Glycation of human lens proteins from diabetic and (nondiabetic) senile cataract patients.

Glycation (nonenzymatic glycosylation) in the human lens (cortex and nucleus) in senile (nondiabetic) and diabetic cataracts was studied by measuring the extent of early and late glycation products, the content of free epsilon-amino groups and the formation of disulfide bonds in the soluble lens proteins. There was a significant (p < 0.001) increase in early and late glycation in the lens nucleus compared to the cortex in both the senile and diabetic groups. Overall these changes were much larger in the diabetic group. The concentration of free epsilon-amino groups was decreased in the senile nucleus as well as in the diabetic nucleus when compared with the senile and diabetic cortex (p < 0.001). Disulfide bond content was in the order of diabetic nucleus > diabetic cortex > senile nucleus > senile cortex. Glycation of the lens proteins is a generalized feature which is enhanced in the diabetic lens compared to senile lens proteins and is associated with a decrease in free epsilon-amino groups and an increase in disulfide bonds formation in the lens proteins.