A Biological Definition of Advanced Glycation End-Products (AGEs)
As time goes on and our bodies change, alterations in the texture and color of our skin serve as a constant reminder of aging. Skin aging is a multifactorial process, reflecting the sum effects of genetic, endogenous, and environmental factors.1 Exogenous sources include exposure to ultraviolet (UV) light and environmental toxins, such as tobacco products and heavy metals, while endogenous sources derived from normal cellular metabolism can also contribute to aging. This includes processes such as glycation, which significantly promotes unwanted changes in human skin.1-3
As time goes on and our bodies change, alterations in the texture and color of our skin serve as a constant reminder of aging. Skin aging is a multifactorial process, reflecting the sum effects of genetic, endogenous, and environmental factors.1 Exogenous sources include exposure to ultraviolet (UV) light and environmental toxins, such as tobacco products and heavy metals, while endogenous sources derived from normal cellular metabolism can also contribute to aging. This includes processes such as glycation, which significantly promotes unwanted changes in human skin.1-3
Factors and Sources Contributing to the Development of AGEs
Skin glycation is the biological process by which glucose and other reducing sugars react with and modify biomolecular entities, such as lipids, nucleic acids, and proteins, to form many complex heterogeneous molecules potentially toxic to cells and tissues. These products of nonenzymatic sugar reactivity with other biological molecules are collectively known as advanced glycation end-products (AGEs).1-3 To date, more than 20 species of AGEs have been identified in human skin and are primarily classified based on differences in their biochemical properties.2,3 The principal mechanism by which these AGEs are created endogenously is known as the Maillard reaction. This nonenzymatic reaction was discovered initially in the 1900s and was shown to give rise to yellowish-to-brown-colored products that develop following the heating of a mixture of amino acids with reducing sugars.2,4 Other mechanisms that can form AGEs and their associated intermediates include sugar autoxidation, lipid peroxidation, and the polyol pathway. Along with the formation of AGEs, these pathways can produce additional reactive compounds (eg, Amadori products, dicarbonyls, Schiff bases, and oxidized compounds) that can disrupt normal cellular physiology (Figure 1).1-3,5
Skin glycation is the biological process by which glucose and other reducing sugars react with and modify biomolecular entities, such as lipids, nucleic acids, and proteins, to form many complex heterogeneous molecules potentially toxic to cells and tissues. These products of nonenzymatic sugar reactivity with other biological molecules are collectively known as advanced glycation end-products (AGEs).1-3 To date, more than 20 species of AGEs have been identified in human skin and are primarily classified based on differences in their biochemical properties.2,3 The principal mechanism by which these AGEs are created endogenously is known as the Maillard reaction. This nonenzymatic reaction was discovered initially in the 1900s and was shown to give rise to yellowish-to-brown-colored products that develop following the heating of a mixture of amino acids with reducing sugars.2,4 Other mechanisms that can form AGEs and their associated intermediates include sugar autoxidation, lipid peroxidation, and the polyol pathway. Along with the formation of AGEs, these pathways can produce additional reactive compounds (eg, Amadori products, dicarbonyls, Schiff bases, and oxidized compounds) that can disrupt normal cellular physiology (Figure 1).1-3,5
Exogenous sources linked to the production and accumulation of AGEs include eating refined and simple carbohydrates, as well as foods that are cooked at high temperatures (eg, grilling, frying, and baking) that have a brown/crunchy consistency (eg, cookies, chicken), which acquires its characteristic color and texture from the Maillard reaction.1-3,6 Excessive alcohol consumption, smoking, and living a sedentary lifestyle can also contribute to the production of AGEs. Other external factors that can increase the content of AGEs in the skin include exposure to pollution, metabolites in tobacco smoke, and UV light.1-3 Individuals should also be aware that self-tanning products contain
