Saliva as a tool to monitor endogenous and dietary glycation compounds

Introduction:

Diabetics were found to show higher blood levels of glycation compounds (also referred to as “Advanced Glycation End Products”, AGEs) due to hyperglycemia [1], which shall contribute to pathogenic complications such as inflammation. The term “AGEs” stands for a number of individual compounds, among which Nε-carboxymethyllysine (CML), Nε–carboxyethyllysine (CEL), pyrraline and the arginine derivative MG-H1 are the most prominent. Physiological consequences resulting from an intake of dietary glycation compounds is under debate [2]. Saliva has become a valuable non-invasive diagnostic tool as saliva mirrors the blood level of many compounds [3]. Based on a dedicated LC-MS/MS method and the use of labelled standards, we present for the first time quantitative data for individual glycation in saliva and provide evidence for a dietary influence.

Methods:

Analysis was performed following an optimized protocol using an LC-MS/MS system. Specific target AGEs and isotopologues were synthesized and used for calibration or as internal standards, respectively.

Results:

We show for the first time that i) CML, CEL, MG-H1, pyrraline as well as Nε-fructosyllysine can be detected and quantitated in saliva, ii) a raw food diet with low amount of glycation compounds leads to a lowering of salivary AGEs levels and iii) the level of some specific AGEs in saliva can be modified by the diet.

Conclusion:

Saliva may be a useful tool for monitoring AGE levels to assess the AGE uptake by the diet. The use of AGEs in saliva as a biomarker for AGE-related diseases such as diabetes has to be further elucidated.

References:

[1] Hellwig M., Henle T. Angew Chem Int Ed 53, 10316 – 10329 (2014).

[2] Förster A., Kühne Y., Henle T. Ann N Y Acad Sci. 1043, 474 – 481 (2005).

[3] Pfaffe T., Cooper-White J., Beyerlein P., Kostner K., Punyadeera C.

Clin Chem 57, 675 – 687 (2011).