Glycation of crystallins in lenses from aging and diabetic individuals

Water-soluble crystallins were obtained from clear human lenses of different age (4-81-year-olds) and lenses of individuals showing senile or diabetic cataracts. Levels of early glycation products were high in the high molecular weight material (HM) and the alpha-crystallin fractions, compared with beta- and gamma-crystallins. This difference becomes more prominent upon aging. The content of total early glycation products in HM and alpha-crystallin increases clearly with age, whereas levels remain relatively constant in the beta- and gamma-crystallins. There is an elevation of early products in cataractous lenses from diabetic individuals compared with those suffering from senile cataract. Specific non-tryptophan fluorescence (excitation/emission wavelengths 370/440 nm), used as an indicator for late glycation products, increased dramatically with age and was 2-fold higher in the diabetic subjects. Levels of fluorescence decreased in the order HM > alpha- > beta- > gamma-crystallins. The results suggest an increase in glycation rate in alpha-crystallin as a result of aging and diabetes, while the rate of glycation of beta- and gamma-crystallins remains almost constant.