that 4 week vitamin E supplementation in diabetic rats protected against the development of increased collagen cross-linking. In the present study we analysed early glycation products as fructosyllysine and amino acid content of tail tendon collagen in rats. 2. The amount of lysine residues in early collagen glycation products in diabetic rats was estimated to be less than 0.2 mol/mol type I collagen, whereas in the diabetic rats the loss of lysine residues was estimated to be 2.5 mol/mol. However, vitamin E supplementation protected against the loss of lysine residues without affecting early glycation products. 3. Thus, it is demonstrated that the amount of early collagen glycation products is quite small compared with the loss of lysine residues in diabetic rats and we suggest that the oxidative modification of lysine residues may be involved in the increased cross-linking observed in hyperglycaemia.