In vitro studies on efficacy and toxicity of aminoguanidine

The glycation of long-lived protein and formation of the advanced glycation end products (AGEs) are associated with the development of diabetic complications. The failure of aminoguanidine (AG) to achieve a successful clinical trial was attributed to its toxicity and apparent lack of efficacy. Our aim was to elucidate the controversial effect of AG, on the cross-linking and fluorescent AGEs formation during in vitro glycation of collagen with reducing sugar or glycated BSA (AGE-BSA). Aliquots of 24 mg/ml pepsin soluble type I collagen were incubated 6 weeks at 37 °C with 250mM glucose and ribose solutions, or 0.5 mg/ml AGE-BSA in the absence or presence of 5-80mM AG. The cross-linking of collagen was detected by gel filtration and SDSPAGE. The AGEs formation was spectrofluorometricaly monitored. After 6 weeks, the formation of 405, 427 and 352 kDa aggregates with glucose, ribose respectively soluble AGE-BSA was observed. In the presence of monosaccharides, AG at all concentrations prevented the cross-linking of collagen peptides, compared to controls but a fluorescence increase was noticed. AG prevented the crosslinking of collagen peptides with AGE-BSA and decreased the fluorescence levels in a concentration-dependent manner. These data suggest that AG is an efficient collagen cross-linking inhibitor and probably the highest increase in fluorescence recorded in the presence of reducing sugar and AG is due to the competition between guanidine group of AG and arginine residues of proteins for some protein-bound dideoxyosones, which could form fluorescent compounds like pentosidine that can interact with AGEs receptor and activate its pathway.