Nε-(1-Carboxyethyl)-L-lysine (Synonyms: CEL)

Nε-(1-Carboxyethyl)-L-lysine (CEL) is an advanced glycation end product (AGE) produced by the reaction of methyl glyoxal with lysine residues in proteins.1 Protein bound, but not free, CEL binds to the receptor for AGEs (RAGE).2 CEL levels are elevated in the lens of diabetic patients with cataract.3 Long-term caloric restriction decreases CEL levels in rat heart mitochondria.4 It decreases glutamate uptake and secretion of S100B in rat hippocampal slices in a RAGE-independent manner when used at a concentration of 1 mM.5

References
1. Ahmed, M.U., Brinkmann, F.E., Degenhardt, T.P., et al. Nε-(carboxyethyl)lysine, a product of the chemical modification of proteins by methylglyoxal, increases with age in human lens proteins. Biochem. J. 324(Pt 2), 565-570 (1997).
2. Xue, J., Ray, R., Singer, D., et al. The receptor for advanced glycation end products (RAGE) specifically recognizes methylglyoxal-derived AGEs. Biochemistry 53(20), 3327-3335 (2014).
3. Hashim, Z., and Zarina, S. Advanced glycation end products in diabetic and non-diabetic human subjects suffering from cataract. Age (Dordr) 33(3), 377-384 (2011).
4. Pamplona, R., Portero-OtÍn, M., Bellmunt, M.J., et al. Aging increases Nepsilon-(carboxymethyl)lysine and caloric restriction decreases Nepsilon-(carboxyethyl)lysine and Nepsilon-(malondialdehyde)lysine in rat heart mitochondrial proteins. Free Radic. Res. 36(1), 47-54 (2002).
5. Hansen, F.K., BattÚ, C.E., Dutra, M.F., et al. Methylglyoxal and carboxyethyllysine reduce glutamate uptake and S100B secretion in the hippocampus independently of RAGE activation. Amino Acids 48(2), 375-385 (2016).