Non-enzymatic glycation of peripheral nerve proteins in human diabetics

We have measured non-enzymatic glycation of proteins in the cytoskeletal and myelin fractions of nerve fascicles from human sural nerves obtained from diabetic and non-diabetic amputation specimens. Levels of the early reversible glycation adduct, measured as furosine did not differ significantly between diabetics and controls in either protein fraction. Pentosidine levels per unit protein were significantly elevated in diabetics relative to controls in both cytoskeletal (5.96 vs 4.47; p = 0.037) and myelin protein (1.35 vs 0.69; p = 0.023) fractions. Protein cross-linkage in the cytoskeletal fraction, probably due to AGEs, was also higher in diabetics than controls (504 vs 349; p = 0.057). These results show that increased AGE accumulation occurs in cytoskeletal, as well as myelin, peripheral nerve proteins in diabetics. This suggests a possible new mechanism contributing to the axonal degeneration polyneuropathy of diabetes which is based upon irreversible glycation of axonal cytoskeletal proteins causing their cross-linkage and altered function.