Question

Advanced glycation products (AGPs) are known to occur as a result of Maillard Reaction. Name 3 AGPs and talk about the advantages or disadvantages of them

Answer 1

When sugar reacts with the free amine of a protein it forms the Schiff base that rearranges to a ketoamine (Amadori Product) that further rearranges or crosslinks with proteins to give AGPs. These AGPs may undergo oxidation, dehydration, polymerization and react with reactive oxidation species (ROS) to generate other AGPs. Three AGPs are discussed below:

1. Carboxymethyl lysine (CML) forms by oxidative degradation of Amadori product or direct addition of glyoxal to lysine.

2. Pentosidine forms by crosslinking of lysine and arginine crosslinked to a pentose.

3. Glyoxal lysine dimer (GOLD) forms by reaction of glyoxal with nitrogens from two different lysines.

There are several disadvantages of AGPs as their formation is involved in various diseases like cardiovascular diseases, diabetes, kidney diseases, and neurodegenerative diseases. They cause these diseases by either disrupting the structure and function of the proteins upon crosslinking or by activating intracellular signalling pathways by interacting with receptors. The receptor of AGPs (RAGE) upon ligand binding activates various kinase-dependent pathways and also induction of transcription factor NF-kB. RAGE also induces oxidative stress by reducing cellular antioxidant defences like glutathione and ascorbic acid.