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The maillard or browning reaction in diabetes

1993; Springer Nature; Volume: 7; Issue: 2 Linguagem: Inglês

10.1038/eye.1993.55

1476-5454

W. Garry John, Edmund J. Lamb,

Diet, Metabolism, and Disease

A major pathophysiological consequence of hyperglycae mia is the extensive chemical interaction of glucose with proteins, leading to its attachment to these proteins with out the aid of enzymes.Even though the Maillard reac tions have been of considerable interest to food chemists since the tum of the century,' it has only been relatively recently that attention has focused on non-enzymic glyca tion of proteins in vivo.Although non-enzymic glycation leading to formation of reversible Amadori products acts on many proteins throughout the body, it is less obvious how these products are related to the pathophysiology of diabetic complications.Recent efforts have focused on biologically important further products of the glycation reaction, which are derived slowly from the Amadori product following a sequence of further reactions and rearrangements?These compounds, in contrast to the Amadori product, are formed irreversibly resulting in accumulation on long-lived proteins; these have been called advanced glycation end (AGE) products. BIOCHEMISTRY OF THE EARLY MAILLARD REACTIONThe initial Maillard reaction is the condensation of the free aldehyde group of carbohydrate with either the f-amino group of lysine or hydroxylysine residues or the a-amino group of the N-terminal amino acid of proteins.2Only open forms of sugars react with proteins, the carbonyl group of an acyclic monosaccharide attaching to a protein amino group via nucleophilic attack to form a labile aldi mine (Schiff base).2This product may hydrolyse back to glucose and protein or undergo an Amadori rearrange ment to form a l-amino-I-deoxyfructose (fructosamine) derivative by a stable, though slightly reversible, keto amine linkage (Fig. 1).This product can cyclise to a ring structure (N-substituted-I-amino-deoxyketopyranose ).2The rate of the Amadori rearrangement is approximately one-sixtieth that of the dissociation to glucose and protein3 and also varies between proteins: for example, the Ama-