Effect of carnosine and related compounds on glucose oxidation and protein glycation in vitro

Abstract

The effects of carnosine and related compounds (CRC) including anserine, homocarnosine, histidine, and beta-alanine, found in most mammalian tissues, were investigated on in, vitro glucose oxidation and glycation of human serum albumin (HSA). Carnosine and anserine were more reactive with D-glucose than with L-lysine, In the presence of 10 mu M Cu (II), although carnosine and anserine at low concentrations effectively inhibited formation of alpha-ketoaldehyde from D-glucose, they increased generation of H2O2 in a dose-dependent manner. Carnosine, homocarnosine, anserine, and histidine effectively inhibited hydroxylation of salicylate and deoxyribose degradation in the presence of glucose and 10 mu M Cu (II), In the presence of 25 mM D-glucose, copper and ascorbic acid stimulated carbonyl formation from HSA, Except for beta-alanine, CRC effectively inhibited the copper-catalyzed carbonyl formation from HSA, The addition of 25 mM D-glucose and/or 10 mu M Cu (II) to low density lipoprotein (LDL) increased formation of conjugated dienes. CRC effectively inhibited the glucose and/or copper-catalyzed LDL oxidation, CRC also inhibited glycation of HSA as determined by hydroxymethyl furfural and lysine with free epsilon-amino group. These results suggest that CRC may play an important role in protecting against diabetic complications by reacting with sugars, chelating copper, and scavenging free radicals.