The Biology of Advanced Glycation End Products

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This chapter is dedicated to the biology of advanced glycation end products (AGEs). In 1912, AGEs were first identified by French chemist Louis-Camille Maillard. Early investigation revealed AGE generation during food preparation (cooking) at high temperatures, wherein carbohydrates (e.g. glucose/glycan) slowly react with various proteins via concomitant generation of Schiff's base and Amadori products. This non-enzymatic process of AGE generation is termed glycation. Later, subsequent investigations revealed that AGE is exogenously produced during cooking and other processing of foodsand also endogenously generated in the human body including blood, skin, and other tissues. To date, more than 20 AGEs are postulated to prevail within human blood, tissues, and food resources. AGEs are optical sensitive molecules and based on their optical sensitivity AGEs are distinguished into fluorescent and non-fluorescent categories. The most important non-fluorescent components are carboxymethyl-lysine (CML), carboxyethyl-lysine (CEL), and pyrrolidine while pentosidine and methylglyoxal-lysine dimer (MOLD) are prominent compounds having fluorescent sensitivity. AGE binds with several receptor molecules, the prominent among whichare receptors for advanced glycation end products (RAGE). Additional cell surface molecules capable of binding with AGE including macrophage scavenger receptors (MSRs) type A, B1 (CD36), oligosaccharyltransferase-48/OST48, also termed "AGE receptor 1" (AGE-R1), 80K-H phosphoprotein (AGE receptor 2, AGE-R2), and galectin-3 (AGE receptor 3, AGE-R3), the scavenger receptor family (SR-A, SR-B, SR-1, SR-E, LOX-1, FEEL-1, FEEL-2, and CD36). This chapter describes the steps of AGE synthesis, their biochemical characterization, and the implication of the AGE-RAGE interactions at the cellular platform.