Classification of AGEs
To date, AGEs have been found in various forms in blood, tissues, and food. There are several ways to classify the numerous AGEs. I am introducing 2 ways of representing them as examples.
First, some researchers categorized AGEs based on their chemical structure, fluorescence ability, molecular weight, and physiological importance, as shown in the table below. [1]
Classification of AGEs with respect to different criteria.
According to another research, AGEs can be named by 2 classifications, which are either focused on the structure of the AGE or instead on the proteins being modified.[2]
The structural classification of AGEs is based on the chemical structure and characteristics of these compounds. The major AGEs studied within this classification include N-carboxymethyllysine(CML), pentosidine, crossline, pyrraline and hydroimidazolone. For example, CML is characterized by the addition of a carboxymethyl group to lysine residues. This modification alters the chemical structure of lysine, leading to the formation of CML. Pentosidine is distinctive due to its pentose sugar moiety. The chemical structure involves the incorporation of a pentose (a five-carbon sugar) into the protein or amino acid, contributing to its uniqueness.
In the second classification (Protein Modification Classification), the subcategories are based on the modifying agent used such as glucose-derived AGEs or glyceraldehyde-derived AGEs and the specific protein that undergoes modification including haemoglobin (HbA1c, an Amadori product), albumin, eye crystallin, collagen type IV, etc.
This classification can be represented in the picture below.
Classification of AGEs according to type of structure and origin of substrate
There is also a report that proposed the pathways by which the six groups of AGEs classified by the above glycation-inducing agents are produced within the body as follows. [3]
Six different AGEs synthesis pathways in vivo
In addition to the classification mentioned above, as discussed in the previous AGES posting, AGEs can also be classified as endogenous or exogenous depending on whether they are produced by metabolic activities within the body or derived from food or external environmental sources. They can also be categorized into three types based on their formation processes. Furthermore, they can be classified as dietary AGEs or toxic AGEs (TAGE) based on their association with food. Additionally, they can be classified based on the specific tissues or organs where they are formed, such as in the blood or lens of the eye. Therefore, the classification methods and outcomes can vary significantly depending on the criteria used.
For reference, I am attaching a table of AGEs-related diseases along with related AGEs based on the above classification. [4]
Effects of AGEs in various diseases.[Reference materials]
[1] Advanced Glycation End-Products (AGEs): Formation, Chemistry, Classification, Receptors, and Diseases Related to AGEs
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9029922/
[2] Toxicity of advanced glycation end products (Review)
https://www.spandidos-publications.com/10.3892/br.2021.1422#f2-br-0-0-01422
[3] Toxic Advanced Glycation End Products (TAGE) Theory in Alzheimer’s Disease https://journals.sagepub.com/doi/pdf/10.1177/1533317506289277
[4] Toxicity of advanced glycation end products (Review)
https://www.spandidos-publications.com/10.3892/br.2021.1422#f2-br-0-0-01422
