Vitamin C and urea inhibit the formation of advanced glycation end products in vitro

Purpose - Advanced glycation end products (AGEs) are continuously formed in the body during normal metabolism and ageing through a non-enzymatic glycosylation reaction between proteins and carbohydrates, known as the Maillard's reaction. Many AGEs are capable of forming cross-links between proteins and most of them have fluorescent properties. Production of AGEs is markedly increased in diabetes mellitus where they play a pathological role. The aim of the present study is to investigate the possible inhibitory effects of urea, metformin and ascorbic acid on in vitro formation of fluorescent AGE products by comparing their inhibitory capacity with a well-known AGEs inhibitor, aminoguanidine.Design methodology approach - Experiments were carried out using bovine serum albumin and D (+) glucose to produce glycated bovine serum albumin, a fluorescent AGE. Fluorometer analysis was then performed to measure AGEs production and fluorescent intensity was compared between glycated samples with and without the inhibitors.Findings - Aminoguanidine which is known to form guanidine-carbonyl adduct, reversing the glycation process. was found to inhibit AGEs formation by 57 per cent. Although urea and metformin inhibits glycation by the same route, it was the most effective inhibitor among all four inhibiting agents used. Ascorbic acid, an antioxidant, also inhibits fluorescent AGEs by 52 per cent. It was also a good cross-link inhibitor. Urea showed an inhibitory effect of 27 per cent. It is suggested that urea formed in the body might be a possible natural protector of AGEs formation. Finally, metformin, an antidiabetic drug inhibits AGEs production by only 12 per cent. It is known to rather increase peripheral sensitivity to insulin and lower blood-glucose level.Originality value - The paper shows that aminoguanidine is the most efficient inhibitor and ascorbic acid supplementation could prove useful in diabetic patients to remove reactive species generated in the Maillard's reaction.