FREE-RADICAL DEPOLYMERIZATION OF HYALURONAN BY MAILLARD REACTION-PRODUCTS - ROLE IN LIQUEFACTION OF AGING VITREOUS

The degradation of hyaluronan was followed by viscosimetry and by HPLC in order to study the possible role of Maillard products (lysine-gluc ose) on the alteration of the vitreous gel in aging and diabetes. Lysi ne-glucose generated Maillard products produced a decrease of viscosit y and of the number average molecular weight (M-n) of hyaluronan durin g a 1 h incubation at 37 degrees C. This effect was comparable to that produced by 1 U/ml of testicular hyaluronidase bur was weaker than th e effect of a Fenton-type reagent (Udenfriend's reagent). The polydisp ersity of hyaluronan incubated with Maillard products appeared higher than with hyaluronidase suggesting a more random reaction. Antioxydant enzymes (SOD, catalase), the iron chelators (desferrioxamine, transfe rrin) and the free radical scavengers (uric acid, carnosine) inhibited the degradation by Maillard products confirming its free radical natu re and the intervention of trace metals. Maillard products have been d etected in diabetic vitreous and may play a role in its accelerated mo difications (liquefaction) in diabetes as compared to normal aging. (C ) 1998 Elsevier Science B.V.