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Effect of Aging and Diabetes Mellitus on Nonenzymatic Glycation of Human Lens Crystallin
Posted on: February 27, 2012

Scientists have examined the nonenzymatic glycation of human lens crystallin, an extremely long-lived protein, from 16 normal human ocular lenses 0.2-99 yr of age, and from 11 diabetic lenses 52-82-yr-old. The glucitol-lysine (Glc-Lys) content of soluble and insoluble crystallin was determined after reduction with H-borohydride followed by acid hydrolysis, boronic acid affinity chromatography, and high pressure cation exchange chromatography.

Normal lens crystallin, soluble and insoluble, had 0.028 ± 0.011 nanomoles Glc-Lys per nanomole crystallin monomer. Soluble and insoluble crystallins had equivalent levels of glycation.

The content of Glc-Lys in normal lens crystallin increased with age in a linear fashion. Thus, the nonenzymatic glycation of nondiabetic lens crystallin may be regarded as a biological clock.

The diabetic lens crystallin samples (n = 11) had a higher content of Glc-Lys (0.070 ± 0.034 nmol/nmol monomer). Over an age range comparable to that of the control samples, the diabetic crystallin samples contained about twice as much Glc-Lys.

The Glc-Lys content of the diabetic lens crystallin samples did not increase with lens age.

Source: Garlick RL, Mazer JS, Chylack LT Jr, Tung WH, Bunn HF.; Nonenzymatic glycation of human lens crystallin. Effect of aging and diabetes mellitus.; J Clin Invest. 1984 Nov;74(5):1742-9.
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